Table 1.

Typical Mechanisms of lipid metabolism in fatty liver diseases.

	Type	Mode	Consequence
Hormone	Insulin	Insulin binds to insulin receptor then activates PI3K-Akt pathway, consequently activates transcription factors such as FoxO family to promote lipogenic genes	Lipid synthesis
	Thyroid hormone (TH)	TH interacts with its receptor and influence fatty uptake proteins to increase free fatty acids uptake. TH can also promote lipogenic transcription factor via MAPK/ERK and PI3K/Akt pathways. TH can promote lipid breakdown by lipase or lipophagy.	Lipid synthesis/ Lipid breakdown
Transcription factor	SIRT1,3,6
	FoxO	FoxO protein stimulates triacylglycerol lipase and activates autophagy to promote lipid breakdown. Besides, FoxO6 has ability to export triglyceride from hepatic cells.	Inhibit lipogenesis and increase lipid breakdown
	SREBPs	Hepatic SREBP-1c mRNA elevates when given a high carbohydrate diet. SREBPs can be modulated by mTORC1. Besides SREBPs activities associate with ubiquitin-dependent proteasomal degradation.	Promote lipogenesis
Inflammatory cytokine	IL-6	IL-6 downregulates TNF-α and increase PPARα meanwhile up-regulates AMPK to exert lipolytic activity.	Promote lipid breakdown and ameliorate hepatic steatosis
	TNF-α	TNF-α Presents together with nonalcoholic steatohepatitis	exacerbate liver damage and hepatic fat deposition