Metformin as adjunct antituberculosis therapy

PP2Ac Modulates AMPK-Mediated Induction of Autophagy in Mycobacterium bovis-Infected Macrophages

Mycobacterium bovis (M. bovis) is the causative agent of bovine tuberculosis in cattle population across the world. Human beings are at equal risk of developing tuberculosis beside a wide range of M. bovis infections in animal species. Autophagic sequestration and degradation of intracellular pathogens is a major innate immune defense mechanism adopted by host cells for the control of intracellular infections. It has been reported previously that the catalytic subunit of protein phosphatase 2A (PP2Ac) is crucial for regulating AMP-activated protein kinase (AMPK)-mediated autophagic signaling pathways, yet its role in tuberculosis is still unclear. Here, we demonstrated that M. bovis infection increased PP2Ac expression in murine macrophages, while nilotinib a tyrosine kinase inhibitor (TKI) significantly suppressed PP2Ac expression. In addition, we observed that TKI-induced AMPK activation was dependent on PP2Ac regulation, indicating the contributory role of PP2Ac towards autophagy induction. Furthermore, we found that the activation of AMPK signaling is vital for the regulating autophagy during M. bovis infection. Finally, the transient inhibition of PP2Ac expression enhanced the inhibitory effect of TKI-nilotinib on intracellular survival and multiplication of M. bovis in macrophages by regulating the host’s immune responses. Based on these observations, we suggest that PP2Ac should be exploited as a promising molecular target to intervene in host–pathogen interactions for the development of new therapeutic strategies towards the control of M. bovis infections in humans and animals.

Host-Targeted Therapeutics against Multidrug Resistant Intracellular Staphylococcus aureus

Staphylococcus aureus is a facultative intracellular pathogen that invades and replicates within many types of human cells. S. aureus has shown to rapidly overcome traditional antibiotherapy by developing multidrug resistance. Furthermore, intracellular S. aureus is protected from the last-resort antibiotics—vancomycin, daptomycin, and linezolid—as they are unable to achieve plasma concentrations sufficient for intracellular killing. Therefore, there is an urgent need to develop novel anti-infective therapies against S. aureus infections. Here, we review the current state of the field and highlight the exploitation of host-directed approaches as a promising strategy going forward.

Harnessing the Immunomodulatory Properties of Bacterial Ghosts to Boost the Anti-mycobacterial Protective Immunity

Tuberculosis (TB) pathogenesis is characterized by inadequate immune cell activation and delayed T cell response in the host. Recent immunotherapeutic efforts have been directed at stimulating innate immunity and enhancing interactions between antigen presenting cells and T cells subsets to improve the protective immunity against TB. In this study, we investigated the immunostimulatory properties of bacterial ghosts (BG) as a novel approach to potentiate the host immunity against mycobacterial infection. BG are intact cytoplasm-free Escherichia coli envelopes and have been developed as bacterial vaccines and adjuvant/delivery system in cancer immunotherapy. However, BG have yet to be exploited as immunopotentiators in the context of infectious diseases. Here, we showed that BG are potent inducers of dendritic cells (DC), which led to enhanced T cell proliferation and differentiation into effector cells. BG also induced macrophage activation, which was associated with enhanced nitric oxide production, a key anti-mycobacterial weapon. We further demonstrated that the immunostimulatory capability of BG far exceeds that of LPS and involves both TLR4-dependent and independent pathways. Consistently, BG treatment, but not LPS treatment, reduced the bacterial burden in infected mice, which correlated with increased influx of innate and adaptive effector immune cells and increased production of key cytokines in the lungs. Finally and importantly, enhanced bacilli killing was seen in mice co-administered with BG and second-line TB drugs bedaquiline and delamanid. Overall, this work paves the way for BG as potent immunostimulators that may be harnessed to improve mycobacteria killing at the site of infection.

Impact of metformin use among tuberculosis close contacts with diabetes mellitus in a nationwide cohort study

BACKGROUND

The protective effect of metformin against active tuberculosis (TB) among TB close contacts is unknown.

METHODS

TB close contacts with diabetes mellitus (DM) and normal renal function were selected from the National Health Insurance Research Database of Taiwan. Metformin users were patients who received ≥90 cumulative defined daily doses within 1 year before the index date. For each metformin user, a propensity-score matched metformin nonuser and an age- and sex-matched healthy TB close contact were selected. The outcome was incident TB, identified using previously validated diagnostic criteria. Independent predictors were investigated using stratified Cox regression analysis. Interaction analysis was also performed.

RESULTS

A total of 5846 TB close contacts who were metformin users, metformin non-users, and healthy contacts were analysed. The incidence of active TB was 755 (600-938), 1117 (927-1335), and 526 (393-689) cases per 100,000 person-years in each group, respectively. Multivariate analysis revealed that healthy contacts had the lowest risk of developing active TB (adjusted hazard ratio [aHR]: 0.42 [0.30-0.60]) and metformin use partially reversed the risk associated with DM (aHR: 0.73 [0.54-0.98]). Subpopulation analysis revealed a significant interaction between insulin use and metformin use.

CONCLUSIONS

Metformin use is associated with a lower risk of developing active TB among TB close contacts with DM, especially for insulin users. It may be an alternative choice for primary prevention against active TB if no contraindications exist. However, prospective studies are needed to confirm the findings.

B Cell-Based Vaccine Transduced With ESAT6-Expressing Vaccinia Virus and Presenting α-Galactosylceramide Is a Novel Vaccine Candidate Against ESAT6-Expressing Mycobacterial Diseases

Early secretory antigenic target-6 (ESAT6) is a potent immunogenic antigen expressed in Mycobacterium tuberculosis as well as in some non-tuberculous mycobacteria (NTM), such as M. kansasii. M. kansasii is one of the most clinically relevant species of NTM that causes mycobacterial lung disease, which is clinically indistinguishable from tuberculosis. In the current study, we designed a novel cell-based vaccine using B cells that were transduced with vaccinia virus expressing ESAT6 (vacESAT6), and presenting α-galactosylceramide (αGC), a ligand of invariant NKT cells. We found that B cells loaded with αGC had increased levels of CD80 and CD86 after in vitro stimulation with NKT cells. Immunization of mice with B/αGC/vacESAT6 induced CD4⁺ T cells producing TNF-α and IFN-γ in response to heat-killed M. tuberculosis. Immunization of mice with B/αGC/vacESAT6 ameliorated severe lung inflammation caused by M. kansasii infection. We also confirmed that immunization with B/αGC/vacESAT6 reduced M. kansasii bacterial burden in the lungs. In addition, therapeutic administration of B/αGC/vacESAT6 increased IFN-γ⁺ CD4⁺ T cells and inhibited the progression of lung pathology caused by M. kansasii infection. Thus, B/αGC/vacESAT6 could be a potent vaccine candidate for the prevention and treatment of ESAT6-expressing mycobacterial infection caused by M. kansasii.

Impact of metformin on the risk and treatment outcomes of tuberculosis in diabetics: a systematic review

BACKGROUND

Tuberculosis (TB) remains one of the infectious diseases with a leading cause of death among adults worldwide. Metformin, a first-line medication for the treatment of type 2 diabetes, may have potential for treating TB. The aims of the present systematic review were to evaluate the impact of metformin prescription on the risk of tuberculosis diseases, the risk of latent TB infection (LTBI) and treatment outcomes of tuberculosis among patients with diabetic mellitus.

