Rat Jejunum Research Articles

The inflammatory effect of infection with Hymenolepis diminuta via the increased expression and activity of COX-1 and COX-2 in the rat jejunum and colon

The aim of this study was to determine whether Hymenolepis diminuta may affect the expression and activity of cyclooxygenase 1 (COX-1) and cyclooxygenase 2 (COX-2), resulting in the altered levels of their main products – prostaglandins (PGE2) and thromboxane B2 (TXB2). The study used the same experimental model as in our previous studies in which we had observed changes in the transepithelial ion transport, tight junctions and in the indicators of oxidative stress, in both small and large intestines of rats infected with H. diminuta. In this paper, we investigated not only the site of immediate presence of the tapeworm (jejunum), but also a distant site (colon).Inflammation related to H. diminuta infection is associated with the increased expression and activation of cyclooxygenase (COX), enzyme responsible for the synthesis of PGE2 and TXB2, local hormones contributing to the enhanced inflammatory reaction in the jejunum and colon in the infected rats. The increased COX expression and activity is probably caused by the increased levels of free radicals and the weakening of the host's antioxidant defense induced by the presence of the parasite. Our immunohistochemical analysis showed that H. diminuta infection affected not only the intensity of the immunodetection of COX but also the enzyme protein localization within intestinal epithelial cells – from the entire cytoplasm to apical/basal regions of cells, or even to the nucleus.

Calcium entry blocking activity of the <i>Elaeagnus umbellata</i> fruit extract explains its use in diarrhea and gut spasm

<p class="Abstract">This study was aimed to explore the pharmacological basis of potential medicinal use of <em>Elaeagnus umbellata</em> in gut disorders. Crude extract of <em>E. umbellata</em>, which was found positive for flavonoids, terpenoids and tannins, provided 9.9-71.9% protection in castor oil-induced diarrhea in mice, like verapamil. In isolated rabbit jejunum preparations, crude extract caused inhibition of spontaneous and high K<sup>+</sup>-induced contractions, with respective EC<sub>50</sub> values of 0.3 (0.1-0.5) and 0.5 mg/mL, suggesting Ca<sup>++</sup> channel blockade (CCB). Pretreatment of tissue with crude extract (0.1–1 mg/mL) caused a rightward shift in Ca<sup>++</sup> concentration-response curves. With the exception of aqueous fraction, <em>n</em>-hexane, chloroform and ethyl acetate inhibited spontaneous and high K<sup>+</sup>-induced contractions and displaced rightward Ca<sup>++</sup> concentration-response curves. Extract was found safe up to 10 mg/kg in mice. Our data shows that anti-diarrheal effect of crude extract of <em>E. umbellate</em> is due to CCB-mediated spasmolytic effect, concentrated in the ethyl acetate fraction and suggests its medicinal importance in diarrhea and spasm.</p><p><strong>Video Clip</strong></p><p><a href="https://youtube.com/v/Qo_y3ULC4E0">Isolation of rat jejunum</a>: 2 min 32 sec </p>

Action of Cleistanthins A and B on Alpha Adrenoceptors in Rats

: Objectives: Cleistanthins A and B (CAB), active phytochemicals present in Cleistanthus collinus, have been proven to have alpha 1-adrenoceptor blocking property. However action on alpha 2-adrenoceptor is not studied. We aimed to study the action of CAB on alpha 2-adrenoceptor by measuring platelet aggregation, insulin and blood glucose levels with yohimbine as a standard comparator control and alpha 1-adrenoceptor by measuring the blockade of relaxation induced by phenylephrine in the jejunum of Wistar albino rats. Materials and methods: Forty eight adult male Wistar rats were divided into eight drug groups of six each, namely control (CMC 0.5%), yohimbine 2 mg/kg, 10, 30 and 100 mg/kg doses of cleistanthin A and cleistanthin B. Blood samples were drawn at baseline, after 5 h and after high-epinephrine dose (5 mg/kg) from the retro-orbital sinus and used for estimation of platelet aggregation and plasma insulin levels. Blood glucose levels were estimated at six different time points. Degree of jejunal relaxation was studied by relaxing the acetylcholine pre-contracted jejunum with phenylephrine. Results: All groups, except control and cleistanthin A 10 mg/kg group, significantly inhibited the platelet aggregation when compared to the respective baseline values (p<0.05). No significant difference was observed between different drug groups in plasma insulin and blood glucose levels. With regard to phenylephrine induced jejunal relaxation, the median IC50 for all three doses of cleistanthin A and cleistanthin B 100 mg/kg differ significantly from that of control (CMC 0.5%). Conclusion: CAB block both alpha 1 and 2-adrenoceptorand hence are non-selective alpha-adrenoceptor blockers.Key words: Cleistanthus Collinus, Cleistanthin A, Cleistanthin B, Alpha-adrenoceptor, Rat, Platelet aggregation.

