Heart failure patients often struggle with neurological issues, including depression and thinking problems, but the reasons for this have remained unclear. In a new paper published in the journal Scientific Reports, Canadian researchers from the University of Guelph (U of G) use a mouse model to explain how the circadian rhythm may play a role in this heart-brain connection.
“Neurosurgeons always look in the brain; cardiologists always look in the heart. This new study looked at both,” said Tami Martino, a professor in U of G’s department of biomedical sciences and director of the Centre for Cardiovascular Investigations.
Human patients with heart failure often have neurological problems such as cognitive impairment and depression, said Martino. She suspected the heart-brain connection may involve the circadian mechanism molecule, called “clock.”
Circadian rhythms in humans and other organisms follow Earth’s 24-hour cycle of light and darkness, signaling when to sleep and when to be awake. Martino’s previous research showed how disrupting circadian rhythms — as with shift workers, jet-lagged travelers and patients disturbed in intensive-care units — can trigger changes that worsen heart disease and impair overall health and well-being.
In the new study, the researchers compared normal mice with mice carrying a mutation in their circadian mechanism (called “clock mice”). They found that the mutation impacted the structure of neurons in brain areas important for cognition and mood. Working with University of Toronto colleagues, the team also found differences in clock regulation of blood vessels in the brains of the clock mice.
After inducing heart failure in mice to simulate human heart failure, they identified key genes in the brain that were altered in neural growth, stress and metabolism pathways. The results show that the circadian mechanism influences neural effects of heart failure, said Martino. Pointing out that no cure exists for the heart condition, she said understanding how the circadian mechanism works in the brain may lead to new strategies to improve patients’ quality of life.
For example, 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,” said Martino.
The study also points to potential health benefits for people in general. Avoiding shift work for individuals with underlying heart conditions or sleep disorders, reducing light at night or avoiding social jet lag (going to bed late and waking up later than usual on weekends) could all help reduce neurobiological impairments.
These problems — and potential solutions — involve not just hearts but brains, she said. “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.”
Source: University of Guelph