The effects of increasing serum calcitriol on energy and fat metabolism and gene expression

Hypothesized pathways for the association of vitamin D status and insulin sensitivity with resting energy expenditure: a cross sectional mediation analysis in Australian adults of European ancestry

Background

The role of vitamin D in human energy expenditure requires confirmation. We explored whether insulin sensitivity (IS)/insulin resistance (IR) mediated the association of vitamin D status (25OHD) on resting energy expenditure (REE).

Methods

REE, body composition (by DEXA) and clinical biochemistry of 155 Australian men and women were collated. A hypothesized mediation pathway through IS/IR on the direct association between 25OHD and REE was modeled, using three surrogate indices of IS/IR: McAuley’s insulin sensitivity index (McA), Quantitative insulin sensitivity check index (QUICKI) and triglyceride to glucose ratio (TYG). The modeling was performed on PROCESS SPSS Macro (version 4.0) based on 5000 bootstrapped samples, with and without the adjustment for covariates.

Results

Unadjusted models indicated a sizeable negative mediation by all IS/IR indices but no significant direct effect of 25OHD on REE. On adjustment for covariates, a negative indirect mediation effect of McA [β coefficient (SE) −2.1(0.821); bootstrapped 95% CI:−3.934, −0.703; p < 0.05] and a similar negative mediation of TYG [−1.935 (0.780); bootstrapped 95% CI: (−3.679, −0.622; p < 0.05] was observed. These models also showed a positive direct effect of 25OHD on REE. In contrast, QUICKI made a smaller contribution to the total effect though in the same direction as the other two measures [−0.783 (0.534); bootstrapped 95% CI: (−1.939, 0.134; P > 0.05].

Conclusions

A sizeable, partial, negative mediation of IS/IR on the direct relationship between 25OHD and REE, dampened the total effect of vitamin D on REE. Validation of the proposed causal framework would clarify vitamin D’s role in human energy metabolism.

Calcitriol promotes the maturation of hepatocyte-like cells derived from human pluripotent stem cells

Human hepatocyte-like cells (HLCs) derived from human pluripotent stem cells (hPSCs) represent a promising cell source for the assessment of hepatotoxicity and pharmaceutical safety testing. However, the hepatic functionality of HLCs remains significantly inferior to primary human hepatocytes. The bioactive vitamin D (VD), calcitriol, promotes the differentiation of many types of cells, and its deficiency is correlated to the severity of liver diseases. Whether calcitriol contributes to the differentiation of HLCs needs to be explored. Here, we found that the supplementation of calcitriol improved the functionalities of hPSCs-derived HLCs in P450 activities, urea production, and albumin secretion. Moreover, calcitriol also enhanced mitochondrial respiratory function with increased protein expression levels of the subunit of respiratory enzyme complexes in HLCs. Further analyses showed that the mitochondrial biogenesis regulators and mitophagy were increased by calcitriol, thus improving the mitochondrial quality. These improvements in functionality and mitochondrial condition were dependent on vitamin D receptor (VDR) because the improvements were abolished under VDR-deficient conditions. Our finding provides a cost-effective chemical process for HLC maturation to meet the demand for basic research and potential clinic applications.

Study on the Improvement of Behavioral and Cognitive Dysfunction of Children with OSAHS by Vitamin D

Objective

This study is aimed at exploring the role of vitamin D in the treatment of children with OSAHS by comparing the clinical symptoms, serum indicators, and behavioral changes of vitamin D intervention.

Method

Healthy children who were examined physically in Rizhao People's Hospital were selected as the control group, and their sex, age, triglyceride, total cholesterol, high-density lipoprotein, low-density lipoprotein, serum 25-OHD levels, and Conners' parental scale were measured. In addition, children diagnosed as OSAHS in the otolaryngology department of Rizhao People's Hospital were selected as experimental subjects. Their body mass index, triglycerides, total cholesterol, high-density lipoprotein, low-density lipoprotein, serum 25-OHD levels, sleep apnea hypopnea index, minimum oxygen saturation, and Conners' parental scale were measured. The experimental subjects were treated with Rocaltrol intervention therapy (0.25 g/QD) for 4 weeks and reanalyzing their triglycerides, total cholesterol, high-density lipoprotein, low-density lipoprotein, serum 25-OHD levels, sleep apnea hypopnea index, minimum oxygen saturation, and Conners' parental scale.

Result

OSAHS children commonly have the situation of obesity, dyslipidemia, and vitamin D deficiency. Behavioral and cognitive dysfunction is common in OSAHS children. There were no significant changes in body mass index, triglycerides, total cholesterol, high-density lipoprotein, low-density lipoprotein, sleep apnea, hypopnea index, and minimum oxygen saturation for OSAHS children after vitamin D treatment, but the serum 25-OHD level is significantly improved, and children with conduct problems, learning problems, and hyperactivity index decrease.

Conclusion

(1) OSAHS children commonly have the situation of obesity, dyslipidemia, vitamin D deficiency, and behavioral and cognitive impairment. (2) Vitamin D supplementation has no therapeutic effect on obesity and dyslipidemia of OSAHS children, but has obvious protective and improving effects on neuron damage caused by hypoxia. Obstructive sleep apnea syndrome (OSAHS) is a common disease. Patients with OSAHS usually have many clinical features, such as obesity, metabolic syndrome, and cardiovascular disease. The decline of cognitive function and learning ability is one of the serious complications of OSAHS patients [1]. Vitamin D (VitD) deficiency is associated with many diseases. Recent studies have shown that the serum 25-OHD level of OSAHS patients is relatively insufficient and related to the disease severity. However, there are few reports on explaining whether vitamin D supplementation can alleviate the clinical symptoms and improve serum indicators and behavioral and cognitive dysfunction in children with OSAHS.

Lack of a relationship between vitamin D status and resting metabolic rate in Iranian adults

OBJECTIVES

Studies suggest a positive relationship between 25-hydroxy vitamin D (25(OH)D)) and resting metabolic rate (RMR). We aimed to determine whether this relationship was also true of populations with very low vitamin D status.

METHODS

Fat mass (FM) and fat free mass (FFM) were determined from multifrequency bioimpedance analysis (InBody 720, Korea). RMR was based on indirect calorimetry (Cortex Metalyser 3B, Germany). Fasting blood measurements of 25(OH)D concentration, glucose and triglycerides were measured. Data were analyzed separately on men and women by tertile of vitamin D status and multiple linear regression analysis.

RESULTS

Two hundred and sixty-three subjects (115 males; 148 females) with a mean age of 37 years and mean %body fat of 30.5% were studied. In women but not men, age, body weight, waist circumference, FM, and FFM increased significantly across tertiles of 25(OH)D. However, there was no difference in unadjusted or adjusted RMR across tertiles of 25OHD in both women and men. Stepwise forward regression analysis showed that age and FFM in men, age and FM in women but not by 25(OH)D, were determinants of RMR. In addition, RMR adjusted for age, sex, FM, FFM and triglyceride-glucose index did not relate to 25(OH)D when linear (r = 0, P = .98), quadratic (r = 0.008, P = .34), or cubic (r = 0.010, P = .43) relationships were tested.

