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Insulin, insulin-like growth factor-1, insulin receptor, and insulin-like growth factor-1 receptor expression in the chick eye and their regulation with imposed myopic or hyperopic defocus.

Penha AM, Schaeffel F, Feldkaemper M - Mol. Vis. (2011)

Bottom Line: Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign.IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations.In the retina, no significant gene expression changes were found when defocus was imposed.

View Article: PubMed Central - PubMed

Affiliation: University Eye Hospital, Institute for Ophthalmic Research, Section of Neurobiology of the Eye, Tuebingen, Germany.

ABSTRACT

Purpose: Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign. However, it is unclear whether the insulin receptor (IR) is expressed at all in the chicken retina in animals 1-2 weeks post-hatching. We have investigated IR expression and whether IR transcript abundance varies in the fundal layers. To elucidate the possible role of insulin and insulin-like growth factor (IGF)-1 signaling in eye growth regulation, mRNA (mRNA) levels were measured for insulin, IGF-1, IR, and IGF-1 receptor (IGF-1R) during imposed negative or positive defocus.

Methods: Chicks were treated binocularly with positive or negative spectacle lenses for 4 or 24 h, or they remained untreated (n=6, for each treatment group). Northern blot analyses were performed to screen for transcription variants in the different fundal layers of untreated animals. Real-time PCR was used to quantify IR, IGF-1R, IGF-1, and insulin mRNA levels in the different fundal layers of the chick eye in the three treatment groups.

Results: IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations. Three major transcripts were detected for IR. The brain, retina, and choroid showed the longest transcript (4.3 kb), which was not present in the liver. Nevertheless, the liver and brain showed a second transcript (2.6 kb) not present in the retina and choroid. A short transcript (1.3 kb) was the predominant form in the liver and choroid, and it seems to be present in the retinal pigment epithelium (RPE) and sclera as well. In the retina, no significant gene expression changes were found when defocus was imposed. Interestingly, in the RPE, both IR and IGF-1R were already downregulated after short periods (4 h) of positive lens wear. In contrast, IR and IGF-1R were upregulated in the choroid and fibrous sclera during treatment with negative, but not positive, lenses.

Conclusions: Differences observed in the IR transcript length in different tissues suggest possibly different functions. The differential regulation of IR and IGF-1R in the RPE, choroid, and fibrous sclera is consistent with their involvement in a signaling cascade for emmetropization.

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Insulin receptor, insulin-like growth factor-1 receptor, and insulin-like growth factor–1 mRNA levels after 24 h of plus (+7D) and minus (−7D) lens treatment in the cartilaginous sclera (A) and fibrous sclera (B). Results are expressed as the mean normalized expression (MNE)±SEM. Nine animals were analyzed per group. Statistically significant differences between the treated groups and the control, as determined by one-way ANOVA (ANOVA) are denoted in the graph (* for p<0.05 and ** for p<0.01). In the cartilaginous sclera, the mRNA contents of the two receptors were not significantly different. In the fibrous sclera, the expression of the insulin and the insulin-like growth factor (IGF)-1 receptor (IGF-1R) was higher in the minus lens–treated group compared to controls.
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f7: Insulin receptor, insulin-like growth factor-1 receptor, and insulin-like growth factor–1 mRNA levels after 24 h of plus (+7D) and minus (−7D) lens treatment in the cartilaginous sclera (A) and fibrous sclera (B). Results are expressed as the mean normalized expression (MNE)±SEM. Nine animals were analyzed per group. Statistically significant differences between the treated groups and the control, as determined by one-way ANOVA (ANOVA) are denoted in the graph (* for p<0.05 and ** for p<0.01). In the cartilaginous sclera, the mRNA contents of the two receptors were not significantly different. In the fibrous sclera, the expression of the insulin and the insulin-like growth factor (IGF)-1 receptor (IGF-1R) was higher in the minus lens–treated group compared to controls.

Mentions: In the cartilaginous sclera, lens treatment influenced neither IR nor IGF-1R mRNA levels after 24 h of lens treatment (Figure 7A). However, in the fibrous sclera (Figure 7B), 24 h of positive-imposed defocus induced a threefold upregulation of IR mRNA levels compared with the control group, and a fourfold upregulation for IGF-1R at the same time point (ANOVA, IR, minus lens versus control p=0.038; IGF-1R, minus lens versus control p=0.005). IGF-1 was expressed at low levels, especially in the cartilaginous sclera. Lens treatment did not induce a significant change in IGF-1 mRNA levels in either layer.


