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Exendin-4 protects retinal cells from early diabetes in Goto-Kakizaki rats by increasing the Bcl-2/Bax and Bcl-xL/Bax ratios and reducing reactive gliosis.

Fan Y, Liu K, Wang Q, Ruan Y, Zhang Y, Ye W - Mol. Vis. (2014)

Bottom Line: It also downregulated the expression of glial fibrillary acidic protein and reduced retinal reactive gliosis.Similar results were found in primary rat Müller cells under high glucose culture in vitro.E4 may protect retinal cells from diabetic attacks by activating GLP-1R, decreasing retinal cell apoptosis, and reducing retinal reactive gliosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Huashan Hospital Affiliated to Fudan University, Shanghai, China.

ABSTRACT

Purpose: Exendin-4 (E4), a long-acting agonist of the hormone glucagon-like peptide 1 receptor (GLP-1R), is administered to treat type II diabetes in the clinical setting and also shows a neuroprotective effect. Our previous studies demonstrated its protective effect in early experimental diabetic retinopathy (DR), but the molecular and cellular mechanisms are largely unknown. This study aimed to investigate the protective mechanism of a GLP-1R agonist E4 against early DR in Goto-Kakizaki (GK) rats.

Methods: Diabetic GK rats and control animals were randomly assigned to receive E4 or vehicle by intravitreal injection. The retinal function and retinal cell counts were evaluated using an electroretinogram and light microscopy. The expressions of retinal GLP-1R, mitochondria-dependent apoptosis-associated genes, reactive gliosis markers, and endoplasmic reticulum stress-related pathway genes were studied by western blotting and immunohistochemistry in vivo and in vitro.

Results: E4 significantly prevented the reduction of the b-wave and oscillatory potential amplitudes and retinal cell loss and maintained the Bcl-2/Bax and Bcl-xL/Bax ratio balances in GK rats. It also downregulated the expression of glial fibrillary acidic protein and reduced retinal reactive gliosis. Similar results were found in primary rat Müller cells under high glucose culture in vitro.

Conclusions: E4 may protect retinal cells from diabetic attacks by activating GLP-1R, decreasing retinal cell apoptosis, and reducing retinal reactive gliosis. Thus, E4 treatment may be a novel approach for early DR.

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Related in: MedlinePlus

Modulation of p-AKT (Ser473) activation and Bcl-2 expression in primary retinal Müller cells (RMCs) by E4 under high glucose culture. E4 stimulation downregulated p-AKT (Ser473) activation (A) and upregulated Bcl-2 expression (B) in primary retinal Müller cells (RMCs) under high glucose culture at different time points (24 h, 48 h, and 72 h; one-way ANOVA followed by Bonferroni’s test: p-AKT [Ser473], control [D-glucose, 5.6 mM] versus control [D-glucose, 20 mM], t=10.07, p<0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 24 h E4 treatment], t=3.391, p=0.040; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 48 h E4 treatment], t=5.191, p=0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 72 h E4 treatment], t=3.315, p=0.047; Bcl-2, control [D-glucose, 5.6 mM] versus control [D-glucose, 20 mM], t=10.76, p<0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 48 h E4 treatment], t=3.876, p=0.015; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 72 h E4 treatment], t=5.213, p=0.001; n=4). *: p<0.05, **: p<0.01, #: p<0.001. E4: Exendin-4. Data are expressed as the means ± SEM. One-way ANOVA followed by Bonferroni’s test.
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f7: Modulation of p-AKT (Ser473) activation and Bcl-2 expression in primary retinal Müller cells (RMCs) by E4 under high glucose culture. E4 stimulation downregulated p-AKT (Ser473) activation (A) and upregulated Bcl-2 expression (B) in primary retinal Müller cells (RMCs) under high glucose culture at different time points (24 h, 48 h, and 72 h; one-way ANOVA followed by Bonferroni’s test: p-AKT [Ser473], control [D-glucose, 5.6 mM] versus control [D-glucose, 20 mM], t=10.07, p<0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 24 h E4 treatment], t=3.391, p=0.040; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 48 h E4 treatment], t=5.191, p=0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 72 h E4 treatment], t=3.315, p=0.047; Bcl-2, control [D-glucose, 5.6 mM] versus control [D-glucose, 20 mM], t=10.76, p<0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 48 h E4 treatment], t=3.876, p=0.015; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 72 h E4 treatment], t=5.213, p=0.001; n=4). *: p<0.05, **: p<0.01, #: p<0.001. E4: Exendin-4. Data are expressed as the means ± SEM. One-way ANOVA followed by Bonferroni’s test.

Mentions: The phosphorylation level of AKT at Ser473 in RMCs after 72 h of high glucose treatment was upregulated to 196% of the normal control level and downregulated to 124.5% of the normal control level after 48 h of E4 treatment (Figure 7A). This finding was consistent with the GLP-1R expression over time that was observed in response to E4 treatment in vitro (Figure 4D). The Bcl-2 expression was downregulated to 51.7% of the normal control level after 72 h of high glucose treatment (Figure 7B, p<0.001) and was upregulated to 162.7% of the high glucose control in RMCs after 72 h of E4 treatment in vitro (Figure 7B, p<0.01).


