Steroidogenic acute regulatory protein mediated variations of gender-specific sex neurosteroids in Alzheimer's disease: Relevance to hormonal and neuronal imbalance.

The steroidogenic acute regulatory (StAR) protein mediates the rate-liming step in neuro/steroid biosynthesis. Multifaceted and delicate changes during aging, disrupting hormonal and neuronal homeostasis, constitute human senescence, an inevitable phenomenon that attributes to increased morbidity and mortality. Aging, along with progressive decreases in bioactive neurosteroids, is the primary risk factor for Alzheimer's disease (AD), which preferentially impacts two-thirds of women and one-third of men. AD is neuropathologically characterized by the accumulation of extracellular amyloid-β and intracellular phosphorylated Tau containing neurofibrillary tangles, resulting in dementia. Postmortem brains pertaining to gender-specific AD patients exhibit varied suppression of StAR and sex neurosteroid levels compared with age-matched cognitively healthy subjects, in which the attenuation of StAR is inversely correlated with the AD pathological markers. Interestingly, retinoid signaling upregulates StAR-motivated neurosteroid biosynthesis and reinstates various neurodegenerative vulnerabilities that promote AD pathogenesis. This review summarizes current understanding of StAR-driven alterations of sex neurosteroids in gender-specific AD risks and provides biochemical and molecular insights into therapeutic interventions for preventing and/or alleviating dementia for healthy aging.