Effects of Capsaicin Supplementation on Eccentric Resistance Training-induced inflammation

Abstract Inflammation is a protective response to injury and infection, yet uncontrolled inflammation contributes to chronic diseases. Eccentric resistance training induces muscle damage and acute inflammation. Capsaicin, a chili pepper-derived compound, exhibits anti-inflammatory properties. This study evaluated capsaicin supplementation on exercise-induced inflammation. Thirty-two male Wistar rats were randomly assigned to four groups (n = 8/group; final n = 5 after 30% attrition), control, eccentric resistance training (6 weeks), training + capsaicin (4 mg/kg/day oral), and capsaicin alone. Biceps muscle histopathology (H&E staining) assessed inflammation, degeneration, necrosis, and atrophy. Gene expression of IL-1β, TNF-α, p50, and NF-κB was quantified via real-time PCR. One-way ANOVA with p < 0.05 determined significance. The training group exhibited significantly increased histopathological inflammation (inflammatory cell infiltration, degeneration, necrosis, atrophy) and elevated IL-1β (3.06 ± 0.45-fold), p50 (2.21 ± 0.18), NF-κB (1.86 ± 0.25), and TNF-α (2.35 ± 0.35) compared to controls (1.00 ± 0, p < 0.05). Capsaicin supplementation significantly reduced these markers relative to control levels, training + capsaicin lowered IL-1β by 72% (0.27 ± 0.22), p50 by 64% (0.35 ± 0.19), NF-κB by 84% (0.15 ± 0.10), and TNF-α by 48% (0.52 ± 0.13) compared to the control group (p < 0.05). The capsaicin-only group showed the greatest reductions (IL-1β: 0.08 ± 0.007; p50: 0.14 ± 0.07; NF-κB: 0.09 ± 0.25; TNF-α: 0.27 ± 0.10). Histopathological findings corroborated these molecular results. Capsaicin supplementation attenuates eccentric resistance training-induced inflammation by downregulating the NF-κB/p50 pathway, suggesting potential as a complementary non-pharmacological intervention for exercise-related inflammation.