Reproductive Profile of Neuronal Androgen Receptor Knockout Female Mice With a Low Dose of DHT

Hyperandrogenism and polycystic ovarian syndrome result from the imbalance or increase of androgen levels in females. Androgen receptor (AR) mediates the effects of androgens, and this study examines whether neuronal AR plays a role in reproduction under normal and increased androgen conditions in female mice. The neuron-specific AR knockout (KO) mouse (SynARKO) was generated from a female mouse (synapsin promoter driven Cre) and a male mouse (Ar fl/y). Puberty onset and the levels of reproductive hormones such as LH, FSH, testosterone, and estradiol were comparable between the control and the SynARKO mice. There were no differences in cyclicity and fertility between the control and SynARKO mice, with similar impairment in both groups on DHT treatment. Neuronal AR KO, as in this SynARKO mouse model, did not alleviate the infertility associated with DHT treatment. These studies suggest that neuronal AR KO neither altered reproductive function under physiological androgen levels, nor restored fertility under hyperandrogenic conditions.

Neuronal AR Regulates Glucose Homeostasis and Energy Expenditure in Lean Female Mice With Androgen Excess

Hyperandrogenemia and polycystic ovary syndrome are a result of the imbalance of androgen levels in females. Androgen receptor (Ar) mediates the effect of androgen, and this study examines how neuronal Ar in the central nervous system mediates metabolism under normal and increased androgen conditions in female mice. The neuron-specific ARKO mouse (SynARKO) was created from female (Ar fl/wt; synapsin promoter driven Cre) and male (Ar fl/y) mice. A glucose tolerance test revealed impaired glucose tolerance that was partially alleviated in the SynARKO-dihydrotestosterone (DHT) mice compared with Con-DHT mice after 4 months of DHT treatment. Heat production and food intake was higher in Con-DHT mice than in Con-veh mice; these effects were not altered between SynARKO-veh and SynARKO-DHT mice, indicating that excess androgens may partially alter calorie intake and energy expenditure in females via the neuronal Ar. The pAkt/Akt activity was higher in the hypothalamus in Con-DHT mice than in Con-veh mice, and this effect was attenuated in SynARKO-DHT mice. Western blot studies show that markers of inflammation and microglia activation, such as NF-kB p-65 and IBA1, increased in the hypothalamus of Con-DHT mice compared with Con-veh. These studies suggest that neuronal Ar mediates the metabolic impacts of androgen excess in females.

Lower FSH With Normal Fertility in Male Mice Lacking Gonadotroph Kisspeptin Receptor

The kisspeptin receptor, crucial for hypothalamic control of puberty and reproduction, is also present in the pituitary gland. Its role in the pituitary gland is not defined. Kisspeptin signaling via the Kiss1r could potentially regulate reproductive function at the level of pituitary gonadotrope. Using Cre/Lox technology, we deleted the Kiss1r gene in pituitary gonadotropes (PKiRKO). PKiRKO males have normal genital development (anogenital distance WT: 19.1 ± 0.4 vs. PKiRKO: 18.5 ± 0.4 mm), puberty onset, testes cell structure on gross histology, normal testes size, and fertility. PKiRKO males showed significantly decreased serum FSH levels compared to WT males (5.6 ± 1.9 vs. 10.2 ± 1.8 ng/ml) with comparable LH (1.1 ± 0.2 vs. 1.8 ± 0.4 ng/ml) and testosterone levels (351.8 ± 213.0 vs. 342.2 ± 183.0 ng/dl). PKiRKO females have normal puberty onset, cyclicity, LH and FSH levels and fertility. Overall, these findings indicate that absence of pituitary Kiss1r reduces FSH levels in male mice without affecting testis function. PKiRKO mice have normal reproductive function in both males and females.

