Copeptin and Estimated Insulin Sensitivity in Adults With and Without Type 1 Diabetes: The CACTI Study

Objectives: Copeptin, a surrogate marker for vasopressin, is elevated in participants with insulin resistance (IR) and type 2 diabetes. Whereas adults with type 1 diabetes also demonstrate elevated copeptin concentrations and IR compared to controls without diabetes, the relationship between copeptin and IR in type 1 diabetes is unclear. Methods: Participants with (n=209) and without (n=244) type 1 diabetes in the Coronary Artery Calcification in Type 1 Diabetes (CACTI) study were assessed for serum copeptin. vitals, estimated glomerular filtration rate, urinary albumin-to-creatinine ratio, glycated hemoglobin and lipid panels. Estimated insulin sensitivity (elS) was calculated by validated equations in participants with and without type 1 diabetes. The relationships among copeptin, IR, waist circumference (WC) and body mass index (BMI) were examined with unadjusted and adjusted linear regression models. RESULTS: Copeptin was correlated with eIS (R=-0.17, R-2=0.029), WC (R=0.16, R-2=0.026) and BMI (R=0.22, R-2=0.048) for type 1 diabetes and with eIS (R=-0.37, R-2=0.14), WC (R=0.40, R-2=0.16) and BMI (R=0.25, R-2=0.063) in non-type 1 diabetes. In multivariable analysis, copeptin correlated with total cholesterol (beta +/- SE: -0.12 +/- 0.04, p=0.008) and low-density lipoprotein (beta +/- SE: -0.11 +/- 0.04, p=0.01) in type 1 diabetes. In non-type 1 diabetes, copeptin was associated with WC (beta +/- SE: 0.14 +/- 0.04, p=0.0024), BMI (beta +/- SE: 0.13 +/- 0.04, p=0.007) and eIS (beta +/- SE: -0.14 +/- 0.04, p=0.0013). Conclusions: Copeptin does not correlate with markers of IR in type 1 diabetes but strongly correlates in non-type I diabetes. Thus, elevated vasopressin activity and IR appear to be independent risk factors for vascular complications in type 1 diabetes. (C) 2018 Canadian Diabetes Association.