Beyond cholesterol: The effect of varied dietary interventions on lipoprotein and postprandial lipid metabolism and assessment of postprandial lipemia on platelet and monocyte function

The goal of this dissertation was to examine the effect of varied diet interventions on plasma lipids and to study potential atherogenic mechanisms of postprandial lipemia. In the first 12 week crossover study 22 normocholesterolemic men and women consumed monounsaturated fatty acids provided by either whole almonds or almond oil as replacement for half of their typical daily fat intake. Both diets had a similar effect on lowering plasma total and LDL cholesterol and triglyceride (4%, 6% and 14% decreases, respectively) and increased HDL cholesterol (6%). Neither diet affected oxidation of LDL cholesterol.; In a second 12 week crossover study 24 normocholesterolemic men and women added whole apples (340 g/day) or apple juice (375 ml/day) to their daily diet. There was no affect on plasma lipid levels but apple juice consumption increased LDL cholesterol oxidation lag time by 20%; both diets reduced conjugated diene formation.; A third study examined fasting and postprandial lipid responses in 9 normocholesterolemic postmenopausal women after consuming 3 isocaloric, low fat, high carbohydrate diets for 4 week periods (31%, 23%, and 14% energy from fat). Fasting and peak postprandial levels of TG in plasma and TGRL plasma were higher during the 23% and 14% fat diet compared to diets with 31% and 37% fat. There was a significant effect of diet on postprandial, but not fasting levels of apo B-48 and apo B-100. Fasting and postprandial levels of TG, apo B-48 and apo B-100 were positively correlated.; The final study examined the effect of postprandial lipemia on activation of platelets and monocytes in 13 healthy young men. Multiparameter flow cytometry using monoclonal antibodies showed postprandial lipemia was associated with an increased percentage of platelets expressing P-selectin and the activated conformation of the fibrinogen receptor compared to fasting levels. The percentage of platelet-monocyte aggregates was increased by 36% at 3½ hours and by 43% at 6 hours postconsumption. The percentage of monocytes expressing intracellular cytokines, tumor necrosis factor-α and interleukin-1β, was increased several fold during the postprandial period.; In summary, these studies emphasize the importance of assessing the effects of varied dietary strategies on fasting and postprandial lipoproteins.