Heightened circulating levels of antimicrobial peptides in tuberculosis-Diabetes co-morbidity and reversal upon treatment

Defensins: A novel weapon against Mycobacterium tuberculosis?

Tuberculosis (TB) is a serious airborne communicable disease caused by organisms of the Mycobacterium tuberculosis (Mtb) complex. Although the standard treatment antimicrobials, including isoniazid, rifampicin, pyrazinamide, and ethambutol, have made great progress in the treatment of TB, problems including the rising incidence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB), the severe toxicity and side effects of antimicrobials, and the low immunity of TB patients have become the bottlenecks of the current TB treatments. Therefore, both safe and effective new strategies to prevent and treat TB have become a top priority. As a subfamily of cationic antimicrobial peptides, defensins are rich in cysteine and play a vital role in resisting the invasion of microorganisms and regulating the immune response. Inspired by studies on the roles of defensins in host defence, we describe their research history and then review their structural features and antimicrobial mechanisms, specifically for fighting Mtb in detail. Finally, we discuss the clinical relevance, therapeutic potential, and potential challenges of defensins in anti-TB therapy. We further debate the possible solutions of the current application of defensins to provide new insights for eliminating Mtb.

A multi-center, prospective cohort study of whole blood gene expression in the tuberculosis-diabetes interaction

Diabetes mellitus (DM) increases tuberculosis (TB) severity. We compared blood gene expression in adults with pulmonary TB, with or without diabetes mellitus (DM) from sites in Brazil and India. RNA sequencing (RNAseq) performed at baseline and during TB treatment. Publicly available baseline RNAseq data from South Africa and Romania reported by the TANDEM Consortium were also analyzed. Across the sites, differentially expressed genes varied for each condition (DM, TB, and TBDM) and no pattern classified any one group across all sites. A concise signature of TB disease was identified but this was expressed equally in TB and TBDM. Pathway enrichment analysis failed to distinguish TB from TBDM, although there was a trend for greater neutrophil and innate immune pathway activation in TBDM participants. Pathways associated with insulin resistance, metabolic dysfunction, diabetic complications, and chromosomal instability were positively correlated with glycohemoglobin. The immune response to pulmonary TB as reflected by whole blood gene expression is substantially similar with or without comorbid DM. Gene expression pathways associated with the microvascular and macrovascular complications of DM are upregulated during TB, supporting a syndemic interaction between these coprevalent diseases.

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.

Longitudinal trends in glycated hemoglobin during and after tuberculosis treatment

AIMS

To investigate the impact of pulmonary TB on glycemic status during and after TB treatment, and associations of glycemic trends with antidiabetic therapy and TB outcomes.

METHODS

Data from two prospective cohort studies of adults in Chennai, India, with pulmonary TB were combined for this analysis. Participants were classified by baseline hemoglobin A1_c (A1C) as having normoglycemia (NG; n = 74), prediabetes (pre-DM; n = 110), or diabetes (DM; n = 244). Repeat A1C measurements were performed at TB treatment months 3 and 6, and then 6 and 12 months after TB treatment completion.

RESULTS

Median A1C at baseline declined after TB treatment initiation in all groups. No baseline NG or pre-DM participants progressed to DM by end of study, while 16.7% of baseline DM participants shifted to pre-DM or NG levels of A1C. In the baseline DM group, rising A1C after the intensive phase of TB treatment was significantly associated with adverse TB outcomes.

CONCLUSIONS

Incident TB promotes transient glucose elevation but was not conclusively shown to promote chronic dysglycemia. Rising A1C during and after TB treatment may predict unfavorable treatment response in persons presenting with A1C ≥ 6.5 % at the time of TB diagnosis.

