Damage to Heart Nerve Cells can Identify Parkinson's Disease

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Highlights:

• Using PET scan, Parkinson's disease (PD) can be deducted at an early stage by tracking the mechanism of heart nerve damage
• Neural damage to the heart causes symptoms like low blood pressure on standing
• The findings can help test new therapies and explore the way the disease puts people at risk of falls and hospitalization

Mechanisms by which damage to heart nerve cells happen can be tracked early in Parkinson's Disease (PD) patients by using positron emission tomography (PET) scan. This can help identify patients well before their symptoms could progress, reveals a new study

Apart from producing motor symptoms, PD also causes serious neurodegeneration of the heart, in turn slowing down the heart's responses to quick changes in activity. Healthy heart nerves accelerate its pumping to match quick changes in activity and blood pressure.

‘Using PET techniques, scientists have deducted the mechanisms underlying early heart nerve damage and can use this understanding to test the efficacy of new drugs that can potentially protect the heart neurons.’

Hence, the slowing down of the heart's reflexes can make PD patients feel lightheadedness or a drop in blood pressure when standing (orthostatic hypotension), and a feeling of fatigue with a sense of generalized weakness; this is the reason why the disease puts people at risk of falls and hospitalization.

"This neural degeneration in the heart means patients' bodies are less prepared to respond to stress and to simple changes like standing up," says Marina Emborg, a University of Wisconsin-Madison professor of medical physics and Parkinson's researcher at the Wisconsin National Primate Research Center. "They have increased risk for fatigue, fainting and falling that can cause injury and complicate other symptoms of the disease."

By the time PD patients are diagnosed with the typical symptoms of tremors and motor-control symptoms most of them also have serious damage to the heart's connections to the sympathetic nervous system. By devising a new way to examine stress and inflammation in the heart will help Parkinson's researchers test new therapies to protect the neurons from damage.

The results are published in the journal npj Parkinson's Disease.

Study Design

Emborg and her research team from the cardiology and medical imaging departments of UW-Madison tested the damage done to heart nerves by using the human-like nervous system and heart of rhesus macaque monkeys that they used as their experimental model for Parkinson's symptoms.

They gave ten monkeys doses of a neurotoxin to induce damage to the nerves in their hearts similar to the way Parkinson's affects human patients.

The monkeys underwent positron emission tomography (PET) scan once before the toxin was given and twice in the weeks following administration. PET is a medical imaging technology that can track chemical processes in the body using radioactive tracers.

The research team used three different tracers or radioligands, to map three different places in the strongest pumping chamber of the monkey's hearts, the left ventricle:

• where the nerves extending into the heart muscle were damaged
• where the heart tissue was experiencing the most inflammation
• where they found the most oxidative stress

Study Results

• The researchers were able to focus on changes over time in specific areas of the heart's left ventricle due to the accurate scans. This helped them visualize in detail where inflammation and oxidative stress was happening in the heart, and how that is connected to how Parkinson's patients lose those neuronal connections in the heart.
• The nerve function recovered much better in the monkeys who were given a drug called pioglitazone, which can protect the central nervous system cells from inflammation and oxidative stress.

Advantages of Performing PET Scans Early

• The radioligands can be used to test the efficacy of new drugs to protect the neurons that control the patients' hearts since they help trace the progression of nerve damage and its causes.
• The method can identify very specifically the differences the treatment made -- whether it was for inflammation or oxidative stress, across the heart.
• The PET techniques may also be used as tools to understand the mechanisms underlying early heart nerve damage since in many patients neurodegeneration of the heart occurs much before motor problems kick in.

The new imaging methods can also be used in other heart problems like heart attack, diabetes and other disorders that cause similar damage to nerves in the heart.

References:

1. What Is Parkinson's? (http://www.parkinson.org/understanding-parkinsons/what-is-parkinsons)
2. The Effect of Parkinson Disease on the Nerves of the Heart (http://annals.org/aim/fullarticle/713857/effect-parkinson-disease-nerves-heart)


Source: Medindia

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