Unravelling the gut-lung axis: insights into microbiome interactions and Traditional Indian Medicine's perspective on optimal health

The gut-lung axis and microbiome dysbiosis in non-tuberculous mycobacterial infections: immune mechanisms, clinical implications, and therapeutic frontiers

Non-tuberculous mycobacteria (NTM) are emerging pathogens of global concern, particularly in regions with declining tuberculosis rates. This review synthesizes current evidence on the epidemiology, immune pathogenesis, and microbiome interactions underlying NTM infections. The rising incidence of NTM is driven by environmental factors, immunocompromised populations, and advanced diagnostics. Clinically, NTM manifests as pulmonary, lymphatic, skin/soft tissue, or disseminated disease, with Mycobacterium avium complex (MAC) and M. abscessus being predominant pathogens. Host immunity, particularly Th1 responses mediated by IL-12/IFN-γ and TLR2 signaling, is critical for controlling NTM, while dysregulated immunity (e.g., elevated Th2 cytokines, PD-1/IL-10 pathways) exacerbates susceptibility. Emerging research highlights the gut-lung axis as a pivotal mediator of disease, where microbiome dysbiosis-marked by reduced Prevotella and Bifidobacterium-impairs systemic immunity and promotes NTM progression. Short-chain fatty acids (SCFAs) and microbial metabolites like inosine modulate macrophage and T-cell responses, offering therapeutic potential. Studies reveal distinct airway microbiome signatures in NTM patients, characterized by enriched Streptococcus and Prevotella, and reduced diversity linked to worse outcomes. Despite advances, treatment remains challenging due to biofilm formation, antibiotic resistance, and relapse rates. This review underscores the need for microbiome-targeted therapies, personalized medicine, and longitudinal studies to unravel causal relationships between microbial ecology and NTM pathogenesis.

Differential responses of lung and intestinal microbiota to SARS-CoV-2 infection: a comparative study of the Wuhan and Omicron strains in K18-hACE2 Tg mice

BACKGROUND

The COVID-19 pandemic, caused by SARS-CoV-2, has led to the emergence of viral variants with distinct characteristics. Understanding the differential impacts of SARS-CoV-2 variants is crucial for effective public health response and treatment development. We investigated the differential effects of the original Wuhan strain and the emergent Omicron variant of SARS-CoV-2 using a K18-hACE2 transgenic mouse model. We compared the mortality rates, viral loads, and histopathological changes in lung and tracheal tissues, as well as alterations in the lung and intestinal microbiota following infection.

RESULTS

Our findings revealed significant differences between the variants, with the Wuhan strain causing higher mortality rates, severe lung pathology, and elevated viral loads compared to the Omicron variant. Microbiome analyses uncovered novel and distinct shifts in the lung and intestinal microbiota associated with each variant, providing evidence for variant-specific microbiome alterations. These changes suggest microbiome-related mechanisms that might modulate disease severity and host responses to SARS-CoV-2 infection.

CONCLUSIONS

This study highlights critical differences between the Wuhan strain and Omicron variant in terms of mortality, lung pathology, and microbiota changes, emphasizing the role of the microbiome in influencing disease outcomes. Novel findings include the identification of variant-specific microbiota shifts, which underscore potential microbiome-related mechanisms underlying differences in disease severity. These insights pave the way for future research exploring microbiome-targeted interventions to mitigate the impacts of SARS-CoV-2 and other viral infections.

Efficacy of yeast beta-glucan 1,3/1,6 supplementation on respiratory infection, fatigue, immune markers and gut health among moderate stress adults in Klang Valley of Malaysia: protocol for a randomised, double-blinded, placebo-controlled, parallel-group study

INTRODUCTION

Yeast beta-glucan (YBG) are recognised for enhancing the immune system by activating macrophages, a key defence mechanism. Given the global prevalence and impact of upper respiratory tract infections (URTIs) on productivity and healthcare costs, YBG has shown promise as a potential therapeutic and preventive strategy for recurrent respiratory tract infections. However, little is known regarding the efficacy of YBG at lower dosages in relation to URTI, fatigue, immune response and uncertainties of how they affect the gut microbiota composition.

