Microbiome interactions with different risk factors in development of myocardial infarction

along with their respective metabolites. Host genetic factors, especially allelic variations in signaling and inflammatory markers, greatly affect the progression or severity of the disease. Despite the established significance of the human microbiome-nutrient-metabolite interplay in associations with CVDs, the unexplored terrain of the gut-heart-oral axis has risen as a critical knowledge gap. Moreover, the pivotal role of the microbiome and the complex interplay with host genetics, compounded by age-related changes, emerges as an area of vital importance in the development of MI. In addition, a distinctive disease susceptibility and severity influenced by gender-based or ancestral differences, adds a crucial insights to the association with increased mortality. Here, we aimed to provide an overview on interactions of microbiome (oral and gut) with major risk factors (tobacco use, alcohol consumption, diet, hypertension host genetics, gender, and aging) in the development of MI and therapeutic regulation.


Introduction
Many developing countries are facing a dual burden of diseases (communicable and non-communicable).In recent years, a rapid transition has been observed in a disease burden from predominantly communicable to non-communicable.According to the World Health Organization, non-communicable diseases accounted for 74 % of all mortality worldwide.Among all, mortality associated with CVDs contributes the most, and therefore, CVDs are of greatest concern in the world.In Sub Saharan Africa, mortality due to CVDs is 13 % (Yuyun et al., 2020).It is the major cause of mortality throughout India and accounts for a quarter of all mortality (Ralapanawa and Sivakanesan, 2021).South Asian populations are at a higher risk of developing CVD than other ethnic groups.The major risk factors of MI include genetic history, tobacco use, hypertension, oral disease, nutrition, or infection of certain microbes (Zodpey et al., 2015;Ralapanawa and Sivakanesan, 2021;Amar et al., 2019).In some countries, the major concern is the onset of MI at a younger age and its association with high mortality (Prabhakaran et al., 2016).The acute myocardial infraction (AMI) hospitalization in young age accounts 32 % (2010-2014) in USA which was significantly higher to 27 % during 1995-1999 (Arora et al., 2019).The modifiable risk factors and genetics account more in younger AMI patients as compared to old age patients (Krittanawong et al., 2023).Human microbiomes, including chronic infections of gut microbes or oral/respiratory infections, are important risk factors contributing to cardiometabolic health (Zodpey et al., 2015;Valles-Colomer et al., 2023).
Current advancements have established a profound link between gut microbiota and basic physiological functions showing the role of human microbiota in processes such as nutrient extraction, immunity and metabolism (Bouskra et al., 2008) prompted by their multipurpose metabolic genes that contribute distinct enzymes and biochemical pathways (Turnbaugh et al., 2006).Additionally, the gut microbiota heavily influences the synthesis of bioactive molecules, including vitamins, amino acids, and lipids (Turnbaugh et al., 2006).Moreover, the human microbiome also serves a pivotal role in development and modulation of immune response, in addition to, protecting the host from external pathogens.This composite interplay accentuates the complex and robust contributions of microbiome to human health, including CVDs.The term microbiota defines the microorganism living in a specific environment, e.g., gut and oral microbiota, whereas, microbiome includes microbial structural elements, metabolites and the environmental conditions in addition to the communities of microorganisms (Berg et al., 2020).
The oral-gut microbiota and its metabolites can interact with host genetics to affect CVD risk and severity (Valles-Colomer et al., 2023).However, the underlying mechanisms are not well understood, in many countries including South Asian populations.Unique genetic, dietary, and environmental patterns that characterize geographically diverse populations make it an intriguing case of exploration in the respective settings.MI pathogenesis is complex and involves multiple factors, including the oral-gut microbiota and host genetics.Therefore, the microbiome and host genetics associated with MI and their dysbiosis lead to increased disease outcomes.The nutrient-host-microbiome interplay and associated metabolic trafficking are crucial to identifying potential targets to intervene in curtailing the CVD burden.In addition, the underlying mechanisms of the gut-heart-oral axis are not well explored and have been raised as an important knowledge gap.In this review, within multiple sections, it is discussed what has been learned so far about the role of the gut microbiome, the oral microbiome, and the role of microbial metabolites in the pathogenesis of MI.

Microbiome and CVD
CVDs, the leading global cause of the illness and death, include conditions like coronary heart disease (or MI), cerebrovascular disease, and peripheral arterial disease, wherein atherosclerosis, obesity, hypertension, dyslipidemia, mental illness, and diabetes are well known contributing factors.However, emerging evidence suggests an important role of the human microbiota in maintaining cardiovascular health, which may potentially contribute to CVDs upon disruption of their balance (Sanchez-Rodriguez, et al., 2020).The potential influence of Fig. 1.Some of the SCFAs (acetate, propionate and butyrate) generated in the gut enter the blood circulation.SCFA first recruit neutrophils at the site myocardial injury following MI.SCFA mediate anti-inflammation (M2 macrophage) and immune response (especially through extrathymic generation of Treg) to clear apoptotic and necrotic bodies of the endothelial cells.SCFA also improve blood pressure which further improve intestinal barrier function.The SCFAs cause epigenetic changes (inhibition of histone deacetylation, and DNA methylation), and interactions with GPCRs to mediate anti-inflammation, post-MI cardiac repair, and epithelial barrier functions.microbiota on host metabolism and CVDs might occur through various metabolic pathways (Fig. 1).Here, we outline the potential pathogenic role of microbiota in CVDs.

