Effect of a high carbohydrate diet on the content of apolipoproteins C-II, C-III and E in human plasma high density lipoprotein subfractions

Abstract

The effect of isocaloric high and low carbohydrate (Carb) diets on the structure and apoprotein composition of plasma high density lipoproteins (HDL) was assessed in four healthy men. The high Carb diet contained 65% calories as Carb and 15% as fat; the low Carb was 15% and 65%, respectively, with protein fixed at 20% of calories in each case. Cholesterol was 400 mg/day and the P/S ratio of the fat was 0.4. Each diet was sequentially consumed for periods of 3 weeks. At the end of each 3-week study period, plasma HDL 2 and HDL3 were isolated by zonal ultracentrifugation and their apoprotein and lipid compositions were determined. Compared to the low Carb diet, the high Carb diet was associated with an increase in the size of HDL 2 (116.0 ± 1.8 vs. 109.1 ± 1.8 Å) and in the content (mean weight % ± SEM) of apoE (2.81 ± 0.71 vs. 1.79 ± 0.49, P < 0.01) and of apoC-II (1.73 ± 0.09 vs. 1.11 ± 0.12, P < 0.01). HDL 2 apoC-III content was not significantly different on the two diets (6.49 ± 0.50 vs. 7.42 ± 1.21). On the two diets, HDL 3 size and HDL 3 apoE content were not significantly changed. HDL 3 apoC-II and apoC-III, however, were higher on the high Carb diet, P < 0.05. The ratio (by weight) of HDL 2 apoE/HDL 2 apoC-II + C-III increased on the high Carb diet compared to the low Carb diet (0.344 ± 0.058 vs. 0.228 ± 0.053, P < 0.01). We suggest that the increased amount of apolipoprotein E in HDL 2 may influence its rate of catabolic clearance and may account for the well-known decrease in plasma HDL-cholesterol in subjects on high Card diets.