Effect of liver denervation on compensatory changes in food intake, body composition and hepatic enzyme induction after food restriction in rats.
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The mechanisms involved in the recovery of body fat and liver metabolism after food restriction and refeeding are not understood. This study's aim was to determine the need for hepatic neural input for the compensatory changes in food intake, body composition and hepatic lipogenic enzymes seen upon realimentation after energy restriction. Rats underwent total surgical hepatic denervation or had sham operations. One group of sham-operated and denervated rats was fed a semipurified diet ad libitum; a second group was restricted to 40% ad libitum levels for 7 d, then given free access to food during a 2-d refeeding period. Body fat content and body fat recovery rate from below "set point" were not altered by hepatic denervation. These observations do not rule out liver involvement because blood-borne factors communicating energy status information to the central nervous system could be released from the liver. The activities of hepatic enzymes--glucose-6-phosphate dehydrogenase, malic enzyme and citrate cleavage enzyme--were stimulated at least twofold by restriction and refeeding when compared to ad libitum feeding. Hepatic denervation had no effect on basal enzyme levels in ad libitum-fed animals or on elevated enzyme activity induced by refeeding after food restriction. This study clearly demonstrates that hepatic innervation is not essential for energy balance and body composition regulation. The induction of lipogenic enzymes by food restriction and refeeding does not depend on central nervous system input to the liver.