Serum concentrations of insulin-like growth factor-I and proteoglycan synthesis rates in young rats: a comparative study between the regional diet of São Paulo state and casein diets.
Insulin-like growth factor-I (IGF-I), also known as somatomedin-C, is an important mediator of growth regulation. Serum concentrations of IGF-I and proteoglycan synthesis rates in the tibial epiphysis, an estimate of the biological response to IGF-I in a target tissue, were compared in weanling Wistar rats fed ad libitum (group 1) and with 50% restriction (group 2) with the regional diet of São Paulo State (RDSPS--a mean diet consumed by low-income families with rice, beans, sugar, meat, milk, fruits and other vegetables) and in pair-fed animals fed with casein diets (groups 3 and 4). Data are reported as mean +/- SD for 8 rats in each group. Proteoglycan synthesis rates (cpm/mg) were significantly higher in rats fed with the RDSPS-based diet (groups 1 and 2: 210.8 +/- 58.8, 136.6 +/- 17.6) than in pair-fed animals fed with an 11% casein diet (groups 3 and 4: 62.9 +/- 11.6, 37.7 +/- 13.7) and in control animals fed ad libitum with a 20% casein diet (group 5: 58.1 +/- 22.7). Furthermore, these rates were higher in animals fed ad libitum than in those fed with the same diets but with 50% restriction. However, similar differences between groups 1 to 4 were not observed in serum concentrations (ng/100 microliters) of IGF-I (group 1: 44.1 +/- 7.1; group 2: 40.8 +/- 3.8; group 3: 46.0 +/- 3.6; group 4: 41.6 +/- 3.4, and group 5: 63.2 +/- 7.8). These results suggest that serum IGF-I levels are not reliable indicators of IGF-I status in this experimental model.
Cardoso
M A
MA
Departamento de Alimentos e Nutrição Experimental, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Brasil.
Tirapegui
J O
JO
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001938:Brazil; D002364:Caseins / Q000008:administration & dosage*; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D004838:Epiphyses / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D011509:Proteoglycans / Q000032:analysis / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D013977:Tibia; D014886:Weaning
D002364:Caseins; D004044:Dietary Proteins; D011509:Proteoglycans; D007334:Insulin-Like Growth Factor I