The Association Between the ZJU Index, Metabolic Dysfunction-Associated Steatotic Liver Disease, and Nephrolithiasis in Adult Men: A Cross-sectional Study

Objective: The ZJU index is a novel composite measure that incorporates blood glucose, body mass index (BMI), blood lipid levels, and liver function, and it is associated with hepatic steatosis and metabolic diseases. This study aims to investigate the potential associations between the ZJU index, metabolic dysfunction-associated steatotic liver disease (MASLD), and the prevalence of nephrolithiasis based on data from a large-scale health examination population. Methods： This study enrolled 43,891 participants who underwent physical examinations at the Northern Jiangsu People's Hospital, China, from January 2021 to June 2023. Based on the results of laboratory tests, ultrasonography, and medical history collection, these participants were divided into two groups: the nephrolithiasis group and the non-nephrolithiasis group. We utilized multivariate logistic regression analysis, restricted cubic spline (RCS) analysis, and subgroup analysis to explore the associations between the ZJU index, MASLD, and the prevalence of nephrolithiasis. Furthermore, we investigated the mediating role of the Uric Acid to High-Density Lipoprotein Cholesterol Ratio (UHR) index in the association between the ZJU index and nephrolithiasis. Results： In the multivariate logistic regression model adjusted for confounding variables such as age,BMI, smoking, diabetes, and hypertension, we found that in the male population, the ZJU index (OR (95% CI): 1.027 (1.013, 1.042), P<0.05), MASLD (OR (95% CI): 1.418 (1.266, 1.587), P<0.05),Triglyceride-Glucose Index (TyG) (OR (95% CI): 1.249 (1.155, 1.352), P<0.05), Atherogenic Index of Plasma( AIP) (OR (95% CI): 1.177 (1.096, 1.264), P<0.05), Non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio(NHHR) (OR (95% CI): 1.040 (1.014, 1.071), P<0.05), UHR(OR (95% CI): 1.005 (1.001, 1.010), P<0.05), Remnant Cholesterol(RC)(OR (95% CI): 1.144 (1.070, 1.220), P<0.05), and Low-Density Lipoprotein Cholesterol(LDL-c)(OR (95% CI): 1.099 (1.031, 1.171), P<0.05) were significantly positively correlated with the prevalence of nephrolithiasis. However, this association was not significant in the female population (P>0.05). The RCS analysis showed a linear association between the ZJU index and the risk of nephrolithiasis in males (P for non-linear > 0.05). Subgroup analysis in males revealed a significant interaction between the ZJU index and nephrolithiasis across different BMI categories (P for interaction < 0.05). Further mediation analysis indicated that the association between the ZJU index and nephrolithiasis in males could be partly mediated by UHR, with a mediation proportion of 16.8% (P<0.05). Conclusion： This study found that the ZJU index and MASLD are significantly and positively correlated with the risk of nephrolithiasis only in males, but not in females. Additionally, the UHR plays a partial mediating role in the association between the ZJU index and the risk of nephrolithiasis in males. These findings suggest that there may be gender differences in the pathogenesis of nephrolithiasis, providing a new direction for developing personalized prevention and treatment strategies for different gender subgroups in the future, and highlighting the importance of further exploring the underlying pathophysiological mechanisms.