From birth until about the age of 30, your muscles continue to grow larger and stronger. But at some point in your 30s, you begin to lose muscle mass and strength which in turn affects your coordination. As part of the natural aging process, this disease, sarcopenia, is most commonly seen in inactive people but it also affects those who remain physically active throughout their lives.
Now UC Berkeley researchers have discovered that oxytocin – the “trust hormone” associated with maternal nurturing, social attachments, childbirth and sex – may combat this age-related muscle wasting. Their new study was recently published in Nature Communications.
Role in Muscle Regeneration
Led by associate professor of bioengineering Irina Conboy, the researchers found in mice that oxytocin is required to maintain healthy muscles, but the level of oxytocin in the blood and the number of oxytocin receptors in muscle stem cells naturally reduce with age. For instance, old (18 to 24 months) mice were found to have 3 times lower circulating levels of oxytocin than young (2 to 4 months) mice.
The research team performed a series of experiments using young and old mice to better understand oxytocin’s role in muscle repair. They injected the mice daily with oxytocin (or a control solution) under the skin for nine consecutive days, while causing a muscle injury midway on day 4. The researchers found that the old mice that received the oxytocin were able to repair their muscle injury at a level comparable to the young mice – far better than the old control group that didn’t get oxytocin. Systemic administration of oxytocin appears to rapidly improve muscle regeneration by enhancing aged muscle stem cell proliferation.
In contrast, the young mice already had sufficient levels of oxytocin and efficient muscle regeneration, so the oxytocin injections had no significant effect. This is important since most molecules that boost tissue repair are also associated with an increased risk of cancer.
“This is good because it demonstrates that extra oxytocin boosts aged tissue stem cells without making muscle stem cells divide uncontrollably,” explained Wendy Cousin, a senior scientist in Conboy’s lab, in a press release.
The researchers also performed similar experiments using mice with an inactivated gene for oxytocin and control mice. At the young age of 3 months, the two groups of mice appeared to have comparable muscle mass and repair efficiency after a muscle injury. However, muscle atrophy and a significant decline in muscle regeneration were observed for the 1-year old adult mice with the disabled oxytocin gene, signifying premature aging due to a lack of oxytocin.
It is unclear how long it will take the researchers to move beyond mice studies to human use. However, oxytocin is already approved by the FDA for clinical use in humans for other applications. For instance, oxytocin is commonly used to help increase contractions and control bleeding during childbirth. So getting approval for human studies should be straightforward once the reseachers are ready.
Conboy's research team is ultimately interested in applications beyond just maintaining healthy muscles. For instance, they are also investigating whether oxytocin could become a viable alternative to hormone replacement therapy to impede the symptoms of male and female aging. They believe that aging is the underlying cause of a number of chronic diseases, including Parkinson’s and Type 2 diabetes.
In fact, researchers around the world are studying the use of oxytocin for seemingly every condition imaginable, including using oxytocin nasal spray to alleviate symptoms associated with mental disorders such as autism, schizophrenia and dementia. However, this research currently demonstrates mixed and inconsistent results, particularly regarding oxytocin's influence on social skills.
The current excitement about oxytocin, particularly as a remedy for autism, could lead to a dangerous situation given the widespread availability of oxytocin supplements – as an accelerator spray, sublingual liquid that is absorbed under the tongue, pills and mouth lozenges. It is important to consult your doctor before taking oxytocin.