Excessive postprandial triglyceride (TG) responses despite normal fasting TG levels have been described in single cases within small groups of healthy subjects and in patients with obesity or precocious atherosclerosis, known to be associated with high insulin fasting levels. To clarify this association, fasting and postprandial TG and insulin levels were studied in 113 healthy young (25.7 +/- 2.6 years), normal weight (body mass index 20.8 +/- 2.3 kg/m2) male subjects who were selected from among 117 subjects on the basis of TG fasting levels < 200 mg/dl. After a 12-hour fast a standardized liquid lipid load was administered containing 58 g mainly saturated fat and 1,017 kcal energy. Both fasting TG values and postprandial TG peak values showed bimodal frequency distributions. Statistical analysis of fasting TG discriminated two groups: a low fasting TG group with normally distributed values < 150 mg/dl (mean +/- SEM: 79.5 +/- 2.7 mg/dl; n = 104) and a high fasting TG group > 150 mg/dl (194.5 +/- 7.2 mg/dl; n = 13). Likewise, two groups could be differentiated according to their maximal postprandial TG response (TG max) to the lipid load: (1) normal responders with TG max < 260 mg/dl (mean +/- SEM: 123 +/- 4.8 mg/dl; n = 96) and (2) high responders with TG max > 260 mg/dl (272.5 +/- 20.5 mg/dl; n = 17). Fasting TG and TG max were highly correlated (r = 0.745; p < 0.0001). However, 9 of 17 (53%) high responders had fasting TG < 150 mg/dl, which means that the prediction of high response is only 47.0% based on fasting TG values. Fasting insulin levels were significantly higher in high responders than in normal responders, whereas they did not differ between the low and high fasting TG group. In conclusion, the bimodal frequency distribution of TG max after a lipid load permitted the differentiation of two groups, normal responders and high responders, with higher fasting insulin levels, which might indicate a link to the metabolic syndrome.

In 13 healthy, male nonsmokers (mean age: 25.7 ± 2.4 years) with normal fasting triglycerides we investigated postprandial changes of triglycerides in several lipoprotein fractions. After a 12-hour overnight fast they ingested a standardized lipid load (1,017 kcal) including 30,000 IU retinyl palmitate. Postprandially, total triglycerides increased significantly (p < 0.001) to a peak value of 221 ± 81 mg/dl at 5 h. Two subjects had an exceptionally strong triglyceride response (peak values: 363 and 390 mg/dl). They had the highest levels of retinyl palmitate in the chylomicron and the nonchylomicron fraction, and one of them showed elevated intermediate-density lipoprotein values throughout the test period. In addition, they showed an altered early and an increased late postprandial insulin response. Thus, our data provide evidence that an exaggerated postprandial triglyceride response may point to an increased atherogenic risk even in healthy subjects with normal fasting triglycerides.

No abstract

No abstract

No abstract