Osteoporosis risk

Feeding acetyl-L-carnitine and lipoic acid to old rats significantly improves metabolic function while decreasing oxidative stress.

Mitochondrial-supported bioenergetics decline and oxidative stress increases during aging. To address whether the dietary addition of acetyl-l-carnitine [ALCAR, 1.5% (wt/vol) in the drinking water] and/or (R)-alpha-lipoic acid [LA, 0.5% (wt/wt) in the chow] improved these endpoints, young (2-4 mo) and old (24-28 mo) F344 rats were supplemented for up to 1 mo before death and hepatocyte isolation. ALCAR+LA partially reversed the age-related decline in average mitochondrial membrane potential and significantly increased (P = 0.02) hepatocellular O(2) consumption, indicating that mitochondrial-supported cellular metabolism was markedly improved by this feeding regimen. ALCAR+LA also increased ambulatory activity in both young and old rats; moreover, the improvement was significantly greater (P = 0.03) in old versus young animals and also greater when compared with old rats fed ALCAR or LA alone. To determine whether ALCAR+LA also affected indices of oxidative stress, ascorbic acid and markers of lipid peroxidation (malondialdehyde) were monitored. The hepatocellular ascorbate level markedly declined with age (P = 0.003) but was restored to the level seen in young rats when ALCAR+LA was given. The level of malondialdehyde, which was significantly higher (P = 0.0001) in old versus young rats, also declined after ALCAR+LA supplementation and was not significantly different from that of young unsupplemented rats. Feeding ALCAR in combination with LA increased metabolism and lowered oxidative stress more than either compound alone.

Proc Natl Acad Sci U S A. 2002 Feb 19;99(4):1870-5

Lipoic acid as an anti-inflammatory and neuroprotective treatment for Alzheimer’s disease.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that destroys patient memory and cognition, communication ability with the social environment and the ability to carry out daily activities. Despite extensive research into the pathogenesis of AD, a neuroprotective treatment - particularly for the early stages of disease - remains unavailable for clinical use. In this review, we advance the suggestion that lipoic acid (LA) may fulfil this therapeutic need. A naturally occurring cofactor for the mitochondrial enzymes pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, LA has been shown to have a variety of properties which can interfere with the pathogenesis or progression of AD. For example, LA increases acetylcholine (ACh) production by activation of choline acetyltransferase and increases glucose uptake, thus supplying more acetyl-CoA for the production of ACh. LA chelates redox-active transition metals, thus inhibiting the formation of hydroxyl radicals and also scavenges reactive oxygen species (ROS), thereby increasing the levels of reduced glutathione. In addition, LA down-regulates the expression of redox-sensitive pro-inflammatory proteins including TNF and inducible nitric oxide synthase. Furthermore, LA can scavenge lipid peroxidation products such as hydroxynonenal and acrolein. In human plasma, LA exists in an equilibrium of free and plasma protein bound form. Up to 150 muM, it is bound completely, most likely binding to high affinity fatty acid sites on human serum albumin, suggesting that one large dose rather than continuous low doses (as provided by “slow release” LA) will be beneficial for delivery of LA to the brain. Evidence for a clinical benefit for LA in dementia is yet limited. There are only two published studies, in which 600 mg LA was given daily to 43 patients with AD (receiving a standard treatment with choline-esterase inhibitors) in an open-label study over an observation period of up to 48 months. Whereas the improvement in patients with moderate dementia was not significant, the disease progressed extremely slowly (change in ADAScog: 1.2 points=year, MMSE: -0.6 points=year) in patients with mild dementia (ADAScog<15). Data from cell culture and animal models suggest that LA could be combined with nutraceuticals such as curcumin, (-)-epigallocatechin gallate (from green tea) and docosahexaenoic acid (from fish oil) to synergistically decrease oxidative stress, inflammation, Abeta levels and Abeta plaque load and thus provide a combined benefit in the treatment of AD.

Adv Drug Deliv Rev. 2008 Oct-Nov;60(13-14): 1463-70

Lipoic acid: a novel therapeutic approach for multiple sclerosis and other chronic inflammatory diseases of the CNS.

The naturally occurring antioxidant lipoic acid (LA) was first described as an essential cofactor for the conversion of pyruvate to Acetyl-CoA, a critical step in respiration. LA is now recognized as a compound that has many biological functions. Along with its reduced form dihydrolipoic acid (DHLA), LA reduces and recycles cellular antioxidants such as glutathione, and chelates zinc, copper and other transition metal ions in addition to heavy metals. LA can also act as a scavenger of reactive oxygen and nitrogen species. By acting as an insulin mimetic agent, LA stimulates glucose uptake in many different cell types and can also modulate insulin signaling. The p38 and ERK MAP kinase pathways, AKT and NFkappaB are all regulated by LA. In addition, LA activates the prostaglandin EP2 and EP4 receptors to stimulate the production of the small molecule cyclic adenosine 5’ monophosphate (cAMP). These diverse actions suggest that LA may be therapeutically effective in treating oxidative stress associated diseases. This review discusses the known biochemical properties of LA, its antioxidant properties, its ability to modulate signal transduction pathways, and the recent progress made in the utilization of LA as a therapeutic alternative for multiple sclerosis, Alzheimer’s disease and diabetic neuropathy.

Endocr Metab Immune Disord Drug Targets. 2008 Jun;8(2):132-42

Prevention of mutation, cancer, and other age-associated diseases by optimizing micronutrient intake.

I review three of our research efforts which suggest that optimizing micronutrient intake will in turn optimize metabolism, resulting in decreased DNA damage and less cancer as well as other degenerative diseases of aging. (1) Research on delay of the mitochondrial decay of aging, including release of mutagenic oxidants, by supplementing rats with lipoic acid and acetyl carnitine. (2) The triage theory, which posits that modest micronutrient deficiencies (common in much of the population) accelerate molecular aging, including DNA damage, mitochondrial decay, and supportive evidence for the theory, including an in-depth analysis of vitamin K that suggests the importance of achieving optimal micronutrient intake for longevity. (3) The finding that decreased enzyme binding constants (increased Km) for coenzymes (or substrates) can result from protein deformation and loss of function due to an age-related decline in membrane fluidity, or to polymorphisms or mutation. The loss of enzyme function can be compensated by a high dietary intake of any of the B vitamins, which increases the level of the vitamin-derived coenzyme. This dietary remediation illustrates the importance of understanding the effects of age and polymorphisms on optimal micronutrient requirements. Optimizing micronutrient intake could have a major effect on the prevention of cancer and other degenerative diseases of aging.

J Nucleic Acids. 2010 Sep 22;2010

The effects and mechanisms of mitochondrial nutrient alpha-lipoic acid on improving age-associated mitochondrial and cognitive dysfunction: an overview.

We have identified a group of nutrients that can directly or indirectly protect mitochondria from oxidative damage and improve mitochondrial function and named them “mitochondrial nutrients”. The direct protection includes preventing the generation of oxidants, scavenging free radicals or inhibiting oxidant reactivity, and elevating cofactors of defective mitochondrial enzymes with increased Michaelis-Menten constant to stimulate enzyme activity, and also protect enzymes from further oxidation, and the indirect protection includes repairing oxidative damage by enhancing antioxidant defense systems either through activation of phase 2 enzymes or through increase in mitochondrial biogenesis. In this review, we take alpha-lipoic acid (LA) as an example of mitochondrial nutrients by summarizing the protective effects and possible mechanisms of LA and its derivatives on age-associated cognitive and mitochondrial dysfunction of the brain. LA and its derivatives improve the age-associated decline of memory, improve mitochondrial structure and function, inhibit the age-associated increase of oxidative damage, elevate the levels of antioxidants, and restore the activity of key enzymes. In addition, co-administration of LA with other mitochondrial nutrients, such as acetyl-L: -carnitine and coenzyme Q10, appears more effective in improving cognitive dysfunction and reducing oxidative mitochondrial dysfunction. Therefore, administrating mitochondrial nutrients, such as LA and its derivatives in combination with other mitochondrial nutrients to aged people and patients suffering from neurodegenerative diseases, may be an effective strategy for improving mitochondrial and cognitive dysfunction.

Neurochem Res. 2008 Jan;33(1):194-203

Alpha-Lipoic acid increases energy expenditure by enhancing adenosine monophosphate-activated protein kinase-peroxisome proliferator-activated receptor-gamma coactivator-1alpha signaling in the skeletal muscle of aged mice.

