Induction of STEAP4 correlates with 1,25-dihydroxyvitamin D3 stimulation of adipogenesis in mesenchymal progenitor cells derived from human adipose tissue

Sesamin ameliorates nonalcoholic hepatic steatosis by inhibiting CD36-mediated hepatocyte lipid accumulation in vitro and in vivo

Hepatic steatosis is a critical factor in the development of nonalcoholic steatohepatitis (NASH). Sesamin (Ses), a functional lignan isolated from Sesamum indicum, possesses hypolipidemic, liver-protective, anti-hypertensive, and anti-tumor properties. Ses has been found to improve hepatic steatosis, but the exact mechanisms through which Ses achieves this are not well understood. In this study, we observed the anti-hepatic steatosis effects of Ses in palmitate/oleate (PA/OA)-incubated primary mouse hepatocytes, AML12 hepatocytes, and HepG2 cells, as well as in high-fat, high-cholesterol diet-induced NASH mice. RNA sequencing analysis revealed that cluster of differentiation 36 (CD36), a free fatty acid (FA) transport protein, was involved in the Ses-mediated inhibition of hepatic fat accumulation. Moreover, the overexpression of CD36 significantly increased hepatic steatosis in both Ses-treated PA/OA-incubated HepG2 cells and NASH mice. Furthermore, Ses treatment suppressed insulin-induced de novo lipogenesis in HepG2 cells, which was reversed by CD36 overexpression. Mechanistically, we found that Ses ameliorated NASH by inhibiting CD36-mediated FA uptake and upregulation of lipogenic genes, including FA synthase, stearoyl-CoA desaturase 1, and sterol regulatory element-binding protein 1. The findings of our study provide novel insights into the potential therapeutic applications of Ses in the treatment of NASH.

The association between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio with type 2 diabetes mellitus: recent findings from NHANES 2007-2018

OBJECTIVE

This study aims to assess the relationship between NHHR (non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio) and Type 2 diabetes mellitus (T2DM) in US adults, using National Health and Nutrition Examination Survey (NHANES) data from 2007 to 2018.

METHODS

This study explored the connection between NHHR and T2DM by analyzing a sample reflecting the adult population of the United States (n = 10,420; NHANES 2007-2018). NHHR was characterized as the ratio of non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol. T2DM was defined based on clinical guidelines. This research used multivariable logistic models to examine the connection between NHHR and T2DM. Additionally, it included subgroup and interaction analyses to assess variations among different groups. Generalized additive models, smooth curve fitting, and threshold effect analysis were also employed to analyze the data further.

RESULTS

The study included 10,420 subjects, with 2160 diagnosed with T2DM and 8260 without. The weighted multivariate logistic regression model indicated an 8% higher probability of T2DM for each unit increase in NHHR (OR: 1.08, 95% CI: 1.01-1.15) after accounting for all covariates. Subgroup analysis outcomes were uniform across various categories, demonstrating a significant positive relationship between NHHR and T2DM. Interaction tests showed that the positive link between NHHR and T2DM remained consistent regardless of age, body mass index, smoking status, moderate recreational activities, hypertension, or stroke history, with all interaction P-values exceeding 0.05. However, participants' sex appeared to affect the magnitude of the connection between NHHR and T2DM (interaction P-value < 0.05). Also, a nonlinear association between NHHR and T2DM was discovered, featuring an inflection point at 1.50.

CONCLUSIONS

Our study suggests that an increase in NHHR may be correlated with a heightened likelihood of developing T2DM. Consequently, NHHR could potentially serve as a marker for estimating the probability of T2DM development.

The impact of vitamin D on the etiopathogenesis and the progression of type 1 and type 2 diabetes in children and adults

Diabetes is a common chronic metabolic disease with complex causes and pathogenesis. As an immunomodulator, vitamin D has recently become a research hotspot in the occurrence and development of diabetes and its complications. Many studies have shown that vitamin D can reduce the occurrence of diabetes and delay the progression of diabetes complications, and vitamin D can reduce oxidative stress, inhibit iron apoptosis, promote Ca2+ influx, promote insulin secretion, and reduce insulin resistance. Therefore, the prevention and correction of vitamin D deficiency is very necessary for diabetic patients, but further research is needed to confirm what serum levels of vitamin D3 are maintained in the body. This article provides a brief review of the relationship between vitamin D and diabetes, including its acute and chronic complications.

Vitamin D and obesity

An inverse association between vitamin D status and obesity has been reported across diverse populations and age groups in humans. In animal model of diet-induced obesity, dysregulation of vitamin D metabolism has been observed. However, the causal relationship between vitamin D status and obesity is not conclusive. Several explanations, such as volumetric dilution, sequestration of vitamin D into adipose tissue, and limited sunlight exposure, have been suggested as the underlying mechanisms linking poor vitamin D status and obesity. Vitamin D can modulate adipose tissue biology, spanning from adipocyte differentiation to adipocyte apoptosis and energy metabolism, indicating its potential impact on adiposity. In this chapter, we will review the prevalence of vitamin D deficiency and determinants of vitamin D deficiency among different populations, as well as changes in vitamin D metabolism associated with obesity. Additionally, we will review vitamin D's regulation of adipogenesis and lipogenesis at the cellular level in order to gain a deeper understanding of the underlying mechanisms linking vitamin D levels and obesity.

The Associations of Vitamin D Level with Metabolic Syndrome and Its Components Among Adult Population: Evidence from National Health and Nutrition Examination Survey 2017-2018

Background and Purpose: Vitamin D can both stimulate and inhibit adipogenesis, indicating that associations of the vitamin D level with some metabolic disorders may be nonlinear. This cross-sectional study aims to explore potential nonlinear associations of the 25-hydroxy vitamin D [25(OH)D] level with metabolic syndrome (MetS) and its components. Methods: Adults without previously diagnosed specific noncommunicable disease were selected from the National Health and Nutrition Examination Survey 2017-2018 (n = 870). Their demographic, physical, and laboratory data were obtained. The associations of serum 25(OH)D with MetS and its components were analyzed using logistic regression. Restricted cubic spline was applied to flexibly model the nonlinear association if the nonlinearity test was statistically significant. Results: The 25(OH)D level was inversely associated with risk of MetS [adjusted odds ratio (OR) = 0.986; 95% confidence interval (CI) = 0.978-0.993] and most MetS components, but not with the risk of raised triglycerides (adjusted OR = 0.996; 95% CI = 0.988-1.005). The association of serum 25(OH)D with central obesity risk was significantly nonlinear (P for the nonlinearity test: 0.037). The OR for risk of central obesity decreased rapidly with increase in serum 25(OH)D concentration until the concentration reached 50 nmol/L, and then, the intensity of decrease in OR slowed down. Conclusions: Vitamin D is inversely associated with MetS, but not all MetS components. A nonlinear association between the vitamin D level and risk of central obesity has been found for the first time among the adult population, which reflects the complex roles of vitamin D in lipid metabolism. Although vitamin D deficiency (<50 nmol/L) was defined to avoid abnormal calcium and phosphorus metabolism, preventing its deficiency may also be beneficial for reduction of central obesity risk.

Interplay between Vitamin D and Adipose Tissue: Implications for Adipogenesis and Adipose Tissue Function

Adipose tissue encompasses various types, including White Adipose Tissue (WAT), Brown Adipose Tissue (BAT), and beige adipose tissue, each having distinct roles in energy storage and thermogenesis. Vitamin D (VD), a fat-soluble vitamin, maintains a complex interplay with adipose tissue, exerting significant effects through its receptor (VDR) on the normal development and functioning of adipocytes. The VDR and associated metabolic enzymes are widely expressed in the adipocytes of both rodents and humans, and they partake in the regulation of fat metabolism and functionality through various pathways. These encompass adipocyte differentiation, adipogenesis, inflammatory responses, and adipokine synthesis and secretion. This review primarily appraises the role and mechanisms of VD in different adipocyte differentiation, lipid formation, and inflammatory responses, concentrating on the pivotal role of the VD/VDR pathway in adipogenesis. This insight furnishes new perspectives for the development of micronutrient-related intervention strategies in the prevention and treatment of obesity.

The Relationship Between Non-HDL-C /HDL-C Ratio (NHHR) and Vitamin D in Type 2 Diabetes Mellitus

Purpose

The objective of this research was to examine the relationship between non-HDL cholesterol/HDL cholesterol ratio (NHHR) and vitamin D in type 2 diabetes mellitus (T2DM).

