Involvement of lipoic acid in plasma metabolites, hepatic oxygen consumption, and metabolic response to a beta-agonist in broiler chickens

The present study was conducted to determine the role of alpha-lipoic acid (LA) in plasma metabolites, hepatic O-2 consumption, and beta-adrenergic re sponse in broilers. In Expt 1, 12-d-old female broiler chicks were divided into three dietary groups and fed on diets with or without LA (5 or 50 mg/k g) until 4 or 6 weeks of age, as a 2 x 3 factorial arrangement. The dietary LA had no effect on growth rates (body weight, abdominal fat, breast muscl e, and liver). The higher level of LA increased plasma non-esterified fatty acid and decreased plasma triacylglycerol concentrations only at 6 weeks o f age. A 42 % increase in hepatic respiration was observed in the 4-week-ol d chickens given 50 mg LA/kg diet. In Expt 2, 3-d-old female broiler chicks were treated with or without dietary LA at 50 mg/kg. At 30 and 31 d old, i soproterenol (2 mg/kg body weight per h) was continuously infused into a wi ng vein for 2 h, and changes in plasma glucose, triacylglycerol, and non-es terified fatty acid concentrations were analysed. Isoproterenol increased p lasma glucose over basal levels maximally at 60 min. Furthermore, the gluco se increase in the LA-treated chickens was 35 % greater than that of the co ntrols at this time. Plasma non-esterified fatty acid and triacylglycerol c oncentrations were decreased by the isoproterenol infusion, regardless of L A administration. Therefore, the present study suggests that dietary LA has repartitioning effects on energy metabolism in chickens (although this dep ends on age-related metabolic state) and is a possible facilitator in the b eta-adrenergic response of plasma glucose to a beta-agonist.