Gut microbiome impact in MI
Experimental evidence supports the important role of angiotensinconverting enzyme 2 (ACE2) in maintaining microbiota diversity and improving intestinal permeability in CVDs (Duan et al., 2019;Hoel et al., 2021).MI in patients with severe COVID-19 was reported to be high and was associated with an amplified risk of death (Giustino et al., 2020).The inflammatory pathways and ACE2/Ang 1-7 axis are crucial for microorganisms to combat the damage in cardiovascular and lung tissues in cardiac patients.ACE2 controls dysbiosis and permeability of the gut, which is an essential mechanism both in cardiovascular and pulmonary complications (Basu et al., 2017;Gheblawi et al., 2020).A critical role of ACE2 has been established in CVD, including pulmonary hypertension (PH), MI, and heart failure (HF) (Patel et al., 2016).SARS-CoV-2 infection also causes blood clotting and leads to severe inflammation in cardiac tissues in a significant number of patients with altered oral and gut microbiome (Tang et al., 2020;Giustino et al., 2020;Wu et al., 2021).Intravascular coagulation was observed in a great number (71.4 %) of the deceased when compared to the survivors (0.6 %) (Tang et al., 2020).The nonsurvivors had also represented increased levels of fibrinogen degradation products and D-dimers (fibrin-related markers) as compared to survivors but are still higher than normal patients.Sepsis leads to disseminated intravascular coagulation (Tang et al., 2020).The diversity richness of the gut microbiome contributes to atherosclerosis as Streptococcus and Enterobacter get enriched in the disease condition (Jie et al., 2017).The microbiome-associated metabolism is crucial to combat associated cardiovascular damage in cardiac patients (Valles-Colomer et al., 2023).Enrichment of pathobionts in gut or gastroenteritis develops systematic inflammatory response and hypercoagulation which can contribute in atherothrombotic events, hypertension and CVDs (Foley and Conway, 2016).A recent report based on nationwide case control analyses revealed greater risk of MI in gastroenteritis patients.The gastroenteritis patients also presented severe clinical outcome and extended hospital stay (Tai et al., 2022).The Chronic microbial infection follows a microbiome dysbiosis and elevated permeability of the gut, which is an essential mechanism both in cardiovascular and pulmonary complications, and are important contributing factors in the disease outcome (Basu et al., 2017;Gheblawi et al., 2020).The bloodstream infection and increased translocation of intestinal bacteria have been associated with the common morbidity of MI and HF (Amar et al., 2019).This suggest gastroenteritis may trigger MI and affect post-MI outcome probably through entry of microbial toxins or microbes entry in circulation through leaky gut, which induces systematic inflammation and hypercoagulation.Gut microbiota stimulate inflammatory responses by activating several signaling pathways which then induce development and progression of CVD.The mechanism of these pathways is not completely comprehended (Silva et al., 2021).The gut microbes produce several metabolites which depend on the nutrients/diet one consumes.Thus microbial metabolites along with microbial metabolic pathways shape/impact many host metabolic pathways ().Some gut microbes (Clostridium, Enterobacteriaceae, and Eubacterial sp) liberate trimethylamine (TMA) via catabolism of choline, carnitine, and lecithin derived from non-vegetarian food (Dekkers et al., 2022).The TMA is further oxidized into trimethylamine-N-oxide (TMAO) in the liver by the hepatic enzymes.TMAO promotes atherosclerosis and increases the risks of CVD (Tang et al., 2013).The microbiome harbors variants of TMA biosynthetic enzymes, carnitine oxygenase (CntA) and choline TMA-lyase (CutC), which affect varying levels of this metabolite (Valles-Colomer et al., 2023).Inhibition of microbial-derived CntA and CutC would be a potential therapeutic target in CVD.Short-chain fatty acids (SCFAs) are the end products of microbial metabolism (fermentation) in the colon and have been well-studied for their beneficial effects on host metabolism.The valeric, butyric, and propionic acids are the SCFAs that improve the gut environment, especially intestinal barrier function, and improve cardio-metabolism (Rath et al., 2017).The effect of SCAFAs on the promotion intestinal barrier involved the assembly of TJs induced by the AMPK activation and Treg-mediated homeostasis (Smith et al., 2013.).The effect of valeric acid is similar to butyric acid but exhibits a broader range of effective biological concentrations than butyric acid.Dietary nutrients shape microbiomes and drive inflammatory pathways that have been established in MI progression (Patel et al., 2016;Valles-Colomer et al., 2023).Host genetics also plays an important role in shaping gut/oral microbiome through interplays of various metabolic pathways and maintaining microbialmetabolite concentration in the circulatory system.Since, different kinds of microbiome (bacteriome, virome and mycobiome) analyses are being utilized to identify microbial diversity and differential abundance and their metabolic (or functional) profiles associated with MI risk.Next, we will discuss these microbiomes separately.

Bacteriome
The human microbiome includes bacteria, viruses and other microorganisms associated with different parts of the body.Gut bacteria play a fundamental role in CVDs, along with other pathophysiological processes, such as cancer and inflammatory bowel disease (Ahlawat et al., 2021;Dhingra et al., 2022).In a healthy human gut, more than 50 phyla of bacteria have been observed (Schloss and Handelsman, 2004), where 2 phyla, "Bacteroidetes and Firmicutes" are present in abundance.The number of bacterial cells varies along the length of gastro-intestinal tract, which is between 10 and 10 3 bacteria per gram in stomach and duodenum, followed by between 10 4 and 10 7 bacteria per gram in jejunum and ileum, increasing to between 10 11 and 10 12 bacteria per gram in the colon (Sekirov et al., 2010).The microbial metabolites liberated in gut, exert anti-inflammatory effects including cell cycle inhibition and apoptosis induction (Li et al., 2018).Bacteroides, genus of gram-negative bacteria, produce conjugated linoleic acid that is antiobesogenic, anti-diabetic, hypolipidemic and antiatherogenic (Rahman et al., 2022).Microbiome dysbiosis and microbial metabolites retained in the circulation have the potential to develop MI by interfering with host signaling pathways involved in inflammation (Jansen et al., 2021).The Enterobacter and Proteobacteria were elevated in gut while lower plenitude of Haemophilus and Firmicutes in oral cavity was observed in MI patients (Kwun et al., 2020).

Virome
Virome includes the viruses that infect humans and bacteriophages infecting a wider range of bacteria that inhabit humans.Viruses could be beneficial or detrimental for health depending on the Viral-Host interaction.Viral exposure varies from individual to individual, depending on the factors such as age, lifestyle and geographic location.Overtime, variation in virome, containing elemental species, is also observed due to continuous occuring mutation and zoonotic transmissions from animals whose virome itself vary from time to time (Delwart, 2013).Influenza viruses had a major role in development of MI.These viruses can potentially generate and regulate an inflammatory response by rupturing atherosclerotic plaque (Bocale et al., 2022).Moreover, the link between patients with SARS-CoV-2 infection and myocardial damage has been observed and associated with severe clinical outcomes including acute MI (Siddamreddy et al., 2020, Tedeschi et al., 2021).Human immunodeficiency virus (HIV), Herpes zoster has also been reported for developing an MI as a post-infection consequence (Parameswaran et al., 2023, Crane et al., 2017).

