title: High fat diet-induced modifications in membrane lipid and mitochondrial-membrane protein signatures precede the development of hepatic insulin resistance in mice.
abstract: OBJECTIVE
  Excess lipid intake has been implicated in the pathophysiology of hepatosteatosis and hepatic insulin resistance. Lipids constitute approximately 50% of the cell membrane mass, define membrane properties, and create microenvironments for membrane-proteins. In this study we aimed to resolve temporal alterations in membrane metabolite and protein signatures during high-fat diet (HF)-mediated development of hepatic insulin resistance.
  
  
  METHODS
  We induced hepatosteatosis by feeding C3HeB/FeJ male mice an HF enriched with long-chain polyunsaturated C18:2n6 fatty acids for 7, 14, or 21 days. Longitudinal changes in hepatic insulin sensitivity were assessed via the euglycemic-hyperinsulinemic clamp, in membrane lipids via t-metabolomics- and membrane proteins via quantitative proteomics-analyses, and in hepatocyte morphology via electron microscopy. Data were compared to those of age- and litter-matched controls maintained on a low-fat diet.
  
  
  RESULTS
  Excess long-chain polyunsaturated C18:2n6 intake for 7 days did not compromise hepatic insulin sensitivity, however, induced hepatosteatosis and modified major membrane lipid constituent signatures in liver, e.g. increased total unsaturated, long-chain fatty acid-containing acyl-carnitine or membrane-associated diacylglycerol moieties and decreased total short-chain acyl-carnitines, glycerophosphocholines, lysophosphatidylcholines, or sphingolipids. Hepatic insulin sensitivity tended to decrease within 14 days HF-exposure. Overt hepatic insulin resistance developed until day 21 of HF-intervention and was accompanied by morphological mitochondrial abnormalities and indications for oxidative stress in liver. HF-feeding progressively decreased the abundance of protein-components of all mitochondrial respiratory chain complexes, inner and outer mitochondrial membrane substrate transporters independent from the hepatocellular mitochondrial volume in liver.
  
  
  CONCLUSIONS
  We assume HF-induced modifications in membrane lipid- and protein-signatures prior to and during changes in hepatic insulin action in liver alter membrane properties - in particular those of mitochondria which are highly abundant in hepatocytes. In turn, a progressive decrease in the abundance of mitochondrial membrane proteins throughout HF-exposure likely impacts on mitochondrial energy metabolism, substrate exchange across mitochondrial membranes, contributes to oxidative stress, mitochondrial damage, and the development of insulin resistance in liver.
authors: Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstrasse 1, 85764 Neuherberg, Munich, Germany ; Member of German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: M
authors: M
authors: Kahle
authors: Research Unit Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany ; Member of German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: A
authors: A
authors: Schäfer
authors: Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstrasse 1, 85764 Neuherberg, Munich, Germany.
authors: A
authors: A
authors: Seelig
authors: Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstrasse 1, 85764 Neuherberg, Munich, Germany ; Member of German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: J
authors: J
authors: Schultheiß
authors: Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstrasse 1, 85764 Neuherberg, Munich, Germany ; Member of German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: M
authors: M
authors: Wu
authors: Research Unit Analytical Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: M
authors: M
authors: Aichler
authors: Institute of Bioinformatics and Systems Biology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: J
authors: J
authors: Leonhardt
authors: German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany ; Gene Center, Ludwig-Maximilians-Universität München, Feodor Lynen-Straße 25, 81377 Munich, Germany.
authors: B
authors: B
authors: Rathkolb
authors: German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany ; Member of German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: J
authors: J
authors: Rozman
authors: Research Unit Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: H
authors: H
authors: Sarioglu
authors: Research Unit Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany ; Member of German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: S M
authors: SM
authors: Hauck
authors: Research Unit Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany ; Member of German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: M
authors: M
authors: Ueffing
authors: Gene Center, Ludwig-Maximilians-Universität München, Feodor Lynen-Straße 25, 81377 Munich, Germany.
authors: E
authors: E
authors: Wolf
authors: Institute of Bioinformatics and Systems Biology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: G
authors: G
authors: Kastenmueller
authors: Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstrasse 1, 85764 Neuherberg, Munich, Germany ; Institute of Experimental Genetics, Genome Analysis Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: J
authors: J
authors: Adamski
authors: Research Unit Analytical Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: A
authors: A
authors: Walch
authors: Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstrasse 1, 85764 Neuherberg, Munich, Germany ; German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany ; Member of German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: M
authors: M
authors: Hrabé de Angelis
authors: Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstrasse 1, 85764 Neuherberg, Munich, Germany ; German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany ; Member of German Center for Diabetes Research (DZD), Ingolstädter Landstraße 1, 85764 Neuherberg, Munich, Germany.
authors: S
authors: S
authors: Neschen
keywords: 2-[14C]DG, 2-[1-14C]deoxyglucose; ALT, alanine aminotransferase; AUC, area under the curve; B, basal; Basal, 17 h fasting; Clamp; DAG, diacylglycerol; Diabetes; EGP, endogenous (hepatic) glucose production; GIR, glucose infusion rate; HF, high-fat diet; Hepatosteatosis; IS, insulin-stimulated; LF, low-fat diet; Metabolomics; Mitochondria; NEFA, non-esterified fatty acids; PCaa, diacylglycerophosphocholine; PCae, glycerophosphocholine; Proteomics; ROS, reactive oxygen species; Ra, rate of appearance; Rd, rate of disappearance; Rg, glucose metabolic index; SM, sphingolipid; TAG, triacylglycerol; WAT, white adipose tissue; lysoPC, lysophosphatidylcholines