CONCLUSIONS

Residual variation in RMR did not relate to vitamin D status in a group of Iranian adults with very low vitamin D status. Future studies could examine whether such a relationship holds true, after the normalization of vitamin D status.

Vitamin D Supplementation Does Not Impact Resting Metabolic Rate, Body Composition and Strength in Vitamin D Sufficient Physically Active Adults

Supplementation with the most efficient form of Vitamin D (VitD3) results in improvements in energy metabolism, muscle mass and strength in VitD deficient individuals. Whether similar outcomes occur in VitD sufficient individuals' remains to be elucidated. The aim of this study is to determine the effect of VitD3 supplementation on resting metabolic rate (RMR), body composition and strength in VitD sufficient physically active young adults. Participants completed pre-supplementation testing before being matched for sunlight exposure and randomly allocated in a counterbalanced manner to the VitD3 or placebo group. Following 12 weeks of 50 IU/kg body-mass VitD3 supplementation, participants repeated the pre-supplementation testing. Thirty-one adults completed the study (19 females and 12 males; mean ± standard deviation (SD); age = 26.6 ± 4.9 years; BMI = 24.2 ± 4.1 kg·m²). The VitD group increased serum total 25(OH)D by 30 nmol/L while the placebo group decreased total serum concentration by 21 nmol/L, reaching 123 (51) and 53 (42.2) nmol/L, respectively. There were no significant changes in muscle strength or power, resting metabolic rate and body composition over the 12-week period. Physically active young adults that are VitD sufficient have demonstrated that no additional physiological effects of achieving supraphysiological serum total 25(OH)D concentrations after VitD3 supplementation.

Vitamin D-vitamin D receptor system down-regulates expression of uncoupling proteins in brown adipocyte through interaction with Hairless protein

Our previous study showed that feeding mice with vitamin D deficiency diet markedly alleviated high-fat-diet-induced overweight, hyperinsulinemia, and hepatic lipid accumulation. Moreover, vitamin D deficiency up-regulated the expression of uncoupling protein 3 (Ucp3) in white adipose tissue (WAT) and brown adipose tissue (BAT). The present study aimed to further investigate the effects of vitamin D and vitamin D receptor (Vdr) on Ucp1–3 (Ucps) expression in brown adipocyte and the mechanism involved in it. Rat primary brown adipocytes were separated and purified. The effects of the 1,25(OH)₂D₃ (1,25-dihydroxyvitamin D3; the hormonal form of vitamin D) and Vdr system on Ucps expression in brown adipocytes were investigated in basal condition and activated condition by isoproterenol (ISO) and triiodothyronine (T3). Ucps expression levels were significantly down-regulated by 1,25(OH)₂D₃ in the activated brown adipocyte. Vdr silencing reversed the down-regulation of Ucps by 1,25(OH)₂D₃, whereas Vdr overexpression strengthened the down-regulation effects. Hairless protein did express in brown adipocyte and was localized in cell nuclei. 1,25(OH)₂D₃ increased Hairless protein expression in the cell nuclei. Hairless (Hr) silencing notably elevated Ucps expression in activated condition induced by ISO and T3. Moreover, immunoprecipitation results revealed that Vdr could interact with Hairless, which might contribute to decreasing expression of Vdr target gene Ucps. These data suggest that vitamin D suppresses expression of Ucps in brown adipocyte in a Vdr-dependent manner and the corepressor Hairless protein probably plays a role in the down-regulation.

Diabetic Hemodialysis: Vitamin D Supplementation and its Related Signaling Pathways Involved in Insulin and Lipid Metabolism

BACKGROUND

This study was conducted to determine the effects of vitamin D supplementation on some of the gene expressions related to insulin and lipid metabolism in diabetic hemodialysis (HD) patients.

METHODS

A double-blind, randomized, placebo-controlled clinical trial was carried out in 55 patients with diabetic HD. The current project used two groups in which each subject received vitamin D supplements (50,000 IU, n=28) or placebo (50,000 IU, n=27) every 2 weeks for 12 weeks. Gene expression analyses (RT-PCR) were included to obtain the rate of gene expression of the related insulin and lipid metabolism genes in peripheral blood mononuclear cells (PBMCs) of patients with diabetic HD.

RESULTS

Our data revealed that consumption of vitamin D supplementation enables to overexpress the peroxisome proliferation-activated receptor gamma (PPAR-γ) (P=0.001), AKT (P=0.04), PI3K (P=0.02), insulin receptor substrate-1 (IRS1) (P0.008) and glucose transporter type 4 (GLUT-4) (P=0.01) and downregulate the expression of protein kinase C (PKC) (P=0.001) in patients with diabetic HD than control group following the 12-week intervention. In addition, vitamin D supplementation downregulated low-density lipoprotein receptor (LDLR) (P=0.03) expression in the subjects with diabetic HD than the control group. Vitamin D supplementation did not show any effects on the expression of pyruvate dehydrogenase kinase 1 (PDK1) (P=0.37), IRS2 (P=0.90) and lipoprotein (a) [Lp(a)] (P=0.05).

CONCLUSION

Our findings confirmed that diabetic HD subjects who received the vitamin D supplementation (for 12 weeks), showed a significant overexpression in the PPAR-γ, AKT, PI3K, IRS1 and GLUT4 genes, and also showed a significant downregulation in the PKC and LDLR genes. Moreover, no effects on PDK1, IRS2 and Lp(a) expression were observed.

Mechanisms of vitamin D action in skeletal muscle

Vitamin D receptor expression and associated function have been reported in various muscle models, including C2C12, L6 cell lines and primary human skeletal muscle cells. It is believed that 1,25-hydroxyvitamin D3 (1,25(OH)2D3), the active form of vitamin D, has a direct regulatory role in skeletal muscle function, where it participates in myogenesis, cell proliferation, differentiation, regulation of protein synthesis and mitochondrial metabolism through activation of various cellular signalling cascades, including the mitogen-activated protein kinase pathway(s). It has also been suggested that 1,25(OH)2D3 and its associated receptor have genomic targets, resulting in regulation of gene expression, as well as non-genomic functions that can alter cellular behaviour through binding and modification of targets not directly associated with transcriptional regulation. The molecular mechanisms of vitamin D signalling, however, have not been fully clarified. Vitamin D inadequacy or deficiency is associated with muscle fibre atrophy, increased risk of chronic musculoskeletal pain, sarcopenia and associated falls, and may also decrease RMR. The main purpose of the present review is to describe the molecular role of vitamin D in skeletal muscle tissue function and metabolism, specifically in relation to proliferation, differentiation and protein synthesis processes. In addition, the present review also includes discussion of possible genomic and non-genomic pathways of vitamin D action.