Therapeutic Role of Antimicrobial Peptides in Diabetes Mellitus

Antimicrobial peptides (AMPs) have recently become widely publicized because they have the potential to function in alternative therapies as “natural” antibiotics, with their main advantage being a broad spectrum of activity. The potential for antimicrobial peptides to treat diabetes mellitus (DM) has been reported. In diabetes mellitus type I (T1D), cathelicidin-related antimicrobial peptide (CRAMP), cathelicidin antimicrobial peptide (CAMP) and mouse-β- defensin 14 (mBD14) are positively affected. Decreased levels of LL-37 and human neutrophil peptide 1-3 (HNP1-3) have been reported in diabetes mellitus type II (T2D) relative to healthy patients. Moreover, AMPs from amphibians and social wasps have antidiabetic effects. In infections occurring in patients with tuberculosis-diabetes or diabetic foot, granulysin, HNP1, HNP2, HNP3, human beta-defensin 2 (HBD2), and cathelicidins are responsible for pathogen clearance. An interesting alternative is also the use of modified M13 bacteriophages containing encapsulated AMPs genes or phagemids.

Human beta defensin levels and vaginal microbiome composition in post-menopausal women diagnosed with lichen sclerosus

Human beta defensins (hBDs) may play an important role in the progression of lichen sclerosus (LS), due to their ability to induce excessive stimulation of extracellular matrix synthesis and fibroblast activation. The genetic ability of the individual to produce defensins, the presence of microbes influencing defensin production, and the sensitivity of microbes to defensins together regulate the formation of an ever-changing balance between defensin levels and microbiome composition. We investigated the potential differences in postmenopausal vaginal microbiome composition and vaginal hBD levels in LS patients compared to non-LS controls. LS patients exhibited significantly lower levels of hBD1 (p = 0.0003), and significantly higher levels of hBD2 (p = 0.0359) and hBD3 (p = 0.0002), compared to the control group. The microbiome of the LS patients was dominated by possibly harmful bacteria including Lactobacillus iners, Streptococcus anginosus or Gardnerella vaginalis known to initiate direct or indirect damage by increasing defensin level production. Our observations highlight that correcting the composition of the microbiome may be applicable in supplementary LS therapy by targeting the restoration of the beneficial flora that does not increase hBD2-3 production.

Super-Resolution Microscopy Reveals a Direct Interaction of Intracellular Mycobacterium tuberculosis with the Antimicrobial Peptide LL-37

The antimicrobial peptide LL-37 inhibits the growth of the major human pathogen Mycobacterium tuberculosis (Mtb), but the mechanism of the peptide–pathogen interaction inside human macrophages remains unclear. Super-resolution imaging techniques provide a novel opportunity to visualize these interactions on a molecular level. Here, we adapt the super-resolution technique of stimulated emission depletion (STED) microscopy to study the uptake, intracellular localization and interaction of LL-37 with macrophages and virulent Mtb. We demonstrate that LL-37 is internalized by both uninfected and Mtb infected primary human macrophages. The peptide localizes in the membrane of early endosomes and lysosomes, the compartment in which mycobacteria reside. Functionally, LL-37 disrupts the cell wall of intra- and extracellular Mtb, resulting in the killing of the pathogen. In conclusion, we introduce STED microscopy as an innovative and informative tool for studying host–pathogen–peptide interactions, clearly extending the possibilities of conventional confocal microscopy.

Adults with Mycobacterium tuberculosis infection and pre-diabetes have increased levels of QuantiFERON interferon-gamma responses

BACKGROUND

Diabetes is associated with increased prevalence of TB infection in the US. We assessed associations between diabetes and interferon-gamma (IFN-γ) TB antigen response among adults with TB infection using US representative data.

METHODS

National Health and Nutrition Examination (NHANES) participants >19 years from 2011 to 2012 with positive QuantiFERON®-TB Gold-In-Tube (QFT) results were eligible. Diabetes was defined by combination of self-report and glycated hemoglobin (HbA1c). Quantitative IFN-γ TB antigen was classified as high (≥10 IU/mL), intermediate (1.01-9.99 IU/mL), or low (0.35-1.00 IU/mL). Analyses accounted for NHANES weighted design.

