| Research Abstract |
1. Klotho gene expression in the new animal model for human ageing and study for insulin deficiency in this model
1) We have recently identified a novel gene, termed klotho (kl), which may suppress several ageing phenotypes. Defect of kl gene expression in the mouse results in a syndrome resembling human ageing, such as arteriosclerosis, skin atrophy, osteoporosis, and pulmonary emphysema. The klotho gene is expressed in the kidney, artery, and lung. The gene sequence was 40% similarity with β-glucosidase. The gene expression in the kidney was decreased-in model rats for hypertension and diabetes mellitus. As the dysfunction of endothelial cells were recovered after parabiosis experiment, we suggest that the klotho gene products can act as a fluid factor, such as hormones and cytokines.
2) To see whether mouse homozygote for the kl mutation (kl/kl) show abnormal glucose metabolism and insulin deficiency, OGTT was performed at 6-8 weeks of age. Blood glucose levels during OGTT in kl/kl mi
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ce were significantly lower than those in wild mice. Whereas, insulin content of the pancreas in kl/kl mice-was significantly lower compared to that of control mice. The decreased insulin production was also supported by Northern blot analysis that showed lower levels of insulin mRNA in kl/kl mice.
3) Histological findings showed that pancreatic β cells were selectively diminished, and α cells were slightly increased in number in the klotho mice. We could not find immunocytes in the islets of pancreas and apoptosis signals were not detectable, suggesting that the insulin deficiency could be due to direct effect by defect of kl gene expression in the klotho mouse.
These findings were published in Nature 1997, Biochem Biophys Res Comm 1998, and reported in several national and international meetings, such as Japan diabetes association, European association for study of the diabetes, and so on.
2. Establishment for the animal model for NIDDM
This study was initiated to see high calorie diet can induce NIDDM in mouse heterozygote for the kl mutation (kl/+) that has increased insulin sensitivity. So far, no animal developped NIDDM for one years.
3. Study for prevention of abnormal glucose metabolism using the purified klotho protein
Purification of klotho protein is now on-going. Once purified and prepared for administration in vivo, this study can performed. Less
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