Not a simple fat-soluble vitamin: Changes in serum 25-(OH)D levels are predicted by adiposity and adipocytokines in older adults

Scientific opinion on the tolerable upper intake level for vitamin D, including the derivation of a conversion factor for calcidiol monohydrate

Following two requests from the European Commission (EC), the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the revision of the tolerable upper intake level (UL) for vitamin D and to propose a conversion factor (CF) for calcidiol monohydrate into vitamin D3 for labelling purposes. Vitamin D refers to ergocalciferol (vitamin D2), cholecalciferol (vitamin D3), and calcidiol monohydrate. Systematic reviews of the literature were conducted to assess the relative bioavailability of calcidiol monohydrate versus vitamin D3 on serum 25(OH)D concentrations, and for priority adverse health effects of excess vitamin D intake, namely persistent hypercalcaemia/hypercalciuria and endpoints related to musculoskeletal health (i.e. falls, bone fractures, bone mass/density and indices thereof). Based on the available evidence, the Panel proposes a CF for calcidiol monohydrates of 2.5 for labelling purposes. Persistent hypercalciuria, which may be an earlier sign of excess vitamin D than persistent hypercalcaemia, is selected as the critical endpoint on which to base the UL for vitamin D. A lowest-observed-adverse-effect-level (LOAEL) of 250 μg/day is identified from two randomised controlled trials in humans, to which an uncertainty factor of 2.5 is applied to account for the absence of a no-observed-adverse-effect-level (NOAEL). A UL of 100 μg vitamin D equivalents (VDE)/day is established for adults (including pregnant and lactating women) and for adolescents aged 11-17 years, as there is no reason to believe that adolescents in the phase of rapid bone formation and growth have a lower tolerance for vitamin D compared to adults. For children aged 1-10 years, a UL of 50 μg VDE/day is established by considering their smaller body size. Based on available intake data, European populations are unlikely to exceed the UL, except for regular users of food supplements containing high doses of vitamin D.

Is Abdominal Obesity a Risk Factor for the Incidence of Vitamin D Insufficiency and Deficiency in Older Adults? Evidence from the ELSA Study

Cross-sectional studies have demonstrated an association between abdominal obesity, determined by waist circumference (WC), and vitamin D (25(OH)D) deficiency in older adults. However, longitudinal evidence is based only on general obesity determined using body mass index (BMI). We investigated whether abdominal obesity is associated with the incidence of 25(OH)D insufficiency (>30 and ≤50 nmol/L) and deficiency (≤30 nmol/L), and whether vitamin D supplementation modifies these associations. We included 2459 participants aged ≥50 years from the English Longitudinal Study of Ageing (ELSA) with 25(OH)D sufficiency (>50 nmol/L) at baseline. Abdominal obesity was defined as >88 cm for women and >102 cm for men. After 4 years, 25(OH)D concentrations were reassessed. Multinomial logistic regression models controlled by covariates were performed. Abdominal obesity increased the risk of the incidence of 25(OH)D insufficiency (RRR = 1.36; 95% CI: 1.01−1.83) and deficiency (RRR = 1.64; 95% CI: 1.05−2.58). These risks were maintained when excluding individuals who took vitamin D supplementation (RRR = 1.38; 95% CI: 1.02−1.88) and (RRR = 1.62; 95% CI: 1.02−2.56). Abdominal obesity is associated with the risk of incidence of low 25(OH)D concentrations. WC seems to be an adequate tool for screening individuals with obesity and at potential risk of developing these conditions.

A comprehensive look into the association of vitamin D levels and vitamin D receptor gene polymorphism with obesity in children

Childhood obesity accounts for several psychosocial and clinical consequences. Psychosocial consequences include lower self-esteem, social isolation, poor academic achievement, peer problems, and depression, whereas clinical consequences are cardiovascular diseases, type 2 diabetes, dyslipidemia, cancer, autoimmune diseases, girls early polycystic ovarian syndrome (PCOS), asthma, bone deformities, etc. A growing number of studies have uncovered the association of childhood obesity and its consequences with vitamin-D (vit-D) deficiency and vitamin-D receptor (VDR) gene polymorphisms such as single nucleotide polymorphisms (SNPs), e.g., TaqI, BsmI, ApaI, FokI, and Cdx2. Considering the impact of vit-D deficiency and VDR gene polymorphisms, identifying associated factors and risk groups linked to lower serum vit-D levels and prevention of obesity-related syndromes in children is of utmost importance. Previously published review articles mainly focused on the association of vit-D deficiency with obesity or other non-communicable diseases in children. The nature of the correlation between vit-D deficiency and VDR gene polymorphisms with obesity in children is yet to be clarified. Therefore, this review attempts to delineate the association of obesity with these two factors by identifying the molecular mechanism of the relationship.

Differences in Fat-Free Mass According to Serum Vitamin D Level and Calcium Intake: Korea National Health and Nutrition Examination Survey 2008-2011

We analyzed the differences in fat-free mass (FFM) according to serum vitamin D level (VitD) and daily calcium intake (Ca) in 14,444 adults aged over 19 years. We used data from the 4th and 5th Korea National Health and Nutrition Examination Surveys (2008–2011). FFM was measured using dual-energy X-ray absorptiometry. VitD was classified as insufficient or sufficient (cutoff: 20 ng/mL). Ca was classified as unsatisfactory or satisfactory (recommended daily intake: 700 mg). In men, the FFM of group 2 (VitD ≥ 20 ng/mL; Ca < 700 mg), group 3 (VitD < 20 ng/mL; Ca ≥ 700 mg) and group 4 (VitD ≥ 20 ng/mL; Ca ≥ 700 mg) was 0.50 kg (95% confidence interval (CI), 0.084–0.92), 0.78 kg (95% CI, 0.26–1.29) and 1.58 kg (95% CI, 0.95–2.21) higher than that of group 1 (VitD < 20 ng/mL; Ca < 700 mg), respectively. In women, a 1 ng/mL increase in VitD was associated with a 0.023 kg increase in FFM (95% CI, 0.003–0.043) and a 1 g increase in Ca was associated with a 0.62 kg increase in FFM (95% CI, 0.067–1.16). High VitD and Ca were associated with a high FFM.

