Effects of sex steroids on the neurotransmitter-specific aromatic amino acids phenylalanine, tyrosine, and tryptophan in transsexual subjects

Combined effects of copper and cadmium exposure on ovarian function and structure in Nile Tilapia (Oreochromis niloticus)

With the rapid development of industrialization and urbanization, the issue of copper (Cu) and cadmium (Cd) pollution in aquatic ecosystems has become increasingly severe, posing threats to the ovarian tissue and reproductive capacity of aquatic organisms. However, the combined effects of Cu and Cd on the ovarian development of fish and other aquatic species remain unclear. In this study, female Nile tilapia (Oreochromis niloticus) were individually or co-exposed to Cu and/or Cd in water. Ovarian and serum samples were collected at 15, 30, 60, 90, and 120 days, and the bioaccumulation, ovarian development, and hormone secretion were analyzed. Results showed that both single and combined exposure significantly reduced the gonadosomatic index and serum hormone levels, upregulated estrogen receptor (er) and progesterone receptor (pr) gene transcription levels, and markedly affected ovarian metabolite levels. Combined exposure led to more adverse effects than single exposure. The data demonstrate that the Cu and Cd exposure can impair ovarian function and structure, with more pronounced adverse effects under Cu and Cd co-exposure. The Cu and Cd affect the metabolic pathways of nucleotides and amino acids, leading to ovarian damage. This study highlights the importance of considering combined toxicant exposure in aquatic toxicology research and provides insights into the potential mechanisms underlying heavy metal-induced reproductive toxicity in fish.

The impact of estradiol on serotonin, glutamate, and dopamine systems

Estradiol, the most potent and prevalent member of the estrogen class of steroid hormones and is expressed in both sexes. Functioning as a neuroactive steroid, it plays a crucial role in modulating neurotransmitter systems affecting neuronal circuits and brain functions including learning and memory, reward and sexual behaviors. These neurotransmitter systems encompass the serotonergic, dopaminergic, and glutamatergic signaling pathways. Consequently, this review examines the pivotal role of estradiol and its receptors in the regulation of these neurotransmitter systems in the brain. Through a comprehensive analysis of current literature, we investigate the multifaceted effects of estradiol on key neurotransmitter signaling systems, namely serotonin, dopamine, and glutamate. Findings from rodent models illuminate the impact of hormone manipulations, such as gonadectomy, on the regulation of neuronal brain circuits, providing valuable insights into the connection between hormonal fluctuations and neurotransmitter regulation. Estradiol exerts its effects by binding to three estrogen receptors: estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), and G protein-coupled receptor (GPER). Thus, this review explores the promising outcomes observed with estradiol and estrogen receptor agonists administration in both gonadectomized and/or genetically knockout rodents, suggesting potential therapeutic avenues. Despite limited human studies on this topic, the findings underscore the significance of translational research in bridging the gap between preclinical findings and clinical applications. This approach offers valuable insights into the complex relationship between estradiol and neurotransmitter systems. The integration of evidence from neurotransmitter systems and receptor-specific effects not only enhances our understanding of the neurobiological basis of physiological brain functioning but also provides a comprehensive framework for the understanding of possible pathophysiological mechanisms resulting to disease states. By unraveling the complexities of estradiol's impact on neurotransmitter regulation, this review contributes to advancing the field and lays the groundwork for future research aimed at refining understanding of the relationship between estradiol and neuronal circuits as well as their involvement in brain disorders.

