Mobilisation des lipides du tissu adipeux et insulinorésistance. Dominique Langin

Transcription

1 Obesity Research Laboratory Institut Universitaire de France Franco-Czech Laboratory for Clinical Research on Obesity Mobilisation des lipides du tissu adipeux et insulinorésistance Dominique Langin Séminaire Pédagogique CNBBMM, Anglet, 215

2 Storage and mobilization of fat in adipocyte After a meal (high insulin levels): fat storage In case of energy needs (low insulin levels): mobilization of fat (adipose tissue lipolysis) Fatty acids Storage Triglycerides Mobilization Fatty acids Muscle Liver

3 Storage and mobilization of fat in adipocyte Triglycerides LPL Fatty acids Esterification Triglycerides Glycerol 3-phosphate Lipolysis Glut4 Fatty Acids + Glycerol To liver, muscle To liver

4 Coordination of the regulation of fat deposition and fat mobilization in white adipose tissue After a meal Triglycerides LPL FAT, Energy needs Gut + Glycerol 3-phophate Fatty acids Esterification + Triglycerides - Catecholamines + ANP, BNP Lipases Pancreas Glut4 Insulin + Fatty Acids + Glycerol To liver, muscle, heart To liver

5 Human adipose tissue lipolysis Insulin receptor Natriuretic peptide receptor A GC PI3-K PKB cgmp MGL PLINA β 1/2 -AR PDE-3B camp 5 AMP PKG PKA HSL TG CGI58 ATGL GS2 Antilipolytic GPCRs (GPR19A, GPR81, ) Prog Lipid Res 29 48: Trends Endocrinol Metab :

6 Insulin action on glucose metabolism Insulin Insulin stimulates glucose uptake in skeletal muscle and inhibits glucose production by the liver. The uptake of glucose in adipose tissue is quantitatively minor but has major systemic effect on insulin sensitivity.

7 Insulin resistance : an obesity-associated metabolic status X Insulin X X Resistance to the action of insulin uptake in skeletal muscle, liver and adipose tissue leads to compensatory hyperinsulinemia.

8 Type 2 diabetes X X X Insulin X Pancreatic b cell failure combined to insulin resistance results in type 2 diabetes.

9 Role of fatty acids and others products of adipose tissue in the appearance of insulin resistance Adipose tissue in excess releases lipids (fatty acids and others) and proteins in blood circulation Insulin does not inhibit glucose production Liver Lipids Proteins Insulin resistance Muscle Insulin does not stimulate glucose use Diabetes Cardiovascular diseases

10 Adipose tissue infiltration by macrophages in obesity

11 Role of fatty acids, lipokines and adipokines in the genesis of obesity complications Immune response Fibrosis Adipocyte dysfunction & death Cell Rep 214 7: FFA / Lipokines / Adipokines Thrombosis Hyperlipidemia NASH production utilization intolerance Insulin resistance Insulinemia Myocardial performance OBESITY COMPLICATIONS

12 Approaches to medical research in human obesity Clinical studies Mouse models Cell lines and primary cultures - In vivo : metabolism and body composition - Ex vivo and in vitro : work on adipose tissue (and other tissue) samples - Transgenic models - Kinetics studies - In vivo : metabolism and body composition - Ex vivo and in vitro : work on adipose tissue (and other tissue) samples - Many human and animal models - Cell lines vs. Primary cultures - Metabolic and signaling pathways - Protein overexpression and gene silencing

13 log HOMA-IR log HOMA-IR Insulin sensitivity and basal lipolysis in humans (glycerol release from adipose tissue explants) Cohort crosssectional study log lipolysis r=.3 p=.1 r=.3 p=.2 log lipolysis Bariatric surgery longitudinal follow up Increased lipolysis is associated with increased insulin resistance PLoS Biol :e11485

14 Putative consequences of low lipolysis in human obesity Trends Endocrinol Metab :

15 Which mouse models to investigate the relationship between adipose tissue lipolysis and insulin sensitivity in human obesity? HSL-/- WT ATGL-/- - Impaired weight gain on high fat diet! - Impaired adipogenesis due to defect in PPARg ligand production - WAT with a brown fat-like phenotype - Marked inflammation of WAT - Increased weight gain on high fat diet - Defect in thermogenesis - BAT with a white fat-like phenotype - Defect in PPARa ligand production premature death from cardiac dysfunction HSL and ATGL null mice are not appropriate models

16 Energy expenditure kcal/day Fat mass (%of body weight) HSL haploinsufficient mice fed high fat diet : a model of partial lipolysis deficiency in obesity (Western blot, lipase activity, in vitro and in vivo lipolysis, EchoMRI, fat pad mass, adipose tissue histology, in vitro adipogenesis, food intake, indirect calorimetry) Wild type mice HSL +/- mice HSL 1 WT HSL +/- HSL O 2 CO Decreased lipolytic capacity No difference in body weight compared to wild type No change in fat mass, weights of adipose tissue depots and adipogenesis capacity No difference in food intake and energy expenditure Day Night O 2 CO 2 PLoS Biol :e11485

17 Adipose tissue immune response and lipolysis inhibition WT (RT-qPCR, flow cytometry, conditioned media) Macrophage and inflammatory marker gene expression HSL +/- WT TG HSL FA HSL +/-? Macrophage number TG HSL FA Adipose tissue inflammation is not altered by HSL inhibition

18 Glycerol (µm) Emr1 mrna levels CD45 and F4/8 positive cells (fold change) Adipose tissue immune response and lipolysis stimulation (human adipocytes and macrophages, TLR4 mutant mice) *** $$$ ** $$ Vehicle HSLi WT TLR4 mut WT TLR4 mut WT TLR4 mut FA FA X TLR4 TG Interleukins FA X Chemiokines Cytokines Dietary and de novo lipogenesis-derived fatty acids do not activate macrophages but promote storage of lipids

