The relationship between residual insulin secretion and subclinical cardiovascular risk indices in young adults with type 1 diabetes

Background: Patients with type 1 diabetes (DM1), even in the setting of adequate glycaemic control, have an excess risk for developing cardiovascular disease. Residual insulin secretion (RIS), measured by detectable C-peptide levels in patients with DM1, might protect against diabetes-related complications. This study aimed to examine the relationship between residual insulin secretion and prognostic markers of cardiovascular complications in patients with DM1. Methods: A total of 137 patients with DM1 were included in this analysis. They were of young age (<45 years), with an established diagnosis of over two years before the study entry and without a history of cardiovascular complications. All patients underwent complete clinical and laboratory evaluation. A c-peptide measurement of >= 0.05 ng/ml was used to identify the presence of RIS. Pulse wave velocity (PWV), cardiac autonomic function assessed both at rest, by total power of heart rate variability and dynamically, by the expiration to inspiration (e/i) index, albumin to creatinine ratio (ACR), and high sensitivity CRP (hs-CRP) were used as predictive biomarkers of cardiovascular complications. Results: Female participants represented 63.5% of the population [mean age: 29.7 (+/- 8.1) years, mean HbA1c: 7.6% (+/- 1.4), median diabetes duration:15 (10-21) years, median age at diabetes diagnosis: 13 (8-17) years]]. The median value of fasting c-peptide was 0.04 (0.03-0.05) ng/ml, and RIS was detected in 32 patients (23.4%). Patients with RIS had a shorter diabetes duration, an older age at diagnosis and a lower BMI, while no significant association was found between residual c-peptide and age or HbA1c. RIS was significantly associated with lower PWV values [8.1 m/s(2) (7-8.7) vs 9.2 m/s(2) (7.8-10.1), p <0,001], higher total power values [1124 Hz (600-3277) vs 577 Hz (207-2091), p <0,001], and higher E/I measurements [1.4 (1.2-1.5) vs. 1.3 (1.2-1.4), p=0.01]. No significant association was noted between RIS and either ACR or hs-CRP. In multivariable linear regression analysis, the association between RIS and lower PWV values remained significant (p= 0.007) regardless of age, sex, diabetes duration or age of diagnosis, blood pressure and BMI. Similarly, residual insulin secretion retained a significant independent association with total power (p= 0.032) and E/I (p=0.045). Conclusion: In young patients with DM1, free of macrovascular complications, residual insulin secretion is independently associated with more favorable prognostic markers of subclinical atherosclerosis and cardiac autonomic function.