Sex Differences in Tryptophan Metabolism: A Systematic Review Focused on Neuropsychiatric Disorders

Tryptophan (Tryp) is an essential amino acid and the precursor of several neuroactive compounds within the central nervous system (CNS). Tryp metabolism, the common denominator linking serotonin (5-HT) dysfunctions and neuroinflammation, is involved in several neuropsychiatric conditions, including neurological, neurodevelopmental, neurodegenerative, and psychiatric diseases. Interestingly, most of those conditions occur and progress in a sex-specific manner. Here, we explore the most relevant observations about the influence of biological sex on Tryp metabolism and its possible relation to neuropsychiatric diseases. Consistent evidence suggests that women have a higher susceptibility than men to suffer serotoninergic alterations due to changes in the levels of its precursor Tryp. Indeed, female sex bias in neuropsychiatric diseases is involved in a reduced availability of this amino acid pool and 5-HT synthesis. These changes in Tryp metabolism could lead to sexual dimorphism on the prevalence and severity of some neuropsychiatric disorders. This review identifies gaps in the current state of the art, thus suggesting future research directions. Specifically, there is a need for further research on the impact of diet and sex steroids, both involved in this molecular mechanism as they have been poorly addressed for this topic.

The Effect of Gender-Affirming Hormone Therapy on Measures of Kidney Function: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Gender-affirming hormone therapy modifies body composition and lean muscle mass in transgender persons. We sought to characterize the change in serum creatinine, other kidney function biomarkers, and GFR in transgender persons initiating masculinizing and feminizing gender-affirming hormone therapy.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We searched PubMed, EMBASE, the Cochrane Library, and ClinicalTrials.gov from inception to September 16, 2020 for randomized controlled trials, observational studies, and case series that evaluated the change in serum creatinine, other kidney function biomarkers, and GFR before and after the initiation of gender-affirming hormone therapy in adult transgender persons. Two reviewers independently screened and abstracted data, and disagreements were resolved by a third reviewer. A random effects meta-analysis was performed to determine the change in outcomes over follow-up of 3, 6, and 12 months.

RESULTS

Of the 4758 eligible studies, 26 met the inclusion criteria, including nine studies that recruited 488 transgender men and 593 women in which data were meta-analyzed. There was heterogeneity in study design, populations, gender-affirming hormone therapy routes, and dosing. At 12 months after initiating gender-affirming hormone therapy, serum creatinine increased by 0.15 mg/dl (95% confidence interval, 0.00 to 0.29) in 370 transgender men and decreased by -0.05 mg/dl (95% confidence interval, -0.16 to 0.05) in 361 transgender women. No study reported the effect of gender-affirming hormone therapy on albuminuria, proteinuria, cystatin C, or measured GFR.

CONCLUSIONS

Gender-affirming hormone therapy increases serum creatinine in transgender men and does not affect serum creatinine in transgender women. The effect on gender-affirming hormone therapy on other kidney function biomarkers and measured GFR is unknown.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Change in Kidney Function Biomarkers in Transgender Persons on Gender Affirmation Hormone Therapy-A Systematic Review and Meta-Analysis, CRD42020214248.

Acupuncture ameliorates breast cancer-related fatigue by regulating the gut microbiota-gut-brain axis

Cancer-related fatigue (CRF) is the most common side effect of chemotherapy for breast cancer (BC). Acupuncture treatment has an anti-fatigue effect and can regulate gut microbiota disturbance in fatigue patients. Related studies have shown that the gut microbiota-gut-brain axis is closely related to the occurrence of CRF. In this study, we first investigated the alterations of acupuncture on fatigue-like behavior, gut microbiota, gut inflammation and neuroinflammation response, gut barriers, HPA axis, and serum metabolomics in CRF mice after BC chemotherapy. Then, the correlation analysis of gut microbiota and other indicators was discussed. Our results showed that acupuncture treatment could exert an anti-fatigue effect and ameliorate the gut barrier, gut inflammation, neuroinflammation, and dysfunction of the HPA axis in CRF mice after chemotherapy for BC. 16S rRNA sequencing showed that acupuncture treatment could enhance the abundance of Candidatus Arthromitus, Lactobacillus, and Clostridia_UCG-014_unclassified and decrease the abundances of Escherichia-Shigella, Burkholderia-Caballeronia-Paraburkholderia, and Streptococcus. Serum metabolomics analysis showed that acupuncture treatment could regulate the differential metabolites N-methylnicotinamide, beta-glycerophosphoric acid, geranyl acetoacetate, serotonin and phenylalanine, tyrosine and tryptophan biosynthesis, taurine and hypotaurine, and beta-alanine metabolic pathways. Correlation analysis indicated that there are certain correlations between gut microbiota and gut inflammation, neuroinflammation, gut barrier, HPA axis function and serum metabolites. In conclusion, our findings revealed that the anti-fatigue mechanism of acupuncture treatment may be closely related to the gut microbiota-gut-brain axis. This study also provided a new reference for basic and clinical research on CRF after breast cancer chemotherapy.

