Androgens and Alzheimer's disease

DHT inhibits REDOX damage and neuroinflammation to reduce PND occurrence in aged mice via mmu_circ_0001442/miR-125a-3p/NUFIP2 axis

BACKGROUND

Perioperative neurocognitive disorder (PND) is the main cause of poor postoperative recovery in elderly patients with age-related reductions in androgen levels. However, the underlying mechanisms have not been completely elucidated.

METHODS

A mouse model of PND was constructed using abdominal surgery. Dihydrotestosterone (DHT), as the primary androgen, can improve the cognitive function of mice with PNDs by reducing REDOX damage. To clarify the role of circular RNA (circRNA) in DHT in improving cognitive function in mice with PND, circRNA sequencing was performed to analyze the expression of circRNA in the hippocampus of mice.

RESULTS

We confirmed that mmu_circ_0001442 is the primary circRNA responsive to DHT stimulation in mice with PND. The mmu_circ_0001442/miR-125a-3p/NUFIP2 axis was predicted and constructed according to the analysis of databases, including pita, miRanda, TargetScan, miRDB, micro-CDS, PolymiRTS, and TarBase v.8. Subsequently, the axis was verified by qPCR and double-luciferase reporter gene assays. In vitro, we found that DHT rarely had an effect on the growth of BV2 cells using the CCK-8 assay, but it attenuated the cytotoxic effect of lipopolysaccharide (LPS) on BV2 cells. In addition, we found that LPS stimulation promoted the release of proinflammatory cytokines, including IL-6 and TNF-α, in BV2 cells, whereas mmu_circ_0001442 knockdown and NUFIP2 knockdown partially abrogated this effect.

CONCLUSIONS

Taken together, DHT inhibited REDOX damage and neuroinflammation in the hippocampus to alleviate cognitive disorders in mice with PNDs via activation of the mmu_circ_0001442/miR-125a-3p/NUFIP2 axis. This study provides a novel rationale for developing DHT as a potential therapeutic agent for PND prevention.

Synthesis of 17β-hydroxysteroid dehydrogenase type 10 steroidal inhibitors: Selectivity, metabolic stability and enhanced potency

17beta-Hydroxysteroid dehydrogenase type 10 (17β-HSD10) is the only mitochondrial member of 17β-HSD family. This enzyme can oxidize estradiol (E2) into estrone (E1), thus reducing concentration of this neuroprotective steroid. Since 17β-HSD10 possesses properties that suggest a possible role in Alzheimer's disease, its inhibition appears to be a therapeutic strategy. After we identified the androsterone (ADT) derivative 1 as a first steroidal inhibitor of 17β-HSD10, new analogs were synthesized to increase the metabolic stability, to improve the selectivity of inhibition over 17β-HSD3 and to optimize the inhibitory potency. From six D-ring derivatives of 1 (17-CO), two compounds (17β-H/17α-OH and 17β-OH/17α-CCH) were more metabolically stable and did not inhibit the 17β-HSD3. Moreover, solid phase synthesis was used to extend the molecular diversity on the 3β-piperazinylmethyl group of the steroid base core. Eight over 120 new derivatives were more potent inhibitors than 1 for the transformation of E2 to E1, with the 4-(4-trifluoromethyl-3-methoxybenzyl)piperazin-1-ylmethyl-ADT (D-3,7) being 16 times more potent (IC₅₀ = 0.14 μM). Finally, D-ring modification of D-3,7 provided 17β-OH/17α-CCH derivative 25 and 17β-H/17α-OH derivative 26, which were more potent inhibitor than 1 (1.8 and 2.4 times, respectively).