Bispyridinium non-oximes: An evaluation of cardiac effects in isolated hearts and smooth muscle relaxing effects in jejunum

Bispyridinium non-oximes seem to be promising candidates for the generic treatment of nerve agent poisoning as they interact with nicotinic and muscarinic acetylcholine receptors. The lead compound MB327 showed therapeutic effectiveness in vitro and in vivo but was toxic at higher doses. In the present study, the effect of various bispyridinium non-oximes on isolated heart and small intestine function was investigated. Bispyridinium non-oximes and oximes were tested in at least seven different concentrations in rat jejunum preparations pre-treated with carbachol. All bispyridinium non-oximes showed classical dose response curves with MB327 being the most effective (EC50=6.6μM) and MB782 being slightly less effective (EC50=10.4μM). Neither the bispyridinium non-oximes nor the oximes showed cardiotoxic effects in the isolated Langendorff heart. The tested bispyridinum compounds showed no direct cardiac effect but had variable smooth muscle relaxing effects. Further in vivo studies are required to get more insight into potential toxic mechanisms of these promising nerve agent antidotes.

COMPARATIVE ANALYSIS OF TIGHT JUNCTIONS OF EPITHELIUM OF RATS JEJUNUM UNDER THE EFFECT OF LIPOPOLYSACCHARIDE AND CHOLERA TOXIN

Comparative study of tight junctions and ultrastructure alterations of enterocytes of mucous membranes of jejunum of rats under the effect of lipopolysaccharides and cholera toxin. Lipopolysaccharides (Sigma-Aldrich, Germany) and cholera toxin (Sigma-Aldrich, Germany) were used. The study was carried out in Wistar line rats. Effect of lipopolysaccharides and cholera toxin on epitheliocytes was carried out by a method of withdrawal of segments of rat jejunum and their incubation with the specified substances. Comparative analysis of ultrathin sections of enterocytes of jejunum of rats and tight junctions between them was carried out in control and under the effect of lipopolysaccharides and cholera toxin. Effect of lipopolysaccharides on ultrastructure of enterocytes of rat jejunum manifested in the change of cell form as a result of increase of intercellular space without destruction of tight junctions. Disappearance of desmosomes, increase of nuclei and more pronounced ER were noted in some epitheliocytes. Effect of cholerogen on epitheliocytes of mucous membrane of rat jejunum by a number of signs is similar to the effect of lipopolysaccharides, that manifested in an alteration of ultrastructure of cell, the form of those also transformed as a result of an increase of intercellular space, this process was not accompanied by destruction of tight junctions. Disappearance of folding of the lateral region of plasmatic membrane of cells and a reduction of a number of microvilli was observed under the effect of cholera toxin. A similar character of effect of lipopolysaccharides and cholera toxins on ultrastructure of cells and region of tight junctions of enterocytes of rat jejunum was detected, both substances caused an increase of intercellular space without the destruction of tight junctions.

Arginine, N-carbamylglutamate, and glutamine exert protective effects against oxidative stress in rat intestine.

