A morphological study of the enteric mucosal epithelium in the streptozotocin-diabetic mouse

SARS-CoV-2 infection causes intestinal cell damage: Role of interferon’s imbalance

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative agent of the newly emerging lung disease pandemic COVID-19. This viral infection causes a series of respiratory disorders, and although this virus mainly infects respiratory cells, the small intestine can also be an important site of entry or interaction, as enterocytes highly express in angiotensin-2 converting enzyme (ACE) receptors. There are countless reports pointing to the importance of interferons (IFNs) with regard to the mediation of the immune system in viral infection by SARS-CoV-2. Thus, this review will focus on the main cells that make up the large intestine, their specific immunology, as well as the function of IFNs in the intestinal mucosa after the invasion of coronavirus-2.

Antihyperglycemic activity of Porphyridium cruentum biomass and extra-cellular polysaccharide in streptozotocin-induced diabetic rats

Porphyridium cruentum, known as red microalga, is able to produce extra-cellular polysaccharides (EPs) that have beneficial health effects. In this study, the effect of P. cruentum biomass and EPs with various doses was studied in streptozotocin (STZ)-induced diabetic rats to determine their antihyperglycemic activity and its potential mechanism. The doses of biomass were 600, 1200 and 1800 mg/kg body weight (BW) while the doses of EPs were 150, 300 and 450 mg/kg BW. P. cruentum biomass and EPs could slightly reduce food intake in STZ-diabetic rats as compared with diabetic group. After a 14-day treatment, P. cruentum EPs could decrease blood glucose levels of STZ-induced diabetic rats while P. cruentum biomass at all doses could not. P. cruentum EPs was as effective as glibenclamide in lowering blood glucose levels of diabetic rats. In addition, P. cruentum EPs could significantly increase (p < 0.05) Langerhans islets areas, the number of β-cells and the height of intestinal villi. Treatment with 450 mg/kg BW of EPs resulted in the most effective antihyperglycemic activity. Thus, P. cruentum has the potential to resolve hyperglycemic and diabetic problems.

Association of Bactericidal Dysfunction of Paneth Cells in Streptozocin-Induced Diabetic Mice with Insulin Deficiency

BACKGROUND Type 1 diabetes mellitus (T1DM) is associated with increased risks of enteric infection. Paneth cells constitute the first line of the gut defense. Little is known about the impact of T1DM on the bactericidal function of intestinal Paneth cells. MATERIAL AND METHODS A T1DM mouse model was induced by intraperitoneal injection of streptozocin. The analysis of intestinal microbiota and the mucosal bactericidal assay were conducted to evaluate intestinal innate defense. Numbers of Paneth cells and their expression of related antimicrobial peptides were analyzed. Expression of total insulin receptor (IR) mRNA and relative levels of IR-A/IR-B were analyzed. The primary mouse small intestinal crypt culture was used to analyze the effect of insulin and glucose on the expression of related antimicrobial peptides of Paneth cells. RESULTS In T1DM mice, bacterial loads were increased and there was an alteration in the composition of the intestinal microflora. Exogenous bacteria had better survival in the small bowel of the T1DM mice. The expression of Paneth cell-derived antimicrobial peptides was significantly decreased in the T1DM mice, although the number of Paneth cells was increased. Relative levels of IR-A/IR-B in Paneth cells of diabetic mice were elevated, but the total IR mRNA did not change. Insulin treatment restored the expression of antimicrobial peptides and normalized the microbiota in the gut of T1DM mice. Subsequently, in vitro culture assay demonstrated that insulin rather than glucose was essential for the optimal expression of Paneth cell-derived antimicrobial peptides. CONCLUSIONS The bactericidal function of intestinal Paneth cells was impaired in STZ-induced diabetic mice, resulting in the altered intestinal flora, and insulin was essential for the optimal expression of Paneth cell-derived antimicrobial peptides.

Abnormal differentiation of intestinal epithelium and intestinal barrier dysfunction in diabetic mice associated with depressed Notch/NICD transduction in Notch/Hes1 signal pathway

Proliferative change and intestinal barrier dysfunction in intestinal mucosa of diabetes have been described, but the differentiation characteristics of intestinal epithelial cells (IECs) and the mechanisms in the IECs development remain unclear. To explore the intestinal epithelial constitution patterns and barrier function, the diabetic mouse model was induced by streptozotocin. Tight junctions between IECs were significantly damaged and the serum level of D-lactate was raised in diabetic mice (P < 0.05). The expression of Zo1 and Ocln in the small intestine of diabetic mice were lower, while the markers for absorptive cell (SI) and Paneth cell (Lyz1) were significantly higher than in control mice (P < 0.05). The expression of Msi1, Notch1, and Dll1 in small intestine gradually increased throughout the course of hyperglycemia in diabetic mice (P < 0.05). However, the expression of NICD, RBP-jκ, Math1, and Hes1 had a reverse trend compared with Msi1 and Notch1. Intestinal absorptive cells and Paneth cells had a high proliferation rate in diabetic mice. However, the intestinal barrier dysfunction associated with the decreased expressions of Zo1 and Ocln was detected throughout hyperglycemia. In conclusion, downregulation of Notch/Hes1 signal pathway caused by depressed Notch/NICD transduction is associated with the abnormal differentiation of IECs and intestinal barrier dysfunction in diabetic mice.

