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

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

Sollid ST ，Hutchinson MY ，Fuskevåg OM ，Figenschau Y ，Joakimsen RM ，Schirmer H ，Njølstad I ，Svartberg J ，Kamycheva E ，Jorde R ... -  《-》

Effect of vitamin D supplementation on oral glucose tolerance in individuals with low vitamin D status and increased risk for developing type 2 diabetes (EVIDENCE): A double-blind, randomized, placebo-controlled clinical trial.

Low serum 25-hydroxyvitamin-D (25(OH)D) concentrations are associated with insulin resistance, β-cell dysfunction and type 2 diabetes. We conducted a 24-week double-blind, randomized, placebo-controlled trial to examine the effect of 28 000 IU of vitamin D3 once weekly on plasma glucose after a 2 hour-75 g oral glucose tolerance test (2hrPC glucose), insulin sensitivity and β-cell function. A total of 71 participants with serum 25(OH)D ≤65 nmol/L, impaired fasting glucose and elevated glycated hemoglobin were randomly assigned to receive 28 000 IU of vitamin D3 (VitD; n = 35) or placebo (n = 36) in cheese once weekly for 24 weeks. The primary outcome was the change in 2hPC glucose. Secondary outcomes were fasting glucose, fasting and postprandial insulin, indices of insulin sensitivity and β-cell function, glycated hemoglobin and lipid profile. Participants underwent an oral glucose tolerance test to determine 2hPC glucose. Mean baseline serum 25(OH)D was 48.1 and 47.6 nmol/L in the VitD and placebo groups, respectively. Serum 25(OH)D significantly increased to 98.7 nmol/L (51 nmol/L increase; P < .0001) in the VitD group. No significant differences in fasting ( P = .42) or 2hPC glucose ( P = .55) or other indices of glucose metabolism, including β-cell function and insulin sensitivity, were observed between groups. A subgroup analysis of individuals with 25(OH)D < 50 nmol/L and prediabetes did not change these results. The VitD group exhibited a significant reduction in LDL cholesterol (-0.27 vs 0.01 mmol/L, P = .03). Weekly doses of vitamin D3 in individuals with suboptimal vitamin D levels who were at risk for type 2 diabetes did not improve oral glucose tolerance or markers of glycaemic status.

Moreira-Lucas TS ，Duncan AM ，Rabasa-Lhoret R ，Vieth R ，Gibbs AL ，Badawi A ，Wolever TM ... -  《-》

Effect of moderate-dose vitamin D supplementation on insulin sensitivity in vitamin D-deficient non-Western immigrants in the Netherlands: a randomized placebo-controlled trial.

Low serum 25-hydroxyvitamin D [25(OH)D] concentrations have been associated with insulin resistance, the metabolic syndrome, and type 2 diabetes. Because many non-Western immigrants in the Netherlands are vitamin D deficient, obese, and at high risk of diabetes, vitamin D supplementation may contribute to prevent diabetes and insulin resistance. We examined the effect of vitamin D supplementation on insulin sensitivity and β cell function in overweight, vitamin D-deficient, non-Western immigrants at high risk of diabetes. The study was a 16-wk, randomized, placebo-controlled trial. A total of 130 non-Western immigrants with prediabetes (fasting glucose concentration >5.5 mmol/L or random glucose concentration from 7.8 to 11.1 mmol/L) and vitamin D deficiency (serum 25[OH]D concentration <50 nmol/L) were randomly assigned after stratification by sex to receive either cholecalciferol (1200 IU/d) or a placebo for 16 wk. All participants received 500 mg Ca/d as calcium carbonate. The primary outcome was the difference in the area under the curve of insulin and glucose after a 75-g oral-glucose-tolerance test after 4 mo of treatment. Secondary outcomes were insulin-sensitivity variables, β cell-function variables, and metabolic syndrome. Mean serum 25(OH)D concentrations increased significantly in the vitamin D compared with placebo groups. After 4 mo of therapy, the mean between-group difference was 38 nmol/L (95% CI: 32.1, 43.9 nmol/L; P < 0.001). There was no significant effect on insulin sensitivity and β cell function. In a post hoc analysis, when patients with diabetes at baseline were excluded, a significant increase in the insulinogenic index was observed in participants who obtained a 25(OH)D concentration ≥60 nmol/L (P = 0.040). Vitamin D supplementation in non-Western vitamin D-deficient immigrants with prediabetes did not improve insulin sensitivity or β cell function or change the incidence of metabolic syndrome. However, after the exclusion of diabetic subjects, an improvement in the insulinogenic index was observed in participants who obtained a 25(OH)D concentration ≥60 nmol/L. This trial was registered at trialregister.nl as NTR1827.

Oosterwerff MM ，Eekhoff EM ，Van Schoor NM ，Boeke AJ ，Nanayakkara P ，Meijnen R ，Knol DL ，Kramer MH ，Lips P ... -  《-》

Effects of Vitamin D Supplementation on Insulin Sensitivity and Insulin Secretion in Subjects With Type 2 Diabetes and Vitamin D Deficiency: A Randomized Controlled Trial.

In observational studies, low vitamin D levels are associated with type 2 diabetes (T2D), impaired glucose metabolism, insulin sensitivity, and insulin secretion. We evaluated the efficacy of vitamin D supplementation on insulin sensitivity and insulin secretion in subjects with T2D and low vitamin D (25-hydroxyvitamin D [25(OH)D] <50 nmol/L). Sixty-two men and women with T2D and vitamin D deficiency participated in a 6-month randomized, double-blind, placebo-controlled trial. Participants received a single dose of 400,000 IU oral vitamin D3 or placebo, and the vitamin D group received an additional 200,000 IU D3 if serum 25(OH)D was <100 nmol/L after 4 weeks. Primary end points were total Rd by euglycemic clamp with assessment of endogenous glucose production and first-phase insulin secretion by intravenous glucose tolerance test. In the vitamin D group, the mean ± SD baseline serum 25(OH)D of 38.0 ± 12.6 nmol/L increased to 96.9 ± 18.3 nmol/L after 4 weeks, 73.2 ± 13.7 nmol/L after 3 months, and 53.7 ± 9.2 nmol/L after 6 months. The total exposure to 25(OH)D during 6 months (area under the curve) was 1,870 ± 192 and 1,090 ± 377 nmol/L per week in the vitamin D and placebo groups, respectively (P < 0.001). Insulin sensitivity, endogenous glucose production, and glycemic control did not differ between or within groups after treatment (P = 0.52). First-phase insulin secretion did not change significantly after treatment (P = 0.10). Replenishment with a large dose of vitamin D3 to patients with T2D and vitamin D deficiency did not change insulin sensitivity or insulin secretion. These findings do not support such use of therapeutic vitamin D3 supplementation to improve glucose homeostasis in patients with T2D.

Gulseth HL ，Wium C ，Angel K ，Eriksen EF ，Birkeland KI ... -  《-》

Effects of 6-month vitamin D supplementation on insulin sensitivity and secretion: a randomised, placebo-controlled trial.

Lemieux P ，Weisnagel SJ ，Caron AZ ，Julien AS ，Morisset AS ，Carreau AM ，Poirier J ，Tchernof A ，Robitaille J ，Bergeron J ，Marette A ，Vohl MC ，Gagnon C ... -  《-》