High Twin Resemblance for Sensitivity to Hypoxia

作者：Masschelein Evi; Van Thienen Ruud; Thomis Martine; Hespel Peter^*

来源：Medicine and Science in Sports and Exercise, 2015, 47(1): 74-81.

DOI：10.1249/MSS.0000000000000386

• ALTITUDE
• MONOZYGOTIC TWINS
• EXERCISE
• ACUTE MOUNTAIN SICKNESS

Purpose Physiological responses to hypoxia vary between individuals, and genetic factors are conceivably involved. Using a monozygotic twin design, we investigated the role of genetic factors in physiological responses to acute hypoxia.
Methods Thirteen pairs of monozygotic twin brothers participated in two experimental sessions in a normobaric hypoxic facility with a 2-wk interval. In one session, fraction of inspired O-2 (FiO2) was gradually reduced to 10.7% (approximately 5300 m altitude) over 5 h. During the next 3 h at 10.7%, FiO2 subjects performed a 20-min submaximal exercise bout (EXSUB, 1.2 Wkg(-1)) and a maximal incremental exercise test (EXMAX). An identical control experiment was done in normoxia. Cardiorespiratory measurements were continuously performed, and 8-h urine output was collected.
Results Compared with normoxia, hypoxia decreased (P < 0.05) arterial O-2 saturation (%SpO(2)) at rest (-22%) and during exercise (-28%). Furthermore, VO2max (-39%), HRmax (HR, -8%), maximal pulmonary ventilation (V-Emax, -11%), and urinary norepinephrine excretion (-31%) were reduced (P < 0.05) whereas HR at rest (25%) and during EXSUB (16%) and V-E at rest (38%) and during EXSUB (70%) were increased (P < 0.05). However, hypoxia-induced changes () were not randomly distributed between subjects. Between-pair variance was substantially larger than within-pair variance (P < 0.05) for %SpO(2) at rest (approximately threefold) and during exercise (approximately fourfold), VO2max (approximately fourfold), HR during exercise (approximately seven- to eightfold), hypoxic ventilatory response (approximately sixfold), and urinary norepinephrine output (approximately threefold). Incidence of acute mountain sickness (AMS) also yielded significant twin similarity (P < 0.05). AMS(+) subjects showed approximately 50% greater drop in urinary norepinephrine and lower hypoxic ventilator response than AMS(-) individuals.
Conclusions Our data suggest that genetic factors regulate cardiorespiratory responses, exercise tolerance, and pathogenesis of AMS symptoms in acute severe hypoxia. Hypoxia-induced sympathetic downregulation was associated with AMS.

• 出版日期2015-1