Glucose intolerance and impairment of insulin secretion in relation to vitamin D deficiency in east London Asians

Associations of Serum Vitamin D Concentration with Cardiovascular Risk Factors and the Healthy Lifestyle Score

Vitamin D status is reportedly associated with risk factors for cardiovascular disease (CVD), although conflicting data have been generated. The healthy lifestyle score (HLS) was formulated as a primary approach toward preventing CVD; however, data on the association between the HLS and vitamin D status remain insufficient. This study aimed to investigate the associations of CVD risk factors and the HLS with serum 25-hydroxyvitamin D concentration in adults who participated in a national survey. HLS components, including body mass index, smoking status, alcohol consumption, physical activity, and dietary pattern, as well as other risk factors, including diabetes mellitus (DM), hypertension (HTN), and dyslipidemia (DL), were fitted in multiple linear regression models to determine their association with vitamin D status. DM, HTN, and DL were inversely associated whereas a balanced dietary pattern, alcohol consumption, and physical activity were positively associated with serum vitamin D concentration (p < 0.01). Furthermore, a strong association was observed between the total HLS and serum vitamin D concentration (p for trend <0.01); the regression coefficient estimate (95% confidence interval) for the highest score was 1.41 (0.65, 2.17) (p < 0.01) compared with that for the lowest. These findings suggest that CVD risk factors and the HLS may reflect vitamin D status.

Vitamin D and bone metabolism in Graves' disease: a prospective study

PURPOSE

Vitamin D and osteoporosis in Graves' disease (GD) have been examined in cross-sectional studies with divergent results. Here, we prospectively studied vitamin D metabolism and bone health in patients with newly diagnosed GD.

METHODS

Thirty consecutive patients with de novo overt thyrotoxicosis diagnosed with GD were included. At diagnosis, none of the patients were treated with vitamin D or anti-osteoporotic drugs. All patients were initially treated with antithyroid drugs. Blood samplings were taken at baseline and at 6 weeks, 3, 6, 12 and 24 months after treatment start. Serum levels of 25OHD3, 1,25OH2D3, calcium, parathyroid hormone (PTH), and C-terminal telopeptides of Type I collagen (CTX-I) were analysed. Bone mineral density (BMD) was measured at baseline, and 1 and 2 years after treatment initiation.

RESULTS

At diagnosis, patients with GD did not have vitamin D deficiency. There were no significant correlations between levels of 25OHD3 and thyrotoxicosis. Upon treatment of the thyrotoxicosis, serum calcium fell transiently, and PTH and 1,25OH2D3 increased. 25OHD3 fell within the normal range and stabilised at 6 months. CTX-I fell over 12 months, BMD increased significantly up to 2 years, p = 0.002, < 0.001 and 0.005 in the spine, left total hip and left femoral neck, respectively.

CONCLUSIONS

The present data underline that thyrotoxicosis has a negative impact on bone health and demonstrate fine-tuned dynamics in bone and vitamin D metabolism. Upon treatment, bone health improved over a follow-up period of 24 months despite rising PTH. Increased conversion of 25OHD3 to 1,25OH2D3 occurs during treatment of GD.

Effects of long-term vitamin D supplementation on metabolic profile in middle-aged and elderly patients with type 2 diabetes

To evaluate the effects of long-term vitamin D supplementation on metabolic profiles in middle-aged to elderly patients with type 2 diabetes (T2D), a randomized controlled trial was conducted among patients with T2D aged 50-70 years. A total of 270 patients underwent randomization with 135 being allocated to the vitamin D group and 135 to the control group, and participants in the vitamin D group received oral vitamin D₃ (800 IU/day) for 30 months. Serum 25(OH)D and metabolic variables were measured at baseline, and after 6, 12, 18, and 30 months of intervention. After 30 months, the vitamin D group showed a greater increase in serum 25(OH)D than the control group (12.39 ± 6.99 vs 5.35 ± 5.29 ng/ml, P < 0.001). Meanwhile, changes in the levels of fasting insulin, HOMA-IR, non-high-density-lipoprotein cholesterol (non-HDL-C), high-sensitivity C-reactive protein (hs-CRP), and uric acid differed significantly between the two groups (all P < 0.05). Stratified analysis indicated that change in uric acid differed significantly between the two groups in subgroup with baseline 25(OH)D ≥ 20 ng/ml (P = 0.042) or subgroup with female patients (P = 0.034). And the change in fasting blood glucose (FBG) differed significantly between the vitamin D group (-0.30 ± 2.52 mmol/L) and the control group (0.49 ± 1.78 mmol/L, P = 0.049) among patients achieving 25(OH)D concentrations of 30 ng/ml at the end of this trial. A significant difference in the change of triglyceride was observed between the two groups among patients with obesity at baseline [0.05(-0.59, 0.23) vs 0.41(-0.01, 0.80) mmol/L, P = 0.023]. These findings suggested that long-term vitamin D supplementation significantly reduced fasting insulin, HOMA-IR, and serum concentrations of non-HDL-C, hs-CRP, and uric acid among middle-aged to elderly patients with T2D. And vitamin D status, gender, and baseline obesity may modify the effects of vitamin D supplementation.

An Exploration of How Solar Radiation Affects the Seasonal Variation of Human Mortality Rates and the Seasonal Variation in Some Other Common Disorders

Many diseases have large seasonal variations in which winter overall mortality rates are about 25% higher than in summer in mid-latitude countries, with cardiovascular diseases and respiratory infections and conditions accounting for most of the variation. Cancers, by contrast, do not usually have pronounced seasonal variations in incidence or mortality rates. This narrative review examines the epidemiological evidence for seasonal variations in blood pressure, cardiovascular disease rates and respiratory viral infections in relation to atmospheric temperature and humidity, and solar UV exposure through vitamin D production and increased blood concentrations of nitric oxide. However, additional mechanisms most likely exist by which solar radiation reduces the risk of seasonally varying diseases. Some studies have been reported with respect to temperature without considering solar UV doses, although studies regarding solar UV doses, such as for respiratory infections, often consider whether temperature can affect the findings. More research is indicated to evaluate the relative effects of temperature and sun exposure on the seasonality of mortality rates for several diseases. Since solar ultraviolet-B (UVB) doses decrease to vanishingly small values at higher latitudes in winter, the use of safe UVB lamps for indoor use in winter may warrant consideration.

Associations of Vitamin D Level and Glucoregulatory Parameters in Type 2 Diabetes Mellitus

Vitamin D is known to affect the functions of pancreatic beta cells, but the effects of vitamin D deficiency on glucoregulatory mechanisms are still inconclusive. The aim of this study was to link vitamin D levels with parameters of insulin resistance and insulin secretion. The study included 70 male and female participants, 40 newly diagnosed patients with type 2 diabetes mellitus (T2DM) and 30 healthy controls. All participants were tested for fasting glucose, hemoglobin A1c, fasting insulin, vitamin D levels, and the HOMA indexes were calculated using HOMA2 calculator. Fasting glucose levels, insulinemia, hemoglobin A1c levels and HOMA IR were all significantly higher in the diabetic group (p<0.001), while vitamin D levels and HOMA S index were significantly lower (p<0.001). HOMA-B values did not differ between the two groups (p=0.31). Vitamin D levels moderately correlated with HOMA S and HOMA B indexes (r=0.466, p<0.001; r=0.394, p<0.001, respectively), whereas a negative correlation was found between vitamin D levels and HOMA IR (r=−0.285; p<0.001). Multiple regression analysis showed that vitamin D levels significantly predicted the values of HOMA B index (p=0.001), but they had no predictive value on HOMA IR (p=0.26). In conclusion, the group of newly diagnosed patients with T2DM showed significantly lower vitamin D values compared to the healthy control group. The connection between vitamin D, glucose levels, hemoglobin A1c and insulin secretion index underlines the role of this vitamin in glucoregulation.

