Suppression of gut dysbiosis reverses Western diet-induced vascular dysfunction

Microbiome miracles and their pioneering advances and future frontiers in cardiovascular disease

Cardiovascular diseases (CVDs) represent a significant global health challenge, underscoring the need for innovative approaches to prevention and treatment. Recent years have seen a surge in interest in unraveling the complex relationship between the gut microbiome and cardiovascular health. This article delves into current research on the composition, diversity, and impact of the gut microbiome on CVD development. Recent advancements have elucidated the profound influence of the gut microbiome on disease progression, particularly through key mediators like Trimethylamine-N-oxide (TMAO) and other microbial metabolites. Understanding these mechanisms reveals promising therapeutic targets, including interventions aimed at modulating the gut microbiome's interaction with the immune system and its contribution to endothelial dysfunction. Harnessing this understanding, personalized medicine strategies tailored to individuals' gut microbiome profiles offer innovative avenues for reducing cardiovascular risk. As research in this field continues to evolve, there is vast potential for transformative advancements in cardiovascular medicine, paving the way for precision prevention and treatment strategies to address this global health challenge.

Role of the intestinal microbiome and its therapeutic intervention in cardiovascular disorder

The gut microbiome is a heterogeneous population of microbes comprising viruses, bacteria, fungi, and protozoa. Such a microbiome is essential for sustaining host equilibrium, and its impact on human health can be altered by a variety of factors such as external variables, social behavior, age, nutrition, and genetics. Gut microbes' imbalances are related to a variety of chronic diseases including cancer, obesity, and digestive disorders. Globally, recent findings show that intestinal microbes have a significant role in the formation of cardiovascular disease (CVD), which is still the primary cause of fatalities. Atherosclerosis, hypertension, diabetes, inflammation, and some inherited variables are all cardiovascular risk variables. However, studies found correlations between metabolism, intestinal flora, and dietary intake. Variations in the diversity of gut microbes and changes in their activity are thought to influence CVD etiology. Furthermore, the gut microbiota acts as an endocrine organ, producing bioactive metabolites such as TMA (trimethylamine)/TMAO (trimethylamine N-oxide), SCFA (short-chain fatty acids), and bile acids, which have a substantial impact on host wellness and disease by multiple mechanisms. The purpose of this overview is to compile current evidence highlighting the intricate links between gut microbiota, metabolites, and the development of CVD. It focuses on how intestinal dysbiosis promotes CVD risk factors such as heart failure, hypertension, and atherosclerosis. This review explores the normal physiology of intestinal microbes and potential techniques for targeting gut bacteria for CVD treatment using various microbial metabolites. It also examines the significance of gut bacteria in disease treatment, including supplements, prebiotics, probiotics, antibiotic therapies, and fecal transplantation, which is an innovative approach to the management of CVD. As a result, gut bacteria and metabolic pathways become increasingly attractive as potential targets for CVD intervention.

Gut microbiota and microbiota-derived metabolites in cardiovascular diseases

ABSTRACT

Cardiovascular diseases, including heart failure, coronary artery disease, atherosclerosis, aneurysm, thrombosis, and hypertension, are a great economic burden and threat to human health and are the major cause of death worldwide. Recently, researchers have begun to appreciate the role of microbial ecosystems within the human body in contributing to metabolic and cardiovascular disorders. Accumulating evidence has demonstrated that the gut microbiota is closely associated with the occurrence and development of cardiovascular diseases. The gut microbiota functions as an endocrine organ that secretes bioactive metabolites that participate in the maintenance of cardiovascular homeostasis, and their dysfunction can directly influence the progression of cardiovascular disease. This review summarizes the current literature demonstrating the role of the gut microbiota in the development of cardiovascular diseases. We also highlight the mechanism by which well-documented gut microbiota-derived metabolites, especially trimethylamine N-oxide, short-chain fatty acids, and phenylacetylglutamine, promote or inhibit the pathogenesis of cardiovascular diseases. We also discuss the therapeutic potential of altering the gut microbiota and microbiota-derived metabolites to improve or prevent cardiovascular diseases.

Gut Microbiome as a Possible Cause of Occurrence and Therapeutic Target in Chronic Obstructive Pulmonary Disease

As a long-term condition that affects the airways and lungs, chronic obstructive pulmonary disease (COPD) is characterized by inflammation, emphysema, breathlessness, chronic cough, and sputum production. Currently, the bronchodilators and anti-inflammatory drugs prescribed for COPD are mostly off-target, warranting new disease management strategies. Accumulating research has revealed the gut-lung axis to be a bidirectional communication system. Cigarette smoke, a major exacerbating factor in COPD and lung inflammation, affects gut microbiota composition and diversity, causing gut microbiota dysbiosis, a condition that has recently been described in COPD patients and animal models. For this review, we focused on the gut-lung axis, which is influenced by gut microbial metabolites, bacterial translocation, and immune cell modulation. Further, we have summarized the findings of preclinical and clinical studies on the association between gut microbiota and COPD to provide a basis for using gut microbiota in therapeutic strategies against COPD. Our review also proposes that further research on probiotics, prebiotics, short-chain fatty acids, and fecal microbiota transplantation could assist therapeutic approaches targeting the gut microbiota to alleviate COPD.

Vascular ageing: moving from bench towards bedside

Prevention of cardiovascular disease (CVD) remains one of the largest public health challenges of our time. Identifying individuals at increased cardiovascular risk at an asymptomatic, sub-clinical stage is of paramount importance for minimizing disease progression as well as the substantial health and economic burden associated with overt CVD. Vascular ageing (VA) involves the deterioration in vascular structure and function over time and ultimately leads to damage in the heart, brain, kidney, and other organs. Vascular ageing encompasses the cumulative effect of all cardiovascular risk factors on the arterial wall over the life course and thus may help identify those at elevated cardiovascular risk, early in disease development. Although the concept of VA is gaining interest clinically, it is seldom measured in routine clinical practice due to lack of consensus on how to characterize VA as physiological vs. pathological and various practical issues. In this state-of-the-art review and as a network of scientists, clinicians, engineers, and industry partners with expertise in VA, we address six questions related to VA in an attempt to increase knowledge among the broader medical community and move the routine measurement of VA a little closer from bench towards bedside.

Do advanced glycation end products contribute to food allergy?

Sugars can bind non-enzymatically to proteins, nucleic acids or lipids and form compounds called Advanced Glycation End Products (AGEs). Although AGEs can form in vivo, factors in the Western diet such as high amounts of added sugars, processing methods such as dehydration of proteins, high temperature sterilisation to extend shelf life, and cooking methods such as frying and microwaving (and reheating), can lead to inordinate levels of dietary AGEs. Dietary AGEs (dAGEs) have the capacity to bind to the Receptor for Advanced Glycation End Products (RAGE) which is part of the endogenous threat detection network. There are persuasive epidemiological and biochemical arguments that correlate the rise in food allergy in several Western countries with increases in dAGEs. The increased consumption of dAGEs is enmeshed in current theories of the aetiology of food allergy which will be discussed.

Extensive Summary of the Important Roles of Indole Propionic Acid, a Gut Microbial Metabolite in Host Health and Disease

Increasing evidence suggests that metabolites produced by the gut microbiota play a crucial role in host-microbe interactions. Dietary tryptophan ingested by the host enters the gut, where indole-like metabolites such as indole propionic acid (IPA) are produced under deamination by commensal bacteria. Here, we summarize the IPA-producing bacteria, dietary patterns on IPA content, and functional roles of IPA in various diseases. IPA can not only stimulate the expression of tight junction (TJ) proteins to enhance gut barrier function and inhibit the penetration of toxic factors, but also modulate the immune system to exert anti-inflammatory and antioxidant effects to synergistically regulate body physiology. Moreover, IPA can act on target organs through blood circulation to form the gut-organ axis, which helps maintain systemic homeostasis. IPA shows great potential for the diagnosis and treatment of various clinical diseases, such as NAFLD, Alzheimer's disease, and breast cancer. However, the therapeutic effect of IPA depends on dose, target organ, or time. In future studies, further work should be performed to explore the effects and mechanisms of IPA on host health and disease to further improve the existing treatment program.

