Adaptive changes in enzyme activity and metabolic pathways in adipose tissue from meal-fed rats.
A number of metabolic factors and the activity of a number of enzymes were determined in meal-fed (animals fed a single daily 2 hr meal) and nibbling (ad libitum-fed) rats. The dependency of the observed adaptive changes on the ingestion of carbohydrate was studied by feeding diets high in carbohydrate or fat. Glucose-6-phosphate dehydrogenase and NADP-malic dehydrogenase were more active in adipose tissue from high carbohydrate meal-fed rats than in tissue from ad libitum-fed rats. The activity in adipose tissue of isocitric dehydrogenase, 6-phosphogluconate dehydrogenase, and NAD-malic dehydrogenase did not increase significantly in response to meal-feeding the high carbohydrate diet. No increase in lipogenesis or enzyme activity could be demonstrated in adipose tissue from rats meal-fed a high fat diet. Lipase activity of adipose tissue was increased by high carbohydrate meal-feeding and decreased by feeding a high fat diet. The in vitro uptake of palmitate-1-(14)C by adipose tissue was depressed by a high fat diet and enhanced in rats meal-fed a high carbohydrate diet. Diaphragm or slices of liver from high fat-fed rats oxidized palmitate-1-(14)C more rapidly than did tissue from ad libitum-fed animals. Evidence is presented for the quantitative importance of citrate as a source of extramitochondrial acetyl CoA in adipose tissue of meal-eating and ad libitum-fed rats. The relationship of extramitochondrially formed citrate to the NAD-malic dehydrogenase-malic enzyme system in adipose tissue is discussed.
D000085:Acetates / Q000378:metabolism*; D000273:Adipose Tissue / Q000201:enzymology* / Q000378:metabolism*; D000818:Animals; D050260:Carbohydrate Metabolism; D002247:Carbon Isotopes; D002951:Citrates / Q000378:metabolism; D003065:Coenzyme A / Q000378:metabolism; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005227:Fatty Acids / Q000096:biosynthesis; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D008049:Lipase / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D008190:Lyases / Q000378:metabolism; D008297:Male; D010088:Oxidoreductases / Q000378:metabolism*; D010169:Palmitic Acids / Q000378:metabolism*; D051381:Rats
D000085:Acetates; D002247:Carbon Isotopes; D002951:Citrates; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005227:Fatty Acids; D010169:Palmitic Acids; D010088:Oxidoreductases; D008049:Lipase; D008190:Lyases; D005947:Glucose; D003065:Coenzyme A