Patients and Methods

This study enrolled 617 T2DM participants. Participants were separated into two groups: no vitamin D deficiency and vitamin D deficiency. Participants were split into two categories: individuals who had a high NHHR and those with a low NHHR, with the median NHHR serving as the cut-off. Eventually, the study participants were classified into two groups by gender, which were further classified into vitamin D deficient and non-vitamin D deficient groups.

Results

NHHR values were substantially greater in vitamin D deficient group than in the non-deficient group in both male and female T2DM patients (P<0.05). The high NHHR group displayed substantially lower vitamin D levels than the low NHHR group [16.21 (12.55,21.35) vs 19.05 (14.59,24.07), P<0.001]. NHHR was discovered to be negatively and independently associated with vitamin D levels, and there was no sex difference.

Conclusion

For the first time, our research revealed a negative relationship between NHHR and vitamin D in patients with T2DM.

Association between Vitamin D Deficiency and Clinical Parameters in Men and Women Aged 50 Years or Older: A Cross-Sectional Cohort Study

Vitamin D deficiency (VDD) is increasingly prevalent on a global scale and is connected to chronic health issues including diabetes, obesity, and inflammation. This study aimed to investigate the association between VDD and various clinical parameters including glycated hemoglobin (HbA1c), body mass index (BMI), and inflammatory markers. This cross-sectional cohort study included Korean men and women aged 50 years and older (290 men, 125 women); VDD was classified as serum 25-hydroxyvitamin D (25[OH]D) levels below 20 ng/mL. Vitamin D deficiency was more prevalent in men (64.5%) compared to that in women (35.2%). Men with VDD had higher fat mass and HbA1c levels, lower muscle strength, and worse physical performance. Among women, VDD was associated with higher BMI, HbA1c, tumor necrosis factor-alpha (TNF-α), and creatinine levels. In women, 25(OH)D levels exhibited an inverse relationship with HbA1c, BMI, and TNF-α concentrations. However, there were no differences in the levels of interleukin-6 and interleukin-1 beta according to vitamin D status in both men and women. Vitamin D deficiency is linked to higher HbA1c, BMI, and inflammatory markers in older Korean women, thus warranting the maintenance of sufficient vitamin D levels for overall health.

Total serum FGF-21 levels positively relate to visceral adiposity differently from its functional intact form

Objective

Increased Fibroblast Growth Factor-21 (FGF-21) circulating levels have been described in obesity. In this observational study, we analysed a group of subjects with metabolic disorders to unravel the putative link between visceral adiposity and FGF-21 serum levels.

Methods

Total and intact serum FGF-21 concentration was measured with an ELISA assay respectively in 51 and 46 subjects, comparing FGF-21 levels in dysmetabolic conditions. We also tested Spearman's correlations between FGF-21 serum levels and biochemical and clinical metabolic parameters.

Results

FGF-21 was not significantly increased in high-risk conditions such as visceral obesity, Metabolic Syndrome, diabetes, smoking, and atherosclerosis. Waist Circumference (WC), but not BMI, positively correlated with total FGF-21 levels (r=0.31, p <0.05), while HDL-cholesterol (r=-0.29, p <0.05) and 25-OH Vitamin D (r=-0.32, p <0.05) showed a significant negative correlation with total FGF-21. ROC analysis of FGF-21 in prediction of increased WC, showed that patients with total FGF-21 level over cut-off value of 161.47 pg/mL presented with impaired FPG. Conversely, serum levels of the intact form of FGF-21 did not correlate with WC and other metabolic biomarkers.

Conclusion

Our newly calculated cut-off for total FGF-21 according to visceral adiposity identified subjects with fasting hyperglycemia. However, waist circumference correlates with total FGF-21 serum levels but does not correlate with intact FGF-21, suggesting that functional FGF-21 does not necessarily relate with obesity and metabolic features.

Vitamin D in Diabetes: Uncovering the Sunshine Hormone's Role in Glucose Metabolism and Beyond

Over the last decades, epidemiology and functional studies have started to reveal a pivotal role of vitamin D in both type 1 and type 2 diabetes pathogenesis. Acting through the vitamin D receptor (VDR), vitamin D regulates insulin secretion in pancreatic islets and insulin sensitivity in multiple peripheral metabolic organs. In vitro studies and both T1D and T2D animal models showed that vitamin D can improve glucose homeostasis by enhancing insulin secretion, reducing inflammation, reducing autoimmunity, preserving beta cell mass, and sensitizing insulin action. Conversely, vitamin D deficiency has been shown relevant in increasing T1D and T2D incidence. While clinical trials testing the hypothesis that vitamin D improves glycemia in T2D have shown conflicting results, subgroup and meta-analyses support the idea that raising serum vitamin D levels may reduce the progression from prediabetes to T2D. In this review, we summarize current knowledge on the molecular mechanisms of vitamin D in insulin secretion, insulin sensitivity, and immunity, as well as the observational and interventional human studies investigating the use of vitamin D as a treatment for diabetes.

Integrated Transcriptome and Microbiota Reveal the Regulatory Effect of 25-Hydroxyvitamin D Supplementation in Antler Growth of Sika Deer

The level of plasma 25-hydroxyvitamin D (25(OH)D) is associated with the growth of the antler, a fast-growing bone organ of Cervidae. However, the benefits of 25(OH)D supplementation on antler growth and the underlying mechanisms remain unclear. Here, the antler growth profile and transcriptome, plasma parameters, rumen bacteria, and metabolites (volatile fatty acids and amino acids) were determined in sika deer in a 25(OH)D supplementation group (25(OH)D, n = 8) and a control group (Ctrl, n = 8). 25(OH)D supplementation significantly increased the antler weight and growth rate. The levels of IGF-1,25(OH)D and 1,25-dihydroxyvitamin D were significantly higher in the 25(OH)D group than in the Ctrl group, while the levels of LDL-C were lower. The levels of valerate and branched-chain amino acids in the rumen fluid were significantly different between the 25(OH)D and Ctrl groups. The bacterial diversity indices were not significantly different between the two groups. However, the relative abundances of the butyrate-producing bacteria (families Lachnospiraceae and Succinivibrionaceae) and the pyruvate metabolism pathway were higher in the 25(OH)D group. The transcriptomic profile of the antler was significantly different between the 25(OH)D and Ctrl groups, with 356 up- and 668 down-regulated differentially expressed genes (DEGs) in the 25(OH)D group. The up-regulated DEGs were enriched in the proteinaceous extracellular matrix and collagen, while the down-regulated DEGs were enriched in the immune system and lipid metabolism pathways. Overall, these results provide novel insights into the effects of 25(OH)D supplementation on the host metabolism, rumen microbiota, and antler transcriptome of sika deer.

A comprehensive insight into the potential roles of VDR gene polymorphism in obesity: a systematic review

Vitamin D receptor (VDR) gene polymorphisms are believed to be involved in the obesity pathogenesis. This study summarises the results of research concerning the association between VDR polymorphisms and obesity. For this survey, the records of common databases were searched until November 2019. Four loci of the VDR gene in four case-controlled and 22 cross-sectional studies were assessed and evaluated. In the case-control studies, no significant association was observed between ApaI and FokI polymorphism with obesity risk. TaqI "T" allele in two studies was related to a higher risk of obesity. One investigation found no relationship between BsmI and obesity, while another article suggested that the "b" allele is more frequently found in obese subjects. The results of cross-sectional studies did not lead to consistent findings. Although the previous studies failed to arrive at conclusive findings, the effects of VDR polymorphism on obesity development cannot be ignored.

Recent insights into vitamin D, adipocyte, and adipose tissue biology

Several studies bring strong evidence for an active role of vitamin D and its metabolites in physiological adipocyte and adipose tissue processes in adulthood. This role includes effects of vitamin D on key adipose tissue and adipocyte biology parameters, including adipogenesis, energy metabolism, and inflammation. Interestingly, recent data also point to a role of maternal vitamin D deficiency in adipocyte and adipose tissue metabolic programming in offspring. This review summarizes the current state of knowledge on the biological effect of vitamin D on adipocyte/adipose tissue physiology.

Vitamin D and Visceral Obesity in Humans: What Should Clinicians Know?

