The Role of Amino Acids in Tuberculosis Infection: A Literature Review

Integrating untargeted and targeted LC-MS-based metabolomics to identify the serum metabolite biomarkers for tuberculosis

Given the limitations of untargeted metabolomics in precise metabolite quantification, our current research employed a novel approach by integrating untargeted and targeted metabolomics utilizing ultra-high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS/MS) to analyze the metabolic profile and potential biomarkers for tuberculosis (TB). A cohort of 36 TB patients and 36 healthy controls (HC) was enlisted to obtain serum samples. Multivariate pattern recognition and univariate statistical analysis were employed to screen and elucidate the differential metabolites, whereas dot plots and receiver operating characteristic (ROC) curves were established for the identification of potential biomarkers of TB. The results indicated a distinct differentiation between the two groups, identifying 99 metabolites associated with five primary metabolic pathways in relation to TB. Of these, 19 metabolites exhibited high levels of sensitivity and specificity, as evidenced by the area under curve values approaching 1. Following targeted quantitative analysis, three potential metabolites, namely, L-asparagine, L-glutamic acid, and arachidonic acid, were demonstrated excellent discriminatory ability as evidenced by the results of the ROC curve, dot plots, and random forest model. Particularly noteworthy was the enhanced diagnostic efficacy of the combination of these three metabolites compared to singular biomarkers, suggesting their potential utility as serum biomarkers for TB diagnosis.

Metabolic insights into HIV/TB co-infection: an untargeted urinary metabolomics approach

INTRODUCTION

Amid the global health crisis, HIV/TB co-infection presents significant challenges, amplifying the burden on patients and healthcare systems alike. Metabolomics offers an innovative window into the metabolic disruptions caused by co-infection, potentially improving diagnosis and treatment monitoring.

AIM

This study uses untargeted metabolomics to investigate the urinary metabolic signature of HIV/TB co-infection, enhancing understanding of the metabolic interplay between these infections.

METHODS

Urine samples from South African adults, categorised into four groups - healthy controls, TB-positive, HIV-positive, and HIV/TB co-infected - were analysed using GCxGC-TOFMS. Metabolites showing significant differences among groups were identified through Kruskal-Wallis and Wilcoxon rank sum tests.

RESULTS

Various metabolites (n = 23) were modulated across the spectrum of health and disease states represented in the cohorts. The metabolomic profiles reflect a pronounced disruption in biochemical pathways involved in energy production, amino acid metabolism, gut microbiome, and the immune response, suggesting a bidirectional exacerbation between HIV and TB. While both diseases independently perturb the host's metabolism, their co-infection leads to a unique metabolic phenotype, indicative of an intricate interplay rather than a simple additive effect.

CONCLUSION

Metabolic profiling revealed a unique metabolic landscape shaped by HIV/TB co-infection. The findings highlight the potential of urinary differential metabolites for co-infection, offering a non-invasive tool for enhancing diagnostic precision and tailoring therapeutic interventions. Future research should focus on expanding sample sizes and integrating longitudinal analyses to build upon these foundational insights, paving the way for metabolomic applications in combating these concurrent pandemics.

Amino Acid Biosynthesis Inhibitors in Tuberculosis Drug Discovery

According to the latest World Health Organization (WHO) report, an estimated 10.6 million people were diagnosed with tuberculosis (TB) in 2022, and 1.30 million died. A major concern is the emergence of multi-drug-resistant (MDR) and extensively drug-resistant (XDR) strains, fueled by the length of anti-TB treatment and HIV comorbidity. Innovative anti-TB agents acting with new modes of action are the only solution to counteract the spread of resistant infections. To escape starvation and survive inside macrophages, Mtb has evolved to become independent of the host by synthesizing its own amino acids. Therefore, targeting amino acid biosynthesis could subvert the ability of the mycobacterium to evade the host immune system, providing innovative avenues for drug discovery. The aim of this review is to give an overview of the most recent progress in the discovery of amino acid biosynthesis inhibitors. Among the hits discovered over the past five years, tryptophan (Trp) inhibitors stand out as the most advanced and have significantly contributed to demonstrating the feasibility of this approach for future TB drug discovery. Future efforts should be directed at prioritizing the chemical optimization of these hits to enrich the TB drug pipeline with high-quality leads.

