Urinary C‐peptide/creatinine ratio: A useful biomarker of insulin resistance and refined classification of type 2 diabetes mellitus

BACKGROUND: The urinary C-peptide/creatinine ratio (UCPCR) is low in patients with type 1 diabetes mellitus, but it has not been well characterized in patients with type 2 diabetes mellitus (T2DM). We aimed to measure the UCPCRs in patients with T2DM and explore the relationships among UCPCR, insulin resistance (IR), and chronic vascular complications of diabetes. METHODS: A cross-sectional study was performed of 1299 Chinese hospitalized patients with T2DM. Binary logistic regression was used to evaluate the relationships between the chronic vascular complications of diabetes and UCPCR. K-means analysis was used to allocate participants to subgroups with five to six variables (age at diagnosis, body mass index [BMI], glycosylated hemoglobin, homoeostasis model assessment 2-estimated beta-cell function (HOMA2-B), and HOMA2-insulin resistance (HOMA2-IR), with or without UCPCR). RESULTS: UCPCR positively correlated with HOMA2-IR (r = 0.448, P < .001). After adjustment for sex, age, duration of diabetes, and other cardiovascular risk factors, UCPCR was positively associated with diabetic kidney disease (DKD) (odds ratio [OR] = 1.198, 95% CI 1.019-1.408, P = .029) and coronary heart disease (CHD) (OR = 1.312, 95% CI 1.079-1.594, P = .006). When UCPCR was added, cluster analysis using the six variables identified five subgroups of T2DM, characterized by differing age at diagnosis, BMI, beta-cell function, IR, and prevalence of vascular complications. CONCLUSIONS: UCPCR is positively associated with IR, DKD, and CHD and represents a promising biomarker that could refine the classification of T2DM.