Effects of Melatonin on Intestinal Microbiota and Oxidative Stress in Colitis Mice

Therapeutic applications of melatonin in disorders related to the gastrointestinal tract and control of appetite

Most animals have large amounts of the special substance melatonin, which is controlled by the light/dark cycle in the suprachiasmatic nucleus. According to what is now understood, the gastrointestinal tract (GIT) and other areas of the body are sites of melatonin production. According to recent studies, the GIT and adjacent organs depend critically on a massive amount of melatonin. Not unexpectedly, melatonin's many biological properties, such as its antioxidant, anti-inflammatory, pro-apoptotic, anti-proliferative, anti-metastasis, and antiangiogenic properties, have drawn the attention of researchers more and more. Because melatonin is an antioxidant, it produces a lot of secretions in the GIT's mucus and saliva, which shields cells from damage and promotes the development of certain GIT-related disorders. Melatonin's ability to alter cellular behavior in the GIT and other associated organs, such as the liver and pancreas, is another way that it functions. This behavior alters the secretory and metabolic activities of these cells. In this review, we attempted to shed fresh light on the many roles that melatonin plays in the various regions of the gastrointestinal tract by focusing on its activities for the first time.

Circadian Rhythm Perturbation Aggravates Gut Microbiota Dysbiosis in Dextran Sulfate Sodium-Induced Colitis in Mice

Circadian rhythm disruption is increasingly considered an environmental risk factor for the development and exacerbation of inflammatory bowel disease. We have reported in a previous study that nychthemeral dysregulation is associated with an increase in intestinal barrier permeability and inflammation in mice with dextran sulfate sodium (DSS)-induced colitis. To investigate the effect of circadian rhythm disruption on the composition and diversity of the gut microbiota (GM), sixty male C57BL/6J mice were initially divided to two groups, with the shifted group (n = 30) exposed to circadian shifts for three months and the non-shifted group (n = 30) kept under a normal light-dark cycle. The mice of the shifted group were cyclically housed for five days under the normal 12:12 h light-dark cycle, followed by another five days under a reversed light-dark cycle. At the end of the three months, a colitis was induced by 2% DSS given in the drinking water of 30 mice. Animals were then divided into four groups (n = 15 per group): sham group non-shifted (Sham-NS), sham group shifted (Sham-S), DSS non-shifted (DSS-NS) and DSS shifted (DSS-S). Fecal samples were collected from rectal content to investigate changes in GM composition via DNA extraction, followed by high-throughput sequencing of the bacterial 16S rRNA gene. The mouse GM was dominated by three phyla: Firmicutes, Bacteroidetes and Actinobacteria. The Firmicutes/Bacteroidetes ratio decreased in mice with induced colitis. The richness and diversity of the GM were reduced in the colitis group, especially in the group with inverted circadian rhythm. Moreover, the GM composition was modified in the inverted circadian rhythm group, with an increase in Alloprevotella, Turicibacter, Bacteroides and Streptococcus genera. Circadian rhythm inversion exacerbates GM dysbiosis to a less rich and diversified extent in a DSS-induced colitis model. These findings show possible interplay between circadian rhythm disruption, GM dynamics and colitis pathogenesis.

Significance of Melatonin in the Regulation of Circadian Rhythms and Disease Management

Melatonin, the 'hormone of darkness' is a neuronal hormone secreted by the pineal gland and other extra pineal sites. Responsible for the circadian rhythm and seasonal behaviour of vertebrates and mammals, melatonin is responsible for regulating various physiological conditions and the maintenance of sleep, body weight and the neuronal activities of the ocular sites. With its unique amphiphilic structure, melatonin can cross the cellular barriers and elucidate its activities in the subcellular components, including mitochondria. Melatonin is a potential scavenger of oxygen and nitrogen-reactive species and can directly obliterate the ROS and RNS by a receptor-independent mechanism. It can also regulate the pro- and anti-inflammatory cytokines in various pathological conditions and exhibit therapeutic activities against neurodegenerative, psychiatric disorders and cancer. Melatonin is also found to show its effects on major organs, particularly the brain, liver and heart, and also imparts a role in the modulation of the immune system. Thus, melatonin is a multifaceted candidate with immense therapeutic potential and is still considered an effective supplement on various therapies. This is primarily due to rectification of aberrant circadian rhythm by improvement of sleep quality associated with risk development of neurodegenerative, cognitive, cardiovascular and other metabolic disorders, thereby enhancing the quality of life.

Melatonin as a Mediator of the Gut Microbiota-Host Interaction: Implications for Health and Disease

In recent years, the role played by melatonin on the gut microbiota has gained increasingly greater attention. Additionally, the gut microbiota has been proposed as an alternative source of melatonin, suggesting that this antioxidant indoleamine could act as a sort of messenger between the gut microbiota and the host. This review analyses the available scientific literature about possible mechanisms involved in this mediating role, highlighting its antioxidant effects and influence on this interaction. In addition, we also review the available knowledge on the effects of melatonin on gut microbiota composition, as well as its ability to alleviate dysbiosis related to sleep deprivation or chronodisruptive conditions. The melatonin-gut microbiota relationship has also been discussed in terms of its role in the development of different disorders, from inflammatory or metabolic disorders to psychiatric and neurological conditions, also considering oxidative stress and the reactive oxygen species-scavenging properties of melatonin as the main factors mediating this relationship.

Melatonin disturbed rumen microflora structure and metabolic pathways in vitro

IMPORTANCE

In in vitro studies, it has been found that the effects of MLT on rumen microorganisms and metabolites can change the rumen flora structure, significantly inhibit the relative abundance of harmful Acinetobacter, and improve the relative abundance of beneficial bacteria. MLT may regulate the "arginine-glutathione" pathway, "phenylalanine, tyrosine and tryptophan biosynthesis-tryptophan generation" branch, "tryptophan-kynurenine" metabolism, and "tryptophan-tryptamine-serotonin" pathway through microorganisms.

Identification of Diagnostic Biomarkers for Compensatory Liver Cirrhosis Based on Gut Microbiota and Urine Metabolomics Analyses

Liver cirrhosis is one of the most prevalent chronic liver disorders with high mortality. We aimed to explore changed gut microbiome and urine metabolome in compensatory liver cirrhosis (CLC) patients, thus providing novel diagnostic biomarkers for CLC. Forty fecal samples from healthy volunteers (control: 19) and CLC patients (patient: 21) were undertaken 16S rDNA sequencing. Chromatography-mass spectrometry was performed on 40 urine samples (20 controls and 20 patients). Microbiome and metabolome data were separately analyzed using corresponding bioinformatics approaches. The diagnostic model was constructed using the least absolute shrinkage and selection operator regression. The optimal diagnostic model was determined by five-fold cross-validation. Pearson correlation analysis was applied to clarify the relations among the diagnostic markers. 16S rDNA sequencing analyses showed changed overall alpha diversity and beta diversity in patient samples compared with those of controls. Similarly, we identified 841 changed metabolites. Pathway analysis revealed that the differential metabolites were mainly associated with pathways, such as tryptophan metabolism, purine metabolism, and steroid hormone biosynthesis. A 9-maker diagnostic model for CLC was determined, including 7 microorganisms and 2 metabolites. In this model, there were multiple correlations between microorganisms and metabolites. Subdoligranulum, Agathobacter, norank_f_Eubacterium_coprostanoligenes_group, Butyricicoccus, Lachnospiraceae_UCG_004, and L-2,3-Dihydrodipicolinate were elevated in CLC patients, whereas Blautia, Monoglobus, and 5-Acetamidovalerate were reduced. A novel diagnostic model for CLC was constructed and verified to be reliable, which provides new strategies for the diagnosis and treatment of CLC.