Metabolic phenotyping and global functional analysis facilitate metabolic signature discovery for tuberculosis treatment monitoring

Tracking alterations in polar metabolite and lipid levels during anti-tuberculosis (TB) interventions is an emerging biomarker discovery and validation approach due to its sensitivity in capturing changes and reflecting on the host status. Here, we employed deep plasma metabolic phenotyping to explore the TB patient metabolome during three phases of treatment: at baseline, during intensive phase treatment, and upon treatment completion. Differential metabolites (DMs) in each period were determined, and the pathway-level biological alterations were explored by untargeted metabolomics-guided functional interpretations that bypassed identification. We identified 41 DMs and 39 pathways that changed during intensive phase completion. Notably, levels of certain amino acids including histidine, bile acids, and metabolites of purine metabolism were dramatically increased. The altered pathways included those involved in the metabolism of amino acids, glycerophospholipids, and purine. At the end of treatment, 44 DMs were discovered. The levels of glutamine, bile acids, and lysophosphatidylinositol significantly increased compared to baseline; the levels of carboxylates and hypotaurine declined. In addition, 37 pathways principally associated with the metabolism of amino acids, carbohydrates, and glycan altered at treatment completion. The potential of each DM for diagnosing TB was examined using a cohort consisting of TB patients, those with latent infections, and controls. Logistic regression revealed four biomarkers (taurine, methionine, glutamine, and acetyl-carnitine) that exhibited excellent performance in differential diagnosis. In conclusion, we identified metabolites that could serve as useful metabolic signatures for TB management and elucidated underlying biological processes affected by the crosstalk between host and TB pathogen during treatment.

Urinary markers of Mycobacterium tuberculosis and dysbiosis in paediatric tuberculous meningitis cases undergoing treatment

BACKGROUND

The pathogenesis of tuberculous meningitis (TBM) involves infection by Mycobacterium tuberculosis in the meninges and brain. However, recent studies have shown that the immune response and inflammatory processes triggered by TBM can have significant effects on gut microbiota. Disruptions in the gut microbiome have been linked to various systemic consequences, including altered immunity and metabolic dysregulation. Inflammation caused by TBM, antibiotic treatment, and changes in host immunity can all influence the composition of gut microbes. This complex relationship between TBM and the gut microbiome is of great importance in clinical settings. To gain a deeper understanding of the intricate interactions between TBM and the gut microbiome, we report innovative insights into the development of the disease in response to treatment. Ultimately, this could lead to improved outcomes, management strategies and quality of life for individuals affected by TBM.

METHOD

We used a targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach to investigate metabolites associated with gut metabolism in paediatric participants by analysing the urine samples collected from a control group (n = 40), and an experimental group (n = 35) with confirmed TBM, which were subdivided into TBM stage 1 (n = 8), stage 2 (n = 11) and stage 3 (n = 16).

FINDINGS

Our metabolomics investigation showed that, of the 78 initially selected compounds of microbiome origin, eight unique urinary metabolites were identified: 2-methylbutyrlglycine, 3-hydroxypropionic acid, 3-methylcrotonylglycine, 4-hydroxyhippuric acid, 5-hydroxyindoleacetic acid, 5-hydroxyhexanoic acid, isobutyrylglycine, and phenylacetylglutamine as urinary markers of dysbiosis in TBM.

CONCLUSION

These results - which are supported by previous urinary studies of tuberculosis - highlight the importance of gut metabolism and of identifying corresponding microbial metabolites as novel points for the foundation of improved management of TBM patients.

Exploring the Potential of Exosomes as Biomarkers in Tuberculosis and Other Diseases

Tuberculosis (TB) is a major cause of morbidity and mortality and remains an important public health issue in developing countries worldwide. The existing methods and techniques available for the diagnosis of TB are based on combinations of laboratory (chemical and biological), radiological, and clinical tests. These methods are sophisticated and laborious and have limitations in terms of sensitivity, specificity, and accuracy. Clinical settings need improved diagnostic biomarkers to accurately detect biological changes due to pathogen invasion and pharmacological responses. Exosomes are membrane-bound vesicles and mediators of intercellular signaling processes that play a significant role in the pathogenesis of various diseases, such as tuberculosis, and can act as promising biomarkers for the monitoring of TB infection. Compared to conventional biomarkers, exosome-derived biomarkers are advantageous because they are easier to detect in different biofluids, are more sensitive and specific, and may be useful in tracking patients' reactions to therapy. This review provides insights into the types of biomarkers, methods of exosome isolation, and roles of the cargo (proteins) present in exosomes isolated from patients through omics studies, such as proteomics. These findings will aid in developing new prognostic and diagnostic biomarkers and could lead to the identification of new therapeutic targets in the clinical setting.

Mycobacterium tuberculosis: Pathogenesis and therapeutic targets

Tuberculosis (TB) remains a significant public health concern in the 21st century, especially due to drug resistance, coinfection with diseases like immunodeficiency syndrome (AIDS) and coronavirus disease 2019, and the lengthy and costly treatment protocols. In this review, we summarize the pathogenesis of TB infection, therapeutic targets, and corresponding modulators, including first-line medications, current clinical trial drugs and molecules in preclinical assessment. Understanding the mechanisms of Mycobacterium tuberculosis (Mtb) infection and important biological targets can lead to innovative treatments. While most antitubercular agents target pathogen-related processes, host-directed therapy (HDT) modalities addressing immune defense, survival mechanisms, and immunopathology also hold promise. Mtb's adaptation to the human host involves manipulating host cellular mechanisms, and HDT aims to disrupt this manipulation to enhance treatment effectiveness. Our review provides valuable insights for future anti-TB drug development efforts.

