Trimethylamine-N-Oxide Promotes Vascular Calcification Through Activation of NLRP3 (Nucleotide-Binding Domain, Leucine-Rich-Containing Family, Pyrin Domain-Containing-3) Inflammasome and NF-κB (Nuclear Factor κB) Signals

Role of the Microbiome in Gut-Heart-Kidney Cross Talk

Homeostasis is a prerequisite for health. When homeostasis becomes disrupted, dysfunction occurs. This is especially the case for the gut microbiota, which under normal conditions lives in symbiosis with the host. As there are as many microbial cells in and on our body as human cells, it is unlikely they would not contribute to health or disease. The gut bacterial metabolism generates numerous beneficial metabolites but also uremic toxins and their precursors, which are transported into the circulation. Barrier function in the intestine, the heart, and the kidneys regulates metabolite transport and concentration and plays a role in inter-organ and inter-organism communication via small molecules. This communication is analyzed from the perspective of the remote sensing and signaling theory, which emphasizes the role of a large network of multispecific, oligospecific, and monospecific transporters and enzymes in regulating small-molecule homeostasis. The theory provides a systems biology framework for understanding organ cross talk and microbe-host communication involving metabolites, signaling molecules, nutrients, antioxidants, and uremic toxins. This remote small-molecule communication is critical for maintenance of homeostasis along the gut-heart-kidney axis and for responding to homeostatic perturbations. Chronic kidney disease is characterized by gut dysbiosis and accumulation of toxic metabolites. This slowly impacts the body, affecting the cardiovascular system and contributing to the progression of kidney dysfunction, which in its turn influences the gut microbiota. Preserving gut homeostasis and barrier functions or restoring gut dysbiosis and dysfunction could be a minimally invasive way to improve patient outcomes and quality of life in many diseases, including cardiovascular and kidney disease.

Modulation of Endothelial Function by TMAO, a Gut Microbiota-Derived Metabolite

Endothelial function is essential in the maintenance of systemic homeostasis, whose modulation strictly depends on the proper activity of tissue-specific angiocrine factors on the physiopathological mechanisms acting at both single and multi-organ levels. Several angiocrine factors take part in the vascular function itself by modulating vascular tone, inflammatory response, and thrombotic state. Recent evidence has outlined a strong relationship between endothelial factors and gut microbiota-derived molecules. In particular, the direct involvement of trimethylamine N-oxide (TMAO) in the development of endothelial dysfunction and its derived pathological outcomes, such as atherosclerosis, has come to light. Indeed, the role of TMAO in the modulation of factors strictly related to the development of endothelial dysfunction, such as nitric oxide, adhesion molecules (ICAM-1, VCAM-1, and selectins), and IL-6, has been widely accepted. The aim of this review is to present the latest studies that describe a direct role of TMAO in the modulation of angiocrine factors primarily involved in the development of vascular pathologies.

Intestinal Flora Metabolite Trimethylamine Oxide Is Inextricably Linked to Coronary Heart Disease

ABSTRACT

Atherosclerotic coronary heart disease is a common cardiovascular disease with high morbidity and mortality. In recent years, the incidence of coronary heart disease has gradually become younger, and biomarkers for predicting coronary heart disease have demonstrated valuable clinical prospects. Several studies have established an association between coronary heart disease and intestinal flora metabolites, including trimethylamine oxide (TMAO), which has attracted widespread attention from researchers. Investigations have also shown that plasma levels of TMAO and its precursors can predict cardiovascular risk in humans; however, TMAO's mechanism of action in causing coronary heart disease is not fully understood. This review examines TMAO's generation, the mechanism through which it causes coronary heart disease, and the approaches used to treat TMAO-caused coronary heart disease to possible avenues for future research on coronary heart disease and find new concepts for the treatment of the condition.

The role of gut-dependent molecule trimethylamine N-oxide as a novel target for the treatment of chronic kidney disease

Trimethylamine N-oxide (TMAO) is an intestinal uremic toxin molecule mainly excreted by the kidney. Therefore, the plasma TMAO concentration is significantly increased in chronic kidney disease (CKD) patients, and plasma TMAO can be cleared by dialysis. Furthermore, TMAO damage the kidney mainly through three mechanisms: oxidative stress, inflammation and endoplasmic reticulum stress. Clinical experiments have indicated that higher TMAO levels are strongly related to the elevated incidence and mortality of cardiovascular (CV) events in CKD patients. Moreover, experimental data have shown that high levels of TMAO directly aggravate atherosclerosis, thrombosis and enhance myocardial contractility, resulting in myocardial ischemia and stroke. Specially, there are currently four potential ways to reduce blood TMAO concentration or block the effect of TMAO, including reducing the intake of trimethylamine (TMA) precursors in the diet, regulating the intestinal flora to reduce TMA production, interrupting the role of flavin-dependent monooxygenase isoforms (FMOs) to reduce the generation of TMAO, and blocking the TMAO receptor protein kinase R-like endoplasmic reticulum kinase (PERK). We hope that more clinical studies and clinicians will focus on clinical treatment to reduce the concentration of TMAO and alleviate renal damage.

Gut Molecules in Cardiometabolic Diseases: The Mechanisms behind the Story

Atherosclerotic cardiovascular disease is the most common cause of morbidity and mortality worldwide. Diabetes mellitus increases cardiovascular risk. Heart failure and atrial fibrillation are associated comorbidities that share the main cardiovascular risk factors. The use of incretin-based therapies promoted the idea that activation of alternative signaling pathways is effective in reducing the risk of atherosclerosis and heart failure. Gut-derived molecules, gut hormones, and gut microbiota metabolites showed both positive and detrimental effects in cardiometabolic disorders. Although inflammation plays a key role in cardiometabolic disorders, additional intracellular signaling pathways are involved and could explain the observed effects. Revealing the involved molecular mechanisms could provide novel therapeutic strategies and a better understanding of the relationship between the gut, metabolic syndrome, and cardiovascular diseases.

Association between prevalence of laxative use and history of bone fractures and cardiovascular diseases in patients with chronic kidney disease: the Fukuoka Kidney disease Registry (FKR) study

BACKGROUND

Constipation is a common complication in patients with chronic kidney disease (CKD) and is involved in the pathogenesis of dysbiosis and progression of CKD. However, little is known about its association with disorders of the bone-cardiovascular axis in patients with CKD.

METHODS

We performed a cross-sectional analysis of 3878 patients with CKD using the baseline dataset of the Fukuoka Kidney disease Registry study, as a multicenter, prospective cohort study of pre-dialysis CKD patients. The main exposure of interest was constipation defined as use of at least one type of laxative. The main outcomes were the histories of bone fractures and cardiovascular diseases (CVDs) as manifestations of disorders of the bone-cardiovascular axis.

RESULTS

The prevalences of laxative use and histories of bone fractures and CVDs increased as kidney function declined. Among the 3878 patients, 532 (13.7%) patients used laxatives, 235 (6.1%) patients had prior bone fractures, and 1001 (25.8%) patients had prior CVDs. Histories of bone fractures and CVDs were significantly more prevalent among laxative users (P < 0.05). Multivariable-adjusted logistic regression analysis revealed that patients with laxatives had a significantly higher odds ratios for histories of bone fractures and CVDs than those without laxatives [adjusted odds ratios (95% confidence intervals) 1.67 (1.20-2.31) and 1.70 (1.30-2.22), respectively, P < 0.05].

CONCLUSIONS

These results suggest that constipation indicated by laxative use is associated with increased prevalences of historical bone fractures and CVDs in pre-dialysis patients with CKD.

Gut-brain axis: Mechanisms and potential therapeutic strategies for ischemic stroke through immune functions

After an ischemic stroke (IS) occurs, immune cells begin traveling to the brain and immune system from the gut and gastrointestinal tract, where most of them typically reside. Because the majority of the body's macrophages and more than 70% of the total immune cell pool are typically found within the gut and gastrointestinal tract, inflammation and immune responses in the brain and immune organs require the mobilization of a large number of immune cells. The bidirectional communication pathway between the brain and gut is often referred to as the gut-brain axis. IS usually leads to intestinal motility disorders, dysbiosis of intestinal microbiota, and a leaky gut, which are often associated with poor prognosis in patients with IS. In recent years, several studies have suggested that intestinal inflammation and immune responses play key roles in the development of IS, and thus may become potential therapeutic targets that can drive new therapeutic strategies. However, research on gut inflammation and immune responses after stroke remains in its infancy. A better understanding of gut inflammation and immune responses after stroke may be important for developing effective therapies. This review discusses the immune-related mechanisms of the gut-brain axis after IS and compiles potential therapeutic targets to provide new ideas and strategies for the future effective treatment of IS.

