PLASMA-LIPOPROTEIN DISTRIBUTION OF APOC-III IN NORMOLIPIDEMIC AND HYPERTRIGLYCERIDEMIC SUBJECTS - COMPARISON OF THE APOC-III TO APOE RATIO IN DIFFERENT LIPOPROTEIN FRACTIONS

In order to assess the relationship between plasma accumulation of tri glyceride-rich lipoproteins (TRL) and lipoprotein levels of apoC-III a nd apoE, we have measured apoC III and apoE in lipoproteins separated according to size (by automated gel filtration chromatography) from pl asma of normolipidemic subjects (plasma triglyceride (TG): 0.84 +/- 0. 10 mmol/l; mean +/- SE, n = 8), and from type III (n = 8) and type TV (n 8) hyper lipoproteinemic patients, matched for plasma TG (5.76 +/- 0.62 v 5.55 +/- 0.45 mmol/l, resp.). Total plasma apoC-III concentrati on was similar in the III and type IV patients (33.1 +/- 3.4 v 37.6 +/ - 4.4 mg/dl, respectively), but was significantly increased compared t o normolipidemic controls (10.0 +/- 1.0 mg/dl, P < 0.001). TRL apoC-II I was lower and high density lipoprotein (HDL) apoC-III was significan tly higher in type LII versus type TV subjects (14.8 +/- 3.2 vs. 22.8 +/- 3.0 mg/dl, P < 0.05; 8.3 +/- 1.0 vs. 5.2 +/- 0.5 mg/dl, P < 0.05). Plasma concentration of apoC-III in lipoproteins that eluted between TRL and HDL (intermediate-sized lipoproteins, ISL) was similar in the two hypertriglyceridemic groups (10.1 +/- 1.3 vs. 9.7 +/- 1.6 mg/dl), but was significantly higher (P < 0.05) than controls (2.2 +/- 0.3 mg/ dl). TRL, ISL, and HDL apoE concentrations were significantly higher i n type III versus type IV subjects (P < 0.05).AII lipoprotein fraction s in type III patients were characterized by lower apoC-III to apoE ra tios. In contrast, the TRL apoC-III to apoE ratio of type IV patients was similar and the ISL apoC III to apoE ratio was significantly highe r, compared to normolipidemic individuals. These results indicate that compared to normolipidemic individuals, remnant-like lipoproteins in the ISL fraction of type IV patients are enriched in apoC-III relative to apoE, whereas those of type III patients are encriched in apoE rel ative to apoC-III.