Opiate-induced constipation related to activation of small intestine opioid μ2-receptors

Effects of Different Cow-Milk Beta-Caseins on the Gut-Brain Axis: A Narrative Review of Preclinical, Animal, and Human Studies

The gut and brain communicate through bidirectional neural, endocrine, and immune signals to coordinate central nervous system activity with gastrointestinal function. Dysregulated inflammation can promote immune cell activation and increase entero-endocrine signaling and intestinal permeability; hence, a functional gut-brain axis is necessary for a healthy digestive system. The consumption of milk products can lead to gut discomfort via effects on gastrointestinal tract function and the inflammatory state, which, in turn, affect the brain. A1 β-casein and A2 β-casein are major components of bovine-milk protein, and their digestion may result in different physiological effects following the consumption of milk products. Peptides derived from A1 β-casein, such as β-casomorphins, may increase gut dysfunction and inflammation, thereby modulating the availability of bioactive metabolites in the bloodstream and contribute to changes in cognitive function. This narrative review examines the functional interrelationships between the consumption of cow-milk-derived β-caseins and their effect on the brain, immune system, and the gut, which together comprise the gut-brain axis.

Anti-diarrheal effect of piperine possibly through the interaction with inflammation inducing enzymes: In vivo and in silico studies

Piperine is a natural alkaloid that possesses a variety of therapeutic properties, including anti-inflammatory, antioxidant, antibacterial, and anticarcinogenic activities. The present study aims to assess the medicinal benefits of piperine as an anti-diarrheal agent in a chick model by utilizing in vivo and in silico techniques. For this, castor oil was administered orally to 2-day-old chicks to cause diarrhea. Bismuth subsalicylate (10 mg/kg), loperamide (3 mg/kg), and nifedipine (2.5 mg/kg) were used as positive controls, while the vehicle was utilized as a negative control. Two different doses (25 and 50 mg/kg b.w.) of the test sample (piperine) were administered orally, and the highest dose was tested with standards to investigate the synergistic activity of the test sample. In our findings, piperine prolonged the latent period while reducing the number of diarrheal feces in the experimental chicks during the monitoring period (4 h). At higher doses, piperine appears to reduce diarrheal secretion while increasing latency in chicks. Throughout the combined pharmacotherapy, piperine outperformed bismuth subsalicylate and nifedipine in terms of anti-diarrheal effects with loperamide. In molecular docking, piperine exhibited higher binding affinities towards different inflammatory enzymes such as cyclooxygenase 1 (-7.9 kcal/mol), cyclooxygenase 2 (-8.4 kcal/mol), nitric oxide synthases (-8.9 kcal/mol), and L-type calcium channel (-8.8 kcal/mol), indicating better interaction of PP with these proteins. In conclusion, piperine showed a potent anti-diarrheal effect in castor oil-induced diarrheal chicks by suppressing the inflammation and calcium ion influx induced by castor oil.

Croton tiglium L. seeds ameliorate loperamide-induced constipation via regulating gastrointestinal hormones and gut microbiota before and after processing

ETHNOPHARMACOLOGICAL RELEVANCE

Crotonis Fructus (CF), the seeds of Croton tiglium L., have been commonly used in the treatment of constipation for more than two thousand years in traditional Chinese medicine (TCM). CF needs to be processed before clinical use and Crotonis Semen Pulveratum (CP) is the processed cream of CF, which could reduce the drastic purgative action and gastrointestinal damages. However, the mechanism of CF and CP in the treatment of constipation is still unclear.

AIM OF THE STUDY

This study was to evaluate the effects of CF and CP on loperamide-induced constipation and the underlying mechanism.

MATERIALS AND METHODS

The chemical compositions of CF and CP were analyzed by UPLC-Q-TOF-MS. Constipated mouse model was established by loperamide (9.6 mg/kg, b.w., i.g.) for two weeks. After successful modeling, the mice were treated with CF or CP (45.5 and 136.5 mg/kg, b.w., i.g.) once a day for seven days. The physiological status, defecation indices, defecation time, and intestinal propulsion rate in mice were measured. Histopathologic examination and serum biochemical parameters were further estimated. 16S rDNA gene sequencing was carried out to characterize the effects of CF and CP on intestinal microbiome structure. Spearman correlation analysis was also performed to explore the association between gut microbiotic abundance and serum indices.

