| First Author | Guo Y | Year | 2005 |
| Journal | Endocrinology | Volume | 146 |
| Issue | 6 | Pages | 2602-9 |
| PubMed ID | 15731363 | Mgi Jnum | J:99271 |
| Mgi Id | MGI:3581918 | Doi | 10.1210/en.2004-1203 |
| Citation | Guo Y, et al. (2005) Pancreatic islet-specific expression of an insulin-like growth factor-I transgene compensates islet cell growth in growth hormone receptor gene-deficient mice. Endocrinology 146(6):2602-9 |
| abstractText | Both GH and IGF-I stimulate islet cell growth, inhibit cell apoptosis, and regulate insulin biosynthesis and secretion. GH receptor gene deficiency (GHR(-/-)) caused diminished pancreatic islet cell mass and serum insulin level and elevated insulin sensitivity. Because IGF-I gene expression was nearly abolished in these mice, we sought to determine whether that had caused the islet defects. To restore IGF-I level, we have generated transgenic mice that express rat IGF-I cDNA under the direction of rat insulin promoter 1 (RIP-IGF). Using RNase protection assay and immunohistochemistry, the IGF-I transgene expression was revealed specifically in pancreatic islets of the RIP-IGF mice, which exhibited normal growth and development and possess no abnormalities in glucose homeostasis, insulin production, and islet cell mass. GHR(-/-) mice exhibited 50% reduction in the ratio of islet cell mass to body weight and increased insulin sensitivity but impaired glucose tolerance. Compared with GHR(-/-) alone, IGF-I overexpression on a GHR(-/-) background caused no change in the diminished blood glucose and serum insulin levels, pancreatic insulin contents, and insulin tolerance but improved glucose tolerance and insulin secretion. Remarkably, islet-specific overexpression of IGF-I gene in GHR(-/-) mice restored islet cell mass, at least partially through cell hypertrophy. Interestingly, double-transgenic male mice demonstrated a transient rescue in growth rates vs. GHR(-/-) alone, at 2-3 months of age. Our results suggest that IGF-I deficiency is part of the underlying mechanism of diminished islet growth in GHR(-/-) mice and are consistent with the notion that IGF-I mediates GH-induced islet cell growth. |
