Reduced alpha(2)-adrenergic sensitivity of subcutaneous abdominal adipocytes as a modulator of fasting and postprandial triglyceride levels in men

This study examined the postprandial lipemia of two groups of men displayin g similar age, body weight, and regional fat distribution, but characterize d by either low (n = 11) or high (n = 15) alpha(2)-adrenergic sensitivity o f subcutaneous abdominal adipocytes, In addition to fat cell lipolysis, adi pose tissue lipoprotein lipase (AT-LPL) as well as postheparin plasma LPL a ctivities were measured in the fasting state. Fasting AT-LPL and PH-LPL act ivities 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-m aximal inhibition of lipolysis (IC50), was significantly different between groups (P < 0.0001). Men with low versus high subcutaneous abdominal fat ce ll alpha(2)-adrenergic sensitivity showed higher fasting TG levels. In the whole group, a positive relationship was observed bet tween log-transformed IC50 UK-14304 values of subcutaneous adipocytes and fasting TG levels (r = 0.39, P < 0.05), suggesting that a lo tv abdominal adipose cell alpha(2)-a drenergic sensitivity is associated with high TG levels. After the consumpt ion of a high-fat meal, subjects with low subcutaneous abdominal adipose ce ll 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 val ues ranging from 0.01 to 0.05). Stepwise regression analysis shelved that t he 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 m easured by CT, as well as subcutaneous abdominal fat cell alpha(2)-adrenoce ptor sensitivity. Taken together, these results indicate that a reduced ant ilipolytic sensitivity of subcutaneous abdominal adipocytes to catecholamin es may increase fasting TG levels, which in turn play a role in the etiolog y of an impaired postprandial TRL clearance in men.-Imbeault, P., C. Couill ard, A. Tremblay, J-P. Despres, and P. Mauriege. Reduced alpha(2)-adrenergi c sensitivity of subcutaneous abdominal adipocytes as a modulator of fastin g and postprandial triglyceride levels in men.