RESULTS

Among NHANES participants >19 years, n = 513 had positive QFT (5.9%). Among those with positive QFT, diabetes prevalence was 22.2% and pre-diabetes was 25.9%. Overall, 16.7% of positive QFT participants had high IFN-γ TB antigen levels including 21.7% among those with diabetes, 20.8% among those with pre-diabetes, and 12.6% among euglycemic participants. In adjusted analyses, high IFN-γ TB antigen response was more common among those with pre-diabetes (aOR 1.9, 95%CI 1.0, 3.6) compared to euglycemic participants.

CONCLUSION

Higher antigen responses may reflect immunopathy consistent with an exaggerated inflammatory but ineffectual response to TB or a reflection of more Mtb replication in participants with pre-diabetes or diabetes.

Diminished systemic levels of antimicrobial peptides in tuberculous lymphadenitis and their reversal after anti-tuberculosis treatment

Pulmonary tuberculosis is associated with higher plasma levels of antimicrobial peptides (AMPs) and lower granulysin levels. However, the association of AMPs with tuberculous lymphadenitis (TBL) is not well studied. Hence, we measured the plasma levels of human beta defensin-2 (HBD2), granulysin, human neutrophil peptides 1-3 (HNP1-3) and cathelicidin (LL37) in TBL compared to latent tuberculosis (LTB) and healthy controls (HC) and in TBL individuals upon completion of anti-tuberculosis treatment (ATT). We examined the association of AMPs with TBL lymph node culture grade or lymph node involvement. Finally, the discriminatory potential of these proteins was assessed using receiver operating characteristic (ROC) analysis. TBL individuals display significantly diminished circulating levels of AMPs (granulysin and HNP1-3) but not HBD-2 and LL-37 in comparison to LTB and HCs. Similarly, after ATT, both HBD-2 and HNP1-3 were significantly elevated and LL-37 was significantly reduced in TBL individuals. Granulysin and HNP1-3 discriminates TBL from LTB and HC individuals upon ROC analysis. AMPs did not exhibit significant correlation either with lymph node culture grades or lymph node involvement. Overall, TBL individuals show decreased AMPs and their reversal after ATT suggesting their association with underlying immune alteration in this poorly studied form of TB disease.

IL-22 produced by type 3 innate lymphoid cells (ILC3s) reduces the mortality of type 2 diabetes mellitus (T2DM) mice infected with Mycobacterium tuberculosis

Previously, we found that pathological immune responses enhance the mortality rate of Mycobacterium tuberculosis (Mtb)-infected mice with type 2 diabetes mellitus (T2DM). In the current study, we evaluated the role of the cytokine IL-22 (known to play a protective role in bacterial infections) and type 3 innate lymphoid cells (ILC3s) in regulating inflammation and mortality in Mtb-infected T2DM mice. IL-22 levels were significantly lower in Mtb-infected T2DM mice than in nondiabetic Mtb-infected mice. Similarly, serum IL-22 levels were significantly lower in tuberculosis (TB) patients with T2DM than in TB patients without T2DM. ILC3s were an important source of IL-22 in mice infected with Mtb, and recombinant IL-22 treatment or adoptive transfer of ILC3s prolonged the survival of Mtb-infected T2DM mice. Recombinant IL-22 treatment reduced serum insulin levels and improved lipid metabolism. Recombinant IL-22 treatment or ILC3 transfer prevented neutrophil accumulation near alveoli, inhibited neutrophil elastase 2 (ELA2) production and prevented epithelial cell damage, identifying a novel mechanism for IL-22 and ILC3-mediated inhibition of inflammation in T2DM mice infected with an intracellular pathogen. Our findings suggest that the IL-22 pathway may be a novel target for therapeutic intervention in T2DM patients with active TB disease.