METHODS

Databases were searched through March 2019. Observational studies reporting the effect of metformin prescription on the risk and treatment outcomes of TB were included in the systematic review. We qualitatively analyzed results of included studies, and then pooled estimate effects with 95% confidence intervals (CIs) of different outcome using random-effect meta-analyses.

RESULTS

This systematic review included 6980 cases from 12 observational studies. The meta-analysis suggested that metformin prescription could decrease the risk of TB among diabetics (pooled odds ratio [OR], 0.38; 95%CI, 0.21 to 0.66). Metformin prescription was not related to a lower risk of LTBI (OR, 0.73; 95%CI, 0.30 to 1.79) in patients with diabetes. Metformin medication during the anti-tuberculosis treatment is significantly associated with a smaller TB mortality (OR, 0.47; 95%CI, 0.27 to 0.83), and a higher probability of sputum culture conversion at 2 months of TB disease (OR, 2.72; 95%CI, 1.11 to 6.69) among patients with diabetes. The relapse of TB was not statistically reduced by metformin prescription (OR, 0.55; 95%CI, 0.04 to 8.25) in diabetics.

CONCLUSIONS

According to current observational evidence, metformin prescription significantly reduced the risk of TB in patients with diabetes mellitus. Treatment outcomes of TB disease could also be improved by the metformin medication among diabetics.

Understanding the glucoregulatory mechanisms of metformin in type 2 diabetes mellitus

Despite its position as the first-line drug for treatment of type 2 diabetes mellitus, the mechanisms underlying the plasma glucose level-lowering effects of metformin (1,1-dimethylbiguanide) still remain incompletely understood. Metformin is thought to exert its primary antidiabetic action through the suppression of hepatic glucose production. In addition, the discovery that metformin inhibits the mitochondrial respiratory chain complex 1 has placed energy metabolism and activation of AMP-activated protein kinase (AMPK) at the centre of its proposed mechanism of action. However, the role of AMPK has been challenged and might only account for indirect changes in hepatic insulin sensitivity. Various mechanisms involving alterations in cellular energy charge, AMP-mediated inhibition of adenylate cyclase or fructose-1,6-bisphosphatase 1 and modulation of the cellular redox state through direct inhibition of mitochondrial glycerol-3-phosphate dehydrogenase have been proposed for the acute inhibition of gluconeogenesis by metformin. Emerging evidence suggests that metformin could improve obesity-induced meta-inflammation via direct and indirect effects on tissue-resident immune cells in metabolic organs (that is, adipose tissue, the gastrointestinal tract and the liver). Furthermore, the gastrointestinal tract also has a major role in metformin action through modulation of glucose-lowering hormone glucagon-like peptide 1 and the intestinal bile acid pool and alterations in gut microbiota composition.

Tissue Metabolic Changes Drive Cytokine Responses to Mycobacterium tuberculosis

Cellular metabolism can influence host immune responses to Mycobacterium tuberculosis. Using a systems biology approach, differential expression of 292 metabolic genes involved in glycolysis, glutathione, pyrimidine, and inositol phosphate pathways was evident at the site of a human tuberculin skin test challenge in patients with active tuberculosis infection. For 28 metabolic genes, we identified single nucleotide polymorphisms that were trans-acting for in vitro cytokine responses to M. tuberculosis stimulation, including glutathione and pyrimidine metabolism genes that alter production of Th1 and Th17 cytokines. Our findings identify novel therapeutic targets in host metabolism that may shape protective immunity to tuberculosis.

Potentials of Host-Directed Therapies in Tuberculosis Management

Tuberculosis (TB) remains as a leading cause of mortality in developing countries, persisting as a major threat to the global public health. Current treatment involving a long antibiotic regimen brings concern to the topic of patient compliance, contributing to the emergence of drug resistant TB. The current review will provide an updated outlook on novel anti-TB therapies that can be given as adjunctive agents to current anti-TB treatments, with a particular focus on modulating the host immune response to effectively target all forms of TB. Additional potential therapeutic pathway targets, including lipid metabolism alteration and vascular endothelial growth factor (VEGF)-directed therapies, are discussed.

Pulmonary tuberculous cavities in diabetic patients: Glycemic control is still the dominant factor despite the emerging role of metformin

BACKGROUND

Previous studies have reported an increased risk of cavities in diabetic patients with pulmonary tuberculosis (PTB), which may be associated with poor glycemic control. Cavities have a negative impact on PTB treatment outcomes; however, the possible interaction of other potentially confounding diabetes-related variables regarding pulmonary cavities have not been fully evaluated.

METHODS

We conducted a retrospective cohort study of diabetic patients with culture-proven PTB. The patients' chest X-rays (CXRs) and computed tomography (CT) scans were reviewed to assess the effects of clinical factors, glycosylated hemoglobin (HbA1c) levels, and antidiabetic agents on cavitary lesions.

RESULTS

Among 128 diabetic PTB patients, those with pulmonary cavities on CXRs and CT scans presented younger ages, lack of metformin treatment, and significantly higher HbA1c levels than those without cavities. Multivariate logistic regression analysis revealed significantly higher HbA1c levels in patients with cavities than in those without cavities on CXRs (odds ratio [OR], 1.34; 95% confidence interval [CI], 1.12-1.61) and CT scans (OR, 1.36; 95% CI, 1.13-1.64). Patients with multiple cavities had significantly higher HbA1c levels than those with a single cavity on CT scans (p = 0.002). No significant differences in other variables, including metformin treatment, were noted between the groups.

CONCLUSION

This study suggests that despite multiple potential confounding variables, including metformin use, poor glycemic control is still the dominant risk factor for cavitary lesions in diabetic patients with PTB. Efforts to improve glycemic control in diabetic PTB patients may be of considerable value in facilitating antimycobacterial treatment.

Manipulation of autophagy for host-directed tuberculosis therapy

Mycobacterium tuberculosis (M. tb) is one of the world’s most successful human pathogens, infecting ~2 billion people worldwide. Although there are effective drugs against M. tb., the disease remains out of control owing to prolonged and toxic treatment. Shorter regimens are urgently required to control TB. Drug-resistant TB (DR-TB) also threatens to derail TB control. These unfulfilled needs could be addressed by the identification and development of host-directed therapeutic agents for TB. Manipulation of the innate immune response, including autophagy, may lead to the identification of cellular pathways that could be exploited to develop host-directed therapeutic interventions. Host-directed therapies (HDTs) aim to augment immune mechanisms against M. tb infection and/or reduce excess inflammation, thus preventing end-organ tissue damage, preserving lung function and/or enhancing the effectiveness of TB drug therapy in eliminating infection. HDTs may also have additional advantages for patients with TB/HIV co-infection, as HDTs may reduce the risk of interaction with antiretroviral drugs and the risk of developing immune reconstitution inflammatory syndrome (IRIS) and death. In this review, we discuss the role of autophagy as a potential pathway that could be exploited as a host-directed TB therapeutic agent.

Persistent inflammation during anti-tuberculosis treatment with diabetes comorbidity

Diabetes mellitus (DM) increases risk for pulmonary tuberculosis (TB) and adverse treatment outcomes. Systemic hyper-inflammation is characteristic in people with TB and concurrent DM (TBDM) at baseline, but the impact of TB treatment on this pattern has not been determined. We measured 17 plasma cytokines and growth factors in longitudinal cohorts of Indian and Brazilian pulmonary TB patients with or without DM. Principal component analysis revealed virtually complete separation of TBDM from TB individuals in both cohorts at baseline, with hyper-inflammation in TBDM that continued through treatment completion at six months. By one year after treatment completion, there was substantial convergence of mediator levels between groups within the India cohort. Non-resolving systemic inflammation in TBDM comorbidity could reflect delayed lesion sterilization or non-resolving sterile inflammation. Either mechanism portends unfavorable long-term outcomes including risk for recurrent TB and for damaging immune pathology.

