Inflammation and Gut-Brain Axis During Type 2 Diabetes: Focus on the Crosstalk Between Intestinal Immune Cells and Enteric Nervous System

Intestinal Motility Dysfunction in Goto-Kakizaki Rats: Role of the Myenteric Plexus

Diabetes mellitus is associated with changes in intestinal morphology and the enteric nervous system. We previously reported constipation in Goto-Kakizaki (GK) rats, a non-obese model for type 2 diabetes mellitus.

AIM

The morpho-quantitative analysis of myenteric plexus neurons in the small and large intestines of 120-day-old male GK rats was investigated.

METHODS

The diabetes was confirmed by high fasting blood glucose levels. The myenteric plexus was evaluated through wholemount immunofluorescence. The morpho-quantitative analyses included evaluating neuronal density (neurons per ganglion) of the total neuronal population, the cholinergic and nitrergic subpopulations, and enteric glial cells per ganglion. The cell body area of 100 neurons per segment per animal was measured.

RESULTS

The total neurons and nitrergic subpopulation were unaltered in the GK rats' small and large intestines. The cholinergic subpopulation exhibited decreased density in the three segments of the small intestine and an increased number in the proximal colon of the GK rats. The number of enteric glial cells increased in the ileum of the GK rats, which could indicate enteric gliosis caused by the intestinal inflammatory state. The area of the cell body was increased in the total neuronal population of the jejunum and ileum of the GK rats. Frequency histograms of the cell body area distribution revealed the contribution of cholinergic neurons to larger areas in the jejunum and nitrergic neurons in the ileum.

CONCLUSION

The constipation previously reported in GK rats might be explained by the decrease in the density of cholinergic neurons in the small intestine of this animal model.

Is the enteric nervous system a lost piece of the gut-kidney axis puzzle linked to chronic kidney disease?

The enteric nervous system (ENS) regulates numerous functional and immunological attributes of the gastrointestinal tract. Alterations in ENS cell function have been linked to intestinal outcomes in various metabolic, intestinal, and neurological disorders. Chronic kidney disease (CKD) is associated with a challenging intestinal environment due to gut dysbiosis, which further affects patient quality of life. Although the gut-related repercussions of CKD have been thoroughly investigated, the involvement of the ENS in this puzzle remains unclear. ENS cell dysfunction, such as glial reactivity and alterations in cholinergic signaling in the small intestine and colon, in CKD are associated with a wide range of intestinal pathways and responses in affected patients. This review discusses how the ENS is affected in CKD and how it is involved in gut-related outcomes, including intestinal permeability, inflammation, oxidative stress, and dysmotility.

Hop (Humulus lupulus L.) extract reverts glycaemic imbalance and cognitive impairment in an animal model of obesity

The rates of overweight and obesity around the world have increased in past years. The body's adipose tissue stimulates the antioxidant and oxidation imbalance capacity at the cellular level. This scenario favors an inflammatory low-grade systemic condition starting with insulin resistance, which in turn may involve diabetes mellitus type 2 and cognitive decline afterward. Neurological diseases have been correlated to senile age diseases over time. This scenario calls for a change in the incidence of obesity in the younger generation. An unhealthy dietary consumption together with sedentary habits might lead to poor gut absorption of nutrients. Several plants and foods have bioactive compounds that can reduce or inhibit radical scavengers, reactive oxygen species, and metal ion complexes that threaten the cerebral defense system. The bitter acids from hops (Humulus lupulus L.) have been demonstrated to have promising effects on lipid and carbohydrate metabolism improvement, reducing inflammatory responses through alpha acids, beta acids, and analogs action. Therefore, the current study aimed to investigate the bioactivity of hop bitter acids in obese and lean mice. For that, a dry hop extract (DHE) was obtained by applying carbon dioxide as the fluid of supercritical extraction. Afterward, seventy-eight male mice of the C57BL/6J strain were weighed and randomly distributed into six groups of 13 animals each according to the diet offered: (NO) normolipidic diet, (NO1) normolipidic diet containing 0.35% alpha acids, (NO2) normolipidic diet containing 3.5% alpha acids, (HP) hyperlipidic diet, (HP1) hyperlipidic diet containing 0.35% alpha acids, and (HP2) hyperlipidic diet containing 3.5% alpha acids. After applying the glycemic tolerance and insulin tolerance tests, a better stabilization of glycemia levels and weight gain among those animals fed with DHE (NO2 and HP2) were observed in comparison to the obese control group (HP) (p < 0.05). There was also an amelioration of antioxidant capacity observed by checking the enzymatic profile by SOD and an apparent mitigation of brain degeneration by checking GSK3β and p-IRS1 proteins expression (p < 0.05). The y-maze cognitive test applied to highlight possible obesity-harmful animal brains did not indicate a statistical difference between the groups. Although the weekly dietary intake between the obese HP2 group (33.32 ± 4.11, p < 0.05) and control HP (42.3 ± 5.88, p < 0.05) was different. The bioactive compounds present in DHE have demonstrated relevant effects on glycemic control, insulin signaling, and the consequent modulatory action of the obesity-related markers with the brain's inflammatory progression.

Gut microbiota and type 2 diabetes mellitus: a focus on the gut-brain axis

Type 2 diabetes mellitus (T2DM) has become one of the most serious public healthcare challenges, contributing to increased mortality and disability. In the past decades, significant progress has been made in understanding the pathogenesis of T2DM. Mounting evidence suggested that gut microbiota (GM) plays a significant role in the development of T2DM. Communication between the GM and the brain is a complex bidirectional connection, known as the "gut-brain axis," via the nervous, neuroendocrine, and immune systems. Gut-brain axis has an essential impact on various physiological processes, including glucose metabolism, food intake, gut motility, etc. In this review, we provide an outline of the gut-brain axis. We also highlight how the dysbiosis of the gut-brain axis affects glucose homeostasis and even results in T2DM.

