Type 2 diabetes mellitus and cardiovascular health: Evidence of causal relationships in a European ancestry population.

AIMS

Type 2 diabetes mellitus (T2DM) is associated with increased cardiovascular disease (CVD) risk, but whether T2DM directly causes adverse cardiac remodelling is uncertain. We performed a comprehensive Mendelian randomization (MR) analysis to investigate the causal relevance of T2DM to CVD outcomes and cardiac structure/function.

METHODS AND RESULTS

Bidirectional two-sample MR was conducted using summary-level data from European-ancestry genome-wide association studies. The T2DM GWAS data included 80 154 cases and 853 816 controls from the DIAGRAM consortium. Outcomes included coronary artery disease (CAD), myocardial infarction (MI), stroke, heart failure, atrial fibrillation, and various quantitative cardiac imaging traits assessed by magnetic resonance imaging. MR analysis revealed causal associations between genetic predisposition to T2DM and increased risk of CAD (odds ratio [OR] 1.104, 95% confidence interval [CI] 1.078-1.130, P = 2.59e-16), MI (OR 1.129, 95% CI 1.094-1.166, P = 6.02e-14) and stroke (OR 1.086, 95% CI 1.064-1.109, P = 1.02e-14). These associations were validated in the FinnGen cohort (CAD: OR 1.117, 95% CI 1.075-1.158, P = 1.56e-9; MI: OR 1.132, 95% CI 1.083-1.184, P = 4.27e-8; stroke: OR 1.138, 95% CI 1.107-1.170, P = 3.52e-20). Multivariable MR show consistent findings (CAD: OR 1.063, 95% CI 1.031-1.097, P = 1.11e-4; MI: OR 1.088, 95% CI 1.042-1.135, P = 1.12e-4; stroke: OR 1.066, 95% CI 1.032-1.101, P = 1.18e-4) after adjusting for cardiometabolic traits. T2DM was causally associated with higher left ventricular mass index (β = 0.473, 95% CI 0.193 to 0.752, P = 0.001), lower indexed right atrial minimum (β = -0.048, 95% CI -0.073 to -0.022, P = 2.1e-5), and maximum (β = -0.042, 95% CI -0.065 to -0.019, P = 4.12e-5) areas. The effects on right atrial size remained significant after adjusting for risk factors (minimum area: β = -0.041, 95% CI -0.072 to -0.010, P = 0.009; maximum area: β = -0.039, 95% CI -0.069 to -0.008, P = 0.012). Both apolipoprotein A1 and SBP are important mediators in the causal relationship between T2DM and left ventricular mass index. No reverse causal associations were identified.

CONCLUSIONS

Our MR study demonstrates that genetic liability to T2DM plays causal roles in CAD, MI, stroke, and cardiac structure changes including left ventricular hypertrophy and reduced right atrial dimensions. These findings provide genetic evidence supporting glycaemic control in T2DM to mitigate cardiovascular complications and adverse cardiac remodelling.