Atrial fibrillation, or A-fib, is an irregular coronary heart rhythm that will increase an individual’s threat of stroke, coronary heart failure and even untimely demise.
Whereas many threat components contribute to A-fib, one stands out for its rising prevalence worldwide: weight problems.
I’m a cardiology researcher, and my group and I uncovered key mechanisms contributing to the dangerous results of weight problems on coronary heart operate. Concentrating on these processes might provide new avenues for therapy.
How weight problems stresses the center
Weight problems is way over a weight challenge – it essentially alters the physique’s biochemistry. This in flip adjustments your metabolism, or the chemical reactions that permit the physique to operate.
Specifically, the elevated presence of fatty acids, an indicator of weight problems, places further pressure on coronary heart cells. Fatty acids can instantly injury coronary heart cells by triggering the elevated manufacturing of reactive oxygen species – particular molecules that may injury tissues and disrupt regular mobile features. These results lead to a disruption of the center’s electrical alerts, resulting in irregular beating.
When antioxidants aren’t in a position to hold dangerous reactive oxygen species in test, the imbalance results in extra stress on the physique.
One main supply of reactive oxygen species is NOX2, an enzyme that turns into extra energetic in folks with weight problems. NOX2 influences the exercise of a number of key proteins that regulate the center’s rhythm. It additionally contributes to oxidative stress within the atria – the center’s higher chambers – altering their measurement, form and performance. This cardiac transforming is a key driver of irregular coronary heart rhythms.
A 2-pronged strategy
My group and I got down to higher perceive how NOX2 impacts the center, and whether or not focusing on it might scale back the chance of creating irregular coronary heart rhythms amongst folks residing with weight problems.
We approached this drawback from two instructions.
First, we used mice fed a high-fat weight loss program to induce weight problems much like that in folks. One group of those mice had been in a position to produce practical NOX2 whereas one other group couldn’t. We examined medicine that particularly inhibit NOX2 and checked how probably the higher chambers of the center had been to develop irregular electrical rhythms.
In parallel, we generated human atrial coronary heart cells from stem cells and handled them with fatty acids to simulate the consequences of weight problems. Whereas our mouse mannequin would seize the consequences of weight problems within the physique as a complete, our cell mannequin would allow us to check the way it impacts the center on the mobile degree.
Electrocardiograms measure the center’s electrical exercise.
Peter Charlton, CC BY-SA
We noticed that elevated NOX2 exercise in each overweight mice and handled human coronary heart cells led to vital adjustments within the coronary heart’s electrical properties. Overweight mice with out NOX2 had much less extreme atrial fibrillation than overweight mice with NOX2. Equally, overweight mice handled with NOX2 inhibitors additionally confirmed enhancements within the severity of their irregular coronary heart rhythms, although to a lesser extent. And blocking NOX2 in coronary heart cells uncovered to fatty acids reversed the mobile adjustments attributable to fatty acid therapy.
In each mice and human coronary heart cells, inhibiting NOX2 diminished oxidative stress and normalized the center’s electrical exercise. This discovering means that NOX2 performs a key function within the improvement of obesity-induced irregular coronary heart rhythms.
Notably, we discovered that NOX2 performs a big function in growing the exercise of a gene referred to as PITX2, which is linked to adjustments within the coronary heart’s electrical operate. Our information confirmed that PITX2 exercise was amplified in each overweight mice and human coronary heart cells, however lowering NOX2 exercise instantly lowered PITX2 ranges. These findings recommend that oxidative stress and genetic components play a task within the improvement of irregular coronary heart rhythms.
Treating atrial fibrillation
Present therapies for atrial fibrillation, significantly for sufferers residing with weight problems, have centered extra on managing signs than addressing the physiological adjustments that trigger it.
Although removed from reaching the clinic, our analysis means that focusing on NOX2 might provide a brand new therapy technique to forestall or scale back the severity of irregular coronary heart rhythms. An extra understanding of the genetic pathways concerned in atrial fibrillation, reminiscent of PITX2, might result in extra personalised therapies sooner or later.
By delving into the molecular mechanisms behind irregular coronary heart rhythms, researchers can develop extra focused approaches that tackle the foundation causes and enhance outcomes for sufferers combating each weight problems and coronary heart situations.
