Objective: Our goal was to investigate whether a polymorphism in the insulin-like growth factor I promoter gene (IGF-I, wild-type, 192 base pairs) and in the insulin gene (INS) variable number of tandem repeat locus influence birth weight and weight gain in infancy.
Patients and methods: We obtained genomic DNA from 768 children. Exclusion criteria were multiple births, gestational diabetes, maternal diabetes, gestational age <37 weeks, >42 weeks, or unclear, and any condition potentially influencing weight gain. SD scores were calculated and adjusted for gestational age and gender. A gain in SD scores for weight between birth and 1 year >0.67 SD scores was defined as accelerated weight gain. Genotyping was performed by fragment length analysis (IGF-I) and by fragment length analysis after using a restriction enzyme-based assay (INS variable number tandem repeat).
Results: Accelerated weight gain was present in 205 of 768 children. IGF-I and INS variable number tandem repeat genotype were not associated with birth weight. The IGF-I 192-base pair allele was less frequent in children with accelerated weight gain and was shown to reduce the risk for accelerated weight gain in a logistic regression model.
Conclusion: The IGF-I 192-base pair allele may reduce the risk for rapid weight gain in early infancy.