Intestinal microbial metabolism of phosphatidylcholine and cardiovascular risk

TMAO levels are associated with cardiovascular disease risks in a variety of cohorts.

“Numerous recent case–control and longitudinal studies have shown a striking association between trimethylamine N‐oxide (TMAO) levels and cardiovascular disease risks in a variety of cohorts.1, 2, 3, 4, 5, 6, 7, 8, 9, 10”

In a cohort of 4007 stable patients evaluated electively for cardiac disease, higher plasma TMAO concentrations were linked to greater 3-year incidence of myocardial infarction or stroke, and this link remained after adjustment for cardiovascular history, standard risk factors, kidney function, and medications; the adjusted risk for the top versus bottom quartile was 1.64-fold (p<0.001).

“Plasma TMAO levels in subjects (N>4000) independently predicted incident (3 yr) thrombosis (heart attack, stroke) risk.”

Multiple clinical studies have found associations between plasma TMAO and coronary atherosclerotic plaque burden and cardiovascular disease risk.

“Finally, an association between plasma TMAO levels and both the extent of coronary atherosclerotic plaque burden and CVD risks has been observed in multiple distinct clinical studies (Wang et al., 2011; Tang et al., 2013; Tang et al., 2014; Lever et al., 2014; Tang et al., 2015).”

Isotope tracer studies before and after oral antibiotics affirmed that gut microbes are obligatory for TMAO generation in humans.

“Moreover, an obligatory role for gut microbes in TMAO generation in humans was affirmed by two distinct studies involving ingestion of either isotope labeled phosphatidylcholine or isotope labeled carnitine as tracer before versus following exposure to an oral cocktail of poorly absorbed antibiotics to suppress intestinal microbes (Tang et al., 2013; Koeth et al., 2013).”

Gut microbes take part in a metaorganismal pathway that contributes to atherosclerosis.

“recent studies reveal participation of gut microbes in a metaorganismal pathway that contributes to the development of atherosclerosis (Wang et al., 2011; Koeth et al., 2013; Tang et al., 2013; Gregory et al., 2015).”

Circulating TMAO levels are associated with cardiovascular disease risks in multiple distinct clinical studies and cohorts.

“circulating levels of TMAO have been shown in multiple distinct clinical studies and cohorts to be associated with CVD risks”

Gut microbes are required for TMAO formation from trimethylamine-containing nutrients, including choline, phosphatidylcholine, L-carnitine, γ-butyrobetaine, and to a lesser extent betaine.

“Animal model and human clinical studies demonstrate an obligatory role for gut microbiota in TMAO formation from TMA-containing nutrients including choline and phosphatidylcholine9, 10, L-carnitine8, and more recently, γ-butyrobetaine15, and to a lesser degree, the choline oxidation metabolite betaine11.”

In a large study of mostly preserved renal function, TMAO predicted three-year major adverse cardiovascular events even after renal function adjustment.

“In one large study of subjects with predominantly preserved renal function, we reported the prognostic value of TMAO for predicting three year risk for major adverse cardiovascular events (MACE = myocardial infarction, stroke or death) remained significant following adjustments for renal function 9.”

Trimethylamine-N-oxide (TMAO) is produced by gut microbes from dietary choline, phosphatidylcholine and L-carnitine.

“Specifically, gut microbiota-mediated metabolism of phosphatidylcholine, choline or L-carnitine each have been shown to ultimately produced trimethylamine-N-oxide (TMAO), and in multiple clinical studies, TMAO levels have been shown to be associated with cardiovascular risks8–10, 13.”

Multiple clinical studies have linked TMAO levels to cardiovascular risk.

“in multiple clinical studies, TMAO levels have been shown to be associated with cardiovascular risks8–10, 13.”

The authors' group has established the obligatory role of intestinal microbiota in TMAO production from dietary choline and other TMA nutrients in humans, and the association between elevated fasting TMAO and higher incident risks of long-term MACEs.

“We have also established the obligatory role of intestinal microbiota in the production of TMAO from dietary choline and other TMA nutrients in humans, 16,17 and the association between elevated fasting levels of TMAO and higher incident risks of long-term MACEs.17”

Elevated TMAO levels predict increased prevalent cardiovascular disease risk and increased incident risk of major adverse cardiovascular events in large-scale human clinical studies.

