Allopregnanolone pleiotropic action in neurons and astrocytes: calcium signaling as a unifying mechanism.

Objective: Allopregnanolone (Allo) is a neurosteroid with pleiotropic action in the brain that includes neurogenesis, oligogenesis, human and rodent neural stem cell regeneration, increased glucose metabolism, mitochondrial respiration and biogenesis, improved cognitive function, and reduction of both inflammation and Alzheimer's disease (AD) pathology. Because the breadth of Allo-induced responses requires activation of multiple systems of biology in the absence of an Allo-specific nuclear receptor, analyses were conducted in both neurons and astrocytes to identify unifying systems and signaling pathways. Methods: Mechanisms of Allo action were investigated in embryonic hippocampal neurons and astrocytes cultured in an Aging Model (AM) media. Cellular morphology, mitochondrial function, and transcriptomics were investigated followed by mechanistic pathway analyses. Results: In hippocampal neurons, Allo significantly increased neurite outgrowth and synaptic protein expression, which were paralleled by upregulated synaptogenesis and long-term potentiation gene expression profiles. Mechanistically, Allo induced Ca2+/CREB signaling cascades. In parallel, Allo significantly increased maximal mitochondrial respiration, mitochondrial membrane potential, and Complex IV activity while reducing oxidative stress, which required both the GABAA and L-type Ca2+ channels. In astrocytes, Allo increased ATP generation, mitochondrial function and dynamics while reducing oxidative stress, inflammasome indicators, and apoptotic signaling. Mechanistically, Allo regulation of astrocytic mitochondrial function required both the GABAA and L-type Ca2+ channels. Furthermore, Allo activated NRF1-TFAM signaling and increased the DRP1/OPA1 protein ratio, which led to increased mitochondrial biogenesis and dynamics. Conclusion: Collectively, the cellular, mitochondrial, transcriptional, and pharmacological profiles provide evidence in support of calcium signaling as a unifying mechanism for Allo pleiotropic actions in the brain.

Breast cancer therapies reduce risk of Alzheimer's disease and promote estrogenic pathways and action in brain.

Worldwide, an ever-increasing number of women are prescribed estrogen-modulating therapies (EMTs) for the treatment of breast cancer. In parallel, aging of the global population of women will contribute to risk of both breast cancer and Alzheimer's disease. To address the impact of anti-estrogen therapies on risk of Alzheimer's and neural function, we conducted medical informatic and molecular pharmacology analyses to determine the impact of EMTs on risk of Alzheimer's followed by determination of EMT estrogenic mechanisms of action in neurons. Collectively, these data provide both clinical and mechanistic data indicating that select EMTs exert estrogenic agonist action in neural tissue that are associated with reduced risk of Alzheimer's disease while simultaneously acting as effective estrogen receptor antagonists in breast.

Allopregnanolone Reverses Bioenergetic Deficits in Female Triple Transgenic Alzheimer's Mouse Model.

Previously, we reported that the neurosteroid allopregnanolone (Allo) promoted neural stem cell regeneration, restored cognitive function, and reduced Alzheimer's Disease (AD) pathology in the triple transgenic Alzheimer's mouse model (3xTgAD). To investigate the underlying systems biology of Allo action in AD models in vivo, we assessed the regulation of Allo on the bioenergetic system of the brain. Outcomes of these analysis indicated that Allo significantly reversed deficits in mitochondrial respiration and biogenesis and key mitochondrial enzyme activity and reduced lipid peroxidation in the 3xTgAD mice in vivo. To explore the mechanisms by which Allo regulates the brain metabolism, we conducted targeted transcriptome analysis. These data further confirmed that Allo upregulated genes involved in glucose metabolism, mitochondrial bioenergetics, and signaling pathways while simultaneously downregulating genes involved in Alzheimer's pathology, fatty acid metabolism, and mitochondrial uncoupling and dynamics. Upstream regulatory pathway analysis predicted that Allo induced peroxisome proliferator-activated receptor gamma (PPARG) and coactivator 1-alpha (PPARGC1A) pathways while simultaneously inhibiting the presenilin 1 (PSEN 1), phosphatase and tensin homolog (PTEN), and tumor necrosis factor (TNF) pathways to reduce AD pathology. Collectively, these data indicate that Allo functions as a systems biology regulator of bioenergetics, cholesterol homeostasis, and ß-amyloid reduction in the brain. These systems are critical to neurological health, thus providing a plausible mechanistic rationale for Allo as a therapeutic to promote neural cell function and reduce the burden of AD pathology.

