Table 1. Elements involved in hepatic lipid metabolism.
| Pathway | Regulation | Postprandial | Insulin resistant |
|---|---|---|---|
| Hepatic VLDL metabolism | |||
| Insulin receptor (IR) | Insulin signal transmission | ↑ IR pY | ↓ IR pY |
| IR → IRS | Cytoplasmic signal transduction | ↑ IRS pY | ↓ IRS pY |
| IRS → PI3K | Activation of PI3K | ↑ PIP3 | ↓ PIP3 |
| PIP3 | ER signal | ↑apoB degraded | ↓ apoB degraded |
| PDKs → pAkt | Activation of Akt | ↑pT308/S473 | ↓T308/S473 |
| pAkt → pFoxO1 | Nuclear export and 14-3-3 binding | ↑pT32, pS253 | ↓phosphorylation Nuclear localization |
| IR → FoxO1-mediated pathway | |||
| ApoCIII | Regulator of lipolysis | ↓ (?) | ↑ |
| MTP | ApoB chaperone and lipid transfer | ↓ (?) | ↑ |
| ApoB | Structural VLDL protein | ↓ (?) | ↑ (?) |
| SREBP-1c | Master regulator of lipogenic genes | ↑ | ↑ |
| Other factors involved in VLDL metabolism | |||
| DGAT1 | Acylation of MG and DG | ? | ? |
| DGAT2 | Acylation of MG and DG | ? | ? |
| ATGL | TG lipolysis | ? | ? |
| ABHD5/CGI-58 | Cofactor for ATGL | ? | ? |
| Acylation of lysophosphatidic acid | |||
ABHD5/CGI-58, abhydrolase domain containing 5 also comparative genome identification 58; Akt, a retroviral oncogene encoding a serine-threonine kinase, 14-3-3 protein; apoCIII, apolipoprotein CIII; ATGL, adipose triglyceride lipase; DG, diacylglyceride; DGAT, diacylglyceride acyltransferase; ER, endoplasmic reticulum; IR, insulin receptor; IRS, insulin receptor substrate; MG, monoacylglyceride; MTP, microsomal triglyceride transfer protein; PDKs, phosphoinositide dependent kinases; PI3K, phosphatidylinositide 3-kinase; PIP3, phosphatidylinositide 3,4,5 tris-phosphate; pS, phosphoserine; pT, phosphothreonine; pY, tyrosine phosphorylation; SREBP-1C, sterol regulatory element binding protein 1C.