Non-genomic mechanisms mediate androgen-induced PSD95 expression

The non-genomic actions of androgen-induced synaptic plasticity have been extensively studied. However, the underlying mechanisms remain controversial. We recently found that testosterone-fetal bovine serum albumin (T-BSA), a cell membrane-impermeable complex, led to a rapid increase in the postsynaptic density 95 (PSD95) protein level through a transcription-independent mechanism in mouse hippocampal HT22 cells. Using T-BSA conjugated FITC, we verified the presence of membrane androgen-binding sites. Here, we show that T-BSA-induced PSD95 expression is mediated by G-protein-coupled receptor (GPCR)-zinc transporter ZIP9 (SLC39A9), one of the androgen membrane binding sites, rather than the membrane-localized androgen receptor. Furthermore, we found that T-BSA induced an interaction between ZIP9 and Gnα11 that lead to the phosphorylation of Erk1/2 MAPK and eIF4E, which are critical in the mRNA translation process. The PSD95 and p-eIF4E expression decreased when knockdown of ZIP9 or Gnα11 expression or inhibition of Erk1/2 activation. Taken together, these findings suggest that ZIP9 mediates the non-genomic action of androgen on synaptic protein PSD95 synthesis through the Gnα11/Erk1/2/eIF4E pathway in HT22 cells. This novel mechanism provides a theoretical basis to understand the neuroprotective mechanism of androgen.

Neuroprotection by dihydrotestosterone in LPS-induced neuroinflammation

Microglia-induced neuroinflammation plays a vital role in the etiology and progression of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and multiple sclerosis. The neuroprotective role of androgens, including testosterone and its metabolite dihydrotestosterone (DHT), has been increasingly demonstrated in these diseases, but few studies investigated the effects of androgen on neuroinflammation. This study investigated the role of DHT in lipopolysaccharide (LPS)-induced neuroinflammation, neuronal damage and behavioral dysfunction, as well as underlying mechanisms. We showed that DHT inhibited LPS-induced release of proinflammatory factors, including TNF-α, IL-1β, IL-6; iNOS, COX-2, NO, and PGE2 in BV2 cells and primary microglia by suppressing the TLR4-mediated NF-κB and MAPK p38 signaling pathways, thus protecting SH-SY5Y neurons from inflammatory damage induced by activated microglia. In an LPS-induced neuroinflammation mouse model, endogenous DHT depletion by castration exacerbated inflammatory responses by upregulating the levels of TNF-α, IL-1β, IL-6, iNOS, and COX-2 in the serum and brain by increasing the LR4-mediated NF-κB and MAPK pathway activation, but these effects were restored by exogenous DHT supplementation. Moreover, DHT also regulated the mRNA levels of the anti-inflammatory cytokines IL-10 and IL-13 in the brain. In addition, DHT modulated the expression of Aβ, the apoptotic proteins caspase-3, Bcl-2, and Bax, and synaptophysin, as well as neuronal damage in LPS-treated mouse brains. Further behavioral tests revealed that DHT ameliorated LPS-induced spatial and learning impairment and motor incoordination, and partly improved the locomotor activity in LPS-injected mice. Therefore, this study suggests that DHT exerts anti-neuroinflammatory and neuroprotective effects; thus, androgen replacement therapy is a potential therapeutic strategy for improving cognitive and behavioral function in neuroinflammation-related diseases.

The role of extracellular matrix metalloproteinase inducer on the action of dihydrotestosterone against the cellular damage induced by Aβ42

Clinical studies have revealed that the risk of Alzheimer's disease (AD) in men is increased by age-related androgen depletion. The level of β-amyloid (Aβ) is elevated in the brains of AD patients, and Aβ is believed to play a critical role in the pathology of AD. Some studies have indicated that androgens affect AD risk by regulating the metabolism of Aβ by an unclear mechanism. In this study, we investigated the role of the extracellular matrix metalloproteinase inducer (CD147) in this action. Initially, we demonstrated that androgens positively regulate the expression of CD147 in adult male rats and SH-SY5Y cells. Furthermore, this regulation may involve androgen receptor (AR). Additionally, interference of CD147 expression decreased the clearance of Aβ in culture medium and reduced cell viability. It also affected the morphology of the cells and the expression of apoptosis-related proteins. Finally, we found that interference of CD147 expression blocked the dihydrotestosterone (DHT)-induced reduction in Aβ and the protection of cells. DHT regulates MMP-2's expression through CD147. Together, these results imply that androgen regulation of Aβ and cell protection may be affected by interfering with the expression of CD147.

