Exercise prevents high-fat diet-induced hyperalgesia in rats: an in vivo microdialysis study

In this study, we investigated pain threshold and β-endorphin concentration in both sedentary and exercise trained rats under high fat diet induced obesity. Forty male Sprague-Dawley rats were assigned to one of four groups: sedentary control (C), exercise trained (T), high fat diet (HFD) and exercise trained under high fat diet (HFD-T). Exercise trained groups were subjected to 5 days / week for 8 weeks of motor driven treadmill exercise. HFD was induced as diet regimen containing 50% fat. Animals were placed individually on a hot plate at 55˚C and withdrawal latency for hind paw was recorded as pain threshold. Initial and final β-endorphin levels in plasma and microdialysate samples from anterior cingulate cortex (ACC) were measured. Animals in T and HFD-T groups had significantly higher exhaustion time compared to C and HFD groups. HFD group had lowest pain threshold latency compared to other groups. At plasma in HFD-T group and in ACC of HFD group had lowest β-endorphin concentrations. We concluded that exercise training restores the hyperalgesic response and partially β-endorphin concentration at ACC in HFD-induced obesity model of rats.