Inflammation, mechanical allodynia and an exaggerated exercise pressor reflex during disease progression in UCD‐type 2 diabetes mellitus rats

Abstract Chronic low‐grade inflammation characterizes type 2 diabetes mellitus (T2DM) and underlies the development of peripheral neuropathy, symptoms of which include mechanical allodynia and an exaggerated exercise pressor reflex. The purpose of this study was to determine whether mechanical allodynia and/or specific concentrations of inflammatory mediators coincide with the presence of an exaggerated exercise pressor reflex. Haemoglobin A1c was assessed to detect diabetes onset (threshold ≥5.6%) in male University of California Davis (UCD)‐T2DM rats ( n = 18). Age‐matched, healthy Sprague–Dawley rats ( n = 18) served as controls. Monthly measurements assessed mechanical allodynia (via paw withdrawal threshold), insulin and inflammatory mediators (via ELISA and multiplex kits). Paw withdrawal threshold was not different between groups prior to diabetes onset. However, by 8 weeks post‐onset, T2DM rats demonstrated a significant decrease in pain threshold compared to that before diabetes onset, which persisted for 8 weeks. This is the same period in diabetes progression as when the exercise pressor reflex is exaggerated. Prior to diabetes onset, UCD‑T2DM rats had significantly higher circulating levels of IL‑6 and IL‑1β, and these elevations persisted throughout disease progression, with only CRP showing a significant increase at 8 weeks post‑onset. These findings offer a useful foundation for further exploration into the assessments of mechanical allodynia and inflammation to determine when those with T2DM are at an increased risk for experiencing adverse cardiovascular events.