Proatherogenic role of elevated CE transfer from HDL to VLDL1 and dense LDL in type 2 diabetes -: Impact of the degree of triglyceridemia

Plasma cholesteryl ester transfer protein (CETP) facilitates intravascular lipoprotein remodeling by promoting the heteroexchange of neutral lipids. To determine whether the degree of triglyceridemia may influence the CETP-mediated redistribution of HDL CE between atherogenic plasma lipoprotein particles in type 2 diabetes, we evaluated CE mass transfer from HDL to apoB-containing lipoprotein accepters in the plasma of type 2 diabetes subjects (n=38). In parallel, we investigated the potential relationship between CE transfer and the appearance of an atherogenic dense LDL profile. The diabetic population was divided into 3 subgroups according to fasting plasma triglyceride (TG) levels: group 1 (G1), TG<100 mg/dL; group 2 (G2), 100<200 mg/dL; and group 3 (G3), TG>200 mg/dL, Type 2 diabetes patients displayed an asymmetrical LDL profile in which the dense LDL subfractions predominated. Plasma levels of dense LDL subfractions were strongly positively correlated with those of plasma triglyceride (TG) (r=0.471; P=0.0003). The rate of CE mass transfer from HDL to apoB-containing lipoproteins was significantly enhanced in G3 compared with G2 or G1 (46.2 +/-8.1, 33.6 +/-5.3, and 28.2 +/-2.7 mug CE transferred . h(-1) . mL(-1) in G3, G2, and G1, respectively; P<0.0001 G3 versus G1, P=0.0001 G2 versus G1, and P=0.02 G2 versus G3). The relative capacities of VLDL and LDL to act as accepters of CE from HDL were distinct between type 2 diabetes subgroups. LDL particles represented the preferential CE acceptor in G1 and accounted for 74% of total CE transferred from HDL. By contrast, in G2 and G3, TG-rich lipoprotein subfractions accounted for 47% and 72% of total CE transferred from HDL, respectively. Moreover, the relative proportion of CE transferred from HDL to VLDL1 in type 2 diabetes patients increased progressively with increase in plasma TG levels. The VLDL1 subfraction accounted for 34%, 43%, and 52% of total CE transferred from HDL to TG-rich lipoproteins in patients from G1, G2, and G3, respectively, Finally, dense LDL acquired an average of 45% of total CE transferred from HDL to LDL in type 2 diabetes patients, In conclusion, CETP contributes significantly to the formation of small dense LDL particles in type 2 diabetes by a preferential CE transfer from HDL to small dense LDL, as well as through an indirect mechanism involving an enhanced CE transfer from HDL to VLDL1, the specific precursors of small dense LDL particles in plasma.