The differential sensitivity of the hypothalamic-hypophysial-ovarian axis to 5-hydroxytryptophan alters the secretion of estradiol

Serotonin [5-hydroxytryptamine (5-HT)] modulates ovarian function. The precursor of 5-HT, 5-hydroxytryptophan (5-HTP), has been used to treat depression. However, the effects of 5-HTP on ovarian and reproductive physiology remain unknown. In this research, we analysed the impact of 5-HTP on the monoaminergic system and its interactions with the reproductive axis and ovarian estradiol secretion when administered by distinct routes. Female rats 30 days of age were injected with 5-HTP i.p. (100 mg/kg), into the ovarian bursa (1.5 µg/40 µL) or into the median raphe nucleus (20 µg/2.5 µL) and were killed 60 or 120 min after injection. As controls, we used rats of the same age injected with vehicle (0.9% NaCl). Monoamine, gonadotrophin and steroid ovarian hormone concentrations were measured. The injection of 5-HTP either i.p. or directly into the ovarian bursa increased the concentrations of 5-HT and the metabolite 5-hydroxyindole-3-acetic acid in the ovary. For both routes of administration, the serum concentration of estradiol increased. After i.p. injection of 5-HTP, the concentrations of luteinizing hormone were decreased and follicle-stimulating hormone increased after 120 min. Micro-injection of 5-HTP into the median raphe nucleus increased the concentrations of 5-HT in the anterior hypothalamus and dopamine in the medial hypothalamus after 120 min. Our results suggest that the administration of 5-HTP either i.p. or directly into the ovarian bursa enhances ovarian estradiol secretion.

The association between indoor air pollution from solid fuels and cognitive impairment: a systematic review and meta-analysis

This study aimed to comprehensively and methodically evaluate the correlation between cognitive impairment and indoor air pollution from solid fuel used for cooking/heating. PubMed, Web of Science, EMBASE, and Cochrane Library databases were searched up to December January 2023. 13 studies from three countries with a total of 277,001 participants were enrolled. A negative correlation was discovered between solid fuel usage for cooking and total cognitive score (β=-0.73, 95 % CI: -0.90 to -0.55) and episodic memory score (β=-0.23, 95 % CI: -0.30 to -0.17). Household solid fuel usage for cooking was considerably associated with a raised risk of cognitive impairment (HR=1.31, 95 % CI: 1.09-1.57) and cognitive decline (HR=1.24, 95 % CI: 1.18-1.30). Compared to continuous solid fuel use for cooking, sustained use of clean fuel and switching from solid fuel to clean fuel were associated with a lower risk of cognitive decline (OR=0.55, 95 % CI: 0.42-0.73; OR=0.81, 95 % CI: 0.71-0.93). A negative association was found between solid fuel usage for heating and total cognitive score (β=-0.43, 95 % CI: -0.59 to -0.26) and episodic memory score (β=-0.22, 95 % CI: -0.34 to -0.10). Our research provided evidence that exposure to indoor air pollution from solid fuel is a potential cause of cognitive impairment and cognitive decline. Making the switch from solid fuels to cleaner fuels could be an important step in preventing cognitive impairment in the elderly.

Host miR-129-5p reverses effects of ginsenoside Rg1 on morphine reward possibly mediated by changes in B. vulgatus and serotonin metabolism in hippocampus