Multiorgan locked-state model of chronic diseases and systems pharmacology opportunities

With increasing human life expectancy, the global medical burden of chronic diseases is growing. Hence, chronic diseases are a pressing health concern and will continue to be in decades to come. Chronic diseases often involve multiple malfunctioning organs in the body. An imminent question is how interorgan crosstalk contributes to the etiology of chronic diseases. We conceived the locked-state model (LoSM), which illustrates how interorgan communication can give rise to body-wide memory-like properties that 'lock' healthy or pathological conditions. Next, we propose cutting-edge systems biology and artificial intelligence strategies to decipher chronic multiorgan locked states. Finally, we discuss the clinical implications of the LoSM and assess the power of systems-based therapies to dismantle pathological multiorgan locked states while improving treatments for chronic diseases.

The roles of dietary lipids and lipidomics in gut-brain axis in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM), one of the main types of Noncommunicable diseases (NCDs), is a systemic inflammatory disease characterized by dysfunctional pancreatic β-cells and/or peripheral insulin resistance, resulting in impaired glucose and lipid metabolism. Genetic, metabolic, multiple lifestyle, and sociodemographic factors are known as related to high T2DM risk. Dietary lipids and lipid metabolism are significant metabolic modulators in T2DM and T2DM-related complications. Besides, accumulated evidence suggests that altered gut microbiota which plays an important role in the metabolic health of the host contributes significantly to T2DM involving impaired or improved glucose and lipid metabolism. At this point, dietary lipids may affect host physiology and health via interaction with the gut microbiota. Besides, increasing evidence in the literature suggests that lipidomics as novel parameters detected with holistic analytical techniques have important roles in the pathogenesis and progression of T2DM, through various mechanisms of action including gut-brain axis modulation. A better understanding of the roles of some nutrients and lipidomics in T2DM through gut microbiota interactions will help develop new strategies for the prevention and treatment of T2DM. However, this issue has not yet been entirely discussed in the literature. The present review provides up-to-date knowledge on the roles of dietary lipids and lipidomics in gut-brain axis in T2DM and some nutritional strategies in T2DM considering lipids- lipidomics and gut microbiota interactions are given.

Nicotinamide Riboside Improves Enteric Neuropathy in Streptozocin-Induced Diabetic Rats Through Myenteric Plexus Neuroprotection

BACKGROUND

Diabetes Mellitus causes a systemic oxidative stress due in part to the hyperglycemia and the reactive oxygen species generated. Up to 75% of diabetic patients present with an autonomic neuropathy affecting the Enteric Nervous System. Deficits in the human population are chronic dysmotilities with either increased (i.e., constipation) or decreased (i.e., diarrhea) total gastrointestinal transit times. These are recapitulated in the streptozocin-induced diabetic rat, which is a model of Type I Diabetes Mellitus.

AIMS

Examine the effects that a precursor of nicotinamide adenosine dinucleotide (NAD), nicotinamide riboside (NR), had on the development of dysmotility in induced diabetic rats and if fecal microbiota transplant (FMT) could produce the same results.

MATERIALS AND METHODS

Utilizing a 6-week treatment paradigm, NR was administered intraperitoneally every 48 h. Total gastrointestinal transit time was assessed weekly utilizing the carmine red method. Three weeks following hyperglycemic induction, FMT was performed between NR-treated animals and untreated animals.

SIGNIFICANT RESULTS

There is improvement in overall gastrointestinal transit time with the use of NR. 16S microbiome sequencing demonstrated decreased alpha and beta diversity in induced diabetic rats without change in animals receiving FMT. Improvements in myenteric plexus ganglia density in small and large intestines in diabetic animals treated with NR were seen.

CONCLUSIONS

NR treatment led to functional improvement in total gastrointestinal transit time in induced diabetic animals. This was associated with neuroprotection in the myenteric plexuses of both small and large intestines of induced diabetic rats. This represents an important first step in showing NR's benefit as a treatment for diabetic enteric neuropathy. Streptozocin-induced diabetic rats have improved transit times and increased myenteric plexus ganglia density when treated with intraperitoneal nicotinamide riboside.

Gut region-specific TNFR expression: TNFR2 is more affected than TNFR1 in duodenal myenteric ganglia of diabetic rats

BACKGROUND

Cytokines are essential in autoimmune inflammatory processes that accompany type 1 diabetes. Tumor necrosis factor alpha plays a key role among others in modulating enteric neuroinflammation, however, it has a dual role in cell degeneration or survival depending on different TNFRs. In general, TNFR1 is believed to trigger apoptosis, while TNFR2 promotes cell regeneration. The importance of the neuronal microenvironment has been recently highlighted in gut region-specific diabetic enteric neuropathy, however, the expression and alterations of different TNFRs in the gastrointestinal tract has not been reported.

AIM

To investigate the TNFR1 and TNFR2 expression in myenteric ganglia and their environment in different intestinal segments of diabetic rats.

METHODS

Ten weeks after the onset of hyperglycemia, gut segments were taken from the duodenum, ileum and colon of streptozotocin-induced (60 mg/body weight kg i.p.) diabetic (n = 17), insulin-treated diabetic (n = 15) and sex- and age-matched control (n = 15) rats. Myenteric plexus whole-mount preparations were prepared from different gut regions for TNFR1/HuCD or TNFR2/HuCD double-labeling fluorescent immunohistochemistry. TNFR1 and TNFR2 expression was evaluated by post-embedding immunogold electron microscopy on ultrathin sections of myenteric ganglia. TNFRs levels were measured by enzyme-linked immun-osorbent assay in muscle/myenteric plexus-containing (MUSCLE-MP) tissue homogenates from different gut segments and experimental conditions.

RESULTS

A distinct region-dependent TNFRs expression was detected in controls. The density of TNFR1-labeling gold particles was lowest, while TNFR2 density was highest in duodenal ganglia and a decreased TNFRs expression from proximal to distal segments was observed in MUSCLE-MP homogenates. In diabetics, the TNFR2 density was only significantly altered in the duodenum with decrease in the ganglia (0.32 ± 0.02 vs 0.45 ± 0.04, P < 0.05), while no significant changes in TNFR1 density was observed. In diabetic MUSCLE-MP homogenates, both TNFRs levels significantly decreased in the duodenum (TNFR1: 4.06 ± 0.65 vs 20.32 ± 3.1, P < 0.001; TNFR2: 11.72 ± 0.39 vs 15.91 ± 1.04, P < 0.01), which markedly influenced the TNFR2/TNFR1 proportion in both the ganglia and their muscular environment. Insulin treatment had controversial effects on TNFR expression.

