Postprandial effects of three isocaloric high-fat meals with differing lipid loads on triglycerides, oxidative stress, and endothelial function

BACKGROUND: 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.