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Manco M, Calvani M, Nanni G, Greco AV, Iaconelli A, Gasbarrini G, Castagneto M, Mingrone G: Low 25-hydroxyvitamin D does not affect insulin sensitivity in obesity after bariatric surgery. Obes Res. 2005 Oct;13(10):1692-700.
OBJECTIVE: A positive correlation between levels of 25-hydroxyvitamin D [25 (OH) D] and insulin sensitivity has been shown in healthy subjects. We aimed to test the hypothesis that concentration of 25 (OH) D influences insulin sensitivity in obesity before and after weight loss. RESEARCH METHODS AND PROCEDURES: We investigated the relation between serum 25 (OH) D and insulin sensitivity (estimated by euglycemic-hyperinsulinemic clamp) in 116 obese women (BMI > or = 40 kg/m2) evaluated before and 5 and 10 years after biliopancreatic diversion (BPD). Body composition was estimated by the isotope dilution method. RESULTS: Prevalence of hypovitaminosis D was 76% in the obese status and 91% and 89% at 5 and 10 years after BPD, respectively, despite ergocalciferol supplementation. 25 (OH) D concentration decreased from 39.2 +/- 22.3 in obesity (p = 0.0001) to 27.4 +/- 16.4 and 25.1 +/- 13.9 nM 5 and 10 years after BPD, respectively. Whole-body glucose uptake increased from 24.27 +/- 4.44 at the baseline to 57.29 +/- 11.56 and 57.71 +/- 8.41 mumol/kg (fat free mass) per minute 5 and 10 years after BPD, respectively (p = 0.0001). Predictor of 25 (OH) D was fat mass (R2 = 0.26, p = 0.0001 in obesity; R2 = 0.20, p = 0.02 after BPD). Parathormone correlated with fat mass (R2 = 0.19; p = 0.0001) and BMI (R2 = 0.053; p = 0.01) and inversely with M value (R2 = 0.16; p = 0.0001), but only in obese subjects. DISCUSSION: A high prevalence of hypovitaminosis D was observed in morbid obesity both before and after BPD. Low 25 (OH) D did not necessarily imply increased insulin resistance after BPD, a condition where, probably, more powerful determinants of insulin sensitivity overcome the low circulating 25 (OH) D levels. However, the present data cannot exclude some kind of influence of vitamin D status on glucose and insulin metabolism. |
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