Serum, Dietary, and Supplemental Vitamin D Levels and Insulin Resistance in 6294 Randomly Selected, Non-Diabetic U.S. Adults

The primary aim of this study was to determine the associations between serum, dietary, and supplemental vitamin D levels and insulin resistance in 6294 non-diabetic U.S. adults. A total of 8 years of data from the 2011−2018 National Health and Nutrition Examination Survey (NHANES) and a cross-sectional design were utilized to answer the research questions. Serum vitamin D levels were quantified using high-performance liquid chromatography−tandem mass spectrometry. Dietary and supplemental vitamin D intakes were assessed using the average of two 24 h dietary recalls taken 3−10 days apart. The homeostatic model assessment (HOMA), based on fasting glucose and fasting insulin levels, was employed to index insulin resistance. Demographic covariates were age, sex, race, and year of assessment. Differences in physical activity, body mass index (BMI), cigarette smoking, body weight, season, and energy intake were also controlled statistically. Serum levels of vitamin D differed significantly, and in a dose−response order, across quartiles of HOMA-IR, after adjusting for year, age, sex, and race (F = 30.3, p < 0.0001) and with all the covariates controlled (F = 5.4, p = 0.0029). Dietary vitamin D levels differed similarly across HOMA-IR quartiles, but to a lesser extent, respectively (F = 8.1, p = 0.0001; F = 2.9, p = 0.0437). Likewise, supplemental vitamin D levels also differed across the HOMA-IR quartiles, respectively (F = 3.5, p = 0.0205; F = 3.3, p = 0.0272). With all the covariates controlled, the odds of having insulin resistance were significantly greater for those in the lowest quartile of serum and supplemental vitamin D intake compared to the other quartiles combined. In conclusion, in this nationally representative sample, serum, dietary, and supplemental vitamin D were each predictive of insulin resistance, especially in those with low serum levels and those with no supplemental intake of vitamin D.

Bioactive Compounds and Diabetes Mellitus: Prospects and Future Challenges

Diabetes mellitus is a metabolic condition that influences the endocrine framework. Hyperglycemia and hyperlipidemia are two of the most widely recognized metabolic irregularities in diabetes, just as two of the most well-known reasons for diabetic intricacies. Diabetes mellitus is a persistent illness brought about by metabolic irregularities in hyperglycemic pancreatic cells. Hyperglycemia can be brought about by an absence of insulin-producing beta cells in the pancreas (Type 1 diabetes mellitus) or inadequate insulin creation that does not work effectively (Type 2 diabetes mellitus). Present diabetes medication is directed toward directing blood glucose levels in the systemic circulation to the typical levels. Numerous advanced prescription medicines have many negative results that can bring about unexpected severe issues during treatment of the bioactive compound from a different source that is beneficially affected by controlling, adjusting metabolic pathways or cycles. Moreover, a few new bioactive medications disengaged from plants have shown antidiabetic action with more noteworthy adequacy than the oral hypoglycemic agent that specialists have utilized in clinical treatment lately. Since bioactive mixtures are collected from familiar sources, they have a great activity in controlling diabetes mellitus. This study discusses bioactive compounds and their activity to manage diabetes mellitus and their prospects. Though bioactive compound has many health beneficial properties, adequate clinical studies still need to gain large acknowledge that they are effective in the management of diabetes mellitus.

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

Findings from epidemiologic studies that evaluated the relationship between serum vitamin D levels and metabolic syndrome (MetS) in children were contradictory. We conducted a systematic review and meta-analysis on the relation of serum 25(OH)D levels and MetS in children. A comprehensive search was conducted in electronic databases, up to November 2020. Eleven cross-sectional studies that reported the link between circulating vitamin D levels and MetS in children were included in the analysis. Combining 11 effect sizes from 11 cross-sectional studies with 22,196 participants revealed that highest versus lowest serum vitamin D concentration was significantly associated with a 50% reduced odds of MetS in children (OR: 0.50; 95%CI: 0.39, 0.64). Subgroup analysis by study location revealed decreased odds of MetS in both non-Asian (OR: 0.45; 95%CI: 0.33, 0.63) and Asian countries (OR: 0.54; 95%CI: 0.39, 0.76) with no heterogeneity in these subgroups. When we confined the studies to those with representative populations (n = 21,611), a significant inverse association was found between highest versus lowest circulating vitamin D level and MetS (OR: 0.55; 95%CI: 0.42, 0.71). Dose-response analysis showed that each 10 ng/ml (or 25 nmol/L) in serum vitamin D was linearly related to a 12% reduced odds of MetS (OR: 0.88; 95%CI: 0.78, 0.99) in children. A nonlinear association was also detected between serum 25(OH)D and MetS. This meta-analysis revealed that circulating vitamin D concentration was inversely associated with odds of MetS in children, in a dose-response fashion. The same finding was found in the studies with representative populations.

1α,25-(OH)2 vitamin D3 prevents insulin resistance and regulates coordinated exocytosis and insulin secretion

Vitamin D₃ is associated with improvements in insulin resistance and glycemia. In this study, we investigated the short-term effect of 1α,25(OH)₂ Vitamin D₃ (1,25-D₃) and cholecalciferol (vitamin D₃) on the glycemia and insulin sensitivity of control and dexamethasone-induced insulin-resistance rats. ⁴⁵Ca²⁺ influx responses to 1,25-D₃ and its role in insulin secretion were investigated in isolated pancreatic islets from control rats. In vivo, 5 d treatment with 1,25-D₃ (i.p.) prevented insulin resistance in dexamethasone-treated rats. Treatment with 1,25-D₃ improved the activities of hepatic enzymes, serum lipids and calcium concentrations in insulin-resistant rats. 25-D₃ (o.g.) does not affect insulin resistance. In pancreatic islets, 1,25-D₃ increased insulin secretion and stimulated rapid response ⁴⁵Ca²⁺ influx. The stimulatory effect of 1,25-D₃ on ⁴⁵Ca²⁺ influx was decreased by diazoxide, apamine, thapsigargin, dantrolene, 2-APB, nifedipine, TEA, PKA, PKC, and cytoskeleton inhibitor, while it was increased by glibenclamide and N-ethylmaleimide. The stimulatory effect of 1,25-D₃ on ⁴⁵Ca²⁺ influx involves the activation of L-type VDCC, K⁺-ATP, K⁺-Ca^2+, and Kv channels, which augment cytosolic calcium. These ionic changes mobilize calcium from stores and downstream activation of PKC, PKA tethering vesicle traffic and fusion at the plasma membrane for insulin secretion. This is the first study highlighting the unprecedented role of 1,25-D₃ (short-term effect) in the regulation of glucose homeostasis and on prevention of insulin resistance. Furthermore, this study shows the intracellular β-cell signal transduction of 1,25-D₃ through the modulation of pivotal ionic channels and proteins exhibiting a coordinated exocytosis of vesicles for insulin secretion.

Vitamin D decreases pancreatic iron overload in type 2 diabetes through the NF-κB-DMT1 pathway

Emerging evidence has deemed vitamin D as a potential candidate for the intervention of type 2 diabetes (T2D). Herein, we explored the underlying mechanisms of T2D prevention by vitamin D, concentrating on pancreatic iron deposition reported recently. Zucker diabetic fatty (ZDF) rats were treated by vitamin D, with age-matched Zucker lean rats as control. As expected, vitamin D treatment for ZDF rats normalized islet morphology and β-cell function. Moreover, vitamin D alleviated iron accumulation and apoptosis in pancreatic cells of ZDF rats, accompanied by lowered divalent metal transporter 1 (DMT1) expression. Consistently, similar results were observed in high glucose-stimulated INS-1 cells treated with or without vitamin D. Nuclear factor-κB (NF-κB), a transcription factor involving DMT1 regulation, was activated in pancreases of ZDF rats and INS-1 cells exposed to high glucose, but inactivated by vitamin D or BAY 11-7082, a NF-κB inhibitor. Futhermore, IL-1β functioning as NF-κB activator abolished the suppression of NF-κB activation, DMT1 induction and the attenuation of apoptosis as a consequence of vitamin D incubation. Our study showed that iron overload in pancreas may contribute to T2D pathogenesis and uncovered a potentially protective role for vitamin D on iron deposition of diabetic pancreas through NF-κB- DMT1 signaling.

