Endothelial function in patients with type 1 diabetes evaluated by skin capillary recruitment

The aim of the present study was to evaluate skin capillary density and recruitment of the upper and lower extremities of patients with type 1 diabetes under chronic treatment without clinical manifestations of diabetes-related complications. This cross-sectional observational study included 59 (27.1 ± 10.6 years) consecutive outpatients with type 1 diabetes [duration 10 (1; 45) years] and 41 age- and sex-matched healthy controls. We used intravital video-microscopy to measure basal and maximal (during venous congestion) skin capillary densities as well as capillary recruitment using post-occlusive reactive hyperemia (PORH) in the dorsum of the fingers and toes. Mean capillary density (MCD) of the fingers at baseline was not different between controls and patients (123.02 ± 22.6 and 132.3 ± 28.9 capillaries/mm2, respectively; P = 0.08). In contrast, baseline MCD of the toes was lower in controls, when compared to patients (84.6 ± 19.8 and 96.2 ± 23.4 capillaries/mm2, respectively; P = 0.01). Capillary recruitment during PORH (% increase of the number of capillaries/mm2) was significantly higher in controls compared to patients both in fingers [7 (− 8; 33) and − 1.0 (− 35, 13), respectively; P = 0.000] and toes [6 (− 20; 46) and 0 (− 24; 20), respectively; P = 0.000]. During venous occlusion, capillary density increase (% increase of the number of capillaries/mm2) was also higher in controls compared to patients both in fingers [3 (− 14; 23) and 0.0 (− 30; 29.2), respectively; P = 0.02] and toes [9.3 (− 18; 51) and − 7 (− 34; 22), respectively; P = 0.000]. Our results showed that patients with type 1 diabetes, although not presenting skin capillary rarefaction, display skin microvascular functional alterations in both extremities characterized by an absence of capillary reserve.