The Diverse Metabolic Roles of Peripheral Serotonin

Spontaneous running wheel exercise during pregnancy prevents later neonatal-anoxia-induced somatic and neurodevelopmental alterations

Introduction

About 15-20 % of babies that suffer perinatal asphyxia die and around 25 % of the survivors exhibit permanent neural outcomes. Minimization of this global health problem has been warranted. This study investigated if the offspring of pregnant female rats allowed to spontaneously exercise on running wheels along a 11-day pregnancy period were protected for somatic and neurodevelopmental disturbs that usually follow neonatal anoxia.

Methods

spontaneous exercise was applied to female rats which were housed in cages allowing free access to running wheels along a 11-day pregnancy period. Their offspring were submitted to anoxia 24-36 h after birth. Somatic and sensory-motor development of the pups were recorded until postnatal day 21 (P21). Myelin basic protein (MBP)-stained areas of sensory and motor cortices were measured at P21. Neuronal nuclei (NeuN)-immunopositive cells and synapsin-I levels in hippocampal formation were estimated at P21 and P75.

Results

gestational exercise and / or neonatal anoxia increased the weight and the size of the pups. In addition, gestational exercise accelerated somatic and sensory-motor development of the pups and protected them against neonatal-anoxia-induced delay in development. Further, neonatal anoxia reduced MBP stained area in the secondary motor cortex and decreased hippocampal neuronal estimates and synapsin-I levels at P21; gestational exercise prevented these effects. Therefore, spontaneous exercise along pregnancy is a valuable strategy to prevent neonatal-anoxia-induced disturbs in the offspring.

Conclusion

spontaneous gestational running wheel exercise protects against neonatal anoxia-induced disturbs in the offspring, including (1) physical and neurobehavioral developmental impairments, and (2) hippocampal and cortical changes. Thus, spontaneous exercise during pregnancy may represent a valuable strategy to prevent disturbs which usually follow neonatal anoxia.

Serotonergic elements in the nervous system of parasite of acipenserid fishes, Acrolichanus auriculatus (Digenea: Allocreadiidae)

The trematode Acrolichanus auriculatus is a widely distributed intestine parasite of acipenserid fishes. For the first time the localization and distribution of the serotonergic nerve elements in A. auriculatus was studied using immunocytochemical method and confocal laser scanning microscopy. The study revealed the presence of biogenic amine, serotonin, in the central and peripheral nervous systems of A. auriculatus, that is in the neurons and neurites of the brain ganglia, brain commissure, the longitudinal nerve cords, and the connective nerve commissures. The innervation of the attachment organs, pharynx, oesophagus and distal regions of the reproductive system by the serotonergic nerve elements is observed. The distribution of serotonergic neurons in A. auriculatus is schematically marked. The comparative analysis of findings obtained in A. auriculatus with those recorded for other digeneans reveals the presence of both conservative and distinctive features in the organization of the serotonergic nervous system in various representatives of trematodes.

Gut microbiota metabolites: potential therapeutic targets for Alzheimer's disease?

Background

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive decline in cognitive function, which significantly increases pain and social burden. However, few therapeutic interventions are effective in preventing or mitigating the progression of AD. An increasing number of recent studies support the hypothesis that the gut microbiome and its metabolites may be associated with upstream regulators of AD pathology.

Methods

In this review, we comprehensively explore the potential mechanisms and currently available interventions targeting the microbiome for the improvement of AD. Our discussion is structured around modern research advancements in AD, the bidirectional communication between the gut and brain, the multi-target regulatory effects of microbial metabolites on AD, and therapeutic strategies aimed at modulating gut microbiota to manage AD.

Results

The gut microbiota plays a crucial role in the pathogenesis of AD through continuous bidirectional communication via the microbiota-gut-brain axis. Among these, microbial metabolites such as lipids, amino acids, bile acids and neurotransmitters, especially sphingolipids and phospholipids, may serve as central components of the gut-brain axis, regulating AD-related pathogenic mechanisms including β-amyloid metabolism, Tau protein phosphorylation, and neuroinflammation. Additionally, interventions such as probiotic administration, fecal microbiota transplantation, and antibiotic use have also provided evidence supporting the association between gut microbiota and AD. At the same time, we propose an innovative strategy for treating AD: a healthy lifestyle combined with targeted probiotics and other potential therapeutic interventions, aiming to restore intestinal ecology and microbiota balance.

Conclusion

Despite previous efforts, the molecular mechanisms by which gut microbes act on AD have yet to be fully described. However, intestinal microorganisms may become an essential target for connecting the gut-brain axis and improving the symptoms of AD. At the same time, it requires joint exploration by multiple centers and multiple disciplines.

Deficiency of 5-HT2B receptors alleviates atherosclerosis by regulating macrophage phenotype through inhibiting interferon signalling

BACKGROUND AND PURPOSE

Elevated levels of 5-HT have been correlated with coronary artery disease and cardiac events, suggesting 5-HT is a potential novel factor in the development of atherosclerotic cardiovascular disease. However, the underlying pathological mechanisms of the 5-HT system in atherosclerosis remain unclear. The 5-HT2B receptor (5-HT2BR), which establishes a positive feedback loop with 5-HT, has been identified as a contributor to pathophysiological processes in various vascular disorders. In this study, we investigated the immunological impact of 5-HT2BR in atherosclerosis-prone apolipoprotein E-deficient (ApoE-/-) mice.

EXPERIMENTAL APPROACH

Plasma levels of 5-HT were measured in mice using an ELISA kit. Atherosclerotic plaque formation, macrophage infiltration and inflammatory signalling were assessed in ApoE-/- mice by employing both pharmacological inhibition and genetic deficiency of 5-HT2BR. Inflammasome activation was elucidated using peritoneal macrophages isolated from 5-HT2BR-deficient mice.

KEY RESULTS

An upregulation of 5-HT2BR expression was observed in the aortas of ApoE-/- mice, exhibiting a strong correlation with the presence of macrophages in plaques. Atherosclerosis was attenuated in mice through pharmacological inhibition and genetic deficiency of 5-HT2BR. Additionally, a significant reduction in atherosclerotic plaque size was achieved through bone marrow reconstitution with 5-HT2BR-deficient cells. 5-HT2BR-deficient macrophages showed attenuated interferon (IFN) signalling, NLRP3 inflammasome activation, and interleukin-1β release. Moreover, macrophages primed with 5-HT2BR deficiency displayed an anti-inflammatory phenotype.

CONCLUSION AND IMPLICATIONS

These findings support the hypothesis that 5-HT2BR in macrophages plays a causal role in the development of atherosclerosis, revealing a novel perspective for potential therapeutic strategies in atherosclerosis-related diseases.

Sodium oligomannate activates the enteroendocrine-vagal afferent pathways in APP/PS1 mice

Enteroendocrine cells (EECs) and vagal afferent neurons constitute functional sensory units of the gut, which have been implicated in bottom-up modulation of brain functions. Sodium oligomannate (GV-971) has been shown to improve cognitive functions in murine models of Alzheimer's disease (AD) and recently approved for the treatment of AD patients in China. In this study, we explored whether activation of the EECs-vagal afferent pathways was involved in the therapeutic effects of GV-971. We found that an enteroendocrine cell line RIN-14B displayed spontaneous calcium oscillations due to TRPA1-mediated calcium entry; perfusion of GV-971 (50, 100 mg/L) concentration-dependently enhanced the calcium oscillations in EECs. In ex vivo murine jejunum preparation, intraluminal infusion of GV-971 (500 mg/L) significantly increased the spontaneous and distension-induced discharge rate of the vagal afferent nerves. In wild-type mice, administration of GV-971 (100 mg· kg-1 ·d-1, i.g. for 7 days) significantly elevated serum serotonin and CCK levels and increased jejunal afferent nerve activity. In 7-month-old APP/PS1 mice, administration of GV-971 for 12 weeks significantly increased jejunal afferent nerve activity and improved the cognitive deficits in behavioral tests. Sweet taste receptor inhibitor Lactisole (0.5 mM) and the TRPA1 channel blocker HC-030031 (10 µM) negated the effects of GV-971 on calcium oscillations in RIN-14B cells as well as on jejunal afferent nerve activity. In APP/PS1 mice, co-administration of Lactisole (30 mg ·kg-1 ·d-1, i.g. for 12 weeks) attenuated the effects of GV-971 on serum serotonin and CCK levels, vagal afferent firing, and cognitive behaviors. We conclude that GV-971 activates sweet taste receptors and TRPA1, either directly or indirectly, to enhance calcium entry in enteroendocrine cells, resulting in increased CCK and 5-HT release and consequent increase of vagal afferent activity. GV-971 might activate the EECs-vagal afferent pathways to modulate cognitive functions.

