Effect of changes in body composition and islet β-cell function on bone mineral density in obese women with normal glucose metabolism at child-bearing age

Objective To investigate effects of changes in body composition and pancreas islet β-cell function on bone mineral density(BMD)in obese women with normal glucose metabolism at child-bearing age.Methods Ninety-five obese women with normal blood glucose at child-bearing age were recruited for the study,20 in non-obese group with body mass index(BMI)less than 23,20 in overweightgroup with BMI equal to or more than 23 and less than 25.28 in obesity Ⅰ group with BMI equal to or more than 25 and less than 30.and 27 in obesity Ⅱ group with BMI equal to or more than 30.Their BMD,body fat and lean mass were measured with by dual energy X-ray absorptiometer(DEXA),and intravenous -glucose tolerance test(IVGTT)was performed.Area under the Curve of insulin(AUCins)and acute jnsulin response(AIR)phase were calculated to assess their early insulin secretion.Homeostasis model assessment β-cell function index(HOMA2-%B)and homeostasis model insulin resistance index(HOMA2-IR)were used to assess their β-cell function and insulin resistance.Results Fat and lean mass in the upper and lower extremities.trunk and whole body and BMD in those women increased with increasing of their BMI(P＜0.05),particularly in fat mass.as well as their otller parameters including plasma insulin level at zerominute of IVGTT(IVGTTins0),AUCins.HOMA2-%B and HOMA2.IR(all P＜0.01).BMD in the upper and lower extremities,trunk and whole body showed a positive correlation with BMI,FPG,lean mass and/or fat mass.respectively(P＜0.05).BMD of the trunk and whole body also had a positive correlation with TVGTTins0,AIR,AUCins and HOMA2-IR.respectively(P＜0.05).Results of multivariate linear regression analysis showed that HOMA2-%B and HOMA2-IR correlated with BMD in a linear pattern.As the vailable body composition was added to the regression model.HOMA2 parameters would be removed from the model.Results of partial correlation analysis showed that islet β-cell function did not correlate with BMD after controlling body composition factors.Conclusions Insulin resistance or islet β-cell function compensation accompanied in obese women with main increase in fat mass have little benefit for their BMD,which may reflect indirectly their change in body compositions.Body composition,especially lean nlass,is the most important determinants of BMD in obese women. Key words: Obesity; β-cell function; Body composition; Bone mineral density