Tuberculosis and comorbid depression: Association with serum indoleamine 2,3-dioxygenase activity

Area of Science:

• Immunology
• Neuroscience
• Infectious Diseases

Background:

• Tuberculosis (TB) is frequently comorbid with depression, negatively impacting treatment outcomes.
• Pro-inflammatory cytokines in TB patients can increase indoleamine 2,3-dioxygenase (IDO) activity.
• The relationship between IDO activity and depression in TB requires further investigation.

Purpose of the Study:

• To investigate the association between indoleamine 2,3-dioxygenase (IDO) activity and comorbid depression in tuberculosis patients.
• To quantify IDO activity using the kynurenine/tryptophan (KYN/TRP) ratio in TB patients with and without depression.

Main Methods:

• Newly diagnosed, treatment-naïve TB patients were assessed for depression using the Patient Health Questionnaire (PHQ)-9 scale.
• Patients were grouped based on PHQ-9 scores (≥5 indicating depression).
• Serum kynurenine (KYN) and tryptophan (TRP) levels were measured via LC-MS to calculate the KYN/TRP ratio as a marker of IDO activity.

Main Results:

• TB patients exhibited significantly higher average PHQ-9 scores (7.09 ± 2.83) compared to healthy controls (2.93 ± 1.20).
• Patients with depression (Group-II) showed significantly lower TRP, higher KYN, and a higher KYN/TRP ratio compared to those without depression (Group-I).
• A significant linear correlation was observed between PHQ-9 scores and KYN, TRP levels, and the KYN/TRP ratio.

Conclusions:

• Increased IDO activity is significantly associated with comorbid depression in tuberculosis patients.
• IDO induction may play a role in the pathophysiology of depression in the context of TB.
• These findings highlight a potential biological mechanism linking TB and depression.