A label-free fluorescence aptamer sensor for point-of-care serotonin detection

Serotonin, a pivotal neurotransmitter regulating various physiological functions, plays a crucial role in disease diagnosis, necessitating precise monitoring of its levels in biological fluids for accurate assessment. Aptamers, known for their high specificity and affinity, have emerged as innovative molecular probes for serotonin analysis. However, existing serotonin aptamer sensing platforms exhibit limitations in terms of portability and rapid detection capabilities. In this study, we introduce a novel, portable, label-free serotonin aptamer sensor utilizing a dye replacement strategy, achieving a short sample-to-result turnaround time and convenient signal readout through a smartphone. The performance of this aptamer sensor was thoroughly assessed across diverse physiological media, demonstrating robust stability in buffer, urine, and serum. Importantly, the detection limit was in the nanomolar range, emphasizing its suitability for the rapid, sensitive, and user-friendly detection of serotonin. This research pioneers an approach for the development of a point-of-care testing (POCT) system for serotonin with practical implications, particularly in resource-limited settings.

Host-microbe serotonin metabolism

As a result of a long evolutionary history, serotonin plays a variety of physiological roles, including neurological, cardiovascular, gastrointestinal, and endocrine functions. While many of these activities can be accommodated within the serotoninergic activity, recent findings have revealed an unsuspected role of serotonin in orchestrating host and microbial dialogue at the tryptophan dining table, to the benefit of local and systemic homeostasis. Herein we review the dual role of serotonin at the host-microbe interface and discuss how unraveling the interconnections among the host and microbial pathways of tryptophan degradation may help to accommodate the versatility of serotonin in physiology and pathology.

The Influence of BMP6 on Serotonin and Glucose Metabolism

Previous studies have suggested a potential role of bone morphogenetic protein 6 (BMP6) in glucose metabolism, which also seems to be regulated by serotonin (5-hydroxytryptamine, 5HT), a biogenic amine with multiple roles in the organism. In this study, we explored possible interactions between BMP6, serotonin, and glucose metabolism regulation. The effect of BMP6 or 5HT on pancreatic β-cells has been studied in vitro using the INS-1 832/13 rat insulinoma cell line. Studies in vivo have been performed on mice with the global deletion of the Bmp6 gene (BMP6-/-) and included glucose and insulin tolerance tests, gene expression studies using RT-PCR, immunohistochemistry, and ELISA analyses. We have shown that BMP6 and 5HT treatments have the opposite effect on insulin secretion from INS-1 cells. The effect of BMP6 on the 5HT system in vivo depends on the tissue studied, with no observable systemic effect on peripheral 5HT metabolism. BMP6 deficiency does not cause diabetic changes, although a mild difference in insulin tolerance test between BMP6-/- and WT mice was observed. In conclusion, BMP6 does not directly influence glucose metabolism, but there is a possibility that its deletion causes slowly developing changes in glucose and serotonin metabolism, which would become more expressed with ageing.

Effects of Different Protein Sources on Amino Acid Absorption and Plasma Appearance of Tryptophan, Large Neutral Amino Acids, and Tryptophan Metabolites in Pigs

BACKGROUND

Absorption of tryptophan (TRP) across the gut epithelium is potentially modulated by competing large neutral amino acids (LNAAs), which could affect the appearance of TRP and its metabolites in the bloodstream.

OBJECTIVES

This study aimed to determine, in a growing pig model of an adult human, the absorption of TRP and other LNAAs from the gastrointestinal tract, and plasma appearance of TRP, LNAAs, and TRP metabolites, in response to dietary proteins varying in TRP content.

METHODS

Pigs were adapted for 7 d to each of 4 diets that differed in their protein source and TRP content: 1) alpha-lactalbumin (AL; 9.95 mg TRP/g diet DM), 2) whey protein (6.59 mg TRP/g), 3) casein (3.73 mg TRP/g), or 4) zein (0.14 mg TRP/g). On day 8, pigs were euthanised after a 12-h fast (baseline), or 1, 2, 3, 4, or 6 h after they received a test meal consisting of 45 g protein, or a protein-free meal (n = 6 pigs at each time in each meal group). Tryptophan and LNAA absorption from the small intestine, and appearance of TRP, LNAAs, and TRP metabolites (melatonin, serotonin, kynurenine pathway metabolites), in the portal vein and systemic circulation, were determined.

RESULTS

AL intake resulted in sustained elevated plasma TRP concentrations after an overnight fast. The amount of TRP absorbed was dose-dependently related to protein TRP content (P = 0.028), with fastest rates for pigs fed AL (371 mg/h). Portal and systemic plasma TRP, TRP/LNAA, and the TRP metabolites were highest (P ≤ 0.05) after AL intake, and remained above baseline levels for ∼4 h postprandially. Absorption rates of TRP correlated with postprandial plasma TRP and TRP metabolites (P ≤ 0.05).

CONCLUSIONS

In adult humans, postprandial plasma TRP and TRP metabolite concentrations can likely be modulated by the TRP content of the meal.

Alterations in tryptophan metabolism and de novo NAD+ biosynthesis within the microbiota-gut-brain axis in chronic intestinal inflammation

Background

Inflammatory bowel disease is an incurable and idiopathic disease characterized by recurrent gastrointestinal tract inflammation. Tryptophan metabolism in mammalian cells and some gut microbes comprise intricate chemical networks facilitated by catalytic enzymes that affect the downstream metabolic pathways of de novo nicotinamide adenine dinucleotide (NAD+) synthesis. It is hypothesized that a correlation exists between tryptophan de novo NAD+ synthesis and chronic intestinal inflammation.

Methods

Transcriptome analysis was performed using high-throughput sequencing of mRNA extracted from the distal colon and brain tissue of Winnie mice with spontaneous chronic colitis and C57BL/6 littermates. Metabolites were assessed using ultra-fast liquid chromatography to determine differences in concentrations of tryptophan metabolites. To evaluate the relative abundance of gut microbial genera involved in tryptophan and nicotinamide metabolism, we performed 16S rRNA gene amplicon sequencing of fecal samples from C57BL/6 and Winnie mice.

Results

Tryptophan and nicotinamide metabolism-associated gene expression was altered in distal colons and brains of Winnie mice with chronic intestinal inflammation. Changes in these metabolic pathways were reflected by increases in colon tryptophan metabolites and decreases in brain tryptophan metabolites in Winnie mice. Furthermore, dysbiosis of gut microbiota involved in tryptophan and nicotinamide metabolism was evident in fecal samples from Winnie mice. Our findings shed light on the physiological alterations in tryptophan metabolism, specifically, its diversion from the serotonergic pathway toward the kynurenine pathway and consequential effects on de novo NAD+ synthesis in chronic intestinal inflammation.

Conclusion

The results of this study reveal differential expression of tryptophan and nicotinamide metabolism-associated genes in the distal colon and brain in Winnie mice with chronic intestinal inflammation. These data provide evidence supporting the role of tryptophan metabolism and de novo NAD+ synthesis in IBD pathophysiology.

Serotonin signalling in cancer: Emerging mechanisms and therapeutic opportunities

BACKGROUND

Serotonin (5-hydroxytryptamine) is a multifunctional bioamine serving as a neurotransmitter, peripheral hormone and mitogen in the vertebrate system. It has pleiotropic activities in central nervous system and gastrointestinal function via an orchestrated action of serotonergic elements, particularly serotonin receptor-mediated signalling cascades. The mitogenic properties of serotonin have garnered recognition for years and have been exploited for repurposing serotonergic-targeted drugs in cancer therapy. However, emerging conflicting findings necessitate a more comprehensive elucidation of serotonin's role in cancer pathogenesis.

MAIN BODY AND CONCLUSION

Here, we provide an overview of the biosynthesis, metabolism and action modes of serotonin. We summarise our current knowledge regarding the effects of the peripheral serotonergic system on tumourigenesis, with a specific emphasis on its immunomodulatory activities in human cancers. We also discuss the dual roles of serotonin in tumour pathogenesis and elucidate the potential of serotonergic drugs, some of which display favourable safety profiles and impressive efficacy in clinical trials, as a promising avenue in cancer treatment.

KEY POINTS

Primary synthesis and metabolic routes of peripheral 5-hydroxytryptamine in the gastrointestinal tract. Advanced research has established a strong association between the serotonergic components and carcinogenic mechanisms. The interplay between serotonergic signalling and the immune system within the tumour microenvironment orchestrates antitumour immune responses. Serotonergic-targeted drugs offer valuable clinical options for cancer therapy.