Aorta- and liver-generated TMAO enhances trained immunity for increased inflammation via ER stress/mitochondrial ROS/glycolysis pathways

We determined whether gut microbiota-produced trimethylamine (TMA) is oxidized into trimethylamine N-oxide (TMAO) in nonliver tissues and whether TMAO promotes inflammation via trained immunity (TI). We found that endoplasmic reticulum (ER) stress genes were coupregulated with MitoCarta genes in chronic kidney diseases (CKD); TMAO upregulated 190 genes in human aortic endothelial cells (HAECs); TMAO synthesis enzyme flavin-containing monooxygenase 3 (FMO3) was expressed in human and mouse aortas; TMAO transdifferentiated HAECs into innate immune cells; TMAO phosphorylated 12 kinases in cytosol via its receptor PERK and CREB, and integrated with PERK pathways; and PERK inhibitors suppressed TMAO-induced ICAM-1. TMAO upregulated 3 mitochondrial genes, downregulated inflammation inhibitor DARS2, and induced mitoROS, and mitoTEMPO inhibited TMAO-induced ICAM-1. β-Glucan priming, followed by TMAO restimulation, upregulated TNF-α by inducing metabolic reprogramming, and glycolysis inhibitor suppressed TMAO-induced ICAM-1. Our results have provided potentially novel insights regarding TMAO roles in inducing EC activation and innate immune transdifferentiation and inducing metabolic reprogramming and TI for enhanced vascular inflammation, and they have provided new therapeutic targets for treating cardiovascular diseases (CVD), CKD-promoted CVD, inflammation, transplantation, aging, and cancer.

The role of the gut microbiome and its metabolites in cerebrovascular diseases

The gut microbiome is critically involved in maintaining normal physiological function in the host. Recent studies have revealed that alterations in the gut microbiome contribute to the development and progression of cerebrovascular disease via the microbiota-gut-brain axis (MGBA). As a broad communication network in the human body, MGBA has been demonstrated to have significant interactions with various factors, such as brain structure and function, nervous system diseases, etc. It is also believed that the species and composition of gut microbiota and its metabolites are intrinsically linked to vascular inflammation and immune responses. In fact, in fecal microbiota transplantation (FMT) research, specific gut microbiota and downstream-related metabolites have been proven to not only participate in various physiological processes of human body, but also affect the occurrence and development of cerebrovascular diseases directly or indirectly through systemic inflammatory immune response. Due to the high mortality and disability rate of cerebrovascular diseases, new treatments to improve intestinal dysbacteriosis have gradually attracted widespread attention to better ameliorate the poor prognosis of cerebrovascular diseases in a non-invasive way. This review summarizes the latest advances in the gut microbiome and cerebrovascular disease research and reveals the profound impact of gut microbiota dysbiosis and its metabolites on cerebrovascular diseases. At the same time, we elucidated molecular mechanisms whereby gut microbial metabolites regulate the expression of specific interleukins in inflammatory immune responses. Moreover, we further discuss the feasibility of novel therapeutic strategies targeting the gut microbiota to improve the outcome of patients with cerebrovascular diseases. Finally, we provide new insights for standardized diagnosis and treatment of cerebrovascular diseases.

Identification of core cuprotosis-correlated biomarkers in abdominal aortic aneurysm immune microenvironment based on bioinformatics

Background

The occurrence of abdominal aortic aneurysms (AAAs) is related to the disorder of immune microenvironment. Cuprotosis was reported to influence the immune microenvironment. The objective of this study is to identify cuprotosis-related genes involved in the pathogenesis and progression of AAA.

Methods

Differentially expressed lncRNAs (DElncRNAs) and mRNAs (DEmRNAs) in mouse were identified following AAA through high-throughput RNA sequencing. The enrichment analyses of pathway were selected through Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG). The validation of cuprotosis-related genes was conducted through immunofluorescence and western blot analyses.

Results

Totally, 27616 lncRNAs and 2189 mRNAs were observed to be differentially expressed (|Fold Change| ≥ 2 and q< 0.05) after AAA, including 10424 up-regulated and 17192 down-regulated lncRNAs, 1904 up-regulated and 285 down-regulated mRNAs. Gene ontology and KEGG pathway analysis showed that the DElncRNAs and DEmRNAs were implicated in many different biological processes and pathways. Furthermore, Cuprotosis-related genes (NLRP3, FDX1) were upregulated in the AAA samples compared with the normal one.

Conclusion

Cuprotosis-related genes (NLRP3,FDX1) involved in AAA immune environment might be critical for providing new insight into identification of potential targets for AAA therapy.

Insights into bone morphogenetic proteins in cardiovascular diseases

Bone morphogenetic proteins (BMPs) are secretory proteins belonging to the transforming growth factor-β (TGF-β) superfamily. These proteins play important roles in embryogenesis, bone morphogenesis, blood vessel remodeling and the development of various organs. In recent years, as research has progressed, BMPs have been found to be closely related to cardiovascular diseases, especially atherosclerosis, vascular calcification, cardiac remodeling, pulmonary arterial hypertension (PAH) and hereditary hemorrhagic telangiectasia (HHT). In this review, we summarized the potential roles and related mechanisms of the BMP family in the cardiovascular system and focused on atherosclerosis and PAH.

Interactions between gut microbes and NLRP3 inflammasome in the gut-brain axis

The role of the gut-brain axis in maintaining the brain's and gut's homeostasis has been gradually recognized in recent years. The connection between the gut and the brain takes center stage. In this scenario, the nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) inflammasome promotes inflammatory cell recruitment. It plays a crucial role in coordinating host physiology and immunity. Recent evidence shows how vital the gut-brain axis is for maintaining brain and gut homeostasis. However, more research is needed to determine the precise causal link between changed gut microbiota structure and NLRP3 activation in pathogenic circumstances. This review examines the connection between gut microbiota and the NLRP3 inflammasome. We describe how both dynamically vary in clinical cases and the external factors affecting both. Finally, we suggest that the crosstalk between the gut microbiota and NLRP3 is involved in signaling in the gut-brain axis, which may be a potential pathological mechanism for CNS diseases and intestinal disorders.

Epigenetics and Gut Microbiota Crosstalk: A potential Factor in Pathogenesis of Cardiovascular Disorders

Cardiovascular diseases (CVD) are the leading cause of mortality, morbidity, and "sudden death" globally. Environmental and lifestyle factors play important roles in CVD susceptibility, but the link between environmental factors and genetics is not fully established. Epigenetic influence during CVDs is becoming more evident as its direct involvement has been reported. The discovery of epigenetic mechanisms, such as DNA methylation and histone modification, suggested that external factors could alter gene expression to modulate human health. These external factors also influence our gut microbiota (GM), which participates in multiple metabolic processes in our body. Evidence suggests a high association of GM with CVDs. Although the exact mechanism remains unclear, the influence of GM over the epigenetic mechanisms could be one potential pathway in CVD etiology. Both epigenetics and GM are dynamic processes and vary with age and environment. Changes in the composition of GM have been found to underlie the pathogenesis of metabolic diseases via modulating epigenetic changes in the form of DNA methylation, histone modifications, and regulation of non-coding RNAs. Several metabolites produced by the GM, including short-chain fatty acids, folates, biotin, and trimethylamine-N-oxide, have the potential to regulate epigenetics, apart from playing a vital role in normal physiological processes. The role of GM and epigenetics in CVDs are promising areas of research, and important insights in the field of early diagnosis and therapeutic approaches might appear soon.

The Role of Gut Bacteriome in Asthma, Chronic Obstructive Pulmonary Disease and Obstructive Sleep Apnoea

The human body contains a very complex and dynamic ecosystem of bacteria. The bacteriome interacts with the host bi-directionally, and changes in either factor impact the entire system. It has long been known that chronic airway diseases are associated with disturbances in the lung bacteriome. However, less is known about the role of gut bacteriome in the most common respiratory diseases. Here, we aim to summarise the evidence concerning the role of the intestinal bacteriome in the pathogenesis and disease course of bronchial asthma, chronic obstructive pulmonary disease, and obstructive sleep apnea. Furthermore, we discuss the consequences of an altered gut bacteriome on the most common comorbidities of these lung diseases. Lastly, we also reflect on the therapeutic potential of influencing the gut microbiome to improve disease outcomes.

Repression of the antiporter SLC7A11/glutathione/glutathione peroxidase 4 axis drives ferroptosis of vascular smooth muscle cells to facilitate vascular calcification

Vascular calcification is a common pathologic condition in patients with chronic kidney disease (CKD). Cell death such as apoptosis plays a critical role in vascular calcification. Ferroptosis is a type of iron-catalyzed and regulated cell death resulting from excessive iron-dependent reactive oxygen species and lipid peroxidation. However, it is unclear whether ferroptosis of vascular smooth muscle cells (VSMCs) regulates vascular calcification in CKD. Our results showed that high calcium and phosphate concentrations induced ferroptosis in rat VSMCs in vitro. Inhibition of ferroptosis by ferrostatin-1 dose-dependently reduced mineral deposition in rat VSMCs under pro-osteogenic conditions, as indicated by alizarin red staining and quantification of calcium content. In addition, gene expression analysis revealed that ferrostatin-1 inhibited osteogenic differentiation of rat VSMCs. Similarly, ferrostatin-1 remarkably attenuated calcification of rat and human arterial rings ex vivo and aortic calcification in vitamin D₃-overloaded mice in vivo. Moreover, inhibition of ferroptosis by either ferrostatin-1 or deferoxamine attenuated aortic calcification in rats with CKD. Mechanistically, high calcium and phosphate downregulated expression of SLC7A11 (a cystine-glutamate antiporter), and reduced glutathione (GSH) content in VSMCs. Additionally, GSH depletion induced by erastin (a small molecule initiating ferroptotic cell death) significantly promoted calcification of VSMCs under pro-osteogenic conditions, whereas GSH supplement by N-acetylcysteine reduced calcification of VSMCs. Consistently, knockdown of SLC7A11 by siRNA markedly promoted VSMC calcification. Furthermore, high calcium and phosphate downregulated glutathione peroxidase 4 (GPX4) expression, and reduced glutathione peroxidase activity. Inhibition of GPX4 by RSL3 promoted VSMC calcification. Thus, repression of the SLC7A11/GSH/GPX4 axis triggers ferroptosis of VSMCs to promote vascular calcification under CKD conditions, providing a novel targeting strategy for vascular calcification.