Effect of melatonin in patients with low anterior resection syndrome (MELLARS): a study protocol for a randomised, placebo-controlled, crossover trial

INTRODUCTION

After rectal cancer surgery, a majority of patients suffer from sequelae known as low anterior resection syndrome (LARS). It is a collection of symptoms consisting of flatus and/or stool incontinence, evacuation frequency, re-evacuation and urgency. The circadian hormone, melatonin, has shown to possess anti-inflammatory properties, and in high doses, it reduces bowel movements. The aim of the study is to investigate if locally administered melatonin has an alleviating effect on LARS. Secondarily, the effect of melatonin on bowel movements, other patient-reported symptoms, quality of life, depression, anxiety, sleep disturbances, motilin levels and rectal mucosa histology will be examined.

METHODS AND ANALYSIS

This is a randomised, placebo-controlled, double-blinded, two-period crossover trial. The participants are randomised to 28 days of 25 mg melatonin administered rectally via an enema daily (or placebo) followed by a 28-day washout and then 28 days of placebo (or melatonin). Three participants will be included in an internal feasibility test. They will receive 25 mg of melatonin daily for 28 days. Data from these participants will be used to assess the feasibility of the rectally administered melatonin and to analyse the course of recruitment and outcome measurements. Afterwards, 18 participants will be included in the crossover trial. The severity of the LARS symptoms will be evaluated using the LARS Score on the first and last day of each treatment period.

ETHICS AND DISSEMINATION

The Regional Ethics Committee, the Danish Medicines Agency and the Data and Development Support in Region Zealand approved this study. The study will be performed according to the Helsinki II declaration. Written informed consent will be obtained from all participants. The results of the study will be submitted to peer-reviewed journals for publication and presented at congresses.

TRIAL REGISTRATION NUMBERS

EudraCT Registry (2020-004442-11) and ClinicalTrial.gov Registry (NCT05042700).

Potential Use of Antioxidant Compounds for the Treatment of Inflammatory Bowel Disease

Since inflammatory bowel diseases (IBDs) are chronic, the development of new effective therapeutics to combat them does not lose relevance. Oxidative stress is one of the main pathological processes that determines the progression of IBD. In this regard, antioxidant therapy seems to be a promising approach. The role of oxidative stress in the development and progression of IBD is considered in detail in this review. The main cause of oxidative stress in IBD is an inadequate response of leukocytes to dysbiosis and food components in the intestine. Passage of immune cells through the intestinal barrier leads to increased ROS concentration and the pathological consequences of exposure to oxidative stress based on the development of inflammation and impaired intestinal permeability. To combat oxidative stress in IBD, several promising natural (curcumin, resveratrol, quercetin, and melatonin) and artificial antioxidants (N-acetylcysteine (NAC) and artificial superoxide dismutase (aSOD)) that had been shown to be effective in a number of clinical trials have been proposed. Their mechanisms of action on pathological events in IBD and clinical manifestations from their impact have been determined. The prospects for the use of other antioxidants that have not yet been tested in the treatment of IBD, but have the properties of potential therapeutic candidates, have been also considered.

The possible effect of lycopene in ameliorating experimentally induced ulcerative colitis in adult male albino rats (A histological, immunohistochemical, and ultrastructural study)

Ulcerative colitis (UC) is considered a long-term inflammatory disorder worldwide. Its pathogenesis is associated with reduced antioxidant capacity. Lycopene (LYC) is a powerful antioxidant with strong free radical scavenging property. The present work has done to assess changes of colonic mucosa in induced UC and the possible ameliorative effects of LYC. Forty-five adult male albino rats were randomly divided into four groups: group I (control), group II was given 5 mg/kg/day (LYC) by oral gavage for 3 weeks. Group III (UC) was received single intra-rectal injection of acetic acid. Group IV (LYC+UC) received LYC in same dose and duration as before and acetic acid on 14th day of the experiment. UC group showed loss of surface epithelium with destructed crypts. Congested blood vessels with heavy cellular infiltration were observed. Significant decrease in goblet cell numbers and the mean area percentage of ZO-1 immunoexpression were noticed. Significant increase in the mean area percentage of collagen and the mean area percentage of COX-2 were also noticed. Ultrastructural changes were matched with light microscopic results that showed abnormal destructive columnar and goblet cells. Histological, immunohistochemical, and ultrastructural findings in group IV supported the ameliorative role of LYC against destructive changes induced by UC.

Melatonin: a potential therapeutic approach for the management of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease that primarily affects the exocrine glands and is mainly characterized by sicca symptoms of the eyes and mouth. Approximately 30-50% of pSS patients develop systemic multi-organ disorders including malignant lymphoma. The etiology of pSS is not well understood; growing evidence suggests that uncontrolled immune/inflammatory responses, excessive oxidative stress, defected apoptosis, dysregulated autophagy, exosomes, and exogenous virus infections may participate in the pathogenesis of pSS. There is no ideal therapeutic method for pSS; the management of pSS is mainly palliative, which aims to alleviate sicca symptoms. Melatonin, as the main secretory product of the pineal gland, has been evidenced to show various physiological functions, including effects of immunoregulation, capability of antioxidation, moderation of autophagy, suppressive activities of apoptosis, regulative capacity of exosomes, properties of anti-infection, and improvement of sleep. The beneficial effects of melatonin have been already validated in some autoimmune diseases such as multiple sclerosis (MS), type 1 diabetes mellitus (T1DM), systemic lupus erythematosus (SLE), and inflammatory bowel disease (IBD). However, our previous research firstly revealed that melatonin might inhibit pathogenic responses of peripheral Th17 and double-negative (DN) T cells in pSS. More importantly, melatonin administration alleviated the development of pSS in animal models with reduced infiltrating lymphocytes, improved functional activity of salivary gland, and decreased production of inflammatory factors as well as autoantibodies. Owing to the important biological properties reported in melatonin are characteristics closely related to the treatment of pSS; the potential role and underlying mechanisms of melatonin in the administration of pSS are certainly worth further investigations. Consequently, the aim of this review is to give a deep insight to the therapeutic potency of melatonin for pSS.

Melatonin Is Neuroprotective in Escherichia coli Meningitis Depending on Intestinal Microbiota

Avian meningitis Escherichia coli (E. coli) can cause acute bacterial meningitis which threatens poultry health, causes great economic losses in the poultry industry, and has recently been speculated as a potential zoonotic pathogen. Melatonin can counteract bacterial meningitis-induced disruption of the blood-brain barrier (BBB), neuroinflammation, and reduce mortality. There are increasing data showing that melatonin's beneficial effects on bacterial meningitis are associated with intestinal microbiota. In this study, our data showed that melatonin alleviated neurological symptoms, enhanced survival rate, protected the integrity of the BBB, reduced the bacterial load in various tissues and blood, and inhibited inflammation and neutrophil infiltration of brain tissue in an APEC TW-XM-meningitis mice model. The results of 16S rRNA showed that melatonin pretreatment significantly maintained the composition of intestinal microbiota in APEC-meningitis mice. The abundance and diversity of intestinal microbiota were disturbed in APEC TW-XM-meningitis mice, with a decreased ratio of Firmicutes to Bacteroides and an increased the abundance of Proteobacteria. Melatonin pretreatment could significantly improve the composition and abundance of harmful bacteria and alleviate the decreased abundance of beneficial bacteria. Importantly, melatonin failed to affect the meningitis neurologic symptoms caused by APEC TW-XM infection in antibiotic-pretreated mice. In conclusion, the results suggest that melatonin can effectively prevent meningitis induced by APEC TW-XM infection in mice, depending on the intestinal microbiota. This finding is helpful to further explore the specific target mechanism of melatonin-mediated intestinal microbiota in the prevention of and protection against Escherichia coli meningitis.