Mycobiome
As compared to bacterial components of microbiome, fungal M. Bijla et al. microbiome or mycobiome is low in diversity.Recently, it has been recognized as a fundamental part of the gut microbiome, as genera like Candida, Saccharomyces and Malasszia have been detected in the GI tract.(Nash et al., 2017).Candida has been reported to be involved in endocarditis in acute myocardial infarction (Aron et al., 2017).Various studies suggest the possible role of gut mycobiota in CVDs and atherosclerosis development.A recent study documented the association of gut mycobiota dysbiosis with carotid atherosclerosis (Chacón et al., 2018).It was observed that Zygomycota was present in abundance, consisting of genus Mucor family Mucoraceae that were negatively correlated with carotid intima-media thickness (Chacón et al., 2018).A strong association was observed between mycobiome dysbiosis and increased levels of both VLDL cholesterol and triglycerides in elderly Danes (Ahmad et al., 2020).Despite the small representation of mycobiome as compared to bacteriome, their intricate interactions have potential impact on gut including maintenance of epithelial integrity (Nash et al., 2017).

Oral microbiome and MI development: pathobionts are risk factors
The oral microbiome, comprising thousands of bacterial species, plays a crucial role in oral as well as cardiac health.Systematic analyses identified periodontal disease as the marker or risk factor for CVD including MI (Humphrey et al., 2008;Vedin et al., 2015).The periodontal pathobionts (Fusobacterium nucleatum and Porphyromonas gingivalis) are well known to be associated with CVD (Ohki et al., 2012).The oral pathobionts are generally gram-negative anaerobes which secrete virulence factors, like collagenase and proteases to invade periodontal tissues.Common practices (brushing, chewing, flossing, dental procedures, etc.) can cause pathobionts to enter the circulatory system and invade the coronary arteries (Forner et al., 2006).The existence of periodontal pathobionts detected in thrombus aspirates and occlusion in acute MI patients (Ohki et al., 2012;Pessi et al., 2013;Lanter et al., 2014).The pathobionts have also shown adverse impacts on the cardiovascular system, including MI (Kesavalu et al., 2012,).A reduction in aortic inflammation was observed following non-surgical periodontal therapy in a mouse model (Cui et al., 2016).Thus, oral pathobionts play a critical role in MI pathogenesis.
F. nucleatum stimulates apoptosis in endothelial cells and destroys endothelial integrity, thus enhancing vascular permeability and leading to atherosclerosis (Wang et al., 2019).The pathobiont also stimulates production of inflammatory factors (TNF, cytokines, MCP, CRP and microRNAs etc.) in macrophages and drives atherosclerosis (Zhou et al., 2022).
Gingipain secreted by P. gingivalis inhibits constitutive autophagy by halting fusion of the autophagosome-lysosome in cardiomyocytes, thus reducing its viability following MI.The autophagy is inhibited by the cleavage of a host protein, vesicle-associated membrane protein 8 (VAMP8) at Lys47 by gingipain (Shiheido-Watanabe et al., 2023).The VAMP-8 interacts with SNAP-receptors (SNAREs) which are lysosomal sensitive factor attachment protein receptors.P. gingivalis infection in cardiomyocytes activates pro-apoptotic protein (Bax) by cleaving it at Arg34 and induces apoptosis (Shiheido et al., 2016).Overall, P. gingivalis causes inhibition of autophagy, a crucial step in the maintenance of cardiomyocytes, and induces its apoptosis.

Role of microbial metabolites
Hundreds of proteins and metabolites are produced by gut microbiomes that modulate many functions within the host, such as Energy homeostasis maintenance, nutrient processing and development of the immune system.From dietary sources, many bacterial derived metabolites originate (Martin-Gallausiaux et al., 2021).

Short chain fatty acids (SCFAs)
Fatty acids, essential for cardiac health by acting as an energy substance, are of three types namely small chain fatty acids or SCFAs (with chain length of 1-6 carbon atoms), medium chain fatty acids (MCFA-chain is 6-12 carbons atoms long) and long chain fatty acids (LCFA having more than 12 carbon atoms) (Hageman et al., 2019).Reportedly, in cardiac energy metabolism, LCFA is involved in β-oxidation.Usefulness of MCFA in cardiac-metabolism through lowering postprandial lipemia has been proved in clinical trial (Panth et al., 2020).The MCFA is useful as a metabolic therapy following MI as it induces epigenetic changes (e.g.mediated by histone acetyltransferase) and induces antioxidant gene expression and dramatically improve cardiac functions (Ienglam et al., 2021).The antioxidant mechanism was mediated by medium-chain acyl-CoA dehydrogenase in cardiomycytes which inhibit apoptosis in MI model.SCFA has been found to play a pivotal role in cardiac energy metabolism.SCFAs, in the colon, are the product of fermentation of dietary fibers especially non-digestible carbohydrates.In general, the SCFAs concentrations vary between 50 and 100 mM in colon (Chambers et al., 2018;Martin-Gallausiaux et al., 2021).Among all SCFAs produced, acetate, propionate and butyrate are present in abundance, represent 60:20:20 molar ratios in colon, and liberated from different biosynthetic pathways.Other SCFAs which are present in very small proportion, includes valerate, caproate and formate.With the length of colon, the concentration of these SCFAs decline.In addition to fermentation of gut bacteria, the production of SCFA can also be done by animal fat as well as plant oil (Hu et al., 2022).
SCFAs play an essential role in the maintenance of intestinal homeostasis.SCFAs maintain integrity of intestinal epithelial cells, gut barrier functions and to modulate the functions of subpopulations, for instance, macophages and enteroendocrine cells through GPCRs and epigenetic changes (Martin-Gallausiaux et al., 2021).There are various potential roles of SCFA in modulating, through direct and indirect routes, metabolic health and CVD risk factors (Fig. 1).SCFA modulate both, systolic and diastolic, blood pressure which could be the most direct route of CVD risk modulation (Chambers et al., 2018).
Propionate mediate cardiac repair in MI mice through recruitment and activation of monocytes and neutrophils to peri-infract zone (Jiang et al., 2020).Chemokine and ROS generated from injured endothelium activate the recruited neutrophils.SCFAs inhibit synthesis of proinflammatory cytokines in monocytes through NF-κB and NLRP3 pathways to protect viable myocardium (Tang et al., 2019).Butyrate inhibit anti-inflammatory cytokines (IL1-β and TNF-α) production and induces synthesis of IL-10 and the injured endothelium get repaired by promotion of polarized M2 macrophages through engulfment of necrotic and apoptotic endothelial cells (Jiang et al., 2020, Lu et al., 2022).Propionate and butyrate induces polarization of T cells and generation of extrathymic Tregs and subsequent activation in rodent MI to ameliorate inflammatory injury in the myocardium (Arpaia et al., 2013;Lu et al., 2022).SCFAs induce epigenetic changes including influence on DNA methylation and subsequent activation of Tregs in post-MI model (Tang et al., 2019).Overall, the in vitro and in vivo (rodent models) studies proves SCFAs meditated recruitment of immune cells and antiinflammatory response and repair of myocardium injuries post-MI to improve cardiac function (Fig. 1).Most of the SCFAs signaling are mediated by inhibition of histone deacetylase and GPCRs (Lu et al., 2022).However, the details of underlying mechanisms are yet to be explored in the MI patients.