The objective of the current study is to evaluate the effects of dietary supplementation with arginine (ARG), N-carbamylglutamate (NCG), and glutamine (GLN) on rat intestinal morphology and antioxidant status under oxidative stress. Rats were fed for 30 d with one of the following iso-nitrogenous diets: basal diet (BD), BD plus 1% ARG, BD plus 0.1% NCG, and BD plus 1% GLN. On day 28, half of the rats fed BD were intraperitoneally injected with 12 mg/kg body weight of diquat (DT; i.e., the DT group) and the other half was intraperitoneally injected with sterile solution (i.e., the control group). The other diet groups were intraperitoneally injected with 12 mg/kg body weight of DT (i.e., DT + 1% GLN [DT + GLN], DT + 1% ARG [DT + ARG], and DT + 0.1% NCG [DT + NCG]). Rat jejunum samples obtained at 48 h after DT injection were analyzed. Results showed that DT significantly decreased catalase (CAT) activity and glutathione (GSH) content by 58.25% and 56.57%, respectively, and elevated malondialdehyde (MDA) content and crypt depth (CD) by 19.39% and 22.13%, respectively, in the jejunum (P < 0.05, relative to the control group). Compared with the DT group, the DT + GLN group exhibited significantly improved villus height (VH), villus width (VW), villus surface area (VSA), CD and total antioxidant capacity (T-AOC) activity (P < 0.05); the DT + ARG group exhibited significantly increased the ratio of VH to CD (H:D) and T-AOC activity (P < 0.05); the DT + GLN, DT + ARG and DT + NCG groups exhibited significantly enhanced CAT activity and GSH content as well as decreased MDA content (P < 0.05). Moreover, VH, VW, VSA, CD and GSH content in the DT + GLN group were higher whereas MDA content was lower compared with the corresponding values observed in both the DT + ARG and the DT + NCG groups (P < 0.05). The H:D ratio in the DT + ARG group significantly increased compared with that in the DT + NCG and DT + GLN groups (P < 0.05). Collectively, this study suggested that dietary supplementation with 1% GLN, 0.1% NCG, and 1% ARG was effective in enhancing the antioxidant status and maintaining the morphological structure of rat jejunum under oxidative stress; of these supplements, 1% GLN exerted the greatest effects on mitigating oxidative stress.

Excised segments of rat small intestine in Ussing chamber studies: A comparison of native and stripped tissue viability and permeability to drugs

Excised rat intestinal tissue mounted in an Ussing chamber can be used for intestinal permeability assessments in drug development. The outer layer of the intestine, the serosa and part of the muscle layer, is traditionally removed since it is considered a barrier to the diffusion of nutrients and oxygen as well as to that of pharmaceutical substances. However, the procedure for removing the serosal-muscle layer, i.e. stripping, is a technically challenging process in the pre-experimental preparation of the tissue which may result in tissue damage and reduced viability of the segment. In this study, the viability of stripped and native (non-stripped) rat small intestine tissue segments mounted in Ussing chambers was monitored and the apparent permeability of the tissue to a set of test compounds across both tissue preparations was determined. Electrical measurements, in particular the potential difference (PD) across the intestinal membrane, were used to evaluate the viability. In this study, there were no differences in initial PD (health status of the tissue) or PD over time (viability throughout the experiment) between native and stripped rat jejunum segments. Overall, there were also no significant differences in permeability between stripped and native rat intestinal tissue for the compounds in this study. Based on these results, we propose that stripping can be excluded from the preparation procedures for rat jejunal tissue for permeability studies when using the Ussing chamber technique.

L-Cysteine enhances nutrient absorption via a cystathionine-β-synthase-derived H2 S pathway in rodent jejunum.

