P274 PIOGLITAZONE SUPPRESSES ONLY PLASMA SMALL, DENSE LDL BUT NOT LARGE LDL IN TYPE 2 DIABETIC PATIENTS

Apolipoprotein C-III, like the other C apoproteins, is distributed in both the triglyceride-rich lipoprotein and in high-density lipoprotein (HDL). High-density lipoprotein acts as a reservoir for the C apoproteins, and during very low-density lipoprotein (VLDL) production or chylomicron production (from exogenous fat intake) apoC's transfer from HDL to chylomicrons for subsequent metabolism. Thus, with increasing triglyceride levels and, hence, increased concentrations of triglyceride-rich particles, greater proportions of apoC-II and apoC-III are present in the triglyceride-rich lipoproteins, with reciprocal decline in the amount of C apoproteins in HDL. During triglyceride-rich lipoprotein catabolism, in which apoC-II activates lipoprotein lipase, the C apoproteins are transferred back to HDL and the catabolic products of triglyceride-rich lipoproteins are taken up by the liver. Thus, it appears that apoC-II activates lipoprotein lipase and exposes apoE for the clearance of such particles by the liver and apoC-III appears to modulate this process. Excessive production of apoCIII, therefore, can lead to hypertriglyceridemic states that are characterized by increased contents of apoC-III relative to other apoproteins in such particles.