Prolactin and sex hormones levels in males with Parkinson's disease

Prolactin is an Endogenous Antioxidant Factor in Astrocytes That Limits Oxidative Stress-Induced Astrocytic Cell Death via the STAT3/NRF2 Signaling Pathway

Oxidative stress-induced death of neurons and astrocytes contributes to the pathogenesis of numerous neurodegenerative diseases. While significant progress has been made in identifying neuroprotective molecules against neuronal oxidative damage, little is known about their counterparts for astrocytes. Prolactin (PRL), a hormone known to stimulate astroglial proliferation, viability, and cytokine expression, exhibits antioxidant effects in neurons. However, its role in protecting astrocytes from oxidative stress remains unexplored. Here, we investigated the effect of PRL against hydrogen peroxide (H2O2)-induced oxidative insult in primary cortical astrocyte cultures. Incubation of astrocytes with PRL led to increased enzymatic activity of superoxide dismutase (SOD) and glutathione peroxidase (GPX), resulting in higher total antioxidant capacity. Concomitantly, PRL prevented H2O2-induced cell death, reactive oxygen species accumulation, and protein and lipid oxidation. The protective effect of PRL upon H2O2-induced cell death can be explained by the activation of both signal transducer and activator of transcription 3 (STAT3) and NFE2 like bZIP transcription factor 2 (NRF2) transduction cascades. We demonstrated that PRL induced nuclear translocation and transcriptional upregulation of Nrf2, concurrently with the transcriptional upregulation of the NRF2-dependent genes heme oxygenase 1, Sod1, Sod2, and Gpx1. Pharmacological blockade of STAT3 suppressed PRL-induced transcriptional upregulation of Nrf2, Sod1 and Gpx1 mRNA, and SOD and GPX activities. Furthermore, genetic ablation of the PRL receptor increased astroglial susceptibility to H2O2-induced cell death and superoxide accumulation, while diminishing their intrinsic antioxidant capacity. Overall, these findings unveil PRL as a potent antioxidant hormone that protects astrocytes from oxidative insult, which may contribute to brain neuroprotection.

Understanding the dopaminergic pathway relative to men's sexual dysfunction in patients with Parkinson's disease: a narrative review with implications for future research

Parkinson's disease (PD) is often most recognized for motor symptoms but associated non-motor symptoms such as sexual dysfunction can significantly impact quality of life. This condition involves a hormonal disruption and has a predilection for male patients, yet there are no formal guidelines for screening or management of sexual health pathology in these patients. While prior publications have addressed the presence of sexual dysfunction (SD) among men with PD, there has been a paucity of work examining the hypothalamic-pituitary-gonadal (HPG) axis and the interplay between dopamine, prolactin (PRL), and testosterone. This review provides an overview of data extracted from the existing peer-reviewed literature regarding hormonal and sexual health changes in men with PD and the impact of dopaminergic and/or androgen replacement therapy. Furthermore, while some research suggests that PD patients are at higher risk for prolactin elevation and testosterone deficiency, heterogeneity of the data limits extrapolation. Additionally, data related to pharmacologic optimization of the HPG axis in this patient population is similarly limited. Prospective studies are needed to better characterize the hormonal pathophysiology of PD as it relates to sexual dysfunction such that men at risk can be effectively identified so as to offer interventions that may improve quality of life.

The effect of drug holidays on sexual dysfunction in men treated with selective serotonin reuptake inhibitors (SSRIs) other than fluoxetine: an 8-week open-label randomized clinical trial

INTRODUCTION

Selective serotonin reuptake inhibitors (SSRIs) are widely used for the treatment of various mental disorders. Sexual dysfunction is one of the most common side effects of SSRIs, and often leads to poor adherence and treatment discontinuation. While several strategies have been employed to manage SSRI-induced sexual dysfunction, drug holidays has not been extensively studied for this purpose. This clinical trial aims to assess the effect of drug holidays on sexual dysfunction in married men under treatment with SSRIs other than fluoxetine (as its long half-life makes drug holidays ineffective).

METHODS

This 8-week double-center, randomized, open-label, controlled trial was conducted in the outpatient clinics of Iran Psychiatric Hospital and Tehran Institute of Psychiatry, from January 2022 to March 2023. We included married men aged between18 and 50 years who had experienced sexual dysfunction during treatment with SSRIs, other than fluoxetine. The Male Sexual Health Questionnaire (MSHQ) and the 28-Question General Health Questionnaire (GHQ-28) were used for the assessment of sexual function and mental health status. The drug holidays group was instructed not to take their medications on the weekends. The control group was asked to continue their regular medication regimen without any changes. Both groups were assessed at baseline, and weeks 4 and 8.

RESULTS

Sixty-three patients were included and randomly assigned to the drug holidays group (N = 32) or the control group (N = 31). Fifty patients (25 in each group) completed the trial. Drug holidays significantly improved erection, ejaculation, satisfaction, and the overall sexual health of the participants (P < 0.001). No significant change was observed in their mental health status. No major side effects were recorded.

CONCLUSIONS

Drug holidays significantly improved the MSHQ scores in 'erection', 'ejaculation', 'satisfaction' and 'total' in married men with sexual dysfunction induced by SSRIs, other than fluoxetine, without causing any significant changes in their mental health status. Further research is needed to reach a certain conclusion.

TRIAL REGISTRATION

The trial was registered at the Iranian Registry of Clinical Trials on 2021.10.25 ( www.irct.ir ; IRCT ID: IRCT20170123032145N6) before the trial.

