Maternal protein restriction early or late in rat pregnancy has differential effects on fetal growth, plasma insulin-like growth factor-I (IGF-I) and liver IGF-I gene expression.

We determined whether the effects of maternal protein restriction at various stages of pregnancy on fetal growth are accompanied by parallel changes in the expression of insulin-like growth factor (IGF)-I and -II in the fetal rat. Pregnant Wistar rats (5-7 per group) fed a low (5%) protein diet throughout gestation or during the last week only of gestation had decreased body weight gain, serum IGF-I, and liver IGF-I peptide and mRNA concentrations compared to control dams fed a normal (20%) protein diet. In contrast, dietary protein restriction during the first 2 weeks followed by the normal diet during the last week of pregnancy had no effect on these maternal indices at term. Pups born from dams fed the low protein diet during the last week only (P5-3d week pups) or throughout gestation (P5-pups) had lower birth weight (-11%; P < 0.05, and -22%; P < 0.001, respectively) and lower liver weight (-13%; P < 0.05, and -29%; P < 0.001) than control pups (P20-pups). Plasma IGF-I, liver IGF-I, and liver IGF-I mRNA concentrations were reduced in both P5-3d week pups (by 34%, 31% and 26%, respectively) and P5-pups (by 56%, 66% and 44%, respectively). In contrast, short- or long-term maternal protein restriction had no effect on neonatal plasma IGF-II peptide and liver IGF-II mRNA concentrations. When imposed only during the first 2 weeks of gestation, maternal protein restriction had no effect on growth or IGF-I and IGF-II expression in newborn pups.(ABSTRACT TRUNCATED AT 250 WORDS)