Expression of 25-hydroxyvitamin D3-1alpha-hydroxylase in pancreatic islets

Effects of Vitamin D deficiency treatment on metabolic markers in Hashimoto thyroiditis patients

Background:

The aim of the current trial was to investigate the effect of Vitamin D treatment on metabolic markers in people with Vitamin D deficiency and thyroid autoimmunity.

Materials and Methods:

In this double-blind, randomized, placebo-controlled clinical trial, 65 Vitamin D deficient euthyroid or hypothyroid patients with positive TPO-Ab were enrolled. They randomly allocated into two groups to receive oral Vitamin D_{3 (}50000 IU weekly) and placebo for 12 weeks. Serum concentration of calcium, phosphorus, albumin, C-reactive protein, blood urea nitrogen, creatinine, glycated hemoglobin (HbA1c), insulin, fasting plasma glucose (FPG), triglyceride (TG), total cholesterol, and high-density lipoprotein were measured in both groups before and after the trial. Homeostasis model assessment estimates of beta cell function (HOMA-B) and HOMA-insulin resistance (HOMA-IR) were calculated before and after trial in both groups.

Results:

Thirty-three and thirty-two participants were allocated to Vitamin D-treated and placebo-treated groups, respectively. Mean (standard error) level of Vitamin D increased significantly in Vitamin D-treated group (45.53 [1.84] ng/mL vs. 12.76 [0.74] ng/mL, P = 0.001). The mean of HbA1c and insulin was increased significantly both in Vitamin D-treated and placebo-treated groups (P < 0.05). Other variables did not meet a significant change after trial (P = NS). In between-group comparison, there was not any significant difference between Vitamin D-treated and placebo-treated groups regarding measures of HOMA-B, HOMA-IR, FPG, HbA1c, and TG (P = NS).

Conclusion:

Our findings showed that weekly 50000 IU oral Vitamin D3 for 12 weeks did not improve metabolic markers, IR, or insulin secretion in Vitamin D deficient patients with Hashimoto thyroiditis.

Are low sun exposure and/or vitamin D risk factors for type 1 diabetes?

Ultraviolet radiation and vitamin D, with their known immunosuppressive effects, have the potential to delay or inhibit type 1 diabetes.

MANAGEMENT OF ENDOCRINE DISEASE: The effect of vitamin D supplementation on glycaemic control in patients with type 2 diabetes mellitus: a systematic review and meta-analysis

OBJECTIVE

Epidemiologic studies suggest that vitamin D status plays a role in glycaemic control in patients with type 2 diabetes. However, intervention studies yielded inconsistent results. The aim of this study is to systematically review the effect of vitamin D supplementation on glycaemic control in patients with type 2 diabetes.

METHODS

Systematic review and meta-analysis. We searched Medline, Embase and the Cochrane Library for RCTs examining the effect of vitamin D supplementation on glycaemic control in patients with type 2 diabetes. A random-effects model meta-analysis was performed to obtain a summarized outcome of vitamin D supplementation on HbA_1c, fasting glucose and homeostasis model assessment - insulin resistance (HOMA-IR).

RESULTS

Twenty-three RCTs were included in this systematic review representing a total of 1797 patients with type 2 diabetes. Mean (± s.d.) change in serum 25-hydroxyvitamin D varied from 1.8 ± 10.2 nmol/L to 80.1 ± 54.0 nmol/L. Nineteen studies included HbA_1c as outcome variable. Combining these studies no significant effect in change of HbA_1c was seen after vitamin D intervention compared with placebo. A significant effect of vitamin D supplementation was seen on fasting glucose in a subgroup of studies (n = 4) with a mean baseline HbA_1c ≥ 8% (64 mmol/mol) (standardized difference in means: 0.36; 95% CI: 0.12-0.61, P = 0.003).

CONCLUSIONS

Current evidence of RCTs does not support short-term vitamin D supplementation in a heterogeneous population with type 2 diabetes. However, in patients with poorly controlled diabetes, a favourable effect of vitamin D is seen on fasting glucose.

Vitamin D on Early Stages of Diabetic Kidney Disease: A Cross-sectional Study in Patients with Type 1 Diabetes Mellitus

CONTEXT

Genetic and environmental factors are involved in the pathogenesis of type 1 diabetes mellitus (T1DM), and vitamin D (VD) deficiency appears as a candidate to risk factor for developing diabetic kidney disease (DKD).

OBJECTIVE

The purpose of study was to evaluate the existence of an association between low levels of VD and the presence and degree of DKD in T1DM.

PATIENTS AND METHODS

We performed a cross-sectional study, between November 2014 and December 2015. Levels of 25(OH)D and albuminuria were analyzed in 37 patients with T1DM and normal glomerular filtration rate. Thirty-six subjects were evaluated as a control group.

RESULTS

Patients with T1DM and hypovitaminosis D had higher levels of albuminuria compared to those with normal VD levels [albuminuria (log10) = 1.92 vs. 1.44; p < 0.05]. When we have separated the group of patients according to stage of DKD in patients with normo, micro, and macroalbuminuria, there are lower levels of 25(OH)D in the last when compared to the first two groups (26.7 ± 6.2, 24.8 ± 7.0, and 15.9 ± 7.6 ng/ml; p < 0.05, respectively). In T1DM group, we have found correlations between VD levels and both albuminuria and DKD stages (r = -0.5; p < 0.01 and r = -0.4; p < 0.05, respectively). A simple linear regression model, with albuminuria as the dependent variable and VD as an independent variable, showed r2 = 0.2 and p < 0.01.

CONCLUSION

Our data suggest an association between reduced levels of VD and the presence and severity of DKD.

Effect of high-dose vitamin D supplementation on cardiometabolic risk factors in subjects with metabolic syndrome: a randomized controlled double-blind clinical trial

PURPOSE

The evidence in support of the effect of vitamin D deficiency on cardiovascular diseases is inconsistent. The objective of this randomized, controlled, double-blind study was to assess the effect of high-dose vitamin D supplementation on cardiometabolic risk factors in subjects with metabolic syndrome.

METHODS

Eighty subjects were randomized to receive 50,000 IU vitamin D or matching placebo weekly for 16 weeks. Fasting blood sugar, homeostasis model assessment of insulin resistance, insulin sensitivity (Quicki), serum lipid profiles (low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride (TG) and total cholesterol), anthropometric factors and blood pressure were assessed before and after intervention. Dietary intake and sun exposure were also determined. The trial was registered at http://www.irct.ir (code: IRCT201409033140N14).

RESULTS

Participants were 40.49 ± 5.04 years and 49 % male. All of the intervention group and 97 % of placebo group were vitamin D deficient or insufficient (25-hydroxyvitamin D <75 nmol/L). After intervention, serum 25(OH)D concentration was increased by 61.93 nmol/L in intervention group, while it was decreased in placebo group (p < 0.001). There was a significant change in TG concentration after 4 months (p < 0.001). Other metabolic or anthropometric factors did not change significantly (p = 0.05).

CONCLUSION

Supplementation with high-dose vitamin D for 4 months improved vitamin D status and decreased TG levels in subjects with metabolic syndrome. However, it did not have any beneficial effects on other cardiometabolic risk factors; this might be due to the inadequate vitamin D status attained in this study which was conducted in a severely deficient region.

Vitamin D-binding protein and 25-hydroxyvitamin D during pregnancy in mothers whose children later developed type 1 diabetes

BACKGROUND

Levels of 25-hydroxyvitamin D (25-OH D) during late pregnancy have been linked to type 1 diabetes risk in the offspring. Vitamin D-binding protein increases in concentration during pregnancy. We aimed to test whether concentrations of vitamin D-binding protein and 25-OH D throughout pregnancy differed between women whose offspring later developed type 1 diabetes (cases) and controls.

METHODS

A nested case-control study was conducted within a cohort of pregnant women from all over Norway in 1992-1994. Offspring registered in The Norwegian Childhood Diabetes Registry, diagnosed with type 1 diabetes before age 15, defined the case women, giving 113 cases in the study. Two hundred twenty controls were randomly selected within the same cohort. One to four serum samples from each participant drawn at different time points during pregnancy were analysed for vitamin D-binding protein and 25-OH D by radioimmunoassay.

RESULTS

Vitamin D-binding protein and 25-OH D significantly increased by gestational week (p < 0.001) and tended to be lower in cases than in controls, -0.27 µmol/L (95% CI -0.57, 0.03) and -5.01 nmol/L (95% CI -8.03, -0.73), respectively. While first and second trimester concentrations of vitamin D-binding protein and 25-OH D alone were not significantly different, lower third trimester concentrations tended to be associated with higher risk of type 1 diabetes in the offspring, albeit at borderline significance after mutual adjustment.

CONCLUSIONS

In this first study of maternal vitamin D-binding protein measured throughout pregnancy and risk of type 1 diabetes in offspring, lower concentration, particularly in the third trimester, tended to be associated with type 1 diabetes. Copyright © 2016 John Wiley & Sons, Ltd.

Tie-2Cre mediated deletion of the vitamin D receptor gene leads to improved skeletal muscle insulin sensitivity and glucose tolerance

A variety of studies have suggested that vitamin D may play a palliative role in improving insulin secretion and glucose tolerance. Endothelial cells of the microcirculation are thought to play an important role in regulating both insulin secretion and insulin sensitivity in target tissues. We have selectively deleted the vitamin D receptor (VDR) gene in endothelial cells of the murine vasculature. These mice demonstrate improved glucose tolerance, improved insulin sensitivity in skeletal muscle, but not in liver, and a reduction in expression and secretion of insulin in the pancreatic islets. Collectively, these data, taken within the context of recent publications in this field, suggest that the endothelial cell VDR plays a tonic inhibitory role in regulating glucose disposal and could prove to be a factor in controlling glucose homeostasis in the intact organism.

