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β1-adrenergic receptor stimulation by agonist Compound 49b restores insulin receptor signal transduction in vivo.

Jiang Y, Zhang Q, Ye EA, Steinle JJ - Mol. Vis. (2014)

Bottom Line: Western blotting or enzyme-linked immunosorbent assay (ELISA) analyses were performed for β1- and β2-adrenergic receptors, as well as key insulin resistance proteins, including TNF-α, SOCS3, IRS-1(Ser307), and IR(Tyr960).Analyses were also performed on key anti- and proapoptotic proteins: Akt, Bcl-xL, Bax, and caspase 3.These results suggest that stimulating β1-adrenergic receptors on retinal endothelial cells or Müller cells can compensate for the loss of β2-adrenergic receptor signaling on Müller cells, restore insulin signal transduction, reduce retinal apoptosis, and enhance retinal function.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN.

ABSTRACT

Purpose: Determine whether Compound 49b treatment ameliorates retinal changes due to the lack of β2-adrenergic receptor signaling.

Methods: Using retinas from 3-month-old β2-adrenergic receptor-deficient mice, we treated mice with our novel β1-/β2-adrenergic receptor agonist, Compound 49b, to assess the effects of adrenergic agonists acting only on β1-adrenergic receptors due to the absence of β2-adrenergic receptors. Western blotting or enzyme-linked immunosorbent assay (ELISA) analyses were performed for β1- and β2-adrenergic receptors, as well as key insulin resistance proteins, including TNF-α, SOCS3, IRS-1(Ser307), and IR(Tyr960). Analyses were also performed on key anti- and proapoptotic proteins: Akt, Bcl-xL, Bax, and caspase 3. Electroretinogram analyses were conducted to assess functional changes, while histological assessment was conducted for changes in retinal thickness.

Results: A 2-month treatment of β2-adrenergic receptor-deficient mice with daily eye drops of 1 mM Compound 49b, a novel β1- and β2-adrenergic receptor agonist, reversed the changes in insulin resistance markers (TNF-α and SOCS3) observed in untreated β2-adrenergic receptor-deficient mice, and concomitantly increased morphological integrity (retinal thickness) and functional responses (electroretinogram amplitude). These results suggest that stimulating β1-adrenergic receptors on retinal endothelial cells or Müller cells can compensate for the loss of β2-adrenergic receptor signaling on Müller cells, restore insulin signal transduction, reduce retinal apoptosis, and enhance retinal function.

Conclusions: Since our previous studies with β1-adrenergic receptor knockout mice confirmed that the reverse also occurs (β2-adrenergic receptor stimulation can compensate for the loss of β1-adrenergic receptor activity), it appears that increased activity in either of these pathways alone is sufficient to block insulin resistance-based retinal cell apoptosis.

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Tumor necrosis factor α and insulin-receptor substrate 1Ser307 phosphorylation in control, β2-adrenergic receptor knockout mice+49b and β2-adrenergic receptor knockout mice. A: Tumor necrosis factor α (TNF-α) levels are returned to near control levels in β2-adrenergic receptor knockout (KO) mice treated with Compound 49b. B: Similar results for the phosphorylation of serine 307 on insulin-receptor substrate 1 (IRS-1). *p<0.05 versus wild-type (WT); #p<0.05 versus β2-adrenergic receptor KO mice. n = 5 for all groups. Data are mean ± standard error of the mean (SEM).
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f2: Tumor necrosis factor α and insulin-receptor substrate 1Ser307 phosphorylation in control, β2-adrenergic receptor knockout mice+49b and β2-adrenergic receptor knockout mice. A: Tumor necrosis factor α (TNF-α) levels are returned to near control levels in β2-adrenergic receptor knockout (KO) mice treated with Compound 49b. B: Similar results for the phosphorylation of serine 307 on insulin-receptor substrate 1 (IRS-1). *p<0.05 versus wild-type (WT); #p<0.05 versus β2-adrenergic receptor KO mice. n = 5 for all groups. Data are mean ± standard error of the mean (SEM).

Mentions: Figure 2A validates our previous work showing that Compound 49b significantly reduces TNF-α levels (p<0.05 versus β2KO, Figure 2A), which we reported previously for retinal endothelial cells [2,3], likely the key retinal cell type involved in signaling in β2-adrenergic receptor knockout mice. Additionally, Figure 2A supported published data that TNF-α is significantly increased in β2-adrenergic receptor knockout mice [6]. Since TNF-α preferentially phosphorylates IRS-1Ser307 to initiate insulin resistance [9,11], we wanted to measure the phosphorylation of IRS-1 on serine 307 in the β2-adrenergic receptor knockout mice and knockout mice treated with Compound 49b. Figure 2B demonstrates that Compound 49b significantly decreased IRS-1Ser307 in β2-adrenegic receptor KO mice. IRS-1Ser307 is increased in β2-adrenergic receptor KO mice with no treatment (p<0.05 versus β2KO, Figure 2B).