Deletion of SIRT6 in vascular smooth muscle cells facilitates vascular calcification via suppression of DNA damage repair

Vascular calcification is an important risk factor for cardiovascular events, accompanied by DNA damage during the process. The sirtuin 6 (SIRT6) has been reported to alleviate atherosclerosis, which is related to the reduction of DNA damage. However, whether smooth muscle cell SIRT6 mediates vascular calcification involving DNA damage remains unclear. Western blot and immunofluorescence revealed that SIRT6 expression was decreased in human vascular smooth muscle cells (HVSMCs), human and mouse arteries during vascular calcification. Alizarin red staining and calcium content assay showed that knockdown or deletion of SIRT6 significantly promoted HVSMC calcification induced by high phosphorus and calcium, accompanied by upregulation of osteogenic differentiation markers including Runx2 and BMP2. By contrast, adenovirus-mediated SIRT6 overexpression attenuated osteogenic differentiation and calcification of HVSMCs. Moreover, ex vivo study revealed that SIRT6 overexpression inhibited calcification of mouse and human arterial rings. Of note, smooth muscle cell-specific knockout of SIRT6 markedly aggravated Vitamin D₃-induced aortic calcification in mice. Mechanistically, overexpression of SIRT6 reduced DNA damage and upregulated p-ATM during HVSMCs calcification, whereas knockdown of SIRT6 showed the opposite effects. Knockdown of ATM in HVSMCs abrogated the inhibitory effect of SIRT6 overexpression on calcification and DNA damage. This study for the first time demonstrates that vascular smooth muscle cell-specific deletion of SIRT6 facilitates vascular calcification via suppression of DNA damage repair. Therefore, modulation of SIRT6 and DNA damage repair may represent a therapeutic strategy for vascular calcification.

Association between trimethylamine N-oxide and prognosis of patients with acute myocardial infarction and heart failure

AIMS

This study aimed to investigate the association between trimethylamine N-oxide (TMAO) and the prognosis and association between high-sensitivity C-reactive protein (hsCRP) and TMAO-associated cardiovascular risk in patients with acute myocardial infarction (AMI) complicated by heart failure (HF).

METHODS AND RESULTS

A total of 985 patients presenting with AMI and HF were consecutively enrolled at the Fuwai Hospital between March 2017 and January 2020. Patients were stratified into groups according to tertiles of TMAO levels and the median hsCRP levels. The primary endpoint was major adverse cardiac events (MACE), including all-cause death, recurrence of myocardial infarction, and rehospitalization due to HF. During a median follow-up of 716 days, 138 (14.0%) patients experienced MACE. Cox regression analyses showed that the adjusted hazard ratio (HR) for MACE was higher in patients in tertile 3 [TMAO > 9.52 μmol/L, HR: 1.85, 95% confidence interval (CI): 1.18-2.89; P = 0.007] than in tertile 1 (TMAO < 4.74 μmol/L), whereas no significant differences were detected between the patients in tertiles 1 and 2 (TMAO = 4.74-9.52 μmol/L, HR: 0.96, 95% CI: 0.59-1.58; P = 0.874). Restricted cubic spline regression depicted an S-shaped association between TMAO and MACE (P for nonlinearity = 0.012). In the setting of hsCRP above the median level (6.68 mg/L), per unit increase of TMAO was associated with a 20% increase of MACE risk (HR: 1.20, 95% CI: 1.05-1.37, P = 0.009); increasing tertiles of TMAO were significantly associated with a higher risk of MACE (adjusted P = 0.007 for interaction; P < 0.001 for trend across tertiles). The Kaplan-Meier analysis indicated that patients in tertile 3 had a significantly lower event-free survival (P = 0.001) when the hsCRP level was above the median level. No similar association between TMAO and MACE was observed when the hsCRP level was below the median level.

CONCLUSIONS

High plasma TMAO levels were independently correlated with poor prognosis in patients with AMI complicated by HF, especially in those with higher hsCRP levels. There was an S-shaped relationship between TMAO and HR for MACE.

Interleukin-8 (IL-8) as a Potential Mediator of an Association between Trimethylamine N-Oxide (TMAO) and Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) among African Americans at Risk of Cardiovascular Disease

Trimethylamine N-oxide (TMAO)-a microbial metabolite derived from the hepatic-gut axis-is linked to inflammation, hyperlipidemia, and cardiovascular disease (CVD). Proprotein convertase subtilisin/kexin type 9 (PCSK9), which is largely hepatically expressed, blocks low-density lipoprotein (LDL) receptor recycling, also leading to hyperlipidemia. The primary objective of this study was to investigate a previously hypothesized potential relationship between TMAO and PCSK9 in order to explore novel mechanisms linking TMAO and CVD risk. African American adults at risk of CVD living in the Washington DC area were recruited to participate in a cross-sectional community-based study (n = 60, 93% female, BMI = 33). Fasting levels of inflammatory cytokines (i.e., interleukin (IL)-1 beta, tumor necrosis factor-alpha, and interleukin-8), TMAO, and PCSK9 were measured using Luminex and ELISA, respectively. Univariate and multivariate linear regression analyses and structural equation mediation analyses were conducted using STATA. All models were adjusted for body mass index (BMI) and atherosclerotic CVD risk score (ASCVD). A significant association between TMAO and PCSK9 was identified (β = 0.31, p = 0.02). Both TMAO and PCSK9 were significantly associated with IL-8 (TMAO: β = 0.45, p = 0.00; PCSK9: β = 0.23, p = 0.05) in adjusted models. Mediation analysis indicated that 34.77% of the relationship between TMAO and PCSK9 was explained by IL-8. Our findings indicate a potential PCSK9-involved pathway for TMAO and CVD risk, with potential mediation by IL-8.

Beneficial effect of the short-chain fatty acid propionate on vascular calcification through intestinal microbiota remodelling

BACKGROUND

Vascular calcification is a major cause of the high morbidity and mortality of cardiovascular diseases and is closely associated with the intestinal microbiota. Short-chain fatty acids (SCFAs) are derived from the intestinal microbiota and can also regulate intestinal microbiota homeostasis. However, it remains unclear whether exogenous supplementation with propionate, a SCFA, can ameliorate vascular calcification by regulating the intestinal microbiota. This study was conducted to explore the roles of propionate and the intestinal microbiota in the process of vascular calcification.

METHODS

In total, 92 patients were enrolled consecutively as the observational cohort to analyse the relationship between SCFAs and vascular calcification in both blood and faecal samples. A rat model of vascular calcification was induced by vitamin D3 and nicotine (VDN) to validate the effect of propionate. Differences in the intestinal microbiota were analysed by 16S ribosomal RNA gene sequencing. Faecal microbiota transplantation and Akkermansia muciniphila transplantation experiments were performed to evaluate the functions of the intestinal microbiota.

RESULTS

The results of the observational cohort study revealed that the levels of SCFAs (particularly propionate) in both blood and faecal samples independently correlated negatively with calcification scores (P < 0.01). To verify the activities of propionate, it was provided to VDN-treated rats, and oral or rectal propionate delivery reshaped the intestinal microbiota, resulted in elevated SCFA production, improved intestinal barrier function and alleviated inflammation, ultimately ameliorating vascular calcification. Furthermore, we demonstrated that transplantation of the propionate-modulated intestinal microbiota induced beneficial outcomes similar to those with oral or rectal propionate administration. Interestingly, linear discriminant analysis (LDA) effect size (LEfSe) revealed that oral or rectal propionate administration and propionate-modulated intestinal microbiota transplantation both enriched primarily Akkermansia. Subsequently, we demonstrated that Akkermansia supplementation could ameliorate VDN-induced vascular calcification in rats.

CONCLUSIONS

Propionate can significantly ameliorate vascular calcification in VDN-treated rats, and this effect is mediated by intestinal microbiota remodelling. The findings in our study indicate that the intestinal tract-vessel axis is a promising target for alleviating vascular calcification. Video Abstract.

