Association Between Serum Klotho and Kidney Stones in US Middle-Aged and Older Individuals with Diabetes Mellitus: Results from 2007 to 2016 National Health and Nutrition Survey

Introduction: Kidney stones (KSs) are associated with hematuria and renal failure and pose a significant clinical and public health concern. Diabetes is associated with a higher risk of KSs. In addition, α-Klotho (Klotho), as a novel antiaging protein, is associated with kidney disease, diabetes, and complications and may participate in the pathological mechanism of KSs. However, studies that used large population-based database research are limited. Therefore, this study aimed to investigate whether or not KS prevalence is associated with serum Klotho levels in diabetic adults in the USA.

Methods: This nationally representative cross-sectional study used data on diabetic adults in the USA aged 40-79 years from the National Health and Nutrition Examination Survey 2007-2016 cycles. Multivariate logistic regression models were used to calculate the association between Klotho and KS. Restricted cubic splines were used to further test for linearity and explore the shape of the dose-response association. Moreover, we performed stratified and interaction analyses to see if the relationship was stable in different subgroups.

Results: Among the 3,537 diabetic patients included in this study (mean age of 61.4 years, consisting of 51.3% males), 543 participants (15.4%) suffered from KS. In the fully adjusted model, Klotho was negatively associated with KS (OR = 0.72; 95% CI: 0.54-0.96; p = 0.027). A negative relationship was observed between the occurrence of KS and Klotho (nonlinear: p = 0.560). Some differences in the association between Klotho and KS were found in stratified analyses; however, these differences lacked statistical significance.

Conclusions: Serum Klotho was negatively associated with the incidence of KS; when ln-transformed Klotho concentration increased by 1 unit, the risk of KS was 28% lower.