title: Reduced alpha(2)-adrenergic sensitivity of subcutaneous abdominal adipocytes as a modulator of fasting and postprandial triglyceride levels in men.
abstract: This study examined the postprandial lipemia of two groups of men displaying similar age, body weight, and regional fat distribution, but characterized by either low (n = 11) or high (n = 15) alpha(2)-adrenergic sensitivity of subcutaneous abdominal adipocytes. In addition to fat cell lipolysis, adipose tissue lipoprotein lipase (AT-LPL) as well as postheparin plasma LPL activities were measured in the fasting state. Fasting AT-LPL and PH-LPL activities were similar in both groups. Maximal adipose cell lipolysis induced by isoproterenol (beta-adrenergic agonist) as well as the beta-adrenergic sensitivity did not differ between both groups of men. The selective alpha(2)-adrenergic agonist UK-14304 promoted a similar antilipolytic response in subcutaneous abdominal adipocytes from both groups. However, the alpha(2)-adrenergic sensitivity, defined as the dose of UK-14304 that produced half-maximal inhibition of lipolysis (IC(50)), was significantly different between groups (P < 0.0001). Men with low versus high subcutaneous abdominal fat cell alpha(2)-adrenergic sensitivity showed higher fasting TG levels. In the whole group, a positive relationship was observed between log-transformed IC(50) UK-14304 values of subcutaneous adipocytes and fasting TG levels (r = 0.39, P < 0.05), suggesting that a low abdominal adipose cell alpha(2)-adrenergic sensitivity is associated with high TG levels. After the consumption of a high-fat meal, subjects with low subcutaneous abdominal adipose cell alpha(2)-adrenergic sensitivity showed higher TG levels in total, medium, and small triglyceride-rich lipoprotein (TRL) fractions at 0- to 6-h time points than men with high adipocyte alpha(2)-adrenergic sensitivity (P values ranging from 0.01 to 0.05). Stepwise regression analysis showed that the fasting TG concentration was the only variable retained as a significant predictor of the area under the curve of TG levels in total TRL fractions (73% of variance) among independent variables such as body weight, percent body fat, visceral and subcutaneous abdominal adipose tissue accumulation measured by CT, as well as subcutaneous abdominal fat cell alpha(2)-adrenoceptor sensitivity. Taken together, these results indicate that a reduced antilipolytic sensitivity of subcutaneous abdominal adipocytes to catecholamines may increase fasting TG levels, which in turn play a role in the etiology of an impaired postprandial TRL clearance in men.
authors.affiliation: Physical Activity Sciences Laboratory, Department of Social and Preventive Medicine, Laval University, Québec, Canada G1K 7P4.
authors.forename: P
authors.initials: P
authors.lastname: Imbeault
authors.forename: C
authors.initials: C
authors.lastname: Couillard
authors.forename: A
authors.initials: A
authors.lastname: Tremblay
authors.forename: J P
authors.initials: JP
authors.lastname: Després
authors.forename: P
authors.initials: P
authors.lastname: Mauriège
mesh_terms: D000005:Abdomen; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D000273:Adipose Tissue / Q000166:cytology / Q000502:physiology*; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism; D000068438:Brimonidine Tartrate; D004837:Epinephrine / Q000494:pharmacology; D005215:Fasting / Q000502:physiology; D005990:Glycerol / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000097:blood; D007545:Isoproterenol / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects / Q000502:physiology*; D008071:Lipoprotein Lipase / Q000097:blood / Q000378:metabolism*; D008074:Lipoproteins / Q000097:blood; D008297:Male; D019518:Postprandial Period / Q000502:physiology*; D011810:Quinoxalines / Q000494:pharmacology; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects / Q000502:physiology*; D012867:Skin
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D001786:Blood Glucose; D007328:Insulin; D008074:Lipoproteins; D011810:Quinoxalines; D018341:Receptors, Adrenergic, alpha-2; D000068438:Brimonidine Tartrate; D008071:Lipoprotein Lipase; D007545:Isoproterenol; D005990:Glycerol; D004837:Epinephrine