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International Journal of Molecular... Jan 2023High-altitude illnesses (HAIs) result from acute exposure to high altitude/hypoxia. Numerous molecular mechanisms affect appropriate acclimatization to hypobaric and/or... (Review)
Review
High-altitude illnesses (HAIs) result from acute exposure to high altitude/hypoxia. Numerous molecular mechanisms affect appropriate acclimatization to hypobaric and/or normobaric hypoxia and curtail the development of HAIs. The understanding of these mechanisms is essential to optimize hypoxic acclimatization for efficient prophylaxis and treatment of HAIs. This review aims to link outcomes of molecular mechanisms to either adverse effects of acute high-altitude/hypoxia exposure or the developing tolerance with acclimatization. After summarizing systemic physiological responses to acute high-altitude exposure, the associated acclimatization, and the epidemiology and pathophysiology of various HAIs, the article focuses on molecular adjustments and maladjustments during acute exposure and acclimatization to high altitude/hypoxia. Pivotal modifying mechanisms include molecular responses orchestrated by transcription factors, most notably hypoxia inducible factors, and reciprocal effects on mitochondrial functions and REDOX homeostasis. In addition, discussed are genetic factors and the resultant proteomic profiles determining these hypoxia-modifying mechanisms culminating in successful high-altitude acclimatization. Lastly, the article discusses practical considerations related to the molecular aspects of acclimatization and altitude training strategies.
Topics: Humans; Altitude; Proteomics; Altitude Sickness; Hypoxia; Acclimatization
PubMed: 36675214
DOI: 10.3390/ijms24021698 -
Journal of the International Society of... Jan 2020The ergogenic effects of supplemental carbohydrate on aerobic exercise performance at high altitude (HA) may be modulated by acclimatization status. Longitudinal... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
The ergogenic effects of supplemental carbohydrate on aerobic exercise performance at high altitude (HA) may be modulated by acclimatization status. Longitudinal evaluation of potential performance benefits of carbohydrate supplementation in the same volunteers before and after acclimatization to HA have not been reported.
PURPOSE
This study examined how consuming carbohydrate affected 2-mile time trial performance in lowlanders at HA (4300 m) before and after acclimatization.
METHODS
Fourteen unacclimatized men performed 80 min of metabolically-matched (~ 1.7 L/min) treadmill walking at sea level (SL), after ~ 5 h of acute HA exposure, and after 22 days of HA acclimatization and concomitant 40% energy deficit (chronic HA). Before, and every 20 min during walking, participants consumed either carbohydrate (CHO, n = 8; 65.25 g fructose + 79.75 g glucose, 1.8 g carbohydrate/min) or flavor-matched placebo (PLA, n = 6) beverages. A self-paced 2-mile treadmill time trial was performed immediately after completing the 80-min walk.
RESULTS
There were no differences (P > 0.05) in time trial duration between CHO and PLA at SL, acute HA, or chronic HA. Time trial duration was longer (P < 0.05) at acute HA (mean ± SD; 27.3 ± 6.3 min) compared to chronic HA (23.6 ± 4.5 min) and SL (17.6 ± 3.6 min); however, time trial duration at chronic HA was still longer than SL (P < 0.05).
CONCLUSION
These data suggest that carbohydrate supplementation does not enhance aerobic exercise performance in lowlanders acutely exposed or acclimatized to HA.
TRIAL REGISTRATION
NCT, NCT02731066, Registered March 292,016.
Topics: Acclimatization; Altitude; Carbohydrates; Dietary Supplements; Exercise; Heart Rate; Humans; Longitudinal Studies; Male; Oxygen Consumption; Physical Exertion
PubMed: 31918720
DOI: 10.1186/s12970-020-0335-2 -
Plant Communications Nov 2020
Topics: Acclimatization; Adaptation, Physiological; Biological Evolution; Plants
PubMed: 33367271
DOI: 10.1016/j.xplc.2020.100118 -
Current Biology : CB Feb 2021The term 'neural adaptation' refers to the common phenomenon of decaying neuronal activities in response to repeated or prolonged stimulation. Many different roles of...
The term 'neural adaptation' refers to the common phenomenon of decaying neuronal activities in response to repeated or prolonged stimulation. Many different roles of adaptation in neural computations have been discussed. On a single-cell level adaptation introduces a high-pass filter operation as a basic element for predictive coding. Interactions of adaptation processes with nonlinearities are key to many more computations including generation of invariances, stimulus selectivity, denoising, and sparsening. Neural adaptation is observed all the way along neuronal pathways from the sensory periphery to the motor output and adaptation usually gets stronger at higher levels. Non-adapting neurons or neurons that increase their sensitivity are rare exceptions. What computations arise by repeated adaptation mechanisms along a processing pathway? After giving some background on neural adaptation, underlying mechanisms, dynamics, and resulting filter properties, I will discuss computational properties of four examples of serial and parallel adaptation processes, demonstrating that adaptation acts together with other mechanisms, in particular threshold nonlinearities, to eventually compute meaningful perceptions. Python code and further details of the simulations illustrating this primer are available at https://github.com/janscience/adaptationprimer.
Topics: Acclimatization; Adaptation, Physiological; Neurons
PubMed: 33561404
DOI: 10.1016/j.cub.2020.11.054 -
Archives of Insect Biochemistry and... Sep 2022
Topics: Acclimatization; Adaptation, Physiological; Animals; Biological Evolution; Evolution, Molecular
PubMed: 36031744
DOI: 10.1002/arch.21960 -
ELife May 2023A combination of imaging and theory suggests a new mechanism for the remodeling of veins in vascular networks.
A combination of imaging and theory suggests a new mechanism for the remodeling of veins in vascular networks.
