Simultaneous intake of oat bran and atorvastatin reduces their efficacy to lower total cholesterol and atherosclerosis in ldl-receptor-deficient mice

Introduction: Both oat bran, rich in the water-soluble fiber b-glucan, and statins lower serum total cholesterol (TC). When used simultaneously both compounds may lower TC additively. However, there might be a risk for a lower statin bioavailability when oat bran is added to the diet. Objectives: To investigate the effects of separate and simultaneous dietary intake of atorvastatin (ATO) and oat bran on TC levels and the degree of atherosclerosis in mice. Methods: Ninety female LDL-receptor-deficient mice were fed a Western-type diet containing either a low dose (0.0025%), high dose (0.01%) or no ATO, with or without oat bran (27%) (n = 15 per group) for 16 weeks. Results: Both ATO and oat bran were effective in reducing serum TC (low ATO: -30%; high ATO: -51%; oats: -21%, compared to control (no ATO/no oats)). When oat bran was added to a low dose ATO, the cholesterol-lowering effects were about 50% lower (reduction in TC: -15%) compared to the low ATO diet alone, whereas TC levels decreased to a similar extent in the groups fed a high dose ATO, with or without oats (reduction in TC in both groups: -50%). Atherosclerotic lesion development showed a similar pattern. Conclusion: The efficacy of oat bran and atorvastatin to lower TC and atherosclerosis is reduced after simultaneous intake. We hypothesize that oat bran decreases the intestinal absorption of atorvastatin and consequently its cholesterol-lowering effects. Future studies should focus on understanding the mechanism and the influence of intake timing and type of statin and dietary fiber.