A little myelin goes a long way to restore nervous system function

October 24, 2017, University of Wisconsin-Madison
The normal mature dog spinal cord (A) has many axons surrounded by thick myelin sheaths (blue). In contrast, in the recovered dog with the genetic abnormality (B), there are many axons with thin myelin sheaths, identical to that seen in remyelination. Credit: University of Wisconsin-Madison

In the central nervous system of humans and all other mammals, a vital insulating sheath composed of lipids and proteins around nerve fibers helps speed the electrical signals or nerve impulses that direct our bodies to walk, talk, breathe, swallow or perform any routine physical act.

But diseases of the nervous system, including multiple sclerosis (MS) in people, degrade this essential insulation known as , disrupting the flow of information between the brain and the body, impairing movement, dimming vision and blunting the ability to function normally.

And while scientists have long studied myelin and understand its role in disease when it degrades, they have puzzled over how myelin repairs itself naturally and whether the thinned sheaths that are a hallmark of the healing nervous system are adequate for restoring the brain's circuitry over the long haul.

This week (Oct. 23, 2017), in a study published in the Proceedings of the National Academy of Sciences, a team of researchers from the University of Wisconsin-Madison reports that in long-lived animals, renewed but thin myelin sheaths are enough to restore the impaired nervous system and can do so for years after the onset of disease.

The team's findings reinforce the idea that thin myelin sheaths are a valid, persistent marker of remyelination, a hypothesis challenged by other recent research. "As the only biomarker of myelin repair available this would leave us without any means of identifying or quantifying myelin repair," explains Ian Duncan, an expert on demyelinating diseases at the UW-Madison School of Veterinary Medicine and the senior author of the new study.

Duncan and his team looked at a unique genetic disorder that naturally afflicts Weimaraners, a breed of dog that as 12- to 14-day-old pups develop a severe tremor and loss of coordination. The condition is known to occur as the development of the in parts of the dog's central nervous system is delayed. The symptoms gradually diminish and in most cases disappear altogether by 3-4 months of age.

"This is a very widespread mutation in the breed," says Duncan, noting that myelin repair mimicking what is seen in remyelination is known to occur in these dogs as the rejuvenated have a thinned myelin sheath.

The new Wisconsin study was made possible as 13 years ago two Weimaraner pups, littermates, were seen as patients at the School of Veterinary Medicine and Duncan was able to maintain contact with the owners after the dogs were adopted and retrieve samples of spinal tissue after the dogs lived out their lives. As they aged, the dogs exhibited few signs of tremor and were deemed 'neurologically normal' up to 13 years of age.

The purpose of the study, says Duncan, was to confirm that thin myelin sheaths persisted and supported normal neurologic function.

To expand on the results, Duncan also looked at a condition in cats, another long-lived species that has been shown to fully recover nervous system function after demyelination. In particular, Duncan's team was interested in remyelination of the optic nerves.

That element of the study, looking at remyelination two years after the onset of the condition, Duncan notes, is an example of "true demyelination and remyelination. We found that nearly every optic fiber was remyelinated with a thin myelin sheath, which is important for understanding human disease because in , the optic nerve is often the first to be demyelinated."

The new findings confirm that the gold standard for evaluating remyelination is the long-term persistence of thin myelin sheaths, which support nerve fiber function and survival, Duncan notes. The results are important for diseases like MS as it means that new therapies designed to promote myelin repair can be safely evaluated and quantified based on the presence of thin myelin sheaths.

Explore further: Rare neurological disease shines light on health of essential nerve cells

More information: Ian D. Duncan el al., "Thin myelin sheaths as the hallmark of remyelination persist over time and preserve axon function," PNAS (2017). www.pnas.org/cgi/doi/10.1073/pnas.1714183114

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Mark Thomas
5 / 5 (2) Oct 24, 2017
In the movie Lorenzo's Oil, the very heroic parents of Lorenzo worked incredibly hard to help develop Lorenzo's Oil, which ultimately helped asymptomatic adrenoleukodystrophy (ALD) patients. Unfortunately, for Lorenzo himself, the damage to his myelin was unrepairable . The article suggests some welcome progress is being made on understanding myelin regeneration.
Solon
3.7 / 5 (3) Oct 24, 2017
I learned from experience the importance of myelin and the illness associated with the lack of it. It turns out the the free MSG found in ever larger quantities in highly processed/junk food inhibits the production of myelin, and the bodies repair mechanisms can then not 'patch' the defects in the nerve sheaths caused by processes occurring naturally in the body. With prolonged, moderate to heavy MSG consumption, the cumulative defects in the nerve sheaths increase the noise levels in the nervous system and disruption of inter-organ communications, despite the bodies very efficient error correcting mechanisms.
It reached a point with me that I had a constant noise in my head, like gibberish voices just below consciousness threshold, similar to schizophrenia symptoms. Also had many chronic physical conditions. After quitting all processed/junk food, it took only 10 days before noticeable improvements in health were evident, and now after 3 years off the poison much, much healthier.
BubbaNicholson
1 / 5 (2) Oct 24, 2017
1st. Myelin is not an insulator. Were that its function, it would vary along an axon as insulating tissues are transited. Generally speaking if biology is doing something "stupid" then it is not the biology which is stupid.
Myelin is part of a system which does not waste energy. Conductance, capacitance, and inductance are parts of the system. The myelin wraps form the capacitance leg. This explains why all the Schwann cells on an axon are always exactly the same size (capacitance sums on a circuit as sum of inverses) & why O2 is not consumed warming axons (heat of resistance).
2nd. Maternal pheromone allows myelination in rodents. Might it have some effect elsewhere? What is the human equivalent? Is there a pheromone which demyelinates? That is likely given that pheromone can build myelin, suggesting influence.
barakn
5 / 5 (1) Oct 25, 2017
It turns out the the free MSG found in ever larger quantities in highly processed/junk food inhibits the production of myelin, and the bodies repair mechanisms can then not 'patch' the defects in the nerve sheaths caused by processes occurring naturally in the body. With prolonged, moderate to heavy MSG consumption, the cumulative defects in the nerve sheaths increase the noise levels in the nervous system and disruption of inter-organ communications, despite the bodies very efficient error correcting mechanisms. -Solon
Utter quackery. MSG is a salt of glutamate. When it enters your stomach, the sodium leaves and it becomes glutamate. When proteins are digested into amino acids by the hydrochloric acid in your stomach, one of them is glutamate. Monosodium glutamate is found naturally in tomatoes, cheese and other foods. Glutamate is such an essential neurotransmitter that your nervous system's own cells can synthesis glutamate from glutamine.

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