Pleiotropic protective effects of Vitamin D against high fat diet-induced metabolic syndrome in rats: One for all

Several lines of evidence point to the association of vitamin D deficiency with the different components of metabolic syndrome. Yet, the effect of vitamin D supplementation on metabolic syndrome is not clearly elucidated. Herein, we tested the hypothesis that administration of vitamin D, either alone or in combination of metformin can improve metabolic and structural derangements associated with metabolic syndrome. Fifty wistar rats were randomly assigned to serve either as normal control (10 rats) or metabolic syndrome rats, by feeding them with a standard or a high fat diet (HFD), respectively. Metabolic syndrome rats were further assigned to receive either vehicle, Metformin (100mg/Kg orally), vitamin D (6ng/Kg SC.) or both, daily for 8 weeks. Body weight, blood pressure, serum glucose, insulin, insulin resistance, lipid profile, oxidative stress, serum uric acid and Ca⁺² were assessed at the end of the study. Histopathological examination of hepatic, renal and cardiac tissues were also performed. Treatment with vitamin D was associated with a significant improvement of the key features of metabolic syndrome namely obesity, hypertension and dyslipidaemia with a neutral effect on Ca⁺² level. When combined with metformin, most of the other metabolic abnormalities were ameliorated. Furthermore, a significant attenuation of the associated hepatic steatosis was observed with vitamin D as well as vitamin D/metformin combination. In conclusion, vitamin D can improve hypertension, metabolic and structural abnormalities induced by HFD, and it provides additional benefits when combined with metformin. Therefore, vitamin D could represent a feasible therapeutic option for prevention of metabolic syndrome.

Vitamin D and spinal cord injury: should we care?

STUDY DESIGN

Narrative review.

OBJECTIVES

This review provides an overview of the etiological factors and consequences of vitamin D insufficiency in relation to spinal cord injury (SCI) as well as important considerations for vitamin D supplementation.

SETTING

Montreal, Canada.

METHODS

Literature search.

RESULTS

Vitamin D insufficiency is common in SCI individuals owing to the presence of many contributing factors including limited sun exposure and intake, use of medication and endocrine perturbations. Although there are several biological plausible mechanisms by which vitamin D may act upon musculoskeletal and cardiometabolic health, the impact of vitamin D insufficiency on such systems remains ill defined in SCI. In the absence of guidelines for the management of vitamin D insufficiency in this high-risk population and in an attempt to provide clinical guidance, considerations for vitamin D supplementation such as the type of vitamin D, dosing regimens and toxicity are discussed and tentative recommendations suggested with particular reference to issues faced by SCI patients.

CONCLUSION

Although high rates of vitamin D insufficiency are encountered in SCI individuals, its consequences and the amount of vitamin D required to prevent insufficiency are still unknown, indicating a need for more intervention studies with well-defined outcome measures. Routine screening and monitoring of vitamin D as well as treatment of suboptimal status should be instituted in both acute and chronic setting. The close interactions between vitamin D and related bone minerals should be kept in mind when supplementing SCI individuals, and practices should be individualized with clinical conditions.

Study of the effect of vitamin D supplementation on glycemic control in type 2 diabetic prevalent hemodialysis patients

Vitamin D is claimed to have an adjuvant effect on glycemic control by dual action on pancreatic β-cells and insulin resistance. The aim of this study was to assess the possible effect of short-term alfacalcidol supply on glycemic control in type 2 diabetic hemodialysis (HD) patients. Twenty type 2 diabetic HD patients (using diet and oral drugs but not insulin) were randomly selected from our dialysis unit as well as 20 non-diabetic HD patients as control. A third group of 12 healthy subjects were studied as well. All three groups were similar in age, sex, and body mass index. Oral alfacalcidol therapy was administrated daily as recommended by Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines for 12 weeks guided by monthly serum phosphorus and Cax PO4 product. Corrected total calcium, phosphorus, intact parathyroid hormone, 25-hydroxy vitamin D (25[OH]D), and glucoparameters (fasting blood glucose, glycated hemoglobin [HbA1c%], insulin resistance by homeostatic model assessment, and β-cell function by HOMA-β%) were measured under basal conditions and after 3 months of therapy. 25(OH)D was non-significantly lower in diabetic than non-diabetic HD patients, but significantly lower than healthy subjects at the start of the study. However, vitamin D level increased significantly after 3 months of trial, although the levels did not reach normal values. This vitamin D rise was associated with highly significant improvement in concentrations of fasting blood sugar (FBS), fasting insulin, HbA1c%, and HOMA-β-cell function in diabetic and non-diabetic controls. However, there was a significant rise in insulin resistance after treatment. The percentage of change was evident more in diabetics regarding FBS and 25(OH)D concentration. Adjustment of 25(OH)D level in type 2 diabetic prevalent HD patients may improve, at least with short-term therapy, glycemic control mainly through improving β-cell function.

Proteomic analysis of the INS-1E secretome identify novel vitamin D-regulated proteins

BACKGROUND

Experimental evidence indicates that vitamin D may have a beneficial role in pancreatic β-cell function.

METHODS

In the present study, stable isotope labelling by amino acids in cell culture (SILAC) in combination with liquid chromatography-tandem mass spectrometry was used to quantitatively assess the impact of the active vitamin D metabolite, 1,25-(OH)2 D3 , on global protein expression in INS-1E cell secretome.

RESULTS

Twenty-one proteins were found up-regulated (≥1.5 fold changes) and three down-regulated (≤0.67) after treatment of INS-1E cells with 1,25-(OH)2 D3 . Up-regulation of proteins implicated in β-cell growth and proliferation, such as IGF2, IGFBP7 and gelsolin, suggest that 1,25-(OH)2 D3 has a positive effect on β-cell growth and proliferation. Moreover, modulations of several proteins implicated in prohormone processing and insulin exocytosis (IGF2, IGFBP7, Scg5, ProSAAS, Fabp5, Ptprn2 and gelsolin) appear to support the hypothesis that 1,25-(OH)2 D3 plays positive modulatory role in insulin processing and secretion.

CONCLUSIONS

Together, we reveal a number of novel vitamin D-regulated proteins that may contribute to a better understanding of the reported beneficial effects of vitamin D on pancreatic β-cells. Copyright © 2016 John Wiley & Sons, Ltd.

IMPROVEMENT IN PANCREATIC β-CELL FUNCTION WITH VITAMIN D AND CALCIUM SUPPLEMENTATION IN VITAMIN D-DEFICIENT NONDIABETIC SUBJECTS

OBJECTIVE

There are varied reports on the effect of vitamin D supplementation on β-cell function and plasma glucose levels. The objective of this study was to examine the effect of vitamin D and calcium supplementation on β-cell function and plasma glucose levels in subjects with vitamin D deficiency.

METHODS

Nondiabetic subjects (N = 48) were screened for their serum 25-hydroxyvitamin D (25-OHD), albumin, creatinine, calcium, phosphorus, alkaline phosphatase, and intact parathyroid hormone (PTH) status. Subjects with 25-OHD deficiency underwent a 2-hour oral glucose tolerance test. Cholecalciferol (9,570 international units [IU]/day; tolerable upper intake level, 10,000 IU/day; according to the Endocrine Society guidelines for vitamin D supplementation) and calcium (1 g/day) were supplemented.

RESULTS

Thirty-seven patients with 25-OHD deficiency participated in the study. The baseline and post-vitamin D/calcium supplementation and the difference (corrected) were: serum calcium, 9 ± 0.33 and 8.33 ± 1.09 mg/dL (-0.66 ± 1.11 mg/dL); 25-OHD, 8.75 ± 4.75 and 36.83 ± 18.68 ng/mL (28.00 ± 18.33 ng/mL); PTH, 57.9 ± 29.3 and 36.33 ± 22.48 pg/mL (-20.25 ± 22.45 pg/mL); fasting plasma glucose, 78.23 ± 7.60 and 73.47 ± 9.82 mg/dL (-4.88 ± 10.65 mg/dL); and homeostasis model assessment-2-percent β-cell function C-peptide secretion (HOMA-2-%B C-PEP), 183.17 ± 88.74 and 194.67 ± 54.71 (11.38 ± 94.27). Significant differences were observed between baseline and post-vitamin D/calcium supplementation serum levels of corrected calcium (Z, -3.751; P<.0001), 25-OHD (Z, -4.9; P<.0001), intact PTH (Z, -4.04; P<.0001), fasting plasma glucose (Z, -2.7; P<.007), and HOMA-2-%B C-PEP (Z, -1.923; P<.05) as determined by Wilcoxon signed rank test. Insulin resistance as measured by HOMA was unchanged.

CONCLUSION

Optimizing serum 25-OHD concentrations and supplementation with calcium improves fasting plasma glucose levels and β-cell secretory reserve. Larger randomized control studies are needed to determine if correction of 25-OHD deficiency will improve insulin secretion and prevent abnormalities of glucose homeostasis.