Association of circulating 25-hydroxyvitamin D and parathyroid hormone with carotid intima media thickness in children and adolescents with excess weight

Evidence on the association of vitamin D and parathyroid hormone (PTH) with cardiovascular risk factors in the young is limited. We therefore assessed the relationships of circulating vitamin D and PTH concentrations and subclinical atherosclerosis in overweight or obese children and adolescents. This was a cross-sectional study, investigated the association of 25-hydroxyvitamin D (25(OH)D), intact PTH (iPTH), and iPTH/25(OH)D ratio with carotid intima-media thickness (cIMT) in 368 Iranian children and adolescents with a body mass index (BMI) ≥1 z-score based on WHO criteria. Ultrasound measurement of cIMT was performed. Multivariable linear and logistic regressions were used to test associations between 25(OH)D, iPTH, and iPTH/25(OH)D ratio using one-ln-unit increment with cIMT. Median (25-75 interquartile range) 25(OH)D and iPTH concentrations were 11.8 (8.2-18.6) ng/ml and 38.2 (25.0-61.4) pg/ml, respectively. Among boys, each one-ln-unit increase of iPTH and iPTH/25(OH)D ratio was significantly associated with 0.194 mm and 0.147 mm increase, respectively, in cIMT, after adjustment for confounders. A similar pattern of association was observed between iPTH (β = 0.143, p = 0.037) and iPTH/25(OH)D ratio (β=0.172, p = 0.007) with cIMT among obese participants. Furthermore, among obese participants in the fully adjusted model, each one-ln-unit increase of iPTH and 25(OH)D/iPTH ratio was significantly associated with 53% and 39% increased odds of having high cIMT, respectively. Girls and those who were overweight did not show any significant association of 25(OH)D, iPTH, and iPTH/25(OH)D ratio with cIMT. High iPTH and iPTH/25(OH)D ratio were associated with increased cIMT in boys and those who are obese.

Determinants of vitamin D receptor gene expression in visceral and subcutaneous adipose tissue in non-obese, obese, and morbidly obese subjects

We aimed to illustrate determinants of VDR gene expression in visceral and subcutaneous adipose tissue among individuals without diabetes. We gathered visceral and subcutaneous adipose tissues during an elective abdominal surgery form 33 morbidly obese (BMI > 40 kg/m²), 23 obese (BMI = 30-40 kg/m²), and 35 non-obese (BMI<30 kg/m²) participants who were free of diabetes. Participants were classified according to their degree of obesity. Before the surgery, habitual dietary intake, physical activity, 25(OH)D, body mass index (BMI), waist circumference (WC), and HOMA-IR was gathered. Non-obese participants had significantly lower mean VDR gene expression in visceral adipose tissues than both the obese and morbidly obese ones and had also lower expression in subcutaneous adipose tissues than the morbidly obese participants. In multiple linear regression models, BMI and HOMA-IR were the independent positive predictors of VDR gene expression in subcutaneous fat. Among non-obese subjects, WC and 25(OH)D were the positive and negative independent predictors of visceral adipose tissue VDR gene expression, respectively. Among obese participants, 25(OH)D was negatively, and BMI and HOMA-IR were positively associated with VDR mRNA levels in visceral adipose tissue. In morbidly obese participants, the independent positive predictors of VDR gene expression in visceral fat were BMI and HOMA-IR, and negative predictors were 25(OH)D and calcium intake. Our findings suggested that 25(OH)D concentrations are the fundamental elements to determine VDR gene expression in visceral fat which by increasing fat depots, the subsequent insulin resistance became another predictor of VDR gene expression.

The effect of daily fortified yogurt consumption on weight loss in adults with metabolic syndrome: A 10-week randomized controlled trial

BACKGROUND AND AIMS

Obesity is a complex and multifaceted condition. Thus, functional foods need investigation as novel adjunct treatments for obesity. The objective was to determine the effects of daily consumption of a fortified yogurt (FY) on weight loss in overweight and obese patients with metabolic syndrome on a caloric-restricted diet.

METHODS AND RESULTS

This was a randomized, double-blind, 10-week study. Participants were randomly allocated to two groups receiving either two servings (2 × 250 g)/day of FY with whey protein, calcium, vitamin D, prebiotic fibre and probiotic cultures (n = 44) or a low-fat plain yogurt (PY) (n = 43). All participants were put on a calorie-restricted diet throughout the 10-week study. Body composition and biochemical indices were assessed before and after the intervention. Body mass decreased by 4.3 ± 1.9 kg and 5.1 ± 3.0 kg in the PY and FY groups, respectively, following the 10-week intervention. Compared to PY, consumption of FY resulted in a significant reduction in body fat mass (FM) (p = 0.023), body fat percentage (p = 0.028), waist circumference (p = 0.002), homoeostasis model of assessment-insulin resistance (HOMA-IR) (p = 0.025), triglyceride concentration (p = 0.003), and a significant increase in total 25-hydroxyvitamin D (25(OH)D) concentration (p < 0.001), high density lipoprotein-cholesterol (HDL-C) (p = 0.009) and quantitative insulin sensitivity check index (QUICKI) (0.022). Participants consuming the FY lost less fat-free mass (FFM) compared to the PY group (Δ = -0.9 ± 3.5 kg vs. Δ = -2.0 ± 2.7 kg; p = 0.025).

CONCLUSIONS

Consuming FY for 10-weeks improved body composition and metabolic parameters, while on a caloric-restricted diet. Further research is needed to elucidate whether FY can be used as a preventative strategy for metabolic syndrome in obese persons.

TRIAL REGISTRATION

www.irct.ir (IRCT2017050633836N1).

Vitamin D Status and Resting Metabolic Rate May Modify through Expression of Vitamin D Receptor and Peroxisome Proliferator-Activated Receptor Gamma Coactivator-1 Alpha Gene in Overweight and Obese Adults

BACKGROUND

Resting metabolic rate (RMR) used to prognosticate and measure the amount of energy required. Vitamin D is known as a new predictor of RMR. The aim of this study is to investigate the relationship between vitamin D effects on RMR in connection with the vitamin D receptor (VDR) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) gene expression.

METHODS

We enrolled 298 overweight and obese adults in this cross-sectional study. Body mass index (BMI), fat mass, fat-free mass, insulin level, visceral fat, and vitamin D status were assessed. RMR was measured by means of indirect calorimetry. The real-time polymerase chain reaction using specific primer pairs for VDR and PGC-1α was performed.

