title: Leucine-sensitive hyperinsulinaemic hypoglycaemia in patients with loss of function mutations in 3-Hydroxyacyl-CoA Dehydrogenase.
abstract: BACKGROUND
  Loss of function mutations in 3-Hydroxyacyl-CoA Dehydrogenase (HADH) cause protein sensitive hyperinsulinaemic hypoglycaemia (HH). HADH encodes short chain 3-hydroxacyl-CoA dehydrogenase, an enzyme that catalyses the penultimate reaction in mitochondrial β-oxidation of fatty acids. Mutations in GLUD1 encoding glutamate dehydrogenase, also cause protein sensitive HH (due to leucine sensitivity). Reports suggest a protein-protein interaction between HADH and GDH. This study was undertaken in order to understand the mechanism of protein sensitivity in patients with HADH mutations.
  
  
  METHODS
  An oral leucine tolerance test was conducted in controls and nine patients with HADH mutations. Basal GDH activity and the effect of GTP were determined in lymphoblast homogenates from 4 patients and 3 controls. Immunoprecipitation was conducted in patient and control lymphoblasts to investigate protein interactions.
  
  
  RESULTS
  Patients demonstrated severe HH (glucose range 1.7-3.2 mmol/l; insulin range 4.8-63.8 mU/l) in response to the oral leucine load, this HH was not observed in control patients subjected to the same leucine load. Basal GDH activity and half maximal inhibitory concentration of GTP was similar in patients and controls. HADH protein could be co-immunoprecipitated with GDH protein in control samples but not in patient samples.
  
  
  CONCLUSIONS
  We conclude that GDH and HADH have a direct protein-protein interaction, which is lost in patients with HADH mutations causing leucine induced HH. This is not associated with loss of inhibitory effect of GTP on GDH (as in patients with GLUD1 mutations).
authors.affiliation: The Institute of Child Health, University College London, London, WC1N 1EH, UK.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Heslegrave
authors.forename: Ritika R
authors.initials: RR
authors.lastname: Kapoor
authors.forename: Simon
authors.initials: S
authors.lastname: Eaton
authors.forename: Bernadette
authors.initials: B
authors.lastname: Chadefaux
authors.forename: Teoman
authors.initials: T
authors.lastname: Akcay
authors.forename: Enver
authors.initials: E
authors.lastname: Simsek
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Flanagan
authors.forename: Sian
authors.initials: S
authors.lastname: Ellard
authors.forename: Khalid
authors.initials: K
authors.lastname: Hussain
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000235:genetics* / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D005260:Female; D005969:Glutamate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006946:Hyperinsulinism / Q000209:etiology / Q000235:genetics*; D007003:Hypoglycemia / Q000209:etiology / Q000235:genetics*; D047468:Immunoprecipitation; D007223:Infant; D007328:Insulin / Q000032:analysis; D007930:Leucine / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D009154:Mutation
chemical_list: D007328:Insulin; D015094:3-Hydroxyacyl CoA Dehydrogenases; D005969:Glutamate Dehydrogenase; D007930:Leucine