The Gly972Arg polymorphism in insulin receptor substrate-1 is associated with decreased birth weight in a population-based sample of brazilian newborns

Abstract

OBJECTIVE - We studied the association between the Gly972Arg polymorphism in insulin receptor substrate-1 (IRS-1) and birth weight in a population-based sample of Brazilian newborns. RESEARCH DESIGN AND METHODS - We studied 194 newborn children with adequate gestational age to identify the association between the Gly972Arg polymorphism and birth weight using PCR-restriction fragment length polymorphism analysis. RESULTS - The data showed that the birth weight was lower in the newborns with the Gly972Arg polymorphism in IRS-1 compared with control subjects (3,141 ± 31.8 vs. 3,373 ± 80.3 g, P < 0.008). The results also showed that the frequency of this polymorphism was increased in newborns with a birth weight <3,000 g (P = 0.041). CONCLUSIONS - These results suggest that the genotype Gly972Arg may influence birth weight, reinforcing the hypothesis that genetically determined insulin resistance and/or reduced insulin secretion can result in impaired insulin-mediated growth in the fetus.