Diffuse gliomas often carry point mutations in isocitrate dehydrogenase (IDH1mut), resulting in metabolic stress. Although IDHmut gliomas are difficult to culture in vitro, they thrive in the brain via diffuse infiltration, suggesting brain‐specific tumor–stroma interactions that can compensate for IDH‐1 deficits. To elucidate the metabolic adjustments in clinical IDHmut gliomas that contribute to their malignancy, we applied a recently developed method of targeted quantitative RNA next‐generation sequencing to 66 clinical gliomas and relevant orthotopic glioma xenografts, with and without the endogenous IDH‐1R132H mutation. Datasets were analyzed in R using Manhattan plots to calculate distance between expression profiles, Ward's method to perform unsupervised agglomerative clustering, and the Mann Whitney U test and Fisher's exact tests for supervised group analyses. The significance of transcriptome data was investigated by protein analysis, in situ enzymatic activity mapping, and in vivo magnetic resonance spectroscopy of orthotopic IDH1mut‐ and IDHwt‐glioma xenografts. Gene set enrichment analyses of clinical IDH1mut gliomas strongly suggest a role for catabolism of lactate and the neurotransmitter glutamate, whereas, in IDHwt gliomas, processing of glucose and glutamine are the predominant metabolic pathways. Further evidence of the differential metabolic activity in these cancers comes from in situ enzymatic mapping studies and preclinical in vivo magnetic resonance spectroscopy imaging. Our data support an evolutionary model in which IDHmut glioma cells exist in symbiosis with supportive neuronal cells and astrocytes as suppliers of glutamate and lactate, possibly explaining the diffuse nature of these cancers. The dependency on glutamate and lactate opens the way for novel approaches in the treatment of IDHmut gliomas.—Lenting, K., Khurshed, M., Peeters, T. H., van den Heuvel, C. N. A. M., van Lith, S. A. M., de Bitter, T., Hendriks, W., Span, P. N., Molenaar, R. J., Botman, D., Verrijp, K., Heerschap, A., ter Laan, M., Kusters, B., van Ewijk, A., Huynen, M. A., van Noorden, C. J. F., Leenders, W. P. J. Isocitrate dehydrogenase 1–mutated human gliomas depend on lactate and glutamate to alleviate metabolic stress. FASEB J. 33, 557–571 (2019). http://www.fasebj.org

Type 2 diabetes mellitus confers a threefold increased risk for tuberculosis, but the underlying immunological mechanisms are still largely unknown. Possible mediators of this increased susceptibility are short-chain fatty acids, levels of which have been shown to be altered in individuals with diabetes. We examined the influence of physiological concentrations of butyrate on cytokine responses to Mycobacterium tuberculosis (Mtb) in human peripheral blood mononuclear cells (PBMCs). Butyrate decreased Mtb-induced proinflammatory cytokine responses, while it increased production of IL-10. This anti-inflammatory effect was independent of butyrate's well-characterised inhibition of HDAC activity and was not accompanied by changes in Toll-like receptor signalling pathways, the eicosanoid pathway, or cellular metabolism. In contrast blocking IL-10 activity reversed the effects of butyrate on Mtb-induced inflammation. Alteration of the gut microbiota, thereby increasing butyrate concentrations, can reduce insulin resistance and obesity, but further studies are needed to determine how this affects susceptibility to tuberculosis.

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SummaryAimsOne potential risk factor for posttraumatic stress disorder (PTSD) involves the low activity (short; s) allelic variant of the serotonin transporter‐linked polymorphic region (5‐HTTLPR), possibly due to reduced prefrontal control over the amygdala. Evidence shows that DNA methylation/demethylation is crucial for fear extinction in these brain areas and is associated with neuronal activation marker c‐Fos expression. We hypothesized that impaired fear extinction in serotonin transporter knockout (5‐HTT −/−) rats is related to changes in DNA (de) methylation and c‐Fos expression in the prefrontal cortex (PFC) and/or amygdala.Methods5‐HTT −/− and 5‐HTT +/+ rats were subjected to fear extinction. 2 hours after the extinction session, the overall levels of DNA methylation (5‐mC), demethylation (5‐hmC), and c‐Fos in fear extinction and nonfear extinction rats were measured by immunohistochemistry.Results5‐HTT −/− rats displayed decreased fear extinction. This was associated with reduced c‐Fos activity in the infralimbic PFC. In the central nucleus of the amygdala, c‐Fos immunoreactivity was increased in the fear extinction group compared to the no‐fear extinction group, regardless of genotype. 5‐hmC levels were unaltered in the PFC, but reduced in the amygdala of nonextinction 5‐HTT −/− rats compared to nonextinction wild‐type rats, which caught up to wild‐type levels during fear extinction. 5‐mC levels were stable in central amygdala in both wild‐type and 5‐HTT −/− extinction rats. Finally, c‐Fos and 5‐mC levels were correlated with the prelimbic PFC, but not amygdala.ConclusionsIn the amygdala, DNA demethylation, independent from c‐Fos activation, may contribute to individual differences in risk for PTSD, as conferred by the 5‐HTTLPR s‐allele.