Skeletal muscle mitochondrial dysfunction is associated with aging and diabetes, which decreases respiratory capacity and increases reactive oxygen species. Lipoic acid (LA) possesses antioxidative and antidiabetic properties. Metabolic action of LA is mediated by activation of adenosine monophosphate-activated protein kinase (AMPK), a cellular energy sensor that can regulate peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha), a master regulator of mitochondrial biogenesis. We hypothesized that LA improves energy metabolism and mitochondrial biogenesis by enhancing AMPK-PGC-1alpha signaling in the skeletal muscle of aged mice. C57BL/6 mice (24 months old, male) were supplemented with or without alpha-LA (0.75% in drinking water) for 1 month. In addition, metabolic action and cellular signaling of LA were studied in cultured mouse myoblastoma C2C12 cells. Lipoic acid supplementation improved body composition, glucose tolerance, and energy expenditure in the aged mice. Lipoic acid increased skeletal muscle mitochondrial biogenesis with increased phosphorylation of AMPK and messenger RNA expression of PGC-1alpha and glucose transporter-4. Besides body fat mass, LA decreased lean mass and attenuated phosphorylation of mammalian target of rapamycin (mTOR) signaling in the skeletal muscle. In cultured C2C12 cells, LA increased glucose uptake and palmitate beta-oxidation, but decreased protein synthesis, which was associated with increased phosphorylation of AMPK and expression of PGC-1alpha and glucose transporter-4, and attenuated phosphorylation of mTOR and p70S6 kinase. We conclude that LA improves skeletal muscle energy metabolism in the aged mouse possibly through enhancing AMPK-PGC-1alpha-mediated mitochondrial biogenesis and function. Moreover, LA increases lean mass loss possibly by suppressing protein synthesis in the skeletal muscle by down-regulating the mTOR signaling pathway. Thus, LA may be a promising supplement for treatment of obesity and/or insulin resistance in older patients.

Metabolism. 2010 Jul;59(7):967-76

Alpha-lipoic acid reduces expression of vascular cell adhesion molecule-1 and endothelial adhesion of human monocytes after stimulation with advanced glycation end products.

Advanced glycation end products (AGEs) have been identified as relevant mediators of late diabetic complications such as atherosclerotic disease. The endothelial migration of monocytes is one of the first steps in atherogenesis and monocyte-endothelial interaction itself is linked to the expression of adhesion molecules like vascular cell adhesion molecule-1 (VCAM-1). Recently, stimulation of VCAM-1 by AGEs has been demonstrated. Since endothelial stimulation by AGEs is followed by generation of oxygen free radicals with subsequent activation of nuclear transcription factor kappaB, we investigated the influence of alpha-lipoic acid on the expression of VCAM-1 and monocyte adherence to endothelial cells in vitro by means of cell-associated chemiluminescence assays and quantitative reverse transcriptase polymerase chain reaction using a constructed recombinant RNA standard. We found that alpha-lipoic acid was able to decrease the number of VCAM-1 transcripts from 41. 0+/-11.2 to 9.5+/-4.7 RNA copies per cell in AGE-stimulated cell cultures. Furthermore, expression of VCAM-1 was suppressed in a time- and dose-dependent manner by alpha-lipoic acid as shown by chemiluminescence endothelial cell assay. Pretreatment of endothelial cells with 0.5 mM or 5 mM alpha-lipoic acid reduced AGE-induced endothelial binding of monocytes from 22.5+/-2.9% to 18. 3+/-1.9% and 13.8+/-1.8% respectively. Thus, we suggest that extracellularly administered alpha-lipoic acid reduces AGE-albumin-induced endothelial expression of VCAM-1 and monocyte binding to endothelium in vitro. These in vitro results may contribute to the understanding of a potential antioxidative treatment of atherosclerosis.

Clin Sci (Lond). 1999 Jan;96(1):75-82

Lipoic acid prevents hypertension, hyperglycemia, and the increase in heart mitochondrial superoxide production.

BACKGROUND: The present study was designed to investigate whether the effects of dietary supplementation with alpha-lipoic acid could prevent the increase in mitochondrial superoxide production in the heart as well as the enhanced formation of advanced glycation end-products (AGE) that are associated with the development of hypertension and insulin resistance in chronically glucose-fed rats. METHODS: Sprague Dawley rats were either given or not given a 10% D-glucose solution to drink during 4 weeks, combined either with a normal chow diet or with alpha-lipoic acid supplemented diet. The oxidative stress was evaluated by measuring the heart mitochondrial superoxide production using the lucigenin chemiluminescence method. The formation of AGE was also assessed in plasma and aorta. RESULTS: Chronic administration of glucose resulted in a 29% increase in blood pressure, 30% increase in glycemia, 286% increase in insulinemia, and 408% increase in insulin resistance index. Chronic glucose feeding also resulted in a 22% greater mitochondrial superoxide anion production in heart and in an increase of 63% in AGE content in aorta. Increases in blood pressure, aorta AGE content and heart mitochondrial superoxide production were prevented in the rats fed glucose supplemented with lipoic acid. The simultaneous treatment with lipoic acid also attenuated the rise in insulin levels as well as in insulin resistance in the glucose fed rats. CONCLUSIONS: These findings demonstrate that alpha-lipoic acid supplementation prevents development of hypertension and hyperglycemia, presumably through its antioxidative properties, as reflected by prevention of an increase in heart mitochondrial superoxide anion production and in AGE formation in the aorta of chronically glucose treated rats.

Am J Hypertens. 2003 Mar;16(3):173-9

Lipoic acid improves glucose utilisation and prevents protein glycation and AGE formation.

The present study investigates the antiglycating effect of alpha-lipoic acid (LA) in high fructose-fed rats in vivo and its potential to inhibit the process of glycation in vitro. In addition, the effect of LA on glucose utilisation in rat diaphragm was also studied. Rats fed a high fructose diet (60% total calories) were administered with 35 mg/kg b.w, lipoic acid (LA) intraperitoneally for 20 days. The effects of LA on plasma glucose, fructosamine, protein glycation and glycated haemoglobin in high fructose rats and on in vitro glycation were studied. In vitro utilization of glucose was carried out in normal rat diaphragm in the presence and absence of insulin in which LA was used as an additive. The contents of glucose, glycated protein, glycated haemoglobin and fructosamine were significantly lowered on LA administration to high fructose-fed rats. LA prevented in vitro glycation and the accumulation of advanced glycation end products. Further LA enhanced glucose utilization in the rat diaphragm. This effect was additive to that of insulin and did not interfere with the action of insulin. The findings provide evidence for the therapeutic utility of lipoic acid in diabetes and its complications.

Pharmazie. 2005 Oct;60(10):772-5

Alpha-lipoic acid as a dietary supplement: molecular mechanisms and therapeutic potential.

Alpha-lipoic acid (LA) has become a common ingredient in multivitamin formulas, anti-aging supplements, and even pet food. It is well-defined as a therapy for preventing diabetic polyneuropathies, and scavenges free radicals, chelates metals, and restores intracellular glutathione levels which otherwise decline with age. How do the biochemical properties of LA relate to its biological effects? Herein, we review the molecular mechanisms of LA discovered using cell and animal models, and the effects of LA on human subjects. Though LA has long been touted as an antioxidant, it has also been shown to improve glucose and ascorbate handling, increase eNOS activity, activate Phase II detoxification via the transcription factor Nrf2, and lower expression of MMP-9 and VCAM-1 through repression of NF-kappa B. LA and its reduced form, dihydrolipoic acid, may use their chemical properties as a redox couple to alter protein conformations by forming mixed disulfides. Beneficial effects are achieved with low micromolar levels of LA, suggesting that some of its therapeutic potential extends beyond the strict definition of an antioxidant. Current trials are investigating whether these beneficial properties of LA make it an appropriate treatment not just for diabetes, but also for the prevention of vascular disease, hypertension, and inflammation.

Biochim Biophys Acta. 2009 Oct;1790(10):1149-60

Vascular oxidative stress and inflammation increase with age: ameliorating effects of alpha-lipoic acid supplementation.

Increased oxidative stress and inflammation causally contribute to cardiovascular diseases, for which advanced age is a major risk factor. We found that indicators of oxidative stress, including NADPH oxidase activity and superoxide levels, were significantly increased in aortas of old (22-24 months) versus young (3-4 months) male F344 rats, whereas superoxide dismutase (SOD) activity was decreased. Aortic mRNA and protein levels of NOX4, the principal catalytic subunit of NADPH oxidase in vascular cells, also were increased with age, but not NOX2 and p22(phox). Indicators of inflammation, including activation of NFkappaB and upregulation of vascular cell adhesion molecule-1 (VCAM-1) in aorta, and monocyte chemotactic protein-1 (MCP-1) in plasma, also were significantly increased in old rats. Supplementation with 0.2% (wt/wt) (R)-alpha-lipoic acid (LA) for 2 weeks caused a nonsignificant decrease in NADPH oxidase activity in aged aorta and a significant decrease in mRNA--but not protein--levels of NOX4 and VCAM-1. Furthermore, LA reversed the age-dependent changes in aortic SOD activity and plasma MCP-1 levels. Hence, vascular oxidative stress and inflammation increase with age and are ameliorated by LA supplementation.