Hydrogen sulphide (H2 S) is generated endogenously from L-cysteine (L-Cys) by the enzymes cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE). In addition, L-Cys is commonly used as a precursor in the food and pharmaceutical industries. The aim of the present study is to determine whether L-Cys regulates intestinal nutrient transport. To that end, the presence of CBS and CSE in the jejunum epithelium was assessed by immunohistochemistry, Western blotting and the methylene blue assay. In addition, in vivo L-Cys (100 mg/kg, administered immediately after the glucose load) significantly increased blood glucose levels 30 min after the oral administration of glucose to mice. This effect of L-Cys was completely blocked by amino-oxyacetic acid (AOA; 50 mg/kg; administered at the same time as L-Cys) an inhibitor of CBS. Measurements of the short-circuit current (Isc) in the rat jejunum epithelium revealed that L-Cys (1 mmol/L; 6 min before the administration of L-alanine) enhances Na(+)-coupled L-alanine or glucose transport, and that this effect is inhibited by AOA (1 mmol/L;10 min before the administration of L-Cys), but not D,L-propargylglycine (PAG;1 mmol/L; 10 min before the administration of L-Cys), a CSE inhibitor. Notably, L-Cys-evoked enhancement of nutrient transport was alleviated by glibenclamide (Gli;0.1 mmol/L; 10 min before the administration of L-Cys), a K(+) channel blocker. Together, the data indicate that L-Cys enhances jejunal nutrient transport, suggesting a new approach to future treatment of nutrition-related maladies, including a range of serious health consequences linked to undernutrition.

Mechanical lengthening in multiple intestinal segments in-series

PurposeCurrent models of mechanical intestinal lengthening employ a single device in an isolated segment. Here we demonstrate that polycaprolactone (PCL) springs can be deployed in-series to lengthen multiple intestinal segments simultaneously to further increase overall intestinal length. MethodsA Roux-en-y jejunojejunostomy with a blind Roux limb was created in the proximal jejunum of rats. Two encapsulated 10-mm PCL springs were placed in-series into the Roux limb and were secured with clips. After 4weeks, the lengthened segments were retrieved for histological analyses. ResultsLengthening two intestinal segments simultaneously was achieved by placing two PCL springs in-series. The total combined length of the lengthened segments in-series was 45±4mm. The two jejunal segments with PCL springs (25±2 and 20±2mm) were significantly longer than control segments without the spring (14±1mm, p<0.05). ConclusionSpring-mediated lengthening can be achieved using multiple springs placed sequentially. The use of the Roux-en-y surgical model allowed easy insertion of springs in a blind Roux limb and arrange them in-series. Combined with relengthening techniques, we can use these methods to increase the length of small intestine to reach clinical significance.Level of Evidence: 1 Experimental

Protective effects of β-casofensin, a bioactive peptide from bovine β-casein, against indomethacin-induced intestinal lesions in rats.

β-casofensin, also known as peptide β-CN(94-123), is a milk bioactive peptide that modulates the intestinal barrier through its action on goblet cells. Here, we evaluated whether oral administration of β-casofensin can prevent indomethacin-induced injury of the jejunum in rats. Rats received β-casofensin (0.01-100 μM) or tap water by daily gavage (4 μL/g) for eight days, then two subcutaneous injections of indomethacin (10 mg/kg, days 9 and 10) and were euthanized on day 12. In vitro, we investigated the effects of β-casofensin on the restitution of a wounded monolayer. Preventive administration of β-casofensin (100 μM) reduced intestinal macroscopic and microscopic damage induced by indomethacin. β-casofensin also prevented the depletion of goblet cells and increased myeloperoxidase activity, as well as tumor necrosis factor-ɑ (TNF-ɑ) expression and immunostaining of active caspase-3 in the jejunum of rats treated with indomethacin. In wound healing experiments, β-casofensin promoted epithelial restitution with no effect on cell proliferation. This effect was inhibited by pre-incubation with an anti-CC chemokine receptor 6 (CCR6) neutralizing antibody. β-casofensin exerts protective effects in indomethacin-induced enteritis through preservation of goblet cells and improvement in wound healing. β-casofensin could therefore become vital in nutritional programs for the prevention of intestinal diseases.

A novel pathway for the production of H2 S by DAO in rat jejunum.

