| Accumulating evidence suggests a pathological role of low-intensity chronic inflammation in the development of glucose intolerance and type 2 diabetes mellitus (T2DM). Recently, a beneficial role of vitamin D in T2DM and insulin resistance has been suggested. There is also strong evidence on the immune and anti-inflammatory effects of vitamin D.;The objective of the study was to evaluate the effect of vitamin D supplementation on C-reactive protein (CRP) and insulin resistance in women with type 2 diabetes mellitus (T2DM).;We conducted a randomized, double blind, placebo-controlled clinical trial in 104 obese/overweight postmenopausal women with T2DM. The intervention group received a capsule containing 4,000 IU of cholecalciferol daily during 6 months, while the control group received a placebo. Primary endpoints were C-reactive protein (CRP) --as a marker of low intensity, chronic inflammation-, and insulin resistance --HOMA-IR-.;After 6 months, there was an increase in serum 25-OH-D of 25+/-2.6 nmol/L in the supplemented group, and an increase of 0.8+/-2.2 nmol/L in the placebo group (p<0.001). Serum calcium was within normal range at baseline (9.95+/-1.0 mg/dL) and it was not affected by the intervention.;There was a 64% reduction on CRP among supplemented women who had baseline CRP concentrations >5.0 mg/L. (p<0.05). A 24% reduction in HOMA-IR after 6 months was observed among supplemented women who had a baseline HOMA-IR >6.0, p=0.06. Improvement in vitamin D status had a protective effect against leptin-induced insulin resistance. Linear regression analysis showed that leptin's effect on insulin resistance and fasting insulin was observed only among women with final serum 25-OH-D concentrations <67 nmol/L: beta=0.17 for HOMA-IR (95% CI: 0.002, 0.35, p= 0.048). For fasting insulin, leptin-related coefficient was beta=0.96 (95% CI: 0.59, 1.33, p<0.001). The leptin regression coefficients were much lower, and were not statistically-significant, for women with final 25-OH-D concentrations ≥67 nmol/L. Results were adjusted by age, fat mass, and triglycerides;In conclusion, our results indicate a beneficial effect of vitamin D supplementation on CRP and insulin resistance in postmenopausal women with T2DM. Further studies are warranted to assess the clinical and long-term implications of these findings. |
