Objectives: As intervention studies have shown a reduction in body weight to be paralleled with a reduction in left ventricular mass (LVM), we quantified a hypothesized causal relationship between fat mass and LVM, and how much of these effects that was mediated by blood pressure (BP), diabetes and adipokines. Also visceral and subcutaneous adipose tissue (VAT and SAT) were explored in the same fashion.
Methods: In the Prospective Study of the Vasculature in Uppsala Seniors study (n = 1016, 50% women, all aged 70 years), LVM was measured by echocardiography (indexed for lean mass, LVMI), fat and lean mass by dual-energy X-ray. VAT and SAT were measured by abdominal MRI (in n = 275).
Results: In a structural equation model adjusting for sex, the total effect of fat mass on LVMI was large (standardized coefficient 0.280, P = 3.2 × 10, 95% confidence interval 0.210-0.349). Out of the total effect of fat mass on LVMI, 29.0% was mediated by BP and glucose (P = 2.4 × 10). The BP pathway was most important, mediating 24.4% of the total effect of fat mass on LVMI (P = 4.6 × 10), while the glucose pathway accounted for 4.6% (P = 0.033). The association of VAT with LVMI (0.202, P = 2.4 × 10) was slightly weaker than that of SAT with LVMI (0.283, P = 1.0 × 10). Of several measured adipokines, leptin was a significant mediator of the effect of fat mass on LVMI (P = 3.0 × 10).
Conclusion: One-third of the hypothesized association between body fat and LVMI was mediated by BP and glucose in this population-based cohort. Leptin was also an important mediator. Visceral adipose tissue was not more closely related to LVMI than subcutaneous abdominal fat.