Trimethylamine N-oxide (TMAO)
TMAO is a uremic toxin, generated by gut microbes from meatderived phosphatidylcholine.TMAO as well as SCFA and bile acids are identified as a significant contributor to CVD (Fig. 2), particularly coronary microvascular disease (CMVD) and coronary artery disease (CAD) (Huang et al., 2023).Various dietary nutrients like betaine, choline, L- carnitine, and lecithin, sourced from vegetables, eggs, fish, peanuts, soybeans, and red meat, serve as carbon fuel for intestinal flora (Kazemian et al., 2020).The gut microbiota contributes to TMAO production through choline as well as TMA, the intermediate molecule, production (Puteri et al., 2022).The gut microbes produce choline using the phospholipase D enzyme (Chittim et al., 2018).Subsequently, the TMA molecule enters the host circulation.After reaching hepatocytes, in the presence of enzyme flavin-containing monooxygenase, TMA is converted to TMAO.TMA levels are typically low in circulation, with excretion of 96 % of TMA or TMAO through the kidneys (Huang et al., 2023).TMAO acts as an osmotic substance within tissues.It functions as a molecular chaperone and stabilizes proteins, as well as preserving the protein folding, and mitigating the impact of denaturing agents like high pressure, pH fluctuations, and urea.This particular property is crucial for maintaining enzyme activity in tissues.Numerous studies have established an association between elevated plasma TMAO levels and the advancement of atherosclerosis, indicating its CAD risk (Fretts et al., 2022;Huang et al., 2023).
TMAO is commonly associated with hypertension (Zhang et al., 2021).TMAO may impact the renin-angiotensin system and amplify the hypertensive effects of Angiotensin II (Ang II) (Ferrario, 2006;Karbach et al., 2016).One potential mechanism involves influence of TMAO on the conformational changes of Ang II receptors, leading to prolonged vasoconstriction.TMAO's ability to act as a chemical chaperone and facilitate protein folding is implicated in this process (Ufnal et al., 2014).Additionally, another study highlights that Th17 cells derived interleukin-17 in the gut can further contribute to the hypertensive effects of Ang II (Madhur et al., 2010;Hu et al., 2022).Conversely, certain investigators argue that the heightened TMAO levels might be a compensatory reaction (Ufnal and Nowiński, 2019).Research indicates that hypertension could result in an augmented permeability of the gut-blood barrier, enabling greater entry of TMA into the circulatory system and subsequently raising the TMAO concentration (Jaworska et al., 2017).The elevated levels of TMAO associated with enrichment of TMAO producers in gut has also been observed in MI patients (Table 1).

Bile acid
Bile acid (BA) is an important signaling regulator in cardiovascular system including that involved in lipid metabolism and absorption.BA act as a ligand that interact to cognate receptors farnesoid X receptor, Ca 2+ -activated potassium (K+) channels, nuclear receptors, and membrane receptors in gut, liver, kidney and cardiovascular tissues (Zhang et al., 2021).Moreover, it helps in preserving the homeostasis of the intestinal microflora and influences the microbial metabolism (Zhang et al., 2021).The secondary BA which is produced by gut microbes from primary BAs was elevated in heart failure (Mayerhofer et al., 2017).Moreover, level of secondary BA generated was associated with severity of HF suggesting gut microbes play an important role cardiovascular function.BA may also be used as therapeutic targets for conditions related to cardiovascular metabolism.

