Pleiotropic Effects of Thyroid Hormones: Learning from Hypothyroidism
Figure 9
Intravascular metabolism of lipoproteins. (a) Very low-density lipoproteins (VLDLs) synthesized by the liver follow a lipolstic cascade up to the formation of low-density lipoproteins (LDLs), which are cleared from plasma by the apo B/apo E hepatic receptor (apoB/E-R). The cholesteryl esters transfer protein (CETP) facilitates the exchange of triglycerides from apo B containing lipoproteins to HDL and cholesteryl esters in the opposite sense. (b) High-density lipoproteins (HDL) pick up cholesterol from peripheral tissues, including the foam cells. HDL cholesterol becomes esterified by the activity of the lecithin:cholesterol acyl transferase (LCAT). Cholesteryl esters are cleared from plasma by the hepatic scavenger receptor class B, type I (SR-BI) or via CETP. Proteins involved in lipid metabolism that are regulated by thyroid hormones have been highlighted with green circles; low expression levels of SR-BI have not been reported (indicated by a green question mark).
