[Evaluation of the combined effect of Arthrospira platensis biomass phycyanin concentrate and soy protein on male Wistar rats fed a high-fat diet with added cholesterol].

One of the approaches to the prevention and dietary correction of carbohydrate and lipid metabolism disorders is the development of new functional foods with the ingredients containing bioactive compounds with hypolipidemic and hypoglycemic properties. Soybean protein and biomass of Arthrospira platensis cyanobacteria containing phycobiliproteins (C-phycocyanin and allophycocyanin) are the sources of such bioactive compounds. The aim of the research was to evaluate the combined effect of phycocyanin concentrate (in two dosages of 30 and 300 mg/kg body weight) and soy protein (50% of the protein in the diet) on disorders, induced in Wistar male rats by consumption of high-fat diet with 2% cholesterol. Material and methods. A 108-day study was performed on 60 growing male Wistar rats. Animals of the control group K1 received a standard semi-synthetic diet. Disturbances in rats of the experimental group G2 were caused by increasing the proportion of the fat component in the diet (up to 29%), adding 2% cholesterol and replacing 20% of cornstarch with sucrose. In experimental groups G3, G4, and G5, 50% of casein in the high-fat diet was replaced with soy protein isolate. Additionally, phycocyanin concentrate was added to the diets of rats in groups G4 and G5 in quantities of 30 and 300 mg/kg of body weight (in terms of phycocyanin), respectively. In all animals, insulin resistance test was conducted, body composition was measured using magnetic resonance relaxometry, blood serum biochemical parameters of protein, lipid, purine metabolism and liver function, and the triglyceride and cholesterol liver levels were determined by spectrophotometric methods using a biochemical analyzer; leptin, ghrelin, C-peptide, insulin, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase and hydroperoxides were determined in blood serum using enzyme immunoassay. Results. The inclusion of only soy protein isolate into the high-fat diet with cholesterol had a hypoglycemic effect, preventing the development of insulin resistance, and led to a reliable decrease in blood level of lipid peroxides (p=0.011) compared to G2 group. The combined introduction of phycocyanin concentrate at a dose of 300 mg/kg body weight and soy protein into the diet significantly reduced blood levels of cholesterol (p=0.022), lipid peroxides (p=0.001) and ALT activity (p=0.032) compared to G2. At the same time, animals of both these groups retained disorders in hormonal status (increased leptin and ghrelin level), antioxidant status (elevated level of MDA and SOD) at the same level as for animals consuming high-fat diet with 2% cholesterol. Phycocyanin concentrate at a dosage of 30 mg/kg body weight together with soy protein in the diet prevented the development of insulin resistance (p=0.049) and reduced serum glucose level (p=0.025); exerted an antioxidant effect, normalizing the level of lipid peroxides (p=0.047), MDA (p=0.015) and SOD (p=0.038), significantly reduced the level of leptin (p=0.037) and ghrelin (p=0.028) compared to animals consuming a high-fat diet with 2% cholesterol. Conclusion. The results characterizing the absence of a beneficial effect of phycocyanins at a dose of 300 mg/kg body weight indicate their possible prooxidant effect, what requires further experimental research. The data on the beneficial effects of a low dose (30 mg/ kg body weight) of phycocyanins in combination with soy protein on lipid and carbohydrate metabolism may be of interest for the development of functional food ingredients with hypoglycemic and hypolipidemic properties.