Revisiting hypoxia therapies for tuberculosis

The spectre of the coming post-antibiotic age demands novel therapies for infectious diseases. Tuberculosis (TB), caused by Mycobacterium tuberculosis, is the single deadliest infection throughout human history. M. tuberculosis has acquired antibiotic resistance at an alarming rate with some strains reported as being totally drug resistant. Host-directed therapies (HDTs) attempt to overcome the evolution of antibiotic resistance by targeting relatively immutable host processes. Here, I hypothesise the induction of hypoxia via anti-angiogenic therapy will be an efficacious HDT against TB. I argue that anti-angiogenic therapy is a modernisation of industrial revolution era sanatoria treatment for TB, and present a view of the TB granuloma as a 'bacterial tumour' that can be treated with anti-angiogenic therapies to reduce bacterial burden and spare host immunopathology. I suggest two complementary modes of action, induction of bacterial dormancy and activation of host hypoxia-induced factor (HIF)-mediated immunity, and define the experimental tools necessary to test this hypothesis.

Metformin: A review of its potential as enhancer for anti tuberculosis efficacy in diabetes mellitus-tuberculosis coinfection patients

Metformin is the most commonly prescribed drug for type 2 diabetes mellitus. Nowadays metformin is also use for efficacy in diabetes mellitus-tuberculosis coinfection patients through several mechanisms, such increasing superoxide production therefore activation isoniazid is increasing; inducing adeno-monophosphate kinase (AMPK) associated autophagy process; and regulating inflammation cytokines. This article will review the mechanism of action of Metformin as enhancer for anti tuberculosis efficacy.

Non-antibiotic adjunctive therapy: A promising approach to fight tuberculosis

Tuberculosis (TB) is currently a clinical and public health problem. There is a concern about the emergence and development of multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) species. Additionally, the lack of effective vaccines is another limitation to control the related infections. To overcome these problems various approaches have been pursued such as finding novel drug candidates with a new mechanism of action or repurposing conventional antibiotics. However, these strategies are still far from clinical application. Hence, the use of adjunctive therapy has been suggested for TB. In this paper, we review non-antibiotic adjunctive treatment options for TB. Natural products, vitamins, micronutrients, and trace elementals, as well as non-antibiotic drugs, are examples of agents which have been used as adjunctive therapies. The use of these adjunctive therapies has been shown to improve disease outcomes and reduce the adverse effects of antibiotic drugs. Employing these agents, either alone or in combination with antibiotics, might be considered as a promising approach to control TB infections and achieve better clinical outcomes. However, supportive evidence from randomized controlled trials is still scant and merits further investigations.

Metformin and Dipeptidyl Peptidase-4 Inhibitor Differentially Modulate the Intestinal Microbiota and Plasma Metabolome of Metabolically Dysfunctional Mice

OBJECTIVES

Recent evidence indicates that gut microbiota is altered considerably by a variety of commonly prescribed medications. This study assessed the impact of 2 antidiabetic therapeutics on gut microbiota and markers of cardiometabolic disease in metabolically dysfunctional mice.

METHODS

C57BL/6 mice were fed a high-fat diet for 24 weeks while receiving 1 of 2 antidiabetic therapeutics-metformin or dipeptidyl peptidase-4 (DPP-4) inhibitor, PKF-275-055-for the final 12 weeks. Mice were assessed for weight gain, glucose and cholesterol metabolism, and adiposity. In addition, cecal microbiota was analyzed by 16S compositional sequencing, and plasma metabolome was analyzed by liquid chromatography with tandem mass spectrometry.

RESULTS

Both therapeutics had similar metabolic effects, attenuating mesenteric adiposity and improving cholesterol metabolism and insulin sensitivity. However, multivariate analyses of microbiota and metabolomics data revealed clear divergence of the therapeutic groups. Although both metformin and PKF-275-055 mice displayed significantly decreased Firmicutes/Bacteroidetes ratios, only metformin harboured metabolic health-associated Akkermansia, Parabacteroides and Christensenella. Paradoxically, metformin also reduced α diversity, a metric frequently associated with host metabolic fitness. PKF-275-055 mice displayed elevated levels of butyrate-producing Ruminococcus and acetogen Dorea, with reduced levels of certain plasma sphingomyelin, phosphatidylcholine and lysophosphatidylcholine entities. In turn, metformin reduced levels of acylcarnitines, a functional group associated with systemic metabolic dysfunction. Finally, several associations were identified between metabolites and altered taxa.

CONCLUSIONS

This study represents the first direct comparison of the microbiota-modifying effects of metformin and a DPP-4 inhibitor, and proposes several putative microbial targets both in terms of novel therapeutic development and adverse effect prevention.

Metformin in tuberculosis: beyond control of hyperglycemia

Two global epidemics, diabetes mellitus (DM) and tuberculosis (TB), have converged making their control even more challenging. We herein have reviewed metformin's (MTF) effect on patients with active and latent TB, as well as discussed its newly discovered biological mechanisms in mycobacteria. Mounting evidence suggests that MTF provides better outcomes in TB patients, especially those with DM. The mechanisms by which MTF produces its benefits are multiple. Though metformin's potential has been proven in patients with DM, larger and more thorough clinical trials, in DM and non-DM-TB patients, need to be conducted. MTF could be added to the arsenal of anti-TB drugs, aiding in the goal of TB eradication worldwide.

Immunometabolism and Pulmonary Infections: Implications for Protective Immune Responses and Host-Directed Therapies

The biology and clinical efficacy of immune cells from patients with infectious diseases or cancer are associated with metabolic programming. Host immune- and stromal-cell genetic and epigenetic signatures in response to the invading pathogen shape disease pathophysiology and disease outcomes. Directly linked to the immunometabolic axis is the role of the host microbiome, which is also discussed here in the context of productive immune responses to lung infections. We also present host-directed therapies (HDT) as a clinically viable strategy to refocus dysregulated immunometabolism in patients with infectious diseases, which requires validation in early phase clinical trials as adjuncts to conventional antimicrobial therapy. These efforts are expected to be continuously supported by newly generated basic and translational research data to gain a better understanding of disease pathology while devising new molecularly defined platforms and therapeutic options to improve the treatment of patients with pulmonary infections, particularly in relation to multidrug-resistant pathogens.

Combination of Repurposed Drug Diosmin with Amoxicillin-Clavulanic acid Causes Synergistic Inhibition of Mycobacterial Growth

Effective therapeutic regimens for the treatment of tuberculosis (TB) are limited. They are comprised of multiple drugs that inhibit the essential cellular pathways in Mycobacterium tuberculosis (Mtb). The present study investigates an approach which enables a combination of Amoxicillin-Clavulanic acid (AMC) and a repurposed drug for its synergistic effect towards TB treatment. We identified Diosmin (DIO), by targeting the active site residues of L,D-transpeptidase (Ldt) enzymes involved in Mtb cell wall biosynthesis by using a structure-based drug design method. DIO is rapidly converted into aglycone form Diosmetin (DMT) after oral administration. Binding of DIO or DMT towards Ldt enzymes was studied using molecular docking and bioassay techniques. Combination of DIO (or DMT) and AMC exhibited higher mycobactericidal activity against Mycobacterium marinum as compared to individual drugs. Scanning electron microscopy study of M. marinum treated with AMC-DIO and AMC-DMT showed marked cellular leakage. M. marinum infected Drosophila melanogaster fly model showed an increased fly survival of ~60% upon treatment with a combination of AMC and DIO (or DMT). Finally, the enhanced in vitro antimicrobial activity of AMC-DIO was validated against Mtb H37Ra and a MDR clinical isolate. Our results demonstrate the potential for AMC and DIO (or DMT) as a synergistic combination for the treatment of TB.