Suppression of trimethylamine N-oxide with DMB mitigates vascular dysfunction, exercise intolerance, and frailty associated with a Western-style diet in mice

Consumption of a Western-style diet (WD; high fat, high sugar, low fiber) is associated with impaired vascular function and increased risk of cardiovascular diseases (CVD), which could be mediated partly by increased circulating concentrations of the gut microbiome-derived metabolite trimethylamine N-oxide (TMAO). We investigated if suppression of TMAO with 3,3-dimethyl-1-butanol (DMB; inhibitor of microbial TMA lyase) in mice could prevent: 1) WD-induced vascular endothelial dysfunction and aortic stiffening and 2) WD-induced reductions in endurance exercise tolerance and increases in frailty, as both are linked to WD, vascular dysfunction, and increased CVD risk. C57BL/6N mice were fed standard chow or WD (41% fat, ∼25% sugar, 4% fiber) for 5 mo beginning at ∼2 mo of age. Within each diet, mice randomly received (n = 11-13/group) normal drinking water (control) or 1% DMB in drinking water for the last 8 wk (from 5 to 7 mo of age). Plasma TMAO was increased in WD-fed mice but suppressed by DMB. WD induced endothelial dysfunction, assessed as carotid artery endothelium-dependent dilation to acetylcholine, and progressive increases in aortic stiffness (measured serially in vivo as pulse wave velocity), both of which were fully prevented by supplementation with DMB. Endurance exercise tolerance, assessed as time to fatigue on a rotarod test, was impaired in WD-fed mice but partially recovered by DMB. Lastly, WD-induced increases in frailty (31-point index) were prevented by DMB. Our findings indicate DMB or other TMAO-lowering therapies may be promising for mitigating the adverse effects of WD on physiological function, and thereby reducing risk of chronic diseases.NEW & NOTEWORTHY We provide novel evidence that increased circulating concentrations of the gut microbiome-derived metabolite trimethylamine N-oxide (TMAO) contribute to vascular dysfunction associated with consumption of a Western-style diet and that this dysfunction can be prevented by suppressing TMAO with DMB, thereby supporting translation of this compound to humans. Furthermore, to our knowledge, we present the first evidence of the role of TMAO in mediating impairments in endurance exercise tolerance and increased frailty in any context.

A modified standard American diet induces physiological parameters associated with metabolic syndrome in C57BL/6J mice

Investigations into the causative role that western dietary patterns have on obesity and disease pathogenesis have speculated that quality and quantity of dietary fats and/or carbohydrates have a predictive role in the development of these disorders. Standard reference diets such as the AIN-93 rodent diet have historically been used to promote animal health and reduce variation of results across experiments, rather than model modern human dietary habits or nutrition-related pathologies. In rodents high-fat diets (HFDs) became a classic tool to investigate diet-induced obesity (DIO). These murine diets often relied on a single fat source with the most DIO consistent HFDs containing levels of fat up to 45-60% (kcal), higher than the reported human intake of 33-35% (kcal). More recently, researchers are formulating experimental animal (pre-clinical) diets that reflect mean human macro- and micronutrient consumption levels described by the National Health and Nutrition Examination Survey (NHANES). These diets attempt to integrate relevant ingredient sources and levels of nutrients; however, they most often fail to include high-fructose corn syrup (HFCS) as a source of dietary carbohydrate. We have formulated a modified Standard American Diet (mSAD) that incorporates relevant levels and sources of nutrient classes, including dietary HFCS, to assess the basal physiologies associated with mSAD consumption. Mice proffered the mSAD for 15 weeks displayed a phenotype consistent with metabolic syndrome, exhibiting increased adiposity, fasting hyperglycemia with impaired glucose and insulin tolerance. Metabolic alterations were evidenced at the tissue level as crown-like structures (CLS) in adipose tissue and fatty acid deposition in the liver, and targeted 16S rRNA metagenomics revealed microbial compositional shifts between dietary groups. This study suggests diet quality significantly affects metabolic homeostasis, emphasizing the importance of developing relevant pre-clinical diets to investigate chronic diseases highly impacted by western dietary consumption patterns.

A Multi-Strain Probiotic Formulation Improves Intestinal Barrier Function by the Modulation of Tight and Adherent Junction Proteins

In healthy individuals, tight junction proteins (TJPs) maintain the integrity of the intestinal barrier. Dysbiosis and increased intestinal permeability are observed in several diseases, such as inflammatory bowel disease. Many studies highlight the role of probiotics in preventing intestinal barrier dysfunction. The present study aims to investigate the effects of a commercially available probiotic formulation of L. rhamnosus LR 32, B. lactis BL 04, and B. longum BB 536 (Serobioma, Bromatech s.r.l., Milan, Italy) on TJPs and the integrity of the intestinal epithelial barrier, and the ability of this formulation to prevent lipopolysaccharide-induced, inflammation-associated damage. An in vitro model of the intestinal barrier was developed using a Caco-2 cell monolayer. The mRNA expression levels of the TJ genes were analyzed using real-time PCR. Changes in the amounts of proteins were assessed with Western blotting. The effect of Serobioma on the intestinal epithelial barrier function was assessed using transepithelial electrical resistance (TEER) measurements. The probiotic formulation tested in this study modulates the expression of TJPs and prevents inflammatory damage. Our findings provide new insights into the mechanisms by which probiotics are able to prevent damage to the gut epithelial barrier.

Sex Differences in Cardiovascular Impact of Early Metabolic Impairment: Interplay between Dysbiosis and Adipose Inflammation

The evolving view of gut microbiota has shifted toward describing the colonic flora as a dynamic organ in continuous interaction with systemic physiologic processes. Alterations of the normal gut bacterial profile, known as dysbiosis, has been linked to a wide array of pathologies. Of particular interest is the cardiovascular-metabolic disease continuum originating from positive energy intake and high-fat diets. Accumulating evidence suggests a role for sex hormones in modulating the gut microbiome community. Such a role provides an additional layer of modulation of the early inflammatory changes culminating in negative metabolic and cardiovascular outcomes. In this review, we will shed the light on the role of sex hormones in cardiovascular dysfunction mediated by high-fat diet-induced dysbiosis, together with the possible involvement of insulin resistance and adipose tissue inflammation. Insights into novel therapeutic interventions will be discussed as well. SIGNIFICANCE STATEMENT: Increasing evidence implicates a role for dysbiosis in the cardiovascular complications of metabolic dysfunction. This minireview summarizes the available data on the sex-based differences in gut microbiota alterations associated with dietary patterns leading to metabolic impairment. A role for a differential impact of adipose tissue inflammation across sexes in mediating the cardiovascular detrimental phenotype following diet-induced dysbiosis is proposed. Better understanding of this pathway will help introduce early approaches to mitigate cardiovascular deterioration in metabolic disease.

Functional Fiber Reduces Mice Obesity by Regulating Intestinal Microbiota

Obesity may cause metabolic syndrome and has become a global public health problem, and dietary fibers (DF) could alleviate obesity and metabolic syndrome by regulating intestinal microbiota. We developed a functional fiber (FF) with a synthetic mixture of polysaccharides, high viscosity, water-binding capacity, swelling capacity, and fermentability. This study aimed to investigate the effect of FF on obesity and to determine its prevention of obesity by modulating the gut microbiota. Physiological, histological, and biochemical parameters, and gut microbiota composition were investigated in the following six groups: control group (Con), high-fat diet group (HFD), low-fat diet group (LFD, conversion of HFD to LFD), high-fat +8% FF group (8% FF), high-fat +12% FF group (12% FF), and high-fat +12% FF + antibiotic group (12% FF + AB). The results demonstrated that 12% FF could promote a reduction in body weight and epididymal adipocyte area, augment insulin sensitivity, and stimulate heat production from brown adipose tissue (BAT) (p < 0.05). Compared with the HFD, 12% FF could also significantly improve the intestinal morphological integrity, attenuate systemic inflammation, promote intestinal microbiota homeostasis, and stabilize the production of short-chain fatty acids (SCFAs) (p < 0.05). Consistent with the results of 12% FF, the LFD could significantly reduce the body weight and epididymal adipocyte area relative to the HFD (p < 0.05), but the LFD and HFD showed no significant difference (p > 0.05) in the level of inflammation and SCFAs. Meanwhile, 12% FF supplementation showed an increase (p < 0.05) in the abundance of the Bifidobacterium, Lactococcus, and Coprococcus genus in the intestine, which had a negative correlation with obesity and insulin resistance. Additionally, the treatment with antibiotics (12% FF + AB) could inhibit the effect of FF in the HFD. The Kyoto Encyclopedia of Genes and Genomes (KEGG) function prediction revealed that 12% FF could significantly inhibit the cyanogenic amino acid metabolic pathway and decrease the serum succinate concentration relative to the HFD group. The overall results indicate that 12% FF has the potential to reduce obesity through the beneficial regulation of the gut microbiota and metabolites.