RESULTS

There were significant differences in terms of fat free mass, fat percentage, insulin levels, RMR/kg body weight, and RMR/BMI, VDR, and PGC-1α among participants were categorized based on the vitamin D status. But after using general linear model for adjusting, all significant results missed their effectiveness except RMR/kg body weight and VDR. Linear regression analysis used to show the mediatory role of VDR and PGC-1α on the RMR/kg body weight and vitamin D status relationship. Our results showed that VDR had a mediatory effect on the relationship between RMR/kg body weight and vitamin D status (β = 0.38, 95% CI -0.48 to 1.60; β = -1.24, 95% CI -5.36 to 1.70). However, PGC-1α did not affect the relationship between RMR/kg body weight and vitamin D status (β = 0.50, 95% CI = -0.02 to 3.42; β = 0.59, 95% CI 0.14-3.90).

CONCLUSION

Our study showed the mediatory effect of VDR gene expression in the association of 25(OH)2D plasma levels and resting metabolic rate among obese individuals.

Extraskeletal actions of vitamin D

The vitamin D receptor (VDR) is found in nearly all, if not all, cells in the body. The enzyme that produces the active metabolite of vitamin D and ligand for VDR, namely CYP27B1, likewise is widely expressed in many cells of the body. These observations indicate that the role of vitamin D is not limited to regulation of bone and mineral homeostasis, as important as that is. Rather, the study of its extraskeletal actions has become the major driving force behind the significant increase in research articles on vitamin D published over the past several decades. A great deal of information has accumulated from cell culture studies, in vivo animal studies, and clinical association studies that confirms that extraskeletal effects of vitamin D are truly widespread and substantial. However, randomized, placebo-controlled clinical trials, when done, have by and large not produced the benefits anticipated by the in vitro cell culture and in vivo animal studies. In this review, I will examine the role of vitamin D signaling in a number of extraskeletal tissues and assess the success of translating these findings into treatments of human diseases affecting those extracellular tissues.

Vitamin D, adipose tissue, and obesity

Epidemiological studies have shown a link between vitamin D deficiency and numerous pathologies such as cancers, immunity diseases, cardiovascular diseases, hypertension, type 2 diabetes, and obesity. Recent studies in vitro and in animal models demonstrated an impact of vitamin D on adipose tissue and adipocyte biology. Such observations are of particular interest and provide mechanistic explanations on the relationship between vitamin D deficiency and obesity.

Vitamin D modulates adipose tissue biology: possible consequences for obesity?

Cross-sectional studies depict an inverse relationship between vitamin D (VD) status reflected by plasma 25-hydroxy-vitamin D and obesity. Furthermore, recent studies in vitro and in animal models tend to demonstrate an impact of VD and VD receptor on adipose tissue and adipocyte biology, pointing to at least a part-causal role of VD insufficiency in obesity and associated physiopathological disorders such as adipose tissue inflammation and subsequent insulin resistance. However, clinical and genetic studies are far less convincing, with highly contrasted results ruling out solid conclusions for the moment. Nevertheless, prospective studies provide interesting data supporting the hypothesis of a preventive role of VD in onset of obesity. The aim of this review is to summarise the available data on relationships between VD, adipose tissue/adipocyte physiology, and obesity in order to reveal the next key points that need to be addressed before we can gain deeper insight into the controversial VD-obesity relationship.

Vitamin D status and insulin sensitivity are novel predictors of resting metabolic rate: a cross-sectional analysis in Australian adults

PURPOSE

Resting metabolic rate (RMR) accounts for two-thirds of the total energy expenditure in sedentary individuals. After accounting for traditional factors, there still remains a considerable unexplained variance in RMR. There is a pandemic of obesity and metabolic syndrome (MetS) which coexists with a high prevalence of vitamin D insufficiency. The aim of this study was to evaluate the potential effects of vitamin D status, insulin sensitivity (IS) and the metabolic syndrome (MetS) on RMR in Australian adults.

METHODS

RMR, respiratory quotient (RQ), McAuley's insulin sensitivity index, fat mass (FM), fat-free mass (FFM) and vitamin D status were assessed in Australian adults. The presence of MetS was evaluated by current standard criteria. Predictors of RMR were examined through multiple linear regression based on stepwise and backward regression approaches with attention to multi-collinearity. All analyses were conducted on SPSS version 21.

RESULTS

One hundred and twenty-seven participants (45 men, 82 women), aged 53.4 ± 11.7 years and BMI 31.9 ± 5.2 kg/m(2), were included. Forty-one subjects were insufficient in vitamin D status (<50 nmol/L), and 75 participants had the MetS. A parsimonious regression model explained 85.8 % of RMR and was given by: RMR (kJ/d) = 1931 + 83.5 × FFM (kg) + 29.5 × FM (kg) + 5.65 × 25(OH)D (nmol/L) - 17.6 × age (years) - 57.51 × IS.

CONCLUSION

Vitamin D status and IS are novel independent predictors of RMR in adults. Future studies could validate a causal role for these factors in human energy metabolism.

Vitamin D status, body composition and hypertensive target organ damage in primary hypertension

Overweight/obesity and high blood pressure during growth period are important risk factors of cardiovascular disease later in life. Cardiovascular system, fat and muscles are among target tissues for vitamin D and low 25(OH)D levels are likely to attenuate potential benefits of its action. The study was aimed to evaluate vitamin D status and body composition in children and adolescents with primary hypertension (PH). The study population comprised 78 patients aged 15.4±2.3yrs (9-18yrs; 15 girls) with diagnosed PH. Total 25(OH)D and parathyroid hormone (PTH) were assayed by Cobas e411 machine (Roche Diagnostics). DXA (Prodigy, GE Lunar) was used to assess total body bone mineral content (TBBMC; g), total body bone mineral density (TBBMD; g/cm(2)), lean body mass (LBM; g), % lean body mass (%LBM), fat mass (FM; g), % fat mass (% FM), Android %Fat, Gynoid %Fat and Trunk fat mass (Trunk FM; g). Hypertensive cases (BMI=25.6±4.2kg/m(2)), compared to reference, had slightly increased TBBMD and TBBMC Z-scores (+0.40±0.91 and +0.59±0.96; both p<0.001), and had markedly increased FM and FM/body weight ratio Z-scores of ±1.83±1.63 (p<0.0001) and +1.43±1.05 (p<0.0001). LBM Z-scores were slightly increased as well (+0.34±1.08, p<0.001). In contrast, markedly reduced LBM/body weight ratio Z-scores of -1.47±0.90 (p<0.0001) and disturbed relationship between FM and LBM as assessed by FM/LBM ratio Z-score of +1.53±1.29 (p<0.0001) were noted. The average serum levels of 25(OH)D of 17.8±6.9ng/mL and PTH of 34.8±16.8pg/mL were noted in PH group. 91% PH cases showed 25(OH)D levels lower than 30ng/mL. 71% of PH subjects revealed vitamin D deficiency (25(OH)D<20ng/ml). 10% of PH cases showed 25(OH)D levels lower than 10ng/mL. 25(OH)D levels negatively correlated with PTH showing r=-0.24 (p=0.03). Absolute LBM/body weight ratio values positively correlated with 25(OH)D levels (r=0.31; p=0.01). In contrast, absolute FM/body weight ratio values correlated negatively with 25(OH)D levels (r=-0.32; p<0.01). Moreover, 25(OH)D levels negatively correlated with absolute Trunk FM (r=-0.29; p<0.05), Android %Fat (r=-0.32; p<0.01) and with Gynoid %Fat (r=-0.28; p<0.05). PTH and 25(OH)D concentrations did not differ when severity of hypertension, left ventricular mass and carotid intima-media thickness were controlled for. Concluding, higher muscle mass stores in body weight coincided with higher 25(OH)D levels. Higher fat mass stores coincided with lower 25(OH)D levels in PH group. Whether vitamin D insufficiency/deficiency in PH group should be considered as a cause of disease or epiphenomenon remains unknown. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

