Avaliação da modulação autonômica cardiovascular de camundongos diabéticos não obesos

Abstract

Introduction: It is known that diabetes is associated with autonomic dysfunction and this is a severe complication that increases the risk of cardiovascular mortality. The non-obese diabetic mice (NOD) is an experimental model of type 1 diabetes which develops insulitis at the 4th week and diabetes between the 14th and the 20th week of life. However, data about autonomic function in these mice remain scarce. Objective: To investigate the cardiovascular autonomic profile of NOD mice. Methods: Female mice (24-28 week old) were divided in two groups: NOD (n=6) and control (n=6, swiss mice). NOD mice with glycemia ≥300 mg/dl were used in this study. Heart rate variability (HRV) was evaluated in time and frequency domains and also through symbolic analysis. Were also analyzed the variability of the blood pressure, and baroreflex sensitivity by means of the bradycardic and tachycardic responses induced by infusion of phenylephrine and sodium nitroprusside. Student t test for independent samples and Pearson's correlation coefficient were used for statistical analyses. The data were described as means and standard error. Results: The heart rate and arterial pressure were similar between the groups, however HRV (total variance of RR interval: NOD = 21.07 ± 3.75 vs. C = 42.02 ± 6.54 ms2) and RMSSD (NOD = 4.01 ± 0.32 vs. C = 8.28 ± 0.97 ms), a vagal modulation index, were lower in NOD group when compared to control group. Moreover, the low frequency component was higher in NOD group (normalized LF: NOD = 61.0 ± 4.0 vs. C = 20.0 ± 4.0%), while the high frequency of HR component was lower in NOD compared with the control group (normalized HF: NOD = 39.0 ± 4.0% vs. C = 80.0 ± 4.0%). Similarly, the 0V pattern of symbolic analysis, indicative of sympathetic activity, was increased in NOD group when compared to the control group (NOD = 11.9 ± 1.4 vs. C = 6.06 ± 0.90%) and the 2LV pattern, indicative of parasympathetic activity, was reduced in the NOD group (NOD = 7.98 ± 1.3 vs. C = 21.2 ± 3.36%). Both responses to arterial pressure changes, tachycardic (NOD = 3.01 ± 0.72 vs. C = 4.54 ± 0.36 bpm/mmHg) and bradycardic (NOD = 2.49 ± 0.31 vs. C = 3.43 ± 0.33 bpm/mmHg) were lower in NOD when compared to the control group. A negative correlation between the indices of vagal modulation (RMSSD, normalized high frequency component and 2LV pattern of symbolic analysis) and blood glucose levels was also observed. Conclusions: The NOD mice present cardiovascular autonomic dysfunction and that is probably associated with glycemic levels.