Causal Assessment of Serum Urate Levels in Cardiometabolic Diseases Through a Mendelian Randomization Study

Background Although epidemiological studies have reported positive associations between circulating urate levels and cardiometabolic diseases, causality remains uncertain. Objective Through a Mendelian randomization approach, we assessed whether serum urate levels are causally relevant in type-2 diabetes (T2D), coronary heart disease (CHD), ischemic stroke and heart failure. Methods We investigated 28 SNPs known to regulate serum urate levels in association with a range of vascular and non-vascular risk factors to assess pleiotropy. To limit genetic confounding, 14 SNPs found exclusively associated with serum urate levels were used in a genetic risk score to assess associations with the following cardiometabolic diseases (cases/controls): T2D (26,488/83,964), CHD (54,501/68,275), ischemic stroke (14,779/67,312) and heart failure (4,526/18,400). As a positive control, we also investigated our genetic instrument in 3,151 gout cases and 68,350 controls. Results Serum urate levels, raised by 1 standard deviation (SD) due to the genetic score, were not associated with T2D (odds ratio OR 0.95, 95% CI, 0.86–1.05), CHD (OR. 1.02, 95% CI, 0.92–1.12), ischemic stroke (OR. 0.99, 95% CI, 0.88–1.12), or heart failure (OR. Q1.07, 95% CI, 0.88–1.30). These results were in contrast with previous prospective studies that observed increased risks of T2D (OR. 1.25, 95% CI, 1.13–1.37), CHD (OR. 1.06, 95% CI, 1.03–1.09), ischemic stroke (OR. 1.17, 95% CI, 1.00–1.37), and heart failure (OR. 1.19, 95% CI, 1.17–1.21) for an equivalent increase in circulating urate levels. However, a 1 SD increase in serum urate levels due to the genetic score was associated with increased risk of gout (OR. 5.84, 95% CI, 4.56–7.49), which was directionally consistent with associations observed in previous epidemiological studies Conclusions Evidence from this study does not support a causal role of circulating serum urate levels in T2D, CHD, ischemic stroke, or heart failure. Lowering serum urate levels may not translate into risk reductions for cardiometabolic conditions.