Relationship between 25 Hydroxyvitamin D, Overweight/Obesity Status, Pro-Inflammatory and Oxidative Stress Markers in Patients with Type 2 Diabetes: A Simplified Empirical Path Model

Vitamin D deficiency is highly prevalent in patients with overweight/obesity and type 2 diabetes (T2DM). Herein, we investigated the relationship between vitamin D status and overweight/obesity status, insulin resistance (IR), systemic inflammation as well as oxidative stress (OS). Anthropometric and laboratory assessments of 25-hydroxyvitamin D (25(OH)D) and glycemic, pro-inflammatory and OS biomarkers were performed in a sample of 47 patients with T2DM who were divided into categories based on overweight and degree of obesity. The main findings were: the overweight/obesity status correlated negatively with the degree of serum 25(OH)D deficiency (ρ = −0.27) with a trend towards statistical significance (p = 0.069); the homeostasis model assessment of insulin resistance (HOMA-IR) was significantly different (p = 0.024) in patients with 25(OH)D deficiency, as was total oxidant status (TOS) and oxidative stress index (OSI) in patients with severe serum 25(OH)D deficiency as compared to those with 25(OH)D over 20 ng/mL (TOS: p = 0.007, OSI: p = 0.008); and 25(OH)D had a negative indirect effect on TOS by body mass index (BMI), but BMI was not a significant mediator of the studied relationship. In a setting of overweight and increasing degree of obesity, patients with T2DM did not display decreasing values of 25(OH)D. Subjects with the lowest values of 25(OH)D presented the highest values of BMI. Patients with 25(OH)D deficiency were more insulin resistant and showed increased OS but no elevated systemic inflammation. The negative effect of 25(OH)D on TOS did not seem to involve BMI as a mediator.

Obesity and leptin influence vitamin D metabolism and action in human marrow stromal cells

Obesity is associated with low serum 25-hydroxyvitamin D [s25(OH)D], high serum leptin, and generally high bone mineral density (BMD). Human Marrow Stromal Cells (hMSCs) differentiate to osteoblasts and are both a target and source of vitamin D metabolites in bone marrow. There is no information about the influence of obesity on vitamin D metabolism and osteoblastogenesis in hMSCs and little about direct effects of leptin on hMSCs. In this study, we tested the hypotheses that 1) obesity has an influence on the ex vivo constitutive expression of vitamin D-hydroxylase genes in hMSCs, and 2) recombinant human (rh) Leptin regulates the D-hydroxylases and promotes osteoblastogenesis in hMSCs. In a cohort of female subjects undergoing joint replacement surgery, the effects of Body Mass Index (BMI) and Fat Mass Index (FMI) on BMD T-scores and s25(OH)D were evaluated. hMSCs were isolated from bone tissues discarded during surgery. The direct effects of rh-Leptin on osteoblast differentiation and D-related genes in hMSCs were examined in vitro. There were positive correlations for BMD T-score of femoral neck and spine with BMI and FMI. Serum 25(OH)D levels in obese subjects were 71% of that in non-obese counterparts (p = 0.001). hMSCs from obese women had higher constitutive expression of CYP27A1/25-hydroxylase and vitamin D receptor. Those findings raised the mechanistic question of how obesity could influence vitamin D metabolism and osteoblast differentiation in hMSCs. Treating hMSCs with rh-Leptin in vitro significantly stimulated osteoblastogenesis. In addition, leptin downregulated CYP24A1 and upregulated CYP27B1, CYP27A1 and VDR, which play vital roles in vitamin D metabolism. Furthermore, co-treatment with leptin and vitamin D₃ metabolites promoted ALP activity compared with either alone. This research demonstrates links between obesity, vitamin D metabolism, and osteoblastogenesis by which leptin's direct effects on D-metabolism and osteoblast differentiation in hMSCs may protect bone from low s25(OH)D in obese subjects.

Vitamin D supplementation and inflammatory and metabolic biomarkers in patients with knee osteoarthritis: post hoc analysis of a randomised controlled trial

The aim of this study was to determine whether vitamin D supplementation and maintaining vitamin D sufficiency are associated with changes in inflammatory and metabolic biomarkers in patients with knee osteoarthritis (OA) and vitamin D deficiency. A total of 413 participants with symptomatic knee OA and vitamin D deficiency were enrolled in a randomised, placebo-controlled trial and received 1·25 mg vitamin D3 or placebo monthly for 24 months across two sites. In this post hoc analysis, 200 participants from one site (ninety-four from the placebo group and 106 from the vitamin D group; mean age 63·1 (sd 7·3) years, 53·3 % women) were randomly selected for measurement of serum levels of inflammatory and metabolic biomarkers at baseline and 24 months using immunoassays. In addition, participants were classified into two groups according to serum 25-hydroxyvitamin D (25(OH)D) levels at months 3 and 24: (1) not consistently sufficient (25(OH)D≤50 nmol/l at either month 3 or 24, n 61), and (2) consistently sufficient (25(OH)D>50 nmol/l at both months 3 and 24, n 139). Compared with placebo, vitamin D supplementation had no significant effect on change in serum high-sensitive C-reactive protein, IL-6, IL-8, IL-10, leptin, adiponectin, resistin, adipsin and apelin. Being consistently vitamin D sufficient over 2 years was also not associated with changes in these biomarkers compared with not being consistently sufficient. Vitamin D supplementation and maintaining vitamin D sufficiency did not alter serum levels of inflammatory and metabolic biomarkers over 2 years in knee OA patients who were vitamin D insufficient, suggesting that they may not affect systemic inflammation in knee OA patients.

Malnutrition in obesity before and after bariatric surgery

Bariatric surgeries are considered the only effective way of weight loss therapy in morbidly obese patients, i.e. body mass index ≥ 35. However, micronutrient deficiencies and malnutrition are common after most bariatric procedures and thus, pre- and postoperative nutritional assessment and corrections are advised. The present review is presented in an effort to describe in some detail about prevalence, and mechanisms of macro- and micronutrient deficiencies in obese and post-bariatric surgery individuals. We also aimed to summarize the data on screening and supplementation of macro- and micronutrients before and after bariatric surgeries.

Obesity and hypovitaminosis D: causality or casualty?

Epidemiological studies reported that vitamin D deficiency represents an increasingly widespread phenomenon in various populations. Vitamin D deficiency is considered a clinical syndrome determined by low circulating levels of 25-hydroxyvitamin D (25(OH)D), which is the biologically-inactive intermediate and represents the predominant circulating form. Different mechanisms have been hypothesized to explain the association between hypovitaminosis D and obesity, including lower dietary intake of vitamin D, lesser skin exposure to sunlight, due to less outdoor physical activity, decreased intestinal absorption, impaired hydroxylation in adipose tissue and 25(OH)D accumulation in fat. However, several studies speculated that vitamin D deficiency itself could cause obesity or prevent weight loss. The fat-solubility of vitamin D leads to the hypothesis that a sequestration process occurs in body fat depots, resulting in a lower bioavailability in the obese state. After investigating the clinical aspects of vitamin D deficiency and the proposed mechanisms for low 25(OH)D in obesity, in this manuscript we discuss the possible role of vitamin D replacement treatment, with different formulations, to restore normal levels in individuals affected by obesity, and evaluate potential positive effects on obesity itself and its metabolic consequences. Food-based prevention strategies for enhancement of vitamin D status and, therefore, lowering skeletal and extra-skeletal diseases risk have been widely proposed in the past decades; however pharmacological supplementation, namely cholecalciferol and calcifediol, is required in the treatment of vitamin D insufficiency and its comorbidities. In individuals affected by obesity, high doses of vitamin D are required to normalize serum vitamin D levels, but the different liposolubility of different supplements should be taken into account. Although the results are inconsistent, some studies reported that vitamin D supplementation may have some beneficial effects in people with obesity.

