The Microbiota in Long COVID

Long COVID clinical evaluation, research and impact on society: a global expert consensus

BACKGROUND

Long COVID is a complex, heterogeneous syndrome affecting over four hundred million people globally. There are few recommendations, and no formal training exists for medical professionals to assist with clinical evaluation and management of patients with Long COVID. More research into the pathology, cellular, and molecular mechanisms of Long COVID, and treatments is needed. The goal of this work is to disseminate essential information about Long COVID and recommendations about definition, diagnosis, treatment, research and social issues to physicians, researchers, and policy makers to address this escalating global health crisis.

METHODS

A 3-round modified Delphi consensus methodology was distributed internationally to 179 healthcare professionals, researchers, and persons with lived experience of Long COVID in 28 countries. Statements were combined into specific areas: definition, diagnosis, treatment, research, and society.

RESULTS

The survey resulted in 187 comprehensive statements reaching consensus with the strongest areas being diagnosis and clinical assessment, and general research. We establish conditions for diagnosis of different subgroups within the Long COVID umbrella. Clear consensus was reached that the impacts of COVID-19 infection on children should be a research priority, and additionally on the need to determine the effects of Long COVID on societies and economies. The consensus on COVID and Long COVID is that it affects the nervous system and other organs and is not likely to be observed with initial symptoms. We note, biomarkers are critically needed to address these issues.

CONCLUSIONS

This work forms initial guidance to address the spectrum of Long COVID as a disease and reinforces the need for translational research and large-scale treatment trials for treatment protocols.

The Microbiota and Evolution of Obesity

Obesity is a major global concern and is generally attributed to a combination of genetic and environmental factors. Several hypotheses have been proposed to explain the evolutionary origins of obesity epidemic, including thrifty and drifty genotypes, and changes in thermogenesis. Here, we put forward the hypothesis of metaflammation, which proposes that due to intense selection pressures exerted by environmental pathogens, specific genes that help develop a robust defense mechanism against infectious diseases have had evolutionary advantages and that this may contribute to obesity in modern times due to connections between the immune and energy storage systems. Indeed, incorporating the genetic variations of gut microbiota into the complex genetic framework of obesity makes it more polygenic than previously believed. Thus, uncovering the evolutionary origins of obesity requires a multifaceted approach that considers the complexity of human history, the unique genetic makeup of different populations, and the influence of gut microbiome on host genetics.

Serotonergic psychedelics as potential therapeutics for post-COVID-19 syndrome (or Long COVID): A comprehensive review

RATIONALE

In our ongoing battle against the coronavirus 2019 (COVID-19) pandemic, a major challenge is the enduring symptoms that continue after acute infection. Also known as Long COVID, post-COVID-19 syndrome (PCS) often comes with debilitating symptoms like fatigue, disordered sleep, olfactory dysfunction, and cognitive issues ("brain fog"). Currently, there are no approved treatments for PCS. Recent research has uncovered that the severity of PCS is inversely linked to circulating serotonin levels, highlighting the potential of serotonin-modulating therapeutics for PCS. Therefore, we propose that serotonergic psychedelics, acting mainly via the 5-HT2A serotonin receptor, hold promise for treating PCS.

OBJECTIVES

Our review aims to elucidate potential mechanisms by which serotonergic psychedelics may alleviate the symptoms of PCS.

RESULTS

Potential mechanisms through which serotonergic psychedelics may alleviate PCS symptoms are discussed, with emphasis on their effects on inflammation, neuroplasticity, and gastrointestinal function. Additionally, this review explores the potential of serotonergic psychedelics in mitigating endothelial dysfunction, a pivotal aspect of PCS pathophysiology implicated in organ dysfunction. This review also examines the potential role of serotonergic psychedelics in alleviating specific PCS symptoms, which include olfactory dysfunction, cognitive impairment, sleep disturbances, and mental health challenges.

CONCLUSIONS

Emerging evidence suggests that serotonergic psychedelics may alleviate PCS symptoms. However, further high-quality research is needed to thoroughly assess their safety and efficacy in treating patients with PCS.

