Conjugated linoleic acid isomer effects in atherosclerosis: growth and regression of lesions.

Conjugated linoleic acid (CLA), a mixture of positional and geometric isomers of octadecadienoic acid, has been shown to inhibit experimentally induced atherosclerosis in rabbits and also to cause significant regression of pre-established atheromatous lesions in rabbits. The two major CLA isomers (cis9,trans11 and trans10,cis12), now available at 90% purity, have been tested individually for their anti-atherogenic or lesion regression potency. The two major isomers and the mixture were fed for 90 d to rabbits fed 0.2% cholesterol. Atherosclerosis was inhibited significantly by all three preparations. The two CLA isomers and the isomer mix were also fed (1.0%) as part of a cholesterol-free diet for 90 d to rabbits bearing atheromatous lesions produced by feeding an atherogenic diet. A fourth group was maintained on a cholesterol-free diet. On the CLA-free diet atherosclerosis was exacerbated by 35%. Reduction of severity of atheromatous lesions was observed to the same extent in all three CLA-fed groups. The average reduction of severity in the three CLA-fed groups was 26 +/- 2% compared with the first control (atherogenic diet) and 46 +/- 1% compared with the regression diet. Insofar as individual effects on atherosclerosis were concerned, there was no difference between the CLA mix and the cis9,trans11 and trans10,cis12 isomers. They inhibit atherogenesis by 50% when fed as a component of a semipurified diet containing 0.2% cholesterol; and when fed as part of a cholesterol-free diet, they reduce established lesions by 26%. Reduction of atheromata to the observed extent by dietary means alone is noteworthy.

Cholesterol vehicle in experimental atherosclerosis 24: avocado oil.

OBJECTIVE: To determine atherogenicity of avocado oil relative to saturated (coconut oil), monounsaturated (olive oil) and polyunsaturated (corn oil) fats. METHODS: New Zealand White rabbits were fed a semipurified diet containing 0.2% cholesterol and 14% fat for 90 days. They were then necropsied and severity of atherosclerosis was determined visually. RESULTS: Coconut oil was the most atherogenic fat. Corn oil was only slightly less atherogenic than either olive or avocado oils. Percentage of serum HDL cholesterol was highest in the rabbits fed the two monounsaturated fats. CONCLUSION: Avocado oil is of the same order of atherogenicity as corn oil and olive oil.

Serum and aortic levels of phytosterols in rabbits fed sitosterol or sitostanol ester preparations.

Campesterol is present in all the phytosterol-containing dietary hypocholesterolemic agents in current use. Campesterol is absorbed more efficiently than sitosterol, and the question of its possible atherogenicity has been raised. To test this possibility, rabbits were fed either a semipurified, cholesterol-free diet that has been shown to be atherogenic for this species or the same diet augmented with 0.5 g of phytosterol-rich diet preparations (spreads) containing either sitosterol or sitostanol. The diets contained 295 mg phytosterol per 100 g. After 60 d, serum cholesterol levels in the two phytosterol groups were 78 +/- 4 mg/dL (sitosterol) and 76 +/- 4 mg/dL (sitostanol), respectively. The serum cholesterol level of rabbits fed the control diet was 105 +/- 8 mg/dL. Serum campesterol (microg/mL) levels were higher than sitosterol or sitostanol levels in all groups. Aortic phytosterols were present in nanogram quantities compared to cholesterol, which was present in microgram quantities. The ratio of campesterol/sitosterol/sitostanol in the aortas was: control, 1.00:0.43:0.02; sitosterol, 1:00:0.32:0.01; sitostanol, 1:00:0.34:0.11. Aortic campesterol was present at 4% the concentration of aortic cholesterol, sitosterol at 1.4%, and sitostanol at 0.14%. Aortic lesions were not present in any of the animals.