Tobacco consumption and alteration in oral microbiome is important risk factor of CVD
Tobacco consumption is one of the leading risk factors associated with CVD related mortality, the specific mechanism of this connection has not been clearly established yet.Smoking tobacco has also been linked to the increasing risk of acute MI, aortic aneurysm and early inception of atherosclerosis (Gallucci et al., 2020).A large study based Fig. 2. Influences of the gut microbiota and oral pathobionts on risk factors associated with MI and other CVD.The dysbiosis in gut microbiota led increment in the some microbial metabolites such as TMAO, and secondary bile acids and decreased levels of SCFAs which adversely impact cardio-metabolic health.Chronic exposure of alcohol and tobacco also impact gut and oral microbiome, respectively.Host genetics, age and sex, hypertension and chronic kidney diseases also influences human microbiome.A dysbiosis of gut microbiome also observed in MI patients that involve elevated level of fermicutes and other pathobionts and decreased abundance of bifidobacteria.* SCFA, short-chain fatty acid, TMAO, trimethylamine N-oxide, LPS, lipopolysaccharide.
M. Bijla et al. on Australian population revealed current smoke doubles the risks of all CVDs and with adjusted hazard ratio in current versus never smokers were 2.16 for AMI and 5.06 for HF (Banks et al., 2019).If exposed to a similar amount of smoke, female smokers exhibit a 25 % higher likelihood of developing CHD than men.This increased susceptibility in females appears to be linked to genes associated with thrombin signaling.
Smoking triggers an enhanced production of prothrombotic factors and it also hinders the fibrinolysis process (Gallucci et al., 2020).Cigarette smoke has more than 7000 chemical compounds of various classes, with a minimum of 72 known carcinogens (Gallucci et al., 2020).Nicotiana tabacum plants have the capacity to collect metals, but this capability can be perilous when toxic metals such as copper, mercury, zinc and nickel accumulate in tobacco products like cigarette smoke (Kozak and Antosiewicz, 2023).
Recent data indicates that cigarette smoking disrupts the balance of metals in the body, potentially triggering chronic diseases (Messner and Bernhard, 2014).These metals can trigger processes that result in oxidative stress, which in turn causes damage and inflammation, serving as the fundamental cause behind non-communicable chronic diseases like CVDs.Mortality from CVDs is greater among female smokers compared to male smokers (Gallucci et al., 2020).The risk of cardiovascular issues can be significantly lowered by smoking cessation.However, for individuals who were heavy smokers, there remains a notable residual risk even after five years of quitting that should not be overlooked or underestimated (Duncan et al., 2019).Areca nut is being largely consumed with or without smokeless tobacco (SLT), it induces ROS generation and pro-inflammatory markers, a systematically affects cardiovascular systems (Garg et al., 2023).Tobacco consumption alters the oral microbiome dysbiosis, enriches pathobionts in supragingival regions, and associates dental caries (Al-Marzooq et al., 2022).The tobacco associated microbiome dysbiosis may cause or exacerbate the inflammatory response in the oral cavity.Use of SLT products enrich some genera like Fusobacterium, Capnocytophaga, Leptotrichia, Prevotella, Porphyromonas, Veillonella, etc., in the oral cavity (Sajid et al., 2023).Altered oral mycobiome was also observed in Indian SLT users representing prevalence of Pichia, Mortierella and Sterigmatomyces (Sajid et al., 2022).The identified fungal enrichment was functionally predicted to be involved in biosynthesis tobacco-specific nitrosamines (TSNAs).TSNAs are carcinogens which and can cause inflammatory response in oral cavity and oral cancer (Sajid et al., 2023).

Excessive alcohol consumption affect gut microbiota dysbiosis and increase risk of MI
The WHO's global status report of 2018 on alcohol and health sates, excessive consumption of Alcohol (Ethanol), was responsible for approximately more than 3 million deaths every year worldwide (World Health Organization, 2018).Alcohol consumption increases CVD risk in a dose dependent manner (Biddinger et al., 2022).A heavy dose (21 or more drinks per week) of alcohol poses worse outcomes, increasing the CVD and death risk (Biddinger et al., 2022).High doses of alcohol might lead to the toxic effects including, heart failure, MI, disturbance of cardigan rhythm, atherosclerosis and hemorrhage (Silva et al., 2021).It has been found that if alcohol is consumed in larger amount, it leads to inflammation throughout the body by initiating a process in the gut (Patel et al., 2015).Through multiple pathways, alcohol and its metabolites induce inflammation of the intestine (Fig. 3).The intestinal inflammation might lead to dysfunction of multiple organs as well as chronic disorders such as inflammation bowel syndrome, neurological diseases, GI tract cancers and chronic liver disease.The alcohol is mainly absorbed by diffusion in upper part of the intestine, which then via portal vein, enters the liver.In the liver cells, hepatocytes, majority of the alcohol is metabolized through oxidative conversion.The alcohol is enzymatically converted into acetate by subsequent reactions of alcohol dehydrogenase and acetaldehyde dehydrogenase.The microsomal ethanol-oxidizing system is an alternative pathway of alcohol metabolism, through which a significant amount of alcohol is metabolized only when it is consumed in larger amount.This pathway can lead to cellular damage, due to the production of free radicals of oxygen.Acetaldehyde is also produced by bacteria in the GI tract (Cederbaum, 2012).
In contrast, low doses are beneficial to overall health as it regulates fibrinolysis, decreases blood coagulation rate, regulation of lipid metabolism, increases HDL levels, improves insulin sensitivity and glucose metabolism.(Silva et al., 2021).

Mechanistic approach for alcohol and gut-derived inflammation
Alcohol affects the cardiovascular system by complex mechanisms which are related to increased low-density lipoprotein (LDL), increased production of cytokines causing inflammation and ROS production (Fig. 3).Other mechanisms including elevated catabolism of protein, apoptotic cell death and mitochondrial stress are also the leading cause of alteration in the cardiovascular system (Silva et al., 2021).Alcohol induces bacterial overgrowth and dysbiosis which then increases endotoxin release, from gram negative bacteria.These secreted endotoxins activate an inflammation promoting immune response (Bishehsari et al., 2017).By direct or indirect (byproduct of affected digestive and intestinal functions) stimulation, alcohol increases bacteria within the intestine (Canesso et al., 2014).This bacterial overgrowth may increase the inflammation risk as intestinal bacteria produce excessive acetaldehyde, independently, by metabolizing alcohol.Acetaldehyde further increases the proinflammatory alcohol metabolites production (Zhong, 2014).People with alcohol use disorder (AUD) tend to have increased permeability of intestine and are more prone to liver disease (Leclercq et al., 2014).Another study showed that along with increasing gut permeability, plasma endotoxin levels were also increased in people with AUD (Parlesak et al., 2000).This intestinal permeability increases due to the disruption of epithelial cells (transepithelial permeability which is caused by cellular damage) and spaces between them (paracellular permeability), residing within the intestinal barrier, where the spaces consist of the cytoskeleton, tight junctions, and multiple associated proteins (Bishehsari et al., 2017).
Alcohol causes oxidative stress in multiple tissues and organs, either directly (by stimulating the ROS production) or indirectly (via increasing susceptibility of cells to other stressors) (Phillips et al., 2021).It was also highlighted that alcohol causes microRNAs, involved in gene silencing, to overexpress.It can influence genes associated with integrity of gut-barrier, by overexpressing their microRNAs (Tang et al., 2014;Bishehsari et al., 2017).
A case control study from 52 countries revealed low level use of alcohol reduces risk of MI, although the association was not uniform across the countries, but the risk was increased in episodic or excessive use of alcohol particularly in older age (Leong et al., 2014).Excessive alcohol use induces gut permeability.Gut bacterial peptidoglycan and LPS translocate into the circulatory system and initiate inflammatory response (Bishehsari et al., 2017).