METHODS AND ANALYSIS

This 12-week randomised, double-blinded, placebo control, parallel-group clinical trial aims to evaluate the efficacy of YBG 1,3/1,6 on respiratory tract infection, fatigue, immune markers and gut health among adults with moderate stress. The study involves 198 adults aged 18-59 years with moderate stress levels as assessed using Perceived Stress Scale 10 (score 14-26) and Patient Health Questionnaire 9 (score ≥9); and had symptoms of common colds for the past 6 months as assessed using Jackson Cold Scale. These participants will be randomised into three groups, receiving YBG 1,3/1,6 at either 120 mg, 204 mg or a placebo. The outcomes measures include respiratory infection symptoms, fatigue, mood state and quality of life assessed using Wisconsin Upper Respiratory Symptoms Scale, Multidimensional Fatigue Inventory, Profile of Mood State and Short Form 36 Health Survey Questionnaire, respectively. In addition, full blood analysis and assessment of immune, inflammatory and oxidative stress biomarkers will be taken. Secondary outcome includes gut microbiota analysis using stool samples via 16S rRNA sequencing.

ETHICS AND DISSEMINATION

The research protocol of the study was reviewed and approved by the Research Ethics Committee of Universiti Kebangsaan Malaysia (UKM/PPI/111/8/JEP-2023-211). The findings will be disseminated to participants, healthcare professionals and researchers via conference presentations and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

ISRCTN48336189.

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.

The Intriguing Connection Between the Gut and Lung Microbiomes

Recent advances in microbiome research have uncovered a dynamic and complex connection between the gut and lungs, known as the gut-lung axis. This bidirectional communication network plays a critical role in modulating immune responses and maintaining respiratory health. Mediated by immune interactions, metabolic byproducts, and microbial communities in both organs, this axis demonstrates how gut-derived signals, such as metabolites and immune modulators, can reach the lung tissue via systemic circulation, influencing respiratory function and disease susceptibility. To explore the implications of this connection, we conducted a systematic review of studies published between 2001 and 2024 (with as much as nearly 60% covering the period 2020-2024), using keywords such as "gut-lung axis", "microbiome", "respiratory disease", and "immune signaling". Studies were selected based on their relevance to gut-lung communication mechanisms, the impact of dysbiosis, and the role of the gut microbiota in respiratory diseases. This review provides a comprehensive overview of the gut-lung microbiome axis, emphasizing its importance in regulating inflammatory and immune responses linked to respiratory health. Understanding this intricate pathway opens new avenues for microbiota-targeted therapeutic strategies, which could offer promising interventions for respiratory diseases like asthma, chronic obstructive pulmonary disease, and even infections. The insights gained through this research underscore the potential of the gut-lung axis as a novel target for preventative and therapeutic approaches in respiratory medicine, with implications for enhancing both gut and lung health.

Gut-lung microbiota dynamics in mice exposed to Nanoplastics

Concern has grown over potential health effects of micro- and nanoplastics (M/NPs) exposure. There is significant interest in understanding their impact on animal and human microbiota due to its crucial role in preserving health, as research in this area is rapidly advancing. We conducted a sub-chronic exposure study involving 12 male mice, divided into two groups: a control group (n = 6) and a PET-NPs exposure group (n = 6). PET-NPs, administered by oral gavage at a dose of 0.5 mg/day in 0.1 ml/mice, were given daily for 28 days. Microbiota analyses were performed on lung, colon, oral cavity, and stool samples using 16S rRNA sequencing. Additionally, fecal short and medium-chain fatty acids were analyzed by GC/MS. No significant changes were observed in the fecal and oral microbiome of the treated mice, nor in the fecal fatty acid levels. However, there were prominent alterations in the colon, characterized by increased abundance of Gram-negative bacteria belonging to Veillonella and Prevotella genera, and of amino acid metabolism pathways, coupled with a decrease in Lactobacillus. PET-NPs ingestion caused unexpected alterations in the lung microbiome with an increase in the Pseudomonas and changes in microbial energy metabolism and nitrogen utilization. This study provides insights into the differential impact of PET-NPs exposure on various microbiome niches.