[Cognition and Long COVID: A PRISMA Systematic Review of Longitudinal Studies]

INTRODUCTION

Long COVID is defined by National Institute for Health and Care Excellence (NICE) as the set of signs and symptoms that develop during or after a SARS-CoV-2 infection and continue for more than twelve weeks without any alternative diagnosis. One of the most frequent persistent symptoms reported by patients and verified in neuroimaging studies is cognitive dysfunction, due to a generalized hypoconnectivity and a diffuse axonal lesion in white matter. Therefore, the objectives of the present review are to determine how long cognitive functions remain affected during Long COVID and to explore which cognitive functions are most affected beyond three months of follow-up in patients up to 65 years of age without previous neuropsychological or psychiatric complications.

METHODS

A systematic review was performed using PRISMA criteria and 11 articles were included through a comprehensive search of five different databases: PubMed, Medline, Scopus, WOS and ProQuest. The risk of bias of the articles was assessed using the Newcastle-Ottawa scale.

RESULTS

Cognitive problems in Long COVID persist over time and improve slowly, although studies seem to agree that most areas improved significantly after one year. The cognitive functions that remained impaired the longest were processing speed and attention.

CONCLUSIONS

These cognitive alterations cause a reduction in the quality of life of the patients and a reduction in work capacity and manifest the need for a cognitive intervention.

Connecting dots of long COVID-19 pathogenesis: a vagus nerve- hypothalamic-pituitary- adrenal-mitochondrial axis dysfunction

The pathogenesis of long COVID (LC) still presents many areas of uncertainty. This leads to difficulties in finding an effective specific therapy. We hypothesize that the key to LC pathogenesis lies in the presence of chronic functional damage to the main anti-inflammatory mechanisms of our body: the three reflexes mediated by the vagus nerve, the hypothalamic-pituitary-adrenal (HPA) hormonal axis, and the mitochondrial redox status. We will illustrate that this neuro-endocrine-metabolic axis is closely interconnected and how the SARS-CoV-2 can damage it at all stages through direct, immune-inflammatory, epigenetic damage mechanisms, as well as through the reactivation of neurotropic viruses. According to our theory, the direct mitochondrial damage carried out by the virus, which replicates within these organelles, and the cellular oxidative imbalance, cannot be countered in patients who develop LC. This is because their anti-inflammatory mechanisms are inconsistent due to reduced vagal tone and direct damage to the endocrine glands of the HPA axis. We will illustrate how acetylcholine (ACh) and cortisol, with its cytoplasmatic and cellular receptors respectively, are fundamental players in the LC process. Both Ach and cortisol play multifaceted and synergistic roles in reducing inflammation. They achieve this by modulating the activity of innate and cell-mediated immunity, attenuating endothelial and platelet activation, and modulating mitochondrial function, which is crucial for cellular energy production and anti-inflammatory mechanisms. In our opinion, it is essential to study the sensitivity of the glucocorticoids receptor in people who develop LC and whether SARS-CoV-2 can cause long-term epigenetic variations in its expression and function.

Gastrointestinal pathophysiology in long COVID: Exploring roles of microbiota dysbiosis and serotonin dysregulation in post-infectious bowel symptoms

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) triggered an unprecedented public health crisis known as the coronavirus disease 2019 (COVID-19) pandemic. Gastrointestinal (GI) symptoms develop in patients during acute infection and persist after recovery from airway distress in a chronic form of the disease (long COVID). A high incidence of irritable bowel syndrome (IBS) manifested by severe abdominal pain and defecation pattern changes is reported in COVID patients. Although COVID is primarily considered a respiratory disease, fecal shedding of SARS-CoV-2 antigens positively correlates with bowel symptoms. Active viral infection in the GI tract was identified by human intestinal organoid studies showing SARS-CoV-2 replication in gut epithelial cells. In this review, we highlight the key findings in post-COVID bowel symptoms and explore possible mechanisms underlying the pathophysiology of the illness. These mechanisms include mucosal inflammation, gut barrier dysfunction, and microbiota dysbiosis during viral infection. Viral shedding through the GI route may be the primary factor causing the alteration of the microbiome ecosystem, particularly the virome. Recent evidence in experimental models suggested that microbiome dysbiosis could be further aggravated by epithelial barrier damage and immune activation. Moreover, altered microbiota composition has been associated with dysregulated serotonin pathways, resulting in intestinal nerve hypersensitivity. These mechanisms may explain the development of post-infectious IBS-like symptoms in long COVID. Understanding how coronavirus infection affects gut pathophysiology, including microbiome changes, would benefit the therapeutic advancement for managing post-infectious bowel symptoms.

