title: Cyclic hypobaric hypoxia improves markers of glucose metabolism in middle-aged men.
abstract: Chronic hypoxia increases dependence on glucose in men and increases insulin sensitivity in men and women. Cyclic Variations in Altitude Conditioning (CVAC) is a novel technology that provides exposure to rapidly fluctuating cyclic hypobaric hypoxia (CHH).
  
  
  OBJECTIVE
  To test the hypothesis that markers of glucose metabolism would change with CVAC CHH, two groups of middle-aged men were exposed to 10 weeks (40 min/day, 3 day/week) of either CHH or sham (SH) sessions.
  
  
  METHODS
  CHH subjects (age: 48 ± 6, weight: 86 ± 12 kg, BMI: 27.1 ± 3, n=11) experienced cyclic pressures simulating altitudes ranging from sea level to 3048 m (week 1) and progressing to 6096 m (by week 5 through week 10). SH subjects (age: 50 ± 4, weight: 89 ± 15 kg, BMI: 27.5 ± 3, n=10) were exposed to slowly-fluctuating pressures up to 607 m (all subjects blinded to elevation). Physical function and blood markers of glucose metabolism were measured at baseline, 3, 6, and 10 weeks.
  
  
  RESULTS
  Two CHH subjects were dropped from analysis for failure to progress past 3048 m (CHH: n=9). Weight and physical activity remained stable for both groups. There was a group-by-time interaction in fasting glucose (CHH: 96 ± 9 to 91 ± 7 mg/dL, SH: 94 ± 7 to 97 ± 9 mg/dL, p<0.05). Reduction in plasma glucose response to oral glucose tolerance test [area under the curve] was greater in CHH compared to SH after 10 weeks of exposure (p<0.03). Neither group experienced changes in fasting insulin, insulin response during the OGTT, or changes in a timed walk test.
  
  
  CONCLUSIONS
  Ten weeks of CVAC CHH exposure improves markers of glucose metabolism in middle-aged men at risk for metabolic syndrome.
authors.affiliation: 1 Clinical Studies Unit, VA Palo Alto Health Care System , Palo Alto, California.
authors.forename: Juan L
authors.initials: JL
authors.lastname: Marquez
authors.forename: Scott
authors.initials: S
authors.lastname: Rubinstein
authors.forename: Jill A
authors.initials: JA
authors.lastname: Fattor
authors.forename: Omer
authors.initials: O
authors.lastname: Shah
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Hoffman
authors.forename: Anne L
authors.initials: AL
authors.lastname: Friedlander
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D005080:Exercise Test; D005951:Glucose Tolerance Test; D006801:Humans; D000860:Hypoxia / Q000097:blood*; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011312:Pressure; D016037:Single-Blind Method; D016138:Walking / Q000502:physiology
chemical_list: D001786:Blood Glucose; D007328:Insulin; D010100:Oxygen