Bone metabolism in androgen receptor-deficient mice

Although the physiological significance of estrogen receptor function on skeletal tissues has been established, that of androgen receptor (AR) function has remained unclear. We show here that inactivation of AR in mice using a Cre-loxP system-mediated gene targeting technique caused bone loss in males, but not in females, which indicated that AR function is indispensable for male-type bone formation and remodeling.     

Premature ovarian failure

Secondary amenorrhoea with elevated gonadotrophins occurring under the age of 40 (premature ovarian failure (POF)), and at the age between 41 and 44 years (early menopause (EM)), respectively, affects 1-2% and 5% of women in the general population. Objective of this study was to evaluate the prevalence of familial cases of POF and EM and to assess the clinical and genetic characteristics of these patients. One hundred and sixty women with idiopathic secondary amenorrhoea before the age of 45 and serum follicle-stimulating hormone (FSH) levels greater than or equal to 40 IU/l were included in the study. Tests performed on patients included complete medical history, pedigree's analysis, clinical pelvic examination, gonadotrophins and thyroid assessment, chromosomal analysis. The 160 patients included in the study showed idiopathic POF (n=130) or EM (n=30). Following pedigree assessment, we were able to identify an incidence of familial cases of 28.5% in the POF group (n=37) and of 50% in the EM group (n=15). POF and EM condition were often present in the same family. There were no differences between POF and EM patients and between familial and sporadic cases regarding age at menarche, personal history, gynaecological history, weight, height and diet habits. There was a statistically significant difference between sporadic and familial cases in age at POF onset: 32.0+/-7.3 years (12-40) compared to 35. 0+/-5.8 (18-40), respectively (P<0.05). The POF and EM families identified showed two or more affected females and transmission through either maternal or paternal relatives; in four families both maternal and paternal transmission was observed. This study suggests that idiopathic POF and EM conditions, differing only in age of menopause onset, may represent a variable expression of the same genetic disease. The different age of menopause onset in these patients may be explained by genetic heterogeneity and/or by different environmental factors. Our results indicate a high rate of familial transmission of the condition. Pedigree's analysis suggests an autosomal or an X-linked dominant sex-limited pattern of inheritance for POF and EM.     

Premature ovarian failure

Premature ovarian failure (POF) is defined by at least four months of amenorrhea with elevated gonadotropins (usually above 40 UI/L) detected on two occasions a few weeks apart, in a woman before the age of 40. It occurs in 1 out of 10,000 in women below the age of 20, 1/1,000 below 30 and 1% in women before the age of 40. In 80% of POF cases, the etiology is unknown, except for Turner syndrome. The different etiologies identified are 1) iatrogenic following chemotherapy and/or radiotherapy, 2) autoimmune, 3) viral, 4) genetic (RFSH, FOXL2, FRAXA, BMP15, GDF9, GALT, 17 hydroxylase...). Management of these patients includes hormone replacement therapy in order to avoid an increase in cardiovascular risk and osteoporosis related to hypoestrogenism. Infertility is common, as only 3 to 10% of the patients will have natural conception. When fertility is desired, women with POF should be oriented towards oocyte donation centers. Research is currently performed in order to identify new genes involved in POF.     

Premature ovarian failure: present aspects

Premature ovarian failure occurs in approximately 1:1000 women before 30 years, 1:250 by 35 years and 1:100 by the age of 40. It is characterized by primary or secondary amenorrhea and cannot be considered as definitive because spontaneous conception may occur in 5 to 10% of cases. In 95% of cases, premature ovarian failure is sporadic. The known causes of premature ovarian failure include chromosomal defects, autoimmune diseases, exposure to radiation or chemotherapy, surgical procedures, and certain drugs. Frequently, however, the etiology is not clear and these cases are considered to be idiopathic. Premature ovarian failure is defined by gonadal failure and high serum follicle-stimulating hormone (FSH) levels. Clinical approach includes emotional support, hormonal therapy with estrogens and progesterone or progestogens, infertility treatment, and prevention of osteoporosis and potential cardiovascular risk.     

