Objective: To identify volatile compounds in the skin which can be used to provide an early diagnosis in Parkinson’s disease (PD).

Background: There is a clear need to detect Parkinson’s disease before manifestation of clinical symptoms as these symptoms are predominantly observable only once the disease has already progressed to an advanced stage. Joy Milne, a ‘super-smeller’ whose husband Les was diagnosed with PD has demonstrated extreme sensitivity to smell [1]. This enables her to be able to detect odors not normally detected by those of average olfactory ability, and to diagnose PD based on a distinctive odor in the sebum, even at a very early stage. Identification and quantification of the metabolites that are associated with this distinctive smell, described as “musky” could enable rapid, early screening of PD as well as providing insights into molecular changes that occur at disease onset and enable stratification of the disease in future.

Methods: We examined sebum samples obtained non-invasively from 64 participants in total (20 controls and 44 PD subjects). We used thermal desorption directly from gauze swabs coupled to gas chromatography mass spectrometry (GC-MS) to best mimic the ability of a super-smeller to detect a distinct ‘musky’ odour in PD patient samples.

Results: By separating and detecting volatile components from sebum we were able to build a classification model based on data from 30 participants. The volatile metabolites of interest deduced from this model were then mined for in a second set of 30 samples from a different cohort. In parallel, four samples from drug naïve PD participants were analyzed on a GC-MS system with an odor port. Associated smell data as a function of GC retention time was recorded with the help of a human super-smeller. We found a panel of volatile metabolites that are differentially expressed in PD and subsequently validated these in an independent cohort.

Conclusions: Our results demonstrate that there is a distinct smell and a distinct volatilome signature associated with PD. Identification of these molecules and their contribution to the scent of PD highlights changes in sebum content as PD manifests. Future work will expand this dataset to larger patient cohorts to gain insight into mechanisms by which metabolomics pathways may alter in Parkinson’s and provide scope for stratification as well as early detection of the disease.

References: [1] J. Morgan, Joy of super smeller: Sebum clues for PD diagnostics, Lancet Neurol. 15 (2016) 138-139. doi:10.1016/S1474-4422(15)00396-8.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/sniffing-parkinsons-in-the-masses-volatilome-analysis-for-parkinsons-disease-diagnostics/