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* Department of Nutrition and
Department of Internal Medicine, University of California, Davis, Davis, CA 95616; ** Department of Clinical and Experimental Medicine, Clinica Medica 4, University of Padova, 35128 Padova, Italy; and
Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Albany, CA, 94710
3 To whom correspondence should be addressed. E-mail: padavis{at}ucdavis.edu.
Walnut consumption is associated with reduced coronary vascular disease (CVD) risk; however, the mechanisms responsible remain incompletely understood. Recent clinical studies suggested that these mechanisms involve nonplasma lipidrelated effects on endothelial function. Male Golden Syrian hamsters (12 groups, n = 1015) were fed for 26 wk atherosclerotic, high-fat, hyperlipidemic diets with increasing concentrations of whole walnuts (61150 g/kg diet), or
-tocopherol (
-T, 8.181 mg/kg diet) and single diets with either walnut oil (32 g/kg diet) or pure
-tocopherol (
-T; 81 mg/kg diet) added. Aortic endothelin 1 (ET-1), an important endothelial regulator, was assayed as mRNA. Aortic cholesterol ester (CE) concentration along with other vascular stress markers (Cu/Zn and Mn superoxide dismutase, biliverdin reductase) and plasma lipid concentrations were determined. Hyperlipidemia (plasma LDL cholesterol
6 times normal) occurred in all groups. Aortic CE concentration, a measure of atherosclerotic plaque, was highest in the lowest
-T only group and declined significantly with increasing
-T. The aortic CE of all walnut groups was decreased significantly relative to the lowest
-T only group but showed no dose response. The diets did not produce changes in the other vascular stress markers, whereas aortic ET-1 mRNA levels declined dramatically with increasing dietary walnuts (to a 75% reduction in the highest walnut content group compared with the lowest
-T group) but were unaltered in the
-T groups or
-T group. The study results are consistent with those of human walnut feeding studies and suggest that the mechanisms underlying those results are mediated in part by ET-1dependent mechanisms. The contrasting results between the
-tocopherol or
-tocopherol diets and the walnut diets also make it unlikely that the nonplasma lipidrelated CVD effects of walnuts are due to their
-tocopherol or
-tocopherol content. Finally, the results indicate that the walnut fat compartment is a likely location for the components responsible for the reduced aortic CE concentration.
KEY WORDS: walnuts endothelin hamsters tocopherol atherosclerosis
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