Type 2 diabetes physically changes the human heart, study finds
Type 2 diabetes doesn’t just raise the risk of heart disease—it physically reshapes the heart itself. Researchers studying donated human hearts found that diabetes disrupts how heart cells produce energy, weakens the muscle’s structure, and triggers a buildup of stiff, fibrous tissue that makes it harder for the heart to pump. These changes are especially severe in people with ischemic heart disease, the most common cause of heart failure.
Researchers at the University of Sydney have uncovered new evidence showing that type 2 diabetes directly changes the heart's structure and how it produces energy. These findings help explain why people living with diabetes face a much higher risk of developing heart failure.
The study, published in EMBO Molecular Medicine, was led by Dr. Benjamin Hunter and Associate Professor Sean Lal from the School of Medical Sciences. The team examined donated human heart tissue from patients receiving heart transplants in Sydney, comparing it with tissue from healthy donors. Their analysis revealed that diabetes drives specific molecular changes inside heart cells and alters the physical makeup of heart muscle. These effects were most pronounced in patients with ischemia cardiomyopathy, which is the leading cause of heart failure.
"We've long seen a correlation between heart disease and type 2 diabetes," said Dr. Hunter, "but this is the first research to jointly look at diabetes and ischemia heart disease and uncover a unique molecular profile in people with both conditions.
"Our findings show that diabetes alters how the heart produces energy, maintains its structure under stress, and contracts to pump blood. Using advanced microscopy techniques, we were able to see direct changes to the heart muscle as a result of this, in the form of a build-up of fibrous tissue."
Heart disease remains the leading cause of death in Australia, and more than 1.2 million Australians are living with type 2 diabetes.
Associate Professor Lal said: "Our research links heart disease and diabetes in ways that have never been demonstrated in humans, offering new insights into potential treatment strategies that could one day benefit millions of people in Australia and globally."
Looking Inside Diseased Human Hearts
To better understand how diabetes affects the heart, the researchers studied heart tissue from both transplant recipients and healthy individuals. This direct examination allowed them to see how diabetes influences heart biology in real human patients rather than relying solely on animal models.
The results showed that diabetes is more than a co-morbidity for heart disease. It actively accelerates heart failure by interfering with essential biological processes and reshaping heart muscle at the microscopic level.
"The metabolic effect of diabetes in the heart is not fully understood in humans," said Dr. Hunter.
How Diabetes Disrupts the Heart's Energy Supply
In healthy hearts, energy is mainly generated from fats, with glucose and ketones also contributing. Previous research has shown that glucose use increases during heart failure. However, diabetes interferes with this process by reducing how sensitive heart cells are to insulin.
"Under healthy conditions, the heart primarily uses fats but also glucose and ketones as fuel for energy. It has previously been described that glucose uptake is increased in heart failure, however, diabetes reduces the insulin sensitivity of glucose transporters -- proteins that move glucose in and out of cells -- in heart muscle cells.