Relationship between beta-cell function, as reflected by fasting C-peptide, and cardiac and angiographic phenotype in patients with diabetes mellitus presenting with acute coronary syndrome

Background:C-peptide reflects endogenous insulin secretion and pancreatic beta-cell reserve, but its cardiovascular significance may vary with diabetes status and metabolic context. Objective:To compare fasting C-peptide levels, cardiac function, and coronary angiographic findings in patients with acute coronary syndrome (ACS) according to diabetes status and to assess associations between C-peptide, left ventricular function, and coronary disease burden. Methods: This single-center comparative cohort study included 40 patients with ACS at Minia University Hospital: 20 with established diabetes mellitus and 20 without previous diabetes. Demographic, metabolic, echocardiographic, and angiographic data were assessed. Between-group comparisons, correlation analyses, false-discovery-rate adjustment, and Firth penalized logistic regression were performed. Results: Median fasting C-peptide was significantly lower in patients with diabetes than in those without diabetes (1.25 [IQR 0.88–2.25] vs 3.00 [2.05–3.70]; p<0.001, q=0.001), despite higher fasting glucose and insulin. Median LVEF was lower in the diabetes group (42% vs 50%; p=0.039), while multivessel coronary disease was more frequent (55% vs 15%; OR 6.93, 95% CI 1.53–31.38; p=0.019). Pooled C-peptide levels correlated positively with LVEF and inversely with diseased-vessel count; however, these associations were not significant after stratification or FDR correction. C-peptide was not independently associated with multivessel disease. Conclusion: In ACS, diabetes was associated with lower C-peptide, reduced LVEF, and greater coronary disease burden. The cardiovascular significance of C-peptide appears dependent on diabetes status and residual beta-cell function.