Evidence in support of chromosomal sex influencing plasma based metabolome vs APOE genotype influencing brain metabolome profile in humanized APOE male and female mice.

Late onset Alzheimer's disease (LOAD) is a progressive neurodegenerative disease with four well-established risk factors: age, APOE4 genotype, female chromosomal sex, and maternal history of AD. Each risk factor impacts multiple systems, making LOAD a complex systems biology challenge. To investigate interactions between LOAD risk factors, we performed multiple scale analyses, including metabolomics, transcriptomics, brain magnetic resonance imaging (MRI), and beta-amyloid assessment, in 16 months old male and female mice with humanized human APOE3 (hAPOE3) or APOE4 (hAPOE4) genes. Metabolomic analyses indicated a sex difference in plasma profile whereas APOE genotype determined brain metabolic profile. Consistent with the brain metabolome, gene and pathway-based RNA-Seq analyses of the hippocampus indicated increased expression of fatty acid/lipid metabolism related genes and pathways in both hAPOE4 males and females. Further, female transcription of fatty acid and amino acids pathways were significantly different from males. MRI based imaging analyses indicated that in multiple white matter tracts, hAPOE4 males and females exhibited lower fractional anisotropy than their hAPOE3 counterparts, suggesting a lower level of white matter integrity in hAPOE4 mice. Consistent with the brain metabolomic and transcriptomic profile of hAPOE4 carriers, beta-amyloid generation was detectable in 16-month-old male and female brains. These data provide therapeutic targets based on chromosomal sex and APOE genotype. Collectively, these data provide a framework for developing precision medicine interventions during the prodromal phase of LOAD, when the potential to reverse, prevent and delay LOAD progression is greatest.

Therapeutic progestin segesterone acetate promotes neurogenesis: implications for sustaining regeneration in female brain.

OBJECTIVE: Neurogenesis is the principal regenerative mechanism to sustain the plasticity potential in adult brains. Decreased neurogenesis parallels the cognition decline with aging, and has been suggested as a common hallmark in the progression of many neurodegeneration diseases. We previously reported that acute exposure to segesterone acetate (ST-1435; Nestorone), alone or in combination with 17ß-estradiol (E2), increased human neural stem cells proliferation and survival both in vitro and in vivo. The present study expanded our previous findings to investigate the more clinical related chronic exposure in combination with E2 on the regenerative capacity of adult brain. METHODS: To mimic the chronic contraception exposure in women, 3-month old female mice (n = 110) were treated with ST-1435, with or without co-administration of E2, for 4 weeks. Neural cell proliferation and survival, and oligodendrocyte generation were assessed. The involvement of insulin-like growth factor 1 signaling was studied. RESULTS: Our results demonstrated that chronic ST-1435 and E2 alone or in combination increased neurogenesis by a comparable magnitude, with minimum to no antagonistic or additive effects between ST-1435 and E2. In addition, chronic exposure of ST-1435 or ST-1435 + E2 stimulated oligodendrocyte generation, indicating potential elevated myelination. Insulin-like growth factor-1 (IGF-1) and IGF-1 receptor (IGF-1R) were also up-regulated after chronic ST-1435 and E2 exposure, suggesting the involvement of IGF-1 signaling as the potential underlined regulatory pathway transducing ST-1435 effect. CONCLUSION: These findings provide preclinical evidence and mechanistic insights for the development of ST-1435 as a neuroregenerative therapy to promote intrinsic regenerative capacity in female brains against aging and neurodegenerative disorders.