“Moreover, elevated levels of TMAO have been shown to predict increased prevalent cardiovascular disease (CVD) risk, and increased incident risk of major adverse cardiovascular events (MACE ¼ myocardial infarction, stroke, and death) in large-scale human clinical studies.14,16,17”

In prior human studies, antibiotic administration had limited effects on circulating choline and betaine levels despite abolishing TMAO levels after ingestion of stable-isotope-labelled d9-phosphatidylcholine.

“Interestingly, the administration of antibiotics in humans in our prior studies had limited effects on circulating choline and betaine levels, despite abolition of TMAO levels, upon ingestion of stable-isotope-labelled d9-PC.17”

Choline, betaine, and TMAO are all metabolites formed following ingestion of dietary phosphatidylcholine.

“Choline, betaine, and TMAO are all metabolites formed following ingestion of dietary PC. 14,17”

Choline, phosphatidylcholine, and carnitine are dietary precursors for TMAO production in mice and humans.

“choline, phosphatidylcholine and carnitine, trimethylamine (TMA)-containing nutrients abundant in foods like meat, egg yolk and high fat dairy products, serve as dietary precursors for trimethylamine N-oxide (TMAO) generation in mice and humans”

TMAO promotes atherosclerosis in animal models.

“both enhances atherosclerosis in animal models”

Intestinal microbe-dependent generation of TMAO is mechanistically linked to increased risk for future cardiovascular events via dietary nutrients such as phosphatidylcholine, choline, and carnitine.

“Our group has recently described a mechanistic link between intestinal microbe-dependent generation of trimethylamine-N-oxide (TMAO) and increased risk for future cardiovascular events (death, myocardial infarction, and stroke) by a pathway involving dietary nutrients such as phosphatidylcholine, choline, and carnitine (10,11).”

TMAO has pro-atherogenic properties.

“While TMAO has been shown to possess pro-atherogenic properties (10,11,17)”

TMAO formation depends on the presence of an intact gut microbiota.

“The formation of TMA, which is subsequently metabolized to TMAO, depends on the presence of an intact gut microbiota [6]”

In multiple human studies, elevated TMAO is independently associated with prevalent CVD and incident risks for MI, stroke, death, and revascularization.

“In multiple human studies, elevated TMAO has been independently associated with prevalent CVD and incident risks for MI, stroke, death, and revascularization.”

Patients in the upper quartile for TMAO had a 2.5-fold increased risk of major adverse cardiac events compared with the lowest quartile, independent of traditional risk factors, renal function, and medication use, and had poorer event-free survival.

“Specifically, patients in the upper quartile for TMAO levels (compared with the lowest quartile) had a significant, 2.5-fold increased risk of experiencing a major adverse cardiac event (MI, stroke, or death), independent of traditional cardiovascular risk factors, renal function, and medication use, as well as overall poorer event-free survival (37).”

TMAO levels are strongly linked to cardiovascular disease risks.

“a metabolite shown to be both mechanistically linked to atherosclerosis and whose levels are strongly linked to cardiovascular disease (CVD) risks.”

In over 4,000 subjects undergoing elective coronary angiography, elevated TMAO levels predicted major adverse cardiac events such as death, MI, and stroke over 3 years.

“In an alternative subsequent expansion study of over 4,000 subjects undergoing elective coronary angiography, elevated TMAO levels predicted major adverse cardiac events such as death, myocardial infarction (MI), and stroke over a 3-year period.”

An obligatory role for gut microbiota in TMA and TMAO formation from ingested phosphatidylcholine was confirmed in germ-free mice and human clinical investigations using egg yolk, isotope-labeled phosphatidylcholine, and oral antibiotics.

“An obligatory role for gut microbiota in both TMA and TMAO formation from ingested PC was confirmed in animal model studies, which included germ-free mice (25), as well as human clinical investigations involving ingestion of egg yolk, isotope-labeled PC, and a cocktail of oral antibiotics (37).”

Intestinal microbiota are obligatory for generating TMAO from multiple dietary nutrients.

“These observations highlight the obligatory role of intestinal microbiota in the generation of TMAO from multiple dietary nutrients, and TMAO as the proatherogenic species likely promoting the striking associations noted between plasma levels and both prevalent and incident CVD risks.”

Later human studies using hard-boiled egg, egg yolk, or labeled phosphatidylcholine confirmed that eating phosphatidylcholine directly generates TMAO.

