The Interaction between Mitochondrial Oxidative Stress and Gut Microbiota in the Cardiometabolic Consequences in Diet-Induced Obese Rats

Abstract

Background: The objective of this study is to determine the role of mitochondrial oxidative stress in the dysbiosis associated with a high fat diet in rats. In addition, the impact of gut microbiota (GM) in the cardiometabolic consequences of diet-induced obesity in rats has been evaluated.

Methods: Male Wistar rats were fed either a high fat diet (HFD) or a control (CT) one for 6 weeks. At the third week, one-half of the animals of each group were treated with the mitochondrial antioxidant MitoTempo (MT; 0.7 mgKg^-1day^-1 i.p).

Results: Animals fed an HFD showed a lower microbiota evenness and diversity in comparison to CT rats. This dysbiosis is characterized by a decrease in Firmicutes/Bacteroidetes ratio and relevant changes at family and genera compared with the CT group. This was accompanied by a reduction in colonic mucin-secreting goblet cells. These changes were reversed by MT treatment. The abundance of certain genera could also be relevant in the metabolic consequences of obesity, as well as in the occurrence of cardiac fibrosis associated with obesity.

Conclusions: These results support an interaction between GM and mitochondrial oxidative stress and its relation with development of cardiac fibrosis, suggesting new approaches in the management of obesity-related cardiometabolic consequences.

Keywords: cardiac fibrosis; insulin resistance; microbiota; mucins; obesity.

Figure 1

Protein levels of (A) fibronectin, (B) periostin, (C) α-smooth muscle actin (SMA) and (D) vimentin in heart from control rats fed a normal chow (CT) and rats fed a high fat diet (HFD) treated with vehicle or with the mitochondrial antioxidant MitoTempo (MT; 0.7 mg/Kg/day i.p). Bars graphs represent the mean ± SEM of 6–8 animals. Protein densitometry was expressed in arbitrary units (AU) once normalized to stain-free gel for protein.* p < 0.05; ** p < 0.01 vs. CT group. ^† p < 0.05, ^†† p < 0.01 vs. HFD group.

Figure 2

(A) Representative microphotographs and (B) quantification of total mucin levels in colon from control animals fed a normal chow (CT) and animals fed a high fat diet (HFD) treated with vehicle or with the mitochondrial antioxidant MitoTempo (MT; 0.7 mg/Kg/day i.p) stained with Alcian Blue (AB)/periodic acid-Schiff (PAS) examined by light microscopy (magnification 20×). Bar graphs represent the mean ± SEM of 5–6 animals normalized to for CT group. *** p < 0.001 vs. CT group; ^†† p < 0.01 vs. HFD group.

Figure 3

Boxplot showing total relative abundance of reads of the four most abundant taxa at Phylum level in the gut microbiota (A) Firmicutes, (B) Bacteroidetes, (C) Protobacteria and (D) Tenericutes in feces from control animals fed a normal chow (CT) and animals fed a high fat diet (HFD) treated with vehicle or with the mitochondrial antioxidant MitoTempo (MT; 0.7 mg/Kg/day i.p). Upper, middle and lower lines represent first quartiles, medians and third quartiles. The whiskers represent a 1.5 * inter-quartile range. Data are expressed as percentage of total reads. * p < 0.05; ** p < 0.01; *** p < 0.001 vs. CT group. ^† p < 0.05, ^†† p < 0.01 vs. HFD group.

Figure 4

LEfSe analysis showing taxonomic differential abundance at family level in feces from control animals fed a normal chow (CT) and animals fed a high fat diet (HFD) treated with vehicle or with the mitochondrial antioxidant MitoTempo (MT; 0.7 mg/Kg/day i.p). (A) Significantly different families among CT, HFD and HFD+MT groups. (B) Significantly enriched and depleted families between CT and HFD groups. (C) Significantly enriched and depleted families between HFD and HFD + MT groups. The length of the horizontal bars represents the LDA score (effect size). p < 0.05; LDA score > 3.0.

Figure 5

LEfSe analysis showing taxonomic differential abundance at genus level in feces from control animals fed a normal chow (CT) and animals fed a high fat diet (HFD) treated with vehicle or with the mitochondrial antioxidant MitoTempo (MT; 0.7 mg/Kg/day i.p). (A) Significantly different genera among CT, HFD and HFD+MT groups. (B) Significantly enriched and depleted genera between CT and HFD groups. (C) Significantly enriched and depleted genera between HFD and HFD + MT groups. The length of the horizontal bars represents the LDA score (effect size). p < 0.05; LDA score > 3.0.

Figure 6

Boxplot showing total relative abundance of metabolic pathways related to gut microbiota in (A) butanoate metabolism, (B) propanoate metabolism and (C) glutathione metabolism and (D) percentage of bacteria involved in lipopolysaccharyde (LPS) production in feces from control animals fed a normal chow (CT) and animals fed a high fat diet (HFD) treated with vehicle or with the mitochondrial antioxidant MitoTempo (MT; 0.7 mg/Kg/day i.p). Upper, middle and lower lines represent first quartiles, medians and third quartiles. The whiskers represent a 1.5 * inter-quartile range. Data are expressed as percentage of total reads. * p < 0.05; ** p < 0.01; *** p < 0.001 vs. CT group. ^† p < 0.05 vs. HFD group.