Premature ovarian failure in mice with oocytes lacking core 1-derived O-glycans and complex N-glycans

Premature ovarian failure (POF) affects up to 1.4% of women under the age of 40 yr and less than 30% of cases have a known cause. Here we describe a new mouse model of POF resulting from oocyte-specific ablation of core 1-derived (mucin) O-glycans and complex and hybrid N-glycans. Females carrying floxed alleles of both the C1galt1 (T-syn) and Mgat1 glycosyltransferase genes and a ZP3Cre transgene, generate oocytes lacking complex O- and N-glycans following oocyte-specific deletion at the primary follicle stage. We previously showed that few double-mutant females are fertile, and those produce only a single small litter. Here we show that ovarian function declined rapidly in double-mutant females with less than 1% ovulating at 11 wk of age after superovulation with exogenous gonadotropins. Ovary weight was significantly decreased in double-mutant females by 3 months of age, consistent with a decrease in the number of developing follicles. FSH levels in double-mutant females were elevated at 3 months of age, and testosterone and inhibin A were decreased, showing that the loss of complex N- and O-glycans from oocyte glycoproteins affected hypothalamic-pituitary-gonadal feedback loops. The absence of developing follicles, ovary dysfunction, reduced testosterone and inhibin A, and elevated FSH in double-mutant females lacking C1galt1 and Mgat1 in oocytes represents a new mouse model for the study of follicular POF.     

Premature ovarian aging in mice deficient for Gpr3

After becoming competent for resuming meiosis, fully developed mammalian oocytes are maintained arrested in prophase I until ovulation is triggered by the luteotropin surge. Meiotic pause has been shown to depend critically on maintenance of cAMP level in the oocyte and was recently attributed to the constitutive Gs (the heterotrimeric GTP-binding protein that activates adenylyl cyclase) signaling activity of the G protein-coupled receptor GPR3. Here we show that mice deficient for Gpr3 are unexpectedly fertile but display progressive reduction in litter size despite stable age-independent alteration of meiotic pause. Detailed analysis of the phenotype confirms premature resumption of meiosis, in vivo, in about one-third of antral follicles from Gpr3-/- females, independently of their age. In contrast, in aging mice, absence of GPR3 leads to severe reduction of fertility, which manifests by production of an increasing number of nondeveloping early embryos upon spontaneous ovulation and massive amounts of fragmented oocytes after superovulation. Severe worsening of the phenotype in older animals points to an additional role of GPR3 related to protection (or rescue) of oocytes from aging. Gpr3-defective mice may constitute a relevant model of premature ovarian failure due to early oocyte aging.     

Premature ovarian failure in women with juvenile idiopathic arthritis (JIA)

OBJECTIVE: To examine the effect of longstanding juvenile idiopathic arthritis (JIA) on menstrual irregularity and the incidence of premature ovarian failure in women. METHODS: Women with longstanding JIA who had abnormal or absent menstrual cycles had their circulating levels of gonadotrophins measured to check for the presence of ovarian failure. Disease demographics and subsets, function, age at onset of menstrual irregularity, previous medical intervention, concurrent diseases and history of pregnancy/delivery were documented. RESULTS: 177/187 (95%) of female adults with JIA who were identified and contacted, participated in the study. The average age at review was 35.4 years (19-78) with average disease duration of 28.7 years. 47.4% of all patients had clinically active arthritis. 44.6% of all patients had severe disability (HAQ score > 1.5). Six patients had premature ovarian failure unrelated to medication use, comprising 3.4% of the females in the study, compared to an expected incidence of 1% in the general population (p < 0.01). In addition, three (1.7%) of these had onset of symptoms before age 30, compared to an expected incidence of 0.1% in the general population (p < 0.01). The average maternal age at first delivery in women with JIA (27.2 years) was higher than the general population (23.5 years). CONCLUSION: Idiopathic premature ovarian failure was more commonly found in individuals with juvenile idiopathic arthritis. In addition a small number of patients had iatrogenic premature ovarian failure related to chlorambucil use.     

Ovarian steroidogenesis and serum androgen levels in patients with premature ovarian failure

Women with premature ovarian failure (POF) have been reported to have lower serum androgen levels compared with normal women. We reviewed the androgen profiles of 143 POF patients and found androgen levels above normal for postmenopausal women in 16% of these subjects. To determine the source of androgens in those women, we studied the available ovarian biopsy samples of 15 POF patients with increased androgen levels using immunohistochemistry, with a panel of antibodies directed against the main steroidogenic enzymes. Five of the ovarian biopsies exhibited abnormal follicles characterized by hypertrophied theca interna expressing steroidogenic enzymes involved in androgen synthesis. In five other biopsies, the steroidogenic activity was scarce and confined to a small number of ovarian stromal cells, sometimes situated in the proximity of follicular remnants. Finally, in five patients, we found no histological evidence of present or past follicular development beyond the quiescent follicular stage, and no steroidogenic cells were detected by immunohistochemistry. Our findings suggest that ovarian theca-derived cells are a source of androgens in some women with POF, whereas in others, as in most postmenopausal patients, the adrenals or the ovarian hilus cells may synthesize a significant quantity of androgens under LH stimulation.     