Design, synthesis, and estrogenic activity of a novel estrogen receptor modulator--a hybrid structure of 17beta-estradiol and vitamin E in hippocampal neurons.

We recently discovered that ICI 182,780 (1), an antagonist of estrogen receptor (ER)-dependent proliferation in reproductive tissues, functions as an estrogenic agonist in primary neurons. The present study investigated whether the agonist properties of 1 in neurons could be translated into structural analogs. 7alpha-[(4R,8R)-4,8,12-trimethyltridecyl]estra-1,3,5-trien-3,17beta-diol (2), a hybrid structure of 17beta-estradiol and vitamin E, was synthesized and found to bind to both ERalpha and ERbeta. In vitro analyses demonstrated that 2 was neuroprotective and effective in activating molecular mechanisms associated with estrogenic agonist activity in rat primary hippocampal neurons. Collectively, the data support an estrogenic agonist profile of 2 action comparable to 1 in primary neurons, confirming that estrogenic activity of 1 in neurons is not a unique phenomenon. These results provide support for the development of a brain-selective ER modulator, with potential as an efficacious and safe estrogen alternative to prevent Alzheimer's disease and cognitive decline in postmenopausal women.

Sex differences in metabolic aging of the brain: insights into female susceptibility to Alzheimer's disease.

Despite recent advances in the understanding of clinical aspects of sex differences in Alzheimer's disease (AD), the underlying mechanisms, for instance, how sex modifies AD risk and why the female brain is more susceptible to AD, are not clear. The purpose of this study is to elucidate sex disparities in brain aging profiles focusing on 2 major areas-energy and amyloid metabolism-that are most significantly affected in preclinical development of AD. Total RNA isolated from hippocampal tissues of both female and male 129/C57BL/6 mice at ages of 6, 9, 12, or 15 months were comparatively analyzed by custom-designed Taqman low-density arrays for quantitative real-time polymerase chain reaction detection of a total of 182 genes involved in a broad spectrum of biological processes modulating energy production and amyloid homeostasis. Gene expression profiles revealed substantial differences in the trajectory of aging changes between female and male brains. In female brains, 44.2% of genes were significantly changed from 6 months to 9 months and two-thirds showed downregulation. In contrast, in male brains, only 5.4% of genes were significantly altered at this age transition. Subsequent changes in female brains were at a much smaller magnitude, including 10.9% from 9 months to 12 months and 6.1% from 12 months to 15 months. In male brains, most changes occurred from 12 months to 15 months and the majority were upregulated. Furthermore, gene network analysis revealed that clusterin appeared to serve as a link between the overall decreased bioenergetic metabolism and increased amyloid dyshomeostasis associated with the earliest transition in female brains. Together, results from this study indicate that: (1) female and male brains follow profoundly dissimilar trajectories as they age; (2) female brains undergo age-related changes much earlier than male brains; (3) early changes in female brains signal the onset of a hypometabolic phenotype at risk for AD. These findings provide a mechanistic rationale for female susceptibility to AD and suggest a potential window of opportunity for AD prevention and risk reduction in women.

Is Melanoma a stem cell tumor? Identification of neurogenic proteins in trans-differentiated cells.

