Might individuals with cystic fibrosis be at greater risk for heart disease given the presence of CFTR in the heart?
Why is this important?
Individuals with CF are living longer and being more active, thus, it is prudent to determine if those with CF are at increased risk for heart problems compared to those without CF.
What did you do?
Mice with cystic fibrosis-like disease (but without lung disease) were used to determine if the heart in the CF mice functioned differently from non-CF mice hearts when lung function is normal. We used two methods that are used clinically to examine heart structure and function in patients - echocardiography and catheterization (passing a long tube through an artery into the heart). Since heart function is influenced by blood vessel stiffness, we also measured the size and stiffness of the aorta.
What did you find?
First, we found that CF mice hearts were thicker and more hyperactive at rest compared to that of non-CF mice. Second, when CF mice hearts where stimulated with a chemical to mimic exercise, their hearts could not increase their activity as much as non-CF mice hearts. Thirdly, CF mouse aortas had smaller diameters and were stiffer than that of non-CF mice.
What does this mean and reasons for caution?
These results suggest that CF hearts might work harder at rest, even with no lung disease, which leads to thicker hearts. This may in part be due to the narrower and stiffer blood vessels in CF mice. Together these properties prevent CF hearts from responding as well to exercise as they would otherwise. While studies in mice have helped us understand human physiology, not all findings in mice translate to similar effects in humans and so it is possible this effect may not be seen in humans.
It will be important to examine heart function in humans with cystic fibrosis to see how their heart functions when they have good lung function. We need to determine if special attention to heart function is necessary as those with CF get older and engage in more strenuous physical activities.