Different adipose tissue development in mice pair fed fish oil and different carbohydrates
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Obesity causes several health problems, including insulin resistance, Type 2 diabetes, heart diseases, disrupted energy metabolism and low-grade inflammation. Being obese increases the risk of getting metabolic syndrome. A high intake of certain carbohydrates is known to cause rapid rise in blood glucose, which increases insulin secretion and over time causes insulin resistance and hyperglycemia. A high consumption of sucrose and glucose is considered harmful beyond being a source of energy due to their ability to disturb energy metabolism. On the other hand, fish oil, enriched in the polyunsaturated fatty acids eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3), can protect against the development of obesity, improve insulin sensitivity, reduce visceral fat, reduce inflammation of adipose tissue and reduce metabolic efficiency. This study seeks to elucidate the potential ameliorating effect of fish oil on the negative effects of high carbohydrate consumption. Two trials using C57BL/6J mice were performed simultaneously. One of the trials investigated the effect of different sugars, namely the disaccharide sucrose and the monosaccharides glucose and fructose. Three groups of mice received either high sucrose, high glucose or high fructose diet in combination with fish oil. The other trial investigated the effects of different starches, namely amylose and amylopectin, in combination with fish oil. One group was given amylose (low GI carbohydrate) and the other group was given amylopectin (high GI). All the five experimental diets were high in fat, primarily fish oil. All groups, except the chow diet controlgroup, were pair-fed. Feed intake was recorded daily and body weight was recorded twice a week. After 9 weeks of experimental feeding, the mice were terminated and tissues and blood samples were collected. Gene expression analysis of the different tissues was performed by quantitative real-time PCR. Blood plasma was analyzed for plasma parameters. Paraffin-embedded, stained sections of adipose tissue were examined in a microscope. Fatty acid compositions were determined in liver and muscle. The results show that fish oil protected the mice given fructose and low GI carbohydrates from developing obesity. These groups had smaller adipose tissues and less inflammation compared to other groups. The primary cause of this seems to be that the PUFAs in fish oil decrease hepatic and adipose tissue lipogenesis.