Impact of insulin and glucocorticoid signalling on hepatic glucose homeostasis in the rat exposed to high-fructose diet and chronic stress.

ABSTRACT

Overconsumption of fructose-enriched beverages and everyday stress are involved in the pathogenesis of metabolic disorders through modulation of hepatic glucose metabolism. The aim of the study was to investigate whether interaction of high-fructose diet and chronic stress alter insulin and glucocorticoid signalling thus affecting hepatic glucose homeostasis. High-fructose diet led to hyperinsulinemia, increased glucose transporter 2 level, elevated protein kinase B (Akt) phosphorylation, increased glucokinase mRNA and phospho-to-total glycogen synthase kinase 3 ratio and decreased expression of gluconeogenic genes. Fructose diet also led to stimulated glucocorticoid prereceptor metabolism, but downstream signalling remained unchanged due to increased glucocorticoid clearance. Stress did not affect hepatic insulin and glucocorticoid signalling nor glucose metabolism, while the interaction of the factors was observed only for glucokinase expression. The results suggest that, under conditions of fructose-induced hyperinsulinemia, suppression of gluconeogenesis and glycogen synthase activation contribute to the maintenance of glucose homeostasis. The increased glucocorticoid inactivation may represent an adaptive mechanism to prevent hyperglycaemia.