Cinnamic Acid, Perillic Acid, and Tryptophan Metabolites Differentially Regulate Ion Transport and Serotonin Metabolism and Signaling in the Mouse Ileum In Vitro

Phytochemicals and tryptophan (Trp) metabolites have been found to modulate gut function and health. However, whether these metabolites modulate gut ion transport and serotonin (5-HT) metabolism and signaling requires further investigation. The aim of this study was to investigate the effects of selected phytochemicals and Trp metabolites on the ion transport and 5-HT metabolism and signaling in the ileum of mice in vitro using the Ussing chamber technique. During the in vitro incubation, vanillylmandelic acid (VMA) reduced (p < 0.05) the short-circuit current, and 100 μM chlorogenic acid (CGA) (p = 0.12) and perillic acid (PA) (p = 0.14) had a tendency to reduce the short-circuit current of the ileum. Compared with the control, PA and N-acetylserotonin treatment upregulated the expression of tryptophan hydroxylase 1 (Tph1), while 100 μM cinnamic acid, indolelactic acid (ILA), and 10 μM CGA or indoleacetaldehyde (IAld) treatments downregulated (p < 0.05) the mRNA levels of Tph1. In addition, 10 μM IAld or 100 μM ILA upregulated (p < 0.05) the expression of monoamine oxidase A (Maoa). However, 10 μM CGA or 100 μM PA downregulated (p < 0.05) Maoa expression. All selected phytochemicals and Trp metabolites upregulated (p < 0.05) the expression of Htr4 and Htr7 compared to that of the control group. VMA and CGA reduced (p < 0.05) the ratios of Htr1a/Htr7 and Htr4/Htr7. These findings may help to elucidate the effects of phytochemicals and Trp metabolites on the regulation of gut ion transport and 5-HT signaling-related gut homeostasis in health and disease.

The janus face of serotonin: Regenerative promoter and chronic liver disease aggravator

The progression of liver diseases, from viral hepatitis and fatty liver disease to cirrhosis and hepatocellular carcinoma (HCC), is the most representative series of pathological events in liver diseases. While serotonin (5-HT) primarily regulates brain functions such as psychology, mood, and appetite in the central nervous system (CNS), peripheral 5-HT plays a crucial role in regulating tumor development, glucose and lipid metabolism, immune function and inflammatory response related to liver diseases. These peripheral physiological processes involving 5-HT are the key mechanisms driving the development of these liver diseases. This study presents an overview of the existing literature, focusing on the role of 5-HT in HCC, cirrhosis, fatty liver disease, viral hepatitis, and liver injury. In summary, while 5-HT promotes liver regeneration, it can also contribute to the progression of chronic liver disease. These findings indicate the potential for the development and use of 5-HT-related drugs for the treatment of liver diseases, including HCC and cirrhosis.

Microbiota metabolites in bone: Shaping health and Confronting disease

The intricate interplay between the gut microbiota and bone health has become increasingly recognized as a fundamental determinant of skeletal well-being. Microbiota-derived metabolites play a crucial role in dynamic interaction, specifically in bone homeostasis. In this sense, short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate, indirectly promote bone formation by regulating insulin-like growth factor-1 (IGF-1). Trimethylamine N-oxide (TMAO) has been found to increase the expression of osteoblast genes, such as Runt-related transcription factor 2 (RUNX2) and bone morphogenetic protein-2 (BMP2), thus enhancing osteogenic differentiation and bone quality through BMP/SMADs and Wnt signaling pathways. Remarkably, in the context of bone infections, the role of microbiota metabolites in immune modulation and host defense mechanisms potentially affects susceptibility to infections such as osteomyelitis. Furthermore, ongoing research elucidates the precise mechanisms through which microbiota-derived metabolites influence bone cells, such as osteoblasts and osteoclasts. Understanding the multifaceted influence of microbiota metabolites on bone, from regulating homeostasis to modulating susceptibility to infections, has the potential to revolutionize our approach to bone health and disease management. This review offers a comprehensive exploration of this evolving field, providing a holistic perspective on the impact of microbiota metabolites on bone health and diseases.

Urinary markers of Mycobacterium tuberculosis and dysbiosis in paediatric tuberculous meningitis cases undergoing treatment

BACKGROUND

The pathogenesis of tuberculous meningitis (TBM) involves infection by Mycobacterium tuberculosis in the meninges and brain. However, recent studies have shown that the immune response and inflammatory processes triggered by TBM can have significant effects on gut microbiota. Disruptions in the gut microbiome have been linked to various systemic consequences, including altered immunity and metabolic dysregulation. Inflammation caused by TBM, antibiotic treatment, and changes in host immunity can all influence the composition of gut microbes. This complex relationship between TBM and the gut microbiome is of great importance in clinical settings. To gain a deeper understanding of the intricate interactions between TBM and the gut microbiome, we report innovative insights into the development of the disease in response to treatment. Ultimately, this could lead to improved outcomes, management strategies and quality of life for individuals affected by TBM.

METHOD

We used a targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach to investigate metabolites associated with gut metabolism in paediatric participants by analysing the urine samples collected from a control group (n = 40), and an experimental group (n = 35) with confirmed TBM, which were subdivided into TBM stage 1 (n = 8), stage 2 (n = 11) and stage 3 (n = 16).

FINDINGS

Our metabolomics investigation showed that, of the 78 initially selected compounds of microbiome origin, eight unique urinary metabolites were identified: 2-methylbutyrlglycine, 3-hydroxypropionic acid, 3-methylcrotonylglycine, 4-hydroxyhippuric acid, 5-hydroxyindoleacetic acid, 5-hydroxyhexanoic acid, isobutyrylglycine, and phenylacetylglutamine as urinary markers of dysbiosis in TBM.

CONCLUSION

These results - which are supported by previous urinary studies of tuberculosis - highlight the importance of gut metabolism and of identifying corresponding microbial metabolites as novel points for the foundation of improved management of TBM patients.

Exploring the serotonin-probiotics-gut health axis: A review of current evidence and potential mechanisms

Modulatory effects of serotonin (5-Hydroxytryptamine [5-HT]) have been seen in hepatic, neurological/psychiatric, and gastrointestinal (GI) disorders. Probiotics are live microorganisms that confer health benefits to their host. Recent research has suggested that probiotics can promote serotonin signaling, a crucial pathway in the regulation of mood, cognition, and other physiological processes. Reviewing the literature, we find that peripheral serotonin increases nutrient uptake and storage, regulates the composition of the gut microbiota, and is involved in mediating neuronal disorders. This review explores the mechanisms underlying the probiotic-mediated increase in serotonin signaling, highlighting the role of gut microbiota in the regulation of serotonin production and the modulation of neurotransmitter receptors. Additionally, this review discusses the potential clinical implications of probiotics as a therapeutic strategy for disorders associated with altered serotonin signaling, such as GI and neurological disorders. Overall, this review demonstrates the potential of probiotics as a promising avenue for the treatment of serotonin-related disorders and signaling of serotonin.

DNAJC12 in Monoamine Metabolism, Neurodevelopment, and Neurodegeneration

Recent studies show that pathogenic variants in DNAJC12, a co-chaperone for monoamine synthesis, may cause mild hyperphenylalaninemia with infantile dystonia, young-onset parkinsonism, developmental delay and cognitive deficits. DNAJC12 has been included in newborn screening, most revealingly in Spain, and those results highlight the importance of genetic diagnosis and early intervention in combating human disease. However, practitioners may be unaware of these advances and it is probable that many patients, especially adults, have yet to receive molecular testing for DNAJC12. Hence, this review summarizes genotype-phenotype relationships and treatment paradigms for patients with pathogenic variants in DNAJC12. It provides an overview of the structure of DNAJC12 protein, known genetic variants, domains, and binding partners, and elaborates on its role in monoamine synthesis, disease etiology, and pathogenesis. © 2023 International Parkinson and Movement Disorder Society.

Genetic differences associated with dopamine and serotonin release mediate fear-induced bradycardia in the human brain

Fear-induced bradycardia, a transient heartbeat deceleration following exposure to threat, is a physiological index observable in humans, especially in fear conditioning experiments. While gaining interest in recent years, it is still currently underemployed in neuroscientific research compared to more popular physiological indices. Besides its use in research, it could also constitute a valuable resource in a clinical psychiatry setting, as many disorders are also characterized by altered heart rate responses. However, differences in fear-induced bradycardia may also be subtended by genetic interindividual differences, thus suggesting precaution when recommending its use in the clinical setting. Here, we discussed the first endeavors that aimed at clarifying the genetic underpinnings of heart rate variations, which suggest that individual genetic differences have a role in defining the characteristics of heart rate responses. Given this, translating heart rate measurements in the clinical setting must be implemented with caution. Future endeavors in this field will aim at identifying these differences even further, thus allowing for more precise clinical interventions.

Medication-overuse headache overlapping with serotonin syndrome

Serotonin syndrome (SS) is an iatrogenic, drug-induced clinical syndrome caused by an increase in the intrasynaptic concentration of serotonin. Serotonin plays a significant role in the pathophysiology of migraines. Upregulation of 5-HT2A receptors is found in medication-overuse headache (MOH). Several migraine medications, both preventative and abortive drugs, act on serotonin receptors. We report two patients with chronic migraine who developed MOH. Besides headache, patients had frequent attacks of dizziness, restlessness, irritability, insomnia, excessive sweating, abdominal discomforts and tremors. These symptoms were suggestive of withdrawal headache. However, on physical examinations, we elicited hyperreflexia, hypertonia, clonus, tachycardia, hypertension, mydriasis and hyperactive bowel sound. Both patients also met the criteria for SS. Cyproheptadine was started. All features, including headaches, got better after cyproheptadine administration within 24 hours. In 7 days, there was practically total improvement. Both patients continued to take cyproheptadine as a preventative medicine, and migraine frequency was under control.

