Curcumin (Curcuma longa) Supplementation Associated with Low-Dose Prednisone Improves Morphofunctional, Histomorphometric and Postsynaptic Aspects of the Rectus Femoris Muscle in Old Female Wistar Rats with Experimental Rheumatoid Arthritis

Objective. Rheumatoid arthritis (RA) is an inflammatory disease. Here we analyzed the effects of the supplementation with curcumin (CM) in a treatment with prednisone (PD) on hind paw’ functionality and rectus femoris histomorphometric and immunohistochemical aspects. Methods. Thirty female 18 months-old Wistar rats were divided in six groups: control (CG), arthritis (AG), arthritis CM (AC), arthritis PD low-dose (APLD), arthritis PD high-dose (APHD) and arthritis PD low-dose and CM (APLDC). The experimental RA was induced by a complete Freund’s adjuvant injection into the knee joint cavity. PD (2 mg/kg/day and 10 mg/kg/day) and CM (C21 H20 O6) (100 mg/kg/day) were used as treatment, using gavage method. Functionality, histomorphometric and immunohistochemical evaluations were performed in the hind paw and in the rectus femoris muscle. Generalized mixed models was used for statistical analysis. Statistical significance was set as P-value 0.05. Results. AG had loss of grip strength, motor function and increase in nociceptive threshold (p < 0.0001). AC and APLDC had positive effects on grip strength and motor function. Histomorphometry revealed degenerative lesions in AG muscular tissue with circulatory disorders, changes in muscle fibers, connective tissue and muscle spindle, major total collagen quantity and smaller perimeter in the postsynaptic region (p < 0.0001). APLDC showed the best recovery in these aspects (p < 0.001). Conclusions. CM supplementation in the treatment with 2 mg/kg/day of PD restored muscle strength, motor function, histomorphometrical and postsynaptic aspects in old female rats with experimentally induced RA.