Conundrum of vitamin D on glucose and fuel homeostasis

As an endocrine hormone, vitamin D plays an important role in bone health and calcium homeostasis. Over the past two decades, the non-calcemic effects of vitamin D were extensively examined. Although the effect of vitamin D on beta cell function were known for some time, the effect of vitamin D on glucose and fuel homeostasis has attracted new interest among researchers. Yet, to date, studies remain inconclusive and controversial, in part, due to a lack of understanding of the threshold effects of vitamin D. In this review, a critical examination of interventional trials of vitamin D in prevention of diabetes is provided. Like use of vitamin D for bone loss, the benefits of vitamin D supplementation in diabetes prevention were observed in vitamin D-deficient subjects with serum 25-hydroxyvitamin D < 50 nmol/L (20 ng/mL). The beneficial effect from vitamin D supplementation was not apparent in subjects with serum 25-hydroxyvitamin D > 75 nmol/L (30 ng/mL). Furthermore, no benefit was noted in subjects that achieved serum 25-hydroxyvitamin D > 100 nmol/L (40 ng/mL). Further studies are required to confirm these observations.

Serum vitamin D levels in relation to type-2 diabetes and prediabetes in adults: a systematic review and dose-response meta-analysis of epidemiologic studies

BACKGROUND

Findings of observational studies that investigated the relationship between vitamin D deficiency and abnormal glucose homeostasis were contradictory. This meta-analysis of epidemiologic studies evaluated the association of vitamin D status and risk of type-2 diabetes (T2D) and prediabetes in adults.

METHODS

A systematic search was conducted on all published articles in five electronic databases (including MEDLINE/PubMed, EMBASE, Institute for Scientific Information, Scopus and Google scholar), up to August 2020. Twenty-eight prospective cohort and nested case-control studies and 83 cross-sectional and case-control investigations that reported relative risks (RRs) or odds ratios (ORs) with 95% confidence intervals (CIs) for abnormal glucose homeostasis in relation to serum vitamin D levels in adults were included in the analysis.

RESULTS

In prospective studies, high versus low level of vitamin D was respectively associated with significant 35%, 30% and 51% decrease in risk of T2D (RR:0.65; 95%CI: 0.55-0.76; 27 effect sizes), combined T2D and pre-diabetes (RR:0.70; 95%CI: 0.52-0.95; 9 effect sizes) and pre-diabetes (RR:0.49; 95%CI: 0.26-0.93; 2 effect sizes). These inverse associations were significant in almost all subgroups. Dose-response analysis in prospective studies showed that each 10 ng/ml increase in serum vitamin D levels resulted in 12% and 11% reduced risk of T2D (RR:0.88; 95%CI: 0.83-0.94) and combined T2D and prediabetes (RR:0.89; 95%CI: 0.87-0.92), respectively. In cross-sectional and case-control studies, highest versus lowest level of serum vitamin D was linked to reduced odds of T2D (OR:0.64; 95%CI: 0.57-0.72; 42 effect sizes) and combined T2D and pre-diabetes (OR:0.79; 95%CI: 0.74-0.85; 59 effect sizes); but not pre-diabetes (OR:0.64; 95%CI: 0.17-2.37; 11 effect sizes).

CONCLUSION

This meta-analysis of epidemiologic studies disclosed that serum vitamin D level was reversely associated with the risk of T2D and combined T2D and prediabetes in adults, in a dose-response manner. However, the association was not remarkable for pre-diabetes.

Dose-response relationship between serum 25-hydroxyvitamin D and the risk of metabolic syndrome

BACKGROUND & AIMS

There are conflicting results for the association of 25-hydroxyvitamin D [25(OH)D] with metabolic syndrome (MetS). The aim of this study was to investigate the relationship between serum 25(OH)D concentration and MetS and its components in a Chinese adult population.

METHODS

A cross-sectional study of 25,691 men and 22,146 women from China was performed in 2017. MetS was defined according to National Cholesterol Education Program Adult Treatment Panel Ш. Logistic and restricted cubic spline regression analyses were used to assess the association between 25(OH)D and MetS.

RESULTS

Of the 43,837 participants aged 18-96 years, the prevalence of MetS was 21.0%. The adjusted odds ratios (ORs) for MetS decreased gradually with increasing 25(OH)D concentrations (P for trend < 0.001). Compared with the lowest 25(OH)D quartile, the adjusted ORs (95% CIs) for MetS from second to the highest quartile were 0.95 (0.88-1.02), 0.82 (0.76-0.88), and 0.70 (0.65-0.75), respectively. We observed a linear dose-response relationship between 25(OH)D concentrations and MetS risk (P for nonlinear trend = 0.35); the risk of MetS decreased by 20% (OR = 0.80, 95%CI: 0.77-0.82) for each 10 ng/ml increment in 25(OH)D concentration. The inverse association was more evident in men and participants with eGFR <60 ml/min/1.73 m² or AST ≥40 U/L (all P for interaction < 0.05). Moreover, significant inverse relationships were observed between 25(OH)D and elevated triglycerides, reduced high-density lipoprotein cholesterol and elevated blood pressure.

CONCLUSIONS

These findings suggested that higher 25(OH)D concentrations were independently associated with a dose-response decreased risk of MetS among Chinese adults.

A randomized controlled clinical trial comparing calcitriol versus cholecalciferol supplementation to reduce insulin resistance in patients with non-alcoholic fatty liver disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the world with no definite treatment. Insulin resistance (IR) and low serum vitamin D are closely linked to NAFLD. Since there is no comparative study on the effect of calcitriol with cholecalciferol on NAFLD based on homeostasis model of insulin resistance (HOMA-IR) as an IR indicator, so we designed this research.

METHODS

A double blind randomized clinical trial was conducted on patients with NAFLD with concomitant vitamin D deficiency/insufficiency at two referral tertiary teaching medical centers, from July 2017 to January 2019. Patients were randomly divided into two groups: calcitriol (1 mcg/day) and cholecalciferol (50,000 IU/week) for 8 weeks. Before and after the intervention, anthropometric and laboratory data were measured and HOMA-IR was calculated for each patient.

RESULTS

54 patients completed the trial. In total, calcitriol supplementation improved serum insulin levels as well as IR based on the HOMA-IR index, significantly compared to the cholecalciferol group. HOMA-IR decreased 1.8 times more in patients receiving calcitriol than in those receiving cholecalciferol, which was clinically meaningful. The observed changes were more pronounced in patients with higher baseline body mass index. Moreover, calcitriol was more associated with a significant decrease in liver enzymes and cholesterol levels comparing to cholecalciferol.

CONCLUSION

Based on the findings of this study, the use of calcitriol supplementation significantly reduced HOMA-IR as an IR indicator in NAFLD patients, compared to cholecalciferol. To confirm this findings, further studies with larger sample sizes are recommended.

The role of yoghurt consumption in the management of type II diabetes

Enrichment of yoghurt with specific ingrdients beneficially affects the management of Type II Diabetes Mellitus (DMII). As far as the role of yoghurt in the management of DMII is concerned, the limited number of randomized clinical trials (RCTs) which have been conducted suggest that daily intake of yoghurt enriched with vitamin D and/or calcium as well as probiotics positively influences glycemic regulation and may contribute to more effective control of the disease. It is argued that the various ingredients which are already contained in the complex matrix of food, such as bioactive peptides, calcium, B-complex vitamins and beneficial microbes, as well as the fact that it can be used as a vehicle for the inclusion of other effective ingredients can have an impact on the metabolic control of diabetic patients. The aim of this review is to present the RCTs which have been conducted in the last decade in patients with DMII in an attempt to highlight the positive effects of yoghurt in the management of the disease.

Why do so many trials of vitamin D supplementation fail?