Neuroactive steroids and Parkinson's disease: Review of human and animal studies

The greater prevalence and incidence of Parkinson's disease (PD) in men suggest a beneficial effect of sex hormones. Neuroactive steroids have neuroprotective activities thus offering interesting option for disease-modifying therapy for PD. Neuroactive steroids are also neuromodulators of neurotransmitter systems and may thus help to control PD symptoms and side effect of dopamine medication. Here, we review the effect on sex hormones (estrogen, androgen, progesterone and its metabolites) as well as androstenediol, pregnenolone and dehydroepiandrosterone) in human studies and in animal models of PD. The effect of neuroactive steroids is reviewed by considering sex and hormonal status to help identify specifically for women and men with PD what might be a preventive approach or a symptomatic treatment. PD is a complex disease and the pathogenesis likely involves multiple cellular processes. Thus it might be useful to target different cellular mechanisms that contribute to neuronal loss and neuroactive steroids provide therapeutics options as they have multiple mechanisms of action.

The conceivable role of prolactin hormone in Parkinson disease: The same goal but with different ways

Parkinson disease (PD) is a progressive neurodegenerative disease (NDD) of the brain. It has been reported that prolactin (PRL) hormone plays a differential effect in PD, may be increasing, reduced or unaffected. PRL level is dysregulated in different neurodegenerative disorders including PD. Preclinical and clinical studies pointed out that PRL may has a neuroprotective against PD neuropathology . Though, the mechanistic role of PRL in PD is not fully elucidated. Therefore, the objective of the present review was to clarify the potential role and mechanistic pathway of PRL in PD neuropathology. The present review highlighted that PRL appears to have a neuroprotective effect against PD neuropathology by inhibiting the expression of pro-inflammatory signaling pathways, antioxidant effects and by inhibiting neuroinflammation. Thus, preclinical and clinical studies are warranted in this regard.

Sexual dysfunction among patients with Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

Previous studies have reported a higher prevalence of sexual dysfunction (SD) in patients with Parkinson's disease (PD). In the current study, we aimed to conduct a systematic review and meta-analysis to investigate the role of PD as a potential risk factor for SD in both genders.

METHODS

We performed a comprehensive search on PubMed, Embase, Scopus, and Web of Science. All observational studies comparing the prevalence of SD in PD with the general population were included.

RESULTS

After screening 22 studies were included in our qualitative and statistical analysis. We included 13 studies that reported odds ratio (OR) and found a significant association between PD and SD (pooled OR = 3.5, 95% CI = 2.19-5.58). Five studies included only male patients and reported an OR of 3.34 (95% CI = 1.34-8.35; heterogeneity I2 = 81%, Tau2 = 0.79, p < 0.00), while seven studies included both sexes and reported an OR of 3.55 (95% CI = 1.89-6.66; heterogeneity I2 = 78%, Tau2 = 0.53, p < 0.00).

CONCLUSION

In conclusion, our study suggests a strong association between PD and SD in both men and women. Our analysis of 22 observational studies reveals that the prevalence of sexual dysfunction is significantly higher in patients with PD compared to the general population. These findings highlight the importance of addressing SD as part of the comprehensive management of patients with PD.

Sexual Dysfunctions in Females with Parkinson's Disease: A Cross-Sectional Study with a Psycho-Endocrinological Perspective

Background and Objectives: Normal human sexual functioning is a complex integration of an intact neuroanatomic substrate, vascular supply, a balanced hormonal profile, and a predominance of excitatory over inhibitory psychological mechanisms. However, sexual functioning in Parkinson's disease (PD) is often overlooked in clinical practice, especially in female patients. Materials and Methods: In this cross-sectional study, we have investigated the frequency of sexual dysfunction and the possible correlation with psycho-endocrinological factors in a sample of women with idiopathic PD. Patients were assessed using a semi-structured sexual interview, in addition to psychometric tools, including the Hamilton Rating Scale for Anxiety and for Depression and the Coping Orientation to the Problems Experiences-New Italian Version. Specific blood tests, including testosterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), estrogen E2, prolactin (PRL), and vitamin D3 were also evaluated. Results: Our results reported a statistical difference in sexual intercourse frequency before and after the onset of PD (p < 0.001). The percentage of women who complained about reduced sexual desire increased after diagnosis (52.7%) compared to the period before the onset of the illness (36.8%). The endocrinological profile in females with PD revealed statistically significant differences regarding testosterone (p < 0.0006), estradiol (p < 0.00), vitamin D3 (p < 0.006), and calcium (0.002). Depression (44% characterized by perceived feelings of anger and frustration during sexual intercourse) and anxiety symptoms (29.5% reported feelings of fear and anxiety for not satisfying the partner) with abnormal coping strategies (48.14% experienced feelings of anger and intolerance) were also found to be statistically significant. This study showed a high frequency of sexual dysfunction in female patients with PD, which correlated with sexual hormone abnormalities, mood/anxiety, and coping strategies alterations. This supports the idea that there is a need to better investigate the sexual function of female patients with PD to provide them with an adequate therapeutic approach and potentially improve quality of life.

The impact of biological clock and sex hormones on the risk of disease

Molecular clocks are responsible for defining 24-h cycles of behaviour and physiology that are called circadian rhythms. Several structures and tissues are responsible for generating these circadian rhythms and are named circadian clocks. The suprachiasmatic nucleus of the hypothalamus is believed to be the master circadian clock receiving light input via the optic nerve and aligning internal rhythms with environmental cues. Studies using both in vivo and in vitro methodologies have reported the relationship between the molecular clock and sex hormones. The circadian system is directly responsible for controlling the synthesis of sex hormones and this synthesis varies according to the time of day and phase of the estrous cycle. Sex hormones also directly interact with the circadian system to regulate circadian gene expression, adjust biological processes, and even adjust their own synthesis. Several diseases have been linked with alterations in either the sex hormone background or the molecular clock. So, in this chapter we aim to summarize the current understanding of the relationship between the circadian system and sex hormones and their combined role in the onset of several related diseases.

