RA and atherosclerosis

Several studies on animal models demonstrated that CLA could retard the development of atherosclerosis. The CLA used in these studies was a mixture of isomers in which RA and trans-10, cis- 2-Ci%a were predominant and present in near equal amounts. Because these two isomers can show identical biological effects in some tissues and dissimilar effects in other tissues, a benefit for RA in these studies cannot be assumed. Nevertheless, there is emerging evidence that RA has anti-atherogenic properties. 

Kritchevsky (1999) reviewed studies conducted with colleagues, which demonstrated that dietary CLA could inhibit the development of cholesterol-induced atherosclerosis in hamsters and in rabbits. Reduction in the severity of pre-existing lesions was also noted. Recently, Kritchevsky (2003) fed rabbits a diet containing 1% of relatively pure RA. This diet significantly inhibited the formation of atherosclerotic lesions in the aortic arch and thoracic aorta, compared to a diet without RA. 

In most cases, the reduced incidence of atherosclerosis in animals fed CLA or RA was not accompanied by a decrease in plasma total or LDL-cholesterol level or an increase in HDL-cholesterol level. Thus, other mechanisms must be responsible for the prevention of atherosclerosis. Atherosclerosis is recognized nowadays as a chronic inflammatory disease, and RA has been shown to exhibit a number of important anti-inflammatory properties (Yu et al., 2002)  

RA was also shown to inhibit the production of series-2 prostaglandins and thromboxanes in endothelial cells from human saphenous vein, which is the vein commonly used in coronary bypass surgery (Urquhart et al., 2002). 

RA is a potent activator of PPARa and PPAR-y (Belury et al., 2002). Yu et al. (2002) found that inhibition of pro-inflammatory products by RA was associated with PPAR-y activation. Likewise, Toomey et al. (2003) showed that the regression of preestablished atherosclerosis in apo E- mice fed RA is associated with an increased expression of PPARy. 

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