The effects of canola oil on metabolic syndrome parameters in diet-induced obese rats
The metabolic syndrome is characterized by obesity, insulin resistance, hypertension and dyslipidemia. It has also been suggested that hepatic steatosis and inflammation should be added to the classical components of the metabolic syndrome. Previous research on obesity and insulin resistance has examined the effects of many different fats and oils, however, the effects of canola oil on metabolic syndrome parameters have yet to be investigated. It is hypothesized that in a diet induced obese (DIO) rodent model, the combination of canola and flax oils will reduce the severity of metabolic syndrome parameters and favorably alter hepatic phospholipid (PL) and triacylglycerol fatty acid composition. The objective of the study was to investigate the biological effects of a 12 week dietary intervention with high fat diets based on various vegetable oils (high oleic canola, canola, canola/flax (3:1; C/F), safflower and soybean) and lard in 6 week old obese prone rats with regards to obesity, insulin resistance, lipidemia, hypertension, inflammation, hepatic steatosis, hepatic fatty acid composition and markers of hepatic fatty acid oxidation and synthesis. Overall the C/F diet attenuated more of the components of the metabolic syndrome, including obesity, glycemia, lipidemia, inflammation and hepatic steatosis, than the other high fat diets in DIO rats. However, each of the dietary treatments attenuated various components of the metabolic syndrome suggesting that all dietary fats and oils have their role in the prevention of different components of the metabolic syndrome. Additionally, the C/F diet led to increased eicosapentaenoic acid and docosahexaenoic acid concentrations in hepatic PL suggesting that α-linolenic acid can be efficiently converted to its very long chain derivatives in DIO rats. Thus, the addition of flax oil to conventional canola oil, in the C/F diet, appeared to enhance the beneficial effects of canola oil on metabolic syndrome parameters.