[Androgens and Parkinson's disease: the role in humans and in experiment]

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. There is evidence that PD has a wider prevalence among men, which indicates the existing role of sex hormones in the pathogenesis of the disease. The article presents an overview of studies devoted to the study of sex differences in the incidence and symptoms of PD. Drug therapy with androgens, androgen precursors, antiandrogens and drugs that modify androgen metabolism is available for the treatment of various endocrine conditions, having translational significance for PD, but none of these drugs has yet shown sufficient effectiveness. Although PD has now been proven to be more common in men than in women, androgens do not always have any effect on the symptoms or progression of the disease. 5α-reductase inhibitors have shown neuroprotective and anti-dyskinetic activity and need further investigation. Despite the fact that the neuroprotective effect of dutasteride was observed only before damage to DA neurons, the absence of a negative effect makes it an attractive drug for use in patients with PD due to its anti-dyskinetic properties.

The association between Parkinson's disease and Sexual dysfunction: Clinical correlation and therapeutic implications

Sexual function which comprises of desire, arousal, orgasm and satisfaction and pain, involves coordinated physiologic responses from multiple different pathways. Sexual dysfunction (SD) occurs when these domains of the sexual response cycle are affected. SD is a common but under-recognized non-motor feature in Parkinson's disease (PD), a common age-related neurodegenerative disorder. SD significantly affects the quality of life of PD patients and their partners. Advanced age, gender, hormone deficiency, neuropsychiatric and medical comorbidities contribute to SD in PD. Possible potential pathological mechanisms include vasculogenic, endocrinologic, neurogenic and psychogenic factors. Various therapeutic interventions, both pharmacological and non-pharmacological modalities have been suggested to improve SD in PD. However, erectile dysfunction (ED) is the only SD with evidence-based treatment available. Non-pharmacological therapies are also offering promising evidence in the improvement of SD. A multidisciplinary approach in the assessment, investigation, and treatment is needed to address the real life complex issues (gender and comorbidities, neurobiological, vasoactive, hormonal as well as psychosocial aspects). Future clinical studies with validated and standardized methods in assessing SD as well as experimental models will be necessary for better insight into the pathophysiology. This would facilitate appropriate therapy and improve sexual rehabilitation in PD patients.

The pathophysiology of sexual dysfunction in Parkinson's disease: An overview

Sexual dysfunction is a common, poorly recognized, poorly discussed (often because of cultural perceptions and sensitivities), bothersome and neglected aspect of the range of non-motor symptoms of Parkinson's disease (PD). The spectrum of sexual dysfunction in PD ranges from hyposexuality-based disturbances to hypersexuality-dominated behaviors in the context of drug-induced impulse control disorder. The pathophysiological mechanisms underlying PD-related sexual dysfunction, specifically for hyposexual disorders, are thus heterogeneous and still not fully understood. However, central and peripheral neural mechanisms secondary to the hallmark pathological alterations of the disease (alpha-synuclein deposition and nigrostriatal degeneration) and to the associated network and neurotransmitter dysfunctions, together with the effects of dopaminergic therapies, seem to play an important role in the development of sexual disturbances. In this chapter, we therefore review the neuroanatomical and neurophysiological basis of sexual function in humans, and we provide insights on the pathophysiological mechanisms of hyposexuality and hypersexuality in PD.

Androgens and Parkinson's Disease: A Review of Human Studies and Animal Models

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease. A greater prevalence and incidence of PD are reported in men than in women, suggesting a potential contribution of sex, genetic difference and/or sex hormones. This review presents an overview of epidemiological and clinical studies investigating sex differences in the incidence and symptoms of PD. This sex difference is replicated in animal models of PD showing an important neuroprotective role of sex steroids. Therefore, although gender and genetic factors likely contribute to the sex difference in PD, focus here will be on sex hormones because of their neuroprotective role. Androgens receive less attention than estrogen. It is well known that endogenous androgens are more abundant in healthy men than in women and decrease with aging; lower levels are reported in PD men than in healthy male subjects. Drug treatments with androgens, androgen precursors, antiandrogens, and drugs modifying androgen metabolism are available to treat various endocrine conditions, thus having translational value for PD but none have yet given sufficient positive effects for PD. Variability in the androgen receptor is reported in humans and is an additional factor in the response to androgens. In animal models of PD used to study neuroprotective activity, the androgens testosterone and dihydrotestosterone have given inconsistent results. 5α-Reductase inhibitors have shown neuroprotective activity in animal models of PD and antidyskinetic activity. Hence, androgens have not consistently shown beneficial or deleterious effects in PD but numerous androgen-related drugs are available that could be repurposed for PD.

Association between Serum Prolactin Levels and Neurodegenerative Diseases: Systematic Review and Meta-Analysis

INTRODUCTION

Prolactin (PRL) exerts inflammatory and anti-inflammatory properties and is also thought to play an important role in the pathogenesis of neurodegenerative diseases (NDs). However, serum PRL levels in patients with NDs were inconsistent in the research literature.

OBJECTIVE

We aimed to assess the serum PRL levels in patients with NDs.

METHODS

Electronic databases, including MEDLINE, Embase, Cochrane Library database, clinicaltrials.gov, Web of Science, and Google Scholar, and reference lists of articles were searched up to December 31, 2020. Pooled standard mean difference (SMD) with 95% confidence interval (CI) was calculated by fixed-effect or random-effect model analysis.

