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Chronic insulin treatment of diabetes does not fully normalize alterations in the retinal transcriptome.

Bixler GV, Vanguilder HD, Brucklacher RM, Kimball SR, Bronson SK, Freeman WM - BMC Med Genomics (2011)

Bottom Line: A subset of genes (Ccr5, Jak3, Litaf) was confirmed at the level of protein expression, with protein levels recapitulating changes in mRNA expression.These results provide the first genome-wide examination of the effects of insulin therapy on retinal gene expression changes with diabetes.Gene expression changes not rescued or prevented by insulin treatment may be critical to the pathogenesis of diabetic retinopathy, as it occurs in diabetic patients receiving insulin replacement, and are prototypical of metabolic memory.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pharmacology, Penn State College of Medicine, Hershey, PA, USA.

ABSTRACT

Background: Diabetic retinopathy (DR) is a leading cause of blindness in working age adults. Approximately 95% of patients with Type 1 diabetes develop some degree of retinopathy within 25 years of diagnosis despite normalization of blood glucose by insulin therapy. The goal of this study was to identify molecular changes in the rodent retina induced by diabetes that are not normalized by insulin replacement and restoration of euglycemia.

Methods: The retina transcriptome (22,523 genes and transcript variants) was examined after three months of streptozotocin-induced diabetes in male Sprague Dawley rats with and without insulin replacement for the later one and a half months of diabetes. Selected gene expression changes were confirmed by qPCR, and also examined in independent control and diabetic rats at a one month time-point.

Results: Transcriptomic alterations in response to diabetes (1376 probes) were clustered according to insulin responsiveness. More than half (57%) of diabetes-induced mRNA changes (789 probes) observed at three months were fully normalized to control levels with insulin therapy, while 37% of probes (514) were only partially normalized. A small set of genes (5%, 65 probes) was significantly dysregulated in the insulin-treated diabetic rats. qPCR confirmation of findings and examination of a one month time point allowed genes to be further categorized as prevented or rescued with insulin therapy. A subset of genes (Ccr5, Jak3, Litaf) was confirmed at the level of protein expression, with protein levels recapitulating changes in mRNA expression.

Conclusions: These results provide the first genome-wide examination of the effects of insulin therapy on retinal gene expression changes with diabetes. While insulin clearly normalizes the majority of genes dysregulated in response to diabetes, a number of genes related to inflammatory processes, microvascular integrity, and neuronal function are still altered in expression in euglycemic diabetic rats. Gene expression changes not rescued or prevented by insulin treatment may be critical to the pathogenesis of diabetic retinopathy, as it occurs in diabetic patients receiving insulin replacement, and are prototypical of metabolic memory.

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Network analysis of genes Not Normalized. Genes and expression values from the Not Normalized category were examined for networks of interrelated genes using Ingenuity Pathway Analysis software. One significant network was centered around Pdgf, Nfkb, and Jnk. Expression values for the control versus diabetic groups is presented in A and for the insulin-treated diabetic versus diabetic comparison in B. Relationships are presented as lines and arrows. Red lines represent activation or positive regulation of expression while green lines indicate inhibition or negative regulation of expression. Grey lines are known protein-protein interactions and dashed lines are indirect relationships. Gene symbols are coded as green for significantly reduced expression, red for significantly reduced expression, and white for no change in expression.
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Figure 3: Network analysis of genes Not Normalized. Genes and expression values from the Not Normalized category were examined for networks of interrelated genes using Ingenuity Pathway Analysis software. One significant network was centered around Pdgf, Nfkb, and Jnk. Expression values for the control versus diabetic groups is presented in A and for the insulin-treated diabetic versus diabetic comparison in B. Relationships are presented as lines and arrows. Red lines represent activation or positive regulation of expression while green lines indicate inhibition or negative regulation of expression. Grey lines are known protein-protein interactions and dashed lines are indirect relationships. Gene symbols are coded as green for significantly reduced expression, red for significantly reduced expression, and white for no change in expression.

Mentions: Analysis of gene networks extends the finding of sets of genes with differential patterns of expression in response to insulin therapy. For example, an inflammation related network of diabetes changes with nodes of Vegf, Pdgf, and NFkB was evident in the comparison of diabetics to non-diabetic controls (Figure 3A). This network was insensitive to insulin therapy (i.e., Not Normalized) (Figure 3B). In, contrast, a transcriptional network centred on Myc and altered in diabetic animals as compared to non-diabetic controls was almost completely normalized by insulin treatment (Additional File 6).