Role of Serotonergic System in Regulating Brain Tumor-Associated Neuroinflammatory Responses

Serotonin signaling regulates wide arrays of both neural and extra-neural functions. Serotonin is also found to affect cancer progression directly as well as indirectly by modulating the immune cells. In the brain, serotonin plays a key role in regulating various functions; disturbance of the normal activities of serotonin leads to various mental illnesses, including the neuroinflammatory response in the central nervous system (CNS). The neuroinflammatory response can be initiated in various psychological illnesses and brain cancer. Serotonergic signaling can impact the functions of both glial as well as the immune cells. It can also affect the tumor immune microenvironment and the inflammatory response associated with brain cancers. Apart from this, many drugs used for treatment of psychological illness are known to modulate serotonergic system and can cross the blood-brain barrier. Understanding the role of serotonergic pathways in regulating neuroinflammatory response and brain cancer will provide a new paradigm in modulating the serotonergic components in treating brain cancer and associated inflammation-induced brain damages.

Trace Amine-Associated Receptors and Monoamine-Mediated Regulation of Insulin Secretion in Pancreatic Islets

Currently, metabolic syndrome treatment includes predominantly pharmacological symptom relief and complex lifestyle changes. Trace amines and their receptor systems modulate signaling pathways of dopamine, norepinephrine, and serotonin, which are involved in the pathogenesis of this disorder. Trace amine-associated receptor 1 (TAAR1) is expressed in endocrine organs, and it was revealed that TAAR1 may regulate insulin secretion in pancreatic islet β-cells. For instance, accumulating data demonstrate the positive effect of TAAR1 agonists on the dynamics of metabolic syndrome progression and MetS-associated disease development. The role of other TAARs (TAAR2, TAAR5, TAAR6, TAAR8, and TAAR9) in the islet's function is much less studied. In this review, we summarize the evidence of TAARs' contribution to the metabolic syndrome pathogenesis and regulation of insulin secretion in pancreatic islets. Additionally, by the analysis of public transcriptomic data, we demonstrate that TAAR1 and other TAAR receptors are expressed in the pancreatic islets. We also explore associations between the expression of TAARs mRNA and other genes in studied samples and demonstrate the deregulation of TAARs' functional associations in patients with metabolic diseases compared to healthy donors.

The effects of Korean Red Ginseng on stress-related neurotransmitters and gene expression: A randomized, double-blind, placebo-controlled trial

Background

Korean Red Ginseng (KRG) is an effective anti-stress treatment. In this study, we investigated the therapeutic potential effects of KRG on relieving stress in a general population using transcriptome analysis.

Methods

We conducted an 8-week clinical pilot study on 90 healthy men who reported stress. The study was completed by 43 participants in the KRG group and 44 participants in the placebo group. Participants were randomized 1:1 to the KRG and placebo groups. We evaluated the stress by stress response inventory (SRI) at baseline and 8 weeks. The main outcomes were changes in the levels of neurotransmitters (NTs) and NT-related gene expression. NTs were analyzed using automated (GC) content, and levels of gene expression were measured by reads per kilobase of transcript per million mapped reads (RPKM).

Results

The KRG group showed significantly preserved epinephrine decrease compared with placebo group at 8 weeks (changes in epinephrine, KRG vs. placebo; -1623.2 ± 46101.5 vs. -35116.3 ± 86288.2, p = 0012). Among subjects who higher SRI score, meaning stress increased compared to baseline, the KRG group showed a smaller decrease in serotonin than the placebo group (changes in serotonin, KRG vs. placebo; -2627.5 ± 5859.1 vs, -8087.4 ± 7162.4, p = 0.005) and a smaller increase in cortisol than the placebo group (changes in cortisol, KRG vs. placebo; 1912.7 ± 10097.75 vs. 8046.2 ± 8050.6 , p = 0.019) in subgroup analysis. Transcriptome findings indicated that KRG intake affects gene expression related with metabolism of choline, adrenalin, and monoamine.

Conclusion

These findings suggest that KRG has beneficial effects on the amelioration of stress response in NTs, and this effect is more prominent in stressful situations. Further clinical studies are required to confirm the anti-stress effect of KRG.

Pink1-/- Rats Demonstrate Swallowing and Gastrointestinal Dysfunction in a Model of Prodromal Parkinson Disease

Early motor and non-motor signs of Parkinson disease (PD) include dysphagia, gastrointestinal dysmotility, and constipation. However, because these often manifest prior to formal diagnosis, the study of PD-related swallow and GI dysfunction in early stages is difficult. To overcome this limitation, we used the Pink1-/- rat, a well-established early-onset genetic rat model of PD to assay swallowing and GI motility deficits. Thirty male rats were tested at 4 months (Pink1-/- = 15, wildtype (WT) control = 15) and 6 months (Pink1-/- = 7, WT = 6) of age; analogous to early-stage PD in humans. Videofluoroscopy of rats ingesting a peanut-butter-barium mixture was used to measure mastication rate and oropharyngeal and pharyngoesophageal bolus speeds. Abnormal swallowing behaviors were also quantified. A second experiment tracked barium contents through the stomach, small intestine, caecum, and colon at hours 0-6 post-barium gavage. Number and weight of fecal emissions over 24 h were also collected. Compared to WTs, Pink1-/- rats showed slower mastication rates, slower pharyngoesophageal bolus speeds, and more abnormal swallowing behaviors. Pink1-/- rats demonstrated significantly delayed motility through the caecum and colon. Pink1-/- rats also had significantly lower fecal pellet count and higher fecal pellet weight after 24 h at 6 months of age. Results demonstrate that swallowing dysfunction occurs early in Pink1-/- rats. Delayed transit to the colon and constipation-like signs are also evident in this model. The presence of these early swallowing and GI deficits in Pink1-/- rats are analogous to those observed in human PD.

Engineering a Cortisol Sensing Enteric Probiotic

Chronic stress can lead to prolonged adrenal gland secretion of cortisol, resulting in human ailments such as anxiety, post-traumatic stress disorder, metabolic syndrome, diabetes, immunosuppression, and cardiomyopathy. Real time monitoring of chronic increases in cortisol and intervening therapies to minimize the physiological effects of stress would be beneficial to prevent these endocrine related illnesses. Gut microbiota have shown the ability to secrete, respond, and even regulate endocrine hormones. One such microbe, Clostridium scindens, responds transcriptionally to cortisol. We engineered these cortisol responsive genetic elements from C. scindens into an enteric probiotic, E. coli Nissle 1917, to drive the expression of a fluorescent reporter allowing for the designing, testing, and building of a robust and physiologically relevant novel cortisol probiotic sensor. This smart probiotic was further engineered to be more sensitive and to respond to elevated cortisol by expressing tryptophan decarboxylase, thereby bestowing the ability to generate tryptamine and serotonin. Here we show that upon cortisol treatment the smart probiotic produces measurable amounts of tryptamine. Accumulated levels of these neuromodulators should improve mood, anxiety, and depression and drive down cortisol levels. Importantly, this work can serve as a model for the engineering of a sense-and-respond probiotic to modulate the gut-brain axis.

Serotonergic regulation of appetite and sodium appetite

Serotonin is a neurotransmitter that is synthesized and released from the brainstem raphe nuclei to affect many brain functions. It is well known that the activity of raphe serotonergic neurons is changed in response to the changes in feeding status to regulate appetite via the serotonin receptors. Likewise, changes in volume status are known to alter the activity of raphe serotonergic neurons and drugs targeting serotonin receptors were shown to affect sodium appetite. Therefore, the central serotonin system appears to regulate ingestion of both food and salt, although neural mechanisms that induce appetite in response to hunger and sodium appetite in response to volume depletion are largely distinct from each other. In this review, we discuss our current knowledge regarding the regulation of ingestion - appetite and sodium appetite - by the central serotonin system.

Stratification of enterochromaffin cells by single-cell expression analysis

Dynamic interactions between gut mucosal cells and the external environment are essential to maintain gut homeostasis. Enterochromaffin (EC) cells transduce both chemical and mechanical signals and produce 5-hydroxytryptamine (5-HT) to mediate disparate physiological responses. However, the molecular and cellular basis for functional diversity of ECs remains to be adequately defined. Here, we integrated single-cell transcriptomics with spatial image analysis to identify fourteen EC clusters that are topographically organized along the gut. Subtypes predicted to be sensitive to the chemical environment and mechanical forces were identified that express distinct transcription factors and hormones. A Piezo2+ population in the distal colon was endowed with a distinctive neuronal signature. Using a combination of genetic, chemogenetic and pharmacological approaches, we demonstrated Piezo2+ ECs are required for normal colon motility. Our study constructs a molecular map for ECs and offers a framework for deconvoluting EC cells with pleiotropic functions.

