PNPLA2 and fatty liver disease: Mechanistically, KAL induced hepatic steatosis and NASH by down-regulating adipose triglyceride lipase (ATGL) and comparative gene identification 58 (CGI-58) by LRP6/Gɑs/PKA/GSK3β pathway through down-regulating peroxisome proliferator-activated receptor γ (PPARγ) and up-regulating kruppel-like factor four (KLF4), respectively.