The Gut Microbiota and Vascular Aging: A State-of-the-Art and Systematic Review of the Literature

The gut microbiota is a critical regulator of human physiology, deleterious changes to its composition and function (dysbiosis) have been linked to the development and progression of cardiovascular diseases. Vascular ageing (VA) is a process of progressive stiffening of the arterial tree associated with arterial wall remodeling, which can precede hypertension and organ damage, and is associated with cardiovascular risk. Arterial stiffness has become the preferred marker of VA. In our systematic review, we found an association between gut microbiota composition and arterial stiffness, with two patterns, in most animal and human studies: a direct correlation between arterial stiffness and abundances of bacteria associated with altered gut permeability and inflammation; an inverse relationship between arterial stiffness, microbiota diversity, and abundances of bacteria associated with most fit microbiota composition. Interventional studies were able to show a stable link between microbiota modification and arterial stiffness only in animals. None of the human interventional trials was able to demonstrate this relationship, and very few adjusted the analyses for determinants of arterial stiffness. We observed a lack of large randomized interventional trials in humans that test the role of gut microbiota modifications on arterial stiffness, and take into account BP and hemodynamic alterations.

From Tumor Cells to Endothelium and Gut Microbiome: A Complex Interaction Favoring the Metastasis Cascade

Metastasis is a complicated process through which tumor cells disseminate to distant organs and adapt to novel tumor microenvironments. This multi-step cascade relies on the accumulation of genetic and epigenetic alterations within the tumor cells as well as the surrounding non-tumor stromal cells. Endothelial cells constitute a major player in promoting metastasis formation either by inducing the growth of tumor cells or by directing them towards dissemination in the blood or lymph. In fact, the direct and indirect interactions between tumor and endothelial cells were shown to activate several mechanisms allowing cancer cells’ invasion and extravasation. On the other side, gastrointestinal cancer development was shown to be associated with the disruption of the gut microbiome. While several proposed mechanisms have been investigated in this regard, gut and tumor-associated microbiota were shown to impact the gut endothelial barrier, increasing the dissemination of bacteria through the systemic circulation. This bacterial dislocation allows the formation of an inflammatory premetastatic niche in the distant organs promoting the metastatic cascade of primary tumors. In this review, we discuss the role of the endothelial cells in the metastatic cascade of tumors. We will focus on the role of the gut vascular barrier in the regulation metastasis. We will also discuss the interaction between this vascular barrier and the gut microbiota enhancing the process of metastasis. In addition, we will try to elucidate the different mechanisms through which this bacterial dislocation prepares the favorable metastatic niche at distant organs allowing the dissemination and successful deposition of tumor cells in the new microenvironments. Finally, and given the promising results of the studies combining immune checkpoint inhibitors with either microbiota alterations or anti-angiogenic therapy in many types of cancer, we will elaborate in this review the complex interaction between these 3 factors and their possible therapeutic combination to optimize response to treatment.

The Contribution of Gut Microbiota and Endothelial Dysfunction in the Development of Arterial Hypertension in Animal Models and in Humans

The maintenance of the physiological values of blood pressure is closely related to unchangeable factors (genetic predisposition or pathological alterations) but also to modifiable factors (dietary fat and salt, sedentary lifestyle, overweight, inappropriate combinations of drugs, alcohol abuse, smoking and use of psychogenic substances). Hypertension is usually characterized by the presence of a chronic increase in systemic blood pressure above the threshold value and is an important risk factor for cardiovascular disease, including myocardial infarction, stroke, micro- and macro-vascular diseases. Hypertension is closely related to functional changes in the endothelium, such as an altered production of vasoconstrictive and vasodilator substances, which lead to an increase in vascular resistance. These alterations make the endothelial tissue unresponsive to autocrine and paracrine stimuli, initially determining an adaptive response, which over time lead to an increase in risk or disease. The gut microbiota is composed of a highly diverse bacterial population of approximately 10¹⁴ bacteria. A balanced intestinal microbiota preserves the digestive and absorbent functions of the intestine, protecting from pathogens and toxic metabolites in the circulation and reducing the onset of various diseases. The gut microbiota has been shown to produce unique metabolites potentially important in the generation of hypertension and endothelial dysfunction. This review highlights the close connection between hypertension, endothelial dysfunction and gut microbiota.

Canagliflozin Prevents Lipid Accumulation, Mitochondrial Dysfunction, and Gut Microbiota Dysbiosis in Mice With Diabetic Cardiovascular Disease

Type 2 diabetes mellitus (T2DM) is associated with cardiovascular disease (CVD) and sodium glucose cotransporter 2 inhibitors, as oral medications for T2DM treatment have shown the potential to improve vascular dysfunction. The aim of this study was to evaluate the ability of canagliflozin (Cana) to relieve CVD in T2DM mice and its possible action mechanism. Mice with diabetic CVD was conducted by a high-fat diet for 24 weeks, followed by oral gavaging with metformin (200 mg/kg/day) or Cana (50 mg/kg/day) for 6 weeks. The result demonstrated that Cana reduced serum lipid accumulation, and decreased the arteriosclerosis index and atherogenic index of plasma. In addition, Cana treatment reduced the circulating markers of inflammation. More importantly, Cana improved cardiac mitochondrial homeostasis and relieved oxidative stress. Moreover, Cana treatment alleviated the myocardial injury with decreasing levels of serous soluble cluster of differentiation 40 ligand and cardiac troponin I. Thus, cardiovascular abnormality was relieved by suppressing fibrosis and basement membrane thickening, while elevating the cluster of differentiation 31 expression level. Importantly, Cana increased the ratio of gut bacteria Firmicutes/Bacteroidetes and the relative abundance of Alistipes, Olsenella, and Alloprevotella, while it decreased the abundance of Mucispirillum, Helicobacter, and Proteobacteria at various taxonomic levels in mice with diabetic CVD. In short, Cana treatment altered the colonic microbiota composition close to the normal level, which was related with blood lipid, inflammation, and oxidative stress, and might play a vital role in CVD. In general, the improvements in the gut microbiota and myocardial mitochondrial homeostasis may represent the mechanism of Cana on CVD treatment.

The Role of AGE-RAGE Signalling as a Modulator of Gut Permeability in Diabetes

There is increasing evidence for the role of intestinal permeability as a contributing factor in the pathogenesis of diabetes; however, the molecular mechanisms are poorly understood. Advanced glycation endproducts, of both exogenous and endogenous origin, have been shown to play a role in diabetes pathophysiology, in part by their ligation to the receptor for advanced glycation endproducts (RAGE), leading to a proinflammatory signalling cascade. RAGE signalling has been demonstrated to play a role in the development of intestinal inflammation and permeability in Crohn's disease and ulcerative colitis. In this review, we explore the role of AGE-RAGE signalling and intestinal permeability and explore whether activation of RAGE on the intestinal epithelium may be a downstream event contributing to the pathogenesis of diabetes complications.

Transplantation of an obesity-associated human gut microbiota to mice induces vascular dysfunction and glucose intolerance

Recent preclinical data suggest that alterations in the gut microbiota may be an important factor linking obesity to vascular dysfunction, an early sign of cardiovascular disease. The purpose of this study was to begin translation of these preclinical data by examining whether vascular phenotypes in humans are transmissible through the gut microbiota. We hypothesized that germ-free mice colonized with gut microbiota from obese individuals would display diminished vascular function compared to germ-free mice receiving microbiota from lean individuals.We transplanted fecal material from obese and lean age-and sex-matched participants with disparate vascular function to germ-free mice. Using Principle Component Analysis, the microbiota of colonized mice separated by donor group along the first principle component, accounting for between 70-93% of the total variability in the dataset. The microbiota of mice receiving transplants from lean individuals was also characterized by increased alpha diversity, as well as increased relative abundance of potentially beneficial bacteria, including Bifidobacterium, Lactobacillus, and Bacteroides ovatis. Endothelium-dependent dilation, aortic pulse wave velocity and glucose tolerance were significantly altered in mice receiving microbiota from the obese donor relative to those receiving microbiota from the lean donor or those remaining germ-free.These data indicate that the obesity-associated human gut microbiota is sufficient to alter the vascular phenotype in germ-free mice in the absence of differences in body weight or dietary manipulation, and provide justification for future clinical trials to test the efficacy of microbiota-targeted therapies in the prevention or treatment of cardiovascular disease.