BACKGROUND: Although several genes and proteins have been implicated in the development of melanomas, the molecular mechanisms involved in the development of these tumors are not well understood. To gain a better understanding of the relationship between the cell growth, tumorigenesis and differentiation, we have studied a highly malignant cat melanoma cell line that trans-differentiates into neuronal cells after exposure to a feline endogenous retrovirus RD114. METHODS: To define the repertoire of proteins responsible for the phenotypic differences between melanoma and its counterpart trans-differentiated neuronal cells we have applied proteomics technology and compared protein profiles of the two cell types and identified differentially expressed proteins by 2D-gel electrophoresis, image analyses and mass spectrometry. RESULTS: The melanoma and trans-differentiated neuronal cells could be distinguished by the presence of distinct sets of proteins in each. Although approximately 60-70% of the expressed proteins were shared between the two cell types, twelve proteins were induced de novo after infection of melanoma cells with RD114 virus in vitro. Expression of these proteins in trans-differentiated cells was significantly associated with concomitant down regulation of growth promoting proteins and up-regulation of neurogenic proteins (p = < 0.001). Based on their physiologic properties, >95% proteins expressed in trans-differentiated cells could be associated with the development, differentiation and regulation of nervous system cells. CONCLUSION: Our results indicate that the cat melanoma cells have the ability to differentiate into distinct neuronal cell types and they express proteins that are essential for self-renewal. Since melanocytes arise from the neural crest of the embryo, we conclude that this melanoma arose from embryonic precursor stem cells. This model system provides a unique opportunity to identify domains of interactions between the expressed proteins that halt the tumorigenic potential of melanoma cells and drive them toward neurogenerative pathways involved in early neurogenesis. A better understanding of these proteins in a well-coordinated signaling network would also help in developing novel approaches for suppression of highly malignant tumors that arise from stem-like embryonic cells.

Ovariectomy induces a shift in fuel availability and metabolism in the hippocampus of the female transgenic model of familial Alzheimer's.

Previously, we demonstrated that reproductive senescence in female triple transgenic Alzheimer's (3×TgAD) mice was paralleled by a shift towards a ketogenic profile with a concomitant decline in mitochondrial activity in brain, suggesting a potential association between ovarian hormone loss and alteration in the bioenergetic profile of the brain. In the present study, we investigated the impact of ovariectomy and 17ß-estradiol replacement on brain energy substrate availability and metabolism in a mouse model of familial Alzheimer's (3×TgAD). Results of these analyses indicated that ovarian hormones deprivation by ovariectomy (OVX) induced a significant decrease in brain glucose uptake indicated by decline in 2-[(18)F]fluoro-2-deoxy-D-glucose uptake measured by microPET-imaging. Mechanistically, OVX induced a significant decline in blood-brain-barrier specific glucose transporter expression, hexokinase expression and activity. The decline in glucose availability was accompanied by a significant rise in glial LDH5 expression and LDH5/LDH1 ratio indicative of lactate generation and utilization. In parallel, a significant rise in ketone body concentration in serum occurred which was coupled to an increase in neuronal MCT2 expression and 3-oxoacid-CoA transferase (SCOT) required for conversion of ketone bodies to acetyl-CoA. In addition, OVX-induced decline in glucose metabolism was paralleled by a significant increase in Aß oligomer levels. 17ß-estradiol preserved brain glucose-driven metabolic capacity and partially prevented the OVX-induced shift in bioenergetic substrate as evidenced by glucose uptake, glucose transporter expression and gene expression associated with aerobic glycolysis. 17ß-estradiol also partially prevented the OVX-induced increase in Aß oligomer levels. Collectively, these data indicate that ovarian hormone loss in a preclinical model of Alzheimer's was paralleled by a shift towards the metabolic pathway required for metabolism of alternative fuels in brain with a concomitant decline in brain glucose transport and metabolism. These findings also indicate that estrogen plays a critical role in sustaining brain bioenergetic capacity through preservation of glucose metabolism.

Early intervention with an estrogen receptor ß-selective phytoestrogenic formulation prolongs survival, improves spatial recognition memory, and slows progression of amyloid pathology in a female mouse model of Alzheimer's disease.

