Serum vitamin D levels in relation to abdominal obesity: A systematic review and dose-response meta-analysis of epidemiologic studies

Association of sleep fragmentation with general and abdominal obesity: a population-based longitudinal study

OBJECTIVE

To evaluate the causal relationship between sleep fragmentation (SF) parameters with general and abdominal obesity in free-living conditions.

METHODS

SF parameters were assessed by ActiGraph accelerometers for 7 consecutive days. Obesity was measured at baseline and 1-year follow-up with InBody S10 body composition analyzer.

RESULTS

At baseline, the mean age of the study population was 18.7 years old (SD = 0.9) and 139 (35.7%) were male. Each 1-unit increase of baseline sleep fragmentation index (SFI) was associated with 0.08 kg/m2-increase of body mass index (BMI) (95% CI: 0.03, 0.14), 0.20%-increase of percentage of body fat (PBF) (95% CI: 0.07, 0.32), 0.15 kg-increase of fat mass (FM) (95% CI: 0.03, 0.27), 0.15 cm-increase of waist circumference (WC) (95% CI: 0.03, 0.26) and 0.91 cm2-increase of visceral fat area (VFA) (95% CI: 0.36, 1.46) at the 1-year follow-up. In addition, each 1-unit increase of baseline SFI was associated with 15% increased risk of general obesity (OR = 1.15, 95% CI = 1.04-1.28; p = 0.006) and 7% increased risk of abdominal obesity (OR = 1.07, 95% CI = 1.01-1.13; p = 0.021) in the following year.

CONCLUSIONS

Fragmented sleep is independently associated with an increased risk of both general and abdominal obesity. The result highlights SF as a modifiable risk factor for the prevention and treatment of obesity.

Vitamin D and the Metabolic Phenotype in Weight Loss After Bariatric Surgery: A Longitudinal Study

PURPOSE

To evaluate the influence of vitamin D (VD) concentrations coupled with metabolic phenotypes preoperatively and 6 months after Roux-en-Y gastric bypass (RYGB) on body variables and weight loss.

MATERIALS AND METHODS

A longitudinal, retrospective, analytical study comprising 30 adult individuals assessed preoperatively (T0) and 6 months (T1) after undergoing Roux-en-Y gastric bypass. The participants were distributed preoperatively into metabolically healthy obese (MHO) and metabolically unhealthy obese individuals (MUHO) according to the HOMA-IR classification, as well as the adequacy and inadequacy of vitamin D concentrations in the form of 25(OH)D. All participants were assessed for weight, height, body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), visceral adiposity index (VAI), body circularity index (BCI), body adiposity index (BAI), weight loss, and assessment of 25(OH)D and 1,25(OH)2D concentrations using high-performance liquid chromatography with an ultraviolet detector (HPLC-UV). The statistical program used was SPSS version 21.

RESULTS

VD adequacy and a healthy phenotype in the preoperative period may play an important role concerning body fat distribution, as the body averages for WHtR (0.020*) and BCI (0.020*) were lower in MHO participants. In comparison, those with VD inadequacy and MUHOs had higher BAI averages (0.000*) in the postoperative period. Furthermore, it is possible that VD inadequacy before and after RYGB, even in the presence of an unhealthy phenotype, may contribute to the increase in VAI values (0.029*) after this surgery. Only those with inadequate VD and MUHOs had higher 25(OH)D concentrations. Besides, this unhealthy phenotype had a greater reduction in BMI in the early postoperative period (p < 0.001).

CONCLUSION

This study suggests that VD adequacy and the presence of a healthy phenotype appear to have a positive impact on the reduction of visceral fat in the context of pre- and postoperative obesity. In addition, there was a greater weight reduction in those with VD inadequacy and in MUHO, which suggests that the volumetric dilution effect of VD and catabolism after bariatric surgery is more pronounced in this specific metabolic phenotype.

Decreased vitamin D bio-availability with altered DNA methylation of its metabolism genes in association with the metabolic disorders among the school-aged children with degree I, II, and III obesity

Obesity is strongly associated with disturbances of vitamin D (VD) metabolites in the animal models. However, the related epidemiological evidence is still controversial, especially the different degrees of obesity children. Hence, in this present representative case-control study, 106 obesity school-age children aged 7-12 years were included and divided into different subgroups as degree I (the age- and sex-specific BMI≥95th percentile, n=45), II (BMI ≥120% percentile, n=34) and III (BMI ≥140% percentile, n=27) obesity groups across the ranges of body mass index (BMI). While the age- and sex-matched subjects without obesity were as the control group. Notably, it was significantly different of body composition, anthropological and clinical characteristics among the above four subgroups with the dose-response relationships (P<.05). Moreover, comparing with the control group, the serum VD concentrations were higher, VD metabolites like 25(OH)D, 25(OH)D3 and 1,25(OH)2D, and related hydroxylases as CYP27A1, CYP2R1 and CYP27B1 were lower in the degree I, II, and III obesity subgroups (P<.05), which were more disorder with the anthropological and clinical characteristics as the obesity was worsen in a BMI-independent manner (P<.05). However, there was a significant increase of CYP27B1 in the degree III obesity group than those in the degree I and II obesity subgroups. Furthermore, the methylation patterns on the genome-wide (Methylation/Hydroxymethylation) and VD metabolism genes (CYP27A1, CYP2R1 and CYP27B1) were negatively correlated with the worse obesity and their related expressions (P<.05). In summary, these results indicated that obesity could affect the homeostasis of VD metabolism related genes such as CYP27A1, CYP2R1, CYP27B1 and etc through abnormal DNA methylation, resulting in the disorders of VD related metabolites to decrease VD bio-availability with the BMI-independent manner. In turn, the lower levels of VD metabolites would affect the liver function to exacerbate the progression of obesity, as the Degree II and III obesity subgroups.

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.

Vitamin D3 supplementation shapes the composition of gut microbiota and improves some obesity parameters induced by high-fat diet in mice

PURPOSE

Individuals with vitamin D (VD) insufficiency have a greater tendency to develop obesity and have increased systemic inflammation. Gut microbiota are involved in the regulation of host inflammation and energy metabolism, which plays a role in the pathogenesis of obesity. Thus, we aimed to evaluate the effects of different doses of VD3 on body weight, serum lipids, inflammatory factors, and intestinal barrier function in obese mice and to explore the regulatory effect of VD3 on gut microbiota in obese mice.

