Fat mobilization and plasma hormone levels in fasted dogs

Abstract

The aim of this work was to study the regulation of ketone body metabolism in the dog during prolonged fasting. In nine nonobese dogs, which were starved for 2 wk, free fatty acids, triglycerides, glycerol, ketone bodies, and glucose were measured as well as insulin, glucagon, growth hormone, T 4 and T 3, and reverse-T 3. Free fatty acids and glycerol concentrations rose gradually during the whole period. Acetoacetate and β-hydroxybutyrate reached levels of 130 ± 50 and 350 ± 125 μmol/liter, respectively. Glucose levels remained constant initially but declined significantly by the end of the starvation period. Insulin levels declined moderately. Glucagon and growth hormone values were not influenced by fasting. T 4 concentrations remained in the normal range, T 3 levels declined significantly, but reverse-T 3 levels did not rise during starvation. The results are compared with data from the literature on human starvation. From the data on the lipid parameters it is concluded that fat mobilization progresses at a slower rate in the dog than in man. The absence of a pronounced hypoglycaemia results in a hormonal setting (unchanged glucagon and growth hormone concentrations, together with an only slightly decreased insulin concentration) which protects the dog from the development of severe ketosis.