Current and emerging therapies to combat persistent intracellular pathogens

Intracellular pathogens such as HIV, hepatitis B virus, and Mycobacterium tuberculosis are responsible for millions of deaths worldwide and represent major obstacles to global health. Current treatment options have improved patient outcomes and extended life-expectancy in many countries; however, challenges such as latency, drug-resistance, and inflammatory pathology have necessitated advancements in curative strategies which go beyond the traditional antimicrobial focus. This review highlights recent advances in host-directed therapies to eradicate intracellular pathogens or augment the endogenous immune response by targeting host cell pathways. The 'kick and kill' strategy for HIV latency, adjunct immunomodulatory compounds for tuberculosis, and pro-apoptotic small-molecule inhibitors in the case of chronic Hepatitis B are promising examples of host-directed therapies that signal a paradigm shift in treatment and management of chronic infectious disease.

Metformin inhibits IL-6 signaling by decreasing IL-6R expression on multiple myeloma cells

IL-6 signaling plays a crucial role in the pathogenesis of a number of diseases, including multiple myeloma, primary amyloidosis, cytokine release syndrome and other inflammatory conditions. It is central for the growth and survival of malignant plasma cells. IL-6R and IL-6ST receptors transduce IL-6 signaling. Molecular mechanisms regulating expression of IL-6R are not well understood and current therapies are based on monoclonal antibody to target IL-6 signaling. Small molecule inhibitors targeting IL-6 signaling are highly desirable. Metformin specifically decreased IL-6R expression which is mediated via AMPK, mTOR, and miR34a. This is a novel finding and adds to existing therapies targeting IL-6 signaling.

Discovery and validation of a prognostic proteomic signature for tuberculosis progression: A prospective cohort study

BACKGROUND

A nonsputum blood test capable of predicting progression of healthy individuals to active tuberculosis (TB) before clinical symptoms manifest would allow targeted treatment to curb transmission. We aimed to develop a proteomic biomarker of risk of TB progression for ultimate translation into a point-of-care diagnostic.

METHODS AND FINDINGS

Proteomic TB risk signatures were discovered in a longitudinal cohort of 6,363 Mycobacterium tuberculosis-infected, HIV-negative South African adolescents aged 12-18 years (68% female) who participated in the Adolescent Cohort Study (ACS) between July 6, 2005 and April 23, 2007, through either active (every 6 months) or passive follow-up over 2 years. Forty-six individuals developed microbiologically confirmed TB disease within 2 years of follow-up and were selected as progressors; 106 nonprogressors, who remained healthy, were matched to progressors. Over 3,000 human proteins were quantified in plasma with a highly multiplexed proteomic assay (SOMAscan). Three hundred sixty-one proteins of differential abundance between progressors and nonprogressors were identified. A 5-protein signature, TB Risk Model 5 (TRM5), was discovered in the ACS training set and verified by blind prediction in the ACS test set. Poor performance on samples 13-24 months before TB diagnosis motivated discovery of a second 3-protein signature, 3-protein pair-ratio (3PR) developed using an orthogonal strategy on the full ACS subcohort. Prognostic performance of both signatures was validated in an independent cohort of 1,948 HIV-negative household TB contacts from The Gambia (aged 15-60 years, 66% female), longitudinally followed up for 2 years between March 5, 2007 and October 21, 2010, sampled at baseline, month 6, and month 18. Amongst these contacts, 34 individuals progressed to microbiologically confirmed TB disease and were included as progressors, and 115 nonprogressors were included as controls. Prognostic performance of the TRM5 signature in the ACS training set was excellent within 6 months of TB diagnosis (area under the receiver operating characteristic curve [AUC] 0.96 [95% confidence interval, 0.93-0.99]) and 6-12 months (AUC 0.76 [0.65-0.87]) before TB diagnosis. TRM5 validated with an AUC of 0.66 (0.56-0.75) within 1 year of TB diagnosis in the Gambian validation cohort. The 3PR signature yielded an AUC of 0.89 (0.84-0.95) within 6 months of TB diagnosis and 0.72 (0.64-0.81) 7-12 months before TB diagnosis in the entire South African discovery cohort and validated with an AUC of 0.65 (0.55-0.75) within 1 year of TB diagnosis in the Gambian validation cohort. Signature validation may have been limited by a systematic shift in signal magnitudes generated by differences between the validation assay when compared to the discovery assay. Further validation, especially in cohorts from non-African countries, is necessary to determine how generalizable signature performance is.

CONCLUSIONS

Both proteomic TB risk signatures predicted progression to incident TB within a year of diagnosis. To our knowledge, these are the first validated prognostic proteomic signatures. Neither meet the minimum criteria as defined in the WHO Target Product Profile for a progression test. More work is required to develop such a test for practical identification of individuals for investigation of incipient, subclinical, or active TB disease for appropriate treatment and care.

AMPK-Targeted Effector Networks in Mycobacterial Infection

AMP-activated protein kinase (AMPK), a key metabolic regulator, plays an essential role in the maintenance of energy balance in response to stress. Tuberculosis (TB), primarily caused by the pathogen Mycobacterium tuberculosis (Mtb), remains one of the most important infectious diseases worldwide, characterized by both high incidence and mortality. Development of new preventive and therapeutic strategies against TB requires a profound understanding of the various host-pathogen interactions that occur during infection. Emerging data suggest that AMPK plays an essential regulatory role in host autophagy, mitochondrial biogenesis, metabolic reprogramming, fatty acid β-oxidation, and the control of pathologic inflammation in macrophages during Mtb infection. As described in this review, recent studies have begun to define the functional properties of AMPK modulators capable of restricting intracellular bacteria and promoting host defenses. Several host defense factors in the context of AMPK activation also participate in autophagic and non-autophagic pathways in a coordinated manner to enhance antimicrobial responses against Mtb infection. A better understanding of these AMPK-targeted effector networks offers significant potential for the development of novel therapeutics for human TB and other infectious diseases.

Host-directed therapies to combat tuberculosis and associated non-communicable diseases

Mycobacterium tuberculosis (Mtb) has coevolved with a human host to evade and exploit the immune system in multiple ways. Mtb is an enormously successful human pathogen that can remain undetected in hosts for decades without causing clinical disease. While tuberculosis (TB) represents a perfect prototype of host-pathogen interaction, it remains a major challenge to develop new therapies to combat mycobacterial infections. Additionally, recent studies emphasize on comorbidity of TB with different non-communicable diseases (NCDs), highlighting the impact of demographic and lifestyle changes on the global burden of TB. In the recent past, host-directed therapies have emerged as a novel and promising approach to treating TB. Drugs modulating host responses are likely to avoid the development of bacterial resistance which is a major public health concern for TB treatment. Interestingly, many of these drugs also form treatment strategies for non-communicable diseases. In general, technological advances along with novel host-directed therapies may open an exciting and promising research area, which can eventually deliver effective TB treatment as well as curtail the emergent synergy with NCDs.

