Fish oil supplementation to a high-fat diet improves both intestinal health and the systemic obese phenotype.

Impaired intestinal health characterized by a dysbiotic microbial community and a dysfunctional epithelial barrier contributes to host inflammation and metabolic dysfunction in obesity. Fish oil (FO)-derived n-3 polyunsaturated fatty acids have been shown to improve aspects of the obese phenotype; however, their effect on obese intestinal health is unknown. This study aimed to determine the effect of dietary FO on the intestinal microenvironment, including the microbial community and epithelial barrier, in a mouse model of high-fat diet induced obesity and metabolic dysfunction. Male C57BL/6 mice were fed (12 weeks) either a high-fat diet (HF, 60% fat as kcal) or an isocaloric HF supplemented with Menhaden FO (5.3% kcal, HF + FO). 16S rRNA sequencing was used to determine changes in fecal microbiota. Intestinal (ileum and colon) and epididymal adipose tissue RNA was used to assess biomarkers of barrier integrity and inflammatory status, respectively. Serum was used to assess adipokine concentrations and insulin resistance. HF + FO diet altered the fecal microbiota by decreasing the abundance of Firmicutes and increasing the abundance of members of the Bacteroidetes phyla, as well as increasing the abundance of antiobesogenic Akkermansia muciniphila, compared to HF. Intestinal epithelial barrier functions were improved by HF + FO evidenced by increased mRNA expression of tight junction components, antimicrobial defenses and mucus barrier components. HF + FO-fed mice exhibited improvements in homeostatic model assessment of insulin resistance, oral glucose tolerance and serum adipokine concentrations and epididymal mRNA expression (increased adiponectin and decreased leptin) versus HF. HF + FO improved obese intestinal health and attenuated metabolic dysfunction associated with obesity.