Background
The improvement of colitis symptoms by treatment with IL-12/23 p40 neutralizing antibody should increase the muscle mass and the function of the sarcopenia phenotype.
Conclusions
Our study demonstrates that Il-12/23 acts directly on muscle to induce atrophy, and the IL-12/23 p40 neutralizing antibody is effective not only in suppressing colitis but also in maintaining muscle mass and improving muscle function in an experimental colitis model.
Methods
An experimental colitis model was induced by oral administration of 2% dextran sulfate sodium (DSS) for 7 days. During induction of colitis, IL-12/23 p40 neutralizing antibody was injected twice on Days 3 and 5. The total body mass index was measured by dual-energy X-ray absorptiometry. The muscle function was measured by forelimb grip strength and fatigue running distance. The muscle fibre cross-sectional area (CSA) was calculated after the transverse section and haematoxylin and eosin staining, and gene expression was confirmed by RT-qPCR. Differentiated C2C12 cells were used as in vitro models and treated with recombinant IL12/23 proteins to mimic the enhanced cytokines in colitis.
Results
The symptoms of colitis were alleviated by injection of IL-12/23 p40 neutralizing antibody compared with phosphate-buffered saline (PBS), and the disease activity index score was significantly lower on Day 8 (0.0 ± 0.00 of cont. vs. 11.3 ± 0.9 of DSS + PBS, P < 0.0001; DSS + PBS vs. 7.7 ± 1.25 of DSS + p40Ab, P < 0.0001). The CSA of the gastrocnemius and tibialis anterior muscle fibres decreased in mice with DSS-induced colitis (gastrocnemius, 1258.2 μm2 ± 176.45 of cont. vs. 640.1 μm2 ± 59.83 of DSS + PBS, P < 0.0001; tibialis anterior, 1251.8 μm2 ± 331.48 of cont. vs. 678.9 μm2 ± 67.59 of DSS + PBS, P < 0.0001), and the treatment of IL-12/23 p40 neutralizing antibody partially restored CSA of the gastrocnemius (640.1 μm2 ± 59.83 of DSS + PBS vs. 1062.0 μm2 ± 83.41 of DSS + p40Ab, P < 0.0001) and tibialis anterior (678.9 μm2 ± 67.59 of DSS + PBS vs. 1105.3 μm2 ± 143.15 of DSS + p40Ab, P = 0.0003).vs. 640.1 μm2 ± 59.83 of DSS + PBS, P < 0.0001) and tibialis anterior (1251.8 μm2 ± 331.48 of cont. vs. 678.9 μm2 ± 67.59 of DSS + PBS, P < 0.0001), and the treatment of IL-12/23 p40 neutralizing antibody partially restored CSA of the gastrocnemius (640.1 μm2 ± 59.83 of DSS + PBS vs. 1062.0 μm2 ± 83.41 of DSS + p40Ab, P < 0.0001) and tibialis anterior (678.9 μm2 ± 67.59 of DSS + PBS vs. 1105.3 μm2 ± 143.15 of DSS + p40Ab, P = 0.0003). In the evaluation of muscle function, grip strength and fatigue distance decreased by colitis were partially restored (grip strength: 139.9 g ± 5.38 of cont. vs. 83.9 g ± 5.48 of DSS + PBS, P < 0.0001; DSS + PBS vs. 118.6 g ± 4.05 of DSS + p40Ab, P < 0.0001; fatigue distance: 872.5 m ± 104.01 of cont. vs. 58.2 m ± 107.72 of DSS + PBS, P < 0.0001; DSS + PBS vs. 328.0 m ± 109.71 of DSS + p40Ab, P = 0.0015) by injection of IL-12/23 p40 neutralizing antibody. Conclusions: Our study demonstrates that Il-12/23 acts directly on muscle to induce atrophy, and the IL-12/23 p40 neutralizing antibody is effective not only in suppressing colitis but also in maintaining muscle mass and improving muscle function in an experimental colitis model.