Platypus and opossum calcitonins exhibit strong activities, even though they belong to mammals.

In mammalian assay systems, calcitonin peptides of non-mammalian species exhibit stronger activity than those of mammals. Recently, comparative analyses of a wide-range of species revealed that platypus and opossum, which diverged early from other mammals, possess calcitonins that are more similar in amino acid sequence to those of non-mammals than mammals. We herein determined whether platypus and opossum calcitonins exhibit similar biological activities to those of non-mammalian calcitonins using an assay of actin ring formation in mouse osteoclasts. We also compared the dose-dependent effects of each calcitonin on cAMP production in osteoclasts. Consistent with the strong similarities in their primary amino acid sequences, platypus and opossum calcitonins disrupted actin rings with similar efficacies to that of salmon calcitonin. Human calcitonin exhibited the weakest inhibitory potency and required a 100-fold higher concentration (EC50=3×10-11M) than that of salmon calcitonin (EC50=2×10-13M). Platypus and opossum calcitonins also induced cAMP production in osteoclast cultures with the same efficacies as that of salmon calcitonin. Thus, platypus and opossum calcitonins exhibited strong biological activities, similar to those of the salmon. In addition, phylogenetic analysis revealed that platypus and opossum calcitonins clustered with the salmon-type group but not human- or porcine-type group. These results suggest that platypus and opossum calcitonins are classified into the salmon-type group, in terms of the biological activities and amino acid sequences.

[Present situation of medical screening system for osteoporosis].

Medical screening system for osteoporosis is important method for detection of osteopenia or osteoporosis in the community. The medical screening for osteoporosis was done for female subjects at age 40, 45, 50, 55, 60, 65, 70 year-old people according to the Health Promotion Act in Japan. The number of females received the screening was 287,782 in 2008, and the number corresponded to 4.7% of the estimated numbers of subjects for the screening in the population. Sixty six percentages of institutions measured bone mass and/or bone mineral density with the purpose other than that proposed by Health Promotion Act at 2009. Calcaneus bone mass was measured in 81% of institutions by quantitative ultrasound(QUS). Because QUS is inexpensive, involves no radiation exposure, and is easily portable, this method should be suitable for medical screening for osteoporosis and its prevalent use in Japan supports this assumption.

Current status of hip bone densitometry in Japan: a nationwide survey.

Hip fracture greatly impairs quality of life in patients with osteoporosis. Measurement of bone mineral density (BMD) in the hip, which is closely related to fracture risk, is therefore diagnostically important. Furthermore, since in some elderly individuals lumbar BMD may be overestimated because of vertebral fracture or spondylosis deformans, measurement of hip BMD is also important. However, hip BMD is unlikely to be measured as often as lumbar BMD in Japan. A questionnaire survey was conducted to determine how many institutions measure hip BMD. A total of 861 institutions responded to the survey, 596 (69%) of which performed hip bone densitometry. The number of such institutions per million population was calculated to be 4.7. Measurement of hip BMD was more frequent in university hospitals than in general hospitals, clinics, and non-medical institutions. Furthermore, 298 (51%) of 590 institutions measured hip BMD in more than 75% of all bone densitometry examinees. This is the first report on the current status of utilization of hip bone densitometry in Japan.

Changes in distribution of bone densitometry equipment from 1996 to 2006 in Japan.

Many types of bone densitometry equipment are available in Japan, but the numbers of such machines and the numbers of institutions that offer bone densitometry have not been clarified. We analyzed the data from annual surveys conducted by the Japan Osteoporosis Foundation from 1996 to 2006, and we obtained the following results on the use of densitometry equipment: (1) In 1996 there were 6,687 units of bone densitometry equipment in 6,483 institutions in Japan; in 2006 there were 16,371 units in 15,020 institutions. (2) In 2006, of the types of institutions with bone densitometry equipment, the number of clinics was the highest, followed in order by general hospitals, other types of institutions, screening institutions and university hospitals. Rates of increase in the installation of equipment in clinics and other types of institutions were high during the 11-year period from 1996. (3) From 1996 to 2006 the region of interest most frequently used for bone densitometry was the radius. However, during the 11-year period, the proportion of radial densitometry equipment in all institutions with bone densitometry equipment decreased, whereas the proportion of calcaneal densitometry equipment increased. (4) The number of dual-energy X-ray absorptiometry (DXA) units was the highest from 1996 to 2006. However, the proportion of DXA machines in all institutions with bone densitometry equipment decreased over the 11-year period, whereas the proportion of quantitative ultrasound (QUS) machines increased. (5) In 2006, bone densitometry equipment was available in 118 institutions per million Japanese people. Central DXA (spine/hip) equipment was available in 15 per million, radial DXA equipment in 63 per million, and calcaneal QUS equipment in 44 per million. (6) In 2006, among those places with bone densitometry equipment, 46% of university hospitals, 14% of general hospitals, 12% of screening institutions, 5% of clinics, and 6% of other types of institutions possessed more than one type of densitometry equipment. (7) In 2006, central DXA (spine/hip) was frequently available in university hospitals, radial densitometry equipment in general hospitals and clinics, and calcaneal densitometry equipment in screening institutions and other types of institutions.