Gender differences in susceptibility to schizophrenia: Potential implication of neurosteroids

Mendelian randomization study of the relationship between blood and urine biomarkers and schizophrenia in the UK Biobank cohort

BACKGROUND

The identification of suitable biomarkers is of crucial clinical importance for the early diagnosis of treatment-resistant schizophrenia (TRS). This study aims to comprehensively analyze the association between TRS and blood and urine biomarkers.

METHODS

Candidate TRS-related single nucleotide polymorphisms (SNPs) were obtained from a recent genome-wide association study. The UK Biobank cohort, comprising 376,807 subjects with blood and urine biomarker testing data, was used to calculate the polygenic risk score (PRS) for TRS. Pearson correlation analyses were performed to evaluate the correlation between TRS PRS and each of the biomarkers, using calculated TRS PRS as the instrumental variables. Bidirectional two-sample Mendelian randomization (MR) was used to assess potential causal associations between candidate biomarkers with TRS.

RESULTS

Here we identify a significant association between TRS PRS and phosphate (r = 0.007, P = 1.96 × 10-4). Sex subgroup analyses identify seven and three candidate biomarkers associated with TRS PRS in male and female participants, respectively. For example, total protein and phosphate for males, creatinine and phosphate for females. Bidirectional two-sample MR analyses indicate that TRS is negatively associated with cholesterol (estimate = -0.363, P  = 0.008). Conversely, TRS is positively associated with total protein (estimate = 0.137, P  = 0.027), mean corpuscular volume (estimate = 0.032, P  = 2.25 × 10-5), and mean corpuscular hemoglobin (estimate = 0.018, P  = 0.007).

CONCLUSIONS

Our findings provide insights into the roles of blood and urine biomarkers in the early detection and treatment of TRS.

Vascular Schizophrenia-like Psychosis in Older Adults

BACKGROUND

The aims of this study were to analyze prevalence and severity of vascular risk factors in older patients referred to our clinic due to onset of Very Late-Onset Schizophrenia-Like Psychosis (VLOSLP) and to create a specific phenotype based on pathophysiological insight rather than age of onset.

METHODS

In a longitudinal study, 103 (M = 39, F = 64; mean age of 80.32 ± 7.65 years) patients were evaluated with cognitive, neuropsychiatric, and functional assessment scales. Blood concentration of hemoglobin (Hb), mean corpuscular volume (MCV), platelets, total protein test (TPT), creatinine, azotemia, glycemia, total cholesterol (TC), triglycerides (TG), uric acid (UA), sodium (Na), potassium (K), chlorine (Cl), calcium (Ca), folate, vitamin B12 (Vit-B12), and homocysteine were measured. Presence/absence of tobacco use, alcohol consumption, psychoactive substance use, hypertension, hyperlipidemia, diabetes mellitus, and history of vascular disease were collected.

RESULTS

Females were more apathetic than males (NPI-Apathy: p = 0.040). Males had a significantly higher level of Hb (p = 0.019) and UA (p = 0.001), and a lower level of platelets (p = 0.004) and Ca (p = 0.003), and used more tobacco (p = 0.046) and alcohol (p = 0.024) than females. Comparing patients < 80 and ≥80 years, we found differences in frequency of vascular risk factors among men (p = 0.027). In total, 102 patients were treated for psychosis (59.16% of them were using atypical antipsychotics).

CONCLUSIONS

The results of this study could be useful for a progressive demonstration of the causal relationship between cardiac and cerebral vascular events and VLOSLP.

Gender and Neurosteroids: Implications for Brain Function, Neuroplasticity and Rehabilitation

Neurosteroids are synthesized de novo in the nervous system; they mainly moderate neuronal excitability, and reach target cells via the extracellular pathway. The synthesis of neurosteroids occurs in peripheral tissues such as gonads tissues, liver, and skin; then, because of their high lipophilia, they cross the blood-brain barrier and are stored in the brain structure. Neurosteroidogenesis occurs in brain regions such as the cortex, hippocampus, and amygdala by enzymes necessary for the in situ synthesis of progesterone from cholesterol. Neurosteroids could be considered the main players in both sexual steroid-induced hippocampal synaptic plasticity and normal transmission in the hippocampus. Moreover, they show a double function of increasing spine density and enhancing long term potentiation, and have been related to the memory-enhancing effects of sexual steroids. Estrogen and progesterone affect neuronal plasticity differently in males and females, especially regarding changes in the structure and function of neurons in different regions of the brain. Estradiol administration in postmenopausal women allowed for improving cognitive performance, and the combination with aerobic motor exercise seems to enhance this effect. The paired association between rehabilitation and neurosteroids treatment could provide a boosting effect in order to promote neuroplasticity and therefore functional recovery in neurological patients. The aim of this review is to investigate the mechanisms of action of neurosteroids as well as their sex-dependent differences in brain function and their role in neuroplasticity and rehabilitation.