The extraskeletal effect of vitamin D on adipose tissue biology and modulation in human obesity is of great interest and has been extensively investigated. Current evidence from preclinical and clinical studies in human adipose tissue suggests that the anti-inflammatory effects of vitamin D are evident and consistent, whereas the effects of vitamin D on adipocyte differentiation, adipogenesis, and energy metabolism and the effects of vitamin D supplementation on adipokine levels are inconclusive. Interventional studies related to medical and surgical weight loss in humans have shown small or no improvement in vitamin D status. Additionally, the benefit of vitamin D supplementation for the reduction in visceral adipose tissue has only been demonstrated in a few studies. Overall, the findings on the relationship between vitamin D and visceral adipose tissue in humans are still inconclusive. Further studies are required to confirm the beneficial effects of vitamin D on ameliorating adipose tissue dysfunction.

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.

Adipose-specific VDR Deletion Leads to Hepatic Steatosis in Female Mice Fed a Low-Fat Diet

Risk factors for nonalcoholic hepatic steatosis include obesity and vitamin D deficiency which commonly coexist. Thus, the role of vitamin D signaling in the prevention of hepatic steatosis in the absence of obesity or a "Western" high-fat diet is unclear. These studies were performed to address the role of the adipocyte vitamin D receptor (VDR) in the prevention of hepatic steatosis in mice fed a chow diet containing 5% fat by weight. Female mice with adipocyte VDR ablation (Adipoq-Cre; VDRflox/flox) exhibited a mild increase in weight gain at age 70 days, accompanied by an increase in visceral white adipose tissue (VAT) weight. While they did not exhibit evidence of hepatic inflammation or fibrosis, an increase in hepatic lipid content was observed. This was accompanied by an increase in the hepatic expression of genes involved in fatty acid transport and synthesis, as well as fatty acid oxidation. Markers of hepatic inflammation and fibrosis were unaffected by adipocyte VDR ablation. Consistent with the increase in VAT weight in the Adipoq-Cre; VDRflox/flox mice, higher levels of transcripts encoding adipogenesis-related genes were observed in VAT. In contrast to other models of impaired vitamin D signaling studied in the setting of a high-fat or "Western" diet, the Adipoq-Cre; VDRflox/flox mice do not exhibit hepatic inflammation or fibrosis. These findings suggest that the adipocyte VDR regulates hepatic lipid accumulation, but in the absence of obesity or a high-fat diet, is not required to prevent hepatic inflammation or fibrosis.

The association between vitamin D levels and metabolic syndrome components among metropolitan adolescent population

OBJECTIVES

Vitamin D promotes both lipolysis and lipogenesis, and some pediatric studies showed inconsistent associations between vitamin D and metabolic syndrome (MetS). This cross-sectional study aimed to examine the association between vitamin D levels and MetS components among metropolitan adolescents.

METHODS

A total of 4,149 adolescents aged 10-18 years were recruited from 23 metropolises in China. The MetS conditions were assessed according to the International Diabetes Federation consensus definition, and the serum 25-hydroxy vitamin D (25(OH)D) concentrations were analyzed. The association between MetS components and serum 25(OH)D levels was analyzed by the logistic regression model. Restricted cubic spline was applied to the model nonlinear association.

RESULTS

Prevalence of vitamin D deficiency was 74.9%, and 41.2% of study participants had at least one MetS component. After adjustment, the significant trend for a lower waist-to-height ratio was not observed in study participants with higher serum 25(OH)D quartile (p=0.57), but a significant nonlinear association between abdominal obesity and serum 25(OH)D levels was found (p=0.04): the highest risk of abdominal obesity occurred at 14.1 ng/mL of serum 25(OH)D. The association of serum 25(OH)D was significantly inverse with MetS (OR: 0.95; 95% CI: 0.92-0.98), but not with raised triglycerides (OR: 0.99; 95% CI: 0.96-1.01), raised blood pressure (OR: 0.99; 95% CI: 0.97-1.01) and impaired fasting glycemia (OR: 1.03; 95% CI: 1.01-1.04).

CONCLUSIONS

The net effect of vitamin D on lipid metabolism may be concentration-dependent, and the actual effect of vitamin D on MetS process may be complex among metropolitan adolescents, though serum 25(OH)D is inversely associated with MetS.

The Action of Vitamin D in Adipose Tissue: Is There the Link between Vitamin D Deficiency and Adipose Tissue-Related Metabolic Disorders?

Adipose tissue plays an important role in systemic metabolism via the secretion of adipocytokines and storing and releasing energy. In obesity, adipose tissue becomes dysfunctional and characterized by hypertrophied adipocytes, increased inflammation, hypoxia, and decreased angiogenesis. Although adipose tissue is one of the major stores of vitamin D, its deficiency is detective in obese subjects. In the presented review, we show how vitamin D regulates numerous processes in adipose tissue and how their dysregulation leads to metabolic disorders. The molecular response to vitamin D in adipose tissue affects not only energy metabolism and adipokine and anti-inflammatory cytokine production via the regulation of gene expression but also genes participating in antioxidant defense, adipocytes differentiation, and apoptosis. Thus, its deficiency disturbs adipocytokines secretion, metabolism, lipid storage, adipogenesis, thermogenesis, the regulation of inflammation, and oxidative stress balance. Restoring the proper functionality of adipose tissue in overweight or obese subjects is of particular importance in order to reduce the risk of developing obesity-related complications, such as cardiovascular diseases and diabetes. Taking into account the results of experimental studies, it seemed that vitamin D may be a remedy for adipose tissue dysfunction, but the results of the clinical trials are not consistent, as some of them show improvement and others no effect of this vitamin on metabolic and insulin resistance parameters. Therefore, further studies are required to evaluate the beneficial effects of vitamin D, especially in overweight and obese subjects, due to the presence of a volumetric dilution of this vitamin among them.

Monocyte-to-HDL Ratio (MHR) Predicts Vitamin D Deficiency in Healthy and Metabolic Women: A Cross-Sectional Study in 1048 Subjects

Vitamin D deficiency is often linked with Metabolic Syndrome, both being more frequent with ageing and associated with an increase inflammatory state. Recently, monocytes-to-high density lipoprotein (HDL) ratio (MHR) has emerged as a powerful index to predict systemic inflammation. In this cross-sectional study, we investigated the association between circulating vitamin D level (25-OH vitamin D) and inflammatory status in a population of 1048 adult individuals. Our study reveals an inverse association between 25-OH vitamin D levels and MHR in the overall population. When the population is stratified by gender, waist circumference, and body mass index (BMI), we observed that while in men this relation is strongly significative only in condition of central obesity, in women a lifelong negative correlation exists between circulating 25-OH vitamin D and MHR and it is independent of the metabolic status. These observations underscore the relevance of circulating biomarkers such as MHR in the prediction of systemic inflammatory conditions sustained by vitamin D deficiency also in healthy and young women.

Association of vitamin D receptor polymorphisms with metabolic syndrome-related components: A cross-sectional study

BACKGROUND

The association between vitamin D receptor (VDR) polymorphisms and metabolic syndrome (MS) has been demonstrated by epidemiological studies while their correlation remain controversial. The aim of this study is to investigate the association of VDR gene polymorphisms with MS and MS-related components in the two communities of Hangzhou.

METHODS

A total of 394 subjects were enrolled in the cross-sectional study. Four VDR gene polymorphisms (ApaI, BsmI, FokI, and TaqI) were selected based on human genome sequence databases and genotyped using the MassARRAY Analyzer Compact.

RESULTS

In lipid profile, the TT genotype of ApaI had a significantly lower risk of hypertriglyceridemia compared with the GG+GT genotypes (recessive model: OR = 0.141; 95% CI = 0.041-0.486; p < 0.01) and the GG genotype (codominant model: OR = 0.155; 95% CI = 0.044-0.545; p < 0.01). The levels of triglyceride (TG) in the TT genotype of ApaI were lower than the GG+GT genotypes (1.29 ± 0.63 vs. 1.78 ± 1.59 mmol/L, p < 0.01). Furthermore, the AA+GA carriers of BsmI had lower levels of high-density lipoprotein cholesterol (HDL-C) than the GG carriers (1.28 ± 0.29 vs. 1.42 ± 0.34 mmol/L, p < 0.05). The CC+TC carriers of TaqI also suffered from lower HDL-C compared with the TT carriers (1.27 ± 0.29 vs. 1.42 ± 0.34 mmol/L, p < 0.01). For arterial blood pressure, the CC carriers had lower systolic blood pressure (SBP) than the TT+TC carriers (p < 0.01) and the TT carriers of FokI (p < 0.05). However, the FokI polymorphisms were not associated with SBP and the mean blood pressure of both groups laid within the normal range.

