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Insulin reduces cerebral ischemia/reperfusion injury in the hippocampus of diabetic rats: a role for glycogen synthase kinase-3beta.

Collino M, Aragno M, Castiglia S, Tomasinelli C, Thiemermann C, Boccuzzi G, Fantozzi R - Diabetes (2008)

Bottom Line: However, the molecular mechanisms underlying the protective effects of insulin remain unknown.Acute administration of insulin or TDZD-8 reduced cerebral I/R injury in diabetic rats.We propose that the inhibitory effect on the activity of GSK-3beta contributes to the protective effect of insulin independently of any effects on blood glucose.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Pharmacology, and Forensic Medicine, University of Turin, Turin, Italy. massimo.collino@unito.it

ABSTRACT

Objective: There is evidence that insulin reduces brain injury evoked by ischemia/reperfusion (I/R). However, the molecular mechanisms underlying the protective effects of insulin remain unknown. Insulin is a well-known inhibitor of glycogen synthase kinase-3beta (GSK-3beta). Here, we investigate the role of GSK-3beta inhibition on I/R-induced cerebral injury in a rat model of insulinopenic diabetes.

Research design and methods: Rats with streptozotocin-induced diabetes were subjected to 30-min occlusion of common carotid arteries followed by 1 or 24 h of reperfusion. Insulin (2-12 IU/kg i.v.) or the selective GSK-3beta inhibitor TDZD-8 (0.2-3 mg/kg i.v.) was administered during reperfusion.

Results: Insulin or TDZD-8 dramatically reduced infarct volume and levels of S100B protein, a marker of cerebral injury. Both drugs induced phosphorylation of the Ser9 residue, thereby inactivating GSK-3beta in the rat hippocampus. Insulin, but not TDZD-8, lowered blood glucose. The hippocampi of the drug-treated animals displayed reduced oxidative stress at 1 h of reperfusion as shown by the decreased generation of reactive oxygen species and lipid peroxidation. I/R-induced activation of nuclear factor-kappaB was attenuated by both drug treatments. At 24 h of reperfusion, TDZD-8 and insulin significantly reduced plasma levels of tumor necrosis factor-alpha; neutrophil infiltration, measured as myeloperoxidase activity and intercellular-adhesion-molecule-1 expression; and cyclooxygenase-2 and inducible-NO-synthase expression.

Conclusions: Acute administration of insulin or TDZD-8 reduced cerebral I/R injury in diabetic rats. We propose that the inhibitory effect on the activity of GSK-3beta contributes to the protective effect of insulin independently of any effects on blood glucose.

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Total infarct volume (A) and hippocampal S100B expression (B). Diabetic rats that underwent 30 min of ischemia followed by 24 h of reperfusion (STZ I/R) showed higher levels of infarct volume and S100B expression than nondiabetic rats exposed to I/R. Additional groups of diabetic rats received 3 mg/kg TDZD-8 (STZ I/R + TDZD-8) or 2–12 IU/kg insulin (STZ I/R + INSULIN) during reperfusion. The infarct volume data are means ± SE of four rats per group. The immunoblot of S100B protein expression and the corresponding β-actin are representative of three separate experiments. •P < 0.05 vs. I/R; ★P < 0.05 vs. STZ I/R.
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f2: Total infarct volume (A) and hippocampal S100B expression (B). Diabetic rats that underwent 30 min of ischemia followed by 24 h of reperfusion (STZ I/R) showed higher levels of infarct volume and S100B expression than nondiabetic rats exposed to I/R. Additional groups of diabetic rats received 3 mg/kg TDZD-8 (STZ I/R + TDZD-8) or 2–12 IU/kg insulin (STZ I/R + INSULIN) during reperfusion. The infarct volume data are means ± SE of four rats per group. The immunoblot of S100B protein expression and the corresponding β-actin are representative of three separate experiments. •P < 0.05 vs. I/R; ★P < 0.05 vs. STZ I/R.

Mentions: Rats that underwent cerebral ischemia followed by 24 h of reperfusion showed an infarct volume of 23.4 ± 3.9% of the total brain volume (I/R group; Fig. 2A). Infarct size was larger in diabetic animals exposed to I/R (STZ I/R group; 34.9 ± 4.8%; P < 0.05). Administration of insulin halved the I/R-induced infarct volume in diabetic animals, but no differences in efficacy were observed for any of the doses tested (2–12 IU/kg). A similar reduction in infarct volume was measured when 3 mg/kg TDZD-8 was administered during reperfusion.


