The woman who can smell Parkinson’s disease

Photo credit: stevepb via pixabay

24 years ago, Joy Milne, a now 67 year old from Perth, noticed a strange and ‘different’ smell on her husband, Les Milne. She described it as a, ‘’tick musk smell. Very different’’, and at the time thought he wasn’t washing himself properly, which caused a bit of tension. Les was, however, to be diagnosed with Parkinson’s disease just ten years later, at the age of 45.

Parkinson’s disease is a disease that affects 1 in 500 people, and 1 in 100 people over the age of 60. It is a neurodegenerative disease that affects the midbrain and results in a loss of dopaminergic neurons from the substantia nigra. The dopaminergic neurons produce the neurotransmitter dopamine which relays messages between the brain and body by crossing synapses between neurons. A reduction of these neurons causes a drop in the dopamine, which results in abnormal movements. The precise cause of this neuronal reduction remains unknown.

The symptoms are very mild and slow onset at first, but with different levels of severity and order of symptoms between individuals, making the disease hard to diagnose. The main three symptoms are tremors, characterised by uncontrolled shaking usually in the arm or hand when the limb is relaxed. Slowness of movement, also known as bradykinesia, resulting in a slow shuffling walk, and also muscle stiffness (rigidity), making it hard to move and form facial expressions.

There is no cure for Parkinson’s disease at the moment, but there are treatments out there aimed at relieving symptoms in suffering individuals.  Alongside drug administration, other therapies, such as physiotherapy and occupational therapy, aim to build strength and help affected individuals to manage their day to day life. The three main drugs that are currently offered are Levodopa, Dopamine agonists and Monoamine oxidase-B inhibitors (MAO-B inhibitors). Levodopa is a drug that is absorbed by nerve cells and converted into dopamine, making up for the loss in the neurotransmitter. The drug, however, losses its effectiveness as more nerve cells are lost, as fewer nerve cells are available to absorb the medicine. Dopamine agonists can also be used, and act as a molecularly similar substitute to dopamine. MAO-B inhibitors prevent the degradation of dopaminergic neurons by blocking the substance or enzyme that breaks them down. These inhibitors improve symptoms but are not as effective as Levodopa. Whilst there may be no cure, it looks like a quick and accurate diagnostic test may be within reach.

After attending a Parkinson’s UK support group, Joy noticed the same ‘musky’ smell on other people with the disease, and her ‘’nose just went ‘wow’’’.  She spoke to scientists, including Dr Tilo Kunath from the Scottish Centre for Regenerative Medicine at the University of Edinburgh and they decided to test her. They got her to smell bags containing sweaty T-shirts worn by either people with Parkinson’s disease or without and asked her to identify which had the disease. She got 11 out of 12 correct, but was adamant that the 12th individual, who was a Parkinson’s-free control, also had the disease. 8 months later, however, the control told Dr Kunath that he had been diagnosed with Parkinson’s disease, meaning that Joy was 100% accurate in the test. This has led to the idea that Parkinson’s is associated with a volatile molecular marker, a compound which can easily evaporate and therefore be smelt, which could potentially be used in diagnostic tests.

Joy has been working with the University of Manchester and they have finally had a breakthrough, with a paper published in the ACS Central Science journal on the 20th of March. She has also been made an honorary lecturer at the University of Manchester for her contribution to identifying the smell markers of the disease. The compounds that were found higher on individuals with Parkinson’s were hippuric acid, eicosane and octadecanal. They are all found in sebum, an oily secretion of the sebaceous glands in the skin, which is often produced in higher levels in people with Parkinson’s disease. These high levels of the compounds are associated with changes in the neurotransmitters, and their levels can now be used as a model to assess the extent of the disease.

The lead author of the paper, Professor Perdita Barran, from the University of Manchester School of Chemistry, told the BBC that they ‘designed some experiments to mimic what Joy does, to use a mass spectrometer to do what Joy can do when she smells these things on people with Parkinson’s’’, to identify the molecules present in the samples by measuring their molecular weight. The newly discovered ‘volatile biomarkers’ will allow researchers to design diagnostic tests, allowing earlier diagnosis of patients. This earlier diagnosis should improve the quality of life of these patients whilst potentially slowing the rate of disease progression.

This post was written by Tara Wagner-Gamble and edited by Ella Mercer.

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