Gut-liver axis: Pathophysiological concepts and clinical implications

Bidirectional crosstalk along the gut-liver axis controls gastrointestinal health and disease and exploits environmental and host mediators. Nutrients, microbial antigens, metabolites, and bile acids regulate metabolism and immune responses in the gut and liver, which reciprocally shape microbial community structure and function. Perturbation of such host-microbe interactions is observed in a variety of experimental liver diseases and is facilitated by an impaired intestinal barrier, which is fueling hepatic inflammation and disease progression. Clinical evidence describes perturbation of the gut-liver crosstalk in non-alcoholic fatty liver disease, alcoholic liver disease, and primary sclerosing cholangitis. In liver cirrhosis, a common sequela of these diseases, the intestinal microbiota and microbial pathogen-associated molecular patterns constitute liver inflammation and clinical complications, such as hepatic encephalopathy. Understanding the intricate metabolic interplay between the gut and liver in health and disease opens an avenue for targeted therapies in the future, which is probed in controlled clinical trials.

Trimethylamine-N-Oxide Promotes Osteoclast Differentiation and Bone Loss via Activating ROS-Dependent NF-κB Signaling Pathway

Trimethylamine-N-oxide (TMAO), an important gut microbiota (GM)-derived metabolite, has been shown to be abnormally increased in osteoporosis. However, the role and underlying mechanism of TMAO in regulating bone loss during osteoporosis have not been fully investigated. In the current study, we found that 100–400 μM TMAO dose-dependently enhanced TRAP-positive osteoclasts, F-actin ring formation, and resorption area on bovine bone slices and up-regulated osteoclast-related gene expression (Calcr, Traf6, Dcstamp, Acp5, C-Fos, and NFATc1). Western blotting validated that TMAO not only activated NF-κB signaling pathway but also stimulated c-Fos and NFATc1 protein expression in a dose-dependent manner. Furthermore, BAY 11-7082, an NF-κB inhibitor, pretreatment markedly suppressed TRAP-positive osteoclast formation and osteoclast-related genes under TMAO treatment. BAY 11-7082 also inhibited p-p65/p65, c-Fos, and NFATc1 protein expression promoted by TMAO. Moreover, TMAO significantly increased ROS production, which was inhibited by N-acetylcysteine (NAC), an ROS antagonist. In addition, we proved that NAC pretreatment could inhibit TMAO-promoted NF-κB activation. NAC also suppressed TRAP-positive osteoclast formation, osteoclast-related gene expression, and protein expression of c-Fos and NFATc1 under TMAO treatment. In vivo studies showed significantly decreased bone mass and increased TRAP-positive osteoclasts in TMAO-treated C57BL/6 mice. Moreover, western-blotting and immunohistochemical staining showed that TMAO administration markedly stimulated NF-κB p65 expression. Additionally, TMAO administration significantly promoted the gene and protein expression of C-Fos and NFATc1. In conclusion, TMAO could promote osteoclast differentiation and induce bone loss in mice by activating the ROS-dependent NF-κB signaling pathway.

Trimethylamine-N-oxide (TMAO) promotes balloon injury-induced neointimal hyperplasia via upregulating Beclin1 and impairing autophagic flux

BACKGROUND AND AIMS

TMAO is a microbiota-dependent metabolite associated with increased risk of various cardiovascular diseases. However, the relationship between TMAO and vascular injury-related neointimal hyperplasia is unclear. This study aimed to explore whether TMAO promotes neointimal hyperplasia after balloon injury and elucidate the underlying mechanism.

METHODS AND RESULTS

Through hematoxylin and eosin staining and immunohistochemistry staining, we found that supplementary TMAO promoted balloon injury-induced neointimal hyperplasia, while reducing TMAO by antibiotic administration produced the opposite result. TMAO showed limited effect on rat aortic vascular smooth muscle cells (RAOSMCs) proliferation and migration. However, TMAO notably induced dysfunction of rat aortic vascular endothelial cells (RAOECs) in vitro and attenuated reendothelialization of carotid arteries after balloon injury in vivo. Autophagic flux was measured by fluorescent mRFP-GFP-LC3, transmission electron microscopy, and western blot. TMAO impaired autophagic flux, as evidenced by the accumulation of p62 and LC3II and high autophagosome to autolysosome ratios. Furthermore, we confirmed that Beclin1 level increased in TMAO-treated RAOECs and carotid arteries. Knocking down Beclin1 alleviated TMAO-induced autophagic flux impairment and neointimal hyperplasia.

CONCLUSIONS

TMAO promoted neointimal hyperplasia through Beclin1-induced autophagic flux blockage, suggesting that TMAO is a potential target for improvement of vascular remodeling after injury.

Dendrobium officinale polysaccharide inhibits vascular calcification via anti-inflammatory and anti-apoptotic effects in chronic kidney disease

Vascular calcification is very common in patients with chronic kidney disease (CKD), but so far, there is no effective treatment. Dendrobium officinale polysaccharide (DOP), a natural component of Chinese herbal medicine, has been shown to exert anti-inflammatory and anti-apoptotic activity. Inflammation and apoptosis play an essential role in the progression of vascular calcification. However, the exact role and molecular mechanisms of DOP in vascular calcification remain unclear. In this study, we investigated the effects of DOP on vascular calcification using vascular smooth muscle cells (VSMCs), arterial rings, and CKD rats. Alizarin red staining and gene expression analysis revealed that DOP inhibited calcification and osteogenic differentiation of rat VSMCs in a dose-dependent manner. Similarly, ex vivo studies revealed that DOP inhibited the calcification of rat arterial rings. Furthermore, the administration of DOP alleviated vascular calcification in CKD rats. Moreover, DOP treatment suppressed VSMC inflammation and apoptosis. Finally, DOP treatment upregulated mRNA and protein levels of heme oxygenase-1 (HMOX-1); both pharmacological inhibition of HMOX-1 by the HMOX-1 inhibitor zinc protoporphyrin-9ZnPP9 and knockdown of HMOX-1 by siRNA markedly abrogated the suppression of inflammation and osteogenic differentiation of VSMCs by DOP. Collectively, these results suggest that DOP alleviates vascular calcification in CKD by suppressing apoptosis and inflammation via HMOX-1 activation. These results may provide a promising treatment for vascular calcification in CKD.

Dietary Meat, Trimethylamine N-Oxide-Related Metabolites, and Incident Cardiovascular Disease Among Older Adults: The Cardiovascular Health Study

BACKGROUND

Effects of animal source foods (ASF) on atherosclerotic cardiovascular disease (ASCVD) and underlying mechanisms remain controversial. We investigated prospective associations of different ASF with incident ASCVD and potential mediation by gut microbiota-generated trimethylamine N-oxide, its L-carnitine-derived intermediates γ-butyrobetaine and crotonobetaine, and traditional ASCVD risk pathways.

METHODS

Among 3931 participants from a community-based US cohort aged 65+ years, ASF intakes and trimethylamine N-oxide-related metabolites were measured serially over time. Incident ASCVD (myocardial infarction, fatal coronary heart disease, stroke, other atherosclerotic death) was adjudicated over 12.5 years median follow-up. Cox proportional hazards models with time-varying exposures and covariates examined ASF-ASCVD associations; and additive hazard models, mediation proportions by different risk pathways.

RESULTS

After multivariable-adjustment, higher intakes of unprocessed red meat, total meat, and total ASF associated with higher ASCVD risk, with hazard ratios (95% CI) per interquintile range of 1.15 (1.01-1.30), 1.22 (1.07-1.39), and 1.18 (1.03-1.34), respectively. Trimethylamine N-oxide-related metabolites together significantly mediated these associations, with mediation proportions (95% CI) of 10.6% (1.0-114.5), 7.8% (1.0-32.7), and 9.2% (2.2-44.5), respectively. Processed meat intake associated with a nonsignificant trend toward higher ASCVD (1.11 [0.98-1.25]); intakes of fish, poultry, and eggs were not significantly associated. Among other risk pathways, blood glucose, insulin, and C-reactive protein, but not blood pressure or blood cholesterol, each significantly mediated the total meat-ASCVD association.

CONCLUSIONS

In this large, community-based cohort, higher meat intake associated with incident ASCVD, partly mediated by microbiota-derived metabolites of L-carnitine, abundant in red meat. These novel findings support biochemical links between dietary meat, gut microbiome pathways, and ASCVD.

Global research trends in atherosclerosis: A bibliometric and visualized study

Background

Increasing evidence has spurred a considerable evolution of concepts related to atherosclerosis, prompting the need to provide a comprehensive view of the growing literature. By retrieving publications in the Web of Science Core Collection (WoSCC) of Clarivate Analytics, we conducted a bibliometric analysis of the scientific literature on atherosclerosis to describe the research landscape.

Methods

A search was conducted of the WoSCC for articles and reviews serving exclusively as a source of information on atherosclerosis published between 2012 and 2022. Microsoft Excel 2019 was used to chart the annual productivity of research relevant to atherosclerosis. Through CiteSpace and VOSviewer, the most prolific countries or regions, authors, journals, and resource-, intellectual-, and knowledge-sharing in atherosclerosis research, as well as co-citation analysis of references and keywords, were analyzed.