METHODS

Male C57BL/6 J mice received a normal chow diet (NCD, 10% fat) or high-fat diet (HFD, 60% fat) to induce obesity within 10 weeks. Then, HFD mice were supplemented with 5650, 8475, or 11,300 IU VD3/kg diet for 8 weeks. Finally, 16 s rRNA analysis was performed to analyze gut microbiota composition in cecal contents. In addition, body weight, serum lipids, inflammatory factors, and intestinal barrier function were analyzed.

RESULTS

VD3 supplementation reduced body weight and the levels of TG, TC, HDL-C, TNF-α, IL-1β and LPS, and increased ZO-1 in HFD-fed mice. Moreover, it increased α-diversity, reduced F/B ratio and altered microbiota composition by increasing relative abundance of Bacteroidetes, Proteobacteria, Desulfovibrio, Dehalobacterium, Odoribacter, and Parabacteroides and reducing relative abundance of Firmicutes and Ruminococcus. There were significant differences between HFD and NCD groups in several metabolic pathways, including endotoxin biosynthesis, tricarboxylic acid cycle, lipid synthesis and metabolism, and glycolysis.

CONCLUSIONS

Low, medium, and high doses of VD3 inhibited weight gain, reduced levels of blood lipids and inflammatory factors, and improved endotoxemia and gut barrier function in obese mice. It also increased the α-diversity of gut microbiota in obese mice and reduced the relative abundance of some intestinal pathogenic bacteria, increased the relative abundance of some beneficial bacteria, and corrected the intestinal flora disorder of obese mice, with the low- and high-dose groups showing better effects than the medium-dose group.

Physiological Evidence and Therapeutic Outcomes of Vitamin D on Cardiovascular Diseases

Vitamin D hormone is an important regulator of various physiological functions, and its deficiency is characterized by an imbalance in parathyroid hormone and calcium homeostasis. The role of vitamin D in cardiovascular physiology is well demonstrated in animal and humanbased studies. In this context, hyperlipidemia, increased atherogenic plaques, cardiac inflammation, hypertension, myocarditis, myocardial infarction, and heart failure are some of the commonest known conditions connected with vitamin D deficiency. Supplementation of vitamin D is recommended to achieve normal serum vitamin D concentrations, nonetheless, in clinical trials often seen discrepancies concerning the supplementation effects and effectiveness. This review summarizes the data on the role of vitamin D in cardiovascular health along with some recent clinical findings regarding the effects of vitamin D supplementation.

Vitamin D status and its relationship with obesity indicators in Moroccan adult women

Background: Although vitamin D deficiency has been studied in various populations, there are few data on its prevalence and associated factors among Moroccan women. Aim: To determine the prevalence of vitamin D deficiency and investigate its association with body mass index (BMI), waist circumference, and serum concentrations of parathyroid hormone, calcium, and phosphorus in a sample of Moroccan adult women. Methods: This is a cross-sectional study conducted at Mohammed V Military Hospital of Instruction, Rabat. Anthropometric measurements and biochemical analyses were performed using standard procedures Results: A total of 714 women aged 18-65 years participated in this study. The overall prevalence of vitamin D deficiency was 74.4%. Approximately 24% and 51% of women had severe and moderate vitamin D deficiency, respectively. Serum 25-hydroxyvitamin D (25(OH)D) concentrations were inversely correlated with BMI in vitamin D-deficient subjects (P = 0.036) and with parathyroid hormone 1-84 (PTH1-84) levels in the study sample (P = 0.010). PTH1-84 concentrations were greater among overweight/obese individuals compared to their non-overweight peers (P = 0.001) and tended to be higher among vitamin D-deficient women than vitamin D-sufficient women (P = 0.053). Conclusion: This study showed a very high prevalence of vitamin D deficiency in this sample of Moroccan women. Lower serum 25(OH)D levels were associated with increased BMI in vitamin D-deficient women and with elevated PTH1-84 levels among the study sample. Although these findings come from a convenience sample of women that attended a nutrition clinic, they underscore the urgent need to develop public health interventions to improve women's vitamin D status.

Obesity and malnutrition in children and adults: A clinical review

Background

In the U.S., children and adults are consuming more low-nutrient foods with added sugar and excess fats as compared to healthy, high-quality calories and micronutrients. This diet is increasing the prevalence of malnutrition and nutritional deficiencies, despite high calorie intake. This is a review of the common micronutrient deficiencies, the risk factors for malnutrition, dietary plans, and the health consequences in children and adults with obesity in the U.S.

Methods

This clinical review of literature was performed on the MEDLINE (PubMed) search engine. A total of 1391 articles were identified and after review, a total of 130 were found to be most pertinent.

Discussion

The most common micronutrient deficiencies found in patients with obesity were vitamin A, thiamine (B1), folate (B9), cobalamin (B12), vitamin D, iron, calcium, and magnesium, especially prior and after bariatric surgery. Diets that produced the most weight reduction also further puts these individuals at risk for worsening malnutrition. Malnutrition and micronutrient deficiencies can worsen health outcomes if not properly managed.

Conclusion

Adequate screening and awareness of malnutrition can improve the health outcomes in patients with obesity. Physiologic changes in response to increased adiposity and inadequate intake increase this population's risk of adverse health effects. Malnutrition affects the individual and contributes to worse public health outcomes. The recommendations for screening for malnutrition are not exclusive to individuals undergoing bariatric procedures and can improve the health outcomes of any patient with obesity. However, clearly, improved nutritional status can assist with metabolism and prevent adverse nutritional outcomes post-bariatric surgery. Clinicians should advise on proper nutrition and be aware of diets that worsen deficiencies.

