Metformin use and tuberculosis

Metformin shows potential as a supportive therapy for tuberculosis (TB), especially in diabetic patients. It may help limit the growth of Mycobacterium tuberculosis by activating certain cellular pathways. Studies suggest that diabetic patients taking metformin have a lower risk of developing active TB. Additionally, metformin appears to improve treatment outcomes by increasing the chances of clearing the infection and reducing TB-related deaths. However, it does not seem to have a significant effect on preventing latent TB infection, indicating that its role is more in strengthening the body’s immune response rather than directly targeting the bacteria.[2]

Despite its benefits, metformin does not appear to reduce the likelihood of TB relapse after treatment. Differences in study methods, particularly in diagnosing latent TB, may explain some of the conflicting findings. TB often remains dormant in the body until the immune system weakens, making it difficult to assess metformin’s full protective effect. However, since metformin enhances the body's defense against TB, it may help prevent latent infections from becoming active disease rather than stopping infection in the first place. This supports the idea that metformin works by boosting the immune system rather than attacking the bacteria directly.[2]

From a study in Korea, the metformin user group had a higher treatment success rate (90.3% vs. 87.6%, p < 0.01) and lower all-cause mortality (9.5% vs. 12.4%, p < 0.01) compared to non-users. No difference was found in TB-related vs. non-TB-related deaths among deceased patients. However, survival probability differed significantly for non-TB-related deaths (p < 0.01). In the PS-matched cohort, metformin users had a lower risk of death (HR 0.77, 95% CI 0.68–0.86, p < 0.01). This protective effect remained consistent across gender and pre-PS matching analyses. Metformin use was linked to reduced all-cause mortality during TB treatment, suggesting a potential role as a host-directed therapy (HDT) in TB–DM patients.[1] 

References:

1. Chung, E., Jeong, D., Mok, J., Jeon, D., Kang, H.Y., Kim, H., Kim, H., Choi, H. and Kang, Y.A., 2024. Relationship between metformin use and mortality in tuberculosis patients with diabetes: a nationwide cohort study. The Korean Journal of Internal Medicine, 39(2), p.306.

2. Yu, X., Li, L., Xia, L., Feng, X., Chen, F., Cao, S. and Wei, X., 2019. Impact of metformin on the risk and treatment outcomes of tuberculosis in diabetics: a systematic review. BMC infectious diseases, 19, pp.1-11.