Association between serum soluble α-klotho and bone mineral density (BMD) in middle-aged and older adults in the United States: a population-based cross-sectional study

Background Osteoporosis is a degenerative disease defined by low bone mineral density, has a high prevalence, and causes fractures at multiple sites throughout the body, greatly affecting the quality of patients. alpha-Klotho is an endocrine factor involved in the regulation of various metabolic processes in humans, and its role in bone metabolism has attracted widespread attention. The relationship between alpha-klotho and bone mineral density has not been uniformly recognized, and no large-scale correlation analysis has been conducted in the middle-aged and elderly population. Objective To determine the relationship between alpha-klotho and bone mineral density in middle-aged and elderly people. Methods Population data of 3120 individuals aged 40-79 years were obtained from the NHANES database for the period 2011-2016. Regression analysis was performed using a general linear model with serum alpha-klotho as the independent variable and total bone mineral density, thoracic bone mineral density, lumbar bone mineral density, pelvic bone mineral density, and trunk bone mineral density as the dependent variables, respectively. The generalized additive model was also used for smoothing curve fitting and threshold effect analysis. Results Serum alpha-klotho was positively correlated with total bone mineral density at lg ( Klotho) <2.97 and with thoracic bone mineral density at lg (Klotho) >2.69 (beta = 0.05, p = 0.0006), and negatively correlated (beta = -0.27, p = 0.0341) with lumbar bone mineral density at lg (Klotho) < 2.69. It also positively correlated with trunk bone mineral density (beta = 0.027, p = 0.03657) and had no segmental effect but did not correlate with pelvic bone mineral density. The positive association of serum alpha-klotho with those aged 40-49 years, female, non-Hispanic White, and without hypertension was clearer. In the population with diabetes, a significantly positive association between total (beta = 0.15, p = 0.01), thoracic (beta = 0.23, p = 0.0404), and lumbar (beta = 0.22, p = 0.0424) bone mineral density and alpha-klotho was observed. Conclusions alpha-Klotho has different relationships with total, thoracic, lumbar, and trunk bone mineral density. Among them, the positive correlation between alpha-klotho and trunk bone mineral density is more valuable for predicting osteoporosis. The significant effect of alpha-klotho on bone mineral density in diabetes patients suggests its potential as a predictive marker of diabetes progression.