Stronger Association between Hemoglobin and Blood Pressure in People Bearing GP.Mur Blood Type

GP.Mur, commonly known as Miltenberger subtype III, is a clinically‐important red blood cell (RBC) phenotype unique among Southeast Asians (SEA). On the GP.Mur+ erythrocyte membrane, glycophorin B‐A‐B hybrid protein is expressed, instead of glycophorin B (GPB). Different from GPB that does not have any known function, GP.Mur hybrid protein promotes expression of anion exchanger‐1 (AE1) on the RBC membrane and support AE1‐relevant physiological functions in GP.Mur+ carriers. In our previous human studies, we unexpectedly uncovered that GP.Mur+ carriers have slightly higher blood pressure (BP) than GP.Mur‐negative people. Since AE1 has been implicated a role in modulation of NO bioavailability and hemoglobin (Hb) is a major NO scavenger, we hypothesized that the slightly but significantly higher BP in GP.Mur carriers might be related to Hb‐mediated NO processing. Methods With the approval of hospital Institutional Review Board, healthy, non‐smoker subjects aged between 20 and 55 were recruited at Taitung MacKay Memorial Hospital (TT‐MMH). Besides general physical assessment, recruited subjects were tested for CBC and RBC phenotypes, including GP.Mur. Results 345 male and 515 female non‐smoker adults were recruited from Taitung County, Taiwan, and 22.1% of them bear GP.Mur blood type. For male and female cohorts, GP.Mur erythrocyte expression was significantly associated with slightly higher systolic BP (SBP) (122.2±12.9 mmHg [non‐GP.Mur male] versus 127.8±14.4 mmHg [GP.Mur male]; 115.0±13.0 mmHg [non‐GP.Mur female] versus 118.0±13.4 mmHg [GP.Mur female]). Hb levels were not affected by GP.Mur. Hb is known to be positively associated with SBP. We indeed found a Pearson correlation of 0.164 between Hb (g/dL) and SBP (mmHg) in non‐GP.Mur male subjects ( *p ~0.007). However, Hb‐SBP associations were not observed in our female cohorts with or without GP.Mur. Intriguingly, the Pearson correlation between Hb and SBP from the GP.Mur male group was doubled, compared to that from the GP.Mur‐negative male group (Pearson correlation: 0.299 [GP.Mur male] versus 0.164 [non‐GP.Mur male]). Conclusion From the differences in Hb‐SBP correlations in male, the effects of NO‐scavenging by Hb were likely more substantial in the presence of GP.Mur and/or higher AE1 expression. We did not observe any positive associations in our SEA female subjects, presumably due to menstrual cycle and that SEA women were generally more anemic.