title: GALNT2 expression is reduced in patients with Type 2 diabetes: possible role of hyperglycemia.
abstract: Impaired insulin action plays a major role in the pathogenesis of type 2 diabetes, a chronic metabolic disorder which imposes a tremendous burden to morbidity and mortality worldwide. Unraveling the molecular mechanisms underlying insulin resistance would improve setting up preventive and treatment strategies of type 2 diabetes. Down-regulation of GALNT2, an UDPN-acetyl-alpha-D-galactosamine polypeptideN-acetylgalactosaminyltransferase-2 (ppGalNAc-T2), causes impaired insulin signaling and action in cultured human liver cells. In addition, GALNT2 mRNA levels are down-regulated in liver of spontaneously insulin resistant, diabetic Goto-Kakizaki rats. To investigate the role of GALNT2 in human hyperglycemia, we measured GALNT2 mRNA expression levels in peripheral whole blood cells of 84 non-obese and 46 obese non-diabetic individuals as well as of 98 obese patients with type 2 diabetes. We also measured GALNT2 mRNA expression in human U937 cells cultured under different glucose concentrations. In vivo studies indicated that GALNT2 mRNA levels were significantly reduced from non obese control to obese non diabetic and to obese diabetic individuals (p<0.001). In vitro studies showed that GALNT2 mRNA levels was reduced in U937 cells exposed to high glucose concentrations (i.e. 25 mmol/l glucose) as compared to cells exposed to low glucose concentration (i.e. 5.5 mmol/l glucose +19.5 mmol/l mannitol). In conclusion, our data indicate that GALNT2 is down-regulated in patients with type 2 diabetes and suggest that this association is, at least partly, secondary to hyperglycemia. Further studies are needed to understand whether GALNT2 down-regulation plays a pathogenic role in maintaining and/or aggravating the metabolic abnormalities of diabetic milieu.
authors.affiliation: Research Unit of Diabetes and Endocrine Diseases, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Marucci
authors.forename: Lazzaro
authors.initials: L
authors.lastname: di Mauro
authors.forename: Claudia
authors.initials: C
authors.lastname: Menzaghi
authors.forename: Sabrina
authors.initials: S
authors.lastname: Prudente
authors.forename: Davide
authors.initials: D
authors.lastname: Mangiacotti
authors.forename: Grazia
authors.initials: G
authors.lastname: Fini
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lotti
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Trischitta
authors.forename: Rosa
authors.initials: R
authors.lastname: Di Paola
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D045744:Cell Line, Tumor; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications / Q000201:enzymology* / Q000235:genetics*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000150:complications / Q000201:enzymology* / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics*; D009765:Obesity / Q000150:complications; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D000097763:Polypeptide N-acetylgalactosaminyltransferase
chemical_list: D001786:Blood Glucose; D017350:N-Acetylgalactosaminyltransferases; D012333:RNA, Messenger; D000097763:Polypeptide N-acetylgalactosaminyltransferase
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