Tibetans exhibit lower hemoglobin concentration and decreased heart response to hypoxia during poikilocapnia at intermediate altitude relative to Han Chinese.

Autor:	Moya EA; Division of Pulmonary, Critical Care, Sleep Medicine, and Physiology, Department of Medicine, University of California San Diego, La Jolla, CA, United States., Yu JJ; Division of Pulmonary, Critical Care, Sleep Medicine, and Physiology, Department of Medicine, University of California San Diego, La Jolla, CA, United States., Brown S; Department of Anesthesiology, Loyola University Medical Center, Maywood, IL, United States., Gu W; Division of Pulmonary, Critical Care, Sleep Medicine, and Physiology, Department of Medicine, University of California San Diego, La Jolla, CA, United States., Lawrence ES; Division of Pulmonary, Critical Care, Sleep Medicine, and Physiology, Department of Medicine, University of California San Diego, La Jolla, CA, United States., Carlson R; School of Medicine, University of Utah, Salt Lake City, UT, United States., Brandes A; School of Medicine, University of Utah, Salt Lake City, UT, United States., Wegeng W; Division of Pulmonary, Critical Care, Sleep Medicine, and Physiology, Department of Medicine, University of California San Diego, La Jolla, CA, United States., Amann K; Department of Emergency Medicine, University of Rochester Medical Center, Rochester, NY, United States., McIntosh SE; Department of Emergency Medicine, University of Utah Health, Salt Lake City, UT, United States., Powell FL; Division of Pulmonary, Critical Care, Sleep Medicine, and Physiology, Department of Medicine, University of California San Diego, La Jolla, CA, United States., Simonson TS; Division of Pulmonary, Critical Care, Sleep Medicine, and Physiology, Department of Medicine, University of California San Diego, La Jolla, CA, United States.
Jazyk:	angličtina
Zdroj:	Frontiers in physiology [Front Physiol] 2024 May 09; Vol. 15, pp. 1334874. Date of Electronic Publication: 2024 May 09 (Print Publication: 2024).
DOI:	10.3389/fphys.2024.1334874
Abstrakt:	Background: High-altitude populations exhibit distinct cellular, respiratory, and cardiovascular phenotypes, some of which provide adaptive advantages to hypoxic conditions compared to populations with sea-level ancestry. Studies performed in populations with a history of high-altitude residence, such as Tibetans, support the idea that many of these phenotypes may be shaped by genomic features that have been positively selected for throughout generations. We hypothesize that such traits observed in Tibetans at high altitude also occur in Tibetans living at intermediate altitude, even in the absence of severe sustained hypoxia. Methodology: We studied individuals of high-altitude ancestry (Tibetans, n = 17 females; n = 12 males) and sea-level ancestry (Han Chinese, n = 6 females; n = 10 males), both who had been living at ∼1300 m (∼4327 ft) for at least 18 months. We measured hemoglobin concentration ([Hb]), hypoxic ventilatory response (HVR), and hypoxic heart rate response (HHRR) with end-tidal CO 2 (PetCO 2 ) held constant (isocapnia) or allowed to decrease with hypoxic hyperventilation (poikilocapnia). We also quantified the contribution of CO 2 on ventilation and heart rate by calculating the differences of isocapnic versus poikilocapnic hypoxic conditions (Δ V ˙ I /ΔPetCO 2 and ΔHR/ΔPetCO 2 , respectively). Results: Male Tibetans had lower [Hb] compared to Han Chinese males ( p < 0.05), consistent with reports for individuals from these populations living at high altitude and sea level. Measurements of ventilation (resting ventilation, HVR, and PetCO 2 ) were similar for both groups. Heart rate responses to hypoxia were similar in both groups during isocapnia; however, HHRR in poikilocapnia was reduced in the Tibetan group ( p < 0.03), and the heart rate response to CO 2 in hypoxia was lower in Tibetans relative to Han Chinese ( p < 0.01). Conclusion: These results suggest that Tibetans living at intermediate altitude have blunted cardiac responses in the context of hypoxia. Hence, only some of the phenotypes observed in Tibetans living at high altitude are observed in Tibetans living at intermediate altitude. Whereas blunted cardiac responses to hypoxia is revealed at intermediate altitudes, manifestation of other physiological adaptations to high altitude may require exposure to more severe levels of hypoxia. Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. (Copyright © 2024 Moya, Yu, Brown, Gu, Lawrence, Carlson, Brandes, Wegeng, Amann, McIntosh, Powell and Simonson.)
Databáze:	MEDLINE
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