Role of diet in maintaining cardiovascular health
It has been found that cardiovascular risks can be significantly decreased by practicing dietary therapies (Sindhu et al., 2021;Rahman et al., 2022).A diet-dependent postprandial glucose level was observed to be related to composition of the gut microbiome.The composition, and hence the gut microbiome environment, can be altered by having dietary therapies regulating these components (Rahman et al., 2022).There was confusion on uptake or elimination of specific dietary cholesterols uptake to reduce the risks for CVDs.The American heart association has devised an advisory regarding uptake of dietary cholesterol and its role in risks of CVDs (Carson et al., 2020).The advisory was based on systematic analyses of human studies with respect to uptake of dietary cholesterol and associated profiles of lipid and lipoproteins in blood, and risks to CVDs.They concluded that there was lack of significant associations of dietary cholesterols and risks for CVDs.They have suggested preferring a healthy dietary pattern (e.g.Mediterranean-diet) which should be rich in vegetables, fruits, whole grains, dairy products (low fat), seeds, nuts and vegetable oils.A fiber rich diet is preferred as it led to increase in microbial diversity in gut and elevate levels of SCFAs production (Filippo et al., 2010).The elevated SCFAs production improve cardiac functions through various mechanisms such as maintaining gut-barrier function, regulation of blood pressure and recruitment immune cells to resolve MI and clear damaged myocardial cells.The details SCFA mediated anti-inflammatory response have been discussed in separate section and represented in Fig. 1.
Examinations of the mature adult microbiome across diverse populations have revealed that the adult microbiota can be altered by kind of nutrient uptake, either temporarily or permanently (Holmes et al., 2008;Filippo et al., 2010).A balanced salt diet would be important for cardiovascular metabolism.High salt intake led development of hypertension by altering that gut microbiome through depletion of Lactobacillus murinus and elevated levels of Th17 cells (Wilck et al., 2017).The study also demonstrated that hypertension was resolved after intervention of L. murinus provoked Th17 cells activation.The plant derived phytochemicals (carotenoids, flavonoids, polyphenols, etc.) are favored due to their inatoxidant and anti-inflammatory properties to improve cardio-metabolism and treatment of CVDs including atherosclerosis, hypertension, MI and HF (Sindhu et al., 2021).
Antibiotic resistance may naturally evolve over time, but the improper or excessive use of antibiotics hastens this development.Additionally, antibiotics have profound repercussions on the human microbiome.A disrupted microbiome, or dysbiosis, jeopardizes crucial functions such as vitamin synthesis and defense against pathogens.Anticipating antibiotic effects is further complicated by factors such as distinct microbial growth stages, variable drug concentrations throughout the body, and interdependence among microbial taxa, antibiotic-induced phage activation, and microbial competition (Langdon et al., 2016).This imbalance in the microbiome is linked to various health issues and has been associated with immunological and metabolic disorders as well as an increased vulnerability to infectious diseases (Holmes et al., 2008;David et al., 2014).

Role of microbiome in hypertension as risk factor for MI
Chronic hypertension is the most crucial preventable risk factor for CVDs including MI (Kjeldsen, 2018).It is evident from preclinical and clinical studies that microbiome modulates blood pressure (Adnan et al., 2017;Avery et al., 2021).A microbiome dysbiosis, especially the elevated F/B ratio significantly associates hypertension in animal model (Yang et al., 2015).Microbes liberate metabolites as TMAO, tryptophol and SCFAs which modulates blood pressure.SCFAs mediated regulation of blood pressure through renin secretion by induction of G-protein coupled receptors (GPCRs) such as Olfr78 and Gpr41 (Avery et al., 2021).GPCRs are important modulators of signaling cascades and mediate diverse cellular functions including inflammation.Certain microbial genera would have protective implications on blood pressure, while some genera have negative implications and considered as risk factors.A bidirectional relationship with casual effect of gut micobiota and hypertension has been established using mendelian randomness analyses (Li et al., 2023).The study revealed Allisonella, Parabacteroides, Phascolarctobacteria, and Senegalimassilia had causal improvements with blood pressure while others such as Anaerostipes, Clostridia, Eubacteria, Eubacterium fissicatena, and Lachnospira were observed as risk factors.The hypertensive-gut also led to elevated level of microbes involved in risk factors for higher blood pressure.The microbial components like TMAO and endotoxins, permeate gut-barrier, and induce inflammation in the circulation (Tang et al., 2019).Thus, a microbiome homeostasis leads to fine balance between microbial metabolites both positive and pathogenic modulators are critical in managing blood pressure and improving cardiovascular health.Hypertension elevates biological aging through cellular senescence including immunosenescence and gut dysbiosis (Afsar and Afsar, 2023).The hypertension associated intricate relations of microbiome have been established, inflammation, immune response, and sympathetic activation in gut dysbiosis (Santisteban et al., 2017;Tang et al., 2019).Randomized control trails and systematic analyses revealed modulation of gut microbiome through probiotic would have a therapeutic implication in hypertension patients by lowering blood pressures (Khalesi et al., 2014;Mähler et al., 2020).This substantiates identification of microbial signatures or biomarkers to control blood pressure and its implications on improving cardiac health including management of MI.

