Parkinson’s disease: from the gut to the brain

Margaret Jarrett was diagnosed with Parkinson’s disease 8 years ago. And although she was bothered by many of the symptoms that commonly afflict Parkinson’s sufferers – resting tremor, uncertain gait and terrible nightmares – one thing that bothered her the most was her loss of the sense of smell.

An avid gardener, she took great pride in her rosarium, but being unable to inhale their perfumed scent, really got her down.

“You take something like your sense of smell for granted,” Jarrett, 72, said. “You don’t realise how precious something is until it’s gone.”

Parkinson’s disease is a combination of movement disorders including resting tremor, muscle rigidity, impaired balance and slowness of movement. It can also cause neurological problems such as depression, insomnia, memory loss and confusion.

Its cause is unknown but it is associated with dopamine depletion and destruction of neurons in the basal ganglia region of the brain.  

The current mainstay of treatment for Parkinson’s disease involves physical therapy as well as medications which act to increase dopamine levels in the brain. One relatively new avenue of potential treatment for Parkinson’s disease is exposure to infrared light therapy.

In 2017 I wrote an article that was published in The Weekend Australian Magazine titled 'Let there be light' about a group of patients in Tasmania who were trialling infrared light therapy for their Parkinson’s disease.

The response was overwhelming, with scores of people contacting myself, the newspaper and researchers named in the article, to request further information on this novel treatment.   

One person whose interest was piqued happened to be Olivia Nassaris, the CEO of Parkinson's South Australia. “When the article was released, it created this massive buzz and I had so many members of my community wanting more information about it,” she told me.

Nassaris contacted Dr Ann Liebert, co-ordinator of photomolecular research at the Australasian Research Institute, Sydney (and co-founder of SYMBYX), who informed her of an upcoming planned trial on infrared light therapy for Parkinson’s disease.  

Nassaris subsequently persuaded the board of Parkinson’s South Australia to partially fund the trial, on the understanding that at least some of the participants would be from South Australia.      

In addition to assessing the effectiveness of infrared light therapy for Parkinson’s disease, Liebert also wished to see if exposure to infrared light could modulate the gastrointestinal tract’s microbiome in humans.

The gut’s microbiome — composing the trillions of bacteria, fungi and protozoa from hundreds of different species that normally inhabit our gastrointestinal tract — has come under increasing scientific attention over the past decade with links being established between the microbiome and a number of conditions including obesity, Type 2 diabetes, cardiovascular disease and depression.

Several studies have also observed that the gut microbiome is markedly altered in patients with Parkinson's disease and that faecel microbiota transplantation can have a protective effect in animal models of Parkinson’s.

The reason for this is unknown; however, an interesting observation is that another common pathology seen in Parkinson’s disease is the accumulation of misfolded α-synuclein proteins, called Lewy bodies, in the brain.

It has been shown that certain sensory cells of the gut contain a-syniclein.  Researchers have hypothesised that it is possible that abnormal forms of the α-synuclein protein could travel from the gut to the brain through the vagus nerve, a phenomenon that has been shown in animal models of Parkinson’s. Further support for this theory comes from findings that people who have had a surgical vagotomy — where branches of the nerve are cut —  have a lower lifetime risk of developing Parkinson's.  

“We know that infrared light can reduce Parkinson’s symptoms and offer protection to brain cells. So, we wanted to test if it could modulate the gut’s microbiome as well,” Liebert said.

One of the principal researchers in Liebert’s planned study, Dr Daniel Johnstone, scientist and lecturer at The University of Sydney’s Bosch Institute, had previously undertaken a study showing that exposure to infrared light altered the gut microbiome in mice. 

“One possibility might be that we’re somehow influencing the microbes in the gut, and that’s having an effect on the brain,” Johnstone said.

Based on the mouse study findings, Liebert and Dr Brian Bicknell, Honorary Fellow in the Faculty of Health Sciences at the Australian Catholic University (and Co-Founder of SYMBYX),  conducted a case study last year that showed that infrared light could modulate the human microbiome as well.

In the study a subject received infrared light therapy (using the PDCare Laser) to the abdomen three times a week for 12 weeks. Faecal sampling showed an increase, after therapy, of some bacteria that are considered beneficial to the gastrointestinal tract including Akkermansia muciniphila, Bifidobacterium and Faecalibacterium.

Liebert wished to see if this finding could be replicated in patients with Parkinson’s and a dozen participants each, from Sydney and Adelaide, were selected, including Jarrett.

Provisional results, from the first half dozen Adelaide participants to have their gut microbiome analysed before treatment and 12 weeks after treatment began, have been promising.

“The six patients that have been put through a similar protocol as the mice showed an increase by up to 20 per cent in the favourable microbiome which is associated with obesity reduction and short chain fatty acid production, and the bacteria associated with rheumatoid arthritis, Crohn’s disease and insulin resistance were all decreased,” Cardiac Health Institute  medical director and Professor of Cardiology at Macquarie University, Hosen Kiat, who oversaw the trial, told me.

Jarrett regained her sense of smell.

“For the last three years I haven’t been able to smell flowers,” Jarrett said. “But several weeks into the trial I started to smell my roses, daphnes and gardenias again and it was wonderful.”

Another participant, Barry Weldon, 70, had a similar experience. “My sense of smell improved significantly” he said. “One day I walked into the house and for the first time in a long time I could actually smell the soup my wife was cooking.”

Ron Till, 68, had an even more dramatic improvement.

“The trial gave me the ability to sleep again,” he said. “It was amazing.”   

Till’s neurologist cautioned him not to get his hopes up before the trial but changed his mind when he saw the results. “He told me it was voodoo medicine and probably wouldn’t work,” Till said. “But after the trial I went back for my three-monthly assessment with him, and he said to me, ‘You’re actually testing better than when you first started with me ten years ago’.”

Retired geologist Sean Kennedy, 76, also experienced an improvement in his co-ordination and balance. “My juggling skills have improved,” he said.   

In a review published in Photobiomodulation, Photomedicine, and Laser Surgery, titled “Photobiomics: Can Light, Including Photobiomodulation, Alter the Microbiome?” Liebert and her co-authors acknowledge that while the exact mechanism by which light therapy alters the microbiome is unknown there is definite potential in light therapy.

“The ability of PBM [light therapy] to influence the microbiome (if proven to be applicable to humans) will allow an additional therapeutic route to target multiple diseases, including cardiovascular disease and Parkinson’s disease, many of which have thus far eluded effective treatment approaches,” the paper concludes.     

....“If we can create non-invasively a metabolically healthier microbiome through this extremely cheap and easy way, then inflammatory diseases and neurodegenerative diseases should be positively influenced,” 

...“The reality is there are no real side effects from low level laser therapy and it’s one of the safest treatments you can ever do,” he says.  

Liebert says the promising results they have seen thus far will inform on a large, double-blinded randomised control trial planned for this year. “It has the potential to apply to huge fields of medicine,” she said....

As for Jarrett, she has no doubts that infrared light therapy has helped her. She is enjoying pottering around in her garden again and has more energy than she has had for a long time.

“I feel like I could take on the world again,” she said. “My garden has never looked better.”

(Photo shows Ann Liebert in her Artarmon practice with a patient holding the  laser used in the Adelaide trial)