title: The Flexibility of Ectopic Lipids.
abstract: In addition to the subcutaneous and the visceral fat tissue, lipids can also be stored in non-adipose tissue such as in hepatocytes (intrahepatocellular lipids; IHCL), skeletal (intramyocellular lipids; IMCL) or cardiac muscle cells (intracardiomyocellular lipids; ICCL). Ectopic lipids are flexible fuel stores that can be depleted by physical exercise and repleted by diet. They are related to obesity and insulin resistance. Quantification of IMCL was initially performed invasively, using muscle biopsies with biochemical and/or histological analysis. ¹H-magnetic resonance spectroscopy (¹H-MRS) is now a validated method that allows for not only quantifying IMCL non-invasively and repeatedly, but also assessing IHCL and ICCL. This review summarizes the current available knowledge on the flexibility of ectopic lipids. The available evidence suggests a complex interplay between quantitative and qualitative diet, fat availability (fat mass), insulin action, and physical exercise, all important factors that influence the flexibility of ectopic lipids. Furthermore, the time frame of the intervention on these parameters (short-term vs. long-term) appears to be critical. Consequently, standardization of physical activity and diet are critical when assessing ectopic lipids in predefined clinical situations.
authors.affiliation: Division of Endocrinology, Diabetes and Clinical Nutrition, Inselspital, Bern University Hospital, University of Bern, CH-3010 Bern, Switzerland. hannah.loher@bluewin.ch.
authors.forename: Hannah
authors.initials: H
authors.lastname: Loher
authors.affiliation: Department of Clinical Research & Institute of Interventional, Diagnostic and Pediatric Radiology, University of Bern, CH-3010 Bern, Switzerland. roland.kreis@insel.ch.
authors.forename: Roland
authors.initials: R
authors.lastname: Kreis
authors.affiliation: Department of Clinical Research & Institute of Interventional, Diagnostic and Pediatric Radiology, University of Bern, CH-3010 Bern, Switzerland. chris.boesch@insel.ch.
authors.forename: Chris
authors.initials: C
authors.lastname: Boesch
authors.affiliation: Division of Endocrinology, Diabetes and Clinical Nutrition, Inselspital, Bern University Hospital, University of Bern, CH-3010 Bern, Switzerland. emanuel.christ@insel.ch.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Christ
mesh_terms: D004032:Diet; D015444:Exercise / Q000502:physiology; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects; D008055:Lipids / Q000032:analysis*; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D004364:Pharmaceutical Preparations / Q000008:administration & dosage; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods
chemical_list: D008055:Lipids; D004364:Pharmaceutical Preparations
keywords: athlete’s paradox; diabetes mellitus; ectopic lipids; exercise; fasting; growth hormone deficiency; insulin resistance; intracardiomyocellular lipids; intrahepatocellular lipids; intramyocellular lipids