Centralized health management based on hot spring resort improves physical examination indicators and sleep quality in people at high risk of chronic diseases: a randomized controlled trial

We study the effects of centralized health management based on hot spring resorts on the physical examination index and sleep quality of people at high risk of chronic diseases. We recruited 114 volunteers at high risk of chronic diseases. We then divided them into 57 in the intervention group and 57 in the control group. The intervention group collectively received 4 weeks (28 days) of comprehensive health management interventions at Tongjing Hotspring Resort, including regular schedules, balanced diet, appropriate exercise, targeted health education, etc. The main outcomes are physical examination indicators (height, weight, waist circumference, blood pressure, lipids, and glucose) and sleep quality. Both groups underwent a questionnaire and physical examination at baseline, 2 weeks and 4 weeks. Intragroup comparisons grouped by exposure criteria showed decreases in BMI, waist circumference, triglycerides, total cholesterol, and blood glucose in the intervention group at both 2 and 4 weeks (all P < 0.05); however, in the control group, only triglycerides decreased at 4 weeks (P < 0.05). Intergroup comparisons showed BMI and waist circumference were significantly lower in the intervention group than in the control group at 4 weeks (all P < 0.05). Intragroup comparisons of insomnia severity index (ISI) scores showed a significant decrease in the intervention group at both 2 and 4 weeks (all P < 0.001) with no significant change in the control group (P > 0.05). Intergroup comparisons showed that the insomnia severity index (ISI) scores were significantly higher in the intervention group than in the control group at baseline (P = 0.006) but became significantly lower than the control group at 2 and 4 weeks (all P < 0.001). Thus, this pattern significantly improved BMI, waist circumference, triglycerides, and sleep in the intervention group. TRIAL REGISTRATION NUMBER: Chinese Clinical Trials Registry: ChiCTR2100053201, registered 14 Nov 2021. (Retroactive Registration).

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.

Vitamin D status and supplementation before and after Bariatric Surgery: Recommendations based on a systematic review and meta-analysis

Bariatric surgery is associated with a postoperative reduction of 25(OH) vitamin D levels (25(OH)D) and with skeletal complications. Currently, guidelines for 25(OH)D assessment and vitamin D supplementation in bariatric patients, pre- and post-surgery, are still lacking. The aim of this work is to analyse systematically the published experience on 25(OH)D status and vitamin D supplementation, pre- and post-surgery, and to propose, on this basis, recommendations for management. Preoperatively, 18 studies including 2,869 patients were evaluated. Prevalence of vitamin D insufficiency as defined by 25(OH)D < 30 ng/mL (75 nmol/L) was 85%, whereas when defined by 25(OH)D < 20 ng/mL (50 nmol/L) was 57%. The median preoperative 25(OH)D level was 19.75 ng/mL. After surgery, 39 studies including 5,296 patients were analysed and among those undergoing either malabsorptive or restrictive procedures, a lower rate of vitamin D insufficiency and higher 25(OH)D levels postoperatively were observed in patients treated with high-dose oral vitamin D supplementation, defined as ≥ 2,000 IU/daily (mostly D3-formulation), compared with low-doses (< 2,000 IU/daily). Our recommendations based on this systematic review and meta-analysis should help clinical practice in the assessment and management of vitamin D status before and after bariatric surgery. Assessment of vitamin D should be performed pre- and postoperatively in all patients undergoing bariatric surgery. Regardless of the type of procedure, high-dose supplementation is recommended in patients after bariatric surgery.

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.

Effects of vitamin D supplementation on cardiometabolic parameters among patients with metabolic syndrome: A systematic review and GRADE evidence synthesis of randomized controlled trials

Various pathophysiologic mechanisms were proposed to underlie the effect of vitamin D on MetS components. In this systematic review, we reviewed randomized control clinical trials to verify whether vitamin D supplementation (VDS) at different doses is effective concomitantly in controlling high-density lipoprotein cholesterol (HDL-c), triglycerides (TG), fasting glucose level, blood pressure, and central obesity in adults diagnosed with MetS. The following scientific databases were searched from 1998 until April 2023: EMBASE, MEDLINE (PubMed), Web of Science, Latin American and Caribbean Health Sciences Literature (Lilacs), the Cochrane Central Register of Controlled Trials, clinicaltrial.gov, and Google Scholar. No language restrictions were applied. Seven studies were included, and they showed a high level of heterogeneity. All studies reported a significant increase in serum 25(OH)D levels in the intervention groups. Of these, only two noted a significant decrease in triglyceride (TG) level and waist circumference. However, the certainty levels of the evidence rating were very low and low for triglyceride (TG) level and waist circumference, respectively, and moderate for fasting glucose level, blood pressure, and HDL-c. In conclusion, despite these benefits, considering the low certainty, the evidence does not support that VDS decreases triglyceride (TG) level and waist circumference in adults with MetS.

Treatment of vitamin D deficiency in children

INTRODUCTION

Vitamin D deficiency affects from 10% to 50% in various pediatric population groups and causes life-threatening hypocalcemia in infants, crippling rickets in infants and children, and increased risk of subsequent adult metabolic and neurologic problems.

AREAS COVERED

An English language literature search of PubMed was performed since 1940 as were the authors' personal literature collections. References identified in the reviewed literature are considered.

DIAGNOSIS

The diagnosis of vitamin D deficiency is based on serum 25-hydroxyvitamin D levels. Clinical features of rickets include bone deformities and elevated alkaline phosphatase. Most children and adolescents who are biochemically vitamin D deficient do not have specific symptoms or signs of deficiency.

PREVENTION

Prevention of vitamin D deficiency is via exposure to sunshine, food and beverage fortification, and dietary supplementation.

TREATMENT

Effective treatment of vitamin D deficiency is via oral or injectable administration of vitamin D. Dosing and duration of vitamin D therapy have been described for healthy children and for children with underlying medical conditions, but recommendations vary.

EXPERT OPINION

Further investigation is needed to determine long-term non-skeletal effects of childhood vitamin D deficiency, benefits of supplementation in asymptomatic individuals with biochemical vitamin D deficiency, and appropriate screening for vitamin D deficiency in asymptomatic children and adolescents.

Association between anthropometric markers of adiposity, adipokines and vitamin D levels

Inverse association between serum levels of vitamin D and obesity has been pointed out in several studies. Our aim was to identify to the associations between vitamin D levels and a large panel of anthropometric markers and adipokines. Cross-sectional study including 6485 participants. Anthropometric markers included body mass index (BMI), % body fat, waist, waist-to-hip (WHR), waist-to-height (WHtR), conicity index, body roundness index (BRI) and a body shape index (ABSI). 55.7% of women and 60.1% of men presented with vitamin D deficiency. Vitamin D levels were negatively associated with most anthropometric markers, with correlation coefficients ranging between −0.017 (ABSI) and −0.192 (BMI) in women and between −0.026 (weight) and −0.130 (% body fat) in men. Vitamin D levels were inversely associated with leptin levels in both sexes and positively associated with adiponectin levels in women only. The likelihood of vitamin D deficiency increased with increasing adiposity levels, except for ABSI (women) and BMI (men). Total body fat, rather than localized or unevenly distributed body fat, is the adiposity marker most associated with decreased vitamin D levels. Monitoring vitamin D levels in people with overweight/obesity is essential.

