Decreased postprandial response to a fat meal in normotriglyceridemic men with hypoalphalipoproteinemia

The plasma level of high density lipoprotein cholesterol (HDL-C) has been reported to be inversely correlated with the level of triglycerides (TGs) and the magnitude of postprandial lipemia because subjects with low HDL-C accompanying high TG levels often have an increased postprandial response to a fat load. However, information is limited regarding the postprandial response to a fat load in subjects with low HDL-C and normal fasting TG values (hypoalphalipoproteinemia [hypoalpha]). We administered an oral fat load (70 g/m² of body surface area) to six subjects with hypoalpha and six aged-matched control subjects. Plasma levels of lipids and lipoproteins and the mass of triglyceride-rich lipoproteins (TRLs: S_f >100 and S_f 20-100) were measured every 2 hours for 8 hours. The mass and chemical composition of S_f > 100 or S_f 20-100 TRLs were not different between the fasting groups; postprandial S_f >100 but not 8,20-100 TRLs (mean±SD) was significantly lower in subjects with hypoalpha (200.4±64.8 nig/dL versus 110.6±50.9 mg/dL; analysis of variance, F test, p=0.04). In the hypoalpha subjects, the compositions of postprandial S_f > 100 TRLs were TG poor and cholesterol and phospholipid enriched (p<0.001) while the S_f 20-100 TRLs were enriched in cholesterol and phospholipid but relatively protein depleted ( p=0.002). When the hypoalpha subjects received gemfibrozil, the masses of both fasting (p=0.014) and postprandial (p=0.0004) S_f 20-100 TRLs were lower compared with baseline, a response that was accompanied by partial normalization of composition in postprandial hypoalpha S_f 20-100 TRLs. Our results indicate that in contrast to subjects with low plasma HDL-C and high TG levels, hypoalpha subjects with normal TG values did not display an increased postprandial response to fat feeding. Rather, the phenotype of hypoalpha appears to have a distinct metabolic component characterized by a reduced number of postprandial S_f >100 TRLs of abnormal composition. Gemfibrozil reduced the mass and altered the composition of S_f 20-100 TRLs in hypoalpha subjects.