FETU-A also inhibits the expression of adiponectin and peroxisome proliferator-activated receptor γ (PPARγ) and activates toll-like receptor 4 (TLR 4) on the surface of adipocytes and immune system cells, reducing the expression of the pro-inflammatory nuclear factor NF-kB and pro-inflammatory cytokines, which also predisposes to metabolic disorders [52]. Here, TLR4 is linked to metabolic disease.