CONCLUSIONS

In our study, VDR polymorphisms show no association with the MS risk. The present results suggest that the VDR ApaI polymorphism is associated with hypertriglyceridemia and predisposed to developing MS, while the variants of BsmI and TaqI seem to affect HDL-C. Nevertheless, the effect of FokI variants with SBP is ambiguous.

Effects of Vitamin D3 Supplementation on Body Composition in the VITamin D and OmegA-3 TriaL (VITAL)

CONTEXT

Although observational studies show inverse associations between vitamin D status and body weight/adiposity, there are few large randomized controlled trials (RCTs) investigating this relationship.

OBJECTIVE

To determine whether vitamin D3 supplementation lowers weight or improves body composition.

DESIGN

The VITamin D and OmegA-3 TriaL (VITAL) was a double-blinded, placebo-controlled RCT including 25 871 US adults. This ancillary study was completed in a sub-cohort that underwent body composition assessments at baseline and 2-year follow-up (89% retention).

SETTING

Harvard Clinical and Translational Science Center in Boston.

PARTICIPANTS

771 participants (men ≥ 50 and women ≥ 55 years).

INTERVENTIONS

2 × 2 factorial design of supplemental vitamin D3 (2000 IU/day) and/or omega-3 fatty acids (1 g/day).

MAIN OUTCOME MEASURES

Endpoints were 2-year changes in weight, body mass index (BMI), waist circumference, and total and/or regional fat and lean tissue measures determined by dual-energy X-ray absorptiometry. Effect modification by clinical variables and total and free 25-hydroxyvitamin D (25[OH]D) levels was explored.

RESULTS

There were no effects of supplemental vitamin D3vs placebo on weight, BMI, or measures of adiposity and lean tissue. Effects did not vary by sex, race/ethnicity, fat mass index, or baseline total or free 25(OH)D levels. Vitamin D3 supplementation did slightly improve body fat percentage in participants with normal BMI at baseline, but not in the overweight or obese (P for interaction = 0.04).

CONCLUSIONS

Daily vitamin D3 supplementation vs placebo in the general older population did not improve weight or body composition. Whether supplemental vitamin D3 may benefit individuals with normal BMI warrants further study.

The association between vitamin D receptor polymorphisms and tissue-specific insulin resistance in human obesity

BACKGROUND/OBJECTIVES

To investigate (1) the association of four VDR polymorphisms (TaqI/rs731236, ApaI/rs7975232, FokI/rs10735810, and Bsml/rs1544410) with markers of adiposity and tissue-specific insulin resistance at baseline, after weight loss and weight maintenance; (2) the effect of the VDR polymorphisms in the SAT transcriptome in overweight/obese Caucasians of the DiOGenes cohort.

METHODS

We included 553 adult obese individuals (mean BMI 34.8 kg/m²), men (n = 197) and women (n = 356) at baseline, following an 8-week weight loss intervention and 26 weeks weight maintenance. Genotyping was performed using an Illumina 660W-Quad SNP chip on the Illumina iScan Genotyping System. Tissue-specific IR was determined using Hepatic Insulin Resistance Index (HIRI), Muscle Insulin Sensitivity Index (MISI), and Adipose Tissue Insulin Resistance Index (Adipo-IR). Expression quantitative trait loci (eQTL) analysis was performed to determine the effect of SNPs on SAT gene expression.

RESULTS

None of the VDR polymorphisms were associated with HIRI or MISI. Interestingly, carriers of the G allele of VDR FokI showed higher Adipo-IR (GG + GA 7.8 ± 0.4 vs. AA 5.6 ± 0.5, P = 0.010) and higher systemic FFA (GG + GA: 637.8 ± 13.4 vs. AA: 547.9 ± 24.7 µmol/L, P = 0.011), even after adjustment with age, sex, center, and FM. However, eQTL analysis showed minor to no effect of these genotypes on the transcriptional level in SAT. Also, VDR polymorphisms were not related to changes in body weight and IR as result of dietary intervention (P > 0.05 for all parameters).

CONCLUSIONS

The VDR Fokl variant is associated with elevated circulating FFA and Adipo-IR at baseline. Nevertheless, minor to no effect of VDR SNPs on the transcriptional level in SAT, indicating that putative mechanisms of action remain to be determined. Finally, VDR SNPs did not affect dietary intervention outcome in the present cohort.

The Role of Vitamin D in Adipose Tissue Biology: Adipocyte Differentiation, Energy Metabolism, and Inflammation

Adipose tissue is composed of diverse cell types and plays a major role in energy homeostasis and inflammation at the local and systemic levels. Adipose tissue serves as the main site for vitamin D storage and is among the most important extraskeletal targets of vitamin D which can modulate multiple aspects of adipose tissue biology. Vitamin D may exert inhibitory or stimulatory effects on adipocyte differentiation depending on cell type, stage of differentiation, and the treatment time point. Moreover, vitamin D controls energy metabolism in adipose tissue by affecting fatty acid oxidation, expression of uncoupling proteins, insulin resistance, and adipokine production. Adipose tissue inflammation can have a significant impact on the metabolic disorders often associated with obesity, and vitamin D can modulate the inflammatory response of immune cells and adipocytes within the adipose tissue. This review discusses the role of adipose tissue in vitamin D metabolism, as well as the regulatory role of vitamin D in adipocyte differentiation, adipose tissue energy metabolism, and inflammation, thereby providing insights into the importance of vitamin D in adipose tissue biology.

Maternal vitamin D deficiency increases the risk of obesity in male offspring mice by affecting the immune response

OBJECTIVES

Recently, many epidemiologic and animal studies have indicated that obesity has its origin in early stages of life, including the inappropriate balance of some nutrients. So the objectives of this study were to determine the risk of obesity in male offspring mice as a consequence of maternal vitamin D (VD) deficiency mediating the disordered immune response.

METHODS

C57BL/6J female mice 4 wk old were fed VD-deficient or normal reproductive diets during pregnancy and lactation. Their male offspring were given control and high-fat diets for 16 wk after weaning and then weighed and euthanized. The serum was collected for biochemical analyses. Epididymal (eWAT) and inguinal white adipose tissue (iWAT) were excised for histologic examination, immunohistochemistry, gene expression of inflammatory factors, and determination by flow cytometry of the proportions of immune cells.

RESULTS

Insufficient maternal VD intake exacerbated the development of obesity in male offspring mice that were both obese and non-obese, as evidenced by larger adipose cells and abnormal glucose and lipid metabolisms. Also, the expressions of proinflammatory cytokines were increased and that of anti-inflammatory cytokines was decreased in eWAT and/or iWAT in the maternal VD-deficient group, accompanied by higher levels of tumor necrosis factor-α and/or interferon-γ and lower levels of interleukin-4 and interleukin-10. Insufficient maternal VD intake was also observed to induce a shift in the profiles of immune cells in the eWAT and/or iWAT of male offspring that were both obese and non-obese, resulting in increased percentages of M1 macrophages, adipose tissue dendritic cells, and CD4⁺ and CD8⁺ T cells but a significant decrease in the percentages of M2 macrophages. All these changes in the immune cell profile were more obvious in the eWAT than those in the iWAT.

CONCLUSIONS

Maternal VD deficiency might promote the development of obesity in male offspring mice partly by modulating the immune cell populations and causing a polarization in the adipose depots.

The Relationship Between Hemoglobin Glycation Variation Index and Vitamin D in Type 2 Diabetes Mellitus

OBJECTIVE

This study aimed to investigate the relationship between hemoglobin glycation variation index (HGI) and vitamin D in patients with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

This is a cross-sectional study that recruited 347 patients with T2DM. The subjects were divided into no vitamin D deficiency group (25(OH)D ≥20 ng/mL) and vitamin D deficiency group (25(OH)D < 20 ng/mL). HGI was calculated as the difference between the measured and predicted values of HbA1c using the linear relationship between HbA1c level and fasting plasma glucose levels. All study participants were divided into high HGI and low HGI groups using the median of HGI as the boundary. At last, the subjects were divided into male group and female group, and these groups were further subdivided into vitamin D deficiency group and no vitamin D deficiency group.