Hydrogen sulfide (H2 S) is endogenously generated from L-cysteine (L-Cys) by the enzymes cystathionine-β-synthase (CBS) and cystathionine-γ-Lyase (CSE). Hydrogen sulfide is also produced from D-cysteine (D-Cys) by D-Amino acid oxidase (DAO). The H2 S production was measured by the methylene blue assay. The expression of DAO was investigated by Western blotting and immunohistochemistry. The short-circuit current (Isc) was recorded using the Ussing chamber technique. The epithelium in rat jejunum possesses DAO, and generates H2 S. D-cysteine, originally used as a negative control for L-Cys, significantly increases the H2 S release, which is inhibited by I2CA, an inhibitor of DAO. In vitro study by Ussing chamber technique reveals that D-Cys decreases the Isc across the epithelium of the rat jejunum and enhances the Na(+) -coupled L-alanine transport. A novel pathway for the production of H2 S by DAO exists in rat jejunum.

Restoration of density of interstitial cells of Cajal in the jejunum of diabetic rats after quercetin supplementation.

Interstitial cells of Cajal (ICC) are required for normal motility in the gastrointestinal tract. Depletion of ICC has been associated with diabetic gastroenteropathy. To determine the effect of quercertin supplementation on anoctamin-1 (Ano1) immunoreactive ICC in the myenteric region (ICC-MY) and deep muscular plexus (ICC-DMP) in the jejunum of diabetic rats. Thirty-two 90-day-old male Wistar rats were distributed into the following groups: normoglycemic (C), normoglycemic supplemented with quercetin (CQ; 40 mg daily), diabetic (D), and diabetic supplemented with quercetin (DQ; 40 mg daily). Diabetes was induced by streptozotocin injection. After 120 days, preparations of the jejunal muscular and submucosal layers were immunostained for Ano1 to visualize ICC. Evaluation of the immunofluorescence intensity as well as density of ICC was performed. The density of ICC-MY was 46% lower in group D compared to group C (p < 0.01); ICC-DMP were reduced by 37% (p > 0.05). After quercertin treatment, the densities of ICC-MY were significantly higher in the DQ group compared to group D (ICC-MY: 58%, p < 0.05). Supplementation with quercetin in normoglycemic animals (CQ) compared with group C did not significantly change the ICC density (p > 0.05). In STZ-treated diabetic rats, diabetes promoted a reduction in the density of jejunal ICC-MY with no significant effect on ICC-DMP. Supplementation with quercetin (DQ) appeared to protect ICC-MY from depletion in diabetes possibly due to its antioxidant action.

Role of Nitric Oxide Produced by Lactobacilli in Relaxation of Intestinal Smooth Muscles.

Application of NO-producing lactobacilli to a rat jejunum segment induced muscle relaxation that was potentiated after activation of bacterial NO production with NO synthase substrate L-arginine. Similar changes in the intestinal contractile activity were observed in response to exogenous NO formed by sodium nitroprusside. These results indicated the involvement of NO synthesized by probiotic lactobacilli in the regulation of the intestinal motor function.

Interaction of Peptide Transporter 1 With d-Glucose and l-Glutamic Acid; Possible Involvement of Taste Receptors

We investigated the influence of sweet and umami (savory) tastants on the intestinal absorption of cephalexin (CEX), a substrate of peptide transporter 1 (PEPT1, SLC15A1) in rats. After oral administration of glucose or mannitol to rats, CEX was administered together with a second dose of glucose or mannitol. Western blot analysis indicated that expression of PEPT1 in rat jejunum membrane was decreased by glucose, compared to mannitol. Furthermore, the maximum plasma concentration (Cmax) of orally administered CEX was reduced by glucose compared to mannitol. The effect of glucose was diminished by nifedipine, a l-type Ca2+ channel blocker. We also found that Cmax of orally administered CEX was reduced by treatment with l-glutamic acid, compared to d-glutamic acid. Thus, excessive intake of glucose and l-glutamic acid may impair oral absorption of PEPT1 substrates.

Expression and function of the Scn5a-encoded voltage-gated sodium channel NaV 1.5 in the rat jejunum.