The impact of gut microbiota on morbidities in preterm infants

The gut microbiota undergoes substantial development from birth, and its development in the initial years of life has a potentially lifelong effect on the health of the individual. However, various factors can disrupt the development of the gut microbiota, leading to a condition known as dysbiosis, particularly in preterm infants. Current studies involving adults have suggested that the gut microbiota not only influences the gut but also has multidimensional effects on remote organs; these pathways are often referred to as the gut-organ axis. Imbalance of the gut microbiota may lead to the development of multiple diseases. Recent studies have revealed that gut dysbiosis in preterm infants may cause several acute morbidities-such as necrotizing enterocolitis, late-onset sepsis, bronchopulmonary dysplasia, and retinopathy of prematurity-and it may also influence long-term outcomes including neurodevelopment and somatic growth. This review mainly presents the existing evidence regarding the relationships between the gut microbiota and these morbidities in preterm infants and explores the role of the gut-organ axis in these morbidities. This paper thus offers insights into the future perspectives on microbiota interventions for promoting the health of preterm infants.

Modulating the gut microbiome in non-small cell lung cancer: Challenges and opportunities

Despite the efficacy of immunotherapy in non-small cell lung cancer (NSCLC), the majority of the patients experience relapse with limited subsequent treatment options. Preclinical studies of various epithelial tumors, such as melanoma and NSCLC, have shown that harnessing the gut microbiome resulted in improvement of therapeutic responses to immunotherapy. Is this review, we summarize the role of microbiome, including lung and gut microbiome in the context of NSCLC, provide overview of the mechanisms of microbiome in efficacy and toxicity of chemotherapies and immunotherapies, and address current ongoing clinical trials for NSCLC including fecal microbiota transplantation (FMT) and live biotherapeutic products (LBPs).

An Assessment of the Knowledge, Attitude, and Practice of Probiotics and Prebiotics among the Population of the United Arab Emirates

Probiotics and prebiotics offer a range of advantageous effects on human health. The knowledge, attitudes, and practices (KAP) of individuals can impact their inclination to consume probiotics and prebiotics. The main objective of this study was to examine the KAP of the people in the United Arab Emirates (UAE) about probiotics and prebiotics consumption. Additionally, the study aimed to assess the impact of KAP and sociodemographic factors on the use of probiotics and prebiotics. In order to accomplish this objective, a verified online questionnaire was used with a five-point Likert scale and distributed using an online platform (Google Forms). A cross-sectional research, non-probability sampling was implemented, and G*Power statistical power analysis was used to estimate a sample size of 385 participants. A total of 408 replies were gathered. The population under study consisted of residents in the UAE between the ages of 18 to 64 years old, excluding populations under the age of 18 and those living outside the UAE. A total of 392 participants met the criteria for inclusion in this study. The research ethics committees of UAE University granted the study approval (ERSC_2024_4359), and the validity of the findings was confirmed through face-to-face interviews with around 50 individuals and a Cronbach's alpha test with result of 0.84. The statistical software SPSS version 29.0 for Mac OS was utilized to examine the relationships between KAP variables, including Chi-square tests and Pearson's correlation coefficients. The tests were selected based on their capacity to handle categorical and continuous data, respectively. The female population was 85.2% of the total, while the male population accounts for 14.8%. The age distribution of participants shows that the largest proportion, 68.4%, falls within the 18-24 age range. Out of the participants, 61.5% held a bachelor's degree. Most of the participants, 56.4%, were students, while 29.1% were employees. The average results indicate a significant inclination towards probiotics and prebiotics, as demonstrated by the scores above the midpoint for the six knowledge questions (M = 2.70), six attitude questions (M = 3.10), and six practice questions (M = 3.04). Several studies have examined this phenomenon; however, additional research comparing individuals in the UAE is necessary to fully comprehend the influence of KAP on the consumption of probiotics and prebiotics in the UAE.