Morphine addiction is closely associated with dysbiosis of the gut microbiota. miRNAs play a crucial role in regulating intestinal bacterial growth and are involved in the development of disease. Ginsenoside Rg1 exhibits an anti-addiction effect and significantly improves intestinal microbiota disorders. In pseudo-germfree mice, supplementation with Bacteroides vulgatus (B. vulgatus) synergistically enhanced Rg1 to alleviate morphine addiction. However, it is currently unknown the relationship between fecal miRNAs in morphine-exposed mice and their potential modulation of gut microbiome, as well as their role in mediating the resistance of ginsenoside Rg1 to drug addiction. Here, we studied the fecal miRNA abundance in mice treated with morphine to explore the different miRNAs expressed, their association with B. vulgatus and their role in the amelioration of morphine reward by ginsenoside Rg1. Our results indicated ginsenoside Rg1 attenuated the significant increase in miR-129-5p expression observed in the feces of morphine-treated mice. The miR-129-5p, specifically, inhibited the growth of B. vulgatus by modulating the transcript of the site-tag BVU_RS11835 and increased the levels of 5-hydroxytryptophan and indole-3-carboxaldehyde in vitro. Subsequently, we noticed that oral administration of synthetic miR-129-5p increased 5-HT levels in the hippocampus and inhibited the reversal effect of ginsenoside Rg1 both on the relative abundance of B. vulgatus in the feces and CPP effect induced by morphine exposure. In short, Ginsenoside Rg1 might play an indirect role in remodeling the B. vulgatus against morphine reward by suppressing miR-129-5p expression. These results highlight the role of miR-129-5p and B. vulgatus in morphine reward and the anti-morphine addiction of ginsenoside Rg1.

An Okinawan-Based Nordic Diet Leads to Profound Effects on Gut Microbiota and Plasma Metabolites Linked to Glucose and Lipid Metabolism

Dietary interventions modify gut microbiota and clinical outcomes. Weight reduction and improved glucose and lipid homeostasis were observed after adopting an Okinawan-based Nordic diet (O-BN) in individuals with type 2 diabetes. The aim of the present study was to explore changes in metabolomics and gut microbiota during O-BN and correlate changes with clinical outcomes. A total of 30 patients (17 women), aged 57.5 ± 8.2 years, diabetes duration 10.4 ± 7.6 years, 90% over-weight, were included. Participants were provided an O-BN for 12 weeks. Before and after intervention, and 16 weeks afterwards, anthropometry and clinical data were estimated and questionnaires were collected, as well as samples of blood and stool. Plasma metabolomics were determined by gas- (GC-MS) or liquid- (LC-MS) chromatography-based mass spectrometry and fecal microbiota determination was based on 16S rRNA amplicons from regions V1-V2. During the intervention, weight (6.8%), waist circumference (6.1%), and levels of glucose, HbA1c, insulin, triglycerides, and cholesterol were decreased. Of 602 metabolites, 323 were changed for any or both periods; 199 (101 lipids) metabolites were decreased while 58 (43 lipids) metabolites were increased during the intervention. Changes in glucose homeostasis were linked to changes in, e.g., 1,5-anhydroglucitol, thyroxine, and chiro-inositol. Changes of microbe beta diversity correlated positively with food components and negatively with IL-18 (p = 0.045). Abundance differences at phylum and genus levels were found. Abundances of Actinobacteria, Bacteroidetes, Firmicutes, and Verrucomicrobia correlated with anthropometry, HbA1c, lipids, inflammation, and food. Changes in metabolites and microbiota were reversed after the intervention. The O-BN-induced changes in metabolomics and gut microbiota correspond to clinical outcomes of reduced weight and inflammation and improved glucose and lipid metabolism.

Association between cord blood metabolites in tryptophan pathway and childhood risk of autism spectrum disorder and attention-deficit hyperactivity disorder

