Physiological levels of glucagon do not influence lipolysis in abdominal adipose tissue as assessed by microdialysis

To determine whether glucagon stimulates lipolysis in adipose tissue, seven healthy young male volunteers were studied, with indwelling microdialysis catheters placed sc in abdominal adipose tissue. Subjects were studied thre e times: 1) during euglucagonemia (EG; glucagon infusion rate, 0.5 ng/kg mi n); 2) during hyperglucagonemia (HG; (glucagon infusion rate, 1.5 ng/kg min ); and 3) during EG and a concomitant glucose infusion mimicking the glucos e profile from the day of HG (EG+G). Somatostatin (450 mug/h) was infused t o suppress hormonal secretion, and replacement doses of insulin and GH were administered. Sampling was done every 30 min for 420 min. Baseline circula ting values of insulin, C-peptide, glucagon, GR, glycerol, and free fatty a cids were comparable in all three conditions. During EG and EG+G, plasma gl ucagon was maintained at fasting level (20-40 ng/L); whereas, during HG, it increased (110-130 ng/L). Interstitial concentrations of glycerol were sim ilar in the three conditions [30,870 +/- 5,946 (EG) vs. 31,074 +/- 7,092 (H G) vs. 29,451 +/- 6,217 (EG+G) mu mol/L.120 min, P = 0.98]. Plasma glycerol (ANOVA, P = 0.5) and free fatty acids (ANOVA, P = 0.3) were comparable dur ing the different glucagon challenges. We conclude that HG per se does not increase interstitial glycerol land thus lipolysis) in abdominal sc adipose tissue; nor does modest hyperglycemia, during basal insulinemia and glucag onemia, influence indices of abdominal sc lipolysis.