“More recent studies examining ingestion of either hard-boiled egg or egg yolk (37,38,62) or ingestion of trimethyl-d9-PC (37) have confirmed direct generation of TMAO from PC ingestion in humans.”

Labeled betaine or phosphatidylcholine given in vivo produced d9-TMA and d9-TMAO directly in plasma and urine.

“In vivo studies in which trimethyl-d9-labeled betaine or PC were ingested showed a direct generation of d9-TMA and d9-TMAO within plasma and urine (37,39,55).”

Choline, in free and esterified forms, and L-carnitine are the most common dietary nutrients ingested that produce TMA and TMAO.

“Choline (free and esterified forms) and L-carnitine are the most common dietary nutrients ingested that produce TMA and TMAO (30,(37)(38)(39)55).”

Intestinal microbiota, dietary trimethylamine-containing nutrients, and cardiovascular disease are linked.

“Our laboratory has elucidated a link between intestinal microbiota, dietary trimethylamine-containing nutrients ( e.g. choline, phosphatidylcholine, and carnitine), andcardiovasculardisease(5-7).”

Plasma TMAO levels in subjects are associated with prevalent and incident cardiovascular disease risks.

“plasma levels in subjects are associated with prevalent and incident cardiovascular disease risks (5, 7, 9, 10).”

An obligatory role for gut microbes in TMAO formation in both mice and humans was shown.

“An obligatory role for gut microbes in TMAO formation in both mice (5, 6) and humans (7) was shown”

Elevated plasma TMAO levels are observed in subjects at risk for incident CVD and adverse CVD events including heart attack, stroke, and death.

“Elevated plasma TMAO levels are observed in subjects at risk for incident cardiovascular disease (CVD) development and adverse CVD events including heart attack, stroke, and death.[1][2][3][4]”

TMAO is a gut microbiota-generated metabolite with mechanistic links to atherosclerotic heart disease.

“Trimethylamine N-oxide (TMAO) is a gut microbiota-generated metabolite with mechanistic links to the pathogenesis of atherosclerotic heart disease.[1][2][3][4][5]”

Studies have shown dose-dependent TMA/TMAO formation with egg ingestion.

“Studies have also shown dose-dependent TMA/TMAO formation with egg ingestion.2,18”

TMAO is generated via a metaorganismal pathway beginning with gut microbiota-dependent formation of TMA from TMA-containing nutrient precursors.

“Trimethylamine N-oxide is generated via a metaorganismal pathway that begins with gut microbiota-dependent formation of trimethylamine (TMA) from TMA containing nutrient precursors (Figure 1A).[1][2][3]16”

In humans, elevated plasma TMAO levels are positively correlated with increased risk for major adverse cardiovascular events.

“In humans, recent clinical studies evidence a positive correlation between elevated plasma levels of TMAO and an increased risk for major adverse cardiovascular events.”

Production of TMA and TMAO is almost totally suppressed with broad-spectrum antibiotics such as Ciprofloxacin, Vancomycin or Metronidazole in rats and humans, but levels return to normal after one month of antibiotic withdrawal.

“some studies performed with antibiotics in rats and humans reveal that the production of TMA and TMAO is almost totally suppressed with the use of broad-spectrum antibiotics, such as Ciprofloxacin, Vancomycin or Metronidazole. However, the levels of TMAO return to normal after one month of the withdrawal of the antibiotics [7,52].”

Elevated plasma TMAO levels have been found in people at risk of CVD, and these patients usually show greater concentrations of TMAO precursors.

“Indeed, elevated plasma TMAO levels have been found in people at risk of CVD. These patients usually show greater concentrations of the TMAO precursors too.”

TMAO could serve as a biomarker in humans to predict prevalence of CVD and increased incidence of major adverse cardiovascular events.

“In this context, it is thought that TMAO could serve as a biomarker in humans to predict prevalence of CVD and increased incidence of major adverse cardiovascular events (MACE), such as myocardial infarction, stroke and even death [7,14,52,53,54,55].”

One month after withdrawal of antibiotics, TMAO levels are detectable again.

“However, one month after the withdrawal of antibiotics, TMAO levels are detectable again [52].”

Antibiotics can affect beneficial bacteria.

“Moreover, antibiotics do not only kill harmful bacteria, but could affect the beneficial too [52].”