Alterations in tryptophan and serotonin have been implicated in various mental disorders; but studies are limited on child neurodevelopmental disabilities such as autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). This prospective cohort study examined the associations between levels of tryptophan and select metabolites (5-methoxytryptophol (5-MTX), 5-hydroxytryptophan (5-HTP), serotonin, N-acetyltrytophan) in cord plasma (collected at birth) and physician-diagnosed ASD, ADHD and other developmental disabilities (DD) in childhood. The study sample (n = 996) derived from the Boston Birth Cohort, which included 326 neurotypical children, 87 ASD, 269 ADHD, and 314 other DD children (mutually exclusive). These participants were enrolled at birth and followed-up prospectively (from October 1, 1998 to June 30, 2018) at the Boston Medical Center. Higher levels of cord 5-MTX was associated with a lower risk of ASD (aOR: 0.56, 95% CI: 0.41, 0.77) and ADHD (aOR: 0.79, 95% CI: 0.65, 0.96) per Z-score increase, after adjusting for potential confounders. Similarly, children with cord 5-MTX ≥ 25th percentile (vs. <25th percentile) had a reduction in ASD (aOR: 0.27, 95% CI: 0.14, 0.49) and ADHD risks (aOR: 0.45, 95% CI: 0.29, 0.70). In contrast, higher levels of cord tryptophan, 5-HTP and N-acetyltryptophan were associated with higher risk of ADHD, with aOR: 1.25, 95% CI: 1.03, 1.51; aOR: 1.32, 95% CI: 1.08, 1.61; and aOR: 1.27, 95% CI: 1.05, 1.53, respectively, but not with ASD and other DD. Cord serotonin was not associated with ASD, ADHD, and other DD. Most findings remained statistically significant in the sensitivity and subgroup analyses.

Edible Mushrooms as a Potential Component of Dietary Interventions for Major Depressive Disorder

Dietary interventions for people suffering from major depressive disorder (MDD) are an ongoing field of research. In this article, we present a comprehensive background for understanding the possibility of using edible medicinal mushrooms as an adjunctive treatment for MDD. We start with a brief history of MDD, its diagnosis, epidemiology and treatment, and the effects of diet on depression symptoms, followed by a review of neurobiological, behavioral, and clinical studies of medicinal mushrooms. We specifically highlight the results of preclinical and clinical studies on dietary supplementation with three selected mushroom species: Lion’s mane (Hericium erinaceus), Caterpillar mushroom (Cordyceps militaris), and Lingzhi/Reishi (Ganoderma lucidum). Preliminary small-sample clinical studies suggest that Lion’s mane can influence well-being of humans. In the case of Reishi, the results of clinical studies are equivocal, while in the case of Caterpillar Mushroom, such studies are underway. Edible mushrooms contain 5-hydroxy-L-tryptophan (5-HTP), which is a direct precursor of serotonin—a neurotransmitter targeted in pharmacotherapy of MDD. Therefore, in light of the well-recognized role of stress as a pathogenic factor of MDD, we also describe the neurobiological mechanisms of the interaction between stress and serotonergic neurotransmission; and summarize the current state of knowledge on dietary supplementation with 5-HTP in MDD.

Large-scale genetic correlation scanning and causal association between deep vein thrombosis and human blood metabolites

Deep vein thrombosis (DVT) refers to the abnormal coagulation of blood in a deep vein. Recently, some studies have found that metabolites are related to the occurrence of DVT and may serve as new markers for the diagnosis of DVT. In this study, we used the GWAS summary dataset of blood metabolites and DVT to perform a large-scale genetic correlation scan of DVT and blood metabolites to explore the correlation between blood metabolites and DVT. We used GWAS summary data of DVT from the UK Biobank (UK Biobank fields: 20002) and GWAS summary data of blood metabolites from a previously published study (including 529 metabolites in plasma or serum from 7824 adults from two European population studies) for genetic correlation analysis. Then, we conducted a causal study between the screened blood metabolites and DVT by Mendelian randomization (MR) analysis. In the first stage, genetic correlation analysis identified 9 blood metabolites that demonstrated a suggestive association with DVT. These metabolites included Valine (correlation coefficient = 0.2440, P value = 0.0430), Carnitine (correlation coefficient = 0.1574, P value = 0.0146), Hydroxytryptophan (correlation coefficient = 0.2376, P value = 0.0360), and 1-stearoylglycerophosphoethanolamine (correlation coefficient = - 0.3850, P value = 0.0258). Then, based on the IVW MR model, we analysed the causal relationship between the screened blood metabolites and DVT and found that there was a suggestive causal relationship between Hydroxytryptophan (exposure) and DVT (outcome) (β = - 0.0378, se = 0.0163, P = 0.0204). Our study identified a set of candidate blood metabolites that showed a suggestive association with DVT. We hope that our findings will provide new insights into the pathogenesis and diagnosis of DVT in the future.