CONCLUSION

Our findings show diabetes-related region-dependent changes in TNFR expression and suggest that TNFR2 is more affected than TNFR1 in myenteric ganglia in the duodenum of type 1 diabetic rats.

Association between inflammation, lipopolysaccharide binding protein, and gut microbiota composition in a New Hampshire Bhutanese refugee population with a high burden of type 2 diabetes

Introduction

South Asian refugees experience a high risk of obesity and diabetes yet are often underrepresented in studies on chronic diseases and their risk factors. The gut microbiota and gut permeability, as assessed through circulating lipopolysaccharide binding protein (LBP), may underlie the link between chronic inflammation and type 2 diabetes (T2D). The composition of the gut microbiota varies according to multiple factors including demographics, migration, and dietary patterns, particularly fiber intake. However, there is no evidence on the composition of the gut microbiota and its relationship with metabolic health in refugee populations, including those migrating to the United States from Bhutan. The objective of this study was to examine glycemic status in relation to LBP, systemic inflammation fiber intake, and gut microbiota composition in Bhutanese refugee adults residing in New Hampshire (n = 50).

Methods

This cross-sectional study included a convenience sample of Bhutanese refugee adults (N = 50) in NH. Established bioinformatics pipelines for metagenomic analysis were used to determine relative genus abundance, species richness, and alpha diversity measures from shallow shotgun sequences. The relationships between inflammatory markers, gut microbiota composition, dietary fiber, and glycemic status were analyzed.

Results

We identified a substantial chronic disease burden in this study population, and observed a correlation between glycemic status, LBP, and inflammation, and a correlation between glycemic status and gut microbiome alpha diversity. Further, we identified a significant correlation between proinflammatory taxa and inflammatory cytokines. SCFA-producing taxa were found to be inversely correlated with age.

Conclusion

To date, this is the most comprehensive examination of metabolic health and the gut microbiome in a Bhutanese refugee population in NH. The findings highlight areas for future investigations of inflammation and glycemic impairment, in addition to informing potential interventions targeting this vulnerable population.

Relationships between Diabetes and the Intestinal Microbial Population

Diabetes is a metabolic disorder characterized by lower responsiveness of tissues to insulin and consequent large variations in circulating levels of glucose. This fluctuation has harmful effects as both hyperglycemia and hypoglycemia can be very injurious. The causes of diabetes are varied but the consequences are rather uniform. Dietary factors are important especially in adult onset type 2 diabetes (T2D) while type 1 diabetes (T1D) is characterized by having a stronger heritable component and involving autoimmune attach on pancreatic beta cells. This review is focused on the relation of the bacterial components found within the intestine, to the establishment and maintenance of diabetes. The precise composition of the gut microbiome is increasingly recognized as a factor in organismic health and its interaction with a variety of disease states has been described. This is especially marked in the case of diabetes since the nature of the diet is an important factor in establishing both the microbiome and the incidence of diabetes. The bidirectional nature of this relationship is discussed. The effects of disease that lead to altered microbiomal composition together with aberrant metabolic changes are also included. Emphasis is given to the important role of short chain fatty acids (SCFAs) as mediators of the microbiome-diabetes relation.

Vagus Nerve Stimulation: A Personalized Therapeutic Approach for Crohn's and Other Inflammatory Bowel Diseases

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are incurable autoimmune diseases characterized by chronic inflammation of the gastrointestinal tract. There is increasing evidence that inappropriate interaction between the enteric nervous system and central nervous system and/or low activity of the vagus nerve, which connects the enteric and central nervous systems, could play a crucial role in their pathogenesis. Therefore, it has been suggested that appropriate neuroprosthetic stimulation of the vagus nerve could lead to the modulation of the inflammation of the gastrointestinal tract and consequent long-term control of these autoimmune diseases. In the present paper, we provide a comprehensive overview of (1) the cellular and molecular bases of the immune system, (2) the way central and enteric nervous systems interact and contribute to the immune responses, (3) the pathogenesis of the inflammatory bowel disease, and (4) the therapeutic use of vagus nerve stimulation, and in particular, the transcutaneous stimulation of the auricular branch of the vagus nerve. Then, we expose the working hypotheses for the modulation of the molecular processes that are responsible for intestinal inflammation in autoimmune diseases and the way we could develop personalized neuroprosthetic therapeutic devices and procedures in favor of the patients.

The Gut-Ex-Vivo System (GEVS) Is a Dynamic and Versatile Tool for the Study of DNBS-Induced IBD in BALB/C and C57BL/6 Mice, Highlighting the Protective Role of Probiotics

BACKGROUND

IBD is a spectrum of pathologies characterized by dysregulated immune activation leading to uncontrolled response against the intestine, thus resulting in chronic gut inflammation and tissue damage. Due to its complexity, the molecular mechanisms responsible for disease onset and progression are still elusive, thus requiring intense research effort. In this context, the development of models replicating the etiopathology of IBD and allowing the testing of new potential therapies is critical.

METHODS

Colon from C57BL/6 or BALB/c mice was cultivated in a Gut-Ex-Vivo System (GEVS), exposed for 5 h to DNBS 1.5 or 2.5 mg/mL, in presence or absence of two probiotic formulations (P1 = Bifidobacterium breve BR03 (DSM16604) and B632 (DSM24706); P2 = Lacticaseibacillus rhamnosus LR04 (DSM16605), Lactiplantibacillus plantarum LP14 (DSM33401) and Lacticaseibacillus paracasei LPC09), and the main hallmarks of IBD were evaluated.

RESULTS

Gene expression analysis revealed the following DNBS-induced effects: (i) compromised tight junction organization, responsible for tissue permeability dysregulation; (ii) induction of ER stress, and (iii) tissue inflammation in colon of C57BL/6 mice. Moreover, the concomitant DNBS-induced apoptosis and ferroptosis pathways were evident in colon from both BALB/c and C57BL/6 mice. Finally, the co-administration of probiotics completely prevented the detrimental effects of DNBS.

