Microdialysis assessment of local adipose tissue lipolysis during β-adrenergic stimulation in upper-body-obese subjects with type II diabetes

The present study was designed to investigate indicators of abdominal adipose tissue lipolysis (microdialysis), and subcutaneous adipose tissue blood flow and whole-body lipolysis, in obesity-associated type II diabetes during overnight-fasted conditions (baseline) and during intravenous infusion of the non-selective β-agonist isoprenaline. Basal subcutaneous adipose tissue blood flow and isoprenaline-induced increases in adipose tissue blood flow were not signifcantly different between subjects with type II diabetes and non-obese, non-diabetic controls. Adipose tissue interstitial glycerol concentrations were significantly higher in subjects with type II diabetes compared with controls (P< 0.01), and during isoprenaline infusion there was a decrease in interstitial glycerol in both groups (P< 0.001). Arterial glycerol concentrations were higher in subjects with type II diabetes compared with controls (P< 0.05), whereas the increases in arterial glycerol concentration in response to isoprenaline infusion were of a similar magnitude in the two groups. Estimated subcutaneous adipose tissue glycerol release was not significantly different between the groups (controls and subjects with type II diabetes: baseline, -129±32 and -97±72 μmol·min^-1·100 g^-1 adipose tissue respectively; isoprenaline, -231±76 and -286±98 μmol·min^-1·100 g^-1 respectively). Values for fat oxidation were not significantly different between groups, whereas the isoprenaline-induced increase in fat oxidation tended to be less pronounced in subjects with type II diabetes compared with controls (0.022±0.008 and 0.038±0.003 g/min respectively; P = 0.058). Thus estimated basal subcutaneous adipose tissue glycerol release, expressed per unit of fat mass, is not different in controls and in subjects with type II diabetes. Additionally, the isoprenaline-induced increases in indicators of local abdominal subcutaneous adipose tissue, systemic lipolysis and abdominal adipose tissue blood flow responses were comparable in obese subjects with type II diabetes and in controls. The last two findings contrast with previous data from obese subjects, indicating that the regulation of lipolysis may differ in obesity and obesity-associated type II diabetes.