Oxidative stress: key player in gastrointestinal complications of diabetes

Hyperglycemic stress induces oxidative damage of enteric glial cells by triggering redoxosomes/p66SHC activation

OBJECTIVES

Diabetic gastrointestinal dysfunction (DGD) is a serious complication of diabetic mellitus (DM), affecting the enteric nervous system (ENS), particular enteric glial cells (EGCs). This study aimed to elucidate the effects and underlying molecular mechanisms of hyperglycemic stress on EGCs in in vitro and in vivo models of DM.

METHODS

In in vitro studies, enteric glial cell line CRL-2690 was exposed to hyperglycemia stress, and cell viability, cell apoptosis and oxidative damage were assessed. In in vivo studies, STZ-induced diabetic mice were constructed, and cell apoptosis and oxidative damage of EGCs in the duodenum of DM mice were assessed.

RESULTS

The results showed that hyperglycemic stress markedly induced oxidative damage of EGCs in in vitro and in vivo models of DM. This damage was found to be dependent on the activation of redoxosomes, which involved the phosphorylation of SRC and Vav2, the up-regulation of active RAC1-GTP, and the activation of NADPH oxidase (NOX). Moreover, inhibitors of redoxosomes, such as the RAC1 inhibitor NSC23766 and the NOX inhibitor VAS2870, effectively mitigated the hyperglycemic stress-induced oxidative damage of EGCs. Additionally, inhibition of p66SHC, a downstream target of redoxosomes, attenuated oxidative damage of EGCs under hyperglycemic stress.

DISCUSSION

Our findings suggest that the redoxosomes/p66SHC signaling is involved in the oxidative damage of EGCs during the pathological process of DGD. This signaling cascade may represent a potential therapeutic target for the treatment of DGD.

Untargeted metabolomics analysis reveals spatial metabolic heterogeneity in different intestinal segments of type 1 diabetic mice

Type 1 diabetes (T1D) has been reported to cause systematic metabolic disorders, but metabolic changes in different intestinal segments of T1D remain unclear. In this study, we analyzed metabolic profiles in the jejunum, ileum, cecum and colon of streptozocin-induced T1D and age-matched control (CON) mice by an LC-MS-based metabolomics method. The results show that segment-specific metabolic disorders occurred in the gut of T1D mice. In the jejunum, we found that T1D mainly led to disordered amino acid metabolism and most amino acids were significantly lower relative to CON mice. Moreover, fatty acid metabolism was disrupted mainly in the ileum, cecum and colon of T1D mice, such as arachidonic acid, alpha-linolenic acid and linoleic acid metabolism. Thus, our study reveals spatial metabolic heterogeneity in the gut of T1D mice and provides a metabolic view on diabetes-associated intestinal diseases.

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.

Dietary pattern in autism increases the need for probiotic supplementation: A comprehensive narrative and systematic review on oxidative stress hypothesis

Autism spectrum disorders (ASDs) are associated with specific dietary habits, including limited food selection and gastrointestinal problems, resulting in an altered gut microbiota. Autistic patients have an elevated abundance of certain gut bacteria associated with increased oxidative stress in the gastrointestinal tract. Probiotic supplementation has been shown to decrease oxidative stress in a simulated gut model, but the antioxidant effects of probiotics on the oxidative stress of the gut in autistic patients have not been directly studied. However, it is speculated that probiotic supplementation may help decrease oxidative stress in the gastrointestinal tract of autistic patients due to their specific dietary habits altering the microbiota. PubMed, Scopus and Web of Science databases and Google Scholar were searched up to May 2023. This systematic-narrative review aims to present the latest evidence regarding the changes in eating habits of autistic children which may further increase the gut microbiota induced oxidative stress. Additionally, this review will assess the available literature on the effects of probiotic supplementation on oxidative stress parameters.

The Role of Small Intestinal Bacterial Overgrowth in Obesity and Its Related Diseases

Obesity has become a major public health problem worldwide and its occurrence is increasing globally. Obesity has also been shown to be involved in the occurrence and development of many diseases and pathological conditions, such as nonalcoholic fatty liver disease (NAFLD), type 2 diabetes mellitus (T2DM), insulin resistance (IR). In recent years, gut microbiota has received extensive attention as an important regulatory part involved in host diseases and health status. A growing body of evidence suggests that gut microbiota dysbiosis has a significant adverse effect on the host. Small intestinal bacterial overgrowth (SIBO), a type of intestinal microbial dysbiosis, has been gradually revealed to be associated with obesity and its related diseases. The presence of SIBO may lead to the destruction of intestinal barrier integrity, increased intestinal permeability, increased endotoxin levels, activation of inflammatory responses, and translocation of bacteria from the colon to the small intestine. However, the causal relationship between SIBO and obesity and the specific mechanisms have not been well elucidated. This review discusses the cross-talk between SIBO and obesity and its related diseases, and expounds its potential mechanisms and interventions, which may help to discover new therapeutic targets for obesity and its related diseases and develop treatment options.

17β-Estradiol Suppresses Gastric Inflammatory and Apoptotic Stress Responses and Restores nNOS-Mediated Gastric Emptying in Streptozotocin (STZ)-Induced Diabetic Female Mice

Gastroparesis (Gp) is a severe complication of diabetes mellitus (DM) observed predominantly in women. It is characterized by abnormal gastric emptying (GE) without mechanical obstruction in the stomach. Nitric oxide (NO) is an inhibitory neurotransmitter produced by neuronal nitric oxide synthase (nNOS). It plays a critical role in gastrointestinal (GI) motility and stomach emptying. Here, we wanted to demonstrate the protective effects of supplemental 17β-estradiol (E2) on NO-mediated gastric function. We showed E2 supplementation to alleviate oxidative and inflammatory stress in streptozotocin (STZ)-induced diabetic female mice. Our findings suggest that daily administration of E2 at therapeutic doses is beneficial for metabolic homeostasis. This restoration occurs via regulating and modulating the expression/function of glycogen synthase kinase-3β (GSK-3β), nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), Phase II enzymes, MAPK- and nuclear factor kappa-light-chain-enhancer of activated B cells (NFkB)-mediated inflammatory cytokines (IL-1β, IL-6, TNFα, IGF-1), and gastric apoptotic regulators. We also showed E2 supplementation to elevate GCH-1 protein levels in female diabetic mice. Since GCH-1 facilitates the production of tetrahydrobiopterin (BH4, cofactor for nNOS), an increase in GCH-1 protein levels in diabetic mice may improve their GE and nitrergic function. Our findings provide new insights into the impact of estrogen on gastric oxidative stress and intracellular inflammatory cascades in the context of Gp.

P2X7 receptor antagonist improves gastrointestinal disorders in spontaneously hypertensive rats

The purinergic system participates in the control of blood pressure. Hypertension promotes the occurrence of gastrointestinal disorders such as intestinal inflammation and gastric emptying delay. This study aimed i) to investigate the participation of the P2X7 receptor blocker Brilliant Blue G (BBG) on gastric emptying of solids and changes in oxidative stress in the gastric fundus, duodenum, and colon of spontaneously hypertensive rats (SHR) and ii) to study the putative relationship of this effect with the renin-angiotensin system. Rats were divided into five groups: Control, SHR, SHR+BBG, SHR+BBG+ATP, and SHR+BBG+ANG II. In the gastrointestinal tract, we assessed gastric emptying (GE) and oxidative stress markers (NOx, MPO, GSH, SOD). We observed a decrease in the GE rate (P<0.05) in SHR vs control rats (21.8±2.0% vs 42.8±3.5%). The decrease in GE was returned (P<0.05) to control levels by BBG in SHR rats (21.8±2.0% vs 41.6±3.2%). Co-administration of ATP or ANG II together with BBG bypassed the effect of the P2X7 antagonist on GE in SHR (P<0.05) (21.9±5.0% vs 25.6±3.0% vs 41.6±3.2%). The MPO activity increased (P<0.05) in the gastric fundus of SHR compared to control rats (6.12±2.26 vs 0.077±0.02 UMPO/mg tissue); this effect was prevented (P<0.05) by BBG (0.55±0.15 vs 6.12±2.26 UMPO/mg tissue). Data demonstrated that blockage of P2X7 receptors with BBG can improve the GE delay and oxidative stress biomarkers in SHR animals. This preventive effect of BBG on GE delay was abrogated by ANG II and ATP, thus prompting crosstalk between renin-angiotensin and the purinergic signaling systems underlying this phenomenon.

