Comparisons of 12 Week Combined Exercise Intervention-mediated Changes of Body Composition, Physical Fitness, and Metabolic Syndrome Risk Factors According to IGF-I Gene Polymorphism in Obese Adolescent Boys

Ahn, Nayoung; Kim, Kijin

Abstract

BACKGROUND
The influence of Insulin-like growth factor I (IGF-I) is considered to be an important stimulatory factor in body composition, bone growth, cell proliferation and metabolism.
METHODS
The study analyzed the polymorphism of the IGF-I gene among subjects composed of middle-school male students (N = 21 obese group, N = 19 non-obese group). Subjects' body composition, blood profiles, and physical fitness were assessed. The changes in these factors, prior to and post-exercise intervention, were compared according to the difference in terms of IGF-1 gene polymorphism.
RESULTS
Out of the total number of subjects, 62.5% had one or two 19 CA (cytosine-adenosine) repeat, 71.4% among the obese group and 52.6% among the normal weight group. According to the IGF-1 gene polymorphism, 5 students (12.4%) were complete 19CA repeat (192 bp allele) homozygous, 20 students (49.6%) were 19CA repeat heterozygous, and 15 students (38%) were 19CA repeat non-carriers. Body composition factors, such as body fat ratio, had a tendency to be greater among the homozygous group compared to either the heterozygous or non carrier groups, however no significant difference was noted. Although no significant difference was noted in the genotype polymorphism for either grip strength (Right) or PEI, there was an increase in non-carrier group. Body fat and HOMA-IR decreased in both groups, especially in the obese group after the 12 week exercise intervention. In contrast to the non-carrier groups, there was a significant increase in change (P = 0.033) in sit up among the homozygous and heterozygous groups of the obese group. There was no significant difference in polymorphism of grip strength (Right) among the homozygous group of the obese group, however, it was far greater than that of the other groups. Body composition of homozygous groups increased in the IGF-I gene polymorphism but failed to increase in other groups.
CONCLUSION
Grip strength and sit-up improved in homozygous groups of the obese group after the 12 week exercise intervention. However, further studies involving greater number of subjects are needed to compare the effects of exercise intervention in relation to IGF-I gene polymorphism.