Chronic use of antibiotics is not viable because it can lead to resistant bacterial strains and repopulation.

“Albeit the use of antibiotics is effective in the suppression of microbiota that produces TMA, the chronic use of antibiotics is not viable since it can lead to resistant bacterial strains and repopulation.”

Broad-spectrum antibiotics such as ciprofloxacin and metronidazole lead to near-complete suppression of TMAO levels.

“The use of broad spectrum antibiotics such us ciprofloxacin and metronidazole leads to near almost complete suppression of TMAO levels.”

Elevated TMAO has been observed in patients with cardiovascular disease and atherosclerosis, highlighting a potential downside to increased protein intake.

“Elevated TMAO has been observed in patients with cardiovascular disease and atherosclerosis, highlighting a potential downside to increased protein intake.[15-17,22, 37]”

Gut microbial production of trimethylamine N-oxide (TMAO) from dietary choline and l-carnitine increases the risk of developing cardiovascular disease in both mice and humans, independently of traditional cardiometabolic risk factors.

“Recently, it has been shown that gut microbial production of trimethylamine N-oxide (TMAO) from dietary choline and l-carnitine increases the risk of developing cardiovascular disease in both mice and humans, independently of traditional cardiometabolic risk factors (89).”

Circulating concentrations of TMAO were predictive of prevalent cardiovascular diseases and future cardiovascular events in clinical cohorts.

“Recent studies by Wang and Tang et al reported that circulating concentrations of trimethylamine N‐oxide (TMAO), a metabolite derived from the gut microbiota, were predictive of prevalent cardiovascular diseases (CVDs)1 and future cardiovascular events3 in clinical cohorts.”

All included studies were clinical cohorts, including patients at higher cardiovascular risk, enriched for baseline heart disease, kidney disease, peripheral artery disease, or diabetes mellitus.

“All of the studies included clinical cohorts, including patients at higher cardiovascular risk, that is, enriched for baseline heart disease,3, 8, 12, 13, 14, 15, 16, 17, 21 kidney disease,10, 11, 18, 19, 20, 22, 23 peripheral artery disease,25 or diabetes mellitus.7, 26”

Of the 19 publications, 16 publications, including 19 data points, were eligible for the main analysis to calculate a pooled RR of elevated TMAO levels as compared with low levels.

“Of the 19 publications, a total of 16 publications, including 19 data points, were eligible for our main analysis to calculate a pooled RR of elevated TMAO levels as compared with low levels3, 7, 8, 10, 11, 13, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26 (Table 1 and Figure 1).”

Wang et al. identified a novel pathway linking dietary lipid intake, the intestinal microbiota, and atherosclerosis.

“Wang et al. identified a novel pathway linking dietary lipid intake, the intestinal microbiota, and atherosclerosis (Figure 3)57, 58.”

Catabolism of choline by the intestinal microbiota forms trimethylamine, which the liver metabolizes into trimethylamine oxide; trimethylamine oxide is strongly associated with increased risk for coronary vascular disease in humans.

“Catabolism of choline by the intestinal microbiota results in the formation of the gas, trimethylamine (TMA), which is metabolized by the liver into trimethylamine oxide (TMAO)—a small molecule that is strongly associated with the increased risk for coronary vascular disease in humans.”

The intestinal microbiota may contribute to atherosclerosis by producing metabolites of the dietary lipid phosphatidylcholine that are associated with risk for coronary vascular disease.

“The intestinal microbiota may also contribute to development of atherosclerosis by producing metabolites of the dietary lipid phosphatidylcholine that are associated with the risk for coronary vascular disease.”

Consuming at least two eggs, which contain mostly PtdCho, increases TMAO formation.

“However, consumption of ≥2 eggs, which contain mostly PtdCho, results in increased formation of TMAO (79,110).”

In 4,007 patients who had elective coronary angiography, higher plasma TMAO levels were linked to greater risk of major adverse cardiovascular events over three years.

“During three years of follow-up in patients (n = 4,007) undergoing elective coronary angiography, increased plasma concentrations of TMAO were associated with increased risks of major adverse cardiovascular events (110).”

In individuals undergoing elective coronary angiography, plasma TMAO correlated with increased serum glucose and diabetic state.

“In individuals undergoing elective coronary angiography, plasma TMAO concentrations were correlated with increased serum glucose and the patient's diabetic state (110).”