CONCLUSIONS

Overall, we have provided results demonstrating that GEVS is a consistent, reliable, and cost-effective system for modeling DNBS-induced IBD, useful for studying the onset and progression of human disease at the molecular level, while also reducing animal suffering. Moreover, we have confirmed the beneficial effect of probiotics administration in promoting the remission of IBD.

Synbiotics and Gut Microbiota: New Perspectives in the Treatment of Type 2 Diabetes Mellitus

The number of people with type 2 diabetes mellitus (T2DM) has increased sharply over the past decades. Apart from genetic predisposition, which may cause some of the diagnosed cases, an unhealthy diet and lifestyle are incentive triggers of this global epidemic. Consumption of probiotics and prebiotics to gain health benefits has become increasingly accepted by the public in recent years, and their critical roles in alleviating T2DM symptoms are confirmed by accumulating studies. Microbiome research reveals gut colonization by probiotics and their impacts on the host, while oral intake of prebiotics may stimulate existing metabolisms in the colon. The use of synbiotics (a combination of prebiotics and probiotics) can thus show a synergistic effect on T2DM through modulating the gastrointestinal microenvironment. This review summarizes the research progress in the treatment of T2DM from the perspective of synbiotics and gut microbiota and provides a class of synbiotics which are composed of lactulose, arabinose, and Lactobacillus plantarum, and can effectively adjust the blood glucose, blood lipid, and body weight of T2DM patients to ideal levels.

Exendin-4 inhibits small intestinal glucose sensing and absorption through repression of T1R2/T1R3 sweet taste receptor signalling in streptozotocin diabetic mice

The small intestine, which is the area where sugars are absorbed, should be considered in the approaches developed for the treatment of diabetes. However, studies on small intestine damage in diabetic individuals, and the effects of current treatments on the small intestine are very limited. This is the first study to investigate the effects of exendin-4, a GLP-1 receptor agonist, on small intestine injury in diabetic mice. BALB/c male mice were divided into 4 groups for this study. The first group was given citrate buffer, the second group was given exendin-4, the third group was given streptozotocin (STZ), and the fourth group was given both exendin-4, and STZ. As the results, we determined a decrease in the edema and deterioration in the integrity of the villi, disruption in continuity of the brush border, fibrosis and enterocyte apoptosis, while the TNFα level and crypt cell proliferation were increased in the small intestinal tissue of exendin-4 treated STZ diabetic mice. Furthermore, the levels of duodenal tissue glucose, SGLT1, and GLUT2 were decreased, whereas there was an increase in GIP level in diabetic mice administered with exendin-4. Moreover, we determined that the sweet taste receptors T1R2/T1R3, downstream molecules PLCβ2, α-gustducin and associated secondary messengers IP3, cAMP, which were increased in the duodenal tissue of STZ-diabetic mice, decreased with exendin-4 administration. These findings were evaluated as that exendin-4 reduces glucose absorption by suppressing the T1R2/T1R3 sweet taste signal perception pathway in duodenum of STZ diabetic mice.

How Brain Infarction Links With the Microbiota-Gut-Brain Axis: Hints From Studies Focusing on the Risk Factors for Ischemic Stroke

Ischemic stroke (IS) is among the top prevalent neurologic disorders globally today. Risk factors such as hypertension, diabetes, and aging, contribute to the development of IS, and patients with these risk factors face heavier therapeutic burden and worse prognosis. Microbiota–gut–brain axis describes the crosstalk between the gut flora, intestine, and center nervous system, which conduct homeostatic effects through the bacterial metabolites, the regulation of immune activity, also the contact with enteric nerve ends and vagus nerve. Nowadays, more studies have paid attention to the important roles that microbiota–gut–brain axis played in the risk factors of IS. In the current article, we will review the recent works focusing on the bi-directional impacts of gut dysbiosis and the pathogenic process of IS-related risk factors, for the purpose to summarize some novel findings in this area, and try to understand how probiotics could limit the development of IS via different strategies.

Effects of Non-Polar Dietary and Endogenous Lipids on Gut Microbiota Alterations: The Role of Lipidomics

Advances in sequencing technologies over the past 15 years have led to a substantially greater appreciation of the importance of the gut microbiome to the health of the host. Recent outcomes indicate that aspects of nutrition, especially lipids (exogenous or endogenous), can influence the gut microbiota composition and consequently, play an important role in the metabolic health of the host. Thus, there is an increasing interest in applying holistic analytical approaches, such as lipidomics, metabolomics, (meta)transcriptomics, (meta)genomics, and (meta)proteomics, to thoroughly study the gut microbiota and any possible interplay with nutritional or endogenous components. This review firstly summarizes the general background regarding the interactions between important non-polar dietary (i.e., sterols, fat-soluble vitamins, and carotenoids) or amphoteric endogenous (i.e., eicosanoids, endocannabinoids-eCBs, and specialized pro-resolving mediators-SPMs) lipids and gut microbiota. In the second stage, through the evaluation of a vast number of dietary clinical interventions, a comprehensive effort is made to highlight the role of the above lipid categories on gut microbiota and vice versa. In addition, the present status of lipidomics in current clinical interventions as well as their strengths and limitations are also presented. Indisputably, dietary lipids and most phytochemicals, such as sterols and carotenoids, can play an important role on the development of medical foods or nutraceuticals, as they exert prebiotic-like effects. On the other hand, endogenous lipids can be considered either prognostic indicators of symbiosis or dysbiosis or even play a role as specialized mediators through dietary interventions, which seem to be regulated by gut microbiota.

5/6 nephrectomy affects enteric glial cells and promotes impaired antioxidant defense in the colonic neuromuscular layer

AIMS

Chronic kidney disease (CKD) produces multiple repercussions in the gastrointestinal tract (GIT), such as alterations in motility, gut microbiota, intestinal permeability, and increased oxidative stress. However, despite enteric glial cells (EGC) having important neural and immune features in GIT physiology, their function in CKD remains unknown. The present study investigates colonic glial markers, inflammation, and antioxidant parameters in a CKD model.