RESULTS

The levels of HGI were significantly higher in the vitamin D deficiency group compared with the no vitamin D deficiency group for all patients. The same was true for female patients but not for male patients. The prevalence of vitamin D deficiency in the high HGI group was higher than that in the low HGI group. The high HGI group had lower vitamin D levels compared to the low HGI group. Compared to the male group, the female group had lower vitamin D levels but higher HGI levels. A negative correlation existed between 25(OH) D and HGI in all subjects, as well as in the female-only subgroups. In the male-only subgroups, there was no correlation between them, and this positive correlation still existed after adjusting for other factors in multilinear regression analysis.

CONCLUSION

Our study showed for the first time that HGI is inversely associated with vitamin D in all patients with T2DM, and the correlation was also found in female patients, but not in male patients.

Vitamin D and Kidney Diseases: A Narrative Review

Vitamin D (Vit. D) is among the most important elements of the human body that play pivotal roles in health and disease. It belongs to the fat-soluble secosteroid family, which is provided by either foods or direct exposure to sunlight that converts 7-hydroxycholesterol to the Vit. D precursor. An alternative step is bio-activation, which delivers an active form of Vit. D (Vit. D3), which participates in various noticeable functions including calcium regulation, bone remodeling, fertility, glucose control, and detoxification. The most recent literature is carefully reviewed (2049 articles) and the relative information was collected and discussed meticulously. Inclusion criteria were the articles that mentioned the relationship between Vit. D, adipokine, and kidney disease and exclusion criteria were nonrelevant articles. Vit. D plays several roles in the normal function of the kidney and metabolism. It has been revealed that Vit. D has a crucial impact on kidney disease and that its deficiency leads to kidney dysfunction and further renal disorder. Apart from the direct relationship of Vit. D with kidney disease, the association of adipocytes and adipokines with Vit. D and kidney function has also been studied. The noticeable role of Vit. D in kidney disease is investigated in various studies. It has been found that Vit. D has a pivotal role in kidney function and metabolism. Further study can reveal the better-detailed information about the exact relation of Vit. D and kidney disorders. The aim of the review was to provide a better insight into the exact role of Vit. D and adipokine in the kidney disease.

The Molecular Mechanisms by Which Vitamin D Prevents Insulin Resistance and Associated Disorders

Numerous studies have shown that vitamin D deficiency is very common in modern societies and is perceived as an important risk factor in the development of insulin resistance and related diseases such as obesity and type 2 diabetes (T2DM). While it is generally accepted that vitamin D is a regulator of bone homeostasis, its ability to counteract insulin resistance is subject to debate. The goal of this communication is to review the molecular mechanism by which vitamin D reduces insulin resistance and related complications. The university library, PUBMED, and Google Scholar were searched to find relevant studies to be summarized in this review article. Insulin resistance is accompanied by chronic hyperglycaemia and inflammation. Recent studies have shown that vitamin D exhibits indirect antioxidative properties and participates in the maintenance of normal resting ROS level. Appealingly, vitamin D reduces inflammation and regulates Ca²⁺ level in many cell types. Therefore, the beneficial actions of vitamin D include diminished insulin resistance which is observed as an improvement of glucose and lipid metabolism in insulin-sensitive tissues.

Vitamin D regulation of adipogenesis and adipose tissue functions

Vitamin D insufficiency is associated with obesity and its related metabolic diseases. Adipose tissues store and metabolize vitamin D and expression levels of vitamin D metabolizing enzymes are known to be altered in obesity. Sequestration of vitamin D in large amount of adipose tissues and low vitamin D metabolism may contribute to the vitamin D inadequacy in obesity. Vitamin D receptor is expressed in adipose tissues and vitamin D regulates multiple aspects of adipose biology including adipogenesis as well as metabolic and endocrine function of adipose tissues that can contribute to the high risk of metabolic diseases in vitamin D insufficiency. We will review current understanding of vitamin D regulation of adipose biology focusing on vitamin D modulation of adiposity and adipose tissue functions as well as the molecular mechanisms through which vitamin D regulates adipose biology. The effects of supplementation or maintenance of vitamin D on obesity and metabolic diseases are also discussed.

Effects of Vitamin D Status on Inflammatory Markers in Obese Subjects: A Systematic Review

Background:

Recent studies have demonstrated the role of micronutrients in the manifestation of comorbidities associated with obesity. Vitamin D deficiency, in particular, appears to be associated with increased levels of inflammatory markers, which may lead to chronic low-grade inflammation, elevating the risk of chronic diseases such as diabetes, metabolic syndrome, and cardiovascular disease. The objective of this study was to perform a systematic review of observational studies conducted to investigate the effect of vitamin D deficiency on inflammatory markers in obese subjects.

Methodology:

This systematic review was conducted in accordance with the “STROBE” and PRISMA recommendations. Observational studies that evaluated the effect of vitamin D status on inflammatory markers in obese subjects were selected and reviewed. Searches were conducted in the PubMed, SciVerse Scopus, and Web of Science databases from February 21 to 22, 2018.

Results:

After the selection and removal of duplicate articles, 10 eligible articles were identified. Results from eight observational studies showed an association between vitamin D deficiency or insufficiency in the body and increased concentrations of inflammatory markers in obese individuals. On the other hand, two of the studies did not demonstrate any correlation. With regard to the inflammatory markers evaluated, eight studies showed high concentrations of ultra-sensitive C-reactive protein, five studies found an increase in interleukin-6 concentrations, and two studies noted increased levels of tumor necrosis factor.

Conclusion:

The data presented in this systematic review provide evidence of the association between vitamin D deficiency and increased inflammation in obesity.

Correlation of serum vitamin D, adipose tissue vitamin D receptor, and peroxisome proliferator-activated receptor γ in women with gestational diabetes mellitus

Background:

Gestational diabetes mellitus (GDM) is a common complication during pregnancy. Obesity and overweight are closely related to metabolic diseases and diabetes. However, the role of adipose tissue in the pathogenesis of GDM remains to be studied. The aim of this study was to investigate the correlation of vitamin D (VD) levels, VD receptor (VDR), and peroxisome proliferator-activated receptor γ (PPARγ) expression with GDM in overweight or obese women.

Methods:

One hundred and forty pregnant women with full-term single-birth cesarean-section were selected as the study subjects and grouped (70 GDM women, including 35 non-overweight/non-obese women [group G1] and 35 women with overweight or obesity [group G2]; 70 pregnant women with normal glucose tolerance, including 35 non-overweight/non-obese women [group N1] and 35 overweight/obese women [group N2]). The levels of serum VD, blood biochemistry, and adiponectin were compared in these women. Subcutaneous adipose tissue was isolated from the abdominal wall incision. VDR and PPARγ messenger RNA (mRNA) transcript levels in these adipose tissues were quantified by real-time polymerase chain reaction. The differences between the levels of PPARγ protein and phosphorylated PPARγ Ser273 were detected by Western blotting.

Results:

The serum VD level of GDM women was lower in comparison to that of women with normal glucose tolerance (G1 vs. N1: 20.62 ± 7.87 ng/mL vs. 25.85 ± 7.29 ng/mL, G2 vs. N2: 17.06 ± 6.74 ng/mL vs. 21.62 ± 7.18 ng/mL, P < 0.05), and the lowest in overweight/obese GDM women. VDR and PPARγ mRNA expression was higher in the adipose tissues of GDM women in comparison to that of women with normal glucose tolerance (VDR mRNA: G1 vs. N1: 210.00 [90.58–311.46] vs. 89.34 [63.74–159.92], G2 vs. N2: 298.67 [170.84–451.25] vs. 198.28 [119.46–261.23], PPARγ mRNA: G1 vs. N1: 100.72 [88.61–123.87] vs. 87.52 [66.37–100.04], G2 vs. N2: 117.33 [100.08–149.00] vs. 89.90 [76.95–109.09], P < 0.05), and their expression was the highest in GDM + overweight/obese women. VDR mRNA levels positively correlated with the pre-pregnancy body mass index (BMI), pre-delivery BMI, fasting blood glucose (FBG), homeostasis model assessment of insulin resistance (HOMA-IR), and PPARγ mRNA while it negatively correlated with the VD and the adiponectin levels (r = 0.395, 0.336, 0.240, 0.190, 0.235, –0.350, –0.294, respectively, P < 0.05). The degree of PPARγ Ser273 phosphorylation increased in obese and GDM pregnant women. PPARγ mRNA levels positively correlated with pre-pregnancy BMI, pre-delivery BMI, FBG, HOMA-IR, serum total cholesterol, triglyceride, free fatty acid, and VDR mRNA, while it negatively correlated with the VD and adiponectin levels (r = 0.276, 0.199, 0.210, 0.230, 0.182, 0.214, 0.270, 0.235, –0.232, –0.199, respectively, P < 0.05).