Our recent developments have yielded a novel phytoestrogenic formulation, referred to as the phyto-ß-SERM formulation, which exhibits an 83-fold binding selectivity for the estrogen receptor subtype ß (ERß) over ERα. Earlier studies indicate that the phyto-ß-SERM formulation is neuroprotective and promotes estrogenic mechanisms in the brain while devoid of feminizing activity in the periphery. Further investigation in a mouse model of human menopause indicates that chronic exposure to the phyto-ß-SERM formulation at a clinically relevant dosage prevents/alleviates menopause-related climacteric symptoms. This study assessed the efficacy, in an early intervention paradigm, of the phyto-ß-SERM formulation in the regulation of early stages of physical and neurological changes associated with Alzheimer's disease (AD) in a female triple transgenic mouse model of AD. Results demonstrated that, when initiated prior to the appearance of AD pathology, a 9-month dietary supplementation with the phyto-ß-SERM formulation promoted physical health, prolonged survival, improved spatial recognition memory, and attenuated amyloid-ß deposition and plaque formation in the brains of treated AD mice. In comparison, dietary supplementation of a commercial soy extract preparation showed no effect on cognitive measures, although it appeared to have a positive impact on amyloid pathology. In overall agreement with the behavioral and histological outcomes, results from a gene expression profiling analysis offered insights on the underlying molecular mechanisms associated with the two dietary treatments. In particular, the data suggests that there may be a crosstalk between ERß and glycogen synthase kinase 3 signaling pathways that could play a role in conferring ERß-mediated neuroprotection against AD. Taken together, these results support the therapeutic potential of the phyto-ß-SERM formulation for prevention and/or early intervention of AD, and warrants further investigations in human studies.

Potentiation of brain mitochondrial function by S-equol and R/S-equol estrogen receptor ß-selective phytoSERM treatments.

Previously we developed an estrogen receptor ß-selective phytoestrogenic (phytoSERM) combination, which contains a mixture of genistein, daidzein, and racemic R/S-equol. The phytoSERM combination was found neuroprotective and non-feminizing both in vitro and in vivo. Further, it prevented or alleviated physical and neurological changes associated with human menopause and Alzheimer's disease. In the current study, we conducted translational analyses to compare the effects of racemic R/S-equol-containing with S-equol-containing phytoSERM therapeutic combinations on mitochondrial markers in rat hippocampal neuronal cultures and in a female mouse ovariectomy (OVX) model. Data revealed that both the S-equol and R/S-equol phytoSERM treatments regulated mitochondrial function, with S-equol phytoSERM combination eliciting greater response in mitochondrial potentiation. Both phytoSERM combination treatments increased expression of key proteins and enzymes involved in energy production, restored the OVX-induced decrease in activity of key bioenergetic enzymes, and reduced OVX-induced increase in lipid peroxidation. Comparative analyses on gene expression profile revealed similar regulation between S-equol phytoSERM and R/S-equol phytoSERM treatments with minimal differences. Both combinations regulated genes involved in essential bioenergetic pathways, including glucose metabolism and energy sensing, lipid metabolism, cholesterol trafficking, redox homeostasis and ß-amyloid production and clearance. Further, no uterotrophic response was induced by either of the phytoSERM combinations. These findings indicate translational validity for development of an ER ß selective S-equol phytoSERM combination as a nutraceutical to prevent menopause-associated symptoms and to promote brain metabolic activity. This article is part of a Special Issue entitled Hormone Therapy.

Continuous versus cyclic progesterone exposure differentially regulates hippocampal gene expression and functional profiles.

This study investigated the impact of chronic exposure to continuous (CoP4) versus cyclic progesterone (CyP4) alone or in combination with 17ß-estradiol (E2) on gene expression profiles targeting bioenergetics, metabolism and inflammation in the adult female rat hippocampus. High-throughput qRT-PCR analyses revealed that ovarian hormonal depletion induced by ovariectomy (OVX) led to multiple significant gene expression alterations, which were to a great extent reversed by co-administration of E2 and CyP4. In contrast, co-administration of E2 and CoP4 induced a pattern highly resembling OVX. Bioinformatics analyses further revealed clear disparities in functional profiles associated with E2+CoP4 and E2+CyP4. Genes involved in mitochondrial energy (ATP synthase α subunit; Atp5a1), redox homeostasis (peroxiredoxin 5; Prdx5), insulin signaling (insulin-like growth factor I; Igf1), and cholesterol trafficking (liver X receptor α subtype; Nr1h3), differed in direction of regulation by E2+CoP4 (down-regulation relative to OVX) and E2+CyP4 (up-regulation relative to OVX). In contrast, genes involved in amyloid metabolism (ß-secretase; Bace1) differed only in degree of regulation, as both E2+CoP4 and E2+CyP4 induced down-regulation at different efficacy. E2+CyP4-induced changes could be associated with regulation of progesterone receptor membrane component 1(Pgrmc1). In summary, results from this study provide evidence at the molecular level that differing regimens of hormone therapy (HT) can induce disparate gene expression profiles in brain. From a translational perspective, confirmation of these results in a model of natural menopause, would imply that the common regimen of continuous combined HT may have adverse consequences whereas a cyclic combined regimen, which is more physiological, could be an effective strategy to maintain neurological health and function throughout menopausal aging.

