Isoflavone and Protein Constituents of Lactic Acid-Fermented Soy Milk Combine to Prevent Dyslipidemia in Rats Fed a High Cholesterol Diet

Abstract

A high cholesterol diet induces dyslipidemia. This study investigated whether isoflavone aglycones in lactic acid-fermented soy milk (LFS) improve lipid metabolism in rats fed a high cholesterol diet. Male Sprague-Dawley rats aged seven weeks were fed an AIN-93G diet, a 1% cholesterol diet (a high cholesterol diet), a high-cholesterol diet containing 4% isoflavone extract of LFS (LFS extract diet), a high-cholesterol diet containing 19.4% ethanol-washed LFS (ethanol-washed LFS diet, isoflavone-poor diet), or a high cholesterol diet containing 23.2% intact LFS (intact LFS diet) for five weeks. The plasma total cholesterol (TC) level was increased in the rats fed the LFS extract diet compared with those fed the high cholesterol diet. The TC level was decreased by the intact LFS and ethanol-washed LFS diets. The cholesterol-lowering effect was stronger in the rats fed the intact LFS diet than those fed the ethanol-washed LFS diet. The plasma triglyceride (TG) level was unchanged in the rats fed the LFS extract diet, but it decreased in rats fed the intact LFS and ethanol-washed LFS diets. Although, compared with the high cholesterol diet, the LFS extract and ethanol-washed LFS diets did not reduce hepatic cholesterol and TG, both levels were remarkably lowered by the intact LFS diet. These results suggest that the improvement in lipid metabolism of rats fed a high-cholesterol diet containing LFS isoflavone aglycones is not due to an independent effect but due to a cooperative effect with soy protein.

Isoflavone Aglycones and Oligopeptides in Lactic Acid-Fermented Soy Milk Differentially Regulate Lipid Metabolism-Related Gene Expression

“…Additionally, an increase in the amount of isoflavone aglycones in fermented soymilk enhances this lipid metabolism-modulating effect [21]. Although we found that the administration of only isoflavone aglycone fraction from fermented soymilk did not improve lipid metabolism in rats fed a high-cholesterol diet, isoflavone aglycon fraction improved lipid metabolism when given together with soy protein [22]. However, the isoflavone fraction used in our pervious paper, ethanol extract from fermented soymilk, contained both isoflavone aglycones and soy peptides [22].…”

“…Although we found that the administration of only isoflavone aglycone fraction from fermented soymilk did not improve lipid metabolism in rats fed a high-cholesterol diet, isoflavone aglycon fraction improved lipid metabolism when given together with soy protein [22]. However, the isoflavone fraction used in our pervious paper, ethanol extract from fermented soymilk, contained both isoflavone aglycones and soy peptides [22]. Peptides and protein hydrolysates reportedly exhibit greater bioactivities relative to intact proteins or amino acid mixtures [3] [23].…”

“…It is therefore assumed that soy peptides, especially those with a molecular weight < 1 kDa, exert lipid metabolism-modulating effects. We previously reported that the isoflavone aglycone fraction from fermented soymilk was not sufficient to improve lipid metabolism in rats fed a highcholesterol diet [22]. However, the mechanism by which fermented soymilk ethanol extract, mixture of soy oligopeptides and isoflavone aglycones, affects lipid metabolism in rats fed an AIN-93G diet remains unclear.…”

Identification of Characteristic Components and Foodstuffs in Healthy Japanese Diet and the Health Effects of a Diet with Increased Use Frequency of these Foodstuffs

“…However, in fermented foods such as miso and soy sauce, the sugar is removed to form the aglycone compounds. In a comparative study of aglycones and glycosides, aglycones were found to have better absorption than glycosides and to improve lipid metabolism in liver …”

“…In a comparative study of aglycones and glycosides, aglycones were found to have better absorption than glycosides and to improve lipid metabolism in liver. [28,29] Stearidonic acid is an omega-3 polyunsaturated fatty acid (similar to eicosapentaenoic acid and docosahexaenoic acid) that is present in vegetable oils and seaweed. [30] Animal studies have shown that ingestion of stearidonic acid increases the levels of eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid in tissues, [31] which suggests that stearidonic acid intake could be beneficial to health.…”