Consumption of a western style high saturated fat diet (HSFD) has been implicated in obesity development as well as progression to Type 2 diabetes. Chronic consumption of HSFD exerts detrimental effects on pancreatic islet function in mice. Whether monounsaturated and polyunsaturated fat are less detrimental for human islet function is also unknown.
AIM: To investigate the impact of different forms of high fat diet on mouse pancreatic islet functions.
METHOD:
Male RAG1-null mice (C57Bl/6 background) at age of 6-8 weeks were placed on one of 4 different diets: normal chow, high saturated fat diet (HSFD), high monounsaturated fat diet (MUFD; fat ratio 3:2:2 being MUFA: PUFD: SFA), or high polyunsaturated fat diet (PUFD; omega 3 to omega 6 fatty acid being 1:3.7). All high fat diets have 45% calories from fat, chow has 8% of calories from fat; n=10 on each diet.
Glucose tolerance tests and insulin tolerance tests were performed before and 16 weeks after diet change. Mice were also placed in a promethion metabolic cage post diet.
RESULTS:
HSFD fed mice had substantial weight gain (p<0.0001 vs chow) along with significant glucose intolerance and insulin intolerance (p<0.005) by 16-week. In contrast, mice fed MUFD or PUFD had insignificant and similar weight gain to mice fed chow (p=0.5852 chow vs MUFD; p=0.9998 for chow vs PUFD). On MUFD and PUFD, glucose tolerance did worsen compared to chow, but with much smaller effect compare to HSFD. Higher energy expenditure was found in mice fed MUFA / PUFD while their food consumption was similar across diets.
CONCLUSION:
Long-term unsaturated-high-fat diet demonstrated significant improvements in body weight and islet function in comparison to HSFD. This suggests replacing saturated fats with unsaturated fats could potentially lower the risks of type 2 diabetes development.