Abstract
BACKGROUND: The type of dietary protein plays an important role in lipid and lipoprotein metabolism. This study tests the hypothesis that different dietary proteins may alter insulin sensitivity in rats after fructose ingestion. OBJECTIVE: The aim is to investigate the effects of different dietary proteins in a rat model of metabolic syndrome created by feeding a high fructose diet. METHODS: Rats were fed with starch or high fructose diet containing casein, egg albumin or soy protein for 8 weeks. Insulin sensitivity, oxidative stress markers, lipid profile and adipokines were measured. RESULTS: F-CAS group registered insulin resistance and oxidative stress. Compared to the F-CAS group, F-EGG and F-SOY animals showed improved insulin sensitivity and lower fasting levels of glucose, insulin and lipids and increased antioxidant protection. In addition, F-EGG and F-SOY animals showed improved glucose metabolism compared to F-CAS group. Protein variation also affects the levels of adipokines and adipokine receptor mRNA expression in liver. CONCLUSIONS: These findings demonstrate that soy protein had a better effect than egg protein with respect to insulin sensitivity, glucose and lipid homeostasis, antioxidant status and adipokine expression, while egg protein was more effective than soy in reducing oxidative damage despite continued intake of fructose.