Modest Sodium Reduction Increases Circulating Short-Chain Fatty Acids in Untreated Hypertensives: A Randomized, Double-Blind, Placebo-Controlled Trial

Upregulated IL-32 Expression And Reduced Gut Short Chain Fatty Acid Caproic Acid in People Living With HIV With Subclinical Atherosclerosis

Despite the success of antiretroviral therapy (ART), people living with HIV (PLWH) are still at higher risk for cardiovascular diseases (CVDs) that are mediated by chronic inflammation. Identification of novel inflammatory mediators with the inherent potential to be used as CVD biomarkers and also as therapeutic targets is critically needed for better risk stratification and disease management in PLWH. Here, we investigated the expression and potential role of the multi-isoform proinflammatory cytokine IL-32 in subclinical atherosclerosis in PLWH (n=49 with subclinical atherosclerosis and n=30 without) and HIV- controls (n=25 with subclinical atherosclerosis and n=24 without). While expression of all tested IL-32 isoforms (α, β, γ, D, ϵ, and θ) was significantly higher in peripheral blood from PLWH compared to HIV- controls, IL-32D and IL-32θ isoforms were further upregulated in HIV+ individuals with coronary artery atherosclerosis compared to their counterparts without. Upregulation of these two isoforms was associated with increased plasma levels of IL-18 and IL-1β and downregulation of the atheroprotective protein TRAIL, which together composed a unique atherosclerotic inflammatory signature specific for PLWH compared to HIV- controls. Logistic regression analysis demonstrated that modulation of these inflammatory variables was independent of age, smoking, and statin treatment. Furthermore, our in vitro functional data linked IL-32 to macrophage activation and production of IL-18 and downregulation of TRAIL, a mechanism previously shown to be associated with impaired cholesterol metabolism and atherosclerosis. Finally, increased expression of IL-32 isoforms in PLWH with subclinical atherosclerosis was associated with altered gut microbiome (increased pathogenic bacteria; Rothia and Eggerthella species) and lower abundance of the gut metabolite short-chain fatty acid (SCFA) caproic acid, measured in fecal samples from the study participants. Importantly, caproic acid diminished the production of IL-32, IL-18, and IL-1β in human PBMCs in response to bacterial LPS stimulation. In conclusion, our studies identified an HIV-specific atherosclerotic inflammatory signature including specific IL-32 isoforms, which is regulated by the SCFA caproic acid and that may lead to new potential therapies to prevent CVD in ART-treated PLWH.

The Gut Microbiome in Hypertension: Recent Advances and Future Perspectives

The pathogenesis of hypertension is known to involve a diverse range of contributing factors including genetic, environmental, hormonal, hemodynamic and inflammatory forces, to name a few. There is mounting evidence to suggest that the gut microbiome plays an important role in the development and pathogenesis of hypertension. The gastrointestinal tract, which houses the largest compartment of immune cells in the body, represents the intersection of the environment and the host. Accordingly, lifestyle factors shape and are modulated by the microbiome, modifying the risk for hypertensive disease. One well-studied example is the consumption of dietary fibers, which leads to the production of short-chain fatty acids and can contribute to the expansion of anti-inflammatory immune cells, consequently protecting against the progression of hypertension. Dietary interventions such as fasting have also been shown to impact hypertension via the microbiome. Studying the microbiome in hypertensive disease presents a variety of unique challenges to the use of traditional model systems. Integrating microbiome considerations into preclinical research is crucial, and novel strategies to account for reciprocal host-microbiome interactions, such as the wildling mouse model, may provide new opportunities for translation. The intricacies of the role of the microbiome in hypertensive disease is a matter of ongoing research, and there are several technical considerations which should be accounted for moving forward. In this review we provide insights into the host-microbiome interaction and summarize the evidence of its importance in the regulation of blood pressure. Additionally, we provide recommendations for ongoing and future research, such that important insights from the microbiome field at large can be readily integrated in the context of hypertension.

Microbiota and Metabolites as Factors Influencing Blood Pressure Regulation

The study of microbes has rapidly expanded in recent years due to a surge in our understanding that humans host a plethora of commensal microbes, which reside in their bodies and depending upon their composition, contribute to either normal physiology or pathophysiology. This article provides a general foundation for learning about host-commensal microbial interactions as an emerging area of research. The article is divided into two sections. The first section is dedicated to introducing commensal microbiota and its known effects on the host. The second section is on metabolites, which are biochemicals that the host and the microbes use for bi-directional communication with each other. Together, the sections review what is known about how microbes interact with the host to impact cardiovascular physiology, especially blood pressure regulation. © 2021 American Physiological Society. Compr Physiol 11:1731-1757, 2021.

Gut Microbiome over a Lifetime and the Association with Hypertension

PURPOSE OF REVIEW

Microorganisms living within an ecosystem create microbial communities and play key roles in ecosystem functioning. During their lifespan, humans share their bodies with a variety of microorganisms. More than 10-100 trillion symbiotic microorganisms live on and within human beings, and the majority of these microorganisms populate the distal ileum and colon (referred to as the gut microbiota). Interactions between the gut microbiota and the host involve signaling via chemical neurotransmitters and metabolites, neuronal pathways, and the immune system. Hypertension is a complex and heterogeneous pathophenotype. A reductionist approach that assumes that all patients who have the same signs of a disease share a common disease mechanism and thus should be treated similarly is insufficient for optimal blood pressure management. Herein, we have highlighted the contribution of the gut microbiome to blood pressure regulation in humans.