Our knowledge of vitamin D has come a long way since the 100 years it took for doctors to accept, between 1860 and 1890, that both sunlight and cod liver oil (a well-known folk remedy) cured and prevented rickets. Vitamins D2/D3 were discovered exactly a hundred years ago, and over the last 50 years vitamin D has been found to have many effects on virtually all human tissues and not just on bone health, while mechanisms affecting the actions of vitamin D at the cellular level are increasingly understood, but deficiency persists globally. Observational studies in humans have shown that better provision of vitamin D is strongly associated, dose-wise, with reductions in current and future health risks in line with the known actions of vitamin D. Randomised controlled trials, commonly accepted as providing a 'gold standard' for assessing the efficacy of new forms of treatment, have frequently failed to provide supportive evidence for the expected health benefits of supplementation. Such RCTs, however, have used designs evolved for testing drugs while vitamin D is a nutrient; the appreciation of this difference is critical to identifying health benefits from existing RCT data and for improving future RCT design. This report aims, therefore, to provide a brief overview of the evidence for a range of non-bony health benefits of vitamin D repletion; to discuss specific aspects of vitamin D biology that can confound RCT design and how to allow for them.

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.

Effect of Vitamin Don Blood Sugar, HbA1c and Serum Insulin Levels in Streptozotocin-Induced Diabetic Rats

Background: Type 2 diabetes mellitus (T2DM) is an increasingly common disorder characterized by chronic hyperglycemia and marked dyslipidemia. This study evaluates the effect of vitamin D supplementation alone and in combination with glimepiride in streptozotocin-induced T2DM in rats. Materials and methods: A total of 30 Wistar albino rats of either sex weighing 150-200 g were included in the study. The effect of oral administration of vitamin D was evaluated in streptozotocin-induced T2DM in rats. Blood glucose, serum insulin, serum HbA1c, and serum vitamin D were evaluated. Results: D treatment has significantly improved hyperglycemia, hyperinsulinemia, and insulin sensitivity compared with the non-treated diabetic rats. Oral administration of vitamin D in streptozotocin-induced T2DM reduced blood sugar levels, increased insulin levels (more prominently when administered along with glimepiride) and decreased HbA1c levels (p<0.005). Conclusions: Administration of vitamin D can improve hyperglycemia and hyperinsulinemia in streptozotocin-induced T2DM in rats. Thus, it could be considered as an add on therapy along with other antidiabetic drugs.

Relationships between Total, Free and Bioavailable Vitamin D and Vitamin D Binding Protein in Early Pregnancy with Neonatal Outcomes: A Retrospective Cohort Study

Maternal vitamin D deficiency has been associated with adverse neonatal outcomes, however, existing results are inconsistent. Current data focus on total 25-hydroxyvitamin D (25(OH)D) as the common measure of vitamin D status, while additional measures including vitamin D-binding protein (VDBP) and free and bioavailable metabolites have not been explored in relation to neonatal outcomes. We examined whether VDBP and total, free, and bioavailable vitamin D metabolites in early pregnancy are associated with subsequent neonatal outcomes. In this retrospective analysis of 304 women in early pregnancy (<20 weeks gestation), demographic and anthropometric data were collected and total 25(OH)D (chemiluminescent assay), VDBP (polyclonal enzyme-linked immunosorbent assay (ELISA)) and albumin (automated colorimetry) were measured in bio-banked samples. Free and bioavailable 25(OH)D were calculated using validated formulae. Neonatal outcomes were derived from a medical record database. Higher maternal total and free 25(OH)D concentrations were associated with higher neonatal birthweight (β = 5.05, p = 0.002 and β = 18.06, p = 0.02, respectively), including after adjustment for maternal covariates including age, body mass index (BMI) and ethnicity (all p ≤ 0.04). Higher total 25(OH)D and VDBP concentrations were associated with a lower likelihood of neonatal jaundice (odds ratio [OR] [95%CI] = 0.997 [0.994, 1.000], p = 0.04 and 0.98 [0.96, 0.99], p = 0.03, respectively), but these were attenuated after adjustment for the above maternal covariates (both p = 0.09). Our findings suggest a novel association between free 25(OH)D and neonatal birthweight. Total 25(OH)D concentrations were also associated with birthweight, and both total 25(OH)D and VDBP were associated with jaundice, but the latter were not significant after adjustment. These results suggest a potential link between these metabolites and neonatal outcomes; however, further large-scale prospective studies are warranted.

Vitamin D3 supplementation improves glycemic control in type 2 diabetic patients: Results from an Italian clinical trial

Background: to evaluate the effects of Vitamin D3 on glyco-metabolic control in type 2 diabetic patients with Vitamin D deficiency. Methods: one hundred and seventeen patients were randomized to placebo and 122 patients to Vitamin D3. We evaluated anthropometric parameters, glyco-metabolic control, and parathormone (PTH) value at baseline, after 3, and 6 months. Results: a significant reduction of fasting, and post-prandial glucose was recorded in Vitamin D3 group after 6 months. A significant HbA_1c decrease was observed in Vitamin D3 (from 7.6% or 60 mmol/mol to 7.1% or 54 mmol) at 6 months compared to baseline, and to placebo (p < 0.05 for both). At the end of the study period, we noticed a change in the amount in doses of oral or subcutaneous hypoglycemic agents and insulin, respectively. The use of metformin, acarbose, and pioglitazone was significantly lower (p = 0.037, p = 0.048, and p = 0.042, respectively) than at the beginning of the study in the Vitamin D3 therapy group. The units of Lispro, Aspart, and Glargine insulin were lower in the Vitamin D3 group at the end of the study (p = 0.031, p = 0.037, and p = 0.035, respectively) than in the placebo group. Conclusions: in type 2 diabetic patients with Vitamin D deficiency, the restoration of value in the Vitamin D standard has led not only to an improvement in the glyco-metabolic compensation, but also to a reduced posology of some oral hypoglycemic agents and some types of insulin used.

The Vitamin D Assessment (ViDA) study - Design and main findings

Accumulating evidence from observational studies indicates that vitamin D status is inversely associated with a many non-skeletal diseases. This has initiated the conduct of several large clinical trials to determine if high dose vitamin D supplementation (≥ 2000 IU/day or monthly equivalent) prevents non-skeletal disease including cardiovascular disease, cancer and mortality. One of these trials is the Vitamin D Assessment (ViDA) Study which recruited 5110 participants, aged 50-84 years, mostly from primary care practices in Auckland, New Zealand. The intervention was a capsule that contained either 100,000 IU vitamin D3 or placebo, two of which were taken by each participant soon after randomization, and then monthly up to 31 July 2015 (median follow-up 3.3 years). Information on study outcomes came from self-completed questionnaires and health data collected routinely by the Ministry of Health. There was no effect of vitamin D on the main outcomes: cardiovascular disease, acute respiratory infections, non-vertebral fractures, falls and all cancer. In contrast, vitamin D increased persistence with taking statins among participants on long term statin therapy. Beneficial effects were seen also for lung function among ever smokers (especially if vitamin D deficient), and in participants with low 25-hydroxyvitamin D levels for bone mineral density and arterial function. The findings support future research being carried out mainly in people who are vitamin D deficient, although there are practical and ethical issues in recruiting such people into future vitamin D supplementation trials.

Complementary feeding practices and nutrient intakes of children aged 6-24 months from Bangladeshi background living in Tower Hamlets, East London: a feasibility study

BACKGROUND

The aim of this study was to assess dietary intakes and complementary feeding practices of children aged 6-24 months who are from Bangladeshi ancestry and living in Tower Hamlets, London, and determine the feasibility of a larger, population-representative study.

METHODS

Questionnaires for demographic variables and feeding practices, and 24-h dietary recalls were administered to 25 mothers to determine whether it would be feasible to conduct a similar study on a representative sample size of the same population. Data from both tools were used to determine adequacy of complementary feeding practices through the WHO indicators and an infant and child feeding index score as well as overall macronutrient and micronutrient intake.

RESULTS

Four children had varying suboptimal complementary feeding practices: two children failed to achieve the minimum dietary diversity, one child was being fed cow's milk before the age of 1 year, and one scored 'poor' on the infant and child feeding index. Most notably, the mean protein intake (39.7 g/day, SD 18.2) was higher than RNIs for all age groups (P = 0.001). Vitamin D intake was below recommendations (P = 0.006) for the 12-24-month age group. For the 10-12-month age group, zinc intake fell below recommendations (P = 0.028). For the 6-9-month combined age group, iron and zinc intakes were below recommendations (P = 0.021 and P = 0.002, respectively).