Serotonin and the serotonin transporter in the adrenal gland

The adrenal glands are key components of the mammalian endocrine system, helping maintain physiological homeostasis and the coordinated response to stress. Each adrenal gland has two morphologically and functionally distinct regions, the outer cortex and inner medulla. The cortex is organized into three concentric zones which secrete steroid hormones, including aldosterone and cortisol. Neural crest-derived chromaffin cells in the medulla are innervated by preganglionic sympathetic neurons and secrete catecholamines (epinephrine, norepinephrine) and neuropeptides into the bloodstream, thereby functioning as the neuroendocrine arm of the sympathetic nervous system. In this article we review serotonin (5-HT) and the serotonin transporter (SERT; SLC6A4) in the adrenal gland. In the adrenal cortex, 5-HT, primarily sourced from resident mast cells, acts as a paracrine signal to stimulate aldosterone and cortisol secretion through 5-HT4/5-HT7 receptors. Medullary chromaffin cells contain a small amount of 5-HT due to SERT-mediated uptake and express 5-HT1A receptors which inhibit secretion. The atypical mechanism of the 5-HT1A receptors and interaction with SERT fine tune this autocrine pathway to control stress-evoked catecholamine secretion. Receptor-independent signaling by SERT/intracellular 5-HT modulates the amount and kinetics of transmitter release from single vesicle fusion events. SERT might also influence stress-evoked upregulation of tyrosine hydroxylase transcription. Transient signaling via 5-HT3 receptors during embryonic development can limit the number of chromaffin cells found in the mature adrenal gland. Together, this emerging evidence suggests that the adrenal medulla is a peripheral hub for serotonergic control of the sympathoadrenal stress response.

Maternal serotonin: implications for the use of selective serotonin reuptake inhibitors during gestation†

Maternal use of antidepressants has increased throughout the last decades; selective serotonin reuptake inhibitors (SSRI) are the most prescribed antidepressants. Despite the widespread use of SSRI by women during reproductive age and pregnant women, an increasing amount of research warns of possible detrimental effects of maternal use of SSRI during pregnancy including low birthweight/small for gestational age and preterm birth. In this review, we revisited the impact of maternal use of SSRI during pregnancy, its impact on serotonin homeostasis in the maternal and fetal circulation and the placenta, and its impact on pregnancy outcomes-particularly intrauterine growth restriction and preterm birth. Maternal use of SSRI increases maternal and fetal serotonin. The increase in maternal circulating serotonin and serotonin signaling likely promotes vasoconstriction of the uterine and placental vascular beds decreasing blood perfusion to the uterus and consequently to the placenta and fetus with potential impact on placental function and fetal development. Several adverse pregnancy outcomes are similar between women, sheep, and rodents (decreased placental size, decreased birthweight, shorter gestation length/preterm birth, neonatal morbidity, and mortality) highlighting the importance of animal studies to assess the impacts of SSRI. Herein, we address the complex interactions between maternal SSRI use during gestation, circulating serotonin, and the regulation of blood perfusion to the uterus and fetoplacental unit, fetal growth, and pregnancy complications.

Untargeted Metabolomic Analysis of Sjögren-Larsson Syndrome Reveals a Distinctive Pattern of Multiple Disrupted Biochemical Pathways

Sjögren-Larsson syndrome (SLS) is a rare inherited neurocutaneous disease characterized by ichthyosis, spastic diplegia or tetraplegia, intellectual disability and a distinctive retinopathy. SLS is caused by bi-allelic mutations in ALDH3A2, which codes for fatty aldehyde dehydrogenase (FALDH) and results in abnormal lipid metabolism. The biochemical abnormalities in SLS are not completely known, and the pathogenic mechanisms leading to symptoms are still unclear. To search for pathways that are perturbed in SLS, we performed untargeted metabolomic screening in 20 SLS subjects along with age- and sex-matched controls. Of 823 identified metabolites in plasma, 121 (14.7%) quantitatively differed in the overall SLS cohort from controls; 77 metabolites were decreased and 44 increased. Pathway analysis pointed to disrupted metabolism of sphingolipids, sterols, bile acids, glycogen, purines and certain amino acids such as tryptophan, aspartate and phenylalanine. Random forest analysis identified a unique metabolomic profile that had a predictive accuracy of 100% for discriminating SLS from controls. These results provide new insight into the abnormal biochemical pathways that likely contribute to disease in SLS and may constitute a biomarker panel for diagnosis and future therapeutic studies.

Ethanol Extract of Mao Jian Green Tea Attenuates Gastrointestinal Symptoms in a Rat Model of Irritable Bowel Syndrome with Constipation via the 5-hydroxytryptamine Signaling Pathway

In a previous study, we demonstrated that the hydro extract of Mao Jian Green Tea (MJGT) promotes gastrointestinal motility. In this study, the effect of MJGT ethanol extract (MJGT_EE) in treating irritable bowel syndrome with constipation (IBS-C) in a rat model constructed via maternal separation combined with an ice water stimulation was investigated. First, a successful model construction was confirmed through the determination of the fecal water content (FWC) and the smallest colorectal distension (CRD) volume. Then, the overall regulatory effects of MJGT_EE on the gastrointestinal tract were preliminarily evaluated through gastric emptying and small intestinal propulsion tests. Our findings indicated that MJGT_EE significantly increased FWC (p < 0.01) and the smallest CRD volume (p < 0.05) and promoted gastric emptying and small intestinal propulsion (p < 0.01). Furthermore, mechanistically, MJGT_EE reduced intestinal sensitivity by regulating the expression of proteins related to the serotonin (5-hydroxytryptamine; 5-HT) pathway. More specifically, it decreased tryptophan hydroxylase (TPH) expression (p < 0.05) and increased serotonin transporter (SERT) expression (p < 0.05), thereby decreasing 5-HT secretion (p < 0.01), activating the calmodulin (CaM)/myosin light chain kinase (MLCK) pathway, and increasing 5-HT₄ receptor (5-HT₄R) expression (p < 0.05). Moreover, MJGT_EE enhanced the diversity of gut microbiota, increased the proportion of beneficial bacteria, and regulated the number of 5-HT-related bacteria. Flavonoids may play the role of being active ingredients in MJGT_EE. These findings suggest that MJGT_EE could serve as a potential therapeutic pathway for IBS-C.

HIV and comorbidities - the importance of gut inflammation and the kynurenine pathway

PURPOSE OF REVIEW

The purpose of this article is to review alterations in microbiota composition, diversity, and functional features in the context of chronic inflammation and comorbidities associated with HIV infection.

RECENT FINDINGS

The gut microbiome is an important mediator of host immunity, and disruption of gut homeostasis can contribute to both systemic inflammation and immune activation. Ageing and HIV share features of intestinal damage, microbial translocation and alterations in bacterial composition that contribute to a proinflammatory state and development of age-related comorbidities. One such inflammatory pathway reviewed is the nicotinamide adenine dinucleotide (NAD+) producing kynurenine pathway (KP). Kynurenine metabolites regulate many biological processes including host-microbiome communication, immunity and oxidative stress and the KP in turn is influenced by the microbiome environment. Age-associated decline in NAD+ is implicated as a driving factor in many age-associated diseases, including those seen in people with HIV (PWH). Recent studies have shown that KP can influence metabolic changes in PWH, including increased abdominal adiposity and cardiovascular disease. Furthermore, KP activity increases with age in the general population, but it is elevated in PWH at all ages compared to age-matched controls. Host or microbiome-mediated targeting of this pathway has merits to increase healthy longevity and has potential therapeutic applications in PWH.

SUMMARY

As a growing proportion of PWH age, many face increased risks of developing age-related comorbidities. Chronic inflammation, a pillar of geroscience, the science of ageing and of age-related disease, is influenced by the gut microbiome and its metabolites. Combined, these contribute to a systemic inflammatory signature. Advances in geroscience-based approaches and therapeutics offer a novel paradigm for addressing age-related diseases and chronic inflammation in HIV infection. Whether targeted inhibition of KP activity alleviates pathological conditions or promotes successful ageing in PWH remains to be determined.

New insight on the mechanism of eating disorder in females based on metabolic differences of bisphenol S in female and male zebrafish

The different capacity of glucuronic acid metabolism might lead to the difference of bisphenol S (BPS) residual in tissues of male and female zebrafish. This may be the fundamental reason why BPS causes different effects in females and males. Here, adult zebrafish are exposed to 1, 10 and 100 μg/L BPS for 35 days to explore the main effect on females. After exposure, the liver of females showed stronger BPS metabolism ability than males, resulting in the accumulation of BPS in the gut of females. The results of neurotransmitters in gut of females revealed that the content of serotonin was decreased by BPS treatments. In addition, the mRNA expression levels of tryptophan 5-monooxygenase (Tph1) that regulated serotonin synthesis was reduced in gut of females in all BPS groups, and Tph1 protein has very high affinity with BPS molecule. Adult females treated with BPS exhibited symptoms including overeating, a decrease of serotonin in the gut, hypoglycemia and hyperlipidemia, a similar effect of Tph1 protein inhibitor LP533401 on adult females. This hypoglycemia stimulates brain agrp/pomc and orexin neurons to induce overfeeding behavior, causing intestinal homeostasis imbalance and hyperlipidemia. Our data elucidate a potential pathogenesis of eating disorder under pollutant stress.