Comparison of Reproductive Function Between Normal and Hyperandrogenemia Conditions in Female Mice With Deletion of Hepatic Androgen Receptor

Obesity, altered glucose homeostasis, hyperinsulinism, and reproductive dysfunction develops in female humans and mammals with hyperandrogenism. We previously reported that low dose dihydrotestosterone (DHT) administration results in metabolic and reproductive dysfunction in the absence of obesity in female mice, and conditional knock-out of the androgen receptor (Ar) in the liver (LivARKO) protects female mice from DHT-induced glucose intolerance and hyperinsulinemia. Since altered metabolic function will regulate reproduction, and liver plays a pivotal role in the reversible regulation of reproductive function, we sought to determine the reproductive phenotype of LivARKO mice under normal and hyperandrogenemic conditions. Using Cre/Lox technology, we deleted the Ar in the liver, and we observed LivARKO female mice have normal puberty timing, cyclicity and reproductive function. After DHT treatment, like control mice, LivARKO experience altered estrous cycling, reduced numbers of corpus lutea, and infertility. Liver Ar is not involved in hyperandrogenemia-induced reproductive dysfunction. The reproductive dysfunction in the DHT-treated LivARKO lean females with normal glucose homeostasis indicates that androgen-induced reproductive dysfunction is independent from metabolic dysfunction.

An Improved Time- and Labor- Efficient Protocol for Mouse Primary Hepatocyte Isolation

Primary hepatocytes are used extensively in liver in vitro research, especially in glucose metabolism studies. A base technique has been adapted based on different needs, like time, labor, cost, and primary hepatocyte usage, resulting in various primary hepatocyte isolation protocols. However, the numerous steps and time-consuming reagent preparations in primary hepatocyte isolation are major drawbacks for efficiency. After comparing different protocols for their pros and cons, the advantages of each were combined, and a rapid and efficient primary hepatocyte isolation protocol was formulated. Within only ~35 min, this protocol could yield as much, if not more, healthy primary hepatocytes as other protocols. Further, glucose metabolism experiments performed using the isolated primary hepatocytes validated the usefulness of this protocol in in vitro liver metabolism studies. We also extensively reviewed and analyzed the significance and purpose of each step in this study so that future researchers can further optimize this protocol based on needs.

Androgen-induced insulin resistance is ameliorated by deletion of hepatic androgen receptor in females

Androgen excess is one of the most common endocrine disorders of reproductive-aged women, affecting up to 20% of this population. Women with elevated androgens often exhibit hyperinsulinemia and insulin resistance. The mechanisms of how elevated androgens affect metabolic function are not clear. Hyperandrogenemia in a dihydrotestosterone (DHT)-treated female mouse model induces whole body insulin resistance possibly through activation of the hepatic androgen receptor (AR). We investigated the role of hepatocyte AR in hyperandrogenemia-induced metabolic dysfunction by using several approaches to delete hepatic AR via animal-, cell-, and clinical-based methodologies. We conditionally disrupted hepatocyte AR in female mice developmentally (LivARKO) or acutely by tail vein injection of an adeno-associated virus with a liver-specific promoter for Cre expression in AR^fl/fl mice (adLivARKO). We observed normal metabolic function in littermate female Control (AR^fl/fl ) and LivARKO (AR^fl/fl ; Cre^+/- ) mice. Following chronic DHT treatment, female Control mice treated with DHT (Con-DHT) developed impaired glucose tolerance, pyruvate tolerance, and insulin tolerance, not observed in LivARKO mice treated with DHT (LivARKO-DHT). Furthermore, during an euglycemic hyperinsulinemic clamp, the glucose infusion rate was improved in LivARKO-DHT mice compared to Con-DHT mice. Liver from LivARKO, and primary hepatocytes derived from LivARKO, and adLivARKO mice were protected from DHT-induced insulin resistance and increased gluconeogenesis. These data support a paradigm in which elevated androgens in females disrupt metabolic function via hepatic AR and insulin sensitivity was restored by deletion of hepatic AR.

Androgen Receptor in the Ovary Theca Cells Plays a Critical Role in Androgen-Induced Reproductive Dysfunction