Chronic insulin treatment of diabetes does not fully normalize alterations in the retinal transcriptome.

Bixler GV, Vanguilder HD, Brucklacher RM, Kimball SR, Bronson SK, Freeman WM - BMC Med Genomics (2011)

Network analysis of genes Not Normalized. Genes and expression values from the Not Normalized category were examined for networks of interrelated genes using Ingenuity Pathway Analysis software. One significant network was centered around Pdgf, Nfkb, and Jnk. Expression values for the control versus diabetic groups is presented in A and for the insulin-treated diabetic versus diabetic comparison in B. Relationships are presented as lines and arrows. Red lines represent activation or positive regulation of expression while green lines indicate inhibition or negative regulation of expression. Grey lines are known protein-protein interactions and dashed lines are indirect relationships. Gene symbols are coded as green for significantly reduced expression, red for significantly reduced expression, and white for no change in expression.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3113923&req=5

Figure 3: Network analysis of genes Not Normalized. Genes and expression values from the Not Normalized category were examined for networks of interrelated genes using Ingenuity Pathway Analysis software. One significant network was centered around Pdgf, Nfkb, and Jnk. Expression values for the control versus diabetic groups is presented in A and for the insulin-treated diabetic versus diabetic comparison in B. Relationships are presented as lines and arrows. Red lines represent activation or positive regulation of expression while green lines indicate inhibition or negative regulation of expression. Grey lines are known protein-protein interactions and dashed lines are indirect relationships. Gene symbols are coded as green for significantly reduced expression, red for significantly reduced expression, and white for no change in expression.
Mentions: Analysis of gene networks extends the finding of sets of genes with differential patterns of expression in response to insulin therapy. For example, an inflammation related network of diabetes changes with nodes of Vegf, Pdgf, and NFkB was evident in the comparison of diabetics to non-diabetic controls (Figure 3A). This network was insensitive to insulin therapy (i.e., Not Normalized) (Figure 3B). In, contrast, a transcriptional network centred on Myc and altered in diabetic animals as compared to non-diabetic controls was almost completely normalized by insulin treatment (Additional File 6).

Bottom Line: A subset of genes (Ccr5, Jak3, Litaf) was confirmed at the level of protein expression, with protein levels recapitulating changes in mRNA expression.These results provide the first genome-wide examination of the effects of insulin therapy on retinal gene expression changes with diabetes.Gene expression changes not rescued or prevented by insulin treatment may be critical to the pathogenesis of diabetic retinopathy, as it occurs in diabetic patients receiving insulin replacement, and are prototypical of metabolic memory.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pharmacology, Penn State College of Medicine, Hershey, PA, USA.

ABSTRACT

Background: Diabetic retinopathy (DR) is a leading cause of blindness in working age adults. Approximately 95% of patients with Type 1 diabetes develop some degree of retinopathy within 25 years of diagnosis despite normalization of blood glucose by insulin therapy. The goal of this study was to identify molecular changes in the rodent retina induced by diabetes that are not normalized by insulin replacement and restoration of euglycemia.

Methods: The retina transcriptome (22,523 genes and transcript variants) was examined after three months of streptozotocin-induced diabetes in male Sprague Dawley rats with and without insulin replacement for the later one and a half months of diabetes. Selected gene expression changes were confirmed by qPCR, and also examined in independent control and diabetic rats at a one month time-point.

Results: Transcriptomic alterations in response to diabetes (1376 probes) were clustered according to insulin responsiveness. More than half (57%) of diabetes-induced mRNA changes (789 probes) observed at three months were fully normalized to control levels with insulin therapy, while 37% of probes (514) were only partially normalized. A small set of genes (5%, 65 probes) was significantly dysregulated in the insulin-treated diabetic rats. qPCR confirmation of findings and examination of a one month time point allowed genes to be further categorized as prevented or rescued with insulin therapy. A subset of genes (Ccr5, Jak3, Litaf) was confirmed at the level of protein expression, with protein levels recapitulating changes in mRNA expression.

Conclusions: These results provide the first genome-wide examination of the effects of insulin therapy on retinal gene expression changes with diabetes. While insulin clearly normalizes the majority of genes dysregulated in response to diabetes, a number of genes related to inflammatory processes, microvascular integrity, and neuronal function are still altered in expression in euglycemic diabetic rats. Gene expression changes not rescued or prevented by insulin treatment may be critical to the pathogenesis of diabetic retinopathy, as it occurs in diabetic patients receiving insulin replacement, and are prototypical of metabolic memory.

Show MeSH
Related in: MedlinePlus