POLYMORPHISM OF INSULIN-LIKE-GROWTH-FACTOR-I GENE AND BONE-MINERAL DENSITY

The polymorphism of insulin-like growth factor-I (IGF-I) gene was exam ined in Japanese postmenopausal women to analyze the genetic backgroun d for osteoporosis. In this study, the dinucleotide (cytosine-adenine; CA) repeat sequence lying upstream of the transcription initiation si te of this gene was examined. We named the most frequent allele includ ing (CA) 19 as J allele. There were 6 alleles (J-4 containing 17 CA re peats: (CA)17, [J-2 (CA)18, J (CP;)19 J+2(CA)20, J+4(CA)21, J+6 (CA)22 ]) in the Japanese population. The genotype distribution was different from that of Caucasians. There was no different in bone mineral densi ty (BMD) between the group with one or two alleles of each genotype an d that without that genotype. When we separate the subjects into three groups having two alleles, one allele, and no alleles, the three subj ects who possess the allele 'J-2' in both strands had low BMD (Z score of L2-4; -1.24 +/- 0.56, total body; -0.943 +/- 0.59, mean a SE). On the other hand, sequence of IGF-I gene in this study was different fro m reported sequence of IGF-I gene; that was 2 base pair (bp) deletion following 3'end of CArepeat (-645adenine/-646guanine). The present stu dy showed that there was no association between the microsatellite pol ymorphism of IGF-I gene and BMD in Japanese postmenopausal women, but some possibility remains that the microsatellite polymorphism of IGF-I gene is useful to detect a kind of particular osteoporosis.