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 - PubMed (original) (raw)

Case Reports

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

Zhike Chen et al. Mol Cell Endocrinol. 2015.

Abstract

Objectives: Aromatase 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.

Methods: We 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.

Results: The 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.

Conclusions: We 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.

Keywords: Aromatase; Aromatase deficiency; CYP19A1; Estrogen replacement; Insulin resistance; Metabolic syndrome.

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Figures

Fig. 1

Photographs and X-rays of the patient with aromatase deficiency. (A) Eunuchoid proportions, long arms, visceral adiposity, and bilateral genu valgum are present in the 24-year-old man. (B) Acanthosis nigricans on the axilla in the man. (C) X-ray of knees reveals incompletely fused epiphyses in the tibiae and fibulae, and bilateral genu valgum. (D) X-ray of the lumbar spine reveals osteopenia. (E) X-ray of hands reveals delayed bone age by 6–8 years.

Fig. 2

Genetic analysis of the CYP19A1 gene. (A) Pedigree of the patient family with two CYP19A1 missense mutations. (B) The DNA sequence chromatogram of the proband compare with that of a normal unrelated individual (wild-type) reveals the proband to have compound heterozygous CYP19A1 mutations comprising an A→G transition at c.384 (arrowed) in exon 3 and a T→C transition at c.1494 (arrowed) in exon 10, which predicts the missense mutations Tyr81Cys (Y81C) and Leu451Pro (L451P), respectively. (C) Evolutionary conservation of aromatase residues with identified aromatase mutants. Multiple protein sequence alignments are done in aromatase orthologs and paralogs. The Tyr81 residue (red), which is adjacent to the A helix, is highly conserved in aromatase orthologs and is conserved in paralogs. The Leu451 residue (red), which is close to the heme binding region, is highly conserved in aromatase orthologs and is conserved in paralogs. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Three-dimensional modeling of aromatase mutant proteins. (A) A three-dimensional modeling of aromatase Y81C mutant compared with the wild-type aromatase. The model is based on the reported crystal structure of human aromatase in complex with androstenedion (PDB code 3EQM). The affected residue Tyr81 (red, left panel), replaced with a cysteine (Cys81, red, right panel) in the mutant, is ajacent to helixes A and A′. An analysis of the predicted structural effect of the Y81C mutant on hydrogen bonds (broken lines) in the helixes A and A′ region shows that Y81C leads to a loss of five hydrogen bonds and causes steric clashes in helixes A and A′ of the Y81C mutant (blue, right panel) as compared with the wild-type aromatase (green, left panel). (B) A three-dimensional modeling of aromatase L451P mutant compared with the wild-type aromatase. The affected residue Leu451 (red, left panel), replaced with a proline (Pro451, red, right panel) in the mutant, is located in the L-helix and is close to the heme binding region (orange) and β7–β9 sheets that contains the β8–β9 loop (purple). The β8–β9 loop contributes important residues (Leu477and Ser478) to the active site/catalytic center and the substrate/product passage channel. An analysis of the predicted effect of the L451P on the structure of aromatase shows that it leads to a loss of a hydrogen bond (arrowed, right panel) in the β8–β9 loop and shift the position of the residue Cys437, the ligand to the heme ion, in the heme binding region. The distance between the Cys437 and the heme ion is 4.0 Å in the L451P mutant (right panel) as compare with 2.4 Å in the wild-type aromatase (left panel). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 4

Functional characterization of aromatase mutants. (A) Expression levels for the wild-type aromatase, Y81C and L451P mutants are similar in transfected CHO whole-cell lysates on Western blotting (B) .B. In-cell aromatase activity assay shows greatly reduced activity in the aromatase mutants. The Y81C mutant has 14.3% wild-type activity, whereas the L451P mutant has 3.1% wild-type activity. (C). Aromatase kinetic analysis of the wild-type aromatase, Y81C and L451P mutants. The upper panel shows the Michaelis–Menton model of the kinetic analysis; the lower panel shows the calculated maximum reaction rate (Vmax), Michaelis constant (Km) and catalytic efficiency (Vmax/Km). The catalytic efficiencies are reduced by 92.5% and 93.5%, respectively, in the Y81C and L451P mutants as compare with the wild-type aromatase.

References

1. Adzhubei IA, Schmidt S, Peshkin L, Ramensky VE, Gerasimova A, Bork P, et al. A method and server for predicting damaging missense mutations. Nat Methods. 2010;7:248–249. - PMC - PubMed
1. Alberti KG, Zimmet P, Shaw J, IDF Epidemiology Task Force Consensus Group The metabolic syndrome – a new worldwide definition. Lancet. 2005;366:1059–1062. - PubMed
1. Baykan EK, Erdogan M, Ozen S, Darcan S, Saygili LF. Aromatase deficiency, a rare syndrome: case report. J Clin Res Pediatr Endocrinol. 2013;5:129–132. - PMC - PubMed
1. Bilezikian JP, Morishima A, Bell J, Grumbach MM. Increased bone mass as a result of estrogen therapy in a man with aromatase deficiency. N Engl J Med. 1998;339:599–603. - PubMed
1. Bouchoucha N, Samara-Boustani D, Pandey AV, Bony-Trifunovic H, Hofer G, Aigrain Y, et al. Characterization of a novel CYP19A1 (aromatase) R192H mutation causing virilization of a 46,XX newborn, undervirilization of the 46,XY brother, but no virilization of the mother during pregnancies. Mol Cell Endocrinol. 2014;390:8–17. - PubMed

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 - PubMed (original) (raw)