Ann N Y Acad Sci. 2010 Aug;1203:151-9

Multifunctional lipoic acid conjugates.

Several hundreds of studies published the last decade have reported that alpha-lipoic acid (LA) possess the potential to intervene in various therapeutically interesting pathways. However, it should be noted that LA reportedly exerts most of its effects at high micromolar concentrations; that amides of LA exhibit higher biological activity than the parent compound; and that molecular combinations (hybrids) obtained by coupling LA with an amino-substituted bioactive moiety, possess multifunctional activity. The design and synthesis of hybrid molecules encompassing two pharmacophores in one molecular scaffold is a well established approach to the synthesis of more potent drugs with dual activity. Using this approach, various research groups have recently designed and synthesized hybrid compounds with antioxidant activity hyphenated with a wide variety of other activities such as neuroprotective, cardioprotective, anti-inflammatory, antidiabetic and anticancer activity as well as enzyme inhibition. Moreover, LA represents an ideal chemical entity for the development of biologically interesting functionalized nanoparticles. Many recent publications describe the use of LA: i) as component of nanospheres and nanoprodrugs, ii) as a linker for the attachment of lipids, carbohydrates, proteins and oligonucleotides on gold nanoparticles to form Self Assembled Monolayers (SAMs) and iii) as surface ligand for cap exchange reactions to prepare water-soluble semiconducting nanocrystal Quantum Dots (QDs). This review is focused on the growing field of the design and synthesis of LA conjugates, for the development of novel molecules with a dual mode of action and the construction of nanosized antioxidants, Self Assembled Monolayers and Quantum Dots.

Curr Med Chem. 2009;16(35):4728-42

Differential activity of lipoic acid enantiomers in cell culture.

It is unclear whether the two enantiomeric forms (R & S) of lipoic acid (LA) share similar pharmacological activity and the exact cellular targets of LA are not well identified. We oxidatively stressed 3 cell culture systems representing different cell types. Mitochondrial metabolism was the primary endpoint. When C6 glioma was damaged by hydrogen peroxide (H2O2), all forms of LA protected. Racemic and S-LA were less effective than the R-isomer that was also protective in tertiary butyl hydroperoxide (TBHP)-damaged C6 glioma. In PC12 cells, little damage was produced by TBHP; R-LA increased mitochondrial metabolism above the level of non-damaged control. In H2O2 damaged PC12 cells, R-LA and racemic LA (but not S-LA) not only protected against damage, but increased mitochondrial metabolism above the non-damaged control level. When BAE cells were damaged with H2O2, R- and racemic LA protected while S-LA was ineffective.

J Herb Pharmacother. 2005;5(3):43-54

Differential effects of lipoic acid stereoisomers on glucose metabolism in insulin-resistant skeletal muscle.

The racemic mixture of the antioxidant alpha-lipoic acid (ALA) enhances insulin-stimulated glucose metabolism in insulin-resistant humans and animals. We determined the individual effects of the pure R-(+) and S-(-) enantiomers of ALA on glucose metabolism in skeletal muscle of an animal model of insulin resistance, hyperinsulinemia, and dyslipidemia: the obese Zucker (fa/fa) rat. Obese rats were treated intraperitoneally acutely (100 mg/kg body wt for 1 h) or chronically [10 days with 30 mg/kg of R-(+)-ALA or 50 mg/kg of S-(-)-ALA]. Glucose transport [2-deoxyglucose (2-DG) uptake], glycogen synthesis, and glucose oxidation were determined in the epitrochlearis muscles in the absence or presence of insulin (13.3 nM). Acutely, R-(+)-ALA increased insulin-mediated 2-DG-uptake by 64% (P < 0.05), whereas S-(-)-ALA had no significant effect. Although chronic R-(+)-ALA treatment significantly reduced plasma insulin (17%) and free fatty acids (FFA; 35%) relative to vehicle-treated obese animals, S-(-)-ALA treatment further increased insulin (15%) and had no effect on FFA. Insulin-stimulated 2-DG uptake was increased by 65% by chronic R-(+)-ALA treatment, whereas S-(-)-ALA administration resulted in only a 29% improvement. Chronic R-(+)-ALA treatment elicited a 26% increase in insulin-stimulated glycogen synthesis and a 33% enhancement of insulin-stimulated glucose oxidation. No significant increase in these parameters was observed after S-(-)-ALA treatment. Glucose transporter (GLUT-4) protein was unchanged after chronic R-(+)-ALA treatment but was reduced to 81 +/- 6% of obese control with S-(-)-ALA treatment. Therefore, chronic parenteral treatment with the antioxidant ALA enhances insulin-stimulated glucose transport and non-oxidative and oxidative glucose metabolism in insulin-resistant rat skeletal muscle, with the R-(+) enantiomer being much more effective than the S-(-) enantiomer.

Am J Physiol. 1997 Jul;273(1 Pt 1):E185-91

Lipid lowering effect of antioxidant alpha-lipoic Acid in experimental atherosclerosis.

Accumulating data demonstrated that hypercholesterolemia and oxidative stress play an important role in the development of atherosclerosis. In the present study, a protective activity of alpha-lipoic acid; a metabolic antioxidant in hypercholesterolemic-induced animals was investigated. Eighteen adult male New Zealand White (NZW) rabbit were segregated into three groups labelled as group N, HCD and ALA (n = 6). Group N (normal control) was fed with normal chow, the rest (HCD and ALA) were fed with 100 g/head/day of 1% cholesterol rich diet to induce hypercholesterolemia. Four point two mg/body weight of alpha lipoic acid was concomintantly supplemented to the ALA group. Drinking water was given ad-libitum. The study was designed for 10 weeks. Blood sampling was taken from the ear lobe vein at the beginning, week 5 and week 10. Plasma was prepared for lipid profile estimation and microsomal lipid peroxidation index indicated with malondialdehyde (MDA) formation. At the end of the experiment, the animals were sacrificed and the aorta were excised for intimal lesion analysis. The plasma total cholesterol (TC) and low density lipoprotein (LDL) levels were found to be significantly low in ALA group compared to that of the HCD group (p<0.05). Similarly, low level of MDA (p<0.05) in ALA group was observed compared to that of the HCD group showing a significant reduction of lipid peroxidation activity. Histomorphometric intimal lesion analysis of the aorta showing less of atheromatous plaque formation in alpha lipoic acid supplemented group (p<0.05) compared to HCD group. These findings suggested that alpha lipoic acid posses a dual lipid lowering and anti-atherosclerotic properties indicated with low plasma TC and LDL levels and reduction of athero-lesion formation in hypercholesterolemic-induced rabbits.

J Clin Biochem Nutr. 2008 Sep;43(2):88-94

Alpha lipoic acid possess dual antioxidant and lipid lowering properties in atherosclerotic-induced New Zealand White rabbit.

There is accumulating data demonstrated hypercholesterolemia and oxidative stress play an important role in the development of atherosclerosis. In the present study, a protective activity of alpha-lipoic acid; a metabolic antioxidant in hypercholesterolemic-induced animals was investigated. Eighteen adult male New Zealand White (NZW) rabbit were segregated into three groups labelled as group K, AT and ALA (n=6). While group K was fed with normal chow and acted as a control, the rest fed with 100 g/head/day with 1% high cholesterol diet to induce hypercholesterolemia. 4.2 mg/body weight of alpha lipoic acid was supplemented daily to the ALA group. Drinking water was given ad-libitum. The study was designed for 10 weeks. Blood sampling was taken from the ear lobe vein at the beginning of the study, week 5 and week 10 and plasma was prepared for lipid profile estimation and microsomal lipid peroxidation index indicated with malondialdehyde (MDA) formation. Animals were sacrificed at the end of the study and the aortas were excised for intimal lesion analysis. The results showed a significant reduction of lipid peroxidation index indicated with low MDA level (p<0.05) in ALA group compared to that of the AT group. The blood total cholesterol (TCHOL) and low density lipoprotein (LDL) levels were found to be significantly low in ALA group compared to that of the AT group (p<0.05). Histomorphometric intimal lesion analysis of the aorta showing less of atheromatous plaque formation in alpha lipoic acid supplemented group (p<0.05) compared to that of AT group. These findings suggested that apart from its antioxidant activity, alpha lipoic acid may also posses a lipid lowering effect indicated with low plasma TCHOL and LDL levels and reduced the athero-lesion formation in rabbits fed a high cholesterol diet.