Antiandrogen or estradiol treatment or both during hormone therapy in transitioning transgender women

BACKGROUND

Gender dysphoria is described as a mismatch between an individual's experienced or expressed gender and their assigned gender, based on primary or secondary sexual characteristics. Gender dysphoria can be associated with clinically significant psychological distress and may result in a desire to change sexual characteristics. The process of adapting a person's sexual characteristics to their desired sex is called 'transition.' Current guidelines suggest hormonal and, if needed, surgical intervention to aid transition in transgender women, i.e. persons who aim to transition from male to female. In adults, hormone therapy aims to reverse the body's male attributes and to support the development of female attributes. It usually includes estradiol, antiandrogens, or a combination of both. Many individuals first receive hormone therapy alone, without surgical interventions. However, this is not always sufficient to change such attributes as facial bone structure, breasts, and genitalia, as desired. For these transgender women, surgery may then be used to support transition.

OBJECTIVES

We aimed to assess the efficacy and safety of hormone therapy with antiandrogens, estradiol, or both, compared to each other or placebo, in transgender women in transition.

SEARCH METHODS

We searched MEDLINE, the Cochrane Central Register of Controlled Trials (CENTRAL), Embase, Biosis Preview, PsycINFO, and PSYNDEX. We carried out our final searches on 19 December 2019.

SELECTION CRITERIA

We aimed to include randomised controlled trials (RCTs), quasi-RCTs, and cohort studies that enrolled transgender women, age 16 years and over, in transition from male to female. Eligible studies investigated antiandrogen and estradiol hormone therapies alone or in combination, in comparison to another form of the active intervention, or placebo control.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane to establish study eligibility.

MAIN RESULTS

Our database searches identified 1057 references, and after removing duplicates we screened 787 of these. We checked 13 studies for eligibility at the full text screening stage. We excluded 12 studies and identified one as an ongoing study. We did not identify any completed studies that met our inclusion criteria. The single ongoing study is an RCT conducted in Thailand, comparing estradiol valerate plus cyproterone treatment with estradiol valerate plus spironolactone treatment. The primary outcome will be testosterone level at three month follow-up.

AUTHORS' CONCLUSIONS

We found insufficient evidence to determine the efficacy or safety of hormonal treatment approaches for transgender women in transition. This lack of studies shows a gap between current clinical practice and clinical research. Robust RCTs and controlled cohort studies are needed to assess the benefits and harms of hormone therapy (used alone or in combination) for transgender women in transition. Studies should specifically focus on short-, medium-, and long-term adverse effects, quality of life, and participant satisfaction with the change in male to female body characteristics of antiandrogen and estradiol therapy alone, and in combination. They should also focus on the relative effects of these hormones when administered orally, transdermally, and intramuscularly. We will include non-controlled cohort studies in the next iteration of this review, as our review has shown that such studies provide the highest quality evidence currently available in the field. We will take into account methodological limitations when doing so.

Plasma tryptophan and kynurenine pathway metabolites in abstinent patients with alcohol use disorder and high prevalence of psychiatric comorbidity

BACKGROUND

Alterations in tryptophan (TRP) metabolism has been linked to drug exposure and mental disorders. However, most of studies have been performed without considering the co-occurrence of both disorders in the context of addiction. This cross-sectional study examines TRP metabolism through the serotonin (5-HT) and kynurenine (KYN) pathways in subjects with alcohol use disorders (AUD) and high prevalence of psychiatric comorbidity.