RESULTS

The results verified the therapeutic effects of CF and CP on loperamide-induced constipation. CF and CP could significantly ameliorate the reduction of fecal number, fecal weight, fecal water content, and intestinal propulsion rate in mice with constipation, and the first stool defecation time was also obviously reduced. Moreover, CF and CP could regulate the secretion of gastrointestinal hormones and inflammatory factors induced by constipation. Histopathologic examination showed that CP was superior to CF in relieving pathological injury and inflammatory cell infiltration. According to 16S rDNA sequencing, CF and CP treatment could improve gut microbiota disturbance in mice with constipation and the abundance of opportunistic pathogens such as Parabacteroides, Parasutterella and Bacillus remarkably declined, while the levels of beneficial bacterial such as Candidatus_Arthromitus significantly increased. Besides, CP may play a better role in correcting the intestinal flora disorder than CF, which was more obvious in the high-dose group. In addition, phytochemical analysis revealed the presence of diterpenoids and alkaloids in CF and CP.

CONCLUSIONS

CF and CP could ameliorate loperamide-induced constipation by regulating gastrointestinal hormones secretion, reducing the levels of inflammatory cytokines and improving the disturbance of gut microbiota. Moreover, CP was superior to CF in the enrichment of beneficial bacteria and reduction of harmful bacteria and histopathological damage induced by constipation, which may be related to the changes in the species and content of diterpenoids after processing. The study provides new evidence for the processing mechanism and clinical application of CF and CP.

Analysis of Opioid-Related Adverse Events in Japan Using FAERS Database

Adverse events associated with opioid use in palliative care have been extensively studied. However, predicting the occurrence of adverse events based on the specific opioid used remains difficult. This study aimed to comprehensively analyze the adverse events related to µ-opioid receptor stimulation of opioids approved in Japan and investigate the tendencies of adverse event occurrence among different opioids. We utilized the FDA Adverse Event Reporting System database to extract reported adverse events for opioids approved in Japan. Cluster analysis was performed on reporting odds ratios (RORs) of adverse event names among opioids to visualize relationships between opioids and adverse events, facilitating a comparative study of their classifications. We calculated the RORs of adverse events for the target opioids. Cluster analysis based on these RORs resulted in five broad clusters based on the reported adverse events: i.e., strong opioids, weak opioids, loperamide, tapentadol, and remifentanil. This study provides a comprehensive classification of the association between μ-opioid-receptor-stimulating opioids and adverse events.

Complement C3-Deficiency-Induced Constipation in FVB/N-C3em1Hlee/Korl Knockout Mice Was Significantly Relieved by Uridine and Liriope platyphylla L. Extracts

Complement component 3 (C3) deficiency has recently been known as a cause of constipation, without studies on the therapeutic efficacy. To evaluate the therapeutic agents against C3-deficiency-induced constipation, improvements in the constipation-related parameters and the associated molecular mechanisms were examined in FVB/N-C3em1Hlee/Korl knockout (C3 KO) mice treated with uridine (Urd) and the aqueous extract of Liriope platyphylla L. (AEtLP) with laxative activity. The stool parameters and gastrointestinal (GI) transit were increased in Urd- and AEtLP-treated C3 KO mice compared with the vehicle (Veh)-treated C3 KO mice. Urd and AEtLP treatment improved the histological structure, junctional complexes of the intestinal epithelial barrier (IEB), mucin secretion ability, and water retention capacity. Also, an improvement in the composition of neuronal cells, the regulation of excitatory function mediated via the 5-hydroxytryptamine (5-HT) receptors and muscarinic acetylcholine receptors (mAChRs), and the regulation of the inhibitory function mediated via the neuronal nitric oxide synthase (nNOS) and inducible NOS (iNOS) were detected in the enteric nervous system (ENS) of Urd- and AEtLP-treated C3 KO mice. Therefore, the results of the present study suggest that C3-deficiency-induced constipation can improve with treatment with Urd and AEtLP via the regulation of the mucin secretion ability, water retention capacity, and ENS function.

