April 2004
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Consortium completes gene sequencing of laboratory rat |
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Insulin-producing cells found in variety of tissues in diabetes |
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Pancreatic hormone affects bone loss |
Consortium completes gene sequencing of laboratory rat
A consortium led by the Human Genome Sequencing Center at Baylor College of Medicine in Houston has announced the completion of the genome sequencing of the Brown Norway rat.
The Rat Genome Sequencing Project Consortium reported that the high quality “draft” sequence of the Brown Norway rat covers over 90 percent of the genome. The results appeared in the April 1 issue of the journal Nature. The BCM center directed the project, which was conducted with major funding from the National Heart, Lung and Blood Institute and the National Human Genome Research Institute.
“Future work aimed at identifying the genomic differences that contribute to evolution and disease will benefit from analyses such as these, which will become increasingly powerful as the repertoire of mammalian genome sequences expands” said Richard Gibbs, PhD, director of the BCM center and principal investigator of the project.
“This is an investment that is destined to yield major payoffs in the fight against human disease,” said NIH Director Elias A. Zerhouni, MD. “For nearly 200 years, the laboratory rat has played a valuable role in efforts to understand human biology and to develop new and better drugs. Now, armed with this sequencing data, a new generation of researchers will be able to greatly improve the utility of rat models and thereby improve human health.”
Peter G.Traber, MD, BCM president and CEO, said, “The genome sequence will further enhance the role of the rat in human medical research, which already has been significant. Scientists have gained a wealth of knowledge in many areas from studies involving the rat, including surgery, cancer, cardiovascular disease, diabetes and psychiatric disorders. The genome sequence will boost all of these research efforts.”
Insulin-producing cells found in variety of tissues in diabetes
Cells that produce insulin have been unexpectedly found in the fat, liver and bone marrow of diabetic mice, said researchers at Baylor College of Medicine in a report that appeared recently in the Proceedings of the National Academy of Sciences.
“In fact, the appearance of insulin-producing cells occurs in both Type 1 (juvenile) and Type 2 (adult-onset) diabetic mice,” said Lawrence Chan, MD, DSc, chief of the BCM endocrinology section and a professor in the department of medicine and molecular and cellular biology.
“The common denominator in all the animals is high blood sugar, not insulin-deficiency,” he said. “High blood sugar causes these cells to produce insulin.”
The numbers of cells and the amount of insulin produced are both very small and do not seem to ameliorate the animals’ disease, said Chan.
Pancreatic hormone affects bone loss
Amylin, a hormone secreted by the same cells that produce insulin in the pancreas, prevents bone loss, said Baylor College of Medicine researchers and an international group of collaborators in a report in a recent issue of the Journal of Cell Biology.
The finding may point the way toward treatments for osteoporosis, a disease of low bone mass that usually affects post-menopausal women but is also observed in Type 1 diabetes patients, said Gèrard Karsenty, MD, PhD, professor of molecular and human genetics at BCM in Houston and senior author.
“If osteoporosis in diabetes is associated with the absence of amylin, this finding has therapeutic implications,” he said.
Amylin, a member of the calcitonin hormone family, inhibits bone loss or resorption. It is secreted by the pancreatic ß-cells at the same as insulin. Type 1 diabetics no longer produce insulin or amylin because their ß-cells no longer function. Mice who lack amylin have less bone mass than those who produce the hormone because they destroy bone more rapidly as it is seen in classical osteoporosis, said Karsenty. Perhaps, he said, finding a way to replace amylin will enable physicians in the future to prevent osteoporosis in Type I diabetes and possibly in other forms of osteoporosis.
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