A cross-sectional study of urinary sodium, cardiac remodeling, and the mediating role of insulin-like growth factor-1: Insights from the UK Biobank

High sodium intake is a known risk factor for cardiovascular disease, but its precise relationship with cardiac remodeling and the potential mediating role of insulin-like growth factor-1 (IGF-1) remain less clear. This study investigates the association between estimated 24-hour urinary sodium levels and cardiac structure/function and explores whether IGF-1 mediates this relationship. This cross-sectional analysis included 28,618 participants from the UK Biobank with complete cardiac magnetic resonance imaging (MRI) data. Estimated 24-hour urinary sodium was calculated from spot urine samples. Linear regression was used to assess associations between sodium and cardiac parameters (left ventricular mass [LVM], ejection fractions). Restricted cubic splines tested for nonlinear relationships. The Karlson-Holm-Breen method was used to analyze the mediating effect of IGF-1. After full adjustment for covariates, higher urinary sodium levels were significantly positively correlated with LVM (P < .01) and negatively correlated with left and right ventricular ejection fractions (LVEF, RVEF; P < .01). IGF-1 was found to be a significant partial mediator of the relationship between sodium and LVM (proportion mediated: 1.54%, P < .05). Significant nonlinear relationships were observed between sodium and both IGF-1 (nonlinear P = .008) and LVM (nonlinear P < .001). In this large community-based sample, higher urinary sodium excretion was associated with adverse cardiac remodeling. IGF-1 appears to partially mediate the relationship between sodium and LVM, which may represent a novel physiological pathway. The nonlinear nature of these associations warrants further investigation.