Evaluation of metformin in combination with rifampicin containing antituberculosis therapy in patients with new, smear-positive pulmonary tuberculosis (METRIF): study protocol for a randomised clinical trial

INTRODUCTION

Shorter duration of treatment for the management of drug-susceptible pulmonary tuberculosis (TB) would be a significant improvement in the care of patients suffering from the disease. Besides newer drugs and regimens, other modalities like host-directed therapy are also being suggested to reach this goal. This study's objective is to assess the efficacy and safety of metformin-containing anti-TB treatment (ATT) regimen in comparison to the standard 6-month ATT regimen in the treatment of patients with newly diagnosed sputum smear-positive drug-sensitive pulmonary TB.

METHODS AND ANALYSIS

We are conducting a multicentric, randomised open-label controlled clinical trial to achieve the study objective. The intervention group will receive isoniazid (H), rifampicin (R), ethambutol (E) and pyrazinamide (Z) along with 1000 mg of daily metformin (Met) for the first 2 months while the control group will receive only HRZE. After 2 months, both the groups will receive HRE daily for 4 months. The primary endpoint is time to sputum culture conversion. Secondary endpoints will include time to detection of Mycobacterium tuberculosis in sputum, pharmacokinetics and pharmacogenomics of study drugs, drug-drug interactions, safety and tolerability of the various combinations and measurement of autophagy and immune responses in the study participants.

ETHICS AND DISSEMINATION

The ethics committee of the participating institutes have approved the study. Results from this trial will contribute to evidence towards constructing a shorter, effective and safe regimen for patients with TB. The results will be shared widely with the National Programme managers, policymakers and stakeholders through open access publications, dissemination meetings, conference abstracts and policy briefs. This is expected to provide a new standard of care for drug-sensitive patients with pulmonary TB who will not only reduce the number of clinic visits and lost to follow-up of patients from treatment but also reduce the burden on the healthcare system.

TRIAL REGISTRATION NUMBER

CTRI/2018/01/011176; Pre-results.

Diabetes and Lung Disease: A Neglected Relationship

BACKGROUND

Diabetes mellitus is a systemic disorder associated with inflammation and oxidative stress which may target many organs such as the kidney, retina, and the vascular system. The pathophysiology, mechanisms, and consequences of diabetes on these organs have been studied widely. However, no work has been done on the concept of the lung as a target organ for diabetes and its implications for lung diseases.

AIM

In this review, we aimed to investigate the effects of diabetes and hypoglycemic agent on lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis, pulmonary hypertension, and lung cancer. We also reviewed the potential mechanisms by which these effects may affect lung disease patients.

RESULTS

Our results suggest that diabetes can affect the severity and clinical course of several lung diseases.

CONCLUSIONS

Although the diabetes-lung association is epidemiologically and clinically well-established, especially in asthma, the underlying mechanism and pathophysiology are not been fully understood. Several mechanisms have been suggested, mainly associated with the pro-inflammatory and proliferative properties of diabetes, but also in relation to micro- and macrovascular effects of diabetes on the pulmonary vasculature. Also, hypoglycemic drugs may influence lung diseases in different ways. For example, metformin was considered a potential therapeutic agent in lung diseases, while insulin was shown to exacerbate lung diseases; this suggests that their effects extend beyond their hypoglycemic properties.

Latent tuberculosis infection and non-infectious co-morbidities: Diabetes mellitus type 2, chronic kidney disease and rheumatoid arthritis

The prevalence of non-communicable diseases is increasing worldwide, which coincides with the persistence of infectious diseases including tuberculosis. These can synergistically affect individual and population health. Three non-communicable diseases that are relevant because of their associated morbidity, mortality and disability are type 2 diabetes mellitus, chronic kidney disease and rheumatoid arthritis. There is some evidence that patients with these conditions are at increased risk of acquiring latent tuberculosis infection (LTBI) and of this progressing to active disease. Unfortunately, evidence on accurate testing and effective prophylactic treatment in these populations is lacking. This review discusses current evidence and recommendations for management of LTBI in these patients.

Metformin as a host-directed therapeutic in tuberculosis: Is there a promise?

To complement the development of new or repurposed drugs for improving the treatment outcomes of drug-susceptible and drug-resistant tuberculosis, current insight also focuses on the use of host-directed therapy. Metformin, a drug often used in the management of type 2 diabetes mellitus, has attracted attention by virtue of its favourable activity as an adjunctive agent against tuberculosis, discovered through laboratory and clinical studies. To definitively establish its role as a host-directed therapeutic in tuberculosis, more preclinical and clinical research is still required to better delineate its mechanism(s) of action and optimal clinical use.

Improving treatment outcomes for MDR-TB - Novel host-directed therapies and personalised medicine of the future

Multidrug-resistant TB (MDR-TB) is a major threat to global health security. In 2017, only 50% of patients with MDR-TB who received WHO-recommended treatment were cured. Most MDR-TB patients who recover continue to suffer from functional disability due to long-term lung damage. Whilst new MDR-TB treatment regimens are becoming available, conventional drug therapies need to be complemented with host-directed therapies (HDTs) to reduce tissue damage and improve functional treatment outcomes. This viewpoint highlights recent data on biomarkers, immune cells, circulating effector molecules and genetics which could be utilised for developing personalised HDTs. Novel technologies currently used for cancer therapy which could facilitate in-depth understanding of host genetics and the microbiome in patients with MDR-TB are discussed. Against this background, personalised cell-based HDTs for adjunct MDR-TB treatment to improve clinical outcomes are proposed as a possibility for complementing standard therapy and other HDT agents. Insights into the molecular biology of the mechanisms of action of cellular HDTs may also aid to devise non-cell-based therapies targeting defined inflammatory pathway(s) in Mtb-driven immunopathology.

Peptidyl-prolyl isomerase-B is involved in Mycobacterium tuberculosis biofilm formation and a generic target for drug repurposing-based intervention

Tuberculosis (TB), a disease caused by Mycobacterium tuberculosis (M.tb), takes one human life every 15 s globally. Disease relapse occurs due to incomplete clearance of the pathogen and reactivation of the antibiotic tolerant bacilli. M.tb, like other bacterial pathogens, creates an ecosystem of biofilm formed by several proteins including the cyclophilins. We show that the M.tb cyclophilin peptidyl-prolyl isomerase (PpiB), an essential gene, is involved in biofilm formation and tolerance to anti-mycobacterial drugs. We predicted interaction between PpiB and US FDA approved drugs (cyclosporine-A and acarbose) by in-silico docking studies and this was confirmed by surface plasmon resonance (SPR) spectroscopy. While all these drugs inhibited growth of Mycobacterium smegmatis (M.smegmatis) when cultured in vitro, acarbose and cyclosporine-A showed bacteriostatic effect while gallium nanoparticle (GaNP) exhibited bactericidal effect. Cyclosporine-A and GaNP additionally disrupted M.tb H₃₇Rv biofilm formation. Co-culturing M.tb in their presence resulted in significant (2–4 fold) decrease in dosage of anti-tubercular drugs- isoniazid and ethambutol. Comparison of the cyclosporine-A and acarbose binding sites in PpiB homologues of other biofilm forming infectious pathogens revealed that these have largely remained unaltered across bacterial species. Targeting bacterial biofilms could be a generic strategy for intervention against bacterial pathogens.