Obesity, Bariatric Surgery, and Vitamin D

The high prevalence of obesity is a worldwide problem associated with multiple comorbidities, including cardiovascular diseases. Vitamin D deficiency with secondary hyperparathyroidism is common in obese individuals and can be aggravated after bariatric surgery. Moreover, there is no consensus on the optimal supplementation dose of vitamin D in postbariatric surgical patients. We present new data on the variability of 25(OH)D response to supplementation in postmenopausal obese women. It is important to recognize and treat vitamin D deficiency before bariatric surgery to avoid postoperative complications, such as metabolic bone disease with associated high fracture risk. The objective of this article is to discuss the bone metabolism consequences of vitamin D deficiency after bariatric surgery.

Effects of vitamin D status on oral health

Normal humans of all ages have the innate ability to produce vitamin D following sunlight exposure. Inadequate vitamin D status has shown to be associated with a wide variety of diseases, including oral health disorders. Insufficient sunlight exposure may accelerate some of these diseases, possibly due to impaired vitamin D synthesis. The beneficial effects of vitamin D on oral health are not only limited to the direct effects on the tooth mineralization, but are also exerted through the anti-inflammatory functions and the ability to stimulate the production of anti-microbial peptides. In this article, we will briefly discuss the genesis of various oral diseases due to inadequate vitamin D level in the body and elucidate the potential benefits of safe sunlight exposure for the maintenance of oral and general health.

Sunlight exposure: Do health benefits outweigh harm?

Vitamin D is a fat-soluble vitamin whose levels within the body are elevated following sunlight exposure. Numerous studies have shown that sunlight exposure can provide protection to a wide variety of diseases, ranging from different types of tumors to hypertension to type 1 diabetes to multiple sclerosis. Moreover, studies have shown that avoiding sunlight may influence the initiation and progression of some of these diseases. Avoidance of sunlight, coupled with the inclination towards consuming supplements, is becoming the primary choice to obtain vitamin D. The purpose of this article is to present evidences from published literature, to show that the expected benefits of vitamin D supplements are minimized by the potential risk of cardiovascular events and beyond. Since hypovitaminosis D status usually reflects reduced sunlight exposure, the obvious primary replacement should be safe sunlight exposure, and not exogenous supplements.

Vitamin D, leptin and impact on immune response to seasonal influenza A/H1N1 vaccine in older persons

BACKGROUND

Influenza-related complications are highest in the elderly. Vaccine efficacy is lower due to immunosenescence. Vitamin D's immunomodulatory role was studied in the context of vaccine response.

METHODS

We evaluated the effect of baseline 25-(OH) D on vaccine-induced immunological response in a cohort of 159 healthy subjects ages 50-74 in Rochester, MN, who received one dose of seasonal trivalent 2010-2011 influenza vaccine, containing A/California/H1N1- like virus. We examined correlations between 25-(OH) D, leptin, and leptin-related gene SNPs to understand the role of leptin and vitamin D's effects.

RESULTS

The median (IQR) baseline for total 25-(OH) D was 44.4 ng/mL (36.6-52.2 ng/mL). No correlation was observed with age. No correlation between 25-(OH) D levels and humoral immune outcomes existed at any timepoint. There was a weak positive correlation between 25-(OH) D levels and change (Day 75-Day 0) in influenza-specific granzyme-B response (r=0.16, p=0.04). We found significant associations between 3 SNPs in the PPARG gene and 25-(OH) D levels (rs1151996, p=0.01; rs1175540, p= 0.02; rs1175544, p=0.03).

CONCLUSION

Several SNPs in the PPARG gene were significantly associated with baseline 25-(OH) D levels. Understanding the functional and mechanistic relationships between vitamin D and influenza vaccine-induced immunity could assist in directing new influenza vaccine design.

Relationship between the Finnish Diabetes Risk Score (FINDRISC), vitamin D levels, and insulin resistance in obese subjects

AIM

To assess the relationship between 25-hydroxyvitamin D [25(OH)D] blood concentrations in subjects with obesity and type 2 diabetes mellitus (T2D) risk according to the Finnish Diabetes Risk Score (FINDRISC) modified for Latin America (LA-FINDRISC).

METHODS

This study was conducted in Ciudad Bolívar, Venezuela. Eighty two women and 20 men (53 obese and 49 nonobese), with an average age of 42.6±12.30 years were enrolled. Weight, height, body mass index (BMI), waist circumference (WC), fasting glucose, basal insulin, plasma lipids, Homeostasis Model Assessment-Insulin Resistance (HOMA-IR), and 25(OH)D levels were measured. FINDRISC with WC cutoff points modified for Latin America was applied.

RESULTS

No difference in 25(OH)D levels between obese and nonobese subjects was found. When anthropometric, clinical, and biochemical variables according to the 25(OH)D status were compared, the only difference detected was higher LA-FINDRISC in the insufficient/low 25(OH)D group compared to normal 25(OH)D levels group (12.75±6.62; vs 10.15±5.21; p=0.031). LA-FINDRISC was negatively correlated with plasma 25(OH)D levels (r=-0.302; p=0.002) and positively correlated with the HOMA-IR index (r=0.637; p=0.0001).

CONCLUSIONS

The LA-FINDRISC significantly correlated with both 25(OH)D levels and insulin resistance markers in this group of patients.