Vitamin D protects against diet-induced obesity by enhancing fatty acid oxidation

Prospective studies reported an inverse correlation between 25-hydroxyvitamin D [25(OH)D] plasma levels and prevalence of obesity and type 2 diabetes. In addition, 25(OH)D status may be a determinant of obesity onset. However, the causality between these observations is not yet established. We studied the preventive effect of vitamin D3 (VD3) supplementation (15,000 IU/kg of food for 10 weeks) on onset of obesity in a diet-induced obesity mouse model. We showed that the VD3 supplementation limited weight gain induced by high-fat diet, which paralleled with an improvement of glucose homeostasis. The limitation of weight gain could further be explained by an increased lipid oxidation, possibly due to an up-regulation of genes involved in fatty acid oxidation and mitochondrial metabolism, leading to increased energy expenditure. Altogether, these data show that VD3 regulates energy expenditure and suggest that VD3 supplementation may represent a strategy of preventive nutrition to fight the onset of obesity and associated metabolic disorders.

Vitamin D supplementation and body weight status: a systematic review and meta-analysis of randomized controlled trials

Vitamin D is anticipated to have many extra-skeletal health benefits. We questioned whether supplementation with the vitamin influenced body weight and composition. A systematic review and meta-analysis was conducted on high-quality, randomized controlled trials (RCTs) that had supplemented vitamin D without imposing any caloric restriction. Eighteen trials reporting either body weight, body mass index (BMI), fat mass (FM), percentage fat mass (%FM) or lean body mass (LBM) met our criteria. Twelve studies provided the required data for the meta-analysis. Vitamin D supplementation did not influence the standardized mean difference (SMD) for body weight, FM, %FM or LBM. A small but non-significant decrease in BMI (SMD = -0.097, 95% confidence interval: [-0.210, 0.016], P = 0.092) was observed. Meta-regression confirmed that neither the absolute vitamin D status achieved nor its change from baseline influenced the SMD of any obesity measure. However, increasing age of the subjects predicted a shift in the SMD for FM towards the placebo treatment, whereas a greater percentage of women in these studies favoured a decrease in FM following vitamin D. Vitamin D supplementation did not decrease measures of adiposity in the absence of caloric restriction. A potential confounding by age and gender was encountered.

The relationship between vitamin D and obesity

Currently, vitamin D deficiency and obesity are pandemic diseases and they are associated with cardiovascular (CV) disease, metabolic syndrome and type 2 diabetes mellitus (T2DM) and other diseases. Concentrations of 25-hydroxyvitamin D (25(OH)D) (25D) are considered as the best indicator of total body vitamin D stores. An association between reduced circulating 25D concentrations and obesity is well known, but the mechanisms are not totally clear. The role of vitamin D supplementation is still uncertain and prospective interventions will establish its influence, if any, in the treatment of obesity. Vitamin D deficiency is associated with the presence of a cardiometabolic risk profile in the obese. Future trials may establish a role for Vitamin D supplementation in individuals at increased CV risk.

Vitamin D and energy homeostasis: of mice and men

The vitamin D endocrine system has many extraskeletal targets, including adipose tissue. 1,25-Dihydroxyvitamin D₃, the active form of vitamin D, not only increases adipogenesis and the expression of typical adipocyte genes but also decreases the expression of uncoupling proteins. Mice with disrupted vitamin D action--owing to gene deletion of the nuclear receptor vitamin D receptor (Vdr) or the gene encoding 1α-hydroxylase (Cyp27b1)--lose fat mass over time owing to an increase in energy expenditure, whereas mice with increased Vdr-mediated signalling in adipose tissue become obese. The resistance to diet-induced obesity in mice with disrupted Vdr signalling is caused at least partially by increased expression of uncoupling proteins in white adipose tissue. However, the bile acid pool is also increased in these animals, and bile acids are known to be potent inducers of energy expenditure through activation of several nuclear receptors, including Vdr, and G-protein-coupled receptors, such as GPBAR1 (also known as TGR5). By contrast, in humans, obesity is strongly associated with poor vitamin D status. A causal link has not been firmly proven, but most intervention studies have failed to demonstrate a beneficial effect of vitamin D supplementation on body weight. The reasons for the major discrepancy between mouse and human data are unclear, but understanding the link between vitamin D status and energy homeostasis could potentially be very important for the human epidemic of obesity and the metabolic syndrome.

Appetite sensations and substrate metabolism at rest, during exercise, and recovery: impact of a high-calcium meal

The aim of this study was to investigate the effects of the calcium content of a high-carbohydrate, pre-exercise meal on substrate metabolism and appetite sensations before, during, and after exercise. Nine active males participated in 2 trials in a double-blind, randomised, crossover design. After consuming a high carbohydrate (1.5 g·kg−1 of body mass) breakfast with a calcium content of either 3 (control trial) or 9 mg·kg−1 of body mass (high milk-calcium (CAL)), participants ran at 60% peak oxygen uptake for 60 min. Following exercise, a recovery drink was consumed and responses were investigated for a further 90 min. Blood and expired gas were sampled throughout to determine circulating substrate and hormone concentrations and rates of substrate oxidation. Visual analogue scales were also administered to determine subjective appetite sensations. Neither whole-body lipid oxidation nor non-esterified fatty acid availability differed between trials. The area under the curve for the first hour following breakfast consumption was 16% (95% confidence interval: 0%–35%) greater for fullness and 10% (95% confidence interval: 2%–19%) greater for insulin in the CAL trial but these differences were transient and not apparent later in the trial. This study demonstrates that increasing the calcium content of a high carbohydrate meal transiently increases insulinemia and fullness but substrate metabolism is unaffected.