Lower plasma concentrations of short-chain fatty acids (SCFAs) in patients with ADHD

Short-chain fatty acids (SCFAs), produced during bacterial fermentation, have been shown to be mediators in the microbiota-gut-brain axis. This axis has been proposed to influence psychiatric symptoms seen in attention deficit hyperactivity disorder (ADHD). However, there is no report of plasma SCFA concentrations in ADHD. The aim of this study was to explore the plasma concentrations of SCFAs in children and adults with ADHD and the possible factors that could influence those levels. We collected data on age group, sex, serum vitamin D levels, delivery mode, body mass index, diet, medication and blood samples from 233 ADHD patients and 36 family-related healthy controls. The concentrations of SCFAs and the intermediary metabolite succinic acid, were measured using liquid chromatography-mass spectrometry. Adults with ADHD had lower plasma concentrations of formic, acetic, propionic and succinic acid than their healthy family members. When adjusting for SCFA-influential factors among those with ADHD, children had lower concentrations of formic, propionic and isovaleric acid than adults, and those who had more antibiotic medications during the last 2 years had lower concentrations of formic, propionic and succinic acid. When adjusting for antibiotic medication, we found that among children, those currently on stimulant medication had lower acetic and propionic acid levels, and adults with ADHD had lower formic and propionic acid concentrations than adult healthy family members. In all, our findings show lower-than-normal plasma concentrations of SCFAs in ADHD explained in-part by antibiotic medication, age and stimulant medication. Whether or not this is of clinical significance is yet to be explored.

Melatonin-Microbiome Two-Sided Interaction in Dysbiosis-Associated Conditions

Melatonin is a pineal indolamine, allegedly known as a circadian rhythm regulator, and an antioxidative and immunomodulatory molecule. In both experimental and clinical trials, melatonin has been shown to have positive effects in various pathologies, as a modulator of important biochemical pathways including inflammation, oxidative stress, cell injury, apoptosis, and energy metabolism. The gut represents one of melatonin's most abundant extra pineal sources, with a 400-times-higher concentration than the pineal gland. The importance of the gut microbial community-namely, the gut microbiota, in multiple critical functions of the organism- has been extensively studied throughout time, and its imbalance has been associated with a variety of human pathologies. Recent studies highlight a possible gut microbiota-modulating role of melatonin, with possible implications for the treatment of these pathologies. Consequently, melatonin might prove to be a valuable and versatile therapeutic agent, as it is well known to elicit positive functions on the microbiota in many dysbiosis-associated conditions, such as inflammatory bowel disease, chronodisruption-induced dysbiosis, obesity, and neuropsychiatric disorders. This review intends to lay the basis for a deeper comprehension of melatonin, gut microbiota, and host-health subtle interactions.

Pretreatment with millet-derived selenylated soluble dietary fiber ameliorates dextran sulfate sodium-induced colitis in mice by regulating inflammation and maintaining gut microbiota balance

Inflammatory activation and intestinal flora imbalance play key roles in the development and progression of inflammatory bowel disease (IBD). Soluble dietary fiber (SDF) and selenium have been proven to be effective for preventing and relieving IBD. This study investigated and compared the therapeutic efficacy of millet-derived selenylated-soluble dietary fiber (Se-SDF) against dextran sulfate sodium (DSS)-induced colitis in mice alone or through the synergistic interaction between selenium and SDF. In female mice, Se-SDF markedly alleviated body weight loss, decreased colon length, reduced histological damage scores, and enhanced IL-10 expression to maintain the barrier function of intestinal mucosa compared to male mice. The 16S rRNA sequence analysis further indicated that pretreatment with Se-SDF restored the gut microbiota composition in female mice by increasing the relative abundance of Lactobacillus and the Firmicutes/Bacteroidetes ratio. In conclusion, these findings demonstrated that Se-SDF can protect against DSS-induced colitis in female mice by regulating inflammation and maintaining gut microbiota balance. This study, therefore, provides new insights into the development of Se-SDF as a supplement for the prevention and treatment of colitis.

Two-Sample Mendelian Randomization Analysis Investigates Causal Associations Between Gut Microbial Genera and Inflammatory Bowel Disease, and Specificity Causal Associations in Ulcerative Colitis or Crohn’s Disease

Background

Intestinal dysbiosis is associated with inflammatory bowel disease (IBD). Ulcerative colitis (UC) and Crohn’s disease (CD), two subtypes of IBD, are characterized by unique microbial signatures, respectively. However, it is unclear whether UC or CD has a specific causal relationship with gut microbiota.

Objective

To investigate the potential causal associations between gut microbial genera and IBD, UC, or CD, two-sample Mendelian randomization (MR) analyses were conducted.

Materials and Methods

We obtained genome-wide association study (GWAS) summary statistics of gut microbiota and IBD, UC, or CD from published GWASs. Two-sample MR analyses were performed to identify potential causal gut microbial genera for IBD, UC, and CD using the inverse-variance weighted (IVW) method. Sensitivity analyses were also conducted to validate the robustness of the primary results of the MR analyses. Finally, a reverse MR analysis was performed to evaluate the possibility of reverse causation.

Results

Combining the results from the primary and sensitivity analyses, six bacterial genera were associated with the risk of IBD, UC, or CD in the IVW method. Briefly, Eubacterium ventriosum group was associated with a lower risk of IBD (P=0.011) and UC (P=1.00×10^-4), whereas Coprococcus 2 was associated with a higher risk of IBD (P=0.022) and UC (P=0.007). In addition, we found a positive association between Oxalobacter with IBD (P=0.001) and CD (P=0.002), and Ruminococcaceae UCG014 with IBD (P=0.005) and CD (P=0.007). We also noticed a negative association between Enterorhabdus (P=0.044) and IBD, and between Lachnospiraceae UCG001 (P=0.023) and CD. We did not find causal effects of IBD, UC, or CD on these bacterial genera in the reverse MR analysis.

Conclusion

This study expanded gut microbial genera that were causally associated with the risk of IBD, and also revealed specificity-gut microbial genera for UC or CD.

β-carotene improves fecal dysbiosis and intestinal dysfunctions in a mouse model of vitamin A deficiency

Vitamin A deficiency (VAD) results in intestinal inflammation, increased redox stress and reactive oxygen species (ROS) levels, imbalanced inflammatory and immunomodulatory cytokines, compromised barrier function, and perturbations of the gut microbiome. To combat VAD dietary interventions with β-carotene, the most abundant precursor of vitamin A, are recommended. However, the impact of β-carotene on intestinal health during VAD has not been fully clarified, especially regarding the VAD-associated intestinal dysbiosis. Here we addressed this question by using Lrat^-/-Rbp^-/- (vitamin A deficient) mice deprived of dietary preformed vitamin A and supplemented with β-carotene as the sole source of the vitamin, alongside with WT (vitamin A sufficient) mice. We found that dietary β-carotene impacted intestinal vitamin A status, barrier integrity and inflammation in both WT and Lrat^-/-Rbp^-/- (vitamin A deficient) mice on the vitamin A-free diet. However, it did so to a greater extent under overt VAD. Dietary β-carotene also modified the taxonomic profile of the fecal microbiome, but only under VAD. Given the similarity of the VAD-associated intestinal phenotypes with those of several other disorders of the gut, collectively known as Inflammatory Bowel Disease (IBD) Syndrome, these findings are broadly relevant to the effort of developing diet-based intervention strategies to ameliorate intestinal pathological conditions.