Evidence that changes in antimicrobial peptides during tuberculosis are related to disease severity, clinical presentation, specific therapy and levels of immune-endocrine mediators

Given the role of host defense peptides (HDPs) in the defensive response against mycobacteria, we analyzed the circulating levels of LL-37, β-defensin-2 and -3 in newly diagnosed patients with pulmonary (PTB) or pleural tuberculosis (PLTB) in whom measurements of pleural fluids were also performed. Severe PTB patients displayed higher circulating amounts of β-defensin-3, statistically different from controls, further decreasing upon antimycobacterial treatment. LL-37 concentrations appeared within the normal range at diagnosis, but tended to increase during treatment, becoming statistically upon its completion in moderate cases. PLTB patients revealed decreased levels of β-defensin-2 in presence of increased amounts of β-defensin-3 and LL-37; in their plasma or pleural fluids. Considering the immune-endocrine dysregulation of tuberculosis, we also performed correlation analysis detecting positive associations between levels of cortisol, IL-6 and β-defensin-3 in plasma from untreated severe patients as did their dehydroepiandrosterone and LL-37 values. Increased presence of β-defensins, may represent an attempt to improve defensive mechanisms; which also take part in the inflammatory reaction accompanying TB, reinforced by the association with immune-endocrine mediators. The divergent profile of PLTB patients, decreased β-defensin-2 but increased β-defensin-3 and LL-37 levels, suggests a differential role of these HDPs in a situation characterized for its better protective response.

Association of Fok1 VDR polymorphism with Vitamin D and its associated molecules in pulmonary tuberculosis patients and their household contacts

Status of Fok I VDR polymorphism along with vitamin D, Vitamin D receptor (VDR), and cathelicidin levels in Tuberculosis (TB) patients compared to household contacts and implication of these findings in susceptibility to TB is not known. 150 active TB patients, 150 household contacts and 150 healthy controls were recruited from North Indian population. Fok1 VDR polymorphism was studied by polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP).VDR mRNA and protein levels were studied using quantitative real time PCR (q rt PCR) and enzyme linked immunosorbent assay (ELISA) respectively. Cathelicidin and Vitamin D levels were measured using ELISA and chemiluminescence immunoassay (CLIA) respectively. Significant association was found between Fok1 polymorphism and susceptibility to TB (P < 0.0005). VDR mRNA, VDR protein and vitamin D levels were significantly lower in active TB group when compared to household contacts and healthy controls (P < 0.0001, 0.0001 and 0.0005 respectively). Cathelicidin levels were higher in active TB patients compared to other groups (P < 0.0001). Expression of VDR and cathelicidin was significantly higher among 'FF' genotypes of VDR (more active form of VDR) compared to 'ff' genotype (less active form of VDR). 'f' allele was associated with increased susceptibility to TB. Higher frequency of 'F' allele, increased VDR expression along with increased vitamin D levels in household contacts compared to active TB group might be responsible for protection against active TB.

Status of vitamin D and the associated host factors in pulmonary tuberculosis patients and their household contacts: A cross sectional study

Innate immunity plays an important role in pathophysiology of tuberculosis which is influenced by various host factors. One such factor is vitamin D which, along with its associated molecule, can alter the host defense against Mycobacterium Tuberculosis (M.Tb.) via altered production of cathelicidin and nitric oxide, both having bactericidal effect. Therefore, assessment of vitamin D and its associated molecules in tuberculosis patients and household contacts as compared to healthy controls were done and the implication of these findings in susceptibility to tuberculosis (TB) was studied. 80 active TB patients, 75 household contacts and 70 healthy controls were included. Vitamin D receptor (VDR), vitamin D binding protein (VDBP) and inducible nitric oxide synthase (iNOS) mRNA levels were studied using quantitative PCR. Serum VDR, cathelicidin, and iNOS levels were measured using ELISA. Vitamin D and NO levels were measured in serum using chemiluminescence based immunoassay and greiss reaction based colorimetry kit respectively. Decreased serum levels of vitamin D were observed in active TB patients as compared to healthy controls (p < 0.001). VDR and iNOS mRNA levels were found to be significantly lower in active TB patients compared to household contacts and healthy controls (p < 0.0001 and 0.005 respectively). VDBP mRNA expression was found to be lower in active TB group as compared to household contacts and healthy controls however the difference was not found to be significant (p > 0.21). Although, mRNA expression of VDR, VDR protein and iNOS along with vitamin D levels were significantly (p < 0.05) higher in household contacts compared to active TB group. However, levels of iNOS, NO and cathelicidin were found to be higher in TB patients as compared to household contacts and healthy controls (p < 0.01, 0.05 and 0.01 respectively). Higher levels of Vitamin D along with VDR and iNOS expression in household contacts as compared to active TB patients suggest vitamin D might have a protective role against TB plausibly decreasing disease susceptibility. Low vitamin D levels in active TB patients warrants further studies to determine the role of vitamin D supplementation in prevention and treatment of TB.