Slowed gastrointestinal transit is associated with an altered caecal microbiota in an aged rat model

Gastrointestinal (GI) motility is largely dependent upon activity within the enteric nervous system (ENS) and is an important part of the digestive process. Dysfunction of the ENS can impair GI motility as is seen in the case of constipation where gut transit time is prolonged. Animal models mimicking symptoms of constipation have been developed by way of pharmacological manipulations. Studies have reported an association between altered GI motility and gut microbial population. Little is known about the changes in gut microbiota profile resulting specifically from pharmacologically induced slowed GI motility in rats. Moreover, the relationship between gut microbiota and altered intestinal motility is based on studies using faecal samples, which are easier to obtain but do not accurately reflect the intestinal microbiome. The aim of this study was to examine how delayed GI transit due to opioid receptor agonism in the ENS modifies caecal microbiota composition. Differences in caecal microbial composition of loperamide-treated or control male Sprague Dawley rats were determined by 16S rRNA gene amplicon sequencing. The results revealed that significant differences were observed at both genus and family level between treatment groups. Bacteroides were relatively abundant in the loperamide-induced slowed GI transit group, compared to controls. Richness and diversity of the bacterial communities was significantly lower in the loperamide-treated group compared to the control group. Understanding the link between specific microbial species and varying transit times is crucial to design interventions targeting the microbiome and to treat intestinal motility disorders.

P2Y1 receptor in the colonic submucosa of rats and its association with opioid‑induced constipation

The aim of the present study was to explore the expression changes of P2Y purinergic receptor 1 (P2Y1) in the distal colonic submucosa of opioid-induced constipation (OIC) rats and its association with the occurrence of OIC, an OIC rat model was generated by intraperitoneal injection of loperamide hydrochloride, a selective agonist of µ-opioid receptors (MORs). At 7 days post-treatment, the model was assessed by analyzing stool scores and calculating the gastrointestinal (GI) transit ratio of rats. The distribution of P2Y1-expressing neurons in the colonic submucosal plexus was demonstrated by immunofluorescence (IF). Western blotting was performed to evaluate the expression changes of MOR, P2Y1 and ATP synthase subunit β (ATPB) proteins in the colonic submucosa, while reverse transcription-quantitative PCR (RT-qPCR) analysis was performed to determine the relative mRNA expression of MOR and P2Y1. After 7 days, the feces of OIC rats exhibited an appearance of sausage-shaped pieces and both the stool weight and GI transit ratio of OIC rats were significantly decreased. IF revealed co-expression of P2Y1 and calbindin and MOR and ATPB in the nerve cells of the distal colonic submucosal plexus. Moreover, RT-qPCR analysis showed that the MOR mRNA levels were significantly increased in the distal colonic submucosa of OIC rats, while mRNA levels of P2Y1 were decreased. WB showed that in the distal colonic submucosa of OIC rats, MOR protein expression was increased, whereas that of P2Y1 was significantly decreased. GI transit ratio analysis suggested that the P2Y agonist ATP significantly relieved constipation symptoms in rats, while the P2Y inhibitor MRS2179 aggravated these symptoms. Finally, P2Y1 expression change was shown to be associated with the occurrence of OIC, while expression of MOR and P2Y1 was associated with OIC development in rats.

Intraoperative Analgesia with Magnesium Sulfate versus Remifentanil Guided by Plethysmographic Stress Index in Post-Bariatric Dermolipectomy: A Randomized Study

BACKGROUND

Magnesium sulfate reduces pain scores and analgesic consumption. Its use as an analgesic resource in opioid-free or opioid-sparing techniques have also been tested. The evaluation of the antinociceptive potency of drugs and doses indirectly, through hemodynamic oscillations has been questioned. A relatively new algorithm called the plethysmographic stress index has been considered sensitive and relatively specific as a parameter for assessing the need for intraoperative analgesia.

OBJECTIVES

The aim of this trial was to assess the intraoperative analgesic capacity of magnesium sulfate compared to remifentanil. The secondary objectives were propofol consumption and its latency, the consumption of opioids, ephedrine, and cisatracurium. Patients and Methods. Forty patients scheduled for post-bariatric dermolipectomy were randomly assigned to two groups to receive total intravenous anesthesia with target-controlled hypnosis induced with propofol. Analgesia was obtained in the remifentanil group with remifentanil at an initial dose of 0.2 μg·kg-1·min-1 and in the magnesium sulfate group with magnesium sulfate 40 mg·kg-1 + 10 mg·kg-1·h-1.

