Acute Coronary Syndrome, a subcategory of coronary artery disease, is characterized by frequently presented syndromes, including angina, myocardial infarction, or sudden cardiac death (Sanchis-Gomar et al., 2016; Kimura et al., 2019; Ralapanawa and Sivakanesan, 2021). With global modernization, the prevalence of ACS has reached a pandemic level (Ruff and Braunwald, 2011). According to the Report on Cardiovascular Health and Diseases in China (2021), the mortality rate of coronary artery disease and acute myocardial infarction has almost doubled in the past decade, with the total prevalence continuously growing nationwide (Hu, 2022). It is also the third leading cause of mortality worldwide and is associated with 17.8 million deaths every year (Brown et al., 2020), constituting an increasing public health burden. Common approaches for treating ACS include surgery, antiplatelet and antianginal medications, as well as risk factor management (Braun et al., 2018). The prognosis of ACS is considered dynamic and complicated to determine, as it is associated with heart function, blood biomarkers level, risk factors, etc. (Xu and Yang, 2020).

Recent studies have highlighted the involvement of gut microbiome in ACS development. Some evidence suggests that trimethylamine N-oxide (TMAO) in serum, a metabolite produced by gut microbiome from certain dietary nutrients, is linked to ACS onset and coronary atherosclerotic plaque burden (Li et al., 2017, 2019a; Gao et al., 2020). ACS can also be accompanied by specific alterations in gut microbial composition, notably the increasing ratio of Firmicutes/Bacteroidetes and the increasing abundance of Firmicutes, Proteobacteria, Gammaproteobacteria, and Aerococcaceae (Alhmoud et al., 2019; Gao et al., 2020; Tascanov et al., 2020; Sawicka-Smiarowska et al., 2021). Another study shows that patients with symptomatic atherosclerosis had an increase in the abundance of genus Collinsella, while controls had an increase in Eubacterium and Roseburia (Ramírez-Macías et al., 2022). In addition, by modulating gut microbiome composition and metabolism, the Mediterranean diet has a potential effect in primary and secondary prevention of ACS because it contains more antioxidants, nitrate, and fibre as well as less saturated/trans fatty acids, sodium, and phosphate (Foscolou et al., 2019; Fernández et al., 2021; Kouvari et al., 2022; Ramírez-Macías et al., 2022). However, most previous studies used 16S rRNA amplicon sequencing to profile the bacterial community, which can result in limited taxonomic resolution and unreliable functional potential inferences (Heidrich and Beule, 2022). Moreover, there is a lack of studies investigating how the gut microbiome alters after common ACS treatments.

Shotgun metagenomic sequencing allows researchers to sequence thousands of organisms in parallel and detect very low abundance members of the microbial community (Durazzi et al., 2021). To address the gap mentioned above, we conducted metagenomic sequencing on the gut microbiome of 38 patients with acute coronary syndrome and an equal number of healthy controls who were family members. We analyzed the possible association between microbial composition and ACS prognosis stages before treatment, one and two months after treatment. We observed community-wide differences in metagenomic composition as treatment progressed and identified species-specific and functional pathways associations with these differences.

The study investigated the changes in gut microbiota composition in patients with ACS before and after treatment. The study found 16 significant species changes driven by ACS and identified 39 differential bacteria before and after treatment. The gut microbiota of patients returned to a relatively stable state 1 month after treatment. The relative abundances of seven pathways related to the biosynthesis of vitamin K2 and its homolog were reduced. Additionally, two pathways related to sugar degradation were more abundant in patients before treatment. The research also found that the gut microbiota of ACS patients treated with atorvastatin and rosuvastatin exhibit unique states. Following treatment with rosuvastatin, there was an increase in the richness of gut microbiota among patients, while patients treated with atorvastatin showed contrasting outcomes. These findings provide insight into specific bacteria and metabolic pathways that may be associated with cardiovascular disease risk and offer opportunities for treatment.

Our findings revealed no significant effect of ACS and its treatment on microbial diversity, which is consistent with some previous studies but contradicts others (Liu et al., 2019; Yoshida et al., 2019; Liu et al., 2020; Toya et al., 2020; Ma et al., 2021). Regarding the factors responsible for the differences in gut microbes, we found that inter-individual differences accounted for a relatively large proportion, although other physiological and pathological factors only explained a small proportion of the variance, which aligned with previous findings. Among these factors, cTnT is an essential biomarker for diagnosing ACS, particularly myocardial infarction, and can also be used to predict prognosis and mortality (Árnadóttir et al., 2018; Desai et al., 2020). BNP is frequently used to assess the short- and intermediate-term prognosis in ACS patients (Bassan et al., 2016). Therefore, we hypothesized that cTnT and BNP may also be involved in the development of ACS by affecting the percentages of metabolites and microbial species.

