Effects of Hydroalcoholic Extract of Soy on Learning, Memory and Synaptic Plasticity Deficits Induced by Seizure in Ovariectomized Rats

Roles of genistein in learning and memory during aging and neurological disorders

Genistein (GEN) is a non-steroidal phytoestrogen that belongs to the isoflavone class. It is abundantly found in soy. Soy and its products are used as food components in many countries including India. The present review is focused to address roles of GEN in brain functions in the context of learning and memory as a function of aging and neurological disorders. Memory decline is one of the most disabling features observed during normal aging and age-associated neurodegenerative disorders namely Alzheimer's disease (AD) and Parkinson's disease (PD), etc. Anatomical, physiological, biochemical and molecular changes in the brain with advancement of age and pathological conditions lead to decline of cognitive functions. GEN is chemically comparable to estradiol and binds to estrogen receptors (ERs). GEN acts through ERs and mimics estrogen action. After binding to ERs, GEN regulates a plethora of brain functions including learning and memory; however detailed study still remains elusive. Due to the neuroprotective, anti-oxidative and anti-inflammatory properties, GEN is used to restore or improve memory functions in different animal models and humans. The present review may be helpful to understand roles of GEN in learning and memory during aging and neurological disorders, its direction of research and therapeutic perspectives.

Ameliorating Effect of Standardized Extract From Textured Soy Protein (Glycine max L.) on Memory Deficit and Learning Insufficiency in Scopolamine-induced Amnesia

Introduction

Textured soy protein (TSP) and nuts are two processed forms of soybean (Glycine max L.) that are widely consumed for nutritional purposes in Iran. Recently, we have reported the antioxidant and anticholinesterase effects of raw soybean (RS) attributed to isoflavones, such as genistein. In this work, we aimed to compare in vitro antioxidant and anticholinesterase effects of TSP, nuts, and RS to select the most effective one for learning capacity and spatial memory studies.

Methods

Genistein content was determined using high-performance thin layer chromatography (HPTLC), while diphenylpicrylhydrazil (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) were used to study antioxidant evaluation and Ellman's colorimetric method was used to measure anticholinesterase. TSP extract (TSPE) was administered to male rats (100 mg/kg, 200 mg/kg and 400 mg/kg, intraperitoneally [i.p] for 7 days) before scopolamine injection (1 mg/kg). Learning capacity and spatial memory were evaluated using passive avoidance test (PAT) and Morris water maze (MWM) methods compared to physostigmine and piracetam.

Results

The greatest antioxidant and anticholinesterase effect was observed for TSPE, which significantly prolonged initially latency in PTA (P<0.05) and improved all indicators in the MWM test at 200 mg/kg.

Conclusion

The memory-improving effect of TSPE may be due to its antioxidant and anticholinesterase effect as well as neuroprotective effects of its isoflavones.

Highlights

Different samples (nuts-raw soybeans-TSP) prepared from soybeans.All samples exhibited antioxidant and anti-cholinesterase effects in vitro studies.TSP showed the most biological activity and the greatest genistein content.TSP significantly improved memory and learning indicators at 200 mg/kg.These effects are attributed to its antioxidant and anticholinesterase activity.Plant isoflavones have neuroprotective effects.

Plain Language Summary

Alzheimer's disease (AD), is one of the problems of the elderly society, which has a lot of emotional and financial costs. AD is a type of progressive brain disease in which neurons are destroyed and memory is lost. This disease currently has no definitive treatment and the only way is to prevent the disease from spreading. Much research has been devoted to finding suitable and effective treatments for AD. Many food and herbal medicines have shown to be effective in controlling this disease. Soybean is a plant that is widely used as food and snacks in Iran in different ways. In this study, we prepared three preparation from soya beans which have been widely used by Iranian people including raw soya, nut (roasted form) and textured soy protein (TSP). The effect of these preparations have been studied on memory and learning in amnestic rats through different pharmacological studies. The results indicated that TSP due to antioxidant and anticholinesterase activity significantly can augment memory enhancing and learning ability Alzheimer's disease (AD), is one of the problems of the elderly society, which has a lot of emotional and financial costs. AD is a type of progressive brain disease in which neurons are destroyed and memory is lost. This disease currently has no definitive treatment and the only way is to prevent the disease from spreading. Much research has been devoted to finding suitable and effective treatments for AD. Many food and herbal medicines have shown to be effective in controlling this disease. Soybean is a plant that is widely used as food and snacks in Iran in different ways. In this study, we prepared three preparation from soya beans which have been widely used by Iranian people including raw soya, nut (roasted form) and textured soy protein (TSP). The effect of these preparations have been studied on memory and learning in amnestic rats through different pharmacological studies. The results indicated that TSP due to antioxidant and anticholinesterase activity significantly can augment memory enhancing and learning ability. TSP also contains some phytochemicals such as phytoestrogens which have shown neuroprotective activity in different studies.