β1-adrenergic receptor stimulation by agonist Compound 49b restores insulin receptor signal transduction in vivo.

Jiang Y, Zhang Q, Ye EA, Steinle JJ - Mol. Vis. (2014)

Tumor necrosis factor α and insulin-receptor substrate 1Ser307 phosphorylation in control, β2-adrenergic receptor knockout mice+49b and β2-adrenergic receptor knockout mice. A: Tumor necrosis factor α (TNF-α) levels are returned to near control levels in β2-adrenergic receptor knockout (KO) mice treated with Compound 49b. B: Similar results for the phosphorylation of serine 307 on insulin-receptor substrate 1 (IRS-1). *p<0.05 versus wild-type (WT); #p<0.05 versus β2-adrenergic receptor KO mice. n = 5 for all groups. Data are mean ± standard error of the mean (SEM).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4067233&req=5

f2: Tumor necrosis factor α and insulin-receptor substrate 1Ser307 phosphorylation in control, β2-adrenergic receptor knockout mice+49b and β2-adrenergic receptor knockout mice. A: Tumor necrosis factor α (TNF-α) levels are returned to near control levels in β2-adrenergic receptor knockout (KO) mice treated with Compound 49b. B: Similar results for the phosphorylation of serine 307 on insulin-receptor substrate 1 (IRS-1). *p<0.05 versus wild-type (WT); #p<0.05 versus β2-adrenergic receptor KO mice. n = 5 for all groups. Data are mean ± standard error of the mean (SEM).
Mentions: Figure 2A validates our previous work showing that Compound 49b significantly reduces TNF-α levels (p<0.05 versus β2KO, Figure 2A), which we reported previously for retinal endothelial cells [2,3], likely the key retinal cell type involved in signaling in β2-adrenergic receptor knockout mice. Additionally, Figure 2A supported published data that TNF-α is significantly increased in β2-adrenergic receptor knockout mice [6]. Since TNF-α preferentially phosphorylates IRS-1Ser307 to initiate insulin resistance [9,11], we wanted to measure the phosphorylation of IRS-1 on serine 307 in the β2-adrenergic receptor knockout mice and knockout mice treated with Compound 49b. Figure 2B demonstrates that Compound 49b significantly decreased IRS-1Ser307 in β2-adrenegic receptor KO mice. IRS-1Ser307 is increased in β2-adrenergic receptor KO mice with no treatment (p<0.05 versus β2KO, Figure 2B).

Bottom Line: Western blotting or enzyme-linked immunosorbent assay (ELISA) analyses were performed for β1- and β2-adrenergic receptors, as well as key insulin resistance proteins, including TNF-α, SOCS3, IRS-1(Ser307), and IR(Tyr960).Analyses were also performed on key anti- and proapoptotic proteins: Akt, Bcl-xL, Bax, and caspase 3.These results suggest that stimulating β1-adrenergic receptors on retinal endothelial cells or Müller cells can compensate for the loss of β2-adrenergic receptor signaling on Müller cells, restore insulin signal transduction, reduce retinal apoptosis, and enhance retinal function.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN.

ABSTRACT

Purpose: Determine whether Compound 49b treatment ameliorates retinal changes due to the lack of β2-adrenergic receptor signaling.

Methods: Using retinas from 3-month-old β2-adrenergic receptor-deficient mice, we treated mice with our novel β1-/β2-adrenergic receptor agonist, Compound 49b, to assess the effects of adrenergic agonists acting only on β1-adrenergic receptors due to the absence of β2-adrenergic receptors. Western blotting or enzyme-linked immunosorbent assay (ELISA) analyses were performed for β1- and β2-adrenergic receptors, as well as key insulin resistance proteins, including TNF-α, SOCS3, IRS-1(Ser307), and IR(Tyr960). Analyses were also performed on key anti- and proapoptotic proteins: Akt, Bcl-xL, Bax, and caspase 3. Electroretinogram analyses were conducted to assess functional changes, while histological assessment was conducted for changes in retinal thickness.

Results: A 2-month treatment of β2-adrenergic receptor-deficient mice with daily eye drops of 1 mM Compound 49b, a novel β1- and β2-adrenergic receptor agonist, reversed the changes in insulin resistance markers (TNF-α and SOCS3) observed in untreated β2-adrenergic receptor-deficient mice, and concomitantly increased morphological integrity (retinal thickness) and functional responses (electroretinogram amplitude). These results suggest that stimulating β1-adrenergic receptors on retinal endothelial cells or Müller cells can compensate for the loss of β2-adrenergic receptor signaling on Müller cells, restore insulin signal transduction, reduce retinal apoptosis, and enhance retinal function.

Conclusions: Since our previous studies with β1-adrenergic receptor knockout mice confirmed that the reverse also occurs (β2-adrenergic receptor stimulation can compensate for the loss of β1-adrenergic receptor activity), it appears that increased activity in either of these pathways alone is sufficient to block insulin resistance-based retinal cell apoptosis.

Show MeSH
Related in: MedlinePlus