Peripheral Administration of Hypertonic Saline Affects Nutrient Metabolism-related Gene Expression in Chicks

When facing dehydration, birds use body fat and proteins as a source of endogenous water. Recently, we found that osmotic stress triggered protein catabolism in skeletal muscles of chicks. In the present study, we investigated whether osmotic stress also affected fat metabolism. Twelve 21-day-old male chicks were allocated to two groups based on body weight. The chicks received either saline (0.15 M NaCl) or hypertonic saline (1.5 M NaCl) intraperitoneally (5 mL/kg body weight). After 1 h of feed and water deprivation, the chicks were euthanized by decapitation. Blood, breast muscle (pectoralis major), abdominal adipose tissue, liver, and kidney samples were collected, followed by analysis of plasma components and gene expression. Hypertonic saline significantly increased the plasma levels of non-esterified fatty acids (NEFA); adipose triglyceride lipase (ATGL) mRNA in adipose tissue; pyruvate dehydrogenase kinase 4 (PDK4) mRNA in breast muscle, adipose tissue, and liver; phosphoenolpyruvate carboxykinase 1 mRNA in the liver; and atrogin-1 mRNA in breast muscle. It also increased the plasma content of the hormone vasotocin. Subsequent intravascular administration of vasotocin significantly elevated plasma NEFA, but not ATGL or PDK4 mRNA in adipose tissue. Collectively, our findings suggest that osmotic stress alters nutrient metabolism in the peripheral tissues of chicks and that vasotocin may be partly involved in fatty acid mobilization.