IL1A and Cachexia: Moreover, the MAPK pathway is subdivided into four distinct branches: ERK1/2, p38 MAPK, c-Jun N-terminal kinase (JNK), and ERK5.435 In skeletal muscle cells, the MAPK signaling pathway regulates myocyte growth and stress responses, particularly in cachexia patients, where MAPK activation promotes protein catabolism.436 This process is primarily mediated by IL-1 or TNF-α.