Inhibition of oxidative stress by testosterone improves synaptic plasticity in senescence accelerated mice

It is well known that synaptic plasticity is associated with cognitive performance in Alzheimer's disease (AD). Testosterone (T) is known to exert protective effects on cognitive deficits in AD, but the underlying mechanisms of androgenic action on synaptic plasticity remain unclear. Thus, the aim of this study was to examine the protective mechanism attributed to T on synaptic plasticity in an AD senescence accelerated mouse prone 8 (SAMP8) model. The following parameters were measured: (1) number of intact pyramidal cells in hippocampal CA1 region (2) phosphorylated N-methyl-D-aspartate receptor-1 (p-NMDAR1) and (3) phosphorylated calmodulin-dependent protein kinase II (p-CaMKII). In addition, the content of whole brain malondialdehyde (MDA) as well as activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were determined. Treatment with T significantly elevated the number of intact pyramidal cells in hippocampal CA1 region and markedly increased hippocampal protein and mRNA expression levels of p-NMDAR1 and p-CaMK II. Further, T significantly decreased whole brain MDA levels accompanied by elevated activities of SOD and GSH-Px. Data suggest that the protective effects of T on synaptic plasticity in a mouse AD model may be associated with reduction of oxidant stress.

Alzheimer's Disease: A Journey from Amyloid Peptides and Oxidative Stress, to Biomarker Technologies and Disease Prevention Strategies-Gains from AIBL and DIAN Cohort Studies

Worldwide there are over 46 million people living with dementia, and this number is expected to double every 20 years reaching about 131 million by 2050. The cost to the community and government health systems, as well as the stress on families and carers is incalculable. Over three decades of research into this disease have been undertaken by several research groups in Australia, including work by our original research group in Western Australia which was involved in the discovery and sequencing of the amyloid-β peptide (also known as Aβ or A4 peptide) extracted from cerebral amyloid plaques. This review discusses the journey from the discovery of the Aβ peptide in Alzheimer's disease (AD) brain to the establishment of pre-clinical AD using PET amyloid tracers, a method now serving as the gold standard for developing peripheral diagnostic approaches in the blood and the eye. The latter developments for early diagnosis have been largely achieved through the establishment of the Australian Imaging Biomarker and Lifestyle research group that has followed 1,100 Australians for 11 years. AIBL has also been instrumental in providing insight into the role of the major genetic risk factor apolipoprotein E ɛ4, as well as better understanding the role of lifestyle factors particularly diet, physical activity and sleep to cognitive decline and the accumulation of cerebral Aβ.

Neurotrophic and Neuroregenerative Effects of GH/IGF1

Introduction. Human neurodegenerative diseases increase progressively with age and present a high social and economic burden. Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are both growth factors exerting trophic effects on neuronal regeneration in the central nervous system (CNS) and peripheral nervous system (PNS). GH and IGF-1 stimulate protein synthesis in neurons, glia, oligodendrocytes, and Schwann cells, and favor neuronal survival, inhibiting apoptosis. This study aims to evaluate the effect of GH and IGF-1 on neurons, and their possible therapeutic clinical applications on neuron regeneration in human subjects. Methods. In the literature, we searched the clinical trials and followed up studies in humans, which have evaluated the effect of GH/IGF-1 on CNS and PNS. The following keywords have been used: “GH/IGF-1” associated with “neuroregeneration”, “amyotrophic lateral sclerosis”, “Alzheimer disease”, “Parkinson’s disease”, “brain”, and “neuron”. Results. Of the retrieved articles, we found nine articles about the effect of GH in healthy patients who suffered from traumatic brain injury (TBI), and six studies (four using IGF-1 and two GH therapy) in patients with amyotrophic lateral sclerosis (ALS). The administration of GH in patients after TBI showed a significantly positive recovery of brain and mental function. Treatment with GH and IGF-1 therapy in ALS produced contradictory results. Conclusions. Although strong findings have shown the positive effects of GH/IGF-1 administration on neuroregeneration in animal models, a very limited number of clinical studies have been conducted in humans. GH/IGF-1 therapy had different effects in patients with TBI, evidencing a high recovery of neurons and clinical outcome, while in ALS patients, the results are contradictory. More complex clinical protocols are necessary to evaluate the effect of GH/IGF-1 efficacy in neurodegenerative diseases. It seems evident that GH and IGF-1 therapy favors the optimal recovery of neurons when a consistent residual activity is still present. Furthermore, the effect of GH/IGF-1 could be mediated by, or be overlapped with that of other hormones, such as estradiol and testosterone.