RESULTS

A total of 36 comparisons out of 29 studies (3 RCTs and 26 case controls) focusing on NDs (including Parkinson's disease, Alzheimer's disease, Huntington's disease [HD], multiple sclerosis [MS], and epilepsy) were reported. The meta-analysis showed that there was no statistically significant difference in serum PRL levels between patients with NDs and healthy controls (SMD = 0.40, 95% CI: -0.16 to 0.96, p = 0.16). Subgroup analysis showed that serum PRL levels in patients with HD and MS were higher than those of healthy controls. Furthermore, patients with NDs aged <45 years had higher serum PRL levels (SMD = 0.97, 95% CI: 0.16-1.78, p = 0.018) than healthy controls. High serum PRL levels were found in subgroups such as the microenzymatic method, Asia, and the Americas.

CONCLUSIONS

Our meta-analysis showed serum PRL levels in patients with HD and MS were significantly higher than those in healthy controls. Serum PRL levels were associated with age, region, and detection method. Other larger sample studies using more uniform detection methods are necessary to confirm our results.

Prolactin and Its Altered Action in Alzheimer's Disease and Parkinson's Disease

BACKGROUND

Prolactin (PRL) is one of the most diverse pituitary hormones and is known to modulate normal neuronal function and neurodegenerative conditions. Many studies have described the influence that PRL has on the central nervous system and addressed its contribution to neurodegeneration, but little is known about the mechanisms responsible for the effects of PRL on neurodegenerative disorders, especially on Alzheimer's disease (AD) and Parkinson's disease (PD).

SUMMARY

We review and summarize the existing literature and current understanding of the roles of PRL on various PRL aspects of AD and PD.

KEY MESSAGES

In general, PRL is viewed as a promising molecule for the treatment of AD and PD. Modulation of PRL functions and targeting of immune mechanisms are needed to devise preventive or therapeutic strategies.

Application of Sebum Lipidomics to Biomarkers Discovery in Neurodegenerative Diseases

Lipidomics is strategic in the discovery of biomarkers of neurodegenerative diseases (NDDs). The skin surface lipidome bears the potential to provide biomarker candidates in the detection of pathological processes occurring in distal organs. We investigated the sebum composition to search diagnostic and, possibly, prognostic, biomarkers of Alzheimer’s disease (AD) and Parkinson’s disease (PD). The observational study included 64 subjects: 20 characterized as “probable AD with documented decline”, 20 as “clinically established PD”, and 24 healthy subjects (HS) of comparable age. The analysis of sebum by GCMS and TLC retrieved the amounts (µg) of 41 free fatty acids (FFAs), 7 fatty alcohols (FOHs), vitamin E, cholesterol, squalene, and total triglycerides (TGs) and wax esters (WEs). Distributions of sebum lipids in NDDs and healthy conditions were investigated with multivariate ANOVA-simultaneous component analysis (ASCA). The deranged sebum composition associated with the PD group showed incretion of most composing lipids compared to HS, whereas only two lipid species (vitamin E and FOH14:0) were discriminant of AD samples and presented lower levels than HS sebum. Thus, sebum lipid biosynthetic pathways are differently affected in PD and AD. The characteristic sebum bio-signatures detected support the value of sebum lipidomics in the biomarkers search in NDDs.

Non-invasive diagnostic tool for Parkinson's disease by sebum RNA profile with machine learning

Parkinson's disease (PD) is a progressive neurodegenerative disease presenting with motor and non-motor symptoms, including skin disorders (seborrheic dermatitis, bullous pemphigoid, and rosacea), skin pathological changes (decreased nerve endings and alpha-synuclein deposition), and metabolic changes of sebum. Recently, a transcriptome method using RNA in skin surface lipids (SSL-RNAs) which can be obtained non-invasively with an oil-blotting film was reported as a novel analytic method of sebum. Here we report transcriptome analyses using SSL-RNAs and the potential of these expression profiles with machine learning as diagnostic biomarkers for PD in double cohorts (PD [n = 15, 50], controls [n = 15, 50]). Differential expression analysis between the patients with PD and healthy controls identified more than 100 differentially expressed genes in the two cohorts. In each cohort, several genes related to oxidative phosphorylation were upregulated, and gene ontology analysis using differentially expressed genes revealed functional processes associated with PD. Furthermore, machine learning using the expression information obtained from the SSL-RNAs was able to efficiently discriminate patients with PD from healthy controls, with an area under the receiver operating characteristic curve of 0.806. This non-invasive gene expression profile of SSL-RNAs may contribute to early PD diagnosis based on the neurodegeneration background.

The association between multiple risk factors, clinical correlations and molecular insights in Parkinson's disease patients from Tamil Nadu population, India

Parkinson's disease (PD) is a neurodegenerative disease with multifactorial aetiology that influences the quality of life. However, the association of possible factors with PD is need to be investigated in Indian population, hence we aimed to determine the association of lifestyle, environmental factors, biochemical parameters and genetic insights of MT-ND1 gene in PD patients. Using a standardised questionnaire, PD patients and control group of about 146 subjects were interviewed on demographic, lifestyle and environmental factors. The subjects includes n = 73 Parkinson's patients [juvenile (n = 4); early-onset (n = 8); late-onset (n = 61)] with equal number of age and sex matched controls, further we had obtained institutional ethical clearance and informed consent from study participants. Biomarker investigations and MT-ND1 alterations were investigated by appropriate molecular techniques. During the average follow-up years of 5.1, significant association was observed among smoking, alcohol, caffeinated drinks, surgery, pesticide exposure at p < 0.05 in varied PD age groups. Occupational exposure to agriculture and industry showed an increased risk among the late-onset group. The biomarkers uric acid (UA) and dopamine (DA) were significant at p < 0.05 in all the three PD age groups. The MT-ND1 alteration with A3843 G variant was significant at p < 0.05 for AG allele in all the three PD groups but the highest prevalence was observed in late-onset group. From our study, smoking, alcohol, caffeinated drinks, occupational influence of agriculture and industry and pesticide exposure had more association with PD occurrence. Hence, to the best of our knowledge, this is the first kind of study in Tamil Nadu population, India to validate the various factors with PD. Therefore we suggest that further research is mandatory to detect other possible associations among PD, using comprehensive larger sample size.

