Increased circulating phenylacetylglutamine concentration elevates the predictive value of cardiovascular event risk in heart failure patients

Gut-Heart Axis: The Role of Gut Microbiota and Metabolites in Heart Failure

Heart failure is a global health issue with significant mortality and morbidity. There is increasing evidence that alterations in the gastrointestinal microbiome, gut epithelial permeability, and gastrointestinal disorders contribute to heart failure progression through various pathways, including systemic inflammation, metabolic dysregulation, and modulation of cardiac function. Moreover, several medications used to treat heart failure directly impact the microbiome. The relationship between the gastrointestinal tract and the heart is bidirectional, termed the gut-heart axis. It is increasingly understood that diet-derived microbial metabolites are key mechanistic drivers of the gut-heart axis. This includes, for example, trimethylamine N-oxide and short-chain fatty acids. This review discusses current insights into the interplay between heart failure, its associated risk factors, and the gut microbiome, focusing on key metabolic pathways, the role of dietary interventions, and the potential for gut-targeted therapies. Understanding these complex interactions could pave the way for novel strategies to mitigate heart failure progression and improve patient outcomes.

Gut microbiota-derived metabolite phenylacetylglutamine in cardiovascular and metabolic disease

The aging of population coupled with unhealthy dietary habits among residents has led to a rise in the incidence of cardiovascular and metabolic diseases (CVMDs). Extensive research has highlighted the role of gut microbiota-derived metabolites in CVMDs. Among these metabolites, phenylacetylglutamine (PAGln), a meta-organismal prothrombotic metabolite, has been proved to promote the progression of CVMDs. This bacterial derived metabolite is a byproduct of amino acid comes from phenylalanine (Phe) in the diet. There are increasing evidence showing that the level of PAGln is associated with the risk of developing CVMDs. To provide a comprehensive understanding of the role of PAGln in CVMDs, this review delves into the production and metabolic pathways of PAGln and discusses the links of PAGln and the pathogenesis of CVMDs.

Changes in Phenylacetylglutamine Levels Provide Add-On Value in Risk Stratification of Hypertensive Patients: A Longitudinal Cohort Study

BACKGROUND

Despite antihypertensive treatment, some high-risk hypertensive patients still experience major adverse cardiovascular events (MACEs). Current risk stratification tools may underestimate the presence of metabolites in hypertension and thereby risk of MACEs.

OBJECTIVES

We aimed to explore the potential value of gut microbiota-derived metabolite phenylacetylglutamine (PAGln) in risk stratification of hypertension.

METHODS

We measured plasma PAGln levels using liquid chromatography tandem mass spectrometry in 1543 high-risk hypertensive patients, dividing them into a discovery cohort (n = 792) and a validation cohort (n = 751). After follow-up, the Kaplan-Meier curve and the Cox regression model were utilized to determine the correlation between PAGln and MACEs (death, non-fatal ischemic stroke and hemorrhagic stroke, non-fatal acute coronary syndrome and unplanned revascularization). We examined the predictive performance of PAGln in different subgroups and evaluated the incremental predictive value of PAGln as an addition to the ASCVD risk assessment model.

RESULTS

Among all high-risk hypertensive patients, 148 patients experienced MACEs after a mean follow-up of 3.02 years. In both cohorts, after adjusting other confounding risk factors, PAGln remained an independent risk factor the MACEs in hypertensive patients. Patients with plasma PAGln ≥ 1.047 μmol/L have a higher risk of MACEs. PAGln concentration provided incremental predictive value to the ASCVD risk model, with better performance in the discovery cohort. It was most effective in female, patients with a systolic blood pressure (SBP) ≥ 130 mmHg and taking angiotensin-converting enzyme inhibitors (ACEIs).

CONCLUSIONS

PAGln was associated with an increased risk of MACEs in hypertension, especially in women or in subgroups with SBP ≥ 130 mmHg and taking ACEIs. PAGln should be considered as an independent predictor in risk stratification to improve prognosis.

Data-driven cluster analysis identifies distinct types of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) exhibits considerable variability in clinical outcomes. Identifying specific phenotypic profiles within MASLD is essential for developing targeted therapeutic strategies. Here we investigated the heterogeneity of MASLD using partitioning around medoids clustering based on six simple clinical variables in a cohort of 1,389 individuals living with obesity. The identified clusters were applied across three independent MASLD cohorts with liver biopsy (totaling 1,099 participants), and in the UK Biobank to assess the incidence of chronic liver disease, cardiovascular disease and type 2 diabetes. Results unveiled two distinct types of MASLD associated with steatohepatitis on histology and liver imaging. The first cluster, liver-specific, was genetically linked and showed rapid progression of chronic liver disease but limited risk of cardiovascular disease. The second cluster, cardiometabolic, was primarily associated with dysglycemia and high levels of triglycerides, leading to a similar incidence of chronic liver disease but a higher risk of cardiovascular disease and type 2 diabetes. Analyses of samples from 831 individuals with available liver transcriptomics and 1,322 with available plasma metabolomics highlighted that these two types of MASLD exhibited distinct liver transcriptomic profiles and plasma metabolomic signatures, respectively. In conclusion, these data provide preliminary evidence of the existence of two distinct types of clinically relevant MASLD with similar liver phenotypes at baseline, but each with specific underlying biological profiles and different clinical trajectories, suggesting the need for tailored therapeutic strategies.

