Fasting and Glucagon Stimulate Gene Expression of Pyruvate Dehydrogenase Kinase 4 in Chickens

Abstract

The excessive accumulation of body fat has become a serious problem in the broiler industry. However, the molecular mechanisms underlying the regulation of lipid metabolism-related genes in broiler chickens are not fully understood. In the present study, we investigated the role of glucagon on the expression of lipid metabolism-related genes in chicken white adipose tissue (WAT). Four hours of fasting significantly increased plasma levels of free fatty acid in broiler chickens. The mRNA levels of adipose triglyceride lipase (ATGL) and pyruvate dehydrogenase kinase 4 (PDK4) in abdominal WAT significantly increased by fasting, whereas the mRNA levels of diacylglycerol O-acyltransferase homolog 2 (DGAT2) and peroxisome proliferator-activated receptor-γ (PPARγ) significantly decreased. The results suggest that fasting stimulates lipolysis and suppresses adipogenesis and re-esterification of TG in chicken WAT. Glucagon significantly increased the mRNA levels of PDK4 in chicken primary adipocytes, whereas there were no significant changes in the mRNA levels of ATGL, DGAT2, and PPARγ. Our findings suggest that glucagon upregulates PDK4 expression and may stimulate lipolysis without affecting the expression of ATGL in chicken WAT.

Role of Corticosterone in Lipid Metabolism in Broiler Chick White Adipose Tissue

“…For example, no homolog of the HSL gene has been identified in the chicken genome, although an HSL-like enzyme has been purified from chicken WAT (Anthonsen et al 1997). However, we found that 4 h of fasting significantly increased mRNA levels of ATGL and reduced mRNA levels of LPL in chicken WAT (Saneyasu et al 2013b;Honda et al 2017). We also showed that plasma NEFA concentrations were significantly elevated after 4 h of fasting (Honda et al 2017).…”

“…However, we found that 4 h of fasting significantly increased mRNA levels of ATGL and reduced mRNA levels of LPL in chicken WAT (Saneyasu et al 2013b;Honda et al 2017). We also showed that plasma NEFA concentrations were significantly elevated after 4 h of fasting (Honda et al 2017). Therefore, transcriptional regulation of LPL and ATGL may play important roles in the regulation of body fat accumulation in chickens.…”

Effect of Fasting on the Spexin System in Broiler Chickens

“…The starvation process is also associated with the stimulation of metabolic processes related to the release of stored energy substances, e.g., in the form of nonesterified fatty acids (NEFA), which result from the intensification of lipolytic processes as well as activation of genes involved in lipid metabolism in fat tissue and liver [ 26 , 27 ]. PDK4 is considered to be involved in re-esterification of fatty acid derived from lipolysis during fasting.…”

“…PDK4 is considered to be involved in re-esterification of fatty acid derived from lipolysis during fasting. [ 26 , 28 ]. Previous studies performed on mammals showed that SPX is able to regulate both of these processes.…”

Post-hatch fasting and infectious bronchitis vaccination affect growth, gastrointestinal development, and morphometric parameters of the small intestine of broiler breeders up to three weeks of age

“…Severe feed restriction in the first weeks of life of chickens promotes protein catabolism associated with elevated levels of uric acid in plasma, due to the process of gluconeogenesis from amino acids and glycerol in the liver (Jahanpour et al, 2013). This process is regulated by the predominance of the effects of glucagon on insulin in response to fasting (Christensen et al, 2013), which also leads to lipolysis for the production of glycerol for the gluconeogenesis process (Honda et al, 2017). In this study, birds exposed to prolonged fasting (48 and 72 h) had allometric growth values of the viscera (gizzard, proventriculus, liver and intestine) superior to 1 at three days of life, which probably can be explained by the degradation of body protein and its use as a source of energy for the maintenance of body homeostasis.…”