The Combination of Intestinal Alkaline Phosphatase Treatment with Moderate Physical Activity Alleviates the Severity of Experimental Colitis in Obese Mice via Modulation of Gut Microbiota, Attenuation of Proinflammatory Cytokines, Oxidative Stress Biomarkers and DNA Oxidative Damage in Colonic Mucosa

Inflammatory bowel diseases (IBD) are commonly considered as Crohn's disease and ulcerative colitis, but the possibility that the alterations in gut microbiota and oxidative stress may affect the course of experimental colitis in obese physically exercising mice treated with the intestinal alkaline phosphatase (IAP) has been little elucidated. Mice fed a high-fat-diet (HFD) or normal diet (ND) for 14 weeks were randomly assigned to exercise on spinning wheels (SW) for 7 weeks and treated with IAP followed by intrarectal administration of TNBS. The disease activity index (DAI), grip muscle strength test, oxidative stress biomarkers (MDA, SOD, GSH), DNA damage (8-OHdG), the plasma levels of cytokines IL-2, IL-6, IL-10, IL-12p70, IL-17a, TNF-α, MCP-1 and leptin were assessed, and the stool composition of the intestinal microbiota was determined by next generation sequencing (NGS). The TNBS-induced colitis was worsened in obese sedentary mice as manifested by severe colonic damage, an increase in DAI, oxidative stress biomarkers, DNA damage and decreased muscle strength. The longer running distance and weight loss was observed in mice given IAP or subjected to IAP + SW compared to sedentary ones. Less heterogeneous microbial composition was noticed in sedentary obese colitis mice and this effect disappeared in IAP + SW mice. Absence of Alistipes, lower proportion of Turicibacter, Proteobacteria and Faecalibacterium, an increase in Firmicutes and Clostridium, a decrease in oxidative stress biomarkers, 8-OHdG content and proinflammatory cytokines were observed in IAP + SW mice. IAP supplementation in combination with moderate physical activity attenuates the severity of murine colitis complicated by obesity through a mechanism involving the downregulation of the intestinal cytokine/chemokine network and oxidative stress, the modulation of the gut microbiota and an improvement of muscle strength.

Therapeutic potential of melatonin in colorectal cancer: Focus on lipid metabolism and gut microbiota

Colorectal cancer (CRC) is one of the most common gastrointestinal malignancies. The occurrence and development of CRC are complicated processes. Obesity and dysbacteriosis have been increasingly regarded as the main risk factors for CRC. Understanding the etiology of CRC from multiple perspectives is conducive to screening for some potential drugs or new treatment strategies to limit the serious side effects of conventional treatment and prolong the survival of CRC patients. Melatonin, a natural indoleamine, is mainly produced by the pineal gland, but it is also abundant in other tissues, including the gastrointestinal tract, retina, testes, lymphocytes, and Harder's glands. Melatonin could participate in lipid metabolism by regulating adipogenesis and lipolysis. Additionally, many studies have focused on the potential beneficial effects of melatonin in CRC, such as promotion of apoptosis; inhibition of cell proliferation, migration, and invasion; antioxidant activity; and immune regulation. Meaningfully, gut microbiota is the main determinant of all aspects of health and disease (including obesity and tumorigenesis). The gut microbiota is of great significance for understanding the relationship between obesity and increased risk of CRC. Although the current understanding of how the melatonin-mediated gut microbiota coordinates a variety of physiological and pathological activities is fairly comprehensive, there are still many unknown topics to be explored in the face of a complex nutritional status and a changeable microbiota. This review summarizes the potential links among melatonin, lipid metabolism, gut microbiota, and CRC to promote the development of melatonin as a preventive and therapeutic agent for CRC.

The antioxidant effects of melatonin in blood platelets during exposure to electromagnetic radiation – an in vitro study

Objectives

The article presents the results of an in vitro study aimed at identifying changes in parameters of oxidative stress – concentration of malondialdehyde (MDA), enzymatic activity of superoxide dismutase (SOD-1) and protective antioxidant role of melatonin (MLT) during the exposure of blood platelets to electromagnetic radiation (EMR) emitted by monitors.

Methods

Platelets were exposed to an EMR for 30- and 60 min. generated by monitors (1 kHz frequency, 220 V/m intensity). In each sample the level of SOD-1 activity and concentration of MDA were determined.

Results

The MDA concentration increased significantly after 30-and 60-min. irradiation, as compared to control values (2.53 vs 1.36; 3.64 vs 1.36 nmol/109 blood platelets) and after the addition of MLT it decreased (2.53 vs 1.55; 3.64 vs 1.12 nmol/109 blood platelets). The activity of SOD-1 increased significantly compared to control values after 30 min. and 60 min. of exposure to EMR (1.97vs 0.75; 2.08 vs 0.75 U/g of protein), and significantly decreased after the addition of MLT only in samples exposed for 60 min. (2.08 vs 0.95 U/g of protein).

Discussion

The results demonstrated the possibly negative effect of EMR on oxygen metabolism of blood platelets and indicated a possible protective role of melatonin in this process.

Effects of the Sex Factor on Mouse Iodine Intake: Interactions between the Gut Microbiota Composition and Metabolic Syndromes

Iodine plays a key role in maintaining thyroid homeostasis, which is influenced by hormones through almost all nucleated cells and is essential for growth and metabolism. The most common kinds of thyroid dysfunction, hypothyroidism and hyperthyroidism, are markedly related to iodine intake. In addition, the prevalence and incidence of hypothyroidism and hyperthyroidism are much higher in women than in men. However, the association between thyroid homeostasis and the gut microbiota is not yet completely clear, especially when comparing women and men. In this study, differences in the gut microbiota compositions, metabolic syndromes, and molecular mechanisms of female and male mice were investigated after iodine supplementation. The gut microbiota in male mice was changed more than that of female mice. The abundances of Muribacium intestinale, Barnesiella, Alloprevotella, Enterococcus, Desulfovibrionaceae, and Clostridium were significantly increased in female mice. This finding indicates that the high risk of thyroid disease in women could be related to the gut microbiota composition.

Effect of dark environment on intestinal flora and expression of genes related to liver metabolism in zebrafish (Danio rerio)

To explore the effects of dark environment on intestinal flora and expression of genes related to liver metabolism in zebrafish, a total of 60 zebrafish were fed for 21 days (24 h dark treatments or 14/10 h light/dark cycle), and the influence of dark environment on gut microbes and liver gene expression was studied using sequencing analysis of intestinal flora and liver. The results showed that the body weight of fish was significantly increased in the dark group than that in the control group (P < 0.05). Compared with the control group, dark environment treatment changed the composition of dominant flora, increased the abundance of unconventional bacteria and reduced probiotics in the intestine of zebrafish. Of these, the ratio of Bacteroidetes to Firmicutes in the intestine was reduced. The genome expression of the liver showed significant changes, and liver metabolites were also affected. Meanwhile, dark environment decreased gene expression associated with changes in blood glucose, lipid metabolism and immunization. Dark environment also caused liver steatosis as observed by histological study. This study shows that dark environment treatment has an important impact on liver metabolism and intestinal microbes in zebrafish.