Mechanisms of Chemotherapy-Induced Neurotoxicity

Since the first clinical trials conducted after World War II, chemotherapeutic drugs have been extensively used in the clinic as the main cancer treatment either alone or as an adjuvant therapy before and after surgery. Although the use of chemotherapeutic drugs improved the survival of cancer patients, these drugs are notorious for causing many severe side effects that significantly reduce the efficacy of anti-cancer treatment and patients’ quality of life. Many widely used chemotherapy drugs including platinum-based agents, taxanes, vinca alkaloids, proteasome inhibitors, and thalidomide analogs may cause direct and indirect neurotoxicity. In this review we discuss the main effects of chemotherapy on the peripheral and central nervous systems, including neuropathic pain, chemobrain, enteric neuropathy, as well as nausea and emesis. Understanding mechanisms involved in chemotherapy-induced neurotoxicity is crucial for the development of drugs that can protect the nervous system, reduce symptoms experienced by millions of patients, and improve the outcome of the treatment and patients’ quality of life.

New Advances on Pathophysiology of Diabetes Neuropathy and Pain Management: Potential Role of Melatonin and DPP-4 Inhibitors

Pre-diabetes and diabetes are growing threats to the modern world. Diabetes mellitus (DM) is associated with comorbidities such as hypertension (83.40%), obesity (90.49%), and dyslipidemia (93.43%), creating a substantial burden on patients and society. Reductive and oxidative (Redox) stress level imbalance and inflammation play an important role in DM progression. Various therapeutics have been investigated to treat these neuronal complications. Melatonin and dipeptidyl peptidase IV inhibitors (DPP-4i) are known to possess powerful antioxidant and anti-inflammatory properties and have garnered significant attention in the recent years. In this present review article, we have reviewed the recently published reports on the therapeutic efficiency of melatonin and DPP-4i in the treatment of DM. We summarized the efficacy of melatonin and DPP-4i in DM and associated complications of diabetic neuropathy (DNP) and neuropathic pain. Furthermore, we discussed the mechanisms of action and their efficacy in the alleviation of oxidative stress in DM.

The prevalence of small intestinal bacterial overgrowth in diabetes mellitus: a systematic review and meta-analysis

OBJECTIVE

We conducted this systematic review and meta-analysis to estimate the prevalence of SIBO in diabetic patients and to determine the association between SIBO and diabetes.

METHODS

A comprehensive literature search of the PubMed, Cochrane Library and EMBASE databases from inception to June 2021 was conducted for studies correlating SIBO with diabetes. Studies were screened, and relevant data were extracted and analysed. The pooled prevalence of SIBO among diabetic patients and the odds ratio of SIBO among diabetic patients compared with controls were calculated.

RESULTS

Fourteen studies including 1417 diabetic patients and 649 controls met the inclusion criteria. The pooled prevalence of SIBO in diabetes was 29% (95% CI 20-39%). The odds ratio of SIBO in diabetic patients was 2.91 (95% CI 0.82-10.32, p=0.1) compared with controls. Subgroup analyses showed that the prevalence of SIBO in diabetes was higher in studies using jejunal aspirate culture for diagnosis (39%, 95% CI 12-66%) than in those using the lactulose breath test (31%, 95% CI 18-43%) or glucose breath test (29%, 95% CI 14-43%). The prevalence of SIBO in diabetes was higher in studies conducted in Western countries (35%, 95% CI 21-49%) than in those conducted in Eastern countries (24%, 95% CI 14-34%), and the prevalence of SIBO in type 1 diabetes (25%, 95% CI 14%-36%) was not significantly different from that in type 2 diabetes (30%, 95% CI 13%-47%).

CONCLUSIONS

Twenty-nine percent of diabetic patients tested positive for SIBO, and the risk of SIBO in diabetic patients was 2.91 times higher than that in patients without diabetes. Diabetes could be a predisposing factor for the development of SIBO, especially among patients diagnosed by jejunal aspirate culture or those in Western populations.

Diurnal efficacy of alpha-lipoic acid/nifedipine/glimepiride combination mitigates diabetic neuropathies in rats

OBJECTIVES

Time-dependent effects of alpha-lipoic acid/nifedipine/glimepiride combination on diabetic neuropathies were investigated in rats. 7 groups (N=9) of rats were used.

MATERIALS AND METHODS

First and second groups were apparently normal and diabetic rats respectively, and were administered 1 mL/kg distilled water. The rest of the groups were diabetic and administered 10 mg/kg glimepiride at night-time (8:00 pm). Groups 4-7 were administered additional 20 mg/kg nifedipine at morning-time (8:00 am), while groups 5-7 were also administered 100 mg/kg alpha-lipoic acid (ALA) in the morning, afternoon and night-time respectively (8:00 am, 2:00 pm and 8:00 pm). During the 28 days of oral treatment, paw pressure, tail immersion and motor coordination tests were conducted. The rats were euthanized on the 29^th day after a charcoal meal. The small intestines were excised to determine intestinal transit while the brain was collected, homogenised and used to determine levels of oxidative stress.

RESULTS

Data show that treatment with ALA at 8:00 am or 2:00 pm significantly (p ≤ 0.01) produced a delay in the onset and improved prognosis of neuropathies. Treatment with ALA at 8:00 pm prevented manifestation of neuropathies throughout the study with positive antioxidant effects.

CONCLUSION

Time-dependent ALA treatment in combination with nifedipine and glimepiride should be studied in humans with an approximately similar circadian timing. This may provide additional clinical therapeutic options for diabetic neuropathies.

An endophytic Schizophyllum commune Fr. exhibits in-vitro and in-vivo antidiabetic activity in streptozotocin induced diabetic rats

The present study aimed at isolation of endophytic basidiomycetous fungi and evaluation of their in-vitro and in-vivo antidiabetic potential. Preliminary screening for in-vitro activity was carried out using α-glucosidase inhibition assay. An endophytic isolate Sch1 (isolated from Aloe vera), identified to be Schizophyllum commune Fr. on molecular basis, exhibiting more than 90% α-glucosidase inhibitiory activity was selected for further studies. Detailed in-vivo investigations for antidiabetic potential of ethyl acetate extract of S. commune (Sch1), at two different doses, were carried out in streptozotocin induced diabetic Wistar rats. Treatment of diabetic rats with S. commune extract caused significant decrease in blood glucose level and increase in body weight after 14 days experimental period. It significantly restored renal parameters including creatinine, blood urea nitrogen, fractional excretion of sodium, and potassium level in diabetic rats. Improvement in lipid profile and level of antioxidant parameters viz. reduced glutathione, thiobarbituric acid reactive species, and superoxide anion generation was also observed after treatment. Liver enzymes (serum glutamic pyruvic transaminase, serum glutamic-oxaloacetic transaminases, and alkaline phosphatase) homeostasis was found to be markedly improved in diabetic rats administered with S. commune extract. The effects were more pronounced at higher concentration and comparable to acarbose which was used as positive control. Phytochemical analysis revealed the presence of phenolics and terpenoids in the ethyl acetate extract. This is the first report highlighting the therapeutic potential of an endophytic S. commune in the management of diabetes.