Integration of Metabolomics and Transcriptomics Reveals Major Metabolic Pathways and Potential Biomarkers Involved in Pulmonary Tuberculosis and Pulmonary Tuberculosis-Complicated Diabetes

Pulmonary tuberculosis (PTB) and diabetes mellitus (DM) are common chronic diseases that threaten human health. Patients with DM are susceptible to PTB, an important factor that aggravates the complications of diabetes. However, the molecular regulatory mechanism underlying the susceptibility of patients with DM to PTB infection remains unknown. In this study, healthy subjects, patients with primary PTB, and patients with primary PTB complicated by DM were recruited according to inclusion and exclusion criteria. Peripheral whole blood was collected, and alteration profiles and potential molecular mechanisms were further analyzed using integrated bioinformatics analysis of metabolomics and transcriptomics. Transcriptional data revealed that lipocalin 2 (LCN2), defensin alpha 1 (DEFA1), peptidoglycan recognition protein 1 (PGLYRP1), and integrin subunit alpha 2b (ITGA2B) were significantly upregulated, while chloride intracellular channel 3 (CLIC3) was significantly downregulated in the group with PTB and DM (PTB_DM) in contrast to the healthy control (HC) group. Additionally, the interleukin 17 (IL-17), phosphatidylinositol 3-kinase (PI3K)-AKT, and peroxisome proliferator-activated receptor (PPAR) signaling pathways are important for PTB infection and regulation of PTB-complicated diabetes. Metabolomic data showed that glycerophospholipid metabolism, carbon metabolism, and fat digestion and absorption processes were enriched in the differential metabolic analysis. Finally, integrated analysis of both metabolomic and transcriptomic data indicated that the NOTCH1/JAK/STAT signaling pathway is important in PTB complicated by DM. In conclusion, PTB infection altered the transcriptional and metabolic profiles of patients with DM. Metabolomic and transcriptomic changes were highly correlated in PTB patients with DM. Peripheral metabolite levels may be used as biomarkers for PTB management in patients with DM. IMPORTANCE The comorbidity of diabetes mellitus (DM) significantly increases the risk of tuberculosis infection and adverse tuberculosis treatment outcomes. Most previous studies have focused on the relationship between the effect of blood glucose control and the outcome of antituberculosis treatment in pulmonary tuberculosis (PTB) with DM (PTB_DM); however, early prediction and the underlying molecular mechanism of susceptibility to PTB infection in patients with DM remain unclear. In this study, transcriptome sequencing and untargeted metabolomics were performed to elucidate the key molecules and signaling pathways involved in PTB infection and the susceptibility of patients with diabetes to PTB. Our findings contribute to the development of vital diagnostic biomarkers for PTB or PTB_DM and provide a comprehensive understanding of molecular regulation during disease progression.

L-Tyrosine Limits Mycobacterial Survival in Tuberculous Granuloma

Caused by the intracellular pathogen Mycobacterium tuberculosis (Mtb), tuberculosis (TB) remains a massive global public health issue. A well-known and key TB trait is caseous necrotic granuloma, which allows mycobacteria to reactivate and disseminate, thus confounding TB eradication programs. Amino acid (AA) metabolism is key to regulating immune responses in Mtb infections; however, it is currently unclear if AAs can be used to treat tuberculous granulomas. Here, we screened 20 proteinogenic AAs using a Mycobacterium marinum-infected zebrafish granuloma model. Only L-tyrosine simultaneously reduced Mycobacterium marinum (M. marinum) levels in zebrafish larvae and adults and inhibited intracellular pathogen survival levels. Mechanistically, L-tyrosine significantly upregulated interferon-γ (IFN-γ) expression in M. marinum -infected zebrafish adults but not in larvae. Using N-acetylcysteine (NAC) to inhibit reactive oxygen species (ROS), L-tyrosine appeared to inhibit Mtb intracellular survival by promoting ROS production. Thus, L-tyrosine as a non-essential AA may reduce mycobacterial survival in both macrophages and tuberculous granulomas. Our research provides a platform for the clinical development of AAs for active or latent TB patients infected with drug-sensitive or drug-resistant Mtb.

