Imaging technique may trace development of Parkinson's disease

While finding a biomarker for Parkinson's disease that would let physicians screen for or track its progression remains an elusive goal, a team led by a University of Illinois at Chicago neuroscientist has shown that a non-invasive brain scanning technique offers promise. The tool may also help advance the development of new drugs or neuroprotective agents to treat or ward off Parkinson's. The findings, now online, will appear in a forthcoming issue of Neurology. David Vaillancourt, assistant professor of kinesiology at UIC, along with colleagues from UIC and Rush University, used a type of MRI scan called diffusion tensor imaging on 28 subjects, half with early symptoms of Parkinson's and the other half without. They scanned an area of the brain called the substantia nigra, a cluster of neurons that produce the neurotransmitter dopamine. Parkinson's patients have been found to have about half the number of dopaminergic neurons in certain areas of the substantia nigra as those without the disease. Determining loss of dopaminergic neurons using conventional methods such as metabolic PET scans is expensive, invasive, and requires injection of radioactive tracer chemicals. But the method studied by Vaillancourt and his group is non-invasive, relatively inexpensive, and does not use radioactive tracers. "We're suggesting it's possible to eventually diagnose Parkinson's disease non-invasively and objectively by examining the part of the brain thought to underlie the causes of the disease," said Vaillancourt. No tool currently available can do that, he said. The researchers say the technique may also help develop neuroprotective agents to treat Parkinson's. Vaillancourt said it's difficult to identify a neuroprotective agent using current measures because the results are skewed by any therapy used to treat symptoms. "When you have a symptomatic effect of the neuroprotective agent, you need a lot of patients from multiple centers to determine if the neuroprotective agent works," he said. "But if you have a disease marker not affected by a dopaminergic therapy, then you would be able to test neuroprotective agents among smaller groups." Vaillancourt thinks that would enable faster development of drugs to treat Parkinson's. He noted that while the technique his group studied works well as a trait biomarker, which allows for diagnosis, it has not yet been shown to measure the state of the disease's progression. Further research is planned.

Coronary Heart Disease Linked to Endogenous Testosterone

Higher levels of endogenous testosterone may associated with an increased risk of coronary heart disease (CHD) in men older than 65 years, according to a large U.S. multi-center study presented at the Endocrine Society’s 92nd annual meeting.
“The study finding contradicts smaller studies that have shown that testosterone levels are not associated with higher rates of cardiovascular disease,” said study investigator Kristen Sueoka, MD, a resident physician in the Department of Internal Medicine at the University of California, San Francisco. “Many in the general public are using testosterone supplements for various medical problems, including low sex drive and mood disorders, which are not life-threatening. These men may unknowingly be placing themselves at higher risk for cardiovascular disease.”

Dr. Sueoka and her colleagues examined endogenous sex hormone levels in older men as an independent risk factor for CHD events. They studied 697 community-dwelling men who were participating in the National Institutes of Health-funded study, Osteoporotic Fractures in Men (MrOS). None of these men were receiving testosterone therapy and all the men were recruited between 2000 and 2002 at six U.S. centers. The men had a mean age of 72 years. Investigators collected and stored fasting serum samples from the subjects at enrollment.
During an average follow-up of 3.9 years, 100 men (14%) had a coronary disease event. Men with total testosterone levels in the highest quartile (495 ng/dL or higher) had a 2.2 times increased risk of a CHD event compared with men in the lowest quartile (below 308 ng/dL). The researchers also found that the results were similar for bioavailable testosterone and free testosterone. Higher sex-hormone-binding globulin levels also were associated with an increased risk for CHD events, but estradiol and estrone levels were not.
“Our findings suggest there is some type of pathogenesis or interaction that is going on,” Dr. Sueoka said. “If a causal relationship is found between high testosterone and cardiovascular disease, then that would suggest that replacement therapy may put people at higher risk for cardiovascular disease.”
The investigators did not divide the men by normal or abnormal testosterone levels because the definition of abnormal levels depends on many factors, including increasing age. “Men with the highest testosterone could potentially be at risk for heart disease regardless of the definition of ‘normal’ levels,” Dr. Sueoka said.