Effects of dietary fish oil and oxidized cholesterol on the concentration of 7β‐hydroxycholesterol in liver, plasma, low density lipoproteins and erythrocytes of rats at various vitamin E supply

Abstract

Effects of dietary fish oil and oxidized cholesterol on the concentration of 7β β-hydroxycholesterol in liver, plasma, low density lipoproteins and erythrocytes of rats at various vitamin E supplyTwo experiments with rats were carried out to investigate the effect of dietary fish oil and oxidized cholesterol on the concentration of 7β-hydroxycholesterol, an oxysterol of mainly nonenzymatic origin, in liver, plasma, low density lipoproteins and erythrocytes of rats at different vitamin E supply. In Experiment 1, four groups of rats received diets with coconut oil or salmon oil (100 g/kg diet) and vitamin E concentrations of 40 or 240 mg α-tocopherol equivalents/kg. In Experiment 2, eight groups of rats received diets supplemented with pure or oxidized cholesterol (5 g/kg), coconut oil or salmon oil (100 g/kg diet) and vitamin E concentrations of 40 or 240 mg α-tocopherol equivalents/kg. Rats fed the salmon oil diets had significantly higher concentrations of 7β-hydroxycholesterol in liver, plasma, low density lipoproteins and erythrocytes than rats fed coconut oil diets. Rats fed the diets supplemented with oxidized cholesterol had significantly higher concentrations of 7β-hydroxycholesterol in all the samples analyzed than rats fed pure cholesterol. Increasing the dietary vitamin E concentration from 40 to 240 mg α-tocopherol equivalents/kg diet reduced the concentration of 7β-hydroxycholesterol in plasma; the concentrations of 7β-hydroxycholesterol in liver, low density lipoproteins and erythrocytes were not influenced by the dietary vitamin E concentration. The study suggests that diets with fish oil or oxidized cholesterol are critical with respect to the formation of 7β-hydroxycholesterol.

An excess dietary vitamin E concentration does not influence Nrf2 signaling in the liver of rats fed either soybean oil or salmon oil

“…Based on the recommendations of vitamin E for rat diets (18 mg α-tocopherol equivalents/kg diet) by NRC [ 18 ], the lowest dietary vitamin E concentration (25 mg α-tocopherol equivalents/kg diet) used in this study might have been sufficient for growing rats. The concentrations of total tocopherols in the liver of rats receiving the diets with 25 mg vitamin E/kg (which were around 25 to 30 nmol/g) were lower than those observed in rats with adequate dietary vitamin E supply which are typically in the range between 50 and 100 nmol/g [ 27 , 40 , 41 ]. However, α-tocopherol concentrations in the liver of rats fed the diets with 25 mg vitamin E/kg in this study were much higher than in rats with strict vitamin E deficiency which were in most cases even below 2 nmol/g [ 27 , 42 ].…”