Effect Of Dietary Fat Type In Combination With High Protein On Plasma Homocysteine Levels And Selected Markers Of Cardiovascular Heart Disease Risk In Human Volunteers

Abstract

Dietary fat type is known to modulate plasma lipid profile but its effects on plasma homocysteine, inflammatory markers and other lipid mediators are unclear. The main objective of the study is to investigate the effects of high-protein Malaysian diets prepared with palm olein, coconut oil or virgin olive oil on plasma homocysteine and selected markers of cardiovascular disease (CVD) in healthy Malaysian adults. A randomised; single-blind, crossover intervention with 3 dietary sequences of 5wk each and a 2 wk wash-out in between were conducted on 45 healthy subjects (36 females, 9 males; aged 30-55 years). The three different test fats, namely palmitic acid(16:O)-rich palm olein (PO), lauric + myristic acids(12:0 + 14:0)-rich coconut oil (CO), and oleic acid(18:1)-rich virgin olive oil (OO), were incorporated at 30% kcal into high-protein (20% kcal) Malaysian diets and provided as breakfast, lunch and dinner to the subjects according to a Latin-square design. During each dietary period, 2-hr postprandial blood samples were collected at the end of the 4th week and 12-hour fasting samples at the end of the 5th week, and analysed for plasma total homocysteine (tHcy) and selected markers of cardiovascular disease. No significant differences were observed on the effects of the three experimental diets on plasma tHcy and the inflammatory markers- high sensitive C-reactive protein (hsCRP), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-1β (IL-1 β), tumor necrosis factor-α (TNF- α) and interferon-γ (IFN- γ) as well as cells adhesion molecules - soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1) and member of the selectin family (E-selectin) in the postprandial and fasting states. Compared to PO and CO diets, OO diet lowered fasting plasma leukotriene B4 (LTB4). No significant difference was also found lowered in postprandial plasma LTB4 comparing OO vs CO diet but not PO. Compared to OO diet, PO diet increased fasting serum 6-keto prostaglandin F-1α (PGFlα) but not different from CO diet. However, the ratio of the serum PGFlα to 11-dehydro thromboxane B2(TXB2) was not altered between the three diets. The diets prepared with PO and OO had comparable non-hypercholesterolemic effects; postprandial TC for both diets and all fasting lipid indices for the OO diet were significantly lower (p < 0.05) compared with the CO diet. CO diet was found to decrease postprandial lipoprotein (a) (Lp(a)) unlike PO and OO. No significant differences were found in serum triglycerides (TAG), total-/HDL cholesterol, apolipoprotein A-1 (apoA-1) and apolipoprotein B (apoB) between the diets.

Saturated fatty acid-rich diets prepared with either PO and CO, or a virgin OO diet high in oleic acid did not alter postprandial nor fasting plasma levels of tHcy and the selected inflammatory markers measured. However, OO diet was suggested to have beneficial effect in lipid mediators by lowering serum LTB4 compare to the other two diets. PO diet was suggested to have favourable effect on thrombosis tendency by raising PGF1α compared to OO diet but not CO. The experimental diets prepared with PO and OO had comparable non-hypercholesterolemic effects, while the 12:0+14:0-rich CO diet was more hypercholesterolemic compared with the 18:1-rich OO diet in the human volunteers.