title: mTORC2 and AMPK differentially regulate muscle triglyceride content via Perilipin 3.
abstract: OBJECTIVE
  We have recently shown that acute inhibition of both mTOR complexes (mTORC1 and mTORC2) increases whole-body lipid utilization, while mTORC1 inhibition had no effect. Therefore, we tested the hypothesis that mTORC2 regulates lipid metabolism in skeletal muscle.
  
  
  METHODS
  Body composition, substrate utilization and muscle lipid storage were measured in mice lacking mTORC2 activity in skeletal muscle (specific knockout of RICTOR (Ric mKO)). We further examined the RICTOR/mTORC2-controlled muscle metabolome and proteome; and performed follow-up studies in other genetic mouse models and in cell culture.
  
  
  RESULTS
  Ric mKO mice exhibited a greater reliance on fat as an energy substrate, a re-partitioning of lean to fat mass and an increase in intramyocellular triglyceride (IMTG) content, along with increases in several lipid metabolites in muscle. Unbiased proteomics revealed an increase in the expression of the lipid droplet binding protein Perilipin 3 (PLIN3) in muscle from Ric mKO mice. This was associated with increased AMPK activity in Ric mKO muscle. Reducing AMPK kinase activity decreased muscle PLIN3 expression and IMTG content. AMPK agonism, in turn, increased PLIN3 expression in a FoxO1 dependent manner. PLIN3 overexpression was sufficient to increase triglyceride content in muscle cells.
  
  
  CONCLUSIONS
  We identified a novel link between mTORC2 and PLIN3, which regulates lipid storage in muscle. While mTORC2 is a negative regulator, we further identified AMPK as a positive regulator of PLIN3, which impacts whole-body substrate utilization and nutrient partitioning.
authors.affiliation: Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark; Institute for Diabetes and Obesity, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Kleinert
authors.affiliation: Charles Perkins Centre, School of Molecular Bioscience, The University of Sydney, Sydney, Australia; Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Australia.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Parker
authors.affiliation: Charles Perkins Centre, School of Molecular Bioscience, The University of Sydney, Sydney, Australia; Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Australia.
authors.forename: Rima
authors.initials: R
authors.lastname: Chaudhuri
authors.affiliation: Charles Perkins Centre, School of Molecular Bioscience, The University of Sydney, Sydney, Australia; Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Australia.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Fazakerley
authors.affiliation: Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Annette
authors.initials: A
authors.lastname: Serup
authors.affiliation: Charles Perkins Centre, School of Molecular Bioscience, The University of Sydney, Sydney, Australia; Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Australia.
authors.forename: Kristen C
authors.initials: KC
authors.lastname: Thomas
authors.affiliation: Charles Perkins Centre, School of Molecular Bioscience, The University of Sydney, Sydney, Australia; Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Australia.
authors.forename: James R
authors.initials: JR
authors.lastname: Krycer
authors.affiliation: Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Lykke
authors.initials: L
authors.lastname: Sylow
authors.affiliation: Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Fritzen
authors.affiliation: Charles Perkins Centre, School of Molecular Bioscience, The University of Sydney, Sydney, Australia; Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Australia.
authors.forename: Nolan J
authors.initials: NJ
authors.lastname: Hoffman
authors.affiliation: Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Jeppesen
authors.affiliation: Institute of Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Schjerling
authors.affiliation: Biozentrum, University of Basel, Basel, Switzerland.
authors.forename: Markus A
authors.initials: MA
authors.lastname: Ruegg
authors.affiliation: Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Bente
authors.initials: B
authors.lastname: Kiens
authors.affiliation: Charles Perkins Centre, School of Molecular Bioscience, The University of Sydney, Sydney, Australia; Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Australia; Sydney Medical School, The University of Sydney, Sydney, Australia.
authors.forename: David E
authors.initials: DE
authors.lastname: James
authors.affiliation: Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark. Electronic address: erichter@nexs.ku.dk.
authors.forename: Erik A
authors.initials: EA
authors.lastname: Richter
keywords: Akt; Metabolism; PLIN3; RICTOR; mTOR