Results

A total of 20,014 publications were retrieved. In terms of publications, the United States remains the most productive country (6,390, 31,93%). The most publications have been contributed by Johns Hopkins Univ (730, 3.65%). ALVARO ALONSO produced the most published works (171, 0.85%). With a betweenness centrality of 0.17, ERIN D MICHOS was the most influential author. The most prolific journal was identified as Atherosclerosis (893, 4.46%). Circulation received the most co-citations (14,939, 2.79%). Keywords with the ongoing strong citation bursts were “nucleotide-binding oligomerization (NOD), Leucine-rich repeat (LRR)-containing protein (NLRP3) inflammasome,” “short-chain fatty acids (SCFAs),” “exosome,” and “homeostasis,” etc.

Conclusion

The research on atherosclerosis is driven mostly by North America and Europe. Intensive research has focused on the link between inflammation and atherosclerosis, as well as its complications. Specifically, the NLRP3 inflammasome, interleukin-1β, gut microbiota and SCFAs, exosome, long non-coding RNAs, autophagy, and cellular senescence were described to be hot issues in the field.

Microbial metabolites and heart failure: Friends or enemies?

Heart failure (HF), a global health issue characterized by structural or functional cardiac dysfunction, which was found to be associated with the gut microbiome recently. Although multiple studies suggested that the gut microbiome may have an impact on the development of cardiovascular diseases, the underlying mechanism of the gut microbiome in HF remains unclear. The study of metabolites from gut microbiota influenced by dietary nutrition uptake suggested that gut microbiota may affect the process of HF. However, on the basis of the microbiota’s complicated roles and their interactions with metabolites, studies of microbial metabolites in HF had rarely been described so far. In this review, we focused on dietary nutrition-related factors that were involved in the development and progression of HF, such as trimethylamine N-oxide (TMAO), short-chain fatty acids (SCFAs), and bile acids (BAs), to summarize their advances and several potential targets in HF. From a therapeutic standpoint, we discussed microbial metabolites as a potential strategy and their applications in HF as well.

TMAO as a potential biomarker and therapeutic target for chronic kidney disease: A review

The gut microbiota and its metabolites have become a hotspot of recent research. Trimethylamine N-oxide (TMAO) metabolized by the gut microbiota is closely related to many diseases such as cardiovascular disease, chronic kidney disease, type 2 diabetes, etc. Chronic kidney disease (CKD) is an important contributor to morbidity and mortality from non-communicable diseases. Recently, increasing focus has been put on the role of TMAO in the development and progress of chronic kidney disease. The level of TMAO in patients with chronic kidney disease is significantly increased, and a high level of TMAO deteriorates chronic kidney disease. This article describes the relationship between TMAO and chronic kidney disease and the research progress of drugs targeted TMAO, providing a reference for the development of anti-chronic kidney disease drugs targeted TMAO.

The short-chain fatty acid butyrate accelerates vascular calcification via regulation of histone deacetylases and NF-κB signaling

Recent studies have shown that short-chain fatty acids (SCFAs), primarily acetate, propionate and butyrate, play a crucial role in the pathogenesis of cardiovascular disease. Whether SCFAs regulate vascular calcification, a common pathological change in cardiovascular tissues, remains unclear. This study aimed to investigate the potential role of SCFAs in vascular calcification. Using cellular and animal models of vascular calcification, we showed that butyrate significantly enhanced high phosphate (Pi)-induced calcification and osteogenic transition of vascular smooth muscle cells (VSMC) in vitro, whereas acetate and propionate had no effects. Subsequent studies confirmed that butyrate significantly promoted high Pi-induced aortic ring calcification ex vivo and high dose vitamin D₃ (vD₃)-induced mouse vascular calcification in vivo. Mechanistically, butyrate significantly inhibited histone deacetylase (HDAC) expression in VSMCs, and a pan HDAC inhibitor Trichostatin A showed similar inductive effects on calcification and osteogenic transition of VSMCs to butyrate. In addition, the SCFA sensing receptors Gpr41 and Gpr109a were primarily expressed by VSMCs, and butyrate induced the rapid activation of NF-κB, Wnt and Akt signaling in VSMCs. Intriguingly, the NF-κB inhibitor SC75741 significantly attenuated butyrate-induced calcification and the osteogenic gene Msx2 expression in VSMCs. We showed that knockdown of Gpr41 but not Gpr109a attenuated butyrate-induced VSMC calcification. This study reveals that butyrate accelerates vascular calcification via its dual effects on HDAC inhibition and NF-κB activation. Our data provide novel insights into the role of microbe-host interaction in vascular calcification, and may have implications for the development of potential therapy for vascular calcification.

Cardioprotection effect of Yiqi-Huoxue-Jiangzhuo formula in a chronic kidney disease mouse model associated with gut microbiota modulation and NLRP3 inflammasome inhibition

BACKGROUND

The pathogenesis and treatment of cardiovascular disease mediated by chronic kidney disease (CKD) are key research questions. Specifically, the mechanisms underlying the cardiorenal protective effect of Yiqi-Huoxue-Jiangzhuo formula (YHJF), a traditional Chinese herbal medicine, have not yet been clarified.

METHODS

A classical CKD mouse model was constructed by 5/6 nephrectomy (Nx) to study the effects of YHJF intervention on 5/6 Nx mice cardiorenal function, gut microbial composition, gut-derived metabolites, and NLRP3 inflammasome pathways.

RESULTS

YHJF improved cardiac dysfunction and reversed left ventricular hypertrophy, myocardial hypertrophy, and interstitial fibrosis in 5/6 Nx mice. In addition, YHJF inhibited activation of the NLRP3 inflammasome and downregulated the expression of TNF-α and IL-1β both in the heart and serum; reconstitution of the intestinal flora imbalance was also found in 5/6 Nx mice treated with YHJF. Spearman's correlation and redundancy analyses showed that changes in the intestinal flora of 5/6 Nx mice were related to clinical phenotype and serum inflammatory levels.

CONCLUSIONS

Treatment with YHJF effectively protected the heart function of 5/6 Nx mice; this effect was attributed to inhibition of NLRP3 inflammasome activation and regulation of intestinal microbial composition and derived metabolites. YHJF has potential for improving intestinal flora imbalance and gut-derived toxin accumulation in patients with CKD, thereby preventing cardiovascular complications.

Serum Trimethylamine N-Oxide Level Is Associated with Peripheral Arterial Stiffness in Advanced Non-Dialysis Chronic Kidney Disease Patients

Trimethylamine N-oxide (TMAO) is a gut-derived uremic toxin involved in cardiovascular diseases (CVD). Peripheral arterial stiffness (PAS), measured by the brachial-ankle pulse wave velocity (baPWV) is a valuable indicator of the existence of CVD alongside other diseases. The study recruited 157 patients with chronic kidney disease (CKD) stages 3 to 5, and aimed to determine the correlation between serum TMAO and PAS, defined as a baPWV of >18.0 m/s. Patients with CKD who were diagnosed with PAS (68 patients, 43.3%) were older, had a higher percentage of hypertension or diabetes mellitus, higher systolic blood pressure, and higher fasting glucose, C-reactive protein, and TMAO levels. Furthermore, besides old age and SBP, patients with CKD who had higher serum TMAO were more likely to have PAS, with an odds ratio of 1.016 (95% confidence interval = 1.002−1.029, p = 0.021) by multivariate logistic regression analysis. Correlation analysis demonstrated that serum TMAO was positively correlated with C-reactive protein level and either left or right baPWV. Thus, we supposed that serum TMAO levels were associated with PAS in patients with advanced non-dialysis CKD.

Downregulation of HDAC9 by the ketone metabolite β-hydroxybutyrate suppresses vascular calcification

Vascular calcification is an actively regulated process resembling bone formation and contributes to the cardiovascular morbidity and mortality of chronic kidney disease (CKD). However, effective therapy for vascular calcification is still lacking. The ketone body β-hydroxybutyrate (BHB) has been demonstrated to have health-promoting effects including anti-inflammation and cardiovascular protective effects. However, whether BHB protects against vascular calcification in CKD remains unclear. In this study, Alizarin Red staining and calcium content assay showed that BHB reduced calcification of vascular smooth muscle cells (VSMCs) and arterial rings. Of note, compared with CKD patients without thoracic calcification, serum BHB levels were lower in CKD patients with thoracic calcification. Supplementation with 1,3-butanediol (1,3-B), the precursor of BHB, attenuated aortic calcification in CKD rats and VitD3-overloaded mice. Furthermore, RNA-Seq analysis revealed that BHB downregulated HDAC9, which was further confirmed by RT-qPCR and western blot analysis. Both pharmacological inhibition and knockdown of HDAC9 attenuated calcification of human VSMCs, while overexpression of HDAC9 exacerbated calcification of VSMCs and aortic rings, indicating that HDAC9 promotes vascular calcification under CKD conditions. Of note, BHB treatment antagonized HDAC9-induced vascular calcification. In addition, HDAC9 overexpression activated NF-κB signaling pathway and inhibition of NF-κB attenuated HDAC9-induced VSMC calcification, suggesting that HDAC9 promotes vascular calcification via activation of NF-κB. In conclusion, our study demonstrates that BHB supplementation inhibits vascular calcification in CKD via modulation of the HDAC9-dependent NF-κB signaling pathway. Moreover, we unveil a crucial mechanistic role of HDAC9 in vascular calcification under CKD conditions, thus nutritional intervention or pharmacological approaches to enhance BHB levels could act as promising therapeutic strategies to target HDAC9 for the treatment of vascular calcification in CKD. This article is protected by copyright. All rights reserved.