MAIN METHODS

A 5/6 nephrectomized rat model was used to induce CKD in rats and Sham-operated animals as a control to suppress. Biochemical measures in plasma and neuromuscular layer such as glutathione peroxidase (GPx) and superoxide dismutase (SOD) activity were carried out. Kidney histopathology was evaluated. Colon morphology analysis and glial fibrillary acid protein (GFAP), connexin-43 (Cx43), nuclear factor-kappa B (NF-κB) p65, and GPx protein expression were performed.

KEY FINDINGS

The CKD group exhibited dilated tubules and tubulointerstitial fibrosis in the reminiscent kidney (p = 0.0002). CKD rats showed higher SOD activity (p = 0.004) in plasma, with no differences in neuromuscular layer (p = 0.9833). However, GPx activity was decreased in the CKD group in plasma (p = 0.013) and neuromuscular layer (p = 0.0338). Morphological analysis revealed alterations in colonic morphometry with inflammatory foci in the submucosal layer and neuromuscular layer straightness in CKD rats (p = 0.0291). In addition, GFAP, Cx43, NF-κBp65 protein expression were increased, and GPx decreased in the neuromuscular layer of the CKD group (p < 0.05).

SIGNIFICANCE

CKD animals present alterations in colonic cytoarchitecture and decreased layer thickness. Moreover, CKD affects the enteric glial network of the neuromuscular layer, associated with decreased antioxidant activity and inflammation.

Brazil Nut (Bertholletia excelsa H.B.K) Retards Gastric Emptying and Modulates Enteric Glial Cells in a Dose-Dependent Manner

BACKGROUND

The role of food and nutrients in the regulation of enteric glial cell functions is unclear. Some foods influence enteric neurophysiology and can affect glial cell functions that include regulation of the intestinal barrier, gastric emptying, and colonic transit. Brazil nuts are the most abundant natural source of selenium, unsaturated fatty acids, fibers, and polyphenols.

OBJECTIVE

The study investigated the effects of a Brazil nut-enriched diet on enteric glial cells and gastrointestinal transit.

METHODS

Two-month-old male Wistar rats were randomized to a standard diet (control group, CG), standard diet containing 5% (wt/wt) Brazil nut (BN5), and standard diet containing 10% (wt/wt) Brazil nut (BN10) (n = 9 per group). After eight weeks, the animals underwent constipation and gastric emptying tests to assess motility. Evaluations of colonic immunofluorescence staining for glial fibrillary acidic protein (GFAP) and myenteric ganglia area were performed.

RESULTS

The BN5 group showed increased weight gain while the BN10 group did not (p < 0.0001). The BN10 group showed higher gastric residue amounts compared to the other groups (p = 0.0008). The colon exhibited an increase in GFAP immunoreactivity in the BN5 group compared to that in the other groups (p = 0.0016), and the BN10 group presented minor immunoreactivity compared to the CG (p = 0.04). The BN10 group presented a minor ganglia area compared to the CG (p = 0.0155).

CONCLUSION

The Brazil nut-enriched diet modified the gastric residual, colonic GFAP immunoreactivity, and myenteric ganglia area after eight weeks in healthy male Wistar rats.

Innate Lymphoid Cells and Natural Killer Cells in Bacterial Infections: Function, Dysregulation, and Therapeutic Targets

Infectious diseases represent one of the largest medical challenges worldwide. Bacterial infections, in particular, remain a pertinent health challenge and burden. Moreover, such infections increase over time due to the continuous use of various antibiotics without medical need, thus leading to several side effects and bacterial resistance. Our innate immune system represents our first line of defense against any foreign pathogens. This system comprises the innate lymphoid cells (ILCs), including natural killer (NK) cells that are critical players in establishing homeostasis and immunity against infections. ILCs are a group of functionally heterogenous but potent innate immune effector cells that constitute tissue-resident sentinels against intracellular and extracellular bacterial infections. Being a nascent subset of innate lymphocytes, their role in bacterial infections is not clearly understood. Furthermore, these pathogens have developed methods to evade the host immune system, and hence permit infection spread and tissue damage. In this review, we highlight the role of the different ILC populations in various bacterial infections and the possible ways of immune evasion. Additionally, potential immunotherapies to manipulate ILC responses will be briefly discussed.

Phenolic Compounds Promote Diversity of Gut Microbiota and Maintain Colonic Health

The role of non-energy-yielding nutrients on health has been meticulously studied, and the evidence shows that a compound can exert significant effects on health even if not strictly required by the organism. Phenolic compounds are among the most widely studied molecules that fit this description; they are found in plants as secondary metabolites and are not required by humans for growth or development, but they can influence a wide array of processes that modulate health across multiple organs and systems. The lower gastrointestinal tract is a prime site of action of phenolic compounds, namely, by their effects on gut microbiota and colonic health. As with humans, phenolic compounds are not required by most bacteria but can be substrates of others; in fact, some phenolic compounds exert antibacterial actions. A diet rich in phenolic compounds can lead to qualitative and quantitative effects on gut microbiota, thereby inducing indirect health effects in mammals through the action of these microorganisms. Moreover, phenolic compounds may be fermented by the gut microbiota, thereby modulating the compounds bioactivity. In the colon, phenolic compounds promote anti-inflammatory, anti-oxidant and antiproliferative actions. The aim of the present review is to highlight the role of phenolic compounds on maintaining or restoring a healthy microbiota and overall colonic health. Mechanisms of action that substantiate the reported evidence will also be discussed.

Optogenetic activation of the distal colon epithelium engages enteric nervous system circuits to initiate motility patterns

Digestive functions of the colon depend on sensory-motor reflexes in the enteric nervous system (ENS), initiated by intrinsic primary afferent neurons (IPANs). IPAN terminals project to the mucosal layer of the colon, allowing communication with epithelial cells comprising the colon lining. The chemical nature and functional significance of this epithelial-neural communication in regard to secretion and colon motility are of high interest. Colon epithelial cells can produce and release neuroactive substances such as ATP and 5-hydroxytryptamine (5-HT), which can activate receptors on adjacent nerve fibers, including IPAN subtypes. In this study, we examined if stimulation of epithelial cells alone is sufficient to activate neural circuits that control colon motility. Optogenetics and calcium imaging were used in ex vivo preparations of the mouse colon to selectively stimulate the colon epithelium, measure changes in motility, and record activity of neurons within the myenteric plexus. Light-mediated activation of epithelial cells lining the distal, but not proximal, colon caused local contractions and increased the rate of colonic migrating motor complexes. Epithelial-evoked local contractions in the distal colon were reduced by both ATP and 5-HT receptor antagonists. Our findings indicate that colon epithelial cells likely use purinergic and serotonergic signaling to initiate activity in myenteric neurons, produce local contractions, and facilitate large-scale coordination of ENS activity responsible for whole colon motility patterns.NEW & NOTEWORTHY Using an all-optical approach to measure real-time cell-to-cell communication responsible for colon functions, we show that selective optogenetic stimulation of distal colon epithelium produced activity in myenteric neurons, as measured with red genetically encoded calcium indicators. The epithelial-induced neural response led to local contractions, mediated by both purinergic and serotonergic signaling, and facilitated colonic motor complexes that propagate from proximal to distal colon.