Effect of exercise on serum vitamin D and tissue vitamin D receptors in experimentally induced type 2 Diabetes Mellitus

This work aimed to study the effect of swimming exercise on serum vitamin D level and tissue vitamin D receptors in experimentally induced type 2 Diabetes Mellitus. Sixty adult male rats were divided into control and diabetic groups. Each was further subdivided into sedentary and exercised subgroups. Diabetes Mellitus was induced by a single intraperitoneal dose of streptozotocin (50 mg/kg) dissolved in cold 0.01 M citrate buffer (pH 4.5). The exercised subgroups underwent swimming for 60 min, 5 times a week for 4 weeks. Serum glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), lipids, vitamin D and tissue Vitamin D receptors (VDR) were evaluated. Significant increase in serum glucose, insulin, HOMA-IR, cholesterol, triglycerides, and low density lipoprotein (LDL) levels in sedentary diabetic rats was detected. On the other hand, high density lipoprotein (HDL), free fatty acids, serum vitamin D and pancreatic, adipose, and muscular VDR showed a significant decrease in the same group. It is evident that all these parameters were reversed by swimming exercise indicating its beneficial role in type 2 Diabetes. In diabetic groups; serum vitamin D was found to be correlated negatively with serum glucose, insulin, HOMA, cholesterol, triglycerides, and LDL and positively correlated with HDL and tissue VDR. In conclusion, Disturbed vitamin D is associated with metabolic impairments in sedentary diabetic rats. Moderate swimming exercise is beneficial in improving these consequences through modulation of vitamin D status. Future studies could be designed to investigate the effect of the combination of vitamin D intake with exercise in diabetic patients.

Vitamin D deficiency as adverse drug reaction? A cross-sectional study in Dutch geriatric outpatients

PURPOSE

Adverse drug reactions as well as vitamin D deficiency are issues of public health concern in older people. However, relatively little is known about the impact of drug use on vitamin D status. Our primary aim is to explore associations between drug use and vitamin D status in older people. Furthermore, prevalences of drug use and vitamin D deficiency are estimated.

METHODS

In a population of 873 community-dwelling Dutch geriatric outpatients, we explored the cross-sectional relationships of polypharmacy (≥5 medications concomitantly used), severe polypharmacy (≥10 medications), and use of twenty-one specific drug groups, with serum 25-hydroxyvitamin D (25(OH)D) by analysis of covariance.

RESULTS

Overall prevalence of polypharmacy was 65 %, of severe polypharmacy 22 %. Depending on the cut-off value, prevalence of vitamin D deficiency was 49 % (<50 nmol/l) or 77 % (<75 nmol/l). Of the patients using a vitamin D supplement, 17 % (<50 nmol/l) or 49 % (<75 nmol/l) were still deficient. In non-users of supplemental vitamin D, after adjustment for age and gender, negative associations were found for severe polypharmacy, metformin, sulphonamides and urea derivatives (SUDs), vitamin K antagonists, cardiac glycosides, loop diuretics, potassium-sparing diuretics, ACE inhibitors, and serotonin reuptake inhibitors; for non-selective monoamine reuptake inhibitors (NSMRIs) the association was positive. The most extreme impacts of drug use on adjusted mean 25(OH)D were -19 nmol/l for SUDs and +18 nmol/l for NSMRIs.

CONCLUSION

Drug use should be considered a risk factor for vitamin D deficiency amongst geriatric outpatients.

Biochemical Assessment of Bone Health in Working Obese Egyptian Females with Metabolic Syndrome; the Effect of Weight Loss by Natural Dietary Therapies

AIM:

To investigate the relation between bone parameters and the metabolic syndrome criteria, before and after the administration of two different natural dietary supplements in middle aged working obese Egyptian women suffering from metabolic syndrome (MetS).

SUBJECTS AND METHODS:

Fifty eight middle aged obese female volunteers suffering from metabolic syndrome were divided into two groups. During the first period, group (A) consumed a low caloric diet and nutritional supplement consisting of doum flour biscuits, while group (B) consumed whole meal wheat flour biscuit with the same instructions. During the second period, both supplements were omitted. Assessment of blood pressure, relevant anthropometric parameters, lipid accumulation product, fasting blood glucose, uric acid, 25 hydroxy vitamin D (25 (OH) D), parathyroid hormone (PTH) and bone-specific alkaline phosphatase were performed.

RESULTS:

Data showed that although both supplements improved the MetS criteria and the bone health parameters, the supplement containing the doum flour proved to be more effective.

CONCLUSION:

These results confirm the benefit of doum in improving bone health parameter [25 (OH) D/PTH axis] in the MetS patients, beside the MetS criteria. So, we can conclude that natural effective supplements lead towards the optimization of biochemical parameters in favor of a healthy outcome.

Vitamin D status, body composition and glycemic control in an ambulatory population with diabetes and chronic kidney disease

BACKGROUND/OBJECTIVES

To determine the interrelationships between body composition, glycemic control and vitamin D status in an ambulatory population with diabetes (DM) and chronic kidney disease (CKD).

SUBJECTS/METHODS

Adult (18-80 years) patients (n=60) with DM and stage 1-4 CKD were recruited from the Northern Alberta Renal Program. Outcome variables included body composition (absolute/regional fat (FM)/lean soft tissue/total mass, percent fat/lean/fat-free (FFM) mass), glycemic control (glycated hemoglobin (HbA1c)), vitamin D intake (dietary/supplemental) and vitamin D status (25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)2D)) measured by validated methodologies. Sarcopenia was determined as an appendicular skeletal mass/height(2) less than 7.26 kg/m(2) (males) and 5.45 kg/m(2) (females).

RESULTS

Suboptimal HbA1c (>7%), 25(OH)D (<50 nmol/l) and 1,25(OH)2D (<43 pmol/l) concentrations were present in 57, 8 and 11% of participants. Ten percent of subjects had sarcopenia. Gender/age/DM type, not CKD, significantly influenced regional/whole body composition. Females, older participants and those with type 2 DM had higher %FM. No significant interrelationships between vitamin D status and glycemic control were observed (P>0.05). Serum 25(OH)D concentrations were inversely associated with arm lean soft tissue/FFM/total mass, weight, appendicular skeletal mass, lean soft tissue/height(2), FFM/height(2), appendicular skeletal mass/height(2) and body mass index (P<0.05). Sarcopenia occurred more frequently in patients with 25(OH)D concentrations ⩾100 nmol/l. Regional/whole body %FM was inversely related to 1,25(OH)2D, not 25(OH)D.

CONCLUSIONS

Body composition, not glycemic control, is associated with vitamin D status in an ambulatory population of adults with DM and CKD.

Effect of vitamin D supplementation alone or with calcium on adiposity measures: a systematic review and meta-analysis of randomized controlled trials

CONTEXT

The independent or interactive effects of vitamin D and calcium on adiposity remain inconclusive.

OBJECTIVE

The objective of this systematic review and meta-analysis was to assess whether vitamin D and calcium supplements cause changes in adiposity.

DATA SOURCES

MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials databases were searched for literature published from 1966 to March 2014.

STUDY SELECTION

A systematic search was conducted for randomized clinical trials with ≥ 50 participants aged ≥ 18 years at baseline who had received at least 12 weeks of treatment. Among the inclusion criteria were supplementation with vitamin D with or without calcium and measurement of adiposity (weight, body mass index [BMI], and/or fat mass).