METHODS

For this purpose, male and female abstinent AUD patients (N = 130) and healthy controls (N = 80) were clinically evaluated for substance use and mental disorders, and blood samples were collected to determine plasma concentrations of TRP, 5-HT, KYN and kynurenic acid (KA) using high performance liquid chromatography. Clinical and biochemical variables were analyzed for potential associations considering AUD, psychiatric comorbidity and sex.

RESULTS

TRP concentrations were significantly associated with an interaction effect between AUD diagnosis and sex (p < .01): TRP concentrations were lower in male AUD patients but higher in female AUD patients compared with their controls. KYN and KA concentrations were significantly associated with AUD diagnosis (p < .01 and p < .05, respectively). Thus, AUD patients showed significantly higher KYN concentrations and lower KA concentrations than controls. Regarding 5-HT concentrations, there were sex differences in the alcohol group (p < .05) and female AUD patients showed lower 5-HT concentrations than male AUD patients. Moreover, there was a significant interaction effect between psychiatric comorbidity and sex on TRP concentrations in the alcohol group (p < .01). Whereas male patients with both comorbid substance use and mental disorders showed lower TRP concentrations than male non-comorbid patients, female patients with comorbid mental disorders showed higher TRP concentrations than female non-comorbid patients.

CONCLUSION

While alterations in the KYN pathway appear to be directly associated with a history of AUD, altered TRP concentrations are associated with the presence of comorbid psychiatric disorders. Finally, sex differences in TRP metabolism must be considered in future studies.

Serotonin-estrogen interactions: What can we learn from pregnancy?

We have reviewed the scientific literature related to four diseases in which to serotonin (5-HT) is involved in the etiology, herein named 5-HT-linked diseases, and whose prevalence is influenced by estrogenic status: depression, migraine, irritable bowel syndrome and eating disorders. These diseases all have in common a sex-dimorphic prevalence, with women more frequently affected than men. The co-occurrence between these 5-HT-linked diseases suggests that they have common physiopathological mechanisms. In most 5-HT-linked diseases (except for anorexia nervosa and irritable bowel syndrome), a decrease in the serotonergic tone is observed and estrogens are thought to contribute to the improvement of symptoms by stimulating the serotonergic system. Human pregnancy is characterized by a unique 5-HT and estrogen synthesis by the placenta. Pregnancy-specific disorders, such as hyperemesis gravidarum, gestational diabetes mellitus and pre-eclampsia, are associated with a hyperserotonergic state and decreased estrogen levels. Fetal programming of 5-HT-linked diseases is a complex phenomenon that involves notably fetal-sex differences, which suggest the implication of sex steroids. From a mechanistic point of view, we hypothesize that estrogens regulate the serotonergic system, resulting in a protective effect against 5-HT-linked diseases, but that, in turn, 5-HT affects estrogen synthesis in an attempt to retrieve homeostasis. These two processes (5-HT and estrogen biosynthesis) are crucial for successful pregnancy outcomes, and thus, a disruption of this 5-HT-estrogen relationship may explain pregnancy-specific pathologies or pregnancy complications associated with 5-HT-linked diseases.