2-Deoxy-D-glucose treatment induces ketogenesis, sustains mitochondrial function, and reduces pathology in female mouse model of Alzheimer's disease.

Previously, we demonstrated that mitochondrial bioenergetic deficits preceded Alzheimer's disease (AD) pathology in the female triple-transgenic AD (3xTgAD) mouse model. In parallel, 3xTgAD mice exhibited elevated expression of ketogenic markers, indicating a compensatory mechanism for energy production in brain. This compensatory response to generate an alternative fuel source was temporary and diminished with disease progression. To determine whether this compensatory alternative fuel system could be sustained, we investigated the impact of 2-deoxy-D-glucose (2-DG), a compound known to induce ketogenesis, on bioenergetic function and AD pathology burden in brain. 6-month-old female 3xTgAD mice were fed either a regular diet (AIN-93G) or a diet containing 0.04% 2-DG for 7 weeks. 2-DG diet significantly increased serum ketone body level and brain expression of enzymes required for ketone body metabolism. The 2-DG-induced maintenance of mitochondrial bioenergetics was paralleled by simultaneous reduction in oxidative stress. Further, 2-DG treated mice exhibited a significant reduction of both amyloid precursor protein (APP) and amyloid beta (Aß) oligomers, which was paralleled by significantly increased α-secretase and decreased γ-secretase expression, indicating that 2-DG induced a shift towards a non-amyloidogenic pathway. In addition, 2-DG increased expression of genes involved in Aß clearance pathways, degradation, sequestering, and transport. Concomitant with increased bioenergetic capacity and reduced ß-amyloid burden, 2-DG significantly increased expression of neurotrophic growth factors, BDNF and NGF. Results of these analyses demonstrate that dietary 2-DG treatment increased ketogenesis and ketone metabolism, enhanced mitochondrial bioenergetic capacity, reduced ß-amyloid generation and increased mechanisms of ß-amyloid clearance. Further, these data link bioenergetic capacity with ß-amyloid generation and demonstrate that ß-amyloid burden was dynamic and reversible, as 2-DG reduced activation of the amyloidogenic pathway and increased mechanisms of ß-amyloid clearance. Collectively, these data provide preclinical evidence for dietary 2-DG as a disease-modifying intervention to delay progression of bioenergetic deficits in brain and associated ß-amyloid burden.

Estrogen receptor ß-selective phytoestrogenic formulation prevents physical and neurological changes in a preclinical model of human menopause.

OBJECTIVE: As an alternative to estrogen therapy, the efficacy of an estrogen receptor ß-selective phytoestrogenic (phyto-ß-SERM) formulation to regulate climacteric symptoms and decline in brain responses associated with ovarian hormone loss in menopause was assessed. METHODS: A phyto-ß-SERM formulation-containing diet was compared with a commercial soy extract diet and a phytoestrogen-free base/control diet in an ovariectomized (OVX) mouse model of human menopause. Two treatment studies were conducted: (1) a 2-month study assessed the effects of experimental diets on tail skin temperature as a model of menopausal hot flashes, and (2) a 9-month study assessed the long-term impact of the diets on overall health, hair thinning/loss, spatial working memory, and associated protein expression in the hippocampus. RESULTS: The phyto-ß-SERM diet prevented OVX-induced menopause-like changes including the rise in skin temperature, hair thinning/loss, deficit in spatial memory function, and reversed OVX-induced decline in the expression of hippocampal proteins involved in neural plasticity and ß-amyloid degradation/clearance. The soy extract diet had no effect or exacerbated OVX-induced changes. CONCLUSIONS: Overall, the phyto-ß-SERM diet induced physical and neurological responses comparable with ovary-intact mice, suggesting the therapeutic potential of the phyto-ß-SERM formulation for the prevention/alleviation of climacteric symptoms and decline in brain responses induced by ovarian hormone loss, which provides the basis for further work in postmenopausal women.

