| 1. |
- Debevec, Tadej, et al.
(författare)
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FemHab : The effects of bed rest and hypoxia on oxidative stress in healthy women
- 2016
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Ingår i: Journal of applied physiology. - : American Chemical Society (ACS). - 8750-7587 .- 1522-1601. ; 120:8, s. 930-938
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Tidskriftsartikel (refereegranskat)abstract
- Independently, both inactivity and hypoxia augment oxidative stress. This study, part of the FemHab project, investigated the combined effects of bed rest-induced unloading and hypoxic exposure on oxidative stress and antioxidant status. Healthy, eumenorrheic women were randomly assigned to the following three 10-day experimental interventions: normoxic bed rest (NBR; n = 11; PIO2 = 133 mmHg), normobaric hypoxic bed rest (HBR; n = 12; PIO2 = 90 mmHg), and ambulatory hypoxic confinement (HAMB; n = 8: PIO2 = 90 mmHg). Plasma samples, obtained before (Pre), during (D2, D6), immediately after (Post) and 24 h after (Post + 1) each intervention, were analyzed for oxidative stress markers [advanced oxidation protein products (AOPP), malondialdehyde (MDA), and nitrotyrosine], antioxidant status [ superoxide dismutase (SOD), catalase, ferric-reducing antioxidant power (FRAP), glutathione peroxidase (GPX), and uric acid (UA)], NO metabolism end-products (NOx), and nitrites. Compared with baseline, AOPP increased in NBR and HBR on D2 (+ 14%; + 12%; P < 0.05), D6 (+ 19%; + 15%; P < 0.05), and Post (+ 22%; + 21%; P < 0.05), respectively. MDA increased at Post + 1 in NBR (+ 116%; P < 0.01) and D2 in HBR (+114%; P < 0.01) and HAMB (+ 95%; P < 0.05). Nitrotyrosine decreased (-45%; P < 0.05) and nitrites increased (+46%; P < 0.05) at Post + 1 in HAMB only. Whereas SOD was higher at D6 (+ 82%) and Post + 1 (+ 67%) in HAMB only, the catalase activity increased on D6 (128%) and Post (146%) in HBR and HAMB, respectively (P < 0.05). GPX was only reduced on D6 (- 20%; P < 0.01) and Post (- 18%; P < 0.05) in HBR. No differences were observed in FRAP and NOx. UA was higher at Post in HBR compared with HAMB (P < 0.05). These data indicate that exposure to combined inactivity and hypoxia impairs prooxidant/antioxidant balance in healthy women. Moreover, habitual activity levels, as opposed to inactivity, seem to blunt hypoxia-related oxidative stress via antioxidant system upregulation.
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| 2. |
- Rittweger, Joern, et al.
(författare)
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On the combined effects of normobaric hypoxia and bed rest upon bone and mineral metabolism : Results from the PlanHab study
- 2016
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Ingår i: Bone. - : Elsevier. - 8756-3282 .- 1873-2763. ; 91, s. 130-138
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Tidskriftsartikel (refereegranskat)abstract
- Bone losses are common as a consequence of unloading and also in patients with chronic obstructive pulmonary disease (COPD). Although hypoxia has been implicated as an important factor to drive bone loss, its interaction with unloading remains unresolved. The objective therefore was to assess whether human bone loss caused by unloading could be aggravated by chronic hypoxia. In a cross-over designed study, 14 healthy young men underwent 21-day interventions of bed rest in normoxia (NBR), bed rest in hypoxia (HBR), and hypoxic ambulatory confinement (HAmb). Hypoxic conditions were equivalent to 4000 m altitude. Bone metabolism (NTX, P1NP, sclerostin, DKK1) and phospho-calcic homeostasis (calcium and phosphate serum levels and urinary excretion, PTH) were assessed from regular blood samples and 24-hour urine collections, and tibia and femur bone mineral content was assessed by peripheral quantitative computed tomography (pQCT). Urinary NTX excretion increased (P<0.001) to a similar extent in NBR and HBR (P = 0.69) and P1NP serum levels decreased (P = 0.0035) with likewise no difference between NBR and HBR (P = 0.88). Serum total calcium was increased during bed rest by 0.059 (day D05, SE 0.05 mM) to 0.091 mM (day D21, P < 0.001), with no additional effect by hypoxia during bed rest (P = 0.199). HAmb led, at least temporally, to increased total serum calcium, to reduced serum phosphate, and to reduced phosphate and calcium excretion. In conclusion, hypoxia did not aggravate bed rest-induced bone resorption, but led to changes in phospho-calcic homeostasis likely caused by hyperventilation. Whether hyperventilation could have mitigated the effects of hypoxia in this study remains to be established.
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| 3. |
- Simpson, Elizabeth J., et al.
(författare)
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PlanHab : the combined and separate effects of 16 days of bed rest and normobaric hypoxic confinement on circulating lipids and indices of insulin sensitivity in healthy men
- 2016
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Ingår i: Journal of applied physiology. - : AMER PHYSIOLOGICAL SOC. - 8750-7587 .- 1522-1601. ; 120:8, s. 947-955
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Tidskriftsartikel (refereegranskat)abstract
- PlanHab is a planetary habitat simulation study. The atmosphere within future space habitats is anticipated to have reduced PO2, but information is scarce as to how physiological systems may respond to combined exposure to moderate hypoxia and reduced gravity. This study investigated, using a randomized-crossover design, how insulin sensitivity, glucose tolerance, and circulating lipids were affected by 16 days of horizontal bed rest in normobaric normoxia [NBR: FIO2 = 0.209; PIO2 = 133.1 (0.3) mmHg], horizontal bed rest in normobaric hypoxia [HBR: FIO2 = 0.141 (0.004); PIO2 = 90.0 (0.4) mmHg], and confinement in normobaric hypoxia combined with daily moderate intensity exercise (HAMB). A mixed-meal tolerance test, with arterialized-venous blood sampling, was performed in 11 healthy, nonobese men (25-45 yr) before (V1) and on the morning of day 17 of each intervention (V2). Postprandial glucose and c-peptide response were increased at V2 of both bed rest interventions (P < 0.05 in each case), with c-peptide: insulin ratio higher at V2 in HAMB and HBR, both in the fed and fasted state (P < 0.005 in each case). Fasting total cholesterol was reduced at V2 in HAMB [-0.47 (0.36) mmol/l; P < 0.005] and HBR [-0.55 (0.41) mmol/l; P < 0.005]. Fasting HDL was lower at V2 in all interventions, with the reduction observed in HBR [-0.30 (0.21) mmol/l] greater than that measured in HAMB [-0.13 (0.14) mmol/l; P < 0.005] and NBR [-0.17 (0.15) mmol/l; P < 0.05]. Hypoxia did not alter the adverse effects of bed rest on insulin sensitivity and glucose tolerance but appeared to increase insulin clearance. The negative effect of bed rest on HDL was compounded in hypoxia, which may have implications for long-term health of those living in future space habitats.
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