title: Long-term effects of type 2 diabetes mellitus on heart rhythm in the Goto-Kakizaki rat.
abstract: In vivo biotelemetry studies have demonstrated a variety of heart rhythm disturbances in type 1 diabetes mellitus. In the streptozotocin (STZ)-induced diabetic rat, these disturbances have included reductions in heart rate (HR) and heart rate variability (HRV) and an electrocardiogram that displays prolonged QRS duration and Q-T interval. The aim of this study was to investigate the chronic effects of type 2 diabetes mellitus on heart rhythm in the Goto-Kakizaki (GK) rat. Transmitter devices were surgically implanted in the peritoneal cavity of young male GK and age-matched Wistar control rats. Electrodes from the transmitter were arranged in Einthoven bipolar lead II configuration. Electrocardiogram, physical activity and body temperature data were recorded in rats from age 2 to 15 months. Data were acquired for 2 weeks each month. Non-fasting blood glucose, glucose tolerance and body weight were measured periodically. In GK rats, growth rate and maximal attained body weight were significantly reduced and non-fasting blood glucose was progressively increased compared with age-matched Wistar control animals. Heart rate was significantly lower in GK compared with control rats at 2, 7 and 15 months of age. At 2 months of age, HR was 316 +/- 6 beats min(-1) in GK rats compared with 370 +/- 7 beats min(-1) in Wistar control animals. There was a progressive age-dependent decline in HRV in Wistar control rats; however, HRV in GK rats did not alter significantly with age. Heart rate variability was significantly reduced in GK compared with Wistar control rats at 2 and 7 months. At 2 months of age, HRV was 28 +/- 2 beats min(-1) in GK rats compared with 38 +/- 3 beats min(-1) in Wistar control rats. Reduced HR in GK rats may be an inherited characteristic. The absence of age-dependent reductions in HRV in GK rats may be a consequence of an underlying impairment of autonomic control which manifests at early age.
authors.affiliation: Department of Physiology, Faculty of Medicine & Health Sciences, Al Ain, Abu Dhabi, United Arab Emirates. chris.howarth@uaeu.ac.ae
authors.forename: Frank C
authors.initials: FC
authors.lastname: Howarth
authors.forename: Michael
authors.initials: M
authors.lastname: Jacobson
authors.forename: Mohamed
authors.initials: M
authors.lastname: Shafiullah
authors.forename: Ernest
authors.initials: E
authors.lastname: Adeghate
mesh_terms: D000200:Action Potentials; D000375:Aging; D000818:Animals; D001786:Blood Glucose; D001831:Body Temperature; D001835:Body Weight; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism / Q000503:physiopathology*; D004195:Disease Models, Animal; D015536:Down-Regulation; D004562:Electrocardiography; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D008297:Male; D009043:Motor Activity; D051381:Rats; D017208:Rats, Wistar; D013686:Telemetry; D013997:Time Factors
chemical_list: D001786:Blood Glucose