DATA EXTRACTION

The primary endpoints assessed were changes in weight, BMI, or fat mass.

DATA SYNTHESIS

Of 953 trials identified, 26 randomized clinical trials (n = 12, vitamin D alone; n = 10, vitamin D plus calcium versus calcium control; n = 4, vitamin D plus calcium versus placebo) with a total of 42,430 participants (median duration, 12 months) met the inclusion criteria. When compared with placebo, vitamin D supplementation had no significant effect on BMI (weighted mean difference [WMD], -0.06 kg/m(2); 95% confidence interval [95%CI], -0.14 to 0.03), weight (WMD, -0.05 kg; 95%CI, -0.32 to 0.23), or fat mass (WMD, -0.43 kg; 95%CI, -1.69 to 0.84). Likewise, no significant reduction in BMI (WMD, 0.02 kg/m(2); 95%CI, -0.11 to 0.14), weight (WMD, 0.12 kg; 95%CI, -0.24 to 0.49), or fat mass (WMD, 0.12 kg; 95%CI, -0.22 to 0.45) was observed in participants who received vitamin D plus calcium compared with those who received calcium control.

CONCLUSIONS

Supplementation with vitamin D showed no effect on adiposity measures in adults.

Adiposity measures and vitamin D concentrations in Northeast Germany and Denmark

BACKGROUND

Body mass index (BMI) and serum 25-hydroxy vitamin D3 (25OHD) concentrations are inversely related. As BMI contains only limited information regarding body fat distribution, we aimed to analyze the cross-sectional associations of abdominal visceral or subcutaneous adipose tissue, next to common adiposity measures, with the 25OHD concentration.

METHODS

Data were obtained from three cohorts of two large epidemiological studies in the northeast of Germany (Study of Health in Pomerania, SHIP-1 and SHIP-Trend), and in Denmark (Health2006). The study populations included adult men and women from the general population (N = 3072 SHIP-1, N = 803 SHIP-Trend, N = 3195 Health2006). Visceral and subcutaneous adipose tissue were quantified by magnetic resonance imagining (SHIP-Trend) or ultrasound (Health2006). Common adiposity measures, including BMI, waist circumference, waist-to-hip ratio, waist-to-height ratio, body surface area, and body fat percentage were determined by standardized methods in SHIP-1 and Health2006.

RESULTS

The average study participant was overweight (median BMI 27.4, 26.6, and 25.2 kg/m(2) in SHIP-1, SHIP-Trend, and Health2006, respectively). Visceral and subcutaneous adipose tissue as well as the common adiposity measures were inversely associated with serum 25OHD concentrations in linear regression models adjusted for age, sex, alcohol consumption, physical activity, smoking status, and month of blood sampling.

CONCLUSIONS

Next to common adiposity measures, also abdominal visceral or subcutaneous adipose tissue are inversely associated with serum 25OHD concentrations in the general adult population.

Vitamin D counteracts fibrogenic TGF-β signalling in human hepatic stellate cells both receptor-dependently and independently

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) is closely linked to obesity and constitutes part of the metabolic syndrome, which have been associated with low serum vitamin D (VD). Due to known crosstalk between VD and transforming growth factor (TGF)-β signalling, VD has been proposed as an antifibrotic treatment.

DESIGN

We evaluated the association between VD, the vitamin D receptor (VDR) and liver fibrosis in primary human hepatic stellate cells (phHSC) and 106 morbidly obese patients with NAFLD.

RESULTS

Treating phHSC with VD ameliorated TGF-β-induced fibrogenesis via both VDR-dependent and VDR-independent mechanisms. Reduction of fibrogenic response was abolished in cells homozygous for GG at the A1012G single nucleotide polymorphisms within the VDR gene. Compared with healthy livers, NAFLD livers expressed higher levels of VDR mRNA and VDR fragments. VDR mRNA was lower in patients homozygous for GG at A1012G and expression of pro-fibrogenic genes was higher in patients carrying the G allele.

CONCLUSIONS

VD may be an antifibrotic treatment option early in the onset of fibrosis in specific genotypes for VDR. Known polymorphisms of the VDR may influence the response to VD treatment.

Metabolic triggered inflammation in osteoarthritis

Osteoarthritis (OA) is a common chronic joint disorder with a multifactorial etiology including genetic and environmental factors. Metabolic triggered inflammation, induced by nutrient overload and metabolic surplus, consists of components such as obesity, pro-inflammatory cytokines and adipokines, abnormal metabolites, acute phase proteins, vitamin D deficiency, and deregulated microRNAs that may play a role in OA pathophysiology. Obesity-related metabolic factors, especially adipokines, contribute to OA development by inducing pro-inflammatory cytokines and degradative enzymes, leading to cartilage matrix impairment and subchondral bone remodeling. Ectopic metabolite deposition and low-grade systemic inflammation can contribute to a toxic internal environment that exacerbates OA. Complement components highly expressed in osteoarthritic joints have also been proposed as causative factors. Vitamin D deficiency has been associated with obesity and is implicated to be associated with cartilage loss in OA. Metabolic microRNAs may explain the inflammatory link between obesity and OA. Therapies targeting metabolic-triggered inflammation and its components are anticipated to have potential for the treatment of OA.

House dust mite induced lung inflammation does not alter circulating vitamin D levels

Low circulating levels of 25-hydroxyvitamin D [25(OH)D] are associated with chronic lung diseases such as asthma. However, it is unclear whether vitamin D is involved in disease pathogenesis or is modified by the inflammation associated with the disease process. We hypothesized that allergic inflammation decreases the level of circulating 25(OH)D and tested this using a mice model of house dust mite (HDM) induced allergic airway inflammation. Cellular influx was measured in bronchoalvelar lavage (BAL) fluid, and allergic sensitization and 25(OH)D levels were measured in serum. Exposure to HDM caused a robust inflammatory response in the lung that was enhanced by prior influenza infection. These responses were not associated with any change in circulating levels of 25(OH)D. These data suggest that alterations in circulating 25(OH)D levels induced by Th-2 driven inflammation are unlikely to explain the cross-sectional epidemiological association between vitamin D deficiency and asthma.

Bone health as a function of adipokines and vitamin D pattern in elderly patients

BACKGROUND

Adiponectin, leptin, and resistin are involved in bone metabolism, but the evidence regarding their effects is not conclusive. We analyzed the relationship between these adipokines, vitamin D, and bone health using a cluster analysis approach.