Tryptophan-enriched diet or 5-hydroxytryptophan supplementation given in a randomized controlled trial impacts social cognition on a neural and behavioral level

Understanding of emotions and intentions are key processes in social cognition at which serotonin is an important neuromodulator. Its precursor is the essential amino acid tryptophan (TRP). Reduced TRP availability leads to weaker impulse control ability and higher aggression, while TRP supplementation promotes confidence. In a double-blind placebo-controlled fMRI study with 77 healthy adults, we investigated the influence of a 4 week TRP enriched diet and an acute 5-hydroxytryptophan (5-HTP) intake on two social-cognitive tasks, a moral evaluation and an emotion recognition task. With 5-HTP, immoral behavior without negative consequences was rated as more reprehensible. Additionally, during story reading, activation in insula and supramarginal gyrus was increased after TRP intake. No significant effects of TRP on emotion recognition were identified for the whole sample. Importantly, emotion recognition ability decreased with age which was for positive emotions compensated by TRP. Since the supramarginal gyrus is associated with empathy, pain and related information integration results could be interpreted as reflecting stricter evaluation of negative behavior due to better integration of information. Improved recognition of positive emotions with TRP in older participants supports the use of a TRP-rich diet to compensate for age related decline in social-cognitive processes.

Paeoniflorin: A neuroprotective monoterpenoid glycoside with promising anti-depressive properties

BACKGROUND

Depression, as a prevalent and debilitating psychiatric disease, severely decreases the life quality of individuals and brings heavy burdens to the whole society. Currently, some antidepressants are applied in the treatment of severe depressive symptoms, while there are still some undesirable drawbacks. Paeoniflorin is a monoterpenoid glycoside that was firstly extracted from Paeonia lactiflora Pall, a traditional Chinese herb that is widely used in the Chinese herbal formulas for treating depression.

PURPOSE

This review summarized the previous pre-clinical studies of paeoniflorin in treating depression and further discussed the potential anti-depressive mechanisms for that paeoniflorin to be further explored and utilized in the treatment of depression clinically.

METHODS

Some electronic databases, e.g., PubMed and China National Knowledge Infrastructure, were searched from inception until April 2021.

RESULTS

This review summarized the effective anti-depressive properties of paeoniflorin, which is related to its functions in the upregulation of the levels of monoaminergic neurotransmitters, inhibition of the hypothalamic-pituitary-adrenal axis hyperfunction, promotion of neuroprotection, promotion of hippocampus neurogenesis, and upregulation of brain-derived neurotrophic factor level, inhibition of inflammatory reaction, downregulation of nitric oxide level, etc. CONCLUSION: This review focused on the pre-clinical studies of paeoniflorin in depression and summarized the recent development of the anti-depressive mechanisms of paeoniflorin, which approves the role of paeoniflorin plays in anti-depression. However, more high-quality pre-clinical and clinical studies are expected to be conducted in the future.

'An Apple a Day'?: Psychiatrists, Psychologists and Psychotherapists Report Poor Literacy for Nutritional Medicine: International Survey Spanning 52 Countries

