The ability to use oxygen effectively is essential for survival. Many significant human diseases, including cardiopulmonary disease, hypertension, sleep apnea, and cancer involve a disruption in oxygen homeostasis. Human populations at high altitude have been challenged by hypoxia for hundreds of generations and show both unique physiological responses to this environmental stress and extremely strong natural selection for genes involved in oxygen transport, which can be demonstrated in relatively small studies. For example, we were the first to demonstrate a relationship between genes in the hypoxia inducible factor (HIF) pathway under natural selection and relatively lower hemoglobin concentration, which is further associated with exercise capacity, in Tibetans. Here we propose a similar integrative and targeted approach to identify the genetic determinants of both adaptive and maladaptive cardiopulmonary responses to hypoxia in Andean natives, who show a wide range of cardiorespiratory phenotypes, including chronic mountain sickness (CMS) rare among Tibetans. CMS is characterized by excessive erythrocytosis, arterial hypoxemia, carbon dioxide retention, and blunted ventilatory chemoreflexes, which are also traits associated with poor outcomes in patients with chronic heart and lung disease. We propose to test the overarching hypothesis that individual differences in cardiopulmonary phenotypes (hemoglobin concentration, arterial oxygen saturation, hypoxic/hypercapnic ventilatory and cardiovascular responses) are predicted by (1) a lack of adaptive variants and/or (2) altered epigenetic regulation at loci identified with powerful state-of-the-art genomic analyses of Andean men and women with and without CMS. We will also test the hypothesis that the severity of sleep apnea underlies epigenetic changes that further modify cardiopulmonary responses as previously demonstrated in animal studies of intermittent hypoxia. Finally, we will determine if genetic and epigenetic variants result in gain- or loss-of-function to pursue therapeutic options for mitigating maladaptive responses to hypoxia in patients at sea level with chronic heart and lung disease.

Public Health Relevance

Individuals with chronic cardiopulmonary diseases as well as populations living at high altitude as are challenge by limited oxygen availability and exhibit some of the same outcomes. Studies of a relatively small number of adapted Andean highlanders provide an exceptional opportunity to understand mechanisms of oxygen transport underlying adaptive or mal-adaptive traits that can be predicted by genetic factors. Such findings provide novel insights into the challenge of low oxygen inherent to many disease states (e.g., heart and lung disease, stroke, hypertension, and cancer) and have broad implications for disease treatment and prevention.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL145470-01
Application #
9643556
Study Section
Respiratory Integrative Biology and Translational Research Study Section (RIBT)
Program Officer
Laposky, Aaron D
Project Start
2019-04-01
Project End
2024-03-31
Budget Start
2019-04-01
Budget End
2020-03-31
Support Year
1
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of California, San Diego
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093