The Histamine-Induced Axon-Reflex Response in People With Type 1 Diabetes With and Without Peripheral Neuropathy and Pain: A clinical, observational study

Small nerve fibres are important when studying diabetic peripheral neuropathy (DPN) as they could be first affected. However, assessing their integrity and function adequately remains a major challenge. The aim of this study was to investigate the association between different degrees of DPN, the presence of neuropathic pain, and the intensity of the axon-reflex flare response provoked by epidermal histamine. Eighty adults were included and divided into 4 groups of 20 with type 1 diabetes and: painful DPN (T1DM+PDPN), non-painful DPN (T1DM+DPN), no DPN and no pain (T1DM-DPN), and 20 persons without diabetes or pain (HC). The vasomotor responses were captured by a Full-field Laser Speckle Perfusion Imager. The response was lowest in T1DM+DPN, followed by T1DM+PDPN, T1DM-DPN and HC. The response was significantly reduced in DPN (T1DM+DPN, T1DM+PDPN) compared with people without (T1DM-DPN, HC) (P < .001). The response was also attenuated in diabetes irrespective of the degree of DPN (T1DM+PDPN, T1DM+DPN, T1DM-DPN) (P < .001). There were no differences in the response between painful neuropathy (T1DM+PDPN) and painless DPN (T1DM+DPN) (P = .189). The method can distinguish between groups with and without diabetes and with and without DPN but cannot distinguish between groups with and without painful DPN. Perspective: This study describes how diabetes attenuates the axon-reflex response, and how it is affected by neuropathy and pain clarifying previous findings. Furthermore, the study is the first to utilize histamine when evoking the response, thus providing a new and fast alternative for future studies into the pathophysiology of neuropathic pain.