Conclusions:

Both GDM and overweight/obese women had decreased serum VD levels and up-regulated VDR and PPARγ mRNA expression in adipose tissue, which was further higher in the overweight or obese women with GDM. VD may regulate the formation and differentiation of adipocytes through the VDR and PPARγ pathways and participate in the occurrence of GDM.

Vitamin D Receptor Gene Expression in Adipose Tissue of Obese Individuals is Regulated by miRNA and Correlates with the Pro-Inflammatory Cytokine Level

Background: Given the role that vitamin D (VD) plays in the regulation of the inflammatory activity of adipocytes, we aimed to assess whether obesity changes the expression of VD-related genes in adipose tissue and, if so, to investigate whether this phenomenon depends on microRNA interference and how it may influence the local inflammatory milieu. Methods: The expression of genes encoding VD 1α-hydroxylase (CYP27B1), 24-hydroxylase (CYP24A1) and receptor (VDR), selected interleukins and microRNAs was evaluated by real-time PCR in visceral (VAT) and in subcutaneous (SAT) adipose tissues of 55 obese (BMI > 40 kg/m²) and 31 normal-weight (BMI 20–24.9 kg/m²) individuals. Results: VDR mRNA levels were higher, while CYP27B1 levels were lower in adipose tissues of obese patients than in those of normal-weight controls (VAT: P = 0.04, SAT: P < 0.0001 and VAT: P = 0.004, SAT: P = 0.016, respectively). The expression of VDR in VAT of obese subjects correlated negatively with levels of miR-125a-5p (P = 0.0006, r_s = −0.525), miR-125b-5p (P = 0.001, r_s = −0.495), and miR-214-3p (P = 0.009, r_s = −0.379). Additionally, VDR mRNA concentrations in visceral adipose tissues of obese subjects correlated positively with mRNA levels of interleukins: 1β, 6 and 8. Conclusions: We observed obesity-associated up-regulation of VDR and down-regulation of CYP27B mRNA levels in adipose tissue. VDR expression correlates with the expression of pro-inflammatory cytokines and may be regulated by miRNAs.

Vitamin D deficiency in the aetiology of obesity-related insulin resistance

The obese insulin-resistant state is often associated with low circulating concentration of vitamin D 25-hydroxyvitamin D₃ [25(OH)D₃ ]. Fat sequestration of vitamin D in the expanded obese adipose tissue mass has been pointed out as a plausible explanation for this circulating vitamin D deficiency. However, the putative mechanisms behind this hypovitaminosis D remain to be elucidated. The presence of vitamin D receptor and vitamin D-metabolizing enzymes in insulin-sensitive organs suggests that vitamin D may be involved in glucose and lipid metabolism and may be related to insulin sensitivity. Indeed, mainly in vitro studies support a role of vitamin D in regulating glucose and lipid metabolism in several insulin-sensitive tissues including adipose tissue, skeletal muscle, liver, as well as pancreatic insulin secretion. A potential role of vitamin D in gut barrier function and metabolism has also been suggested. This review summarizes recent knowledge on vitamin D deficiency in the aetiology of obesity-related insulin resistance and discusses potential underlying mechanisms. Finally, the role of vitamin D supplementation on insulin sensitivity and glycaemic control is discussed.

Effect of Vitamin D3 on the Postprandial Lipid Profile in Obese Patients: A Non-Targeted Lipidomics Study

Abstract: Postprandial lipemia can lead to an accumulation of atherogenic lipoproteins in the circulation associated with systemic low-grade inflammation and an increased risk of cardiovascular disease. Lifestyle and pharmacological treatments are usually prescribed for prevention. Vitamin D₃ (cholecalciferol), as an anti-atherogenic agent, is being taken into consideration due to its potential beneficial effects in lipid metabolism and its anti-inflammatory potency. To assess the effects of vitamin D₃ in the postprandial lipid profile in obese, vitamin D-deficient women, a non-targeted lipidomics approach using liquid chromatography coupled to a quadrupole time-of flight mass spectrometer was used to identify and quantitate a wide-range of circulating lipid species, including diglycerides, lysophosphatidylcholines, phosphatidylcholines, phosphatidylethanolamines, sphingomyelins and triglycerides. The most important changes were found in plasmatic sphingomyelin levels, which experience a decrease after vitamin D₃ intake. Our results suggest a turnover of sphingomyelins, probably due to an increased activity of neutral sphingomyelinases, and, therefore, with implications in the clearance of chylomicrons, LDL and VLDL, decreasing postprandial inflammation and macrophage adherence to endothelia, potentially improving cardiovascular disease risk.

Crosstalk among adipose tissue, vitamin D level, and biomechanical properties of hypertrophic burn scars

PURPOSE

This cross-sectional study aimed to investigate whether adipose tissue loss and reduced vitamin D levels following severe burn injury are associated with pathologic scar formation and biomechanical scar properties.

METHODS

A total of 492 male subjects with hypertrophic burn scars were enrolled from January 2014 to July 2018 and analyzed. Body fat content was measured using dual-energy X-ray absorptiometry. Values of melanin, erythema, and trans-epidermal water loss (TEWL) and the distensibility and elasticity of hypertrophic scars were examined using pigment- and TEWL-measuring devices and a suction skin elasticity meter.

RESULTS

Burn patients with higher fat percentage tended to have higher 25(OH) vitamin D levels (P < 0.001). As body fat percentage increased, hypertrophic scars showed higher mean value of Uf (distensibility, P < 0.001) and lower mean value of Uv/Ue (viscoelasticity or interstitial fluid shifting, P < 0.001). Burn patients with higher 25(OH) vitamin D levels tended to have higher mean values of Uf (P < 0.001) and Ua/Uf (gross elasticity, P = 0.013) and lower mean value of Uv/Ue (P = 0.008).

CONCLUSION

Adipose tissue loss and decreased 25(OH) vitamin D levels following burn injury were related to scar rigidity and slow interstitial fluid shifting in hypertrophic scars.

1α,25(OH)2 D3 alleviates high glucose-induced lipid accumulation in rat renal tubular epithelial cells by inhibiting SREBPs

Lipid accumulation is a vital event in the progression of diabetic nephropathy. 1,25-Dihydroxyvitamin D3 (1α,25(OH)₂ D₃ ) is considered to have a protective effect on diabetic nephropathy. However, it remains unclear whether 1α,25(OH)₂ D₃ can inhibit lipid accumulation, and the potential mechanisms responsible for lipid metabolism are incompletely understood. In this study, we evaluated the effects of 1α,25(OH)₂ D₃ on lipid metabolism in high glucose-exposed rat renal tubular epithelial NRK-52E cells. Results indicated that high glucose-enhanced lipid accumulation in NRK-52E cells and 1α,25(OH)₂ D₃ can remarkably decrease high glucose-induced lipid accumulation. Western blot showed that 1α,25(OH)₂ D₃ alleviated high glucose-induced upregulation of sterol regulatory element-binding protein-1c (SREBP-1c) and SREBP2, along with their established target genes fatty acid synthase (FASN) and hydroxymethylglutaryl CoA reductases (HMGCR). Overall, these findings suggest that 1α,25(OH)₂ D₃ downregulated the expressions of SREBPs to inhibit high glucose-induced lipid accumulation, which provides new sights into the protective effects of 1α,25(OH)₂ D₃ on diabetic nephropathy.

Analysis of Association between Vitamin D Deficiency and Insulin Resistance

Recent evidence revealed extra skeleton activity of vitamin D, including prevention from cardiometabolic diseases and cancer development as well as anti-inflammatory properties. It is worth noting that vitamin D deficiency is very common and may be associated with the pathogenesis of insulin-resistance-related diseases, including obesity and diabetes. This review aims to provide molecular mechanisms showing how vitamin D deficiency may be involved in the insulin resistance formation. The PUBMED database and published reference lists were searched to find studies published between 1980 and 2019. It was identified that molecular action of vitamin D is involved in maintaining the normal resting levels of ROS and Ca²⁺, not only in pancreatic β-cells, but also in insulin responsive tissues. Both genomic and non-genomic action of vitamin D is directed towards insulin signaling. Thereby, vitamin D reduces the extent of pathologies associated with insulin resistance such as oxidative stress and inflammation. More recently, it was also shown that vitamin D prevents epigenetic alterations associated with insulin resistance and diabetes. In conclusion, vitamin D deficiency is one of the factors accelerating insulin resistance formation. The results of basic and clinical research support beneficial action of vitamin D in the reduction of insulin resistance and related pathologies.