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

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

Rationale and design of Diabetes Prevention with active Vitamin D (DPVD): a randomised, double-blind, placebo-controlled study

INTRODUCTION

Recent research suggests that vitamin D deficiency may cause both bone diseases and a range of non-skeletal diseases. However, most of these data come from observational studies, and clinical trial data on the effects of vitamin D supplementation on individuals with pre-diabetes are scarce and inconsistent. The aim of the Diabetes Prevention with active Vitamin D (DPVD) study is to assess the effect of eldecalcitol, active vitamin D analogue, on the incidence of type 2 diabetes among individuals with pre-diabetes.

METHODS AND ANALYSIS

DPVD is an ongoing, prospective, multicentre, randomised, double-blind and placebo-controlled outcome study in individuals with impaired glucose tolerance. Participants, men and women aged ≥30 years, will be randomised to receive eldecalcitol or placebo. They will also be given a brief (5-10 min long) talk about appropriate calorie intake from diet and exercise at each 12-week visit. The primary end point is the cumulative incidence of type 2 diabetes. Secondary endpoint is the number of participants who achieve normoglycaemia at 48, 96 and 144 weeks. Follow-up is estimated to span 144 weeks.

ETHICS AND DISSEMINATION

All protocols and an informed consent form comply with the Ethics Guideline for Clinical Research (Japan Ministry of Health, Labour and Welfare). The study protocol has been approved by the Institutional Review Board at Kokura Medical Association and University of Occupational and Environmental Health. The study will be implemented in line with the CONSORT statement.

TRIAL REGISTRATION NUMBER

UMIN000010758; Pre-results.

25-Hydroxyvitamin D and Parathyroid Hormone Levels Are Independently Associated with the Hemoglobin A1c Level of Korean Type 2 Diabetic Patients: The Dong-Gu Study

In type 2 diabetic patients, the relationships between 25-hydroxyvitamin D and parathyroid hormone levels, and glycemic control, remain unclear. We evaluated associations between 25-hydroxyvitamin D, parathyroid hormone, and hemoglobin A_1c levels after adjusting for other covariates, including log transformed 25-hydroxyvitamin D levels and log transformed parathyroid hormone levels, in Korean patients with type 2 diabetes. In total, 1,175 patients with type 2 diabetes were selected from 8,857 individuals who completed the baseline survey of the Dong-gu study, conducted in Korea from 2007 to 2010. After adjusting for other covariates, we found that the mean hemoglobin A_1c level was inversely associated with the 25-hydroxyvitamin D level (Q1: 7.47% [7.30–7.63], Q2: 7.25% [7.09–7.40], Q3: 7.17% [7.02–7.32], Q4: 7.19% [7.02–7.35]; p for trend = 0.021, p for between groups = 0.050) and the parathyroid hormone level (Q1: 7.35% [7.19–7.51], Q2: 7.34% [7.19–7.50], Q3: 7.28% [7.13–7.43], Q4: 7.09% [6.94–7.24]; p for trend = 0.022, p for between groups = 0.048). However, the mean fasting glucose level was not associated with either the 25-hydroxyvitamin D or parathyroid hormone level. In conclusion, inverse associations were evident between hemoglobin A_1c, 25-hydroxyvitamin D and parathyroid hormone levels in Korean patients with type 2 diabetes. The associations remained significant after adjusting for other covariates, including the log transformed 25-hydroxyvitamin D levels and log transformed parathyroid hormone levels.

Genetic Polymorphism of CYP27B1-1260 as Associated With Impaired Fasting Glucose in Patients With Chronic Hepatitis C Undergoing Antiviral Therapy

BACKGROUND

Recent studies have indicated that abnormal glucose levels and diabetes are negatively associated with the prognosis of patients with chronic hepatitis C virus (HCV) infection. The genetic polymorphism of the promoter region -1260 of a gene encoding the enzyme 1-alpha-hydroxylase (CYP27B1-1260) has been shown to have an impact on the signaling pathways involved in insulin secretion.

OBJECTIVES

The aim is to investigate the effect of CYP27B1-1260 polymorphism on the fasting plasma glucose (FPG) levels in patients with chronic HCV undergoing antiviral therapy.

PATIENTS AND METHODS

A total of 461 patients with chronic HCV infection and 300 volunteers without HCV infection were enrolled in an observational cohort study in the China-Japan Union hospital of Jilin University and the Second Hospital of Daqing, Changchun, Jilin Province. Both groups were further divided into normal and abnormal FPG subgroups. The frequencies of the three CYP27B1-1260 genotypes (AA, AC, and CC) were determined in each subgroup. FPG levels were monitored at baseline in HCV and control participants, and both during and after antiviral therapy in HCV infected patients. The frequency of each genotype was determined. Logistic regression analysis was performed to evaluate the risk factors associated with abnormal FPG levels in HCV infected patients undergoing antiviral therapy.

RESULTS

In HCV infected patients with abnormal FPG levels, the frequency of the genotype CC was significantly higher than that in patients with normal FPG levels (19% vs. 7%, P < 0.001). In contrast, in the control participants, the CC genotype was not significantly different between FPG groups. At baseline, the CC genotype was associate with four times more risk of IFG after adjusting for multiple variables (OR: 4.11; 95%CI: 1.98 - 8.52, P = 0.0001). During 24 weeks of anti-HCV treatment, 38 HCV participants developed newly-diagnosed impaired fasting glucose. The CC genotype markedly increased the risk for newly developed IFG (OR: 26.54; 95%CI: 7.80 - 90.32, P < 0.0001). Other risk factors included age and body mass index.

CONCLUSIONS

CYP27B1-1260 polymorphism is associated with abnormal glucose metabolism in HCV infected patients. HCV infected individuals with CYP27B1-1260 genotype CC appeared to have an increased risk of developing abnormal FPG levels.

Vitamin D deficiency is associated with high prevalence of diabetes in Kuwaiti adults: results from a national survey

BACKGROUND

Vitamin D homeostasis may play a critical role in glucose metabolism. Little is known on vitamin D deficiency and its association with diabetes in countries of the Arabia Gulf where the population is experiencing a rapid increase in the incidence of diabetes.

METHODS

In a cross-sectional study of 960 adults enrolled in the first National Nutrition Survey of the State of Kuwait (NNSSK), we examined vitamin D status in association with the prevalence of diabetes and prediabetes. Vitamin D status was measured by serum levels of 25-hydroxyvitami D (25(OH)D). Prevalences of diabetes and prediabetes were determined based on fasting glucose and HbA1C levels.

RESULTS

The median level of serum 25(OH)D in Kuwaiti adults was 13.8 ng/ml. Approximately 56 % of the Kuwaiti adults had vitamin D inadequacy (25(OH)D = 12-19.9 ng/ml), and 27 % had vitamin D deficiency (25(OH)D < 12 ng/ml). The prevalences of prediabetes and diabetes were 40 and 27 %, respectively. Vitamin D inadequacy (OR = 1.7, 95 % CI: 1.0-2.9) and deficiency (OR =2.0, 95 % CI: 1.1-3.3) was each associated with about two-fold increased odds of prediabetes compared to sufficient vitamin D status (25(OH)D ≥ 20 ng/ml). Vitamin D inadequacy (OR =2.1, 95 % CI: 1.2-3.7) and deficiency (OR =2.0, 95 % CI: 1.1-3.9) were also associated with two-fold increased odds of diabetes.

CONCLUSIONS

Data from Kuwaiti's first nutrition nutritional survey suggests a very high prevalence of vitamin D deficiency in Kuwaiti adults. Associations of low vitamin D status and high prevalence of diabetes point to the need of continuous monitoring of vitamin D status and further evaluating potential health consequences in this high-risk population.

The effect of vitamin D supplementation on blood sugar and different indices of insulin resistance in patients with non-alcoholic fatty liver disease (NAFLD)

BACKGROUND

Vitamin D supplementation has been shown to decrease insulin resistance through which it might cause fatty liver. Fatty liver increasingly results in type 2 diabetes mellitus (T2DM). Insulin resistance and fatty liver are particularly closely related. The aim of present study is to examine the effect of vitamin D supplementation on blood sugar and different indices of insulin resistance in patients with non-alcoholic fatty liver disease (NAFLD).

MATERIALS AND METHODS

This randomized placebo-controlled clinical trial was conducted on 60 patients with NAFLD, who were divided equally into intervention and control groups. Patients in the intervention group received vitamin D3 (50,000 IU) and patients in the control group received placebo capsules every week for 10 weeks. Blood sugar, homeostatic model assessment-insulin resistance (HOMA-IR), and homeostatic model assessment-beta cell (HOMA-B) were checked at baseline and after 10 weeks of the intervention. Adjustment for variables was performed by analysis of covariance (ANCOVA).

RESULTS

Vitamin D supplementation resulted in increased serum 25-hydroxy vitamin D [25(OH) D] concentration in the intervention group compared to the control group [+68 (12) vs. -1.9 (2.44); P = 0.001]. Intake of vitamin D supplements led to a marginally significant decrease in fasting blood glucose [FBS: -12 (4) in the intervention group compared to - 3 (2) in the control group; P = 0.055]. Also, HOMA-IR decreased in the intervention group compared to the control group [-1.75 (0.23) vs. 0.12 (0.41); P = 0.066].

CONCLUSIONS

Vitamin D supplementation resulted in decreased HOMA-IR and FBS concentration in patients with NAFLD; however, it did not affect the insulin level and HOMA-B significantly.

