Allopregnanolone-based treatments for postpartum depression: Why/how do they work?

Progesterone - Friend or foe?

Estradiol is the "prototypic" sex hormone of women. Yet, women have another sex hormone, which is often disregarded: Progesterone. The goal of this article is to provide a comprehensive review on progesterone, and its metabolite allopregnanolone, emphasizing three key areas: biological properties, main functions, and effects on mood in women. Recent years of intensive research on progesterone and allopregnanolone have paved the way for new treatment of postpartum depression. However, treatment for premenstrual syndrome and premenstrual dysphoric disorder as well as contraception that women can use without risking mental health problems are still needed. As far as progesterone is concerned, we might be dealing with a two-edged sword: while its metabolite allopregnanolone has been proven useful for treatment of PPD, it may trigger negative symptoms in women with PMS and PMDD. Overall, our current knowledge on the beneficial and harmful effects of progesterone is limited and further research is imperative.

PPAR and functional foods: Rationale for natural neurosteroid-based interventions for postpartum depression

Allopregnanolone, a GABAergic neurosteroid and progesterone derivative, was recently approved by the Food and Drug Administration for the treatment of postpartum depression (PPD). Several mechanisms appear to be involved in the pathogenesis of PPD, including neuroendocrine dysfunction, neuroinflammation, neurotransmitter alterations, genetic and epigenetic modifications. Recent evidence highlights the higher risk for incidence of PPD in mothers exposed to unhealthy diets that negatively impact the microbiome composition and increase inflammation, all effects that are strongly correlated with mood disorders. Conversely, healthy diets have consistently been reported to decrease the risk of peripartum depression and to protect the body and brain against low-grade systemic chronic inflammation. Several bioactive micronutrients found in the so-called functional foods have been shown to play a relevant role in preventing neuroinflammation and depression, such as vitamins, minerals, omega-3 fatty acids and flavonoids. An intriguing molecular substrate linking functional foods with improvement of mood disorders may be represented by the peroxisome-proliferator activated receptor (PPAR) pathway, which can regulate allopregnanolone biosynthesis and brain-derived neurotropic factor (BDNF) and thereby may reduce inflammation and elevate mood. Herein, we discuss the potential connection between functional foods and PPAR and their role in preventing neuroinflammation and symptoms of PPD through neurosteroid regulation. We suggest that healthy diets by targeting the PPAR-neurosteroid axis and thereby decreasing inflammation may offer a suitable functional strategy to prevent and safely alleviate mood symptoms during the perinatal period.

Allopregnanolone: From molecular pathophysiology to therapeutics. A historical perspective

Allopregnanolone is synthesized in the central nervous system either de novo from cholesterol or from steroid hormone precursors like progesterone and pregnenolone. Over the past 30 years, direct and rapid, non-genomic actions of allopregnanolone and its derivatives via GABA_A receptors have been demonstrated. Changes in brain levels of allopregnanolone during pregnancy and in the postpartum period, or during exposure to protracted stress appear to play a crucial role in the pathophysiology of mood disorders. The discovery that allopregnanolone at low (nanomolar) concentrations elicits marked anxiolytic, anti-stress and antidepressant effects by facilitating allosterically the action of GABA at extrasynaptic GABA_A receptors has provided new perspectives for the discovery of novel drugs useful for the treatment of mood disorders. These findings have led to the seminal clinical studies that recently demonstrated that treatment with allopregnanolone (i.e., brexanolone) can dramatically and rapidly improve the symptoms of postpartum depression in many patients.