Tao Ma:
The obesogenic effects of polyunsaturated fatty acids are dependent on background diets

Date: 15-07-2011    Supervisor: Karsten Kristiansen & Lise Madsen

Polyunsaturated n-3 fatty acids (n-3 PUFAs) are reported to protect against high fat diet-induced obesity and inflammation in adipose tissue. While it has previously been reported that the adipogenic effects of n-6 PUFAs are dependent on the macronutrient composition of the diet, whether n-3 PUFAs metabolism is subjected to similar impact by carbohydrates and proteins in the diet is not well explored. In the present thesis two studies are described. Isocaloric high fat diets enriched with protein and carbohydrate with different weight ratio or with various carbohydrate sources were fed to male C57BL/6J mice. We show that increasing the amount of sucrose at the expense of protein in the diet correlated with increased energy efficiency and fat mass irrespective of fat sources. We propose that this effect is a result of reduced thermogenesis in fat tissues, combined repression of gluconeogenesis and ureagenesis in the liver. Also, high fat diets induced glucose intolerance regardless of the adiposity of the animals. Moreover, by using carbohydrates with differing glycemic indices we provide evidence that insulin plays a central role in promoting adiposity and inflammation in fat tissues. This idea was strengthened further by exploring pharmaceutical drugs to modulate insulin secretion.

In summary, the ability of background diet, namely carbohydrates and proteins, in regulating insulin secretion significantly modulates the beneficial effects of n-3 PUFAs in development of obesity, glucose intolerance and adipose tissue inflammation.