Association between an IGF-I gene polymorphism and body fatness: differences between generations

Area of Science:

• Genetics and Epigenetics
• Human Physiology
• Obesity Research

Background:

• A known polymorphism in the Insulin-like Growth Factor-I (IGF-I) gene promoter influences serum IGF-I levels, height, and birth weight.
• Understanding the impact of this polymorphism on body composition is crucial for identifying genetic predispositions to metabolic health.

Purpose of the Study:

• To investigate the association between an IGF-I gene promoter polymorphism and body composition in two distinct, generational cohorts of young, healthy Dutch subjects.
• To explore potential gene-environmental interactions influencing body composition related to this IGF-I variant.

Main Methods:

• An observational study with repeated measurements was conducted on two comparable Dutch cohorts.
• The older cohort (n=359) was born between 1961-1965, with measurements from 13-36 years.
• The younger cohort (n=258) was born between 1981-1989, with measurements from 8-14 years. Body composition metrics were compared between wild-type and variant IGF-I genotypes.

Main Results:

• In the younger cohort, female variant carriers exhibited significantly higher body weight, BMI, fat mass, and waist circumference compared to wild-type carriers.
• A similar trend was observed in male variant carriers of the younger cohort.
• The younger cohort, irrespective of genotype, displayed significantly higher total fat mass, body weight, and BMI compared to the older cohort.

Conclusions:

• The IGF-I gene promoter polymorphism appears to have a minor influence on body composition, with small genetic variability effects.
• Associations between the IGF-I polymorphism and body composition likely reflect a gene-environmental interaction.
• An environment promoting obesity may lead to more pronounced fat accumulation in variant carriers of the IGF-I polymorphism.