Exendin-4 suppresses SRC activation and reactive oxygen species production in diabetic Goto-Kakizaki rat islets in an Epac-dependent manner.
OBJECTIVE
Reactive oxygen species (ROS) is one of most important factors in impaired metabolism secretion coupling in pancreatic β-cells. We recently reported that elevated ROS production and impaired ATP production at high glucose in diabetic Goto-Kakizaki (GK) rat islets are effectively ameliorated by Src inhibition, suggesting that Src activity is upregulated. In the present study, we investigated whether the glucagon-like peptide-1 signal regulates Src activity and ameliorates endogenous ROS production and ATP production in GK islets using exendin-4.


METHODS
Isolated islets from GK and control Wistar rats were used for immunoblotting analyses and measurements of ROS production and ATP content. Src activity was examined by immunoprecipitation of islet lysates followed by immunoblotting. ROS production was measured with a fluorescent probe using dispersed islet cells.


RESULTS
Exendin-4 significantly decreased phosphorylation of Src Tyr416, which indicates Src activation, in GK islets under 16.7 mmol/l glucose exposure. Glucose-induced ROS production (16.7 mmol/l) in GK islet cells was significantly decreased by coexposure of exendin-4 as well as PP2, a Src inhibitor. The Src kinase-negative mutant expression in GK islets significantly decreased ROS production induced by high glucose. Exendin-4, as well as PP2, significantly increased impaired ATP elevation by high glucose in GK islets. The decrease in ROS production by exendin-4 was not affected by H-89, a PKA inhibitor, and an Epac-specific cAMP analog (8CPT-2Me-cAMP) significantly decreased Src Tyr416 phosphorylation and ROS production.


CONCLUSIONS
Exendin-4 decreases endogenous ROS production and increases ATP production in diabetic GK rat islets through suppression of Src activation, dependently on Epac.
Department of Diabetes and Clinical Nutrition, Kyoto University, Japan.
Eri
E
Mukai
Shimpei
S
Fujimoto
Hiroki
H
Sato
Chitose
C
Oneyama
Rieko
R
Kominato
Yuichi
Y
Sato
Mayumi
M
Sasaki
Yuichi
Y
Nishi
Masato
M
Okada
Nobuya
N
Inagaki
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D000077270:Exenatide; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D015151:Immunoblotting; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology / Q000503:physiopathology*; D010455:Peptides / Q000494:pharmacology*; D010766:Phosphorylation; D051381:Rats; D011919:Rats, Inbred Strains; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors*; D013045:Species Specificity; D014688:Venoms / Q000494:pharmacology*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors*
D007004:Hypoglycemic Agents; D010455:Peptides; D017382:Reactive Oxygen Species; D014688:Venoms; D000255:Adenosine Triphosphate; D000077270:Exenatide; D019061:src-Family Kinases