Biomed Pharmacother. 2008 Dec;62(10):716-22

Effect of combined treatment with alpha-Lipoic acid and acetyl-L-carnitine on vascular function and blood pressure in patients with coronary artery disease.

Mitochondria produce reactive oxygen species that may contribute to vascular dysfunction. alpha-Lipoic acid and acetyl-L-carnitine reduce oxidative stress and improve mitochondrial function. In a double-blind crossover study, the authors examined the effects of combined alpha-lipoic acid/acetyl-L-carnitine treatment and placebo (8 weeks per treatment) on vasodilator function and blood pressure in 36 subjects with coronary artery disease. Active treatment increased brachial artery diameter by 2.3% (P=.008), consistent with reduced arterial tone. Active treatment tended to decrease systolic blood pressure for the whole group (P=.07) and had a significant effect in the subgroup with blood pressure above the median (151+/-20 to 142+/-18 mm Hg; P=.03) and in the subgroup with the metabolic syndrome (139+/-21 to 130+/-18 mm Hg; P=.03). Thus, mitochondrial dysfunction may contribute to the regulation of blood pressure and vascular tone. Further studies are needed to confirm these findings and determine the clinical utility of alpha-lipoic acid/acetyl-L-carnitine as antihypertensive therapy.

J Clin Hypertens (Greenwich). 2007 Apr;9(4):249-55

The osteoblast: an insulin target cell controlling glucose homeostasis.

The past five years have witnessed the emergence and discovery of unexpected functions played by the skeleton in whole-organism physiology. Among these newly described tasks is the role of bone in the control of energy metabolism, which is achieved through the secretion of osteocalcin, an osteoblasts-derived hormone regulating insulin secretion, insulin sensitivity, and energy expenditure. These initial findings raised several fundamental questions on the nature of insulin action in bone. Discoveries made independently by our two groups have provided answers recently to some of these questions. Through the analysis of mice lacking insulin receptor (InsR) only in osteoblasts, we found that insulin signaling in these cells favors whole-body glucose homeostasis. Importantly, this function of insulin signaling in osteoblasts was achieved through the negative regulation of osteocalcin carboxylation and bioavailability. Our studies also established that insulin signaling in osteoblasts was a positive regulator not only of postnatal bone acquisition but also of bone resorption. Interestingly, it appears that insulin signaling in osteoblasts induced osteocalcin activation by stimulating osteoclast activity. Indeed, the low pH generated during bone resorption is a sufficient means to decarboxylate osteocalcin. Our findings establish that the osteoblast is an important target used by insulin to control whole-body glucose homeostasis and identify bone resorption as the mechanism regulating osteocalcin activation.

J Bone Miner Res. 2011 Apr;26(4):677-80

Integrative physiology: defined novel metabolic roles of osteocalcin.

The prevailing model of osteology is that bones constantly undergo a remodeling process, and that the differentiation and functions of osteoblasts are partially regulated by leptin through different central hypothalamic pathways. The finding that bone remodeling is regulated by leptin suggested possible endocrinal effects of bones on energy metabolism. Recently, a reciprocal relationship between bones and energy metabolism was determined whereby leptin influences osteoblast functions and, in turn, the osteoblast-derived protein osteocalcin influences energy metabolism. The metabolic effects of bones are caused by the release of osteocalcin into the circulation in an uncarboxylated form due to incomplete gamma-carboxylation. In this regard, the Esp gene encoding osteotesticular protein tyrosine phosphatase is particularly interesting because it may regulate gamma-carboxylation of osteocalcin. Novel metabolic roles of osteocalcin have been identified, including increased insulin secretion and sensitivity, increased energy expenditure, fat mass reduction, and mitochondrial proliferation and functional enhancement. To date, only a positive correlation between osteocalcin and energy metabolism in humans has been detected, leaving causal effects unresolved. Further research topics include: identification of the osteocalcin receptor; the nature of osteocalcin regulation in other pathways regulating metabolism; crosstalk between nutrition, osteocalcin, and energy metabolism; and potential applications in the treatment of metabolic diseases.

J Korean Med Sci. 2010 Jul;25(7):985-91

Bone: from a reservoir of minerals to a regulator of energy metabolism.

Besides locomotion, organ protection, and calcium-phosphorus homeostasis, the three classical functions of the skeleton, bone remodeling affects energy metabolism through uncarboxylated osteocalcin, a recently discovered hormone secreted by osteoblasts. This review traces how energy metabolism affects osteoblasts through the central control of bone mass involving leptin, serotoninergic neurons, the hypothalamus, and the sympathetic nervous system. Next, the role of osteocalcin (insulin secretion, insulin sensitivity, and pancreas β-cell proliferation) in the regulation of energy metabolism is described. Then, the connections between insulin signaling on osteoblasts and the release of uncarboxylated osteocalcin during osteoclast bone resorption through osteoprotegerin are reported. Finally, the understanding of this new bone endocrinology will provide some insights into bone, kidney, and energy metabolism in patients with chronic kidney disease.

Kidney Int Suppl. 2011 Apr;(121):S14-9

Physiology of bone.

Bone serves three main physiological functions. Its mechanical nature provides support for locomotion and offers protection to vulnerable internal organs, it forms a reservoir for storage of calcium and phosphate in the body, and it provides an environment for bone marrow and for the development of haematopoietic cells. The traditional view of a passive tissue responding to hormonal and dietary influences has changed over the past half century to one of a dynamic adaptive tissue responding to mechanical demands. This chapter gathers together some recent advances in bone physiology and molecular cell biology and discusses the potential application of the bone’s functional adaptation to loading in enhancing bone strength during childhood and adolescence.

Endocr Dev. 2009;16:32-48

The new kidney disease: improving global outcomes (KDIGO) guidelines - expert clinical focus on bone and vascular calcification.

Chronic kidney disease-mineral and bone disorder (CKD-MBD) defines a triad of interrelated abnormalities of serum biochemistry, bone and the vasculature associated with chronic kidney disease (CKD). The new kidney disease: improving global outcomes (KDIGO) guidelines define the quality and depth of evidence supporting therapeutic intervention in CKD-MBD. They also highlight where patient management decisions lack a strong evidence base. Expert interpretation of the guidelines, along with informed opinion, where evidence is weak, may help develop effective clinical practice. The body of evidence linking poor bone health and reservoir function (the ability of bone to buffer calcium and phosphorus) with vascular calcification and cardiovascular outcomes is growing. Treating renal bone disease should be one of the primary aims of therapy for CKD. Evaluation of the biochemical parameters of CKD-MBD (primarily phosphorus, calcium, parathyroid hormone and vitamin D levels) as early as CKD Stage 3, and an assessment of bone status (by the best means available), should be used to guide treatment decisions. The adverse effects of high phosphorus intake relative to renal clearance (including stimulation of hyperparathyroidism) precede hyperphosphatemia, which presents late in CKD. Early reduction of phosphorus load may ameliorate these adverse effects. Evidence that calcium load may influence progression of vascular calcification with effects on mortality should also be considered when choosing the type and dose of phosphate binder to be used. The risks, benefits, and strength of evidence for various treatment options for the abnormalities of CKD-MBD are considered.

Clin Nephrol. 2010 Dec;74(6):423-32

Osteoporosis.

Bone is a complex organ which contains an organic matrix which serves as scaffolding, includes mineral as calcium distributed in a pattern providing structure and serves as an ion reservoir for the body. Throughout life it dynamically changes in response to changes in activity, body mass, and weight bearing. It is important to define patients at risk for bone loss, since accrued bone loss leading to osteoporosis in the older population of both men and women is unacceptable. There are many different therapies including biphosphonates which can decrease loss of bone and decrease fracture risk in patients who already have had sustained a fracture. Newer therapies such as parathyroid hormone may improve the fracture risk even more than biphosphonates over a shorter period of time.

Clin Geriatr Med. 2005 Aug;21(3):603-29

Control of bone remodeling by nervous system. Regulation of glucose metabolism by skeleton. - Tangent point with nervous system.

It has been demonstrated that osteocalcin, osteoblast-secreted molecule, regulates energy metabolism through acting on pancreatic β-cells and adipocytes, while it has been established that the adipocyte-derived hormone leptin regulates bone metabolism through central nervous system and sympathetic nervous system. Recently, it has been reported that sympathetic tone into osteoblasts is a mediator of leptin regulation of insulin secretion. These functional relationship between bone and multiple organs illustrates the pivotal role of the skeleton in the regulation of our major physiological functions including energy metabolism.

Clin Calcium. 2010 Dec;20(12):1814-9

Energy regulation by the skeleton.

