Lizard saliva an unlikely boon to Parkinson’s patients

A common diabetes drug based on lizard saliva might also moderate the symptoms of Parkinson’s disease, according to research published in the British medical journal, The Lancet.

In a year-long study funded by the Michael J Fox Foundation for Parkinson’s Research, scientists found that weekly injections of a diabetes medication called exenatide – in addition to the standard suite of drugs – resulted in an improvement in motor skills in Parkinson’s patients.

The study, led by Tom Foltynie of University College London in the UK, involved 60 people with Parkinson’s, with half being given exenatide and the remainder a placebo.

The program continued for 48 weeks, with a final check-up at 60 weeks. 

Foltynie’s team found that on the standard 132-point scale used to measure tremors, agility and speech in Parkinson’s sufferers, patients using the diabetes drug recorded a four-point better score than those on the placebo. The result was described as “statistically significant”.

The improved result was still present at the 60-week mark, three months after the medication course ended.

The motor skill improvements were not noticeable while patients were taking standard treatments. However, when all medications were suspended – usual practice to allow neurologists to properly assess the progress of the disease – the difference between the two cohorts became clear.

In their paper Foltynie and colleagues note that the results do not reveal whether the diabetes drug actually affects the progress of Parkinson’s or just induces “long-lasting symptomatic effects”. 

For this reason, they conclude, “exenatide represents a major new avenue for 

investigation … , and effects on everyday symptoms should be examined in longer-term trials.”

The drug itself was first marketed in 2005 as a treatment for Type 2 diabetes. It is derived from a substance found in the saliva of the Gila monster (Heloderma suspectum), a venomous lizard found in southern US and northern Mexico.

Described as “a glucagon-like peptide-1 (GLP-1) receptor agonist”, it activates receptors for a hormone known as GLP-1 in the pancreas and stimulates the production of insulin.

GLP-1 receptors are also located in the brain. Stimulating them has been linked to increased dopamine reception and decreased inflammation.

Several teams of researchers are investigating the role of GLP-1 in facilitating molecular communication between the gastro-intestinal tract and the central nervous system.

Its presence in diabetes meds is the focus of keen interest, not least because Type 2 diabetes is considered a risk factor for neurodegenerative diseases such as Parkinson’s and Alzheimer’s.

In April this year a study in the journal Cell Transplant identified Type 2 diabetes medications as prime targets for Parkinson’s research.

The report noted that “several double blind clinical trials of GLP-1R agonists, including exenatide, in [Parkinson’s Disease] and other neurodegenerative disease are already underway or are about to be initiated.”

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