Soy protein without isoflavones reduces aortic total and cholesterol ester concentrations greater than soy protein with isoflavones compared with casein in hypercholesterolemic hamsters

The addition of whole soy flour to cafeteria diet reduces metabolic risk markers in wistar rats

BACKGROUND

Soybean is termed a functional food because it contains bioactive compounds. However, its effects are not well known under unbalanced diet conditions. This work is aimed at evaluating the effect of adding whole soy flour to a cafeteria diet on intestinal histomorphometry, metabolic risk and toxicity markers in rats.

METHODS

In this study, 30 male adult Wistar rats were used, distributed among three groups (n = 10): AIN-93 M diet, cafeteria diet (CAF) and cafeteria diet with soy flour (CAFS), for 56 days. The following parameters were measured: food intake; weight gain; serum concentrations of triglycerides, total cholesterol, HDL-c, glycated hemoglobin (HbA1c), aspartate (AST) and alanine (ALT) aminotransferases and Thiobarbituric Acid Reactive Substances (TBARS); humidity and lipid fecal content; weight and fat of the liver. The villous height, the crypt depth and the thickness of the duodenal and ileal circular and longitudinal muscle layers of the animals were also measured.

RESULTS

There was a significant reduction in the food intake in the CAF group. The CAFS showed lower serum concentrations of triglycerides and serum TBARS and a lower percentage of hepatic fat, with a corresponding increase in thickness of the intestinal muscle layers. In the CAF group, an increase in the HbA1c, ALT, lipid excretion, liver TBARS and crypt depth, was observed associated with lower HDL-c and villous height. The addition of soy did not promote any change in these parameters.

CONCLUSIONS

The inclusion of whole soy flour in a high-fat diet may be helpful in reducing some markers of metabolic risk; however, more studies are required to clarify its effects on unbalanced diets.

Cholesterol-lowering activity of soy-derived glyceollins in the golden Syrian hamster model

Hypercholesterolemia is one of the major factors contributing to the risk of cardiovascular disease (CVD), which is the leading cause of death in developed countries. Consumption of soy foods has been recognized to lower the risk of CVD, and phytochemicals in soy are believed to contribute to the health benefits. Glyceollin is one of the candidate phytochemicals synthesized in stressed soy that may account for many unique biological activities. In this study, the in vivo cholesterol-lowering effect of glyceollins was investigated. Male golden Syrian hamsters were fed diets including (1) 36 kcal% fat diet, (2) 36 kcal% fat diet containing 250 mg/kg diet glyceollins, or (3) chow for 28 days. Hepatic cholesterol esters and free cholesterol, hepatic total lipid content, plasma lipoproteins, fecal bile acid, fecal total cholesterol, and cholesterol metabolism related gene expressions were measured. Glyceollin supplementation led to significant reduction of plasma VLDL, hepatic cholesterol esters, and total lipid content. Consistent with changes in circulating cholesterol, glyceollin supplementation also altered expression of the genes related to cholesterol metabolism in the liver. In contrast, no change in plasma LDL and HDL, fecal bile acid, or cholesterol content was observed. The cholesterol-lowering effect of glyceollins appeared not to go through the increase of bile excretion. These results supported glyceollins' role as novel soy-derived cholesterol-lowering phytochemicals that may contribute to soy's health effects.