Androgen and its receptor (AR) play a critical role in reproductive function under both physiological and pathophysiological conditions. Female AR global knockout mice are subfertile due to both neuroendocrine and ovarian defects. Female offspring from prenatally androgenized heterozygous AR pregnant mice showed rescued estrous cyclicity and fertility. Ar is expressed in granulosa cells, theca interstitial cells, and oocytes in the ovary. We created mice with theca-specific deletion of Ar (ThARKO) by crossing Cyp17-iCre mice that express Cre recombinase under cytochrome P450 17A1 (Cyp17) promoter with Arfl/fl mice. ThARKO mice exhibited no significant differences in pubertal onset or fertility compared with control littermates, and neither estrogen or testosterone levels were different between these groups. Therefore, Ar expression in theca cells likely does not influence fertility nor androgen levels in female mice. We then tested the role of AR in theca cells under hyperandrogenemic condition. After treatment with a pathophysiological level of dihydrotestosterone (DHT), control mice (control-DHT) showed acyclicity and infertility. However, estrous cycles and fertility were altered to a significantly less degree in ThARKO-DHT mice than in control-DHT mice. Messenger RNA (mRNA) levels of Lhcgr (luteinizing hormone receptor) and Timp1 (tissue inhibitor of metalloproteinase 1, and inhibitor of matrix metalloproteinase) were significantly lower in control-DHT ovary compared with control-no DHT ovaries, whereas mRNA levels of Fshr (follicle-stimulating hormone receptor) were significantly higher. Timp1 gene expression was comparable in the ThARKO-DHT and the control-no DHT ovary. We speculate that the preserved level of Timp1 in ThARKO-DHT mice contributes to retained reproductive function.

Weight Gain in Infancy and Overweight or Obesity in Childhood across the Gestational Spectrum: a Prospective Birth Cohort Study

This study aimed to investigate the optimal degree of weight gain across the gestational spectrum in 1971 children enrolled at birth and followed up to age 7 years. Weight gain in infancy was categorized into four groups based on weight gain z-scores: slow (<-0.67), on track (-0.67 to 0.67), rapid (0.67 to 1.28), and extremely rapid (>1.28). Underweight and overweight or obesity (OWO) were defined as a body mass index ≤5(th) and ≥85(th) percentile, respectively, for age and gender. In our population, OWO was far more common than underweight (39.7% vs. 3.6%). Weight gain tracked strongly from age 4 to 24 months, and was positively associated with OWO and an unfavorable pattern of metabolic biomarkers, although the degree of weight gain for the risk was different across gestational categories. Extremely rapid weight gain led to a particularly high risk of OWO among children born early term and late preterm: odds ratio: 3.3 (95% confidence interval: 1.9 to 5.5) and 3.7 (1.8 to 7.5), respectively, as compared to those with on track weight gain. Our findings suggest that monitoring and ensuring optimal weight gain across the entire gestational spectrum beginning from birth represents a first step towards primary prevention of childhood obesity.

The regulation of reproductive neuroendocrine function by insulin and insulin-like growth factor-1 (IGF-1)

The mammalian reproductive hormone axis regulates gonadal steroid hormone levels and gonadal function essential for reproduction. The neuroendocrine control of the axis integrates signals from a wide array of inputs. The regulatory pathways important for mediating these inputs have been the subject of numerous studies. One class of proteins that have been shown to mediate metabolic and growth signals to the CNS includes Insulin and IGF-1. These proteins are structurally related and can exert endocrine and growth factor like action via related receptor tyrosine kinases. The role that insulin and IGF-1 play in controlling the hypothalamus and pituitary and their role in regulating puberty and nutritional control of reproduction has been studied extensively. This review summarizes the in vitro and in vivo models that have been used to study these neuroendocrine structures and the influence of these growth factors on neuroendocrine control of reproduction.

Obesity-induced infertility and hyperandrogenism are corrected by deletion of the insulin receptor in the ovarian theca cell

Women with polycystic ovary syndrome (PCOS) exhibit elevated androgen levels, oligoanovulation, infertility, and insulin resistance in metabolic tissues. The aims of these studies were to determine the role of insulin signaling in the development and function of ovarian theca cells and the pathophysiologic effects of hyperinsulinism on ovarian function in obesity. We disrupted the insulin receptor (IR) gene specifically in the theca-interstitial (TI) cells of the ovaries (Cyp17IRKO). No changes in reproductive development or function were observed in lean Cyp17IRKO female mice, suggesting that insulin signaling in TI cell is not essential for reproduction. However, when females were fed a high-fat diet, diet-induced obesity (DIO) wild-type (DIO-WT) mice were infertile and experienced increased circulating testosterone levels, whereas DIO-Cyp17IRKO mice exhibited improved fertility and testosterone levels comparable to those found in lean mice. The levels of phosphorylated IRS1 and CYP17 protein were higher in the ovary of DIO-WT compared with DIO-Cyp17IRKO or lean mice. Ex vivo studies using a whole ovary culture model demonstrated that insulin acts independently or additively with human chorionic gonadotropin to enhance androstenedione secretion. These studies reveal the causal pathway linking hyperinsulinism with ovarian hyperandrogenism and the infertility of obesity.