Insulin reduces cerebral ischemia/reperfusion injury in the hippocampus of diabetic rats: a role for glycogen synthase kinase-3beta.

Collino M, Aragno M, Castiglia S, Tomasinelli C, Thiemermann C, Boccuzzi G, Fantozzi R - Diabetes (2008)

Total infarct volume (A) and hippocampal S100B expression (B). Diabetic rats that underwent 30 min of ischemia followed by 24 h of reperfusion (STZ I/R) showed higher levels of infarct volume and S100B expression than nondiabetic rats exposed to I/R. Additional groups of diabetic rats received 3 mg/kg TDZD-8 (STZ I/R + TDZD-8) or 2–12 IU/kg insulin (STZ I/R + INSULIN) during reperfusion. The infarct volume data are means ± SE of four rats per group. The immunoblot of S100B protein expression and the corresponding β-actin are representative of three separate experiments. •P < 0.05 vs. I/R; ★P < 0.05 vs. STZ I/R.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2606878&req=5

f2: Total infarct volume (A) and hippocampal S100B expression (B). Diabetic rats that underwent 30 min of ischemia followed by 24 h of reperfusion (STZ I/R) showed higher levels of infarct volume and S100B expression than nondiabetic rats exposed to I/R. Additional groups of diabetic rats received 3 mg/kg TDZD-8 (STZ I/R + TDZD-8) or 2–12 IU/kg insulin (STZ I/R + INSULIN) during reperfusion. The infarct volume data are means ± SE of four rats per group. The immunoblot of S100B protein expression and the corresponding β-actin are representative of three separate experiments. •P < 0.05 vs. I/R; ★P < 0.05 vs. STZ I/R.
Mentions: Rats that underwent cerebral ischemia followed by 24 h of reperfusion showed an infarct volume of 23.4 ± 3.9% of the total brain volume (I/R group; Fig. 2A). Infarct size was larger in diabetic animals exposed to I/R (STZ I/R group; 34.9 ± 4.8%; P < 0.05). Administration of insulin halved the I/R-induced infarct volume in diabetic animals, but no differences in efficacy were observed for any of the doses tested (2–12 IU/kg). A similar reduction in infarct volume was measured when 3 mg/kg TDZD-8 was administered during reperfusion.

Bottom Line: However, the molecular mechanisms underlying the protective effects of insulin remain unknown.Acute administration of insulin or TDZD-8 reduced cerebral I/R injury in diabetic rats.We propose that the inhibitory effect on the activity of GSK-3beta contributes to the protective effect of insulin independently of any effects on blood glucose.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Pharmacology, and Forensic Medicine, University of Turin, Turin, Italy. massimo.collino@unito.it

ABSTRACT

Objective: There is evidence that insulin reduces brain injury evoked by ischemia/reperfusion (I/R). However, the molecular mechanisms underlying the protective effects of insulin remain unknown. Insulin is a well-known inhibitor of glycogen synthase kinase-3beta (GSK-3beta). Here, we investigate the role of GSK-3beta inhibition on I/R-induced cerebral injury in a rat model of insulinopenic diabetes.

Research design and methods: Rats with streptozotocin-induced diabetes were subjected to 30-min occlusion of common carotid arteries followed by 1 or 24 h of reperfusion. Insulin (2-12 IU/kg i.v.) or the selective GSK-3beta inhibitor TDZD-8 (0.2-3 mg/kg i.v.) was administered during reperfusion.

Results: Insulin or TDZD-8 dramatically reduced infarct volume and levels of S100B protein, a marker of cerebral injury. Both drugs induced phosphorylation of the Ser9 residue, thereby inactivating GSK-3beta in the rat hippocampus. Insulin, but not TDZD-8, lowered blood glucose. The hippocampi of the drug-treated animals displayed reduced oxidative stress at 1 h of reperfusion as shown by the decreased generation of reactive oxygen species and lipid peroxidation. I/R-induced activation of nuclear factor-kappaB was attenuated by both drug treatments. At 24 h of reperfusion, TDZD-8 and insulin significantly reduced plasma levels of tumor necrosis factor-alpha; neutrophil infiltration, measured as myeloperoxidase activity and intercellular-adhesion-molecule-1 expression; and cyclooxygenase-2 and inducible-NO-synthase expression.

Conclusions: Acute administration of insulin or TDZD-8 reduced cerebral I/R injury in diabetic rats. We propose that the inhibitory effect on the activity of GSK-3beta contributes to the protective effect of insulin independently of any effects on blood glucose.

Show MeSH
Related in: MedlinePlus