PPARGC1B and fatty liver disease: On the other hand, Pgc-1β null mice display altered expression of various nuclear-encoded genes that are responsible for mitochondrial and metabolic functions in BAT, while HFD-feeding induces hepatic steatosis and increases serum TG and cholesterol levels in these mice [196], suggesting that PGC-1β plays an important role in controlling mitochondrial oxidative energy metabolism.