Preterm birth and random plasma insulin levels at birth and in early childhood

IMPORTANCE

Although previous reports have linked preterm birth with insulin resistance in children and adults, it is not known whether altered insulin homeostasis is detectable at birth and tracks from birth through childhood.

OBJECTIVE

To investigate whether preterm birth is associated with elevated plasma insulin levels at birth and whether this association persists into early childhood.

DESIGN, SETTING, AND PARTICIPANTS

A prospective birth cohort of 1358 children recruited at birth from 1998 to 2010 and followed-up with prospectively from 2005 to 2012 at the Boston Medical Center in Massachusetts.

MAIN OUTCOMES AND MEASURES

Random plasma insulin levels were measured at 2 time points: at birth (cord blood) and in early childhood (venous blood). The median age was 1.4 years (interquartile range [IQR], 0.8-3.3) among 4 gestational age groups: full term (≥39 wk), early term (37-38 wk), late preterm (34-36 wk), and early preterm (<34 wk).

RESULTS

The geometric mean of insulin levels at birth were 9.2 µIU/mL (95% CI, 8.4-10.0) for full term; 10.3 µIU/mL (95% CI, 9.3-11.5) for early term; 13.2 µIU/mL (95% CI, 11.8-14.8) for late preterm; and 18.9 µIU/mL (95% CI, 16.6-21.4) for early preterm. In early childhood, these levels were 11.2 µIU/mL (95% CI, 10.3-12.0) for full term; 12.4 µIU/mL (95% CI, 11.3-13.6) for early term; 13.3 µIU/mL (95% CI, 11.9-14.8) for late preterm; and 14.6 µIU/mL (95% CI, 12.6-16.9) for early preterm. Insulin levels at birth were higher by 1.13-fold (95% CI, 0.97-1.28) for early term, 1.45-fold (95% CI, 1.25-1.65) for late preterm, and 2.05-fold (95% CI, 1.69-2.42) for early preterm than for those born full term. In early childhood, random plasma insulin levels were 1.12-fold (95% CI, 0.99-1.25) higher for early term, 1.19-fold (95% CI, 1.02-1.35) for late preterm, and 1.31-fold (95% CI, 1.10-1.52) for early preterm than those born full term. The association was attenuated after adjustment for postnatal weight gain and was not significant after adjustment for insulin levels at birth. Infants ranked in the top insulin tertile at birth were more likely to remain in the top tertile (41.2%) compared with children ranked in the lowest tertile (28.6%) in early childhood.

CONCLUSIONS AND RELEVANCE

There was an inverse association between gestational age and elevated plasma insulin levels at birth and in early childhood. The implications for future development of insulin resistance and type 2 diabetes warrant further investigation.

Reproductive tissues maintain insulin sensitivity in diet-induced obesity

Reproductive dysfunction is associated with obesity. We previously showed that female mice with diet-induced obesity (DIO) exhibit infertility and thus serve as a model of human polycystic ovary syndrome (PCOS). We postulated that differential insulin signaling of tissues leads to reproductive dysfunction; therefore, a comparison of insulin signaling in reproductive tissues and energy storage tissues was performed. Pituitary-specific insulin receptor knockout mice were used as controls. High-fat diet-induced stress, which leads to insulin resistance, was also investigated by assaying macrophage infiltration and phosphorylated Jun NH(2)-terminal kinase (pJNK) signaling. In lean mice, reproductive tissues exhibited reduced sensitivity to insulin compared with peripheral metabolic tissues. However, in obese mice, where metabolic tissues exhibited insulin resistance, the pituitary and ovary maintained insulin sensitivity. Pituitaries responded to insulin through insulin receptor substrate (IRS)2 but not IRS1, whereas in the ovary, both IRS1 and IRS2 were activated by insulin. Macrophage infiltration and pJNK signaling were not increased in the pituitary or ovary of lean mice relative to DIO mice. The lack of inflammation and cytokine signaling in the pituitary and ovary in DIO mice compared with lean mice may be one of the reasons that these tissues remained insulin sensitive. Retained sensitivity of the pituitary and ovary to insulin may contribute to the pathophysiology of PCOS.