Multiple human and animal studies support mechanistic and clinical prognostic associations between TMAO formation and cardiometabolic disease risks.

“multiple human and animal studies supporting both mechanistic and clinical prognostic associations between TMAO formation and cardiometabolic disease risks have been reported8–16.”

Plasma trimethylamine-N-oxide (TMAO), a choline metabolite, is a novel and independent risk factor for promoting atherosclerosis.

“A recent metabolomics approach identified that plasma trimethylamine-N-oxide (TMAO), a choline metabolite, is a novel and independent risk factor for promoting AS (2, 3).”

TMAO induces atherosclerosis by affecting cholesterol metabolism through inhibiting hepatic bile acid synthesis.

“TMAO has been shown to induce AS by affecting cholesterol metabolism through inhibiting hepatic bile acid (BA) synthesis (2–4).”

Plasma TMAO is a metabolite strongly associated with atherosclerosis.

“Recently, plasma TMAO was identified as a metabolite strongly associated with AS (2–4).”

TMAO partially contributes to the development of atherosclerosis by regulating the major pathway of cholesterol metabolism and the bile acid synthetic pathway.

“Previous studies suggest that TMAO partially contributes to the development of AS by regulating the major pathway of cholesterol metabolism and the bile acid synthetic pathway.4, 5, 6”

Trimethylamine-N-oxide (TMAO) is a novel and independent risk factor for promoting atherosclerosis through inducing vascular inflammation.

“Trimethylamine‐N‐oxide (TMAO) has recently been identified as a novel and independent risk factor for promoting atherosclerosis through inducing vascular inflammation.”

In a large independent clinical cohort (n=4007), elevated TMAO levels were associated with significantly increased risk for major adverse cardiovascular events (2.54 for highest versus lowest TMAO quartile; P<0.001).

“In a large independent clinical cohort (n=4007), elevated TMAO levels were associated with significantly increased risk for major adverse cardiovascular events (2.54 for highest versus lowest TMAO quartile; P<0.001).5”

Within the cohort examined, the hazard ratio for TMAO was significantly higher than that for traditional risk factors such as LDL cholesterol.

“Within the cohort examined, the hazard ratio for TMAO was significantly higher than that for traditional risk factors such as LDL cholesterol.”

Elevated TMAO levels retained a strong prognostic value for predicting incidence of adverse cardiovascular events, even after adjustment for traditional risk factors and renal function.

“Furthermore, elevated TMAO levels retained a strong prognostic value for predicting the incidence of adverse cardiovascular events, even after adjustment for traditional risk factors and renal function.5”

Plasma TMAO is a novel and independent risk factor for promoting AS.

“Recently, plasma TMAO was identified as a novel and independent risk factor for promoting AS.”

Follow-up targeted studies with choline challenge and microbiota characterization/manipulation showed that consuming foods rich in choline or carnitine (eggs, milk, liver, meat, fish) produced high TMAO concentrations in humans and animals that had the requisite microbiota for converting choline or carnitine to trimethylamine, the immediate TMAO precursor.

“Hazen and coworkers showed that consumption of foods rich in choline or carnitine, such as eggs, milk, liver, meat, or fish, produced high concentrations of TMAO in both humans and animals who possessed the requisite microbiota for metabolizing choline or carnitine to trimethylamine, the immediate precursor of TMAO (108, 171, 172).”

In a cohort of more than 2000 cardiovascular disease patients, those in the highest quartile of plasma TMAO had a 2-fold risk of heart attack or stroke compared with those in the lowest quartile.

“Subjects from a cohort of .2000patients with cardiovascular disease, who were in the highest quartile for plasma TMAO concentrations, had a .2-foldrisk of a heart attack or stroke compared with subjects from the lowest quartile (108, 172).”

The microbiota play an important role in choline diet-induced trimethylamine N-oxide production, which has been implicated in CVD.

“The microbiota play an important role in choline diet–induced trimethylamine N-oxide production, which has been implicated in CVD.”

High TMAO levels linked to TMA oxidation by the human hepatic flavin monooxygenase FMO3 have been associated with cardiovascular diseases.

“These observations are of interest because high TMAO levels linked to TMA oxidation by the human hepatic flavin monooxygenase FMO3 have been associated with cardiovascular diseases (CVDs) (Tang et al., 2013; Wang et al., 2011), while it is known that RYGB is associated with a lower CVD risk (Sjöström et al., 2012).”

