Five healthy male subjects and five patients with mild
hypertriglyceridemia were studied following the administration of 800-kcal liquid meals containing 40% of energy from fat, 40% from
carbohydrate, and 20% from
protein. On the first day of the study, the fat source was
corn oil (long-chain
triglyceride), whereas medium-chain
triglyceride (MCT) oil was used the second day. Meals were infused into the duodenum using a peristaltic pump. Plasma samples, obtained at hourly intervals for 8 hours, were analyzed for
glucose,
cholesterol,
triglyceride, and
apolipoproteins C-II and C-III. The distribution of
apoC-II and
apoC-III between ultracentrifugally-separated
triglyceride-rich
lipoproteins (TRL) and
high-density lipoproteins (HDL) was also evaluated. The patient group had significantly elevated fasting levels of
triglyceride,
apoC-II and
apoC-III, as well as much greater lipemic response to the meal containing
corn oil. In both groups, TRL
apoC-II and
apoC-III levels were positively correlated with the
triglyceride level as it increased following the
corn oil meal. These correlations were also observed in the normal subjects when the MCT oil meal was administered, even though changes in plasma
triglycerides were minimal. In normal subjects, whole plasma levels of
apoC-II and
apoC-III decreased significantly following the meal containing
corn oil, whereas no net changes occurred following the MCT oil meal. In hypertriglyceridemic subjects, small decreases in plasma
apoC-II and
apoC-III levels occurred after both meals, although the changes in
apoC-II were not statistically significant. The tendency for decreased plasma
apoC levels following alimentary
lipemia confirms previous reports, and provides further data to support the concept that some
apoC is cleared from plasma in association with TRL remnants. The finding that mildly hypertriglyceridemic subjects responded similarly to both conventional fat and MCT may indicate that their rates of remnant clearance were similar following the two meals.