Vitamin D, inflammation, and relations to insulin resistance in premenopausal women with morbid obesity

Abstract

Objective In this study, the associations between vitamin D, insulin sensitivity, and inflammation and their relationships with adipose tissue expression of vitamin D receptor (VDR) and inflammatory markers in women with morbid obesity were determined. Methods An oral glucose tolerance test prior to surgery was completed by healthy premenopausal women (n = 76) seeking bariatric surgery. Abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were collected during surgery. Results Approximately, 70% of our subjects were vitamin D sufficient or optimal, and 80% had normal glucose tolerance. No significant association between serum 25-hydroxyvitamin D [25(OH)D] with circulating inflammatory markers or insulin sensitivity was identified. In subjects with waist circumference of <139 cm (n = 42), log25(OH)D positively predicted VAT logIL-6 mRNA expression (P = 0.003). LogVDR expression was positively correlated with the expression of inflammatory markers in both SAT (logIL-1β mRNA: r = 0.95, P < 0.0001; logTNF mRNA: r = 0.82, P < 0.0001) and VAT (logIL-1β mRNA: r = 0.89, P < 0.0001; logTNF mRNA: r = 0.75, P < 0.0001). VAT logVDR expression positively predicted logHOMA-IR in non-African American subjects (P = 0.05). Conclusions The beneficial effects of vitamin D on inflammation and insulin sensitivity were not supported by our findings. VDR does not appear to possess a protective effect in adipose tissue.