RESULTS

There was no statistical hemodynamic difference between the groups before and after orotracheal intubation (p = 0.062) and before and after the surgical incision (p = 0.656). There was also no statistical difference in the variation of mean arterial pressure before and after intubation (p = 0.656) and before and after the surgical incision (p = 0.911). There was similar consumption of cisatracurium, ephedrine, and postoperative opioids between the groups. Some patients in the magnesium sulfate group needed more intraoperative fentanyl and propofol, although the latency of propofol was similar in both the groups.

CONCLUSION

We conclude that using magnesium sulfate in intravenous general anesthesia for post-bariatric dermolipectomy is related to a significant reduction in opioid consumption without compromising hemodynamic stability. Overall, PSI monitoring was helpful in driving the analgesic strategy. The use of magnesium sulfate proved to be an important adjunct in the scenario presented, allowing the use of opioids to be avoided in certain cases. We found no statistical differences in the consumption of neuromuscular blocker and vasoconstrictor. Substituting opioids for magnesium sulfate leads to an increase in propofol consumption in the scenario presented. Studies with a larger sample are needed to corroborate the results presented and evaluate other potential advantages in reducing opioid consumption.

Evaluation of Antidiarrheal Activity of 80% Methanolic Extract of the Leaves of Cordia africana (Lamiaceae) in Mice

Background

Diarrheal disease is a major cause of morbidity and mortality throughout the world, particularly in developing countries. Currently available drugs are linked with adverse effects, contraindications, and risk of resistance. Traditionally, the leaf concoction of Cordia africana is claimed to be used for diarrhea. However, the safety and efficacy of the leaf extract have not been scientifically approved yet. Therefore, the study was conducted to validate its antidiarrheal activity and safety profile in mice.

Method

The hydromethanolic extract was obtained by the cold maceration technique in 80% methanol. Phytochemical screening tests were done for secondary metabolites by using standard tests. The antidiarrheal activity of the test extract at the doses of 100, 200, and 400 mg/kg was evaluated by using castor oil-induced diarrheal, gastrointestinal transit, and enteropooling models in mice.

Result

In an acute toxicity study, there were no visible signs of toxicity and mortality following a single oral administration of 2000 mg/kg. Phytochemical screening tests revealed the presence of alkaloids, saponins, flavonoids, terpenoids, phenols, and tannins. The hydromethanolic extract significantly prolonged the onset of diarrhea and reduced the weight of wet and total feces at 100 (P < 0.01), 200 (P < 0.001), and 400 mg/kg (P < 0.001) in the castor oil-induced diarrheal model. However, in the gastrointestinal transit model, a significant (P < 0.001) reduction in the charcoal meal travel was observed in the middle (200 mg/kg) and higher (400 mg/kg) test doses. Similarly, the extract produced a significant (P < 0.001) reduction in the weight and volume of intestinal contents at the aforementioned doses.

Conclusion

The study demonstrated that the test extract showed promising antidiarrheal activity. Hence, this study supports its antidiarrheal use in Ethiopian folklore medicine.

Yeokwisan, a Standardized Herbal Formula, Enhances Gastric Emptying via Modulation of the Ghrelin Pathway in a Loperamide-induced Functional Dyspepsia Mouse Model

Background: Yeokwisan, a standardized herbal formula, has exhibited clinical benefit for patients suffering from refractory functional dyspepsia (FD) in Korea since 2016. However, data about the mechanism of action of this formula are yet not available. Aim of the study: To evaluate and explore the effects of Yeokwisan on gastric emptying, a major symptom of functional dyspepsia, and its underlying mechanisms of action using a mouse model. Materials and methods: BALB/C mice were pretreated with Yeokwisan (100, 200, and 400 mg/kg, po) or mosapride (3 mg/kg, po) for 5 days and then treated with loperamide (10 mg/kg, ip) after 20 h of fasting. A solution of 0.05% phenol red (500 μL) or diet of 5% charcoal (200 μL) was orally administered, followed by assessment of gastric emptying or intestinal transit. Plasma acyl-ghrelin (ELISA), C-kit (immunofluorescence and western blotting), nNOS (western blotting) and gastric contraction- and ghrelin-related gene/protein expression levels were examined in stomach and small intestine tissues. Results: Loperamide injection substantially delayed gastric emptying, while Yeokwisan pretreatment (especially 200 and 400 mg/kg Yeokwisan) significantly attenuated this peristaltic dysfunction, as evidenced by the quantity of phenol red retained in the stomach (p < 0.05 or 0.01) and stomach weight (p < 0.05 or 0.01). The levels of plasma acyl-ghrelin and expression of gastric ghrelin-related genes, such as growth hormone secretagogue receptor (GHSR), ghrelin-O-acyltransferase (GOAT), adrenergic receptor β1 (ADRB1) and somatostatin receptor (SSTR), were significantly normalized (p < 0.05 or 0.01) by Yeokwisan (400 mg/kg). Yeokwisan (400 mg/kg) significantly tempered the loperamide-induced alterations in the c-kit and nNOS levels (p < 0.01) as well as the expression of contraction- and ghrelin-related genes, such as 5-HT4 receptor (5-HT4R), anoctamin-1 (ANO1), ryanodine receptor 3 (RYR3) and smooth muscle myosin light chain kinase (smMLCK), in the stomach, but not in the small intestine. Conclusion: The present results showed the clinical relevance of Yeokwisan, in treating FD, especially in promoting gastric emptying but not small intestinal transit. The main mechanisms corresponding to these effects may involve the modulation of the ghrelin pathway and activation of interstitial cells of Cajal in stomach tissue.

