GFAP and sarcopenia: At the same time, aging microglia and a weakened BBB promote the systemic release of inflammatory mediators such as IL-6, TNF-α, tissue inhibitor of metalloproteinase 1 (TIMP-1), intercellular adhesion molecule 1, and glial fibrillary acidic protein, which closely correlate with the severity of sarcopenia and frailty [48].