Impact of insulin on microvascular blood flow and endothelial cell function in the postprandial state in patients with Type 1 diabetes

The aim of the present study was to investigate postprandial microvascular blood flow following a standardized test meal in nondiabetic subjects and in patients with Type 1 diabetes after regular insulin or insulin lispro.

In this open-label, randomised cross-over study, 20 nondiabetic participants and 20 patients with Type 1 diabetes were enrolled. To valuate the postprandial time course of skin microvascular blood flow, laser Doppler flux (LDF) readings were obtained at baseline and every 30 min following a standardized test meal. Furthermore, the microvascular response to acetylcholine (Ach) was measured, and blood was collected for the measurement of serum insulin and blood glucose levels. Patients with Type 1 diabetes received single doses of regular insulin or insulin lispro, respectively, in a randomised sequence, while in nondiabetics, no insulin substitution was performed.

In nondiabetic participants, skin microvascular blood flow showed an early increase in LDF by median 6.0 arbitrary units (AU; interquartile range: 1.8–14.0 AU) within the first postprandial hour. The microvascular response to Ach also increased with a median response of 26.0 (19.0–49.3) AU at 30 min pp and 50.0 (31.7–65.1) AU at 60 min pp. In patients with Type 1 diabetes, the time course of postprandial LDF measurements observed after the administration of insulin lispro was nearly similar to the one observed in nondiabetic controls and differed from that after subcutaneous regular insulin treatment. The postprandial microvascular response to Ach was stronger following insulin lispro compared with regular insulin [30 min pp: 26.0 (19.0–49.3) vs. 20.9 (9.7–26.1) AU, P=.0001].

Postprandial microvascular blood flow is disturbed in patients with Type 1 diabetes. Improvement of postprandial metabolic control was found to improve postprandial microvascular function.