title: Prolonged (48-hour) modest hyperinsulinemia decreases nocturnal heart rate variability and attenuates the nocturnal decrease in blood pressure in lean, normotensive humans.
abstract: BACKGROUND
  Heart rate variability (HRV), an index of cardiac vagal activity, is decreased in individuals with metabolic disease. The relationship between decreased HRV and metabolic disease is unclear.
  
  
  OBJECTIVE
  The objective of this study was to determine whether experimentally induced glucose intolerance decreases HRV in a circadian relevant manner in healthy individuals.
  
  
  METHODS
  This was a within-subject, randomized design study with subjects infused for 48 h with saline (50 ml/h) or 15% glucose (200 mg/m2.min). HRV was evaluated using time domain measurements taken over the 48-h period. Blood pressure and heart rate were monitored, and blood samples were taken.
  
  
  METHODS
  This study was performed at the General Clinical Research Center of the Hospital of the University of Pennsylvania.
  
  
  METHODS
  Sixteen healthy subjects (eight men and eight women; 18-30 yr old; mean body mass index, 21.7 +/- 1.6 kg/m2) were studied.
  
  
  RESULTS
  After glucose infusion, mean plasma glucose was increased by 16.8% (P < 0.0001), and plasma insulin was increased by 99.4% (P < 0.0001) compared with after saline infusion. Significant decreases in homeostasis model assessment indicated a decrease in insulin sensitivity (saline, 0.52 + 0.13; glucose, 0.34 + 0.12; P < 0.0001). The nocturnal root mean square successive difference, an index of cardiac vagal activity, was significantly decreased (P < 0.01), and nocturnal HR (P < 0.001) and blood pressure were significantly elevated (saline, 107.4 +/- 2.7; glucose, 112.5 +/- 3.3 mm Hg; P < 0.05) compared with the saline control. The change in homeostasis model assessment due to glucose infusion was significantly correlated with the change in root mean square successive difference (r = 0.48; P < 0.01).
  
  
  CONCLUSIONS
  Prolonged mild hyperinsulinemia disrupts the circadian rhythm of cardiac autonomic activity. Early changes in the neural control of cardiac activity may provide a potential mechanism mediating the pathophysiological link between impaired glucose tolerance and cardiovascular disease.
authors.affiliation: Monell Chemical Senses Center, 3500 Market Street, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Maja
authors.initials: M
authors.lastname: Petrova
authors.forename: Raymond
authors.initials: R
authors.lastname: Townsend
authors.forename: Karen L
authors.initials: KL
authors.lastname: Teff
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D001794:Blood Pressure; D015992:Body Mass Index; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D018149:Glucose Intolerance / Q000503:physiopathology; D005951:Glucose Tolerance Test; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006946:Hyperinsulinism / Q000503:physiopathology*; D007022:Hypotension / Q000453:epidemiology / Q000503:physiopathology*; D008297:Male; D012016:Reference Values; D013851:Thinness
chemical_list: D001786:Blood Glucose