CONCLUSIONS

Given the feasibility of this study, the results obtained require a large-scale study to be conducted to confirm findings. Our initial results indicated that children from Bangladeshi heritage may not be meeting nutritional requirements; thus, a future intervention tailored to the needs of the Bangladeshi population may be required to improve aspects of complementary feeding practices and nutrient intakes of those children.

Association between serum 25-hydroxyvitamin D concentrations and metabolic syndrome in the middle-aged and elderly Chinese population in Dalian, northeast China: A cross-sectional study

AIMS/INTRODUCTION

To investigate the association between serum 25-hydroxyvitamin D (25-[OH]D) concentrations and metabolic syndrome (MetS) in the middle-aged and elderly Chinese population.

METHODS

The present study included 2,764 participants (aged >50 years). The joint interim statement was used for the standard definition of MetS. Serum 25-(OH)D concentrations were measured by electrochemiluminescence immunoassay. The study participants were categorized into quartiles based on serum 25-(OH)D concentrations, and the quartiles were calculated for the differences using anova and the χ2 -test for continuous and categorical data, respectively. A logistic regression analysis model was applied to estimate the odds ratios and 95% confidence intervals (95% CI) for each quartile of serum 25-(OH)D concentrations compared with the highest quartile.

RESULTS

Serum 25-(OH)D levels were markedly lower in men in the MetS group than in those without MetS. We observed a negative correlation between the higher quartiles of serum 25-(OH)D levels and the presence of MetS among men. The correlation between serum 25-(OH)D levels and the prevalence of MetS persisted even after adjusting for potential confounders, including age, cigarette smoking status, alcohol consumption, physical activity, low-density lipoprotein, creatinine and total serum cholesterol. Adjusted odds ratios of MetS in the second through fourth compared with the lowest quartile for serum 25-(OH)D levels were 0.93 (95% CI 0.54-1.59), 0.89 (95% CI 0.50-1.56) and 0.48 (95% CI 0.28-0.84), respectively.

CONCLUSIONS

Decreased serum 25-(OH)D level is significantly correlated with MetS in middle-aged men.

The prevalence of vitamin D deficiency among patients with type 2 diabetes seen at a referral hospital in Kenya

Introduction

The prevalence of diabetes mellitus is rising at an alarming rate, calling for more insights into its pathogenetic mechanisms, and other factors involved in its progression. The prevalence of vitamin D deficiency is higher in diabetic compared to non-diabetic patients, and is associated with poor glycaemic control. This has not been documented among diabetic patients in Kenya. Aims: to determine the prevalence of hypovitaminosis D among type 2 diabetic patients at Kenyatta National Hospital in Nairobi, Kenya.

Methods

We recruited type 2 diabetic patients on follow-up at Kenyatta National Hospital. Measurements of height, weight and waist/hip ratios were taken. We drew 6mls of peripheral blood to determine vitamin D, zinc and HbA1c levels.

Results

A total of 151 participants were recruited, with 69.5% females and mean age of 58.2 years. Hypertension was found in 72.8% of the participants, and obesity in 37.7%. The mean HbA1c levels were 8.46%, and 62.9% had poor glycaemic control. The mean vitamin D level was 31.40ng/ml. Vitamin D deficiency and insufficiency was found in 38.4% and 21.9% of the participants respectively. We found a significant inverse correlation between vitamin D and glycaemic control (r = -0.09, p = 0.044) and vitamin D and BMI (r = - 0.145, p = 0.045).

Conclusion

In this study population on long-term follow-up for diabetes, there was high prevalence of vitamin D deficiency. This forms a basis for further management of patients with poor glycaemic control. Further studies are needed to document the causal association between poor glycaemic control and vitamin D deficiency.

The Efficacy of Vitamin D Supplementation against Nonalcoholic Fatty Liver Disease: A Meta-Analysis

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of liver disease worldwide. If this disease is not appropriately controlled, it can eventually cause chronic liver damage, including cirrhosis and hepatocellular carcinoma. Accordingly, the adoption of appropriate interventions to control NAFLD is important for any healthcare system. The aim of the present systematic review and meta-analysis was to clarify the effect of vitamin D supplementation on NAFLD. PubMed, Scopus, Science Direct, ISI Web of Science, and Google Scholar were systematically searched up to March 2019 to find clinical trials that examined the effects of vitamin D supplementation on liver enzyme levels in NAFLD patients. Means for liver enzymes and potential sources of heterogeneity were extracted. A subgroup analysis was performed to detect potential sources of interstudy heterogeneity. Nine trials (10 arms) comprising 467 participants were eligible for meta-analysis. The results from a pooled analysis did not reveal a significant effect of vitamin D intake on alanine aminotransferase (-2.88 U/L; 95% CI, -6.03 to 0.27; I² = 85%), aspartate aminotransferase (-0.10 U/L; 95% CI, -1.18 to 0.97; I² = 26%), and γ-glutamyltransferase levels (0.12 U/L; 95% CI, -5.94 to 6.18; I² = 38%). The meta-analysis suggested a significant reduction in alkaline phosphatase (-13.79 U/L; 95% CI, -22.13 to -5.45; I² = 72%) following vitamin D supplementation. This effect was robust in the subgroup in which > 3,000 IU/day vitamin D was administered (-19.74 U/L; 95% CI, -25.36 to -14.12; I² = 0.0%). The present meta-analysis does not suggest the efficacy of vitamin D supplementation on NAFLD treatment.

25-Hydroxyvitamin D and the risk of incident diabetes in Hong Kong Chinese

OBJECTIVE

To investigate the relationship between serum 25-hydroxyvitamin D (25(OH)D) and risk of incident diabetes in Hong Kong Chinese, after accounting for the effect of multiple bone- and mineral-related markers.

DESIGN

We conducted a retrospective study on the Hong Kong Osteoporosis Study cohort. Incident diabetes was ascertained using electronic medical records. Serum 25(OH)D was measured at baseline and its association with incident diabetes was evaluated using multivariable Cox proportional-hazard regression.

PARTICIPANTS

Individuals (n 4342) aged 20 years or above (1395 men, 2947 women; mean age 54·3 (sd 16·5) years) from the Hong Kong Osteoporosis Study, who were free of diabetes at baseline, were included.

RESULTS

During 40 124·7 person-years of follow-up (a median of 9·2 years), 443 participants developed diabetes. Mean 25(OH)D was 63·34 (sd 13·07) nmol/l. Age-, sex- and BMI-adjusted Cox proportional-hazard regression showed no significant difference in the risk of incident diabetes between the lowest and the highest quintiles of 25(OH)D. In the analysis of the interaction effect between 25(OH)D and serum Ca, the interaction term did not affect the risk of incident diabetes significantly (P = 0·694). Similarly, there was no significant interaction of different subgroups (age, sex, BMI, femoral-neck T-score, serum Ca levels) with serum 25(OH)D.

CONCLUSIONS

The present study finds that serum vitamin D level is not associated with the risk of incident diabetes in Hong Kong Chinese and this relationship is not modified by serum Ca level.

The Effect of Vitamin D Supplementation on Glycaemic Control in Women with Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

Vitamin D deficiency is highly prevalent amongst pregnant women and is linked to a range of adverse complications, including gestational diabetes. However, there is no consensus among researchers regarding the impact of vitamin D supplementation in alleviating adverse effects in gestational diabetes. The objective of this systematic review and meta-analysis was to determine whether supplementation of vitamin D given to women with gestational diabetes can promote glycaemic control. EMBASE and PubMed were searched up to November, 2018. The selection criteria included randomised controlled trials of the effect of vitamin D supplementation (1000-4762 IU/day) on pregnant women with gestational diabetes mellitus. Study data and outcome measures (fasting blood glucose, glycated haemoglobin and serum insulin) were extracted from included studies. Random-effects models were used for meta-analyses. Heterogeneity tests, and analysis of the risk of bias were conducted. Most of the studies were graded as having either low risk or moderate risk of bias although two studies had a high risk of bias in the areas of blinding of participants and personnel, and incomplete outcome data. On the other hand, the heterogeneity statistic (I²) ranged from 0-41% in the studies included. Five randomised controlled trials were selected for this review and meta-analysis (involving a total of 173 participants supplemented with vitamin D and 153 participants as control drawn from the studies). Vitamin D supplementation was associated with a decrease in fasting blood glucose by a mean of 0.46 mmol/L (-0.68, -0.25) (p < 0.001), glycated haemoglobin by a mean of 0.37% (-0.65, -0.08) (p < 0.01) and serum insulin concentration by mean of 4.10 µIU/mL (-5.50, -2.71) (p < 0.001) compared to controls. This review shows evidence that vitamin D supplementation has the potential to promote glycaemic control in women with Gestational Diabetes Mellitus (GDM). However, due to the limited number of studies in the meta-analysis, the conclusion should be interpreted with caution. Further studies are needed to fully understand the exact mechanism by which vitamin D influences glucose metabolism.