Exploring the Diverse Immune and Genetic Landscape of Psoriatic Arthritis

Psoriatic arthritis (PsA) is characterized by delays in diagnosis and modest effect of treatment in terms of joint response. An understanding of molecular pathomechanisms may aid in developing diagnostic and prognostic models. Genetic susceptibility (e.g., HLA class I genes, IL-23-related genes) can be responsible for the pattern of psoriatic manifestations and affinity for tissue involvement. Gene expression analysis indicates an inflammatory profile that is distinct for PsA, but disparate across tissues. This has clinical implications, as for example, dual blockade of IL-17A and IL-17F can lead to superior clinical effects if there is differential expression of IL-17 receptors in tissues. Structural and functional impairment of barrier tissue, including host-microbiome interactions, may be the source of immune activation. Interplay between different cell populations of innate and adaptive immunity is emerging, potentially providing a link between the transition of skin-to-joint disease. Th17 subsets, IL-17A, IL-17F and IL-23 are crucial in PsA pathogenesis, with both clinical and experimental evidence suggesting a differential molecular landscape in cutaneous and articular compartments.

Vasodilator Dysfunction in Human Obesity: Established and Emerging Mechanisms

ABSTRACT

Human obesity is associated with insulin resistance and often results in a number of metabolic abnormalities and cardiovascular complications. Over the past decades, substantial advances in the understanding of the cellular and molecular pathophysiological pathways underlying the obesity-related vascular dysfunction have facilitated better identification of several players participating in this abnormality. However, the complex interplay between the disparate mechanisms involved has not yet been fully elucidated. Moreover, in medical practice, the clinical syndromes stemming from obesity-related vascular dysfunction still carry a substantial burden of morbidity and mortality; thus, early identification and personalized clinical management seem of the essence. Here, we will initially describe the alterations of intravascular homeostatic mechanisms occurring in arteries of obese patients. Then, we will briefly enumerate those recognized causative factors of obesity-related vasodilator dysfunction, such as vascular insulin resistance, lipotoxicity, visceral adipose tissue expansion, and perivascular adipose tissue abnormalities; next, we will discuss in greater detail some emerging pathophysiological mechanisms, including skeletal muscle inflammation, signals from gut microbiome, and the role of extracellular vesicles and microRNAs. Finally, it will touch on some gaps in knowledge, as well as some current acquisitions for specific treatment regimens, such as glucagon-like peptide-1 enhancers and sodium-glucose transporter2 inhibitors, that could arrest or slow the progression of this abnormality full of unwanted consequences.

The effect of atrazine on intestinal histology, microbial community and short chain fatty acids in Pelophylax nigromaculatus tadpoles

The intestine is the main organ for nutrient absorption in amphibians. It is sensitive to atrazine, which is a herbicide widely used in agricultural areas. At present, there is a lack of systematic research on the effect of atrazine on the amphibian intestine. In this study, we evaluated the effects of atrazine exposure (0, 50 μg/L, 100 μg/L, and 500 μg/L) for 20 days on intestinal histology, microbiota and short chain fatty acids in Pelophylax nigromaculatus tadpoles. Our research showed that 500 μg/L atrazine exposure significantly decreased the height of microvilli and epithelial cells, and altered the composition and diversity of intestinal microbiota in P. nigromaculatus tadpoles compared to the control. At the phylum level, the abundance of Bacteroidetes and Fusobacteria increased significantly, while that of Verrucomicrobia and Firmicutes decreased significantly in the 500 μg/L atrazine treatment group. At the genus level, Akkermansia and Lactococcus had significantly lower abundance in the 100 μg/L and 500 μg/L atrazine exposure group, while Cetobacterium was only detected in the 100 μg/L and 500 μg/L atrazine treated group. Also, function prediction of intestinal microbiota showed that atrazine treatment significantly changed the metabolism pathways of P. nigromaculatus tadpoles. In addition, 500 μg/L atrazine exposure changed the content of short chain fatty acids by significantly increasing the content of total SFCAs, butyric acid, and valeric acid, and decreasing the content of isovaleric acid in the intestine. Taken together, atrazine exposure could affect the intestinal histology and induce intestinal microbiota imbalance and metabolic disorder in amphibian tadpoles.

Gut Microbiome, Functional Food, Atherosclerosis, and Vascular Calcifications-Is There a Missing Link?

The gut microbiome is represented by the genome of all microorganisms (symbiotic, potential pathogens, or pathogens) residing in the intestine. These ecological communities are involved in almost all metabolic diseases and cardiovascular diseases are not excluded. Atherosclerosis, with a continuously increasing incidence in recent years, is the leading cause of coronary heart disease and stroke by plaque rupture and intraplaque hemorrhage. Vascular calcification, a process very much alike with osteogenesis, is considered to be a marker of advanced atherosclerosis. New evidence, suggesting the role of dietary intake influence on the diversity of the gut microbiome in the development of vascular calcifications, is highly debated. Gut microbiota can metabolize choline, phosphatidylcholine, and L-carnitine and produce vasculotoxic metabolites, such as trimethylamine-N-oxide (TMAO), a proatherogenic metabolite. This review article aims to discuss the latest research about how probiotics and the correction of diet is impacting the gut microbiota and its metabolites in the atherosclerotic process and vascular calcification. Further studies could create the premises for interventions in the microbiome as future primary tools in the prevention of atherosclerotic plaque and vascular calcifications.

The Interplay between Nutrition, Innate Immunity, and the Commensal Microbiota in Adaptive Intestinal Morphogenesis

The gastrointestinal tract is a functionally and anatomically segmented organ that is colonized by microbial communities from birth. While the genetics of mouse gut development is increasingly understood, how nutritional factors and the commensal gut microbiota act in concert to shape tissue organization and morphology of this rapidly renewing organ remains enigmatic. Here, we provide an overview of embryonic mouse gut development, with a focus on the intestinal vasculature and the enteric nervous system. We review how nutrition and the gut microbiota affect the adaptation of cellular and morphologic properties of the intestine, and how these processes are interconnected with innate immunity. Furthermore, we discuss how nutritional and microbial factors impact the renewal and differentiation of the epithelial lineage, influence the adaptation of capillary networks organized in villus structures, and shape the enteric nervous system and the intestinal smooth muscle layers. Intriguingly, the anatomy of the gut shows remarkable flexibility to nutritional and microbial challenges in the adult organism.

Comparative Efficacy of Two Types of Antibiotic Mixtures in Gut Flora Depletion in Female C57BL/6 Mice

Over the last decade, interest in the role of the microbiome in health and disease has increased. The use of germ-free animals and depletion of the microbial flora using antimicrobials are 2 methods commonly used to study the microbiome in laboratory mice. Germ-free mice are born, raised, and studied in isolators in the absence of any known microbes; however, the equipment, supplies, and training required for the use of these mice can be costly and time-consuming. The use of antibiotics to decrease the microbial flora does not require special equipment, can be used for any mouse strain, and is relatively inexpensive; however, mice treated in this manner still retain microbes and they do not live in a germ-free environment. One commonly used antibiotic cocktail regimen uses ampicillin, neomycin, metronidazole, and vancomycin in the drinking water for 2 to 4 wk. We found that the palatability of this mixture is low, resulting in weight loss and leading to removal of mice from the study. The addition of sucralose to the medicated water and making wet food (mash) with the medicated water improved intake; however, the low palatability still resulted in a high number of mice requiring removal. The current study evaluated a new combination of antibiotics designed to reduce the gut microbiota while maintaining body weights. C57BL/6NCrl mice were placed on one of the following drinking water regimens: ampicillin/neomycin/metronidazole/vancomycin water (n = 16), enrofloxacin/ampicillin water ( n = 12), or standard reverse osmosis deionized water (RODI) ( n = 11). During an 8 day regimen, mice were weighed and water consumption was measured. Feces were collected before and after 8 d of treatment. Quantitative real-time PCR (real-time qPCR) for 16S bacterial ribosome was performed on each sample, and values were compared among groups. The combination of enrofloxacin and ampicillin improved water intake, together with a greater reduction in gut flora.

