A Diet Rich in Alpha-Linolenic Acid Diminishes Atherosclerosis in Apolipoprotein E-Deficient Mice and Reduces Arachidonic Acid in Red Cell Membranes.

Background: The beneficial effects of long-chain n-3 fatty acids (LC-n-3 FA) of marine origin on lipids and cardiovascular events are well documented. However, the relevance of plant-derived C18-n-3 FA (alpha-linolenic acid, ALA) on atherogenesis and on arachidonic acid (AA, the proaggregatory precursor of thromboxane) remains unclear. Furthermore, the capacity for chain elongation is thought to be minimal in mammals. We have reported on the potential benefits of increased concentrations of ALA in alpine milk products (“The alpine paradox”).

Aims: We tested if an ALA-rich diet

• reduces atherosclerosis,

• induces a favorable lipid profile including a reduced content of AA in red cell membranes, liver and adipose tissue, and

• promotes chain elongation of ALA into LC-n-3 FA.

Methods and Results: Eight weeks old male apolipoprotein E knockout (ApoE^{− /−}) mice were fed a 0.15% cholesterol diet for 16 weeks containing either a high ALA (high, 7g/100g; n=10) or a low ALA content (low, 0.03g/100g; n=10). ALA was given as flaxseed oil, the control diet was compensated with cocoa butter. Plaque area in the aortic arch as quantified by oil-red O staining was reduced by 53% (P<0.05) in the high ALA group. Furthermore, T cells, expression of VCAM-1 and TNF-α in plaques were all diminished in mice fed a high ALA diet (P<0.05). Weight gain was similar in both groups. The content of LC-n-3 FA in red cell membranes, liver and adipose tissue was analyzed by gas chromatography and given as FA percentage (Table). The high ALA diet induced a marked increase in ALA incorporation in all tissues. In addition, we found a 5x shift in the red cell LC-n-3 FA (EPA, DPA, and DHA) content a measure of chain elongation which was even 7x in the liver. Adventitial adipose tissue contained higher concentrations of LC-n-3 FA than the subcutaneous or the perirenal fat. In addition, ALA strongly reduced AA in various tissues: We found an almost 5- fold reduction in in red cell AA and the liver samples contained less than half of the AA content. The differences in adipose tissues were less pronounced.

Conclusions: A diet rich in ALA decreases atherosclerosis, T cells and the expression of VCAM-1 and TNF-α in ApoE^−/− mice. These beneficial findings are associated with a favorable FA profile (increased chain elongation into LC-n-3 FA) and reduced AA in red cells, liver, and adipose tissue. Given the limited fishery resources, plant-derived ALA may represent an attractive nutritional supplement with atheroprotective and anti-inflammatory effects.