Sequential Treatment with Eldecalcitol After PTH Improves Bone Mechanical Properties of Lumbar Spine and Femur in Aged Ovariectomized Rats

Parathyroid hormone (PTH) analogs have a powerful anabolic effect on bone and are used in the treatment of patients with severe osteoporosis. However, there are limitations to how long they can be safely administered. Withdrawal of PTH results in the cancelation of its effects, necessitating subsequent treatment to maintain the bone quantity and quality. This study assessed the effects of Eldecalcitol (ELD), an active vitamin D3 derivative, after PTH in estrogen-deficient osteoporotic rats. Six-month-old female rats were ovariectomized, and PTH administration was started 7 weeks later. After 4 weeks of PTH treatment, the animals were divided into three groups and either continued to receive PTH (PTH-PTH), or were switched to ELD (PTH-ELD) or vehicle (PTH-Veh) for an additional 4 weeks. In the femur, increased BMD by 4 weeks treatment of PTH was significantly reduced in PTH-Veh but not in PTH-PTH and PTH-ELD. The same tendency was observed in the lumbar vertebrae. MicroCT imaging and histomorphometry analysis revealed that the favorable bone structure changes by PTH administration were also maintained in the femurs and tibias of the PTH-PTH and PTH-ELD groups. Increased bone strength by 4-week treatment of PTH in lumber also maintained in PTH-ELD. Furthermore, minimodeling was observed in the PTH-ELD group. These results demonstrate that treatment with ELD sequentially following PTH prevented the bone quantity and strength reduction that accompanies PTH withdrawal in estrogen-deficient rats.

Mobilising vitamin D from adipose tissue: The potential impact of exercise

Vitamin D is lipophilic and accumulates substantially in adipose tissue. Even without supplementation, the amount of vitamin D in the adipose of a typical adult is equivalent to several months of the daily reference nutrient intake (RNI). Paradoxically, despite the large amounts of vitamin D located in adipose tissue, individuals with obesity are often vitamin D deficient according to consensus measures of vitamin D status (serum 25-hydroxyvitamin D concentrations). Thus, it appears that vitamin D can become 'trapped' in adipose tissue, potentially due to insufficient lipolytic stimulation and/or due to tissue dysfunction/adaptation resulting from adipose expansion. Emerging evidence suggests that exercise may mobilise vitamin D from adipose (even in the absence of weight loss). If exercise helps to mobilise vitamin D from adipose tissue, then this could have important ramifications for practitioners and policymakers regarding the management of low circulating levels of vitamin D, as well as chronically low levels of physical activity, obesity and associated health conditions. This perspective led us to design a study to examine the impact of exercise on vitamin D status, vitamin D turnover and adipose tissue vitamin D content (the VitaDEx project). The VitaDEx project will determine whether increasing physical activity (via exercise) represents a potentially useful strategy to mobilise vitamin D from adipose tissue.

Maternal vitamin D deficiency and developmental origins of health and disease (DOHaD)

Vitamin D is an essential nutrient that is metabolized in the body to generate an active metabolite (1,25(OH)2D) with hormone-like activity and highly diverse roles in cellular function. Vitamin D deficiency (VDD) is a prevalent but easily preventable nutritional disturbance. Emerging evidence demonstrates the importance of sufficient vitamin D concentrations during fetal life with deficiencies leading to long-term effects into adulthood. Here, we provide a detailed review and perspective of evidence for the role of maternal VDD in offspring long term health, particularly as it relates to Developmental Origins of Health and Disease (DOHaD). We focus on roles in neurobehavioral and cardiometabolic disorders in humans and highlight recent findings from zebrafish and rodent models that probe potential mechanisms linking early life VDD to later life health outcomes. Moreover, we explore evidence implicating epigenetic mechanisms as a mediator of this link. Gaps in our current understanding of how maternal VDD might result in deleterious offspring outcomes later in life are also addressed.

Role or Synergistic Interaction of Adenosine and Vitamin D3 Alongside High-Intensity Interval Training and Isocaloric Moderate Intensity Training on Metabolic Parameters: Protocol for an Experimental Study

Background

Obesity is known as one of the major causes of epidemiologic diseases worldwide; therefore, the introduction of treatment strategies by medical professionals, such as the use of various medicines and exercise programs to reduce fat or prevent obesity, is on the rise. Recently, researchers have shown special interest in assessing the effect of lipolytic adenosine and vitamin D deficiency, as well as the effect of exercise, on decreasing body fat percentage.

Objective

This study has been designed to examine the effect of adenosine and vitamin D3 injections, in conjunction with high-intensity interval training and isocaloric moderate-intensity training, on the metabolic parameters of obesity induced by a high-fat diet.

Methods

This is an experimental study using 92 Wistar rats. At 6 weeks of age, the rats' weights will be recorded, after which they will have 1 week to adapt to their new environment before being divided into 12 groups. The rats will participate in a 2-stage experimental intervention, including a 13-week fattening diet phase followed by a 12-week exercise training phase consisting of an exercise program and the injection of adenosine and vitamin D3. Groups 1 and 2 will have a normal diet, and the other groups will have a diet of 40% fat, with free access to food and water up to the second half of the second stage of the study (end of the sixth week of training). After termination of the interventions, tissue collection and molecular assessments (blood for biochemical, tissues for gene expression analyses, and anthropometrical indexes) will be performed.

Results

The project was initiated in April 2017 and completed in December 2017. Data analysis is under way, and the first results are expected to be submitted for publication in November 2018.

Conclusions

We hypothesize that weight loss–induced molecular changes and upregulation will be observed in line with an increase in lipolysis and beta oxidation in muscle and fat tissue as a result of performing isocaloric training in drug-receiving rats and groups on a high-fat diet.

International Registered Report Identifier (IRRID)

RR1-10.2196/10753

Sex-Specific Association of Serum 25-Hydroxyvitamin D3 with Insulin Resistance in Chinese Han Patients with Newly Diagnosed Type 2 Diabetes Mellitus

This study aimed to explore the association between serum 25-hydroxyvitamin D (25(OH)D) and insulin resistance as well as β-cell function in Chinese Han patients with newly diagnosed type 2 diabetes mellitus (T2DM). A total of 264 patients was included in this study. Serum 25(OH)D, plasma glucose, serum insulin and other biochemical parameters were assayed. Postprandial venous blood was collected after a mixed-nutrient load. Insulin resistance was assessed by the homeostasis model assessment for insulin resistance (HOMA-IR) and Matsuda insulin sensitivity index (Matsuda ISI). The β-cell function was assessed by the homeostasis model assessment for insulin secretion (HOMA-β) and the change in insulin divided by change in glucose from 0 to 30 min (ΔI_0-30/ΔG_0-30). Patients were divided into three groups according to tertiles of serum 25(OH)D levels. There were significant differences in HOMA-IR and Matsuda ISI among the three groups (HOMA-IR, p=0.005; Matsuda ISI, p=0.009). Pearson correlation analyses showed that serum 25(OH)D was negatively correlated with fasting serum insulin (FIns) (r=-0.209, p=0.012) and HOMA-IR (r=-0.273, p=0.001), and positively correlated with Matsuda ISI (r=0.219, p=0.009) only in the male population. Multiple stepwise regression analyses showed that in the male population, serum 25(OH)D was an independent predictor for both HOMA-IR and Matsuda ISI before and after adjustment for confounding factors, respectively (p<0.05 for both). This study indicates the association of vitamin D with insulin resistance in male patients with newly diagnosed T2DM, which may contribute to the understanding of the mechanism underlying the onset of T2DM in the Chinese Han population.