The SCN5A-encoded voltage-gated sodium channel NaV 1.5 is expressed in human jejunum and colon. Mutations in NaV 1.5 are associated with gastrointestinal motility disorders. The rat gastrointestinal tract expresses voltage-gated sodium channels, but their molecular identity and role in rat gastrointestinal electrophysiology are unknown. The presence and distribution of Scn5a-encoded NaV 1.5 was examined by PCR, Western blotting and immunohistochemistry in rat jejunum. Freshly dissociated smooth muscle cells were examined by whole cell electrophysiology. Zinc finger nuclease was used to target Scn5a in rats. Lentiviral-mediated transduction with shRNA was used to target Scn5a in rat jejunum smooth muscle organotypic cultures. Organotypic cultures were examined by sharp electrode electrophysiology and RT-PCR. We found NaV 1.5 in rat jejunum and colon smooth muscle by Western blot. Immunohistochemistry using two other antibodies of different portions of NaV 1.5 revealed the presence of the ion channel in rat jejunum. Whole cell voltage-clamp in dissociated smooth muscle cells from rat jejunum showed fast activating and inactivating voltage-dependent inward current that was eliminated by Na(+) replacement by NMDG(+) . Constitutive rat Scn5a knockout resulted in death in utero. NaV 1.5 shRNA delivered by lentivirus into rat jejunum smooth muscle organotypic culture resulted in 57% loss of Scn5a mRNA and several significant changes in slow waves, namely 40% decrease in peak amplitude, 30% decrease in half-width, and 7 mV hyperpolarization of the membrane potential at peak amplitude. Scn5a-encoded NaV 1.5 is expressed in rat gastrointestinal smooth muscle and it contributes to smooth muscle electrophysiology.

Positive/negative surface charge of chitosan based nanogels and its potential influence on oral insulin delivery

To develop insulin delivery system for the treatment of diabetes, two insulin-loaded nanogels with opposite zeta potential (−15.94±0.449mV for insulin:CMCS/CS-NGs(−) and +17.15±0.492mV for insulin:CMCS/CS-NGs(+)) were obtained. Ex vivo results showed that the nanogels with opposite surface charge exhibited different adhesion and permeation in specific intestinal segments. There was no significant differences in adhesion and permeation in rat duodenum, but in rat jejunum, insulin:CMCS/CS-NGs(−) exhibited enhanced adhesion and permeation, which were about 3 folds (adhesion) and 1.7 folds (permeation) higher than insulin:CMCS/CS-NGs(+). These results demonstrated that the surface charge property of nanogels determined the absorption sites of CMCS/CS-NGs in small intestine. In vivo study, the blood glucose level in insulin:CMCS/CS-NGs(−) group had 3mmol/L lower than insulin:CMCS/CS-NGs(+) group during 1h to 11h after the oral administration, which demonstrated that negative insulin:CMCS/CS-NGs had a better management of blood glucose than positive ones.

Vitamins C and E (ascorbate/α-tocopherol) provide synergistic neuroprotection in the jejunum in experimental diabetes

The present study evaluated the synergistic effects of the association of ascorbic acid and α-tocopherol on myenteric in the jejunum of diabetic rats. The rats were randomly divided into four equal groups: untreated normoglycemic (UC), untreated diabetic (UD), ascorbic acid and α-tocopherol-treated normoglycemic (CAE) and ascorbic acid and α-tocopherol-treated diabetic (DAE). The rats from the CAE and DAE group received supplementation with ascorbic acid (1g/L in water) and α-tocopherol (1% in chow). At 210-days-old, the animals were sacrified and their jejunum was collected and submitted to immunohistochemistry. Quantitative and/or morphometric analysis were performed. Supplementation with ascorbic acid and α-tocopherol prevented the cell loss of myenteric neurons expressing HuC/D and TrkA in an equivalent proportion. We also observed a reduction of the CGRP nerve fiber varicosities and the prevention of the increased cell body size of submucosal VIP neurons (p<0.05). The association of ascorbic acid and α-tocopherol reduced the deleterious effects of diabetes promoting protection on the enteric neurons.

Morphological aspects of protective influence of carbonic enterosorbent and granulocyte colony stimulating factor on small intestine in case of Melphalan administration.