Inhibition of GSK-3β restores delayed gastric emptying in obesity-induced diabetic female mice

Diabetic gastroparesis (DG) is a clinical syndrome characterized by delayed gastric emptying (DGE). Loss of nuclear factor erythroid 2-related factor 2 (Nrf2) is associated with reduced neuronal nitric oxide synthase-α (nNOSα)-mediated gastric motility and DGE. Previous studies have shown that nuclear exclusion and inactivation of Nrf2 is partly regulated by glycogen synthase kinase 3β (GSK-3β). In the current study, the molecular signaling of GSK-3β-mediated Nrf2 activation and its mechanistic role on DG were investigated in high-fat diet (HFD)-induced obese/Type 2 diabetes (T2D) female mice. Adult female C57BL/6J mice were fed with HFD or normal diet (ND) with or without GSK-3β inhibitor (SB 216763, 10 mg/kg body wt ip) start from the 14th wk and continued feeding mice for an additional 3-wk time period. Our results show that treatment with GSK-3β inhibitor SB attenuated DGE in obese/T2D mice. Treatment with SB restored impaired gastric 1) Nrf2 and phase II antioxidant enzymes through PI3K/ERK/AKT-mediated pathway, 2) tetrahydrobiopterin (BH₄, cofactor of nNOS) biosynthesis enzyme dihydrofolate reductase, and 3) nNOSα dimerization in obese/T2 diabetic female mice. SB treatment normalized caspase 3 activity and downstream GSK-3β signaling in the gastric tissues of the obese/T2 diabetic female mice. In addition, GSK-3β inhibitor restored impaired nitrergic relaxation in hyperglycemic conditions. Finally, SB treatment reduced GSK3 marker, pTau in adult primary enteric neuronal cells. These findings emphasize the importance of GSK-3β on regulating gastric Nrf2 and nitrergic mediated gastric emptying in obese/diabetic rodents.NEW & NOTEWORTHY Inhibition of glycogen synthase kinase 3β (GSK-3β) with SB 216763 attenuates delayed gastric emptying through gastric nuclear factor erythroid 2-related factor 2 (Nrf2)-phase II enzymes in high-fat diet-fed female mice. SB 216763 restored impaired gastric PI3K/AKT/ β-catenin/caspase 3 expression. Inhibition of GSK-3β normalized gastric dihydrofolate reductase, neuronal nitric oxide synthase-α expression, dimerization and nitrergic relaxation. SB 216763 normalized both serum estrogen and nitrate levels in female obese/Type 2 diabetes mice. SB 216763 reduced downstream signaling of GSK-3β in enteric neuronal cells in vitro.

Supplementation of 17β-Estradiol Normalizes Rapid Gastric Emptying by Restoring Impaired Nrf2 and nNOS Function in Obesity-Induced Diabetic Ovariectomized Mice

Gastroparesis (Gp) is a multifactorial condition commonly observed in females and is characterized by delayed or rapid gastric emptying (GE). The role of ovarian hormones on GE in the pathogenesis of obesity induced type 2 diabetes mellitus (T2DM) is completely unknown. The aims of our study are to investigate whether supplementation of 17β-estradiol (E2) or progesterone (P4) restores impaired nuclear factor erythroid 2-related factor 2 (Nrf2, an oxidative stress-responsive transcription factor) and nitric oxide (NO)-mediated gastric motility in ovariectomized (OVX) mice consuming a high-fat diet (HFD, a model of T2DM). Groups of OVX+HFD mice were administered daily subcutaneous doses of either E2 or P4 for 12 weeks. The effects of E2 and P4 on body weight, metabolic homeostasis, solid GE, gastric antrum NO-mediated relaxation, total nitrite levels, neuronal nitric oxide synthase (nNOSα), and its cofactor expression levels were assessed in OVX+HFD mice. HFD exacerbated hyperglycemia and insulinemia while accelerating GE (p < 0.05) in OVX mice. Exogenous E2, but not P4, attenuated rapid gastric emptying and restored gastric nitrergic relaxation, total nitrite levels, nNOSα, and cofactor expression via normalizing Nrf2-Phase II enzymes, inflammatory response, and mitogen-activated protein kinase (MAPK) protein expression in OVX+HFD mice. We conclude that E2 is beneficial in normalizing metabolic homeostasis and gastric emptying in obese, diabetic OVX mice consuming a fat-rich diet.

Oxidative stress and inflammatory markers in type 2 diabetic patients

BACKGROUND

Type 2 diabetes mellitus (T2DM) is most demanding public health problem of 21st century. Uncontrolled diabetes may cause complications affecting any part of gut from mouth to rectum presenting as vomiting, nausea, bloating, abdominal pain, constipation and diarrhoea. The aim of this study was to compare levels of oxidative stress and inflammatory markers in small intestinal bacterial overgrowth (SIBO)-positive and negative diabetic patients.

SUBJECTS AND METHODS

An observational analytical study was conducted on 300 T2DM (>5 years' duration) attending Diabetic Clinic. A total of 200 age- and sex-matched healthy individuals were enrolled as controls. Noninvasive glucose hydrogen breath test was used to diagnose SIBO. A total of 5 mL blood was taken. Plasma was used for measurement of inflammatory cytokines (TNF-α, IL-6 and IL-10) by ELISA. Hemolysate was used for measurement of lipid peroxidation, reduced GSH, superoxide dismutase and catalase.

RESULTS

It was observed that constipation was present in 59.6% T2DM patients. SIBO was observed significantly higher (P < .0001) in T2DM patients than controls. Inflammatory and oxidative stress markers were significantly (P < .001) higher in diabetic and SIBO-positive patients than controls and SIBO negative. Reduced GSH was significantly (P < .05) lower whereas superoxide dismutase (SOD) and catalase antioxidant enzymes were significantly (<.05) higher in diabetic and SIBO-positive patients than controls and SIBO-negative patients.

CONCLUSION

From this study, it could be concluded that SIBO in T2DM patients can cause oxidative stress and inflammation. Therefore, SIBO should be taken care to prevent further damage to intestine.

Isolation and hypoglycemic effects of water extracts from mulberry leaves in Northeast China

Diabetes is the main chronic disease that greatly affects human life.

Constipation in chronic kidney disease: it is time to reconsider

Constipation is highly prevalent in patients with chronic kidney disease (CKD) and is primarily characterized by decreased intestinal motility. This chronic disorder affects the quality of life of patients. However, nephrologist and dialysis clinicians have long had a disproportionately limited understanding of constipation. Accumulating evidence has revealed a relationship between constipation and cardiovascular disease and CKD. The pathogenesis of constipation in CKD patients is multifactorial: decreased physical activity, comorbidities affecting bowel movement, such as diabetes mellitus, cerebrovascular disease, and hyperparathyroidism, a restricted dietary intake of plant-based fiber-rich foods, and multiple medications, including phosphate binders and potassium-binding resins, have all been implicated. CKD is associated with alterations in the composition and function of the gut microbiota, so-called gut dysbiosis. Recent studies showed that CKD-related gut dysbiosis decreased intestinal motility via intestinal inflammation or the increased generation of gut-derived uremic toxins, such as indoxyl sulfate and p-cresyl sulfate. Furthermore, the gastrointestinal secretion of mucin was found to be decreased in CKD animal models, which may delay colonic transit by diminished lubrication in the alimentary tract. Thus, CKD-related gut dysbiosis may play a role in constipation, but limited information is currently available. Since constipation is often intractable, particularly in CKD patients, every available means needs to be employed in its treatment. The effects of probiotics, prebiotics, and synbiotics on the composition of the gut microbiota and gut-derived uremic toxins have been increasingly reported. However, their effects on stool consistency or frequency in CKD patients remain unclear. Some laxatives may be beneficial for improving not only bowel habits but also gut dysbiosis. Further studies are required to elucidate the CKD-specific pathogenesis of constipation and develop novel effective treatment options.

Genetic variability of inflammation and oxidative stress genes does not play a major role in the occurrence of adverse events of dopaminergic treatment in Parkinson's disease

BACKGROUND

Inflammation and oxidative stress are recognized as important contributors to Parkinson's disease pathogenesis. As such, genetic variability in these pathways could have a role in susceptibility for the disease as well as in the treatment outcome. Dopaminergic treatment is effective in management of motor symptoms, but poses a risk for motor and non-motor adverse events. Our aim was to evaluate the impact of selected single-nucleotide polymorphisms in genes involved in inflammation and oxidative stress on Parkinson's disease susceptibility and the occurrence of adverse events of dopaminergic treatment.

