Hydrogen sulfide stimulates lipid biogenesis from glutamine that is dependent on the mitochondrial NAD(P)H pool.

Mammalian cells synthesize H2S from sulfur-containing amino acids and are also exposed to exogenous sources of this signaling molecule, notably from gut microbes. As an inhibitor of complex IV in the electron transport chain, H2S can have a profound impact on metabolism, suggesting the hypothesis that metabolic reprogramming is a primary mechanism by which H2S signals. In this study, we report that H2S increases lipogenesis in many cell types, using carbon derived from glutamine rather than from glucose. H2S-stimulated lipid synthesis is sensitive to the mitochondrial NAD(P)H pools and is enabled by reductive carboxylation of α-ketoglutarate. Lipidomics analysis revealed that H2S elicits time-dependent changes across several lipid classes, e.g., upregulating triglycerides while downregulating phosphatidylcholine. Direct analysis of triglyceride concentration revealed that H2S induces a net increase in the size of this lipid pool. These results provide a mechanistic framework for understanding the effects of H2S on increasing lipid droplets in adipocytes and population studies that have pointed to a positive correlation between cysteine (a substrate for H2S synthesis) and fat mass.

Mycobacterium tuberculosis progresses through two phases of latent infection in humans.

Little is known about the physiology of latent Mycobacterium tuberculosis infection. We studied the mutational rates of 24 index tuberculosis (TB) cases and their latently infected household contacts who developed active TB up to 5.25 years later, as an indication of bacterial physiological state and possible generation times during latent TB infection in humans. Here we report that the rate of new mutations in the M. tuberculosis genome decline dramatically after two years of latent infection (two-sided p < 0.001, assuming an 18 h generation time equal to log phase M. tuberculosis, with latency period modeled as a continuous variable). Alternatively, assuming a fixed mutation rate, the generation time increases over the latency duration. Mutations indicative of oxidative stress do not increase with increasing latency duration suggesting a lack of host or bacterial derived mutational stress. These results suggest that M. tuberculosis enters a quiescent state during latency, decreasing the risk for mutational drug resistance and increasing generation time, but potentially increasing bacterial tolerance to drugs that target actively growing bacteria.

The time required to diagnose and treat lung cancer in Delhi, India: an updated experience of a public referral center

Background: Delays that postpone the evaluation and management of malignancy may lead to considerable morbidity. The primary objective of this study was to assess the time required to diagnose and treat lung cancer at an Indian public referral center that predominantly serves lower-income patients. Methods: A review of patients diagnosed with lung cancer between January 2008 and December 2016 was completed. We computed the median time intervals and inter-quartile ranges between symptom onset, definitive diagnostic investigation, confirmed histologic diagnosis, and chemotherapy initiation. Median intervals were correlated with baseline demographics and disease characteristics using Kruskal-Wallis test. Results: One thousand, three hundred and-seventy patients were selected. A majority (94.5%) with non-small cell lung cancer were diagnosed with advanced disease. After developing symptoms, patients required 101 [56­168] days to undergo a definitive diagnostic study, 107 [60­173] days to confirm a diagnosis, and 126 [85­196.8] days to initiate treatment. Patients who were previously treated for tuberculosis required more time to receive chemotherapy compared to those who were not (187 [134­261.5] days vs. 113 [75­180] days, p < 0.0001). A specialty Lung Cancer Clinic was implemented in 2012, and the mean referrals per month increased nearly four-fold (p < 0.0001), but the time required to administer treatment was not shortened. Conclusion: Among lower-income Indian patients, the most prominent delays occur prior to diagnosis. Efforts should be directed toward encouraging physicians to maintain a high index of clinical suspicion and educating patients to report concerning symptoms as early as possible.