Low-Molecular-Weight Compounds Produced by the Intestinal Microbiota and Cardiovascular Disease

Cardiovascular disease is the main cause of mortality in industrialized countries, with over 500 million people affected worldwide. In this work, the roles of low-molecular-weight metabolites originating from the gut microbiome, such as short-chain fatty acids, hydrogen sulfide, trimethylamine, phenylacetic acid, secondary bile acids, indoles, different gases, neurotransmitters, vitamins, and complex lipids, are discussed in relation to their CVD-promoting or preventing activities. Molecules of mixed microbial and human hepatic origin, such as trimethylamine N-oxide and phenylacetylglutamine, are also presented. Finally, dietary agents with cardioprotective effects, such as probiotics, prebiotics, mono- and poly-unsaturated fatty acids, carotenoids, and polyphenols, are also discussed. A special emphasis is given to their gut microbiota-modulating properties.

Effects of Phenylacetylglutamine on the Susceptibility of Atrial Fibrillation in Overpressure-Induced HF Mice

Phenylacetylglutamine (PAGln), a gut metabolite is substantially elevated in heart failure (HF). The increase of PAGln in plasma is associated with atrial fibrillation (AF), and contributes to AF pathogenesis. However, the role of PAGln in AF with HF remains uncertain. Therefore, this study aimed to determine the effect of PAGln on AF after HF. Thoracic aortic coarctation (TAC) created overpressure-induced HF mice for 4 weeks. Histopathology, biochemical, echocardiographic for assessment of cardiac function, and electrophysiological examination of several electrophysiological indexes (ERP, SNRT, and the occurrence rate of AF) were performed at the end of the HF mice model. We found that plasma PAGln levels were significantly elevated in PAGln-treated HF mice and that PAGln aggravated maladaptive structural remodeling and electrical remodeling, which aggravated the vulnerability of AF, shortened the ERP duration, prolonged the SNRT, increased the occurrence rate of AF in HF mice. Mechanistically, PAGln exacerbated ROS accumulation and increased the levels of phosphorylated PLB and CAMK II. Overall, PAGln played a vital role in promoting the occurrence of AF in HF mice by activating the CAMK II signaling pathway.

Heart Failure: a Punch from the Gut

PURPOSE OF REVIEW

This article seeks to elucidate the mechanisms underlying the bidirectional relationship between the gut and the heart, focusing on the pathophysiology of heart failure. We have previously demonstrated that Heart failure (HF) has significant effects on splanchnic vasculature and leads to key alterations in the gut microbiome, portending greater comorbidity with HF.

RECENT FINDINGS

A growing field of research is focused on the effects of a "leaky gut" in the development of disease across organ systems. The leaky gut hypothesis centers on intestinal epithelial barrier dysfunction causing increased permeability of the gut and subsequent alterations to gut composition by endotoxins and microbial metabolites. Changes in the quantities of metabolites including short-chain fatty acids, trimethylamine N-oxide and other amino acid metabolites, and various bile acid species have been shown to result in gut dysbiosis and worsening HF. The gut plays a highly significant role in HF prognosis and requires greater attention for future therapeutic interventions. Treatments targeting gut composition could have very beneficial effects on HF prognosis.

Gut microbiota-dependent phenylacetylglutamine in cardiovascular disease: current knowledge and new insights

Phenylacetylglutamine (PAGln) is an amino acid derivate that comes from the amino acid phenylalanine. There are increasing studies showing that the level of PAGln is associated with the risk of different cardiovascular diseases. In this review, we discussed the metabolic pathway of PAGln production and the quantitative measurement methods of PAGln. We summarized the epidemiological evidence to show the role of PAGln in diagnostic and prognostic value in several cardiovascular diseases, such as heart failure, coronary heart disease/atherosclerosis, and cardiac arrhythmia. The underlying mechanism of PAGln is now considered to be related to the thrombotic potential of platelets via adrenergic receptors. Besides, other possible mechanisms such as inflammatory response and oxidative stress could also be induced by PAGln. Moreover, since PAGln is produced across different organs including the intestine, liver, and kidney, the cross-talk among multiple organs focused on the function of this uremic toxic metabolite. Finally, the prognostic value of PAGln compared to the classical biomarker was discussed and we also highlighted important gaps in knowledge and areas requiring future investigation of PAGln in cardiovascular diseases.

