LONG-TERM EFFECT OF SOLUBLE-FIBER FOODS ON POSTPRANDIAL FAT-METABOLISM IN DYSLIPIDEMIC SUBJECTS WITH APO E3 AND APO E4 GENOTYPES

To determine the long-term effect of soluble fiber on postprandial fat metabolism, we studied 33 dyslipidemic subjects, 16 with apolipoprote in (ape) E3/3 (E3)and 17 with E3/4 or E4/4 (E4) genotypes. They ate pr eweighed low-fat (20% of energy), high-fiber (> 5.7 g/MJ) diets for tw o 4-mo periods separated by a 2-mo washout period according to a rando mized, crossover design. One diet contained foods rich in insoluble fi ber and the other foods rich in soluble fiber. On 1 d during the last 2 wk of each diet, subjects ingested a standard, fiber-free, fatty liq uid meal containing retinyl palmitate as a marker of intestinally deri ved lipoproteins. Plasma samples were obtained at hourly intervals for 10 h. Compared with the insoluble-fiber diet, soluble fiber reduced f asting plasma total cholesterol in both E3 (6.6 +/- 2.1%, P = 0.007) a nd E4 subjects (5.6 +/- 2.1%, P = 0.017). Soluble fiber increased feca l total bile acid output in both E3 (76 +/- 18%, P < 0.001) and El sub jects (85 +/- 19%, P < 0.001). The incremental area under the chylomic ron triacylglycerol response curve was significantly greater after sol uble fiber than after insoluble fiber in E3 (3.56 +/- 0.56 compared wi th 2.87 +/- 0.38 mmol.h/L, respectively, P = 0.046) but not in E4 subj ects (5.19 +/- 0.78 compared with 4.92 +/- 0.81 mmol.h/L). Kinetic ana lysis suggested an increase in retinyl palmitate absorption in E3 subj ects after soluble fiber, but no difference in E4 subjects. These resu lts suggest that a long-term increase in dietary soluble fiber has no effect on postprandial fat metabolism in subjects with an apo E3/4 or E4/4 genotype. However, soluble fiber enhances apparent fat absorption in E3 subjects, which could be due to an increased bile acid pool and increased micelle formation.