title: Increased high-frequency heart rate variability during insulin-induced hypoglycaemia in healthy humans.
abstract: Despite causing sympathetic activation, prolonged hypoglycaemia produces little change in HR (heart rate) in healthy young adults. One explanation could be concurrent parasympathetic activation, resulting in unchanged net effects of autonomic influences. In the present study, hypoglycaemic (2.7 mmol/l) and normoglycaemic (4.7 mmol/l) hyperinsulinaemic clamp studies were performed after normoglycaemic baseline clamp periods with 15 healthy volunteers (seven male; mean age, 27 years) on two occasions in a randomized single-blind cross-over design. Non-invasive indices of cardiac autonomic activity and hormones were measured at baseline and 1 h after the beginning of hypoglycaemia or control normoglycaemia. Plasma insulin levels and mean HR were similar during both conditions. During hypoglycaemia, there was a 485% increase in plasma adrenaline (epinephrine). A shortening of the pre-ejection period by 45% suggested strong sympathetic cardiac activation. High-frequency (0.15-0.45 Hz) HRV (HR variability) increased, indicating a concomitant increase in parasympathetic tone. Thus, during hypoglycaemia-induced sympathetic cardiac activation in healthy adults, parasympathetic mechanisms are involved in stabilizing mean HR.
authors.affiliation: Department of Internal Medicine, Clinical Research Center and Division of Psychosomatic Medicine, University Hospital, 4031 Basel, Switzerland. Hartmut.Schaechinger@unibas.ch
authors.forename: Hartmut
authors.initials: H
authors.lastname: Schächinger
authors.forename: Johannes
authors.initials: J
authors.lastname: Port
authors.forename: Stuart
authors.initials: S
authors.lastname: Brody
authors.forename: Lilly
authors.initials: L
authors.lastname: Linder
authors.forename: Frank H
authors.initials: FH
authors.lastname: Wilhelm
authors.forename: Peter R
authors.initials: PR
authors.lastname: Huber
authors.forename: Daniel
authors.initials: D
authors.lastname: Cox
authors.forename: Ulrich
authors.initials: U
authors.lastname: Keller
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004837:Epinephrine / Q000097:blood; D005260:Female; D006334:Heart Function Tests; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007003:Hypoglycemia / Q000097:blood / Q000503:physiopathology*; D007328:Insulin / Q000097:blood; D008297:Male; D012129:Respiratory Function Tests; D016037:Single-Blind Method
chemical_list: D007328:Insulin; D004837:Epinephrine