Influence of lipoic acid on lipid metabolism and beta-adrenergic response to intravenous or oral administration of clenbuterol in broiler chickens

The effects of lipoic acid (LA) on muscle growth, metabolic response and hepatic respiration in broilers treated with or without clenbuterol (CLE) were examined. In 4-week-old chickens, dietary LA administration (100 mg x kg(-1)) enhanced the beta-adrenergic response of plasma nonesterified fatty acid with an intravenous injection of CLE (50 microg x kg(-1), estimated from the response area for 120 min (-7,860 vs. 874 micromol x L(-1) min in control and LA-treated groups, respectively; P < 0.05). When chickens received long-term oral administration of CLE (0.25 mg x kg(-1)) for 30 d, LA interfered with the repartitioning action of CLE, decreased abdominal fat weight (P < 0.05) and increased protein concentration of the breast muscle (P < 0.05), in 7-week-old chickens. In addition, the LA supplementation alone increased both plasma nonesterified fatty acid (P < 0.05) and triacylglycerol (P < 0.05), whereas these effects were not associated with CLE administration. These findings suggest that the dietary LA level used stimulates rapid lipolytic response of plasma nonesterified fatty acid to CLE injection and fatty acid turnover between adipose tissue and the liver, but does not facilitate the repartitioning action of CLE during long-term treatment in broilers.