February 15, 2021

Parkinson’s disease (PD) is characterized by motor-related symptoms, including tremors, rigidity and stooping posture. Lesser known is damage to nerves in the heart, which progresses over time, is independent of motor symptoms and is not responsive to current therapies.

Marina Emborg, senior scientist at the Wisconsin National Primate Research Center and University of Wisconsin–Madison professor of medical physics, has been working on preclinical models for treating PD for the past three decades. She says by the time patients are diagnosed, about 60 percent have serious damage to nerve connections in the heart.

“When healthy, these nerves stimulate the heart to accelerate its pumping to rapidly respond to changes in activity and blood pressure. Loss of this control causes patients to be less responsive to exercise, subject to intense lightheadedness upon standing and at high risk of falling.”

Emborg’s team, which includes scientists Valerie Joers, Jeanette Metzger, UW–Madison cardiovascular medicine professor Timothy Kamp and neurology professor Catherine Gallagher, had not been able to look at exactly what was causing the heart damage until now.

They mimicked PD cardiac neurodegeneration in adult rhesus macaques and then used positron emission tomography (PET) imaging to follow nerves within the monkeys’ hearts after they administered new-generation radiolabeled biomarkers (i.e., radioligands). The researchers were successful in detecting inflammation and signs of oxidative stress as nerves were deteriorating in real time.

The study suggests cardiac PET imaging combined with new-generation radioligands will be useful in detecting heart disease and evaluating new therapies that specifically target nerve disease within the human heart.

“Many doctors are not aware of this condition, which significantly affects PD patients’ health,” said Emborg. After the study results had been published, several people who have PD reached out to thank her for studying this aspect of the disease. She realized this study gave patients the evidence and confidence they need to talk with their doctors about treatments.

Other diseases share this problem as well, Emborg said. Diabetes, heart attacks and other disorders cause similar damage to nerves in the heart. People who have these health issues could potentially benefit from therapies tested with visualization models. 

Emborg envisions the day when this technique is credited with developing new therapies as well as predicting heart damage in those who have PD.

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