Effects of the ratio of polyunsaturated and monounsaturated fatty acid to saturated fatty acid on rat plasma and liver lipid concentrations

Jun 13, 1998Lipids

How the balance of healthy to saturated fats affects fat levels in rat blood and liver

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Abstract

A high dietary intake of monounsaturated fatty acids (MUFA) may lead to increased plasma total cholesterol and liver cholesterol levels in rats.

Rats fed a diet with 28.1 energy% MUFA exhibited increased plasma total cholesterol, triacylglycerol, and phospholipid compared to those on a low-MUFA diet.
Significant increases in plasma very low density lipoprotein (VLDL) cholesterol and triglycerides were observed with high MUFA consumption, while high density lipoprotein (HDL) levels remained unchanged.
The high-MUFA diet resulted in greater liver cholesterol accumulation but less triacylglycerol accumulation.
When saturated fatty acid (SFA) was held constant, higher MUFA levels correlated with increased plasma and liver cholesterol compared to a low-MUFA diet.
A higher PUFA and MUFA/SFA ratio significantly decreased plasma HDL cholesterol and triacylglycerol levels.
The PUFA/SFA ratio alone did not predict changes in plasma cholesterol, indicating that high dietary MUFA may elevate lipid levels.

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The effects of dietary monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid + MUFA/saturated fatty acid (PUFA + MUFA/SFA) ratio on plasma and liver lipid concentrations were studied. In experiment I, when rats were fed with 40% fat (energy%, PUFA/SFA ratio 1.0) and 1% (w/w) cholesterol (C) diets for 21 d, a large amount of MUFA (28.1 energy%, PUFA + MUFA/SFA = 5.7) in the diet was found to increase the plasma total C, triacylglycerol (TAG), and phospholipid (PL) as compared with the low-MUFA diet (7.0 energy%, PUFA + MUFA/SFA = 1.4). The plasma very low density lipoprotein (VLDL)-C, VLDL-TAG, VLDL-PL, and low density lipoprotein (LDL)-C increased significantly in the high-MUFA diet group, but high density lipoprotein (HDL)-C did not change significantly. The high-MUFA diet resulted in greater accumulation of liver C but lesser accumulation of TAG. In experiment II, when dietary SFA was fixed at a certain level (13.2 energy%; PUFA + MUFA/SFA = 2.0), rats given a larger amount of MUFA (23.1 energy%; PUFA/MUFA = 0.2; MUFA/SFA = 1.8) showed higher plasma and liver C levels than did the low-MUFA diet (7.7 energy%; PUFA/MUFA = 2.5; MUFA/SFA = 0.6). When PUFA was fixed at a certain level (24.4 energy%), there was not a significant difference in the plasma C level between the high- and low-MUFA dietary groups (PUFA + MUFA/SFA = 4.8 and 8.4), but the higher PUFA + MUFA/SFA diet, which was high in MUFA/SFA ratio, significantly decreased the plasma HDL-C and TAG levels. However, when MUFA content was fixed at a certain level (16.4 energy%), no significant difference was observed between the two groups with different PUFA/SFA ratios of 0.2 and 4.1, but liver C level was raised in the higher PUFA/SFA diet. It appears that the PUFA/SFA ratio alone is unsuitable to predict the change of plasma C level, because a large amount of dietary MUFA may lead to an increase of plasma and liver lipids in rats. It seems that the prerequisites for keeping low plasma and liver C are (i) low MUFA/SFA ratio, (ii) high PUFA/MUFA ratio, and (iii) PUFA + MUFA/SFA ratio not to exceed 2.

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Effects of the ratio of polyunsaturated and monounsaturated fatty acid to saturated fatty acid on rat plasma and liver lipid concentrations

Abstract

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