The Correlations Of Bone Phenotypes And Relationship Between Interleukin-6 Gene And Bone Phenotypes

Osteoporosis is becoming one of the major public health problems throughout the world. Bone mineral content (BMC), bone mineral density (BMD), and bone size are three important surrogate phenotypes for osteopcrosis. A majority of genetic studies on osteoporosis focus on BMD, only a few studies employed bone size as surrogate phenotype. Interleukin-6 (IL-6) is a pleiotropic cytokine that is involved in osteoclast differentiation and function. The present study has two aims: the first is to determine genetic correlation ( p_G ), environmental correlation (p_E), and phenotypic correlation (p_p) between BMD, BMC, and bone size by the bivariate variance decomposition analyses in Chinese nuclear families. The other is to test association and linkage between IL-6 gene (CA)n polymorphism with BMD and bone size by quantitative transmission disequilibrium test (QTDT) program. All subjects were from 401 Chinese nuclear famimies. BMC (g), BMD (g/cm~2) and bone size (cm~2) were measured at the lumbar spine and the hip region using dual-energy X-ray absorptiometry (DXA). Genotyping of the IL-6 (CA)n polymorphism was performed using PE377 automated sequencer and affiliated software. The results showed that p_E, p_G, and p_p betweon BMD, BMC, and bone size weresignificant, except for pE between BMD and bone size at the hip (p = 0. 361). The majority variation of BMD and BMC at the same skeletal site attributed to the common set of genetic and environmental factors. pE, pG, andpP between BMD and BMC were 0.872, 0.928, and 0.897, respectively, at the spine, and 0. 745, 0. 775, and 0. 752, respectively, at the hip. The genetic pleiotropic effects {pi) between BMD and BMC were 0.861 and 0. 600 at the spine and hip, respectively. That was to say, 86. 1 percent of the genetic variation of BMD and BMC at the spine and 60 percent of those at the hip attributed to the common genetic factors. However, the shared genetic and environmental factors between BMD and bone size at the same skeletal site were limited. Only 14.5% of BMD and bone size genetic variation at the spine and 4. 2% of those at the hip may due to the shared genetic factors. Site-specific pG and pE were found between BMD, BMC, and bone size at the spine and hip, especially between BMD and bone size. e. g., pE between BMD and bone size was significant (p = 0. 001) at the spine, but not significant (p = 0. 361) at the hip. The obtained results suggested that, bone size may be used as another surrogate phenotype for osteoporosis independent of BMD; different skeletal sites may be investigated to search for genetic and environmental factors...