A network-driven approach for genome-wide association mapping

MOTIVATION

It remains a challenge to detect associations between genotypes and phenotypes because of insufficient sample sizes and complex underlying mechanisms involved in associations. Fortunately, it is becoming more feasible to obtain gene expression data in addition to genotypes and phenotypes, giving us new opportunities to detect true genotype-phenotype associations while unveiling their association mechanisms.

RESULTS

In this article, we propose a novel method, NETAM, that accurately detects associations between SNPs and phenotypes, as well as gene traits involved in such associations. We take a network-driven approach: NETAM first constructs an association network, where nodes represent SNPs, gene traits or phenotypes, and edges represent the strength of association between two nodes. NETAM assigns a score to each path from an SNP to a phenotype, and then identifies significant paths based on the scores. In our simulation study, we show that NETAM finds significantly more phenotype-associated SNPs than traditional genotype-phenotype association analysis under false positive control, taking advantage of gene expression data. Furthermore, we applied NETAM on late-onset Alzheimer's disease data and identified 477 significant path associations, among which we analyzed paths related to beta-amyloid, estrogen, and nicotine pathways. We also provide hypothetical biological pathways to explain our findings.

AVAILABILITY AND IMPLEMENTATION

Software is available at http://www.sailing.cs.cmu.edu/

CONTACT

: epxing@cs.cmu.edu.

Accelerated reduction of serum thyroxine and hippocampal histone acetylation links to exacerbation of spatial memory impairment in aged CD-1 mice pubertally exposed to bisphenol-a

Age-related cognitive decline has been associated with changes in endogenous hormones and epigenetic modification of chromatin, including histone acetylation. Developmental exposure to endocrine disrupting chemicals, such as bisphenol-A (BPA) that produces endocrine disruption and epigenetic changes, may be a risk factor for accelerating cognitive deficits during aging. Thus, we exposed CD-1 mice to BPA (0, 1, and 100 mg/l BPA in the drinking water) orally during puberty (from postnatal days 28 to 56) and investigated whether pubertal BPA exposure exacerbates the age-related impairment of spatial cognition in old age (18 months old) and whether serum sex and thyroid hormones or hippocampal histone acetylation (H3K9ac and H4K8ac) are associated with cognitive effects. A young control group (6 months old) was added to analyze the age effect. Results showed untreated aged mice had marked decline of spatial learning and memory in the novel location recognition and radial six-arm water maze tasks, with decreased levels of these hormones and hippocampal H3K9ac and H4K8ac compared to young controls. The BPA treatment exacerbated age-related spatial cognitive impairment and accelerated the reduction of free thyroxine (FT4), H3K9ac, and H4K8ac, and the 100 mg/l BPA group showed more significant impact. Additionally, correlation analyses revealed that lower levels of FT4, H3K9ac, and H4K8ac were accompanied by decreased spatial memory abilities. We concluded that accelerated reduction of serum FT4 and hippocampal H3K9ac and H4K8ac might be linked to exacerbation of age-related spatial cognitive impairment due to pubertal BPA exposure.

