A Metabolic Profile of Fed and Fasting Genetically Obese Mice at 4-5 Months of Age

Summary

Indices of both carbohydrate and lipid metabolism were examined in obese (C57BL/6J ob/ob) mice and lean controls at 4-5 months of age in both the fed and fasted condition. Swiss albino mice (1.5-2 months in age), weightmatched to the inbred lean mice, were also investigated but differences in the metabolic parameters between these groups of mice were confounded by the dissimilarity in age. The concentrations of lactate and alanine in plasma were significantly higher in ob/ob mice than the lean controls in the fed state but this difference disappeared with fasting. Plasma levels of FFA and glycerol were similar in all three groups of mice in both the fed and fasted states. The significantly lower concentrations of plasma ketone bodies in ob/ob mice than the lean controls after a 24 h fast would suggest that the transition from the fed to fasted condition in the hepatic metabolism of the obese mouse does indeed occur more slowly. Yet after a 48 h fast, ob/ob mice had significantly higher levels of hepatic glycogen than comparably fasted lean control. Likewise, plasma glucose values decreased in ob/ob mice during food deprivation but remained significantly higher than those of the lean controls after 48 h fast. Excessive accumulation of triacylglycerols in liver and heart found in ob/ob mice in the fed condition was maintained during a fast of 48 h even though their level in plasma was significantly lower than in the comparably fasted lean control. We propose that an increase in the concentration of triacylglycerols in liver, heart and skeletal muscle may be an intracellular index of decreased insulin effectiveness in the genetically obese mouse.

Key-Words:

C57BL/6J ob/ob Mice - Fasting - Triacylglycerols - Glycogen - Liver - Heart