Neuroprotective Effects of Estrogens: Cross-Talk Between Estrogen and Intracellular Insulin Signalling

The incidence of neurodegenerative diseases is higher in postmenopausal women that young women. In this sense, Alzheimer's and Parkinson's diseases, ischemic brain injury and memory or cognitive dysfunction increase dramatically when the ovarian function declines. On the other hand, insulin resistance represents an independent factor in the etiology of age-associated coronary and cerebrovascular disease. Therefore, depression, neurodegenerative diseases such as Alzheimer's and Parkinson's diseases and memory or cognitive dysfunction should be considered, in some cases, a result of metabolic syndrome, and that postmenopausal women are more vulnerable that young women to these diseases. Several studies have suggested that the molecular mechanism by which estradiol exerts its neuroprotective effects involves activation of the PI3-k signalling pathway, which is activated by insulin and IGF-1. Therefore, it seems possible that ERα can interact with these signalling pathways, mainly with PI3-k and IRS-1, to promote neuroprotective effects in the brain. In particular, IGF-I seems to be particularly important in the process of neuroprotection; it can reverse age-related effects and attenuate the age-related decrease in cerebral glucose utilization. Moreover, gonadal hormones have been found to regulate IGF-I receptor. Therefore, it seems clear that the interaction of both systems plays a role in the prevention of neuronal age-related effects. These findings suggest that by interacting with some components of the IGF-I signalling pathway, ERα affects the actions of IGF-I in the brain and suggest future avenues of research. The relationship between insulin resistance states associated with aging in females, and the cross-talk between estradiol and proteins includes in the IRS-1/PI3-k/Akt and IGF-1-IR signalling pathways, will lead to a more complete understanding of the precise mechanism underlying estradiol-mediated neuroprotection. Numerous clinical studies have demonstrated that the incidence of neurodegenerative diseases in higher in postmenopausal women that young women. In this sense, Alzheimer's and Parkinson's disease, ischemic brain injury and memory or cognitive dysfunction increase dramatically when the ovarian function declines. Moreover, estrogen replacement therapy seems to be a good element in order to decrease the risk and/or severity of neurodegenerative conditions, and it would be able to improve some aspects related to memory and learning process.