Serum Metabolomics Study of Nonsmoking Female Patients with Non-Small Cell Lung Cancer Using Gas Chromatography-Mass Spectrometry

The incidence of nonsmoking female patients with non-small cell lung cancer (NSCLC) has increased in recent decades; however, the pathogenesis of patients is unclear, and early diagnosis biomarkers are in urgent need. In this study, 136 nonsmoking female subjects (65 patients with NSCLC, 6 patients with benign lung tumors, and 65 healthy controls) were enrolled, and their metabolic profiling was investigated by using pseudotargeted gas chromatography-mass spectrometry. A total of 56 annotated metabolites were found and verified to be significantly different in nonsmoking females with NSCLC compared with the control. The metabolic profiling was featured by disturbed energy metabolism, amino acid metabolism, oxidative stress, lipid metabolism, and so on. Cysteine, serine, and 1-monooleoylglycerol were defined as the biomarker panel for the diagnosis of NSCLC patients. 98.5 and 91.4% of subjects were correctly distinguished in the discovery and validation sets, respectively. The biomarker panel was also useful for the diagnosis of in situ malignancy patients, with an accuracy of 97.7 and 97.8% in the discovery and validation sets, respectively. The study provides a biomarker panel for the auxiliary diagnosis of nonsmoking females with NSCLC.

Untargeted metabolomic analysis in non-fasted diabetic dogs by UHPLC-HRMS

INTRODUCTION

We recently identified variances in serum metabolomic profiles between fasted diabetic and healthy dogs, some having similarities to those identified in human type 1 diabetes.

OBJECTIVES

Compare untargeted metabolomic profiles in the non-fasted state.

METHODS

Serum from non-fasted diabetic (n = 6) and healthy control (n = 6) dogs were analyzed by liquid chromatography-high resolution mass spectrometry.

RESULTS

Clear clustering of metabolites between groups were observed, with multiple perturbations identified that were similar to those previously observed in fasted diabetic dogs.

CONCLUSION

These findings further support the development of targeted assays capable of detecting metabolites that may be useful as biomarkers of canine diabetes.

Mechanisms of pain modulation by sex hormones in migraine

A number of pain conditions, acute as well as chronic, are much more prevalent in women, such as temporomandibular disorder (TMD), irritable bowel syndrome, fibromyalgia, and migraine. The association of female sex steroids with these nociceptive conditions is well known, but the mechanisms of their effects on pain signaling are yet to be deciphered. We reviewed the mechanisms through which female sex steroids might influence the trigeminal nociceptive pathways with a focus on migraine. Sex steroid receptors are located in trigeminal circuits, providing the molecular substrate for direct effects. In addition to classical genomic effects, sex steroids exert rapid nongenomic actions to modulate nociceptive signaling. Although there are only a handful of studies that have directly addressed the effect of sex hormones in animal models of migraine, the putative mechanisms can be extrapolated from observations in animal models of other trigeminal pain disorders, like TMD. Sex hormones may regulate sensitization of trigeminal neurons by modulating expression of nociceptive mediator such as calcitonin gene-related peptide. Its expression is mostly positively regulated by estrogen, although a few studies also report an inverse relationship. Serotonin (5-Hydroxytryptamine [5-HT]) is a neurotransmitter implicated in migraine; its synthesis is enhanced in most parts of brain by estrogen, which increases expression of the rate-limiting enzyme tryptophan hydroxylase and decreases expression of the serotonin re-uptake transporter. Downstream signaling, including extracellular signal-regulated kinase activation, calcium-dependent mechanisms, and cAMP response element-binding activation, are thought to be the major signaling events affected by sex hormones. These findings need to be confirmed in migraine-specific animal models that may also provide clues to additional ion channels, neuropeptides, and intracellular signaling cascades that contribute to the increased prevalence of migraine in women.

Emotional states of love moderate the association between catecholamines and female sexual responses in the laboratory

INTRODUCTION

Research suggests that there are three interrelated, yet distinct, emotion-motivation brain systems for human love (lust, romantic love, and attachment), each associated with a unique catecholaminergic and hormonal profile. Of interest for the current study are norepinephrine (NE) and dopamine (DA), which have a hypothesized connection with romantic love. As NE and DA are also known to facilitate sexual arousal, it is plausible that NE and DA may have a greater positive association with the sexual arousal responses of women in romantic love compared with women in lust.

AIM

This study investigated if the effects of NE and DA activity on sexual arousal responses would differ depending on emotion-motivation state (Lust or Romantic).

