title: Physiological levels of glucagon do not influence lipolysis in abdominal adipose tissue as assessed by microdialysis.
abstract: 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 three times: 1) during euglucagonemia (EG; glucagon infusion rate, 0.5 ng/kg.min); 2) during hyperglucagonemia (HG; (glucagon infusion rate, 1.5 ng/kg.min); and 3) during EG and a concomitant glucose infusion mimicking the glucose profile from the day of HG (EG+G). Somatostatin (450 microg/h) was infused to suppress hormonal secretion, and replacement doses of insulin and GH were administered. Sampling was done every 30 min for 420 min. Baseline circulating values of insulin, C-peptide, glucagon, GH, glycerol, and free fatty acids were comparable in all three conditions. During EG and EG+G, plasma glucagon was maintained at fasting level (20-40 ng/L); whereas, during HG, it increased (110-130 ng/L). Interstitial concentrations of glycerol were similar in the three conditions [30,870 +/- 5,946 (EG) vs. 31,074 +/- 7,092 (HG) vs. 29,451 +/- 6,217 (EG+G) micromol/L.120 min, P = 0.98]. Plasma glycerol (ANOVA, P = 0.5) and free fatty acids (ANOVA, P = 0.3) were comparable during the different glucagon challenges. We conclude that HG per se does not increase interstitial glycerol (and thus lipolysis) in abdominal sc adipose tissue; nor does modest hyperglycemia, during basal insulinemia and glucagonemia, influence indices of abdominal sc lipolysis.
authors.affiliation: Department of Endocrinology M and Medical Research Laboratories, Arhus University Hospital, Denmark. ch.gravholt@dadlnet.dk
authors.forename: C H
authors.initials: CH
authors.lastname: Gravholt
authors.forename: N
authors.initials: N
authors.lastname: Møller
authors.forename: M D
authors.initials: MD
authors.lastname: Jensen
authors.forename: J S
authors.initials: JS
authors.lastname: Christiansen
authors.forename: O
authors.initials: O
authors.lastname: Schmitz
mesh_terms: D000005:Abdomen; D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002096:C-Peptide / Q000032:analysis; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005934:Glucagon / Q000097:blood / Q000494:pharmacology*; D005990:Glycerol / Q000378:metabolism; D006801:Humans; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D017551:Microdialysis
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D005230:Fatty Acids, Nonesterified; D005934:Glucagon; D005990:Glycerol