Objective: The effects of three dietary proteins (casein, cod, soy) and low dose simvastatin, an inhibitor of hydroxymethyl-glutaryl coenzyme A (HMG-CoA) reductase, on serum lipids were investigated.
Methods: New Zealand rabbits were fed purified diet (20% protein, 11% fat and 0.06% cholesterol) for 28 days. Animals received either 1.4 mg simvastatin or placebo orally during the last 14 days. A randomized 3 x 2 factorial design was used for the administration of diet and drug treatments.
Results: Mean food intake and body weight of the animals in all groups were similar. In placebo groups, soy protein decreased (p = 0.06) total cholesterolemia with significantly (p = 0.009) lower high-density lipoprotein (HDL) cholesterol, and significantly (p = 0.004) higher very low-density lipoprotein (VLDL) triglycerides (TG), compared to animal proteins. Addition of low dose simvastatin to soy protein induced a further decrease of serum total cholesterol, decreased VLDL and low-density lipoprotein (LDL) cholesterol, and LDL (apolipoprotein B), as well as improved VLDL-TG and HDL cholesterol levels. No similar reduction was seen when simvastatin was combined with casein or cod protein.
Conclusion: These results show that low dose simvastatin may enhance the hypocholesterolemic effect of soy protein compared to animal proteins in the rabbit.