Leptin blocks the inhibitory effect of vitamin D on adipogenesis and cell proliferation in 3T3-L1 adipocytes

Recently, we demonstrated high serum leptin and 25(OH)D (calcidiol) in obese animals, with high C/EBP_β and PPAR_γ expression in adipose tissue. Since the role of vitamin D in adipogenesis remains controversial and hyperleptinemia is found in obesity, we asked if leptin could interfere in vitamin D action on adipocytes. Here, we studied the direct effect of these two hormones upon 3T3L1 preadipocytes incubated with or without 1,25(OH)2D (100 nM, 24 h) and with leptin (10^-7 M, 4 h later). RT-PCR (VDR and Cyp27b1/1α-hydroxylase), western blotting (VDR, Cyp27b1/1α-hydroxylase, ObR-b, C/EBP_β, PPAR_γ and Bax content), a cell proliferation assay and an Annexin V-FITC binding assay were performed. Incubation with 1,25(OH)2D decreased Cyp27b1/1α-hydroxylase and VDR. Co-incubation of 1,25(OH)2D and leptin did not change Cyp27b1/1α-hydroxylase and had no additive effect upon the decreased VDR mRNA. Incubation with 1,25(OH)2D decreased C/EBP_β and PPARγ. In the cell proliferation assay, 1,25(OH)2D decreased the number of 3T3L1 cells. No changes in OBR-b or apoptotic parameters (Bax and annexin-V) were observed. The 1,25(OH)2D decreased pro-adipogenic factors and proliferation of adipocytes. However, since it inhibits the conversion of 25(OH)D to 1,25(OH)2D and VDR mRNA long-term, it could decrease the vitamin D response in adipocytes, leading to greater adipogenesis. The co-incubation of both hormones, simulating what occurs in obesity, even neutralizing the effect on Cyp27b1/1α-hydroxylase, did not change the vitamin D sensitivity but decreased SOCS-3 and pSTAT-3. Thus, an excess of vitamin D and hyperleptinemia could decrease vitamin D sensitivity in adipocytes, contributing to increased adipogenesis.

1,25-Dihydroxyvitamin D regulates lipid metabolism and glucose utilization in differentiated 3T3-L1 adipocytes

It is well established that adipose tissue can both store and metabolize vitamin D. The active form of vitamin D, 1,25 dihydroxyvitamin D [1,25(OH)₂D], regulates adipocyte differentiation and inflammation, highlighting the multifaceted role that vitamin D plays in adipose tissue physiology. However, there is limited evidence regarding vitamin D regulation of mature adipocyte lipid metabolism. We hypothesize that 1,25(OH)₂D alters lipid and glucose metabolism in differentiated 3T3-L1 adipocytes to reduce triacylglycerol (TAG) accumulation. In this study, 1,25(OH)₂D (10 nmol/L) stimulated a 21% reduction in TAG accumulation in differentiated 3T3-L1 adipocytes after 4 days (P = .01) despite a significant increase in fatty acid uptake (P < .01). Additionally, 1,25(OH)₂D stimulated a 2.5-fold increase in ¹⁴CO₂ production from [1-¹⁴C] palmitic acid (P < .01), indicative of an elevated rate of fatty acid β-oxidation, while stimulating a 9% reduction in de novo fatty acid synthesis (P = .03). Interestingly, d-[U-¹³C]glucose incorporation into fatty acids was reduced by 30% in response to 1,25(OH)₂D (P < .01), indicating a reduced contribution of glucose as a substrate for de novo lipogenesis. Consistent with these findings, mRNA expression of the anaplerotic enzyme pyruvate carboxylase was reduced by 41% (P < .01). In summary, 1,25(OH)₂D stimulated fatty acid oxidation and reduced TAG accumulation in differentiated adipocytes. Furthermore, 1,25(OH)₂D reduced glucose utilization as a substrate for fatty acid synthesis potentially by downregulating pyruvate carboxylase and stimulating glucose disposal as glycerol. Collectively, these 1,25(OH)₂D-induced changes in lipid metabolism and glucose utilization may contribute to the reduction in TAG accumulation and be protective against excessive fat mass accumulation and associated metabolic disorders.

Marrow Fat-a New Target to Treat Bone Diseases?

PURPOSE OF REVIEW

The goal of this review is to summarize recent findings on marrow adipose tissue (MAT) function and to discuss the possibility of targeting MAT for therapeutic purposes.

RECENT FINDINGS

MAT is characterized with high heterogeneity which may suggest both that marrow adipocytes originate from multiple different progenitors and/or their phenotype is determined by skeletal location and environmental cues. Close relationship to osteoblasts and heterogeneity suggests that MAT consists of cells representing spectrum of phenotypes ranging from lipid-filled adipocytes to pre-osteoblasts. We propose a term of adiposteoblast for describing phenotypic spectrum of MAT. Manipulating with MAT activity in diseases where impairment in energy metabolism correlates with bone functional deficit, such as aging and diabetes, may be beneficial for both. Paracrine activities of MAT might be considered for treatment of bone diseases. MAT has unrecognized potential, either beneficial or detrimental, to regulate bone homeostasis in physiological and pathological conditions. More research is required to harness this potential for therapeutic purposes.

The role of vitamin D in adipogenesis

Vitamin D, a secosteroid predominately obtained by endogenous production, has in recent years been linked to obesity and its comorbidities. The purpose of this review is to draw conclusions from animal and human studies on the effects of vitamin D on adipogenesis to identify the molecular links between vitamin D and obesity. The information presented herein was obtained from 4 databases (PubMed, CINAHL, Cochrane Library, Scopus) using predefined search terms, as well as research literature and other reviews. The effects of vitamin D on adipogenesis have been researched in several animal models, and the majority of these studies suggest vitamin D plays an inhibitory role in adipogenesis. Studies into vitamin D status and obesity in humans are limited, with the majority being observational epidemiological studies that provide no conclusions on cause and effect or clear links on the molecular mechanisms. The few cell culture and supplementation studies that have investigated adipogenesis in human cells indicate that, in contrast to findings from rodent studies, vitamin D is proadipogenic. There is insufficient evidence to determine whether 1) vitamin D deficiency is associated with a lean or obese phenotype, 2) vitamin D deficiency is a consequence of obesity, or (3) the effects of vitamin D on fat tissue are due to interactions with calcium.

In utero vitamin D deficiency predisposes offspring to long-term adverse adipose tissue effects

The fetal period represents an important window of susceptibility for later obesity and metabolic disease. Maternal vitamin D deficiency (VDD) during pregnancy is a global concern that may have long-lasting consequences on offspring metabolic health. We sought to determine whether a VDD in utero environment affects fetal adipose tissue development and offspring metabolic disease predisposition in adulthood. Furthermore, we sought to explore the extent to which the VDD intrauterine environment interacts with genetic background or postnatal environment to influence metabolic health. Eight-week-old P₀ female C57BL/6J mice were fed either a VDD diet or sufficient diet (VDS) from four weeks before pregnancy (periconception) then bred to male A^vy/a mice. Females were maintained on the diets throughout gestation. At weaning, A^vy/a and a/a male F₁ offspring were randomized to low-fat (LFD) or high-fat diet (HFD) until 19 weeks of age, at which point serum and adipose tissue were harvested for analyses. Mice born to VDD dams weighed less at weaning than offspring born to VDS dams but experienced rapid weight gain in the four weeks post weaning, and acquired a greater ratio of perigonadal (PGAT) to subcutaneous (SQAT) than control offspring. Additionally, these mice were more susceptible to HFD-induced adipocyte hypertrophy. Offspring of VDD dams also had greater expression of Pparg transcript. These novel findings demonstrate that in utero VDD, an easily correctable but highly prevalent health concern, predisposes offspring to long-term adipose tissue consequences and possible adverse metabolic health complications.

STEAP4: its emerging role in metabolism and homeostasis of cellular iron and copper

Preserving energy homeostasis in the presence of stressors such as proinflammatory cytokines and nutrient overload is crucial to maintaining normal cellular function. Six transmembrane epithelial antigen of the prostate 4 (STEAP4), a metalloreductase involved in iron and copper homeostasis, is thought to play a potentially important role in the cellular response to inflammatory stress. Genome-wide association studies have linked various mutations in STEAP4 with the development of metabolic disorders such as obesity, metabolic syndrome and type 2 diabetes. Several studies have shown that expression of Steap4 is modulated by inflammatory cytokines, hormones and other indicators of cellular stress and that STEAP4 may protect cells from damage, helping to maintain normal metabolic function. STEAP4 appears to be particularly relevant in metabolically oriented cells, such as adipocytes, hepatocytes and pancreatic islet cells. These cells struggle to maintain their function in iron or copper overloaded states, presumably due to increased oxidative stress, suggesting STEAP4's role in metal homeostasis is critical to the maintenance of cellular homeostasis in general, and in preventing the onset of metabolic disease. In this review, we explore genetic associations of STEAP4 with metabolic disorders, and we examine STEAP4 tissue expression, subcellular localization, regulation, structure and function as it relates to metabolic diseases. We then examine how STEAP4's role as a regulator of cellular iron and copper may relate to type 2 diabetes.

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.