Tuberculosis, caused by Mycobacterium tuberculosis, is the leading cause of death due to a single infectious agent. New therapeutic options are needed, and repurposing clinically approved drugs to destroy biofilms is an attractive approach, as these microbial communities are often less susceptible to antibiotics. A team lead by Seyed Hasnain at the Indian Institute of Technology Delhi identified an enzyme, PpiB, from M. tuberculosis that promoted biofilm formation and showed that PpiB interacts with several drugs that are currently used to treat diabetes, immunological diseases and cancer. These drugs destabilise M. tuberculosis biofilms in culture and enhanced the potency of two current anti-tuberculosis antibiotics. Future work is needed to test these medications against tuberculosis in humans, but given PpiB is found in different bacteria, there may be broader promise of using these repurposed drugs to combat other infections.

Metformin induced autophagy in diabetes mellitus - Tuberculosis co-infection patients: A case study

Metformin (MET) is a potential combination drug to elevate anti-TB efficacy. However, the clinical effect, especially smear reversion, during metformin applied with anti-tuberculosis and insulin in patients with type 2 DM newly TB co-infection were remain unknown. An observational clinical study was done in DM newly TB co-infection outpatients at Surabaya Paru Hospital. This study evaluated MET therapy, at least 2 months, accompanying with insulin and anti-TB regimens and compared to comparison group. The smear, microtubule-associated Protein1 Light Chain 3B (MAP1LC3B) level, as the presentation of autophagy, Superoxide Dismutase (SOD) level, Interferon (IFN)-γ and Interleukin (IL)-10 levels were evaluated twice. From 42 participants in this study, 22 participants of observation group that received additional MET therapy, 100% had sputum smear reversion after 2-months intensive phase of anti-TB therapy. Whereas 25% of 20 participants of comparison group did not undergo reversion inserts sputum smear. As conclusion, MET has the potential of being an additive combination therapy to enhance the bactericidal effect of anti-TB on DM-TB coinfection patients. Metformin enhances the effects of anti-TB and insulin therapy in increasing the smear reversion by increasing autophagy.

Host-targeted therapy for tuberculosis: Time to revisit the concept

Tuberculosis (TB) is an important cause of morbidity and mortality worldwide. Every year millions of people die due to TB. Drug resistance has been a major factor that has obstructed successful control and treatment of TB. As the rate of spread of drug-resistant TB outpaces the rate of discovery of new anti-tubercular drugs, targeted therapy may provide a new approach to TB cure. In a scenario where drug resistance is spreading rapidly, and existing drugs regimens seem to be dwindling away, this review summarizes the concept of host-targeted therapy which may be the ray of hope for the effective management and control of the rapidly spreading drug-resistant TB (multidrug resistant and extensively drug resistant).

Elevated circulating levels of monocyte activation markers among tuberculosis patients with diabetes co-morbidity

Alteration in the frequency of monocyte subsets is a hallmark of tuberculosis-diabetes co-morbidity (TB-DM). To study this association, we examined the plasma levels of sCD14, sCD163, C-reactive protein (CRP) and soluble tissue factor (sTF) in individuals with TB-DM, TB or diabetes mellitus (DM), and in healthy controls (HC). Circulating levels of sCD14, sCD163 and sTF were significantly increased in TB-DM and DM compared with TB and HC; however, CRP was significantly increased in TB-DM and TB compared with DM and HC. During longitudinal follow up, sCD14, CRP and sTF levels remained significantly increased in TB-DM compared with TB from baseline (pre-treatment), during treatment (2nd month) and at the completion (6th month) of anti-TB treatment (ATT), whereas sCD163 was significantly higher in TB-DM compared with TB only at baseline. Moreover, the levels of sCD14 and sCD163 were significantly higher in TB-DM individuals with bilateral and cavitary disease and exhibited a significant positive relationship with bacterial burden. Levels of sCD14, sCD163 and CRP exhibited a positive relationship with HbA1c levels. Within the TB-DM group, those with known diabetes before incident TB (KDM) exhibited significantly higher levels of sCD14 and sCD163 compared with individuals with newly diagnosed DM with TB (NDM). Finally, KDM individuals on metformin treatment exhibited significantly lower levels of sCD14, sCD163 and CRP compared with those on non-metformin-containing regimens. Our data demonstrate that systemic monocyte activation marker levels reflect baseline disease severity and extent in TB-DM, differentiate KDM from NDM and are modulated by ATT and metformin therapy.

Thiazolidinediones and reduced risk of incident bacterial abscess in adults with type 2 diabetes: A population-based cohort study

AIM

Previous research has suggested that peroxisome proliferator-activated receptor-gamma (PPAR-γ) may play an important role in immunomodulation. We aimed to examine the association between thiazolidinediones, PPAR-γ agonists and incidence of bacterial abscess among patients with type 2 diabetes.

MATERIALS AND METHODS

This retrospective cohort study between 2000 and 2010 included 46 986 propensity (PS)-matched patients diagnosed with type 2 diabetes. We compared the incidence of bacterial abscess, including liver and non-liver abscesses, between patients treated with metformin plus a thiazolidinedione (M + T, N = 7831) or metformin plus a sulfonylurea (M + S, N = 39 155). Data were retrieved from a population-based Taiwanese database. We applied Cox proportional hazard regression models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), comparing M + T and M + S after PS matching.

RESULTS

During a median follow-up of 4.5 years, the incidence rate of bacterial abscess was lower with M + T than with M + S treatment (1.89 vs 3.15 per 1000 person-years) in the PS-matched cohort. M + T was associated with a reduced risk of bacterial abscess (HRs after PS matching, 0.58; 95% CI, 0.42-0.80 for total bacterial abscess; 0.54; 95% CI, 0.28-1.07 for liver abscess; 0.59; 95% CI, 0.41-0.85 for non-liver abscess). Results did not change materially after accounting for unmeasured confounding factors using high-dimenional PS matching and differential censoring between regimen groups. Rosiglitazone and pioglitazone, in combination with metformin, produced similar reductions in risk of all abscess outcomes.

CONCLUSION

We found that M + T may provide a protective benefit in reducing the incidence of bacterial abscesses. These findings merit further investigation.

Translational Research in the Nonhuman Primate Model of Tuberculosis

Infection with Mycobacterium tuberculosis predominantly establishes subclinical latent infection over the lifetime of an individual, with a fraction of infected individuals rapidly progressing to active disease. The immune control in latent infection can be perturbed by comorbidities such as diabetes mellitus, obesity, smoking, and coinfection with helminthes or HIV. Modeling the varying aspects of natural infection remains incomplete when using zebrafish and mice. However, the nonhuman primate model of tuberculosis offers a unique and accurate model to investigate host responses to infection, test novel therapeutics, and thoroughly assess preclinical vaccine candidates. Rhesus macaques and cynomolgus macaques manifest the full gamut of clinical and pathological findings in human Mycobacterium tuberculosis infection, including the ability to co-infect macaques with Simian Immunodeficiency Virus to model HIV co-infection. Here we discuss advanced techniques to assay various clinical outcomes of the natural progression of infection as well as therapeutics in development and novel preclinical vaccines. Finally, we survey the translational aspects of nonhuman primate research and argue the urgent need to thoroughly examine preclinical therapeutics and vaccines using this model prior to clinical implementation.

The Negative Clinical Impact of Diabetes on Tuberculosis: A Cross-Sectional Study in New Jersey

Context

Numerous studies have investigated a link between tuberculosis (TB) and type 2 diabetes mellitus (DM) in high-incidence countries. There is a need to characterize the relationship of TB and DM in the United States.

Objective

To characterize the clinical and demographic differences in patients with TB with and without DM.

Design

Cross-sectional.