Topics: Veins; Cardiovascular System; Adaptation, Physiological; Acclimatization
PubMed: 37227267
DOI: 10.7554/eLife.88052 -
Animal Models and Experimental Medicine Dec 2021Oxygen plays a pivotal role in the metabolism and activities of mammals. However, oxygen is restricted in some environments-subterranean burrow systems or habitats at... (Review)
Review
Oxygen plays a pivotal role in the metabolism and activities of mammals. However, oxygen is restricted in some environments-subterranean burrow systems or habitats at high altitude or deep in the ocean-and this could exert hypoxic stresses such as oxidative damage on organisms living in these environments. In order to cope with these stresses, organisms have evolved specific strategies to adapt to hypoxia, including changes in physiology, gene expression regulation, and genetic mutations. Here, we review how mammals have adapted to the three high-altitude plateaus of the world, the limited oxygen dissolved in deep water habitats, and underground tunnels, with the aim of better understanding the adaptation of mammals to hypoxia.
Topics: Acclimatization; Adaptation, Physiological; Altitude; Animals; Hypoxia; Mammals
PubMed: 34977482
DOI: 10.1002/ame2.12189 -
Nature Ecology & Evolution Dec 2021
Topics: Acclimatization; Adaptation, Physiological; Agriculture
PubMed: 34725489
DOI: 10.1038/s41559-021-01594-x -
Molecular Ecology Mar 2022How individual organisms adapt to nonoptimal conditions through physiological acclimatization is central to predicting the consequences of unusual abiotic and biotic...
How individual organisms adapt to nonoptimal conditions through physiological acclimatization is central to predicting the consequences of unusual abiotic and biotic conditions such as those produced by marine heat waves. The Northeast Pacific, including the Gulf of Alaska, experienced an extreme warming event (2014-2016, "The Blob") that affected all trophic levels and led to large-scale changes in the community. The marine copepod Neocalanus flemingeri is a key member of the subarctic Pacific pelagic ecosystem. During the spring phytoplankton bloom this copepod builds substantial lipid stores as it prepares for its nonfeeding adult phase. A 3-year comparison of gene expression profiles of copepods collected in Prince William Sound in the Gulf of Alaska between 2015 and 2017 included two high-temperature years (2015 and 2016) and one year with very low phytoplankton abundances (2016). The largest differences in gene expression were between high and low chlorophyll years, and not between warm and cool years. The observed gene expression patterns were indicative of physiological acclimatization. The predominant signal in 2016 was the down-regulation of genes involved in glycolysis and its incoming pathways, consistent with the modulation of metabolic rates in response to prolonged low food conditions. Despite the down-regulation of genes involved in metabolism, there was no evidence of suppression of protein synthesis based on gene expression or behavioural activity. Genes involved in muscle function were up-regulated, and the copepods were actively swimming and responsive to stimuli at collection. However, genes involved in fatty acid metabolism were down-regulated in 2016, suggesting reduced lipid accumulation.
Topics: Acclimatization; Animals; Copepoda; Ecosystem; Phytoplankton; Zooplankton
PubMed: 35048451
DOI: 10.1111/mec.16354 -
The Journal of Physiology Nov 2022Maturational differences exist in cardiopulmonary and cerebrovascular function at sea-level, but the impact of maturation on acclimatization responses to high altitude...
Maturational differences exist in cardiopulmonary and cerebrovascular function at sea-level, but the impact of maturation on acclimatization responses to high altitude is unknown. Ten children (9.8 ± 2.5 years) and 10 adults (34.7 ± 7.1 years) were assessed at sea-level (BL), 3000 m and twice over 4 days at 3800 m (B1, B4). Measurements included minute ventilation ( ), end-tidal partial pressures of oxygen ( ) and carbon dioxide, echocardiographic assessment of pulmonary artery systolic pressure (PASP) and stroke volume (SV) and ultrasound assessment of blood flow through the internal carotid and vertebral arteries was performed to calculate global cerebral blood flow (gCBF). At 3000 m, was increased from BL by 19.6 ± 19.1% (P = 0.031) in children, but not in adults (P = 0.835); SV was reduced in children (-11 ± 13%, P = 0.020) but not adults (P = 0.827), which was compensated for by a larger increase in heart rate in children (+26 beats min vs. +13 beats min , P = 0.019). Between B1 and B4, adults increased by 38.5 ± 34.7% (P = 0.006), while did not increase further in children. The rise in PASP was not different between groups; however, ∆PASP from BL was related to ∆ in adults (R = 0.288, P = 0.022), but not children. At BL, gCBF was 43% higher in children than adults (P = 0.017), and this difference was maintained at high altitude, with a similar pattern and magnitude of change in gCBF between groups (P = 0.845). Despite increasing in children but not adults at a lower altitude, the pulmonary vascular and cerebrovascular responses to prolonged hypoxia are similar between children and adults. KEY POINTS: Children have different ventilatory and metabolic requirements from adults, which may present differently in the pulmonary and cerebral vasculature upon ascent to high altitude. Children (ages 7-14) and adults (ages 23-44) were brought from sea level to high altitude (3000 to 3800 m) and changes in ventilation, pulmonary artery systolic pressure (PASP) and cerebral blood flow (CBF) were assessed over 1 week. Significant increases in ventilation and decreases in left ventricle stroke volume were observed at a lower altitude in children than adults. PASP and CBF increased by a similar relative amount between children and adults at 3800 m. These results help us better understand age-related differences in compensatory responses to prolonged hypoxia in children, despite similar changes in pulmonary artery pressure and CBF between children and adults.
Topics: Humans; Child; Adolescent; Young Adult; Adult; Blood Flow Velocity; Acclimatization; Altitude; Cerebrovascular Circulation; Hypoxia
PubMed: 36165275
DOI: 10.1113/JP283419