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

Multi-omics characterization of type 2 diabetes mellitus-induced gastroenteropathy in the db/db mouse model

Objective

Gastrointestinal dysfunction are often associated with type 2 diabetes mellitus (T2DM), a complicated metabolic illness. Contributing factors have been proposed, including genetic predisposition, gene environmental, and lifestyle interactions, but the pathophysiology remains unknown.

Methods

We aim to explore the possible causes behind gastrointestinal dysfunction caused by type 2 diabetes in this study. A comprehensive analysis of the gastric sinus metabolome, transcriptome, and proteome in db/db mice with gastrointestinal dysfunction was conducted.

Results

The model group of mice had considerably lower small intestine propulsion and gastric emptying rates, higher blood glucose levels, and were significantly obese compared to the control group. We identified 297 genes, 350 proteins, and 1,001 metabolites exhibiting significant differences between db/db and control mice (p < 0.05). Moreover, multi-omics analysis revealed that the genes, proteins, and metabolites in the T2DM-induced gastroenteropathy mice group were involved in arachidonic acid metabolism, glycerophospholipid metabolism and vitamin digestion and absorption. Specifically, Cbr3, Etnppl, and Apob were the major mRNAs associated with T2DM-induced gastrointestinal dysfunction, while Cyp2b10, Cyp2b19, Pgs1, Gpat3, Apoa4, and Tcn2 were the major proteins associated with T2DM-induced gastrointestinal injury, and 16(R)-HET, 5-HETE, LysoPC (22:0), and Pantothenic acid were the major metabolites associated with T2DM-induced gastrointestinal disorders.

Conclusion

The mechanism of action of diabetic gastroenteropathy may be related to vitamin digestion and absorption, glycerophospholipid metabolism, and arachidonic acid metabolism.

Common Pathophysiological Mechanisms and Treatment of Diabetic Gastroparesis

Diabetic gastroparesis (DGP) is a common complication of diabetes mellitus, marked by gastrointestinal motility disorder, a delayed gastric emptying present in the absence of mechanical obstruction. Clinical manifestations include postprandial fullness and epigastric discomfort, bloating, nausea, and vomiting. DGP may significantly affect the quality of life and productivity of patients. Research on the relationship between gastrointestinal dynamics and DGP has received much attention because of the increasing prevalence of DGP. Gastrointestinal motility disorders are closely related to a variety of factors including the absence and destruction of interstitial cells of Cajal, abnormalities in the neuro-endocrine system and hormone levels. Therefore, this study will review recent literature on the mechanisms of DGP and gastrointestinal motility disorders as well as the development of prokinetic treatment of gastrointestinal motility disorders in order to give future research directions and identify treatment strategies for DGP.

Perspectives About Ascorbic Acid to Treat Inflammatory Bowel Diseases

It is known that reactive oxygen species cause abnormal immune responses in the gut during inflammatory bowel diseases (IBD). Therefore, oxidative stress has been theorized as an agent of IBD development and antioxidant compounds such as vitamin C (L-ascorbic acid) have been studied as a new tool to treat IBD. Therefore, the potential of vitamin C to treat IBD was reviewed here as a critical discussion about this field and guide future research. Indeed, some preclinical studies have shown the beneficial effects of vitamin C in models of ulcerative colitis in mice and clinical and experimental findings have shown that deficiency in this vitamin is associated with the development of IBD and its worsening. The main mechanisms that may be involved in the activity of ascorbic acid in IBD include its well-established role as an antioxidant, but also others diversified actions. However, some experimental studies employed high doses of vitamin C and most of them did not perform dose-response curves and neither determined the minimum effective dose nor the ED50. Allometric extrapolations were also not made. Also, clinical studies on the subject are still in their infancy. Therefore, it is suggested that the research agenda in this matter covers experimental studies that assess the effective, safe, and translational doses, as well as the appropriate administration route and its action mechanism. After that, robust clinical trials to increase knowledge about the role of ascorbic acid deficiency in IBD patients and the effects of their supplementation in these patients can be encouraged.

