[A comparative evaluation of the effect of soy protein and its enzymatic hydrolysate on lipid metabolism in male Wistar rats with induced obesity].

Among various food proteins, soybean proteins have the greatest traditions of application for the dietary correction and prevention of lipid metabolism disorders and related complications. Aim. In an in vivo experiment using male Wistar rats, the lipid-lowering properties of soy protein and its enzymatic hydrolysate were tested to evaluate their possible use as ingredients of specialized foods. Material and methods. Animals were randomly divided into 3 groups: control group G1 and 2 experimental groups G2 and G3. The total duration of the experiment was 70 days. The animals of the control group G1 were fed with high-lipid semi-synthetic diet. Animals of the experimental groups G2 and G3 received the same high-fat semi-synthetic diet, but with a 50% replacement of casein with soy protein isolate (SPI) and enzymatic hydrolyzate of SPI (EHSPI), respectively. The blood glucose was measured once per 2 weeks. At the end of the experiment on the 71st day the level of glycated hemoglobin was determined in the blood; the levels of triglycerides, cholesterol, high density lipoproteins (HDL), low density lipoproteins (LDL) and the concentration of malon dialdehyde were determined in the serum. Results and discussion. Starting from the 6th week of the experiment and prior to its completion, the average food intake of animals from the G3 group was significantly (р<0.05) lower compared to animals of the G1 control group. The food intake of animals of group G2 was significantly (р<0.05) reduced compared with this indicator for animals of group G1, starting from the week 8 of the experiment and prior to its completion. The monitoring of the body weight gain did not reveal significant differences between all groups of animals, despite differences in the food intake. Replacing casein in the diet by 50% with SPI had a pronounced antioxidant and cholesterol-lowering effect. The total cholesterol content (1.65±0.05 mmol/l) decreased significantly (р<0.05) due to a decrease in LDL (0.90±0.03 mmol/l), and malon dialdehyde level lowered (3.7±0.5 μmol/l, р<0.05) in the serum of group G2 rats compared with animals of the control group G1 (2.01±0.13 and 1.12±0.09 mmol/l; 5.1±0.4 μmol/l, respectively). Replacing casein by 50% with EHSPI in the diet of G3 rats was unfavorable, significantly (р<0.05) increasing the level of total cholesterol (2.76±0.16 mmol/l) and cholesterol in LDL (1.66±0.12 mmol/l) in blood of these animals compared with animals of both comparison groups G1 and G2. Conclusion. A preclinical comparative study of the cholesterol-lowering and antioxidant properties of the SPI substantiates the prospect of its following clinical trials with the aim of including into the composition of specialized foods for prevention and diet therapy of the disorders of endogenous cholesterol homeostasis.