2005 Ohio Student Research Forum

Abstract

Electrocardiographic Abnormalities in Insulin-Dependent Diabetic Rats
Tamika White
Ohio State University, School of Pharmacy
Mentor(s): Dr. Cynthia Carnes and Veronique Lacombe

Objectives
The objectives are: 1) To develop a reliable model of insulin-dependent diabetes (type 1) in an animal, which will develop subsequently cardiovascular complications; 2) to characterize in vivo electrophysiological abnormalities in animals with diabetic cardiomyopathy.

Significance
Diabetes is a worldwide disease affecting both humans and animals. About 150 million people suffer worldwide from diabetes and approximately 1 million of those people in the US have insulin-dependent diabetes. Diabetes is characterized by insulin dysfunction and impairment of glucose uptake in insulin-sensitive tissues. Up to two-thirds of diabetic patients will develop heart disease, and in particular arrhythmias and heart failure, which may lead to death. However, the mechanisms of diabetes-induces-cardiovascular diseases are not well understood yet.

Methodology
Insulin-dependent diabetic rats and age matched control rats were included in this study. Diabetes was induced by a single dose of streptozotocin (STZ) IP. For each rat, electrocardiographic (ECG) recordings were performed at baseline (normal condition), at 4 weeks and 8 weeks after the onset of diabetes. For each recording, we anesthetized rats with isofurane and oxygen and we did a full-length recording for one minute using a Physiologic Data Acquisition system (BioPac Software system). All the ECGs were analyzed off-site using Acqknowledge software, by performing both a qualitatively and quantitatively assessment of ECGs in a blinded fashion. The amplitude of P wave and QRS complex, and PR, RR, QT intervals were calculated.

Results
Diabetes in our animal model is characterized by the presence of persistence hyperglycemia from the onset of diabetes and up to 8 weeks.

From ECG analyses, Rmax and QRS amplitude were increased by 83% and 44%, respectively in diabetic rats at 8 weeks after STZ injection compared to age-matched control rats. Other ECGs parameters such as QTc, and RR intervals, and heart rate were also altered in diabetic animals. Heart rates decreased by 15% and RR intervals increased by 35% at 8 weeks after the onset of diabetes. All these changes were noticed at 4 weeks, but not 3 days after the onset of diabetes. No significant changes in all the ECG parameters were observed in the control group throughout the experiment.

Conclusions
We found electrocardiographic abnormalities in diabetic compared to age-matched control rats. This study will help to characterize diabetic cardiomyopathy, and to understand why abnormal heartbeats occur in diabetic patients. Furthermore, this research helps me to understand the principle and interpretation of ECG, which can be applied to any species including humans.