Age-dependent glycolysis and gluconeogenesis enzyme activities in starved-refed rats.
Food intake, plasma glucose, insulin (I) and glucagon (G), hepatic glycogen and fructose 2,6-bisphosphate (F-2, 6-P2) and liver glucokinase, glucose 6-phosphatase (G6-Pase), 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (6-PF-2 kinase/F-2, 6-P2ase), pyruvate kinase (PK-L) and phosphoenolpyruvate carboxykinase (PEPCK) activities were measured in 2 and 22-month-old rats before 3 d starvation and after 2, 4, 6, 24 and 48 h refeeding a high carbohydrate (HC, 74% w/w) diet. Expressed per 100 g of body weight, the food intake of old rats was 55% lower than that of young rats and the amount of carbohydrate absorbed hourly during the first 6 h of refeeding was 2.4-fold higher in young than in old rats. During the first 6 h of refeeding plasma glucose increased 2-fold and returned to normal values after 24 h in young rats, while plasma glucose did not change during refeeding in old rats. In young rats [I] fell by 85% after starvation and returned to normal values 2 h after refeeding. [I] was higher in old than in young rats; it decreased by 40% after starvation and returned to the basal value 4 h after refeeding. No marked changes were observed in plasma [G] in both groups. No difference was observed in hepatic glycogen in the two groups, while F-2, 6-P2 was higher in old than in young rats. In young rats, the opposite changes in liver glucokinase and G6-Pase activities occurring after starvation and during refeeding were
Bois-Joyeux
B
B
Centre de Recherche sur la Nutrition, CNRS, Meudon, France.
Chanez
M
M
Peret
J
J
D000375:Aging / Q000378:metabolism*; D000818:Animals; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004435:Eating / Q000502:physiology*; D005934:Glucagon / Q000097:blood; D005943:Gluconeogenesis / Q000502:physiology*; D006019:Glycolysis / Q000502:physiology*; D007328:Insulin / Q000097:blood; D008099:Liver / Q000201:enzymology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation / Q000201:enzymology*
D004040:Dietary Carbohydrates; D007328:Insulin; D005934:Glucagon