The role of mosapride and levosulpiride in gut function and glycemic control in diabetic rats

BACKGROUND AND STUDY AIMS

Gastroparesis is a well-known consequence of long-standing diabetes that presents with gastric dysmotility in the absence of gastric outlet obstruction. This study aimed to evaluate the therapeutic effects of mosapride and levosulpiride on improving gastric emptying in type 2 diabetes mellitus (T2DM) while regulating glycemic levels.

MATERIAL AND METHODS

Rats were divided into the normal control, untreated diabetic, metformin-treated (100 mg/kg/day), mosapride-treated (3 mg/kg/day), levosulpiride-treated (5 mg/kg/day), metformin (100 mg/kg/day) + mosapride (3 mg/kg/day)-treated, and metformin (100 mg/kg/day) + levosulpiride (5 mg/kg/day)-treated diabetic groups. T2DM was induced by a streptozotocin-nicotinamide model. Fourweeks from diabetes onset, the treatment was started orally daily for 2 weeks. Serum glucose, insulin, and glucagon-like peptide 1 (GLP-1) levels were measured. Gastric motility study was performed using isolated rat fundus and pylorus strip preparations. Moreover, the intestinal transit rate was measured.

RESULTS

Mosapride and levosulpiride administration showed a significant decrease in serum glucose levels with improvement of gastric motility and intestinal transit rate. Mosapride showed a significant increase in serum insulin and GLP-1 levels. Metformin with mosapride and levosulpiride co-administration showed better glycemic control and gastric emptying than either drug administered alone.

CONCLUSION

Mosapride and levosulpiride showed comparable prokinetic effects. Metformin administration with mosapride and levosulpiride showed better glycemic control and prokinetic effects. Mosapride provided better glycemic control than levosulpiride. Metformin + mosapride combination provided superior glycemic control and prokinetic effects.

The impact of oxidative stress-induced mitochondrial dysfunction on diabetic microvascular complications

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycaemia, with absolute insulin deficiency or insulin resistance as the main cause, and causes damage to various target organs including the heart, kidney and neurovascular. In terms of the pathological and physiological mechanisms of DM, oxidative stress is one of the main mechanisms leading to DM and is an important link between DM and its complications. Oxidative stress is a pathological phenomenon resulting from an imbalance between the production of free radicals and the scavenging of antioxidant systems. The main site of reactive oxygen species (ROS) production is the mitochondria, which are also the main organelles damaged. In a chronic high glucose environment, impaired electron transport chain within the mitochondria leads to the production of ROS, prompts increased proton leakage and altered mitochondrial membrane potential (MMP), which in turn releases cytochrome c (cyt-c), leading to apoptosis. This subsequently leads to a vicious cycle of impaired clearance by the body's antioxidant system, impaired transcription and protein synthesis of mitochondrial DNA (mtDNA), which is responsible for encoding mitochondrial proteins, and impaired DNA repair systems, contributing to mitochondrial dysfunction. This paper reviews the dysfunction of mitochondria in the environment of high glucose induced oxidative stress in the DM model, and looks forward to providing a new treatment plan for oxidative stress based on mitochondrial dysfunction.

Atractylenolide‑1 alleviates gastroparesis in diabetic rats by activating the stem cell factor/c‑kit signaling pathway

Diabetic gastroparesis (DGP), also known as delayed gastric emptying, is a common complication of diabetes mellitus. There are numerous clinical symptoms associated with DGP, as well as high treatment costs and markedly reduced patient quality of life. However, the pathogenesis of DGP is not clear, thus effective treatment methods are yet to be established. In the present study, a DGP rat model was established in Sprague‑Dawley rats by the intraperitoneal injection of streptozotocin (STZ). DGP model rats were treated with different doses of atractylenolide‑1 to detect alterations in gastrointestinal function, including gastroparesis, gastric emptying, gastric motility, gastric peristalsis and gastric blood flow. Compared with the DGP group, atractylenolide‑1 treatment significantly reduced glycaemia and the level of glycated hemoglobin, as well as restoring gastrointestinal function. Gastroparesis, gastric emptying, gastric motility, gastric peristalsis and gastric blood flow were significantly impaired in the STZ‑induced group compared with the vehicle control group. Moreover, the STZ‑induced group displayed downregulated expression levels of the DGP indicator KIT proto‑oncogene, receptor tyrosine kinase (c‑kit), as investigated by immunohistochemistry, and stem cell factor (SCF) protein, as assessed using ELISA, significantly enhanced rat interstitial cells of Cajal (ICC) apoptosis, and significantly altered levels of oxidative stress‑related markers (malondialdehyde and superoxide dismutase) in the serum and gastric tissues compared with the vehicle control group. By contrast, treatment with atractylenolide‑1 significantly counteracted the effects of DGP on peristalsis, inhibited apoptosis and suppressed oxidative stress by regulating the expression of heme oxygenase 1 in STZ‑induced DGP model rats. Further research indicated that atractylenolide‑1 regulated oxidative stress reactions and improved gastric function by activating the SCF/c‑kit signaling pathway. Collectively, the results of the present study suggested that atractylenolide‑1 promoted ICC survival and preserved the structure of the gastric tissue network in a DGP rat model via the SCF/c‑kit signaling pathway, providing novel insights for the treatment of DGP.