Ruminal Microbes Exhibit a Robust Circadian Rhythm and Are Sensitive to Melatonin

Gut hormones are not only able to regulate digestive, absorptive, and immune mechanisms of the intestine through biological rhythms, but impact the host through their interactions with intestinal microorganisms. Whether hormones in ruminal fluid have an association with the ruminal ecology is unknown. Objectives of the study were to examine relationships between the diurnal change in ruminal hormones and microbiota in lactating cows, and their associations in vivo and in vitro. For the in vivo study, six cows of similar weight (566.8 ± 19.6 kg), parity (3.0 ± 0.0), and milk performance (8,398.7 ± 1,392.9 kg/y) were used. They were adapted to natural light for 2 weeks before sampling and fed twice daily at 07:00 a.m. and 14:00 p.m. Serum, saliva, and ruminal fluid samples were collected at 02:00, 10:00, and 18:00 on the first day and 06:00, 14:00, and 22:00 on the second day of the experimental period. The concentrations of melatonin (MLT), growth hormone (GH), and prolactin (PRL) were measured via radioimmunoassay, whereas amplicon sequencing data were used to analyze relative abundance of microbiota in ruminal fluid. JTK_CYCLE analysis was performed to analyze circadian rhythms of hormone concentrations as well as the relative abundance of microbiota. For the in vitro study, exogenous MLT (9 ng) was added into ruminal fluid incubations to investigate the impacts of MLT on ruminal microbiota. The results not only showed that rumen fluid contains MLT, but the diurnal variation of MLT and the relative abundance of 9% of total rumen bacterial operational taxonomic units (OTUs) follow a circadian rhythm. Although GH and PRL were also detected in ruminal fluid, there was no obvious circadian rhythm in their concentrations. Ruminal MLT was closely associated with Muribaculaceae, Succinivibrionaceae, Veillonellaceae, and Prevotellaceae families in vivo. In vitro, these families were significantly influenced by melatonin treatment, as melatonin treatment increased the relative abundance of families Prevotellaceae, Muribaculaceae while it reduced the relative abundance of Succinivibrionaceae, Veillonellaceae. Collectively, ruminal microbes appear to maintain a circadian rhythm that is associated with the profiles of melatonin. As such, data suggest that secretion of melatonin into the rumen could play a role in host-microbe interactions in ruminants.

The Effect of Oxidative Stress on the Chicken Ovary: Involvement of Microbiota and Melatonin Interventions

The poultry ovary is used as a classic model to study ovarian biology and ovarian cancer. Stress factors induced oxidative stress to cause follicle atresia, which may be a fundamental reason for the reduction in fertility in older laying hens or in aging women. In the present study, we set out to characterize the relationships between oxidative stress and ovarian function. Layers (62 weeks of age; BW = 1.42 ± 0.12 kg) were injected with tert-butyl hydroperoxide (tBHP) at 0 (CON) and 800 μmol/kg BW (oxidative stress group, OS) for 24 days and the role of melatonin (Mel) on tBHP-induced ovary oxidative stress was assessed through ovary culture in vitro. The OS (800 μmol/kg BW tert-butyl hydroperoxide) treatment decreased the reproduction performance and ovarian follicle numbers. OS decreased the expression of SIRT1 and increased the P53 and FoxO1 expression of the ovary. A decreased Firmicutes to Bacteroidetes ratio, enriched Marinifilaceae (family), Odoribacter (genus) and Bacteroides_plebeius (species) were observed in the cecum of the OS group. Using Mel in vitro enhanced the follicle numbers and decreased the ovary cell apoptosis induced by tBHP. In addition, it increased the expression of SIRT1 and decreased the P53 and FoxO1 expression. These findings indicated that oxidative stress could decrease the laying performance, ovarian function and influence gut microbiota and body metabolites in the layer model, while the melatonin exerts an amelioration the ovary oxidative stress through SIRT1-P53/FoxO1 pathway.

Melatonin as a powerful antioxidant

Melatonin is a hormone that has many body functions and, for several decades, its antioxidant potential has been increasingly talked about. There is a relationship between failure in melatonin production in the pineal gland, an insufficient supply of this hormone to the body, and the occurrence of free radical etiology diseases such as neurodegenerative diseases, cardiovascular diseases, diabetes, cancer and others. Despite the development of molecular biology, numerous in vitro and in vivo studies, the exact mechanism of melatonin antioxidant activity is still unknown. Nowadays, the use of melatonin supplementation is more and more common, not only to prevent insomnia, but also to slow down the aging process and provide protection against diseases. The aim of this study is to get acquainted with current reports on melatonin, antioxidative mechanisms and their importance in diseases of free radical etiology.

Melatonin Attenuates Dextran Sodium Sulfate Induced Colitis in Obese Mice

Epidemiological studies have indicated that obesity is an independent risk factor for colitis and that a high-fat diet (HFD) increases the deterioration of colitis-related indicators in mice. Melatonin has multiple anti-inflammatory effects, including inhibiting tumor growth and regulating immune defense. However, the mechanism of its activity in ameliorating obesity-promoted colitis is still unclear. This study explored the possibility that melatonin has beneficial functions in HFD-induced dextran sodium sulfate (DSS)-induced colitis in mice. Here, we revealed that HFD-promoted obesity accelerated DSS-induced colitis, while melatonin intervention improved colitis. Melatonin significantly alleviated inflammation by increasing anti-inflammatory cytokine release and reducing the levels of proinflammatory cytokines in HFD- and DSS-treated mice. Furthermore, melatonin expressed antioxidant activities and reversed intestinal barrier integrity, resulting in improved colitis in DSS-treated obese mice. We also found that melatonin could reduce the ability of inflammatory cells to utilize fatty acids and decrease the growth-promoting effect of lipids by inhibiting autophagy. Taken together, our study indicates that the inhibitory effect of melatonin on autophagy weakens the lipid-mediated prosurvival advantage, which suggests that melatonin-targeted autophagy may provide an opportunity to prevent colitis in obese individuals.

An out of box thinking: the changes of iron-porphyrin during meat processing and gastrointestinal tract and some methods for reducing its potential health hazard

Iron-porphyrin is a very important substance in organisms, especially in animals. It is not only the source of iron in human body, but is also the catalytic center of many reactions. Previous studies suggested that adequate intake of iron was important for the health of human, especially for children and pregnant women. However, associated diseases caused by iron over-intake and excessive meat consumption suggested its potential harmfulness for human health. During meat processing, Iron-porphyrin will cause the oxidation of proteins and fatty acids. In the gastrointestinal tract, iron-porphyrin can induce the production of malondialdehyde, fats oxidation, and indirectly cause oxidation of amino acids and nitrates etc. Iron-porphyrin enters the intestinal tract and disturbs the balance of intestinal flora. Finally, some common measures for inhibiting its activity are introduced, including the use of chelating agent, antioxidants, competitive inhibitor, etc., as well as give the hypothesis that sodium chloride increases the catalytic activity of iron-porphyrin. The purpose of this review is to present an overview of current knowledge about the changes of iron-porphyrin in the whole technico- and gastrointesto- processing axis and to provide ideas for further research in meat nutrition.

