Hematologic and systemic metabolic alterations due to Mediterranean class II G6PD deficiency in mice

Abstract

Deficiency of Glucose 6 phosphate dehydrogenase (G6PD) is the single most common enzymopathy, present in approximately 400 million humans (e.g., 5% of humans). Its prevalence is hypothesized to be due to conferring resistance to malaria. However, G6PD deficiency also results in hemolytic sequelae from oxidant stress. Moreover, G6PD deficiency is associated with kidney disease, diabetes, pulmonary hypertension, immunological defects, and neurodegenerative diseases. To date, the only available mouse models have decreased levels of wild-type stable G6PD caused by promoter mutations. However, human G6PD mutations are missense mutations that result in decreased enzymatic stability. As such, this results in very low activity in red blood cells that cannot synthesize new protein. To generate a more accurate model, the human sequence for a severe form of G6PD deficiency (Med -) was knocked into the murine G6PD locus. As predicted, G6PD levels were extremely low in RBCs and deficient mice have increased hemolytic sequalae to oxidant stress. Non-erythroid organs had metabolic changes consistent with mild G6PD deficiency, consistent with what has been observed in humans. Juxtaposition of G6PD deficient and wild-type mice revealed altered lipid metabolism in multiple organ systems.Together, these findings both establish a new mouse model of G6PD deficiency that more accurately reflects human G6PD deficiency and also advance our basic understanding of altered metabolism in this setting. Introduction:Glucose-6-phosphate dehydrogenase (G6PD) is the first and rate determining enzyme in the pentose phosphate pathway (PPP), which utilizes glucose to generate NADPH; the latter is the major reducing equivalent that fuels multiple pathways by which cells handle oxidative stress.Deficiency in the activity of G6PD is the single most common enzymopathy in humans, estimated to be present in approximately 400 million people worldwide(1). The complete absence of G6PD is not compatible with life, and the vast majority of mutations leading to G6PD deficiency in humans are missense mutations leading to an unstable G6PD enzyme. Based upon the mutation and resulting G6PD levels, disease can range from mild to severe deficiency (2, 3). RBCs from humans with G6PD deficiency are particularly susceptible to oxidant stress for two prevailing reasons. First, because RBCs lack mitochondria, the PPP is their main source of NADPH. Second, mature RBCs are unable to synthesize new proteins. When G6PD deficient humans encounter an illness or consume a drug or food that increases oxidant stress (e.g., antimalarial quinone drugs or fava beans), they can manifest symptoms of acute hemolysis, ranging from mild to lethal(4, 5).Recent findings have also linked G6PD deficiency to many other diseases outside the RBC compartment, including immunological(1), cardiovascular(6), endocrine(7), renal(7), neurological(8), and pulmonary pathologies(9). Because G6PD deficiency is so prevalent in humans, and because its biology remains poorly understood, a translatable anim...

Reprogramming of red blood cell metabolism in Zika virus–infected donors

“…However, a basal activation of this pathway at the expense of the Embden-Meyerhof-Parnas glycolytic pathway may result in an energetically challenged RBC with an effective antioxidant system, 92 hence more susceptible to the severity of the storage lesion, in like fashion to donors who lack the capacity to activate the pentose phosphate pathway owing to the deficiency in the activity of the rate-limiting enzyme, glucose 6-phosphate dehydrogenase. 54,93,94 These results are consistent with the reported increase in oxidant stress (e.g., increased protein carbonylation, decreased activity of key antioxidant enzymes such as catalase and superoxide dismutase) in cells infected by ZIKV. 95 Similar to our findings in RBCs from patients with coronavirus disease 2019 (COVID-19), 22 we observed increased tryptophan oxidation to kynurenine in IgMpositive donors, consistent with a correlation between the activation of this pathway and seroconversion in patients with COVID-19.…”

“…During storage in the blood bank, a metabolic switch from glycolysis to the pentose phosphate pathway ensures a strategy to cope with storage‐induced oxidant stress. However, a basal activation of this pathway at the expense of the Embden‐Meyerhof‐Parnas glycolytic pathway may result in an energetically challenged RBC with an effective antioxidant system, 92 hence more susceptible to the severity of the storage lesion, in like fashion to donors who lack the capacity to activate the pentose phosphate pathway owing to the deficiency in the activity of the rate‐limiting enzyme, glucose 6‐phosphate dehydrogenase 54,93,94 . These results are consistent with the reported increase in oxidant stress (e.g., increased protein carbonylation, decreased activity of key antioxidant enzymes such as catalase and superoxide dismutase) in cells infected by ZIKV 95 …”

Genome-wide metabolite quantitative trait loci analysis (mQTL) in red blood cells from volunteer blood donors

“…88 Here we report that the levels of pyruvate in fresh RBCs and pyruvate/lactate ratios in stored RBCs are associated with the same G6PD polymorphisms. A causal role of this correlation is established in humanized murine models of G6PD deficiency, since the same metabolic change is seen in RBCs that differ only in their form of G6PD (African or Mediterranean 64 variants vs. nondeficient human form). These observations could be partly explained by the compensatory over-activation of NADH-dependent methemoglobin reductase to cope with increased oxidant stress in G6PD deficient erythrocytes.…”

ZOOMICS: Comparative Metabolomics of Red Blood Cells From Guinea Pigs, Humans, and Non-human Primates During Refrigerated Storage for Up to 42 Days

“…This pathway is critical to RBC storage lesion severity in that it regulates post-transfusion clearance. In mice this varies due to polymorphisms causing excess activation of the STEAP3 ferrireductase ( D’Alessandro et al, 2021c ). Similarly, oxidant stress induces fatty acid desaturase-dependent NADH consumption in mature RBCs, a process that is partially observable during storage ( Thomas et al, 2021 ).…”