Heart Failure and Brain Function
The most common cause of heart failure, coronary heart disease, causes one in three deaths in Canada, according to the Heart and Stroke Foundation. It can cause even further complications beyond the coronary issues.
A new study from the University of Guelph sheds light on reasons why heart failure patients often have trouble with thinking and suffer from depression. The study also gives pointers on preventing and treating both heart and brain maladies by way of circadian medicine, according to an article in Science Daily.
The study, which was published recently in Nature's Scientific Reports, shows how cognition and mood in mice are regulated by the body clock. It also provides insight as to how certain brain regions are impaired in heart failure, according to Tami Martino, a professor in the University of Guelph's Department of Biomedical Sciences and director of the Centre for Cardiovascular Investigations. She recently received a Mid-Career Investigator Award from the Heart and Stroke Foundation of Canada.
Martino, whose work in the emerging field of circadian medicine is supported by funding from the Canadian Institutes of Health Research, explained, "Neurosurgeons always look in the brain; cardiologists always look in the heart. This new study looked at both." Martino added that human patients with heart failure often have neurological conditions such as cognitive impairment and depression.
Martino’s theory was that the heart-brain connection involved the circadian mechanism molecule, called "clock." Circadian rhythms in living organisms follow earth's 24-hour cycle of light and darkness. They provide signals for being asleep or awake.
In prior research, Martino discovered how interfering with circadian rhythms -- as with shift workers, jet-lagged travelers and patients disturbed in intensive-care units -- can cause changes that have negative impact on heart disease and damage overall health and well-being. The recent study compared normal mice with mice who had a mutation in their circadian mechanism (called "clock mice"). The mutation impacted the structure of neurons in brain areas critical for cognition and mood.
Working with researchers at the University of Toronto, the University of Guelph team also discovered differences in clock regulation of blood vessels in the brains of the clock mice. After inducing heart failure in the mice, the researchers used microarray profiling to identify key genes in the brain that were changed in neural growth, stress and metabolism pathways.
Results indicate that the circadian mechanism influences neural effects of heart failure. Matino, who pointed out that there is no cure for the heart condition, said that understanding how the circadian mechanism works in the brain could lead to new strategies to improve quality of life.
As Martino explained, “Patients recovering from heart attacks often experience disturbed circadian rhythms from light, noise and interactions with hospital staff at night. Maintaining circadian rhythms, especially for patients with heart disease, could lead to better health outcomes."
There could be other takeaways for health benefits. People with heart conditions or sleep disorders might need to avoid shift work, reduce light at night or avoid jet lag and late nights in order to cut down neurobiological impairments.
Martino summarized, "If we're not yet able to cure heart failure, we should at least be focusing on how we can improve quality of life for patients."