Sex Hormone Decline and Amyloid β Synthesis, Transport and Clearance in the Brain

Sex hormones (SH) are essential regulators of the central nervous system. The decline in SH levels along with ageing may contribute to compromised neuroprotection and set the grounds for neurodegeneration and cognitive impairments. In Alzheimer's disease, besides other pathological features, there is an imbalance between amyloid β (Aβ) production and clearance, leading to its accumulation in the brain of older subjects. Aβ accumulation is a primary cause for brain inflammation and degeneration, as well as concomitant cognitive decline. There is mounting evidence that SH modulate Aβ production, transport and clearance. Importantly, SH regulate most of the molecules involved in the amyloidogenic pathway, their transport across brain barriers for elimination, and their degradation in the brain interstitial fluid. This review brings together data on the regulation of Aβ production, metabolism, degradation and clearance by SH.

The impact of luteinizing hormone and testosterone on beta amyloid (Aβ) accumulation: Animal and human clinical studies

This article is part of a Special Issue "SBN 2014". Hormonal changes associated with ageing have been implicated in the pathogenesis of Alzheimer's disease (AD), the most common form of dementia. Reductions in serum testosterone and increases in luteinizing hormone (LH) are established AD risk factors for dementia in men and have important roles in modulating AD pathogenesis. One of the defining features of AD is the accumulation of amyloid-beta (Aβ) in the brain, which has a key role in the neurodegenerative cascade. Both testosterone and LH have been shown to modulate CNS Aβ accumulation in animal studies, and associations with cerebral amyloid load in human studies have supported this. The underlying mechanisms by which these hormones modulate Aβ accumulation and contribute to neurodegeneration are not completely understood, however they have been shown to regulate Aβ metabolism, enhance its clearance and alter the processing of its parent molecule, the amyloid precursor protein. This review will discuss underlying mechanisms by which testosterone and LH modulate Aβ and provide an update on therapeutic approaches targeting these hormones.

The practical management of testosterone deficiency in men

Despite increased global interest in testosterone deficiency in men and its treatment with testosterone therapy, practical aspects of care remain confusing to many practitioners. Testosterone deficiency can result from testicular dysfunction (primary hypogonadism) or hypothalamic-pituitary dysfunction (secondary hypogonadism), and be congenital or acquired. Sexual and nonsexual symptoms of testosterone deficiency can negatively affect quality of life and cause considerable general health concerns. Investigation of testosterone deficiency should be undertaken in men with symptoms of reduced libido, erectile dysfunction, depression, fatigue, poor concentration, and poor memory. Total and free testosterone are the most frequently used tests and evaluating serum concentrations of luteinizing hormone aids determination of primary versus secondary testosterone deficiency. Multiple formulations of testosterone therapy are available, but symptomatic benefits might not manifest for several weeks to many months; long-acting formulations are convenient and improve compliance. Concerns regarding cardiovascular and prostate cancer risks are not supported by current evidence, monitoring during therapy is mandatory. On balance, testosterone therapy can be considered a safe and effective treatment for testosterone deficiency.

Androgen Modulation of Hippocampal Structure and Function

Androgens have profound effects on hippocampal structure and function, including induction of spines and spine synapses on the dendrites of CA1 pyramidal neurons, as well as alterations in long-term synaptic plasticity (LTP) and hippocampally dependent cognitive behaviors. How these effects occur remains largely unknown. Emerging evidence, however, suggests that one of the key elements in the response mechanism may be modulation of brain-derived neurotrophic factor (BDNF) in the mossy fiber (MF) system. In male rats, orchidectomy increases synaptic transmission and excitability in the MF pathway. Testosterone reverses these effects, suggesting that testosterone exerts tonic suppression on MF BDNF levels. These findings suggest that changes in hippocampal function resulting from declining androgen levels may reflect the outcome of responses mediated through normally balanced, but opposing, mechanisms: loss of androgen effects on the hippocampal circuitry may be compensated, at least in part, by an increase in BDNF-dependent MF plasticity.

