Obesity and Hypothalamic Inflammation from High Fat Diets of Different Fatty Acid Profile

Abstract

One of the significant changes in the Western diet, preceding and continuing concurrently with the obesity epidemic, has been a change in fatty acid profile from saturated and monounsaturated and towards polyunsaturated fatty acids, primarily n-6 linoleic acid (LA). The objective of this study is to observe the obesity inducing ability of different types of fatty acids within a high fat diet (HFD). Forty-eight male C57BL6/J mice were divided into 4 dietary treatment groups (n=12): control (10% kcals fat) and 3 HFDs (45% kcals fat) with the different percentages of LA constituting the 45% fat. The first HFD had 1% kcals from linoleic acid (LA); the second HFD had 15% LA; and the third had 22.5% kcals from LA. The primary source of LA was soybean oil and the primary source of saturated fat was coconut oil. During the 12-week study, body weight and food intake were recorded. After 12 weeks, MRI body composition, indirect calorimetry and glucose and insulin tolerance tests were performed. Hypothalamic, liver and adipose tissues and blood serum were collected for protein and mRNA analysis. All HFD groups were heavier, had higher fat to lean body composition and slower glucose disposal compared to the control group. The two high LA groups had a small but statistically significant higher bodyweight than the low LA group. Molecular data on inflammatory and metabolic markers in the hypothalamus and peripheral tissues are still being collected. These results suggest that in the mouse both highly saturated and highly unsaturated HFDs induce obesity relative to low fat diet but that contrary to current thought saturated fats do not cause greater weight gain and are potentially less obesogenic