The effect of vitamin D supplementation on insulin and glucose metabolism in overweight and obese individuals: systematic review with meta-analysis

The aim of this systematic review was to assess the effect of vitamin D supplementation on glucose and insulin metabolism in overweight and obese subjects. The search process was based on the selection of publications listed in the databases: PubMed, Scopus, Web of Knowledge, Embase and the Cochrane library that met the inclusion criteria. Twelve randomized controlled trials were included. The analysed population consisted of 1181 individuals with BMIs >23 kg/m2. Changes in the concentration of 25(OH)D, fasting glucose, insulin and the HOMA-IR index were assessed. In the meta-regression analysis, a restricted maximum likelihood method was applied. To combine individual study results, a meta-analysis was performed. Vitamin D supplementation did not have an effect on glucose concentrations, insulin level and HOMA-IR values when the supplemented dose, time of supplementation and baseline of 25(OH)D concentration were taken under consideration in subgroup-analysis. This meta-analysis provides evidence that vitamin D supplementation has no significant effect on glucose and insulin metabolism in overweight and obese individuals.

The Effect of Vitamin D Supplementation on Glycemic Control and Lipid Profile in Patients with Type 2 Diabetes Mellitus

AIM

The aim of this study was to evaluate the effect of vitamin D supplementation in patients with type 2 diabetes mellitus (T2DM) with regard to their glycemic control and lipid profile.

METHODS

One hundred subjects with T2DM were recruited and given 4500 IU/day of vitamin D for 2 months. 25-Hydroxyvitamin D [25(OH)D], fasting blood glucose (FBG), glycosylated hemoglobin A1c (HbA1c), and lipid profile were measured pre- and postsupplementation.

RESULTS

There was a significant increase in the mean value of 25(OH)D level after supplementation (baseline level 16 ± 5.3 ng/ml vs. after supplement level 49.2 ± 17.7 ng/ml, p < 0.05). Both FBG and HbA1c but not lipid profile were significantly decreased after supplementation. However, the univariate general linear model between 25(OH)D percentiles and lipid profile levels showed that diabetic subjects with high 25(OH)D levels (>61 ng/ml) had significantly lower levels of total cholesterol and low-density lipoprotein cholesterol (LDL-C) in comparison to those in the low or middle percentiles. Furthermore, participants in a higher percentile had a significantly higher level of high-density lipoprotein cholesterol (HDL-C) than those in the middle percentile. Lipid profile levels were not affected by the supplement except for triglycerides (TG) levels in females, which were significantly decreased.

CONCLUSIONS

Vitamin D supplementation may be beneficial to diabetic subjects because it improved glycemic control. Diabetic subjects with high 25(OH)D levels (>61 ng/ml) had better lipid profiles.

Effect of Vitamin D Supplementation on Glycemic Control in Patients With Type 2 Diabetes (SUNNY Trial): A Randomized Placebo-Controlled Trial

OBJECTIVE

Low vitamin D status has been associated with impaired glycemic control in patients with type 2 diabetes. The purpose of our study was to evaluate the effect of vitamin D supplementation on glycemic control in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This randomized, double-blind, placebo-controlled trial was conducted in 275 adult patients with type 2 diabetes without insulin treatment. Patients were randomly assigned to receive either vitamin D3 (50,000 IU/month) or placebo for 6 months. To assess the primary outcome of the study, change in HbA(1c), we performed a linear regression analysis.

RESULTS

Mean baseline serum 25-hydroxyvitamin D [25(OH)D] increased from 60.6 ± 23.3 to 101.4 ± 27.6 nmol/L and 59.1 ± 23.2 to 59.8 ± 23.2 nmol/L in the vitamin D and placebo group, respectively. Mean baseline HbA(1c) was 6.8 ± 0.5% (51 ± 6 mmol/mol) in both groups. After 6 months, no effect was seen on HbA(1c) (mean difference: β = 0.4 [95% CI -0.6 to 1.5]; P = 0.42) and other indicators of glycemic control (HOMA of insulin resistance, fasting insulin, and glucose) in the entire study population. Subgroup analysis in patients with a serum 25(OH)D <50 nmol/L or an HbA(1c) level >7% (53 mmol/mol) did not differ the results.

CONCLUSIONS

In a well-controlled group of patients with type 2 diabetes, intermittent high-dose vitamin D supplementation did not improve glycemic control.

Vitamin D status is associated with skin autofluorescence in patients with type 2 diabetes mellitus: a preliminary report

Background

Skin autofluorescence is a non-invasive measurement of advanced glycation end products (AGE), which are suggested to be one of the major agents in the pathogenesis and progression of diabetes related cardiovascular complications. Recently, low vitamin D status has been linked to the progression of type 2 diabetes mellitus (T2DM) and cardiovascular disease. The aim of this study is to investigate the association between vitamin D status and skin autofluorescence in patients with T2DM.

Methods

In this preliminary report skin autofluorescence was measured non-invasively with an AGE-reader in 245 patients with T2DM treated with lifestyle advice, metformin and/or sulphonylurea-derivatives. All patients were randomly assigned to receive either vitamin D 50,000 IU/month or placebo for 6 months.

Results

Skin autofluorescence was significantly higher in patients with a serum 25(OH)D <50 nmol/l compared to patients with a serum 25(OH)D >75 nmol/l (2.81 versus 2.41; p < 0.001). Mean serum 25(OH)D was 60.3 ± 23.4 nmol/l and was independently associated with skin autofluorescence (β −0.006; p < 0.001). Mean vitamin D increased from 60.8 to 103.6 nmol/l in the intervention group, however no effect was seen on accumulation of skin AGEs after 6 months compared to placebo.

Conclusions

Vitamin D status is independently associated with skin auto fluorescence in patients with well-controlled T2DM. No effect was seen on the amount of skin AGEs after a short period of 6 months vitamin D supplementation. Further research with longer follow-up and measurement of circulating advanced glycation end products is needed to elucidate the causality of the association.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-015-0250-z) contains supplementary material, which is available to authorized users.

The Effects of Vitamin D Supplementation on Glucose Control and Insulin Resistance in Patients with Diabetes Type 2: A Randomized Clinical Trial Study

Background:

Vitamin D deficiency is prevalent in diabetes type 2 and this vitamin may be related to insulin action. This randomized controlled trial study was done to evaluate the effect of vitamin D supplementation on glucose control and insulin resistance in patients with diabetes type 2.

Methods:

Participants of this randomized clinical trial study consisted of 28 patients with type 2 diabetes who received 100 microgram (4000 IU) vitamin D and 30 diabetic patients who received placebo for 2 months between September 2012 and February 2013. The effect of vitamin D on glucose control was assessed by measuring HbA1c and insulin resistance as HOMA-IR at the baseline and the end of the intervention.

Results:

The results showed a significant decrease in HbA1c (from 7.29 ± 0.22 % to 6.76 ± 0.18 %, P<0.001) and insulin concentration (from 8.24 ± 0.97 μIU/mL to 6.55 ± 0.28 μIU/mL, P=0.048), but a non-significant decrease in HOMA-IR in vitamin D group. Also, HDL-C level increased significantly in both of vitamin D (P=0.046) and placebo groups (P=0.028).

Conclusion:

It seems that vitamin D supplementation has beneficial effects on glucose homeostasis and can increases insulin sensitivity in diabetic 2 patients.

A therapeutic role for vitamin D on obesity-associated inflammation and weight-loss intervention

Vitamin D plays an essential role in the regulation of skeletal metabolism as well as calcium and phosphate homeostasis, while vitamin D receptor (VDR) regulates de novo lipid synthesis, thereby contributing to the development of obesity. Furthermore, obese individuals are at a greater risk for vitamin D deficiency which may increase the potential risk for chronic inflammation, insulin resistance, and metabolic syndrome. While acute exercise enhances the activation of inflammatory signaling pathways, chronic exercise training may attenuate elevated pro-inflammatory cytokine production, resulting in the improvement of cardiovascular and metabolic health in obese individuals. Supplementation with vitamin D coupled with exercise or mild caloric restriction has been shown to improve markers of fitness and inflammation as well as cholesterol. Therefore, this review primarily addresses the impact of vitamin D deficiency in obesity-related inflammatory imbalances and how exercise and weight-loss interventions may enhance the beneficial effects on vitamin D-mediated inflammation in obesity.

Discovery of novel vitamin D-regulated proteins in INS-1 cells: a proteomic approach

BACKGROUND

Experimental evidence indicates that vitamin D may have a beneficial role in pancreatic β-cell function. Global gene expression studies have shown that the active metabolite 1,25-dihydroxyvitamin D3 [1,25-(OH)2 D3 ] modulates genes involved in ion transport, lipid metabolism and insulin secretion.

METHODS

We employed stable isotope labelling by amino acids in cell culture in combination with liquid chromatography-tandem mass spectrometry to quantitatively assess the impact of two vitamin D metabolites, 1,25-(OH)2 D3 and 25-hydroxyvitamin D3 [25-(OH)D3 ], on global protein expression on a model rat β-cell line, insulinoma-derived INS-1 cells.

RESULTS

Although treatment with 1,25-(OH)2 D3 resulted in 31 differentially expressed proteins, 25-(OH)D3 had no impact on protein expression. Of these 31 proteins, 29 were upregulated, whereas two showed a decrease in abundance. Proteins whose expression levels markedly increased in the presence of 1,25-(OH)2 D3 included Crat, Hmgn2, Protein Tmsbl1 and Gdap1. One of the most important findings in this study is upregulation of proteins implicated in insulin granule motility and insulin exocytosis, suggesting a positive effect on insulin secretion. Moreover, modulation of several membrane transport proteins suggests that 1,25-(OH)2 D3 has an impact on the homeostatic regulation of ions, which is critical for most functions in the β-cell.