Intrinsic Therapeutic Link between Recuperative Cerebellar Con-Nectivity and Psychiatry Symptom in Schizophrenia Patients with Comorbidity of Metabolic Syndrome

Components of metabolic syndrome might be predictors of the therapeutic outcome of psychiatric symptom in schizophrenia, whereas clinical results are inconsistent and an intrinsic therapeutic link between weaker psychiatric symptoms and emergent metabolic syndrome remains unclear. This study aims to reveal the relationship and illustrate potential mechanism by exploring the alteration of cerebellar functional connectivity (FC) in schizophrenia patients with comorbidity metabolic syndrome. Thirty-six schizophrenia patients with comorbidity of metabolic syndrome (SCZ-MetS), 45 schizophrenia patients without metabolic syndrome (SCZ-nMetS) and 39 healthy controls (HC) were recruited in this study. We constructed FC map of cerebello-cortical circuit and used moderation effect analysis to reveal complicated relationship among FC, psychiatric symptom and metabolic disturbance. Components of metabolic syndrome were significantly correlated with positive symptom score and negative symptom score. Importantly, the dysconnectivity between cognitive module of cerebellum and left middle frontal gyrus in SCZ-nMetS was recuperative increased in SCZ-MetS, and was significantly correlated with general symptom score. Finally, we observed significant moderation effect of body mass index on this correlation. The present findings further supported the potential relationship between emergence of metabolic syndrome and weaker psychiatric symptom, and provided neuroimaging evidence. The mechanism of intrinsic therapeutic link involved functional change of cerebello-cortical circuit.

Effect of lactic acid fermented foods on glycemic control in diabetic adults: a systemic review and meta-analysis of randomized controlled trials

Lactic acid bacteria (LAB) fermented foods are reported to have potential in managing glycemic control. This systematic review aimed to evaluate the effectiveness of LAB-fermented foods on improving glycemic control in adults with prediabetics or type 2 diabetes mellitus (T2DM). Randomized controlled trials (RCTs) on LAB fermentation-related foods were searched on PubMed, Cochrane, Excerpta Medica database (EMBASE), Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Web of Science. Sixteen RCTs were included, and the results concluded LAB-fermented food had significant effects in HbA1c (Z = 6.24, MD = -0.05, CI: -0.07 to -0.04, p ≤ 0.00001), fasting plasma glucose (Z = 2.50, MD = -0.16, CI: -0.29 to -0.04, p = 0.01) and fasting serum insulin (Z = 2.51, MD = -0.20, CI: -0.35 to -0.04, p = 0.01). There were significant effects on lipid profile, inflammatory markers, and body mass index in secondary analyses. Subgroup analysis suggests LAB-fermented consumption with a longer duration, younger age group and adults with T2DM, had a larger effect size. Clinicians could offer LAB-fermented food as dietary recommendations for prediabetic and diabetic adults. Larger trials are warranted to verify LAB-fermented food benefits on glycemic control. Systematic Review Registration: PROSPERO Registration No. CRD42022295220.

Multi-omics analysis reveals the host-microbe interactions in aged rhesus macaques

Aging is a complex multifactorial process that greatly affects animal health. Multi-omics analysis is widely applied in evolutionary biology and biomedical research. However, whether multi-omics can provide sufficient information to reveal comprehensive changes in aged non-human primates remains unclear. Here, we explored changes in host-microbe interactions with aging in Chinese rhesus macaques (Macaca mulatta lasiota, CRs) using multi-omics analysis. Results showed marked changes in the oral and gut microbiomes between young and aged CRs, including significantly reduced probiotic abundance and increased pathogenic bacterial abundance in aged CRs. Notably, the abundance of Lactobacillus, which can metabolize tryptophan to produce aryl hydrocarbon receptor (AhR) ligands, was decreased in aged CRs. Consistently, metabolomics detected a decrease in the plasma levels of AhR ligands. In addition, free fatty acid, acyl carnitine, heparin, 2-(4-hydroxyphenyl) propionic acid, and docosahexaenoic acid ethyl ester levels were increased in aged CRs, which may contribute to abnormal fatty acid metabolism and cardiovascular disease. Transcriptome analysis identified changes in the expression of genes associated with tryptophan metabolism and inflammation. In conclusion, many potential links among different omics were found, suggesting that aged CRs face multiple metabolic problems, immunological disorders, and oral and gut diseases. We determined that tryptophan metabolism is critical for the physiological health of aged CRs. Our findings demonstrate the value of multi-omics analyses in revealing host-microbe interactions in non-human primates and suggest that similar approaches could be applied in evolutionary and ecological research of other species.

The development of the Metabolic-associated Fatty Liver Disease during pharmacotherapy of mental disorders - a review

Introduction: Metabolic-associated Fatty Liver Disease (MAFLD) is a term for Non-alcoholic Fatty Liver Disease (NAFLD) that highlights its association with components of the Metabolic Syndrome (MetS). MAFLD is becoming a clinically significant problem due to its increasing role in the pathogenesis of cryptogenic cirrhosis of the liver.

Material and methods: The resulting work is a review of the most important information on the risk of MAFLD development in the context of the use of particular groups of psychotropic drugs. The study presents the epidemiology, with particular emphasis on the population of psychiatric patients, pathophysiology and scientific reports analyzing the effect of the psychotropic medications on MAFLD development.

Results: The drugs that can have the greatest impact on the development of MAFLD are atypical antipsychotics, especially olanzapine, and mood stabilizers (MS) - valproic acid (VPA). Their effect is indirect, mainly through dysregulation of organism’s carbohydrate and lipid metabolism.

Conclusions: The population of psychiatric patients is particularly vulnerable to the development of MAFLD. At the root of this disorder lies the specificity of mental disorders, improper dietary habits, low level of physical activity and tendency to addictions. Also, the negative impact of the psychotropic drugs on the systemic metabolism indirectly contributes to the development of MAFLD. In order to prevent fatty liver disease, it is necessary to monitor metabolic and liver parameters regularly, and patients should be screened by ultrasound examination of the liver. There are also important preventive actions from the medical professionals, including education of patients and sensitizing to healthy lifestyle.

A scalable framework for the discovery of functional helicase substrates and helicase-driven regulatory switches

Helicases are ubiquitous motor enzymes that remodel nucleic acids (NA) and NA-protein complexes in key cellular processes. To explore the functional repertoire and specificity landscape of helicases, we devised a screening scheme-Helicase-SELEX (Systematic Evolution of Ligands by EXponential enrichment)-that enzymatically probes substrate and cofactor requirements at global scale. Using the transcription termination Rho helicase of Escherichia coli as a prototype for Helicase-SELEX, we generated a genome-wide map of Rho utilization (Rut) sites. The map reveals many features, including promoter- and intrinsic terminator-associated Rut sites, bidirectional Rut tandems, and cofactor-dependent Rut sites with inverted G > C skewed compositions. We also implemented an H-SELEX variant where we used a model ligand, serotonin, to evolve synthetic Rut sites operating in vitro and in vivo in a ligand-dependent manner. Altogether, our data illustrate the power and flexibility of Helicase-SELEX to seek constitutive or conditional helicase substrates in natural or synthetic NA libraries for fundamental or synthetic biology discovery.

Lactobacillus rhamnosus GG normalizes gut dysmotility induced by environmental pollutants via affecting serotonin level in zebrafish larvae

Intestinal peristalsis is essential for gastrointestinal function, which could maintain the appropriate progression and digestion of food and reduce bacterial aggregation through mixing function. Even though certain ingredients of foodstuff are known to increase or decrease intestinal peristalsis, the role of environmental pollutants on intestinal peristalsis is relatively unknown. Therefore, the effects of four typical environmental pollutants (oxytetracycline, arsenic, polychlorinated biphenyls and chlorpyrifos) on intestinal peristalsis in the zebrafish model and then tested the recovery effect of the constipation-resistant probiotic. The results showed that 4-day environmental pollutants exposures on the zebrafish embryos at 1 day post fertilization clearly decreased the intestinal peristalsis through decreasing the serotonin (5-HT) production and down-regulating the expression of key genes involved in 5-HT synthesis. Pollutants-evoked change of gut motility could be normalized in the presence of Lactobacillus rhamnosus GG (LGG) via increasing 5-HT secretion. Exogenous 5-hydroxytryptophan (100 µg/L) could also rescue the dysfunction of gut motility in pollutants-treated zebrfish. The data identified that LGG normalized disorder of intestinal peristalsis induced by environmental pollutants through increasing 5-HT level. The stimulant effect of LGG on peristalsis may be associated with 5-HT system, which could provide references for the application of probiotics in regulation of gut dysmotility.