High cellulose diet promotes intestinal motility through regulating intestinal immune homeostasis and serotonin biosynthesis

It is widely accepted dietary fiber intimately linked to inflammatory and nervous diseases, which often been described with altered gastrointestinal (GI) motility. However, how dose dietary fiber modulate inflammation and crosstalk influence GI function has not been explained in detail. We found fiber-free diet reduced intestinal motility, accompanied by upregulated proinflammatory immunocytes and inflammatory cytokines in colon of mice. We also discovered high-cellulose diet increased synthesis of serotonin and expression of neurotrophic factors, both of that have been reported involved in promoting intestinal motility. In addition, metabolomics analysis showed increased tryptophan metabolites in high-cellulose diet mice, which happened to be required for serotonin biosynthesis. Further analysis revealed high-cellulose diet changed the composition of gut microbiota, in particular by altering the ratio of Firmicutes to Bacteroidetes, consequently, concentration of short-chain fatty acids (SCFAs), especially acetate. Orally administration of acetate confirmed its modulating to serotonin synthesis, neurotrophic factors expression and immunocyte differentiation through regulating histone deacetylase (HDAC3) activity in colon. Together, our results demonstrated high-cellulose diet promote intestinal motility through regulating intestinal homeostasis and enteric nervous system by increasing acetate production and HDAC3 inhibition. Thus, rich cellulose diet or acetate supplement can be considered as dietary advice to improve clinically intestinal motility insufficiency.

Intestinal Mucosal Barrier Is Regulated by Intestinal Tract Neuro-Immune Interplay

Inflammatory bowel disease, irritable bowel syndrome and severe central nervous system injury can lead to intestinal mucosal barrier damage, which can cause endotoxin/enterobacteria translocation to induce infection and is closely related to the progression of metabolic diseases, cardiovascular and cerebrovascular diseases, tumors and other diseases. Hence, repairing the intestinal barrier represents a potential therapeutic target for many diseases. Enteral afferent nerves, efferent nerves and the intrinsic enteric nervous system (ENS) play key roles in regulating intestinal physiological homeostasis and coping with acute stress. Furthermore, innervation actively regulates immunity and induces inherent and adaptive immune responses through complex processes, such as secreting neurotransmitters or hormones and regulating their corresponding receptors. In addition, intestinal microorganisms and their metabolites play a regulatory role in the intestinal mucosal barrier. This paper primarily discusses the interactions between norepinephrine and β-adrenergic receptors, cholinergic anti-inflammatory pathways, nociceptive receptors, complex ENS networks, gut microbes and various immune cells with their secreted cytokines to summarize the key roles in regulating intestinal inflammation and improving mucosal barrier function.

High-fat diet impairs duodenal barrier function and elicits glia-dependent changes along the gut-brain axis that are required for anxiogenic and depressive-like behaviors

BACKGROUND

Mood and metabolic disorders are interrelated and may share common pathological processes. Autonomic neurons link the brain with the gastrointestinal tract and constitute a likely pathway for peripheral metabolic challenges to affect behaviors controlled by the brain. The activities of neurons along these pathways are regulated by glia, which exhibit phenotypic shifts in response to changes in their microenvironment. How glial changes might contribute to the behavioral effects of consuming a high-fat diet (HFD) is uncertain. Here, we tested the hypothesis that anxiogenic and depressive-like behaviors driven by consuming a HFD involve compromised duodenal barrier integrity and subsequent phenotypic changes to glia and neurons along the gut-brain axis.

METHODS

C57Bl/6 male mice were exposed to a standard diet or HFD for 20 weeks. Bodyweight was monitored weekly and correlated with mucosa histological damage and duodenal expression of tight junction proteins ZO-1 and occludin at 0, 6, and 20 weeks. The expression of GFAP, TLR-4, BDNF, and DCX were investigated in duodenal myenteric plexus, nodose ganglia, and dentate gyrus of the hippocampus at the same time points. Dendritic spine number was measured in cultured neurons isolated from duodenal myenteric plexuses and hippocampi at weeks 0, 6, and 20. Depressive and anxiety behaviors were also assessed by tail suspension, forced swimming, and open field tests.

RESULTS

HFD mice exhibited duodenal mucosa damage with marked infiltration of immune cells and decreased expression of ZO-1 and occludin that coincided with increasing body weight. Glial expression of GFAP and TLR4 increased in parallel in the duodenal myenteric plexuses, nodose ganglia, and hippocampus in a time-dependent manner. Glial changes were associated with a progressive decrease in BDNF, and DCX expression, fewer neuronal dendritic spines, and anxiogenic/depressive symptoms in HFD-treated mice. Fluorocitrate (FC), a glial metabolic poison, abolished these effects both in the enteric and central nervous systems and prevented behavioral alterations at week 20.

CONCLUSIONS

HFD impairs duodenal barrier integrity and produces behavioral changes consistent with depressive and anxiety phenotypes. HFD-driven changes in both peripheral and central nervous systems are glial-dependent, suggesting a potential glial role in the alteration of the gut-brain signaling that occurs during metabolic disorders and psychiatric co-morbidity.