Setting

This study was performed at an institutional center providing TB care for New Jersey.

Patients or Other Participants

A total of 353 cases of TB were seen at the Lattimore Clinic between 2009 and 2014. After excluding those with HIV infection and those under 19 years of age, 73 cases of TB were reviewed.

Intervention(s)

No interventions performed.

Main Outcome Measure(s)

Sputum culture positivity, time to culture conversion, extent of disease on chest x-ray, and degree of cavitation on chest x-ray. Outcome measures were determined prior to data collection.

Results

Extent of disease on chest x-ray was higher for DM+ cases compared with DM− cases (P = 0.007). A total of 24% of DM+ cases had evidence of cavitation on chest x-ray compared with 5% of DM− cases (P = 0.03). DM+ cases were slightly more likely to have positive sputum cultures than were DM− cases (P = 0.07). The median time to sputum culture conversion was 27.5 days in the DM+ group vs 18.0 days in the DM− group (P = 0.26).

Conclusions

Extent of disease on chest x-ray was significantly more severe in the DM+ group than in the DM− group.

AMP-Activated Protein Kinase and Host Defense against Infection

5′-AMP-activated protein kinase (AMPK) plays diverse roles in various physiological and pathological conditions. AMPK is involved in energy metabolism, which is perturbed by infectious stimuli. Indeed, various pathogens modulate AMPK activity, which affects host defenses against infection. In some viral infections, including hepatitis B and C viral infections, AMPK activation is beneficial, but in others such as dengue virus, Ebola virus, and human cytomegaloviral infections, AMPK plays a detrimental role. AMPK-targeting agents or small molecules enhance the antiviral response and contribute to the control of microbial and parasitic infections. In addition, this review focuses on the double-edged role of AMPK in innate and adaptive immune responses to infection. Understanding how AMPK regulates host defenses will enable development of more effective host-directed therapeutic strategies against infectious diseases.

Gut microbiota and intestinal FXR mediate the clinical benefits of metformin

The anti-hyperglycemic effect of metformin is believed to be caused by its direct action on signaling processes in hepatocytes, leading to lower hepatic gluconeogenesis. Recently, metformin was reported to alter the gut microbiota community in humans, suggesting that the hyperglycemia-lowering action of the drug could be the result of modulating the population of gut microbiota. However, the critical microbial signaling metabolites and the host targets associated with the metabolic benefits of metformin remained elusive. Here, we performed metagenomic and metabolomic analysis of samples from individuals with newly diagnosed type 2 diabetes (T2D) naively treated with metformin for 3 d, which revealed that Bacteroides fragilis was decreased and the bile acid glycoursodeoxycholic acid (GUDCA) was increased in the gut. These changes were accompanied by inhibition of intestinal farnesoid X receptor (FXR) signaling. We further found that high-fat-diet (HFD)-fed mice colonized with B. fragilis were predisposed to more severe glucose intolerance, and the metabolic benefits of metformin treatment on glucose intolerance were abrogated. GUDCA was further identified as an intestinal FXR antagonist that improved various metabolic endpoints in mice with established obesity. Thus, we conclude that metformin acts in part through a B. fragilis-GUDCA-intestinal FXR axis to improve metabolic dysfunction, including hyperglycemia.

The Immune Mechanisms of Lung Parenchymal Damage in Tuberculosis and the Role of Host-Directed Therapy

Impaired lung function is common in people with a history of tuberculosis. Host-directed therapy added to tuberculosis treatment may reduce lung damage and result in improved lung function. An understanding of the pathogenesis of pulmonary damage in TB is fundamental to successfully predicting which interventions could be beneficial. In this review, we describe the different features of TB immunopathology that lead to impaired lung function, namely cavities, bronchiectasis, and fibrosis. We discuss the immunological processes that cause lung damage, focusing on studies performed in humans, and using chest radiograph abnormalities as a marker for pulmonary damage. We highlight the roles of matrix metalloproteinases, neutrophils, eicosanoids and cytokines, like tumor necrosis factor-α and interleukin 1β, as well as the role of HIV co-infection. Finally, we focus on various existing drugs that affect one or more of the immunological mediators of lung damage and could therefore play a role as host-directed therapy.

Biguanides enhance antifungal activity against Candida glabrata

Candida spp. are the fourth leading cause of nosocomial blood stream infections in North America. Candida glabrata is the second most frequently isolated species, and rapid development of antifungal resistance has made treatment a challenge. In this study, we investigate the therapeutic potential of metformin, a biguanide with well-established action for diabetes, as an antifungal agent against C. glabrata. Both wild type and antifungal-resistant isolates of C. glabrata were subjected to biguanide and biguanide-antifungal combination treatment. Metformin, as well as other members of the biguanide family, were found to have antifungal activity against C. glabrata, with MIC₅₀ of 9.34 ± 0.16 mg/mL, 2.09 ± 0.04 mg/mL and 1.87 ± 0.05 mg/mL for metformin, phenformin and buformin, respectively. We demonstrate that biguanides enhance the activity of several antifungal drugs, including voriconazole, fluconazole, and amphotericin, but not micafungin. The biguanide-antifungal combinations allowed for additional antifungal effects, with fraction inhibition concentration indexes ranging from 0.5 to 1. Furthermore, metformin was able to lower antifungal MIC₅₀ in voriconazole and fluconazole-resistant clinical isolates of C. glabrata. We also observed growth reduction of C. glabrata with rapamycin and an FIC of 0.84 ± 0.09 when combined with metformin, suggesting biguanide action in C. glabrata may be related to inhibition of the mTOR complex. We conclude that the biguanide class has direct antifungal therapeutic potential and enhances the activity of select antifungals in the treatment of resistant C. glabrata isolates. These data support the further investigation of biguanides in the combination treatment of serious fungal infections.

Inhalable poly(lactic-co-glycolic acid) (PLGA) microparticles encapsulating all-trans-Retinoic acid (ATRA) as a host-directed, adjunctive treatment for Mycobacterium tuberculosis infection

Ending the tuberculosis (TB) epidemic by 2030 was recently listed in the United Nations (UN) Sustainable Development Goals alongside HIV/AIDS and malaria as it continues to be a major cause of death worldwide. With a significant proportion of TB cases caused by resistant strains of Mycobacterium tuberculosis (Mtb), there is an urgent need to develop new and innovative approaches to treatment. Since 1989, researchers have been assessing the anti-bacterial effects of the active metabolite of vitamin A, all trans-Retinoic acid (ATRA) solution, in Mtb models. More recently the antibacterial effect of ATRA has been shown to regulate the immune response to infection via critical gene expression, monocyte activation and the induction of autophagy leading to its application as a host-directed therapy (HDT). Inhalation is an attractive route for targeted treatment of TB, and therefore we have developed ATRA-loaded microparticles (ATRA-MP) within the inhalable size range (2.07 ± 0.5 µm) offering targeted delivery of the encapsulated cargo (70.5 ± 2.3%) to the site of action within the alveolar macrophage, which was confirmed by confocal microscopy. Efficient cellular delivery of ATRA was followed by a reduction in Mtb growth (H37Ra) in THP-1 derived macrophages evaluated by both the BACT/ALERT® system and enumeration of colony forming units (CFU). The antibacterial effect of ATRA-MP treatment was further assessed in BALB/c mice infected with the virulent strain of Mtb (H37Rv). ATRA-MP treatments significantly decreased the bacterial burden in the lungs alongside a reduction in pulmonary pathology following just three doses administered intratracheally. The immunomodulatory effects of targeted ATRA treatment in the lungs indicate a distinct yet effective mechanism of action amongst the formulations. This is the first study to-date of a controlled release ATRA treatment for TB suitable for inhalation that offers improved targeting of a HDT, retains antibacterial efficacy and improves pulmonary pathology compared to ATRA solution.