Alterations in the gut microbiome (dysbiosis) have been shown to cause chronic inflammation³ (Buttó and Haller, 2016; Li et al., 2019b; Moludi et al., 2021)—a key factor in ACS. It has been suggested that Firmicutes and Bacteroidetes play a role in inflammation due to their short-chain fatty acids (SCFAs) production (Tang and Hazen, 2014; Kim, 2018). Firmicutes mainly produce butyrate, while Bacteroidetes produce acetate and propionate (Magne et al., 2020). Butyrate favours cardiovascular disease-related disorders, as it induces AMPK activation and GLUT4 expression in adipose tissue, suppresses atherosclerotic plaque formation, and reduces reactive oxygen species (Gao et al., 2019; Mamic et al., 2021). However, acetate is considered a risk factor for obesity, as it induces lipid accumulation in the liver and stimulates appetite (Lecomte et al., 2015; Magne et al., 2020). Some Bacteroidetes spp., such as B. thetaiotaomicron, can contribute to diet-induced obesity and hypertension (Tan et al., 2019; Calderón-Pérez et al., 2020; Cho et al., 2022). Therefore, the Firmicutes/Bacteroidetes ratio was higher in healthy individuals than in patients with coronary heart disease, which could explain our result. Our study found that the Firmicutes/Bacteroidetes ratio was lower in ACS patients compared to healthy subjects, but this ratio increased after therapy. Moreover, Parabacteroides, Escherichia, and Blautia were significantly abundant in patients before treatment in our study. A higher abundance of Blautia has been associated with an increased risk of developing coronary artery disease in the Chinese population and may contribute to diseases through the production of pro-inflammatory metabolites and depletion of beneficial gut bacteria (Liu et al., 2019). In addition, Blautia can produce butyric acid, which is involved in forming short-chain fatty acids (SCFAs) (Liu et al., 2019). We also found that A. colihominis, C. evryensis, and F. fastidiosum significantly increased in ACS patients. F. fastidiosum is a typical oral bacterium which is often present in patients with periodontal disease (Deng et al., 2017; Krishnan et al., 2017). Periodontal disease is a risk factor for cardiovascular disease (Khalighinejad et al., 2016; Deng et al., 2017), generally manifested by increased inflammation and potential changes in hypercoagulability and insulin resistance (Mathews et al., 2016). The increase in the abundance of pro-inflammatory bacteria may be associated with ACS disease.

Also, gut bacteria produce several metabolites that may influence heart health. We found that the abundance of G. pamelaeae, E. eligens, B. hansenii, and R. ilealis decreased. The reduction of these species and metabolites may lead to elevated substances associated with cardiovascular disease in humans, such as cholesterol, visceral fat area, visceral fat mass, and plasma high-density lipoprotein. G. pamelaeae can produce urolithin (Selma et al., 2014), which can be anti-atherosclerotic (Stromsnes et al., 2020) and prevent cardiometabolic risk (Furlanetto et al., 2012; Giménez-Bastida et al., 2012; Selma et al., 2018). E. eligens produces butyric acid, which inhibits obesity and prevents coronary heart disease (Jie et al., 2017). Other studies also found that ACS patients had fewer E. eligens in the gut (Liu et al., 2020; Nakai et al., 2021). There is a decrease in the abundance of beneficial bacterial strains in ACS patients.

Otherwise, we have identified certain intestinal flora metabolic pathways that can potentially impact the development and treatment of ACS. Sugar metabolism, particularly glucose metabolism, plays a significant role in the development and progression of ACS (Mao et al., 2019). Our study found that pathways related to sugar degradation were less abundant after treatment, while pathways related to sugar molecule biosynthesis were more abundant. This suggests that the glucose metabolism disorder in the patient’s body improved after treatment. Our study revealed the importance of vitamin K2, specifically menaquinone-7, in regulating calcium deposition in the arterial wall and preventing arterial calcification, a key risk factor for atherosclerosis and subsequent acute coronary events (Mandatori et al., 2021). Higher dietary intake or supplementation of vitamin K2 has been associated with a lower risk of cardiovascular disease, including ACS (Schurgers and Vermeer, 2000; Beulens et al., 2009; Vissers et al., 2013; Knapen et al., 2015). Our study revealed that seven pathways related to the biosynthesis of vitamin K2 and its homolog were reduced after treatment. This may indicate that the patient’s symptoms related to atherosclerosis were relieved, and there was no need to produce more vitamin K2.