Treatment of Diabetes and Osteoporosis—A Reciprocal Risk?

Diabetes mellitus is a metabolic and systematic disorder that requires individualized therapy. The disease leads to various consequences, resulting in the destruction of tissues and organs. The aforementioned outcomes also include bone mineral disorders, caused by medications as well as diet therapy and physical activity. Some drugs may have a beneficial effect on both bone mineral density and the risk of fractures. Nevertheless, the impact of other medications remains unknown. Focusing on pharmacotherapy in diabetes may prevent bone mineral disorders and influence both the treatment and quality of life in patients suffering from diabetes mellitus. On the other hand, anti-osteoporosis drugs, such as antiresorptive or anabolic drugs, as well as drugs with a mixed mechanism of action, may affect carbohydrate metabolism, particularly in patients with diabetes. Therefore, the treatment of diabetes as well as osteoporosis prevention are vital for this group of patients.

Association of Serum 25(OH)D with Metabolic Syndrome in Chinese Women of Childbearing Age

Objective: To analyze the associations between serum 25(OH)D levels and the risk of metabolic syndrome (MetS) and its components, and the related genetic and non-genetic factors in non-diabetic women of childbearing age in China. Methods: Subjects were randomly selected from the 2015 Chinese Adult Chronic Disease and Nutrition Surveillance. The data of sociodemographic characteristics and lifestyle factors were obtained through questionnaire survey. Anthropometry was measured by trained interviewers, and fasting blood was collected to test 25-hydroxyvitamin D [25(OH)D], total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), fasting blood glucose (FBG), and other related parameters. Generalized linear mode and multivariate logistic analysis were performed to analyze the associations between serum 25(OH)D and MetS and its components, adjusting for the possible confounders. Results: Body mass index (BMI), serum alanine aminotransferase (ALT), hypersensitive C-reactive protein (hs-CRP), 25(OH)D, phosphorus (P), and parathyroid hormone (PTH) levels were associated with the number of MetS’s components. G allele carriers of GC rs2282679 had higher diastolic blood pressure (DBP) and FBG levels compared with the TT genotypes, while higher genetic risk score (GRS) seemed to be associated with reduced HDL-C level. The odds ratio (OR) for MetS in lowest group of 25(OH)D was 1.533 (0.980−2.399) after adjusting for season, district, area type, latitude, age, BMI, PTH, P, ALT, CRE, interleukin-6 (IL-6), and hs-CRP, compared with the median group, but the association was not significant. An insufficient 25(OH)D concentration (<14.22 ng/mL) was significantly related to the risk of elevated waist circumference (WC) (OR = 1.612 (1.014−2.561)) and TG (OR = 2.210 (1.318−3.706)), and reduced HDL-C (OR = 1.639 (1.206−2.229)) after adjusting for the confounders among these women. Moreover, these relationships were not affected by vitamin D metabolism-related gene polymorphisms. Conclusion: After comprehensively considering various influencing factors, significant associations between insufficient serum 25(OH)D and MetS‘s components, including elevated WC, TG, and reduced HDL-C, were observed. However, MetS, hypertension, and hyperglycemia were not found independently associated with 25(OH)D levels.

Deficiency and Insufficiency of Vitamin D in Women of Childbearing Age: A Systematic Review and Meta-analysis

OBJECTIVE

 To estimate the prevalence of inadequate vitamin D level and its associated factors for women of childbearing age in Brazil.

METHODS

 A systematic review was conducted (last updated May 2020). Meta-analyses were performed using the inverse-variance for fixed models with summary proportion calculation by Freeman-Tukey double arcsine. Reporting and methodological quality were assessed using the Joanna Briggs Institute tool for prevalence studies.

RESULTS

 Our review identified 31 studies, comprising 4,006 participants. All the studies had at least one weakness, mainly due to the use of convenience sampling and small sample size. The overall prevalence of vitamin D deficiency, insufficiency, and both deficiency and insufficiency were 35% (confidence interval, 95%CI: 34-37%), 42% (95%CI: 41-44%), and 72% (95%CI: 71-74%), respectively.

CONCLUSION

 Although the magnitude of the prevalence of inadequate levels of vitamin D is uncertain, the evidence suggests that presence of vitamin D deficiency or insufficiency in women of reproductive age can cause moderate to severe problems.

Serum Vitamin D Levels in Relation to Hypertension and Pre-hypertension in Adults: A Systematic Review and Dose–Response Meta-Analysis of Epidemiologic Studies

Background

Findings of observational studies that evaluated the association of serum vitamin D status and high blood pressure were contradictory. This meta-analysis of epidemiologic studies assessed the relation of serum vitamin D levels to hypertension (HTN) and pre-hypertension in adults.

Methods

We conducted a systematic search of all published articles up to March 2021, in four electronic databases (MEDLINE (PubMed), Web of Science (ISI), Embase and Scopus), and Google scholar. Seventy epidemiologic studies (10 prospective cohort, one nested case–control, and 59 cross-sectional investigations) that reported relative risks (RRs), odds ratios (ORs), hazard ratios, or prevalence ratios with 95% CIs for HTN or pre-hypertension in relation to serum vitamin D concentrations in adults were included in the analysis.

Results

In prospective studies, a 16% decrease in risk of hypertension was observed in participants with high levels of serum vitamin D compared to low levels (RR: 0.84; 95%CI: 0.73, 0.96; 12 effect sizes). Dose–response analysis in prospective studies revealed that each 25 nmol/L increase in serum vitamin D concentrations resulted in 5% reduced risk of HTN (RR: 0.95; 95% CI: 0.90, 1.00). Also, a significant nonlinear relationship between serum vitamin D levels and HTN was found (P_nonlinearity < 0.001). In cross-sectional investigations, highest vs. lowest level of serum vitamin D was related to reduced odds of HTN (OR: 0.84; 95%CI: 0.79, 0.90; 66 effect sizes) and pre-hypertension (OR: 0.75; 0.95%CI: 0.68, 0.83; 9 effect sizes). Dose–response analysis in these studies showed that each 25 nmol/L increase in serum vitamin D levels was related to a significant 6% reduction in odds of hypertension in all populations (RR: 0.94; 95%CI: 0.90, 0.99) and 3% in studies with representative populations (RR: 0.97; 95%CI: 0.95, 0.99).