Chronic modafinil therapy ameliorates depressive-like behavior, spatial memory and hippocampal plasticity impairments, and sleep-wake changes in a surgical mouse model of menopause

Depression, cognitive deficits, and sleep disturbances are common and often severe in menopausal women. Hormone replacement cannot effectively alleviate these symptoms and sometimes elicits life-threatening adverse reactions. Exploring effective therapies to target psychological problems is urgently needed. In this work, we developed a mouse model of menopause by bilateral ovariectomies (OVXs) and investigated whether menopausal mental symptoms can be ameliorated by psychostimulant modafinil (MOD) as well as explored the underlying mechanisms. At ~3 weeks after OVXs, mice got daily intraperitoneal administrations of MOD at the beginning of the active phase. Several behavioral tests and electroencephalogram (EEG) recordings were conducted. Electrophysiological and immunohistochemical experiments were carried out to evaluate the synaptic plasticity and neurogenesis, respectively. We found that chronic MOD administration in OVX mice significantly decreased immobility time. The spatial memory performance of OVX mice improved significantly in response to MOD administration in the Morris water-maze test. The OVX mice were characterized by an attenuation of hippocampal synaptic transmission and synaptic long-term potentiation and had fewer 5-ethynyl-2'-deoxyuridine-labeled cells in the dentate gyrus, which were restored after MOD administration. Antagonists of dopamine D₁ and D₂ receptors and GABA_A receptor agonists were involved in MOD-exerted anti-depressant actions and augments of hippocampal neurogenesis in OVX mice. Moreover, night-dosed MOD therapy significantly promoted the night-time delta-band EEG power during wakefulness and the day-time rapid eye movement sleep amount, which were significantly reduced by OVXs. Collectively, these findings suggest that MOD is a promising therapeutic candidate for menopausal women.

Daidzein Pro-cognitive Effects Coincided with Changes of Brain Neurotensin1 Receptor and Interleukin-10 Expression Levels in Obese Hamsters

At present, concerns are pointing to "tasteful" high-fat diets as a cause of conditioning physical-social states that through alterations of some key emotional- and nutritional-related limbic circuits such as hypothalamic and amygdalar areas lead to obesity states. Feeding and energetic homeostatic molecular mechanisms are part of a complex neuronal circuit accounting for this metabolic disorder. In an attempt to exclude conventional drugs for treating obesity, daidzein, a natural glycosidic isoflavone, which mimics estrogenic neuroprotective properties against increased body weight, is beginning to be preferred. In this study, evident anxiolytic-like behaviors were detected following treatment of high-fat diet hamsters with daidzein as shown by extremely evident (p < 0.001) exploration tendencies in novel object recognition test and a notably greater amount of time spent (p < 0.01) in open arms of elevated plus maze. Moreover, the isoflavone promoted a protective role against neurodegeneration processes as shown by few, if any, amino cupric silver granules in amygdalar, hypothalamic and hippocampal neuronal fields when compared with obese hamsters. Interestingly, elevated expression levels of the anorexic neuropeptide receptor neurotensin1 in the above limbic areas of obese hamsters were extremely reduced by daidzein, especially during recovery of cognitive events. Contextually, such effects were strongly paralleled by increased levels of the anti-neuroinflammatory cytokine, interleukin-10. Our results corroborate a neuroprotective ability of this natural glycosidic isoflavone, which through its interaction with the receptor neurotensin1 and interleukin-10 pathways is correlated not only to improved feeding states, and subsequently obesity conditions, but above all to cognitive performances.

Depletion of dietary phytoestrogens reduces hippocampal plasticity and contextual fear memory stability in adult male mouse

Introduction: Phytoestrogens are non-steroidal estrogen analogues and are found primarily in soy products. They have received increasing attention as dietary supplements for estrogen deficiency and as modulators of endogenous estrogen functions, including cognition and emotion. In addition to modifying the levels of circulating sex hormones, phytoestrogens also exert direct effects on estrogen and androgen receptors in the brain and thus effectively modulate the neural circuit functions.Objective: The aim of this study was to investigate the long-term effects of low phytoestrogen intake (∼6 weeks) on the hippocampal plasticity and hippocampus-dependent memory formation in the adult C57BL/6 male mice.Methods and Results: In comparison to mice on a diet with normal phytoestrogen content, mice on low phytoestrogen diet showed a significant reduction in the phosphorylation of NR2B subunit, a molecular correlate of plasticity in the Schaffer collateral-CA1 synapse. We observed a profound decrease in long-term potentiation (LTP) in the ventral hippocampus, whereas no effect on plasticity was evident in its dorsal portion. Furthermore, we demonstrated that acute perfusion of slices with an estrogen analogue equol, an isoflovane metabolized from daidzein produced by the bacterial flora in the gut, was able to rescue the observed LTP deficit. Examining potential behavioral correlates of the plasticity attenuation, we found that mice on phytoestrogen-free diet display decreased contextual fear memory at remote but not at recent time points after training.Conclusions: Our data suggests that nutritional phytoestrogens have profound effects on the plasticity in the ventral hippocampus and ventral hippocampus-dependent memory.