Epigenetic Regulation of Gut Microbial Dysbiosis

Microbiota inside the gut plays a vital role in maintaining human health. Microbial dysbiosis is associated with various complications leading to a range of diseases. Epigenetic changes enforced by various environmental and lifestyle factors lead to heritable modifications. These epigenetic modifications include DNA methylation, histone modifications, chromatin remodelling, and ribonucleic acid-based mechanisms. This review summarizes the impacts of environmental factors on the gut microbiome, epigenetic modifications, and their role in cardiovascular diseases.

Impaired intestinal barrier function in type 2 diabetic patients measured by serum LPS, Zonulin, and IFABP

INTRODUCTION

The epithelial tight junctions of intestine were impaired in murine model of type 2 diabetes mellitus (T2DM). The aim of this work was to investigate the alteration of intestinal barrier in T2DM patients.

METHODS

90 patients with T2DM and 28 healthy controls were recruited. Serum lipopolysaccharide (LPS), Zonulin, and intestinal fatty acid binding protein (IFABP) were measured by ELISA, based on which a derived permeability risk score (PRS) was calculated. Subgroup analyses were conducted based on the glycemic control (HbA1c < 7%, or HbA1c ≥ 7%), the amount of chronic diabetic complications, and the use of aspirin at the time.

RESULTS

Serum LPS, Zonulin, and IFABP, and PRS of T2DM group were significantly higher than those of the control group (p < 0.05 for all). Serum LPS and PRS was higher in T2DM patients with poor glycemic control (both p < 0.05). Patients with more chronic complications of diabetes had higher serum LPS and IFABP, and PRS (all p < 0.05). No differences were found in these serum markers between T2DM patients being treated with aspirin or not.

CONCLUSIONS

Intestinal barrier function was impaired in T2DM patients. Poor glycemic control and more chronic complications of diabetes were associated with worse intestinal barrier function. Treatment with aspirin did not aggravate the impairment of intestinal barrier in T2DM patients.

Oral Amylin Treatment Reduces the Pathological Cascade of Alzheimer's Disease in a Mouse Model

Intraperitoneal injection of amylin or its analog reduces Alzheimer's disease (AD) pathology in the brains. However, self-injecting amylin analogs is difficult for patients due to cognitive deficits. This work aims to study the effects of amylin on the brain could be achieved by oral delivery as some study reported that amylin receptor may be present in the gastrointestinal tract. A 6-week course of oral amylin treatment reduced components of AD pathology, including the levels of amyloid-β, phosphorylated tau, and ionized calcium binding adaptor molecule 1. The treatment reduced active forms of cyclin-dependent kinase 5. Oral amylin treatment led to improvements in social deficit in AD mouse. Using immunofluorescence, we observed the amylin receptor complexed with the calcitonin receptor and receptor activity-modifying proteins in the enteric neurons. The study suggests the potential of the oral delivery of amylin analogs for the treatment of AD and other neurodegenerative diseases through enteric neurons.

Niacin and Butyrate: Nutraceuticals Targeting Dysbiosis and Intestinal Permeability in Parkinson's Disease

Dysbiosis is implicated by many studies in the pathogenesis of Parkinson's disease (PD). Advances in sequencing technology and computing have resulted in confounding data regarding pathogenic bacterial profiles in conditions such as PD. Changes in the microbiome with reductions in short-chain fatty acid (SCFA)-producing bacteria and increases in endotoxin-producing bacteria likely contribute to the pathogenesis of PD. GPR109A, a G-protein coupled receptor found on the surface of the intestinal epithelium and immune cells, plays a key role in controlling intestinal permeability and the inflammatory cascade. The absence of GPR109A receptors is associated with decreased concentration of tight junction proteins, leading to increased intestinal permeability and susceptibility to inflammation. In inflammatory states, butyrate acts via GPR109A to increase concentrations of tight junction proteins and improve intestinal permeability. Niacin deficiency is exacerbated in PD by dopaminergic medications. Niacin supplementation has been shown to shift macrophage polarization from pro-inflammatory to an anti-inflammatory profile. Niacin and butyrate, promising nutrients and unique ligands for the G protein-coupled receptor GPR109A, are reviewed in this paper in detail.

Innate Lymphoid Cells in Crohn's Disease

Innate lymphoid cells (ILCs) are a large family of cells of the immune system that performs various functions in immune defense, inflammation, and tissue remodeling. As a part of the innate immune system, ILCs are a distinct form of lymphocytes different from T and B cells. ILCs can provide host defense against the source of infection and initiate the repair and remodeling processes to restore and maintain host body homeostasis. The number of patients with Crohn’s disease (CD) worldwide has continued to increase in recent years and this disease has brought sickness and death to many families. Numerous studies have found that ILCs also undergo a series of alternations during the development of CD and contribute to this disease. Despite this, the pathogenesis of CD is still not fully explained. So, we keep researching and exploring. In this review, we have closely linked the latest progress on ILCs and CD, and introduced, in detail, the specific roles of four different types of ILCs in CD. We also describe new progress in the pathogenesis of CD, with particular emphasis on the plasticity of ILC3s in this disease. These new studies and findings may provide new insights and breakthrough points for the treatment of CD.

The Potential Effects of Probiotics and ω-3 Fatty Acids on Chronic Low-Grade Inflammation

Chronic low-grade inflammation negatively impacts health and is associated with aging and obesity, among other health outcomes. A large number of immune mediators are present in the digestive tract and interact with gut bacteria to impact immune function. The gut microbiota itself is also an important initiator of inflammation, for example by releasing compounds such as lipopolysaccharides (LPS) that may influence cytokine production and immune cell function. Certain nutrients (e.g., probiotics, ω-3 fatty acids [FA]) may increase gut microbiota diversity and reduce inflammation. Lactobacilli and Bifidobacteria, among others, prevent gut hyperpermeability and lower LPS-dependent chronic low-grade inflammation. Furthermore, ω-3 FA generate positive effects on inflammation-related conditions (e.g., hypertriglyceridemia, diabetes) by interacting with immune, metabolic, and inflammatory pathways. Ω-3 FA also increase LPS-suppressing bacteria (i.e., Bifidobacteria) and decrease LPS-producing bacteria (i.e., Enterobacteria). Additionally, ω-3 FA appear to promote short-chain FA production. Therefore, combining probiotics with ω-3 FA presents a promising strategy to promote beneficial immune regulation via the gut microbiota, with potential beneficial effects on conditions of inflammatory origin, as commonly experienced by aged and obese individuals, as well as improvements in gut-brain-axis communication.

