Vitamin D receptor gene polymorphism: Correlation with bone mineral density in a Brazilian population with insulin-dependent diabetes mellitus

Patients with insulin-dependent diabetes mellitus (IDDM) are at higher risk of developing osteoporosis. Among the genetic factors related to die devel opment of osteoporosis, a possible association between vitamin D receptor ( VDR) gene polymorphism and bone mineral density (BMD) has been described in some populations. We characterized the VDR gene polymorphism in a healthy adult Brazilian population and in a group of patients with IDDM and correla ted these findings with densitometric values in both groups. The Brazilian population is characterized by an important racial heterogeneity and theref ore is considered an ethnically heterogeneous population. We recruited 94 h ealthy adult Brazilian volunteers (63 women and 31 men), mean (+/- SD) age 32.4 +/- 6.5 years (range 18-39 years), and 78 patients with IDDM (33 women and 45 men) diagnosed before 18 years of age, mean (+/- SD) age 23.3 +/- 5 .5 years (range 18-39 years). VDR genotype was assessed by polymerase chain reaction amplification followed by BsmI digestion on DNA isolated from per ipheral blood leukocytes. Statistical analysis included Bonferroni t-test t o compare densitometric values within different genotypes in bath groups an d multiple regression analysis of bone density adjusted for potential confo unding factors. The IDDM group had a lower BMD compared with the control gr oup. The VDR genotype distribution in the control group was 43 Bb (45.7%), 39 bb (41.5%) and 12 BB (12.8%). This distribution did not differ from that observed in the IDDM group: 39 Bb (50%), 26 bb (33.3%) and 13 BB (16.7%). In the IDDM group, patients with the Bb genotype had a higher body weight w hen compared with the BB genotype (p = 0.02). However, when diabetic patien ts were controlled for age, sea and body mass index, BB genotype was associ ated with a lower mean BMD at lumbar spine and femoral neck than in Bb and bb patients. BE patients had a shorter duration of IDDM than bb and Bb pati ents. These findings suggest a small influence of VDR gene polymorphism on BRID of a racially heterogeneous population with IDDM.