Analysis of the postprandial lipid metabolism: Use of a 3-point test

Objectives: The oral fat load tests used to study postprandial lipemia are complex and costly and time consuming. A simplified fat load test could be more convenient and more appropriate in routine clinical practice because o f the number of lipid determinations required. Research design and methods: We evaluated the capacity of a postprandial te st model that reduced the number of blood samples taken in thirty three nor mal weight controls and 17 normotriglyceridemic obese patients (study 1), 1 0 normolipidemic type 2 diabetic patients and 7 healthy controls (study 2), and 10 hyperlipidemic type 2 diabetic patients studied before and after hy polipidemic therapy (study 3). Blood samples were taken before and up to 8 hours after giving the oral fat load containing retinol. Triglyceride (TG a nd retinyl palmitate (RP) concentrations in the plasma, chylomicrons (CM) a nd non-chylomicron (nCM) fractions were measured. Postprandial lipid respon ses using conventional area under the curves (AUCc using 5 to 7 lipid deter minations) were compared to a 3-point test that uses only three sample poin ts to predict the area under the curve AUCp: triglycerides at TO, triglycer ides at average peak-time (T4), and triglycerides at T8). Results: The AUCc and AUCp for triglycerides and retinyl palmitate were hig hly correlated in each of the groups and whatever the lipid subfraction (r = 0.664 - 0.995, p < 0.0001). When incremental AUC (iAUC) were used, the co efficients of correlation for triglycerides remained highly significant bet ween AUCc and iAUCp (r = 0.718 - 0.979, p < 0.01 - 0.0001). The same trend of differences was found between cases and controls when AUCp was used inst ead of AUCc. The means of differences between AUCc and AUCp for triglycerid e values were small (0.34 - 0.74 mmol/L.h), and the confidence intervals we re acceptable considering the range of the AUCs values (5.60 to 79.8 mmol/L .h for plasma triglycerides). Conclusions: We found that data obtained with a simplified model of ALIC us ing only 3 points to analyse postprandial lipemia are well correlated with those obtained by conventional ALIC, and that the AUCp allows to the same c onclusions as AUCc when healthy subjects were compared to patients with alt ered postprandial metabolism. Thus AUCp may be a good evaluation of the AUC c, and the simplified 3-point protocol may well be used and suitable for st udies on large groups of subjects who are eligible for an oral fat load tes t.