Bones of the skeleton are constantly remodeled through bone resorption by cells called osteoclasts and bone formation by cells called osteoblasts. Both cell types are under multi-hormone control. New research findings demonstrate that bone formation by osteoblasts is negatively regulated by the hormone leptin, which is secreted by adipocytes and acts through the leptin receptor in the central nervous system and ultimately through the sympathetic nervous system. Leptin deficiency leads to increased osteoblast activity and increased bone mass. Reciprocally, expression of the Esp gene, exclusive to osteoblasts, regulates glucose homeostasis and adiposity through controlling the osteoblastic secretion of the hormone-like substance osteocalcin. An undercarboxylated form of osteocalcin acts as a regulator of insulin in the pancreas and adiponectin in the adipocyte to modulate energy metabolism. Osteocalcin deficiency in knockout mice leads to decreased insulin and adiponectin secretion, insulin resistance, higher serum glucose levels and increased adiposity.

Nutr Rev. 2008 Apr;66(4):229-33

Insulin signaling in osteoblasts integrates bone remodeling and energy metabolism.

The broad expression of the insulin receptor suggests that the spectrum of insulin function has not been fully described. A cell type expressing this receptor is the osteoblast, a bone-specific cell favoring glucose metabolism through a hormone, osteocalcin, that becomes active once uncarboxylated. We show here that insulin signaling in osteoblasts is necessary for whole-body glucose homeostasis because it increases osteocalcin activity. To achieve this function insulin signaling in osteoblasts takes advantage of the regulation of osteoclastic bone resorption exerted by osteoblasts. Indeed, since bone resorption occurs at a pH acidic enough to decarboxylate proteins, osteoclasts determine the carboxylation status and function of osteocalcin. Accordingly, increasing or decreasing insulin signaling in osteoblasts promotes or hampers glucose metabolism in a bone resorption-dependent manner in mice and humans. Hence, in a feed-forward loop, insulin signals in osteoblasts activate a hormone, osteocalcin, that promotes glucose metabolism.

Cell. 2010 Jul 23;142(2):296-308

Intermittent injections of osteocalcin improve glucose metabolism and prevent type 2 diabetes in mice.

The uncarboxylated form of the osteoblast-specific secreted molecule osteocalcin is a hormone favoring glucose handling and increasing energy expenditure. As a result, the absence of osteocalcin leads to glucose intolerance in mice, while genetically modified mice with an increase in uncarboxylated osteocalcin are protected from type 2 diabetes and obesity. Here, we tested in the mouse the therapeutic potential of intermittent administration of osteocalcin. We found that daily injections of osteocalcin at either 3 or 30ng/g/day significantly improved glucose tolerance and insulin sensitivity in mice fed a normal diet. This was attributable, in part, to an increase in both β-cell mass and insulin secretion. When mice were fed a high-fat diet (HFD), daily injections of osteocalcin partially restored insulin sensitivity and glucose tolerance. Moreover, mice treated with intermittent osteocalcin injections displayed additional mitochondria in their skeletal muscle, had increased energy expenditure and were protected from diet-induced obesity. Finally, the hepatic steatosis induced by the HFD was completely rescued in mice receiving osteocalcin daily. Overall, these results provide evidence that daily injections of osteocalcin can improve glucose handling and prevent the development of type 2 diabetes.

Bone. 2011 Apr 29

Cross-sectional evidence of a signaling pathway from bone homeostasis to glucose metabolism.

Context: Preclinical studies suggested the existence of a signaling pathway connecting bone and glucose metabolisms. Supposedly leptin modulates osteocalcin bioactivity, which in turn stimulates insulin and adiponectin secretion, and β-cell proliferation. Objective: The objective of the investigation was to study the reciprocal relationships of adiponectin, leptin, osteocalcin, insulin resistance, and insulin secretion to verify whether such relationships are consistent with a signaling pathway connecting bone homeostasis and glucose metabolism. Design: This was a cross-sectional analysis. Setting: The study was conducted with community-dwelling volunteers participating in the Baltimore Longitudinal Study of Aging. Participants: Two hundred eighty women and 300 men with complete data on fasting plasma adiponectin, leptin, and osteocalcin, oral glucose tolerance test (plasma glucose and insulin values available at t = 0, 20, and 120 min), and anthropometric measures participated in the study. Main Outcome Measures: Linear regression models were used to test independent associations of adiponectin, osteocalcin, and leptin with the indices of insulin resistance and secretion. The expected reciprocal relationship between different biomarkers was verified by structural equation modeling. Results: In linear regression models, leptin was strongly associated with indices of both insulin resistance and secretion. Both adiponectin and osteocalcin were negatively associated with insulin resistance. Structural equation modeling revealed a direct inverse association of leptin with osteocalcin; a direct positive association of osteocalcin with adiponectin; and an inverse relationship of osteocalcin with insulin resistance and adiponectin with insulin resistance and secretion, which is cumulatively consistent with the hypothesized model. Conclusions: Bone and glucose metabolisms are probably connected through a complex pathway that involves leptin, osteocalcin, and adiponectin. The clinical relevance of such a pathway for bone pathology in diabetes should be further investigated.

J Clin Endocrinol Metab. 2011 Jun;96(6):E884-90

Leptin resistance and obesity.

The prevalence of obesity, and the human and economic costs of the disease, creates a need for better therapeutics and better understanding of the physiological processes that balance energy intake and energy expenditure. Leptin is the primary signal from energy stores and exerts negative feedback effects on energy intake. In common obesity, leptin loses the ability to inhibit energy intake and increase energy expenditure; this is termed leptin resistance. This review discusses the evidence in support of leptin resistance in mouse models and humans and the possible mechanisms of leptin resistance.

Obesity (Silver Spring). 2006 Aug;14 Suppl 5:254S-258S

Plasma leptin: associations with metabolic, inflammatory and haemostatic risk factors for cardiovascular disease.

BACKGROUND AND AIM: Leptin, an adipocyte-derived protein, regulating food intake and metabolism has been implicated in the development of coronary heart disease. We have examined the relationship between leptin and vascular risk factors including insulin resistance, metabolic, inflammatory and haemostatic risk factors. METHODS AND RESULTS: The study was carried out in 3,640 non-diabetic men aged 60-79 years drawn from general practices in 24 British towns and who were not on warfarin. Leptin was strongly positively correlated with waist circumference (r=0.58; p<0.0001). Leptin concentrations decreased significantly with increasing physical activity and were lowered in cigarette smokers and elevated in men with pre-existing coronary heart disease and stroke; alcohol intake showed no association with leptin concentration. After adjustment for waist circumference and these lifestyle factors, increased leptin was independently associated with significant increases in insulin resistance, triglycerides, inflammatory markers (interleukin-6, C-reactive protein, fibrinogen, plasma viscosity), coagulation factor VIII, endothelial markers von Willebrand factor, tissue plasminogen activator, and fibrin D-dimer levels; and a decrease in HDL-cholesterol. No association was seen between leptin and blood pressure, total cholesterol, glucose or white cell count after adjusting for waist circumference. Further adjustment for insulin resistance abolished the relationships between leptin and triglycerides and HDL-cholesterol, weakened the associations with the haemostatic factors although they remained significant, but made minor differences to the associations with inflammatory markers.

Atherosclerosis. 2007 Apr;191(2):418-26

Elevated circulating leptin levels in arterial hypertension: relationship to arteriovenous overflow and extraction of leptin.

Leptin, a peptide hormone produced mainly in fat cells, appears to be important for the regulation of metabolism, insulin secretion/sensitivity and body weight. Recently, elevated plasma leptin levels have been reported in patients with arterial hypertension. Because a change in circulating leptin concentrations in such patients could be caused by altered rates of production or disposal, or both, the aim of the present study was to identify regions of leptin overflow into the bloodstream and of leptin extraction. Patients with arterial hypertension (n=12) and normotensive controls (n=20) were studied during catheterization with elective blood sampling from different vascular beds (artery, and renal, hepatic, iliac and cubital veins). Plasma leptin was determined by a radioimmunoassay. Patients with hypertension had significantly elevated levels of circulating leptin (12.8 ng/l, compared with 4.1 ng/l in the controls; P<0.001), and this was also the case when adjusted for body mass index (BMI) [0.435 and 0.167 ng/l per unit BMI (kg/m(2)) respectively; P<0.001]. Circulating leptin was directly related to arterial blood pressure (r=0.38-0.62, P</=0.05-0.005) and immunoreactive insulin (r=0.51, P<0.62), but not to plasma renin activity. A significant renal extraction ratio for leptin was seen in the hypertensive patients, but this was not significantly lower than that in the controls (0.09 compared with 0. 16; P=0.1). The hypertensive patients had a significantly higher hepatic venous/arterial leptin ratio than the controls (1.02 compared with 0.93; P<0.02), and this ratio was correlated directly with the BMI (r=0.38, P=0.05) and immunoreactive insulin (r=0.43, P<0.05). In both hypertensive patients and controls there was a significant spillover of leptin into the iliac vein, but not into the cubital vein. In conclusion, the high concentration of circulating leptin in patients with arterial hypertension is probably caused by increased release of leptin from abdominal (especially mesenteric and omental) and gluteal adipose tissue stores, and renal extraction is slightly reduced. Leptin kinetics in arterial hypertension require further investigation.

