POSTPRANDIAL EFFECTS OF THREE ISOCALORIC HIGH-FAT MEALS WITH DIFFERING LIPID LOADS ON TRIGLYCERIDES, OXIDATIVE STRESS, AND ENDOTHELIAL FUNCTION

Abstract

There have been numerous studies that compare the relationship of postprandial lipemia, oxidative stress, and endothelial dysfunction, but there is a lack of information as to the dose response nature of isocaloric high-fat meals (HFM). OBJECTIVE: To examine the dose response of lipemia (isocaloric HFM consisting of ~25%, ~50%, and ~75% fat) on plasma triglycerides (TG), oxidative stress, and endothelial function. It was hypothesized that the highest fat load would produce the greatest amount of oxidative stress and endothelial dysfunction; whereas each lipid load would be significantly higher than the previous. METHODS: Ten young inactive healthy men (22.8 ± 2.9 yrs) participated in three randomized challenge meals consisting of 25%, 50%, and 75% fat. Endothelial function, as measured by flow-mediated dilation (FMD) and blood samples were taken at baseline, 2 and 4 hours postprandial. Samples were assayed for blood biomarkers of TG and oxidative stress (3-nitrotyrosine (3- NT) and thiobarbuiuric acid reactive substances (TBARS)). RESULTS: TG were found to be significant with the 50% fat meal compared to the 25% fat meal (p = .001); but not between the other comparisons. Significance was also found for TG between 25% and 50% fat meals at 2 hours postprandial (p = .000) but not for any of the other comparisons. No changes were observed with either measure of oxidative stress. FMDs were found to be significant with the 50% fat meals compared to the 25% fat meal (p = .026), and the 75% fat meals compared to the 25% fat meal (p = .002); but not between the 50% and

75% fat meals (p = .142). Significance was also found for FMDs at 2 hours postprandial between 25%

and 75% fat meals (p = .027) and at 4 hours postprandial between 25% and 50% (p = .017) and 25% and

75% fat meals (p = .013). CONCLUSIONS: Thus, it appears young healthy inactive men do not exhibit a dose response in lipemia following an isocaloric HFM consisting of 25%, 50%, and 75% fat. Interpretation of the oxidative stress and endothelial dysfunction results are more difficult to interpret without a dose response in lipemia. However, other measures of oxidative stress should be considered before strong conclusions can be drawn.