A Potential Mechanism Underlying the Therapeutic Effects of Progesterone and Allopregnanolone on Ketamine-Induced Cognitive Deficits

Ketamine exposure can model cognitive deficits associated with schizophrenia. Progesterone (PROG) and its active metabolite allopregnanolone (ALLO) have neuroprotective effects and the pathway involving progesterone receptor membrane component 1 (PGRMC1), epidermal growth factor receptor (EGFR), glucagon-like peptide-1 receptor (GLP-1R), phosphatidylinositol 3 kinase (PI3K), and protein kinase B (Akt) appears to play a key role in their neuroprotection. The present study aimed to investigate the effects of PROG (8,16 mg kg⁻¹) and ALLO (8,16 mg kg⁻¹) on the reversal of cognitive deficits induced by ketamine (30 mg kg⁻¹) via the PGRMC1 pathway in rat brains, including hippocampus and prefrontal cortex (PFC). Cognitive performance was evaluated by Morris water maze (MWM) test. Western blot and real-time quantitative polymerase chain reaction were utilized to assess the expression changes of protein and mRNA. Additionally, concentrations of PROG and ALLO in plasma, hippocampus and PFC were measured by a liquid chromatography-tandem mass spectrometry method. We demonstrated that PROG or ALLO could reverse the impaired spatial learning and memory abilities induced by ketamine, accompanied with the upregulation of PGRMC1/EGFR/GLP-1R/PI3K/Akt pathway. Additionally, the coadministration of AG205 abolished their neuroprotective effects and induced cognitive deficits similar with ketamine. More importantly, PROG concentrations were markedly elevated in PROG-treated groups in hippocampus, PFC and plasma, so as for ALLO concentrations in ALLO-treated groups. Interestingly, ALLO (16 mg kg⁻¹) significantly increased the levels of PROG. These findings suggest that PROG can exert its neuroprotective effects via activating the PGRMC1/EGFR/GLP-1R/PI3K/Akt pathway in the brain, whereas ALLO also restores cognitive deficits partially via increasing the level of PROG in the brain to activate the PGRMC1 pathway.

Cortisol-dehydroepiandrosterone ratios are inversely associated with hippocampal and prefrontal brain volume in schizophrenia

While high levels of glucocorticoids are generally neuro-damaging, a related adrenal steroid, dehydroepiandrosterone (DHEA), has anti-glucocorticoid and neuroprotective properties. Previous work has shown increased circulating levels of DHEA and abnormal cortisol/DHEA ratios in people with schizophrenia, however reports are limited and their relationship to neuropathology is unclear. We performed the largest study to date to compare levels of serum DHEA and cortisol/DHEA ratios in people with schizophrenia and healthy controls, and investigated the extent to which cortisol/DHEA ratios predict brain volume. Serum cortisol and DHEA were assayed in 94 people with schizophrenia and 81 healthy controls. T1-weighted high-resolution anatomical scans were obtained using a 3 T Achieva scanner on a subset of 59 people with schizophrenia and 60 healthy controls. Imaging data were preprocessed and analyzed using SPM12. People with schizophrenia had significantly increased serum DHEA levels (p = 0.002), decreased cortisol/DHEA ratios (p = 0.02) and no difference in cortisol levels compared to healthy controls. Cortisol/DHEA ratios were inversely correlated with hippocampal (r = -0.33 p = 0.01) and dorsolateral prefrontal cortex (r = -0.30, p = 0.02) volumes in patients. Our findings suggest that the cortisol/DHEA ratio may be a molecular blood signature of hippocampal and cortical damage. These results further implicate the role of DHEA and hypothalamic-pituitary-adrenal axis dysfunction in the pathophysiology of schizophrenia.

Sex differences in steroid levels and steroidogenesis in the nervous system: Physiopathological role

The nervous system, in addition to be a target for steroid hormones, is the source of a variety of neuroactive steroids, which are synthesized and metabolized by neurons and glial cells. Recent evidence indicates that the expression of neurosteroidogenic proteins and enzymes and the levels of neuroactive steroids are different in the nervous system of males and females. We here summarized the state of the art of neuroactive steroids, particularly taking in consideration sex differences occurring in the synthesis and levels of these molecules. In addition, we discuss the consequences of sex differences in neurosteroidogenesis for the function of the nervous system under healthy and pathological conditions and the implications of neuroactive steroids and neurosteroidogenesis for the development of sex-specific therapeutic interventions.

Cortisol and DHEAS Related to Metabolic Syndrome in Patients with Schizophrenia

BACKGROUND

Both dehydroepiandrosterone (DHEAS) and cortisol are secreted by the adrenal glands and may modulate metabolic syndrome (MetS), which often affects the health of patients with schizophrenia. The relationship between the serum levels of these hormones and MetS has not been established.

PURPOSE

In this pilot study, we investigated the serum levels in schizophrenia patients with and without MetS and compared them with those in healthy volunteers.

PATIENTS AND METHODS

After obtaining informed consent, 110 patients with acute paranoid schizophrenia were recruited directly after admission to the Mental Health Research Institute. The control group consisted of 51 persons reported on questioning to be mentally and somatically healthy. Blood samples to prepare serum were drawn after an 8-h overnight fast during one of the first days of admission. Serum cortisol and DHEAS concentrations were quantified by enzyme-linked immunosorbent assay.

