Institute of Laboratory Animal Science

There is mounting scientific evidence indicating a robust association between gut microbiota and nonalcoholic fatty liver disease (NAFLD). Exposure to commensal microbiota in germ-free mice has a significant impact on the regulatory mechanisms of gut genes, in contrast to those conventionally raised. In this study, we have successfully inoculated the gut microbiota from healthy individuals and NAFLD patients into germ-free mice, with the objective of developing a humanized mouse model that accurately replicates the gut microenvironment of NAFLD patients. Changes in blood composition and liver pathology in these mice were systematically measured. Furthermore, we have conducted a detailed analysis of the variations in fecal microbiota and differential metabolites in the blood composition. Our findings indicate a high degree of similarity in disease characteristics between mice colonized with microbiota and humans suffering from NAFLD. Notably, we have observed a strong correlation between alterations in serum differential metabolites and gut microbiota in these mice. KEY MESSAGES: A humanized NFALD mouse model was established based on sterile mice. In microbiota-colonized mice and humans with NAFLD, disease characteristics showed a high degree of similarity. There was a strong association between changes in serum differential metabolites and gut microbiota in mice colonized by intestinal microbiota.

ABSTRACT The markedly reduced pathogenicity of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Omicron variant in comparison to earlier strains has raised critical questions regarding its underlying mechanisms. To elucidate the host immune responses driving these differences, we performed single-cell transcriptomic profiling of lung and blood samples from human angiotensin-converting enzyme 2 (hACE2) transgenic mice infected with either the SARS-CoV-2 prototype strain or the Omicron BA.1 variant at 5 days post-inoculation. Both strains induced a reduction in lung cell numbers, with capillary endothelial cells showing the highest number of differentially expressed genes (DEGs). Shared transcriptional responses included upregulation of chemokine (e.g. Gnaq, Lyn, Ccl5) and IL-17 signaling pathways. Notably, Omicron BA.1 infection resulted in downregulation of Txnip, a key gene involved in oxidative stress responses. Genes associated with neutrophil granules and pro-inflammatory functions (Mmp8, S100a8, S100a9) were also downregulated, whereas wound healing pathways were upregulated in immature neutrophils. Additionally, Omicron BA.1 altered gene expression associated with neutrophil migration from blood to lung, and decreased the activation of cell chemotaxis, cytokine-mediated signaling, IL-17 and NF-κB pathways in pro-inflammatory monocytes and pulmonary interstitial macrophages. These findings highlight distinct immunological signatures contributing to the attenuated pathogenicity of Omicron BA.1, particularly through the modulation of neutrophil and monocyte-macrophage responses.

Abstract The protein DDA1 is involved in protein degradation, cell cycle regulation, and DNA damage repair. Recent studies have revealed its differential expression across various tumor types. However, the manner in which how DDA1 functions as a tumorigenic factor remains to be elucidated. Through experiments in multiple glioblastoma cell models, we identified a physical association between cytoplasmic DDA1 and Raptor, a key component of lysosome-associated mTORC1. Amino acid stimulation triggers phosphorylation of DDA1 at serine 33, promoting its nuclear translocation and involvement in DNA damage repair. Integrated genomic and transcriptomic analysis revealed that the amino-acid-mTORC1-DDA1S33-DNA repair axis regulates the expression of a subset of metabolic genes, including ENO2, a glycolytic enzyme; CA12, which contributes to intracellular and extracellular pH homeostasis; and NMRK1, a key enzyme in nicotinamide riboside metabolism. Notably, DDA1 deficiency markedly impaired glioblastoma growth and triggered a compensatory upregulation of metabolic activity to sustain tumor cell survival. These metabolic genes supply essential nutrients required for effective DNA repair. Our findings establish DDA1 as a previously unrecognized phosphorylation target downstream of amino-acid-mTORC1, serving as both a critical mediator of mTORC1-driven DNA damage response and a key regulator of glioblastoma progression, thereby expanding our understanding of gliomagenesis.

Organ-specific metabolic pathways, including those related to mitochondrial metabolism, could provide insight into mechanisms underlying sepsis-induced organ dysfunction. However, it remains unclear if metabolic changes result from or precede clinical organ dysfunction. To determine if blood concentrations of the mitochondrial metabolites acetylcarnitine and l-carnitine correlate with organ-specific signals of sepsis-induced dysfunction, we performed a series of translational analyses of two cohorts of human sepsis and experiments using a murine model of polymicrobial sepsis. We evaluated the association between mitochondrial metabolites and clinical indices of organ function. In the blood of patients with sepsis or septic shock, we found metabolic signals of dysfunctional mitochondrial β-oxidation that were correlated with clinical measures of renal and liver dysfunction. The relevance of these findings was corroborated in an experimental model that showed distinct patterns of change in organ metabolism that correlated with the blood acetylcarnitine to l-carnitine ratio. In addition, sepsis-induced changes in organ metabolism were distinct in the liver and kidney, highlighting the unique energy economies of each organ. Importantly, metabolic changes preceded changes in clinical indices of organ function and histological evidence of cellular apoptosis. On the basis of these findings, sepsis-induced disruption in blood concentrations of specific metabolites could serve as more physiologically relevant indicators of early organ dysfunction than those we presently use. These early metabolite signals provide mechanistic insights into altered metabolism that may hold the key to timely identification of impending organ dysfunction. This could lead to strategies directed at the interruption of sepsis-induced organ failure.