METHODS

In total, 224 patients were enrolled, and their demographic and clinical data on the disease course were collected. Furthermore, a control group of 146 healthy Slovenian blood donors were included for Parkinson's disease' risk evaluation. Peripheral blood was obtained for DNA isolation. Genotyping was performed for NLRP3 rs35829419, CARD8 rs2043211, IL1β rs16944, IL1β rs1143623, IL6 rs1800795, CAT rs1001179, CAT rs10836235, SOD2 rs4880, NOS1 rs2293054, NOS1 rs2682826, TNF-α rs1800629, and GPX1 rs1050450. Logistic regression was used for analysis of possible associations.

RESULTS

We observed a nominally significant association of the IL1β rs1143623 C allele with the risk for Parkinson's disease (OR = 0.59; 95%CI = 0.38-0.92, p = 0.021). CAT rs1001179 A allele was significantly associated with peripheral edema (OR = 0.32; 95%CI = 0.15-0.68; p = 0.003). Other associations observed were only nominally significant after adjustments: NOS1 rs2682826 A allele and excessive daytime sleepiness and sleep attacks (OR = 1.75; 95%CI = 1.00-3.06, p = 0.048), SOD2 rs4880 T allele and nausea/vomiting (OR = 0.49, 95%CI = 0.25-0.94; p = 0.031), IL1β rs1143623 C allele and orthostatic hypotension (OR = 0.57, 95%CI = 0.32-1.00, p = 0.050), and NOS1 rs2682826 A allele and impulse control disorders (OR = 2.59; 95%CI = 1.09-6.19; p = 0.032). We did not find any associations between selected polymorphisms and motor adverse events.

CONCLUSIONS

Apart from some nominally significant associations, one significant association between CAT genetic variability and peripheral edema was observed as well. Therefore, the results of our study suggest some links between genetic variability in inflammation- and oxidative stress-related pathways and non-motor adverse events of dopaminergic treatment. However, the investigated polymorphisms do not play a major role in the occurrence of the disease and the adverse events of dopaminergic treatment.

The Role of Glucagon-Like Peptide-1 in Energy Homeostasis

Energy homeostasis is coordinated by bidirectional communication pathways between the brain and peripheral organs, including adipose tissue, muscle, the pancreas, liver, and gut. Disruption of the integrated chemical, hormonal, and neuronal signals that constitute the gut-brain axis significantly contributes to disorders of metabolism and body weight. Initial studies of glucagon-like peptide-1 (GLP-1), a gut hormone released in response to the ingestion of nutrients, focused on its incretin actions to improve postprandial glucose homeostasis by enhancing meal-induced insulin secretion. However, GLP-1 is also a key player in the gut-brain regulatory axis with multiple effects on appetite and energy metabolism outside of its peripheral glucoregulatory actions. In this review, we explore the function of GLP-1 as a component of the gut-brain axis in the regulation of energy homeostasis, and consider the implications of this role for the development of therapeutic treatment options for obesity.

Diabetic gastroparesis: current challenges and future prospects

Diabetic gastroparesis (DMGP) is a condition of delayed gastric emptying after gastric outlet obstruction has been excluded. Symptoms of nausea, vomiting, early satiety, bloating, and abdominal pain are associated with DMGP. Uncontrolled symptoms can lead to overall poor quality of life and financial burdens on the healthcare system. A combination of antiemetics and prokinetics is used in symptom control; metoclopramide is the main prokinetic available for clinical use and is the only U.S. Food and Drug Administration-approved agent in the United States. However, a black box warning in 2009 reporting its association with tardive dyskinesia and recommending caution in chronically using this agent beyond 3 months has decreased its role in clinical practice. There is an unmet need for new prokinetics with good efficacy and safety profiles. Currently, there are several new drugs with different mechanisms of action in the pipeline that are under investigation and show promising preliminary results. Surgically combining gastric electrical stimulation with pyloroplasty is considered "gold" standard. Advances in therapeutic endoscopic intervention with gastric per-oral endoscopic pyloromyotomy have also been shown to improve gastric emptying and gastroparesis (GP) symptoms. In this review, we will comment on the challenges encountered when managing patients with DMGP and provide an update on advances in drug development and endoscopic and surgical interventions.

Acupuncture relieves motion sickness via the IRβ-ERK1/2-dependent insulin receptor signalling pathway

OBJECTIVE

Acupuncture has been widely used for the treatment of motion sickness (MS), but the underlying mechanisms are unclear. The aim of this research was to study the mechanism of acupuncture in the treatment of MS.

METHODS

To observe the effects of acupuncture in the treatment of MS, 80 rats were randomised into five groups that were subjected to acceleration and either remained untreated (CTRL), or received restraint (REST), scopolamine (SCOP) or acupuncture at SP4 (sham) or PC6+ST36 (verum) acupuncture points. To study the mechanism underlying the effects of acupuncture in the treatment of MS, 48 rats were randomised into three groups: acupuncture+extracellular regulated protein kinases (ERK) 1/2 inhibitor (ERKinh), acupuncture+insulin receptor (IR) antagonist (IRant), and acupuncture+vehicle (VEH). After acceleration, the MS index (MSI) and spontaneous activity (SA) of the rats were recorded. Serum stress hormones, Fos-positive cells, c-fos mRNA in the vestibular nucleus, and IRβ-, p-IRβ-, ERK1/2- and p-ERK1/2-positive cells in the dorsal motor nucleus of the vagus nerve (DMV) were detected.

RESULTS

After acceleration, MS symptoms in the PC6+ST36 and SCOP groups were reduced compared with the CTRL, REST, and SP4 groups. The number of p-IRβ- and p-ERK1/2-positive cells and insulin levels were higher in the PC6+ST36 group than in the CTRL, REST, and SP4 groups. After ERK1/2 inhibitor and IR antagonist treatment, MS symptoms in the VEH group were lower than in the ERKinh and IRant groups.

CONCLUSIONS

Our study demonstrates that acupuncture significantly alleviates MS through the IRβ-ERK1/2-dependent insulin receptor signalling pathway in the DMV.

Daily intake of broccoli sprouts normalizes bowel habits in human healthy subjects

Chronic oxidative stress impairs regular defecation. Sulforaphane (SFN) enhances anti-oxidant systems, ameliorating oxidative injury. SFN inhibits overgrowth of anaerobic microflora and protects small intestine from oxidative injury. We assessed whether daily intake of SFN-rich broccoli sprouts (BS) improves defecation in humans. Forty-eight subjects, with a constipation scoring system (CSS) >2 points, were assigned to either the BS group (n = 24) or the alfalfa sprouts (AS) group (n = 24), and were requested to eat 20 g daily of raw BS or AS, respectively, for 4 weeks. BS contains 4.4 mg/g sulforaphane glucosinolates (SGS), while AS contains no SGS. CSS-based questionnaires were performed to evaluate bowel habit. Stool samples were collected to evaluate intestinal microflora using a terminal restriction fragment length polymorphism flora analysis. Intervention with BS, but not AS, caused a significant decrease in the duration of attempted defecation and the total CSS score. Intervention with BS decreased the percentage of Bifidobacterium in the stool. These results suggest that daily intake of BS improves bowel habit in human subjects. Since BS treatment enhance antioxidant enzyme activities, these effects of BS appear to relate with the SFN-mediated modulation of the intestinal motility during exposure to oxidative stress. (UMIN Clinical Trial Registration Number: UMIN-000021207).

Vitamin C Improves Gastroparesis in Diabetic Rats: Effects on Gastric Contractile Responses and Oxidative Stress

BACKGROUND

Diabetic gastroparesis is a common complication of diabetes mellitus, which mainly affects women. Previous studies have demonstrated that oxidative stress is involved in its onset and development.

AIMS

This study evaluated the role of vitamin C on diabetes-associated gastric dysmotility.