Metformin use is associated with a low risk of tuberculosis among newly diagnosed diabetes mellitus patients with normal renal function: A nationwide cohort study with validated diagnostic criteria

Human studies on the use of metformin as host-directed therapy (HDT) for tuberculosis (TB) are rare. We performed a nationwide cohort study to evaluate the effect of metformin on mitigating the risk of active TB among patients with diabetes mellitus (DM). Among newly diagnosed DM patients identified in the Taiwan National Health Insurance Research Database, metformin users, defined on the basis of >90 cumulative defined daily doses within 1 year, and propensity-score-matched metformin nonusers were selected. The primary outcome was incident TB, identified using diagnostic criteria validated by real patient data at a medical center. Independent predictors were investigated using Cox regression analysis. Similar analysis was performed in a subpopulation without a history of hypertensive nephropathy and renal replacement therapy. A total of 88,866 metformin users and 88,866 propensity-score-matched nonusers were selected. Validation results showed that the TB diagnostic criteria had a sensitivity of 99.13% and specificity of 99.90%. During follow-up, 707 metformin users and 807 nonusers developed active TB. Metformin use was independently associated with a lower risk of incident TB (hazard ratio [HR]: 0.84 [0.74-0.96]). TB risk was lower in high-dose metformin users than in low-dose users (HR: 0.83 [0.72-0.97]). The effect of metformin remained when analysis was restricted in the subpopulation without renal function impairment. Newly diagnosed diabetic patients without contraindication should receive metformin as an anti-diabetic medication, with potential additional benefit against TB.

The Synergistic Effects of the Glutathione Precursor, NAC and First-Line Antibiotics in the Granulomatous Response Against Mycobacterium tuberculosis

Mycobacterium tuberculosis (M. tb), the causative bacterial agent responsible for tuberculosis (TB) continues to afflict millions of people worldwide. Although the human immune system plays a critical role in containing M. tb infection, elimination proves immensely more challenging. Consequently, there has been a worldwide effort to eradicate, and limit the spread of M. tb through the conventional use of first-line antibiotics. Unfortunately, with the emergence of drug resistant and multi-drug resistant strains of M. tb the archetypical antibiotics no longer provide the same ascendancy as they once did. Furthermore, when administered, these first-line antibiotics commonly present severe complications and side effects. The biological antioxidant glutathione (GSH) however, has been demonstrated to have a profound mycobactericidal effect with no reported adverse consequences. Therefore, we examined if N-Acetyl Cysteine (NAC), the molecular precursor to GSH, when supplemented in combination with suboptimal levels of standalone first-line antibiotics would be sufficient to completely clear M. tb infection within in vitro derived granulomas from healthy subjects and individuals with type 2 diabetes (T2DM). Our results revealed that by virtue of immune modulation, the addition of NAC to subprime levels of isoniazid (INH) and rifampicin (RIF) was indeed capable of inducing complete clearance of M. tb among healthy individuals.

Tolerating the Unwelcome Guest; How the Host Withstands Persistent Mycobacterium tuberculosis

Our understanding of the host response to infections has historically focused on “resistance” mechanisms that directly control pathogen replication. However, both pathogen effectors and antimicrobial immune pathways have the capacity to damage host tissue, and the ability to tolerate these insults can also be critical for host survival. These “tolerance” mechanisms may be equally as important as resistance to prevent disease in the context of a persistent infection, such as tuberculosis, when resistance mechanisms are ineffective and the pathogen persists in the tissue for long periods. Host tolerance encompasses a wide range of strategies, many of which involve regulation of the inflammatory response. Here we will examine general strategies used by macrophages and T cells to promote tolerance in the context of tuberculosis, and focus on pathways, such as regulation of inflammasome activation, that are emerging as common mediators of tolerance.

Metformin Decreases Risk of Tuberculosis Infection in Type 2 Diabetes Patients

BACKGROUND

Metformin may show an antibiotic effect, but whether its use can reduce the risk of tuberculosis infection has rarely been investigated in population-based studies.

METHODS

This is a retrospective cohort analysis of the Taiwan's National Health Insurance database. New-onset type 2 diabetes patients, 148,468 ever users and 15,799 never users of metformin, identified during 1999⁻2005 were followed up until 31 December 2011 for the incidence of tuberculosis infection. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score.

RESULTS

A total of 360 never users and 1976 ever users developed a tuberculosis infection with respective incidence of 510.91 and 282.94 per 100,000 person⁻years. The overall hazard ratio of presenting a tuberculosis infection among metformin ever users in respect to never users was 0.552 (95% confidence interval: 0.493⁻0.617). The hazard ratios for the first (<27.10 months), second (27.10⁻58.27 months), and third (>58.27 months) tertile of cumulative duration of metformin therapy were 1.116 (0.989⁻1.261), 0.543 (0.478⁻0.618), and 0.200 (0.171⁻0.233), respectively; and were 1.037 (0.918⁻1.173), 0.533 (0.469⁻0.606), and 0.249 (0.215⁻0.288), respectively, for the first (<817,000 mg), second (817,000⁻2,047,180 mg), and third (>2,047,180 mg) tertile of cumulative doses of metformin. The findings were consistent when analyses were restricted to pulmonary tuberculosis. Additionally, regular users of metformin tended to have greater benefit than irregular users.

CONCLUSIONS

Metformin use is associated with a reduced risk of tuberculosis infection in a dose⁻response pattern in type 2 diabetes patients.

T Cell Metabolism Has Evolved to Tolerate Tuberculosis

Although T cells are important in preventing tuberculosis progression, their role in disease tolerance is unknown. Recently in Science Immunology, Tzelepis et al. (2018) have revealed that mitochondrial cyclophilin D controls T cell metabolism and proliferation, contributing to tolerance. Cyclophilin D loss leads to immunopathology and increased mortality, without impacting bacterial burden.

The effect of metformin on culture conversion in tuberculosis patients with diabetes mellitus

BACKGROUND/AIMS

Patients with diabetes mellitus (DM) and tuberculosis (TB) have increased morbidity and a high risk of treatment failure or recurrence. It is important to manage both diseases simultaneously. Among anti-diabetic drugs, metformin inhibits intracellular growth of mycobacteria. Therefore, we examined the effects of metformin on TB treatment, especially in patients with DM.

METHODS

This retrospective cohort study included patients with culture-positive pulmonary TB diagnosed between 2011 and 2012. The primary study outcome was sputum culture conversion after 2 months of treatment.

RESULTS

Of 499 patients diagnosed with culture-positive pulmonary TB, 105 (21%) had DM at diagnosis. Among them, 62 (59.5%) were treated with metformin. Baseline characteristics, except for the presence of chronic renal disease, were not significantly different between the metformin and non-metformin groups. Metformin treatment had no significant effect on sputum culture conversion (p = 0.60) and recurrence within 1 year after TB treatment completion (p = 0.39). However, metformin improved the sputum culture conversion rate in patients with cavitary pulmonary TB, who have higher bacterial loads (odds ratio, 10.8; 95% confidence interval, 1.22 to 95.63).

CONCLUSION

Among cavitary pulmonary TB patients with DM, metformin can be an effective adjunctive anti-TB agent to improve sputum culture conversion after 2 months of treatment.