Genetic Basis for Growth Hormone Action Identified

They found that administration of growth hormone to aged mice whose livers had been partially removed significantly increased the activity of the Foxm1b gene. The livers of these animals regenerated at a pace similar to that of young mice. Cell proliferation peaked at just two days, and the liver was fully restored within a week. Liver regeneration in aged mice that did not receive hormone injections required a month or longer.

Growth hormone treatment of young mice that had been genetically engineered to lack the Foxm1b gene failed to restore regenerating liver cell DNA replication and mitosis caused by Foxm1b deficiency. These results, published in the December, 2003, issue of Hepatology, provided strong evidence that the presence of Foxm1b was essential for growth hormone to stimulate regenerating liver cell proliferation.

"Growth hormone levels decline as we grow older; as a result, the Foxm1b gene stops working and our bodies are less capable of repairing damage,” explained senior author Dr. Robert Costa, professor of biochemistry and molecular genetics at the University of Illinois at Chicago. "These results clearly demonstrate that Foxm1b is essential for growth hormone to spur liver regeneration.”




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