Targeting the Enteric Nervous System to Treat Metabolic Disorders? "Enterosynes" as Therapeutic Gut Factors

The gut-brain axis is of crucial importance for controlling glucose homeostasis. Alteration of this axis promotes the type 2 diabetes (T2D) phenotype (hyperglycaemia, insulin resistance). Recently, a new concept has emerged to demonstrate the crucial role of the enteric nervous system in the control of glycaemia via the hypothalamus. In diabetic patients and mice, modification of enteric neurons activity in the proximal part of the intestine generates a duodenal hyper-contractility that generates an aberrant message from the gut to the brain. In turn, the hypothalamus sends an aberrant efferent message that provokes a state of insulin resistance, which is characteristic of a T2D state. Targeting the enteric nervous system of the duodenum is now recognized as an innovative strategy for treatment of diabetes. By acting in the intestine, bioactive gut molecules that we called "enterosynes" can modulate the function of a specific type of neurons of the enteric nervous system to decrease the contraction of intestinal smooth muscle cells. Here, we focus on the origins of enterosynes (hormones, neurotransmitters, nutrients, microbiota, and immune factors), which could be considered therapeutic factors, and we describe their modes of action on enteric neurons. This unsuspected action of enterosynes is proposed for the treatment of T2D, but it could be applied for other therapeutic solutions that implicate communication between the gut and brain.

Microbiome and type 1 diabetes

The steep increase in the incidence of type 1 diabetes (T1D), in the Western world after World War II, cannot be explained solely by genetic factors but implies that this rise must be due to crucial interactions between predisposing genes and environmental changes. Three parallel phenomena in early childhood – the dynamic development of the immune system, maturation of the gut microbiome, and the appearance of the first T1D-associated autoantibodies – raise the question whether these phenomena might reflect causative relationships. Plenty of novel data on the role of the microbiome in the development of T1D has been published over recent years and this review summarizes recent findings regarding the associations between islet autoimmunity, T1D, and the intestinal microbiota.

Repeated clodronate-liposome treatment results in neutrophilia and is not effective in limiting obesity-linked metabolic impairments

Depletion of macrophages is thought to be a therapeutic option for obesity-induced inflammation and metabolic dysfunction. However, whether the therapeutic effect is a direct result of reduced macrophage-derived inflammation or secondary to decreases in fat mass is controversial, as macrophage depletion has been shown to disrupt energy homeostasis. This study was designed to determine if macrophage depletion via clodronate-liposome (CLD) treatment could serve as an effective intervention to reduce obesity-driven inflammatory and metabolic impairments independent of changes in energy intake. After 16 wk on a high-fat diet (HFD) or the AIN-76A control (low-fat) diet (LFD) ( n = 30/diet treatment), male C57BL/6J mice were assigned to a CLD- or PBS-liposome treatment ( n = 15/group) for 4 wk. Liposomes were administered biweekly via intraperitoneal injections (8 administrations in total). PBS-liposome-treated groups were pair-fed to their CLD-treated dietary counterparts. Metabolic function was assessed before and after liposome treatment. Adipose tissue, as well as the liver, was investigated for macrophage infiltration and the presence of inflammatory mediators. Additionally, a complete blood count was performed. CLD treatment reduced energy intake. When controlling for energy intake, CLD treatment was unable to regress metabolic dysfunction or nonalcoholic fatty liver disease and impaired adipose tissue insulin action. Moreover, repeated CLD treatment induced neutrophilia and anemia, increased adipose tissue mRNA expression of the proinflammatory cytokines IL-6 and IL-1β, and augmented circulating IL-6 and monocyte chemoattractant protein-1 concentrations ( P < 0.05). This study suggests that repeated intraperitoneal administration of CLD to deplete macrophages attenuates obesity by limiting energy intake. Moreover, after controlling for the benefits of weight loss, the accompanying detrimental side effects limit regular CLD treatment as an effective therapeutic strategy.

Innate Lymphoid Cells: A Link between the Nervous System and Microbiota in Intestinal Networks

Innate lymphoid cells (ILCs) are a novel family of innate immune cells that act as key coordinators of intestinal mucosal surface immune defense and are essential for maintaining intestinal homeostasis and barrier integrity by responding to locally produced effector cytokines or direct recognition of exogenous or endogenous danger patterns. ILCs are also involved in the pathogenesis of inflammatory bowel disease (IBD). Many studies have demonstrated the occurrence of crosstalk between ILCs and intestinal microbiota, and ILCs have recently been shown to be connected to the enteric nervous system (ENS). Thus, ILCs may act as a key link between the nervous system and microbiota in intestinal networks. In this review, we briefly summarize the role of the ILCs in the intestinal tract (particularly in the context of IBD) and discuss the relationship between ILCs and the microbiota/ENS.

The Impact of Starvation on the Microbiome and Gut-Brain Interaction in Anorexia Nervosa

Interactions between the gut microbiome and the brain are of increasing interest to both researchers and clinicians. Evidence is mounting on the causal role of an altered gut microbiome in inflammatory diseases such as arthritis, inflammatory bowel disease, obesity and diabetes, and psychiatric diseases like anxiety and depression. Mechanisms include altered energy harvest from food, hormonal changes, increased gut permeability, inflammation, immune response, and a direct influence on the brain and behavior. Anorexia nervosa (AN) is the third most common disease in adolescence and exacts a high burden on patients and caregivers. It often becomes chronic and has the highest mortality of all psychiatric diseases. As AN is characterized by nutritional restrictions, weight loss, and severe behavioral symptoms including weight phobia, comorbid anxiety and depression, accompanied by endocrine alterations, increased inflammation, and immune response, exploring the role of the gut microbiome is crucial. Here, we present an overview of the potential mechanisms of interaction between the gut microbiome, the host and particularly the brain in AN and summarize the initial findings of microbiome research on AN. We conclude by identifying future research directions and potential therapeutic approaches, including nutritional interventions, probiotics, prebiotics and food supplements, that could become important additions to current AN therapy.