Autonomic and circulatory function in type 1 diabetes mellitus
Date of Award
Doctor of Philosophy (Ph.D.)
First Committee Member
Barry E. Hurwitz, Committee Chair
The primary purpose of this study was to examine to what extent alterations in parasympathetic function at rest: (1) extend to baroreflex-mediated compensatory parasympathetic responses, (2) are associated with alterations in sympathetic function; and (3) are linked to abnormal vasodilatory and vasoconstrictive function.Subjects included 41 DM1 and 35 non-diabetic healthy control individuals; mean (+/-SE) age was 32.3 (+/-1.0) years, with moderate to good glycemic control for DM1 subjects (mean HbA1c = 7.5 +/- 0.3), and with mean duration of diabetes 18.5 (+/-1.1) years. The 76 subjects (54% DM1) were represented by a variety of ethnic backgrounds, including non-Hispanic White (n = 38), Hispanic American (n = 27), and Black American (n = 11) persons of both genders (35 = men; 41 = women). Subjects were recruited from the Miami-Dade community. A quantitative clustering methodology, based upon measures of supine resting HR and vagal cardiac input (indexed by RSAe during two minutes of deep paced respiration) and diabetic status, yielded 3 groups. The three groups were termed DM1a (normal parasympathetic function, DM1), DM1b (low parasympathetic function, DM1), and Control (normal parasympathetic function, no DM1).The study results showed that DM1 subjects with diminished resting parasympathetic function displayed: (1) altered resting cardiovascular regulation including elevated blood pressure and TPR and diminished contractility and (2) less TPR response per given change in blood pressure during alpha-adrenergic receptor activation with phenylephrine and in response to the cold pressor task relative to other subjects. Additional findings were that both groups of DM1 subjects compared with Control subjects displayed: (1) diminished baroreceptor sensitivity; (2) more diminished vasodilatory response to nitroprusside stimulation; and (3) less sympathetically mediated cardiac compensatory response to the nitroprusside-induced decline in blood pressure.The cross-sectional design of the study prevents the definitive conclusion that the DM1b subjects reflect a group that is more progressed than the DM1a subjects in terms of diabetes-related cardiovascular complications. Nevertheless, the present findings support the suggestion that the DM1b subjects may be further disease progressed by virtue of the apparent additional involvement of deficits in resting parasympathetic chronotropic function and sympathetically-mediated contractility as well as in vasoconstrictive function. If the DM1b subjects reflect a group of individuals who are at a more progressed point in a continuum of disease progression relative to the DM1a subjects, then it may be concluded that cardiac and vascular pathophysiological alterations in DM1 precede parasympathetic alterations. (Abstract shortened by UMI.)
Hart, Candace Teresa, "Autonomic and circulatory function in type 1 diabetes mellitus" (2005). Dissertations from ProQuest. 2268.