Role of melatonin in murine "restraint stress"-induced dysfunction of colonic microbiota

Intestinal diseases caused by physiological stress have become a severe public health threat worldwide. Disturbances in the gut microbiota-host relationship have been associated with irritable bowel disease (IBD), while melatonin (MT) has anti-inflammatory and antioxidant effects. The objective of this study was to investigate the mechanisms by which MT-mediated protection mitigated stress-induced intestinal microbiota dysbiosis and inflammation. We successfully established a murine restraint stress model with and without MT supplementation. Mice subjected to restraint stress had significantly elevated corticosterone (CORT) levels, decreased MT levels in their plasma, elevated colonic ROS levels and increased bacterial abundance, including Bacteroides and Tyzzerella, in their colon tract, which led to elevated expression of Toll-like receptor (TLR) 2/4, p-P65 and p-IKB. In contrast, supplementation with 20 mg/kg MT reversed the elevation of the plasma CORT levels, downregulated the colon ROS levels and inhibited the changes in the intestinal microbiota induced by restraint stress. These effects, in turn, inhibited the activities of TLR2 and TLR4, p-P65 and p-IκB, and decreased the inflammatory reaction induced by restraint stress. Our results suggested that MT may mitigate "restraint stress"-induced colonic microbiota dysbiosis and intestinal inflammation by inhibiting the activation of the NF-κB pathway.

Role of the gut microbiome in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia, affecting millions of individuals each year and this number is expected to significantly increase. The complicated microorganisms residing in human gut are closely associated with our health. Emerging evidence has suggested possible involvement of human gut microbiome in AD. Symbiotic gut microbiomes are known to maintain brain health by modulating host's barriers integrity, metabolic system, immune system, nervous system and endocrine system. However, in the event of gut dysbiosis and barriers disruption, gut pathobionts disrupt homeostasis of the metabolic system, immune system, nervous system, and endocrine system, resulting in deterioration of neurological functions and subsequently promoting development of AD. Multiple therapeutic approaches, such as fecal microbiome transplant, antibiotics, prebiotics, probiotics, symbiotic, and diet are discussed as potential treatment options for AD by manipulating the gut microbiome to reverse pathological alteration in the systems above.

Antioxidant Therapy in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are a group of chronic, incurable diseases of the digestive tract, the etiology of which remains unclear to this day. IBD result in significant repercussions on the quality of patients’ life. There is a continuous increase in the incidence and prevalence of IBD worldwide, and it is becoming a significant public health burden. Pharmaceuticals commonly used in IBD management, for example, mesalamine, sulfasalazine, corticosteroids, and others, expose patients to diverse, potentially detrimental side effects and frequently do not provide sufficient disease control. The chronic inflammation underlies the etiology of IBD and closely associates with oxidative/nitrosative stress and a vast generation of reactive oxygen/nitrogen species. Relative to this, several substances with antioxidant and anti-inflammatory properties are now intensively researched as possible adjunctive or independent treatment options in IBD. Representatives of several different groups, including natural and chemical compounds will be characterized in this dissertation.

Melatonin and Cancer: A Polyhedral Network Where the Source Matters

Melatonin is one of the most phylogenetically conserved signals in biology. Although its original function was probably related to its antioxidant capacity, this indoleamine has been “adopted” by multicellular organisms as the “darkness signal” when secreted in a circadian manner and is acutely suppressed by light at night by the pineal gland. However, melatonin is also produced by other tissues, which constitute its extrapineal sources. Apart from its undisputed chronobiotic function, melatonin exerts antioxidant, immunomodulatory, pro-apoptotic, antiproliferative, and anti-angiogenic effects, with all these properties making it a powerful antitumor agent. Indeed, this activity has been demonstrated to be mediated by interfering with various cancer hallmarks, and different epidemiological studies have also linked light at night (melatonin suppression) with a higher incidence of different types of cancer. In 2007, the World Health Organization classified night shift work as a probable carcinogen due to circadian disruption, where melatonin plays a central role. Our aim is to review, from a global perspective, the role of melatonin both from pineal and extrapineal origin, as well as their possible interplay, as an intrinsic factor in the incidence, development, and progression of cancer. Particular emphasis will be placed not only on those mechanisms related to melatonin’s antioxidant nature but also on the recently described novel roles of melatonin in microbiota and epigenetic regulation.

Efficacy and Safety of Melatonin as an Adjunctive Therapy on Clinical, Biochemical, and Quality of Life in Patients with Ulcerative Colitis

Ulcerative colitis (UC) is characterized by recurring episodes of inflammation limited to the mucosal layer of the colon. The exact etiology of UC is unknown, but the role of autoimmunity and activated inflammatory cascade is quite clear. Melatonin possesses anti-inflammatory and immune-modulative properties in animal and clinical trials. The aim of the present study was to evaluate the efficacy and safety of oral melatonin as an adjudicative therapy in clinical, biochemical, and quality of life in UC patients. Thirty patients diagnosed with mild to moderate UC, were randomly allocated to either receive melatonin (3 mg/d) or the placebo group for three months. Simple clinical colitis activity index (SCCAI), fecal calprotectin (FC), C-reactive protein (CRP), Erythrocyte Sedimentation Rate (ESR), and Sf-36 questionnaire have been used for assessment at the baseline and the end of the trial. Melatonin significantly improve SCCAI score, FC, role-emotional, energy and general health relative to placebo (p = 0.03, 0.05, 0.002, 0.032, 0.004 respectively). Regarding CRP, ESR, and the other components of SF-36 there is not any significant difference between melatonin and placebo group. Melatonin supplementation over a three-month period is effective and safe in improving clinical index, FC, and some quality of life in patients with mild to moderate UC.

Effects of a synbiotic on symptoms, and daily functioning in attention deficit hyperactivity disorder - A double-blind randomized controlled trial

Some prebiotics and probiotics have been proposed to improve psychiatric symptoms in children with autism. However, few studies were placebo-controlled, and there is no study on persons with an attention deficit hyperactivity disorder (ADHD) diagnosis. Our aim was to study effects of Synbiotic 2000 on psychiatric symptoms and functioning in children and adults with ADHD without an autism diagnosis. Children and adults (n = 182) with an ADHD diagnosis completed the nine weeks randomized double-blind parallel placebo-controlled trial examining effects of Synbiotic 2000 on the primary endpoints ADHD symptoms, autism symptoms and daily functioning, and the secondary endpoint emotion regulation, measured using the questionnaires SNAP-IV, ASRS, WFIRS, SCQ, AQ and DERS-16. Levels at baseline of plasma C-reactive protein and soluble vascular cell adhesion molecule-1 (sVCAM-1), central to leukocyte-endothelial cell adhesion facilitating inflammatory responses in tissues, were measured using Meso Scale Discovery. Synbiotic 2000 and placebo improved ADHD symptoms equally well, and neither active treatment nor placebo had any statistically significant effect on functioning or sub-diagnostic autism symptoms. However, Synbiotic 2000, specifically, reduced sub-diagnostic autism symptoms in the domain restricted, repetitive and stereotyped behaviors in children, and improved emotion regulation in the domain of goal-directed behavior in adults. In children with elevated sVCAM-1 levels at baseline as well as in children without ADHD medication, Synbiotic 2000 reduced both the total score of autism symptoms, and the restricted, repetitive and stereotyped behaviors. In adults with elevated sVCAM-1 at baseline, Synbiotic 2000 significantly improved emotion regulation, both the total score and four of the five subdomains. To conclude, while no definite Synbiotic 2000-specific effect was detected, the analysis of those with elevated plasma sVCAM-1 levels proposed a reduction of autism symptoms in children and an improvement of emotion regulation in adults with ADHD. Trial registration number: ISRCTN57795429.