17ß-Estradiol regulates insulin-degrading enzyme expression via an ERß/PI3-K pathway in hippocampus: relevance to Alzheimer's prevention.

Insulin-degrading enzyme (IDE), an enzyme that primarily degrades insulin, has recently been demonstrated to play a significant role in the catabolism of amyloid ß (Aß) protein in the brain. Reduced IDE expression and/or activity have been associated with the etiology and development of Alzheimer's disease (AD). Using three model systems, the present investigation provides the first documentation indicating that estrogen robustly regulates the expression of IDE in normal, menopausal and early-stage AD brains. In vitro analyses in primary cultures of rat hippocampal neurons revealed that 17ß-estradiol (17ß-E2) increased IDE in both mRNA and protein levels in a time-dependent manner. Further pharmacological analyses indicated that 17ß-E2-induced IDE expression was dependent upon estrogen receptor (ER) ß and required activation of phosphatidylinositol 3-kinase (PI3-K). In vivo analyses in adult female rats revealed a brain region-specific responsive profile. Ovariectomy (OVX) induced a significant decline in IDE expression in the hippocampus, which was prevented by 17ß-E2. Neither OVX nor 17ß-E2 affected IDE expression in the cerebellum. In vivo analyses in triple transgenic AD (3xTg-AD) female mice revealed an inverse correlation between the age-related increase in Aß load and the decrease in IDE expression in the hippocampal formation. Treatment with 17ß-E2 attenuated Aß accumulation/plaque formation and elevated hippocampal IDE expression in 12-month-old 3xTg-AD OVX mice. Collectively, these findings indicate that 17ß-E2 regulates IDE expression in a brain region-specific manner and such a regulatory role in the hippocampus, mediated by an ERß/PI3-K pathway, could serve as a direct mechanism underlying estrogen-mediated preventative effect against AD when initiated at the onset of menopause.

The effect of dietary soy isoflavones before and after ovariectomy on hippocampal protein markers of mitochondrial bioenergetics and antioxidant activity in female monkeys.

Estrogen therapy can promote cognitive function if initiated within a 'critical window' during the menopausal transition. However, in the absence of a progestogen, estrogens increase endometrial cancer risk which has spurred research into developing estrogenic alternatives that have the beneficial effects of estrogen but which are clinically safer. Soy protein is rich in isoflavones, which are a class of potential estrogenic alternatives. We sought to determine the effects of two diets, one with casein-lactalbumin as the main protein source and the other with soy protein containing isoflavones, on protein markers of hippocampal bioenergetic capacity in adult female cynomolgus macaques (Macaca fascicularis). Further, we assessed the effects of dietary soy isoflavones before or after ovariectomy. Animals receiving soy diet premenopausally then casein/lactalbumin post-ovariectomy had higher relative hippocampal content of glycolytic enzymes glyceraldehyde 3-phosphate dehydrogenase and pyruvate dehydrogenase subunit e1α. Post-ovariectomy consumption of soy was associated with higher succinate dehydrogenase α levels and lower levels of isocitrate dehydrogenase, both proteins involved in the tricarboxylic acid cycle, significantly decreased expression of the antioxidant enzyme peroxiredoxin-V, and a non-significant trend towards decreased manganese superoxide dismutase expression. None of the diet paradigms significantly affected expression levels of oxidative phosphorylation enzyme complexes, or of mitochondrial fission and fusion proteins. Together, these data suggest that long-term soy diet produces minimal effects on hippocampal expression of proteins involved in bioenergetics, but that switching between a diet containing primarily animal protein and one containing soy isoflavones before and after menopause may result in complex effects on brain chemistry.