CONCLUSIONS

In this study, we discovered a number of novel 1,25-(OH)2 D3 -regulated proteins, which may contribute to a better understanding of the reported beneficial effects of vitamin D on pancreatic β-cells. All in all, our findings should pave the way for future studies providing insights into molecular mechanisms by which 1,25-(OH)2 D3 regulates protein expression in pancreatic β-cells.

Vitamin D Levels Decline with Rising Number of Cardiometabolic Risk Factors in Healthy Adults: Association with Adipokines, Inflammation, Oxidative Stress and Advanced Glycation Markers

INTRODUCTION

Hypovitaminosis D associates with obesity, insulin resistance, hypertension, and dyslipoproteinemia. We asked whether the presence of multiple cardiometabolic risk factors, and which particular combination, exerts additive negative effects on 25(OH)D3 levels; and whether 25(OH)D3 levels associate with markers of inflammation and oxidative stress.

SUBJECTS AND METHODS

In non-diabetic medication-free adults central obesity (waist-to-height ratio > 0.5); elevated blood pressure (systolic BP≥130 mm Hg and/or diastolic BP ≥85 mm Hg); increased atherogenic risk (log(TAG/HDL) ≥ 0.11); and insulin resistance (QUICKI < 0.322) were considered as cardiometabolic risk factors. 25(OH)D3 status was classified as deficiency (25(OH)D3 ≤20 ng/ml); insufficiency (levels between 20-to-30 ng/ml), or as satisfactory (>30 ng/ml). Plasma adipokines, inflammatory and oxidative stress markers, advanced glycation end-products, and their soluble receptor were determined.

RESULTS

162 subjects were cardiometabolic risk factors-free, 162 presented increased (i.e. 1 or 2), and 87 high number (i.e. 3 or 4) of cardiometabolic risk factors. Mean 25(OH)D3 decreased with rising number of manifested risk factors (36 ± 14 ng/ml, 33 ± 14 ng/ml, and 31 ± 15 ng/ml, respectively; pANOVA: 0.010), while prevalence of hypovitaminosis D did not differ significantly. Elevated blood pressure and insulin resistance appeared as significant determinants of hypovitaminosis D. Subjects presenting these risk factors concurrently displayed the lowest 25(OH)D3 levels (29 ± 15 ng/ml). Plasma adipokines, inflammatory and oxidative stress markers, advanced glycation end-products, and their soluble receptor generally differed significantly between the groups, but only advanced oxidation protein products and advanced glycation end-products associated fluorescence of plasma showed significant independent association with 25(OH)D3 levels.

CONCLUSION

In apparently healthy adults increasing number of cardiometabolic risk factors associates with poorer 25(OH)D3 status, while the association between 25(OH)D3 status and inflammatory or oxidative stress markers remains equivocal.

Vitamin D for the prevention of cardiovascular disease: Are we ready for that?

A general concept of clinical benefit of vitamin D supplementation has emerged from the evidence in prevention of osteoporosis. From the cardiovascular point of view, clinical benefit of such supplementation remains less clear. Studies in vitro and in animal models demonstrated the expression of vitamin D receptors in endothelial cells, vascular smooth muscle and cardiomyocytes. Vitamin D has been directly implicated in endothelium-mediated vasodilation, anti-coagulant activity and inhibition of the inflammatory response. Indirectly, it may favor the reduction of blood pressure, myocardial hypertrophy and ventricular arrhythmias. In contrast to these mechanistic findings, cross-sectional, longitudinal and small clinical trials have not been consistent in demonstrating association between cardiovascular events and vitamin D. Besides, methodological issues in the tests for serum levels of vitamin D may also contribute to this puzzle. Hence, in the current state of knowledge, it may be too early to consider or to rule out vitamin D as a tool to either estimate or mitigate residual cardiovascular risk. In this review, we discuss recent advances and potential limitations in mechanistic and clinical evidences that are outlining the framework of interaction between vitamin D and cardiovascular risk.

Effect of Vitamin D supplementation on glycemic parameters and progression of prediabetes to diabetes: A 1-year, open-label randomized study

BACKGROUND

Whether Vitamin D supplementation in prediabetes subjects prevents the development of diabetes is a matter of debate, and the results are inconsistent. This open-label, randomized study in subjects with prediabetes evaluated the effect of 12 months of Vitamin D supplementation on glycemic parameters and progression of prediabetes to diabetes in an ethnically homogeneous Kashmiri population.

MATERIALS AND METHODS

A total of 147 subjects were diagnosed as prediabetes out of which 137 subjects were randomized to receive in addition to standard lifestyle measures, either Vitamin D 60,000 IU weekly for 4 weeks and then 60,000 IU monthly (n = 69) or no Vitamin D (n = 68). Fasting plasma glucose (FPG), 2-h plasma glucose and A1C levels were estimated at 0, 6 and 12 months. Changes in FPG, 2-h plasma glucose, A1C level and the proportion of subjects developing diabetes were assessed among 129 subjects.

RESULTS

At 12 months, A1C levels were significantly lesser (5.7% ± 0.4%) in the Vitamin D supplemented group when compared with non-Vitamin D supplemented (6.0% ± 0.3%). Similarly, FPG (97 ± 7) and 2-h plasma glucose (132 ± 16) were significantly less in Vitamin D supplemented group as compared with non-Vitamin D supplemented group (FPG = 116 ± 6 and 2-h plasma glucose = 157 ± 25) at 12 months. Nine out of 65 in non-Vitamin D supplemented and seven out of 64 in the Vitamin D supplemented group developed diabetes.

CONCLUSIONS

Vitamin D supplementation in prediabetes subjects significantly lowered FPG, 2-h plasma glucose and A1C levels.

Vitamin D and diabetes mellitus: an update 2013

Vitamin D deficiency and diabetes mellitus are two common conditions and they are widely prevalent across all ages, races, geographical regions, and socioeconomic conditions. Epidemiologic studies have shown association of vitamin D deficiency and increased risk of chronic diseases, such as cancer, cardiovascular disease, type 2 diabetes, and autoimmune diseases, such as multiple sclerosis and type 1 diabetes mellitus. The identification of 1,25(OH)2D receptors and 1-α-hydroxilase expression in pancreatic beta cells, in cells of the immune system, and in various others tissues, besides the bone system support the role of vitamin D in the pathogenesis of type 2 diabetes. Observational studies have revealed an association between 25(OH) D deficiency and the prevalence of type 1 diabetes in children and adolescents. This review will focus on the concept of vitamin D deficiency, its prevalence, and its role in the pathogenesis and risk of diabetes mellitus and cardiovascular diseases.

Low circulating 25-hydroxyvitamin D concentrations are associated with defects in insulin action and insulin secretion in persons with prediabetes

BACKGROUND

Individuals with prediabetes mellitus (PreDM) and low circulating 25-hydroxyvitamin D [25(OH)D] are at increased risk of type 2 diabetes mellitus (T2DM).

OBJECTIVE

We aimed to determine whether low 25(OH)D concentrations are associated with defects in insulin action and insulin secretion in persons with PreDM.

METHODS

In this cross-sectional study, we stratified 488 nondiabetic subjects as having PreDM or normal fasting glucose (NFG) and a 25(OH)D concentration ≤20 ng/mL (deficient) or >20 ng/mL (sufficient). We determined insulin resistance by steady state plasma glucose (SSPG) concentration and homeostasis model assessment of insulin resistance (HOMA-IR) and insulin secretion by homeostasis model assessment of β-cell function (HOMA-β). We compared insulin resistance and secretion measures in PreDM and NFG groups; 25(OH)D-deficient and 25(OH)D-sufficient groups; and PreDM-deficient, PreDM-sufficient, NFG-deficient, and NFG-sufficient subgroups, adjusting for age, sex, race, body mass index, multivitamin use, and season.

RESULTS

In the PreDM group, mean SSPG concentration and HOMA-IR were higher and mean HOMA-β was lower than in the NFG group (P < 0.001 for all comparisons). In the 25(OH)D-deficient group, mean SSPG concentration was higher (P < 0.001), but neither mean HOMA-IR nor HOMA-β was significantly different from that in the 25(OH)D-sufficient group. In the PreDM-deficient subgroup, mean (95% CI) SSPG concentration was higher (P < 0.01) than in the PreDM-sufficient, NFG-deficient, and NFG-sufficient subgroups [192 (177-207) mg/dL vs. 166 (155-177) mg/dL, 148 (138-159) mg/dL, and 136 (127-144) mg/dL, respectively]. Despite greater insulin resistance, mean HOMA-β was not significantly higher in the PreDM-deficient subgroup than in the PreDM-sufficient, NFG-deficient, and NFG-sufficient subgroups [98 (85-112) vs. 91 (82-101), 123 (112-136), and 115 (106-124), respectively].

CONCLUSION

Subjects with PreDM and low circulating 25(OH)D concentrations are the subgroup of nondiabetic individuals who are the most insulin resistant and have impaired β-cell function, attributes that put them at enhanced risk of T2DM.

Vitamin D and its effects on glucose homeostasis, cardiovascular function and immune function

In recent years there has been increasing interest in the non-skeletal effects of vitamin D. It has been suggested that vitamin D deficiency may influence the development of diabetes, cardiovascular dysfunction and autoimmune diseases. This review focuses on the current knowledge of the effects of vitamin D and its deficiency on cardiovascular function, glucose homeostasis and immune function, with a particular focus on children. Although, there is good evidence to show that there is an association between vitamin D deficiency and an abnormality of the above systems, there is little evidence to show that vitamin D supplementation leads to an improvement in function, especially in childhood.