Host genetics and the gut microbiota
The involvement in the host immunity, metabolism and health makes the human gut microbiome a complex ecosystem that may vary between individuals depending, mainly, on environmental factors (Rothschild et al., 2018).Nevertheless, the evidence of inheritance of some gut microbiota yields a possibility that host genetics might affect the inter-individual variance of the human gut microbiota (Turpin et al., 2016;Sanna et al., 2022aSanna et al., , 2022b)).A better understanding of host and microbe interaction can help in gaining cognizance of human health.A case study was conducted to elucidate the impact of host genetic factors on the attributes of microbial species leveraging metagenomic sequencing data obtained from 1514 subjects.The study successfully discerned the association of 9 loci with microbial taxonomic categorization and 33 distinct loci with microbial pathways (Bonder et al., 2016).Several multi-bacterial genome-wide studies (mbGWAS) conducted mainly across European populations (Turpin et al., 2016;Wang et al., 2016) have identified multiple relevant genetic loci including Ctype lectins (regulator of microbiota composition in other organisms) and LCT (Bonder et al., 2016), ABO (Rühlemann et al., 2021), and the vitamin D receptor gene (Wang et al., 2016).Interestingly, vitamin D has previously been attributed to play a role in CVD.However, results for most of these loci lacked consistent replication, except for two loci -the LCT and ABO (Sanna et al., 2022a).
During their expansion across the globe, humans evolved (and probably their microbiota too) by adapting genetically to the local environments driven by selection pressure exerted by novel climates, pathogens and diet (Scheinfeldt and Tishkoff, 2013;Pathak et al., 2022).Since microbes have shorter life cycles, they evolve faster than their host, resulting in the altered selective pressures over their host (Suzuki and Ley, 2020).Studies have observed the adaptation to different environments playing a role in the association between host allele and adaptive microbial functions (e.g., LCT-Bifidobacterium and AMY1-Ruminococcus interactions) suggesting the host mechanisms capable of substituting or recruiting advantageous microbial functions during local adaptation (Suzuki and Ley, 2020).Microbial involvement in well described human genetic adaptations across adaptations to diet, climate and pathogens that include shared metabolic pathways (e.g., alcohol and fatty acid metabolism), physiological responses (e.g., blood pressure regulation), and defenses against the local pathogens (e.g., malaria resistance) underscore the microbial potential to affect host evolution by altering adaptive landscape (Suzuki and Ley, 2020).
Therefore, investigating host gene-microbe interactions in the context of human adaptation may yield valuable insights into role of microbiota in occurrence and etiology of diseases, such as CVD/CAD in different populations as genes under strong selection in humans are often linked to metabolic and other disorders and display populationspecific variation.This becomes important especially in case of poorly analyzed CAD specific to South Asian populations, which are uniquely diverse in the environments (e.g., diet, temperature) and genes (Pathak, 2021) because current understanding of microbial functions and host gene-microbe links is primarily focused on the observations found in Western populations.

The role of sex differences in gut microbiota for CVDs
A prominent non-modifiable risk factor causing CVD is biological sex.Many histological and imaging studies have shown sex differential changes in terms of plaque size and composition, women tend to have more stable and diffuse plaques when compared to men who are generally at a greater risk for plaque rupture (Hellings et al., 2007).Plaque burden and composition changes significantly with age in women, suggesting an interaction between age and sex.Epidemiological data shows that women have lower prevalence of MI which they catch up with men in their seventh decade (Virani et al., 2020).
Gut microbiome and its involvement in CVDs are emerging as a key modulator for cardiovascular health.Differences in dietary intake between men and women serve as an important switch for microbiota composition and its respective metabolite production involved in CVDs.In comparison to healthy women, the Bacteroidetes abundance of healthy men was lower which further decreased with increase of BMI (Haro et al., 2016).The microbiota-derived pro-atherogenic metabolite derived from animal foods, TMAO levels are higher in females than in males (Baranyi et al., 2022) resulting in greater thrombotic risk in women.Another gut microbial metabolite SCFA produced by diets rich in fiber and plant proteins maintains intestinal borders and reduces CVD risk.Less SCFA results in increased susceptibility to dyslipidemia in men compared to women.
Cardiovascular physiology and pathology is modulated by complex interaction between sex hormones and gut microbiome.Sex hormones, e.g.17β-estradiol (E2) alter the gut microbiome composition, function, and distribution whereas microbial communities alter sex hormonal levels indicating bidirectional response (Baker et al., 2017).The gut microbiome is crucial in maintaining estrogen cycle via secreting β-glucuronidase leading to its subsequent physiological downstream effects (Markle et al., 2013).A causative-relationship between sex differences, gut microbiota and CVD development are yet to be determined, however, indications are there that the gut microbiome changes not only in regard to biological sex but also with the modifiable risk factors such as dietary habits which could lead to cardiovascular diseases.

Aging microbiome in MI
Aging is also an important contributor in shaping the human microbiome and age-related changes in microbial diversity (Roswall et al., 2021).At the time of birth, the microbiome develops according to the mode of delivery, and it influences infants by feeding type during the growth.The microbiome shapes as age passes through adulthood according to food pattern, genetics, mood, lifestyle, and environment (Salazar et al., 2019).In general, microbiota diversity increases with time, and the ratio of firmicutes to bacteroidetes (F/B) increases.The elevated F/B ratio leads to increase in TMAO level and decrease in SCFAs (Liu et al., 2023).In the centenarian, microbiota diversity, F/B ratio and SCFAs level decreased due to elevated inflammation but TMAO level increased (Biagi et al., 2010;Liu et al., 2023).The elevated TMAO in older ages can be due to deterioration of renal function (Rath et al., 2021).
In age-related CVDs, microbiome associated mitochondrial dysfunction plays an important role.Microbial metabolites promote mutation in mtDNA, ROS generation, calcium overload, oxidative stress, mitochondrial autophagy and induce apoptotic pathways (Han et al., 2021;Liu et al., 2023).Microbiota diversity and metabolites, bile acids, SCFAs and TMAOs mediates age-related CVDs progression.The agerelated changes in microbiome, physiology and immunity associates' reduction in expression of tight-junctions proteins, thus increase gut permeability, and inflammatory response (DeJong et al., 2020).Translocation of microbes or its components in the circulatory system induces inflammatory response and promotes cardiovascular events after MI (Zhou et al., 2018).

Integrated multiomics approach to investigate microbiome interactions in MI pathogenesis
The variable regions of 16s rRNA encoding gene are being utilized for identification of bacteria or microbial communities in a specific environment (Kumar et al., 2022, Jogi et al., 2024).The potential microbial functions can be inferred partially by metagenomics based on prediction model of the functional gene content from microbial 16S rRNA data.Metabolomics combined with metagenomics can be a potential approach to identify altered microbial taxa and associated microbial metabolites to be associated with MI (Chiu et al., 2022).The genome wide associations studies utilizing a larger base of participants could generate categorical variable microbiome communities (at genus level) of the participants, and applying a logistic regression model or Mandalian randomization analyses to explore the potential associations with host genetic loci and cardiovascular health (Qin et al., 2022).
Limitation in our present knowledge about the microbiome dynamics shape at the level of individual hosts and its associative or causal link in MI need further integrated multiomic approaches.Expression signature (metatranscriptomic), functional annotation (metaproteomics) of microbial taxa in gut alongwith metabolomics and host genetics can give deeper insight with regard to the relative impact of host genetics and environment factors over the variation of individual host level microbiome composition with a potential effect over the MI.A metatranscriptomics represent microbial transcriptomes in a habitant and which can be studied by random shotgun sequencing to functional profile of active taxa of the microbiota (Ojala et al., 2023).Large cohort studies from underrepresented populations with broader set of phenotype categories would better to explain the variation in microbiome composition at a greater level (Qin et al., 2022).The intricate relation of microbial metabolites and associated active metabolic pathways with host genetics which are involved in MI pathogenesis are under-researched and need to be explored.Besides genetic factors, environment factors including diet are also crucial for interventions of precision nutrition, prebiotics or probiotics, and fecal microbiota transplantations, in the management of MI.

