Mixed small- and- large fiber diabetic neuropathy affects microcirculatory response to exercise. Pilot study

Abstract

Microcirculation dysfunction is common in type 2 diabetes (DT2) and plays a crucial role in diabetic neuropathy (NP) development. Some microcirculatory vasomotor changes are altered in DT2 with NP. Acute exercise is known to induce a skin vasodilatory response dependent in part on endothelial and neurogenic factors. In this way, we hypothesised that microcirculatory response to exercise could be blunted in DT2 patients with small fiber neuropathy. To compare cutaneous blood flow in basal conditions and in response to acute sub-maximal exercise in DT2 patients without and with small or/and large fiber NP. Forty-two patients with DT2 were included. Cutaneous blood flow (CBF) on the dorsal foot was assessed using Laser Speckle Contrast Imaging at rest and during 10 minutes after the six-minutes walking test. Diabetic neuropathy had been assessed with sural nerve conduction for large fiber and thermal testing for small fiber. Four diabetic groups were thus obtained: DT2 without NP ( n = 14); SNP with small fiber NP ( n = 11); LNP with large fiber NP ( n = 9); SLNP with mixed small and large fiber NP ( n = 8). Statistical comparisons between DT2 and each NP group were performed by one-way and repeated measures ANOVA. Diabetes duration, HbA1c, arterial pressure and exercise performance were not different between groups. At rest, SLNP had significantly higher CBF than DT2 (37.9 ± 9.7 and 29.6 ± 7.6 PU; P < 0.05) whereas SNP and LNP only tended to have higher CBF than DT2 ( P = 0.08). After exercise, DT2, SNP and LNP had increased CBF, which decreased progressively during the 10min-recovery without difference between groups. By contrast, SLNP did not change their CBF after exercise. This lack of CBF changes in response to exercise in DT2 with small- and large fiber neuropathy may suggest a loss of vasodilatory reserve.