Evidence for the Contribution of Gut Microbiota to Age-Related Anabolic Resistance

Globally, people 65 years of age and older are the fastest growing segment of the population. Physiological manifestations of the aging process include undesirable changes in body composition, declines in cardiorespiratory fitness, and reductions in skeletal muscle size and function (i.e., sarcopenia) that are independently associated with mortality. Decrements in muscle protein synthetic responses to anabolic stimuli (i.e., anabolic resistance), such as protein feeding or physical activity, are highly characteristic of the aging skeletal muscle phenotype and play a fundamental role in the development of sarcopenia. A more definitive understanding of the mechanisms underlying this age-associated reduction in anabolic responsiveness will help to guide promyogenic and function promoting therapies. Recent studies have provided evidence in support of a bidirectional gut-muscle axis with implications for aging muscle health. This review will examine how age-related changes in gut microbiota composition may impact anabolic response to protein feeding through adverse changes in protein digestion and amino acid absorption, circulating amino acid availability, anabolic hormone production and responsiveness, and intramuscular anabolic signaling. We conclude by reviewing literature describing lifestyle habits suspected to contribute to age-related changes in the microbiome with the goal of identifying evidence-informed strategies to preserve microbial homeostasis, anabolic sensitivity, and skeletal muscle with advancing age.

Novel insights in the relationship of gut microbiota and coronary artery diseases

Atherosclerosis is a chronic, progressive, inflammatory disease in the vasculature and is common in both coronary and peripheral arteries. Human beings harbor a complex and dynamic population of microorganisms defined as the microbiota. Importantly, alterations in the bacterial composition (dysbiosis) and the metabolic compounds produced by these bacteria have been associated with the pathogenesis of many inflammatory diseases and infections. There is also a close relationship between intestinal microbiota and cardiovascular diseases. The aim of this review was to analyze how changes in the gut microbiota and their metabolites might affect coronary artery diseases. The most representative groups of bacteria that make up the intestinal microbiota are altered in coronary artery disease patients, resulting in a decrease in Bacteroidetes and an increase in Firmicutes. In relation to metabolites, trimethylamine-N-oxide plays an important role in atherosclerosis and may act as a cardiovascular risk predictor. In addition, the use of probiotics, prebiotics, diet modulation, and fecal transplantation, which may represent alternative treatments for these diseases, is thoroughly discussed. Finally, the role of lipid-lowering treatments is also analyzed as they may affect and alter the gut microbiota and, conversely, gut microbiota diversity could be associated with resistance or sensitivity to these treatments.

Intestinal barrier dysfunction as a therapeutic target for cardiovascular disease

The gut microbiome and intestinal dysfunction have emerged as potential contributors to the development of cardiovascular disease (CVD). Alterations in gut microbiome are well documented in hypertension, atherosclerosis, and heart failure and have been investigated as a therapeutic target. However, a perhaps underappreciated but related role for intestinal barrier function has become evident. Increased intestinal permeability is observed in patients and mouse models of CVD. This increased intestinal permeability can enhance systemic inflammation, alter gut immune function, and has been demonstrated as predictive of adverse cardiovascular outcomes. The goal of this review is to examine the evidence supporting a role for intestinal barrier function in cardiovascular disease and its prospect as a novel therapeutic target. We outline key studies that have investigated intestinal permeability in hypertension, coronary artery disease, atherosclerosis, heart failure, and myocardial infarction. We highlight the central mechanisms involved in the breakdown of barrier function and look at emerging evidence for restored barrier function as a contributor to promising treatment strategies such as short chain fatty acid, probiotic, and renin angiotensin system-targeted therapeutics. Recent studies of more selective targeting of the intestinal barrier to improve disease outcomes are also examined. We suggest that although current data supporting a contribution of intestinal permeability to CVD pathogenesis are largely associative, it appears to be a promising avenue for further investigation. Additional studies of the mechanisms of barrier restoration in CVD and testing of intestinal barrier-targeted compounds will be required to confirm their potential as a new class of CVD therapeutic.

Lifelong voluntary aerobic exercise prevents age- and Western diet- induced vascular dysfunction, mitochondrial oxidative stress and inflammation in mice

KEY POINTS

The results of the present study establish the temporal pattern of age-related vascular dysfunction across the adult lifespan in sedentary mice consuming a non-Western diet, and the underlying mechanisms The results demonstrate that consuming a Western diet accelerates and exacerbates vascular ageing across the lifespan in sedentary mice They also show that lifelong voluntary aerobic exercise has remarkable protective effects on vascular function throughout the lifespan, in the setting of ageing alone, as well as ageing compounded by Western diet consumption Overall, the results indicate that amelioration of mitochondrial oxidative stress and inflammation are key mechanisms underlying the voluntary aerobic exercise-associated preservation of vascular function across the lifespan in both the presence and absence of a Western dietary pattern ABSTRACT: Advancing age is the major risk factor for cardiovascular diseases, driven largely by vascular endothelial dysfunction (impaired endothelium-dependent dilatation, EDD) and aortic stiffening (increased aortic pulse wave velocity, aPWV). In humans, vascular ageing occurs in the presence of differences in diet and physical activity, but the interactive effects of these factors are unknown. We assessed carotid artery EDD and aPWV across the lifespan in mice consuming standard (normal) low-fat chow (NC) or a high-fat/high-sucrose Western diet (WD) in the absence (sedentary, SED) or presence (voluntary wheel running, VWR) of aerobic exercise. Ageing impaired nitric oxide-mediated EDD (peak EDD 88 ± 12% 6 months P = 0.003 vs. 59 ± 9% 27 months NC-SED), which was accelerated by WD (60 ± 18% 6 months WD-SED). In NC mice, aPWV increased 32% with age (423 ± 13 cm/s at 24 months P < 0.001 vs. 321 ± 12 cm/s at 6 months) and absolute values were an additional ∼10% higher at any age in WD mice (P = 0.042 vs. NC-SED). Increases in aPWV with age in NC and WD mice were associated with 30-65% increases in aortic intrinsic wall stiffness (6 vs. 19-27 months, P = 0.007). Lifelong aerobic exercise prevented age- and WD-related vascular dysfunction across the lifespan, and this protection appeared to be mediated by mitigation of vascular mitochondrial oxidative stress and inflammation. Our results depict the temporal impairment of vascular function over the lifespan in mice, acceleration and exacerbation of that dysfunction with WD consumption, the remarkable protective effects of voluntary aerobic exercise, and the underlying mechanisms.

Gut microbes in cardiovascular diseases and their potential therapeutic applications

Microbial ecosystem comprises a complex community in which bacteria interact with each other. The potential roles of the intestinal microbiome play in human health have gained considerable attention. The imbalance of gut microbial community has been looked to multiple chronic diseases. Cardiovascular diseases (CVDs) are leading causes of morbidity worldwide and are influenced by genetic and environmental factors. Recent advances have provided scientific evidence that CVD may also be attributed to gut microbiome. In this review, we highlight the complex interplay between microbes, their metabolites, and the potential influence on the generation and development of CVDs. The therapeutic potential of using intestinal microbiomes to treat CVD is also discussed. It is quite possible that gut microbes may be used for clinical treatments of CVD in the near future.

Microbial metabolite indole-3-propionic acid supplementation does not protect mice from the cardiometabolic consequences of a Western diet

Emerging evidence suggests that intestinal microbes regulate host physiology and cardiometabolic health, although the mechanism(s) by which they do so is unclear. Indoles are a group of compounds produced from bacterial metabolism of the amino acid tryptophan. In light of recent data suggesting broad physiological effects of indoles on host physiology, we examined whether indole-3-propionic acid (IPA) would protect mice from the cardiometabolic consequences of a Western diet. Male C57BL/6J mice were fed either a standard diet (SD) or Western diet (WD) for 5 mo and received normal autoclaved drinking water or water supplemented with IPA (0.1 mg/mL; SD + IPA and WD + IPA). WD feeding led to increased liver triglycerides and makers of inflammation, with no effect of IPA. At 5 mo, arterial stiffness was significantly higher in WD and WD + IPA compared with SD (WD: 485.7 ± 6.7 and WD + IPA: 492.8 ± 8.6 vs. SD: 436.9 ± 7.0 cm/s, P < 0.05) but not SD + IPA (SD + IPA: 468.1 ± 6.6 vs. WD groups, P > 0.05). Supplementation with IPA in the SD + IPA group significantly increased glucose AUC compared with SD mice (SD + IPA: 1,763.3 ± 92.0 vs. SD: 1,397.6 ± 64.0, P < 0.05), and no significant differences were observed among either the WD or WD + IPA groups (WD: 1,623.5 ± 77.3 and WD + IPA: 1,658.4 ± 88.4, P > 0.05). Gut microbiota changes were driven by WD feeding, whereas IPA supplementation drove differences in SD-fed mice. In conclusion, supplementation with IPA did not improve cardiometabolic outcomes in WD-fed mice and may have worsened some parameters in SD-fed mice, suggesting that IPA is not a critical signal mediating WD-induced cardiometabolic dysfunction downstream of the gut microbiota.NEW & NOTEWORTHY The gut microbiota has been shown to mediate host health. Emerging data implicate gut microbial metabolites of tryptophan metabolism as potential important mediators. We examined the effects of indole-3-propionic acid in Western diet-fed mice and found no beneficial cardiometabolic effects. Our data do not support the supposition that indole-3-propionic acid (IPA) mediates beneficial metabolic effects downstream of the gut microbiota and may be potentially deleterious in higher circulating levels.