Gene expression profiling of early Parkinson's disease patient reveals redox homeostasis

Parkinson's disease (PD) is slowly progressive. Due to the lack of specific and sensitive biomarkers, the majority of PD patients are in the advanced stages when diagnosed. This study aimed to investigate biomarkers for early PD diagnosis. We first selected differential mRNAs by analysis of a Gene Expression Omnibus (GEO) data set. Next, we performed RNA sequencing to select differential mRNAs. After an integrated analysis of GEO and RNAseq data, we identified the PD early diagnosis biomarkers associated with oxidative stress. By function analysis, cellular response to hormone stimulus and response to the oxygen-containing compound was involved in the top Gene Set Enrichment Analysis (GSEA)s of the two cohorts. Moreover, SOCS7 was included in these GSEAs coincidentally. Further, by analyzing SOCS7 and its physical interactors, we found they mainly participate in immunity and redox homeostasis related processes, which might play a significant role in PD. Thus, our results suggest SOCS7 might be the potential diagnostic marker for PD.

Decoding signaling pathways involved in prolactin-induced neuroprotection: A review

It has been well recognized that prolactin (PRL), a pleiotropic hormone, has many functions in the brain, such as maternal behavior, neurogenesis, and neuronal plasticity, among others. Recently, it has been reported to have a significant role in neuroprotection against excitotoxicity. Glutamate excitotoxicity is a common alteration in many neurological and neurodegenerative diseases, leading to neuronal death. In this sense, several efforts have been made to decrease the progression of these pathologies. Despite various reports of PRL's neuroprotective effect against excitotoxicity, the signaling pathways that underlie this mechanism remain unclear. This review aims to describe the most recent and relevant studies on the molecular signaling pathways, particularly, PI3K/AKT, NF-κB, and JAK2/STAT5, which are currently under investigation and might be implicated in the molecular mechanisms that explain the PRL effects against excitotoxicity and neuroprotection. Remarkable neuroprotective effects of PRL might be useful in the treatment of some neurological diseases.

Sexual Disorders and Quality of Life in Parkinson's Disease

Introduction

Sexual disorders are the most neglected nonmotor symptoms in Parkinson's disease (PD). Although doctors seek greater priority to motor manifestations, which are the basis for the diagnosis of PD, the nonmotor symptoms deserve to be highlighted as much as the motor problems because of their strong presence and discomfort in the patients, causing the important impairment in the quality of life (QoL) of the individual with PD.

Aim

Provide the prevalence of sexual disorders among patients with PD and alert the medical profession to investigate and be familiar with problems related to QoL and sexual disorders in PD.

Methods

This is a large literature review on sexual disorders in PD and impaired QoL.

Main Outcome Measures

Sexual disorders in PD and prevalence between genders have been described in epidemiological studies. Neuroanatomy, pathophysiology, risk factors, QoL, and etiologies were reviewed.

Results

The estimate of the prevalence of sexual dysfunction in the form of compulsive sexual behavior in PD is higher in men by 5.2% than in women by 0.5%. This diagnosis is a determinant of intense and persistent suffering and is related to several health problems of a social, economic, personal, family, psychological, and occupational nature, which can even culminate in sexual abuse. It is most commonly associated with the use of drugs commonly used in PD therapy in 98.1% of cases. In addition to this serious public health problem, another common condition of sexual dysfunction occur with the decreased libido by loss of the neurotransmitter dopamine proper of the pathophysiology of PD.

Conclusion

The presence of sexual disorders in PD should be tracked and monitored because of its harmful consequences, whether due to increased sexual behavior or associated psychological distress, as well as the impacts on QoL. Early recognition and adequate treatment of PD in its fullness and richness of associated symptoms are essential for improving QoL.

Santa Rosa Malcher CM, Roberto da Silva Gonçalves Oliveira K, Fernandes Caldato MC, et al. Sexual Disorders and Quality of Life in Parkinson's Disease. Sex Med 2021;9:100280.

Parkinson's disease determinants, prediction and gene-environment interactions in the UK Biobank

OBJECTIVE

To systematically investigate the association of environmental risk factors and prodromal features with incident Parkinson's disease (PD) diagnosis and the interaction of genetic risk with these factors. To evaluate whether existing risk prediction algorithms are improved by the inclusion of genetic risk scores.

METHODS

We identified individuals with an incident diagnosis of PD (n=1276) and controls (n=500 406) in UK Biobank. We determined the association of risk factors with incident PD using adjusted logistic regression models. We constructed polygenic risk scores (PRSs) using external weights and selected the best PRS from a subset of the cohort (30%). The PRS was used in a separate testing set (70%) to examine gene-environment interactions and compare predictive models for PD.

RESULTS

Strong evidence of association (false discovery rate <0.05) was found between PD and a positive family history of PD, a positive family history of dementia, non-smoking, low alcohol consumption, depression, daytime somnolence, epilepsy and earlier menarche. Individuals with the highest 10% of PRSs had increased risk of PD (OR 3.37, 95% CI 2.41 to 4.70) compared with the lowest risk decile. A higher PRS was associated with earlier age at PD diagnosis and inclusion of the PRS in the PREDICT-PD algorithm led to a modest improvement in model performance. We found evidence of an interaction between the PRS and diabetes.