Recent advances in biofabricated gut models to understand the gut-brain axis in neurological diseases

Increasing evidence has accumulated that gut microbiome dysbiosis could be linked to neurological diseases, including both neurodegenerative and psychiatric diseases. With the high prevalence of neurological diseases, there is an urgent need to elucidate the underlying mechanisms between the microbiome, gut, and brain. However, the standardized aniikmal models for these studies have critical disadvantages for their translation into clinical application, such as limited physiological relevance due to interspecies differences and difficulty interpreting causality from complex systemic interactions. Therefore, alternative in vitro gut–brain axis models are highly required to understand their related pathophysiology and set novel therapeutic strategies. In this review, we outline state-of-the-art biofabrication technologies for modeling in vitro human intestines. Existing 3D gut models are categorized according to their topographical and anatomical similarities to the native gut. In addition, we deliberate future research directions to develop more functional in vitro intestinal models to study the gut–brain axis in neurological diseases rather than simply recreating the morphology.

Activation of uroepithelial 5-HT4R inhibits mechanosensory activity of murine bladder afferent nerves

Serotonin (5-HT) is known to act via multiple 5-HT receptors at spinal and supraspinal levels to regulate micturition. However, the contribution of peripheral 5-HT and its receptors in bladder physiology and pathology is not very well understood, despite evidence showing expression of multiple 5-HT receptors in the bladder wall and 5-HT may activate bladder afferent nerves. The current study was designed to investigate the possible role of 5-HT4R in modulation of the sensitivity of bladder afferents to bladder filling. Immunofluorescent staining showed abundant 5-HT4R immunoreactivity largely confined to the uroepithelium in wild type (WT) but not 5-HT4R−/− mice. In the ex vivo bladder-pelvic nerve preparation, intravesical application of the 5-HT4R agonist RS67333 (1–30 μm) caused concentration-dependent decreases of the pelvic nerve response to bladder filling. Such effect was not observed in the presence of 5-HT4R antagonist GR125487 or in 5-HT4R−/− preparations. A cohort of 5-HT4R−/− and WT control mice were treated with intraperitoneal injections of cyclophosphamide (CYP) (75 mg/kg, three times at 2 days interval) to induce chronic cystitis. Void spot analysis showed that CYP-treated 5-HT4R−/− mice urinated more frequently than their CYP-treated WT counterparts. Concomitantly, bladder afferents of CYP-treated 5-HT4R−/− mice displayed exaggerated sensitivity to bladder filling in comparison with the CYP-treated WT controls. These data suggest that 5-HT4R expressed on uroepithelial cells plays an inhibitory role in mechanosensory transduction in the bladder. Loss of 5-HT4R-mediated inhibition may enhance bladder afferent sensitivity and exacerbate bladder overactivity in pathological conditions. We propose that 5-HT4R agonists might be exploited for the treatment of overactive and painful bladder symptoms.

Effect of chronic heat stress on gastrointestinal histology and expression of feed intake-regulatory hormones in broiler chickens

Heat stress (HS) dramatically impairs the growth performance of broiler chickens, mainly as a consequence of reduced feed intake due to the loss of appetite. This study was aimed at evaluating the alterations induced by chronic HS conditions on the morphological and morphometric features of the gastrointestinal (GI) tract and on the expression of some enteroendocrine cells (EECs) involved in the regulation of feed intake in chickens. Three hundred male chickens (Ross 308) were divided into two experimental groups and raised either in thermoneutral environment for the whole fattening period (0-41 days) (TNT group) or subjected to chronic HS conditions (30 °C for 24 h/day) from 35 to 41 days (HS group). Samples of proventriculus, duodenum, jejunum and cecum were collected from 24 broilers (12/group). Haematoxylin-eosin was used for the morphometric evaluations, while immunohistochemistry was applied for the evaluation of EECs expressing ghrelin (GHR), cholecystokinin (CCK), neuropeptide Y (NPY), glucagon-like peptide-1 (GLP-1), and serotonin (5-HT). In the proventriculus, HS reduced total wall thickness and mucous layer height (P ≤ 0.01) as well as mean diameter, circumference, and area of the compound tubular glands (P ≤ 0.001) with respect to TNT. The small intestine of HS birds was characterised by decreased villous height and total thickness (duodenum, P ≤ 0.01; jejunum, P ≤ 0.001), whereas crypt depth and width were reduced only in the jejunum (P ≤ 0.01). HS had negligible effects on the morphological aspects of the cecum. In the proventriculus, an increase in GHR and NPY EECs was observed in response to HS (P ≤ 0.001). Similarly, the small intestine villi of the HS group showed greater GLP-1 (P ≤ 0.05), 5-HT (P ≤ 0.001) and CCK (P ≤ 0.01) EECs. Moreover, the expression of 5-HT EECs was higher in the duodenal (P ≤ 0.01) and jejunal (P ≤ 0.01) crypts of HS birds, whereas GLP-1 and CCK EECs increased only in jejunal crypts (P ≤ 0.05). Finally, 5-HT EEC expression was increased in the cecum of HS group (P ≤ 0.01). In conclusion, these outcomes demonstrate that chronic HS induces morphometric alterations not only in the small intestine but also in a key organ such as the proventriculus. Furthermore, HS conditions affect the presence and distribution of EECs, suggesting that some GI peptides and biogenic amine may be implicated in the regulation of appetite and voluntary feed intake in heat-stressed broiler chickens.

Improvement of several stress response and sleep quality hormones in men and women after sleeping in a bed that protects against electromagnetic fields

BACKGROUND

The electromagnetic fields (EMFs) emitted by the technologies affect the homeostatic systems (nervous, endocrine, and immune systems) and consequently the health. In a previous work, we observed that men and women, after 2 months of using a bed with a registered HOGO system, that prevents and drain EMFs, improved their immunity, redox and inflammatory states and rejuvenated their rate of aging or biological age. Since, EMFs can act as a chronic stressor stimulus, and affect the sleep quality. The objective of this work was to study in men and women (23-73 years old) the effect of sleeping for 2 months on that bed in the blood concentrations of several hormones related to stress response and sleep quality as well as to corroborate the rejuvenation of their biological age.

METHODS

In 18 men and women, plasma concentration of cortisol, dehydroepiandrosterone (DHEA), catecholamines (epinephrine, norepinephrine and dopamine), serotonin, oxytocin and melatonin were analyzed before and after 2 months of using the HOGO beds. A group of 10 people was used as placebo control. In another cohort of 25 men (20 experimental and 5 placebo), the effects of rest on the HOGO system on the concentration of cortisol and testosterone in plasma were studied. In all these volunteers, the biological age was analyzed using the Immunity Clock model.

RESULTS

There is a significant increase in plasma concentration of DHEA, norepinephrine, serotonin, oxytocin, and melatonin as well as in testosterone, after resting for 2 months in that bed with the EMFs avoiding system. In addition, decreases in Cortisol/DHEA and Testosterone/cortisol ratio and plasma dopamine concentration were observed. No differences were found in placebo groups. In all participants that slept on HOGO beds, the biological age was reduced.

CONCLUSIONS

Sleeping in a bed that isolates from EMFs and drain them can be a possible strategy to improve the secretion of hormones related to a better response to stress and sleep quality, which means a better endocrine system, and consequently better homeostasis and maintenance of health. This fact was confirmed with the slowdown in the rate of aging checked with a rejuvenation of the biological age.

Role of 5-HT in the enteric nervous system and enteroendocrine cells

Since the 1950s, considerable circumstantial evidence had been presented that endogenous 5-HT (serotonin) synthesized from within the wall of the gastrointestinal (GI) tract played an important role in GI motility and transit. However, identifying the precise functional role of gut-derived 5-HT has been difficult to ascertain, for a number of reasons. Over the past decade, as recording techniques have advanced significantly and access to new genetically modified animals improved, there have been major new insights and major changes in our understanding of the functional role of endogenous 5-HT in the GI tract. Data from many different laboratories have shown that major patterns of GI motility and transit still occur with minor or no, change when all endogenous 5-HT is pharmacologically or genetically ablated from the gut. Furthermore, antagonists of 5-HT3 receptors are equally, or more potent at inhibiting GI motility in segments of intestine that are completely depleted of endogenous 5-HT. Here, the most recent findings are discussed with regard to the functional role of endogenous 5-HT in enterochromaffin cells and enteric neurons in gut motility and more broadly in some major homeostatic pathways.

Neurochemical classification of serotonin-immunoreactive neurons co-innervating motor endplates in the mouse esophagus

Serotonin immunoreactivity was previously found in myenteric neurons co-innervating motor endplates in the mouse esophagus striated muscle and an involvement in motility control was suggested. However, it is not known if other neuroactive substances are present in these neurons and to what extent they co-localize. First, vasoactive intestinal peptide (VIP) was established as a bona fide marker for putative inhibitory myenteric neurons by evaluating co-localization with neuronal nitric oxide synthase (nNOS) and neuropeptide Y (NPY). Then, co-localization of serotonin and VIP was tested in co-innervating axons on motor endplates, which were visualized with α-bungarotoxin (α-BT) by multilabel immunofluorescence. Myenteric ganglia were also surveyed for co-localization in neuronal perikarya and varicosities. nNOS, NPY, and VIP were completely co-localized in enteric co-innervating nerve terminals on motor endplates. After co-staining with VIP, we found (a) serotonin (5-HT)-positive nerve endings without VIP (44% of 5-HT-positively innervated endplates), (b) 5-HT- and VIP-positive endings without co-localization (35%), and (c) 5-HT- and VIP-positive endings with co-localization (21%). About one-fifth of nerve terminals on motor endplates containing 5-HT originate from putative inhibitory peptidegic nitrergic neurons. However, the majority represents a different population presumably subserving different functions.