Background. High toxicity of anti-cancer drugs limits the efficacy of the treatment of malignant tumors. The most frequent side effects are the injury of highly proliferative cell and tissues: hematologic and gastrointestinal toxicity. Our previous study showed high myeloprotective activity of combination of carbonic enterosorbent and granulocyte colony stimulating factor. The objective of this investigation is to study the morphologic characteristic of small intestine in case of melphalan injection and pharmacocorrection with carbonic granulated enterosorbent C2 and filgrastim. Methods. Histologic structure of jejunum of healthy male inbred rats, after the melphalan injection (4 mg/kg) and its correction with enterosorption and filgrastim apart, and in combination was investigated. Results. Cytostatic melphalan caused the dilation of microcirculatory vessels and expressed perivasal edema leading to enlargement of intestinal villi. It was revealed a large amount of lymphocytes and histiocytes in stroma and signs of increasing secretory activity of glandular cells. Dystrophic changes of the epithelium were seen. The enteral sorptive therapy showed prominent improvement of morphologic characteristic of jejunum. But sighs of increased mucus production were still seen. The granulocyte colony stimulating factor has no effects on small intestine structures. The combination of carbonic enterosorbent and filgrastim improved the histologic picture maximally. Conclusion. Combination of enterosorption and granulocyte colony stimulating factor is a prospective approach to diminish the gastrointestinal toxicity of cytostatic therapy.

Aqueous Extract of Nypa fruticans Wurmb. Vinegar Alleviates Postprandial Hyperglycemia in Normoglycemic Rats.

Nypa fruticans Wurmb. vinegar, commonly known as nipa palm vinegar (NPV) has been used as a folklore medicine among the Malay community to treat diabetes. Early work has shown that aqueous extract (AE) of NPV exerts a potent antihyperglycemic effect. Thus, this study is conducted to evaluate the effect of AE on postprandial hyperglycemia in an attempt to understand its mechanism of antidiabetic action. AE were tested via in vitro intestinal glucose absorption, in vivo carbohydrate tolerance tests and spectrophotometric enzyme inhibition assays. One mg/mL of AE showed a comparable outcome to the use of phloridzin (1 mM) in vitro as it delayed glucose absorption through isolated rat jejunum more effectively than acarbose (1 mg/mL). Further in vivo confirmatory tests showed AE (500 mg/kg) to cause a significant suppression in postprandial hyperglycemia 30 min following respective glucose (2 g/kg), sucrose (4 g/kg) and starch (3 g/kg) loadings in normal rats, compared to the control group. Conversely, in spectrophotometric enzymatic assays, AE showed rather a weak inhibitory activity against both α-glucosidase and α-amylase when compared with acarbose. The findings suggested that NPV exerts its anti-diabetic effect by delaying carbohydrate absorption from the small intestine through selective inhibition of intestinal glucose transporters, therefore suppressing postprandial hyperglycemia.

Fasting stimulates 2-AG biosynthesis in the small intestine: role of cholinergic pathways.

The endocannabinoids are lipid-derived signaling molecules that control feeding and energy balance by activating CB1-type cannabinoid receptors in the brain and peripheral tissues. Previous studies have shown that oral exposure to dietary fat stimulates endocannabinoid signaling in the rat small intestine, which provides positive feedback that drives further food intake and preference for fat-rich foods. We now describe an unexpectedly broader role for cholinergic signaling of the vagus nerve in the production of the endocannabinoid, 2-arachidonoyl-sn-glycerol (2-AG), in the small intestine. We show that food deprivation increases levels of 2-AG and its lipid precursor, 1,2-diacylglycerol, in rat jejunum mucosa in a time-dependent manner. This response is abrogated by surgical resection of the vagus nerve or pharmacological blockade of small intestinal subtype-3 muscarinic acetylcholine (m3 mAch) receptors, but not inhibition of subtype-1 muscarinic acetylcholine (m1 mAch). We further show that blockade of peripheral CB1 receptors or intestinal m3 mAch receptors inhibits refeeding in fasted rats. The results suggest that food deprivation stimulates 2-AG-dependent CB1 receptor activation through a mechanism that requires efferent vagal activation of m3 mAch receptors in the jejunum, which, in turn, may promote feeding after a fast.