Study on the Mechanisms of Banxia Xiexin Decoction in Treating Diabetic Gastroparesis Based on Network Pharmacology

In China, Banxia Xiexin decoction (BXD) is applied to treat diabetic gastroparesis (DGP), but its key active ingredients and mechanisms against DGP are unclear. This study is designated to reveal the molecular mechanisms of BXD in treating DGP by adopting a creative approach known as network pharmacology to explore the active ingredients and therapeutic targets of BXD. In our study, 730 differentially expressed genes of DGP were obtained, and 30 potential targets of BXD against DGP were screened out (including ADRB2, DRD1, FOS, MMP9, FOSL1, FOSL2, JUN, MAP2, DRD2, MYC, F3, CDKN1A, IL6, NFKBIA, ICAM1, CCL2, SELE, DUOX2, MGAM, THBD, SERPINE1, ALOX5, CXCL11, CXCL2, CXCL10, RUNX2, CD40LG, C1QB, MCL1, and ADCYAP1). Based on the findings, BXD contains 60 compounds with therapeutic effect on DGP, including the key active ingredients such as quercetin, wogonin, baicalein, beta-sitosterol, and kaempferol. Sixty-eight pathways including TNF signaling pathway, IL-17 signaling pathway, and AGE-RAGE signaling pathway were significantly enriched. In this study, the mechanisms of BXD in treating DGP are affirmed to be a complex network with multi-target and multi-pathway, which provides a reference for future experimental studies.

Signaling pathways underlying changes in the contractility of the stomach fundus smooth muscle in diabetic rats

Dysfunction of gastrointestinal (GI) motility is a common complication in patients with diabetes mellitus (DM). Studies related to changes in fundus contraction induced by inhibitors in DM are not well known. Therefore, this study aimed to investigate the signaling pathways involved in the changes in the contraction of fundus smooth muscle obtained from control and DM rats. DM was induced by injecting streptozotocin (65 mg/kg) into Sprague-Dawley rats. The rats were sacrificed after 14 days. Fundus smooth muscle contraction was stimulated using electrical field stimulation (amplitude, 50 V; duration, 1 min; frequency, 2-20 Hz) and acetylcholine (0.1 mM). The inhibitor-mediated cell membrane was pre-treated with atropine, verapamil, methysergide, ketanserin, ondansetron, and GR 113808. Inhibitors related to intracellular signaling, such as U73122, chelerythrine, L-NNA, were also used. ML-9 and Y-27632 were identified as inhibitors of factors of myosin light chain (MLC). The contractility was observed to be lower in the DM group than in the control group. Further, the activities of phospholipase C (PLC), protein kinase C (PKC), and myosin light chain kinase (MLCK) were decreased in the DM group. DM reduced the activity of PLC, PKC, and MLCK, which resulted in a decrease in the contractility of the fundus smooth muscle. Therefore, our results present the mechanism of this DM-mediated GI disorder.

Chronic Restraint Stress Induces Gastric Mucosal Inflammation with Enhanced Oxidative Stress in a Murine Model

Background

Although the underlying mechanisms of chronic stress are still unknown, this condition has been related to the pathophysiology of gastric mucosal inflammation, whose development is accelerated by oxidative stress. The present study investigates how chronic stress influences gastric mucosal oxidative stress and inflammation.

