A study recently published in Clinical Endocrinology has uncovered some of the mechanisms through which site-specific bone mineral density (BMD) may relate to anthropometric and glucose homeostasis traits.
Specifically, researchers have found that insulin’s anabolic effects may function by mechanical loading from lean mass, that higher levels of glucose in women may create a direct negative effect at sites rich in cortical bone, and that bone mass can be reliably predicted by lean mass.
The risk for fracture is higher in individuals with type 2 diabetes despite a BMD that is at or above normal levels.
Due to the difficulty in differentiating between the roles of hyperglycemia and insulin resistance in bone remodeling, there is indeterminate data on the association between glucose homeostasis and BMD phenotypes. This study sought to clarify the association between site-specific BMD and both anthropometric and glucose homeostasis traits.
This cross-sectional study included 787 individuals (448 female, 339 male) who underwent euglycemic-hyperinsulinemic clamps, dual X-ray absorptiometry, and testing for oral glucose tolerance from the Mexican-American Coronary Artist Disease (MACAD) cohort study in Los Angeles. The study researchers used univariate and multivariate analyses to investigate the link between site-specific BMD and both anthropometric and glucose homeostasis traits, the latter of which included insulin sensitivity (M-value), fasting insulin, 2-hour glucose, fasting glucose, insulin clearance, and insulinogenic index.
In women, there was a negative correlation between 2-hour glucose and arm BMD that persisted in multivariate analysis (β=–0.15; P =.0015). Positive associations between fasting insulin and BMD at load-bearing sites such as the legs (β=0.17; P =.001) and pelvis (β=0.22; P <.0001) did not maintain significance in multivariate analysis. There were robust positive associations between lean mass and BMD at several different sites in both men and women.
The study researchers conclude that “(i) anabolic effects of insulin might work via mechanical loading from lean mass; (ii) a direct negative effect of increasing glucose might be more prominent at cortical-bone-rich sites in women; and (iii) lean mass is a strong positive predictor of bone mass.”
Kim SM, Cui J, Rhyu J, et al. Association between site-specific bone mineral density and glucose homeostasis and anthropometric traits in healthy men and women[published online March 25, 2018]. Clin Endocrinol. doi: 10.1111/cen.13602.