Analgesic effect of magnesium sulfate during total intravenous anesthesia: randomized clinical study

INTRODUCTION AND OBJECTIVE

Opioids have usually been used as intraoperative analgesic components, regardless of the many adverse effects they are associated with, such as nausea, vomiting, respiratory depression, and hyperalgesia. Several approaches have been investigated to reduce doses used, and magnesium sulfate has been shown to be a valuable analgesic adjunct. The main objective of the present trial was to evaluate the effectiveness of magnesium sulfate as the chief intraoperative analgesic, and the secondary objectives were to assess propofol consumption, postoperative analgesia, and intraoperative hemodynamic stability.

METHODS

In this prospective, double-blind trial, 50 patients scheduled to undergo post-bariatric abdominoplasty under general intravenous anesthesia were divided into two groups, to receive remifentanil or magnesium sulfate as intraoperative analgesic. Fentanyl 1 µg kg-1 was the rescue analgesic.

RESULTS

Among the patients in the group receiving Magnesium Sulfate (MSG), 64% did not need supplemental analgesia and none of the patients in the Remifentanil Group (RG) required fentanyl. MSG patients showed propofol consumption 36.6% higher (guided by the Bispectral Index - BIS). MSG patients consumed significantly less ephedrine (mean ± SD) than RG patients, respectively 1.52 ± 4.38 mg and 10 ± 10.39 mg, p < 0.001. Mean values of blood concentrations of magnesium were comparable to values previously described in the literature.

CONCLUSION

Magnesium sulfate is a safe and effective option for intraoperative analgesia, when avoiding or decreasing opioid use is required.

Heat-inactivated Lactobacillus plantarum nF1 promotes intestinal health in Loperamide-induced constipation rats

Constipation is a common condition that affects individuals of all ages, and prolonged constipation needs to be prevented to avoid potential complications and reduce the additional stress on individuals with pre-medical conditions. This study aimed to evaluate the effects of heat-inactivated Lactobacillus plantarum (HLp-nF1) on loperamide-induced constipation in rats. Constipation-induced male rats were treated orally with low to high doses of HLp-nF1 and an anti-constipation medication Dulcolax for five weeks. Study has 8 groups, control group; loperamide-treated group; Dulcolax-treated group; treatment with 3.2 × 10¹⁰, 8 × 10¹⁰ and 1.6 × 10¹¹, cells/mL HLp-nF1; Loperamide + Dulcolax treated group. HLp-nF1 treated rats showed improvements in fecal pellet number, weight, water content, intestinal transit length, and contractility compared to the constipation-induced rats. Also, an increase in the intestine mucosal layer thickness and the number of mucin-producing crypt epithelial cells were observed in HLp-nF1-treated groups. Further, the levels of inflammatory cytokines levels were significantly downregulated by treatment with HLp-nF1 and Dulcolax. Notably, the metagenomics sequencing analysis demonstrated a similar genus pattern to the pre-preparation group and control with HLp-nF1 treatment. In conclusion, the administration of >3.2 × 10¹⁰ cells/mL HLp-nF1 has a positive impact on the constipated rats overall health.