Effect of l-glutamine on myenteric neuron and of the mucous of the ileum of diabetic rats

The objective of this work was to investigate the effect of the L-glutamine supplementation to prevent - diabetes induced changes in myenteric neurons and also to verify the effect on the mucosa of the ileum of Wistar rats. The animals were divided in five groups (n = 5): untreated normoglycaemic (UN), normoglycaemic treated with L-glutamine (NG), untreated diabetics (UD), diabetics treated with L-glutamine, starting on the 4th (DG4) or 45th day following diabetes induction (DG45). The amino acid was added to the diet at 1%. The density and size of neurons, the metaphasic index in the crypt, the height of the villus, the depth of the crypt and the number of globet cells were determined. There was no difference in the neuronal density and in the cellular body area of the myosin-stained myenteric neurons of groups DG4 and DG45 when compared to group D. The metaphase index and the number of goblet cells showed no significant differences when all groups were compared (P > 0.05). The villi height of groups DG4 and DG45 were 45.5% (P < 0.05) and 32.4% (P > 0.05) higher than those in group UD, respectively. The analyzed crypts showed similar depth for all studied groups.

Morphofunctional changes underlying intestinal dysmotility in diabetic RIP-I/hIFNβ transgenic mice

The pathogenetic mechanisms underlying gastrointestinal dysmotility in diabetic patients remain poorly understood, although enteric neuropathy, damage to interstitial cells of Cajal (ICC) and smooth muscle cell injury are believed to play a role. The aim of this study was to investigate the morphological and functional changes underlying intestinal dysmotility in RIP-I/hIFNβ transgenic mice treated with multiple very low doses of streptozotocin (20 mg/kg, i.p., 5 days). Compared with vehicle-treated mice, streptozotocin-treated animals developed type 1 diabetes mellitus, with sustained hyperglycaemia for 3.5 months, polyphagia, polydipsia and increased faecal output without changes in faecal water content (metabolic cages). Diabetic mice had a longer intestine, longer ileal villi and wider colonic crypts (conventional microscopy) and displayed faster gastric emptying and intestinal transit. Contractility studies showed selective impaired neurotransmission in the ileum and mid-colon of diabetic mice. Compared with controls, the ileal and colonic myenteric plexus of diabetic mice revealed ultrastructural features of neuronal degeneration and HuD immunohistochemistry on whole-mount preparations showed 15% reduction in neuronal numbers. However, no immunohistochemical changes in apoptosis-related markers were noted. Lower absolute numbers of neuronal nitric oxide synthase- and choline acetyltransferase-immunopositive neurons and enhanced vasoactive intestinal polypeptide and substance P immunopositivity were observed. Ultrastructural and immunohistochemical analyses did not reveal changes in the enteric glial or ICC networks. In conclusion, this model of diabetic enteropathy shows enhanced intestinal transit associated with intestinal remodelling, including neuroplastic changes, and overt myenteric neuropathy. Such abnormalities are likely to reflect neuroadaptive and neuropathological changes occurring in this diabetic model.

Anal pressure in experimental diabetes

PURPOSE

Diabetes mellitus is a metabolic endocrine disorder that affects many systems, the gastrointestinal system often being among the affected systems. This experimental study work was designed to demonstrate altered anal sphincter pressures in an experimental model of diabetes mellitus (DM).

MATERIALS AND METHODS

Male Wistar rats (mean weight = 250 g) were used and randomized in two groups (n = 10): CO = control and DM. DM was induced by administering a single dose of streptozotocin. Glycemic levels were measured at the start (time = 0) and end (time = 60) of the experiment and anorectal manometry at the end.

RESULTS

DM rats presented a significant increase in glycemia at day 60 (DM = 407.14 +/- 73.76) as compared to the control group (time 0 = 175.7 +/- 18.62 and time 60 = 198.04 +/- 28.66). Anorectal manometry showed a significant decrease in anal pressure in the DM group at day 60 (DM = 34.2 +/- 4.97) as compared to the CO group at the same time (CO = 67.4 +/- 2.06), with P < 0.01 and P < 0.001 (Student's t test).

CONCLUSIONS

The results suggest that DM, due to the high glycemic levels, lead to alterations such as anal sphincter hypotony, which may cause complications such as fecal incontinence.

Vitamin E (alpha-tocopherol) supplementation in diabetic rats: effects on the proximal colon

Background

Neuropathy is one of the complications caused by diabetes mellitus which is directly related to the gastrointestinal manifestations of the disease. Antioxidant substances, such as vitamin E, may play an important role in the reduction of the neurological damage caused by diabetes mellitus. The aim of the present study was to determine whether vitamin E (α-tocopherol) at different concentrations induces any effects on the morphology of the intestinal wall and intrinsic innervation in the proximal colon of diabetic rats.