Artificial microbiome heterogeneity spurs six practical action themes and examples to increase study power-driven reproducibility

With >70,000 yearly publications using mouse data, mouse models represent the best engrained research system to address numerous biological questions across all fields of science. Concerns of poor study and microbiome reproducibility also abound in the literature. Despite the well-known, negative-effects of data clustering on interpretation and study power, it is unclear why scientists often house >4 mice/cage during experiments, instead of ≤2. We hypothesized that this high animal-cage-density  practice abounds in published literature because more mice/cage could be perceived as a strategy to reduce housing costs. Among other sources of 'artificial' confounding, including cyclical oscillations of the 'dirty-cage/excrement microbiome', we ranked by priority the heterogeneity of modern husbandry practices/perceptions across three professional organizations that we surveyed in the USA. Data integration (scoping-reviews, professional-surveys, expert-opinion, and 'implementability-score-statistics') identified Six-Actionable Recommendation Themes (SART) as a framework to re-launch emerging protocols and intuitive statistical strategies to use/increase study power. 'Cost-vs-science' discordance was a major aspect explaining heterogeneity, and scientists' reluctance to change. With a 'housing-density cost-calculator-simulator' and fully-annotated statistical examples/code, this themed-framework streamlines the rapid analysis of cage-clustered-data and promotes the use of 'study-power-statistics' to self-monitor the success/reproducibility of basic and translational research. Examples are provided to help scientists document analysis for study power-based sample size estimations using preclinical mouse data to support translational clinical trials, as requested in NIH/similar grants or publications.

Fuzhuan Brick Tea Attenuates High-Fat Diet-Induced Obesity and Associated Metabolic Disorders by Shaping Gut Microbiota

An increasing amount of evidence suggests that the metabolic improvement of high-fat diet (HFD)-induced obese mice by Fuzhuan brick tea (FBT) is associated with gut microbiota. However, the causalities between FBT and gut microbiota have not yet been elucidated and the underlying mechanisms of action remain unclear. To impart direct evidence for the essential role of gut microbiota in the attenuation of obesity by FBT, the effects of FBT on healthy mice and microbiota-depleted mice that were treated with antibiotics were compared in an HFD-induced obesity mouse model. The results showed that FBT dramatically ameliorated obesity, serum lipid parameters, blood glucose homeostasis, hepatic steatosis, adipocyte hypertrophy, and tissue inflammation. However, the microbiota-depleted mice with single bacterium (Escherichia-Shigella) after antibiotic treatment were resistant to FBT-induced antiobesity and metabolic improvement. The beneficial effects of FBT resulted from its shift on gut microbiota composition and structure in mice. HFD-induced increase in the phyla Firmicutes/Bacteroidetes (F/B) ratio was remarkably restored by FBT. Furthermore, FBT-induced increase in abundances of beneficial bacteria Clostridiaceae, Bacteroidales, and Lachnospiraceae and decreases in harmful Ruminococcaceae, Peptococcaceae, Peptostreptococcaceae, and Erysipelotrichaceae were causal antecedents for FBT to reduce obesity and improve metabolic disorders.

The gut microbiome and heart failure: A better gut for a better heart

Despite the development of new drugs and therapeutic strategies, mortality and morbidity related to heart failure (HF) remains high. It is also the leading cause of global mortality. Several concepts have been proposed to explore the underlying pathogenesis of HF, but there is still a strong need for more specific and complementary therapeutic options. In recent years, accumulating evidence has demonstrated that changes in the composition of gut microbiota, referred to as dysbiosis, might play a pivotal role in the development of several diseases, including HF. HF-associated decreased cardiac output, resulting in bowell wall oedema and intestine ischaemia, can alter gut structure, peamibility and function. These changes would favour bacterial translocation, exacerbating HF pathogenesis at least partly through activation of systemic inflammation. Although our knowledge of the precise molecular mechanisms by which gut dysbiosis influance HF is still limited, a growing body of evidence has recently demonstrated the impact of a series of gut microbiome-derived metabolites, such as trimetylamine N-oxide, short-chain fatty acids or secondary bile acids, which have been shown to play critical roles in cardiac health and disease. This review will summarize the role of gut microbiota and its metabolites in the pathogenesis of HF. Current and future preventive and therapeutic strategies to prevent HF by an adequate modulation of the microbiome and its derived metabolites are also discussed.

Circulating Metabolites Originating from Gut Microbiota Control Endothelial Cell Function

Cardiovascular functionality strictly depends on endothelial cell trophism and proper biochemical function. Any condition (environmental, pharmacological/toxicological, physical, or neuro-humoral) that changes the vascular endothelium has great consequences for the organism’s wellness and on the outcome and evolution of severe cardiovascular pathologies. Thus, knowledge of the mechanisms, both endogenous and external, that affect endothelial dysfunction is pivotal to preventing and treating these disorders. In recent decades, significant attention has been focused on gut microbiota and how these symbiotic microorganisms can influence host health and disease development. Indeed, dysbiosis has been reported to be at the base of a range of different pathologies, including pathologies of the cardiovascular system. The study of the mechanism underlying this relationship has led to the identification of a series of metabolites (released by gut bacteria) that exert different effects on all the components of the vascular system, and in particular on endothelial cells. The imbalance of factors promoting or blunting endothelial cell viability and function and angiogenesis seems to be a potential target for the development of new therapeutic interventions. This review highlights the circulating factors identified to date, either directly produced by gut microbes or resulting from the metabolism of diet derivatives as polyphenols.

Gut microbiota regulates cardiac ischemic tolerance and aortic stiffness in obesity

The gut microbiota has emerged as an important regulator of host physiology, with recent data suggesting a role in modulating cardiovascular health. The present study determined if gut microbial signatures could transfer cardiovascular risk phenotypes between lean and obese mice using cecal microbiota transplantation (CMT). Pooled cecal contents collected from obese leptin-deficient (Ob) mice or C57Bl/6j control (Con) mice were transplanted by oral gavage into cohorts of recipient Ob and Con mice maintained on identical low-fat diets for 8 wk (n = 9-11/group). Cardiovascular pathology was assessed as the degree of arterial stiffness (aortic pulse wave velocity) and myocardial infarct size following a 45/120 min ex vivo global cardiac ischemia-reperfusion protocol. Gut microbiota was characterized by 16S rDNA sequencing, along with measures of intestinal barrier function and cecal short-chain fatty acid (SCFA) composition. Following CMT, the gut microbiota of recipient mice was altered to resemble that of the donors. Ob CMT to Con mice increased arterial stiffness, left ventricular (LV) mass, and myocardial infarct size, which were associated with greater gut permeability and reduced cecal SCFA concentrations. Conversely, Con CMT to Ob mice increased cecal SCFA, reduced LV mass, and attenuated myocardial infarct size, with no effects on gut permeability or arterial stiffness. Collectively, these data demonstrate that obesity-related changes in the gut microbiota, independent of dietary manipulation, regulate hallmark measures of cardiovascular pathology in mice and highlight the potential of microbiota-targeted therapeutics for reducing cardiovascular pathology and risk in obesity.NEW & NOTEWORTHY These data are the first to demonstrate that cecal microbiota transplantation (CMT) can alter cardiovascular pathology in lean and obese mice independent from alterations in dietary intake. Myocardial infarct size was reduced in obese mice receiving lean CMT and worsened in lean mice receiving obese CMT. Lean mice receiving obese CMT also displayed increased aortic stiffness. These changes were accompanied by alterations in short-chain fatty acids and gut permeability.

The gut microbiome and cardiovascular disease: current knowledge and clinical potential

Cardiovascular disease (CVD) is the leading cause of death worldwide. The human body is populated by a diverse community of microbes, dominated by bacteria, but also including viruses and fungi. The largest and most complex of these communities is located in the gastrointestinal system and, with its associated genome, is known as the gut microbiome. Gut microbiome perturbations and related dysbiosis have been implicated in the progression and pathogenesis of CVD, including atherosclerosis, hypertension, and heart failure. Although there have been advances in the characterization and analysis of the gut microbiota and associated bacterial metabolites, the exact mechanisms through which they exert their action are not well understood. This review will focus on the role of the gut microbiome and associated functional components in the development and progression of atherosclerosis. Potential treatments to alter the gut microbiome to prevent or treat atherosclerosis and CVD are also discussed.

