Metabolically and immunologically beneficial impact of extra virgin olive and flaxseed oils on composition of gut microbiota in mice

Abstract

Purpose: Extra virgin olive oil (EVOO) and flaxseed oil (FO) contain a variety of constituents beneficial for chronic inflammation and cardio-metabolic derangement. However, little is known about the impact of EVOO and FO on dysbiosis of gut microbiota, intestinal immunity, and barrier. We, therefore, aimed to assess the impact of EVOO and FO on gut microbiota, mucosal immunity, barrier integrity, and metabolic health in mice.

Methods: C57BL/6 J mice were exposed to a low-fat (LF), lard (HF), high fat-extra virgin olive oil (HF-EVOO), or high fat-flaxseed oil (HF-FO) diet for 10 weeks. Gut microbiota assessment was undertaken using 16S rRNA sequencing. Levels of mRNA for genes involved in intestinal inflammation and barrier maintenance in the intestine and bacterial infiltration in the liver were measured by qPCR.

Results: HF-EVOO or HF-FO mice showed greater diversity in gut microbiota as well as a lower abundance of the Firmicutes phylum in comparison with HF mice (P < 0.05). The qPCR analyses revealed that mRNA level of FoxP3, a transcription factor, and IL-10, an inducer of regulatory T cells, was significantly elevated in the intestines of mice-fed HF-EVOO in comparison with mice-fed HF (P < 0.05). The mRNA level of the antimicrobial peptide, RegӀӀӀγ, was markedly elevated in the intestines of HF-EVOO and HF-FO compared with HF group (P < 0.05).

Conclusions: Our data suggest that the consumption of EVOO or FO can beneficially impact gut microbiota, enhance gut immunity, and assist in the preservation of metabolic health in mice.

Keywords: Antimicrobial peptide; Extra virgin olive oil; Flaxseed oil; Gut microbiota; Regulatory T cells.

Fig. 1

Selected metabolic parameters in mice-fed LF, HF, HF-EVOO, and HF-FO diets. a Body weight gain (*Indicates difference between HF and LF; #Indicates difference between HF and HF-EVOO groups), b average energy intake and c blood glucose levels when fed ad libitum (taken from tail vein). All data were analyzed using one-way ANOVA followed by post hoc Tukey’s multiple comparison test. Data indicate mean ± SEM. n = 5 mice per group. *P < 0.05; **P < 0.01

Fig. 2

Plasma SCFA profile of mice-fed LF, HF, HF-EVOO, and HF-FO diets. a Total concentration of plasma SCFAs, b–e individual plasma SCFA concentrations (acetate, propionate, butyrate, and valerate, respectively) and f plasma ratio of acetate to butyrate plus propionate. Data indicate mean ± SEM. All data were analyzed using one-way ANOVA followed by post hoc Tukey’s multiple comparison test. n = 5 mice per group. *P < 0.05; **P < 0.01, ***P < 0.001; ****P < 0.0001

Fig. 3

Diversity and composition of gut microbiota in mice-fed LF, HF, HF-EVOO, and HF-FO diets. a Rarefaction curve for PD, b box plot showing alpha diversity measured by PD, c principal coordinate analysis of gut microbiota composition based on unweighted UniFrac, d correlation of observed OTUs with blood glucose levels, e relative abundance of major phyla composition, f–h relative abundance of selected phyla highlighting significant differences among groups, i relative abundance of major genera and j–r relative abundance of selected genera highlighting significant differences among groups, m correlation of Bacteroides genera with plasma TG concentration. All data were analyzed using non-parametric, Kruskal–Wallis test. Data indicate mean ± SEM. n = 5 mice per group *P < 0.05; **P < 0.01, ***P < 0.001

Fig. 3

Diversity and composition of gut microbiota in mice-fed LF, HF, HF-EVOO, and HF-FO diets. a Rarefaction curve for PD, b box plot showing alpha diversity measured by PD, c principal coordinate analysis of gut microbiota composition based on unweighted UniFrac, d correlation of observed OTUs with blood glucose levels, e relative abundance of major phyla composition, f–h relative abundance of selected phyla highlighting significant differences among groups, i relative abundance of major genera and j–r relative abundance of selected genera highlighting significant differences among groups, m correlation of Bacteroides genera with plasma TG concentration. All data were analyzed using non-parametric, Kruskal–Wallis test. Data indicate mean ± SEM. n = 5 mice per group *P < 0.05; **P < 0.01, ***P < 0.001

Fig. 3

Diversity and composition of gut microbiota in mice-fed LF, HF, HF-EVOO, and HF-FO diets. a Rarefaction curve for PD, b box plot showing alpha diversity measured by PD, c principal coordinate analysis of gut microbiota composition based on unweighted UniFrac, d correlation of observed OTUs with blood glucose levels, e relative abundance of major phyla composition, f–h relative abundance of selected phyla highlighting significant differences among groups, i relative abundance of major genera and j–r relative abundance of selected genera highlighting significant differences among groups, m correlation of Bacteroides genera with plasma TG concentration. All data were analyzed using non-parametric, Kruskal–Wallis test. Data indicate mean ± SEM. n = 5 mice per group *P < 0.05; **P < 0.01, ***P < 0.001

Fig. 4

Relative mRNA level in proximal colon of mice-fed LF, HF, HF-EVOO, and HF-FO diets for a FOXP3 and b IL-10. All data were analyzed using one-way ANOVA followed by post hoc Tukey’s multiple comparison test. Data indicate mean ± SEM. n = 5 mice per group. *P < 0.05

Fig. 5

Relative mRNA level of a RegӀӀӀγ in ileum, b RegӀӀӀγ in proximal colon and c lipopolysaccharide-binding protein (LBP) in liver of mice-fed LF, HF, HF-EVOO, or HF-FO diets. All data were analyzed using one-way ANOVA followed by post hoc Tukey’s multiple comparison test. Data indicate mean ± SEM. n = 5 mice per group. *P < 0.05; **P < 0.01; ***P < 0.001