INTERPRETATION

Here, we used UK Biobank data to reproduce several well-known associations with PD, to demonstrate the validity of a PRS and to demonstrate a novel gene-environment interaction, whereby the effect of diabetes on PD risk appears to depend on background genetic risk for PD.

Sex-dependent effect of APOE on Alzheimer's disease and other age-related neurodegenerative disorders

The importance of apolipoprotein E (APOE) in late-onset Alzheimer's disease (LOAD) has been firmly established, but the mechanisms through which it exerts its pathogenic effects remain elusive. In addition, the sex-dependent effects of APOE on LOAD risk and endophenotypes have yet to be explained. In this Review, we revisit the different aspects of APOE involvement in neurodegeneration and neurological diseases, with particular attention to sex differences in the contribution of APOE to LOAD susceptibility. We discuss the role of APOE in a broader range of age-related neurodegenerative diseases, and summarize the biological factors linking APOE to sex hormones, drawing on supportive findings from rodent models to identify major mechanistic themes underlying the exacerbation of LOAD-associated neurodegeneration and pathology in the female brain. Additionally, we list sex-by-genotype interactions identified across neurodegenerative diseases, proposing APOE variants as a shared etiology for sex differences in the manifestation of these diseases. Finally, we present recent advancements in 'omics' technologies, which provide a new platform for more in-depth investigations of how dysregulation of this gene affects the development and progression of neurodegenerative diseases. Collectively, the evidence summarized in this Review highlights the interplay between APOE and sex as a key factor in the etiology of LOAD and other age-related neurodegenerative diseases. We emphasize the importance of careful examination of sex as a contributing factor in studying the underpinning genetics of neurodegenerative diseases in general, but particularly for LOAD.

Hormonal responses in gambling versus alcohol abuse: A review of human studies

The endocrine system plays an essential role in communication between various organs of the body to maintain homeostasis. Both substance use disorders (SUDs) and non-substance abuse disrupt this system and lead to hormonal dysregulations. Here, we focus on the comparison between the function of the endocrine system in gambling disorders and alcohol addiction to understand the commonalities and differences in their neurobiological and psychological underpinnings. We review human research to compare findings on gambling addiction and alcohol dependence pertaining to the dynamic interplay between testosterone and cortisol. Understanding and classifying similarities in hormonal responses between behavioural addiction and SUDs may facilitate development of treatments and therapeutic interventions across different types of addictive disorders, while describing differences may shed light on therapeutic interventions for specific disorders. Although research on gambling addiction is in its infancy, such evaluation may still have a positive effect for addiction research, thereby stimulating discovery of "crossover" pharmacotherapies with benefits for both SUDs and nonsubstance addictions.

Sexual hormones regulate the redox status and mitochondrial function in the brain. Pathological implications

Compared to other organs, the brain is especially exposed to oxidative stress. In general, brains from young females tend to present lower oxidative damage in comparison to their male counterparts. This has been attributed to higher antioxidant defenses and a better mitochondrial function in females, which has been linked to neuroprotection in this group. However, these differences usually disappear with aging, and the incidence of brain pathologies increases in aged females. Sexual hormones, which suffer a decrease with normal aging, have been proposed as the key factors involved in these gender differences. Here, we provide an overview of redox status and mitochondrial function regulation by sexual hormones and their influence in normal brain aging. Furthermore, we discuss how sexual hormones, as well as phytoestrogens, may play an important role in the development and progression of several brain pathologies, including neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, stroke or brain cancer.

•

Sex hormones are reduced with aging, especially in females, affecting redox balance.

•

Normal aging is associated to a worse redox homeostasis in the brain.

•

Young females show better mitochondrial function and higher antioxidant defenses.

•

Development of brain pathologies is influenced by sex hormones and phytoestrogens.

Cell-free microRNAs in Parkinson's disease: potential biomarkers that provide new insights into disease pathogenesis

MicroRNAs (miRNAs) are master post-transcriptional regulators of gene expression and their specific footprints reflect disease conditions. Over the last few years, several primary reports have described the deregulation of cell-free miRNAs in Parkinson's disease (PD), however, results have been rather inconsistent due to preanalytical and analytical challenges. This study integrated the data across twenty-four reports to identify steadily deregulated miRNAs that may assist in the path towards biomarker development and molecular characterization of the underlying pathology. Stringent KEGG pathway analysis of the miRNA targets revealed FoxO, Prolactin, TNF, and ErbB signaling pathways as the most significantly enriched categories while Gene Ontology analysis revealed that the protein targets are mostly associated with transcription. Chromosomal location of the consistently deregulated miRNAs revealed that over a third of them were clustered at the same location at Chr14q32 suggesting that they are co-regulated by specific transcription factors. This genomic region is inherently unstable due to expanded TGG repeats and responsible for human abnormalities. Stringent analysis of transcription factor sites surrounding the deregulated miRNAs revealed that CREB1, CEBPB and MAZ sites existed in approximately half of the miRNAs, including all of the miRNAs located at Chr14q32. Additional studies are now needed to determine the biomarker potential of the consistently deregulated miRNAs in PD and the therapeutic implications of these bioinformatics insights.