Regulation of tartary buckwheat-resistant starch on intestinal microflora in mice fed with high-fat diet

Resistant starch (RS) is closely related to the composition of intestinal flora. Based on many studies on the physiological functions of probiotics and short-chain fatty acids (SCFAs), it is possible that RS can improve the intestinal health of the host. Therefore, we speculated that tartary buckwheat-resistant starch (TBRS) can also regulate the intestinal flora disorder caused by high-fat diet. We randomly divided 36 SPF C57BL/6J mice into low-fat diet, high-fat diet (HF-CS), high-fat diet supplemented with TBRS (HF-BRS), and high-fat diet supplemented with corn-resistant starch (HF-CRS). We analyzed the diversity and richness of gut microbiota based on PCR and Illumina high-throughput sequencing technology. In community abundance, the HF-BRS group was significantly higher than the other three groups (p < .05). TBRS improved the gut microbiota dysbiosis, including decreasing the Firmicutes-to-Bacteroidetes ratios (F/B) and contributing to the growth of Bacteroides and Blautia as well significantly inhibiting the growth of Bifidobacterium, Faecalibaculum, and Erysipelatoclostridium. We also analyzed the production of SCFAs by GC-MS, and the concentration of total SCFAs increased in the HF-CS group. However, TBRS significantly increased the production of SCFAs, especially the propionate concentration compared with the HF-CRS group (p < .05). These results elucidated that TBRS has the potential to improve intestinal health by altering the structure of gut microbiota and increasing the production of SCFAs. Our findings have important implications for TBRS as functional food ingredient to manipulate intestinal microflora.

The Links Between the Gut Microbiome, Aging, Modern Lifestyle and Alzheimer's Disease

Gut microbiome is a community of microorganisms in the gastrointestinal tract. These bacteria have a tremendous impact on the human physiology in healthy individuals and during an illness. Intestinal microbiome can influence one's health either directly by secreting biologically active substances such as vitamins, essential amino acids, lipids et cetera or indirectly by modulating metabolic processes and the immune system. In recent years considerable information has been accumulated on the relationship between gut microbiome and brain functions. Moreover, significant quantitative and qualitative changes of gut microbiome have been reported in patients with Alzheimer's disease. On the other hand, gut microbiome is highly sensitive to negative external lifestyle aspects, such as diet, sleep deprivation, circadian rhythm disturbance, chronic noise, and sedentary behavior, which are also considered as important risk factors for the development of sporadic Alzheimer's disease. In this regard, this review is focused on analyzing the links between gut microbiome, modern lifestyle, aging, and Alzheimer's disease.

SOD1 deficiency alters gastrointestinal microbiota and metabolites in mice

Redox imbalance induces oxidative damage and causes age-related pathologies. Mice lacking the antioxidant enzyme SOD1 (Sod1^-/-) exhibit various aging-like phenotypes throughout the body and are used as aging model mice. Recent reports suggested that age-related changes in the intestinal environment are involved in various diseases. We investigated cecal microbiota profiles and gastrointestinal metabolites in wild-type (Sod1^+/+) and Sod1^-/- mice. Firmicutes and Bacteroidetes were dominant in Sod1^+/+ mice, and most of the detected bacterial species belong to these two phyla. Meanwhile, the Sod1^-/- mice had an altered Firmicutes and Bacteroidetes ratio compared to Sod1^+/+ mice. Among the identified genera, Paraprevotella, Prevotella, Ruminococcus, and Bacteroides were significantly increased, but Lactobacillus was significantly decreased in Sod1^-/- mice compared to Sod1^+/+ mice. The correlation analyses between cecal microbiota and liver metabolites showed that Bacteroides and Prevotella spp. were grouped into the same cluster, and Paraprevotella and Ruminococcus spp. were also grouped as another cluster. These four genera showed a positive and a negative correlation with increased and decreased liver metabolites in Sod1^-/- mice, respectively. In contrast, Lactobacillus spp. showed a negative correlation with increased liver metabolites and a positive correlation with decreased liver metabolites in Sod1^-/- mice. These results suggest that the redox imbalance induced by Sod1 loss alters gastrointestinal microflora and metabolites.

Melatonin: An important anticancer agent in colorectal cancer

Colorectal cancer is one of the most common cancers among the elderly, which is also seen in the forms of hereditary syndromes occurring in younger individuals. Numerous studies have been conducted to understand the molecular and cellular pathobiology underlying colorectal cancer. These studies have found that cellular signaling pathways are at the core of colorectal cancer pathology. Because of this, new agents have been proposed as possible candidates to accompany routine therapy regimens. One of these agents is melatonin, a neuro-hormone known best for its essential role in upholding the circadian rhythm and orchestrating the many physiologic changes it accompanies. Melatonin is shown to be able to modulate many signaling pathways involved in many essential cell functions, which if deregulated cause an accelerated pace towards cancer. More so, melatonin is involved in the regulation of immune function, tumor microenvironment, and acts as an antioxidant agent. Many studies have focused on the beneficial effects of melatonin in colorectal cancers, such as induction of apoptosis, increased sensitivity to chemotherapy agents and radiotherapy, limiting cellular proliferation, migration, and invasion. The present review aims to illustrate the known significance of melatonin in colorectal cancer and to address possible clinical use.

Dietary Quercetin Increases Colonic Microbial Diversity and Attenuates Colitis Severity in Citrobacter rodentium-Infected Mice

Disturbed balance between microbiota, epithelial cells, and resident immune cells within the intestine contributes to inflammatory bowel disease (IBD) pathogenesis. The Citrobacter rodentium-induced colitis mouse model has been well documented. This model allows the analysis of host responses to enteric bacteria and facilitates improved understanding of the potential mechanisms of IBD pathogenesis. The current study evaluated the effects of dietary 30 mg/kg quercetin supplementation on C. rodentium-induced experimental colitis in C57BL/6 mice. Following dietary quercetin supplementation, the mice were infected with 5 × 10⁸ CFU C. rodentium, and the pathological effects of C. rodentium were measured. The results showed that quercetin alleviated the effects of C. rodentium-induced colitis, suppressed the production of pro-inflammatory cytokines, such as interleukin (IL)-17, tumor necrosis factor alpha, and IL-6 (p < 0.05), and promoted the production of IL-10 in the colon tissues (p < 0.05). Quercetin supplementation also enhanced the populations of Bacteroides, Bifidobacterium, Lactobacillus, and Clostridia and significantly reduced those of Fusobacterium and Enterococcus (p < 0.05). These findings indicate that dietary quercetin exerts therapeutic effects on C. rodentium-induced colitis, probably due to quercetin’s ability to suppress pro-inflammatory cytokines and/or modify gut microbiota. Thus, these results suggest that quercetin supplementation is effective in controlling C. rodentium-induced inflammation.

