Recently, new subcomponent strata of diabetes have been proposed to provide individualized and precise treatments to patients with diabetes. However, the causal relationship between these diabetes subtypes and cardiovascular disease has not yet been effectively assessed. Given the high prevalence of cardiovascular disease in the population with diabetes, we conducted a two-sample MR study to assess the potential association between different subtypes of diabetes and cardiovascular disease. The principal findings were as follows: 1) SIDD has a potential positive causal association with PAD; and 2) SAID is positively and causally associated with peripheral arterial disease, and there is evidence suggestive of a negative causal association between SAID and atrial fibrillation.
The incidence of cardiovascular disease is significantly higher in patients with diabetes, and it has become one of the leading causes of death in these patients [21]. Diabetes is a major global public health concern. In 2018, researchers classified diabetes into five new subtypes using cluster analysis, laying the groundwork for precision medicine for diabetes [4]. This study aimed to determine the association between these five subtypes of diabetes and cardiovascular disease using two-sample MR analysis and further enhance our understanding of the relationship between diabetes and cardiovascular pathogenesis. Hernández et al. [22] conducted a cross-sectional study and included 71 patients with latent autoimmune diabetes in adults (LADA), 191 patients with type 2 diabetes mellitus, and 116 patients with type 1 diabetes mellitus. They found that carotid plaques were more frequent and multiple plaques were more common in patients with LADA than in the remaining two diabetic populations. This is consistent with the positive causal association between SAID and peripheral arterial observed in this study. The relationship between diabetes and the development of atrial fibrillation remains controversial [23]. In this study, we found that SAID might have a protective effect against the development of atrial fibrillation. Wei et al. [24] included 550 patients with autoimmune diabetes, 2,001 patients with type 2 diabetes, 1,573 patients with type 1 diabetes, and 2,355 individuals without diabetes in a case-control study and found that patients with autoimmune diabetes had an higher risk of cardiovascular morbidity; however, patients with diabetes with low autoimmune antibodies had a lower risk of cardiovascular morbidity than those with high autoimmune antibody diabetes. However, we did not observe a statistically significant association between SAID scores and coronary heart disease, hypertension, or heart failure, which may be explained by the variability in autoimmune levels between populations. Furthermore, a potentially positive causal association was observed between the SSID subtype and peripheral arterial disease.
Notably, in the analyses of SIRD, MOD, and MARD, we observed no significant correlation between the subtypes of diabetes and cardiovascular disease. Li et al. [5] conducted a retrospective cohort study that included 712 patients with diabetes mellitus and classified them into SAID, SIDD, SIRD, MOD, and MARD; they found a significant increase in cardiovascular mortality in patients with diabetes mellitus in each of these subgroups. This seems to contradict the results of the current study, and we hypothesized that this disparity could be attributed to the following: 1) a substantial amount of the data in this study came from a European population, and there may have been heterogeneity in the population; and 2) the sample size was insufficient, with an average of approximately 4 000 subtyped populations with diabetes included in the present study (Supplementary Table 1), which may have contributed to insufficient statistical power that contributed to these negative results.
Strengths and limitations
This study combined GWAS data to present more objective results for the causal relationship between subtypes of diabetes mellitus and cardiovascular disease and synthesized a variety of MR analyses, including IVW, weighted median, MR-Egger, and leave-one-out sensitivity analysis, and the findings were robust. Additionally, this study included multiple types of diabetes and cardiovascular disease, providing a more comprehensive insight into the cardiovascular–diabetes interrelationship.
The limitations of this study are as follows. We observed the presence of targeted pleiotropy; thus, the results may be affected by confounders, necessitating cautious interpretation. Furthermore, this study is based mainly on analyses of European populations; therefore, the generalizability of the results is limited. In the future, GWAS data should be analyzed on a larger scale and in multiple populations to exclude potential confounding factors and increase the reliability of the results.