Association between vitamin D status and glycemic profile in postmenopausal women with type 2 diabetes

The aim of this study is to evaluate the association between vitamin D status and glycemic profile in postmenopausal women with type 2 diabetes. A cross-sectional study was carried out with 70 (59.47 ± 6.47 years; 1.56 ± 0.05 m; 73.56 ± 13.01 kg; 30.30 ± 5.00 BMI kg/m²) postmenopausal women with type 2 diabetes (T2D). The blood samples were collected after fasting for 12 h and the main outcome parameters were serum follicle-stimulating hormone (FSH), estradiol; 25-OH vitamin D; insulin; C-Reactive Protein; cholesterol total (CT), triglycerides (TG), high density lipoprotein (HDL-cholesterol), glucose; calcium, HDL-cholesterol. The average serum 25(OH)D level in this study was 28.45 ± 8.26 ng/mL. The prevalence of hypovitaminosis D was 60%. Table 1 displays mean and standard deviation values for participants' characteristics. The postmenopause status of the women studied was confirmed by FSH and estradiol measurement. All the clinical and anthropometric characteristics did not show difference (p > 0.05) between the groups (Table 2). Triglycerides level was highest (p < 0.0391) in the hypovitaminosis D group. The other serum markers did not show statistical differences (p > 0.05) between the groups. In conclusion, our results suggest that only TG level shows a negative correlation with vitamin D status in postmenopausal women with type 2 diabetes.

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.

DOES THE 25-OH-VITAMIN D LEVEL AFFECT THE INSULIN RESISTANCE IN THE PATIENTS WITH NON-DIABETIC CHRONIC KIDNEY DISEASE?

Introduction

The aim of this study was to investigate the effects of vitamin D deficiency on insulin resistance in patients with non-diabetic chronic kidney disease.

Materials and Method

A total of 104 patients with non-diabetic, stage 2 and 3 chronic kidney disease, who had presented to the outpatient clinic during 2 winters, were included in the study. HOMA-IR rate of > 2.6 was accepted as insulin resistance. Severe 25-OH-vitamin D deficiency was defined as < 10 ng/mL, and 10-30 ng/mL was defined as vitamin D insufficiency. The difference in insulin resistance between the patients determined as having severe vitamin D deficiency and vitamin D insufficiency was investigated.

Results

Severe vitamin D deficiency was observed to be higher among women (61.8% vs. 38.2%), whereas insufficiency was more common among men (63.3% vs. 26.7%, p<0.05). Insulin resistance was observed to be higher in the group with severe deficiency (11.5 vs. 7.82, p<0.05). Insulin resistance was observed in 60% and 36.7% of the groups with severe deficiency and insufficiency, respectively (p<0.05).

Conclusion

Severe vitamin D deficiency had resulted in insulin resistance at a greater rate compared to vitamin D insufficiency in patients with non-diabetic chronic kidney disease (stage 2-3).

Vitamin D fortification of foods and prospective health outcomes

Vitamin D is essential for bone health and has significant roles in non-skeletal health and organ function. Dermal synthesis through exposure to ultraviolet B light is the major natural source of vitamin D, while only a small portion of the necessary amount can be acquired by a diet without fortified foods. In recent years, vitamin D deficiency as a result of lifestyles with inadequate sun exposure, has received increased attention due to its association with the increased risk of serious chronic diseases. This review summarizes our current understanding of food fortification strategies with vitamin D and the resulting health impact. Conventional and biotechnological approaches can be used for the production of new and novel vitamin D rich or vitamin D fortified foods. The availability of a wider range of every-day consumed fortified foods as part of a "Daily D" public health policy can contribute to the improvement of vitamin D status and to prevention of vitamin D deficiency.

Impact of vitamin D treatment on 25 hydroxy vitamin D levels and insulin homeostasis in obese African American adolescents in a randomized trial

BACKGROUND

Obesity is affecting children in epidemic proportions in the United States with nearly 25% of children being obese. Consequences of obesity including dyslipidemia, type 2 diabetes and cardiovascular disease are leading to morbidity at younger ages. Parallel to the obesity and diabetes epidemics, the prevalence of vitamin D deficiency has reached very high levels and has been associated with insulin resistance and dyslipidemia. Studies exploring the impact of vitamin D repletion on insulin sensitivity and dyslipidemia in children are sparse.The aim of this study was to determine the impact of treatment with vitamin D (ergocalciferol) in obese African American (AA) children on vitamin D levels and insulin secretion and sensitivity.

METHODS

This pilot study was conducted in a tertiary care Pediatric Emergency Department (ED). African American obese children (n = 29; 22 female) 13-17 y, with 25-hydroxy vitamin D level [25(OH)D] <20 ng/ml, were randomized to receive either 50,000 IU vitamin D2/week or a placebo for 12 weeks. Pre- and post- oral glucose tolerance testing with glucose and insulin levels drawn at 0, 30, 60, 90 and 120 min were performed. Pre/post intervention lipid profiles and calcium levels were also evaluated.

RESULTS

There was no difference in serum 25(OH)D between groups at baseline. Follow-up 25(OH)D level was greater in the treatment vs. placebo group, and significantly increased from baseline in the treatment group only. However, there was no difference between groups in baseline vs. follow-up insulin- or lipid-related parameters. Follow-up serum 25(OH)D was positively correlated with fasting insulin and high-density lipoprotein (HDL) level in the vitamin D treated group only.

CONCLUSION

While serum 25(OH)D levels in obese AA teens increased adequately with vitamin treatment for 12 weeks and correlated with fasting insulin, it did not significantly impact insulin secretion or sensitivity. Larger studies are required over a longer period of time to confirm and explore the reasons for this finding.

Evaluation of vitamin D receptor gene polymorphisms (Fok-I and Bsm-I) in T1DM Saudi children

BACKGROUND

Vitamin D deficiency conferred strongest susceptibility to pathogenesis of type 1 diabetes mellitus (T1DM). Altered gene expression and function have strong effect on VDR gene polymorphism.

OBJECTIVES

We aimed to check for the association of two single nucleotide polymorphisms (SNPs) in VDR gene (Fok-I and Bsm-I) with T1DM in Saudi children.

SUBJECTS AND METHODS

Cross-sectional study included 100 T1DM Saudi children, plus 102 unrelated healthy subjects. PCR technique was used for detection of Fok-I and Bsm-I SNPs in VDR gene.

RESULTS

Regarding the Fok-I polymorphisms, T1DM cases showed a significant increased frequency of the heterozygous genotype (Ff) than controls (33% vs 21%, OR = 1.9, 95% CI = 1.006-3.587, P = .04). In the meantime, they showed significantly lower frequency of the homozygous (ff) genotype (64% vs 79%, OR = 0.51, 95% CI = 0.28-0.96, P = .03). Cases showed also a significantly lower frequency of the (f) allele than controls (80.5% vs 87.7%, OR = 0.57, 95% CI = 0.33-0.995, P = .04). On the other hand, cases showed significantly higher frequency of the Bsm-I homozygous (bb) and heterozygous (Bb) genotypes (25% vs 11.8%, P = .01, OR = 2.5, 95% CI = 1.18-5.31) & (45% vs 27.5%, P = .0, OR = 2.1, 95 % CI = 1.20-3.89, respectively). Cases showed also significantly higher frequency of (b) allele compared to control (47.5% vs 25.5%, P = .0, OR = 2.6, 95% CI = 1.74-4.02). Haplotype analysis showed an increased risk with the fB and fb haplotypes.

