TLR4 and fetal growth restriction: Various studies have demonstrated that IUGR piglets exhibit upregulated gene and protein expression of pro-inflammatory cytokines including toll-like receptor 4 (TLR4), interleukin-1 beta (IL-1β), nuclear factor kappa B (NF-κB), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) in both the liver and intestine [19,63,64,65].