Conclusion

This meta-analysis of epidemiologic studies disclosed that serum vitamin D concentrations were inversely related to the risk of HTN in adults, in a dose–response manner in both prospective cohort and cross-sectional studies.

Systematic Review Registration:http://www.crd.york.ac.uk/Prospero, identifier: CRD42021251513.

Serum Vitamin D Levels in Relation to Abdominal Obesity in Children and Adolescents: A Systematic Review and Dose-Response Meta-Analysis

Background

Findings of epidemiological studies that investigated the relationship between serum vitamin D levels and abdominal obesity were inconsistent. To evaluate the relationship between blood vitamin D levels and abdominal obesity in children and adolescents, we did a comprehensive review and dose-response meta-analysis.

Methods

A comprehensive search in electronic databases including Scopus, Web of Science (ISI), MEDLINE (Pubmed), EMBASE, and Google Scholar was conducted, up to May 2021, for epidemiological studies that investigated the linkage between serum vitamin D levels (as the exposure) and abdominal obesity (as the outcome) in children and adolescents.

Results

Combining 19 effect sizes from 14 cross-sectional studies that included 29,353 apparently healthy children illustrated that the highest vs. lowest level of serum vitamin D was related to a 35% reduced odds of abdominal obesity [odds ratio (OR): 0.65; 95% CI: 0.50, 0.84]. Linear dose-response analysis revealed that each 10 ng/ml increase in serum vitamin D levels was related to a 7% decrease in odds of abdominal obesity (OR: 0.93; 95% CI: 0.90, 0.95), only among investigations that used percentiles of waist circumference (>75th or 90th) to define the disorder (including 6,868 total subjects and 1,075 cases with abdominal obesity). Increasing serum vitamin D levels from 20 to 40 ng/ml was related to reduce odds of abdominal obesity in children.

Conclusion

A negative relationship between blood vitamin D levels and abdominal obesity in children and adolescents was discovered in this meta-analysis of epidemiologic studies. Among investigations that used waist circumference percentiles to define the disorder, the relationship was in a dose-response manner. To affirm this relationship, more research studies are needed, particularly using a prospective design.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021261319, PROSPERO 2021, identifier: CRD42021261319.

25-hydroxyvitamin D levels are inversely related to metabolic syndrome risk profile in northern Chinese subjects without vitamin D supplementation

BACKGROUND

The comparatively low 25 hydroxyvitamin D [25(OH)D] levels have been reported in patients with metabolic syndrome (MetS). Herein we investigated the cross-sectional and longitudinal relationships between serum 25(OH)D levels and MetS risk profile in northern middle-aged Chinese subjects without vitamin D supplementation.

METHODS

A cohort of 211 participants including 151 MetS patients and 60 controls at 20-69 years of age were enrolled from suburban Beijing, China. The recruited MetS patients were subjected to diet and exercise counselling for 1-year. All subjects at baseline and MetS patients after intervention underwent clinical evaluations.

RESULTS

Serum 25(OH)D levels were significantly decreased in MetS patients. 25(OH)D levels were inversely related to MetS score, fasting blood glucose (FBG) and triglyceride-glucose index (TyG) after adjusting for cofounders (all P < 0.05). Participants in the lowest tertile of 25(OH)D levels had increased odds for MetS (P = 0.045), elevated FBG (P = 0.004) in all subjects, and one MetS score gain in MetS patients (P = 0.005). Longitudinally, the metabolic statuses as well as 25(OH)D levels of MetS patients were significantly improved (all P < 0.05), and the increase of 25(OH)D levels were inversely related to MetS scores, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), FBG, and TyG, while positively related to high-density lipoprotein cholesterol (HDL-C) after adjusting for confounders.

CONCLUSIONS

25(OH)D levels were significantly decreased in MetS patients, and it was negatively associated with metabolic dysfunctions at baseline and 1-year after. Metabolic aberrations of MetS patients were significantly ameliorated with 1-year follow-up counselling accompanying by notably elevated 25(OH)D levels.

Urban Neighbourhood Environments, Cardiometabolic Health and Cognitive Function: A National Cross-Sectional Study of Middle-Aged and Older Adults in Australia

Population ageing and urbanisation are global phenomena that call for an understanding of the impacts of features of the urban environment on older adults' cognitive function. Because neighbourhood characteristics that can potentially have opposite effects on cognitive function are interdependent, they need to be considered in conjunction. Using data from an Australian national sample of 4141 adult urban dwellers, we examined the extent to which the associations of interrelated built and natural environment features and ambient air pollution with cognitive function are explained by cardiometabolic risk factors relevant to cognitive health. All examined environmental features were directly and/or indirectly related to cognitive function via other environmental features and/or cardiometabolic risk factors. Findings suggest that dense, interconnected urban environments with access to parks, blue spaces and low levels of air pollution may benefit cognitive health through cardiometabolic risk factors and other mechanisms not captured in this study. This study also highlights the need for a particularly fine-grained characterisation of the built environment in research on cognitive function, which would enable the differentiation of the positive effects of destination-rich neighbourhoods on cognition via participation in cognition-enhancing activities from the negative effects of air pollutants typically present in dense, destination-rich urban areas.

Vitamin D Effects on Selected Anti-Inflammatory and Pro-Inflammatory Markers of Obesity-Related Chronic Inflammation

BACKGROUND

Obesity is related to changes in adipokine secretion, activity of adipose tissue macrophages, helper T cells, and regulatory T cells. It has been confirmed that vitamin D has potent anti-inflammatory properties. It contributes to reduction in pro-inflammatory mediators and an increase in anti-inflammatory cytokines. There is also evidence that vitamin D could decrease C-reactive protein (CRP) and affect selected haematological indices.

AIM OF THE STUDY

We aimed to evaluate the effect of vitamin D on interleukin (IL)-10, IL-17, CRP, blood leukocyte profile, and platelet (PLT) count in overweight and obese children before and after six months of vitamin D supplementation.

MATERIAL AND METHODS

The study group consisted of 67 overweight and obese children aged 9.08-17.5 years. The control group included 31 normal weight peers age- and sex-matched. None of the studied children had received vitamin D supplementation before the study. Data were analyzed at baseline and after vitamin D supplementation.