The beneficial role of vitamin D in obesity: possible genetic and cell signaling mechanisms

The prevalence rates of overweight and obesity are considered an important public issue in the United States, and both of these conditions are increasing among both children and adults. There is evidence of aberrations in the vitamin D-endocrine system in obese subjects. Vitamin D deficiency is highly prevalent in patients with obesity, and many studies have demonstrated the significant effect of calcitriol on adipocytes. Genetic studies have provided an opportunity to determine which proteins link vitamin D to obesity pathology, including the vitamin D receptor, toll-like receptors, the renin-angiotensin system, apolipoprotein E, vascular endothelial growth factor, and poly (ADP-ribose) polymerase-1. Vitamin D also exerts its effect on obesity through cell-signaling mechanisms, including matrix metalloproteinases, mitogen-activated protein kinase pathways, the reduced form of nicotinamide adenine dinucleotide phosphate, prostaglandins, reactive oxygen species, and nitric oxide synthase.

In conclusion, vitamin D may have a role in obesity. The best form of vitamin D for use in the obese individuals is calcitriol because it is the active form of the vitamin D₃ metabolite, its receptors are present in adipocytes, and modulates inflammatory cytokine expression.

25-Hydroxyvitamin D Supplementation and BMI Change: A Meta-Analysis of Randomized Controlled Trials

The impact of 25-hydroxyvitamin D (25[OH]D) supplementation on weight change remains controversial. The objective of this study was to summarize the effects of 25[OH]D supplementation (cholecalciferol or ergocalciferol) on BMI change through a meta-analysis of published clinical trials. We completed a systematic review of English articles, using MEDLINE (Ovid, Pubmed) from January 1, 1998 through January 1, 2013. The articles selected focused on 25[OH]D supplementation and body mass index (BMI) in randomized controlled trials (RCT’s). The association between 25[OH]D and mean BMI change was estimated utilizing a random effects model. A total of 30 studies were reviewed and 9 were included in the meta-analysis. Total participants included 1651 adults (82.6% women and mean age 47.9 years) and mean follow-up ranged between 6 to 196 weeks and mean daily 25[OH]D dose ranged from 200 IU to 1,110 IU. Five of the 9 studies included calcium supplementation in both groups. Average baseline BMI was 30.7 and 30.4 kg/m² in the intervention and control groups, respectively. Five studies suggested a beneficial effect for 25[OH]D supplementation for BMI change whereas 3 studies showed no effect of 25[OH]D supplementation on BMI change, and one showed a non-perceptible change. Meta-analysis of BMI values at end of trial showed no statistically significant difference in BMI change by use of 25[OH]D supplementation. Based on existing published trials, oral 25[OH]D supplementation does not significantly impact BMI change.

Vitamin D signalling in adipose tissue

Vitamin D deficiency and the rapid increase in the prevalence of obesity are both considered important public health issues. The classical role of vitamin D is in Ca homoeostasis and bone metabolism. Growing evidence suggests that the vitamin D system has a range of physiological functions, with vitamin D deficiency contributing to the pathogenesis of several major diseases, including obesity and the metabolic syndrome. Clinical studies have shown that obese individuals tend to have a low vitamin D status, which may link to the dysregulation of white adipose tissue. Recent studies suggest that adipose tissue may be a direct target of vitamin D. The expression of both the vitamin D receptor and 25-hydroxyvitamin D 1α-hydroxylase (CYP27B1) genes has been shown in murine and human adipocytes. There is evidence that vitamin D affects body fat mass by inhibiting adipogenic transcription factors and lipid accumulation during adipocyte differentiation. Some recent studies demonstrate that vitamin D metabolites also influence adipokine production and the inflammatory response in adipose tissue. Therefore, vitamin D deficiency may compromise the normal metabolic functioning of adipose tissue. Given the importance of the tissue in energy balance, lipid metabolism and inflammation in obesity, understanding the mechanisms of vitamin D action in adipocytes may have a significant impact on the maintenance of metabolic health. In the present review, we focus on the signalling role of vitamin D in adipocytes, particularly the potential mechanisms through which vitamin D may influence adipose tissue development and function.

Vitamin D deficiency and calcium intake in reference to increased body mass index in children and adolescents

Vitamin D deficiency has been linked to several chronic diseases in adults. Studies focusing on children and adolescents, however, are limited. In this randomized cross-sectional study, we aimed to determine the prevalence of vitamin D deficiency and its relationship with childhood obesity and dietary calcium intake among a population of healthy urban Saudi children and adolescents. To achieve this, 331 randomly selected Saudi children (53.8% females and 46.2% males) aged 6-17 years were included. Demographic, medical, and dietary information were collected; anthropometrics were measured. Levels of serum fasting glucose, lipid profile, 25(OH) D, and for albumin corrected calcium were analyzed. Vitamin D deficiency was noted in all subjects, with girls having significantly lower vitamin D levels than boys. Mean calcium intake was found to be 60% of the required dietary allowance (RDA), while the mean vitamin D intake was 23% of RDA. Vitamin D status and calcium intake were comparable in both normal and overweight/obese children and adolescents. Vitamin D status was highest among children who had calcium intake >800 mg/day. In adolescents there was insignificant but decreasing trend in BMI, which was observed to be highest among those whose calcium intake was <250 mg/day and lowest among those taking >800 mg/day.

CONCLUSION

results from this study suggest the importance of vitamin D fortification and increased dietary calcium in the Saudi diet to meet RDA requirements and avoid onset of vitamin D deficiency-related diseases in Saudi children and adolescents.

The link between obesity and low circulating 25-hydroxyvitamin D concentrations: considerations and implications

Obesity and vitamin D deficiency have both been recognized as major public health issues worldwide, and there is growing evidence that they are related, although the cause-effect relationship remains unclear. Could obesity be contributing to low circulating 25-hydroxyvitamin D concentrations? Alternatively, could low vitamin D status predispose to obesity? In this review, the relationship between low circulating 25-hydroxyvitamin D and obesity, and possible underlying reasons from both perspectives, is presented. One potential mechanism by which obesity could contribute to low serum 25-hydroxyvitamin D is adipose sequestration of vitamin D. On the other hand, adipose tissue has both the vitamin D receptor and the ability to synthesize 1,25-dihydroxyvitamin D, and there is evidence that vitamin D may regulate adipose tissue mass, differentiation and metabolism in ways that might contribute to obesity. Of particular interest, vitamin D deficiency is common both before and after bariatric surgery, and is often difficult to treat, particularly with the more malabsorptive procedures. Additional research is needed to elucidate the complex and multifaceted factors underlying the association between low circulating 25-hydroxyvitamin D and obesity, and to identify optimal treatment approaches in obese individuals and in bariatric surgical patients both before and after surgery.

