The metabolic response of human macrophages to Mycobacterium tuberculosis infection

Mitochondrial dynamics and metabolism are closely associated, however, if these interactions play a role in the human macrophage response to Mycobacterium tuberculosis (Mtb) remain largely unknown. Here, human induced-pluripotent stem cell derived macrophages (iPSDM) were used to define whether mitochondrial dynamics and metabolism are modulated by Mtb infection. Macrophage bioenergetic response to infection was analysed by extracellular flux analysis (Seahorse) and unbiased metabolomics. In a complementary approach, high-content live cell imaging and single cell analysis was used to investigate changes in mitochondrial dynamics and Mtb intracellular replication. The metabolic profile of infected human macrophages showed an increase in the oxygen consumption and extracellular acidification rate after 48h of infection. Moreover, the lipidomics analysis showed a significant upregulation in the total levels of sphingomyelin and ceramide. Interestingly, these changes in metabolism were not associated with a disruption of the mitochondrial network. However, infection decreased mitochondrial protein levels, which correlated with RNA-Seq analysis showing downregulation of mitochondrial transcripts. The inhibition of glycolysis with 2-Deoxy-d-glucose promoted Mtb replication, whereas oxamate (a lactate dehydrogenase inhibitor) impaired Mtb growth. Our results show that macrophage metabolic reprogramming is required for the control of Mtb replication. Unlike other intracellular pathogens, Mtb did not induce fragmentation of the mitochondrial network, suggesting that manipulation of host cell metabolism might correlate with disruption of mitochondrial function rather than morphology.