Although carbon monoxide inhalation is dangerous because it can cause blood poisoning, research suggests that production of carbon monoxide in the body may actually protect cells during exposure to hypoxic environments as well as during ischemic-reperfusion injuries. Carbon monoxide is produced in the body by the enzyme heme oxygenase. This enzyme is responsible for converting heme into biliverdin and generates carbon monoxide in the process. Interestingly, carbon monoxide levels are higher in Tibetans (The average elevation of Tibet is 14,000 feet) as well as deep-diving mammals such as northern elephant seals. It is suspected that the higher levels of carbon monoxide may actually protect cells in the body from damage caused by low oxygen environments (Tift et al., 2020).
In a new study, researchers compared the expression of carboxyhemoglobin in adults with Tibetan and Han Chinese ancestry who were living in Xining, China (elevation: 7,218 ft) as well as those living in Salt Lake City, Utah, USA (elevation: 4,637 ft). Because people with Tibetan ancestry were known to have variations in the heme oxygenase gene, it was suspected they would produce more carbon monoxide, even when living at elevations lower than Tibet. Since carboxyhemoglobin is formed when carbon monoxide binds to hemoglobin, it was suspected that individuals with Tibetan ancestry would have higher levels.
Consistent with this hypothesis, the researchers measured 97% higher levels of carboxyhemoglobin in adults with Tibetan ancestry living in Xining as compared to Han Chinese descendants. Likewise, they found Tibetans living in Salt Lake City had 2 times higher levels of carboxyhemoglobin compared to adults who descended from Han Chinese. Higher production of carbon monoxide is thought to have evolved in Tibetans to protect their tissues from damage caused by hypoxia at high altitudes.
Sources:
A Lin, M Kong, W Gu, E Moya, E Lawrence, J Yu, T Simonson. Identification of HMOX2 promoter variants linked to adaptation in Tibetans. 2023 American Physiology Summit Abstracts. Physiology. 38: S1, 2023.
MS Tift, RW Alves de Souza, J Weber, EC Heinrich, FC Villafuerte, A Malhotra, LE Otterbein, TS Simonson. Adaptive potential of the heme oxygenase/carbon monoxide pathway during hypoxia. Frontiers in Physiology. 11: 886, 2020.
Categories: Environment, Hibernation and Hypoxia, Nature's Solutions
Tags: American Physiological Society, American Physiology Summit, carbon monoxide, high altitude, Tibet
Life Lines by Dr. Dolittle 