METHODS

Female rats with streptozotocin-induced diabetes were treated with vehicle (water, 1 mL/kg, p.o.), vitamin C (300 mg/kg/day, p.o.), or insulin (6 IU/day, s.c.). Gastric emptying, in vitro gastric contractility, and biochemistry parameters were analyzed at the end of the treatment (i.e. 8 weeks after the diabetes induction).

RESULTS

Vitamin C reversed the delayed gastric emptying of diabetic rats to normal levels, and avoided the changes in the contractile responses to acetylcholine (0.1 nM-1 µM), but not to 5-hydroxytryptamine (0.1 nM-1 µM), in the pylorus and fundus from diabetic rats. Moreover, the contraction evoked by KCl (40 mM) in the fundus, but not in the pylorus, was intensely increased in diabetic rats treated with vitamin C. Notably, the vitamin C reestablished the reduced glutathione levels by 77% and decreased the reactive oxygen species content by 60% in the gastric tissue from diabetic rats. Despite the effects on gastric motility, vitamin C treatment did not change the fasting glycaemia or the glycated hemoglobin of diabetic rats. Unsurprisingly, insulin treatment normalized all parameters evaluated.

CONCLUSIONS

Vitamin C exhibited a remarkable beneficial effect on gastric emptying dysfunction in diabetic rats, which was mediated by attenuation of oxidative stress and maintenance of the cholinergic contractile responses in fundus and pylorus.

Resveratrol alleviates oxidative damage in enteric neurons and associated gastrointestinal dysfunction caused by chemotherapeutic agent oxaliplatin

Oxaliplatin is a first-line chemotherapeutic agent used for the treatment of colorectal cancer. Its use is associated with severe gastrointestinal (GI) side-effects, associated with oxidative damage and neurotoxicity to the enteric neurons. Resveratrol is a potent anti-oxidant that has been shown to protect against oxidative damage and neurotoxicity in other neurons and could therefore prevent oxaliplatin-induced damage to enteric neurons. We determined whether co-administration of resveratrol with oxaliplatin alleviates enteric neuron toxicity and GI dysfunction in mice. Colons were collected for immunohistochemical analysis of myenteric neurons and assessment of motor activity in organ-bath experiments. Morphological damage to the colonic mucosa and muscles was analysed. Oxaliplatin treatment induced translocation of nitrated proteins into the nuclei of myenteric neurons and significant damage to the mucosal lining, vacuolisation and a decrease in muscle thickness. This damage is linked to motor dysfunction due to inhibition of the amplitude of colonic contractions, leading to chronic constipation. Co-treatment with resveratrol prevented oxaliplatin-induced neurotoxicity, alleviated damage to GI mucosa, crypts and muscle layer, resulting in improved contractility and a decrease in constipation. Resveratrol could be integrated as part of a therapeutic regimen to help alleviate oxaliplatin-induced GI dysfunction.

Effects of hemin on heme oxygenase-1, gastric emptying, and symptoms in diabetic gastroparesis

BACKGROUND

Therapeutic options for management of diabetic gastroparesis are limited. Failure to maintain upregulation of heme oxygenase (HO1) leads to loss of interstitial cells of Cajal and delayed gastric emptying (GE) in non-obese diabetic mice. Our hypothesis was that hemin upregulation of HO1 would restore normal GE in humans with gastroparesis.

AIMS

To compare effects of hemin and placebo infusions on HO1 activity and protein, GE, autonomic function, and gastrointestinal symptoms in diabetic gastroparesis.

METHODS

In a single-center, double-blind, placebo-controlled, randomized clinical trial, we compared intravenous hemin, prepared in albumin, or albumin alone (placebo) in 20 patients, aged 41 ± 5 (SEM) years with diabetic gastroparesis. After infusions on days 1, 3, and 7, weekly infusions were administered for 7 additional weeks. Assessments included blood tests for HO1 protein and enzyme activity levels, GE with ¹³ C-spirulina breath test, autonomic functions (baseline and end), and gastrointestinal symptoms every 2 weeks.

KEY RESULTS

Nine of 11 patients randomized to hemin completed all study procedures. Compared to placebo, hemin increased HO1 protein on days 3 (p = 0.0002) and 7 (p = 0.008) and HO1 activity on day 3 (p = 0.0003) but not after. Gastric emptying, autonomic functions, and symptoms did not differ significantly in the hemin group relative to placebo.

CONCLUSIONS & INFERENCES

Hemin failed to sustain increased HO1 levels beyond a week and did not improve GE or symptoms in diabetic gastroparesis. Further studies are necessary to ascertain whether more frequent hemin infusions or other drugs would have a more sustained effect on HO1 and improve GE.

Bowel movement frequency, oxidative stress and disease prevention

The significance of diet for disease prevention has long been recognised. Dietary recommendations have therefore been integrated in health promotion messages. Gastrointestinal functioning is essential for the digestion of nutrients. Oxidative stress has been observed in patients with constipation, as well as in those with colorectal cancer, cardiovascular disease and other chronic illnesses associated with constipation. The coexistence of colorectal neoplasia and coronary artery disease has been incriminated for exposure to common risk factors associated with increased oxidative stress. It was recently demonstrated that bowel movement frequency is inversely associated with cardiovascular mortality. The aim of the present study was to review the relevant literature in light of these findings. It was concluded that suboptimal functioning of the large bowel may contribute to oxidative stress and, therefore, to increased mortality. Bowel movement frequency may represent a simple quantifiable indicator of adequate colonic function and it is dependent on diet, exercise and other lifestyle factors, but also on individual characteristics, including colonic microbiota. Future health promotion actions may improve the prevention of a number of diseases by advocating lifestyle personalisation for assuring optimal intestinal functioning.

High-fat diet-induced obesity alters nitric oxide-mediated neuromuscular transmission and smooth muscle excitability in the mouse distal colon

We tested the hypothesis that colonic enteric neurotransmission and smooth muscle cell (SMC) function are altered in mice fed a high-fat diet (HFD). We used wild-type (WT) mice and mice lacking the β1-subunit of the BK channel (BKβ1 (-/-)). WT mice fed a HFD had increased myenteric plexus oxidative stress, a 28% decrease in nitrergic neurons, and a 20% decrease in basal nitric oxide (NO) levels. Circular muscle inhibitory junction potentials (IJPs) were reduced in HFD WT mice. The NO synthase inhibitor nitro-l-arginine (NLA) was less effective at inhibiting relaxations in HFD compared with control diet (CD) WT mice (11 vs. 37%, P < 0.05). SMCs from HFD WT mice had depolarized membrane potentials (-47 ± 2 mV) and continuous action potential firing compared with CD WT mice (-53 ± 2 mV, P < 0.05), which showed rhythmic firing. SMCs from HFD or CD fed BKβ1 (-/-) mice fired action potentials continuously. NLA depolarized membrane potential and caused continuous firing only in SMCs from CD WT mice. Sodium nitroprusside (NO donor) hyperpolarized membrane potential and changed continuous to rhythmic action potential firing in SMCs from HFD WT and BKβ1 (-/-) mice. Migrating motor complexes were disrupted in colons from BKβ1 (-/-) mice and HFD WT mice. BK channel α-subunit protein and β1-subunit mRNA expression were similar in CD and HFD WT mice. We conclude that HFD-induced obesity disrupts inhibitory neuromuscular transmission, SMC excitability, and colonic motility by promoting oxidative stress, loss of nitrergic neurons, and SMC BK channel dysfunction.

