Testosterone prevents protein loss via the hepatic urea cycle in human.
Eur J Endocrinol
; 176(4): 489-496, 2017 Apr.
Article
em En
| MEDLINE
| ID: mdl-28122810
ABSTRACT
CONTEXT The urea cycle is a rate-limiting step for amino acid nitrogen elimination. The rate of urea synthesis is a true indicator of whole-body protein catabolism. Testosterone reduces protein and nitrogen loss. The effect of testosterone on hepatic urea synthesis in humans has not been studied. OBJECTIVE:
To determine whether testosterone reduces hepatic urea production.DESIGN:
An open-label study. PATIENTS AND INTERVENTION Eight hypogonadal men were studied at baseline, and after two weeks of transdermal testosterone replacement (Testogel, 100 mg/day). MAIN OUTCOMESMEASURES:
The rate of hepatic urea synthesis was measured by the urea turnover technique using stable isotope methodology, with 15N2-urea as tracer. Whole-body leucine turnover was measured, from which leucine rate of appearance (LRa), an index of protein breakdown and leucine oxidation (Lox), a measure of irreversible protein loss, were calculated.RESULTS:
Testosterone administration significantly reduced the rate of hepatic urea production (from 544.4 ± 71.8 to 431.7 ± 68.3 µmol/min; P < 0.01), which was paralleled by a significant reduction in serum urea concentration. Testosterone treatment significantly reduced net protein loss, as measured by percent Lox/LRa, by 19.3 ± 5.8% (P < 0.05). There was a positive association between Lox and hepatic urea production at baseline (r2 = 0.60, P < 0.05) and after testosterone administration (r2 = 0.59, P < 0.05).CONCLUSION:
Testosterone replacement reduces protein loss and hepatic urea synthesis. We conclude that testosterone regulates whole-body protein metabolism by suppressing the urea cycle.
Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Testosterona
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Ureia
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Terapia de Reposição Hormonal
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Hipogonadismo
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Fígado
Limite:
Adult
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Humans
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Male
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Middle aged
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article