Evaluation of In Vivo Antidiarrheal Activities of Hydroalcoholic Leaf Extract of Dodonaea viscosa L.(Sapindaceae) in Swiss Albino Mice

Traditionally people used Dodonaea viscosa for the treatment of various ailments, including diarrhea. Therefore, this study was aimed to evaluate the antidiarrheal activity of the 80% methanolic leaf extract of D viscosa against castor oil-induced diarrhea in mice models. Different doses of 80% methanolic leaf extract of D viscosa (100, 200, and 400 mg/kg) were evaluated for their antidiarrheal activities using castor oil-induced diarrhea, gastrointestinal transit, and enteropooling models in Swiss albino mice. At all test doses, the plant extract showed significant (P < .05) inhibition in the frequency of defecation of wet feces and total fecal output as compared to the control group. Similarly, at all dose ranges used the plant extract demonstrated significant (P < .05) reduction in an intraluminal fluid accumulation as compared to the untreated group. Besides, at higher doses, the plant extract also indicated significant (P < .05) antimotility activity in comparison with the control. In conclusion, these findings illustrated that the 80% methanolic leaf extract of D viscosa supported the traditional claim of antidiarrheal activity of the plant though further investigations are warranted.

Radiographic dose-dependency study of loperamide effects on gastrointestinal motor function in the rat. Temporal relationship with nausea-like behavior

BACKGROUND

Loperamide is a potent mu opioid receptor agonist available over the counter to treat diarrhea. Although at therapeutic doses loperamide is devoid of central effects, it may exert them if used at high doses or combined with drugs that increase its systemic and/or central bioavailability. Recently, public health and scientific interest on loperamide has increased due to a growing trend of misuse and abuse, and consequent reports on its toxicity. Our aim was to evaluate in the rat the effects of increasing loperamide doses, with increasing likelihood to induce central effects, on gastrointestinal motor function (including gastric dysmotility and nausea-like behavior).

METHODS

Male Wistar rats received an intraperitoneal injection of vehicle or loperamide (0.1, 1, or 10 mg kg^-1 ). Three sets of experiments were performed to evaluate: (a) central effects (somatic nociceptive thresholds, immobility time, core temperature, spontaneous locomotor activity); (b) general gastrointestinal motility (serial X-rays were taken 0-8 hours after intragastric barium administration and analyzed semiquantitatively, morphometrically, and densitometrically); and (c) bedding intake (a rodent indirect marker of nausea). Animals from sets 1 and 3 were used to evaluate gastric dysmotility ex vivo at 2 and 4 hours after administration, respectively.

KEY RESULTS

Loperamide significantly induced antinociception, hypothermia, and hypolocomotion (but not catalepsy) at high doses and dose-dependently reduced gastrointestinal motor function, with the intestine exhibiting higher sensitivity than the stomach. Whereas bedding intake occurred early and transiently, gastric dysmotility was much more persistent.

CONCLUSIONS AND INFERENCES

Our results suggest that loperamide-induced nausea and gastric dysmotility might be temporally dissociated.

Enhanced intestinal 2-deoxy-2-[18F]fluoro-D-glucose uptake under metformin is not fully suppressed by loperamide

OBJECTIVE

This study investigated whether the metformin (Met)-induced enhanced intestinal uptake of 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) is reduced by loperamide, a long-acting anti-diarrheal agent.

METHODS

Mean 18F-FDG uptake in the mouse small intestine and colon with Met exposure was compared with that in control mice. In the Met group, high-dose (1.0 mg/kg body weight) and low-dose (0.1 mg/kg body weight) loperamide were introduced, and 18F-FDG uptake in the small intestine and colon was compared with that of control mice administered high-dose loperamide. The percent injected dose of 18F-FDG per gram of tissue (%ID/g) in the extracted tissues was then determined.

RESULTS

18F-FDG uptake increased significantly in the small intestine (0.64±0.06 vs. 1.01±0.15, p=0.040) and, especially, the colon (0.46±0.13 vs. 2.16±0.51, p<0.001) after Met exposure. Neither high-dose nor low-dose loperamide significantly reduced 18F-FDG uptake in the small intestine (0.82±0.31 vs. 0.84±0.22, p=0.93 and 0.78±0.25 vs. 0.70±0.15, p=0.13, respectively) or colon (2.13±0.41 vs. 1.67±0.55, p=0.063 and 1.77±0.39 vs. 1.80±0.25, p=0.56, respectively). The colonic %ID/g was significantly higher in Met groups irrespective of loperamide introduction than in control group, whereas the significant difference in the small intestine was observed only between Met and control groups.

