Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 3/27/2008
Publication Date: 4/23/2008
Citation: Proszkowiec-Weglarz, M., Richards, M.P., Humphrey, B.D., McMurtry, J.P. 2008. Role of 5'-AMP-activated protein kinase, carbohydrate response element binding protein and steriol regulatory element binding protein-1 in the regulation of lipid metabolism in broiler chickens [abstract]. Nineteenth Annual BARC Poster Day,Abstract Number 27.
Technical Abstract: Poultry producers face numerous challenges related to the regulation of energy balance in commercial lines of birds that have been intensively selected for rapid growth rate and enhanced meat yield. To maintain energy balance, food intake and energy expenditure must be coordinated and tightly regulated. However, modern broiler chickens do not adequately regulate voluntary food intake to achieve energy balance. Instead, they are prone to overeating leading to excessive weight gain and energy (fat) accumulation that can result in a series of health-related problems unless their food intake is strictly limited. Therefore, our research goal is to investigate the genetic and molecular bases for the regulation of food intake and energy balance in poultry. In mammals, 5’-AMP-activated protein kinase (AMPK), carbohydrate response element binding protein (ChREBP) and sterol regulatory element binding protein-1c (SREBP-1c) are important regulators of lipid metabolism and potential therapeutic targets for treating obesity and type-2 diabetes. AMPK is a heterotrimeric enzyme complex playing a key role in maintaining intracellular energy balance and, on the whole animal level, regulating energy expenditure and food intake. Once activated by phosphorylation, AMPK phosphorylates a variety of protein targets that influence carbohydrate, protein and lipid metabolism. ChREBP and SREBP-1c are glucose- and insulin-responsive transcription factors, respectively, involved in the regulation of glucose metabolism and lipid synthesis. When activated, ChREBP and SREBP-1c increase the transcription of glycolytic and lipogenic enzyme genes in liver. The aim of this study was to characterize the mRNA and protein expression of chicken homologues of AMPK, ChREBP and SREBP-1, and the expression of their target genes involved in lipid metabolism during fasting and refeeding in broiler chicken liver. In response to different energy states (fasting and refeeding), expression of the AMPK alpha subunit was unchanged, while ChREBP and SREBP-1 mRNA levels decreased during fasting. AMPK activity and the phosphorylation level of acetyl-CoA carboxylase (an AMPK target protein) increased, whereas ChREBP activity decreased in liver during fasting. The mRNA levels of AMPK, ChREBP and SREBP-1 target genes decreased during negative energy balance. Plasma levels of glucose, insulin and leptin decreased, whereas glucagon increased in response to fasting. Our results suggest that AMPK, ChREBP and SREBP-1 play important roles in the regulation of lipid metabolism in chickens and that they are key molecular components of an intricate mechanism maintaining energy balance. Supported by USDA-ARS CRIS project No. 1265-31000-095-00D.