CBR1 (carbonyl reductase 1) is an NADPH-dependent oxidoreductase with broad substrate specificity that catalyzes the reduction of diverse carbonyl compounds 1. Physiologically, CBR1 metabolizes endogenous substrates including prostaglandins, converting prostaglandin E2 to prostaglandin F2α 2, and participates in glucocorticoid metabolism by reducing cortisol to 20β-dihydrocortisol [UniProt data supported by metabolic pathway literature]. Pharmacologically, CBR1 metabolizes anthracycline anticancer drugs (doxorubicin, daunorubicin) to their cardiotoxic alcohol metabolites (doxorubicinol, daunorubicinol) 3. CBR1 expression is transcriptionally regulated by the antioxidant-responsive transcription factor Nrf2 through antioxidant response elements in its promoter 4. Functionally, genetic variants like CBR1 V88I affect catalytic activity and NADPH binding affinity, influencing both prostaglandin and anthracycline metabolism 2. In brown adipose tissue, CBR1-mediated prostaglandin F2α production improves systemic insulin sensitivity through m6A-dependent mRNA decay regulation 56. CBR1 knockout increases doxorubicin-induced cardiotoxicity in cardiomyocytes 3, while CBR1 protein levels are retained after resistance training, suggesting a role in skeletal muscle adaptation 7. CBR1 overexpression associates with aggressive hepatocellular carcinoma 8.