Related Experiment Videos
Blunting of the immediate-early gene and mitogenic response in hepatectomized type 1 diabetic animals
S Chin1, S Ramirez, L E Greenbaum
1Department of Genetics, Children's Hospital of Philadelphia, Pennsylvania, USA.
Abstract:
Studies suggest that liver regeneration is delayed in insulin-deficient animals, but defining a role of insulin as a growth factor in hepatic regeneration has remained elusive. By examining gene expression of hepatectomized liver in type 1 diabetic BB rats, we have identified dramatic changes in the expression of primary or immediate-early growth response genes compared with normal animals. These include altered expression of insulin-regulated genes such as glucose-6-phosphatase (G-6-Pase), phosphoenolpyruvate carboxykinase (PEPCK), and beta-actin, and genes such as CL-6 and map kinase phosphatase-1 (MKP-1) that were previously unlinked to insulin action in animals. Abnormal elevation of mRNAs encoding G-6-Pase, MKP-1, and PEPCK in the time 0 diabetic liver results in decreased induction after partial hepatectomy. Other genes, such as CL-6 and beta-actin, are induced at a lower level in the hepatectomized diabetic animals. The net effect is a blunting of the immediate-early gene response after partial hepatectomy in diabetic animals. As determined by DNA synthesis assays, the regenerative capacity of insulin-deficient BB diabetic livers is reduced, and this defect is corrected at least in part by insulin therapy. These findings suggest that because of insulin deficiency, common intracellular signaling pathways that are required for both metabolism and mitogenesis are aberrant in the type 1 diabetic liver and, as a result, the regenerative response is deficient.
Insights
Insulin deficiency impairs liver regeneration by altering key growth response genes in type 1 diabetic rats. Insulin therapy partially restores this regenerative capacity, highlighting insulin
Area of Science:
- Hepatology and Endocrinology
- Molecular Biology and Genetics
Background:
- Insulin's role as a growth factor in hepatic regeneration remains unclear.
- Type 1 diabetes is associated with delayed liver regeneration in animal models.
Purpose of the Study:
- To investigate the impact of insulin deficiency on gene expression during liver regeneration.
- To determine if insulin therapy can restore the regenerative capacity of diabetic livers.
Main Methods:
- Gene expression analysis of hepatectomized livers in type 1 diabetic BB rats.
- Comparison of gene expression patterns between diabetic and normal rats.
- DNA synthesis assays to assess liver regenerative capacity.
- Evaluation of insulin therapy's effect on regeneration.
Main Results:
- Diabetic rats showed altered expression of immediate-early growth response genes, including insulin-regulated genes (G-6-Pase, PEPCK, beta-actin) and previously unlinked genes (CL-6, MKP-1).
- Abnormal mRNA levels of G-6-Pase, MKP-1, and PEPCK in diabetic livers led to decreased induction post-hepatectomy.
- Reduced induction of CL-6 and beta-actin was observed in hepatectomized diabetic animals.
- Overall, a blunted immediate-early gene response was noted in diabetic livers after partial hepatectomy.
- Liver regenerative capacity, measured by DNA synthesis, was reduced in insulin-deficient diabetic livers.
- Insulin therapy partially corrected the regenerative defect in diabetic rats.
Conclusions:
- Insulin deficiency in type 1 diabetes disrupts intracellular signaling pathways essential for both metabolism and cell proliferation in the liver.
- This disruption results in a deficient hepatic regenerative response.
- Insulin plays a crucial role in supporting liver regeneration, acting as a mitogen in addition to its metabolic functions.