Inflammation as a mediator of arterial ageing

NEW FINDINGS

What is the topic of this review? This review summarizes and synthesizes what is known about the contribution of inflammation to age-related arterial dysfunction. What advances does it highlight? This review details observational evidence for the relationship of age-related inflammation and arterial dysfunction, insight from autoimmune inflammatory diseases and their effects on arterial function, interventional evidence linking inflammation and age-related arterial dysfunction, insight into age-related arterial inflammation from preclinical models and interventions to ameliorate age-related inflammation and arterial dysfunction.

ABSTRACT

Advanced age is a primary risk factor for cardiovascular disease, the leading cause of death in the industrialized world. Two major components of arterial ageing are stiffening of the large arteries and impaired endothelium-dependent dilatation in multiple vascular beds. These two alterations are major contributors to the development of overt cardiovascular disease. Increasing inflammation with advanced age is likely to play a role in this arterial dysfunction. The purpose of this review is to synthesize what is known about inflammation and its relationship to age-related arterial dysfunction. This review discusses both the initial observational evidence for the relationship of age-related inflammation and arterial dysfunction and the evidence that inflammatory autoimmune diseases are associated with a premature arterial ageing phenotype. We next discuss interventional and mechanistic evidence linking inflammation and age-related arterial dysfunction in older adults. We also attempt to summarize the relevant evidence from preclinical models. Lastly, we discuss interventions in both humans and animals that have been shown to ameliorate age-related arterial inflammation and dysfunction. The available evidence provides a strong basis for the role of inflammation in both large artery stiffening and impairment of endothelium-dependent dilatation; however, the specific inflammatory mediators, the initiating factors and the relative importance of the endothelium, smooth muscle cells, perivascular adipose tissue and immune cells in arterial inflammation are not well understood. With the expansion of the ageing population, ameliorating age-related arterial inflammation represents an important potential strategy for preserving vascular health in the elderly.

Suppression of the gut microbiome ameliorates age-related arterial dysfunction and oxidative stress in mice

KEY POINTS

Age-related arterial dysfunction, characterized by oxidative stress- and inflammation-mediated endothelial dysfunction and arterial stiffening, is the primary risk factor for cardiovascular diseases. To investigate whether age-related changes in the gut microbiome may mediate arterial dysfunction, we suppressed gut microbiota in young and old mice with a cocktail of broad-spectrum, poorly-absorbed antibiotics in drinking water for 3-4 weeks. In old mice, antibiotic treatment reversed endothelial dysfunction and arterial stiffening and attenuated vascular oxidative stress and inflammation. To provide insight into age-related changes in gut microbiota that may underlie these observations, we show that ageing altered the abundance of microbial taxa associated with gut dysbiosis and increased plasma levels of the adverse gut-derived metabolite trimethylamine N-oxide. The results of the present study provide the first proof-of-concept evidence that the gut microbiome is an important mediator of age-related arterial dysfunction and therefore may be a promising therapeutic target for preserving arterial function with ageing, thereby reducing the risk of cardiovascular diseases.

ABSTRACT

Oxidative stress-mediated arterial dysfunction (e.g. endothelial dysfunction and large elastic artery stiffening) is the primary mechanism driving age-related cardiovascular diseases. Accumulating evidence suggests the gut microbiome modulates host physiology because dysregulation ('gut dysbiosis') has systemic consequences, including promotion of oxidative stress. The present study aimed to determine whether the gut microbiome modulates arterial function with ageing. We measured arterial function in young and older mice after 3-4 weeks of treatment with broad-spectrum, poorly-absorbed antibiotics to suppress the gut microbiome. To identify potential mechanistic links between the gut microbiome and age-related arterial dysfunction, we sequenced microbiota from young and older mice and measured plasma levels of the adverse gut-derived metabolite trimethylamine N-oxide (TMAO). In old mice, antibiotics reversed endothelial dysfunction [area-under-the-curve carotid artery dilatation to acetylcholine in young: 345 ± 16 AU vs. old control (OC): 220 ± 34 AU, P < 0.01; vs. old antibiotic-treated (OA): 334 ± 15 AU; P < 0.01 vs. OC] and arterial stiffening (aortic pulse wave velocity in young: 3.62 ± 0.15 m  s-1  vs. OC: 4.43 ± 0.38 m  s-1 ; vs. OA: 3.52 ± 0.35 m  s-1 ; P = 0.03). These improvements were accompanied by lower oxidative stress and greater antioxidant enzyme expression. Ageing altered the abundance of gut microbial taxa associated with gut dysbiosis. Lastly, plasma TMAO was higher with ageing (young: 2.6 ± 0.4 μmol  L-1   vs. OC: 7.2 ± 2.0 μmol  L-1 ; P < 0.0001) and suppressed by antibiotic treatment (OA: 1.2 ± 0.2 μmol  L-1 ; P < 0.0001 vs. OC). The results of the present study provide the first evidence for the gut microbiome being an important mediator of age-related arterial dysfunction and oxidative stress and suggest that therapeutic strategies targeting gut microbiome health may hold promise for preserving arterial function and reducing cardiovascular risk with ageing in humans.

How diet and the microbiome shape health or contribute to disease: A mini-review of current models and clinical studies

IMPACT STATEMENT

The studies reviewed in this article combine diet in the context of disease progression or treatment with analysis of the microbiome. First, we present findings on how diet manipulation impacts the microbiome and disease pathogenesis in a broad variety of rodent models of disease. Then, we describe results from clinical trials that are using diet therapies to attempt to shift the microbiome and treat disease symptoms. Finally, we discuss what these studies have taught us about the influence of the microbiome of disease and health states and highlight the evidence suggesting that dietary modulation of the microbiome is an emerging therapeutic option for a variety of different diseases.

Crosstalk between gut microbiota and antidiabetic drug action

Type 2 diabetes (T2D) is a disorder characterized by chronic inflated blood glucose levels (hyperglycemia), at first due to insulin resistance and unregulated insulin secretion but with tendency towards global spreading. The gut microbiota is recognized to have an influence on T2D, although surveys have not formed a clear overview to date. Because of the interactions between gut microbiota and host homeostasis, intestinal bacteria are believed to play a large role in various diseases, including metabolic syndrome, obesity and associated disease. In this review, we highlight the animal and human studies which have elucidated the roles of metformin, α-glucosidase inhibitors, glucagon-like peptide-1 agonists, peroxisome proliferator-activated receptors γ agonists, inhibitors of dipeptidyl peptidase-4, sodium/glucose cotransporter inhibitors, and other less studied medications on gut microbiota. This review is dedicated to one of the most widespread diseases, T2D, and the currently used antidiabetic drugs and most promising new findings. In general, the gut microbiota has been shown to have an influence on host metabolism, food consumption, satiety, glucose homoeostasis, and weight gain. Altered intestinal microbiota composition has been noticed in cardiovascular diseases, colon cancer, rheumatoid arthritis, T2D, and obesity. Therefore, the main effect of antidiabetic drugs is on the microbiome composition, basically increasing the short-chain fatty acids-producing bacteria, responsible for losing weight and suppressing inflammation.

Dietary Polyphenols Targeting Arterial Stiffness: Interplay of Contributing Mechanisms and Gut Microbiome-Related Metabolism

Increased arterial stiffness is a degenerative vascular process, progressing with age that leads to a reduced capability of arteries to expand and contract in response to pressure changes. This progressive degeneration mainly affects the extracellular matrix of elastic arteries and causes loss of vascular elasticity. Recent studies point to significant interference of dietary polyphenols with mechanisms involved in the pathophysiology and progression of arterial stiffness. This review summarizes data from epidemiological and interventional studies on the effect of polyphenols on vascular stiffness as an illustration of current research and addresses possible etiological factors targeted by polyphenols, including pathways of vascular functionality, oxidative status, inflammation, glycation, and autophagy. Effects can either be inflicted directly by the dietary polyphenols or indirectly by metabolites originated from the host or microbial metabolic processes. The composition of the gut microbiome, therefore, determines the resulting metabolome and, as a consequence, the observed activity. On the other hand, polyphenols also influence the intestinal microbial composition, and therefore the metabolites available for interaction with relevant targets. As such, targeting the gut microbiome is another potential treatment option for arterial stiffness.