Plasmatic trimethylamine N-oxide and its relation to stroke: A systematic review and dose-response meta-analysis

BACKGROUND

Elevated circulating concentrations of the gut metabolite, trimethylamine N-oxide (TMAO), were found in patients who experienced stroke. However, it has not been reported whether a high level of TMAO is associated with a significantly increased risk of stroke. This study aimed to review the available scientific evidence about the relationship between TMAO levels and the risk of stroke in a dose-response meta-analysis.

METHODS

The PubMed, Embase, Cochrane library, and China National Knowledge Infrastructure databases were searched for studies starting from September 1996 to December 2020. Nine studies including 4402 subjects were reviewed in this study.

RESULTS

The results of meta-analysis showed that high levels of circulating TMAO were associated with an increased risk of stroke in patients in the random-effects model (odds ratio [OR], 1.64; 95% confidence interval [CI], 1.12-2.41; P = 0.047). The OR for the prevalence of stroke increased by 48% per 5-μmol/L increment (OR, 1.05; 95% CI, 1.16-1.78; P < 0.001) and by 132% per 10-μmol/L increment (OR, 2.32; 95% CI, 1.38-3.86; P < 0.001) in circulating TMAO concentration according to the dose-response meta-analysis.

CONCLUSION

There was a significant association between higher plasma TMAO concentrations and the risk of stroke. Further in-depth studies are warranted to validate this interaction and explore potential mechanisms.

Ecklonia cava extracts decrease hypertension-related vascular calcification by modulating PGC-1α and SOD2

Vascular calcification (VC) is induced by a decrease in sirtuin 3 (SIRT3) and superoxide dismutase (SOD)2 and increases mitochondrial reactive oxygen species (mtROS), eventually leading to mitochondrial dysfunction and phenotype alterations in vascular smooth muscle cells (VSMCs) into osteoblast-like cells in hypertension. Ecklonia cava extract (ECE) is known to increase peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α) and SOD2. In this study, we evaluated the effect of ECE on decreasing VC by increasing PGC-1α which increased SOD2 activity and decreased mtROS in an in vitro VSMC model of treating serums from Wistar Kyoto (WKY), spontaneous hypertensive rats (SHRs), and ECE-treated SHRs. Furthermore, the decreasing effect of ECE on VC was evaluated with an in vivo SHR model. PGC-1α expression, SIRT3 expression, and SOD2 activity were decreased by the serum from the SHRs and increased by the serum from the ECE-treated SHRs in the VSMCs. PGC-1α silencing eliminated those increases. mtROS generation and mitochondrial DNA (mtDNA) damage increased in the SHRs but decreased with ECE. Mitochondrial fission increased in the SHRs but decreased by ECE. Mitochondrial fusion, mitophagy, and mitochondrial biogenesis were decreased in the SHRs but increased by ECE. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and calcium deposition in the medial layer of the aorta increased in the SHRs but decreased with ECE. Therefore, ECE decreases VC via the upregulation of PGC-1α and SIRT3, which increases SOD2 activity. Activated SOD2 decreases mtDNA damage and mtROS generation, which sequentially decreases NADPH oxidase activity and changes the mitochondrial dynamics, thereby decreasing VC.

Endoplasmic Reticulum Stress and Pathogenesis of Vascular Calcification

Vascular calcification (VC) is characterized by calcium phosphate deposition in blood vessel walls and is associated with many diseases, as well as increased cardiovascular morbidity and mortality. However, the molecular mechanisms underlying of VC development and pathogenesis are not fully understood, thus impeding the design of molecular-targeted therapy for VC. Recently, several studies have shown that endoplasmic reticulum (ER) stress can exacerbate VC. The ER is an intracellular membranous organelle involved in the synthesis, folding, maturation, and post-translational modification of secretory and transmembrane proteins. ER stress (ERS) occurs when unfolded/misfolded proteins accumulate after a disturbance in the ER environment. Therefore, downregulation of pathological ERS may attenuate VC. This review summarizes the relationship between ERS and VC, focusing on how ERS regulates the development of VC by promoting osteogenic transformation, inflammation, autophagy, and apoptosis, with particular interest in the molecular mechanisms occurring in various vascular cells. We also discuss, the therapeutic effects of ERS inhibition on the progress of diseases associated with VC are detailed.

Indoleamine 2,3-Dioxygenase 1 Deletion-Mediated Kynurenine Insufficiency in Vascular Smooth Muscle Cells Exacerbates Arterial Calcification

BACKGROUND

IDO1 (indoleamine 2,3-dioxygenase 1) is the rate-limiting enzyme for tryptophan metabolism. IDO1 malfunction is involved in the pathogenesis of atherosclerosis. Vascular smooth muscle cells (VSMCs) with an osteogenic phenotype promote calcification and features of plaque instability. However, it remains unclear whether aberrant IDO1-regulated tryptophan metabolism causes VSMCs osteogenic reprogramming and calcification.

METHODS

We generated global Apoe (apolipoprotein E) and Ido1 double knockout mice, and Apoe knockout mice with specific deletion of IDO1 in VSMCs or macrophages. Arterial intimal calcification was evaluated by a Western diet-induced atherosclerotic calcification model.

RESULTS

Global deficiency of IDO1 boosted calcific lesion formation without sex bias in vivo. Conditional IDO1 loss of function in VSMCs rather than macrophages promoted calcific lesion development and the abundance of RUNX2 (runt-related transcription factor 2). In contrast, administration of kynurenine via intraperitoneal injection markedly delayed the progression of intimal calcification in parallel with decreased RUNX2 expression in both Apoe^-/- and Apoe^-/- Ido1^-/- mice. We found that IDO1 deletion restrained RUNX2 from proteasomal degradation, which resulted in enhanced osteogenic reprogramming of VSMCs. Kynurenine administration downregulated RUNX2 in an aryl hydrocarbon receptor-dependent manner. Kynurenine acted as the endogenous ligand of aryl hydrocarbon receptor, controlled resultant interactions between cullin 4B and aryl hydrocarbon receptor to form an E3 ubiquitin ligase that bound with RUNX2, and subsequently promoted ubiquitin-mediated instability of RUNX2 in VSMCs. Serum samples from patients with coronary artery calcification had impaired IDO1 activity and decreased kynurenine catabolites compared with those without calcification.

CONCLUSIONS

Kynurenine, an IDO1-mediated tryptophan metabolism main product, promotes RUNX2 ubiquitination and subsequently leads to its proteasomal degradation via an aryl hydrocarbon receptor-dependent nongenomic pathway. Insufficient kynurenine exerts the deleterious role of IDO1 ablation in promoting RUNX2-mediated VSMCs osteogenic reprogramming and calcification in vivo.

Deficiency of proline/serine-rich coiled-coil protein 1 (PSRC1) accelerates trimethylamine N-oxide-induced atherosclerosis in ApoE-/- mice

AIMS

The main therapeutic strategies for coronary artery disease (CAD) are mainly based on the correction of abnormal cholesterol levels; however, residual risks remain. The newly proven gut microbial metabolite trimethylamine N-oxide (TMAO) linked with CAD has broadened our horizons. In this study, we determined the role of proline/serine-rich coiled-coil protein 1 (PSRC1) in TMAO-driven atherosclerosis.

METHODS AND RESULTS

We first analyzed the levels of TMAO and PSRC1 in patients with or without atherosclerosis with a target LDL-C < 1.8 mmol/L. Plasma TMAO levels were increased and negatively associated with decreased PSRC1 in peripheral blood mononuclear cells. Animals and in vitro studies showed that TMAO inhibited macrophage PSRC1 expression due to DNA hypermethylation of CpG islands. ApoE^-/- mice fed a choline-supplemented diet exhibited reduced PSRC1 expression accompanied by increased atherosclerotic lesions and plasma TMAO levels. We further deleted PSRC1 in apoE^-/- mice and PSRC1 deficiency significantly accelerated choline-induced atherogenesis, characterized by increased macrophage infiltration, foam cell formation and M1 macrophage polarization. Mechanistically, we overexpressed and knocked out PSRC1 in cultured macrophages to explore the mechanisms underlying TMAO-induced cholesterol accumulation and inflammation. PSRC1 deletion impaired reverse cholesterol transport and enhanced cholesterol uptake and inflammation, while PSRC1 overexpression rescued the proatherogenic phenotype observed in TMAO-stimulated macrophages, which was partially attributed to sulfotransferase 2B1b (SULT2B1b) inhibition.

CONCLUSIONS

Herein, clinical data provide evidence that TMAO may participate in the development of CAD beyond well-controlled LDL-C levels. Our work also suggests that PSRC1 is a negative regulator mediating the unfavorable effects of TMAO-containing diets. Therefore, PSRC1 overexpression and reduced choline consumption may further alleviate atherosclerosis.