Protective effects of testosterone on presynaptic terminals against oligomeric β-amyloid peptide in primary culture of hippocampal neurons

Increasing lines of evidence support that testosterone may have neuroprotective effects. While observational studies reported an association between higher bioavailable testosterone or brain testosterone levels and reduced risk of Alzheimer's disease (AD), there is limited understanding of the underlying neuroprotective mechanisms. Previous studies demonstrated that testosterone could alleviate neurotoxicity induced by β-amyloid (Aβ), but these findings mainly focused on neuronal apoptosis. Since synaptic dysfunction and degeneration are early events during the pathogenesis of AD, we aim to investigate the effects of testosterone on oligomeric Aβ-induced synaptic changes. Our data suggested that exposure of primary cultured hippocampal neurons to oligomeric Aβ could reduce the length of neurites and decrease the expression of presynaptic proteins including synaptophysin, synaptotagmin, and synapsin-1. Aβ also disrupted synaptic vesicle recycling and protein folding machinery. Testosterone preserved the integrity of neurites and the expression of presynaptic proteins. It also attenuated Aβ-induced impairment of synaptic exocytosis. By using letrozole as an aromatase antagonist, we further demonstrated that the effects of testosterone on exocytosis were unlikely to be mediated through the estrogen receptor pathway. Furthermore, we showed that testosterone could attenuate Aβ-induced reduction of HSP70, which suggests a novel mechanism that links testosterone and its protective function on Aβ-induced synaptic damage. Taken together, our data provide further evidence on the beneficial effects of testosterone, which may be useful for future drug development for AD.

Effects of dihydrotestosterone on synaptic plasticity of hippocampus in male SAMP8 mice

The senescence-accelerated-prone mouse 8 (SAMP8) has been proposed as a suitable, naturally derived animal model for investigating the fundamental mechanisms of Alzheimer's disease (AD). In addition, the serum testosterone levels decrease quickly in the natural growth process of this model. This study investigated the effect of androgen deficiency on the synaptic plasticity of hippocampus in male SAMP8 mice after castration and dihydrotestosterone (DHT) administration. We observed the dendritic spines and synapses using Golgi staining and transmission electron microscope. Androgen deficiency after castration significantly reduced the number of apical dendritic thorns, and the abnormal ultrastructure of excitatory synapses was more obvious. Androgen replacement therapy reversed this change. To explore the protective mechanisms and neurological basis of DHT, we researched the changes of expression of GluN1 subunit-containing N-methyl-D-aspartate receptors (NMDARs) and synaptophysin (SYN), which are closely related to synaptic plasticity. Comparisons were made among results observed with immunohistochemistry techniques, Western blots analysis and RT-PCR analysis. The GluN1 and SYN regulation at the protein and mRNA levels probably be related to the DHT-induced morphological synaptic plasticity. This study will be helpful for understanding the function of androgen, and it provides a valuable theoretical basis about the protective and therapeutic targets of androgen in AD.

Testosterone depletion in adult male rats increases mossy fiber transmission, LTP, and sprouting in area CA3 of hippocampus

Androgens have dramatic effects on neuronal structure and function in hippocampus. However, androgen depletion does not always lead to hippocampal impairment. To address this apparent paradox, we evaluated the hippocampus of adult male rats after gonadectomy (Gdx) or sham surgery. Surprisingly, Gdx rats showed increased synaptic transmission and long-term potentiation of the mossy fiber (MF) pathway. Gdx rats also exhibited increased excitability and MF sprouting. We then addressed the possible underlying mechanisms and found that Gdx induced a long-lasting upregulation of MF BDNF immunoreactivity. Antagonism of Trk receptors, which bind neurotrophins, such as BDNF, reversed the increase in MF transmission, excitability, and long-term potentiation in Gdx rats, but there were no effects of Trk antagonism in sham controls. To determine which androgens were responsible, the effects of testosterone metabolites DHT and 5α-androstane-3α,17β-diol were examined. Exposure of slices to 50 nm DHT decreased the effects of Gdx on MF transmission, but 50 nm 5α-androstane-3α,17β-diol had no effect. Remarkably, there was no effect of DHT in control males. The data suggest that a Trk- and androgen receptor-sensitive form of MF transmission and synaptic plasticity emerges after Gdx. We suggest that androgens may normally be important in area CA3 to prevent hyperexcitability and aberrant axon outgrowth but limit MF synaptic transmission and some forms of plasticity. The results also suggest a potential explanation for the maintenance of hippocampal-dependent cognitive function after androgen depletion: a reduction in androgens may lead to compensatory upregulation of MF transmission and plasticity.