Differential effects in CGRPergic, nitrergic, and VIPergic myenteric innervation in diabetic rats supplemented with 2% L-glutamine

ABSTRACT The objective of this study was to investigate the effects of 2% L-glutamine supplementation on myenteric innervation in the ileum of diabetic rats, grouped as follows: normoglycemic (N); normoglycemic supplemented with L-glutamine (NG); diabetic (D); and diabetic supplemented with L-glutamine (DG). The ileums were subjected to immunohistochemical techniques to localize neurons immunoreactive to HuC/D protein (HuC/D-IR) and neuronal nitric oxide synthase enzyme (nNOS-IR) and to analyze varicosities immunoreactive to vasoactive intestinal polypeptide (VIP-IR) and calcitonin gene-related peptide (CGRP-IR). L-Glutamine in the DG group (i) prevented the increase in the cell body area of nNOS-IR neurons, (ii) prevented the increase in the area of VIP-IR varicosities, (iii) did not prevent the loss of HuC/D-IR and nNOS-IR neurons per ganglion, and (iv) reduced the size of CGRP-IR varicosities. L-Glutamine in the NG group reduced (i) the number of HuC/D-IR and nNOS-IR neurons per ganglion, (ii) the cell body area of nNOS-IR neurons, and (iii) the size of VIP-IR and CGRP-IR varicosities. 2% L-glutamine supplementation exerted differential neuroprotective effects in experimental diabetes neuropathy that depended on the type of neurotransmitter analyzed. However, the effects of this dose of L-glutamine on normoglycemic animals suggests there are additional actions of this beyond its antioxidant capacity.

The effect of low or high molecular weight oat beta-glucans on the inflammatory and oxidative stress status in the colon of rats with LPS-induced enteritis

PURPOSE

The aim of the study was to investigate the protective effect of low and high molecular weight beta-glucans on the chosen immunological parameters, markers of antioxidative potential in rats' colon tissue, the number of lactic acid bacteria (LAB) and the concentration of short-chain fatty acids (SCFA) in rats' faeces.

METHODS

The experiment was carried out on 72 8-week old male Sprague-Dawley rats: control (n = 36) and experimental (n = 36). In half of the animals from each group enteritis was induced by LPS (10 mg kg(-1)). Rats from the experimental group were divided into two groups receiving high (GI) or low (GII) molecular weight beta-glucans for 6 consecutive weeks.

RESULTS

LPS evoked enteritis in all the treated animals, manifested by changes in the levels of IL-10, IL-12 and TNF-alpha, as well as in the number of intraepithelial lymphocytes (IELs) and lamina propria lymphocytes (LPLs) in the colon tissue. Dietary supplementation with beta-glucans following LPS treatment partially reversed this effect. The changes in SCFA concentration were noted, indicating an improvement of the fermentation process in the colon. This effect coincided with an increased number of LAB, pointing at the prebiotic properties of beta-glucans. The positive influence of beta-glucans was also manifested by the improved values of antioxidative potential markers (TAS, SOD, GR and GPx activity, TBARS concentration), noted especially in rats with LPS-induced enteritis. This influence was more pronounced in the case of low molecular weight oat beta-glucan (GII).

CONCLUSIONS

The present study showed a positive effect of beta-glucans, especially the low molecular weight form, on the colon tissue of healthy rats, as well as animals with LPS-induced enteritis.

Novel insights into the effects of diabetes on gastric motility

Recent data from the Diabetes Control and Complications Trial/Epidemiology of Diabetic Interventions and Complications cohort indicate that the disease burden of gastroparesis in diabetes remains high, consistent with the outcome of cross-sectional studies in type 1 and 2 diabetes. An improved understanding of the pathogenesis of diabetic gastroparesis at the cellular level has emerged in the last decade, particularly as a result of initiatives such as the National Institute of Health funded Gastroparesis Clinical Research Consortium in the US. Management of diabetic gastroparesis involves dietary and psychological support, attention to glycaemic control, and the use of prokinetic agents. Given that the relationship between upper gastrointestinal symptoms and the rate of gastric emptying is weak, therapies targeted specifically at symptoms, such as nausea or pain, are important. The relationship between gastric emptying and postprandial glycaemia is complex and inter-dependent. Short-acting glucagon-like peptide-1 agonists, that slow gastric emptying, can be used to reduce postprandial glycaemic excursions and, in combination with basal insulin, result in substantial reductions in glycated haemoglobin in type 2 patients.

Epigenetic effects of casein-derived opioid peptides in SH-SY5Y human neuroblastoma cells

Background

Casein-free, gluten-free diets have been reported to mitigate some of the inflammatory gastrointestinal and behavioral traits associated with autism, but the mechanism for this palliative effect has not been elucidated. We recently showed that the opioid peptide beta-casomorphin-7, derived from bovine (bBCM7) milk, decreases cysteine uptake, lowers levels of the antioxidant glutathione (GSH) and decreases the methyl donor S-adenosylmethionine (SAM) in both Caco-2 human GI epithelial cells and SH-SY5Y human neuroblastoma cells. While human breast milk can also release a similar peptide (hBCM-7), the bBCM7 and hBCM-7 vary greatly in potency; as the bBCM-7 is highly potent and similar to morphine in it's effects. Since SAM is required for DNA methylation, we wanted to further investigate the epigenetic effects of these food-derived opioid peptides. In the current study the main objective was to characterize functional pathways and key genes responding to DNA methylation effects of food-derived opioid peptides.

Methods

SH-SY5Y neuroblastoma cells were treated with 1 μM hBCM7 and bBCM7 and RNA and DNA were isolated after 4 h with or without treatment. Transcriptional changes were assessed using a microarray approach and CpG methylation status was analyzed at 450,000 CpG sites. Functional implications from both endpoints were evaluated via Ingenuity Pathway Analysis 4.0 and KEGG pathway analysis was performed to identify biological interactions between transcripts that were significantly altered at DNA methylation or transcriptional levels (p < 0.05, FDR <0.1).

Results

Here we show that hBCM7 and bBCM7, as well as morphine, cause epigenetic changes affecting gene pathways related to gastrointestinal disease and inflammation. These epigenetic consequences exhibited the same potency order as opiate inhibition of cysteine uptake insofar as hBCM7 was less potent than bBCM7, which was less potent than morphine.

Conclusion

Our findings indicate that epigenetic effects of milk-derived opiate peptides may contribute to GI dysfunction and inflammation in sensitive individuals. While the current study was performed using SH-SY5Y neuronal cellular models, similar actions on other cells types might combine to cause symptoms of intolerance. These actions may provide a potential contributing mechanism for the beneficial effects of a casein-free diet in alleviating gastrointestinal symptoms in neurological conditions including autism and other conditions. Lastly, our study also contributes to the evolving awareness of a “gut-brain connection”.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-015-0050-1) contains supplementary material, which is available to authorized users.

Role of estrogen in diabetic gastroparesis

Gastroparesis is a highly prevalent chronic disorder of the stomach, which is characterized by delayed gastric emptying and accompanied by a series of upper gastrointestinal symptoms. Diabetic gastroparesis (DGP) is one of the severe complications of diabetes, seriously affecting the patient's quality of life. At present, the pathogenesis of DGP is still unclear. The majority of DGP patients are women, and women's symptoms change with the fluctuation of the level of estrogen. Therefore, we speculate that estrogen may play an vital role in the stomach motility. Gastric emptying is an objective index for the diagnosis of gastroparesis. This article reviews the role of estrogen in DGP and the possible mechanisms.

Establishment and evaluation of animal models of diabetic gastroparesis

The incidence of diabetic gastrointestinal disease, one of the most common complication of diabetes, is growing in recent years. Establishing an adequate animal model of diabetic gastrointestinal disease could effectively lay a solid foundation for the exploration of its mechanism and treatment. The rate of gastric emptying in diabetic gastrointestinal disease varies from acceleration to deceleration in different stages, and there is a lack of objective indicators to evaluate it. The establishment and evaluation of animals with diabetic gastrointestinal disease is still in the exploration stage. In this paper we summarize the establishment and evaluation of animal models of diabetic gastrointestinal disease. We compare the advantages and disadvantages of these animal models, in order to provide a reference for further study and treatment of this disease.

Influence of cinaciguat on gastrointestinal motility in apo-sGC mice

BACKGROUND

Cinaciguat (BAY 58-2667), an NO- and heme-independent sGC activator, was shown to be more effective when the heme-group of sGC is oxidized in vascular tissue. In apo-sGC mice (sGCβ1 (His105Phe) knockin) both sGC isoforms (sGCα1 β1 and sGCα2 β1 ) are heme-deficient and can no longer be activated by NO; these mice, showing decreased gastrointestinal nitrergic relaxation and decreased gastric emptying, can be considered as a model to study the consequence of heme-oxidation in sGC. Our aim was to compare the influence of cinaciguat, on in vitro muscle tone of gastrointestinal tissues, and on gastric emptying in WT and apo-sGC mice.

