Relationship among Insulin Therapy, Insulin Resistance, and Severe Coronary Artery Disease in Type 2 Diabetes Mellitus

Objectives.The effect of insulin therapy on coronary artery disease (CAD) remains controversial. This study aimed to analyze the association between insulin resistance and the morbidity of severe CAD in type 2 diabetes mellitus (T2DM). Methods. A total of 2044 T2DM patients aged ≥40 years were included in this cross-sectional observational study. Clinical information and laboratory results were collected from the medical records. Those who underwent percutaneous coronary intervention (PCI) were classified as severe CAD, while those who did not have a history of and were not suffering from CAD were classified as patients without CAD. Results. T2DM patients with severe CAD and without CAD had no significant differences in glycosylated hemoglobin A1c (8.55% ± 2.10% vs. 8.39% ± 1.77%, P = 0.234). The proportion of insulin treatment was also similar between the two groups (56.85% vs. 53.65%, odds ratio = 1.138, P = 0.310). In the patients without insulin treatment, the levels of fasting C peptide (FCP) correlated with severe CAD prevalence. FCP was categorized into 3 tertiles (<1.5 ng/mL, 1.5 ng/mL- 3 ng/mL, and ≥3 ng/mL), and the prevalence rates of severe CAD were 7.88%, 14.31%, and 18.28%, respectively (P < 0.05). In the patients with insulin treatment, the body mass index (BMI) was the significant risk factor of severe CAD. The prevalence of severe CAD according to BMI tertiles (<24 kg/m², 24 kg/m²–28 kg/m², and ≥28 kg/m²) was 11.22%, 14.61%, and 24.62%, respectively (P < 0.01). Conclusions. Our results showed that insulin resistance, rather than insulin therapy, increases the risk of severe CAD in T2DM patients with inadequate glycemic control. Non-insulin treated patients with high FCP and insulin-treated patients with high BMI are at higher risk of severe CAD.