Aromatase deficiency in a Chinese adult man caused by novel compound heterozygous CYP19A1 mutations: Effects of estrogen replacement therapy on the bone, lipid, liver and glucose metabolism

• Novel CYP19A1 missense mutations (Y81C and L451P) in an aromatase-deficient man.
• Structural modeling predicts that Y81C and L451P mutants disrupt protein structure.
• Y81C and L451P mutants decrease aromatase activity but have residual function.
• Estrogen therapy has great impact on the bone, lipid, liver and glucose metabolism.
• Estrogen therapy fails to improve insulin resistance in the man.

ObjectivesAromatase deficiency is a rare disorder resulting in estrogen insufficiency in humans. It has been reported in remarkably few men with loss-of-function mutations in the CYP19A1 gene encoding the aromatase, a cytochrome P450 enzyme that plays a crucial role in the biosynthesis of estrogens from androgens. We investigated a non-consanguineous family including an adult man with clinical features of aromatase deficiency, and studied the effects of estrogen replacement in the man.MethodsWe investigated the clinical and biochemical phenotype, performed CYP19A1 mutational analysis in the family and 50 unrelated persons, studied the effects of CYP19A1 mutations on aromatase protein structure, functionally characterized the mutations by cell-based aromatase activity assays, and studied the effects of estrogen replacement on the bone, lipid, liver and glucose metabolism.ResultsThe man with clinical features of aromatase deficiency had novel compound heterozygous CYP19A1 mutations (Y81C and L451P) that were not found in 50 unrelated persons. Three-dimensional modeling predicted that Y81C and L451P mutants disrupted protein structure. Functional studies on the basis of in vitro expression showed that Y81C and L45P mutants significantly decreased the aromatase activity and catalytic efficiency. Estrogen replacement in the man increased bone mineral density, accelerated bone maturation, improved lipid profile and liver steatosis, and improved glucose levels but not insulin resistance.ConclusionsWe have identified two novel CYP19A1 missense mutations in an aromatase-deficient man. Estrogen replacement in the man shows great impact on recovering the impairments in the bone, lipid, liver and glucose metabolism, but fails to improve insulin resistance.

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