Project Grant R01HL183979

FATTY ACID METABOLISM IN NORMAL AND PATHOLOGICAL ERYTHROPOIESIS - PROJECT SUMMARY THE PRODUCTION OF RED BLOOD CELLS (RBC), KNOWN AS 'ERYTHROPOIESIS', SERVES AS A PARADIGM FOR UNDERSTANDING CELLULAR DIFFERENTIATION AND TERMINAL MATURATION. DEFECTS IN ERYTHROPOIESIS OR RBC FUNCTION CAUSE VARIOUS FORMS OF ANEMIA, A HEALTH BURDEN AFFECTING NEARLY ONE-THIRD OF THE GLOBAL POPULATION. EACH STEP OF ERYTHROPOIESIS, INCLUDING LINEAGE SPECIFICATION, PROLIFERATION, DIFFERENTIATION, AND TERMINAL MATURATION INTO RBCS FILLED WITH HEMOGLOBIN FOR OXYGEN TRANSPORT, HAS UNIQUE METABOLIC REQUIREMENTS WITH POTENTIAL OPPORTUNITIES FOR THERAPEUTIC INTERVENTION. FOR INSTANCE, RECENT EVIDENCE INDICATES THAT HEMOGLOBINOPATHIES CAN BE TREATED BY STIMULATING GLYCOLYSIS WITH PYRUVATE KINASE AGONISTS. WE DEMONSTRATED PREVIOUSLY THAT GLUTAMINE SYNTHESIS IS UNIQUELY UPREGULATED DURING ERYTHROPOIESIS TO DETOXIFY AMMONIUM GENERATED BY HEME SYNTHESIS AND THAT ENHANCED GLUTAMINE SYNTHETASE ACTIVITY ALLEVIATES -THALASSEMIA. HOWEVER, THE COMPREHENSIVE METABOLIC REGULATION OF ERYTHROPOIESIS REMAINS POORLY UNDERSTOOD, WHICH LIMITS THERAPEUTIC OPPORTUNITIES. TO ADDRESS THIS KNOWLEDGE GAP, WE PERFORMED GLOBAL METABOLOMIC PROFILING, ISOTOPE TRACING AND TRANSCRIPTOME ANALYSIS OF STAGED ERYTHROID PRECURSORS FROM MOUSE FETAL LIVER AND BONE MARROW. WE DISCOVERED THAT DISTINCT, ONTOGENY-SPECIFIC METABOLIC PROCESSES GOVERN ERYTHROPOIESIS. WHILE GLUCOSE IS THE PRIMARY NUTRIENT FOR BIOENERGETICS AND BIOSYNTHESIS IN FETAL LIVER ERYTHROID PRECURSORS, MITOCHONDRIAL FATTY ACID B-OXIDATION (FAO) BECOMES MORE ACTIVE DURING POSTNATAL BONE MARROW ERYTHROPOIESIS. SURPRISINGLY, ISOTOPE TRACING SHOWED THAT LONG CHAIN FATTY ACIDS ARE ESSENTIAL METABOLIC PRECURSORS FOR TCA CYCLE INTERMEDIATES AND HEME DURING ADULT-TYPE ERYTHROPOIESIS. MOREOVER, GENETIC DISRUPTION OF FAO ENZYMES CAUSED IMPAIRED ERYTHROPOIESIS AND ANEMIA IN ADULT MICE, WHEREAS ERYTHROID FAO WAS PROFOUNDLY DYSREGULATED IN SICKLE CELL DISEASE (SCD). THESE FINDINGS SUPPORT OUR CENTRAL HYPOTHESES THAT FAO PROVIDES ESSENTIAL NUTRIENTS TO SUPPORT ERYTHROPOIETIC ENERGY DEMANDS AND BIOSYNTHETIC NEEDS, INCLUDING HEME BIOSYNTHESIS, AND THAT DYSFUNCTIONAL FAO CONTRIBUTES TO THE PATHOPHYSIOLOGY OF SCD. THUS, THE OBJECTIVE OF THIS PROJECT IS TO ELUCIDATE THE FUNCTIONAL AND MECHANISTIC ROLES OF FATTY ACID METABOLISM AS A NEW REGULATORY PATHWAY IN ERYTHROPOIESIS AND RBC DISORDERS ACCORDING TO THREE SPECIFIC AIMS: 1) DEFINE THE FUNCTIONAL ROLES OF FAO IN ERYTHROPOIESIS; 2) ELUCIDATE THE MECHANISTIC ROLES OF FATTY ACID METABOLISM IN ERYTHROCYTE DEVELOPMENT AND FUNCTION; AND 3) DETERMINE THE ROLE OF FATTY ACID METABOLISM IN THE PATHOPHYSIOLOGY OF SICKLE CELL DISEASE. OUR HYPOTHESES AND THE FEASIBILITY OF PROPOSED STUDIES ARE SUPPORTED BY EXTENSIVE PRELIMINARY DATA COMBINING ORTHOGONAL, STATE-OF-THE-ART METABOLIC AND TRANSCRIPTOMIC APPROACHES WITH ORTHOGONAL MOUSE AND HUMAN MODELS TO ANALYZE ERYTHROPOIESIS IN VIVO. NOW WE WILL ELUCIDATE FATTY ACID METABOLISM AS A CRITICAL METABOLIC REGULATOR OF NORMAL POSTNATAL ERYTHROPOIESIS AND A POTENTIAL THERAPEUTIC TARGET FOR SCD.