Natural products for Gut-X axis: pharmacology, toxicology and microbiology in mycotoxin-caused diseases

Introduction: The gastrointestinal tract is integral to defending against external contaminants, featuring a complex array of immunological, physical, chemical, and microbial barriers. Mycotoxins, which are toxic metabolites from fungi, are pervasive in both animal feed and human food, presenting substantial health risks. Methods: This review examines the pharmacological, toxicological, and microbiological impacts of natural products on mycotoxicosis, with a particular focus on the gut-x axis. The analysis synthesizes current understanding and explores the role of natural products rich in polysaccharides, polyphenols, flavonoids, and saponins. Results: The review highlights that mycotoxins can disrupt intestinal integrity, alter inflammatory responses, damage the mucus layer, and disturb the bacterial balance. The toxins' effects are extensive, potentially harming the immune system, liver, kidneys, and skin, and are associated with serious conditions such as cancer, hormonal changes, genetic mutations, bleeding, birth defects, and neurological issues. Natural products have shown potential anticancer, anti-tumor, antioxidant, immunomodulatory, and antitoxic properties. Discussion: The review underscores the emerging therapeutic strategy of targeting gut microbial modulation. It identifies knowledge gaps and suggests future research directions to deepen our understanding of natural products' role in gut-x axis health and to mitigate the global health impact of mycotoxin-induced diseases.

Gut-Lung Microbiota Characterization in Patients with Non-Small Cell Lung Carcinoma and COVID-19 Coinfection

BACKGROUND

Non-small cell lung cancer (NSCLC) patients with COVID-19 have an excessive chance of morbidity and mortality. The fecal-nasopharyngeal microbiota compositions of NSCLC patients were assessed in this study.

METHODS

In total, 234 samples were collected from 17 NSCLC patients infected with COVID-19, 20 NSCLC patients without confirmed COVID-19, 40 non NSCLC patients with COVID-19, and 40 healthy individuals.

RESULTS

In lung microbiota, the abundance of Streptococcus spp. in NSCLC patients with confirmed COVID-19 was significantly higher than the two control groups. Pseudomonas aeruginosa and Staphylococcus aureus were listed as the most frequent pulmonary bacterial groups that colonized COVID-19 patients. In fecal specimens, the numbers of Bacteroidetes, Firmicutes, and Actinobacteria phyla were significantly higher amongst NSCLC patients with COVID-19. NSCLC patients infected with COVID-19 showed lower levels of Lactobacillus spp., Akkermansia muciniphila, and Bifidobacterium spp. The counts of Streptococcus spp., in NSCLC patients with COVID-19 were significantly higher than those of healthy individuals (8.49±0.70 log CFU/g wet feces vs 8.49±0.70 log CFU/g wet feces). Prevotella spp. were enriched in the gut and respiratory tracts of COVID-19 patient groups. The unbiased analysis showed an increment in Enterococcus spp., Streptococcus spp., and Prevotella spp.

CONCLUSION

Eventually, it was found that compared to control groups, COVID-19 patients with NSCLC showed diminished gut bacteria diversity and increase in Lactobacillus spp., A. muciniphila, and Bifidobacterium spp. The overgrowth of Enterococcus spp., Streptococcus spp., and Prevotella spp. could be potential predictive biomarkers in the gut-lung axis of NSCLC patients with COVID-19.

The uncharted territory of host-pathogen interaction in tuberculosis

Mycobacterium tuberculosis (M.tb) effectively manipulates the host processes to establish the deadly respiratory disease, Tuberculosis (TB). M.tb has developed key mechanisms to disrupt the host cell health to combat immune responses and replicate efficaciously. M.tb antigens such as ESAT-6, 19kDa lipoprotein, Hip1, and Hsp70 destroy the integrity of cell organelles (Mitochondria, Endoplasmic Reticulum, Nucleus, Phagosomes) or delay innate/adaptive cell responses. This is followed by the induction of cellular stress responses in the host. Such cells can either undergo various cell death processes such as apoptosis or necrosis, or mount effective immune responses to clear the invading pathogen. Further, to combat the infection progression, the host secretes extracellular vesicles such as exosomes to initiate immune signaling. The exosomes can contain M.tb as well as host cell-derived peptides that can act as a double-edged sword in the immune signaling event. The host-symbiont microbiota produces various metabolites that are beneficial for maintaining healthy tissue microenvironment. In juxtaposition to the above-mentioned mechanisms, M.tb dysregulates the gut and respiratory microbiome to support its replication and dissemination process. The above-mentioned interconnected host cellular processes of Immunometabolism, Cellular stress, Host Microbiome, and Extracellular vesicles are less explored in the realm of exploration of novel Host-directed therapies for TB. Therefore, this review highlights the intertwined host cellular processes to control M.tb survival and showcases the important factors that can be targeted for designing efficacious therapy.