Neuroendocrinology and neurobiology of sebaceous glands

The nervous system communicates with peripheral tissues through nerve fibres and the systemic release of hypothalamic and pituitary neurohormones. Communication between the nervous system and the largest human organ, skin, has traditionally received little attention. In particular, the neuro-regulation of sebaceous glands (SGs), a major skin appendage, is rarely considered. Yet, it is clear that the SG is under stringent pituitary control, and forms a fascinating, clinically relevant peripheral target organ in which to study the neuroendocrine and neural regulation of epithelia. Sebum, the major secretory product of the SG, is composed of a complex mixture of lipids resulting from the holocrine secretion of specialised epithelial cells (sebocytes). It is indicative of a role of the neuroendocrine system in SG function that excess circulating levels of growth hormone, thyroxine or prolactin result in increased sebum production (seborrhoea). Conversely, growth hormone deficiency, hypothyroidism, and adrenal insufficiency result in reduced sebum production and dry skin. Furthermore, the androgen sensitivity of SGs appears to be under neuroendocrine control, as hypophysectomy (removal of the pituitary) renders SGs largely insensitive to stimulation by testosterone, which is crucial for maintaining SG homeostasis. However, several neurohormones, such as adrenocorticotropic hormone and α-melanocyte-stimulating hormone, can stimulate sebum production independently of either the testes or the adrenal glands, further underscoring the importance of neuroendocrine control in SG biology. Moreover, sebocytes synthesise several neurohormones and express their receptors, suggestive of the presence of neuro-autocrine mechanisms of sebocyte modulation. Aside from the neuroendocrine system, it is conceivable that secretion of neuropeptides and neurotransmitters from cutaneous nerve endings may also act on sebocytes or their progenitors, given that the skin is richly innervated. However, to date, the neural controls of SG development and function remain poorly investigated and incompletely understood. Botulinum toxin-mediated or facial paresis-associated reduction of human sebum secretion suggests that cutaneous nerve-derived substances modulate lipid and inflammatory cytokine synthesis by sebocytes, possibly implicating the nervous system in acne pathogenesis. Additionally, evidence suggests that cutaneous denervation in mice alters the expression of key regulators of SG homeostasis. In this review, we examine the current evidence regarding neuroendocrine and neurobiological regulation of human SG function in physiology and pathology. We further call attention to this line of research as an instructive model for probing and therapeutically manipulating the mechanistic links between the nervous system and mammalian skin.

Neuroendocrine Disturbances in Neurodegenerative Disorders: A Scoping Review

BACKGROUND

Neurodegenerative diseases cause progressive irreversible neuronal loss that has broad downstream effects. The neuroendocrine system regulates homeostasis of circuits that control critical functions such as the stress response, metabolism, reproduction, fluid balance, and glucose control. These systems are frequently disrupted in neurodegenerative disorders yet often overlooked in clinical practice.

OBJECTIVE

This review aims to gather the available data regarding these disturbances in Alzheimer's disease, Parkinson's disease, frontotemporal dementia, amyotrophic lateral sclerosis, and Huntington's disease and also to demonstrate the volume of literature in these individual arenas.

METHODS

Using the scoping review framework, a literature search was performed in PubMed to identify relevant articles published within the past 30 years (January 1988 to November 2018). The search criteria produced a total of 2022 articles, 328 of which were identified as relevant to this review.

RESULTS

Several major themes emerged from this review. These neuroendocrine disturbances may be a precursor to the illness, a part of the primary pathophysiology, or a direct consequence of the disease or independent of it. They have the potential to further understanding of the disease, exacerbate the underlying pathology, or provide therapeutic benefit.

CONCLUSIONS

By synthesizing the data from a systems' perspective, we aim to broaden how clinicians think about these illnesses and provide care.

Bone loss caused by dopaminergic degeneration and levodopa treatment in Parkinson's disease model mice

Accumulating evidence have shown the association of Parkinson’s disease (PD) with osteoporosis. Bone loss in PD patients, considered to be multifactorial and a result of motor disfunction, is a hallmark symptom that causes immobility and decreased muscle strength, as well as malnutrition and medication. However, no known experimental evidence has been presented showing deleterious effects of anti-PD drugs on bone or involvement of dopaminergic degeneration in bone metabolism. Here, we show that osteoporosis associated with PD is caused by dopaminergic degeneration itself, with no deficit of motor activity, as well as treatment with levodopa, the current gold-standard medication for affected patients. Our findings show that neurotoxin-induced dopaminergic degeneration resulted in bone loss due to accelerated osteoclastogenesis and suppressed bone formation, which was associated with elevated prolactin. On the other hand, using an experimental model of postmenopausal osteoporosis, dopaminergic degeneration did not result in exacerbation of bone loss due to estrogen deficiency, but rather reduction of bone loss. Thus, this study provides evidence for the regulation of bone metabolism by the dopaminergic system through both gonadal steroid hormone-dependent and -independent functions, leading to possible early detection of osteoporosis development in individuals with PD.

Gender differences in Parkinson's disease: A clinical perspective

Available data indicate that there are gender differences in many features of Parkinson's disease (PD). Precise identification of the gender differences is important to tailor treatment, predict outcomes, and meet other individual and social needs in women and men with PD. The aim of this study was to review the available clinical data on gender differences in PD. Original articles and meta-analyses published between 1990 and 2016 systematically exploring gender differences in PD were reviewed. There is slight male preponderance in incidence and prevalence of PD. PD starts earlier in men. Women tend to be more prone to develop tremor-dominant PD but are less rigid than men. Motor improvement after deep brain stimulation is equal in both sexes, but women tend to show better improvement in activities of daily living. Furthermore, women with PD show better results on tests for general cognitive abilities, outperform men in verbal cognitive tasks, show more pain symptoms, and score higher on depression scales. It seems, however, that the differences in cognition, mood, and pain perception are not disease specific as similar gender differences can be found in healthy subjects and in other neurological conditions. Despite PD being the most frequently studied movement disorder, studies investigating gender differences in PD are still scarce with most of the studies being cross-sectional. Good-quality, prospective, longitudinal studies analyzing gender differences in PD and comparing them to matched healthy controls are needed in order to properly address the issues of gender differences in PD.