Infection resisters: targets of new research for uncovering natural protective immunity against Mycobacterium tuberculosis

“Infection resisters” are broadly defined as individuals who despite significant exposure to Mycobacterium tuberculosis remain persistently unreactive to conventional detection assays, suggesting that they remain uninfected or rapidly clear their infection early on following exposure. In this review, we highlight recent studies that point to underlying host immune mechanisms that could mediate this natural resistance. We also illustrate some additional avenues that are likely to be differently modulated in resisters and possess the potential to be targeted, ranging from early mycobacterial sensing leading up to subsequent killing. Emerging research in this area can be harnessed to provide valuable insights into the development of novel therapeutic and vaccine strategies against M. tuberculosis.

Heterogeneity in the cytokine profile of tuberculosis - diabetes co-morbidity

Tuberculosis - diabetes (TB-DM) co-morbidity is characterized by heterogeneity in clinical and biochemical parameters between newly diagnosed diabetic individuals with TB (TB-NDM) and known diabetic individuals at incident TB (TB-KDM). However, the immunological profile underlying this heterogeneity is not explored. To identify the cytokine profiles in TB-NDM and TB-KDM individuals, we examined the plasma cytokine levels as well as TB-antigen stimulated levels of pro-inflammatory cytokines. TB-KDM individuals exhibit significantly higher levels of IFNγ, IL-2, TNFα, IL-17A, IL-1α, IL-1β and IL-6 in comparison to TB-NDM, TB alone and DM alone individuals. TB-NDM individuals are characterized by significantly lower levels of blood glucose and glycated hemoglobin in comparison to TB-KDM with both groups exhibiting a significant lowering of glycated hemoglobin levels at 6  months of anti-tuberculosis therapy (ATT). TB-NDM individuals are characterized by significantly diminished - unstimulated levels of IFNγ, IL-2, TNFα, IL-17A, IL-1α, IL-1β and IL-12 at pre-treatment, of IFNγ, IL-2 and IL-1α at 2  months of ATT and IL-2 at post-treatment in comparison to TB-KDM. TB-NDM individuals are also characterized by significantly diminished TB-antigen stimulated levels of IFNγ, IL-2, TNFα, IL-17A, IL-17F, IL-1α, IL-1β and/or IL-6 at pre-treatment and at 2  months of ATT and IFNγ, IL-2, IL-1α and IL-1β at post-treatment. In addition, TB-NDM individuals are characterized by significantly diminished mitogen - stimulated levels of IL-17F and IL-6 at pre-treatment and IL-6 alone at 6 months of ATT. Therefore, our data reveal considerable heterogeneity in the immunological underpinnings of TB-DM co-morbidity. Our data also suggest that TB-NDM exhibits a characteristic profile, which is both biochemically and immunologically distinct from TB-KDM.

Metabolomics applied to the discovery of tuberculosis and diabetes mellitus biomarkers

Tuberculosis (TB) and diabetes mellitus Type 2 (DM2) are two diseases as ancient as they are harmful to human health. The outcome for both diseases in part depends on immune and metabolic individual responses. DM2 is increasing yearly, mainly due to environmental, genetic and lifestyle habits. There are multiple evidence that DM2 is one of the most important risk factor of becoming infected with TB or reactivating latent TB. Mass spectrometry-based metabolomics is an important tool for elucidating the metabolites and metabolic pathways that influence the immune responses to M. tuberculosis infection during diabetes. We provide an up-to-date review highlighting the importance and benefit of metabolomics for identifying biomarkers as candidate molecules for diagnosis, disease activity or prognosis.