[Effects of high oleic and different fatty acid composition edible oils on glucose and lipid metabolism in middle-aged and elderly rats].

OBJECTIVE: Discussion on the effects of edible oils with different fatty acid compositions on glucose and lipid metabolism in middle-aged and elderly rats under free-feeding conditions with a fat energy ratio of 35%.

METHODS: The experiment randomized 50 male rats aged 8-10 months into five groups: a control group(NC, fed AIN93 M diet), a monounsaturated fatty acid(MUFA) group(fed high oleic sunflower oil diet), a polyunsaturated fatty acid(PUFA) group(fed regular sunflower oil diet), an animal-based saturated fatty acid(ASFA) group(fed lard diet), and a vegetable-based saturated fatty acid(VSFA) group(fed coconut oil diet). The rats were fed continuously for 12 weeks. During the experiment, the body weight and food intake of the rats were measured weekly. At the end of the 12th week, an oral glucose tolerance test was performed on the rats. After the experiment, dual-energy X-ray absorptiometry(DEXA) was used to measure the body fat and abdominal fat content of the rats. Blood samples were collected from the abdominal aorta for the determination of fasting blood glucose and blood lipid levels. The perirenal fat and epididymal fat of rats were removed and weighed, and the ratios of these fat masses to the body weight were calculated respectively. Additionally, HE staining was used to observe the liver pathological lipids of the rats.

RESULTS: Body weight and food intake result showed that compared to the NC group, the total food intake of rats in all four experimental groups decreased. The energy intake of the VSFA group and the energy utilization of the PUFA and VSFA groups increased, with these differences being statistically significant(P<0.05). In terms of blood lipid levels, compared to the NC group, the the triglyceride(TG) level in the MUFA group decreased, while the TG, total cholesterol, high density lipoprotein cholesterol(HDL-C), nonesterified fatty acid(NEFA)and Non-HDL-C levels in the PUFA group significantly decreased. The HDL-C and NEFA levels in the ASFA group also decreased, and the low density lipoprotein cholesterol(LDL-C) level in the VSFA group significantly decreased, all with statistically significant differences(P<0.01 or P<0.05). In terms of blood glucose levels, the FBG levels of rats in the PUFA and ASFA groups were lower than in the NC group(P<0.05). The perirenal and epididymal fat masses of rats in the MUFA and VSFA groups were higher than those in the control group(P < 0.01, P < 0.05). The perirenal fat mass of rats in the ASFA group was higher than that in the NC group(P<0.05). The abdominal and total body fat content of rats in the MUFA group was significantly higher than in the NC group(P<0.01, P<0.05). Hepatic histopathological result showed that the lipid vacuoles in the liver of the VSFA group were significantly more than in the NC group, while that in the other groups were between the two.

CONCLUSION: Under the condition of ad libitum feeding and a fat energy contribution ratio of 35%, PUFA oil are beneficial for improving glucose and lipid metabolism levels, thereby potentially reducing the risk of cardiovascular disease. MUFA oil may lead to an increase in abdominal and overall body fat in rats, ASFA oil may help lower blood glucose levels, while VSFA oil may exacerbate the accumulation of liver fat in rats.