A collaborative research group of Kanazawa University, Tokyo Medical and Dental University, Okayama University and others discovered that the bone loss that occurs in space is suppressed by melatonin.
Stimulation is required for bone growth and maintenance, and in the universe without gravity, calcium is released from the bone and bone mass decreases (bone resorption).In order to solve the problem of bone loss of astronauts who stay in space for a long time, this research group elucidates the behavior of osteoclasts (cells that dissolve bone) and osteoblasts (cells that make bone) under microgravity. Has been working on.
This time, we conducted a space experiment at the International Space Station "Kibo" using the scales of goldfish, which show a hormonal response similar to that of mammalian bones, as a bone model.First, it was clarified that melatonin, a hormone that regulates circadian rhythm, is produced in uroko osteoblasts, and that the expression of enzymes involved in melatonin synthesis is reduced in outer space, resulting in a decrease in melatonin.
Therefore, in order to investigate the action of melatonin in outer space, a comparative experiment was conducted in which scales were cultured in a medium containing melatonin and a medium not containing melatonin.As a result, it was found that in the medium without addition of melatonin, several osteoclasts were fused to form polynuclearized active osteoclasts in a culture of only 3 days, and bone resorption was promoted.Furthermore, it was found that the gene expression of Rankl, which is a factor that promotes bone resorption, is increased in osteoblasts, and the gene expression of calcitonin, which is a hormone that suppresses bone resorption, is suppressed.On the other hand, in the medium supplemented with melatonin, the expression of Rankl was suppressed and the expression of calcitonin was also normal.
From the above, it was clarified that the decrease in melatonin and the suppression of calcitonin secretion in space are one of the mechanisms that promote bone resorption.Conversely, it can be said that melatonin has the effect of stimulating the secretion of calcitonin and suppressing bone resorption.From this finding, it is expected that melatonin will be utilized as a preventive / therapeutic agent for astronauts' bone loss in the future.
Paper information:[Journal of Pineal Research] Melatonin is a potential drug for the prevention of bone loss during space flight
