Smelling Parkinson's

In the news this week you might have seen a perplexing story about a lady who can smell Parkinson's! Her husband was diagnosed with Parkinson's and she noticed a strange smell. She only connected the dots when she attended a Parkinson's UK support group and was suddenly surrounded by the smell.

This is not the first report of people being able to smell diseases. Patients with Type 1 diabetes whose sugars have gone very high and blood acidic start to smell like pear drops. There are many reports of nurses who can smell specific types of bacteria.

This phenomena is not limited to humans either! One of my colleagues at medical school presented on the fascinating topic of animals that can smell diseases which included rats which can smell tuberculosis and dogs which can smell cancer. (Also a non-smell related one but equally interesting is that pidgeons can be trained to identify breast cancer on mammograms and pathology slides)

Joy Milne was given 12 t shirts to smell, 6 had been worn by Parkinson's patients and 6 were from people without Parkinson's. She correctly identified the 6 people with Parkinson's and also thought that one of the healthy controls had the smell as well, this person was subsequently diagnosed with Parkinson's so she had 100% accuracy at smelling Parkinson's.

From a scientific point of view, there must be a particular chemical that she is smelling and she has been working with a team in Manchester to try to identify the chemical that she is smelling. Fortunately they have found two chemicals that could be the source of this smell. This is a really important finding because it can lead to a potential quick test to diagnose Parkinson's. This test could even be used to diagnose Parkinson's earlier.

Discovery of volatile biomarkers of Parkinson’s disease from sebum

Drupad K Trivedi, Eleanor Sinclair, Yun Xu, Depanjan Sarkar, Camilla Liscio, Phine Banks, Joy Milne, Monty Silverdale, Tilo Kunath, Royston Goodacre, Perdita Barran

Parkinson’s disease (PD) is a progressive, neurodegenerative disease that presents with significant motor symptoms, for which there is no diagnostic test. We have serendipitously identified a hyperosmic individual, a ‘Super Smeller’ that can detect PD by odor alone, and our early pilot studies have indicated that the odor was present in the sebum from the skin of PD subjects. Here, we have employed an unbiased approach to investigate the volatile metabolites of sebum samples obtained noninvasively from the upper back of 64 participants in total (21 controls and 43 PD subjects). Our results, validated by an independent cohort, identified a distinct volatiles-associated signature of PD, including altered levels of perillic aldehyde and eicosane, the smell of which was then described as being highly similar to the scent of PD by our ‘Super Smeller’

Crying out for a new biomarker

The hunt for a biomarker for Parkinson's has led researchers to investigate a lot of different bodily fluids and techniques! A biomarker is a test that can diagnose Parkinson's, at the moment the only way to diagnose Parkinson's is by using your eyes and your ears. Previously people have tested blood, CSF (the fluid around your brain), skin, saliva, MRI scans, skin samples and even samples of colon. But this pilot study is about a potential location for a biomarker that I had not yet heard of: Tears.

Its well known already that people with Parkinson's have reduced amounts of tears and a lower blink rate. And the researchers point out the the nerves that control the tear gland (lacrimal gland) connect to the brainstem. The brainstem is where a lot of the changes in early Parkinson's take place.

In this study they took 36 people with Parkinson's and 18 healthy people without Parkinson's and collected their tears by using some filter paper to absorb them. They then extracted the proteins from the collected tears.

They found that the Parkinson's participants had a smaller volume of tears but the protein concentration in the tears was about the same as healthy controls. They also identified 21 proteins that people with Parkinson's had significantly higher amounts of and 19 that were significantly reduced in Parkinson's too.

This is only a very small pilot study so we need some further studies in larger groups of patients before we draw any conclusions. But tears are a very attractive biomarker simply because they are so accessible. So this is definitely one to keep in mind and watch out for any further studies about.

Parkinsonism Relat Disord. 2019 Mar 6. pii: S1353-8020(19)30094-X. doi:

Proteomic analysis of tear fluid reveals disease-specific patterns in patients with Parkinson's disease - A pilot study.

Boerger M¹, Funke S², Leha A³, Roser AE⁴, Wuestemann AK⁵, Maass F⁶, Bähr M⁷, Grus F⁸, Lingor P⁹.

Abstract

BACKGROUND:

The diagnosis of Parkinson's disease (PD) is still challenging and biomarkers could contribute to an improved diagnostic accuracy. Tear fluid (TF) is an easily accessible body fluid reflecting pathophysiological changes in systemic and ocular diseases and is already used as a biomarker source for several ophthalmological disorders. Here, we analyzed the TF of patients with PD and controls (CTR) to describe disease-related changes in TF and identify putative biomarkers for the diagnosis of PD.