MAIN OUTCOME MEASURES

Physiological sexual arousal was assessed by photoplethysmography and subjective sexual arousal was assessed with a participant-controlled lever.

METHODS

Seventeen women were included in the Lust group and 29 in the Romantic group. All participants provided a urine sample (to assess NE and DA) and completed a psychophysiological assessment.

RESULTS

Elevated NE was positively and significantly associated with greater subjective and physiological sexual arousal for the Lust group, but not for the Romantic group. Similarly, elevated DA was positively and significantly associated with greater subjective sexual arousal for the Lust group, but not for the Romantic group.

CONCLUSIONS

The sexual arousal responses of women in the Lust group, but not in the Romantic group, were positively and significantly associated with elevated NE and DA. It is feasible that, when women are seeking a partner (Lust), NE and DA may facilitate attention toward sexually relevant stimuli.

Sex, hormones and neuroeffector mechanisms

Incidence and rate of cardiovascular disease differ between men and women across the life span. Although hypertension is more prominent in men than women, there is a group of vasomotor disorders [i.e. Raynaud's disease, postural orthostatic tachycardia syndrome and vasomotor symptoms (hot flashes) of menopause and migraine] with a female predominance. Both sex and hormones interact to modulate neuroeffector mechanisms including integrated regulation of the Sry gene and direct effect of sex steroid hormones on synthesis, release and disposition of monoamine neurotransmitters, and distribution and sensitivity of their receptors in brain areas associated with autonomic control. The interaction of the sex chromosomes and steroids also modulates these effector tissues, that is, the heart, vascular smooth muscle and endothelium. Although involvement of central serotonergic centres has been studied in regard to mood disorders such as depression, their contribution to cardiovascular risk is gaining attention. Studies are needed to further evaluate how hormonal treatments and drugs used to modulate adrenergic and serotonergic activity affect progression and risk for cardiovascular disease in men and women.

Contextual influences on sexual risk-taking in the transgender community

High HIV prevalence and incidence rates and high-risk sexual activity have been documented in certain subgroups of the transgender community; however, less is known about the sexual experiences and risks shared by these subgroups. To identify contextual features influencing the sexual risk-taking of transgender adults, semi-structured interviews conducted with 41 self-identified transgender adults were analyzed via constant comparative analysis, a technique rooted in grounded theory. Seven aspects of the transgender experience, including stigma, financial hardship, sexual objectification, a lack of outreach, hormones, a second puberty, and gender role issues, created a unique context of risk. Findings indicate that traditional HIV prevention efforts might not be suited to the unique needs of transgender adults. Tailoring HIV prevention efforts to this community will warrant further attention to contextual influences on sexual risk and safety.

Dopaminergic and serotonergic activity in neostriatum and nucleus accumbens enhanced by intranasal administration of testosterone

Testosterone was administered intranasally in anesthetized male rats, and its effects on the activity of dopaminergic and serotonergic neurons in the neostriatum and nucleus accumbens were assessed by means of microdialysis and HPLC. The treatment (0.5, 1.0 or 2.0 mg/kg of testosterone or vehicle, 10 microl volume) was applied in both nostrils, half (5 microl) into each. Subcutaneous injections of testosterone (2.0, 4.0 or 8.0 mg/kg) or vehicle were tested in other subjects. Samples were collected for 5 h. In the neostriatum, an increase of dopamine occurred after 2.0 mg/kg. Serotonin levels increased after 1.0 mg/kg dose. In the nucleus accumbens, dopamine and serotonin increased after 1.0 mg/kg and 2.0 mg/kg doses. Subcutaneous administration of 8.0 mg/kg testosterone increased dopamine and serotonin in the neostriatum only. We conclude that intranasal administration of testosterone is a more efficacious way for targeting the brain than the subcutaneous route, and may be considered as a means to activate central dopaminergic and serotonergic systems.