Clin Sci (Lond). 2000 Dec;99(6):527-34

Increase of bone resorption and the parathyroid hormone in postmenopausal women in the long-term after Roux-en-Y gastric bypass.

BACKGROUND: The effects of Roux-en-Y Gastric Bypass (RYGB) on bone in the long-term remains unclear. We assessed bone metabolism and bone mineral density (BMD) 1 to 5 years after RYGB.METHODS: We designed a retrospective cohort study in 26 postmenopausal women (58.0+/-3.9 years old) with RYGB 3.5+/-1.1 years before (body mass index (BMI) 29.5+/-3.8 kg/m2, presurgery 43.6+/-5.5 kg/m2) and 26 nonoperated women (57.5+/-4.7 years old, BMI 29.2+/-4.1 kg/m2) matched by age and BMI. The main measures were BMD, serum carboxy telopeptide (CTx), total alkaline phosphatases (ALP), parathyroid hormone (PTH), 25-hydroxyvitamin D (25OHD), and ghrelin. RESULTS: RYGB group, compared to nonoperated women, had higher CTx (0.71+/-0.21 vs. 0.43+/-0.15 ng/ml; P<0.01) and PTH (68.3+/-35 vs. 49.4+/-16 pg/ml; P=0.02). There were no differences between RYGB and nonoperated women in: calcium and vitamin D intake (759+/-457 vs. 705+/-460 mg/day; 176+/-160 vs. 111+/-86 UI/day), ghrelin (763+/-336 vs. 621+/-274 pg/ml), ALP (101+/-22 vs. 94+/-25 UI/l), 25OHD (18.8+/-7.6 vs. 17.4 +/- 5.9 ng/ml), lumbar spine BMD (1.059+/-0.32 vs. 1.071+/-0.207 g/cm2), or femoral neck BMD (0.892+/-0.109 vs. 0.934+/-1.1 g/cm2). CONCLUSIONS: RYGB is associated to high bone resorption and hyperparathyroidism prevalence in postmenopausal women in the long-term. This occurs independently of the intake of calcium, vitamin D status, or ghrelin and does not seem to affect BMD after RYGB.

Obes Surg. 2009 Aug;19(8):1132-8

Metabolic bone disease after gastric bypass surgery for obesity.

BACKGROUND: The popularity of gastric bypass surgery for treatment of morbid obesity has been increasing in recent years. Osteomalacia and osteoporosis are commonly observed in patients who have had partial gastric resections for treatment of peptic ulcer disease. Recently, we encountered four patients with previous gastric bypass surgery who had metabolic bone disease similar to that reported in the older literature in patients who had partial gastrectomies. METHODS: Review of clinical data of four patients who developed osteomalacia and osteoporosis 9 to 12 years after gastric bypass surgery for morbid obesity.RESULTS: All subjects were women, 43 to 58 years old. Three had Roux-en-Y gastric bypass, and the other had a biliopancreatic diversion 9 to 12 years prior to presentation. Weight loss averaged 41.8 kg. Patients reported fatigue, myalgias, and arthralgias. They had symptoms for many months or years before the correct diagnosis was established. All were osteopenic or osteoporotic with hypocalcemia, very low or undetectable 25-hydroxyvitamin D levels, secondary hyperparathyroidism, increased 1,25-dihydroxyvitamin D levels, and increased serum alkaline phosphatase. CONCLUSIONS: Relatively little has been published in the general medical literature about this postoperative complication of bariatric surgery. Yet, nearly all patients after bariatric surgery will receive their long-term follow-up from a primary care physician. Physicians and patients need to be aware of this complication and take measures to identify and prevent it.

Am J Med Sci. 2005 Feb;329(2):57-61

Gastric banding or bypass? A systematic review comparing the two most popular bariatric procedures.

OBJECTIVE: Bariatric surgical procedures have increased exponentially in the United States. Laparoscopic adjustable gastric banding is now promoted as a safer, potentially reversible and effective alternative to Roux-en-Y gastric bypass, the current standard of care. This study evaluated the balance of patient-oriented clinical outcomes for laparoscopic adjustable gastric banding and Roux-en-Y gastric bypass. METHODS: The MEDLINE database (1966 to January 2007), Cochrane clinical trials database, Cochrane reviews database, and Database of Abstracts of Reviews of Effects were searched using the key terms gastroplasty, gastric bypass, laparoscopy, Swedish band, and gastric banding. Studies with at least 1 year of follow-up that directly compared laparoscopic adjustable gastric banding with Roux-en-Y gastric bypass were included. Resolution of obesity-related comorbidities, percentage of excess body weight loss, quality of life, perioperative complications, and long-term adverse events were the abstracted outcomes. RESULTS: The search identified 14 comparative studies (1 randomized trial). Few studies reported outcomes beyond 1 year. Excess body weight loss at 1 year was consistently greater for Roux-en-Y gastric bypass than laparoscopic adjustable gastric banding (median difference, 26%; range, 19%-34%; P < .001). Resolution of comorbidities was greater after Roux-en-Y gastric bypass. In the highest-quality study, excess body weight loss was 76% with Roux-en-Y gastric bypass versus 48% with laparoscopic adjustable gastric banding, and diabetes resolved in 78% versus 50% of cases, respectively. Both operating room time and length of hospitalization were shorter for those undergoing laparoscopic adjustable gastric banding. Adverse events were inconsistently reported. Operative mortality was less than 0.5% for both procedures. Perioperative complications were more common with Roux-en-Y gastric bypass (9% vs 5%), whereas long-term reoperation rates were lower after Roux-en-Y gastric bypass (16% vs 24%). Patient satisfaction favored Roux-en-Y gastric bypass (P=.006).CONCLUSION: Weight loss outcomes strongly favored Roux-en-Y gastric bypass over laparoscopic adjustable gastric banding. Patients treated with laparoscopic adjustable gastric banding had lower short-term morbidity than those treated with Roux-en-Y gastric bypass, but reoperation rates were higher among patients who received laparoscopic adjustable gastric banding. Gastric bypass should remain the primary bariatric procedure used to treat obesity in the United States.

Am J Med. 2008 Oct;121(10):885-93

The effects of obesity surgery on bone metabolism: what orthopedic surgeons need to know.

Morbid obesity affects approximately 9 million Americans. Obesity is associated with a reduced risk of osteoporosis, whereas weight loss decreases bone density. Obesity surgery has profound effects on bone, which are well described in the gastrointestinal literature; yet, there are virtually no reports in the orthopedic literature. The Roux-en-Y procedure is the leading bariatric operation performed in the United States. In this surgery, the primary sites for calcium absorption are bypassed. Patients become calcium- and Vitamin D-deficient, and the body then up-regulates parathyroid hormone, causing increased production of Vitamin D and increased calcium resorption from bone. Gastric banding utilizes a restrictive band and has not been shown to produce the same bone loss as the Roux-en-Y procedure, nor has there been evidence of secondary hyperparathyroidism. It is important for orthopedists to be aware of the types of obesity surgery and their sequelae on bone, as this may impact bone density, fracture risk, and fracture healing.

Am J Orthop (Belle Mead NJ). 2009 Feb;38(2):77-9

Bone and gastric bypass surgery: effects of dietary calcium and vitamin D.

OBJECTIVE: To examine bone mass and metabolism in women who had previously undergone Roux-en-Y gastric bypass (RYGB) and determine the effect of supplementation with calcium (Ca) and vitamin D. RESEARCH METHODS AND PROCEDURES: Bone mineral density and bone mineral content (BMC) were examined in 44 RYGB women (> or = 3 years post-surgery; 31% weight loss; BMI, 34 kg/m(2)) and compared with age- and weight-matched control (CNT) women (n = 65). In a separate analysis, RYGB women who presented with low bone mass (n = 13) were supplemented to a total 1.2 g Ca/d and 8 microg vitamin D/d over 6 months and compared with an unsupplemented CNT group (n = 13). Bone mass and turnover and serum parathyroid hormone (PTH) and 25-hydroxyvitamin D were measured. RESULTS: Bone mass did not differ between premenopausal RYGB and CNT women (42 +/- 5 years), whereas postmenopausal RYGB women (55 +/- 7 years) had higher bone mineral density and BMC at the lumbar spine and lower BMC at the femoral neck. Before and after dietary supplementation, bone mass was similar, and serum PTH and markers of bone resorption were higher (p < 0.001) in RYGB compared with CNT women and did not change significantly after supplementation. DISCUSSION: Postmenopausal RYGB women show evidence of secondary hyperparathyroidism, elevated bone resorption, and patterns of bone loss (reduced femoral neck and higher lumbar spine) similar to other subjects with hyperparathyroidism. Although a modest increase in Ca or vitamin D does not suppress PTH or bone resorption, it is possible that greater dietary supplementation may be beneficial.