Human microbiome in post-acute COVID-19 syndrome (PACS)

The global COVID-19 pandemic, which began in 2019, is still ongoing. SARS-CoV-2, also known as the severe acute respiratory syndrome coronavirus 2, is the causative agent. Diarrhea, nausea, and vomiting are common GI symptoms observed in a significant number of COVID-19 patients. Additionally, the respiratory and GI tracts express high level of transmembrane protease serine 2 (TMPRSS2) and angiotensin-converting enzyme-2 (ACE2), making them primary sites for human microbiota and targets for SARS-CoV-2 infection. A growing body of research indicates that individuals with COVID-19 and post-acute COVID-19 syndrome (PACS) exhibit considerable alterations in their microbiome. In various human disorders, including diabetes, obesity, cancer, ulcerative colitis, Crohn's disease, and several viral infections, the microbiota play a significant immunomodulatory role. In this review, we investigate the potential therapeutic implications of the interactions between host microbiota and COVID-19. Microbiota-derived metabolites and components serve as primary mediators of microbiota-host interactions, influencing host immunity. We discuss the various mechanisms through which these metabolites or components produced by the microbiota impact the host's immune response to SARS-CoV-2 infection. Additionally, we address confounding factors in microbiome studies. Finally, we examine and discuss about a range of potential microbiota-based prophylactic measures and treatments for COVID-19 and PACS, as well as their effects on clinical outcomes and disease severity.

Effects of sulphur thermal water inhalations in long-COVID syndrome: Spa-centred, double-blinded, randomised case-control pilot study

BACKGROUND

The long-COVID syndrome is characterised by a plethora of symptoms. Given its social and economic impact, many studies have stressed the urgency of proposing innovative strategies other than hospital settings. In this double-blinded, randomised, case-control trial, we investigate the effects of sulphur thermal water inhalations, rich in H2S, compared to distilled water inhalations on symptoms, inflammatory markers and nasal microbiome in long-COVID patients.

METHODS

About 30 outpatients aged 18-75 with positive diagnosis for long-COVID were randomised in two groups undergoing 12 consecutive days of inhalations. The active group (STW) received sulphur thermal water inhalations whereas the placebo group received inhalations of sterile distilled non-pyrogenic water (SDW). Each participant was tested prior treatment at day 1 (T0), after the inhalations at day 14 (T1) and at 3 months follow-up (T2). At each time point, blood tests, nasal swabs for microbiome sampling, pulmonary functionality tests (PFTs) and pro-inflammatory marker measure were performed.

RESULTS

The scores obtained in the administered tests (6MWT, Borg score and SGRQ) at T0 showed a significant variation in the STW group, at T1 and T2. Serum cytokine levels and other inflammatory biomarkers reported a statistically significant decrease. Some specific parameters of PFTs showed ameliorations in the STW group only. Changes in the STW nasopharyngeal microbiota composition were noticed, especially from T0 to T2.

CONCLUSIONS

Inhalations of sulphur thermal water exerted objective and subjective improvements on participants affected by long-COVID. Significant reduction of inflammatory markers, dyspnoea scores and quantitative and qualitative changes in the nasopharyngeal microbiome were also assessed.

The Silent Syndrome of Long COVID and Gaps in Scientific Knowledge: A Narrative Review

COVID-19 is still a major public health concern, mainly due to the persistence of symptoms or the appearance of new symptoms. To date, more than 200 symptoms of long COVID (LC) have been described. The present review describes and maps its relevant clinical characteristics, pathophysiology, epidemiology, and genetic and nongenetic risk factors. Given the currently available evidence on LC, we demonstrate that there are still gaps and controversies in the diagnosis, pathophysiology, epidemiology, and detection of prognostic and predictive factors, as well as the role of the viral strain and vaccination.