RECENT FINDINGS

Gut dysbiosis-an imbalance in the composition and function of the gut microbiota-has been shown to be associated with hypertension. Gut dysbiosis occurs via environmental pressures, including caesarean section, antibiotic use, dietary changes, and lifestyle changes over a lifetime. This review highlights how gut dysbiosis may affect a host's blood pressure over a lifetime. The review also clarifies future challenges in studies of associations between the gut microbiome and hypertension.

Network and 16S rRNA Sequencing-Combined Approach Provides Insightal Evidence of Vitamin K2 for Salt-Sensitive Hypertension

Vitamin K₂ (VK2), found to act to treat hypertension, has been widely used in the food and pharmaceutical industries nowadays. However, the potential targets and molecular mechanisms of VK2 for salt-sensitive hypertension have not been fully investigated. Therefore, the study aimed to investigate the potential molecular mechanisms of VK2 for salt-sensitive hypertension using network pharmacology and 16S rRNA sequencing strategy. The network pharmacology-based findings from KEGG enrichment analysis revealed that VK2-treated salt-sensitive hypertension was mechanically associated with the complement and coagulation cascades, calcium signaling pathway, renin–angiotensin system, etc. A total of 29 different bacteria in an animal experiment after VK2 supplementation were screened and functionally enriched using PICRUSt2. Additionally, 10 signaling pathways were identified in which the renin–angiotensin system was found to be the potential molecular mechanisms with the greatest change in multiple and statistical significance. Moreover, the results of the renin–angiotensin system-related protein expression exhibited VK2-inhibited renin–angiotensin system in salt-induced hypertensive mice, which significantly verified the previous biological and functional prediction analysis. Finally, spearman correlation analysis showed the different bacteria such as Dubosiella, Ileibacterium, etc., had a positive or negative correlation with renin–angiotensin system-related proteins in salt-induced mice. In conclusion, the potential molecular mechanisms of VK2 for salt-sensitive hypertension may be beneficially achieved by the specific inhibition of the renin–angiotensin system, contributing to the development for a new preventive strategy of salt-sensitive hypertension.

Role and mechanism of action of butyrate in atherosclerotic diseases: a review

Butyrate is a bioactive molecule produced by the intestinal flora and plays a major role in a variety of inflammatory diseases. Increasing evidence indicates that butyrate can regulate the occurrence and development of atherosclerosis (AS). Coincidentally, it reduces hyperlipidemia and hyperglycemia, which are major risk factors of AS. However, the mechanism by which butyrate regulates the development of AS remains unclear. In this article, we review the effect of butyrate treatment on AS with a focus on the mechanisms of butyrate-mediated modulation of several atherosclerotic processes. These include the improvement of monocyte-endothelial interactions, macrophage lipid accumulation, smooth muscle cell proliferation and migration, and lymphocyte differentiation and function. The existing research indicates that butyrate treatment may be a potentially effective strategy for the prevention of AS. Identity and underlying mechanisms of the molecular pathways of these interactions should be explored in the future to counter AS effectively.

A cross-talk between gut microbiome, salt and hypertension

Cardiac disorders contribute to one of the major causes of fatality across the world. Hypertensive patients, even well maintained on drugs, possess a high risk to cardiovascular diseases. It is, therefore, highly important to identify different factors and pathways that lead to risk and progression of cardiovascular disorders. Several animals and human studies suggest that taxonomical alterations in the gut are involved in the cardiovascular physiology. In this article, with the help of various experimental evidences, we suggest that the host gut-microbiota plays an important in this pathway. Short chain fatty acids (SCFAs) and Trimethyl Amine -n-Oxide (TMAO) are the two major products of gut microbiome. SCFAs present a crucial role in regulating the blood pressure, while TMAO is involved in pathogenesis of atherosclerosis and other coronary artery diseases, including hypertension. We prove that there exists a triangular bridge connecting the gap between dietary salt, hypertension and gut microbiome. We also present some of the dietary interventions which can regulate and control microbiota that can prevent cardiovascular complications.We strongly believe that this article would improve the understanding the role of gut microbiota in hypertension, and will be helpful in the development of novel therapeutic strategies for prevention of hypertension through restoring gut microbiome homeostasis in the near future.

Gastrointestinal symptoms associated with COVID-19: impact on the gut microbiome

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the greatest worldwide pandemic since the 1918 flu. The consequences of the coronavirus disease 2019 (COVID-19) are devastating and represent the current major public health issue across the globe. At the onset, SARS-CoV-2 primarily attacks the respiratory system as it represents the main point of entry in the host, but it also can affect multiple organs. Although most of the patients do not present symptoms or are mildly symptomatic, some people infected with SARS-CoV-2 that experience more severe multiorgan dysfunction. The severity of COVID-19 is typically combined with a set of comorbidities such as hypertension, diabetes, obesity, and/or advanced age that seriously exacerbates the consequences of the infection. Also, SARS-CoV-2 can cause gastrointestinal symptoms, such as vomiting, diarrhea, or abdominal pain during the early phases of the disease. Intestinal dysfunction induces changes in intestinal microbes, and an increase in inflammatory cytokines. Thus, diagnosing gastrointestinal symptoms that precede respiratory problems during COVID-19 may be necessary for improved early detection and treatment. Uncovering the composition of the microbiota and its metabolic products in the context of COVID-19 can help determine novel biomarkers of the disease and help identify new therapeutic targets. Elucidating changes to the microbiome as reliable biomarkers in the context of COVID-19 represent an overlooked piece of the disease puzzle and requires further investigation.