Dr. D.Y. Patil Biotechnology & Bioinformatics Institute
Phytoestrogens are plant-derived compounds that contain estrogen, particularly found in soy and red clover. It is a diverse group of naturally occurring nonsteroidal plant compounds. Their structure is similar to estradiol (1,7-β-estradiol), having the ability to produce estrogenic/antiestrogenic factors. Due to similarities in the molecular level, phytoestrogen sometimes mildly mimics its estrogen counterpart. Phytoestrogens belong to the class of natural phenolic compounds. The coumestans, prenylflavonoids, and isoflavones are three of the most active in the class of natural phenolic compounds in estrogenic effects, out of which the best researched and the most bioavailable is isoflavones. Major isoflavones in soybean include genistein, daidzein and an intermediate pathway product known as naringenin, which is sequentially converted into the isoflavone genistein by two legume-specific enzymes, isoflavone synthase, and a dehydratase. Phytoestrogens are believed to have the function of cognition-promoting agents via the estrogen receptors.
Before diving into the brief cognizance between Phytoestrogen and Alzheimer’s disease, here is a short synopsis of the disease. Dementia, the common form of the Alzheimer’s disease is a neurodegenerative disorder characterized by a major loss of cognitive function. Usually, menopausal women are placed at the highest risk because natural aging in the woman causes a decrease in concentrations of estrogen. The continuous lack of estrogen results in the degradation of estrogen receptors in the brain. Incidentally, lack of receptors is linked to a gradual decline in cognition and impairment in memory. Neuroprotective effects potentially exhibited by phytoestrogens have been extensively researched to address the increasing problems of Alzheimer’s disease. Therefore, the prevalence of dementia in women was statistically higher compared to men as studies by the scientists. So, to avert this dangerous disorder, hormone replacement therapy (HRT) was used. Unfortunately, continuous exposure to HRT leads to cancers, strokes, and thrombosis.
Hence, phytoestrogens can be considered as the best replacement without causing major side effects compared to the factory manufactured hormones. Although there is saying — “Too much of something is not good”, similarly, one should be careful with the higher intake of phytoestrogen as the repercussions may include- hormonal imbalance, breast cancer and endometriosis. Therefore, diet plays a vital role in determining the severity of the disorder and to retain the poise of the nutrition. The pathway of this disease is complex. Aβ toxicity is the abnormal modification of tau protein (Cell skeleton structure modifier) has been widely accepted as the possible mechanism to Alzheimer’s disease because Aβs have been detected as senile plaques in the brain tissues of Alzheimer’s disease. Therefore, phytoestrogens, particularly soyabean’s isoflavones, protect neurons and prevent brain cell degeneration by anti-oxidation. Genisin being the bioactive form has been used and reported to enhance the spatial memory of the patients.
Phytoestrogens can protect brain tissues and nerve cells by exerting antioxidant, anti-inflammatory, and anti-apoptotic effects and by providing vascular endothelial protection to improve synapse function and prevent Alzheimer’s disease. Additional studies are necessary to explore the underlying mechanisms of the antiapoptotic and estrogen-like effects of phytoestrogens on Alzheimer’s disease. Furthermore, large-scale population studies and interference experiments must be conducted to deliver a highly effective theoretical foundation for the prevention and treatment of the disease.
Secondly, oxidative stress-induced cellular apoptosis is one of the initiations of Alzheimer’s disease, with mitochondria being the key organelle to protect the neurons. Phytoestrogens also increase the activity of antioxidant enzymes such as catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase, and can have a defensive outcome counter to oxidative stress and accumulation of oxidative damage. Phytoestrogen up-regulates the antiapoptotic genes and down-regulates the proapoptotic genes. Genisin alone or in combination with FA down-regulates caspase-3 and Bax and up-regulates Bcl-2, exhibiting antiapoptotic effects. However, the underlying molecular mechanism remains unclear.