Therapeutic regulation of gut microbiota
Various diseases such as hypertension, obesity, heart related diseases, diabetes, can be affected by the changes in microbiota.Chemicals released by microbes can alter drug's pharmacokinetics and pharmacodynamic effects.Almost all of the orally consumed medications or drugs influence the gut microbiome in one way or another.Gut microbiota has been found as a potent therapeutic target as it connected to pathogenesis of various diseases.Recently, a publication reported that antibiotics were used to inhibit TMAO (Rahman et al., 2022).These antibiotics can lead to negative effects, such as clostridium colitis development, when taken for a long period of time.(Nie et al., 2018).Nevertheless, TMAO indicates the modification to be made in the inhibition; hence, the risks of thrombosis can be minimized.(Roberts et al., 2018;Rahman et al., 2022).SCFAs transplantation or dietary supplementation following MI improved cardiac repair (Tang et al., 2019).Exercise leads to protection in MI patients through metabolites liberated by gut microbes.The microbial metabolites 3HBA and 3HPA mediate the protective effect of exercise against MI (Zhou et al., 2022).

Prebiotic, probiotic and postbiotic interventions
Wide ranges of fermented foods including yogurt, kefir, sauerkraut, tempeh, and kimchi are potential sources of probiotics.Currently well known, probiotics include the Saccharomyces and bacteria like Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, Propionibacterium, Bifidobacterium, etc.They can activate natural killer cells and macrophages, which can help to provoke nonspecific cellular immune response (Pandey et al., 2015).Probiotics help to improve the mechanism of digestion by enhancing the minerals absorption and vitamins synthesis (Oniszczuk, Anna et al., 2021).Probiotic strains have significant antioxidant activity and enhance colonic mucosal detoxification enzymes to strengthen defenses against ROS.Probiotic interventions have shown therapeutic implication in controlling blood pressure in randomized controlled trail (Mähler et al., 2020).Thus improving gut homeostasis in hypertensive patients would be in important preventive target to manage MI.A probiotic (Lactobacillus johnsonii) intervention in a post-AMI animal model mediates remodeling of gut-microbiome and improves cardiac function (Zhong et al., 2023).
Moreover, prebiotics are indigestible plant oligosaccharides, helps to balance and promote the growth of beneficial microorganisms.The gut bacteria ferment them and liberate SCFAs.Potential benefits of SCFAs production include augmented intestinal membrane integrity and mineral absorption, modification of metabolic, cardiovascular, and inflammatory biomarkers (Delgado et al., 2018).The preclinical analyses in hypertensive mice model revealed propionate a kind of SCFA protect against the cardiovascular damage ( Bartolomaeus et al., 2019).A fiber rich diet improved homeostasis of gut microbiota, modulated production microbial metabolites and immune response towards curative impact on MI in mice model (Zhao et al., 2022).The preclinical and clinical evidence strongly support targeted nutritional interventions of probiotics and prebiotics to ameliorate cardiac functions in MI patients through remodeling of gut microbiome.The elevated gut permeability in MI patients need to be considered while interventions of probiotics as the test strain can breach epithelial barrier and enter to blood circulation.In such case, biosafety assessment of a probiotic is important especially the binding affinity of test strain to fibrinogen shall be assessed (Yadav and Kumar, 2022).Moreover, postbiotics (the metabolic byproducts of probiotics or prebiotics) can also be used to strengthen intestinal microbiota and improve clinical outcome in MI patients (Park et al., 2022).These are the complex mixtures of probioticsecreted metabolites, including enzymes, secreted proteins and biosurfactants, SCFAs, vitamins, and organic compounds from cell-free supernatants can be processed easily (by heat treatment etc.) to overcome the limitations of probiotics (Nataraj et al., 2020).

Conclusion and future perspectives
A growing number of studies have substantiated the connection between gut microbiota and CVD, shedding light on the underlying mechanisms involved in these associations.The role of metabolomics is intriguing in this aspect, which facilitates the understanding how the interplay between gut microbiota and diet (environment) lead to CVD risk through gut-produced metabolites that significantly contribute to CVD pathogenesis.Latest research findings have identified distinct microbial taxa associated with CVD and highlighted that the gut-derived metabolites, such as TMAO or SCFAs can promote or attenuate CVD.However, the predominant focus of current investigations to bacterial communities, neglecting the potential role played by other gut microbiota such as viruses, fungi, and archaea indicate there is still much to explore.Integrating these components into the analysis of microbiota-CVD association might unveil new potential therapeutics for future.Supporting the case for integrating host genomic and microbiome data with cardiovascular functions in the models of precision medicine, which may refine risk predictions and therapeutic interventions by improvement of patient characterization, emphasizing the significant role of microbiota in precision medicine.
Further explorations of intricate mechanisms that affect the microbiota and MI development considering factors like ethnicity, sex, and utilizing advanced technologies such as nanomedicine, data sciences and machine learning is crucial to elucidate the gut bacterial-mediated mechanisms.The advanced techniques might pave the way for more effective and precise microbiome-based preventative and therapeutic approaches for CAD in coming times.

Fig. 3 .
Fig. 3. Disruption of the intestinal barrier homeostasis by Alcohol.It increases permeability of this barrier via two routes, i.e., transcellular (through the epithelial cells) and paracellular routes (through the tight junctions between epithelial cells).Alcohol and its metabolites compromises cell membrane, via transcellular route, through multiple mechanisms, one of which involves oxidative stress induced by Reactive Oxidative Species (ROS).

Table 1
Microbiome interactions with different risk factors in development of myocardial infarction.