Insulin, insulin-like growth factor-1, insulin receptor, and insulin-like growth factor-1 receptor expression in the chick eye and their regulation with imposed myopic or hyperopic defocus.

Penha AM, Schaeffel F, Feldkaemper M - Mol. Vis. (2011)

Insulin receptor, insulin-like growth factor-1 receptor, and insulin-like growth factor–1 mRNA levels after 24 h of plus (+7D) and minus (−7D) lens treatment in the cartilaginous sclera (A) and fibrous sclera (B). Results are expressed as the mean normalized expression (MNE)±SEM. Nine animals were analyzed per group. Statistically significant differences between the treated groups and the control, as determined by one-way ANOVA (ANOVA) are denoted in the graph (* for p<0.05 and ** for p<0.01). In the cartilaginous sclera, the mRNA contents of the two receptors were not significantly different. In the fibrous sclera, the expression of the insulin and the insulin-like growth factor (IGF)-1 receptor (IGF-1R) was higher in the minus lens–treated group compared to controls.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108898&req=5

f7: Insulin receptor, insulin-like growth factor-1 receptor, and insulin-like growth factor–1 mRNA levels after 24 h of plus (+7D) and minus (−7D) lens treatment in the cartilaginous sclera (A) and fibrous sclera (B). Results are expressed as the mean normalized expression (MNE)±SEM. Nine animals were analyzed per group. Statistically significant differences between the treated groups and the control, as determined by one-way ANOVA (ANOVA) are denoted in the graph (* for p<0.05 and ** for p<0.01). In the cartilaginous sclera, the mRNA contents of the two receptors were not significantly different. In the fibrous sclera, the expression of the insulin and the insulin-like growth factor (IGF)-1 receptor (IGF-1R) was higher in the minus lens–treated group compared to controls.
Mentions: In the cartilaginous sclera, lens treatment influenced neither IR nor IGF-1R mRNA levels after 24 h of lens treatment (Figure 7A). However, in the fibrous sclera (Figure 7B), 24 h of positive-imposed defocus induced a threefold upregulation of IR mRNA levels compared with the control group, and a fourfold upregulation for IGF-1R at the same time point (ANOVA, IR, minus lens versus control p=0.038; IGF-1R, minus lens versus control p=0.005). IGF-1 was expressed at low levels, especially in the cartilaginous sclera. Lens treatment did not induce a significant change in IGF-1 mRNA levels in either layer.

Bottom Line: Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign.IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations.In the retina, no significant gene expression changes were found when defocus was imposed.

View Article: PubMed Central - PubMed

Affiliation: University Eye Hospital, Institute for Ophthalmic Research, Section of Neurobiology of the Eye, Tuebingen, Germany.

ABSTRACT

Purpose: Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign. However, it is unclear whether the insulin receptor (IR) is expressed at all in the chicken retina in animals 1-2 weeks post-hatching. We have investigated IR expression and whether IR transcript abundance varies in the fundal layers. To elucidate the possible role of insulin and insulin-like growth factor (IGF)-1 signaling in eye growth regulation, mRNA (mRNA) levels were measured for insulin, IGF-1, IR, and IGF-1 receptor (IGF-1R) during imposed negative or positive defocus.

Methods: Chicks were treated binocularly with positive or negative spectacle lenses for 4 or 24 h, or they remained untreated (n=6, for each treatment group). Northern blot analyses were performed to screen for transcription variants in the different fundal layers of untreated animals. Real-time PCR was used to quantify IR, IGF-1R, IGF-1, and insulin mRNA levels in the different fundal layers of the chick eye in the three treatment groups.

Results: IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations. Three major transcripts were detected for IR. The brain, retina, and choroid showed the longest transcript (4.3 kb), which was not present in the liver. Nevertheless, the liver and brain showed a second transcript (2.6 kb) not present in the retina and choroid. A short transcript (1.3 kb) was the predominant form in the liver and choroid, and it seems to be present in the retinal pigment epithelium (RPE) and sclera as well. In the retina, no significant gene expression changes were found when defocus was imposed. Interestingly, in the RPE, both IR and IGF-1R were already downregulated after short periods (4 h) of positive lens wear. In contrast, IR and IGF-1R were upregulated in the choroid and fibrous sclera during treatment with negative, but not positive, lenses.

Conclusions: Differences observed in the IR transcript length in different tissues suggest possibly different functions. The differential regulation of IR and IGF-1R in the RPE, choroid, and fibrous sclera is consistent with their involvement in a signaling cascade for emmetropization.

Show MeSH
Related in: MedlinePlus