Based on their proposed metabolic effects, we examined whether
fish oil (FO) and SCFA, alone or in combination, accelerate
weight loss and the resultant metabolic improvements.
Obesity was induced in male C57BL/6J mice by high-energy feeding for 10 weeks. The mice were transferred to a
low-fat diet (2·5w%) for 4 weeks, the source of fat being either FO, a
lard-
safflower oil mix (control), or both types combined with SCFA. Weight, fasting
insulin, tissue and serum
lipid concentrations, as well as
mRNA amount of genes related to adipose
inflammation and hepatic fat oxidation were determined. All groups lost weight and showed reduced fasting
insulin concentrations and reduced liver TAG. However,
weight loss on the control-fat diet caused significant increase in hepatic and cardiac
NEFA. Substituting 20 % of the fat with SCFA increased
weight loss by 48 % and reduced fasting
insulin 1·5-fold more than the no-SCFA diets. It furthermore significantly increased the amount of
mRNA for
PPAR-α, and decreased the
mRNA amount for NF-κB in the liver and white adipose tissue. The FO diets enhanced improvement of tissue
lipid levels. Thus, FO improved liver TAG and
NEFA levels compared with
weight loss on the control diet. Combining FO and SCFA further reduced tissue
NEFA accumulation. In conclusion, we found that dietary SCFA had a significant impact on gene expression in the liver and adipose tissue, and that the effect of FO on tissue
NEFA content was modified by SCFA. Thus, interactions between
fatty acids should be considered when studying the effects of specific
fatty acids.