In NASH, TLR4 (that recognizes LPS, a gram-negative bacteria wall component), TLR5 (known to recognize bacterial flagellin from invading mobile bacteria), TLR2 (that recognizes many bacterial, fungal, viral, and endogenous substances) and TLR9 (a specific receptor for double-stranded bacterial DNA) have been shown to play a key pathogenetic role [281]. This evidence concerns the gene TLR9 and metabolic dysfunction-associated steatohepatitis.