CONCLUSION

This study emphasizes a positive association between SNPs (Fok-I and Bsm-I) and T1DM among Saudi children with increased risk with the Fok-I F and Bsm-I b alleles.

Vitamin D and pancreas: The role of sunshine vitamin in the pathogenesis of diabetes mellitus and pancreatic cancer

Increasing evidence suggests that vitamin D exerts multiple effects beyond bone and calcium metabolism. Vitamin D seems to play a role in pancreatic disease, including type 1 and type 2 diabetes mellitus as well as pancreatic cancer. Vitamin D's immune-modulatory action suggests that it could help prevent type 1 diabetes. In type 2 diabetes, vitamin D may influence β-cell function, insulin sensitivity, and systematic inflammation-all characteristic pathways of that disease. Data from observational studies correlated vitamin D deficiency with risk of type 1 and type 2 diabetes. Prospective and ecological studies of pancreatic cancer incidence generally support a beneficial effect of higher 25-hydroxyvitamin D concentration as well as inverse correlations between UVB dose or exposure and incidence and/or mortality rate of pancreatic cancer. This review discusses the literature regarding vitamin D's role in risk of diabetes and pancreatic cancer. The results to date generally satisfy Hill's criteria for causality regarding vitamin D and incidence of these pancreatic diseases. However, large randomized, blinded, prospective studies are required to more fully evaluate the potential therapeutic role of vitamin D in preventing pancreatic diseases.

Association of Vitamin D Receptor Gene Polymorphism in Adults With Type 2 Diabetes in the Kashmir Valley

OBJECTIVES

Approx 1 billion people across various ethnic and age groups have vitamin D deficiency. The high prevalence of such a deficiency is an imperative public health issue because hypovitaminosis D is an autonomous risk factor for mortality in the general population. Beyond bone integrity and calcium homeostasis, it is involved in numerous physiologic and pathologic processes. The role of vitamin D in the pathogenesis and prevention of type 2 diabetes mellitus has sparked universal interest.

METHODS

This hospital-based case-control study was designed to study the association between 25-hydroxy vitamin D (25[OH]D) levels and the vitamin D receptor (VDR) gene polymorphism with diabetes and to evaluate their roles as risk factors for diabetes. 100 cases and controls were taken. 25(OH)D levels were analyzed by the chemilumenescence method using a Siemens ADVIA Centaur analyzer. Genomic DNA was extracted and Taq-1 and Bsm-1 genotyping in the VDR gene was done by using the polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP).

RESULTS

25(OH)D levels of patients with diabetes were significantly lower than those of controls (19.26±0.95 ng/mL vs. 25.49±1.02 ng/mL; p=0.001). 25(OH)D levels were found to be inversely associated with glycated hemoglobin percentages in cases (r²=0.74). The results suggested that the single nucleotide polymorphisms Taq-1 t(T) allele and b (G allele) in Bsm-1 might be a susceptibility allele for diabetes in the Kashmiri population.

CONCLUSIONS

VDR gene polymorphisms appear to be an important genetic determinant in the progression of diabetes. Considering the important predisposition risk factor, we observed that Taq-1 and Bsm-1 were strongly associated with diabetes in northern Indians. But requires further study as a probable genetic risk marker for diabetes.

Vitamin D3 intake as regulator of insulin degrading enzyme and insulin receptor phosphorylation in diabetic rats

Insulin-degrading enzyme (IDE, insulysin) is a rate-limiting enzyme in the insulin degradation process. It is an intracellular 110-kDa thiol zinc-metalloendopeptidase located in the cytosol, peroxisomes, endosomes and cell surface. IDE catalyzes degradation of several small proteins including insulin, amylin and β-amyloid protein. In addition, insulin clearance was expressed as a target in the treatment of type 2 diabetes given the role of hyperinsulinemia in the pathogenesis of insulin resistance. In this study, fourtyadult male Wistar albino rats were used, thirty rats received 20% fructose in drinking water (HFW) for six weeks to induce diabetes. Subsequently, these rats developed significantly higher body weights, dyslipidemia, hyperglycemia and insulin resistance compared to their controls. Significant increase in the levels of serum glucagon, IDE in liver tissue along with an inhibition of insulin receptor phosphorylation were also observed. Concurrent oral administration of vitamin D3 along with HFW resulted in significant decrease of serum glucose, total cholesterol, triacylglycerol and LDL-C levels. Vitamin D alleviated also insulin resistance, where both IDE, glucagon levels showed significant decrease along with activation of insulin receptor phosphorylation. Normal rats, received vitamin D3 only demonstrated non significant changes of the studied biomarkers. We concluded that vitamin D3 ameliorated insulin resistance and hyperinsulinemia in diabetic rat model received HFW through reduction of IDE and activation of insulin receptor phosphorylation.

Serum 25-Hydroxyvitamin D Concentration Is Independently Inversely Associated with Insulin Resistance in the Healthy, Non-Obese Korean Population

BACKGROUND

We evaluated the associations between 25-hydroxyvitamin D (25(OH)D) concentrations in serum and insulin resistance in the healthy Korean population.

METHODS

We conducted this cross-sectional analysis in 1,807 healthy Korean people (628 men and 1,179 women) aged 30 to 64 years in the Cardiovascular and Metabolic Disease Etiologic Research Center study. All participants were assessed for 25(OH)D, fasting glucose, and insulin levels, and completed a health examination and lifestyle questionnaire according to standard procedures. Insulin resistance was defined as the homeostasis model assessment insulin resistance higher than the 75 percentile.

RESULTS

Compared to those in the highest tertile (≥14.3 ng/mL), the odds ratio (OR) for insulin resistance was 1.37 (95% confidence interval [CI], 1.01 to 1.86) for the 1st tertile (<9.7 ng/mL) and 1.19 (95% CI, 0.08 to 1.62) for the 2nd tertile (9.7 to 14.3 ng/mL) after adjusting for age, gender, waist circumference, alcohol consumption, smoking status, physical exercise, season, and cohort. After stratification of the subjects by adiposity, these associations remained only in non-obese subjects (lowest tertile vs. highest tertile, multivariable OR, 1.64; 95% CI, 1.05 to 2.56).

CONCLUSION

Serum 25(OH)D has an independent inverse association with insulin resistance in the healthy, non-obese Korean population, even among people with vitamin D insufficiency.

Effect of daily calcitriol supplementation with and without calcium on disease regression in non-alcoholic fatty liver patients following an energy-restricted diet: Randomized, controlled, double-blind trial

BACKGROUND & AIMS

Despite evidence for beneficial effects of vitamin D, to our knowledge, no study has compared the effects of calcium supplementation with vitamin D on non-alcoholic fatty liver disease (NAFLD) regression during a hypo-energetic program. We compared the effect of the vitamin D supplementation with and without calcium on anthropometric measures and biochemical parameters in NAFLD patients during a weight-loss program.

METHODS

A 12-week, randomized, controlled, double-blind trial was conducted in 120 NAFLD patients randomly assigned to receive 25 μg calcitriol (n = 37), 500 mg calcium carbonate + 25 μg calcitriol (n = 37), or placebo (n = 36) every day with their lunch meals while following a weight-loss program.

RESULTS

Weight, BMI and fat mass reduction were significant in each group after 12 wk of intervention (p < 0.001), but differences among the groups was not significant after 12 wk of the study, adjusted to the baseline measurements. Significant reduction in fasting plasma glucose (FPG), insulin, insulin resistance (by HOMA-IR) and TG concentrations and an increase in HDL.C was seen over the 12 wk of study in each group (p < 0.001). Adjusting to the baseline measurements, there was significant difference in FPG (p < 0.001), HOMA-IR (p < 0.001), serum insulin (p = 0.01), TG (p = 0.01) and HDL.C (p < 0.001) among the groups after 12 wk of the study. The calcium plus calcitriol group showed a significant decrease in ALT and FPG and increase in HDL.C level compared with the calcitriol group, adjusted to the baseline measures (p < 0.001).

