A new study published Jan. 25 in Nature by researchers from the Salk Institute showed that low levels of the amino acid serine put diabetic mice at risk for developing peripheral neuropathy.
The scientists are now using their findings to develop a test that can indicate whether a patient could benefit from serine supplementation. To test this hypothesis, scientists fed mice a serine-free diet combined with either a low-fat or high-fat diet for 12 months. A control group was also part of the study. According to the research team, a low-serine, high-fat diet speeds up the development of peripheral neuropathy in diabetic mice. Serine supplements, on the other hand, helped delay of neuropathy
Serine is a nonessential amino acid, meaning the body produces it on its own and doesn’t need to get it from external food sources the way it does essential amino acids. The term “nonessential” is not a reflection on how important they are to functioning; the molecules are used for energy metabolism and are involved in the synthesis of peptides, like glutathione. They’re also the building blocks of sphingolipids, fat molecules found heavily in the nervous system that are thought to be involved in tissue development, cell adhesion and more.
Serine-rich foods include soybeans, nuts, eggs, chickpeas, lentils, meat, and fish.
Who does peripheral neuropathy affect?
Peripheral neuropathy can affect anyone, regardless of age, sex, race or ethnicity, personal circumstances, medical history, etc. However, some people are at greater risk for specific types of peripheral neuropathy (see below under Causes and Symptoms for more about this).
Peripheral neuropathy is also very common with some age-related diseases. That means the risk of developing peripheral neuropathy increases as you get older.
How common is this condition?
Peripheral neuropathy is common, partly because this term refers to so many conditions. About 2.4% of people globally have a form of peripheral neuropathy. Among people 45 and older, that percentage rises to between 5% and 7%.
How peripheral neuropathy develops, particularly the timeline of its progress, depends very much on what causes it. Injuries can cause it to develop instantaneously or within minutes or hours. Some toxic and inflammation-based forms of peripheral neuropathy may develop rapidly over days or weeks, while most other conditions take months, years or even decades to develop.
What are the symptoms of peripheral neuropathy?
There are many different symptoms of peripheral neuropathy. This condition can affect a single nerve, a connected group of related nerves, or many nerves in multiple places throughout your body. The symptoms also depend on the type of nerve signals affected, and multiple signal types may be involved.
The symptom types (with more about them below) are:
Motor.
Sensory and pain.
Autonomic.
Motor symptoms
Your peripheral nervous system carries motor signals, which are commands sent from your brain to your muscles. These signals are what make it possible for you to move around. Your muscles need nerve connections to the brain to stay healthy and work properly.
Motor symptoms include:
Muscle weakness and paralysis. Nerve deterioration from peripheral neuropathy weakens the connected muscles. That can cause paralysis, which may cause difficulty moving the toes, foot drop and hand weakness. Weakness can also affect muscles in the thighs, arms and elsewhere.
Muscle atrophy. Loss of nerve connection can cause muscles to shrink in size, as well as weaken. This especially happens in the feet, lower legs and hands with peripheral neuropathy. Sometimes there are deformities of the feet and hands because of muscle loss.
Uncontrolled muscle movements. Sometimes, nerves that lose their connection to the brain because of peripheral neuropathy become hyperactive on their own, causing cramps.
Sensory symptoms
Your peripheral nerves convert information about the outside world into nerve signals. Those signals then travel to your brain, which processes those signals into what you can sense of the world around you. Peripheral neuropathy can disrupt what your senses pick up from the outside world or the ability of those senses to communicate with your brain.
The sensory symptoms of peripheral neuropathy include:
Tingling. This happens when there’s a problem with nerves that carry signals to your brain. This is like radio static you hear when you’re too far from the broadcasting station.
Numbness. This happens when nerves can’t send or relay sensory signals, causing the loss of specific types of sensations. An example of this would be picking up a cold pop can, but not feeling the smoothness or coldness of the can, or not being able to feel the texture of carpet or the temperature of the floor through your feet.
Imbalance and clumsiness. Nerves also carry sensations that your brain uses to keep track of the location of your hands and feet. You’re not consciously aware of these sensations, but they’re critical for balance and coordination. Without these sensations, you can experience a loss of balance, especially in the dark, and clumsiness with your hands.
Pain. Nerve damage from peripheral neuropathy can cause malfunctions in how and when nerves send pain signals, making pain signals more intense (hyperalgesia) or happen too easily (allodynia). It can even cause nerves to generate pain signals spontaneously. This is known as “neuropathic” pain, and it’s the most noticeable and disruptive symptom of peripheral neuropathy.