METHODS

We used cross-sectional data coming from the InCHIANTI study, in which bone density and area were estimated using computed tomography. The sample size was 690 (women, 57.5%; mean age, 75.2 years; range, 65-102). Five clusters were generated on the basis of gender, age, adipokines, and vitamin D concentrations. The clusters were characterized, respectively, by higher resistin and older age (hR-O, n=134), higher vitamin D and younger age (hD-Y, n=152), higher adiponectin (hA, n=65), and higher leptin (hL, n=52). The last cluster had intermediate values of all the constituting variables (I, n=287). The clusters were compared with respect to bone parameters and clinical characteristics.

RESULTS

Cluster hR-O had the lowest total and cortical bone density. Cluster hD-Y had the lowest adiponectin (9.29 g/mL) and leptin (7.9 ng/mL) serum concentrations, the highest prevalence of men (71.1%), and total/cortical bone density and area. No statistically significant difference across clusters was observed for age- and sex-standardized measures of bone mineral density and bone area, but leptin was associated with these parameters in a linear model adjusted for age, gender, vitamin D, resistin, and leptin.

CONCLUSIONS

In an elderly population, age and sex almost completely explain the variability in bone status across cluster characterized by different levels of circulating adipokines and vitamin D. The role of leptin, however, seems worthy of consideration.

Vitamin d and its relationship with obesity and muscle

The skin synthesis of vitamin D represents the first step of a metabolic pathway whose features have been extensively studied and clarified in the last decades. In particular, the production of active and inactive forms of the hormone and the actions of the corresponding enzymes have offered new insights into the knowledge of vitamin D metabolism. Additionally, the description of the different organs and tissues expressing the vitamin D receptor and its possible functions, as well as its genetic determinants, have allowed focusing on the interrelationship between vitamin D and many physiological and pathological functions. In this context, many studies reported the association between vitamin D and adipose tissue metabolism, as well as the possible role of the hormone in obesity, weight, and fat mass distribution. Finally, many reports focused on the vitamin D-related effects on skeletal muscle, particularly on the mechanisms by which vitamin D could directly affect muscle mass and strength. This paper is mainly aimed to review vitamin D metabolism and its relationship with obesity and skeletal muscle function.

Hypovitaminosis D and Obesity - Coincidence or Consequence?

Vitamin D has attracted much scientific interest in recent years, mostly due to its newly described roles in metabolism regulation and cell proliferation. Along with hypovitaminosis D, the incidence of obesity has risen and has become a public health concern. The association between these two conditions is not merely coincidence and is being deeply investigated regarding its prevalence, mechanism, and even a possible causal relation. The data are still inconclusive but there is important evidence indicating that vitamin D is involved with fat accumulation, the responsible mechanism however still the principal question. The three main hypotheses are: adipose tissue sequestration, genetic modulation, such as polymorphism of the vitamin D receptor (VDR), or an organism evolutionary adaptation to cold weather. In conclusion, more evidence is needed to determine what the correct direction of this connection is and the possible therapeutic strategies of vitamin D replenishment and obesity control.

Serum 25-hydroxy vitamin D levels in relation to body mass index: a systematic review and meta-analysis

BACKGROUND

Although several cross-sectional studies have investigated serum vitamin D levels in relation to body mass index (BMI), findings are inconsistent.

OBJECTIVE

This systematic review and meta-analysis of published cross-sectional data was conducted to summarize the evidence on the link between serum vitamin D levels and BMI in adults.

METHODS

PubMed, ISI Web of Science, Scopus and Google scholar database were searched to May 2012 for all relevant published papers. We found 34 articles that reported the correlation coefficients between serum 25-hydroxy vitamin D (25(OH)D) levels and BMI in apparently healthy adults (>18 years). The primary analysis was done on these 34 papers that reported 37 correlation coefficients. To find the source of between-study heterogeneity, our secondary analysis was confined to eight studies that had used random sampling method and reported the correlations for the whole population.

RESULTS

Our meta-analysis on 34 relevant papers revealed an overall significant inverse, but weak, association between serum 25(OH)D levels and BMI (Fisher's Z = -0.15, 95% CI: -0.19, -0.11) with a significant heterogeneity between studies. In the subgroup analysis based on gender and study location (East vs. West), the inverse associations were significant in both genders (male: Fisher's Z = -0.11, 95% CI: -0.14, -0.08 and female: -0.14, 95% CI: -0.21, -0.08) and both study locations (East: -0.09, 95% CI: -0.14, -0.04 and West: -0.23, 95% CI: -0.31, -0.17). In the subgroup analysis based on developmental status of countries, the weak inverse association remained significant in developed countries (-0.17, 95% CI: -0.21, -0.14), but not in developing nations (-0.10, 95% CI: -0.20, 0.01). Using meta-regression, we found that latitude (P = 0.91) or longitude (P = 0.2) of cities did not significantly contribute to the computed effect sizes. When we restricted our analysis to eight selected studies that used random sampling method, we reached the same findings. In this analysis, gender and developmental status of countries explained the between-study heterogeneity.

CONCLUSION

There is a significant inverse weak correlation between serum 25(OH)D levels and BMI in adult population, except for women living in developing countries. Further research particularly in developing countries and populations living near the equator is needed.

Hypovitaminosis D and incidence of obesity: a prospective study

The aim of this study was to assess the relationship between obesity and vitamin D status cross-sectionally, the relationship between obesity and the incidence of hypovitaminosis D prospectively and inversely the relationship between vitamin D status and incidence of obesity in a population-based cohort study in Spain. At baseline (1996-1998), 1226 subjects were evaluated and follow-up assessments were performed in 2002-2004 and 2005-2007, participants undergoing an interview and clinical examination with an oral glucose tolerance test. At the second visit, 25-hydroxyvitamin D and intact parathyroid hormone concentrations were also measured. Prevalence of obesity at the three visits was 28.1, 36.2 and 39.5%, respectively. The prevalence of vitamin D deficiency (25-hydroxyvitamin D ≤ 20 ng/ml (≤ 50 nmol/l)) was 34.7%. Neither obesity at baseline (OR=0.98, 95% CI: 0.69-1.40, P=0.93) nor the development of obesity between baseline and the second evaluation (OR=0.80, 95% CI: 0.48-1.33, P=0.39) were significantly associated with vitamin D status. In subjects who were non-obese (BMI <30 kg/m²) at the second evaluation, 25-hydroxyvitamin D values ≤ 17 ng/ml (≤ 42.5 nmol/l) were significantly associated with an increased risk of developing obesity in the next 4 years (OR=2.35, 95% CI: 1.03-5.4, P=0.040 after diverse adjustments). We conclude that vitamin D deficiency is associated with an increased risk of developing obesity.

