title: Column chromatographic characterization of complex formation of pro-IGF-II isoforms with acid labile subunit and IGF-binding proteins associated with non-islet cell tumour induced hypoglycaemia.
abstract: OBJECTIVE
  Non-islet cell tumour induced hypoglycaemia (NICTH) is a paraneoplastic phenomenon that is associated with the formation of several isoforms of pro-insulin like growth factor 2 (pro-IGF-II), or so called "big" IGF-II. Disturbance of ternary complex formation by big IGF-II is assumed to be a crucial early event in the pathogenic cascade of hypoglycaemia. By size-exclusion chromatography, we investigated complex formation by adding different naturally occurring isoforms of pro-IGF-II to pooled normal adult serum. Results were compared with the analysis of the serum from a patient with NICTH.
  
  
  RESULTS
  Gel filtration experiments with the serum of a patient with NICTH demonstrated that ternary complex formation was severely compromised. The various forms of pro-IGF-II did not induce a shift of IGF-binding protein 3 (IGFBP-3) from 150kD towards smaller binary complexes in the normal adult serum, suggesting that they did not interfere with the interaction between the acid labile subunit and IGFBP-3. Instead, unglycosylated recombinant pro-IGF-II[1-104] was capable of forming a 150kD complex. In contrast, predominantly glycosylated and unglycosylated pro-IGF-II[1-87] eluted in the free unbound form. We showed that mature IGF-II and isoforms of pro-IGF-II were able to phosphorylate the IGF-I receptors of MC7 cells, albeit to a markedly lesser extent than IGF-I. When the patient's serum was tested in this system, the IGF-I receptor phosphorylation activity was considerably less than that in sera from age matched healthy individuals.
  
  
  CONCLUSIONS
  We postulate that, alongside the presence of big IGF-II in the circulation, additional steps are required to stimulate the release of IGF-II and pro-IGF-II isoforms from IGFBPs in vivo. These factors may be proteases, that are present in the local environment of the tumour and in insulin-sensitive tissues.
authors.affiliation: Dept. Internal Medicine, Dr. Horacio E. Oduber Hospital, Oranjestad, Aruba; Dept. Internal Medicine, Rijnland Hospital, Leiderdorp, The Netherlands. Electronic address: kristinvv@hotmail.com.
authors.forename: K M
authors.initials: KM
authors.lastname: van Veggel
authors.affiliation: Dept. Internal Medicine, Dr. Horacio E. Oduber Hospital, Oranjestad, Aruba; Center for Infectious Diseases, ID4C, Military Hospital Queen Astrid, Brussels, Belgium.
authors.forename: R M H G
authors.initials: RM
authors.lastname: Huits
authors.affiliation: Dept. Clinical Chemistry and Hematology, Laboratory of Endocrinology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: G H
authors.initials: GH
authors.lastname: Donker
authors.affiliation: Dept. Clinical Chemistry and Hematology, Laboratory of Endocrinology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: E G W M
authors.initials: EG
authors.lastname: Lentjes
authors.affiliation: Dept. Clinical Chemistry and Hematology, Laboratory of Endocrinology, University Medical Center Utrecht, Utrecht, The Netherlands; Dept. Medical Genetics, Section Metabolic Diseases, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: van Doorn
mesh_terms: D000328:Adult; D006528:Carcinoma, Hepatocellular / Q000150:complications / Q000378:metabolism* / Q000473:pathology; D002850:Chromatography, Gel / Q000379:methods*; D006801:Humans; D007003:Hypoglycemia / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D008113:Liver Neoplasms / Q000150:complications / Q000378:metabolism* / Q000473:pathology; D008297:Male; D010257:Paraneoplastic Syndromes / Q000150:complications / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D020033:Protein Isoforms; D011498:Protein Precursors / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D018969:Insulin-Like Growth Factor Binding Proteins; D020033:Protein Isoforms; D011498:Protein Precursors; C066038:proinsulin-like growth factor II; D014443:Tyrosine; D007335:Insulin-Like Growth Factor II
keywords: Big IGF-II; Complex formation; Hypoglycaemia; IGF; Non-islet cell tumour hypoglycaemia