Methods

Eight-week-old C57BL/6J male mice were subjected to two-week intermittent restraint stress. The expressions of CD11b (a specific for monocyte/macrophage), monocyte/macrophage cell surface markers (CD68 and F4/80), NADPH oxidase-4 (Nox-4) and 8-hydroxy-2’-deoxyguanosine (8-OHdG, a sensitive biomarker of oxidative stress) were determined using immunohistochemistry, RT-PCR, and enzyme-linked immunosorbent assay, respectively. The expressions of antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, were examined by RT-PCR and Western blotting. The expressions of proinflammatory cytokines, including monocyte chemoattractant protein-1 (MCP-1), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α), were determined using immunohistochemistry and RT-PCR, respectively.

Results

Chronic stress increased the lymphocytic infiltration and inflammation within the gastric mucosa of mice. Stress remarkably increased the expression levels of CD11b and mRNA expression levels of CD68 and F4/80 in the mucosa of the stomach of stressed mice. Stress remarkably increased both mRNA and plasma concentrations of Nox-4 and 8-OHdG; and markedly reduced gastric mRNA and protein expression levels of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase. The expressions of proinflammatory cytokines (MCP-1, IL-1β, and TNF-α) were predominantly observed in the gastric mucosal layers of the stressed mice. Furthermore, stress remarkably elevated the gastric mucosal mRNA expression levels of MCP-1, IL-1β, and TNF-α.

Conclusion

Two weeks of restraint stress induced gastric inflammation in the murine model with enhanced oxidative stress and reduced anti-oxidative system.

Vitamin C, omega-3 and paracetamol pharmacokinetic interactions using saliva specimens as determiners

Background With its low side effects profile and availability as an over-the-counter drug, paracetamol has been utilized extensively worldwide as an antipyretic and analgesic agent for decades. This is associated with the increasing concern over its ease of access and/or unawareness of the consumers to this issue of paracetamol-induced hepatotoxicity. Paracetamol-induced liver injury today is a big problem where most of the researchers are interested in the possible role of the naturally available antioxidants to ameliorate hepatotoxicity through kinetic interference. So the present study was designed to evaluate the effect of vitamin C and omega-3 on the pharmacokinetic property of paracetamol. Methods Six young (average age 29) healthy volunteers participated in the study. The study included three consecutive periods, each of which preceded by overnight fasting and separated by 6 day washout periods. The first period involved the ingestion of a single paracetamol dose. The second one included the ingestion of paracetamol and vitamin C concomitantly, and the final period included paracetamol plus omega-3. Saliva samples were collected and prepared for High-performance liquid chromatography analysis. Results There was a significant increase in saliva paracetamol level after 30 min of administration when given concomitantly with vitamin C compared with the remaining groups. No significant differences in the paracetamol concentration profile between the subjects for each group were observed at 60, 90, 120 and 150 min in all treated groups. Conclusion Concurrent administration of vitamin C with paracetamol increases significantly the Cmax level (maximum measured concentration) in saliva and increases the extent of absorption and the possibility of drug-drug interaction and risk of side effects.

Effects of AMPK on Apoptosis and Energy Metabolism of Gastric Smooth Muscle Cells in Rats with Diabetic Gastroparesis