Vascular Calcification in Chronic Kidney Disease: An Update and Perspective

Chronic kidney disease is a devastating condition resulting from irreversible loss of nephron numbers and function and leading to end-stage renal disease and mineral disorders. Vascular calcification, an ectopic deposition of calcium-phosphate salts in blood vessel walls and heart valves, is an independent risk factor of cardiovascular morbidity and mortality in chronic kidney disease. Moreover, aging and related metabolic disorders are essential risk factors for chronic kidney disease and vascular calcification. Marked progress has been recently made in understanding and treating vascular calcification in chronic kidney disease. However, there is a paucity of systematic reviews summarizing this progress, and investigating unresolved issues is warranted. In this systematic review, we aimed to overview the underlying mechanisms of vascular calcification in chronic kidney diseases and discuss the impact of chronic kidney disease on the pathophysiology of vascular calcification. Additionally, we summarized potential clinical diagnostic biomarkers and therapeutic applications for vascular calcification with chronic kidney disease. This review may offer new insights into the pathogenesis, diagnosis, and therapeutic intervention of vascular calcification.

Translational Medicine in Uremic Vascular Calcification: Scavenging ROS Attenuates p-Cresyl Sulfate-Activated Caspase-1, NLRP3 Inflammasome and Eicosanoid Inflammation in Human Arterial Smooth Muscle Cells

We formerly proved that uremic vascular calcification (UVC) correlates tightly with oxidative elastic lamina (EL) injury and two cell fates (apoptosis and osteocytic conversion) in smooth muscle cells (SMC) of chronic kidney disease (CKD) patients and eliminating p-cresyl sulfate (PCS)-activated intracellular ROS ameliorates the MAPK signaling pathway in a human arterial SMC (HASMC) model. Nonetheless, whether ROS scavenger attenuates PCS-triggered inflammasome activation and eicosanoid inflammation in the UVC process remains unknown. Patients with lower extremity amputation were categorized into CKD and normal control group according to renal function. We used immunohistochemistry stain to analyze UVC in arterial specimens, including oxidative injury (8-hydroxy-2′-deoxyguanosine (8-OHdG) and internal EL disruption), cytosolic phospholipase A2 (cPLA2), cyclooxygenase 2 (COX2), interleukin-1 beta (IL-1β), caspase-1 and NLRP3. To simulate the patho-mechanism of human UVC, the therapeutic effects of ROS scavenger on PCS-triggered inflammatory pathways was explored in a HASMC model. We found CKD patients had higher circulating levels of PCS and an increase in medial arterial calcification than the control group. In CKD arteries, the severity of UVC corresponded with expressions of oxidative EL disruption and 8-OHdG. Furthermore, coupling expressions of cPLA2 and COX2 were accentuated in CKD arteries, indicative of eicosanoid inflammation. Notably, tissue expressions of IL-1β, caspase-1 and NLRP3 were enhanced in parallel with UVC severity, indicative of inflammasome activation. From bedside to bench, ROS scavenger attenuates PCS-activated expressions of cPLA2/COX2, pro-caspase-1 and NLRP3 in the HASMC model. UVC as an inevitable outcome is predictive of death in CKD patients. Nonetheless, UVC remain pharmacoresistant despite the evolution of treatment for mineral-parathyroid hormone-vitamin D axis. Beyond the mineral dysregulation, the stimulation of pro-oxidant PCS alone results in eicosanoid inflammation and inflammasome activation. Concerning the key role of Caspase-1 in pyroptosis, cell fates of HASMC in uremic milieu are not limited to apoptosis and osteogenesis. In view of this, reducing ROS and PCS may act as a therapeutic strategy for UVC-related cardiovascular events in CKD patients.

Programmed cell death in atherosclerosis and vascular calcification

The concept of cell death has been expanded beyond apoptosis and necrosis to additional forms, including necroptosis, pyroptosis, autophagy, and ferroptosis. These cell death modalities play a critical role in all aspects of life, which are noteworthy for their diverse roles in diseases. Atherosclerosis (AS) and vascular calcification (VC) are major causes for the high morbidity and mortality of cardiovascular disease. Despite considerable advances in understanding the signaling pathways associated with AS and VC, the exact molecular basis remains obscure. In the article, we review the molecular mechanisms that mediate cell death and its implications for AS and VC. A better understanding of the mechanisms underlying cell death in AS and VC may drive the development of promising therapeutic strategies.

Uremic Toxins and Cardiovascular Risk in Chronic Kidney Disease: What Have We Learned Recently beyond the Past Findings?

Patients with chronic kidney disease (CKD) have an elevated prevalence of atheromatous (ATH) and/or non-atheromatous (non-ATH) cardiovascular disease (CVD) due to an array of CKD-related risk factors, such as uremic toxins (UTs). Indeed, UTs have a major role in the emergence of a spectrum of CVDs, which constitute the leading cause of death in patients with end-stage renal disease. The European Uremic Toxin Work Group has identified over 100 UTs, more than 25 of which are dietary or gut-derived. Even though relationships between UTs and CVDs have been described in the literature, there are few reviews on the involvement of the most toxic compounds and the corresponding physiopathologic mechanisms. Here, we review the scientific literature on the dietary and gut-derived UTs with the greatest toxicity in vitro and in vivo. A better understanding of these toxins' roles in the elevated prevalence of CVDs among CKD patients might facilitate the development of targeted treatments. Hence, we review (i) ATH and non-ATH CVDs and the respective levels of risk in patients with CKD and (ii) the mechanisms that underlie the influence of dietary and gut-derived UTs on CVDs.

Irisin protects against vascular calcification by activating autophagy and inhibiting NLRP3-mediated vascular smooth muscle cell pyroptosis in chronic kidney disease

Irisin protects the cardiovascular system against vascular diseases. However, its role in chronic kidney disease (CKD) -associated vascular calcification (VC) and the underlying mechanisms remain unclear. In the present study, we investigated the potential link among Irisin, pyroptosis, and VC under CKD conditions. During mouse vascular smooth muscle cell (VSMC) calcification induced by β-glycerophosphate (β-GP), the pyroptosis level was increased, as evidenced by the upregulated expression of pyroptosis-related proteins (cleaved CASP1, GSDMD-N, and IL1B) and pyroptotic cell death (increased numbers of PI-positive cells and LDH release). Reducing the pyroptosis levels by a CASP1 inhibitor remarkably decreased calcium deposition in β-GP-treated VSMCs. Further experiments revealed that the pyroptosis pathway was activated by excessive reactive oxygen species (ROS) production and subsequent NLR family pyrin domain containing 3 (NLRP3) inflammasome activation in calcified VSMCs. Importantly, Irisin effectively inhibited β-GP-induced calcium deposition in VSMCs in vitro and in mice aortic rings ex vivo. Overexpression of Nlrp3 attenuated the suppressive effect of Irisin on VSMC calcification. In addition, Irisin could induce autophagy and restore autophagic flux in calcified VSMCs. Adding the autophagy inhibitor 3-methyladenine or chloroquine attenuated the inhibitory effect of Irisin on β-GP-induced ROS production, NLRP3 inflammasome activation, pyroptosis, and calcification in VSMCs. Finally, our in vivo study showed that Irisin treatment promoted autophagy, downregulated ROS level and thereby suppressed pyroptosis and medial calcification in aortic tissues of adenine-induced CKD mice. Together, our findings for the first time demonstrated that Irisin protected against VC via inducing autophagy and inhibiting VSMC pyroptosis in CKD, and Irisin might serve as an effective therapeutic agent for CKD-associated VC.

Capsaicin Attenuates Arterial Calcification Through Promoting SIRT6-Mediated Deacetylation and Degradation of Hif1α (Hypoxic-Inducible Factor-1 Alpha)

BACKGROUND

Sustained Hif1α (hypoxic-inducible factor-1 alpha) accumulation plays a central role in osteogenic transdifferentiation and subsequent calcification. Capsaicin, the potent agonist of TRPV1 (transient receptor potential vanilloid type 1), was found to mitigate hypoxic-related injury and reverse phenotypic switch of vascular smooth muscle cells. However, its role in arterial calcification and the underlying mechanisms remain unexplored.

METHODS

We used data from Multi-Ethnic Study of Atherosclerosis to examine the association of coronary artery calcification and chili consumption. Chronic kidney disease mice and high phosphate-induced vascular smooth muscle cells calcification models were established to investigate the anticalcification effect of capsaicin, evaluated by calcium deposition and changes in phenotype markers.

RESULTS

Chili consumption was negatively correlated with coronary artery calcification and conferred a smaller progression burden during follow-up. Capsaicin reduced calcium deposition and osteogenic transdifferentiation both in vivo and in vitro. Using siTRPV1 and capsazepine, the anticalcification effect of capsaicin was abrogated. Hif1α was increased in Pi-treated vascular smooth muscle cells and its degradation was accelerated by capsaicin. Retaining Hif1α stability using CoCl2 or MG132 abolished the protective effect of capsaicin. We further identified an increased expression of SIRT6 in response to capsaicin and confirmed the physical interaction between SIRT6 and Hif1α. Acetylated Hif1α was decreased, whereas hydroxylated Hif1α was increased under capsaicin treatment. Using immunohistochemistry analysis, we observed increased SIRT6 and reduced Hif1α in both SIRT6 transgenic and capsaicin-treated chronic kidney disease mice.