19 µmol palmitate/kg/min Lipid metabolism in HSL haploinsufficient mice fed high fat diet ( 14 C-palmitate turnover) Wild type mice HSL +/- mice TG HSL FA TG oxidation TG TG * *** *** WT HSL +/- HSL TG FA TG oxidation TG TG Oxidation Storage Turnover Decreased fatty acid turnover : decreased lipolysis decreased storage and oxidation Decreased triacylglycerol content in skeletal muscle, liver and heart

20 pirs1tyr612/irs1 (arbitrary unit) pakt Ser473/Akt (arbitrary unit) (g/l) metabolism in high fat diet-fed mice with lower HSL activity (insulin, glucose and pyruvate tolerance tests; respiratory quotient; in vivo 14 C-2 deoxyglucose uptake; skeletal muscle glucose oxidation, liver insulin signaling, liver de novo lipogenesis) Wild type mice Glc oxidation insulin * * Time (min) HFD NCD WT HSL +/- HSL +/- mice Glc oxidation insulin Saline Insulin * 1.5 ** WT HSL +/- WT HSL +/- Increased use of carbohydrates, glucose uptake and glucose oxidation Increased insulin and glucose tolerance in mice with decreased lipolysis. Improvement of insulin action in skeletal muscle and liver

21 Effect of a selective HSL inhibitor on insulin tolerance in obese mice (g/l) AUC (a.u.) Body weight (g) Triolein hydrolysis (%) % of basal glucose AUC (a.u.) Insulin 15 min (ng/ml) 12 Cos7 cells 8 4 Chemical structure of HSLi Basal HSLi HSL Basal HSLi ATGL High fat diet-fed mice Lepr db / Lepr db mice ** Time (min) Fat mass Lean mass %of body weight Vehicle HSLi Time (min) * Body weight (g)4 Chronic pharmacological inhibition of HSL improves insulin action without affecting body weight.

22 metabolism in adipose tissue and systemic insulin action B. Kahn s lab Insulin K. Frayn s lab RBP4 Lipokines? RBP4 Lipokines? ChREBP DNL Compared to control mice, plasma RBP4 levels are no modified in HSL +/- and HSLi-treated mice.

23 carbon incorporation in fatty acids uptake WAT sirna-mediated knockdown of HSL in human adipocytes (glucose uptake, glucose and fatty acid oxidation, de novo lipogenesis) sigfp (control cells) Insulin Glycerol-3-P Triacylglycerol HSL Glycerol Fatty acid Fatty acid sigfp sihsl Basal sigfp sihsl Basal * Insulin * Insulin sihsl Insulin Glycerol-3-P Triacylglycerol HSL Glycerol Fatty acid Fatty acid Decreased lipolysis decreased fatty acid oxidation Increased glucose uptake and de novo lipogenesis

24 Upregulation of glycolysis and de novo lipogenesis genes in human adipocytes (DNA microarray, RTqPCR) Upregulation of glucose transporter 4 Other genes are known targets of the lipogenic transcription factor ChREBP

25 De novo lipogenesis and lipolytic capacity in humans (DNA microarray, glycerol release from adipose tissue explants) transporter 4 gene expression is negatively associated with lipolysis as are the lipogenic transcription factor ChREBP and fatty acid synthase

26 Chronic inhibition of adipocyte lipolysis and de novo lipogenesis gene expression in humans (isolated adipocytes, RTqPCR) Eight week treatment with the antilipolytic drug, nicotinic acid, upregulates de novo lipogenesis mrna levels in adipocytes from obese men

27 The improvement in glucose flux and intracellular fate is (at least partially) dependent on ChREBP sirna-mediated knockdown of HSL and ChREBP in human adipocytes (glucose uptake, glucose oxidation, de novo lipogenesis) uptake GLUT4 gene expression oxidation De novo lipogenesis

28 De novo lipogenesis? Liver Triglycerides Lipolysis Fatty acids Insulin resistance Muscle The inhibition of fat mobilization (lipolysis) by fat cells decreases insulin resistance by increasing de novo lipogenesis De novo lipogenesis Triglycerides Lipolysis? Fatty acids Restoration of insulin sensitivity Liver Muscle

29 New class of lipids : derivatives of hydroxy fatty acids OAHFAs: (O-acyl)- -hydroxy fatty acids OA HPA Stabilization of meibomian lipid films (a.k.a. tear films) FAHFAs : fatty acid esters of hydroxy fatty acids

30 Putative role of FAHFAs Yore et al. 214 Cell 159:

31 Conclusion Insulin? DNL? Adipokines Liver TG? Lipolysis Lipokines NEFA Restoration of insulin sensitivity Muscle Deciphering the cell autonomous (intracellular and/or paracrine) and endocrine mechanisms of insulin sensitivity improvement induced by lipolysis inhibition.

32 Marianne Houssier Pauline Morigny Amandine Girousse Sylvie Caspar-Bauguil Isabelle Vila Geneviève Tavernier Valentin Barquissau Diane Beuzelin Carine Valle Corinne Lefort Marie-Adeline Marques Catherine Koldtitz Aline Mairal Laurent Monbrun Etienne Mouisel Nathalie Viguerie Cédric Moro Peter Arner, Stockholm Rudolf Zechner, Graz Catherine Postic, Paris Mikael Ryden, Stockholm Stefan Hallen, Göteborg Anne Bouloumié, Toulouse Cecilia Holm, Lund Thierry Sulpice, Toulouse Hervé Guillou, Toulouse Jacques Grober, Dijon Lenka Rossmeislova, Prague Vladimir Stich, Prague AstraZeneca