The nature of the ingested protein has no effect on lean body mass during energy restriction in overweight rats.
Severe energy restriction in obesity not only leads to fat mass loss but also to lean mass loss. The aim of this study was to compare the capacity of casein, a slowly digested protein, and milk soluble proteins (MSP; rapidly digested) to limit the loss of lean mass induced by energy restriction. Obesity was first induced in male Wistar rats by a 5-week feeding with a high-fat high-sucrose diet. The impact of energy restriction was then studied with high-protein (32%) diets containing either casein, MSP, or a 50/50 mixture of both proteins for 3 weeks (n = 10 per group). Food intake, body weight, nitrogen balance, creatinine, and 3-methyl-histidine excretion were measured during energy restriction. Then, tissue weights, plasma metabolic parameters (amino acids, glucose, insulin, cholesterol, triglycerides), and in vivo liver and extensor digitorum longus (EDL) muscle protein synthesis rates were measured in postabsorptive state at the end of the experimental period. Although significant differences relevant to protein metabolism were observed between groups (protein intake, plasma amino acid concentrations, fecal nitrogen excretion, muscle protein synthesis rates), week per week, there were no significant differences in nitrogen balance whatever the protein used. In conclusion, our results show that in young overweight energy restricted rats, using a high-protein diet, the nature of protein intake has no influence on body protein retention.
Adechian
Solange
S
INRA, UMR 1019 Nutrition Humaine, F-63122, Saint Genès Champanelle, France.
Rémond
Didier
D
Gaudichon
Claire
C
Dardevet
Dominique
D
Mosoni
Laurent
L
D000596:Amino Acids / Q000097:blood; D000818:Animals; D001823:Body Composition; D031204:Caloric Restriction; D002364:Caseins / Q000008:administration & dosage / Q000378:metabolism; D004041:Dietary Fats / Q000009:adverse effects; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D019422:Dietary Sucrose / Q000009:adverse effects; D004063:Digestion; D007700:Kinetics; D008297:Male; D008894:Milk Proteins / Q000008:administration & dosage / Q000378:metabolism; D009124:Muscle Proteins / Q000096:biosynthesis; D018482:Muscle, Skeletal / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D050177:Overweight / Q000097:blood / Q000178:diet therapy* / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D000596:Amino Acids; D002364:Caseins; D004041:Dietary Fats; D004044:Dietary Proteins; D019422:Dietary Sucrose; D008894:Milk Proteins; D009124:Muscle Proteins; D009584:Nitrogen