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Exendin-4 suppresses SRC activation and reactive oxygen species production in diabetic Goto-Kakizaki rat islets in an Epac-dependent manner.

Mukai E, Fujimoto S, Sato H, Oneyama C, Kominato R, Sato Y, Sasaki M, Nishi Y, Okada M, Inagaki N - Diabetes (2010)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Diabetes and Clinical Nutrition, Kyoto University, Japan.

ABSTRACT

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.

Research design and 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.

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Related in: MedlinePlus

Exendin-4 increases ATP content at high glucose in GK islets. Effects of exendin-4 and PP2 on ATP content in the presence of high glucose for 30 min in GK (A) and Wistar (B) islets. After preincubation in the presence of 2.8 mmol/l glucose for 30 min, islets were incubated in the presence of 2.8 or 16.7 mmol/l glucose with or without 100 nmol/l exendin-4, 10 μmol/l PP2, or both for 30 min. Data are expressed as means ± SE (n = 7–8). *P < 0.05; †P < 0.01.
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Figure 4: Exendin-4 increases ATP content at high glucose in GK islets. Effects of exendin-4 and PP2 on ATP content in the presence of high glucose for 30 min in GK (A) and Wistar (B) islets. After preincubation in the presence of 2.8 mmol/l glucose for 30 min, islets were incubated in the presence of 2.8 or 16.7 mmol/l glucose with or without 100 nmol/l exendin-4, 10 μmol/l PP2, or both for 30 min. Data are expressed as means ± SE (n = 7–8). *P < 0.05; †P < 0.01.

Mentions: In Wistar islets, 16.7 mmol/l glucose-exposure significantly increased ATP content compared with that in the presence of 2.8 mmol/l glucose, as shown in Fig. 4B. Exendin-4, PP2, or exendin-4 plus PP2 did not affect the ATP content in the presence of 16.7 mmol/l glucose in Wistar islets. The ATP content in GK islets exposed to 16.7 mmol/l glucose was not increased compared with that in the presence of 2.8 mmol/l glucose (Fig. 4A). Exendin-4 as well as PP2 significantly increased the ATP content in the presence of 16.7 mmol/l glucose. Further increase of ATP content by combined exendin-4 and PP2 was not observed.


Exendin-4 suppresses SRC activation and reactive oxygen species production in diabetic Goto-Kakizaki rat islets in an Epac-dependent manner.

Mukai E, Fujimoto S, Sato H, Oneyama C, Kominato R, Sato Y, Sasaki M, Nishi Y, Okada M, Inagaki N - Diabetes (2010)

Exendin-4 increases ATP content at high glucose in GK islets. Effects of exendin-4 and PP2 on ATP content in the presence of high glucose for 30 min in GK (A) and Wistar (B) islets. After preincubation in the presence of 2.8 mmol/l glucose for 30 min, islets were incubated in the presence of 2.8 or 16.7 mmol/l glucose with or without 100 nmol/l exendin-4, 10 μmol/l PP2, or both for 30 min. Data are expressed as means ± SE (n = 7–8). *P < 0.05; †P < 0.01.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3012174&req=5

Figure 4: Exendin-4 increases ATP content at high glucose in GK islets. Effects of exendin-4 and PP2 on ATP content in the presence of high glucose for 30 min in GK (A) and Wistar (B) islets. After preincubation in the presence of 2.8 mmol/l glucose for 30 min, islets were incubated in the presence of 2.8 or 16.7 mmol/l glucose with or without 100 nmol/l exendin-4, 10 μmol/l PP2, or both for 30 min. Data are expressed as means ± SE (n = 7–8). *P < 0.05; †P < 0.01.
Mentions: In Wistar islets, 16.7 mmol/l glucose-exposure significantly increased ATP content compared with that in the presence of 2.8 mmol/l glucose, as shown in Fig. 4B. Exendin-4, PP2, or exendin-4 plus PP2 did not affect the ATP content in the presence of 16.7 mmol/l glucose in Wistar islets. The ATP content in GK islets exposed to 16.7 mmol/l glucose was not increased compared with that in the presence of 2.8 mmol/l glucose (Fig. 4A). Exendin-4 as well as PP2 significantly increased the ATP content in the presence of 16.7 mmol/l glucose. Further increase of ATP content by combined exendin-4 and PP2 was not observed.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Diabetes and Clinical Nutrition, Kyoto University, Japan.

ABSTRACT

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.

Research design and 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.

Show MeSH
Related in: MedlinePlus