This study aimed to investigate the effect of AMPK on apoptosis and energy metabolism of gastric smooth muscle cells in diabetic rats and to explore the role of AMPK in the pathogenesis of diabetic gastroparesis (DGP). After establishment of a diabetic rat model, rats were divided into normal control (NC), 4-week (DM4W), 6-week (DM6W), and 8-week (DM8W) diabetic model groups. The gastric residual pigment ratio, intestinal transit rate, and intestinal propulsion rate in each group were detected to confirm the successful establishment of the DGP model. The spontaneous contraction in isolated gastric smooth muscle strips of the NC and DM8W groups was experimentally observed. The expression of phospho-AMPK, AMPK, phospho-LKB1, LKB1, phospho-TAK1, TAK1, and CaMMKβ in rat gastric smooth muscle tissues was detected by western blot analysis; ADP, AMP, ATP contents, and the energy charge were detected using Elisa; and apoptosis of gastric smooth muscle cells was detected by flow cytometry. The rat gastric smooth muscle cells were cultured in vitro, and treated with an AMPK inhibitor and an agonist. At 24 and 48 h, the effects of AMPK on apoptosis and energy metabolism of gastric smooth muscle cells were observed. Reduced spontaneous contractions, AMPK activation, cell apoptosis, and energy metabolism disorders were observed in gastric smooth muscle tissues of a diabetic rat, and AMPK activation was associated with an increased ratio of ADP/ATP, AMP/ATP, LKB1 activity, and CaMMKβ expression. From in vitro cell culture experiments, we found that AMPK activation of high-glucose conditions promoted cell apoptosis. Inhibition of AMPK had no obvious effect on apoptosis at the early stage with high glucose, but the inhibitory effect was significant at the late stage with high glucose. AMPK can regulate both mitochondrial metabolism and glycolysis pathways under high-glucose conditions. During the early stage with high glucose, AMPK was the main promotion factor of the mitochondrial metabolism pathway, but did not increase the ATP production, AMPK also promoted the glycolysis pathway. During the late stage with high glucose, AMPK was a major inhibitor of the mitochondrial pathway, and still played a role in promoting the glycolytic pathway, which acted as the main regulator. Apoptosis and energy metabolism disorders were present in gastric smooth muscle cells during the occurrence of DGP. Under high-glucose condition, AMPK was activated, which can promote apoptosis, change the energetic metabolism pathway of cells, inhibit mitochondrial energy metabolism, and promote glycolysis.

Delayed gastric emptying and altered antrum protein metabolism during activity-based anorexia

BACKGROUND

Anorexia nervosa, a restrictive eating disorder, is often associated with gastrointestinal disorders, particularly a delayed gastric emptying. However, the mechanisms remained poorly documented. Thus, we aimed to evaluate gastric emptying and antrum protein metabolism in the Activity-Based Anorexia model (ABA).

METHODS

Females C57Bl/6 mice were randomized into 3 groups: Control, ABA, and Limited Food Access (LFA). Food access has been progressively limited from 6 h/day at day 6 to 3 h/day at day 9 and until day 17. ABA mice had free access to an activity wheel. Gastric emptying was assessed. On gastric extracts, a proteomic analysis was performed, as well as an evaluation of protein synthesis and protein oxidation.

KEY RESULTS

Both LFA and ABA mice exhibited a delayed gastric emptying compared with Controls (P < .05). Proteomic approach revealed 15 proteins that were differentially expressed. Among these proteins, we identified 2 clusters of interest contributing to (i) the organization of muscle fiber with ACTA2, VCL, KRT19, KRT8, and DES proteins and (ii) "heat shock proteins" with STIP1, HSPD1, and HSPA8 proteins. ABA mice specifically exhibited an increased rate of gastric oxidized proteins.

CONCLUSIONS AND INFERENCES

Delayed gastric emptying observed in anorectic conditions appears to be secondary to malnutrition. However, an oxidative stress is specifically present in the stomach of ABA mice. Its role remains to be further studied.

Ascorbic acid inhibits senescence in mesenchymal stem cells through ROS and AKT/mTOR signaling

Mesenchymal stem cell (MSC) aging seriously affects its function in stem cell transplantation for treatment. Extensive studies have focused on how to inhibit senescence in MSCs. However, the mechanism of senescence in MSC was not clear. In this study, we used D-galactose to induce MSC aging. Then we found that the number of aging cells was increased compared with untreated MSCs. We discovered that ascorbic acid could inhibit the production of reactive oxygen species (ROS) and activation of AKT/mTOR signaling in MSCs caused by D-galactose. Especially, when treated together with a ROS scavenger or AKT inhibitor, the senescent cells were obviously decreased in D-galactose-induced MSCs. Taken together, we identify that ascorbic acid owns the potential to inhibit the senescence of MSCs through ROS and Akt/mTOR signaling. Together, our data supports that ascorbic acid can be used to prevent MSCs from senescence, which can enhance the efficiency of stem cell transplantation in the clinic.