Altered expression of Alzheimer's disease-related proteins in male hypogonadal mice

Age-related depletion of estrogens and androgens is associated with an increase in Alzheimer's disease (AD) brain pathology and diminished cognitive function. Here we investigated AD-associated molecular and cellular changes in brains of aged hypogonadal (hpg) male and female mice. hpg Mice have a spontaneous, inactivating genetic mutation in the GnRH gene resulting in life-long deficiency of gonadotropins and gonadal sex hormones. Western blot analysis revealed low levels of amyloid precursor protein and high levels of presenilin 1, amyloid precursor protein C-terminal fragment, and β-amyloid 42 in brains of aged male, but not female, hpg mice. Changes were confined to the hippocampus and were not evident in the cerebellum or other brain tissues. Male hpg mice tended to have lower levels of IL-1β protein than male littermate controls. Immunohistochemical staining of the basal forebrain revealed that male hpg mice had lower choline acetyltransferase levels per neuron compared with controls. These AD-like changes specific to male hpg mice supports a link between androgen depletion and the development of AD pathology.

Tissue-selective regulation of androgen-responsive genes

INTRODUCTION

Androgens regulate a wide array of physiological processes, including male sexual development, bone and muscle growth, and behavior and cognition. Because androgens play a vital role in so many tissues, changes in androgen signaling are associated with a plethora of diseases. How such varied responses are achieved by a single stimulus is not well understood. Androgens act primarily through the androgen receptor (AR), a hormone nuclear receptor that is expressed in a select variety of tissues.

METHODS

In order to gain a better understanding of how the tissue-selective effects of androgens are achieved, we performed a comparison of microarray data, using previously published datasets and several of our own microarray datasets. These datasets were derived from clinically relevant, AR-expressing tissues dissected from rodents treated with the full androgen dihydrotestosterone (DHT).

RESULTS

We found that there is a diverse response to DHT, with very little overlap of androgen regulated genes in each tissue. Gene ontology analyses also indicated that, while several tissues regulate similar biological processes in response to DHT, most androgen regulated processes are specific to one or a few tissues. Thus, it appears that the disparate physiological effects mediated by androgens begin with widely varying effects on gene expression in different androgen-sensitive tissues.

CONCLUSION

The analysis completed in this study will lead to an improved understanding of how androgens mediate diverse, tissue-specific processes and better ways to assess the tissue-selective effects of AR modulators during drug development.

Neurosteroid and GABA-A receptor alterations in Alzheimer's disease, Parkinson's disease and multiple sclerosis

