Prolonged (48-hour) modest hyperinsulinemia decreases nocturnal heart rate variability and attenuates the nocturnal...

Area of Science:

• Cardiology
• Metabolic Physiology
• Autonomic Neuroscience

Background:

• Heart rate variability (HRV), a measure of cardiac autonomic function, is often reduced in metabolic diseases.
• The precise relationship between diminished HRV and metabolic dysfunction remains incompletely understood.

Purpose of the Study:

• To investigate if experimentally induced glucose intolerance impacts HRV in a manner relevant to circadian rhythms in healthy individuals.
• To explore the potential link between altered glucose metabolism and autonomic nervous system function.

Main Methods:

• A within-subject, randomized crossover design was employed, with participants receiving either saline or a 15% glucose infusion over 48 hours.
• Heart rate variability (HRV) was assessed using time-domain measurements throughout the 48-hour infusion period.
• Blood pressure, heart rate, and plasma glucose/insulin levels were monitored, and insulin sensitivity was evaluated using the homeostasis model assessment (HOMA).

Main Results:

• Glucose infusion led to significant increases in plasma glucose and insulin, alongside a marked decrease in insulin sensitivity (HOMA).
• A significant reduction in nocturnal HRV (assessed by root mean square successive difference) was observed following glucose infusion.
• Nocturnal heart rate and blood pressure were significantly elevated during glucose infusion compared to saline control.

Conclusions:

• Prolonged mild hyperinsulinemia disrupts the normal circadian patterns of cardiac autonomic activity.
• These findings suggest that early alterations in the neural control of cardiac function may represent a key mechanism connecting impaired glucose tolerance to the development of cardiovascular disease.