A new study just published in the journal Diabetologia by researchers from Aarhus University, the University of Oxford, Imperial College and other institutions shows that patients with type 2 diabetes have a high prevalence of swellings on the sensory nerves in the skin which – when functioning normally – make us able to feel touch, temperature and pain. This makes it important not only to count the number of sensory nerves in the skin of people with type 2 diabetes, but also to examine their appearance, as they may be an early disease marker.

It is now known that many people with diabetes lose these sensory nerves and consequently develop neuropathy or diabetic neuropathy. Typical symptoms of neuropathy include loss of tactile sense, with patients saying that they cannot feel a light touch, for example, or that it feels as though they are walking on air because they cannot feel their feet when walking. Some patients also develop chronic foot pain, often described as burning pain or like being pricked with needles. These painful symptoms often get worse when at rest.

"The research team concluded that the swellings may be an early sign of sensory nerve disease or damage, and that they may appear before patients with diabetes begin to lose their sensory nerves and develop symptoms of neuropathy. The question is then whether it will be possible to intervene and prevent further damage to the sensory nerves before they disappear and symptoms begin. The Aarhus research team will now investigate this."

Loss of sensory nerves can be demonstrated by taking a small skin sample and counting how many nerves there are. While quantifying sensory nerve density is a good diagnostic tool,  it tells us nothing about the condition of the remaining nerves. They may be hyperactive, hypoactive or perfectly normal. Patients both with and without painful neuropathy have the same loss of sensory nerves. In other words, there is little correlation between the number of nerves and the symptoms that patients develop.

Both the Aarhus team and other researchers have previously shown that patients with diabetes have fewer sensory nerves in their skin, while the remaining nerves have swellings on them. The clinical significance of these swellings has, however, been unclear. Perhaps somewhat surprisingly, the new study showed that many patients with type 2 diabetes – both with and without diabetic neuropathy – have a higher incidence of these swellings. The study also showed that the number of swellings was correlated with HbA1c long-term blood sugar. This makes it important not only to count the number of sensory nerves in the skin of patients with type 2 diabetes, but also to examine their appearance.

The research team concluded that the swellings may be an early sign of sensory nerve disease or damage, and that they may appear before patients with diabetes begin to lose their sensory nerves and develop symptoms of neuropathy. The question is then whether it will be possible to intervene and prevent further damage to the sensory nerves before they disappear and symptoms begin. The Aarhus research team will now investigate this.

Páll Karlsson of the Pain Research Center in Aarhus and the International Diabetic Neuropathy Consortium is first author of the article. He is a former Danish Diabetes Academy postdoc who now sits on the Academy’s National Advisory Forum. He received the DDA-Funded Scientist Award 2020. As well as researching, he is an active teacher and speaker, and he is a contributor to a textbook, due out later this year, on diabetes and diabetic neuropathy.

CONTACT
Páll Karlsson, Associate Professor
Department of Clinical Medicine - Danish Pain Research Center
Palle Juul-Jensens Boulevard 165
8200 Aarhus N
Denmark
pall@clin.au.dk

READ THE ARTICLE HERE
Axonal swellings are related to type 2 diabetes, but not to distal diabetic sensorimotor polyneuropathy
https://link.springer.com/article/10.1007/s00125-020-05352-9
Published: 23 January 2021 – Open Access.