Lipid Metabolism

de novo lipogenesis
Fatty acid synthesis: FAS ACC 6GPD
-FAS involved in the condensation of acetyl-CoA, malonyl-CoA, and NADPH catalyzes de novo fatty acid synthesis .
-ACC is the first rate limiting enzyme in the de novo lipogenesis process.
-As a key enzyme, 6GPD is related in NADPH production which is essential for fatty acid biosynthesis.
Ref：https://doi.org/10.1155/2022/6743690

Lipid catabolism
β-oxidation:
-critical enzymes such as LPL, HSL, and CPT1
-transcription factors such as SREBP1, PPARα, and PPARβ

Fatty acid transporter : slc27a2a slc27a6-like
Fatty acid translocase : cd36

Very low-density lipoprotein (VLDL)
Under the postprandial state, the liver uptakes dietary fats to synthesize triglycerides for very low-density lipoprotein (VLDL)-mediated secretion and transport to adipose tissue for storage, or transport to the heart and skeletal muscle for β-oxidation. During fasting, fatty acids are mobilized from adipocytes to the liver for energy supply.
Very low-density lipoprotein (VLDL) is essential for the transport of triglycerides from the liver into the circulation. It is well-known that apolipoproteins are a key component of VLDL, and have abundant subtypes expressed in liver.
apolipoprotein genes : apoa1b, apoa2, apoa4b.1, apoea, apoc1, apoc2, apo3b, apoa4b.2, apobb.1, apom, apoa4a, apoba, apodb, apoa1a, and apoc4.
Ref:https://doi.org/10.3390/biology10020092

Schematic diagram of starvation triggering hepatic steatosis by regulating liver fatty acid intake, β oxidation, de novo lipogenesis and lipid transport. Starvation up-regulated transcription of slc27a2a, slc27a6-like, and cd36, promoting extrahepatic fatty acid
uptake. In liver, starvation induces the expression of lipogenesis-related genes (srebf1, srebf2, fasn, and scdb) by activating the PPARα/RXR pathway, thereby promoting lipogenesis. Meanwhile, the fatty acid metabolism pathway was inhibited. Thus, most ingested extrahepatic fatty acids are used for lipogenesis rather than β oxidation. However, synthetic fat appears to be blocked in the liver, because starvation inhibits the expression of numerous apolipoprotein genes. Red arrows indicateup-regulated genes, green arrows indicate down-regulated genes. FFA: free fatty acid.