Obes Res. 2004 Jan;12(1):40-7

Current understanding of osteoporosis associated with liver disease.

Osteoporosis is a common complication of many types of liver disease. Research into the pathogenesis of osteoporosis has revealed that the mechanisms of bone loss differ between different types of liver disease. This Review summarizes our current understanding of osteoporosis associated with liver disease and the new advances that have been made in this field. The different mechanisms by which cholestatic and parenchymal liver disease can lead to reduced bone mass, the prevalence of osteopenia and osteoporosis in patients with early and advanced liver disease, and the influence of osteoporotic fractures on patient survival are discussed along with the advances in our understanding of the molecular pathways associated with bone loss. The role of the CSF1-RANKL system and that of the liver molecule, oncofetal fibronectin, a protein that has traditionally been viewed as an extracellular matrix protein are also discussed. The potential impact that these advances may have for the treatment of osteoporosis associated with liver disease is also reviewed.

Nat Rev Gastroenterol Hepatol. 2009 Nov;6(11):660-70

Daily oral 25-hydroxycholecalciferol supplementation for vitamin D deficiency in haemodialysis patients: effects on mineral metabolism and bone markers.

BACKGROUND: Vitamin D deficiency is frequently observed in end-stage renal disease (ESRD) patients; however, the effects of vitamin D supplementation have rarely been reported. We aimed to assess the effects of daily 25(OH)D(3) supplementation on mineral metabolism, bone markers and Kidney Disease Outcomes Quality Initiative (KDOQI) targets in haemodialysis (HD) patients for a period of 6 months. METHODS: HD patients were included in this study if their serum 25(OH)D level was <75 mmol/L. Oral 25(OH)D(3) was administered daily at 10-30 microg/day based on the severity of the deficiency. Characteristics of the patients were compared from the baseline to 6 months on the basis of their response to 25(OH)D(3) administration and the patients were divided into three groups. Patients who showed partial response [serum 25(OH)D <75 nmol/L] were placed in group 1, those who showed normal response [serum 25(OH)D ranging from 75 to 150 nmol/L] were placed in group 2 and those who showed excessive response [serum 25(OH)D >150 nmol/L] were placed in group 3. RESULTS: Of the 253 HD patients, 225 (89%) showed vitamin D insufficiency or deficiency, 172 were included in the study and 149 patients completed the study. After 6 months of treatment [mean daily 25(OH)D(3): 16 +/- 5 microg/day], the serum 25(OH)D level increased (30 +/- 19 to 126 +/- 46 nmol/ L, P < 0.001), with 13% of patients in group 1, 57% in group 2 and 30% in group 3. The serum intact parathyroid hormone (iPTH) level decreased (235 +/- 186 to 189 +/- 137 pg/mL, P = 0.05), except in group 1. Bone alkaline phosphatase (BALP) showed a tendency to normalize (23 +/- 16 to 18.3 +/- 11 microg/L, P < 0.05), leading to a decrease in alfacalcidol administration from 66% to 43% (P < 0.05), except in group 1. The KDOQI targets achieved increased significantly for serum calcium (76% to 85%) and phosphate levels (66% to 77%) in all patients. The serum albumin level increased in all groups (34.6 +/- 4 to 36.8 +/- 4 g/L, P < 0.05), without any significant improvement in normalized protein catabolic rate (nPCR) or C-reactive proteins (CRP). CONCLUSION: With a daily dose ranging from 10 to 30 microg, daily oral 25(OH)D(3) supplementation corrects most vitamin D deficiencies or insufficiencies in HD patients, without any evident toxicity. The main effects observed included correction of excessive bone turnover, despite less alfacalcidol administration, increase in serum albumin level and increase in the percentage of patients with serum calcium and phosphorus levels within the recommendation of the KDOQI guidelines.

Nephrol Dial Transplant. 2008 Nov;23(11):3670-6

Evidence for persistent vitamin D 1-alpha-hydroxylation in hemodialysis patients: evolution of serum 1,25-dihydroxycholecalciferol after 6 months of 25-hydroxycholecalciferol treatment.

BACKGROUND: End-stage renal disease (ESRD) patients are thought to have impaired 1-alpha-hydroxylase capacity, but an extrarenal source of 1,25(OH)(2)D has been recognized. OBJECTIVE: The aim of this study was to assess the evolution of serum 1,25(OH)(2)D in hemodialysis (HD) patients with vitamin D deficiency after 6 months of 25(OH)D(3) supplementation, and to identify the factors associated with persistent 1,25(OH)(2)D production. METHODS: HD patients in a HD center with vitamin D deficiency (i.e. 25(OH)D <75 nmol/l) who were not receiving any vitamin D derivatives or calcimimetics were studied. Patients who had previously undergone parathyroidectomy or nephrectomy or those with uncontrolled hypercalcemia or hyperphosphatemia were excluded from this study. The patients were administrated a dose of 10-30 microg/day of oral 25(OH)D(3) based on the severity of their deficiency. The serum levels of 25(OH)D and 1,25(OH)(2)D evolution after 6 months were recorded. Responders were defined as patients with an increase in serum 1,25(OH)(2)D levels greater than the median value. Changes in mineral metabolism parameters were compared with those in the nonresponders. RESULTS: Of the 253 patients, 225 (89%) were vitamin D-deficient, and 43 met the inclusion criteria. The patients were 72.6 +/- 10 years old and had been on dialysis for 71 +/- 70 months; 39% of the patients were female and 45% were diabetics. From baseline to 6 months of treatment, serum 25(OH)D levels increased from 27.8 +/- 18 to 118 +/- 34 nmol/l (p < 0.001) and serum 1,25(OH)(2)D levels increased from 7.7 +/- 5 to 30.5 +/- 15 pmol/l (p < 0.001) with a median increase of 20 pmol/l. The mean serum calcium level increased from 2.19 +/- 0.1 to 2.25 +/- 0.1 mmol/l (p = 0.009), the intact parathyroid hormone (iPTH) level decreased from 144 +/- 108 to 108 +/- 63 pg/ml (p = 0.05), and the bone alkaline phosphatase (BALP) level remained unchanged. The serum phosphate level increased slightly from 1.22 +/- 0.3 to 1.34 +/- 0.2 mmol/l (p = 0.04) with reduced hypophosphatemia. Compared with the responders (n = 24), most of the nonresponders (n = 19) were diabetic (63 vs. 29%, p = 0.02) and had a lesser increase of their 25(OH)D serum level. The serum level of FGF-23 was not significant. A positive correlation was observed between serum 1,25(OH)(2)D and serum 25(OH)D levels after 6 months of 25(OH)D(3) treatment (p = 0.02). CONCLUSION: The Kidney Disease Outcomes Quality Improvement (KDOQI) guidelines do not recommend checking and treating vitamin D deficiency in chronic kidney disease (CKD) stage 5 patients due to the supposed lack of 1,25(OH)(2)D production. These data confirm persistent renal or extra-renal production of 1,25(OH)(2)D in HD patients after 6 months of 25(OH)D(3) administration. Diabetes is the main factor associated with impaired 1,25(OH)(2)D production. 25(OH)D(3 )administration corrects vitamin D deficiency with few effects on mineral metabolism and stability of bone turnover markers.

Nephron Clin Pract. 2008;110(1):c58-65

Liver disease in older women.

Clinicians are seeing increasing number of patients with chronic liver disease (CLD). The prevalence of diseases such as nonalcoholic fatty liver disease is increasing dramatically, our population is ageing and people with CLD are surviving into old age. Signs and symptoms of CLD in the older patient are often subtle and non-specific and a high index of suspicion is required in order to investigate. A number of diseases, which are predominate in women, tend to present in middle to older age. The menopause may render the liver more susceptible to disease progression and although hormone replacement appears safe in CLD but it is not recommended for liver protection. Osteoporosis is common in CLD but robust evidence is lacking on fracture prevention. Vigilance is required when interpreting investigations as there are no age-associated changes in clinical liver function testing. Management strategies are similar irrespective of age or gender, but evidence is lacking specific to older populations.

Maturitas. 2010 Mar;65(3):210-4

A new equation to estimate glomerular filtration rate.