Bone metabolism in estrogen receptor-deficient mice

Mouse models have been established with a deficiency of ERalpha, ERbeta, or both to elucidate the function of estradiol in bone metabolism. This review focuses on data accumulated from studies of estrogen receptor-deficient mice.     

Reduction of arthritis severity in protease-activated receptor-deficient mice

OBJECTIVE: Protease-activated receptor 1 (PAR-1) is the cell surface receptor for thrombin. It is unclear whether thrombin contributes to inflammation other than by effects on coagulation. We investigated the proinflammatory participation of PAR-1 in antigen-induced arthritis (AIA). METHODS: Arthritis was induced by intraarticular injection of methylated bovine serum albumin (mBSA) in preimmunized PAR-1-deficient (PAR-1(-/-)) and wild-type (WT) mice. The disease was assessed after 7 days by histologic examination of knee joints after decalcification and Safranin O/toluidine blue staining. Serum levels of anti-mBSA IgG, interferon-gamma, and interleukin-4 (IL-4) were determined by enzyme-linked immunosorbent assay. T cell proliferation response was determined by measuring the incorporation of (3)H-thymidine. Cytokine messenger RNA (mRNA) expression was detected in synovial tissues and peritoneal cells by real-time polymerase chain reaction. RESULTS: Arthritis severity was significantly reduced in PAR-1(-/-) mice compared with WT mice (P = 0.017). Analysis of individual aspects of joint histology revealed significant reductions in synovial exudates (P < 0.001), cartilage degradation (P < 0.01), and bone damage (P = 0.05) in PAR-1(-/-) mice. Synovial IL-1, IL-6, and matrix metalloproteinase 13 (MMP-13) mRNA was significantly reduced in PAR-1(-/-) mice. The titers of antigen-specific serum anti-mBSA total IgG, IgG1, and IgG2a were significantly reduced, and serum IL-4 was significantly increased in arthritic PAR-1(-/-) mice. In contrast, no difference was observed in antigen-induced T cell proliferation between PAR-1(-/-) and WT mice. In vitro, thrombin-induced (but not lipopolysaccharide-induced) IL-1, IL-6, and MMP-13 mRNA expression was significantly impaired in PAR-1(-/-) mice compared with WT controls. CONCLUSION: These data demonstrate the requirement of PAR-1 for the expression of AIA, the development of an antigen-specific Ig response, thrombin-induced macrophage cytokine and MMP expression, and the inhibitory effect of PAR-1 on serum IL-4. We conclude that PAR-1 plays a significant role in this model of arthritis.     

Premature ovarian failure and FMR1 gene mutations: An update

Screening for fragile X premutations is recommended for the routine work-up for any woman presenting with premature ovarian failure (POF). The reason for this is that women with POF have an approximate 5% chance of conceiving and this possibility may be increased further in the FRAXA premutation subgroup. Women need to be informed if they are at risk of having a child with fragile X syndrome. In addition, the identification of a family in which the fragile X repeat site is expanded can lead to the identification of other female family members at risk of transmitting fragile X syndrome. The identification of an index case should therefore trigger genetic counseling throughout the pedigree according to the wishes of the family.     

Body weight and fat deposition in prolactin receptor-deficient mice

To explore the roles of the lactogens in adipose tissue development and function, we measured body weight, abdominal fat content, and plasma leptin concentrations in a unique model of lactogen resistance: the PRL receptor (PRLR)-deficient mouse. The absence of PRLRs in knockout mice was accompanied by a small (5-12%), but progressive, reduction in body weight after 16 weeks of age. Females were affected to a greater degree than males. The reduction in weight in female PRLR-deficient mice (age 8-9 months) was associated with a 49% reduction in total abdominal fat mass and a 29% reduction in fat mass expressed as a percentage of body weight. Lesser reductions were noted in male mice. Plasma leptin concentrations were reduced in females but not in males. That the reductions in abdominal fat may reflect in part the absence of lactogen action in the adipocyte is suggested by the demonstration of PRLR messenger RNA in normal mouse white adipose tissue. Nevertheless, steady state levels of PRLR messenger RNA in mature adipocytes are very low, suggesting that the effects of lactogens might be mediated by other hormones or cellular growth factors. Our observations suggest roles for the lactogens in adipose tissue growth and metabolism in pregnancy and postnatal life.