The liver-gut peripheral neural axis and nonalcoholic fatty liver disease pathologies via hepatic serotonin receptor 2A

Serotonin (5-HT) is one of the key bioamines of nonalcoholic fatty liver disease (NAFLD). Its mechanism of action in autonomic neural signal pathways remains unexplained; hence, we evaluated the involvement of 5-HT and related signaling pathways via autonomic nerves in NAFLD. Diet-induced NAFLD animal models were developed using wild-type and melanocortin 4 receptor (MC4R) knockout (MC4RKO) mice, and the effects of the autonomic neural axis on NAFLD physiology, 5-HT and its receptors (HTRs), and lipid metabolism-related genes were assessed by applying hepatic nerve blockade. Hepatic neural blockade retarded the progression of NAFLD by reducing 5-HT in the small intestine, hepatic HTR2A and hepatic lipogenic gene expression, and treatment with an HTR2A antagonist reproduced these effects. The effects were milder in MC4RKO mice, and brain 5-HT and HTR2C expression did not correlate with peripheral neural blockade. Our study demonstrates that the autonomic liver-gut neural axis is involved in the etiology of diet-induced NAFLD and that 5-HT and HTR2A are key factors, implying that the modulation of the axis and use of HTR2A antagonists are potentially novel therapeutic strategies for NAFLD treatment.

This article has an associated First Person interview with the first author of the paper.

Summary: The hepatic-gut neural axis plays a role in NAFLD progression via serotonin and the serotonin receptor HTR2A in hepatocytes, suggesting that HTR2A antagonists are potential therapeutic agents for NAFLD.

Branched-Chain and Aromatic Amino Acids Related to Visceral Adipose Tissue Impact Metabolic Health Risk Markers

CONTEXT

Visceral (VAT) and subcutaneous adipose tissue (SAT) function as endocrine organs capable of influencing metabolic health across adiposity levels.

OBJECTIVE

We aimed to investigate whether metabolites associated with VAT and SAT impact metabolic health through metabolite concentrations.

METHODS

Analyses are based on 1790 participants from the population-based Rhineland Study. We assessed plasma levels of methionine (Met), branched-chain amino acids (BCAA), aromatic amino acids (AAA), and their metabolic downstream metabolites with liquid chromatography-mass spectrometry. VAT and SAT volumes were assessed by magnetic resonance imaging (MRI). Metabolically healthy and unhealthy phenotypes were defined using Wildman criteria.

RESULTS

Metabolically unhealthy participants had higher concentrations of BCAA than metabolically healthy participants (P < 0.001). In metabolically unhealthy participants, VAT volumes were significantly associated with levels of L-isoleucine, L-leucine, indole-3-lactic acid, and indole-3-propionic acid (in log SD units: β = 0.16, P = 0.003; β = 0.12, P = 0.038; β = 0.11, P = 0.035 and β = -0.16, P = 0.010, respectively). Higher concentrations of certain BCAA and AAA-downstream metabolites significantly increased the odds of cardiometabolic risk markers. The relation between VAT volume and cardiometabolic risk markers was mediated by BCAA (indirect effects 3.7%-11%, P = 0.02 to < 0.0001), while the effect of VAT on systemic inflammation was mediated through higher kynurenine concentrations (indirect effect 6.4%, P < 0.0001).

CONCLUSION

Larger volumes of VAT in metabolically unhealthy individuals are associated with altered concentrations of circulating BCAA and AAA-downstream metabolites, increasing the odds of cardiometabolic risk markers. This suggests that these metabolites are involved in the mechanisms that underlie the relationship of abdominal VAT with metabolic health.

Effect of sarpogrelate treatment on 5-HT modulation of vascular sympathetic innervation and platelet activity in diabetic rats

This study aimed to investigate whether the 5-HT₂ receptor blockade alters the 5-HT effect on vascular sympathetic neurotransmission and platelet activation in type 1 diabetes. 28-day diabetes was obtained by alloxan (150 mg/kg; s.c.) in male Wistar rats, administering sarpogrelate (5-HT₂ blocker; 30 mg/kg/day; p.o.) for 14 days. Blood glucose and body weight were monitored for 28 days. After 4 weeks of diabetes induction, food and drink intake, urine, plasma-platelet 5-HT, and platelet activation were determined in normoglycemic, non-treated diabetic and sarpogrelate-treated diabetic rats. Another set of diabetic rats were pithed to run the vascular sympathetic stimulation or exogenous noradrenaline administration, examining the induced vasoconstrictor responses. Sarpogrelate treatment significantly reduced drink intake and urine, whereas BW gain, hyperglycemia, and food intake were not modified in diabetic rats. The platelet activation and plasma 5-HT concentration were decreased (increasing the stored 5-HT platelet) by 5-HT₂ blockade in diabetic animals. The sympathetic-induced vasoconstrictions were higher in non-treated than in sarpogrelate-treated diabetic rats. 5-HT inhibited these vasopressor responses, reproduced exclusively by the 5-HT_1/5/7 receptor agonist, 5-CT. The 5-CT-produced inhibition was partly reversed by 5-HT_1D or 5-HT₇ antagonists (LY310762 or SB-258719, respectively), and totally annulled by the mixture of LY310762+SB-258719. Noradrenaline-caused vasoconstrictions were also decreased by 5-CT. In conclusion, our results reveal that 14-day sarpogrelate treatment improves polydipsia and polyuria, reduces platelet hyperactivation, plasma 5-HT and the vascular sympathetic tone, and changes 5-HT receptors inhibiting noradrenergic drive in diabetic rats: pre and/or postjunctional 5-HT_1D/7 are involved in the sympatho-inhibition.

Altered gut microbiota and metabolites profile are associated with reduced bone metabolism in ethanol-induced osteoporosis

Objective

Chronic heavy drinking causes ethanol‐induced osteoporosis (EIO). The present study aimed to explore the role of GM in EIO.

Material and Methods

A rat EIO model was established by chronic ethanol intake. Taking the antibiotic application as the matched group of dysbacteriosis, an integrated 16S rRNA sequencing and liquid chromatography–tandem mass spectrometry‐based metabolomics in serum and faeces were applied to explore the association of differential metabolic phenotypes and screen out the candidate metabolites detrimental to ossification. The colon organoids were used to track the source of 5‐HT and the effect of 5‐HT on bone formation was examined in vitro.

Results

Compared with antibiotics application, ethanol‐gavaged decreased the BMD in rats. We found that both ethanol and antibiotic intake affected the composition of GM, but ethanol intake increased the ratio of Firmicutes to Bacteroidetes. Elevated serotonin was proved to be positively correlated with the changes of the composition of GM and faecal metabolites and inhibited the proliferation and mineralization of osteogenesis‐related cells. However, the direct secretory promotion of serotonin was absent in the colon organoids exposed to ethanol.

Conclusion

This study demonstrated that ethanol consumption led to osteoporosis and intestinal‐specific dysbacteriosis. Conjoint analysis of the genetic profiles of GM and metabolic phenotypes in serum and faeces allowed us to understand the endogenous metabolite, 5‐HT, as detrimental regulators in the gut‐bone axis to impair bone formation.

Mild hypoxia exposure impacts peripheral serotonin uptake and degradation in Gulf toadfish, Opsanus beta

Plasma 5-HT homeostasis is maintained through the combined processes of uptake (via the 5-HT transporter SERT, and others), degradation (via monoamine oxidase, MAO), and excretion. Previous studies have shown that inhibiting SERT, which would inhibit 5-HT uptake and degradation, attenuates parts of the cardiovascular hypoxia reflex in Gulf toadfish (Opsanus beta), suggesting that these 5-HT clearance processes may be important during hypoxia exposure. Therefore, the goal of this experiment was to determine the effects of mild hypoxia on 5-HT uptake and degradation in the peripheral tissues of toadfish. We hypothesized that 5-HT uptake and degradation would be upregulated during hypoxia resulting in lower plasma 5-HT, with uptake occurring in the gill, heart, liver, and kidney. Fish were exposed to normoxia (97.6% O2 saturation, 155.6 torr), or 2-min, 40-min or 24 h mild hypoxia (50% O2 saturation, ∼80 torr), injected with radiolabeled [3H]5-HT and blood, urine, bile and tissues taken. Plasma 5-HT levels were reduced by 40% after 40 min of hypoxia exposure and persisted through 24 h. 5-HT uptake by the gill was upregulated following 2 min of hypoxia exposure, and degradation in the gill was upregulated at 40 min and 24 h. Interestingly, there was no change in 5-HT uptake by the heart and degradation in the heart decreased by 58% within 2 min of hypoxia exposure and by 85% at 24 h. These results suggest that 5-HT clearance is upregulated during hypoxia and is likely driven, in part, by mechanisms within the gill and not the heart.