Multimodal plasma metabolomics and lipidomics in elucidating metabolic perturbations in tuberculosis patients with concurrent type 2 diabetes

Type 2 diabetes mellitus (DM) poses a major burden for the treatment and control of tuberculosis (TB). Characterization of the underlying metabolic perturbations in DM patients with TB infection would yield insights into the pathophysiology of TB-DM, thus potentially leading to improvements in TB treatment. In this study, a multimodal metabolomics and lipidomics workflow was applied to investigate plasma metabolic profiles of patients with TB and TB-DM. Significantly different biological processes and biomarkers in TB-DM vs. TB were identified using a data-driven, knowledge-based framework. Changes in metabolic and signaling pathways related to carbohydrate and amino acid metabolism were mainly captured by amide HILIC column metabolomics analysis, while perturbations in lipid metabolism were identified by the C18 metabolomics and lipidomics analysis. Compared to TB, TB-DM exhibited elevated levels of bile acids and molecules related to carbohydrate metabolism, as well as the depletion of glutamine, retinol, lysophosphatidylcholine, and phosphatidylcholine. Moreover, arachidonic acid metabolism was determined as a potential important factor in the interaction between TB and DM pathophysiology. In a correlation network of the significantly altered molecules, among the central nodes, chenodeoxycholic acid was robustly associated with TB and DM. Fatty acid (22:4) was a component of all significant modules. In conclusion, the integration of multimodal metabolomics and lipidomics provides a thorough picture of the metabolic changes associated with TB-DM. The results obtained from this comprehensive profiling of TB patients with DM advance the current understanding of DM comorbidity in TB infection and contribute to the development of more effective treatment.

Small molecule bio-signature in childhood intra-thoracic tuberculosis identified by metabolomics

The diagnosis of pediatric tuberculosis (TB) remains a major challenge, hence the evaluation of new tools for improved diagnostics is urgently required. We investigated the serum metabolic profile of children with culture-confirmed intra-thoracic TB (ITTB) (n = 23) and compared it with those of non-TB controls (NTCs) (n = 13) using proton NMR spectroscopy-based targeted and untargeted metabolomics approaches. In targeted metabolic profiling, five metabolites (histidine, glycerophosphocholine, creatine/phosphocreatine, acetate, and choline) differentiated TB children from NTCs. Additionally, seven discriminatory metabolites (N-α-acetyl-lysine, polyunsaturated fatty acids, phenylalanine, lysine, lipids, glutamate + glutamine, and dimethylglycine) were identified in untargeted metabolic profiling. The pathway analysis revealed alterations in six metabolic pathways. The altered metabolites were associated with impaired protein synthesis, hindered anti-inflammatory and cytoprotective mechanisms, abnormalities in energy generation processes and membrane metabolism, and deregulated fatty acid and lipid metabolisms in children with ITTB. The diagnostic significance of the classification models obtained from significantly distinguishing metabolites showed sensitivity, specificity, and area under the curve of 78.2%, 84.6%, and 0.86, respectively, in the targeted profiling and 92.3%, 100%, and 0.99, respectively, in the untargeted profiling. Our findings highlight detectable metabolic changes in childhood ITTB; however, further validation is warranted in a large cohort of the pediatric population.

Impact and cost-effectiveness evaluation of nutritional supplementation and complementary interventions for tuberculosis treatment outcomes under mukti pay-for-performance model in Madhya Pradesh, India: A study protocol

Background

A.

"pay-for-performance" (P4P) intervention model for improved tuberculosis (TB) outcomes, called "Mukti," has been implemented in an underdeveloped tribal area of central India. The target of this project is to improve nutritional status, quality of life (QoL), and treatment outcomes of 1000 TB patients through four interventions: food baskets, personal counseling, peer-to-peer learning and facilitation for linkage to government schemes. The current study aims to assess the success of this model by evaluating its impact and cost-effectiveness using a quasi-experimental approach.

Methods

Data for impact assessment have been collected from 1000 intervention and control patients. Study outcomes such as treatment completion, sputum negativity, weight gain, and health-related QoL will be compared between matched samples. Micro costing approach will be used for assessing the cost of routine TB services provision under the national program and the incremental cost of implementing our interventions. A decision and Markov hybrid model will estimate long-term costs and health outcomes associated with the use of study interventions. Measures of health outcomes will be mortality, morbidity, and disability. Cost-effectiveness will be assessed in terms of incremental cost per quality-adjusted life-years gained and cost per unit increase in patient weight in intervention versus control groups.

Results

The evidence generated from the present study in terms of impact and cost-effectiveness estimates will thus help to identify not only the effectiveness of these interventions but also the optimal mode of financing such measures. Our estimates on scale-up costs for these interventions will also help the state and the national government to consider scale-up of such interventions in the entire state or country.

Discussion

The study will generate important evidence on the impact of nutritional supplementation and other complementary interventions for TB treatment outcomes delivered through P4P financing models and on the cost of scaling up these to the state and national level in India.