Corn oil versus lard: Metabolic effects of omega-3 fatty acids in mice fed obesogenic diets with different fatty acid composition

Jul 8, 2015Biochimie

Omega-3 fatty acids' metabolic effects in mice fed high-fat diets based on corn oil versus lard

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Abstract

High-fat diets containing as much as 35% lipids induce similar weight gain and insulin sensitivity impairment regardless of being based on saturated or polyunsaturated fatty acids.

Both saturated fatty acid (SFA) and polyunsaturated fatty acid (Omega-6) diets resulted in comparable weight gain and insulin resistance in mice.
The SFA-rich diet led to increased fat accumulation in the liver and higher activity of a specific enzyme (SCD1).
Mice on the SFA diet had lower levels of fats in the blood compared to those on the Omega-6 diet.
Supplementing the SFA diet with marine omega-3 fatty acids (EPA+DHA) reduced liver fat but did not improve insulin sensitivity.
The supplemented SFA diet did not affect overall body fat or weight of specific fat tissues when compared to the supplemented Omega-6 diet.

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Mixed results have been obtained regarding the level of insulin resistance induced by high-fat diets rich in saturated fatty acids (SFA) when compared to those enriched by polyunsaturated fatty acids (PUFA), and how metabolic effects of marine PUFA of n-3 series, i.e. docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), depend on dietary lipid background. Here we compared two high-fat diets, in which the major lipid constituent was based either on SFA in the form of pork lard (LHF diet) or PUFA of n-6 series (Omega-6) as corn oil (cHF diet). Both cHF and LHF parental diets were also supplemented with EPA+DHA (∼30 g/kg diet) to produce cHF+F and LHF+F diet, respectively. Male C57BL/6N mice were fed the experimental diets for 8 weeks. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamps in mice fed LHF and cHF diets, and then metabolic effects of cHF+F and LHF+F diets were assessed focusing on the liver and epididymal white adipose tissue (eWAT). Both LHF and cHF induced comparable weight gain and the level of insulin resistance, however LHF-fed mice showed increased hepatic steatosis associated with elevated activity of stearoyl-CoA desaturase-1 (SCD1), and lower plasma triacylglycerol levels when compared to cHF. Despite lowering hepatic SCD1 activity, which was concomitant with reduced hepatic steatosis reaching the level observed in cHF+F mice, LHF+F did not decrease adiposity and the weight of eWAT, and rather further impaired insulin sensitivity relative to cHF+F, that tended to improve it. In conclusion, high-fat diets containing as much as ∼35 weight% as lipids induce similar weight gain and impairment of insulin sensitivity irrespective whether they are based on SFA or Omega-6. Although the SFA-rich diet containing EPA+DHA efficiently reduced hepatic steatosis, it did so without a corresponding improvement in insulin sensitivity and in the absence of effect on adiposity.

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Corn oil versus lard: Metabolic effects of omega-3 fatty acids in mice fed obesogenic diets with different fatty acid composition

Abstract

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