METHODS

Gastrointestinal smooth muscle strips were mounted in organ baths for isometric force recording and cGMP levels were determined by enzyme immunoassay. Protein levels of sGC subunits were assessed by immunoblotting. Gastric emptying was determined by phenol red recovery.

KEY RESULTS

Although protein levels of the sGC subunits were lower in gastrointestinal tissues of apo-sGC mice, cinaciguat induced concentration-dependent relaxations and increased cGMP levels in apo-sGC fundus and colon to a similar or greater extent than in WT mice. The sGC inhibitor ODQ increased cinaciguat-induced relaxations and cGMP levels in WT fundus and colon. In apo-sGC antrum, pylorus and jejunum, cinaciguat was not able to induce relaxations. Cinaciguat did not improve delayed gastric emptying in apo-sGC mice.

CONCLUSIONS & INFERENCES

Cinaciguat relaxes the fundus and colon efficiently when sGC is in the heme-free condition; the non-effect of cinaciguat in pylorus explains its inability to improve the delayed gastric emptying in apo-sGC mice.

Diabetic gastrointestinal motility disorders and the role of enteric nervous system: current status and future directions

BACKGROUND

Gastrointestinal manifestations of diabetes are common and a source of significant discomfort and disability. Diabetes affects almost every part of gastrointestinal tract from the esophagus to the rectum and causes a variety of symptoms including heartburn, nausea, vomiting, abdominal pain, diarrhea and constipation. Understanding the underlying mechanisms of diabetic gastroenteropathy is important to guide development of therapies for this common problem. Over recent years, the data regarding the pathophysiology of diabetic gastroenteropathy is expanding. In addition to autonomic neuropathy causing gastrointestinal disturbances the role of enteric nervous system is becoming more evident.

PURPOSE

In this review, we summarize the reported alterations in enteric nervous system including enteric neurons, interstitial cells of Cajal and neurotransmission in diabetic animal models and patients. We also review the possible underlying mechanisms of these alterations, with focus on oxidative stress, growth factors and diabetes induced changes in gastrointestinal smooth muscle. Finally, we will discuss recent advances and potential areas for future research related to diabetes and the ENS such as gut microbiota, micro-RNAs and changes in the microvasculature and endothelial dysfunction.

Impact of the gut microbiota on the development of obesity and type 2 diabetes mellitus

Obesity and its associated disorders are a major public health concern. Although obesity has been mainly related with perturbations of the balance between food intake and energy expenditure, other factors must nevertheless be considered. Recent insight suggests that an altered composition and diversity of gut microbiota could play an important role in the development of metabolic disorders. This review discusses research aimed at understanding the role of gut microbiota in the pathogenesis of obesity and type 2 diabetes mellitus (TDM2). The establishment of gut microbiota is dependent on the type of birth. With effect from this point, gut microbiota remain quite stable, although changes take place between birth and adulthood due to external influences, such as diet, disease and environment. Understand these changes is important to predict diseases and develop therapies. A new theory suggests that gut microbiota contribute to the regulation of energy homeostasis, provoking the development of an impairment in energy homeostasis and causing metabolic diseases, such as insulin resistance or TDM2. The metabolic endotoxemia, modifications in the secretion of incretins and butyrate production might explain the influence of the microbiota in these diseases.

Electroacupuncture regulates apoptosis/proliferation of intramuscular interstitial cells of cajal and restores colonic motility in diabetic constipation rats

Injury of interstitial cells of Cajal (ICC) is associated with gut dysmotility in diabetic rats. We have shown an acceleration of the colonic contractility by electroacupuncture stimulation (EAS). However, little is known about potential roles of EAS on colonic transit and ICC. In this study, we evaluate the effect of EAS on colonic transit and investigate whether apoptosis/proliferation of ICC was involved in regulative effect of EAS on colonic transit. Rats were randomly assigned to normal, diabetic, diabetic-plus-sham stimulation, diabetic-plus-low-frequency stimulation, and diabetic-plus-high-frequency stimulation groups. Bead expulsion test was used for measuring the distal colonic transit. The Kit (ICC marker) was detected by western blot. Apoptotic ICC was detected by terminal dUTP nucleotide end labeling. Proliferating ICC was identified by Kit/Ki67 double immunofluorescent staining on whole mount preparations. Ultrastructure changes of ICC were studied using electron microscopy. Results showed that high-frequency stimulation significantly promoted colonic transit. Low- and high-frequency stimulation markedly rescued intramuscular ICC from apoptosis. Abundant proliferating intramuscular ICC was found in low- and high-frequency stimulation groups. Our results indicate that high-frequency EAS has stimulatory effect on the distal colonic transit, which may be mediated by downregulation of the apoptosis and upregulation of the proliferation of intramuscular ICC.

Opportunities and challenges for gut microbiome studies in the Indian population

The gut microbiome is a complex ecosystem that affects the development, immunological responses and nutritional status of the host. Efforts are being made to unravel the complex interaction between the gut microbiome and host to have a greater understanding about its role in human health. Colonization of the gut by microbes begins at birth, but the succession and composition of the microbial community depends on a number of factors including, but not limited to, the age, diet, genetic composition, gender, geographic location, and health status of an individual. Therefore, inclusion of diverse human subjects in the study of the gut microbiome is indispensable. However, conducting such studies in India presents unique opportunities and challenges. The vast diversity in human genetic composition, dietary habits, and geographic distribution that exists in the Indian population adds to the complexity in understanding the gut microbiome. Gut microbiome-related studies from other parts of the world have reported a possible association of diseases such as obesity and diabetes with the human gut microbiome. In contrast, an in-depth assessment of risk factors associated with altered gut microbiome in such diseases in the Indian population is lacking. Studies including the Indian population may give insights into the association of the gut microbiome with various factors and diseases that may not be possible from studies on western populations. This review briefly discusses the significance of the gut microbiome on human health and the present status of gut microbiome studies in the Indian population. In addition, this review will highlight the unique opportunities and challenges for gut microbiome studies in the Indian population.

Beta-arrestin2 is involved in the increase of distal colonic contraction in diabetic rats

Colonic dysmotility occurs in diabetes and the patients exhibit diarrhea or constipation. The pathogenetic mechanisms underlying colonic dysmotility in diabetic patients remain poorly understood. The effects of β-arrestin2 on colonic contraction in diabetic rats were investigated for the first time. Male SD rats were treated with a single intraperitoneally injected dose of streptozotocin, and those displaying sustained high blood glucose were selected as diabetes mellitus models. Longitudinal muscle strips of the distal colon were prepared to monitor contraction of the colon in vitro. Expression of β-arrestin2 was investigated by Western blot analysis. Anti-β-arrestin2 antibody had no direct effect on the contraction of distal colonic strips in both normal and diabetic rats. Carbachol-induced contractions of distal colonic strips were higher in diabetic rats than in normal rats. Anti-β-arrestin2 antibody partly blocked carbachol-induced increases of distal colonic strips in diabetic rats. The expression level of β-arrestin2 protein in the colon was higher in diabetic rats than in normal rats. These results suggest that β-arrestin2 is involved in the increase of distal colonic contraction in diabetic rats.

