Pyruvate Dehydrogenase Kinase 4 Gene Expression Is Highly Responsive to Hypertonic Saline Administration in Chicks

Proteins and lipids are used as sources of endogenous water under dehydrated conditions in birds. However, it is unclear whether protein and fat are catabolized by dehydration in chickens. Elevated plasma osmolality is one of the responses to dehydration. The present study attempted to clarify the dose-dependent effects of hypertonic saline on plasma components and protein and lipid metabolism-related gene expression in the breast muscle and adipose tissue of chicks. The intraperitoneal administration of 1.2 M NaCl (5 mL/kg body weight) to 21-day-old chicks significantly increased the plasma concentration of nonesterified fatty acids, pyruvate dehydrogenase kinase 4 (PDK4) mRNA levels in breast muscle and adipose tissue, and atrogin-1 mRNA levels in breast muscle after 60 min. In the case of 0.6 M NaCl, a significant effect was only observed in PDK4 mRNA levels in both tissues. PDK4 functions as the metabolic switch from glucose to fatty acid utilization. Thus, hypertonic saline-induced changes in gene expression profiles suggest a potential shift toward lipid utilization in the peripheral tissues of chicks.