Summary
Activities of key enzymes in hepatic glucose utilization were compared between obese
(C57BL/6J ob/ob) mice, their lean controls and outbred Swiss albino mice in the fed condition and
during fasting. As liver hyperplasia and hepatocyte hypertrophy were present in the
ob/ob mice at 4-5 months of age and changes in hepatic cellularity did occur with fasting,
enzyme activity was expressed on the basis of protein, DNA, and wet weight. In the
fed state, activities of glucokinase + hexokinase (glucose phosphorylating capability),
phosphofructokinase and pyruvate kinase were significantly greater in livers of ob/ob mice when compared to those of the lean control. Glucokinase + hexokinase activities
in livers of ob/ob mice remained significantly higher throughout the 48 h fast yet the activities of
hepatic phosphofructokinase and pyruvate kinase, when expressed per g wet wt or mg
protein, decreased so that a statistical difference from the fasted lean control was
no longer detected. When expressed per 100 g body weight, hepatic glucokinase + hexokinase
as well as phosphofructokinase and pyruvate kinase activities in obese mice were higher
both in the fed and fasted states when compared to lean controls in the comparable
nutritional condition. This increased capacity of key enzyme activities in hepatic
glucose utilization can be attributed to liver hyperplasia found in ob/ob mice in both the fed and fasted condition. While higher hepatic glucose phosphorylating
capability was maintained during fasting, the elevated specific activities of hepatic
phosphofructokinase and pyruvate kinase in the obese mouse in the fed state decreased
with starvation to values found in the lean control.
Key-Words:
Obese Hyperglycaemic (ob/ob) Mice
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Glucokinase + Hexokinase
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Phosphofructokinase
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Pyruvate Kinase
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Fasting
