TLR4 and obesity due to melanocortin 4 receptor deficiency: It has been reported that free fatty acids (FFAs), a Tlr-4 agonist, and TNF-α combinedly create a superior environment to trigger inflammatory cytokine secretion during obesity, which is mediated by the TLR4/TRIF/IRF3 signaling cascade [31], and LPS (100 ng/mL) is a potent stimulator of IL-6 secretion in 3T3-L1 cells via the Tlr-4/NfkB pathway [32].