Prognostic value of gut microbe-generated metabolite phenylacetylglutamine in patients with heart failure

AIM

Phenylacetylglutamine (PAGln) is a phenylalanine-derived metabolite produced by gut microbiota with mechanistic links to heart failure (HF)-relevant phenotypes. We sought to investigate the prognostic value of PAGln in patients with stable HF.

METHODS AND RESULTS

Fasting plasma PAGln levels were measured by stable-isotope-dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) in patients with stable HF from two large cohorts. All-cause mortality was assessed at 5-year follow-up in the Cleveland cohort, and HF, hospitalization, or mortality were assessed at 3-year follow-up in the Berlin cohort. Within the Cleveland cohort, median PAGln levels were 4.2 (interquartile range [IQR] 2.4-6.9) μM. Highest quartile of PAGln was associated with 3.09-fold increased mortality risk compared to lowest quartile. Following adjustments for traditional risk factors, as well as race, estimated glomerular filtration rate, amino-terminal pro-B-type natriuretic peptide, high-sensitivity C-reactive protein, left ventricular ejection fraction, ischaemic aetiology, and HF drug treatment, elevated PAGln levels remained predictive of 5-year mortality in quartile comparisons (adjusted hazard ratio [HR] [95% confidence interval, CI] for Q4 vs Q1: 1.64 [1.07-2.53]). In the Berlin cohort, a similar distribution of PAGln levels was observed (median 3.2 [IQR 2.0-4.8] μM), and PAGln levels were associated with a 1.92-fold increase in 3-year HF hospitalization or all-cause mortality risk (adjusted HR [95% CI] for Q4 vs Q1: 1.92 [1.02-3.61]). Prognostic value of PAGln appears to be independent of trimethylamine N-oxide levels.

CONCLUSION

High levels of PAGln are associated with adverse outcomes independent of traditional cardiac risk factors and cardio-renal risk markers.

Role of the Gut Bacteria-Derived Metabolite Phenylacetylglutamine in Health and Diseases

Over the past few decades, it has been well established that gut microbiota-derived metabolites can disrupt gut function, thus resulting in an array of diseases. Notably, phenylacetylglutamine (PAGln), a bacterial derived metabolite, has recently gained attention due to its role in the initiation and progression of cardiovascular and cerebrovascular diseases. This meta-organismal metabolite PAGln is a byproduct of amino acid acetylation of its precursor phenylacetic acid (PAA) from a range of dietary sources like egg, meat, dairy products, etc. The microbiota-dependent metabolism of phenylalanine produces PAA, which is a crucial intermediate that is catalyzed by diverse microbial catalytic pathways. PAA conjugates with glutamine and glycine in the liver and kidney to predominantly form phenylacetylglutamine in humans and phenylacetylglycine in rodents. PAGln is associated with thrombosis as it enhances platelet activation mediated through the GPCRs receptors α2A, α2B, and β2 ADRs, thereby aggravating the pathological conditions. Clinical evidence suggests that elevated levels of PAGln are associated with pathology of cardiovascular, cerebrovascular, and neurological diseases. This Review further consolidates the microbial/biochemical synthesis of PAGln and discusses its role in the above pathophysiologies.

Advancing lifelong precision medicine for cardiovascular diseases through gut microbiota modulation

The gut microbiome is known as the tenth system of the human body that plays a vital role in the intersection between health and disease. The considerable inter-individual variability in gut microbiota poses both challenges and great prospects in promoting precision medicine in cardiovascular diseases (CVDs). In this review, based on the development, evolution, and influencing factors of gut microbiota in a full life circle, we summarized the recent advances on the characteristic alteration in gut microbiota in CVDs throughout different life stages, and depicted their pathological links in mechanism, as well as the highlight achievements of targeting gut microbiota in CVDs prevention, diagnosis and treatment. Personalized strategies could be tailored according to gut microbiota characteristics in different life stages, including gut microbiota-blood metabolites combined prediction and diagnosis, dietary interventions, lifestyle improvements, probiotic or prebiotic supplements. However, to fulfill the promise of a lifelong cardiovascular health, more mechanism studies should progress from correlation to causality and decipher novel mechanisms linking specific microbes and CVDs. It is also promising to use the burgeoning artificial intelligence and machine learning to target gut microbiota for developing diagnosis system and screening for new therapeutic interventions.

Gut-Kidney-Heart: A Novel Trilogy

The microbiota represents a key factor in determining health and disease. Its role in inflammation and immunological disorders is well known, but it is also involved in several complex conditions, ranging from neurological to psychiatric, from gastrointestinal to cardiovascular diseases. It has recently been hypothesized that the gut microbiota may act as an intermediary in the close interaction between kidneys and the cardiovascular system, leading to the conceptualization of the "gut-kidney-heart" axis. In this narrative review, we will discuss the impact of the gut microbiota on each system while also reviewing the available data regarding the axis itself. We will also describe the role of gut metabolites in this complex interplay, as well as potential therapeutical perspectives.