Calcium ameliorates obesity induced by high-fat diet and its potential correlation with p38 MAPK pathway

To investigate whether and on which pathway dietary calcium influence the obesity induced by high-fat diet, thirty male Kunming mice were fed in six groups for 4 weeks and mouse preadipocytes were divided into eight groups for different treatment. Body weight gain was measured each week. Calcium in serum and tissues, intracellular free Ca(2+) concentration ([Ca(2+)]i), blood fat and intracellular lipid content were also measured. The expression of Lipid metabolism-related genes were measured by q RT-PCR. Compared with control group, body weight gain (P < 0.05) and fat pad weight (P < 0.01) in Low calcium group decreased. Triglycerides (TG) and total Cholesterol (TC) level decreased (P < 0.01), while HDL-Cholesterol (HDL) level increased (P < 0.01). And calcium supply increased calcium content in blood serum and tissues. In tissues, adipogenesis and vitamin D receptor (VDR) genes expression decreased but lipoclasis genes expression increased. These anti-obesity effects were more obvious when supplying with 2.8% calcium, but the effects were reduced while supplying Nifedipine at the same time. The results in preadipocytes indicated that calcium-treated can reduce intracellular lipid content, along with adipogenesis and lipoclasis genes expression decrease, promoted the expression levels of p38 MAPK pathway upstream gene MKK6 (P < 0.01) and downstream gene MAPKAPK2 (P < 0.01). Treated with SB203580 could increase adipogenesis genes expression, decrease lipoclasis genes expression and ([Ca(2+)]i) (P < 0.01). These results implied that dietary calcium had remarkable effect on anti-obesity effect and p38 MAPK pathway potentially participated in calcium-mediated lipid accumulation and lipolysis in mouse preadipocytes.

Daily consumption of vitamin D- or vitamin D + calcium-fortified yogurt drink improved glycemic control in patients with type 2 diabetes: a randomized clinical trial

BACKGROUND

Low serum concentrations of 25-hydroxyvitamin D [25(OH)D] have been associated with impaired glucose tolerance and diabetes.

OBJECTIVE

This study aimed to compare the effects of daily intake of vitamin D- or vitamin D(3) + calcium-fortified yogurt drink on glycemic status in subjects with type 2 diabetes (T2D).

DESIGN

Ninety diabetic subjects were randomly allocated to 3 groups to consume plain yogurt drink (PY; containing no vitamin D and 150 mg Ca/250 mL), vitamin D-fortified yogurt drink (DY; containing 500 IU vitamin D(3) and 150 mg Ca/250 mL), or vitamin D + calcium-fortified yogurt drink (DCY; containing 500 IU vitamin D(3) and 250 mg Ca/250 mL) twice per day for 12 wk. Fasting serum glucose (FSG), glycated hemoglobin (Hb A(1c)), homeostasis model assessment of insulin resistance (HOMA-IR), serum lipid profile, and percentage fat mass (FM) were assessed before (baseline) and after the intervention.

RESULTS

In both the DY and DCY groups, mean serum 25(OH)D(3) improved (+32.8 ± 28.4 and +28.8 ± 16.1 nmol/L, respectively; P < 0.001 for both), but FSG [-12.9 ± 33.7 mg/dL (P = 0.015) and -9.6 ± 46.9 mg/dL (P = 0.035)], Hb A(1c) [-0.4 ± 1.2% (P < 0.001) and -0.4 ± 1.9% (P < 0.001)], HOMA-IR [-0.6 ± 1.4 (P = 0.001) and -0.6 ± 3.2 (P < 0.001)], waist circumference (-3.6 ± 2.7 and -2.9 ± 3.3; P < 0.001 for both), and body mass index [in kg/m(2); -0.9 ± 0.6 (P < 0.001) and -0.4 ± 0.7 (P = 0.005)] decreased significantly more than in the PY group. An inverse correlation was observed between changes in serum 25(OH)D(3) and FSG (r = -0.208, P = 0.049), FM (r = -0.219, P = 0.038), and HOMA-IR (r = -0.219, P = 0.005).

CONCLUSION

Daily intake of a vitamin D-fortified yogurt drink, either with or without added calcium, improved glycemic status in T2D patients. This trial was registered at clinicaltrials.gov as NCT01229891.

Influence of calcium and vitamin D supplementation on weight and fat loss in obese women

BACKGROUND

Dairy products not only reduce the risk of hypertension and cardiovascular diseases but may play a role in the treatment of obesity. As there is some evidence that calcium (Ca) and vitamin D may play a role in effective weight management, we decided to evaluate the influence of Ca and vitamin D supplementation on weight and fat loss in obese women.

MATERIAL AND METHODS

Forty obese women were enrolled in this study. Subjects were divided into 2 groups comparable with body mass index (BMI) and age. Group 1 was provided with calcium carbonate and 1-(OH)-vitamin D supplementation. Group 2 was provided with only a diet. Subjects participated in a 3-month weight reduction therapy (balanced diet, modification of life style, and regular physical exercise). Blood samples (serum concentration of Ca, phosphorus (P), parathormone (PTH), 25-(OH)-D3) and clinical characteristics (weight, height, BMI, body composition) were taken at baseline and after the 3-month program.

RESULTS

No significant differences of body weight, body fat content, serum parathormone, 25-(OH)-D3 concentration, and plasma total Ca and P concentration were observed between analyzed groups both before and after the treatment. Additionally, we did not observe any significant influence of Ca and vitamin D supplementation on weight and fat loss.

CONCLUSION

Ca plus vitamin D supplementation during a 3-month low caloric diet has no additional effect on weight and fat loss in obese women.

Dairy calcium supplementation in overweight or obese persons: its effect on markers of fat metabolism

BACKGROUND

Dairy calcium supplementation has been proposed to increase fat oxidation and to inhibit lipogenesis.

OBJECTIVE

We aimed to investigate the effects of calcium supplementation on markers of fat metabolism.

DESIGN

In a placebo-controlled, crossover experiment, 10 overweight or obese subjects who were low calcium consumers received 800 mg dairy Ca/d for 5 wk. After 4 wk, adipose tissue was taken for biopsy for analysis of gene expression. Respiratory exchange, glycerol turnover, and subcutaneous adipose tissue microdialysis were performed for 7 h after consumption of 400 mg Ca or placebo, and the ingestion of either randomized slow-release caffeine (SRC; 300 mg) or lactose (500 mg). One week later, the test was repeated with the SRC or lactose crossover.

RESULTS

Calcium supplementation increased urinary calcium excretion by 16% (P = 0.017) but did not alter plasma parathyroid hormone or osteocalcin concentrations. Resting energy expenditure (59.9 +/- 3.0 or 59.6 +/- 3.3 kcal/h), fat oxidation (58.4 +/- 2.5 or 53.8 +/- 2.2 mg/min), plasma free fatty acid concentrations (0.63 +/- 0.02 or 0.62 +/- 0.03 mmol/L), and glycerol turnover (3.63 +/- 0.41 or 3.70 +/- 0.38 micromol . kg(-1) . min(-1)) were similar with or without calcium, respectively. SRC significantly increased free fatty acid concentrations, resting fat oxidation, and resting energy expenditure. During microdialysis, epinephrine increased dialysate glycerol concentrations by 250% without and 254% with calcium. Expression of 7 key metabolic genes in subcutaneous adipose tissue was not affected by calcium supplementation.