Decreased serum vitamin D levels are associated with diabetic peripheral neuropathy in a rural area of Turkey

Data examining the association between vitamin D and diabetic peripheral neuropathy are limited. This study investigated the serum levels of vitamin D, vitamin D-binding protein (VDBP), and vitamin D receptor (VDR) in diabetics in the Yozgat region of Turkey, and assessed their relationships with diabetic peripheral neuropathy. 69 diabetic patients and 49 age- and sex-matched control subjects were enrolled in this clinical prospective study. All the diabetics underwent conventional sensory and motor nerve conduction studies, and diabetic peripheral neuropathy was confirmed or ruled out according to the electromyography findings and Douleur Neuropathique 4 questions. Serum vitamin D, VDBP and VDR levels were measured using commercial enzyme-linked immunosorbent assay kits. The serum vitamin D levels (p = 0.001) were significantly lower, while the VDR levels (p = 0.003) were higher, in diabetics than in controls. The serum VDBP levels were similar in both groups (p > 0.05). The serum vitamin D levels were significantly lower in diabetics with diabetic peripheral neuropathy than in those without (p = 0.032), whereas the serum VDBP and VDR levels were similar in these two groups (p > 0.05). The lower serum vitamin D levels in diabetics, especially in those with peripheral neuropathy, may suggest a neurotrophic effect of vitamin D.

No association between 25-hydroxyvitamin D levels and prediabetes in Brazilian patients. A cross-sectional study

CONTEXT AND OBJECTIVE

Several studies have evaluated the role of low 25-hydroxyvitamin D (25OHD3) in the pathogenesis of type 2 diabetes (T2DM) and have presented controversial results. The metabolic processes that culminate in T2DM begin under prediabetic conditions. Our aim was to analyze the association between 25OHD3 and glucose metabolism in individuals who were free from but at elevated risk of diabetes.

DESIGN AND SETTING

Cross-sectional study at a tertiary hospital.

METHODS

Anthropometric and laboratory profiles were determined in patients with one or more of the following risk factors: hypertension; body mass index (BMI) ≥ 25 kg/m2; waist circumference > 80 cm for women and > 94 cm for men; first-degree relatives with diabetes; women with large-for-gestational-age newborns or with gestational T2DM; HDL-cholesterol (high density lipoprotein) < 35 mg/dl; and triglycerides > 250 mg/dl. The patients were divided into two groups: one with prediabetes (abnormal fasting plasma glucose or oral glucose tolerance test) and the other with normal glucose (euglycemic).

RESULTS

There was no statistically significant difference between the prediabetic group (n = 38) and euglycemic group (n = 15) regarding age (66.4 ± 10.6 versus 62.6 ± 9.1 years), gender (52.6 versus 73.3% female) and BMI (30.1 ± 4.61 versus 27.9 ± 4.7 kg/m2). Low serum levels of 25OHD3 were found in both groups, without any statistically significant difference between them (29.1 ± 11.8 versus 26.87 ± 9.2 ng/dl).

CONCLUSION

There was no association between 25OHD3 levels and the clinical or laboratorial variables analyzed.

Vitamin D and risk of CVD: a review of the evidence

This review summarises evidence for an association between vitamin D status and CVD and the mechanisms involved. Vitamin D3 is predominantly provided by the action of UVB from sunlight on skin. Average UK diets supply 2-3 μg/d vitamin D but diets containing at least one portion of oily fish per week supply about 7 μg/d. Pharmacological doses of vitamin D2 (bolus injection of 7500 μg or intakes >50 μg/d) result in a smaller increase in plasma 25(OH)D than those of D3 but physiological doses 5-25 μg/d seem equivalent. Plasma 25(OH)D concentrations are also influenced by clothing, obesity and skin pigmentation. Up to 40 % of the population have plasma 25(OH)D concentrations <25 nmol/l in the winter compared with <10 % in the summer. The relative risk of CVD death is 1·41 (95 % CI 1·18, 1·68) greater in the lowest quintile of plasma 25(OH)D according to meta-analysis of prospective cohort studies. Acute deficiency may inhibit insulin secretion and promote inflammation thus increasing the risk of plaque rupture and arterial thrombosis. Chronic insufficiency may increase arterial stiffness. There is no evidence to support claims of reduced CVD from existing trials with bone-related health outcomes where vitamin D was usually co-administered with calcium. Although several trials with cardiovascular endpoints are in progress, these are using pharmacological doses. In view of the potential toxicity of pharmacological doses, there remains a need for long-term trials of physiological doses of D2 and D3 with CVD incidence as the primary outcome.

Vitamin D: A new player in non-alcoholic fatty liver disease?

Vitamin D through its active form 1a-25-dihydroxyvtamin D [1,25(OH)₂D] is a secosteroid hormone that plays a key role in mineral metabolism. Recent years have witnessed a significant scientific interest on vitamin D and expanded its actions to include immune modulation, cell differentiation and proliferation and inflammation regulation. As our understanding of the many functions of vitamin D has grown, the presence of vitamin D deficiency has become one of the most prevalent micronutrient deficiencies worldwide. Concomitantly, non-alcoholic fatty liver disease (NAFLD) has become the most common form of chronic liver disease in western countries. NAFLD and vitamin D deficiency often coexist and epidemiologic evidence has shown that both of these conditions share several cardiometabolic risk factors. In this article we provide an overview of the epidemiology and pathophysiology linking NAFLD and vitamin D deficiency, as well as the available evidence on the clinical utility of vitamin D supplementation in NAFLD.

Vitamin D supplementation ameliorates hypoinsulinemia and hyperglycemia in static magnetic field-exposed rat

The purpose of this study is to evaluate the effects of vitamin D supplementation on glucose and lipid metabolism in static magnetic field (SMF)-exposed rats. Rats exposed to SMF (128 mT; 1 h/day) during 5 consecutive days showed an increase in plasma glucose level and a decrease in plasma insulin concentration. By contrast, the same treatment failed to alter body weight and plasmatic total cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, and triglyceride levels. Interestingly, supplementation with vitamin D (1,600 IU/100 g, per os) corrected and restored glycemia and insulinemia in SMF-exposed rats. The same treatment had no effects on lipid metabolism.

Effect of Vitamin D Supplementation on Glucose Control and Inflammatory Response in Type II Diabetes: A Double Blind, Randomized Clinical Trial

BACKGROUND

Diabetes mellitus (DM) and vitamin D deficiency are major health concerns around the world. Evidence suggests a possible role of vitamin D in improvement of insulin secretion and sensitivity.

OBJECTIVES

We assessed whether vitamin D supplementation could be used in vitamin D deficient-type II diabetes to improve glucose metabolism, components of metabolic syndrome (MetS) and specific inflammatory biomarkers.

PATIENTS AND METHODS

A double blind, randomized clinical trial was conducted in King Khalid University Hospital, Saudi Arabia to evaluate the effect of cholecalciferol supplementation on glycemic control, MetS components and specific inflammatory biomarkers including tumor necrosis factor-alpha (TNF-α), Interleukin (IL-6), leptin, adiponectin and vascular cell adhesion molecule-1 (VCAM-1). Twenty-two patients with type II diabetes with insulin resistance, glycated hemoglobin (HbA1c) ≥ 6 (42 mmol/mol) and serum 25(OH)D < 50 nmol/L were randomized using a computer program to receive either supplementation with cholecalciferol (5000 IU/day) or placebo for 12 weeks. The primary outcome was change in HbA1c levels from baseline.

RESULTS

Median [IQR] 25(OH)D levels increased significantly in the vitamin D group as 58.1 [48, 67.3] nmol/L (P = 0.002). There was no significant difference in the change of HbA1c between the groups (P = 0.5) with a decrease of -0.1% [-1, 0.5] in the vitamin D group and an increase of 0.15% [0.1, 0.2] in the placebo group. A significant improvement was observed in the homeostasis model of assessment of β-cell activity (HOMA-%B) (P = 0.03) with vitamin D supplementation compared to baseline.

CONCLUSIONS

Vitamin D repletion for 12 weeks increased serum vitamin D concentrations and improved β-cell activity in vitamin D-deficient type II diabetes with no significant changes in HbA1c or insulin sensitivity.

The relationship between immediate preoperative serum 25-hydroxy-vitamin D₃ levels and cardiac function, dysglycemia, length of stay, and 30-d readmissions in cardiac surgery patients

OBJECTIVES

Vitamin D has pleiotropic effects on cardiac, renal, and endocrine diseases like diabetes mellitus and deficiency has been correlated with increased Intensive Care Unit (ICU) morbidity and mortality. We studied the relationship between preoperative Vitamin D levels and several short-term endpoints including cardiovascular events, glucose levels, ICU, and hospital length of stay.

METHODS

Standard demographic data were obtained. Blood samples were drawn for 25-hydroxy-vitamin D3 (Vit D) levels at baseline (just before induction of anesthesia) and on postoperative day (POD #1). The number of inotropes used on POD # 0, 1, and 2 was recorded as well as the Cardiac Index (CI). Baseline glucose, Blood Urea Nitrogen and Creatinine (Cr) levels were obtained and repeated on POD # 1 & 2. Other variables studied are number of days of ICU and hospital stay.