Nutritional interventions have beneficial effects on certain psychiatric disorder symptomatology and common physical health comorbidities. However, studies evaluating nutritional literacy in mental health professionals (MHP) are scarce. This study aimed to assess the across 52 countries. Surveys were distributed via colleagues and professional societies. Data were collected regarding self-reported general nutrition knowledge, nutrition education, learning opportunities, and the tendency to recommend food supplements or prescribe specific diets in clinical practice. In total, 1056 subjects participated in the study: 354 psychiatrists, 511 psychologists, 44 psychotherapists, and 147 MHPs in-training. All participants believed the diet quality of individuals with mental disorders was poorer compared to the general population (p < 0.001). The majority of the psychiatrists (74.2%) and psychologists (66.3%) reported having no training in nutrition. Nevertheless, many of them used nutrition approaches, with 58.6% recommending supplements and 43.8% recommending specific diet strategies to their patients. Only 0.8% of participants rated their education regarding nutrition as 'very good.' Almost all (92.9%) stated they would like to expand their knowledge regarding 'Nutritional Psychiatry.' There is an urgent need to integrate nutrition education into MHP training, ideally in collaboration with nutrition experts to achieve best practice care.

The Uniqueness of Tryptophan in Biology: Properties, Metabolism, Interactions and Localization in Proteins

Tryptophan (Trp) holds a unique place in biology for a multitude of reasons. It is the largest of all twenty amino acids in the translational toolbox. Its side chain is indole, which is aromatic with a binuclear ring structure, whereas those of Phe, Tyr, and His are single-ring aromatics. In part due to these elaborate structural features, the biosynthetic pathway of Trp is the most complex and the most energy-consuming among all amino acids. Essential in the animal diet, Trp is also the least abundant amino acid in the cell, and one of the rarest in the proteome. In most eukaryotes, Trp is the only amino acid besides Met, which is coded for by a single codon, namely UGG. Due to the large and hydrophobic π-electron surface area, its aromatic side chain interacts with multiple other side chains in the protein, befitting its strategic locations in the protein structure. Finally, several Trp derivatives, namely tryptophylquinone, oxitriptan, serotonin, melatonin, and tryptophol, have specialized functions. Overall, Trp is a scarce and precious amino acid in the cell, such that nature uses it parsimoniously, for multiple but selective functions. Here, the various aspects of the uniqueness of Trp are presented in molecular terms.

Short communication: The effect of ruminal administration of 5-hydroxy-l-tryptophan on circulating serotonin concentrations

The monoamine serotonin has been shown to regulate peripartal calcium homeostasis in multiparous cows and be a possible mitigation tool for hypocalcemia. Increasing circulating serotonin concentrations via prepartum intravenous (IV) administration of the serotonin precursor 5-hydroxy-L-tryptophan (5-HTP) increases postpartum calcium concentrations. However, the ability of 5-HTP to be used orally or ruminally to alter circulating serotonin concentrations has not been established. Hence, our objective was to determine if ruminal administration of 5-HTP altered circulating serotonin concentrations. Four ruminally cannulated, nonlactating, nonpregnant multiparous Holstein dairy cows were randomly assigned to 1 of 4 treatments in a 4 × 4 replicated Latin square with 4-d periods separated by a 7-d washout. On d 1 and 2 of each period, cows were dosed with 1 of 4 experimental treatments as follows: (1) 0 mg/kg of body weight (BW) of 5-HTP, (2) 1 mg/kg of BW of intraruminal 5-HTP, (3) 2 mg/kg of BW of intraruminal 5-HTP, or (4) 1 mg/kg of BW of IV 5-HTP. Infusions were administered over a 1-h period, and all groups not receiving 5-HTP IV were infused with an equal volume of IV saline to that of IV 1 mg/kg of BW of 5-HTP treatment. Continuous serial blood samples were collected beginning after d 2 of treatment administration. Whole blood serotonin concentrations were higher in cows dosed with 2 mg/kg of BW of intraruminal 5-HTP immediately after dosing when compared with cows dosed with 0 mg/kg of BW of 5-HTP on d 2, but were similar on d 3 and 4 of the experimental period. Cows receiving IV 5-HTP had the highest circulating serotonin concentrations relative to all other treatments. These findings demonstrated that 2 intraruminal dosings of 5-HTP at 2 mg/kg of BW resulted in elevated circulating serotonin concentrations relative to the control immediately after dosing. This supports the potential for 5-HTP to be used orally to manipulate circulating serotonin concentrations.