Addressing Post-Acute COVID-19 Syndrome in Cancer Patients, from Visceral Obesity and Myosteatosis to Systemic Inflammation: Implications in Cardio-Onco-Metabolism

Cardiovascular disease and cancer are the two leading causes of morbidity and mortality in the world. The emerging field of cardio-oncology described several shared risk factors that predispose patients to both cardiovascular disease and cancer. Post-acute COVID-19 syndrome is a chronic condition that occurs in many patients who have experienced a SARS-CoV-2 infection, mainly based on chronic fatigue, sedentary lifestyle, cramps, breathing difficulties, and reduced lung performance. Post-acute COVID-19 exposes patients to increased visceral adiposity, insulin resistance, myosteatosis, and white adipose tissue content (surrounded by M1 macrophages and characterized by a Th1/Th17 phenotype), which increases the risk of cardiovascular mortality and cancer recurrence. In this review, the main metabolic affections of post-acute COVID-19 syndrome in cancer patients at low and high risk of cardiomyopathies will be summarized. Furthermore, several non-pharmacological strategies aimed at reducing atherosclerotic and cardiac risk will be provided, especially through anti-inflammatory nutrition with a low insulin and glycemic index, appropriate physical activity, and immune-modulating bioactivities able to reduce visceral obesity and myosteatosis, improving insulin-related signaling and myocardial metabolism.

Alterations in microbiota of patients with COVID-19: implications for therapeutic interventions

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) recently caused a global pandemic, resulting in more than 702 million people being infected and over 6.9 million deaths. Patients with coronavirus disease (COVID-19) may suffer from diarrhea, sleep disorders, depression, and even cognitive impairment, which is associated with long COVID during recovery. However, there remains no consensus on effective treatment methods. Studies have found that patients with COVID-19 have alterations in microbiota and their metabolites, particularly in the gut, which may be involved in the regulation of immune responses. Consumption of probiotics may alleviate the discomfort caused by inflammation and oxidative stress. However, the pathophysiological process underlying the alleviation of COVID-19-related symptoms and complications by targeting the microbiota remains unclear. In the current study, we summarize the latest research and evidence on the COVID-19 pandemic, together with symptoms of SARS-CoV-2 and vaccine use, with a focus on the relationship between microbiota alterations and COVID-19-related symptoms and vaccine use. This work provides evidence that probiotic-based interventions may improve COVID-19 symptoms by regulating gut microbiota and systemic immunity. Probiotics may also be used as adjuvants to improve vaccine efficacy.

Potential Beneficial Effects of Naringin and Naringenin on Long COVID-A Review of the Literature

Coronavirus disease 2019 (COVID-19) caused a severe epidemic due to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Recent studies have found that patients do not completely recover from acute infections, but instead, suffer from a variety of post-acute sequelae of SARS-CoV-2 infection, known as long COVID. The effects of long COVID can be far-reaching, with a duration of up to six months and a range of symptoms such as cognitive dysfunction, immune dysregulation, microbiota dysbiosis, myalgic encephalomyelitis/chronic fatigue syndrome, myocarditis, pulmonary fibrosis, cough, diabetes, pain, reproductive dysfunction, and thrombus formation. However, recent studies have shown that naringenin and naringin have palliative effects on various COVID-19 sequelae. Flavonoids such as naringin and naringenin, commonly found in fruits and vegetables, have various positive effects, including reducing inflammation, preventing viral infections, and providing antioxidants. This article discusses the molecular mechanisms and clinical effects of naringin and naringenin on treating the above diseases. It proposes them as potential drugs for the treatment of long COVID, and it can be inferred that naringin and naringenin exhibit potential as extended long COVID medications, in the future likely serving as nutraceuticals or clinical supplements for the comprehensive alleviation of the various manifestations of COVID-19 complications.