RESULTS

The study group had lower baseline 25(OH)D (p<0.001) and higher white blood cell (WBC) (p=0.014), granulocyte (p=0.015), monocyte (p=0.009) and CRP (p=0.002) compared to the control group. In the study group, vitamin D levels were related negatively to nutritional status. Leukocyte profile parameters, PLT, CRP, IL-10 or IL-17 were not related to baseline 25(OH)D. Baseline IL-17 levels correlated with monocytes (R= 0.36, p=0.003) independently on 25(OH)D deficit. In children with vitamin D <15ng/ml, the baseline 25(OH)D was related to CRP (R=-0.42, p=0.017). After six months of vitamin D supplementation, we noticed a decrease in CRP levels (p=0.0003). Serum 25(OH)D correlated with IL-10 in that period (R=0.27, p=0.028). Moreover, we noticed that IL-10 correlated with monocyte (R=-0.28, p=0.023). We did not find any significant associations between 25(OH)D and leukocyte profile parameters, PLT, or IL-17. The multivariable stepwise regression analysis identified IL-10 as the parameter positively associated with 25(OH)D.

CONCLUSIONS

Our study confirmed beneficial effects of vitamin D supplementation in overweight and obese paediatric populations. Vitamin D intake seems to exert its anti-inflammatory effect mainly via decreasing the CRP level and protecting stabile values of IL-10, rather than its impact on pro-inflammatory factors such as lL-17 and leukocyte profile parameters.

Associations between serum 25-hydroxyvitamin D, body mass index and body fat composition among Emirati population: Results from the UAE healthy future study

INTRODUCTION

Vitamin D deficiency and insufficiency are highly prevalent among several populations across the globe. Numerous studies have shown a significant correlation between body-mass-index (BMI) and Vitamin D status, however, some results differed according to ethnicity. Despite the abundance of sunshine throughout the year, vitamin D deficiency is prominent in the United Arab Emirates (UAE). In this study, we analyzed the UAE Healthy Future Study (UAEHFS) pilot data to investigate the association between serum 25-hydroxyvitamin D (25(OH)D) and % body fat (BF) composition as well as BMI.

MATERIAL AND METHODS

Data from a total of 399 Emirati men and women aged ≥ 18 years were analyzed. Serum 25(OH)D and standard measures of weight and height were included in the analyses. Vitamin D deficiency was defined as serum 25(OH)D concentration<20 ng/ml. Multivariate quantile regression models were performed to explore the relationship between serum 25(OH)D levels and % BF composition and BMI correspondingly.

RESULTS

There were 281 (70.4%) males and 118 (29.6%) females included in this study. More than half of the study participants had vitamin D insufficiency (52.4%), and nearly a third had vitamin D deficiency (30.3%); while only 17.3% had optimal levels. A statistically significant negative association between serum 25(OH) D levels and % BF composition was observed at intermediate percentiles while a statistically significant negative association between serum 25(OH)D and BMI was only observed at the median (50th percentile).

CONCLUSION

The study findings support the association between low serum 25(OH) D levels (low vitamin D status) and high % BF composition and high BMI among adult Emiratis. Further longitudinal data from the prospective UAEHFS could better elucidate the relationship between serum 25(OH) D levels, % BF composition, and BMI in the context of various health outcomes among this population.

25-hydroxyvitamin D and testosterone levels association through body mass index: A cross-sectional study of young men with obesity

BACKGROUNDS

Vitamin D and testosterone deficiency have been widely related to obesity. However, only a few studies have investigated the effect of vitamin D on testosterone in the context of obesity, in which controversial results have been raised.

OBJECTIVES

The purpose of this study was to determine the relationship between serum 25-hydroxyvitamin D (25(OH)D) and testosterone levels in young men with different grade of obesity.

DESIGN AND METHODS

This cross-sectional study included 269 healthy young men with obesity (body mass index (BMI) ≥ 30 kg/m²). Participants were divided into two groups based on their serum 25(OH)D levels (134 subjects with vitamin D sufficiency and 135 participants with vitamin D deficiency, according to the 50^th percentile of 25(OH)D). Serum 25(OH)D and sex hormones have been measured. The relationships between 25(OH)D, sex hormones, and obesity grades were investigated with linear and binary logistic regression analyses, as well as mediation analysis.

RESULTS

Compared to the 25(OH)D sufficiency group, total and free testosterone levels were found to be decreased, whereas serum androstenedione levels were increased in the 25(OH)D deficiency group (p<0.05). Using multivariable lineal regression analyses, 25(OH)D was correlated with the majority of sex hormones (p<0.05). When mediation with BMI was performed, the direct effect between 25(OH)D and sex hormones disappeared, and only the indirect effect via BMI remained (demonstrating the importance of BMI). Furthermore, after controlling for age and smoking status, we discovered that total testosterone and SHBG were both significantly associated with 25(OH)D (p<0.05) in subjects with obesity type III. Using a mediation analysis, we discovered that BMI had a partial effect on the association between 25(OH)D and total testosterone levels in morbidly obese participants, indicating that a direct association between 25(OH)D and total testosterone levels, and that BMI partially mediated this association.

CONCLUSIONS

Serum 25(OH)D is associated with total testosterone levels in only those subjects with morbid obesity, suggesting a specific benefit in severe cases of obesity. Additional research is needed to elucidate possible common mechanisms.

Frequency of vitamin d deficiency in patients with lumbar spinal stenosis and its relationship with obesity, depression, and pain intensity: a cross-sectional study

ABSTRACT Objective This study was conducted to determine the frequency of vitamin D deficiency in patients with lumbar spinal stenosis and to define the relationship between vitamin D levels and obesity, depression, and pain intensity. Methods This study was conducted with 69 patients (Male = 32, Female = 37) diagnosed with lumbar spinal stenosis. The participants’ 25(OH)D levels were measured by radioimmunoassay. In addition, bone metabolic status, including bone mineral density and bone turnover markers, was also evaluated. The Beck Depression Inventory was used to determine the depression statuses of the patients, while the McGill Melzack Pain Questionnaire was administered to measure pain intensity. The results were evaluated at a significance level of p<0.05. Results Vitamin D deficiency (<20 ng/mL) was found in 76.8% of the patients. Binary logistic regression analysis showed a significantly higher frequency of vitamin D deficiency in patients who: 1) had higher body mass indexes (OR 3.197, 95% CI 1.549-6.599); 2) fared higher in Beck’s depression score (OR 1.817, 95% CI 1.027–3.217); and 3) were female rather than male (OR 1.700, 95% CI 0.931-3.224) (p<0.05). Conclusion In this study, vitamin D deficiency was prevalent in lumbar spinal stenosis patients. In addition, obese, depressed, and female individuals have higher risks of vitamin D deficiency.