Gut microbes can convert otherwise beneficial dietary compounds, such as choline, into metabolites that are detrimental to human health.

“Likewise, gut microbes can also convert otherwise beneficial dietary compounds, such as choline, into metabolites that are detrimental to human health (7–10).”

TMAO is linked to cholesterol accumulation in macrophages and foam cell deposition and to higher risk of a major adverse cardiac event.

“a metabolite linked to accumulation of cholesterol in macrophages and foam cell deposition127, and higher risk of a major adverse cardiac event128.”

In humans, phosphatidylcholine or L-carnitine administration augments TMA plasma levels and increases cardiovascular disease risk; antibiotic treatment dramatically reduces TMA levels.

“Also in humans, PC or LC administration augmented TMA plasma levels, and increased the risk for cardiovascular disease; notably, antibiotic treatment dramatically reduced TMA levels in these subjects [68, 70].”

Recent studies reveal a link between microbiota and atherogenesis.

“a series of recent studies [68-70] revealed a link between microbiota and atherogenesis.”

Food is a major determinant of the proportional representation of organisms in the gut microbiota and of its gene content.

“Food is a major factor that shapes the proportional representation of organisms present in the gut microbial community (microbiota), and its gene content (microbiome).”

The gut microbiota and microbiome help extract and metabolize dietary ingredients.

“The microbiota/microbiome in turn plays an important role in extracting and metabolizing dietary ingredients9-14.”

TMA produced by gut microbiota from dietary quaternary amines, mainly choline and carnitine, is associated with atherosclerosis and severe cardiovascular disease.

“This is exemplified by trimethylamine (TMA), a microbial metabolite that is produced by various taxa of the gut microbiota from dietary quaternary amines, mainly choline and carnitine. TMA is absorbed via the intestinal epithelium and further oxidized to trimethylamine N-oxide (TMAO), which was associated with atherosclerosis and severe cardiovascular disease in several independent studies [1–4].”

Trimethylamine N-oxide is a metaorganismal metabolite formed following ingestion of dietary nutrients abundant in a Western diet, such as lecithin, choline, and carnitine.

“The first studies revealing a potential causal link between the gut microbiome and CVD focused on trimethylamine N-oxide (TMAO), a metaorganismal metabolite formed following ingestion of dietary nutrients abundant in a Western diet (e.g. lecithin, choline, carnitine)7–9.”

Generation of trimethylamine N-oxide in humans and mice occurs via a multistep, metaorganismal pathway starting with dietary precursors choline, phosphatidylcholine, and carnitine.

“Through these and other studies, generation of TMAO in humans and mice has been shown to occur via a multistep, metaorganismal pathway starting with the dietary precursors choline9, phosphatidylcholine8, 9, and carnitine7.”

In healthy humans given phosphatidylcholine challenge, plasma levels of TMAO were suppressed by oral administration of broad spectrum antibiotics.

“Further evidence that the production of TMAO is dependent on metabolism by intestinal microbiota is provided by studies in healthy humans given phosphatidylcholine challenge, in which the plasma levels of TMAO were suppressed by oral administration of broad spectrum antibiotics [14].”

TMAO is either transported to tissues for accumulation as an osmolyte or cleared by the kidney.

“TMAO is then either transported to the tissues for accumulation as an osmolyte or, more commonly, cleared by the kidney [3,9,13,14].”

In health participants, suppression of intestinal microbiota with oral broad-spectrum antibiotic reduced plasma TMAO levels after a phosphatidylcholine challenge.

“Indeed, in health participants, suppression of intestinal microbiota with oral broad spectrum antibiotic reduced plasma TMAO levels after a phosphatidylcholine challenge [14].”

TMAO levels increased one month after stopping antibiotics.

“TMAO levels increased one month after stopping antibiotics [14].”

The mechanisms through which hPDI could reduce CHD risk are likely shared with the mechanisms for type 2 diabetes risk reduction.

“The mechanisms through which hPDI could reduce CHD risk are likely shared with the mechanisms for type 2 diabetes risk reduction.(2, 24–32)”

These dietary factors could aid in weight loss/maintenance, enhance glycemic control and insulin regulation, improve lipid profile, reduce blood pressure, improve vascular health, decrease inflammation, and foster more favorable diet-gut microbiome interactions, thereby lowering CHD risk.

