Neural Androgen Receptors Modulate Gene Expression and Social Recognition But Not Social Investigation.

The role of sex and androgen receptors (ARs) for social preference and social memory is rather unknown. In this study of mice we compared males, females and males lacking ARs specifically in the nervous system, AR(NesDel), with respect to social preference, assessed with the three-chambered apparatus test, and social recognition, assessed with the social discrimination procedure. In the social discrimination test we also evaluated the tentative importance of the sex of the stimulus animal. Novel object recognition and olfaction were investigated to complement the results from the social tests. Gene expression analysis was performed to reveal molecules involved in the effects of sex and androgens on social behaviors. All three test groups showed social preference in the three-chambered apparatus test. In both social tests an AR-independent sexual dimorphism was seen in the persistence of social investigation of female conspecifics, whereas the social interest toward male stimuli mice was similar in all groups. Male and female controls recognized conspecifics independent of their sex, whereas AR(NesDel) males recognized female but not male stimuli mice. Moreover, the non-social behaviors were not affected by AR deficiency. The gene expression analyses of hypothalamus and amygdala indicated that Oxtr, Cd38, Esr1, Cyp19a1, Ucn3, Crh, and Gtf2i were differentially expressed between the three groups. In conclusion, our results suggest that ARs are required for recognition of male but not female conspecifics, while being dispensable for social investigation toward both sexes. In addition, the AR seems to regulate genes related to oxytocin, estrogen and William's syndrome.

Role of androgen and estrogen receptors for the action of dehydroepiandrosterone (DHEA).

Dehydroepiandrosterone (DHEA) is an abundant steroid hormone, and its mechanism of action is yet to be determined. The aim of this study was to elucidate the importance of androgen receptors (ARs) and estrogen receptors (ERs) for DHEA function. Orchidectomized C57BL/6 mice were treated with DHEA, DHT, 17ß-estradiol-3-benzoate (E2), or vehicle. Orchidectomized AR-deficient (ARKO) mice and wild-type (WT) littermates were treated with DHEA or vehicle for 2.5 weeks. At termination, bone mineral density (BMD) was evaluated, thymus and seminal vesicles were weighted, and submandibular glands (SMGs) were histologically examined. To evaluate the in vivo ER activation of the classical estrogen signaling pathway, estrogen response element reporter mice were treated with DHEA, DHT, E2, or vehicle, and a reporter gene was investigated in different sex steroid-sensitive organs after 24 hours. DHEA treatment increased trabecular BMD and thymic atrophy in both WT and ARKO mice. In WT mice, DHEA induced enlargement of glands in the SMGs, whereas this effect was absent in ARKO mice. Furthermore, DHEA was able to induce activation of classical estrogen signaling in bone, thymus, and seminal vesicles but not in the SMGs. In summary, the DHEA effects on trabecular BMD and thymus do not require signaling via AR and DHEA can activate the classical estrogen signaling in these organs. In contrast, DHEA induction of gland size in the SMGs is dependent on AR and does not involve classical estrogen signaling. Thus, both ERs and ARs are involved in mediating the effects of DHEA in an organ-dependent manner.

Estrogen receptor-α expression in neuronal cells affects bone mass.

It has generally been assumed that bone mass is controlled by endocrine mechanisms and the local bone environment. Recent findings demonstrate that central pathways are involved in the regulation of bone mass. Estrogen is involved in the regulation of bone homeostasis and the CNS is also a target for estrogen actions. The aim of this study was to investigate in vivo the role of central estrogen receptor-α (ERα) expression for bone mass. Nestin-Cre mice were crossed with ERα(flox) mice to generate mice lacking ERα expression specifically in nervous tissue (nestin-ERα(-/-)). Bone mineral density was increased in both the trabecular and cortical bone compartments in nestin-ERα(-/-) mice compared with controls. Femoral bone strength was increased in nestin-ERα(-/-) mice, as demonstrated by increased stiffness and maximal load of failure. The high bone mass phenotype in nestin-ERα(-/-) mice was mainly caused by increased bone formation. Serum leptin levels were elevated as a result of increased leptin expression in white adipose tissue (WAT) and slightly increased amount of WAT in nestin-ERα(-/-) mice. Leptin receptor mRNA levels were reduced in the hypothalamus but not in bone. In conclusion, inactivation of central ERα signaling results in increased bone mass, demonstrating that the balance between peripheral stimulatory and central inhibitory ERα actions is important for the regulation of bone mass. We propose that the increased bone mass in nestin-ERα(-/-) mice is mediated via decreased central leptin sensitivity and thereby increased secretion of leptin from WAT, which, in turn, results in increased peripheral leptin-induced bone formation.