title: Effects of different levels of protein intake and physical training on growth and nutritional status of young rats.
abstract: This study aimed to investigate the effects of physical training, and different levels of protein intake in the diet, on the growth and nutritional status of growing rats. Newly-weaned Wistar rats (n=48) were distributed into six experimental groups; three of them were subjected to physical swim training (1 h per day, 5 d per week, for 4 wk, after 2 wk of familiarization) and the other three were considered as controls (non-trained). Each pair of groups, trained and non-trained, received diets with a different level of protein in their composition: 14%, 21% or 28%. The animals were euthanized at the end of the training period and the following analyses were performed: proteoglycan synthesis as a biomarker of bone and cartilage growth, IGF-I (insulin-like growth factor-I) assay as a biomarker of growth and nutritional status, total RNA and protein concentration and protein synthesis measured in vivo using a large-dose phenylalanine method. As a main finding, increased dietary protein, combined with physical training, was able to improve neither tissue protein synthesis nor muscle growth. In addition, cartilage and bone growth seem to be deteriorated by the lower and the higher levels of protein intake. Our data allow us to conclude that protein enhancement in the diet, combined with physical exercise, does not stimulate tissue protein synthesis or muscle mass growth. Furthermore, physical training, combined with low protein intake, was not favorable to bone development in growing animals.
authors.affiliation: School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, SP, Brazil. smlribeiro@usp.br
authors.forename: Sandra Maria Lima
authors.initials: SM
authors.lastname: Ribeiro
authors.forename: Marcelo Macedo
authors.initials: MM
authors.lastname: Rogero
authors.forename: Reury Frank Pereira
authors.initials: RF
authors.lastname: Bacurau
authors.forename: Patrícia Lopes
authors.initials: PL
authors.lastname: de Campos
authors.forename: Silmara dos Santos
authors.initials: Sdos S
authors.lastname: Luz
authors.forename: Antonio Herber
authors.initials: AH
authors.lastname: Lancha
authors.forename: Julio
authors.initials: J
authors.lastname: Tirapegui
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001846:Bone Development / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage*; D051457:Hyaline Cartilage / Q000254:growth & development* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D024510:Muscle Development / Q000502:physiology*; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D009752:Nutritional Status / Q000502:physiology*; D009929:Organ Size; D010805:Physical Conditioning, Animal / Q000502:physiology*; D014176:Protein Biosynthesis; D011509:Proteoglycans / Q000096:biosynthesis; D012313:RNA / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014886:Weaning; D015430:Weight Gain / Q000502:physiology*
chemical_list: D015415:Biomarkers; D004044:Dietary Proteins; D009124:Muscle Proteins; D011509:Proteoglycans; D012313:RNA; D007334:Insulin-Like Growth Factor I