CONCLUSIONS

Capsaicin facilitates deacetylation and degradation of Hif1α by upregulating SIRT6, which inhibits osteogenic transdifferentiation and protects against arterial calcification. These data highlight a promising therapeutic target for the management of arterial calcification.

TMAO-Activated Hepatocyte-Derived Exosomes Are Widely Distributed in Mice with Different Patterns and Promote Vascular Inflammation

Background

Trimethylamine-N-oxide (TMAO) has been shown to be an important player in cardiovascular disease (CVD) by promoting vascular inflammation and endothelial dysfunction. We recently found that exosomes (Exos) released from TMAO-activated hepatocytes (TMAO-Exos) could significantly induce inflammation and endothelial dysfunction. However, understandings of how are the Exos secreted by hepatocytes, where are they distributed in vivo, and what effects will they have on vascular inflammation remain limited. The present study aimed to explore the hub genes involved in the production of TMAO-Exos and their distributions in vivo and effects on inflammation.

Methods

The transcriptome profiles of primary rat hepatocytes stimulated with TMAO were obtained from the GSE135856 dataset in the Gene Expression Omnibus repository, and the hub genes associated with Exos were screened and verified by qPCR. Next, Exos derived from TMAO-treated hepatocytes were isolated using differential centrifugation and given intravenously to mice. After 24 h, the distributions of DiI-labelled Exos were visualized with a fluorescence microscope, and the levels of proinflammatory genes in the aorta were detected by qPCR.

Results

Phgdh, Mdh2, Echs1, Rap2a, Gpd1l, and Slc3a2 were identified as hub genes that may be involved in the production of TMAO-Exos. And TMAO-Exos were found to be efficiently taken up by cardiomyocytes, hepatocytes, and endothelial cells in the aorta and gastrocnemius muscle. Furthermore, TMAO-Exos, but not control-Exos, could significantly promote the mRNA expressions of Tnf, Icam1, Sele, and Cox-2 in the aorta.

Conclusions

We provided clues about how TMAO may stimulate hepatocytes to produce Exos and further offered evidence that Exos secreted by TMAO-treated hepatocytes could be widely distributed in vivo and promote vascular inflammation.

Trimethylamine N-Oxide Promotes Abdominal Aortic Aneurysm Formation by Aggravating Aortic Smooth Muscle Cell Senescence in Mice

Trimethylamine N-oxide (TMAO) has been linked to cardiovascular disease morbidity and mortality. However, the role of TMAO in the development of abdominal aortic aneurysms (AAAs) is not known. This study investigated the association between TMAO and AAA formation. TMAO and saline were added to the drinking water of angiotensin II (AngII)- and calcium chloride (CaCl₂)-induced AAA model mice, respectively. After 4 weeks, the effects of TMAO on AAA development were determined by histology and immunohistology of aortic tissue. The in vitro effects of TMAO were also examined in mouse aortic smooth muscle cells (SMCs). The maximal aortic diameter, incidence of AAA, and degree of elastin degradation were significantly increased in TMAO-treated mice. TMAO also increased the accumulation of the senescence markers p21 and p16, as well as of reactive oxygen species (ROS), matrix metalloproteinase-2 (MMP2), and matrix metalloproteinase-9 (MMP9) in vivo and in vitro. TMAO promoted AAA development in mouse AAA models induced by AngII and CaCl₂ by a mechanism involving cellular senescence.

Lipoprotein (a)-mediated vascular calcification: population-based and in vitro studies

BACKGROUND

Lipoprotein (a) [Lp(a)] is a causal risk factor for cardiovascular diseases, while its role in vascular calcification has not been well-established. Here, we investigated an association of Lp(a) with vascular calcification using population-based and in vitro study designs.

METHODS

A total of 2806 patients who received coronary computed tomography were enrolled to assess the correlation of Lp(a) with the severity of coronary artery calcification (CAC). Human aortic smooth muscle cells (HASMCs) were used to explore mechanisms of Lp(a)-induced vascular calcification.

RESULTS

In the population study, Lp(a) was independently correlated with the presence and severity of CAC (all p < 0.05). In vitro study showed that cell calcific depositions and alkaline phosphatase (ALP) activity were increased and the expression of pro-calcific proteins, including bone morphogenetic protein-2 (BMP2) and osteopontin (OPN), were up-regulated by Lp(a) stimulation. Interestingly, Lp(a) activated Notch1 signaling, resulting in cell calcification, which was inhibited by the Notch1 signaling inhibitor, DAPT. Lp(a)-induced Notch1 activation up-regulated BMP2-Smad1/5/9 pathway. In contrast, Noggin, an inhibitor of BMP2-Smad1/5/9 pathway, significantly blocked Lp(a)-induced HASMC calcification. Notch1 activation also induced translocation of nuclear factor-κB (NF-κB) accompanied by OPN overexpression and elevated inflammatory cytokines production, while NF-κB silencing alleviated Lp(a)-induced vascular calcification.

CONCLUSIONS

Elevated Lp(a) concentrations are independently associated with the presence and severity of CAC and the impact of Lp(a) on vascular calcification is involved in the activation of Notch1-NF-κB and Notch1-BMP2-Smad1/5/9 pathways, thus implicating Lp(a) as a potential novel therapeutic target for vascular calcification.

Gut Microbial Metabolite Trimethylamine N-Oxide Aggravates Pulmonary Hypertension

Trimethylamine N-oxide (TMAO), a metabolite derived from intestine microbial flora, enhances vascular inflammation in a variety of cardiovascular disease, and the bacterial communities associated with trimethylamine N-oxide (TMAO) metabolism is higher in pulmonary hypertension (PH) patients. The effects of TMAO on PH, however, has not been elucidated. In the present study, we found that circulating TMAO was elevated in intermediate to high-risk PH patients when compared to healthy control or low-risk PH patients. In monocrotaline-induced rat PH models, circulating TMAO was elevated; and reduction of TMAO using 3,3-dimethyl-1-butanol (DMB) significantly decreased right ventricle systolic pressure, pulmonary vascular muscularization in both monocrotaline-induced rat PH and hypoxia induced mice PH models. RNA sequencing of rat lungs revealed that DMB treatment significant suppressed the pathways involved in cytokine-cytokine receptor interaction, and cytokine and chemokine signaling. Protein-protein interaction analysis of the differentially expressed transcripts regulated by DMB showed 5 hub genes with a strong connectivity of proinflammatory cytokines and chemokines including Kng1, Cxcl1, Cxcl2, CxcL6 and Il6. In vitro, TMAO significantly increased the expression of Kng1, Cxcl1, Cxcl2, CxcL6 and Il6 in bone marrow derived macrophage. And TMAO-treated conditioned medium from macrophage increased the proliferation and migration of pulmonary artery smooth muscle cells; but TMAO treatment did not change the proliferation or migration of pulmonary artery smooth muscle cells. In conclusion, our study demonstrates that TMAO is increased in severe PH, and the reduction of TMAO decreases pulmonary vascular muscularization and alleviates PH via suppressing the macrophage production of chemokines and cytokines.

Proteomics-Based Identification of Interaction Partners of the Xenobiotic Detoxification Enzyme FMO3 Reveals Involvement in Urea Cycle

The hepatic xenobiotic metabolizing enzyme flavin-containing monooxygenase 3 (FMO3) has been implicated in the development of cardiometabolic disease primarily due to its enzymatic product trimethylamine-N oxide (TMAO), which has recently been shown to be associated with multiple chronic diseases, including kidney and coronary artery diseases. Although TMAO may have causative roles as a pro-inflammatory mediator, the possibility for roles in metabolic disease for FMO3, irrespective of TMAO formation, does exist. We hypothesized that FMO3 may interact with other proteins known to be involved in cardiometabolic diseases and that modulating the expression of FMO3 may impact on these interaction partners. Here, we combine a co-immunoprecipitation strategy coupled to unbiased proteomic workflow to report a novel protein:protein interaction network for FMO3. We identified 51 FMO3 protein interaction partners, and through gene ontology analysis, have identified urea cycle as an enriched pathway. Using mice deficient in FMO3 on two separate backgrounds, we validated and further investigated expressional and functional associations between FMO3 and the identified urea cycle genes. FMO3-deficient mice showed hepatic overexpression of carbamoylphosphate synthetase (CPS1), the rate-limiting gene of urea cycle, and increased hepatic urea levels, especially in mice of FVB (Friend leukemia virus B strain) background. Finally, overexpression of FMO3 in murine AML12 hepatocytes led to downregulation of CPS1. Although there is past literature linking TMAO to urea cycle, this is the first published work showing that FMO3 and CPS1 may directly interact, implicating a role for FMO3 in chronic kidney disease irrespective of TMAO formation.