RESULTS

A total of 42 patients had MetS and 68 patients were without MetS. The cortisol blood level was significantly (p = 0.012) higher in schizophrenia patients without MetS in comparison to healthy controls, while patients with schizophrenia and a MetS have significantly (p = 0.014) lower DHEAS levels than healthy volunteers. These differences could, however, exclusively be attributed to female participants. Analysis of covariance adjusted for gender and age demonstrated a significant relationship between age and DHEAS levels (F = 9.512, р = 0.003).

CONCLUSION

Lower DHEAS serum levels in relationship to MetS become evident in women, but not in men, and have age differences as a confounding factor.

Spatial skills

Spatial skills represent an important part of our cognitive processes and have been widely studied in the last decades. The term "spatial skills" includes several abilities, some of them clearly sexually dimorphic. Thus men usually perform better than women in mental rotation and spatial orientation tasks, whereas women outperform men in object location memory tests. Skills like visualization and perception could account for these differences, but they could also be modulated by the cognitive style. Obviously, disease can interfere in certain brain structures underlying learning and memory, thus altering spatial abilities in both genders. In this chapter, spatial skills and sexual dimorphism are briefly reviewed, focusing on processes underlying performance as well as models used to explain how we perceive information from the environment. The chapter also includes references to the brain, providing some cues regarding the anatomic regions underlying some of these behaviors.

Schizophrenia spectrum and other psychotic disorders

Since its earliest conceptualization, schizophrenia has been considered a disorder of "young men." Contemporary research suggests that there are sex differences in schizophrenia that are both transdiagnostic and representative of general sex/gender differences across the psychopathology spectrum. This chapter selectively summarizes representative sex/gender differences in clinical expression, epidemiology, risk factors, treatment, as well as course and outcome in schizophrenia. The consistent sex differences found, such as onset age, generic brain anomalies, and hormonal involvement, are not specific to schizophrenia or necessarily to psychopathology. It is suggested that in working with those diagnosed as meeting the current criteria for schizophrenia, clinicians adopt a transdiagnostic framework informed by sex and gender role processes.

Detection of circular RNA expression and related quantitative trait loci in the human dorsolateral prefrontal cortex

BACKGROUND

Circular RNAs (circRNAs) are implicated in various biological processes. As a layer of the gene regulatory network, circRNA expression is also an intermediate phenotype bridging genetic variation and phenotypic changes. Thus, analyzing circRNA expression variation will shed light on molecular fundamentals of complex traits and diseases.

RESULTS

We systematically characterize 10,559 high-quality circRNAs in 589 human dorsolateral prefrontal cortex samples. We identify biological and technical factors contributing to expression heterogeneity associated with the expression levels of many circRNAs, including the well-known circRNA CDR1as. Combining the expression levels of circRNAs with genetic cis-acting SNPs, we detect 196,255 circRNA quantitative trait loci (circQTLs). By characterizing circQTL SNPs, we find that partial circQTL SNPs might influence circRNA formation by altering the canonical splicing site or the reverse complementary sequence match. Additionally, we find that a subset of these circQTL SNPs is highly linked to genome-wide association study signals of complex diseases, especially schizophrenia, inflammatory bowel disease, and type II diabetes mellitus.

CONCLUSIONS

Our results reveal technical, biological, and genetic factors affecting circRNA expression variation among individuals, which lead to further understanding of circRNA regulation and thus of the genetic architecture of complex traits or diseases.

Testosterone, DHEA and DHEA-S in patients with schizophrenia: A systematic review and meta-analysis

Neuroactive steroids, including testosterone, dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S) might play an important role in the pathophysiology of schizophrenia. Therefore, we performed a systematic review and meta-analysis of studies comparing the levels of testosterone, DHEA and DHEA-S in patients with schizophrenia and healthy controls. We searched electronic databases from their inception until Oct 29, 2017. Effect size (ES) estimates were calculated as Hedges' g. Data analysis was performed using random-effects models. Our analysis included 34 eligible studies, representing 1742 patients and 1604 controls. Main analysis revealed elevated DHEA-S levels in the whole group of patients (ES = 0.75, 95%CI: 0.23-1.28, p = 0.005). In subgroup analyses, patients with first-episode psychosis (FEP) had significantly higher levels of free testosterone (ES = 1.21, 95%CI: 0.30-2.12, p = 0.009) and DHEA-S (ES = 1.19, 95%CI: 0.66-1.71, p < 0.001). Acutely relapsed schizophrenia patients presented significantly higher levels of total testosterone (ES = 0.50, 95%CI: 0.21-0.70, p < 0.001). Total testosterone levels were also elevated in stable multi-episode schizophrenia (sMES) females (ES = 0.56, 95%CI: 0.33-0.80, p < 0.001) and reduced in sMES males (ES = -0.62, 95%CI: -1.07 to 0.18, p = 0.006). Increased levels of biologically active, free testosterone and DHEA-S in FEP suggest that these alterations might appear as a response to stress that becomes blunted during subsequent exacerbations of schizophrenia. Differential changes in total testosterone levels in male and female sMES patients might represent medication effects related to prolactin-releasing effects of antipsychotics.