Gut microbiota and inflammation in chronic kidney disease and their roles in the development of cardiovascular disease

The health and proper functioning of the cardiovascular and renal systems largely depend on crosstalk in the gut-kidney-heart/vessel triangle. Recent evidence suggests that the gut microbiota has an integral function in this crosstalk. Mounting evidence indicates that the development of chronic kidney and cardiovascular diseases follows chronic inflammatory processes that are affected by the gut microbiota via various immune, metabolic, endocrine, and neurologic pathways. Additionally, deterioration of the function of the cardiovascular and renal systems has been reported to disrupt the original gut microbiota composition, further contributing to the advancement of chronic cardiovascular and renal diseases. Considering the interaction between the gut microbiota and the renal and cardiovascular systems, we can infer that interventions for the gut microbiota through diet and possibly some medications can prevent/stop the vicious cycle between the gut microbiota and the cardiovascular/renal systems, leading to a decrease in chronic cardiovascular and renal diseases.

Diabetic gut microbiota dysbiosis as an inflammaging and immunosenescence condition that fosters progression of retinopathy and nephropathy

The increased prevalence of type 2 diabetes mellitus (T2DM) and life expectancy of diabetic patients fosters the worldwide prevalence of retinopathy and nephropathy, two major microvascular complications that have been difficult to treat with contemporary glucose-lowering medications. The gut microbiota (GM) has become a lively field research in the last years; there is a growing recognition that altered intestinal microbiota composition and function can directly impact the phenomenon of ageing and age-related disorders. In fact, human GM, envisaged as a potential source of novel therapeutics, strongly modulates host immunity and metabolism. It is now clear that gut dysbiosis and their products (e.g. p-cresyl sulfate, trimethylamine‑N‑oxide) dictate a secretory associated senescence phenotype and chronic low-grade inflammation, features shared in the physiological process of ageing ("inflammaging") as well as in T2DM ("metaflammation") and in its microvascular complications. This review provides an in-depth look on the crosstalk between GM, host immunity and metabolism. Further, it characterizes human GM signatures of elderly and T2DM patients. Finally, a comprehensive scrutiny of recent molecular findings (e.g. epigenetic changes) underlying causal relationships between GM dysbiosis and diabetic retinopathy/nephropathy complications is pinpointed, with the ultimate goal to unravel potential pathophysiological mechanisms that may be explored, in a near future, as personalized disease-modifying therapeutic approaches.

Western diet triggers Toll-like receptor 4 signaling-induced endothelial dysfunction in female Wistar rats

Overconsumption of a diet rich in fat and carbohydrates, called the Western diet, is a major contributor to the global epidemic of cardiovascular disease. Despite previously documented cardiovascular protection exhibited in female rats, this safeguard may be lost under certain metabolic stressors. We hypothesized that female Wistar rats challenged by a Western diet composed of 21% fat and 50% carbohydrate (34.1% sucrose) for 17 wk would develop endothelial dysfunction via endothelial Toll-like receptor 4 (TLR4) signaling. Western diet-fed female rats exhibited dysregulation of metabolism, revealing increased body weight and abdominal fat, decreased expression of adiponectin in white adipose tissue, glucose intolerance, and impaired insulin sensitivity. Western diet exposure increased hepatic triglycerides and cholesterol alongside hepatic steatosis, categorizing nonalcoholic fatty liver disease. Moreover, a Western diet negatively affected vascular function, revealing hypertension, impaired endothelium-dependent vasorelaxation, aortic remodeling, and increased reactive oxygen species (ROS) production. Aortic protein expression of TLR4 and its downstream proteins were markedly increased in the Western diet-fed group in association with elevated serum levels of free fatty acids. In vitro experiments were conducted to test whether free fatty acids contribute to vascular ROS overproduction via the TLR4 signaling pathway. Cultured endothelial cells were stimulated with palmitate in the presence of TAK-242, a TLR4 signaling inhibitor. Palmitate-induced overgeneration of ROS in endothelial cells was abolished in the presence of TAK-242. Our data show that a Western diet induced endothelial dysfunction in female rats and suggest that endothelial TLR4 signaling may play a key role in abolishing female cardiovascular protection. NEW & NOTEWORTHY A Western diet induced elevated levels of free fatty acids, produced nonalcoholic fatty liver disease, and provoked endothelial dysfunction in female rats in association with Toll-like receptor 4 signaling-mediated vascular reactive oxygen species production. Limited consumption of a Western diet in premenopausal women may decrease their risk of cardiovascular complications.

Gut microbiota derived metabolites in cardiovascular health and disease

Trillions of microbes inhabit the human gut, not only providing nutrients and energy to the host from the ingested food, but also producing metabolic bioactive signaling molecules to maintain health and elicit disease, such as cardiovascular disease (CVD). CVD is the leading cause of mortality worldwide. In this review, we presented gut microbiota derived metabolites involved in cardiovascular health and disease, including trimethylamine-N-oxide (TMAO), uremic toxins, short chain fatty acids (SCFAs), phytoestrogens, anthocyanins, bile acids and lipopolysaccharide. These gut microbiota derived metabolites play critical roles in maintaining a healthy cardiovascular function, and if dysregulated, potentially causally linked to CVD. A better understanding of the function and dynamics of gut microbiota derived metabolites holds great promise toward mechanistic predicative CVD biomarker discoveries and precise interventions.

Imbalance of gut microbiome and intestinal epithelial barrier dysfunction in cardiovascular disease

The main function of the intestinal barrier is to regulate the absorption of nutrients, electrolytes, and water from the lumen into circulation and to prevent the entry of pathogenic microorganisms and toxic luminal substances. To maintain this function, an ideal microbiota balance is required and gut microbiota are critical for the intestinal epithelial barrier dysfunction and for the maintenance of physiological homeostasis. There is a demonstrable link between dysbiosis and intestinal dysfunction and diseases such as diabetes, obesity, and cardiovascular disease. However, links amongst gut pathology, microbial ecology, and blood pressure remain elusive. In a recent issue of Clinical Science (vol. 132, issue 6, 701-718), Kim et al. demonstrate a crucial link between gut microbiota and bacterial metabolites such as butyrate, gut leakiness, and hypertension.

SGLT2 inhibition via dapagliflozin improves generalized vascular dysfunction and alters the gut microbiota in type 2 diabetic mice

Background

Type 2 diabetes (T2D) is associated with generalized vascular dysfunction characterized by increases in large artery stiffness, endothelial dysfunction, and vascular smooth muscle dysfunction. Sodium glucose cotransporter 2 inhibitors (SGLT2i) represent the most recently approved class of oral medications for the treatment of T2D, and have been shown to reduce cardiovascular and overall mortality. Although it is currently unclear how SGLT2i decrease cardiovascular risk, an improvement in vascular function is one potential mechanism. The aim of the current study was to examine if dapagliflozin, a widely prescribed STLT2i, improves generalized vascular dysfunction in type 2 diabetic mice. In light of several studies demonstrating a bi-directional relation between orally ingested medications and the gut microbiota, a secondary aim was to determine the effects of dapagliflozin on the gut microbiota.

Methods

Male diabetic mice (Db, n = 24) and control littermates (Con; n = 23) were randomized to receive either a standard diet or a standard diet containing dapagliflozin (60 mg dapagliflozin/kg diet; 0.006%) for 8 weeks. Arterial stiffness was assessed by aortic pulse wave velocity; endothelial function and vascular smooth muscle dysfunction were assessed by dilatory responses to acetylcholine and sodium nitroprusside, respectively.

Results

Compared to untreated diabetic mice, diabetic mice treated with dapagliflozin displayed significantly lower arterial stiffness (Db = 469 cm/s vs. Db + dapa = 435 cm/s, p < 0.05), and improvements in endothelial dysfunction (area under the curve [AUC] Db = 57.2 vs. Db + dapa = 117.0, p < 0.05) and vascular smooth muscle dysfunction (AUC, Db = 201.7 vs. Db + dapa = 285.5, p < 0.05). These vascular improvements were accompanied by reductions in hyperglycemia and circulating markers of inflammation. The microbiota of Db and Con mice were distinctly different, and dapagliflozin treatment was associated with minor alterations in gut microbiota composition, particularly in Db mice, although these effects did not conclusively mediate the improvements in vascular function.

Conclusions

Dapagliflozin treatment improves arterial stiffness, endothelial dysfunction and vascular smooth muscle dysfunction, and subtly alters microbiota composition in type 2 diabetic mice. Collectively, the improvements in generalized vascular function may represent an important mechanism underlying the cardiovascular benefits of SGLT2i treatment.