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Spaceflight Activates Lipotoxic Pathways in Mouse Liver.

ABSTRACT: Spaceflight affects numerous organ systems in the body, leading to metabolic dysfunction that may have long-term consequences. Microgravity-induced alterations in liver metabolism, particularly with respect to lipids, remain largely unexplored. Here we utilize a novel systems biology approach, combining metabolomics and transcriptomics with advanced Raman microscopy, to investigate altered hepatic lipid metabolism in mice following short duration spaceflight. Mice flown aboard Space Transportation System -135, the last Shuttle mission, lose weight but redistribute lipids, particularly to the liver. Intriguingly, spaceflight mice lose retinol from lipid droplets. Both mRNA and metabolite changes suggest the retinol loss is linked to activation of PPAR?-mediated pathways and potentially to hepatic stellate cell activation, both of which may be coincident with increased bile acids and early signs of liver injury. Although the 13-day flight duration is too short for frank fibrosis to develop, the retinol loss plus changes in markers of extracellular matrix remodeling raise the concern that longer duration exposure to the space environment may result in progressive liver damage, increasing the risk for nonalcoholic fatty liver disease.

SUBMITTER: Jonscher KR

PROVIDER: S-EPMC4838331 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Spaceflight Activates Lipotoxic Pathways in Mouse Liver.

Jonscher Karen R KR Alfonso-Garcia Alba A Suhalim Jeffrey L JL Orlicky David J DJ Potma Eric O EO Ferguson Virginia L VL Bouxsein Mary L ML Bateman Ted A TA Stodieck Louis S LS Levi Moshe M Friedman Jacob E JE Gridley Daila S DS Pecaut Michael J MJ

PloS one 20160420 4

Spaceflight affects numerous organ systems in the body, leading to metabolic dysfunction that may have long-term consequences. Microgravity-induced alterations in liver metabolism, particularly with respect to lipids, remain largely unexplored. Here we utilize a novel systems biology approach, combining metabolomics and transcriptomics with advanced Raman microscopy, to investigate altered hepatic lipid metabolism in mice following short duration spaceflight. Mice flown aboard Space Transportati ...[more]

PMID: 27097220

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Project description:Background and aimsHepatic macrophages can be activated by many factors such as gut-derived bacterial components and factors released from damaged hepatocytes. Macrophage polarization toward a proinflammatory phenotype (M1) represents an important event in the disease progression of nonalcoholic fatty liver disease (NAFLD). However, the underlying molecular mechanisms remain incompletely understood. Exosomes have been identified as important mediators for cell-cell communication by transferring various biological components such as microRNAs (miRs), proteins, and lipids. The role of exosomes in crosstalk between hepatocytes and macrophages in disease progression of NAFLD is yet to be explored.Approach and resultsIn the present study, we reported that lipotoxic injury-induced release of hepatocyte exosomes enriched with miR-192-5p played a critical role in the activation of M1 macrophages and hepatic inflammation. Serum miR-192-5p levels in patients with NAFLD positively correlated with hepatic inflammatory activity score and disease progression. Similarly, the serum miR-192-5p level and the number of M1 macrophages, as well as the expression levels of the hepatic proinflammatory mediators, were correlated with disease progression in high-fat high-cholesterol diet-fed rat models. Lipotoxic hepatocytes released more miR-192-5p-enriched exosomes than controls, which induced M1 macrophage (cluster of differentiation 11b-positive [CD11b+ ]/CD86+ ) activation and increase of inducible nitric oxide synthase, interleukin 6, and tumor necrosis factor alpha expression. Furthermore, hepatocyte-derived exosomal miR-192-5p inhibited the protein expression of the rapamycin-insensitive companion of mammalian target of rapamycin (Rictor), which further inhibited the phosphorylation levels of Akt and forkhead box transcription factor O1 (FoxO1) and resulted in activation of FoxO1 and subsequent induction of the inflammatory response.ConclusionsHepatocyte-derived exosomal miR-192-5p plays a critical role in the activation of proinflammatory macrophages and disease progression of NAFLD through modulating Rictor/Akt/FoxO1 signaling. Serum exosomal miR-192-5p represents a potential noninvasive biomarker and therapeutic target for nonalcoholic steatohepatitis.

Dataset Information

Spaceflight Activates Lipotoxic Pathways in Mouse Liver.

Publications

Spaceflight Activates Lipotoxic Pathways in Mouse Liver.

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