Metabolic changes in rats fed a low protein diet during post-weaning growth.
Metabolic changes in rats fed a low protein diet were investigated during 3 weeks after weaning using lactalbumin (LP) as dietary protein source. The energy intake was higher and the weight gain lower in rats fed the low protein diet (6%, LP group) than in control rats (13% lactalbumin, C group). Low protein diet induced no changes in plasma glucose, free fatty acids, or triacylglycerol concentrations; however, plasma protein and urea concentrations were lower in LP than in C rats. Plasma free T3 was higher in LP than in C rats (+38%, day 21) and insulin progressively decreased during the experimental period (-56%, day 21) without change in glucagon. Liver glycogen and triacylglycerol concentrations (+40% and +180%, respectively, day 21), and cytosolic and mitochondrial redox states increased (+100% and +100%, day 21), and protein concentration was decreased (-15%, day 21). Pyruvate kinase (PK) and malic enzyme activities were higher in LP than in C rats throughout the experiment (+80% and +210%, respectively, day 21), and glucose-6-phosphate dehydrogenase (G6PDH) activity progressively decreased (-65%, day 21). Phosphoenolpyruvate carboxykinase (PEPCK) activity increased after 2 weeks on a LP diet (+35%, day 21) and fatty acid synthetase (FAS) activity increased only during the first week on the diet (+100%, day 7). Such hormonal and metabolic changes appeared to be associated with the development of a futile energy-wasting cycle between pyruvate and phosphoenolpyruvate.
Claeyssens
S
S
Groupe de Biochimie et de Physiopathologie Digestive et Nutritionnelle, Saint Etienne du Rouvray, France.
Lavoinne
A
A
Fresel-Ragot
M
M
Bois-Joyeux
B
B
Chanez
M
M
Peret
J
J
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005934:Glucagon / Q000097:blood; D006128:Growth; D007328:Insulin / Q000097:blood; D007768:Lactalbumin / Q000008:administration & dosage; D008099:Liver / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D008297:Male; D009929:Organ Size; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D014280:Triglycerides / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014508:Urea / Q000097:blood; D014886:Weaning; D015430:Weight Gain
D001786:Blood Glucose; D001798:Blood Proteins; D004044:Dietary Proteins; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014280:Triglycerides; D014284:Triiodothyronine; D014508:Urea; D005934:Glucagon; D007768:Lactalbumin