UCalgary research lends insight into a heart arrhythmia common for many with Type 1 diabetes

Scientists are a step closer to understanding and preventing atrial fibrillation (AF) for people living with Type 1 diabetes, based on findings from a study led by Dr. Robert Rose, PhD, a professor in the departments of Cardiac Sciences and Physiology and Pharmacology within the University of Calgary’s Cumming School of Medicine (CSM). The study, published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), provides new insights into the cause of AF in Type 1 diabetes and a targeted treatment approach.

AF is the most common form of cardiac arrhythmia and can negatively affect a person’s quality of life, leading to heart failure and stroke, for some. The condition is prevalent for people living with Type 1 diabetes however, AF presents differently for that group compared to AF in people living with other conditions. This suggests that treatment for AF in diabetes may also need to be unique.

Type 1 diabetes is an autoimmune disease in which the immune system destroys the insulin-producing cells of the pancreas. It leaves people reliant on external insulin and affects about five per cent of the population.

“The thing that excites me is that we’ve learned, at least in part, why atrial fibrillation occurs in diabetes and we’ve been able to identify pathways that could lead to targeted therapies for this condition,” says Rose, a member of the Libin Cardiovascular Institute at the CSM and recent Heart and Stroke Foundation of Canada new investigator. “Diabetes is a very complicated illness and prior to this research there was very little understanding of how this chronic condition leads to atrial fibrillation in so many people.”

Researchers used mouse models in the study and found that blood sugar levels and the loss of normal insulin production can have dramatic effects on AF susceptibility. Maintaining proper insulin levels can reduce the occurrence and severity of AF, which currently has few options for treatment. 

In this study, the Rose lab demonstrated that mice with Type 1 diabetes are highly susceptible to developing AF due to impaired electrical conduction in the heart. In particular, the study shows that increased occurrence of AF in Type 1 diabetes is associated with the loss of function of a critical ion channel in the atria called the sodium channel. The study went on to show that controlling insulin levels prevents these changes in atrial sodium channel function and reduces the occurrence of AF.

“Diabetes is complicated, and it was fascinating to learn that insulin signaling, and its effects on the sodium channel, plays such an important role in the development of AF,” says Dr. Hailey Jansen, PhD, co-first author and Killam Postdoctoral Fellow.  “We identified the importance of maintaining proper insulin levels for reducing the occurrence of AF. We are hopeful this will lead to different treatment options for Type 1 diabetics.”

This study is supported by the Canadian Institutes of Health Research.