CONCLUSION

Dairy calcium supplementation in overweight subjects with habitually low calcium intakes failed to alter fat metabolism and energy expenditure under resting conditions and during acute stimulation by caffeine or epinephrine.

Effect of dietary calcium and dairy proteins on the adipose tissue gene expression profile in diet-induced obesity

BACKGROUND/AIMS

Calcium and dairy proteins have been postulated to explain why the intake of dairy products correlates inversely with body mass index in several populations. We have shown that a high-calcium diet with whey protein attenuates weight gain and now we describe the effects of this diet on adipose tissue gene expression.

METHODS

Nine-week-old C57Bl/6J mice were divided into two groups (n = 10/group). The control diet was a standard high-fat diet (60% of energy) low in calcium (0.4%). The whey protein diet was a high-calcium (1.8%), high-fat diet with whey protein. After the 21-week treatment, adipose tissue transcript profiling (2 mice/group) was performed using Affymetrix Mouse Genome 430 2.0.

RESULTS

The high-calcium diet with whey protein altered the expression of 129 genes (+/- 1.2 fold). Quantitative RT-PCR analysis confirmed the significant up-regulation of Adrb3 (p = 0.002) and leptin (p = 0.0019) in the high-calcium whey group. Insulin and adipocytokine signaling pathways were enriched among the up-regulated genes and the fatty acid metabolism pathway among the down-regulated genes.

CONCLUSIONS

High-calcium diet with whey protein significantly modifies adipose tissue gene expression. These preliminary findings reveal that targets of a high-calcium diet with whey protein include genes for Adrb3 and leptin, and help to explain how the intake of dairy products might attenuate obesity.

The effects of hydralazine on lipolysis in subcutaneous adipose tissue in humans

Recent evidence from animal research and in vitro experiments indicates that changes in dietary calcium intake could cause changes in lipolysis through alterations of the intracellular calcium concentration in adipocytes. The objective of the study was to examine whether the calcium antagonist hydralazine affects blood flow and lipolysis in subcutaneous abdominal adipose tissue in vivo in humans. Three different concentrations of hydralazine (12.2, 24.4, and 48.8 micromol/L) were locally administered in adipose tissue using the microdialysis technique to assess effects on lipolysis and blood flow in subcutaneous adipose tissue in the abdominal region. Subjects from the general community were studied ambulatorily at a university hospital. Eight healthy men (age, 33.1 +/- 3.3 years; body mass index, 24.2 +/- 0.2 kg/m(2)) were recruited by local announcement. Subcutaneous adipose tissue in the abdominal region was perfused with increasing concentrations of hydralazine. The main outcome measures were adipose tissue lipolysis and blood flow. Hydralazine had no effect on ethanol outflow-inflow ratios, but significantly increased interstitial glycerol concentration at the highest concentration (P < .05). The present results indicate that hydralazine increases lipolysis in abdominal subcutaneous adipose tissue in healthy lean subjects, but hydralazine had no significant effects on local blood flow in adipose tissue.

Calcitriol and calcium regulate cytokine production and adipocyte-macrophage cross-talk

OBJECTIVE

The objective of this study was to investigate the effects of calcitriol on adipocyte and macrophage cytokine expression as well as release and on adipocyte-macrophage cross-talk in local modulation of inflammation.

RESEARCH PROCEDURES AND RESULTS

We investigated calcitriol modulation of the expression of macrophage inhibitory factor (MIF) and macrophage surface-specific protein CD14, two key factors in regulating macrophage function and survival, in differentiated human adipocytes. Calcitriol significantly increased MIF and CD14 expression by 59% and 33%, respectively, while calcium-channel antagonism with nifedipine completely reversed these effects, indicating that calcitriol stimulates MIF and CD14 expression via a calcium-dependent mechanism. Similar results were also found in cultured 3T3-L1 adipocytes; in addition, calcitriol also up-regulated macrophage colony-stimulating factor, macrophage inflammatory protein, interleukin-6 (IL-6) as well as monocyte chemoattractant protein-1 expression in 3T3-L1 adipocytes and stimulated tumor necrosis factor as well as IL-6 expression in RAW 264 macrophages. These effects were blocked by either a calcium-channel antagonist (nifedipine) or a mitochondrial uncoupler (dinitrophenol). Moreover, co-culture of 3T3-L1 adipocytes with RAW 264 macrophages significantly increased the expression and production of multiple inflammatory cytokines in response to calcitriol in both cell types.

CONCLUSIONS

These data demonstrate that calcitriol regulates local inflammation via modulating the interaction between adipocytes and macrophages as well as regulating inflammatory cytokine production in each cell type via calcium-dependent and mitochondrial uncoupling-dependent mechanisms. These data provide further mechanistic explanation for our recent observations that suppression of calcitriol by dietary calcium reduces inflammatory cytokine expression and oxidative stress in adipose tissue.

An intervention study of the effects of calcium intake on faecal fat excretion, energy metabolism and adipose tissue mRNA expression of lipid-metabolism related proteins

CONTEXT

In various observational studies, an inverse relation between calcium intake and body weight has been observed. A possible explanation could be an increased calcium excretion through the faeces caused by an increased dietary calcium intake.

OBJECTIVE

To examine whether an increased calcium intake could lead to changes in faecal fat and energy excretion.

DESIGN

Four different isocaloric diets with various calcium contents (400, 1200 and 2500 mg from dairy and 1200 mg from calcium carbonate (1200S)) were administered in a crossover design for 7 days each.

SUBJECTS

Five healthy men and five healthy women (age=28+/-2, body mass index=24.1+/-0.4, body fat%=25.6+/-2.4) were recruited by local announcement.

MEASUREMENTS

At the end of every intervention period, faecal samples were collected for determination of fat, energy and calcium content, blood samples were obtained for determination of relevant blood parameters; and fat samples were obtained for measurement of the mRNA expression. Furthermore, resting energy expenditure and fat oxidation were measured with the ventilated-hood technique.

RESULTS

We observed a non-significant 56% increase in fat excretion (P=0.159) on the 2500 mg diet, compared to the 400 mg diet. The 2500 mg diet significantly reduced the expression of fatty acid synthase (FAS) mRNA (P<0.05) and the calcium content of the diets significantly affected calcium excretion. Furthermore, we saw a significant decrease of serum triglycerides on the 1200S diet (P<0.05).

CONCLUSION

In this study, we observed a trend towards a higher fat excretion on the high-calcium diet, but this difference failed to reach statistical significance. It is possible that the relatively high protein content of the experimental diets increased calcium absorption from the intestine, thus decreasing the amount of calcium available for binding to fat and eliminating possible effects of dietary calcium on fat excretion. Furthermore, we observed decreases in FAS mRNA expression and serum triglycerides as a result of a high calcium intake.