Developmental Programming by Androgen Affects the Circadian Timing System in Female Mice1

Abstract

Circadian clocks play essential roles in the timing of events in the mammalian hypothalamo-pituitary-ovarian (HPO) axis. The molecular oscillator driving these rhythms has been localized to tissues of the HPO axis. It has been suggested that synchrony among these oscillators is a feature of normal reproductive function. The impact of fertility disorders on clock function and the role of the clock in the etiology of endocrine pathology remain unknown. Polycystic ovarian syndrome (PCOS) is a particularly devastating fertility disorder, affecting 5%-10% of women at childbearing age with features including a polycystic ovary, anovulation, and elevated serum androgen. Approximately 40% of these women have metabolic syndrome, marked by hyperinsulinemia, dyslipidemia, and insulin resistance. It has been suggested that developmental exposure to excess androgen contributes to the etiology of fertility disorders, including PCOS. To better define the role of the timing system in these disorders, we determined the effects of androgen-dependent developmental programming on clock gene expression in tissues of the metabolic and HPO axes. Female PERIOD2::luciferase (PER2::LUC) mice were exposed to androgen (dihydrotestosterone [DHT]) in utero (Days 16-18 of gestation) or for 9-10 wk (DHT pellet) beginning at weaning (pubertal androgen excess [PAE]). As expected, both groups of androgen-treated mice had disrupted estrous cycles. Analysis of PER2::LUC expression in tissue explants revealed that excess androgen produced circadian misalignment via tissue-dependent effects on phase distribution. In vitro treatment with DHT differentially affected the period of PER2::LUC expression in tissue explants and granulosa cells, indicating that androgen has direct and tissue-specific effects on clock gene expression that may account for the effects of developmental programming on the timing system.

Clock genes alterations and endocrine disorders

“…SiRNA-mediated knock-down of CLOCK expression significantly reduced prolactin-mRNA levels in GH3 cells, whereas knock-down of BMAL1 expression did not change them. 48 In particular, the E-box133 site binds a specific array of circadian F I G U R E 2 Diurnal secretion and sleep-wake regulation of selected endocrine factors. 46 However, animal models, such as the BMAL1-R91A mutant rat, exhibited loss of the circadian pattern of endogenous clock-controlled genes and prolactin-gene suggesting the presence of a local oscillator in the pituitary.…”

“…According to recent data, the timing of ovulation depends not only on the SCN-dependent rhythm of LH secretion, but also on the timing of ovarian sensitivity to gonadotropins set by the ovarian clock. 59 Both male and female mice knock-down for BMAL1 have been shown to suffer from infertility; 60 BMAL1 knock-down male mice, in particular, were deficient in the production of testosterone. 54 BMAL1 was also expressed in mouse Leydig cells and was linked to circadian oscillations.…”

“…47 It was further revealed that prolactin pulse activity depends on a specific promoter-binding region of E-box. 48 In particular, the E-box133 site binds a specific array of circadian F I G U R E 2 Diurnal secretion and sleep-wake regulation of selected endocrine factors. The melatonin and leptin reach their highest level at midnight and 01:00 AM, respectively.…”

“…Androgens also exhibit direct and tissue-specific effects on clock gene expression. 59 Both male and female mice knock-down for BMAL1 have been shown to suffer from infertility; 60 BMAL1 knock-down male mice, in particular, were deficient in the production of testosterone. 60 BMAL1 knock-down females mice exhibited delayed puberty, irregular oestrous cycles, and smaller ovaries and uterus although there were able to ovulate.…”

Decreased brain and muscle ARNT-like protein 1 expression mediated the contribution of hyperandrogenism to insulin resistance in polycystic ovary syndrome

“…An appropriately classical pharmacological treatment combined with melatonin is recommended for PCOS patients to restore their endocrine-metabolic and reproductive functions [11]. More importantly, hyperandrogenism, the primary PCOS inducer, disrupts circadian organization in female rats [12] and female mice [13]. Although morning circadian misalignment is suggested associated with worse insulin sensitivity and higher serum free testosterone levels in girls with PCOS and obesity [14], the association among hyperandrogenism, metabolic homeostasis, and circadian clock function at the cellular level remains poorly understood.…”