Mice fed extracts of a creature called a sea squirt – so-called because they tend to squirt water when plucked from their briny home – reversed some of the signs of ageing, according to a recent study from China.
The extracts fed to the mice are called plasmalogens – a type of lipid (fat) found in the membrane of cells in human organs such as the brain, kidneys, muscle and lungs. They have a variety of functions, including regulating how cells exchange information, protecting the cells from DNA damage and decreasing inflammation.
Past research has shown that the amount of plasmalogens in the blood decreases with age and especially in people with Alzheimer’s disease, the most common form of dementia.
Significant amounts of plasmalogens are found in foods such as chicken, pork, beef, mussels, scallops and, of course, sea squirts, which are eaten in Korea and Japan.
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In this latest study, researchers gave plasmalogens to middle-aged female mice in much higher concentrations (around 300 to 500 times higher) than would normally be found in a portion of, say, chicken or scallops. They then assessed the mice’s memory and some important parameters that change in the brain with age.
This included the number of neural stem cells, which generate new neurons (brain cells), and the number of connections between neurons. These are both important for maintaining the ability to learn, remember and reason.
They found that all of these parameters were improved when the mice were fed plasmalogens for two months. Also, inflammation was greatly decreased in the mice given plasmalogen compared with those on a normal diet (the control group). Inflammation increases with age and is thought to be an important cause of worsening symptoms of Alzheimer’s disease.
The researchers also showed that mice had improved memory. To do this, they used a test – called a Morris water maze – that uses sensory skills, including good eyesight, to learn to perform a task.
Unfortunately, mice tend to suffer a loss of sensory skills such as blindness and hearing with age and therefore these findings need to be treated with caution. The perceived improvement in memory could be the result of improved sensory skills rather than memory.
However, these latest findings are supported by an earlier study in which people with mild cognitive impairment were fed plasmalogens (this time from scallops) twice a day for 24 weeks. The participants given the plasmalogens showed improved memory. However, this improvement was only observed in a subgroup of patients who were female and younger than 77 years old. The reason it only worked for this subgroup is not clear and needs to be studied further with a larger group of participants.
Geroprotectors
Although these findings are interesting, more work is needed to find out if plasmalogens really are “geroprotectors” – drugs that delay cellular ageing, thereby reducing the risk of developing many age-related diseases. It’s important to find out how plasmalogens delay ageing and whether their effects go beyond the brain to include other important organs, such as the heart, the muscle and the immune system.
Over 200 geroprotectors have been tested in animals. In many studies, researchers have shown that geroprotectors can improve the function of vital organs. A handful of these have also been shown to delay the onset and severity of age-related chronic conditions such as osteoarthritis, heart disease, osteoporosis and Alzheimer’s disease in lab animals.
The next step is to test these drugs in patients, but this is difficult because of the way drugs are tested and approved for use. This is usually in patients with a specific disease and once the disease has been diagnosed. However, these drugs are more likely to give the best results when taken to stave off age-related diseases.
They may even prevent more than one disease at the same time. To test them, researchers need to identify who is at risk of developing one or more age-related diseases and then undertake a long and expensive trial to find out who gets the disease and who is protected.
To reduce the time of testing, researchers are now developing ways to identify who will develop specific age-related diseases in advance. But even if these studies are successful, the question remains of whether using geroprotectors to prevent diseases is cost-effective and safe. Perhaps other measures, such as an improved diet and exercise, may be just as good, if not better.
Ilaria Bellantuono is an employee of the University of Sheffield and receives funding from Horizon2020, MRC, BBSRC