Analysis of Gut Microbiota in Coronary Artery Disease Patients: a Possible Link between Gut Microbiota and Coronary Artery Disease

Abstract

Aim: Recent studies have suggested that metabolic disorders such as obesity and type 2 diabetes are associated with gut microbiota. The association between atherosclerosis and gut microbiota has also been attracting increased attention. Our aim was to specify a characteristic trend of gut microbiota in coronary artery disease (CAD).

Methods: This study included 39 CAD patients, 30 age- and sex-matched no-CAD controls (Ctrls) with coronary risk factors and 50 healthy volunteers (HVs) without coronary risk factors. Bacterial DNA was extracted from their fecal samples and analyzed by terminal restriction fragment length polymorphism.

Results: A characteristic change of gut microbiota was observed in CAD patients, where the order Lactobacillales was increased (CAD, Ctrl vs. HV; 13.6%±12.0%, 6.2%±7.7% vs. 4.1%±5.9%; p＜0.001) and the phylum Bacteroidetes (Bacteroides＋Prevotella) was decreased (CAD, Ctrl vs. HV;35.5%±11.6%, 43.9%±11.2% vs. 47.4%±11.5%; p＜0.001). The CAD group was over-represented in enterotype "others" (III), compared with the Ctrl or HV group (p＜0.001, chi-squared test), although we could not deny the possibility that some drugs affect the gut flora types.

Conclusions: Although this study had some limitations, we demonstrated that the incidence of CAD was linked with an alteration of gut microbiota. A prospective study is desired to clarify a causal relationship between CAD and gut microbiota.

Fig. 1.

Distribution of gut microbiota and classification of enterotype in the coronary artery disease (CAD), control, and healthy volunteer groups (A) Representative profiles of gut microbiota. (B) Dendrogram of the similarity was shown. (C) Enterotype “others” (III) was enriched in CAD group (p < 0.001, chi-squared test). The terminal restriction fragment length polymorphism patterns were analyzed using Pearson's correlation and the unweighted pair-group method with arithmetic mean algorithm. Enterotypes were defined as follows: I, > 30% Bacteroides; II, > 15% Prevotella; and the remaining as “others” (III).

Fig. 2.

Comparison of the order Lactobacillales. (A) The percentage of each group of gut microbiota was compared among the coronary artery disease (CAD), control (Ctrl), and healthy volunteer (HV) groups. The percentage of the order Lactobacillales was increased (B) in the CAD group (CAD, Ctrl vs. HV) (C) especially in CAD patients with multi-vessel disease (multiand single-vessel disease vs. Ctrl). Closed circles indicate the CAD group; gray squares indicate the Ctrl group, whereas open triangles indicate the HV group. Single- or multi-vessel disease referred to the number of major coronary vessels demonstrating > 75% stenosis on diagnostic coronary angiography. Kruskal–Wallis test followed by Dunn's post-hoc analysis was used to calculate p-values (*p < 0.05, **p < 0.01, and ***p < 0.001).

Fig. 3.

Comparison of the phylum Bacteroidetes and the Firmicutes/Bacteroidetes (F/B) ratio. (A) The phylum Bacteroidetes (Prevotella + Bacteroides) was decreased; (B) the F/B ratio was increased in the coronary artery disease (CAD) group. Kruskal -Wallis test followed by Dunn's post-hoc analysis was used to calculate p-values (*p < 0.05, **p < 0.01, and ***p < 0.001). The phylum Firmicutes = Lactobacillales + Clostridium. The phylum Bacteroidetes = Bacteroides + Prevotella.

Supplemental Fig. 1.

Relationship between the severity of coronary artery disease and each group of gut microbiota. The percentage of each group of gut microbiota was compared between Ctrl, CAD with single-vessel disease and CAD with multi-vessel disease. Single- or multi-vessel disease referred to the number of major coronary vessels demonstrating > 75% stenosis on diagnostic coronary angiography. Kruskal-Wallis test followed by Dunn's post-hoc analysis was used to calculate p-values (**p < 0.01).

Supplemental Fig. 2.

Obesity and distribution of gut microbiota. Correlations between BMI and (A) the order Lactobacillales, (B) the phylum Bacteroidetes (Prevotella+ Bacteroides) or (C) the Firmicutes/Bacteroidetes (F/B) ratio were shown. Pearson's correlation analysis was used for statistical correlation between two parameters.

Supplemental Fig. 3.

Type 2 diabetes and distribution of gut microbiota. Correlations between HbA1c (%) and (A) the order Lactobacillales, (B) the phylum Bacteroidetes (Prevotella + Bacteroides) or (C) the Firmicutes/Bacteroidetes (F/B) ratio were shown. Pearson's correlation analysis was used for statistical correlation between two parameters.

Supplemental Fig. 4.

The comparison of Lactobacillales after adjusting medication. (A) The percentage of the order Lactobacillales tended to be increased in CAD patients with PPI/H2 blocker, compared with Ctrls with PPI/H2 blocker (CAD with PPI/H2 blocker vs. Ctrls with PPI/H2 blocker; 13.8 ± 12.1% vs 9.2 ± 9.2%; p= 0.24, Figure not shown), especially in those with multi-vessel disease (multi-, single-vessel disease vs. Ctrl; 17.0 ± 12.8%, 6.3 ± 6.1% vs. 9.2 ± 9.2%; p= 0.025). (B) The percentage of the order Lactobacillales was also tended to be increased in CAD patients with statin, compared with Ctrls with statin (CAD with statin vs. Ctrls with statin; 13.9 ± 12.1% vs. 10.5 ± 10.3%; p= 0.41, Figure not shown), especially in those with multi-vessel disease with statin (multi-, single-vessel disease vs. Ctrl; 17.2 ± 12.7%, 6.3 ± 6.1% vs. 10.5 ± 10.3%, p= 0.034). Kruskal-Wallis test followed by Dunn's post-hoc analysis or Mann-Whitney U test were used to calculate p-values (*p < 0.05). Single- or multi-vessel disease referred to the number of major coronary vessels demonstrating > 75% stenosis on diagnostic coronary angiography.