Efeitos de uma Intervenção Profilática-Terapêutica com Exercício Resistido e Suplementação de Cúrcuma com Óleo de Peixe no Músculo Extensor Longo dos Dedos em Ratos Wistar Submetidos a um Modelo de Artrite Reumatoide

Abstract

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that affects the joints and can cause damage to muscle tissues. It is a disabling condition treated primarily with medication; however, the continuous, long-term use of these drugs can lead to unwanted side effects. Consequently, there is growing interest in low-cost, accessible integrative interventions, such as resistance exercise (RE) and supplementation with turmeric solubilized in fish oil. Therefore, this study aimed to evaluate the morphofunctional and immunological effects of prophylactic and therapeutic interventions involving resistance exercise and turmeric/fish oil supplementation—administered either alone or in combination—on the *extensor digitorum longus* muscle of Wistar rats subjected to an RA model. Sixty-eight male Wistar rats (15 weeks old) were used and divided into six groups: Control Group (GC, n=8), RA Group (GA, n=12), Exercise and Supplementation Group (GES, n=12), RA and Exercise Group (GAE, n=12), RA and Supplementation Group (GAS, n=12), and RA, Exercise, and Supplementation Group (GAES, n=12). A ladder-climbing resistance exercise protocol was employed, consisting of five days of unloaded training for adaptation followed by 16 training sessions on alternate days—eight interventions prior to RA induction and eight afterward. Load progression was set at 25%, 35%, and 50% of body weight, while the number of sets and repetitions remained fixed (three sets of eight repetitions with a two-minute rest interval). Supplementation was administered orally for 31 consecutive days using an adjustable volume pipette; the daily dose was 500 mg/kg of *Curcuma longa* L. dry extract diluted in 500 µL of fish oil to enhance bioavailability. Arthritis (RA) was induced using the Complete Freund's Adjuvant (CFA) model. A baseline assessment was performed on day 1, followed by six functional assessments throughout the study (days 8, 15, 22, 25, 28, and 31) to measure joint edema, grip strength, and nociception. Animals were euthanized on day 32. The extensor digitorum longus (EDL) muscle was harvested and divided into two portions: the proximal portion was processed for morphological analysis of muscle fibers and tissue. Arthritic groups exhibited significant increases in joint edema and higher levels of nociception compared to control groups (p < 0.01). The GES group maintained higher grip strength, whereas arthritic groups showed a reduction in this parameter. These results indicate functional impairment associated with RA that was not fully reversed by the tested interventions. Regarding body weight, the GES group showed a higher mean, with no significant differences in naso-anal length. The GA group exhibited greater EDL muscle weight, while the GES group showed greater muscle length. This finding suggests that inflammatory processes or edema may influence the increase in muscle weight in arthritic animals. Histometric analyses revealed no significant differences in fiber area and diameter, or in the number of capillaries and muscle fibers. However, the GA group showed a higher number of peripheral nuclei and—along with the GAS and GAES groups—a larger nuclear cross-sectional area. The IHP was higher in the GA group, whereas the GAE group displayed characteristics closer to those of the control group. Furthermore, an increase in fibroblasts and disorganization of the extracellular matrix were observed in the GA group, indicating greater structural muscle damage. It was concluded that moderate ladder-based resistance exercise, applied both preventively and therapeutically, was effective in improving the muscle microstructure of the EDL—particularly in the GAE group—but did not yield significant effects on muscle strength or nociception. Thus, the results suggest that the benefits of the interventions were predominantly structural, without a direct correlation to functional improvement during the analyzed period, indicating a need to adjust protocols or intervention durations in future studies.