Role of Glutamine Metabolism in Host Defense Against Mycobacterium tuberculosis Infection

Abstract

Background: Rewiring cellular metabolism is important for activation of immune cells during host defense against Mycobacterium tuberculosis. Glutamine has been implicated as an immunomodulatory nutrient, but its role in the response to M. tuberculosis is unknown.

Methods: We assessed expression of glutamine pathway genes in M. tuberculosis-infected macrophages and blood transcriptomic profiles of individuals with latent M. tuberculosis infection or tuberculosis. Subsequently, we studied the effect of blocking glutaminolysis on M. tuberculosis-induced cytokines. Finally, we examined whether polymorphisms in genes involved in the glutamine pathway influence M. tuberculosis-induced cytokines in a cohort of 500 individuals.

Results: Glutamine pathway genes were differentially expressed in infected macrophages and patients with tuberculosis. Human peripheral blood mononuclear cells stimulated with M. tuberculosis displayed decreased cytokine (ie, interleukin 1β, interferon γ, and interleukin 17) responses when medium was devoid of glutamine. Specific inhibitors of the glutamine pathway led to decreased cytokine responses, especially T-cell cytokines (ie, interferon γ, interleukin 17, and interleukin 22). Finally, genetic polymorphisms in glutamine metabolism genes (including GLS2, SLC1A5, and SLC7A5) influenced ex vivo cytokine responses to M. tuberculosis, especially for T-cell cytokines.

Conclusions: Cellular glutamine metabolism is implicated in effective host responses against M. tuberculosis. Targeting immunometabolism may represent new strategies for tuberculosis prevention and/or treatment.

Keywords: M. tuberculosis; Tuberculosis; cytokines; glutamine metabolism; immune response; immunometabolism.