Exendin-4 protects retinal cells from early diabetes in Goto-Kakizaki rats by increasing the Bcl-2/Bax and Bcl-xL/Bax ratios and reducing reactive gliosis.

Fan Y, Liu K, Wang Q, Ruan Y, Zhang Y, Ye W - Mol. Vis. (2014)

Modulation of p-AKT (Ser473) activation and Bcl-2 expression in primary retinal Müller cells (RMCs) by E4 under high glucose culture. E4 stimulation downregulated p-AKT (Ser473) activation (A) and upregulated Bcl-2 expression (B) in primary retinal Müller cells (RMCs) under high glucose culture at different time points (24 h, 48 h, and 72 h; one-way ANOVA followed by Bonferroni’s test: p-AKT [Ser473], control [D-glucose, 5.6 mM] versus control [D-glucose, 20 mM], t=10.07, p<0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 24 h E4 treatment], t=3.391, p=0.040; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 48 h E4 treatment], t=5.191, p=0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 72 h E4 treatment], t=3.315, p=0.047; Bcl-2, control [D-glucose, 5.6 mM] versus control [D-glucose, 20 mM], t=10.76, p<0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 48 h E4 treatment], t=3.876, p=0.015; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 72 h E4 treatment], t=5.213, p=0.001; n=4). *: p<0.05, **: p<0.01, #: p<0.001. E4: Exendin-4. Data are expressed as the means ± SEM. One-way ANOVA followed by Bonferroni’s test.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f7: Modulation of p-AKT (Ser473) activation and Bcl-2 expression in primary retinal Müller cells (RMCs) by E4 under high glucose culture. E4 stimulation downregulated p-AKT (Ser473) activation (A) and upregulated Bcl-2 expression (B) in primary retinal Müller cells (RMCs) under high glucose culture at different time points (24 h, 48 h, and 72 h; one-way ANOVA followed by Bonferroni’s test: p-AKT [Ser473], control [D-glucose, 5.6 mM] versus control [D-glucose, 20 mM], t=10.07, p<0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 24 h E4 treatment], t=3.391, p=0.040; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 48 h E4 treatment], t=5.191, p=0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 72 h E4 treatment], t=3.315, p=0.047; Bcl-2, control [D-glucose, 5.6 mM] versus control [D-glucose, 20 mM], t=10.76, p<0.001; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 48 h E4 treatment], t=3.876, p=0.015; control [D-glucose, 20 mM] versus E4 treatment [20 mM D-glucose + 72 h E4 treatment], t=5.213, p=0.001; n=4). *: p<0.05, **: p<0.01, #: p<0.001. E4: Exendin-4. Data are expressed as the means ± SEM. One-way ANOVA followed by Bonferroni’s test.
Mentions: The phosphorylation level of AKT at Ser473 in RMCs after 72 h of high glucose treatment was upregulated to 196% of the normal control level and downregulated to 124.5% of the normal control level after 48 h of E4 treatment (Figure 7A). This finding was consistent with the GLP-1R expression over time that was observed in response to E4 treatment in vitro (Figure 4D). The Bcl-2 expression was downregulated to 51.7% of the normal control level after 72 h of high glucose treatment (Figure 7B, p<0.001) and was upregulated to 162.7% of the high glucose control in RMCs after 72 h of E4 treatment in vitro (Figure 7B, p<0.01).

Bottom Line: It also downregulated the expression of glial fibrillary acidic protein and reduced retinal reactive gliosis.Similar results were found in primary rat Müller cells under high glucose culture in vitro.E4 may protect retinal cells from diabetic attacks by activating GLP-1R, decreasing retinal cell apoptosis, and reducing retinal reactive gliosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Huashan Hospital Affiliated to Fudan University, Shanghai, China.

ABSTRACT

Purpose: Exendin-4 (E4), a long-acting agonist of the hormone glucagon-like peptide 1 receptor (GLP-1R), is administered to treat type II diabetes in the clinical setting and also shows a neuroprotective effect. Our previous studies demonstrated its protective effect in early experimental diabetic retinopathy (DR), but the molecular and cellular mechanisms are largely unknown. This study aimed to investigate the protective mechanism of a GLP-1R agonist E4 against early DR in Goto-Kakizaki (GK) rats.

Methods: Diabetic GK rats and control animals were randomly assigned to receive E4 or vehicle by intravitreal injection. The retinal function and retinal cell counts were evaluated using an electroretinogram and light microscopy. The expressions of retinal GLP-1R, mitochondria-dependent apoptosis-associated genes, reactive gliosis markers, and endoplasmic reticulum stress-related pathway genes were studied by western blotting and immunohistochemistry in vivo and in vitro.

Results: E4 significantly prevented the reduction of the b-wave and oscillatory potential amplitudes and retinal cell loss and maintained the Bcl-2/Bax and Bcl-xL/Bax ratio balances in GK rats. It also downregulated the expression of glial fibrillary acidic protein and reduced retinal reactive gliosis. Similar results were found in primary rat Müller cells under high glucose culture in vitro.

Conclusions: E4 may protect retinal cells from diabetic attacks by activating GLP-1R, decreasing retinal cell apoptosis, and reducing retinal reactive gliosis. Thus, E4 treatment may be a novel approach for early DR.

Show MeSH
Related in: MedlinePlus