RESULTS

Of the 64 patients included in the cohort, 3 were excluded because of inadequate data. 69% had Vit D levels <20 ng/mL and 31% had levels ≥20 ng/mL. More than 90% of the cohort had a significant decrease in POD # 1 Vit D levels (P < 0.001). Age, sex, race, and body mass index did not predict the preoperative Vit D levels; however, the timing of surgery was associated with preoperative Vit D levels, lowest in subjects who had surgery performed during winter. Preoperative Vit D levels had no effect on postoperative glycemic control, cardiac index, or composite outcome-arrhythmias, respiratory failure, or prolonged inotropic support. On regression analysis, preoperative Vit D levels did show a significant effect on ICU and hospital length of stay in this cohort.

CONCLUSIONS

The low levels in this study truly represent the Vit D status as they were obtained before any intervention, including surgery or fluid administration. Vit D levels decreased rapidly after surgery and hence future studies on Vit D may need to focus on premorbid levels obtained at the time of initial presentation and not those obtained after resuscitation or ICU admission. In contrast to epidemiologic reports, we found no association between low Vit D levels and postoperative cardiovascular events. However, low Vit D levels did affect the ICU and hospital length of stay in patients who were undergoing cardiac surgery. This is an important finding especially when many institutions and regulatory agencies are investigating novel therapies and processes to reduce the length of hospitalization. More studies are required to investigate the effect on hospital length of stay of early preadmission or preoperative Vit D supplementation before elective surgery.

A randomised controlled trial of high dose vitamin D in recent-onset type 2 diabetes

AIMS

Vitamin D insufficiency has been associated with impaired pancreatic beta-cell function. We aimed to determine if high dose oral vitamin D3 (D) improves beta-cell function and glycaemia in type 2 diabetes.

METHODS

Fifty adults with type 2 diabetes diagnosed less than 12 months, with normal baseline serum 25-OH D (25D), were randomised to 6000 IU D (n=26) or placebo (n=24) daily for 6 months. Beta-cell function was measured by glucagon-stimulated serum C-peptide (delta C-peptide [DCP], nmol/l). Secondary outcome measures were fasting plasma glucose (FPG), post-prandial blood glucose (PPG), HbA1c and insulin resistance (HOMA-IR).

RESULTS

In the D group, median serum 25D (nmol/l) increased from 59 to 150 (3 months) and 128 (6 months) and median serum 1,25D (pmol/l) from 135 to 200 and 190. After 3 months, change in DCP from baseline in D (+0.04) and placebo (-0.08) was not different (P=0.112). However, change in FPG (mmol/l) was significantly lower in D (-0.40) compared to placebo (+0.1) (P=0.007), as was the change in PPG in D (-0.30) compared to placebo (+0.8) (P=0.005). Change in HbA1c (%) between D (-0.20) and placebo (-0.10) was not different (P=0.459). At 6 months, changes from baseline in DCP, FPG, PPG and HbA1c were not different between groups.

CONCLUSION

Oral D3 supplementation in type 2 diabetes was associated with transient improvement in glycaemia, but without a measurable change in beta-cell function this effect is unlikely to be biologically significant. High dose D3 therefore appears to offer little or no therapeutic benefit in type 2 diabetes.

Vitamin D supplementation in obese type 2 diabetes subjects in Ajman, UAE: a randomized controlled double-blinded clinical trial

OBJECTIVES

To study the effect of Vitamin D3 supplementation on metabolic control in an obese type 2 diabetes Emirati population.

METHODS

This randomized double-blind clinical trial was conducted with 87 vitamin D-deficient obese, type 2 diabetic participants. The vitamin D-group (n=45) and the placebo group (n=42) were matched for gender, age, HbA1c and 25-hydroxy vitamin D (25(OH) D) at the baseline. The study was divided into two phases of 3 months each; in phase 1, the vitamin D-group received 6000 IU vitamin D3/day followed by 3000 IU vitamin D3/day in phase 2, whereas the placebo group (n=42) received matching placebo.

RESULTS

After supplementation, serum 25(OH) D peaked in the vitamin D-group in phase 1 (77.2±30.1 nmol/l, P=0.003) followed by a decrease in the phase 2 (61.4±18.8 nmol/l, P=0.006), although this was higher compared with baseline. In the placebo group, no difference was observed in the serum 25(OH) D levels throughout the intervention. Relative to baseline serum, parathyroid hormone decreased 24% (P=0.003) in the vitamin D-group in phase 2, but remained unchanged in the placebo group. No significant changes were observed in blood pressure, fasting blood glucose, HbA1c, C-peptide, creatinine, phosphorous, alkaline phosphatase, lipids, C-reactive protein or thyroid stimulating hormone concentrations compared with baseline in either group.

CONCLUSIONS

Six months of vitamin D3 supplementation to vitamin D-deficient obese type 2 diabetes patients in the UAE normalized the vitamin D status and reduced the incidence of eucalcemic parathyroid hormone elevation but showed no effect on the metabolic control.

VITamin D supplementation in renAL transplant recipients (VITALE): a prospective, multicentre, double-blind, randomized trial of vitamin D estimating the benefit and safety of vitamin D3 treatment at a dose of 100,000 UI compared with a dose of 12,000 UI in renal transplant recipients: study protocol for a double-blind, randomized, controlled trial

Background

In addition to their effects on bone health, high doses of cholecalciferol may have beneficial non-classic effects including the reduction of incidence of type 2 diabetes mellitus, cardiovascular disease, and cancer. These pleiotropic effects have been documented in observational and experimental studies or in small intervention trials. Vitamin D insufficiency is a frequent finding in renal transplant recipients (RTRs), and this population is at risk of the previously cited complications.

Methods/design

The VITALE study is a prospective, multicentre, double-blind, randomized, controlled trial with two parallel groups that will include a total of 640 RTRs. RTRs with vitamin D insufficiency, defined as circulating 25-hydroxyvitamin D levels of less than 30 ng/ml (or 75 nmol/l), will be randomized between 12 and 48 months after transplantation to blinded groups to receive vitamin D₃ (cholecalciferol) either at high or low dose (respectively, 100,000 UI or 12,000 UI every 2 weeks for 2 months then monthly for 22 months) with a follow-up of 2 years. The primary objective of the study is to evaluate the benefit/risk ratio of high-dose versus low-dose cholecalciferol on a composite endpoint consisting of de novo diabetes mellitus; major cardiovascular events; de novo cancer; and patient death. Secondary endpoints will include blood pressure (BP) control; echocardiography findings; the incidences of infection and acute rejection episodes; renal allograft function using estimated glomerular filtration rate; proteinuria; graft survival; bone mineral density; the incidence of fractures; and biological relevant parameters of mineral metabolism.

Discussion

We previously reported that the intensive cholecalciferol treatment (100 000 IU every 2 weeks for 2 months) was safe in RTR. Using a pharmacokinetic approach, we showed that cholecalciferol 100,000 IU monthly should maintain serum 25-hydroxyvitamin D at above 30 ng/ml but below 80 ng/ml after renal transplantation. Taken together, these results are reassuring regarding the safety of the cholecalciferol doses that will be used in the VITALE study. Analysis of data collected during the VITALE study will demonstrate whether high or low-dose cholecalciferol is beneficial in RTRs with vitamin D insufficiency.

Trial registration

ClinicalTrials.gov Identifier: NCT01431430.

Electronic supplementary material

The online version of this article (doi:10.1186/1745-6215-15-430) contains supplementary material, which is available to authorized users.

No association between vitamin D and β-cell autoimmunity in Finnish and Estonian children

BACKGROUND

Vitamin D has immunomodulatory properties, such as regulation of FOXP3 expression and regulatory T-cell activity. Our aim was to investigate whether plasma 25-hydroxyvitamin D [25(OH)D] concentrations associate with the development of β-cell autoimmunity and the transcriptional activity of FOXP3 or vitamin D3 convertase gene (CYP27B1) in CD4+ memory T cells.

METHODS

We studied 83 Finnish and 32 Estonian children participating in the DIABIMMUNE and DIPP studies. Twenty-nine Finnish and six Estonian children tested positive for at least one diabetes-associated autoantibody. The plasma concentrations of 25(OH)D and 1,25(OH)₂D were analysed with an enzyme immunoassay. Gene expression of FOXP3 and CYP27B1 in the isolated CD4+ memory T cells was studied with reverse transcription quantitative polymerase chain reaction.

RESULTS

Vitamin D status did not differ between subjects positive and negative for β-cell autoantibodies. Finnish children had higher vitamin D status than Estonian children (p < 0.001). FOXP3 expression was higher in Estonian CD4+ memory T-cell samples than in Finnish samples (p < 0.01) even when including in both groups only children with serum 25(OH)D concentrations in the range of 50-80 nmol/L (p < 0.001).

CONCLUSIONS

These findings do not support a crucial role of circulating 25(OH)D as a regulator of β-cell autoimmunity or FOXP3 expression.

Plasma vitamin D is associated with fasting insulin and homeostatic model assessment of insulin resistance in young adult males, but not females, of the Jerusalem Perinatal Study

OBJECTIVE

To examine cross-sectional relationships between plasma vitamin D and cardiometabolic risk factors in young adults.

DESIGN

Data were collected from interviews, physical examinations and biomarker measurements. Total plasma 25-hydroxyvitamin D (25(OH)D) was measured using LC-tandem MS. Associations between 25(OH)D and cardiometabolic risk factors were modelled using weighted linear regression with robust estimates of standard errors.

SETTING

Individuals born in Jerusalem during 1974-1976.

SUBJECTS

Participants of the Jerusalem Perinatal Study (n 1204) interviewed and examined at age 32 years. Participants were oversampled for low and high birth weight and for maternal pre-pregnancy obesity.

