Autonomic neural dysfunction in recently diagnosed diabetic subjects

Area of Science:

• Endocrinology
• Neurology
• Internal Medicine

Background:

• Diabetic autonomic neuropathy is a common complication, but its early onset and mechanisms remain unclear.
• Sensitive and quantitative measures are needed to assess autonomic nervous system (ANS) function in recent-onset diabetes.

Purpose of the Study:

• To investigate early autonomic nervous system (ANS) dysfunction in recent-onset non-insulin-dependent (NIDD) and insulin-dependent (IDD) diabetes mellitus.
• To establish sensitive and quantitative measures for assessing ANS function in diabetic patients.

Main Methods:

• Assessed RR-variation during beta-adrenergic blockade to measure cardiac parasympathetic nervous system (PNS) activity.
• Measured dark-adapted pupil size after topical PNS blockade to evaluate iris sympathetic nervous system (SNS) activity.
• Evaluated pupillary latency time as an index of iris PNS pathway reflex.

Main Results:

• Both NIDD and IDD subjects showed reduced RR-variation, indicating cardiac PNS impairment.
• Dark-adapted pupil size was smaller in both NIDD and IDD groups, suggesting SNS impairment.
• Pupillary latency was prolonged in NIDD subjects, but not significantly altered in IDD subjects.

Conclusions:

• Autonomic nervous system (ANS) impairment occurs soon after the diagnosis of diabetes mellitus in both NIDD and IDD.
• Early ANS impairment is hypothesized to be common in both NIDD and IDD.
• Abnormal carbohydrate metabolism may play a significant role in the etiology of diabetic autonomic neuropathy.