Targeting Gut Microbiome Interactions in Service-Related Gastrointestinal and Liver Diseases of Veterans

The role of gut microbiota in intestinal disease: from an oxidative stress perspective

Recent studies have indicated that gut microbiota-mediated oxidative stress is significantly associated with intestinal diseases such as colorectal cancer, ulcerative colitis, and Crohn's disease. The level of reactive oxygen species (ROS) has been reported to increase when the gut microbiota is dysregulated, especially when several gut bacterial metabolites are present. Although healthy gut microbiota plays a vital role in defending against excessive oxidative stress, intestinal disease is significantly influenced by excessive ROS, and this process is controlled by gut microbiota-mediated immunological responses, DNA damage, and intestinal inflammation. In this review, we discuss the relationship between gut microbiota and intestinal disease from an oxidative stress perspective. In addition, we also provide a summary of the most recent therapeutic approaches for preventing or treating intestinal diseases by modifying gut microbiota.

Gut-brain pathogenesis of post-acute COVID-19 neurocognitive symptoms

Approximately one third of non-hospitalized coronavirus disease of 2019 (COVID-19) patients report chronic symptoms after recovering from the acute stage of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Some of the most persistent and common complaints of this post-acute COVID-19 syndrome (PACS) are cognitive in nature, described subjectively as "brain fog" and also objectively measured as deficits in executive function, working memory, attention, and processing speed. The mechanisms of these chronic cognitive sequelae are currently not understood. SARS-CoV-2 inflicts damage to cerebral blood vessels and the intestinal wall by binding to angiotensin-converting enzyme 2 (ACE2) receptors and also by evoking production of high levels of systemic cytokines, compromising the brain's neurovascular unit, degrading the intestinal barrier, and potentially increasing the permeability of both to harmful substances. Such substances are hypothesized to be produced in the gut by pathogenic microbiota that, given the profound effects COVID-19 has on the gastrointestinal system, may fourish as a result of intestinal post-COVID-19 dysbiosis. COVID-19 may therefore create a scenario in which neurotoxic and neuroinflammatory substances readily proliferate from the gut lumen and encounter a weakened neurovascular unit, gaining access to the brain and subsequently producing cognitive deficits. Here, we review this proposed PACS pathogenesis along the gut-brain axis, while also identifying specific methodologies that are currently available to experimentally measure each individual component of the model.

Prevalence of gastrointestinal disease in US Military Veterans under outpatient care at the Veterans Health Administration

Objectives:

There are currently no reliable estimates of the prevalence of gastrointestinal disease in the US Military Veterans. Hence, the study aims to determine its prevalence in military Veterans in the United States.

Methods:

This study utilized a retrospective, correlational design using a patient record database from the Department of Veteran’s Affairs. The participants in the study were Veterans diagnosed with gastrointestinal disease. Specific gastrointestinal diseases include more than 500,000 ambulatory care visits annually in the United States, which included peptic ulcer disease, gastroesophageal reflux disease, diverticular disease, ulcerative colitis, Crohn’s disease, irritable bowel syndrome, and functional dyspepsia, as well as the symptoms of constipation and nausea/vomiting. This study revealed the exact prevalence of gastrointestinal disease diagnosed in Veterans served in outpatient settings by the Veterans Health Administration and broke down this prevalence over time and by the Veteran period of service.

Results:

Findings revealed that gastrointestinal disease prevalence among Veterans varied according to their period of service.

Conclusions:

Findings may help improve screening for Veterans with this increased risk factor. However, further research should be performed to verify the prevalence of gastrointestinal disease in Veterans as compared to the general American population.

Gastrointestinal problems, mechanisms and possible therapeutic directions in Gulf war illness: a mini review

By its nature, Gulf war illness (GWI) is multisymptomatic and affects several organ systems in the body. Along with other symptoms, veterans who suffer from GWI commonly report chronic gastrointestinal issues such as constipation, pain, indigestion, etc. However, until recently, most attention has been focused on neurological disturbances such as cognitive impairments, chronic fatigue, and chronic pain among affected veterans. With such high prevalence of gastrointestinal problems among Gulf war (GW) veterans, it is surprising that there is little research to investigate the mechanisms behind these issues. This review summarizes all the available works on the mechanisms behind gastrointestinal problems in GWI that have been published to date in various databases. Generally, these studies, which were done in rodent models, in vitro and human cohorts propose that an altered microbiome, a reactive enteric nervous system or a leaky gut among other possible mechanisms are the major drivers of gastrointestinal problems reported in GWI. This review aims to draw attention to the gastrointestinal tract as an important player in GWI disease pathology and a potential therapeutic target.

The interplay between gastrointestinal and cardiovascular diseases: a narrative review focusing on the clinical perspective

Both cardiovascular and gastrointestinal disorders represent considerable health burden on community clinics and hospitals with overwhelming economic cost. An overlap in the occurrence of these disorders is encountered in daily practice. Both affect each other in bidirectional manner through several mechanisms including altered hemodynamics, systemic inflammation, bacterial overgrowth and interactions and adverse effects of medications. In addition, to the known overlap in the symptoms occurrence of upper gastrointestinal tract diseases and cardiovascular diseases (CVDs). Awareness of this interplay and its clinical manifestations optimizes patient management, and could prevent catastrophic consequences and even save lives. In this review, we highlighted the clinical aspects of this bidirectional association between gastrointestinal and CVDs aiming to shed light on this topic and improve patients' care.

Chronic Liver Diseases and the Microbiome-Translating Our Knowledge of Gut Microbiota to Management of Chronic Liver Disease

Chronic liver disease is reaching epidemic proportions with the increasing prevalence of obesity, nonalcoholic liver disease, and alcohol overuse worldwide. Most patients are not candidates for liver transplantation even if they have end-stage liver disease. There is growing evidence of a gut microbial basis for many liver diseases, therefore, better diagnostic, prognostic, and therapeutic approaches based on knowledge of gut microbiota are needed. We review the questions that need to be answered to successfully translate our knowledge of the intestinal microbiome and the changes associated with liver disease into practice.

Biomimetic Gut Model Systems for Development of Targeted Microbial Solutions for Enhancing Warfighter Health and Performance

The human gut microbiome plays a vital role in both health and disease states and as a mediator of cognitive and physical performance. Despite major advances in our understanding of the role of gut microbes in host physiology, mechanisms underlying human-microbiome dynamics have yet to be fully elucidated.

The human gut microbiome plays a vital role in both health and disease states and as a mediator of cognitive and physical performance. Despite major advances in our understanding of the role of gut microbes in host physiology, mechanisms underlying human-microbiome dynamics have yet to be fully elucidated. This knowledge gap represents a major hurdle to the development of targeted gut microbiome solutions influencing human health and performance outcomes. The microbiome as it relates to warfighter health and performance is of interest to the Department of Defense (DoD) with the development of interventions impacting gut microbiome resiliency among its top research priorities. While technological advancements are enabling the development of experimental model systems that facilitate mechanistic insights underpinning human health, disease, and performance, translatability to human outcomes is still questionable. This review discusses some of the drivers influencing the DoD’s interest in the warfighter gut microbiome and describes current in vitro gut model systems supporting direct microbial-host interactions.