BACKGROUND: Equations to estimate glomerular filtration rate (GFR) are routinely used to assess kidney function. Current equations have limited precision and systematically underestimate measured GFR at higher values. OBJECTIVE: To develop a new estimating equation for GFR: the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.DESIGN: Cross-sectional analysis with separate pooled data sets for equation development and validation and a representative sample of the U.S. population for prevalence estimates. SETTING: Research studies and clinical populations (“studies”) with measured GFR and NHANES (National Health and Nutrition Examination Survey), 1999 to 2006. PARTICIPANTS: 8254 participants in 10 studies (equation development data set) and 3896 participants in 16 studies (validation data set). Prevalence estimates were based on 16,032 participants in NHANES. MEASUREMENTS: GFR, measured as the clearance of exogenous filtration markers (iothalamate in the development data set; iothalamate and other markers in the validation data set), and linear regression to estimate the logarithm of measured GFR from standardized creatinine levels, sex, race, and age. RESULTS: In the validation data set, the CKD-EPI equation performed better than the Modification of Diet in Renal Disease Study equation, especially at higher GFR (P < 0.001 for all subsequent comparisons), with less bias (median difference between measured and estimated GFR, 2.5 vs. 5.5 mL/min per 1.73 m(2)), improved precision (interquartile range [IQR] of the differences, 16.6 vs. 18.3 mL/min per 1.73 m(2)), and greater accuracy (percentage of estimated GFR within 30% of measured GFR, 84.1% vs. 80.6%). In NHANES, the median estimated GFR was 94.5 mL/min per 1.73 m(2) (IQR, 79.7 to 108.1) vs. 85.0 (IQR, 72.9 to 98.5) mL/min per 1.73 m(2), and the prevalence of chronic kidney disease was 11.5% (95% CI, 10.6% to 12.4%) versus 13.1% (CI, 12.1% to 14.0%). LIMITATION: The sample contained a limited number of elderly people and racial and ethnic minorities with measured GFR.CONCLUSION: The CKD-EPI creatinine equation is more accurate than the Modification of Diet in Renal Disease Study equation and could replace it for routine clinical use.

Ann Intern Med. 2009 May 5;150(9):604-12

Chronic liver disease in an ageing population.

The prevalence of chronic liver disease is increasing in the elderly population. With a mostly asymptomatic or non-specific presentation, these diseases may easily go undiagnosed. Abnormal liver function tests of unknown cause are a common reason for referral to secondary care. Investigating the older person with abnormal liver function is important; even with mild abnormalities, the same vigilance should be applied to an older person as in a young person. Liver biopsy is safe but often overlooked in this age group and may provide useful information to diagnose, direct therapy and prognosticate. Treatment options are similar for all age groups, with a few subtle differences, although further evidence is frequently required for the older population. Morbidity and age-adjusted mortality are often more severe in older people, and therefore early diagnosis and intervention is important. Presented here are the most common chronic liver diseases that geriatricians are likely to encounter in clinical practise. Their epidemiology, clinical features, investigation, treatment and mortality are described with a particular focus on the elderly population.

Age Ageing. 2009 Jan;38(1):11-8

Bone mineral density and disorders of mineral metabolism in chronic liver disease.

AIM: To estimate the prevalence and identify the risk factors for metabolic bone disease in patients with cirrhosis. METHODS: The study was performed on 72 Indian patients with cirrhosis (63 male, nine female; aged < 50 years). Etiology of cirrhosis was alcoholism (n = 37), hepatitis B (n = 25) and hepatitis C (n = 10). Twenty-three patients belonged to Child class A, while 39 were in class B and 10 in class C. Secondary causes for metabolic bone disease and osteoporosis were ruled out. Sunlight exposure, physical activity and dietary constituents were calculated. Complete metabolic profiles were derived, and bone mineral density (BMD) was measured using dual energy X ray absorptiometry. Low BMD was defined as a Z score below -2. RESULTS: Low BMD was found in 68% of patients. Lumbar spine was the most frequently and severely affected site. Risk factors for low BMD included low physical activity, decreased sunlight exposure, and low lean body mass. Calcium intake was adequate, with unfavorable calcium: protein ratio and calcium: phosphorus ratio. Vitamin D deficiency was highly prevalent (92%). There was a high incidence of hypogonadism (41%). Serum estradiol level was elevated significantly in patients with normal BMD. Insulin-like growth factor (IGF) 1 and IGF binding protein 3 levels were below the age-related normal range in both groups. IGF-1 was significantly lower in patients with low BMD. Serum osteocalcin level was low (68%) and urinary deoxypyridinoline to creatinine ratio was high (79%), which demonstrated low bone formation with high resorption. CONCLUSION: Patients with cirrhosis have low BMD. Contributory factors are reduced physical activity, low lean body mass, vitamin D deficiency and hypogonadism and low IGF-1 level.

World J Gastroenterol. 2009 Jul 28;15(28):3516-22

Vitamin D—a panacea in nephrology and beyond.

Vitamin D and its active analogues play an essential role in maintaining the calcium and phosphate homeostasis. Vitamin D deficiency may be a consequence of insufficient dietary supply, impaired intestinal absorption, insufficient exposure of the skin to the ultraviolet radiation, or liver and kidney failure. The consequences of mineral metabolism disorders and in particular vitamin D depletion are osteoporosis, increased cardiovascular diseases, immune system impairment and increased morbidity and mortality in patients with end stage of renal disease. These abnormalities are common in patients with chronic kidney disease. Recent clinical studies have shown that vitamin D supplementation in patients with its deficiency, contribute to decreased frequency of bone disorders, cardiovascular incidents, lower risk of several malignancies and to improvement of immune system response regardless of renal function.

Pol Merkur Lekarski. 2009 Nov;27(161):437-41

Chronic kidney disease-mineral-bone disorder: a new paradigm.

Disturbances in mineral and bone metabolism are prevalent in chronic kidney disease (CKD) and an important cause of morbidity, decreased quality of life, and extraskeletal calcification that have been associated with increased cardiovascular mortality. These disturbances have traditionally been termed renal osteodystrophy and classified on the basis of bone biopsy. Kidney Disease: Improving Global Outcomes (KDIGO) recently sponsored a Controversies Conference to evaluate this definition. The recommendations were that (1) the term renal osteodystrophy be used exclusively to define alterations in bone morphology associated with CKD and (2) the term CKD-mineral and bone disorder (CKD-MBD) be used to describe the broader clinical syndrome that develops as a systemic disorder of mineral and bone metabolism as a result of CKD. CKD-MBD is manifested by an abnormality of any one or a combination of the following: laboratory-abnormalities of calcium, phosphorus, PTH, or vitamin D metabolism; bone-changes in bone turnover, mineralization, volume, linear growth, or strength; and calcification-vascular or other soft-tissue calcification. The pathogenesis and clinical manifestations of these components of CKD-MBD are described in detail in this issue of Advances in Chronic Kidney Disease.

Adv Chronic Kidney Dis. 2007 Jan;14(1):3-12

Age-related increases in parathyroid hormone may be antecedent to both osteoporosis and dementia.

BACKGROUND: Numerous studies have reported that age-induced increased parathyroid hormone plasma levels are associated with cognitive decline and dementia. Little is known about the correlation that may exist between neurological processing speed, cognition and bone density in cases of hyperparathyroidism. Thus, we decided to determine if parathyroid hormone levels correlate to processing speed and/or bone density. METHODS: The recruited subjects that met the inclusion criteria (n = 92, age-matched, age 18-90 years, mean = 58.85, SD = 15.47) were evaluated for plasma parathyroid hormone levels and these levels were statistically correlated with event-related P300 potentials. Groups were compared for age, bone density and P300 latency. One-tailed tests were used to ascertain the statistical significance of the correlations. The study groups were categorized and analyzed for differences of parathyroid hormone levels: parathyroid hormone levels <30 (n = 30, mean = 22.7 +/- 5.6 SD) and PTH levels >30 (n = 62, mean = 62.4 +/- 28.3 SD, p <or= 02). RESULTS: Patients with parathyroid hormone levels <30 showed statistically significantly less P300 latency (P300 = 332.7 +/- 4.8 SE) relative to those with parathyroid hormone levels >30, which demonstrated greater P300 latency (P300 = 345.7 +/- 3.6 SE, p = .02). Participants with parathyroid hormone values <30 (n = 26) were found to have statistically significantly higher bone density (M = -1.25 +/- .31 SE) than those with parathyroid hormone values >30 (n = 48, M = -1.85 +/- .19 SE, p = .04). CONCLUSION: Our findings of a statistically lower bone density and prolonged P300 in patients with high parathyroid hormone levels may suggest that increased parathyroid hormone levels coupled with prolonged P300 latency may become putative biological markers of both dementia and osteoporosis and warrant intensive investigation.

BMC Endocr Disord. 2009 Oct 13;9:21