title: Effects of insulin-induced hypoglycaemia on lipolysis rate, lipid oxidation and adipose tissue signalling in human volunteers: a randomised clinical study.
abstract: The aims of this study were to determine the role of lipolysis in hypoglycaemia and define the underlying intracellular mechanisms.
  
  
  
  Nine healthy volunteers were randomised to treatment order of three different treatments (crossover design). Treatments were: (1) saline control; (2) hyperinsulinaemic hypoglycaemia (HH; i.v. bolus of 0.1 U/kg insulin); and (3) hyperinsulinaemic euglycaemia (HE; i.v. bolus of 0.1 U/kg insulin and 20% glucose). Inclusion criteria were that volunteers were healthy, aged >18 years, had a BMI between 19 and 26 kg/m2, and provided both written and oral informed consent. Exclusion criteria were the presence of a known chronic disease (including diabetes mellitus, epilepsy, ischaemic heart disease and cardiac arrhythmias) and regular use of prescription medication. The data was collected at the medical research facilities at Aarhus University Hospital, Denmark. The primary outcome was palmitic acid flux. Participants were blinded to intervention order, but caregivers were not.
  
  
  
  Adrenaline (epinephrine) and glucagon concentrations were higher during HH than during both HE and control treatments. NEFA levels and lipid oxidation rates (determined by indirect calorimetry) returned to control levels after 105 min. Palmitate flux was increased to control levels during HH (p = NS) and was more than twofold higher than during HE (overall mean difference between HH vs HE, 114 [95% CI 64, 165 μmol/min]; p < 0.001). In subcutaneous adipose tissue biopsies, we found elevated levels of hormone-sensitive lipase (HSL) and perilipin-1 phosphorylation 30 min after insulin injection during HH compared with both control and HE. There were no changes in the levels of adipose triglyceride lipase (ATGL), comparative gene identification-58 (CGI-58) or G0/G1switch gene 2 (G0S2) proteins. Insulin-stimulated phosphorylation of Akt and mTOR were unaffected by hypoglycaemia. Expression of the G0S2 gene increased during HE and HH compared with control, without changes in ATGL (also known as PNPLA2) or CGI-58 (also known as ABHD5) mRNA levels.
  
  
  
  These findings suggest that NEFAs become a major fuel source during insulin-induced hypoglycaemia and that lipolysis may be an important component of the counter-regulatory response. These effects appear to be mediated by rapid stimulation of protein kinase A (PKA) and HSL, compatible with activation of the β-adrenergic catecholamine signalling pathway.
  
  
  
  ClinicalTrials.gov NCT01919788 FUNDING: : The study was funded by Aarhus University, the Novo Nordisk Foundation and the KETO Study Group/Danish Agency for Science Technology and Innovation (grant no. 0603-00479, to NM).
authors.affiliation: Department of Clinical Medicine, Aarhus University, Aarhus C, Denmark. tsvo@clin.au.dk.|Department of Endocrinology and Internal Medicine Aarhus University Hospital, Nørrebrogade 44, 8000, Aarhus C, Denmark. tsvo@clin.au.dk.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Voss
authors.affiliation: Department of Nuclear Medicine, Aarhus University Hospital, Aarhus C, Denmark.
authors.forename: Mikkel H
authors.initials: MH
authors.lastname: Vendelbo
authors.affiliation: Department of Endocrinology and Internal Medicine Aarhus University Hospital, Nørrebrogade 44, 8000, Aarhus C, Denmark.
authors.forename: Ulla
authors.initials: U
authors.lastname: Kampmann
authors.affiliation: Department of Endocrinology and Internal Medicine Aarhus University Hospital, Nørrebrogade 44, 8000, Aarhus C, Denmark.
authors.forename: Steen B
authors.initials: SB
authors.lastname: Pedersen
authors.affiliation: Integrative Physiology Section, Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Nielsen
authors.affiliation: Section for Forensic Chemistry, Department of Forensic Medicine, Aarhus University, Aarhus C, Denmark.
authors.forename: Mogens
authors.initials: M
authors.lastname: Johannsen
authors.affiliation: Department of Clinical Medicine, Aarhus University, Aarhus C, Denmark.|Department of Endocrinology and Internal Medicine Aarhus University Hospital, Nørrebrogade 44, 8000, Aarhus C, Denmark.
authors.forename: Mads V
authors.initials: MV
authors.lastname: Svart
authors.affiliation: Department of Clinical Medicine, Aarhus University, Aarhus C, Denmark.|Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus C, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Jessen
authors.affiliation: Department of Clinical Medicine, Aarhus University, Aarhus C, Denmark.|Department of Endocrinology and Internal Medicine Aarhus University Hospital, Nørrebrogade 44, 8000, Aarhus C, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Møller
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002096:C-Peptide / Q000097:blood; D018592:Cross-Over Studies; D004837:Epinephrine / Q000097:blood; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005934:Glucagon / Q000097:blood; D006801:Humans; D007003:Hypoglycemia / Q000139:chemically induced* / Q000503:physiopathology*; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D019344:Lactic Acid / Q000097:blood; D050356:Lipid Metabolism / Q000502:physiology; D015227:Lipid Peroxidation / Q000502:physiology; D008066:Lipolysis / Q000502:physiology*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D019344:Lactic Acid; D005934:Glucagon; D009638:Norepinephrine; D004837:Epinephrine
keywords: ATGL; Adrenaline; HSL; Hypoglycaemia; Insulin; Intracellular signalling; Lipid oxidation; Lipolysis; PKA