Impaired gene and protein expression of exocytotic soluble N-ethylmaleimide attachment protein receptor complex proteins in pancreatic islets of type 2 diabetic patients.
Exocytosis of insulin is dependent on the soluble N-ethylmaleimide attachment protein receptor (SNARE) complex proteins in the B-cells. We assessed insulin release as well as gene and protein expression of SNARE complex protein in isolated pancreatic islets of type 2 diabetic patients (n = 4) and nondiabetic control subjects (n = 4). In islets from the diabetic patients, insulin responses to 8.3 and 16.7 mmol/l glucose were markedly reduced compared with control islets (4.7 +/- 0.3 and 8.4 +/- 1.8 vs. 17.5 +/- 0.1 and 24.3 +/- 1.2 microU . islet(-1) . h(-1), respectively; P < 0.001). Western blot analysis revealed decreased amounts of islet SNARE complex and SNARE-modulating proteins in diabetes: syntaxin-1A (21 +/- 5% of control levels), SNAP-25 (12 +/- 4%), VAMP-2 (7 +/- 4%), nSec1 (Munc 18; 34 +/- 13%), Munc 13-1 (27 +/- 4%), and synaptophysin (64 +/- 7%). Microarray gene chip analysis, confirmed by quantitative PCR, showed that gene expression was decreased in diabetes islets: syntaxin-1A (27 +/- 2% of control levels), SNAP-25 (31 +/- 7%), VAMP-2 (18 +/- 3%), nSec1 (27 +/- 5%), synaptotagmin V (24 +/- 2%), and synaptophysin (12 +/- 2%). In conclusion, these data support the view that decreased islet RNA and protein expression of SNARE and SNARE-modulating proteins plays a role in impaired insulin secretion in type 2 diabetic patients. It remains unclear, however, to which extent this defect is primary or secondary to, e.g., glucotoxicity.
Ostenson
Claes-Goran
CG
Department of Molecular Medicine and Surgery, Endocrine and Diabetes Unit, Karolinska University Hospital, Stockholm, Sweden. claes-goran.ostenson@karolinska.se
Gaisano
Herbert
H
Sheu
Laura
L
Tibell
Annika
A
Bartfai
Tamas
T
D000368:Aged; D000369:Aged, 80 and over; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005934:Glucagon / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000235:genetics / Q000378:metabolism; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D050600:SNARE Proteins / Q000096:biosynthesis* / Q000235:genetics*
D007328:Insulin; D050600:SNARE Proteins; D005934:Glucagon