Nicotinamide adenine dinucleotide (NAD+) is crucial for energy metabolism, oxidative stress, DNA damage repair, longevity regulation, and several signaling processes. To date, three NAD+ synthesis pathways have been found in microbiota and hosts, but the potential relationship between gut microbiota and their hosts in regulating NAD+ homeostasis remains unknown. Here, we show that an analog of the first-line tuberculosis drug pyrazinamide (a bacterial NAD+ synthesis inhibitor) affected NAD+ levels in the intestines and liver of mice and disrupted the intestinal microecological balance. Furthermore, using microbiota expressing the pyrazinamidase/nicotinamidase (PncA) gene, which is a target of pyrazinamide, hepatic NAD+ levels were greatly increased and significantly increased compared with other NAD+ precursors, and diet-induced non-alcoholic fatty liver disease (NAFLD) in mice was improved. Overall, the PncA gene in microbiota plays an important role in regulating NAD+ synthesis in the host, thereby providing a potential target for modulating the host’s NAD+ level.HighlightsPncA inhibitors disrupt gut microbiome homeostasis and reduce host NAD+ levels but do not affect NAD+ levels in cultured cellsPncA gene in microbiota affects host liver NAD metabolismPncA affects lipid metabolism-related genes and metabolites in mice with NAFLDDiet-induced NAFLD is improved by PncA overexpression in the liver of miceGraphical abstract

Traditional pathological diagnoses and clinical methods are insufficient to accurately predict the prognosis of lung adenocarcinoma (LUAD). Epithelial-mesenchymal transition (EMT) process is closely related to tumor cell migration. However, the prognostic value of EMT-related genes in LUAD is still unclear. In this study, we collected bulk RNA-sequencing (RNA-seq) and microarray data of LUAD patients from public databases and identified different expressed EMT-related genes in tumor and normal tissues. Then, we used the least absolute shrinkage and selection operator Cox regression model to develop a multigene signature in the cancer genome atlas (TCGA) cohort and validated the model in the OncoSG (Singapore Oncology Data Portal) cohort as well as other datasets. Finally, we constructed a 12-gene signature to divide LUAD patients into high-risk and low-risk groups of overall survival (OS), which has a better stability and accuracy in predicating the OS of patients compared with some other published signatures of LUAD. In addition, evaluation of the risk model using the time-related receiver operating characteristic (ROC) curve confirmed the predictive ability of the model. Functional analysis showed that these genes are related to immunity. CD8 T cell and CD4 T cell types were significantly negatively correlated with the risk score in the analysis of immune infiltration. In general, our model provides useful information that may help clinicians better predict the prognosis of LUAD patients and provides potential targets for immunotherapy of LUAD.

Background: Glycyrrhizic acid (GA), a saponin compound often used as a flavoring, can elicit anti-inflammatory and anti-tumor effects, and alleviate aging. However, the specific mechanism by which GA alters immune cell populations to produce these beneficial effects is currently unclear. Results: In this study, we systematically analyzed single-cell sequencing data of peripheral blood mononuclear cells from young mice, aged mice, and GA-treated aged mice. Our in vivo results show that GA reduced senescence-induced increases in macrophages and neutrophils, and increased numbers of lymphoid lineage subpopulations specifically reduced by senescence. In vitro, GA significantly promoted differentiation of Lin-CD117+ hematopoietic stem cells toward lymphoid lineages, especially CD8+ T cells. Moreover, GA inhibited differentiation of CD4+ T cells and myeloid (CD11b+) cells by binding to S100 calcium-binding protein 8 (S100A8) protein. Overexpression of S100A8 in Lin- CD117+ hematopoietic stem cells enhanced cognition in aged mice and the immune reconstitution of severely immunodeficient B-NDG mice. Conclusions: Collectively, GA exerts anti-aging effects by binding to S100A8 to remodel the immune system of aged mice.

Background Glycyrrhizic acid (GA), a saponin compound often used as a flavoring agent, can elicit anti-inflammatory and anti-tumor effects, and alleviate aging. However, the specific mechanism by which GA alters immune cell populations to produce these beneficial effects is currently unclear. Results In this study, we systematically analyzed single-cell sequencing data of peripheral blood mononuclear cells from young mice, aged mice, and GA-treated aged mice. Our in vivo results show that GA reduced senescence-induced increases in macrophages and neutrophils, and increased numbers of lymphoid lineage subpopulations specifically reduced by senescence. In vitro, GA significantly promoted differentiation of Lin−CD117+ hematopoietic stem cells toward lymphoid lineages, especially CD8+ T cells. Moreover, GA inhibited differentiation of CD4+ T cells and myeloid (CD11b+) cells by binding to S100 calcium-binding protein 8 (S100A8) protein. Overexpression of S100A8 in Lin− CD117+ hematopoietic stem cells enhanced cognition in aged mice and the immune reconstitution of severely immunodeficient B-NDG (NOD.CB17-Prkdcscid/l2rgtm1/Bcgen) mice. Conclusions Collectively, GA exerts anti-aging effects by binding to S100A8 to remodel the immune system of aged mice.

Nicotinamide adenine dinucleotide (NAD+) is crucial for energy metabolism, oxidative stress, DNA damage repair, longevity regulation, and several signaling processes. To date, several NAD+ synthesis pathways have been found in microbiota and mammals, but the potential relationship between gut microbiota and their hosts in regulating NAD+ homeostasis remains largely unknown. Here, we showed that an analog of the first-line tuberculosis drug pyrazinamide, which is converted by nicotinamidase/pyrazinamidase (PncA) to its active form, affected NAD+ level in the intestines and liver of mice and disrupted the homeostasis of gut microbiota. Furthermore, by overexpressing modified PncA of Escherichia coli, NAD+ levels in mouse liver were significantly increased, and diet-induced non-alcoholic fatty liver disease (NAFLD) was ameliorated in mice. Overall, the PncA gene in microbiota plays an important role in regulating NAD+ synthesis in the host, thereby providing a potential target for modulating host NAD+ level.