Simultaneous quantification of F2-isoprostanes and prostaglandins in human urine by liquid chromatography tandem-mass spectrometry

A specific and sensitive LC-MS/MS method for analysis of F(2)-isoprostanes (F(2)-IsoPs) and prostaglandins (PGs) in urine was developed and validated to examine the levels of F(2)-IsoPs and prostaglandin F(2α) (PGF(2α)), in human urine in patients undergoing cardiac surgery. The rapid extraction for F(2)-IsoPs and PGs from urine was achieved using a polymeric weak anion solid phase extraction cartridge. The base-line separation of 8-iso-PGF(2α), 8-iso-15(R)-PGF(2α), PGF(2α), and 15(R)-PGF(2α) was carried out on a Hydro-RP column (250mm×2.0mm i.d., Phenomenex, CA) using a linear gradient of methanol:acetonitrile (1:1, v/v) in 0.1% formic acid at a flow rate of 0.2mL/min. The method was proved to be accurate and precise for simultaneous quantification of each analyte over a linear dynamic range of 0.05-50ng/mL with correlation coefficients greater than 0.99. The intra-day and inter-day assay precision at the lowest quality control (0.07ng/mL) level were less than 17%. The mean extraction recoveries of F(2)-IsoPs and PGs were in a range of 79-100%. In applications of this method to patients undergoing cardiac surgery, post-surgery urinary concentrations of 8-iso-PGF(2α) increased significantly in patients (n=14) who did not develop acute kidney (AKI) (pre-surgery 0.344±0.039 vs. post-surgery 0.682±0.094ng/mg creatinine, p<0.01), whereas there was no significant change in this isoprostane in the patients (n=4) who developed AKI (pre-surgery 0.298±0.062 vs. post-surgery 0.383±0.117ng/mg creatinine, NS). Therefore, the method is suitable for the analysis of individual F(2)-IsoPs and PGF(2α)'s in both clinical and research studies.

2, 3, 5, 4'-Tetrahydroxystilbene-2-O-beta-D-glucoside improves gastrointestinal motility disorders in STZ-induced diabetic mice

Oxidative stress has recently been considered as a pivotal player in the pathogenesis of diabetic gastrointestinal dysfunction. We therefore investigated the role of 2, 3, 5, 4'-tetrahydroxystilbene-2-O-beta-D-glucoside (THSG) that has a strong anti-oxidant property, in diabetic gastrointestinal dysmotility as well as the underlying protective mechanisms. THSG restored the delayed gastric emptying and the increased intestinal transit in streptozotocin (STZ)-induced diabetic mice. Loss of neuronal nitric oxide synthase (nNOS) expression and impaired nonadrenergic, noncholinergic (NANC) relaxations in diabetic mice were relieved by long-term preventive treatment with THSG. Meanwhile, THSG (10(-7)~10(-4) mol/L) enhanced concentration-dependently NANC relaxations of isolated colons in diabetic mice. Diabetic mice displayed a significant increase in Malondialdehyde (MDA) level and decrease in the activity of glutathione peroxidase (GSH-Px), which were ameliorated by THSG. Inhibition of caspase-3 and activation of ERK phosphorylation related MAPK pathway were involved in prevention of enhanced apoptosis in diabetes afforded by THSG. Moreover, THSG prevented the significant decrease in PPAR-γ and SIRT1 expression in diabetic ileum. Our study indicates that THSG improves diabetic gastrointestinal disorders through activation of MAPK pathway and upregulation of PPAR-γ and SIRT1.

A metagenome-wide association study of gut microbiota in type 2 diabetes

Assessment and characterization of gut microbiota has become a major research area in human disease, including type 2 diabetes, the most prevalent endocrine disease worldwide. To carry out analysis on gut microbial content in patients with type 2 diabetes, we developed a protocol for a metagenome-wide association study (MGWAS) and undertook a two-stage MGWAS based on deep shotgun sequencing of the gut microbial DNA from 345 Chinese individuals. We identified and validated approximately 60,000 type-2-diabetes-associated markers and established the concept of a metagenomic linkage group, enabling taxonomic species-level analyses. MGWAS analysis showed that patients with type 2 diabetes were characterized by a moderate degree of gut microbial dysbiosis, a decrease in the abundance of some universal butyrate-producing bacteria and an increase in various opportunistic pathogens, as well as an enrichment of other microbial functions conferring sulphate reduction and oxidative stress resistance. An analysis of 23 additional individuals demonstrated that these gut microbial markers might be useful for classifying type 2 diabetes.

Effect of Tangweian Jianji on upper gastrointestinal remodeling in streptozotocin-induced diabetic rats

AIM: To investigate the effect of Tangweian Jianji (TWAJJ) on the biomechanical and morphometrical remodeling of the upper gastrointestinal tract in diabetic rats.

METHODS: Diabetes was induced in 27 rats by injecting streptozotocin (40 mg/kg body weight), the animals were then divided into three groups (n = 9 in each group), i.e., diabetic control (DM); high dose (10 g/kg, T1) and low dose (5 g/kg, T2). Another 10 rats acted as normal controls (Control). TWAJJ was administered by gavage once daily. Blood glucose and serum insulin levels were measured. Circumferential length, wall thickness and opening angle were measured from esophageal, duodenal, jejunal and ileal ring segments. The residual strain was calculated from the morphometric data. Step-wise distension was carried out on esophageal and jejunal segments. The obtained data on the length, diameter and pressure changes were then used to calculate the circumferential and longitudinal stresses and strains. Real-time reverse transcription polymerase chain reaction was used to detect the receptor of advanced glycation end-products (RAGE) mRNA level in jejunal tissues.

RESULTS: At the end of the experiment, the blood glucose level was significantly higher and the serum insulin level was significantly lower in DM, T1 and T2 groups than in the control group (Glucose: 30.23 ± 0.41 mmol/L, 27.48 ± 0.27 mmol/L and 27.84 ± 0.29 mmol/L vs 5.05 ± 0.04 mmol/L, P = 1.65 × 10^-16, P = 5.89 × 10^-19 and P = 1.63 × 10^-18, respectively; Insulin: 1.47 ± 0.32 μg/L, 2.66 ± 0.44 μg/L, 2.03 ± 0.29 μg/L and 4.17 ± 0.54 μg/L, P = 0.0001, P = 0.029 and P = 0.025, respectively). However, these levels did not differ among the DM, T1 and T2 groups. The wet weight per unit length, wall thickness and opening angle of esophageal and intestinal segments in the DM group were significantly higher than those in the control group (from P = 0.009 to P = 0.004). These parameters in the T1 group were significantly lower than those in the DM group (wet weight, duodenum: 0.147 ± 0.003 g/cm vs 0.158 ± 0.001 g/cm, P = 0.047; jejunum, 0.127 ± 0.003 g/cm vs 0.151 ± 0.002 g/cm, P = 0.017; ileum, 0.127 ± 0.004 g/cm vs 0.139 ± 0.003 g/cm, P = 0.046; wall thickness, esophagus: 0.84 ± 0.03 mm vs 0.94 ± 0.02 mm, P = 0.014; duodenum: 1.27 ± 0.06 mm vs 1.39 ± 0.05 mm, P = 0.031; jejunum: 1.19 ± 0.07 mm vs 1.34 ± 0.04 mm, P = 0.047; ileum: 1.09 ± 0.04 mm vs 1.15 ± 0.03 mm, P = 0.049; opening angle, esophagus: 112.2 ± 13.2˚ vs 134.7 ± 14.7˚, P = 0.027; duodenum: 105.9 ± 12.3˚ vs 123.1 ± 13.1˚, P = 0.046; jejunum: 90.1 ± 15.4˚ vs 115.5 ± 13.3˚, P = 0.044; ileum: 112.9 ± 13.4˚ vs 136.1 ± 17.1˚, P = 0.035). In the esophageal and jejunal segments, the inner residual stain was significantly smaller and the outer residual strain was larger in the DM group than in the control group (P = 0.022 and P = 0.035). T1 treatment significantly restored this biomechanical alteration (P = 0.011 and P = 0.019), but T2 treatment did not. Furthermore, the circumferential and longitudinal stiffness of the esophageal and jejunal wall increased in the DM group compared with those in the control group. T1, but not T2 treatment, significantly decreased the circumferential wall stiffness in the jejunal segment (P = 0.012) and longitudinal wall stiffness in the esophageal segment (P = 0.023). The mRNA level of RAGE was significantly decreased in the T1 group compared to that in the DM group (P = 0.0069).

CONCLUSION: TWAJJ (high dose) treatment partly restored the morphometric and biomechanical remodeling of the upper gastrointestinal tract in diabetic rats.