The relation of fat and protein catabolic actions of cortisol to glucose homeostasis in fasting sheep

Abstract

Cortisol (50 or 150 mg. daily) given to mature sheep throughout a fast of 10 days increased the blood glucose level but greatly diminished the increases in blood ketone and plasma free fatty acid concentrations in comparison with those observed in fasting control sheep. Cortisol treatment did not change the plasma amino acid nitrogen level, but urinary nitrogen excretion of treated sheep continued at a higher rate throughout the fast. Phloridzin treatment reduced the elevated blood glucose of cortisol-treated sheep and increased circulating ketone, free fatty acid and amino acid nitrogen levels, as well as increasing urinary nitrogen excretion and causing glycosuria in both control and cortisol-treated sheep. Subcutaneously administered insulin, while also abolishing the hyperglycemia, decreased or prevented increases in the blood ketone, free fatty acid and amino acid nitrogen concentrations of cortisol-treated sheep. It is concluded from the relationships between the circulating concentration of glucose and the levels of ketones, free fatty acids and amino acids that the minor effect of cortisol on protein catabolism, and the antilipolytic and antiketogenic actions of cortisol in the sheep are dependent on the presence of hyperglycemia and probably reflect a compensatory hypersecretion of insulin accompanying this hyperglycemia.