The Vitamin D Decrease in Children with Obesity Is Associated with the Development of Insulin Resistance during Puberty: The PUBMEP Study

Obesity and cardiometabolic risk have been associated with vitamin D levels even in children. The objective of the present study was to evaluate the association between insulin resistance (IR), cardiometabolic risk factors, and vitamin D in children from prepubertal to pubertal stages. A total of 76 children from the PUBMEP study, aged 4–12 years at baseline, were included. Children were evaluated in prepubertal and pubertal stages. Anthropometric measurements and selected cardiometabolic risk biomarkers, such as plasma glucose, blood lipids, insulin, adiponectin, leptin, and blood pressure, and serum 25-hydroxyvitamin D (25(OH)D) were determined. Children were categorized by obesity degree and IR status combined before and after puberty. Paired t-test and multivariate linear regression analyses were conducted. During puberty, the increase in triacylglycerols, insulin, and HOMA-IR and the decrease in QUICKI were significantly associated with the reduction in 25(OH)D (B = −0.274, p = 0.032; B = −0.219, p = 0.019; B = −0.250, p = 0.013; B = 1.574, p = 0.013, respectively) after adjustment by BMI-z, sex, and pubertal stage. Otherwise, prepubertal non-IR children with overweight/obesity that became IR during puberty showed a significant decrease in 25(OH)D and HDL-c, and an increase in waist circumference and triacylglycerol concentrations (p < 0.05 for all) over time. These results suggest that changes in IR seem to be associated with an effect on 25(OH)D levels during puberty, especially in children with overweight.

Vitamin D: Dosing, levels, form, and route of administration: Does one approach fit all?

The 4^th International Conference on Controversies in Vitamin D was held as a virtual meeting in September, 2020, gathering together leading international scientific and medical experts in vitamin D. Since vitamin D has a crucial role in skeletal and extra-skeletal systems, the aim of the Conference was to discuss improved management of vitamin D dosing, therapeutic levels and form or route of administration in the general population and in different clinical conditions. A tailored approach, based on the specific mechanisms underlying vitamin D deficiency in different diseases that were discussed, was recommended. Specifically, in comparison to healthy populations, higher levels of vitamin D and greater amounts of vitamin D were deemed necessary in osteoporosis, diabetes mellitus, obesity (particularly after bariatric surgery), and in those treated with glucocorticoids. Emerging and still open issues were related to target vitamin D levels and the role of vitamin D supplementation in COVID-19 since low vitamin D may predispose to SARS-CoV-2 infection and to worse COVID-19 outcomes. Finally, whereas oral daily cholecalciferol appears to be the preferred choice for vitamin D supplementation in the general population, and in most clinical conditions, active vitamin D analogs may be indicated in patients with hypoparathyroidism and severe kidney and liver insufficiency. Parenteral vitamin D administration could be helpful in malabsorption syndromes or in states of vitamin D resistance.Specific guidelines for desired levels of vitamin D should be tailored to the different conditions affecting vitamin D metabolism with the goal to define disease-specific normative values.

The use of finite mixture models to examine the serum 25(OH)D levels among Saudis

BACKGROUND

Recorded serum 25(OH)D in survey data varies with observed and unobserved respondent characteristics. The aim of this study was to expose latent population sub-groups and examine variation across groups regarding relationships between serum 25(OH)D and observable characteristics.

METHODS

This study explored the role of unobserved heterogeneity on associations between surveyed 25(OH)D and various factors using a sample (n = 2,641) extracted from the Saudi Health Interview Survey (2013). Linear regression and finite mixture models (FMM) were estimated and compared. The number of latent classes in the FMM was chosen based on BIC score.

RESULT

Three latent classes were identified. Class I (39.82%), class II (41.03%), and class III (19.15%) with mean 25(OH)D levels of 22.79, 34.88, and 57.45 ng/ml respectively. Distinct patterns of associations with nutrition, behaviour and socio-demographic variables were recorded across classes that were not revealed in pooled linear regression.

CONCLUSION

FMM has the potential to provide additional insights on the relationship between 25(OH)D levels and observable characteristics. It should be more widely considered as a method of investigation in this area.

Causal Links between Hypovitaminosis D and Dysregulation of the T Cell Connection of Immunity Associated with Obesity and Concomitant Pathologies

Subclinical inflammation in morbid obesity is associated with immune activation and the development of concomitant diseases. Impaired immune homeostasis and immune cell dysregulation in adipose tissue are associated with phenotypic and functional changes in the pool of T lymphocytes and the development of chronic hypovitaminosis D. Low vitamin D levels in obesity lead to the activation, proliferation and production of pro-inflammatory mediators by T cells. Hypovitaminosis D is the cause of a decrease in the functional potential of regulatory and anti-inflammatory lymphocytes and the maintenance of the inflammatory response. The exact molecular genetic mechanisms of the effect of vitamin D on T lymphocytes have not been fully elucidated. Therefore, uncovering the functional role of T cells and their relationship to vitamin D homeostasis in the context of obesity development may contribute to the development of new pathogenetic methods for clinical prediction of the risk of metabolic, oncologic, autoimmune and infectious complications. The review presents the molecular genetic mechanisms of the effect of vitamin D on adipose tissue resident T lymphocytes and the characteristics of vitamin D receptor expression, and analyzes the phenotypic and functional characteristics of potentially pathogenic T lymphocytes in relation to the development of obesity and its associated complications.

Vitamin D status and obesity markers in older adults: results from West China Health and Aging Trends study

Backgrounds

Vitamin D deficiency and insufficiency in older adults seems to be common, but the prevalence estimates are lacking in West China. Previous studies suggested that low vitamin D status was associated with obesity. However, most of them evaluated obesity based on body mass index (BMI) and there are no studies at present exploring the association between vitamin D status and different obesity markers. The present study aims to investigate the prevalence of low vitamin D status and evaluate the association between the vitamin D status and different obesity markers among older adults in West China.