Hippocampal responsiveness to 17ß-estradiol and equol after long-term ovariectomy: implication for a therapeutic window of opportunity.

A 'critical window of opportunity' has been proposed for the efficacy of ovarian hormone intervention in peri- and post-menopausal women. We sought to address this hypothesis using a long-term ovariectomized non-human primate (NHP) model, the cynomolgus macaque (Macaca fascicularis). In these studies, we assessed the ability of 17ß-estradiol and equol to regulate markers of hippocampal bioenergetic capacity. Results indicated that 17ß-estradiol treatment significantly increased expression of mitochondrial respiratory chain proteins complex-I and -III in the hippocampus when compared to non-hormone-treated animals. Expression of the TCA cycle protein succinate dehydrogenase α was decreased in animals treated with equol compared to those treated with 17ß-estradiol. There were no significant effects of either 17ß-estradiol or equol treatment on glycolytic protein expression in the hippocampus, nor were there significant effects of treatment on expression levels of antioxidant enzymes. Similarly, 17ß-estradiol and equol treatment had no effect on mitochondrial fission and fusion protein expression. In summary, findings indicate that while 17ß-estradiol induced a significant increase in several proteins, the overall profile of bioenergetic system proteins was neutral to slightly positively responsive. The profile of responses with the ERß-preferring molecule equol was consistent with overall nonresponsiveness. Collectively, the data indicate that long-term ovariectomy is associated with a decline in response to estrogens and estrogen-like compounds. By extension, the data are consistent with a primary tenet of the critical window hypothesis, i.e., that the brains of post-menopausal women ultimately lose their ability to respond positively to estrogenic stimulation.

A select combination of clinically relevant phytoestrogens enhances estrogen receptor beta-binding selectivity and neuroprotective activities in vitro and in vivo.

We have previously shown that a number of naturally occurring phytoestrogens and derivatives were effective to induce some measures of neuroprotective responses but at a much lower magnitude than those induced by the female gonadal estrogen 17beta-estradiol. In the present study, we sought to investigate whether a combination of select phytoestrogens could enhance neural responses without affecting the reproductive system. We performed a range of comparative analyses of the estrogen receptor (ER) alpha/beta binding profile, and in vitro to in vivo estrogenic activities in neural and uterine tissues induced by clinically relevant phytoestrogens: genistein, daidzein, equol, and IBSO03569, when used alone or in combination. Our analyses revealed that both the ERalpha/beta binding profile and neural activities associated with individual phytoestrogens are modifiable when used in combination. Specifically, the combination of genistein plus daidzein plus equol resulted in the greatest binding selectivity for ERbeta and an overall improved efficacy/safety profile when compared with single or other combined formulations, including: 1) an approximate 30% increase in ERbeta-binding selectivity (83-fold over ERalpha); 2) a greater effect on neuronal survival against toxic insults in primary neurons; 3) an enhanced activity in promoting neural proactive defense mechanisms against neurodegeneration, including mitochondrial function and beta-amyloid degradation; and 4) no effect on uterine growth. These observations suggest that select phytoestrogens in combination have the therapeutic potential of an alternative approach to conventional estrogen therapy for long-term safe use to reduce the increased risk of cognitive decline and neurodegenerative disease associated with menopause in women.

Inferring protein-protein interaction networks from protein complex data.

Present day approaches for the determination of protein-protein interaction networks are usually based on two hybrid experimental measurements. Here we consider a computational method that uses another type of experimental data: instead of direct information about protein-protein interactions, we consider data in the form of protein complexes. We propose a method for using these complexes to provide predictions of protein-protein interactions. When applied to a dataset obtained from a cat melanoma cell line we find that we are able to predict when a protein pair belongs to a complex with approximately 96% accuracy. Further, we are able to extrapolate the experimentally identified interaction pairs to the entire cat proteome.