CONCLUSIONS

Our results suggest that calcium plus calcitriol supplementation for 12 weeks may be potentially effective for biochemical parameters in NAFLD patients. Further additional larger controlled trials are needed to confirm these findings.

REGISTRATION

Registered under ClinicalTrials.gov Identifier no. IRCT201408312709N29.

The effect of a single dose of vitamin D on glycemic status and C-reactive protein levels in type 2 diabetic patients with ischemic heart disease: a randomized clinical trial

AIMS

To assess whether a single parental dose of 25-hydroxy vitamin D [25(OH)Vit D] could improve glucose control and inflammation in type 2 diabetic patients (T2D) with ischemic heart disease (IHD).

METHODS

A randomized, placebo-controlled, double-blind trial was performed on 95 patients (47-placebo and 48-vitamin D groups). Participants were randomized using a randomization table to a single dose of either vitamin D (300,000 IU, IM) or a matching placebo. Fasting blood sugar (FBS), glycosylated hemoglobin (HbA1c), 25(OH)Vit D and high-sensitivity C-reactive protein (hs-CRP) were measured at baseline and at 8 weeks.

RESULTS

No significant differences in baseline values were noted between groups, except in HbA1c, which was lower in the placebo group. In the supplemented group, the level of serum 25(OH)Vit D increased (29.6 ± 20.8 vs. 44.5 ± 19.2 ng/mL) and those of FBS and HbA1c decreased significantly [186.5 ± 64.1 vs. 165.1 ± 58.5 mg/dL and 8.2 ± 2.0 % (66.3 ± 21.8 mmol/mol) vs. 7.7 ± 1.8 % (61.7 ± 20.0 mmol/mol), respectively] (all p < 0.05), and no changes, however, were observed in the placebo group. We also compared change of marginal means of outcome variables (HbA1c, FBS, 25(OH)Vit D and hs-CRP) from baseline between the vitamin D versus placebo group, using ANCOVA, adjusted for the baseline of each variable itself, season at study entry, age and body mass index. During trial, only HbA1c level decreased significantly [0.48 % (standard error: 0.17), p = 0.04]. No any adverse effect was seen.

CONCLUSIONS

A single parenteral dose of vitamin D in T2D patients with IHD improved glycemic control, but not inflammatory status.

CLINICAL TRIAL REGISTRY

Australian New Zealand Clinical Trial Registry.

CLINICAL TRIAL NUMBER

ACTRN12614000529640.

Metabolic effects of vitamin D supplementation in vitamin D deficient patients (a double-blind clinical trial)

BACKGROUND

Vitamin D has recently been given a lot of attention for its role in controlling insulin secretion. Many studies have spoken of its role in weight management, blood sugar control and many other metabolic variables.

PATIENT AND METHODS

In a randomized double-blind clinical trial, 210 people with vitamin D deficiency were randomly allocated into two groups receiving vitamin D (50,000 units per week) or placebo for 8 weeks.

RESULTS

Vitamin D levels were significantly increased in the group receiving vitamin D supplementation (13.7±5.2 unit increase versus 0.8±2.8). The increased levels of vitamin D lead to significant changes in fasting insulin levels (6.8±8.1 unit reduction versus 2.3±3.7), a 2-h insulin (31.1±34.9 unit reduction versus 4.5±24.6) and Homeostasis Model Assessment (HOMA) indices.

CONCLUSION

Correction of vitamin D deficiency leads to increased insulin sensitivity that was significantly able to maintain glucose in the normal range with lower levels of insulin.

The Potential Protective Action of Vitamin D in Hepatic Insulin Resistance and Pancreatic Islet Dysfunction in Type 2 Diabetes Mellitus

Vitamin D deficiency (i.e., hypovitaminosis D) is associated with increased insulin resistance, impaired insulin secretion, and poorly controlled glucose homeostasis, and thus is correlated with the risk of metabolic diseases, including type 2 diabetes mellitus (T2DM). The liver plays key roles in glucose and lipid metabolism, and its dysregulation leads to abnormalities in hepatic glucose output and triglyceride accumulation. Meanwhile, the pancreatic islets are constituted in large part by insulin-secreting β cells. Consequently, islet dysfunction, such as occurs in T2DM, produces hyperglycemia. In this review, we provide a critical appraisal of the modulatory actions of vitamin D in hepatic insulin sensitivity and islet insulin secretion, and we discuss the potential roles of a local vitamin D signaling in regulating hepatic and pancreatic islet functions. This information provides a scientific basis for establishing the benefits of the maintenance, or dietary manipulation, of adequate vitamin D status in the prevention and management of obesity-induced T2DM and non-alcoholic fatty liver disease.

No Effect of High-Dose Vitamin D Treatment on β-Cell Function, Insulin Sensitivity, or Glucose Homeostasis in Subjects With Abnormal Glucose Tolerance: A Randomized Clinical Trial

OBJECTIVE

There has been conflicting evidence regarding the potential role of vitamin D in glucose homeostasis. This study was designed to investigate the effect of high-dose vitamin D3 treatment on β-cell function, insulin sensitivity, and glucose tolerance in subjects with prediabetes or diet-treated type 2 diabetes.

RESEARCH DESIGN AND METHODS

Subjects (n = 44) were randomized to 30,000 IU vitamin D3 once weekly or placebo for 8 weeks. Hyperglycemic clamp assessed first-phase (0-12 min) and second-phase (12-120 min) insulin response, insulin sensitivity, and disposition index (DI). An oral glucose tolerance test assessed glucose tolerance and glycosylated hemoglobin assessed glycemic control.

RESULTS

A total of 21 (vitamin D) and 22 (placebo) subjects completed the study, respectively. Season-adjusted 25-OH-vitamin D [25(OH)D] levels were doubled in the active treated group (43-82 nmol/L). No effect of vitamin D treatment, compared with placebo, was seen on first-phase or second-phase insulin secretion. There were no group differences in insulin sensitivity, DI, or any measures of glycemic control. No hypercalcemia or other adverse effects of vitamin D treatment were seen compared with placebo. Subgroup analyses of those with the lowest basal and greatest increase in 25(OH)D levels did not change these results.

CONCLUSIONS

This study gives no support for any substantial effect of high-dose vitamin D treatment for 8 weeks in prediabetes or diet-treated type 2 diabetes on β-cell function, insulin sensitivity, or glycemic control.

FokI polymorphism in vitamin D receptor gene: Differential expression of TNFα in peripheral mononuclear cells of type 2 diabetic subjects

INTRODUCTION

FokI polymorphism has been associated with obesity and type 2 diabetes (T2D) in some populations.

OBJECTIVE

To investigate the frequencies of a genetic polymorphism of Vitamin D receptor (FokI) in patients with T2D and control subjects and investigate the role of 1,25(OH)2D3 in the expression of pro-inflammatory markers in peripheral blood mononuclear cells (PBMCs).

METHODS

The case-control study was conducted in 160 patients with T2D and 160 control subjects, men and women (30-74 years old). The genotype and allele frequency of FokI polymorphisms were determined in these subjects. Subsequently a subgroup of 40 subjects was included from which PBMCs were removed. In vitro, the culture medium was supplemented with two different concentrations of 1,25(OH)2D3(10- 8 M and 10- 10 M). The expression profiles of TNFα and mRNA were analysed by qPCR, and GAPDH and β-actin were used as housekeeping genes.

RESULTS

The control subjects have an increased frequency of the FF genotype. In subjects with T2D, the ff genotype was associated with higher HOMA-IR values than individuals with genotype Ff (p = 0.021). In vitro study in PBMCs showed differential expression of TNFα mRNA by FokI genotype, with a lower expression of this marker of inflammation in FF genotype subjects at a concentration of 10- 8 M of 1,25(OH)2D3.

CONCLUSION

Our data suggest that VDR FokI polymorphism is associated with T2D, and the genotypes Ff and ff of this variant show a reduced response or resistance to the anti-inflammatory action of VitD, which could indicate a functional role of FokI polymorphism of VDR.