METHODS:

Unstimulated TF samples of a pilot cohort with 36 PD patients and 18 CTR were collected via Schirmer tear test strips and then analyzed via a Bottom-up liquid chromatography electrospray ionization tandem mass spectrometry (BULCMS) workflow, followed by functional analysis encompassing protein-protein interaction as well as cellular component and pathway analysis.

RESULTS:

BULCMS analysis lead to the identification of 571 tear proteins (false discovery rate, FDR < 1%), whereby 31 proteins were exclusively detected in the PD group and 7 only in the CTR group. Whereas 21 proteins were significantly increased in the PD versus CTR groups, 19 proteins were significantly decreased. Core networks of proteins involved in immune response, lipid metabolism and oxidative stress were distinctly altered in PD patients.

CONCLUSIONS:

To our best knowledge, this is the first description of TF proteome in PD patients. Tear protein level alterations suggest the contribution of different disease-related mechanisms in ocular pathology in PD and propose candidate proteins to be validated as potential biomarkers in larger cohorts.

PLAIN ENGLISH: Organ transplants and risk of Parkinson's

This is another interesting study borne out of large USA health insurance databases (Medicare database). The team from Washington noticed, whilst using the same data to see if they could identify people at high risk of Parkinson’s, that people with Parkinson’s were less likely to have received an organ transplant than someone without Parkinson’s. This implies that people who have had organ transplants have a reduced risk of Parkinson’s. They decided to investigate this further because it could important implications in developing a medication to prevent Parkinson’s.

They identified 94,155 people with Parkinson’s and then they randomly selected 118,295 people without Parkinson’s in a similar age group. Overall 278 people with Parkinson’s had also had a tissue transplant and 302 of the people without Parkinson’s had a tissue transplant. They found that the odds of having Parkinson’s after a tissue transplant were reduced.

It’s unclear what is causing this effect but one of the possibilities is the medication that transplant patients are on. People who have received transplants are usually started on medication that lowers the body’s immune system to prevent the body rejecting the transplant. It is possible that these medications could be protecting the brain in some way from Parkinson’s. Unfortunately we cannot be sure at the moment and more research is needed to understand the science underlying this!

Parkinsonism Relat Disord. 2019 Feb 14. pii: S1353-8020(19)30059-8. doi: 10.1016/j.parkreldis.2019.02.013. [Epub ahead of print]

Transplant and risk of Parkinson disease.

Fan J¹, Searles Nielsen S², Faust IM³, Racette BA⁴.

Author information

Abstract

INTRODUCTION:

The pathophysiology of Parkinson's disease (PD) remains unclear, but growing evidence supports a role of neuroinflammation. The purpose of this study was to investigate the association between tissue transplantation and PD risk, given the importance of immunosuppressants in post-transplant management.

METHODS:

We performed a case-control study among Medicare beneficiaries age 66-90 using claims from 2004 to 2009. We used International Classification of Diseases, Ninth Edition (ICD-9) and Current Procedural Terminology (CPT) codes to identify PD (89,790 incident cases, 118,095 population-based controls) and history of tissue transplant (kidney, heart, liver, lung, and bone marrow). We investigated risk of PD in relation to tissue transplant in logistic regression models, adjusting for age, sex, race, smoking, and overall use of medical care.

RESULTS:

Beneficiaries who had received a tissue transplant at least five years prior to PD diagnosis or reference had a lower risk of PD (odds ratio [OR] 0.63, 95% confidence interval [CI] 0.53, 0.75) than those without tissue transplant. This inverse association was observed for kidney (OR 0.63, 95% CI 0.47, 0.84), heart (OR 0.58, 95% CI 0.40, 0.83), lung (OR 0.41, 95% CI 0.21, 0.77), and bone marrow (OR 0.57, 95% 0.38, 0.85) transplants. Associations were attenuated, but remained, following adjustment for indications for the respective type of transplant. Liver transplant was not associated with PD risk.

CONCLUSIONS:

Patients undergoing tissue transplant may have a lower risk of developing PD than the general population. Further studies are needed to determine if this association is causal and if immunosuppressants mediate this association.

The Parkinson’s Drug Trial: A Miracle Cure?

I’m sure many of you have seen the programme about a landmark Parkinson’s study, that was aired on the BBC last night (28^th February 2019). It is a very well-produced fly-on-the-wall documentary that follows the investigators, inventors and some participants that have pioneered a truly ‘disruptive’ trial. If you haven’t seen it, stop reading and watch now (UK readers only).

The inimitable Tom Isaacs, who was one of the first patients into the study, and who's charity the Cure Parkinson's Trust funded this study.

What made it so unique – after all, there are thousands of drug studies that take place across the UK every day. Usually a study is designed to test one thing – most often a drug. In this study, they didn’t just test if the new drug worked. They had to invent new hardware – that needed to be tested. They had to invent a new kind of brain surgery – that needed to be tested. They had to persuade fairly risk-averse regulatory bodies and ethics panels that doing all three, together, at once was fair, safe and acceptable. Regardless of the outcomes of the study, I can only marvel at the courage and dedication shown by every person involved, from the chief investigator and the whole study team, to each and every participant and their families. Medicine usually progresses by small evolution, this study was a major revolution.