RESULTS

Mean total 25(OH)D concentration among participants was 21·7 (sd 8·9) ng/ml. Among males, 25(OH)D was associated with homeostatic model assessment of insulin resistance (natural log-transformed, β=-0·011, P=0·004) after adjustment for BMI. However, these associations were not present among females (P for sex interaction=0·005).

CONCLUSIONS

We found evidence for inverse associations of 25(OH)D with markers of insulin resistance among males, but not females, in a healthy, young adult Caucasian population. Prospective studies and studies conducted on other populations investigating sex-specific effects of vitamin D on cardiometabolic risk factors are warranted.

Association of vitamin D and vitamin D receptor gene polymorphisms with chronic inflammation, insulin resistance and metabolic syndrome components in type 2 diabetic Egyptian patients

Background

To date the published data concerning the possible interplay between vitamin D (VitD) and Vit D receptor (VDR) gene polymorphism with the immune/inflammatory mediators in type 2 diabetes mellitus (DM) is insufficient. Some of the immune non-classical actions of vitamin D may point to its role in the pathogenesis of type 2 DM through down-regulation of cytokines (IL-6). Although there is evidence to support a relationship among vitamin D status, chronic inflammation and insulin resistance, the underlying mechanism requires further exploration. We aimed to investigate the role of vitamin D in chronic inflammation and insulin resistance in type 2 DM. Moreover, to examine the association of VDR gene polymorphisms [VDR 2228570 C > T (FokI); VDR 1544410 A > G (BsmI)] with the components of metabolic syndrome (MetSyn) in type 2 diabetic Egyptian patients .

Subjects and methods

A total of 190 subjects were enrolled in this study, 60 controls and 130 type 2 diabetic patients (Group II). Group II was subdivided into 63 patients without MetSyn (subgroup IIa) and 67 patients with MetSyn (subgroup IIb). Genetic analysis for VDR gene polymorphisms was done in all subjects. VitD and IL-6 plasma levels were estimated.

Results

The TT genotype for the VDR FokI was significantly more frequent in subgroup IIb than in subgroup IIa and controls (X² = 6.83, P = 0.03 and X² = 16.592, P = 0.000) respectively. The T allele was more frequent in the MetSyn group as compared to diabetics without MetSyn (p = 0.001), odds ratio (OR) and 95% CI for the T allele of C > T (FokI) = 2.30 (1.37–3.86). We did not detect any significant difference in VDR BsmI genotypes between patients and control groups (P = 0.947). FokI VDR was significantly associated with the lipid profile parameters, VitD and IL-6 plasma levels in subgroup IIa and associated with HOMA-IR, insulin, VitD, IL-6 levels, waist circumference (WC) and body mass index (BMI) in subgroup IIb while BsmI VDR variant was associated only with VitD values in both subgroups.

Conclusion

The present study suggests an interaction between VDR polymorphisms and important components of MetSyn, VitD and pro-inflammatory cytokines (IL-6). FokI VDR polymorphisms may be linked to mild inflammation and insulin resistance and might represent a genetic determinant for developing MetSyn in type 2 diabetic Egyptian patients. The challenge is determining the mechanisms of VitD action for recommendation of VitD supplementation that reduces the risks of MetSyn, insulin resistance and progression to type 2 diabetes.

25-Hydroxyvitamin D levels and survival in advanced pancreatic cancer: findings from CALGB 80303 (Alliance)

BACKGROUND

Data from animal and cell-line models suggest that vitamin D metabolism plays an important role in pancreatic tumor behavior. Although vitamin D deficiency has been implicated in numerous cancers, the vitamin D status of patients with advanced pancreatic cancer and the effect of baseline vitamin D levels on survival are unknown.

METHODS

Participants in this correlative study (CALGB 151006) were enrolled in CALGB 80303, which was a randomized trial of patients with advanced pancreatic cancer that demonstrated no difference in overall survival (OS) among patients treated with gemcitabine plus placebo vs gemcitabine plus bevacizumab. We measured baseline serum 25-hydroxyvitamin D (25[OH]D) levels and examined associations between baseline 25(OH)D levels and progression-free survival and OS using the Cox rank score test. All statistical tests were two-sided.

RESULTS

Of 256 patients with available serum, the median 25(OH)D level was 21.7ng/mL (range 4 to 77). 44.5% of patients were vitamin D deficient (25[OH]D <20ng/mL), and 32.4% were insufficient (25[OH]D ≥20 and <30ng/mL). 25(OH)D levels were lower in black patients compared with white patients, and patients of other/undisclosed race (10.7 vs 22.4 vs 20.9ng/mL, P < .001). Baseline 25(OH)D levels were not associated with PFS (HR = 1.00, 95% CI = 0.99 to 1.01, P = .60) or OS (HR = 1.00, 95% CI = 0.99 to 1.01, P = .95).

CONCLUSION

Vitamin D deficiency was highly prevalent among patients with a new diagnosis of advanced pancreatic cancer. Black patients had statistically significantly lower 25(OH)D levels than white patients. In this cohort of patients with advanced pancreatic cancer receiving gemcitabine-based chemotherapy, baseline 25(OH)D levels were not associated with PFS or OS.

No effect of high-dose vitamin D supplementation on glycemic status or cardiovascular risk factors in subjects with prediabetes

OBJECTIVE

In observational studies, low serum 25-hydroxyvitamin D [25(OH)D] concentrations have been associated with insulin resistance and other risk factors for cardiovascular disease.

RESEARCH DESIGN AND METHODS

We present 1-year data from an ongoing 5-year trial in 511 individuals with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) randomly assigned to 20,000 IU/week vitamin D3 or placebo. An oral glucose tolerance test was performed at baseline and after 1 year.

RESULTS

Mean baseline serum 25(OH)D was 59.9 nmol/L and 61.1 nmol/L in the vitamin D and placebo groups, respectively, and increased by 45.8 nmol/L and 3.4 nmol/L, respectively. With adjustment for baseline concentrations, no differences in measures of glucose metabolism, insulin secretion or sensitivity, blood pressure, or hs-CRP were found after 1 year. There was a slight, but significant decrease in total and LDL cholesterol in the vitamin D group compared with the placebo group, but as there was also a decrease in HDL cholesterol, the change in the total/HDL cholesterol ratio did not differ significantly. Only analyzing subjects with 25(OH)D <50 nmol/L did not change the results.

CONCLUSIONS

This study shows that vitamin D supplementation does not improve glycemic indices, blood pressure, or lipid status in subjects with IFG and/or IGT.

Serum 25-hydroxyvitamin D and insulin resistance in apparently healthy adolescents

PURPOSE

Vitamin D deficiency is a common condition that is associated with diabetes and insulin resistance. However, the association between vitamin D and insulin resistance has not been fully studied, especially in the general adolescent population. Therefore, we assessed the association between serum 25-hydroxyvitamin D [25(OH)D] level and insulin resistance among apparently healthy Korean adolescents.

METHODS

A total of 260 (135 male and 125 female) adolescents in a rural high school were assessed for serum 25(OH)D, fasting plasma glucose, and insulin. All of the participants were aged 15 to 16 years old, and without known hypertension or diabetes. Serum 25(OH)D was analyzed both as a continuous and categorical variable in association with insulin resistance. Insulin resistance was estimated by homeostasis model assessment (HOMA-IR). Increased insulin resistance was operationally defined as a HOMA-IR value higher than the sex-specific 75th percentile.

RESULTS

In male adolescents, every 10 ng/ml decrease in 25(OH)D level was associated with a 0.25 unit increase in HOMA-IR (p = 0.003) after adjusting for age and BMI. Compared to those in the highest quartile, male adolescents in the lowest 25(OH)D quartile were at significantly higher risk for insulin resistance: unadjusted odds ratio 4.06 (95% CI, 1.26 to 13.07); age and BMI adjusted odds ratio 3.59 (95% CI, 1.03 to 12.57). However, 25(OH)D level, either in continuous or categorical measure, was not significantly associated with insulin resistance among female adolescents.

CONCLUSIONS

This study suggests that serum 25(OH)D level may be inversely associated with insulin resistance in healthy male adolescents.

Low Vitamin D Serum Levels May Be a Modifiable Risk Factor for Obesity and Cognitive Impairment in Middle-Age Egyptian Women

OBJECTIVE: To evaluate the levels of serum vitamin D (25-hydroxyvitamin D) among obese Egyptian females and search possible association with cognitive functions and insulin resistance.SUBJECTS AND METHODS: This study included 2 groups, Group-1(cases) consists of 120 obese females and Group-2 (controls) consists of 30 non-obese females. The included females were subjected to full clinical examination, anthropometric measurements and Kendrick Battery for evaluation of cognitive functions (short term memory and attention). Evaluation of serum Vitamin D, Parathyroid hormone, C-peptide and fasting blood glucose were done. The obese group was put on a balanced low caloric diet (900-1000 K Calories/day) for 2 months, where reevaluation was performed.RESULTS: Comparing obese group with non-obese control group revealed significant lower mean level of serum vitamin D associated with significant lower cognitive functions test and higher fasting blood glucose. After 2 months of low caloric diet, a significant increase in the serum level of vitamin D, accompanied with improvement in cognitive functions and decrease in fasting blood glucose and improved insulin resistance was seen. A correlation is found between vitamin D serum level and cognitive functions.CONCLUSION: A lower vitamin D serum level could be a modifiable risk factor for obesity, insulin resistance and cognitive impairment in middle age females.