Methods

Data was based on the baseline of West China Health and Aging Trends study (WCHAT). All of the participants were older than 60 years old in the present study. Vitamin D status was based on laboratory data, and obesity markers were assessed by bioelectrical impedance analysis (BIA) using the InBody 770 analyzer. Multiple linear regression was performed to find the association between the vitamin D status and various obesity markers.

Results

The study included 2661 individuals (mean age: 67.7 ± 6.0 years; males: 41 %). The mean vitamin D level was 18.8 ± 6.3 ng/ml (range: 5 to 59 ng/ml); 5.2 % of participants had a sufficient level of vitamin D, 31.8 % had vitamin D insufficiency, and 63.0 % had vitamin D deficiency. Our results showed that vitamin D status was negatively associated with fat mass index (FMI), visceral fat area (VFA), and waist-hip ratio (WHR) in both sexes. Comparing to other obesity markers, WHR had the strongest correlation with vitamin D status in both sexes (β = -6.090, P = 0.046 in males; β = -11.253, P < 0.001 in females). No significant association was found between vitamin D status and BMI in males.

Conclusion

The prevalence of vitamin D insufficiency and deficiency among older adults in West China was high. Among the older adults in west China, WHR showed stronger association with vitamin D status and was better for the prediction of vitamin D insufficiency or deficiency in both sexes, compared to BMI.

Trial registration

Chinese Clinical Trial Registry: ChiCTR1800018895.

Gender-Dependent Characteristics of Serum 1,25-Dihydroxyvitamin D/25-Hydroxyvitamin D Ratio for the Assessment of Bone Metabolism

Objectives Vitamin D deficiency, which is common worldwide, increases the risks of falls and fractures and can lead to increased morbidity and mortality. However, the clinical utility and relevance of vitamin D activation remain unknown. The aim of the present study was to clarify the clinical usefulness of serum 1,25-dihydroxyvitamin D (1,25D)/25-hydroxyvitamin D (25D) ratio for assessment of the extent of bone metabolism. Methods We retrospectively screened data for 87 patients whose serum 1,25D and 25D levels were measured. Eight patients who were taking vitamin D preparations were excluded, and data for 79 patients (33 males and 46 females) were analyzed. Since menopausal status can be associated with serum vitamin D level, we divided the patients by gender and divided the female patients into two groups at the age of 50 years. Results The median serum 1,25D/25D ratio was significantly lower in males than in females, with the most considerable difference in all males [4.1 (interquartile range: 2.3-5.8) × 10-3] versus elderly females (aged ≧50 years) [7.9 (3.3-10.1) × 10-3). Main disorders were endocrine (30.6%), inflammatory (18.5%), and bone-related (16.7%) disorders. The ratios of serum 1,25D/25D had significant negative correlations with femoral dual-energy X-ray absorptiometry % young adult mean (DEXA %YAM) (R=-0.35) and lumbar DEXA %YAM (R=-0.32). Significant correlations were found between the 1,25D/25D ratio and serum levels of inorganic phosphate (iP), parathyroid hormone, and alkaline phosphatase (ALP). The 1,25D/25D ratio had gender-specific characteristics: the ratio was significantly correlated with age in males (R=-0.49), while it was significantly correlated with BMI in females (R=0.34). Conclusions The results of this study suggested that vitamin D activity is negatively correlated with bone mineral density, being reduced in aged males but enhanced in obese females.

Serum vitamin D levels in relation to metabolic syndrome: A systematic review and dose-response meta-analysis of epidemiologic studies

Several epidemiological studies examined the association of serum vitamin D with metabolic syndrome (MetS), but the findings were inconsistent. We conducted a systematic review and dose-response meta-analysis to quantify the association between blood vitamin D levels and MetS in adults. A systematic search up to December 2020 was conducted in MEDLINE (PubMed), ISI (Web of Science), Scopus, and Google Scholar databases for epidemiological studies that assessed the relation of serum 25-hydroxyvitamin D (as the exposure) and MetS (as the outcome) in adults. Eligible cross-sectional studies were restricted to those with representative populations. Finally, 43 studies were included in the analysis (38 cross-sectional, one nested case-control, and four cohorts studies). Combining 41 effect sizes from 38 cross-sectional studies included 298,187 general adult population revealed that the highest level of serum vitamin D, compared with the lowest level, was significantly related to a 43% decreased odds of MetS in developed countries (odds ratio [OR]: 0.57; 95% confidence interval [CI]: 0.49-0.65) and 40% in developing countries (OR: 0.60; 95% CI: 0.52-0.70). Linear dose-response analysis (including 222,175 healthy individuals and 39,308 MetS patients) revealed that each 25 nmol/L increase in serum vitamin D level was significantly associated with a 15% decreased odds of MetS (OR: 0.85; 95% CI: 0.80-0.91); however, we found no significant nonlinear association. Meta-analysis of five prospective studies with 11,019 participants revealed no significant relation (relative risk [RR]: 0.70; 95% CI: 0.37-1.32). This meta-analysis indicated an inverse association between serum vitamin D concentrations and risk of MetS in general adult populations in cross-sectional studies in a dose-response manner. However, no significant association was found in a small number of cohorts. More prospective studies are needed to confirm the causality of this relationship.

Vitamin D and new insights into pathophysiology of type 2 diabetes

Deficiency in vitamin D plays a role in the onset and development of insulin resistance (IR) and type 2 diabetes (T2DM). A normal level of vitamin D is able to reduce low grade inflammation, which is a major process in inducing insulin resistance. It is also engaged in maintaining low resting levels of reactive species and radicals, normal Ca²⁺ signaling, a low expression of pro-inflammatory cytokines but increased formation of anti-inflammatory cytokines. Vitamin D is also able to prevent hypermethylation (of DNA) and consequent functional inactivation of many genes, as well as other epigenetic alterations in β cells and in other insulin-sensitive peripheral tissues, mainly liver, adipose tissue and muscle. Vitamin D deficiency thus belongs to key factors accelerating the development of IR and consequently T2DM as well. However, vitamin D supplementation aimed at the control of glucose homeostasis in humans showed controversial effects. As a result, further studies are running to gain more detailed data needed for the full clinical utilization of vitamin D supplementation in the prevention and treatment of T2DM. Until new results are published, supplementation with high doses of vitamin D deficiency is not recommended. However, prevention of vitamin D deficiency and its correction are highly desired.