So what did the study show? ***Spoiler alert*** (The second part of the documentary is due to be aired next week. Here I will review the peer-reviewed scientific data that was published in two papers this year)

The one sentence summary from the first paper might, on the surface, appear to indicate defeat, “At the 40-week point, however, we have not shown clinical benefit despite this putamen-wide tissue engagement.” However, despite the headline ‘failure’, there is so much to celebrate.

Firstly, the managed to recruit (in fact, for 42 study ‘spots’, they had over 200 people volunteer). This is no small challenge, especially when there is the very real risk of making people worse off, and asking people with Parkinson’s to travel to Bristol every month for nearly a year.

Secondly, they proved that the hardware and surgery worked, and worked safely. 

Image from BBC.com

Thirdly, and very importantly, they showed that after 40 weeks, there was no change in the dopamine-scan in those who’d had placebo; but in the GDNF group there was a marked change that took the appearances back to those expected at the early stage of Parkinson’s. Bear in mind that on average, the participants had had symptoms of Parkinson’s for over 10 years, and in some for well over 15 years!

Fourthly, at the end of 40 weeks, no patients in the placebo group had movement scores that improved by 10 or more points. However, 9 out of the 17 participants given GDNF improved by between 10 and 16 points. This was not only statistically significant (albeit as a post hoc analysis), but most definitely clinically significant.

So what else can be said? Well, firstly, there was a very strong placebo effect. At one point in the film, the mother of one of the participants says, “To have a huge operation like that, and then have to have a placebo. Is that human? Not really, is it!” The BBC have produced a very good summary on the placebo (and nocebo) effects. The fact that the placebo group did improve so much, means that there is much less of a difference between the two groups. This doesn’t necessarily mean that the GDNF didn’t work, it means that the effect is ‘lost’ in the statistical analysis. 

Furthermore, the numbers in the study were very small, with only 41 patients in total, (21 GDNF, 20 placebo.) This further reduces the chance of finding statistical differences.

A - model showing the novel equipment that was designed and made specifically for this study. B - the port that participants lived with, with which they were 'hooked up' to treatment. C - brain scan showing that the drug delivery worked exactly where it needed to. D - patient sat being infused with treatment via the 'head port'. E - A (not-so) ordinary infusion suite. (image from linked Brain paper)

After the original 40 week study, both groups continued to get another 40 weeks treatment, this time with everyone getting the GDNF. At the end of this phase, there was still no overall group differences from the very beginning to the very end between those who had 80 weeks vs 40 weeks of GDNF treatment, in terms of the movement scores off all treatment. However, those who’d had GDNF all along had fewer increases in their regular medication (to a tune of nearly 5 tablets-worth per day (59mg vs 289mg)). There was also ongoing improvement in the ability to do daily activities in those having GDNF for 80 weeks, and a continued improvement in the proportion of the day when the medication was working well.

There are several other factors that need to be borne in mind. The study cost £3m. Divided over each of the participants amounts to over £73,000 per person. Although this seems like a lot, the actual treatment cost, should this every come to clinical practice would likely be much lower, as it includes all the extra costs associated with running a complex clinical trial. Furthermore, if GDNF is ultimately shown to slow the progression of the condition, if it means that someone maintains their independence and can either carry on working (and paying tax), or stay in their own home independently, rather than take early retirement or move to a nursing home, this really is small change – and when you factor in Quality of Life benefits, must surely be a price worth paying.

Finally (and thank you for bearing with me to this point), all these patients had a diagnosis of Parkinson’s disease for around 8 years. This means that they had the pathology for approaching 20 years. Many were profoundly affected by their symptoms. To use a metaphor I’ve used previously on this blog, it is easier to blow out a match than fight a forest fire. The brain of someone with advanced Parkinson’s is vastly more effected than at the early, or even pre-symptomatic stages. Any restorative attempts are far more likely to work if you can catch it early and intervene early. This is the overwhelming conclusion from treating infections and the whole concept of cancer treatment. 

Hopefully, you and your friends will help us reach that goal with Parkinson’s. You can do your bit by helping us to identify the very earliest phase of Parkinson’s: www.predictpd.com. Taking part involves 25 minutes in front of your own computer at home, and certainly doesn’t pose any of the risks that this study did!

As a final note, I would like to say that this programme reminded me how much of a privilege it is to look after people with Parkinson’s in the clinics of the Royal Free and Luton & Dunstable Hospital; how much of a privilege it is to be at the forefront of Parkinson’s research, funded by Parkinson’s UK, and how much this motivates me while training for the London Landmarks half-marathon and Virgin Money London Marathon.

RNR