The exposure of fetuses and children to endocrine disrupting chemicals: a European Society for Paediatric Endocrinology (ESPE) and Pediatric Endocrine Society (PES) call to action statement

OBJECTIVE

During recent years, evidence has accumulated that both wildlife species and humans are exposed to ubiquitous endocrine-disrupting chemicals. Some are persistent in our bodies; others are nonpersistent but are produced in large quantities. Hitherto, the bulk of research in this area has been carried out by basic and experimental scientists and wildlife researchers. Relatively few clinical scientists have been engaged in research on this topic to date. The aim of this statement is to have pediatric endocrinologists consider the issue of endocrine disrupters in their clinical work and research.

PARTICIPANTS

Six pediatric endocrinologists who belonged to working groups on endocrine disrupters endorsed by the European Society for Paediatric Endocrinology (ESPE) and the Pediatric Endocrine Society (PES) participated, including three members from each society. Meetings were limited to the members of the working groups. No funding was associated with the work.

EVIDENCE

Important data sources were publications from the World Health Organization, the European Science Foundation, and The Endocrine Society. Several of the participants have made long-standing contributions to the field of endocrine disruption. No unpublished work was considered.

CONSENSUS PROCESS

The statement was written by the committee members together, using e-mail and phone. A draft was submitted to the Boards of the ESPE and PES. After some changes, the draft was accepted by both Boards.

CONCLUSIONS

Pediatric endocrinologists are urged to be alert to the possible significance of endocrine-disrupting chemicals when assessing both clinical problems and research data where etiologies of endocrine symptoms or diseases are unknown.

Temporal and spatial regulation of CRE recombinase expression in gonadotrophin-releasing hormone neurones in the mouse

Gonadotrophin-releasing hormone (GnRH) neurones located within the brain are the final neuroendocrine output regulating the reproductive hormone axis. Their small number and scattered distribution in the hypothalamus make them particularly difficult to study in vivo. The Cre/loxP system is a valuable tool to delete genes in specific cells and tissues. We report the production of two mouse lines that express the CRE bacteriophage recombinase in a GnRH-specific manner. The first line, the GnRH-CRE mouse, contains a transgene in which CRE is under the control of the murine GnRH promoter and targets CRE expression specifically to GnRH neurones in the hypothalamus. The second line, the GnRH-CRETeR mouse, uses the same murine GnRH promoter to target CRE expression to GnRH neurones, but is modified to be constitutively repressed by a tetracycline repressor (TetR) expressed from a downstream tetracycline repressor gene engineered within the transgene. GnRH neurone-specific CRE expression can therefore be induced by treatment with doxycycline which relieves repression by TetR. These GnRH-CRE and GnRH-CRETeR mice can be used to study the function of genes expressed specifically in GnRH neurones. The GnRH-CRETeR mouse can be used to study genes that may have distinct roles in reproductive physiology during the various developmental stages.

Proton ATPases in bacteria: comparison to Escherichia coli F1F0 as the prototype

The F1F0 ATP synthase complex of Escherichia coli functions reversibly in coupling proton translocation to ATP synthesis or hydrolysis. The structural organization and subunit composition corresponds to that seen in many other bacteria, i.e. a membrane extrinsic F1 sector with five subunits in an alpha 3 beta 3 gamma delta epsilon stoichiometry, and a membrane-traversing F0 sector with three subunits in an a1b2c12 stoichiometry. The structure of much of the F1 sector is known from a X-ray diffraction model. During function, The gamma subunit is known to rotate within a hexameric ring of alternating alpha and beta subunits to promote sequential substrate binding and product release from catalytic sites on the three beta subunits. Proton transport through F0 must be coupled to this rotation. Subunit c folds in the membrane as a hairpin to two alpha helices to generate the proton-binding site in F0. Its structure was determined by NMR, and the structure of the c oligomer was deduced by cross-linking experiments and molecular mechanics calculations. The implications of the oligomeric structure of subunit c will be considered and related to the H+/ATP pumping ratio, P/O ratios and the cation-binding site in other types of F0. The possible limits of the structure in changing the ion-binding specificity, stoichiometry and routes of proton entrance/exit to the binding site will be considered.