Soya protein reverses dyslipidaemia and the altered capacity of insulin-stimulated glucose utilization in the skeletal muscle of sucrose-rich diet-fed rats

The present study investigates the benefits of dietary intake of soya protein upon dyslipidaemia and insulin resistance in rats chronically (8 months) fed a sucrose-rich (63 %) diet (SRD). For this purpose, we analysed the effectiveness of soya protein isolate in improving or reversing these metabolic abnormalities. Wistar rats were fed a SRD for 4 months. By the end of this period, stable dyslipidaemia and insulin resistance were present in the animals. From months 4 to 8, half the animals continued with the SRD and the other half were fed a SRD in which the source of protein casein was substituted by soya. The control group received a diet in which the source of carbohydrate was maize starch. The results showed that: (1) soya protein normalized plasma TAG, cholesterol and NEFA levels in the SRD-fed rats. Moreover, the addition of soya protein reversed the hepatic steatosis. (2) Glucose homeostasis was normalized without changes in circulating insulin levels. Whole-body peripheral insulin sensitivity substantially improved. Besides, soya protein moderately decreases body weight gain limiting the accretion of visceral fat. (3) By shifting the source of dietary protein from casein to soya during the last 4 months of the feeding period it was possible to reverse both the diminished insulin-stimulated glucose oxidation and disposal in the skeletal muscle of SRD-fed rats. This study provides new data showing the beneficial effect of soya protein upon lipid and glucose homeostasis in the experimental model of dyslipidaemia and insulin resistance.