Egg Protein Transferrin-Derived Peptides IRW and IQW Regulate Citrobacter rodentium-Induced, Inflammation-Related Microbial and Metabolomic Profiles

Bioactive peptides that target the gastrointestinal tract can strongly affect the health of animals and humans. This study aimed to evaluate the abilities of two peptides derived from egg albumin transferrin, IRW and IQW, to treat enteritis in a mouse model of Citrobacter rodentium-induced colitis by evaluating serum metabolomics and gut microbes. Forty-eight mice were randomly assigned to six groups: basal diet (CTRL), intragastric administration Citrobacter rodentium (CR), basal diet with 0.03%IRW (IRW), CR with 0.03% IRW (IRW+CR), basal diet with 0.03%IQW (IQW) and CR with 0.03% IQW (IQW+CR). CR administration began on day 10 and continued for 7 days. After 14 days of IRW and IQW treatment, serum was collected and subjected to a metabolomics analysis. The length and weight of each colon were measured, and the colon contents were collected for 16srRNA sequencing. The colons were significantly longer in the CR group, compared to the CTRL group. A serum metabolomics analysis revealed no significant difference in microbial diversity between the six groups. Compared with the CTRL group, the proportions of Firmicutes and Actinobacteria species decreased significantly and the proportions of Bacteroidetes and Proteobacteria species increased in the CR group. There were no significant differences between the CTRL and other groups. The serum metabolomics analysis revealed that Infected by CR increased the levels of oxalic acid, homogentisic acid and prostaglandin but decreased the levels of L-glutamine, L-acetyl carnitine, 1-methylhistidine and gentisic acid. Therefore, treatment with IRW and IQW was shown to regulate the intestinal microorganisms associated with colonic inflammation and serum metabolite levels, thus improving intestinal health.

Melatonin Treatment Alleviates Spinal Cord Injury-Induced Gut Dysbiosis in Mice

Spinal cord injury (SCI) disturbs the autonomic nervous system and induces dysfunction in multiple organs/tissues, such as the gastrointestinal (GI) system. The neuroprotective effects of melatonin in SCI models have been reported; however, it is unclear whether the beneficial effects of melatonin are associated with alleviation of gut dysbiosis. In this study, we showed that daily intraperitoneal injection with melatonin following spinal cord contusion at thoracic level 10 in mice improved intestinal barrier integrity and GI motility, reduced expression levels of certain proinflammatory cytokines, improved animal weight gain and metabolic profiling, and promoted locomotor recovery. Analysis of gut microbiome revealed that melatonin treatment decreased the Shannon index and reshaped the composition of intestinal microbiota. Melatonin-treated SCI animals showed decreased relative abundance of Clostridiales and increased relative abundance of Lactobacillales and Lactobacillus, which correlated with alteration of cytokine (monocyte chemotactic protein 1) expression and GI barrier permeability, as well as with locomotor recovery. Experimental induction of gut dysbiosis in mice before SCI (i.e., by oral delivery of broad-spectrum antibiotics) exacerbates neurological impairment after SCI, and melatonin treatment improves locomotor performance and intestinal integrity in antibiotic-treated SCI mice. The results suggest that melatonin treatment restores SCI-induced alteration in gut microbiota composition, which may underlie the ameliorated GI function and behavioral manifestations.

Benzoic Acid Used as Food and Feed Additives Can Regulate Gut Functions

As a kind of antibacterial and antifungal preservative, benzoic acid is widely used in foods and feeds. Recently, many studies showed that it could improve the growth and health, which should, at least partially, be derived from the promotion of gut functions, including digestion, absorption, and barrier. Based on the similarity of gut physiology between human and pigs, many relative studies in which piglets and porcine intestinal epithelial cells were used as the models have been done. And the results showed that using appropriate benzoic acid levels might improve gut functions via regulating enzyme activity, redox status, immunity, and microbiota, but excess administration would lead to the damage of gut health through redox status. However, the further mechanisms that some intestinal physiological functions might be regulated are not well understood. The present review will, in detail, summarize the effect of benzoic acid on gut functions.

The Role of Microbiome in Insomnia, Circadian Disturbance and Depression

Good sleep and mood are important for health and for keeping active. Numerous studies have suggested that the incidence of insomnia and depressive disorder are linked to biological rhythms, immune function, and nutrient metabolism, but the exact mechanism is not yet clear. There is considerable evidence showing that the gut microbiome not only affects the digestive, metabolic, and immune functions of the host but also regulates host sleep and mental states through the microbiome-gut-brain axis. Preliminary evidence indicates that microorganisms and circadian genes can interact with each other. The characteristics of the gastrointestinal microbiome and metabolism are related to the host's sleep and circadian rhythm. Moreover, emotion and physiological stress can also affect the composition of the gut microorganisms. The gut microbiome and inflammation may be linked to sleep loss, circadian misalignment, affective disorders, and metabolic disease. In this review article, we discuss various functions of the gut microbiome and how its activities interact with the circadian rhythms and emotions of the host. Exploring the effects of the gut microbiome on insomnia and depression will help further our understanding of the pathogenesis of mental disorders. It is therefore important to regulate and maintain a normal gastrointestinal micro-ecological environment in patients when treating mental disorders.

Effect of Quercetin Monoglycosides on Oxidative Stress and Gut Microbiota Diversity in Mice with Dextran Sodium Sulphate-Induced Colitis

The pathogenesis of inflammatory bowel disease (IBD) is linked to an intricate association of environmental, microbial, and host-related factors. This study examined the potential effects of dietary addition of two preparations from onion, one comprising quercetin aglycone alone (Q: 0.15% polyphenols, quercetin aglycone:quercetin monoglycosides, 98:2) and another comprising quercetin aglycone with monoglycosides (Q+MQ: 0.15% total polyphenols, quercetin aglycone:quercetin monoglycosides, 69:31), on dextran sodium sulphate- (DSS-) induced colitis in mice. The results revealed a significant decrease in the body weight gain of the mice with DSS-induced colitis, which was counteracted by the dietary Q or Q+MQ supplementation. Meanwhile, the oxidative stress indicated by myeloperoxidase (MPO), reduced glutathione (GSH), malondialdehyde (MDA), and serum nitrate (NO) concentrations was higher in mice with DSS-induced colitis than in the control group mice, but dietary Q or Q+MQ supplementation counteracted this trend. The colitis mice demonstrated reduced Chao1, angiotensin-converting enzyme (ACE), and Shannon indices and an increased Simpson index, but the colitis mice receiving dietary Q or Q+MQ exhibited higher Chao1, ACE, and Shannon indices and a reduced Simpson index. In conclusion, this research showed that even at a low dose, dietary Q or Q+MQ supplementation counteracts DSS-induced colitis in mice, indicating that Q or Q+MQ may be used as an adjuvant therapy for IBD patients.

Regulation of Immune Function by Polyphenols

Immune dysfunction is caused by various factors, including changes in relevant immune regulators and environmental stress. Immune system imbalance leads to a variety of diseases in humans. Nutrition may play an essential role in immunity by interfering with proinflammatory cytokine synthesis, immune cell regulation, and gene expression. Polyphenols, one of many categories of natural substances, exhibit a range of biological activities. Polyphenols promote immunity to foreign pathogens via various pathways. Different immune cells express multiple types of polyphenol receptors that recognise and allow cellular uptake of polyphenols, which subsequently activate signalling pathways to initiate immune responses. Furthermore, the polyphenols curcumin and epigallocatechin gallate can induce epigenetic changes in cells. In summary, polyphenols can be used to regulate intestinal mucosal immune responses, allergic diseases, and antitumour immunity.