“all of which could aid in weight loss/maintenance, enhance glycemic control and insulin regulation, improve lipid profile, reduce blood pressure, improve vascular health, decrease inflammation, and foster more favorable diet- gut microbiome interactions (e.g. through lowered levels of trimethylamine N-oxide), thereby lowering CHD risk.”

Gut microbes transform dietary phosphatidylcholine and l-carnitine to trimethylamine, which is absorbed and further oxidized by hepatic flavin monooxygenase to trimethylamine-N-oxide (TMAO).

“Gut microbes transform phosphatidylcholine and l‐carnitine from ingested nutrients to trimethylamine, which is absorbed and further oxidized by hepatic flavin monooxygenase to trimethylamine‐N‐oxide (TMAO)”

TMAO promotes atherogenesis partly by promoting the formation of foam cells from macrophages.

“a metabolite that could promote atherogenesis partly by promoting the formation of foam cells from macrophages.4, 5”

TMAO level has been suggested to be involved in atherosclerosis.

“Although the TMAO level has been suggested to be involved in atherosclerosis,4, 5”

Many cohort studies have suggested that an increased number of adverse outcomes are associated with high TMAO levels.

“many cohort studies have suggested that an increased number of adverse outcomes are associated with high TMAO levels,4, 5, 6, 7”

Recent data suggest that gut microbiota may play a role in the development and maintenance of CVD and metabolic disorders such as obesity, diabetes and metabolic syndrome.

“However, recent data suggest that it may also play a role in the development and maintenance of CVD and metabolic disorders such as obesity, diabetes and metabolic syndrome11–14.”

Consumption of choline and L-carnitine rich diets offer the necessary precursors for the production of TMAO.

“Indeed, consumption of choline and L-carnitine rich diets offer the necessary precursors for the production of TMAO.2,3”

Several recent studies have identified trimethylamine N-oxide, a metabolite of the gut microbiota, as an independent risk factor for cardiovascular disease.

“Several recent studies have identified trimethylamine N-oxide, a metabolite of the gut microbiota, as an independent risk factor for cardiovascular disease.17,18,34”

Trimethylamine and trimethylamine N-oxide, gut microbiota metabolites of dietary phosphatidylcholine, are associated with cardiovascular disease and with atherosclerosis.

“Trimethylamine (TMA) and TMA N-oxide, which are gut microbiota metabolites of dietary phosphatidylcholine, are known to be associated with cardiovascular disease and with the atherosclerosis process in particular.3,4”

OCA reverses fibrosis in patients with nonalcoholic steatohepatitis (NASH).

“its ability to reverse fibrosis in patients with nonalcoholic steatohepatitis (NASH) was demonstrated in a proof-of-concept study followed by a randomized control trial (RCT)150,151.”

Few connections between the microbiome and vascular and cardiovascular diseases have been identified with mechanistic certainty.

“Despite an explosion of associative studies involving the microbiome and vascular and cardiovascular diseases, few connections have been identified with mechanistic certainty[2,3].”

Higher plasma levels of trimethylamine-N-oxide (TMAO) conferred an increased risk of major cardiovascular events during a 3-year follow-up; plasma TMAO is the product of gut microbial metabolism of dietary choline to trimethylamine, followed by hepatic oxidation to TMAO.

“higher plasma levels of the vascular toxin trimethylamine-N-oxide (TMAO) conferred an increased risk of major cardiovascular events during a 3-year follow-up.157 They also demonstrated that plasma TMAO is the product of gut microbial metabolism of dietary choline to trimethylamine (TMA), followed by hepatic oxidation of TMA to TMAO.”

Gut ecology is associated with cancer, cardiovascular disease, obesity, diabetes, and muscle wasting.

“associations between gut ecology and cancer [16], cardiovascular disease [17], obesity [6], diabetes [18], and muscle wasting [19]”

The gut microbiota metabolizes choline, phosphatidylcholine, and l-carnitine to produce trimethylamine (TMA), which is oxidized in the liver into the proatherogenic metabolite trimethylamine-N-oxide (TMAO).

“Previous studies have shown that the gut microbiota metabolizes choline, phosphatidylcholine, and l-carnitine to produce trimethylamine (TMA), which is oxidized in the liver into the proatherogenic metabolite, trimethylamine-N-oxide (TMAO)11–13.”