Protective effect of metformin against tuberculosis infections in diabetic patients: an observational study of south Indian tertiary healthcare facility

Elevated levels of matrix metalloproteinases reflect severity and extent of disease in tuberculosis-diabetes co-morbidity and are predominantly reversed following standard anti-tuberculosis or metformin treatment

Background

Matrix metalloproteinases (MMPs) are considered to be key mediators of tuberculosis (TB) pathology but their role in tuberculosis – diabetes comorbidity (TB-DM) is not well understood.

Methods

To study the association of MMP levels with severity and extent of disease as well as bacterial burden in TB-DM, we examined the systemic levels of MMP-1, − 2, − 3, − 7, − 8, − 9, − 10, − 12 and − 13 in individuals with TB-DM and compared them to those with TB alone (TB) or healthy controls (HC).

Results

Circulating levels of MMP-1, − 2, − 3, − 7, − 10 and − 12 were significantly higher in TB-DM compared to both TB and HC and MMP -13 levels were higher in comparison to HC alone. To understand the effect of standard anti-tuberculosis therapy (ATT) on these MMP levels in TB-DM, we measured the levels of MMPs at the end of treatment (post-treatment). Our findings indicate that ATT is associated with a significant reduction in the levels of MMP-1, − 2, − 3, − 8 and − 13 post-treatment. Moreover, the levels of MMP-1, − 2, − 3, − 9 and − 12 were significantly higher in TB-DM individuals with cavitary disease and/or bilateral disease at baseline but not post-treatment. Similarly, the levels of MMP -1, − 2, − 3 and − 8 exhibited a significant positive relationship with bacterial burden and HbA1c levels at baseline but not post-treatment. Within the TB-DM group, those known to be diabetic before incident TB (KDM) exhibited significantly higher levels of MMP-1, − 2, − 10 and − 12 at baseline and of MMP-1 and -3 post-treatment compared to those newly diagnosed with DM (NDM). Finally, KDM individuals on metformin treatment exhibited significantly lower levels of MMP-1, − 2, − 3, − 7, − 9 and − 12 at baseline and of MMP-7 post-treatment.

Conclusions

Our data demonstrate that systemic MMP levels reflect baseline disease severity and extent in TB-DM, differentiate KDM from NDM and are modulated by ATT and metformin therapy.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3246-y) contains supplementary material, which is available to authorized users.

Metformin is associated with a lower risk of active tuberculosis in patients with type 2 diabetes

BACKGROUND AND OBJECTIVE

Metformin is an oral anti-diabetic therapy (ADT) to manage type 2 diabetes mellitus (T2DM), and has been reported to have potential anti-tuberculosis (TB) effects. This study investigates the risk of active TB among persons with T2DM who were treated with various ADT and insulin therapies.

METHODS

We conducted a nationwide population-based cohort study using the Taiwan Longitudinal Health Insurance Database, including 49 028 T2DM patients who were metformin users (n = 44 002) or non-users (n = 5026). A total of 5026 propensity score-matched pairs of metformin users and non-users with T2DM were evaluated from 1998 to 2010. The data were analysed using Cox proportional hazard models.

RESULTS

Patients with T2DM had a significantly higher rate of incident TB than did the control subjects (adjusted hazard ratio: 2.01; 95% confidence interval (95% CI): 1.80-2.25). After adjusting for comorbidities, diabetes complications, ADT type and statin use, metformin use was an independent factor for predicting a reduced risk of active TB (adjusted relative risk (aRR): 0.24; 95% CI: 0.18-0.32). The association between metformin use and active TB risk was also consistent in most subgroup analyses, except for patients with metabolic disorders (aRR: 0.46; 95% CI: 0.11-1.87). This protective effect of metformin was dose-dependent but diminished gradually in the elderly population.

CONCLUSION

Among all types of ADT and insulin therapies, metformin is the only agent with a decreased risk of active TB in the T2DM population. However, this effect was diminished in the elderly population and was not observed in patients with metabolic disorders.

Is metformin poised for a second career as an antimicrobial?

Metformin, a widely used antihyperglycaemic, has a good safety profile, reasonably manageable side-effects, is inexpensive, and causes a desirable amount of weight loss. In 4 studies of patients with tuberculosis (1 prospective and 3 retrospective), metformin administration resulted in better outcomes. In mice with several models of endotoxemia, metformin diminished levels of proinflammatory cytokines and improved survival. Laboratory studies showed effectiveness of the drug on multiple pathogens, including Trichinella spiralis, Staphylococcus aureus, Pseudomonas aeruginosa, hepatitis B virus, hepatitis C virus, and human immunodeficiency virus. Metformin administration in humans and mice produced major changes in the composition of the gut microbiota. These recently discovered microbe-modulating properties of the drug have led investigators to predict wide therapeutic utility for metformin. The recent easing in United States Food and Drug Administration (FDA) guidelines regarding administration of metformin to patients with kidney disease, and reduced anxiety about patient safety in terms of lactic acidosis, increase the probability of broadening of metformin's usage as a treatment of infectious agents. In this text we review articles pertinent to metformin's effects on microorganisms, both pathogens and commensals. We highlight the possible role of metformin in a wide range of infectious diseases and a possible expansion of its therapeutic profile in this field. A systematic review was done of PubMed indexed articles that examined the effects of metformin on a wide range of pathogens. Metformin was found to have efficacy as an antimicrobial agent in patients with tuberculosis. Mice infected with Trypanosomiasis cruzi had higher survival when also treated with metformin. The drug in vitro was active against T. spiralis, S. aureus, P. aeruginosa, and hepatitis B virus. In addition there is emerging literature on its role in sepsis. We conclude that metformin may have a potential role in the therapy for multiple infectious diseases. Metformin, in addition to its traditional effects on glucose metabolism, provides anti-microbial benefits in patients with tuberculosis and in a very wide range of other infections encounters in vitro and in vivo.