Effect of the 5α-reductase enzyme inhibitor dutasteride in the brain of intact and parkinsonian mice

Dutasteride is a 5alpha-reductase inhibitor in clinical use to treat endocrine conditions. The present study investigated the neuroprotective mechanisms of action of dutasteride in intact and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mice using a low dose of MPTP not affecting motor activity modeling early stages of Parkinson's disease (PD). We hypothesized that dutasteride neuroprotection is due to altered steroids levels. Dutasteride pre-treatment prevented loss of striatal dopamine (DA) and its metabolite DOPAC. Dutasteride decreased effects of MPTP on striatal dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2) and D2 DA receptor specific binding while D1 receptor specific binding remained unchanged. Dutasteride enhanced DAT specific binding and the glycosylated form of DAT in intact mice. MPTP-lesioned mice had plasma and brain testosterone and dihydrotestosterone levels lower than control mice whereas progesterone and its metabolites (dihydroprogesterone, isopregnanolone and tetrahydroprogesterone) pathway showed increases. Dutasteride treatment by inhibiting transformation of progesterone and testosterone to its metabolites elevated plasma and brain concentrations of testosterone compared to MPTP mice and decreased DHT levels in intact mice. Plasma and brain estradiol levels were low and remained unchanged by MPTP and/or dutasteride treatment. Dutasteride treatment did not affect striatal phosphorylation of Akt and its downstream substrate GSK3β as well as phosphorylation of ERK1/2 in intact and MPTP lesioned MPTP mice. Striatal glial fibrillary acidic protein (GFAP) levels were markedly elevated in MPTP compared to control mice and dutasteride reduced GFAP levels in MPTP mice. Treatment with dutasteride post-lesion left unchanged striatal DA levels. These results suggest dutasteride as promising drug for PD neuroprotection.

Parkinson's Disease: From Pathogenesis to Pharmacogenomics

Parkinson's disease (PD) is the second most important age-related neurodegenerative disorder in developed societies, after Alzheimer's disease, with a prevalence ranging from 41 per 100,000 in the fourth decade of life to over 1900 per 100,000 in people over 80 years of age. As a movement disorder, the PD phenotype is characterized by rigidity, resting tremor, and bradykinesia. Parkinson's disease -related neurodegeneration is likely to occur several decades before the onset of the motor symptoms. Potential risk factors include environmental toxins, drugs, pesticides, brain microtrauma, focal cerebrovascular damage, and genomic defects. Parkinson's disease neuropathology is characterized by a selective loss of dopaminergic neurons in the substantia nigra pars compacta, with widespread involvement of other central nervous system (CNS) structures and peripheral tissues. Pathogenic mechanisms associated with genomic, epigenetic and environmental factors lead to conformational changes and deposits of key proteins due to abnormalities in the ubiquitin-proteasome system together with dysregulation of mitochondrial function and oxidative stress. Conventional pharmacological treatments for PD are dopamine precursors (levodopa, l-DOPA, l-3,4 dihidroxifenilalanina), and other symptomatic treatments including dopamine agonists (amantadine, apomorphine, bromocriptine, cabergoline, lisuride, pergolide, pramipexole, ropinirole, rotigotine), monoamine oxidase (MAO) inhibitors (selegiline, rasagiline), and catechol-O-methyltransferase (COMT) inhibitors (entacapone, tolcapone). The chronic administration of antiparkinsonian drugs currently induces the "wearing-off phenomenon", with additional psychomotor and autonomic complications. In order to minimize these clinical complications, novel compounds have been developed. Novel drugs and bioproducts for the treatment of PD should address dopaminergic neuroprotection to reduce premature neurodegeneration in addition to enhancing dopaminergic neurotransmission. Since biochemical changes and therapeutic outcomes are highly dependent upon the genomic profiles of PD patients, personalized treatments should rely on pharmacogenetic procedures to optimize therapeutics.

Increased Risk of Parkinson's Disease in Patients With Obstructive Sleep Apnea: A Population-Based, Propensity Score-Matched, Longitudinal Follow-Up Study

Obstructive sleep apnea (OSA), characterized by repetitive episodes of apnea/hypopnea and hypoxia, is associated with systemic inflammation and induces metabolic, endocrine, and cardiovascular diseases. Inflammation might have an impact on neurodegenerative diseases. This study investigates the possible association between OSA and Parkinson's disease (PD). Random samples out of 1 million individuals were collected from Taiwan's National Health Insurance database. A total of 16,730 patients with newly diagnosed OSA from 2002 to 2008 were recruited and compared with a cohort of 16,730 patients without OSA matched for age, gender, and comorbidities using propensity scoring. All patients were tracked until a diagnosis of PD, death, or the end of 2011.During the mean 5.6-year follow-up period, the incidence rates of PD were 2.30 per 1000 person-years in the OSA cohort and 1.71per 1000 person-years in the comparison group. The incidence rate ratio (IRR) for PD was greater in older patients (≧ 65 years) and male patients with OSA than the controls, respective IRRs being 1.34 and 1.47. After adjustment for the comorbidities, patients with OSA were 1.37 times more likely to have PD than patients without (95% CI = 1.12-1.68, P < 0.05). Subgroup analysis showed that older patients and patients with coronary artery disease, stroke, or chronic kidney disease had a higher risk for PD than their counter parts. Log-rank analysis revealed that patients with OSA had significantly higher cumulative incidence rates of PD than the comparison group (P = 0.0048). Patients with OSA are at an increased risk for subsequent PD, especially elderly male patients.