Steroid hormones (e.g. estrogens, androgens, progestagens) which are synthesized de novo or metabolized within the CNS are called neurosteroids. There is substantial evidence from animal studies suggesting that these steroids can affect brain function by modulating neurotransmission, and influence neuronal survival, neuronal and glial differentiation and myelination in the CNS by regulating gene expression of neurotrophic factors and anti-inflammatory molecules. Indeed, evidence is emerging that expression of the enzymes responsible for the synthesis of neurosteroids changes in neurodegenerative diseases. Some of these changes may contribute to the pathology, while others, conversely, may represent an attempted rescue program in the diseased brain. Here we review the data on changes in neurosteroid levels and neurosteroid synthesis pathways in the human brain in three neurodegenerative conditions, Alzheimers's (AD) and Parkinson's (PD) diseases and Multiple Sclerosis (MS) and the extent to which these findings may implicate protective or pathological roles for neurosteroids in the course of these diseases.Some neurosteroids can modulate neurotransmitter activity, for example, the pregnane steroids allopregnanolone and 3α5α-tetrahydro-deoxycorticosterone which are potent positive allosteric modulators of ionotropic GABA-A receptors. Therefore, neurosteroid-modulated GABA-A receptor subunit alterations found in AD and PD will also be discussed. These data imply an involvement of neurosteroid changes in the neurodegenerative and neuroinflammatory processes and suggest that they may deserve further investigation as potential therapeutic agents in AD, PD and MS. Finally, suggestions for therapeutic strategies will be included. This article is part of a Special Issue entitled: Neuroactive Steroids: Focus on Human Brain.

International web survey shows high prevalence of symptomatic testosterone deficiency in men

INTRODUCTION

Though the clinical significance of testosterone deficiency is becoming increasingly apparent, its prevalence in the general population remains unrecognised. A large web-based survey was undertaken over 3 years to study the scale of this missed diagnosis.

METHODS

An online questionnaire giving the symptoms characterising testosterone deficiency syndrome (Aging Male Symptoms-AMS-scale) was set up on three web sites, together with questions about possible contributory factors.

RESULTS

Of over 10,000 men, mainly from the UK and USA, who responded, 80% had moderate or severe scores likely to benefit from testosterone replacement therapy (TRT). The average age was 52, but with many in their 40s when the diagnosis of 'late onset hypogonadism' is not generally considered. Other possible contributory factors to the high testosterone deficiency scores reported were obesity (29%), alcohol (17.3%), testicular problems such as mumps orchitis (11.4%), prostate problems (5.6%), urinary infection (5.2%) and diabetes 5.7%.

CONCLUSIONS

In this self-selected large international sample of men, there was a very high prevalence of scores which if clinically relevant would warrant a therapeutic trial of testosterone treatment. This study suggests that there are large numbers of men in the community whose testosterone deficiency is neither being diagnosed nor treated.

A selective androgen receptor modulator enhances male-directed sexual preference, proceptive behavior, and lordosis behavior in sexually experienced, but not sexually naive, female rats

Androgens influence many aspects of reproductive behavior, including sexual preference of females for males. In oophorectomized women with sexual desire disorder, testosterone patches improve libido, but their use is limited because of adverse side effects. Selective androgen receptor modulators offer an improved safety profile for both sexes: enhancing libido and muscle and bone growth in a manner similar to steroidal androgens but with fewer adverse effects, such as hirsutism, acne, and prostate growth. The current study investigated the action of a novel selective androgen receptor modulator (LGD-3303 [9-chloro-2-ethyl-1-methyl-3-(2,2,2-trifluoroethyl)-3H-pyrrolo-[3,2-f]quinolin-7(6H)-one]) on male-directed sexual preference, proceptivity, and lordosis behavior of female rats. LGD-3303 is a nonsteroidal, nonaromatizable, highly selective ligand for the androgen receptor and effectively crosses the blood-brain barrier. Gonadectomized female rats were treated with LGD-3303 (3-30 mg/kg) or vehicle by daily oral gavage. Results showed that LGD-3303 treatment enhanced sexual preference of females for males but only if females had previous sexual experience. This occurred after 1 or 7 d of treatment. In contrast, preference for males was inhibited by LGD-3303 treatments of sexually naive females. The LGD-3303 increase in male preference was blocked by pretreatment with the androgen receptor antagonist flutamide. LGD-3303 treatment increased lordosis and proceptivity behaviors in ovariectomized females primed with suboptimal doses of estradiol benzoate plus progesterone. These data support the concept that LGD-3303 can stimulate aspects of female sexual behavior and may serve as a potential therapeutic for women with sexual desire disorders.