WEDNESDAY, June 8 (HealthDay News) -- Some teens with type 2 diabetes already show signs of impaired heart function, researchers report.

"Past studies in adults with type 2 diabetes show that their heart and blood vessels' ability to adapt to exercise may be impaired. Our study shows that these changes in heart function may begin to happen very early after type 2 diabetes occurs," study author Dr. Teresa Pinto, a pediatric endocrinologist at the Dalhousie University IWK Health Center in Halifax, Nova Scotia, said in an Endocrine Society news release.

Pinto and colleagues examined how the heart and blood vessels of 13 teens with type 2 diabetes responded to exercise, compared to 27 non-diabetic overweight or obese teens and 19 non-diabetic normal-weight teens. The participants were aged 12 to 20, and the study was conducted while Pinto was at the University of Auckland in New Zealand.

MRI scans revealed that during exercise, the hearts of teens with type 2 diabetes did not expand and fill up with blood between heart beats as well as the hearts of the teens in the other two groups. The amount of blood pumped out by the heart was normal in all three groups.

"We showed that the heart's pumping function is strong, but it is not filling as well as normal between heart beats. This is known as diastolic dysfunction," Pinto said. "Although this study did not determine the reason for this, we know that with diabetes, the heart can become stiffer, limiting its ability to stretch and expand."

Pinto and her colleagues also found that teens with diabetes had significantly less blood flow through the femoral arteries (large arteries in the thigh) during exercise compared to the other two groups.

"It appears that irrespective of weight, type 2 diabetes seems to have a negative effect on the heart and blood vessels in adolescents," Pinto said. "This impaired exercise capacity may be reversible with exercise training however, as some literature in adults suggests, but further studies are required to determine this."

The study was slated for presentation this week at the Endocrine Society's annual meeting in Boston. Experts noted that research presented at meetings should be viewed as preliminary until published in a peer-reviewed journal.

More information

The Nemours Foundation has more about diabetes in children and teens.