Possible role of hyperinsulinemia and insulin resistance in lower vitamin D levels in overweight and obese patients

A cohort of 66 healthy overweight and obese patients, 53 women and 13 men were examined. Waist circumference and fasting 25(OH)D, insulin, glucose, lipid (cholesterol, HDL cholesterol, and triglyceride), C-reactive protein (CRP), and complement 3 (C₃), and 4 (C₄) serum concentrations were measured. Insulin resistance was assessed by the homeostasis model assessment (HOMA_IR). Results. 25(OH)D levels showed a significant negative correlation with BMI (P < 0.01), waist circumference (P < 0.05), fasting insulin (P < 0.01), HOMA_IR (P < 0.01), triglycerides (P < 0.01), CRP (P < 0.01), C₃ (P < 0.05), and C₄ (P < 0.05). Multiple regression analyses were performed with 25(OH)D as the dependent variable and BMI (or waist circumferences), fasting insulin (or HOMA_IR), triglycerides, and CRP (or C₃ or C₄) as independent variables. Only insulin or HOMA_IR maintained a significant independent association with 25(OH)D levels, whereas vitamin D did not maintain a significant independent association with CRP or C₃ or C₄ concentrations. Conclusions. The present study, performed in overweight and obese subjects, shows that 25(OH)D levels are negatively associated with inflammatory parameters such as CRP and C₃ and C₄ levels, but not independently of BMI, body fat distribution, insulin levels, or insulin resistance. Our results suggest that hyperinsulinemia and/or insulin resistance are directly responsible for decrease of 25(OH)D levels in obesity.

Vitamin D deficiency amongst minority ethnic groups in the UK: a cross sectional study

BACKGROUND

Vitamin D deficiency is common amongst minority groups in Britain but its magnitude amongst South Asian (SA) and Black African-Caribbean (AC) groups is not well defined. The steroidal, endocrine nature of vitamin D provides it with a putative link with cardiovascular disease (CVD), and we hypothesised that aberrant levels of this hormone would reflect a heightened risk of CVD in these ethnic groups.

METHODS

SA (n=1105, 57% male) and AC (n=748, 51% male) were recruited as part of a community heart failure study from 20 primary care practices, Birmingham, UK. Vitamin D2/D3 levels were measured to determine rates of total vitamin D status, which were age/sex adjusted.

RESULTS

The majority of SAs had severe vitamin D deficiency (42.2%, 95% CI: 39.2-45.1), which was more frequent than in AC (12.5%, 10.2-14.9, p<0.001. Vitamin status in SA and AC was unrelated to the presence of osteoporosis, and on multivariate analysis of SA, vitamin D levels were independently associated with age (β=0.18, p<0.001), haemoglobin (β=0.12, p=0.002), and negatively with alkaline phosphatase (a marker of bone mineralisation, β=-0.11, p=0.022). Amongst AC, vitamin D was independently associated with having ever smoked (β=-0.13, p=0.006) and systolic blood pressure (β=0.10, p=0.038).

CONCLUSIONS

Vitamin D deficiency is a frequent biochemical observation amongst minority groups in Britain but the clinical significance is unclear, and ethnically specific. A proportionate susceptibility to bone disease is not apparent in either minority group.

Changes in vitamin D supplement use and baseline plasma 25-hydroxyvitamin D concentration predict 5-y change in concentration in postmenopausal women

Few studies have prospectively examined predictors of change in plasma concentrations of 25-hydroxyvitamin D [25(OH)D]. We sought to determine the predictors of 5-y change in 25(OH)D. Plasma 25(OH)D concentrations were assessed at baseline (1997-2000) and 5 y later (2002-2005) in 668 postmenopausal women enrolled in the Osteoporosis and Periodontal Disease Study. Baseline and changes in demographic, dietary, lifestyle, and health-related factors were tested as predictors of change in 25(OH)D concentrations by using multivariable linear regression. The mean 5-y change in 25(OH)D (mean ± SD) was 7.7 ± 0.7 nmol/L (P < 0.001). In our predictive model (n = 643), predictors explained 31% of the variance in change in 25(OH)D concentrations and included baseline 25(OH)D, baseline and change in vitamin D supplementation and physical activity, change in season of blood draw, BMI, whole-body T score, and baseline hormone therapy use. Baseline 25(OH)D and change in vitamin D supplementation explained the most variation (25%) in 25(OH)D. Exploratory analyses showed a borderline significant interaction between tertiles of baseline 25(OH)D and change in vitamin D supplementation over time (P = 0.06). The greatest mean increase in 25(OH)D (22.9 ± 16.8 nmol/L), with adjustment for other statistically significant predictors, occurred in women whose baseline 25(OH)D concentration was ≤51.0 nmol/L (tertile 1) and who increased supplementation use over time. These results confirm the importance of supplementation in increasing 25(OH)D concentrations in aging women, even after other statistically significant predictors are controlled for. These data also suggest that this is especially true among aging women with inadequate 25(OH)D (e.g., <50 nmol/L).

Vitamin D insufficiency and chronic diseases: hype and reality

In recent years an increasing number of observational studies have suggested that a low vitamin D status contributes to the development of all sorts of chronic diseases. In reality, however, studies that had been adequately controlled for confounding factors ruled out any link between vitamin D insufficiency and, for example, metabolic disorders, arterial hypertension, multiple sclerosis or cognitive dysfunction. Furthermore, a role of vitamin D insufficiency in autoimmune diseases is evident only in animal models but has not yet been established in humans. In respect to many malignancies, vitamin D insufficiency is only one out of many risk factors and its specific impact on disease incidence has never been assessed. There is convincing evidence, however, that vitamin D insufficiency is a major risk factor for osteoporosis, colorectal and breast cancer as well as for cardiovascular disease and mortality. However, it is debatable that circulating 25-hydroxyvitamin D concentrations of 100-150 nmol l(-1) are required for optimal health outcomes. These are overestimates which would afford to raise vitamin D intake to 4000 IU day(-1). In reality, high doses of vitamin D can cause serious health problems because of the U-shaped dose-response relationships that exist in some cases. Data from large cohort studies clearly indicate that serum 25-(OH)D concentrations around 50 nmol l(-1) are sufficient to minimize the risk of osteoporotic fractures, colorectal and breast cancer, and cardiovascular mortality. The fact that the risk-reducing potential of vitamin D depends on adequate calcium nutrition is widely ignored. I here summarize the evidence that efficient disease prevention does not require intake of more vitamin D and calcium than currently recommended for maintaining optimal bone health.