Methods

Thirty rats (90-day-old) were assigned to the following groups: N (normoglycemic), NE1 (normoglycemic supplemented with vitamin E 0.1%), NE2 (normoglycemic supplemented with vitamin E 2%), D (diabetic), DE1 (diabetic supplemented with vitamin E 0.1%), and DE2 (diabetic supplemented with vitamin E 2%). Animals received vitamin E supplementation for 120 days and were sacrificed when they were 210 days old. The proximal colon of each animal was subjected to histology to study the intestinal wall and goblet cells and processed for whole-mount preparations to morphoquantitatively determine the total myenteric population.

Results

Supplementation with vitamin E significantly reduced glycemia and glycated hemoglobin values and preserved the number of myenteric neurons in group DE2, without affecting intestinal area or thickness of the intestinal wall or muscular tunic.

Conclusion

Vitamin E (2%) influenced the glycemic parameters and had a neuroprotective effect on the total myenteric population, but the morphometric characteristics of the intestinal wall were unaffected.

Diabetes mellitus and anal sphincter pressures: an experimental model in rats

PURPOSE

Symptoms of the gastrointestinal tract, frequent in patients with diabetes mellitus, which may be related to an increase in the production of free radicals, include alterations in the function of the sphincter anal musculature. Such alterations are characterized by a decrease of muscular tone associated with different degrees of fecal incontinence. This study was performed to show the alterations in the anal sphincter pressures of diabetic rats and to evaluate the role of nitric oxide and oxidative stress in this situation.

METHODS

Male Wistar rats weighing 250 to 400 g were used. The animals were divided in two groups: control and diabetic. Diabetes was induced through intraperitoneal injection of streptozotocin and the anal pressures were gauged by anorectal manometry. Nitric oxide was evaluated through measures of nitrites and nitrates, and oxidative stress through the technique of chemoluminescence.

RESULTS

There was a significant decrease in the sphincter anal pressure of diabetic animals 60 days after induction (P < 0.05). This pressure returned to basal values after administration of a nitric oxide synthase antagonist. The levels of nitrites and nitrates as well as of lipoperoxidation were significantly increased in the diabetic compared with the control group (P < 0.05).

CONCLUSIONS

In this study, hyperglycemia of diabetes mellitus caused an increase in the oxidative stress. Apparently the elevation of nitric oxide levels was one of the responsible factors for the decrease of anal sphincter pressures.

Morphological Alterations in Small Intestine of Rats with Myenteric Plexus Denervation

We aimed to investigate the effect of myenteric denervation by benzalkonium chloride (BAC) on small intestine morphology in the rat, and whether segmental myenteric denervation alters morphology elsewhere in the small intestine. Forty male Sprague-Dawley rats were equally divided into 4 groups: control (0.9% NaCl); denervation (0.062% BAC); chemical inflammation (5% acetic acid), and intraluminal stasis produced by partial obstruction. 28 days after operation tissue samples were taken from the treated segment, 10 cm distal to the treated segment, and 20 cm proximal to the treated segment. Morphological changes and the number of ganglion cells were examined under the light microscope. BAC application reduced the number of myenteric neurons by 85% in the treated segment. Denervation increased villus height and crypt depth in the treated and proximal segments. But changes in muscle thickness were seen throughout the intestine. As a result, although myenteric plexus denervation caused mucosa morphology in the treated and proximal segments, it caused smooth muscle changes throughout the small intestine.

Comparison of therapeutic regimens in the amelioration of alterations in rat gastrointestinal mucosal DNA, RNA and protein induced by streptozotocin diabetes mellitus

Type 1 diabetes mellitus is characterized by hyperglycemia, insulinopenia, and secondary neural, renal and vascular complications. Clinical manifestations in the gastrointestinal tract range from initial mild complications to more severe complications as the disease progresses, but as of yet, are poorly understood. The current study has two main foci 1) to monitor the alterations in gastrointestinal DNA, RNA and protein content induced by streptozotocin diabetes and 2) to use these parameters to monitor the efficacy of intensive insulin treatment versus pancreatic islet transplantation in the amelioration of the diabetes induced alterations. Female Wistar Furth rats were rendered diabetic by streptozotocin injection and measured for alterations in gastrointestinal DNA, RNA and protein content. Similarly, animals which had streptozotocin-induced diabetes were also treated by intensive insulin therapy or pancreatic islet transplant and monitored for alterations in gastrointestinal DNA, RNA and protein content. In general, diabetes induced increases in stomach, duodenal, jejunal and colonic macromolecular content. With few exceptions, treatment with either intensive insulin or pancreatic islet transplantation returned each variable measured back to control levels. In every case, pancreatic islet transplantation was comparable to intensive insulin therapy. In the short term the treatments are comparable, but long term analyses are needed to determine if the treatments offer any difference in their ability to prevent the long term complications related to diabetes mellitus.