Vitamin D release across abdominal adipose tissue in lean and obese men: The effect of ß-adrenergic stimulation

Obesity is characterized by a blunted lipolytic response in abdominal subcutaneous adipose tissue (SAT) and low circulating vitamin D levels. Here we investigated whether an impaired SAT lipolytic response coincides with an impaired SAT vitamin D release in eight lean and six obese men. 25-hydroxyvitamin D₃ [25(OH)D₃ ] and 1,25-dihydroxyvitamin D₃ [1,25(OH)₂ D₃ ] fluxes across SAT were measured using arterio-venous blood sampling in combination with AT blood flow measurements after an overnight fast and during 1-hr intravenous infusion of the non-selective ß-adrenergic agonist isoprenaline (20 ng·kg FFM^-1 ·min^-1 ). 1,25(OH)₂ D₃ was released across abdominal SAT during isoprenaline infusion in lean [-0.01 (-0.04 to 0.00) pmol*100 g tissue^-1 *min^-1 , p = .017 vs. zero flux], but not in obese men [0.01 (0.00 to 0.02) pmol*100 g tissue^-1 *min^-1 , p = .116 vs. zero flux], and accompanied by an impaired isoprenaline-induced lipolytic response in abdominal SAT of obese versus lean men. Isoprenaline had no significant effects on net 25(OH)D₃ release across abdominal SAT and plasma vitamin D metabolites in lean and obese men. To conclude, a blunted isoprenaline-mediated lipolysis is accompanied by reduced release of 1,25(OH)₂ D₃ vitamin D across abdominal SAT in obesity.