Suitability of a new diet-induced model of metabolic syndrome for immunophysiological studies in rats

Studying the pathogenesis of metabolic syndrome and its complications as well as contribution of immune cells to these processes is impossible without relevant laboratory animal models. The nutritional model based on the Western diet was proven to be applicable for these purposes. It correlates with the nutritional pattern of modern humans by reproducing obesity, carbohydrate and lipid metabolism disorders, and low-intensity systemic inflammation. However, this diet involves the use of specialized commercial food, which is currently in limited access, thus requiring the development of a native diet based on the ratio of food ingredients proposed in well-known publications, with efficiency assessment of the selected model. Therefore, the purpose of present study was to evaluate the perspectives of a novel dietary modification based on a Western diet for modeling metabolic syndrome in Wistar rats. The diet of experimental group of rats included 30% standard food, 25% lard, 25% sucrose, 2% salt. The protein fraction in the diet was replenished by adding soy protein. The animals were fed a Western diet for 18 weeks, starting at 8 weeks of age. The examination of animals was based on biometric parameters, general blood counts, biochemical analysis of blood plasma, and histochemical staining of liver sections for lipids. Results: It was found that, starting from 6 weeks, the rats from experimental group significantly exceeded the control ones in the body mass. After 18 weeks, they showed a significant increase in body weight, waist circumference, visceral fat mass compared to the controls, fasting hyperglycemia (with unchanged levels of glycated hemoglobin), along with signs of dyslipidemia (increased levels of triglycerides, LDL and VLDL cholesterol, atherogenic quotient), and increased insulin resistance index HOMA-IR. We could not, however, reproduce the development of fatty hepatosis in experimental rats, which should be considered a limiting factor of the proposed model. The nutritional model of metabolic syndrome based on the Western diet closely resembles the nutritional habits of modern humans. The proposed diet and the exposure time allowed us to achieve the development of the main signs (obesity) and several additional criteria of metabolic syndrome (hyperglycemia, dyslipidemia) in the rat model. Thus, the chosen experimental model may be successfully used to study the immunophysiological aspects of metabolic syndrome. However, the absence of fatty liver disease in experimental animals should be taken into account.