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MetaboLights MTBLS26 - GNPS Lipidomic analysis of lipid droplets from murine hepatocytes reveals distinct signatures for nutritional stress.

ABSTRACT: This data set was downloaded from MetaboLights (http://www.ebi.ac.uk/metabolights/) accession number MTBLS26 Abstract:Liver steatosis can be induced by fasting or high-fat diet. We investigated by lipidomic analysis whether such metabolic states are reflected in the lipidome of hepatocyte lipid droplets (LDs) from mice fed normal chow diet (FED), fasted (FAS), or fed a high-fat diet (HFD). LC-MS/MS at levels of lipid species profiles and of lipid molecular species uncovered a FAS phenotype of LD enriched in triacylglycerol (TG) molecular species with very long-chain (VLC)-PUFA residues and an HFD phenotype with less unsaturated TG species in addition to characteristic lipid marker species. Nutritional stress did not result in dramatic structural alterations in diacylglycerol (DG) and phospholipid (PL) classes. Moreover, molecular species of bulk TG and of DG indicated concomitant de novo TG synthesis and lipase-catalyzed degradation to be active in LDs. DG species with VLC-PUFA residues would be preferred precursors for phosphatidylcholine (PC) species, the others for TG molecular species. In addition, molecular species of PL classes fitted the hepatocyte Kennedy and phosphatidylethanolamine methyltransferase pathways. We demonstrate that lipidomic analysis of LDs enables phenotyping of nutritional stress. TG species are best suited for such phenotyping, whereas structural analysis of TG, DG, and PL molecular species provides metabolic insights.

INSTRUMENT(S): LTQ-FT Thermo Scientific

ORGANISM(S): Murine

SUBMITTER: Kofeler

PROVIDER: MSV000081123 | GNPS | Tue May 30 14:26:00 BST 2017

REPOSITORIES: GNPS

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Project description:Background: Genetic elimination of c-Met signaling in the liver has been shown to impact many cellular pathways involved in repair, regeneration, lipid homeostasis and redox balance. In this study, we analyzed a nutritional model of hepatic steatosis in Met fl/fl ; Alb-Cre +/- (MetKO) mice in a 129SV/C57BL/6 background fed a high cholesterol diet for 30 days. Methods: Liver injury was determined by histopathology and plasma enzymes, transcriptomic changes were examined using gene expression microarrays, and evaluation of key molecules involved in liver damage and lipid homestasis were evaluated by Western blot analysis. Results: We observed that in comparison with wild type mice subjected to the same diet, MetKO mice developed a strong liver lipid deposition, inflammatory infiltration and increment in total bile acids synthesis and liver damage markers. Global transcriptomic changes analysis confirmed the steatosis and cholestasis induced by the high cholesterol diet. In addition, we found affected pathways related to amino acids, glutathione and lipid metabolism, oxidative stress and mitochondria dysfunction. Oxidative stress exacerbation was corroborated by lipid and protein oxidation in liver tissue. To address further, Western blot studies revealed downregulation on Erk, NF-kB and Nrf2 survival pathways and target genes (cyclin D1, SOD1, gamma-GCS), an increment in proapoptotic proteins (p53, caspase 3) and changes in nuclear receptors such as RAR and RXR, which were increased, and CAR, FXR and PPAR alfa, which were decreased, in the MetKO diet. These results are in agreement with the steatosis and cholestasis phenotype. Conclusion: Our data provide evidence of c-Met signaling involvement in lipid metabolism, and bile acids synthesis and excretion. Disruption of these pathways leads to liver dysfunction, improper metabolism and hepatocellular damage. Global transcriptome changes between WT mice vs. c-Met KO mice fed a 2% cholesterol and 0.5% sodium cholate diet (high cholesterol) or a Chow regular diet (Chow) as control. Mice were fed a high cholesterol or chow regular diet for 30 days. Liver tissue was obtained, and RNA was extracted and subjected to Illumina microarray analysis.

Project description:Purpose: To investigate alterations in subcutaneous white adipose gene expression induced by genetic AMPK activation in vivo, in mice fed a chow or a high-fat diet. Methods: Subcutaneous white adipose tissue mRNA profiles of wild-type transgenic (WT-Tg) mice and mice expressing a gain-of-function AMPK mutant gamma1 subunit (D316A-Tg) were generated by deep sequencing. Results: RNA sequencing revealed over 3000 differentially expressed genes between WT-Tg and D316A-Tg subcutaneous white adipose tissue (WATsc) from mice fed a high fat diet (HFD), of which many were classified as 'skeletal muscle-associated'. Interestingly, uncoupling protein 1 (UCP1), associated with 'beige' adipocyte formation in WATsc, was not differentially expressed. On a chow diet, many differentially expressed genes were also identified, with gene ontology analysis identifiying glycolysis, TCA cycle and brown fat differentiation as highly enriched; key features of brown adipocyte identity. HFD-associated skeletal-muscle associated gene expression was either not significantly altered, or significantly down-regulated on a chow diet, indicating a diet-induced gene signature in D316A-Tg WATsc. Conclusions: Our study revealed gene signatures indicative of brown adipocyte development on a chow diet, where no overt metabolic phenotype was observed in gain-of-function animals. When fed a HFD, WATsc from D316A-Tg mice displayed a muscle-like gene signature, expressing key components of creatine and calcium thermogenic cycles including Ckmt2 (creatine kinase, mitochondrial 2) Atp2a1 (SERCA1-sarco/endoplasmic reticulum ATPase 1) and ryr1 (ryanodine receptor 1). UCP1 expression was not altered between WT-Tg and D316A-Tg mice fed a HFD. Our findings suggest a novel role for AMPK in the regulation of white adipocyte identity and a potentially novel cell population that, when metabolically challenged, preferrentially utilise muscle-like thermogenic futile cycles independent of UCP1 to mediate whole organism energy expenditure.

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MetaboLights MTBLS26 - GNPS Lipidomic analysis of lipid droplets from murine hepatocytes reveals distinct signatures for nutritional stress.

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