Metformin Use Reverses the Increased Mortality Associated With Diabetes Mellitus During Tuberculosis Treatment

Background

The global type 2 diabetes mellitus (DM) epidemic threatens progress made in reducing tuberculosis (TB)-related mortality worldwide. Previous clinical studies have not fully evaluated potential confounding variables in addressing the impact of DM on TB treatment outcomes. The antidiabetic agent metformin regulates autophagy and may play a role as a host-directed therapeutic adjuvant to antitubercular treatment.

Methods

We conducted a retrospective cohort study comprising patients aged ≥13 years undergoing treatment for culture-confirmed, drug-susceptible pulmonary TB. We assessed the effect of DM on mortality during TB treatment and 2-month TB sputum-culture conversion. We also evaluated the effect of metformin use on survival during TB treatment.

Results

Among 2416 patients undergoing TB treatment, after adjusting for age, sex, chronic kidney disease, cancer, hepatitis C, tobacco use, cavitary disease, and treatment adherence, patients with DM had 1.91 times higher odds (95% confidence interval [CI], 1.51-2.40) of death during TB treatment than patients without DM, and 1.72 (95% CI, 1.25-2.38) times higher odds of remaining culture-positive at 2 months. Metformin use in patients with DM was significantly associated with decreased mortality during TB treatment (hazard ratio, 0.56 [95% CI, .39-.82]), and metformin users had similar mortality as patients without DM.

Conclusions

This study suggests that despite multiple potential confounding variables, DM poses an increased risk of adverse TB treatment outcomes. There was a significant association between metformin use and decreased mortality during TB treatment, suggesting a potential role for this agent as adjunctive, host-directed therapy.

The Risk of TB in Patients With Type 2 Diabetes Initiating Metformin vs Sulfonylurea Treatment

BACKGROUND

Metformin and the sulfonylureas are common initial antidiabetic agents; the former has demonstrated anti-TB action in in vitro and animal studies. The comparative effect of metformin vs the sulfonylureas on TB risk in patients with type 2 diabetes mellitus (T2DM) remains unclear.

METHODS

In this retrospective cohort study, patients without chronic kidney disease who received a T2DM diagnosis during 2003 to 2013 were identified from the Taiwan National Health Insurance Research Database. Participants with ≥ 2 years of follow-up were reviewed and observed for TB until December 2013. Patients receiving metformin ≥ 60 cumulative defined daily dose (cDDD) and sulfonylureas < 15 cDDD in the initial 2 years were defined as metformin majors; it was the inverse for sulfonylurea majors. The two groups were matched 1:1 by propensity score and compared for TB risk by multivariate Cox regression analysis.

RESULTS

Among 40,179 patients with T2DM, 263 acquired TB (0.65%) over a mean follow-up of 6.1 years. In multivariate analysis, the initial 2-year dosage of metformin, but not that of the sulfonylureas, was an independent predictor of TB (60-cDDD increase (adjusted hazard ratio [HR], 0.931; 95% CI, 0.877-0.990) after adjustment by cofactors, including adapted diabetes complication severity index. Metformin majors had a significantly lower TB risk than that of sulfonylurea majors before and after matching (HR, 0.477; 95% CI, 0.268-0.850 and HR, 0.337; 95% CI, 0.169-0.673; matched pairs, n = 3,161). Compared with the reference group (initial 2-year metformin < 60 cDDD), metformin treatment showed a dose-dependent association with TB risk (60-219 cDDD; HR, 0.860; 95% CI, 0.637-1.161; 220-479 cDDD, HR, 0.706; 95% CI, 0.485-1.028; ≥ 480 cDDD, HR, 0.319; 95% CI, 0.118-0.863).

CONCLUSIONS

Metformin use in the initial 2 years was associated with a decreased risk of TB, and metformin users had a reduced risk compared with their sulfonylurea comparators.

Metformin Adjunctive Therapy Does Not Improve the Sterilizing Activity of the First-Line Antitubercular Regimen in Mice

Preliminary preclinical and observational studies suggest the potential utility of metformin as an adjunctive, host-directed agent for treatment of tuberculosis (TB). In this study, we sought to investigate the bactericidal and sterilizing activities of human-like exposures of metformin when given in combination with the first-line regimen against chronic tuberculosis in BALB/c mice. Mice receiving metformin adjunctive therapy had similar lung bacillary burdens with control mice during treatment, and the proportion of mice with microbiological relapse was similar between the two groups.