Proteins linked to narcolepsy also linked to osteoporosis
June 25, 2014
According to a study published in the journal Cell Metabolism, orexin proteins, which cause daytime sleepiness, play a significant role in the formation of bones. The new findings could allow researchers to uncover a better treatment for osteoporosis.
Osteoporosis affects close to 200 million women worldwide, according to the International Osteoporosis Foundation. The condition greatly increases people's chances of fragility fractures, with more than 8.9 million bone fractures occurring annually. Based on these numbers, someone experiences a fracture close to every 3 seconds.
Researchers from the UT Southwestern Medical Center discovered orexin proteins more than 15 years ago. They discovered that the proteins are used by nerves to communicate with one another. They regulate several behaviors, like appetite and arousal, and most notably, wakefulness. So those who lack orexin proteins are found to be narcoleptic.
Recently, the researchers worked with colleagues in Japan, discovering that mice with a deficiency in orexin proteins also had very brittle bones. They believe their fragility was caused by a lack of cells known as osteoblasts, which build bones.
The findings showed that orexin proteins both block and build bones. Within the bones, the protein interacts with another type of similar protein known as orexin receptor 1. This protein is known for decreasing hunger levels, and results in a slowing of production for new osteoblasts. But, orexin also interacts with a different protein at the same time, known as orexin receptor 2. This protein, which is found in the brain, decreases the amount of a hormone known as leptin, which has been linked to bone deterioration. So, prevention for osteoporosis can be found by either inhibiting or activating either of these receptor proteins.
The researchers found the findings to be similar to a balance of ying and yang. Mice that were lacking in both receptor proteins had brittle bones as well as difficulty building bone mass, where those who had higher levels of orexin had stronger bones and an easier bone production.
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