Serum 25-hydroxyvitamin D3 and body composition in an elderly cohort from Germany: a cross-sectional study

Background

Emerging evidence indicates that there is an association between vitamin D and obesity. The aim of this study was to investigate whether the level of serum 25-hydroxyvitamin D₃ [25(OH)D₃] in the elderly is influenced by parameters of anthropometry and body composition independent of potential confounding lifestyle factors and the level of serum intact parathyroid hormone (iPTH).

Methods

Cross-sectional data of 131 independently living participants (90 women, 41 men; aged 66–96 years) of the longitudinal study on nutrition and health status in senior citizens of Giessen, Germany were analysed. Concentrations of 25(OH)D₃ and iPTH were ascertained by an electrochemiluminescence immunoassay. Body composition was measured by a bioelectrical impedance analysis. We performed univariate and multiple regression analyses to examine the influence of body composition on 25(OH)D₃ with adjustments for age, iPTH and lifestyle factors.

Results

In univariate regression analyses, 25(OH)D₃ was associated with body mass index (BMI), hip circumference and total body fat (TBF) in women, but not in men. Using multiple regression analyses, TBF was shown to be a negative predictor of 25(OH)D₃ levels in women even after controlling for age, lifestyle and iPTH (ß = −0.247; P = 0.016), whereas the associations between BMI, hip circumference and 25(OH)D₃ lost statistical significance after adjusting for iPTH. In men, 25(OH)D₃ was not affected by anthropometric or body composition variables.

Conclusions

The results indicate that 25(OH)D₃ levels are affected by TBF, especially in elderly women, independent of lifestyle factors and iPTH.

Modest reversal of metabolic syndrome manifestations with vitamin D status correction: a 12-month prospective study

Numerous cross-sectional studies have noted significant negative associations between circulating levels of 25-hydroxyvitamin D and cardiometabolic risk factors, highlighting potential extraskeletal functions of this sterol hormone. Prospective studies, however, have been limited; and hence, no cause-and-effect relations can be inferred. This study aims to determine whether vitamin D status correction can reverse already established manifestations of the metabolic syndrome (MetS). A total of 59 adult nondiabetic, overweight, and obese Saudis (31 male, 28 female) were prospectively enrolled in this 1-year interventional study. Anthropometry and biochemical evaluation were performed, including determination of serum 25-hydroxyvitamin D, calcium, and phosphorous concentrations, as well as fasting blood glucose and lipid profile. Subjects were advised to regularly expose themselves to sunlight and increase intake of vitamin D-rich foods. All measurements were repeated 6 and 12 months later. At the initial baseline visit, the prevalence of both low high-density lipoprotein cholesterol and hypertension was significantly increased among patients with 25-vitamin D deficiency (P < .05), even after adjusting for sex and body mass index. Overall prevalence of MetS patients by the modified National Health and Nutrition Examination Survey Adult Treatment Panel III definition decreased from 25.2% to 13.0%; and this was largely due to a parallel decrease in the prevalence of low high-density lipoprotein cholesterol, triglycerides, and hypertension. Optimization of vitamin D status through sun exposure and increased intake of a vitamin D-rich diet can lead to an improved cardiometabolic profile, offering a promising nonpharmacologic approach in the prevention of MetS manifestations.

Low serum IL-6 is associated with high 6-minute walking performance in asymptomatic women aged 20 to 70years

Cross-sectional associations between low physical performance and inflammatory biomarkers have been reported in healthy subjects and in persons with specific disease conditions. In asymptomatic subjects, whether the inverse association between physical fitness and inflammatory biomarkers is dependent or is independent of fat mass, a significant source of inflammatory cytokines, and is independent of age, muscle mass and strength, endocrine, metabolic, and lifestyle factors is not known. Two hundred and twenty asymptomatic women aged 20 to 72years with a C-reactive protein <5mg/L were assessed for their mean speed over the 6-minute walking test (6MWS) and their serum IL-6, as well as body height, body weight, body lean and fat mass (measured by DXA), waist-to-hip ratio, grip and knee extension strength, physical activities (quantified by the QUANTAP questionnaire), tobacco consumption, serum 25(OH) vitamin D, parathyroid hormone (PTH), estradiol (E2), free testosterone, dehydroepiandrosterone sulfate (DHEAS), insulin-like growth factor (IGF-I), sex hormone-binding globulin (SHBG), calcium, albumin, and creatinine. In the stepwise multiple linear regression model, a 6MWS in the highest quartile (over 1.4m/s) was associated with lower values of serum IL-6 (p=0.02) and with higher values of grip strength (p=0.04) and creatinine (p=0.04). In conclusion, present results demonstrate that the relationship between lower levels of serum IL-6 and higher values of physical fitness in asymptomatic women is independent of age, body composition, and lifestyle, endocrine and metabolic confounders. It remains to be determined whether the inverse relationship between IL-6 and fitness reflects the presence of preclinical inflammatory diseases that could potentially influence fitness in asymptomatic women.

Influence of age and gender on associations of body mass index with bone mineral density, bone turnover markers and circulating calcium-regulating and bone-active sex hormones

Although it is well known that body mass index (BMI) and bone mineral density (BMD) are positively correlated, the mechanisms by which adiposity reduces the risk of osteoporotic fractures are not fully understood. The present study was initiated to gain deeper insight into the mechanisms underlying the osteoprotective effect of adiposity, and to assess particularly the relevance that BMI-associated changes in circulating hormone levels could have for the build-up of additional bone mineral density. Using data from a previous study on a large cohort of healthy adult Austrians, we analyzed correlations of BMI with (i) BMD at sites in the lumbar spine and hip region, (ii) bone resorption and formation markers, (iii) circulating levels of vitamin D, parathyroid hormone, testosterone and estrogen, and (iv) rates of daily vitamin D and calcium intake. After adjustment for age, positive correlations between BMI and BMD were highly significant (P<0.0001) at all skeletal sites across the entire study cohort. Associations were stronger in post-menopausal women than in pre-menopausal women and in men. In absolute values, the gain in BMD at the lumbar spine from an incremental rise of BMI in post-menopausal women was 1.5-fold higher than in pre-menopausal women, and three times of that observed in men (P<0.05). Inverse relations between BMI and β-crosslaps were consistently found in men (P<0.01) and in women before and after menopause (P<0.01 and P<0.05, respectively), suggesting that inhibition of osteoclastic bone resorption is responsible at least in part for the positive effect of high BMI on BMD. Sub-group analysis revealed that increasing BMI was associated with a significant fall of testosterone in men (P<0.05), and of 25-(OH)D in pre- and post-menopausal women (P<0.001 and P<0.05, respectively), but with a significant rise in PTH (P<0.01) in women before menopause. Since all these hormonal changes would cause bone loss, this excludes their playing any role in the osteoprotective effect of adiposity.