Ethanol-extracted soy protein isolate does not modulate serum cholesterol in Golden Syrian hamsters: A model of postmenopausal hypercholesterolemia

Soy protein consumption has been linked to reduction in hypercholesterolemi a, a risk for coronary heart disease. However, to what extent soy protein i tself or its non-nutritive components, e.g., isoflavones and saponins, exer t this cholesterol-lowering effect requires further investigation. To evalu ate the effect of the protein component alone on lipid variables, ethanol-e xtracted, isoflavone-depleted soy protein isolate (SPe) was studied in ovar ian hormone-deficient hamsters. Forty-eight 6-month-old female Golden Syria n hamsters were either sham-operated or ovariectomized and fed casein-based or SPe-based diets for 70 d. Ovariectomy, but not protein source, signific antly (P < 0.05) increased serum phospholipids and total, non-high density lipoprotein, free and esterified cholesterol concentrations. Serum HDL chol esterol concentrations were not altered with either treatment. No significa nt differences were observed in liver total lipids or liver total cholester ol among the groups. Soy protein isolate, however, lowered serum triglyceri de concentrations in both sham-operated and ovariectomized hamsters. These findings confirm the ovariectomized hamster as a model of postmenopausal hy percholesterolemia. The results are consistent with earlier observations th at isoflavones or other nonprotein components, perhaps in combination with soy protein, play an important role in exerting this hypocholesterolemic ef fect. Further studies are needed to investigate whether isolated nonprotein components of soy would be able to prevent the ovarian hormone deficiency- associated rise in serum cholesterol regardless of dietary protein source.