The use of aromatase inhibitors in boys with short stature: what to know before prescribing?
ARCHIVES OF ENDOCRINOLOGY METABOLISM
Authors: Linardi, Alessandra; Damiani, Durval; Longui, Carlos A.
Aromatase is a cytochrome P450 enzyme (CYP19A1 isoform) able to catalyze the conversion of androgens to estrogens. The aromatase gene mutations highlighted the action of estrogen as one of the main regulators of bone maturation and closure of bone plate. The use of aromatase inhibitors (AI) in boys with short stature has showed its capability to improve the predicted final height. Anastrozole (ANZ) and letrozole (LTZ) are nonsteroidal inhibitors able to bind reversibly to the heme group of cytochrome P450. In this review, we describe the pharmacokinetic profile of both drugs, discussing possible drug interactions between ANZ and LTZ with other drugs. AIs are triazolic compounds that can induce or suppress cytochrome P450 enzymes, interfering with metabolism of other compounds. Hydroxilation, N-dealkylation and glucoronidation are involved in the metabolism of AIs. Drug interactions can occur with azole antifungals, such as ketoconazole, by inhibiting CYP3A4 and by reducing the clearance of AIs. Antiepileptic drugs (lamotrigine, phenobarbital, and phenytoin) also inhibit aromatase. Concomitant use of phenobarbital or valproate has a synergistic effect on aromatase inhibition. Therefore, it is important to understand the pharmacokinetics of AIs, recognizing and avoiding possible drug interactions and offering a safer prescription profile of this class of aromatase inhibitors.
Lipotoxicity Impairs Granulosa Cell Function Through Activated Endoplasmic Reticulum Stress Pathway
Authors: Hua, Dongxu; Zhou, Yu; Lu, Yingfei; Zhao, Chengcheng; Qiu, Wei; Chen, Jianquan; Ju, Rong
Obesity is closely related to reproductive disorders, which may eventually lead to infertility in both males and females. Ovarian granulosa cells play a critical role during the maintenance of oocyte development through the generation of sex steroids (mainly estradiol and progesterone) and different kinds of growth factors. However, the molecular mechanism of obesity-induced granulosa cell dysfunction remains poorly investigated. In our current study, we observed that high-fat diet feeding significantly increased the level of glucose-regulated protein 78 kDa (GRP78) protein expression in mouse granulosa cells; testosterone-induced estradiol generation was impaired accordingly. To further evaluate the precise mechanism of lipotoxicity-induced granulosa cell dysfunction, mouse primary granulosa cells were treated with palmitate, and the expression levels of ER stress markers were evaluated by real-time PCR and western blot. Lipotoxicity significantly increased ER stress but impaired the mRNA expression of granulosa cell function-related makers, including androgen receptor (Ar), cytochrome P450 family 19 subfamily A member 1 (Cyp19a1), hydroxysteroid 17-beta dehydrogenase 1 (Hsd17b1), and insulin receptor substrate 1 (Irs1). Impaired testosterone-induced estradiol generation was also observed in cultured mouse granulosa cells after palmitate treatment. Insulin augmented testosterone induced estradiol generation through activation of the AKT pathway. However, palmitate treatment abolished insulin-promoted aromatase expression and estradiol generation by the stimulation of ER stress. Overexpression of IRS1 significantly ameliorated palmitate- or tunicamycin-induced impairment of aromatase expression and estradiol generation. Taken together, our current study demonstrated that lipotoxicity impaired insulin-stimulated estradiol generation through activated ER stress and inhibited IRS1 pathway.