Our findings suggest that rosuvastatin and atorvastatin have distinct effects on the gut microbiota composition in acute coronary syndrome patients. After two months of treatment, the intestinal microbial diversity of ACS patients taking rosuvastatin showed an increasing trend, while the intestinal microbial diversity of ACS patients taking atorvastatin showed the opposite decreasing trend. Rosuvastatin was associated with increased gut microbiota richness, consistent with previous research (Liu et al., 2018; Kummen et al., 2020). It is speculated that atorvastatin treatment of hypercholesterolemia can selectively restore the relative abundance of several dominant and functionally important taxa that are disrupted after illness, but further studies are needed to verify this (Khan et al., 2018). Specifically, rosuvastatin promoted the growth of anti-inflammatory bacteria, such as F. prausnitzii (Sokol et al., 2008; Khan et al., 2018; Saber et al., 2021), while reducing the abundance of pro-inflammatory bacteria, including Escherichia (Nolan et al., 2017), R. gnavus (Henke et al., 2021), P. bivia (Strömbeck et al., 2007; Hou et al., 2022), and V. parvula (Zhan et al., 2022). F. prausnitzii is known for its anti-inflammatory effects, including the inhibition of NF-κB activation and IL-8 production (Breyner et al., 2017; Lopez-Siles et al., 2017; Lenoir et al., 2020). It also produces butyrate, which has anti-inflammatory properties. Conversely, certain strains of R. gnavus have been associated with inflammatory bowel disease and other inflammatory conditions (Hall et al., 2017). Veillonella has been found to induce inflammation in clinical conditions (Zhan et al., 2022; Zeng et al., 2023). Atorvastatin decreased the levels of pro-inflammatory bacteria such as Enterobacteriaceae (Zeng et al., 2017; Baldelli et al., 2021), as well as anti-inflammatory bacteria like Blautia and Lactococcus (Ma et al., 2023). Lactococcus, particularly Lactococcus lactis, has demonstrated potential as a probiotic strain with anti-inflammatory properties, particularly in treating colitis and mucositis (Luerce et al., 2014; Liu et al., 2019). It has been shown to have immunomodulatory activity, enhancing Th1-type immune responses, which can contribute to anti-inflammatory effects. Additionally, atorvastatin was associated with increased abundance of the Bacteroides genus. Studies have shown that atorvastatin treatment increased the relative abundance of Bacteroides genera in high-fat diet-induced hypercholesterolemic rats (Khan et al., 2018). Rosuvastatin and atorvastatin both affect the gut microbiota through variability in FXR receptor signalling. Rosuvastatin alters the host gene expression of bile acid metabolism pathways, while atorvastatin leads to decreased secondary bile acids (Tuteja and Ferguson, 2019). These results contribute to our understanding of the potential microbiota-related mechanisms underlying the therapeutic effects of these statins.

This study has several limitations expected to be improved in future research. Firstly, we included a relatively small cohort primarily due to losing many patients during follow-up. Inter-individual variation accounted for 69.6% of the variance in our study’s relative abundance of species’ levels, a common issue in metagenomic research. To address the sample size limitation, we employed stringent inclusion criteria to reduce individual differences. We utilized metagenomic sequencing to maximize the information extracted from each sample. Secondly, the cross-sectional nature of this study involved sampling patients from only one hospital in Zhuhai, which may not fully capture the diversity of the broader population, thus constraining the generalizability of the findings. Thirdly, the intricate interplay among medication use, gut microbiota, and confounding factors presents several limitations in our study. Medication administration signifies alterations in the host’s health status, which may be accompanied by changes in lifestyle factors (such as smoking, alcohol consumption, and physical activity) known to impact gut microbiota composition. While we controlled for dietary patterns (within the same regional population) and age (within a specific age range), we could not regulate the influence of comorbidities (such as diabetes or obesity), medications (particularly antibiotics, as well as proton pump inhibitors, nonsteroidal anti-inflammatory drugs, and metformin), and genetics (inter-individual genetic variability). Fourthly, this study solely relies on empirical analysis using genome sequencing data and lacks animal experiments to delve deeper into the mechanisms underpinning these observations. Considering the limitations above, we intend to gather a larger sample size to monitor taxonomic and functional changes in gut microbiota to validate the existing findings. Furthermore, we aim to incorporate animal experiments to validate the underlying mechanisms.

In summary, we identified risk biomarkers between ACS patients and healthy individuals and detected significant alterations in the gut microbiota of ACS patients before and after treatment. We also analyzed the differences in gut microbiomes in patients after using two different statins. These may mediate the development and treatment of ACS by translating into metabolisms. Further research utilizing advanced multi-omic detection and joint analysis techniques in prospective studies is necessary to better understand the role of gut microbiota in the pathogenesis of coronary heart disease and identify potential therapeutic targets.

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/Supplementary material.

The studies involving humans were approved by Ethical clearance was obtained from the IRB of Zhuhai People’s Hospital (Zhuhai Clinical Medical College of Jinan University) (approve no. 24, 2020). The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

YG: Writing – original draft, Investigation, Resources, Funding acquisition. SZ: Formal analysis, Writing – original draft, Visualization, Writing – review & editing. JL: Formal analysis, Writing – original draft. WZ: Formal analysis, Writing – original draft. ZG: Formal analysis, Writing – original draft. YL: Investigation, Writing – original draft. XJ: Project administration, Writing – review & editing. JuL: Investigation, Resources, Writing – original draft. JiL: Investigation, Resources, Writing – original draft. XC: Writing – review & editing, Investigation, Funding acquisition. ZiZ: Conceptualization, Methodology, Writing – review & editing. ZhZ: Conceptualization, Project administration, Funding acquisition, Methodology, Resources, Writing – review & editing.