CONCLUSION

Metformin increased 18F-FDG uptake in intestines especially in colon. Loperamide administration partially, but not sufficiently, suppresses the Met-induced increased colonic uptake of 18F-FDG.

Characterization the response of Korl:ICR mice to loperamide induced constipation

Animal models of constipation induced with drugs and diet have been widely employed to investigate therapeutic effects and the action mechanism of drugs against this disease. ICR mice were selected to produce this disease model through oral administration of loperamide (Lop), even though SD rats are commonly utilized in studies of constipation. To compare the responses of ICR mice obtained from three different sources to constipation inducers, alterations in stool number, histopathological structure, mucin secretion and opioid-receptor downstream signaling pathway were measured in Korl:ICR (Korea FDA source), A:ICR (USA source) and B:ICR (Japan source) injected with low and high concentrations of Lop (LoLop and HiLop). The number, weight and moisture content of stools decreased significantly in the Lop treated group of all ICR relative to the Vehicle treated group. Additionally, decreased mucosa layer thickness, muscle thickness, and mucin secretion were observed in the transverse colon of Lop treated ICR mice, while a similar number of goblet cells and crypt of lieberkuhn were detected in the same group. Furthermore, a similar change in the level of Gα expression and PKC phosphorylation was detected in the Lop treated group relative to the vehicle treated group, while some differences in the change pattern were observed in the B:ICR group. Therefore, these results of the present study provide strong additional evidence that Korl:ICR, A:ICR and B:ICR derived from different sources have a similar overall response to constipation induced by Lop injection, although there were a few differences in the magnitude of their responses.

Efficacy and Safety of Methylnaltrexone for Opioid-Induced Constipation in Patients With Chronic Noncancer Pain: A Placebo Crossover Analysis

In patients with chronic noncancer pain, subcutaneous methylnaltrexone for opioid-induced constipation (OIC) was examined in a randomized controlled trial (RCT) followed by an open-label extension (OLE). This study examined the reproducibility of RCT findings by analyzing data from placebo-treated patients who crossed over to methylnaltrexone.

Tracking gastrointestinal transit of solids in aged rats as pharmacological models of chronic dysmotility

BACKGROUND

Dysmotility in the gastrointestinal (GI) tract often leads to impaired transit of luminal contents leading to symptoms of diarrhea or constipation. The aim of this research was to develop a technique using high resolution X-ray imaging to study pharmacologically induced aged rat models of chronic GI dysmotility that mimic accelerated transit (diarrhea) or constipation. The 5-hydroxytryptamine type 4 (5-HT4 ) receptor agonist prucalopride was used to accelerate transit, and the opioid agonist loperamide was used to delay transit.

METHODS

Male rats (18 months) were given 0, 1, 2, or 4 mg/kg/day prucalopride or loperamide (in dimethyl sulfoxide, DMSO) for 7 days by continuous 7-day dosing. To determine the GI region-specific effect, transit of six metallic beads was tracked over 12 h using high resolution X-ray imaging. An established rating scale was used to classify GI bead location in vivo and the distance beads had propagated from the caecum was confirmed postmortem.

KEY RESULTS

Loperamide (1 mg/kg) slowed stomach emptying and GI transit at 9 and 12 h. Prucalopride (4 mg/kg) did not significantly alter GI transit scores, but at a dose of 4 mg/kg beads had moved significantly more distal than the caecum in 12 h compared to controls.

CONCLUSIONS & INFERENCES

We report a novel high-resolution, non-invasive, X-ray imaging technique that provides new insights into GI transit rates in live rats. The results demonstrate that loperamide slowed overall transit in aged rats, while prucalopride increased stomach emptying and accelerates colonic transit.

Coronary artery spasm after ingestion of Imodium (loperamide) in a 14-year-old boy

We report a 14-year-old boy who presented with acute chest pain, following the ingestion of loperamide for acute diarrhea. Twelve lead electrocardiogram (ECG) showed evidence of acute ischemia indicating acute coronary artery spasm. The changes reverted with treatment within a few hours with no permanent effect on myocardial function. This report highlights a rare side effect of loperamide, often debated in adults and never reported in adolescents.

Development of a novel mouse constipation model

AIM: To establish a novel mouse constipation model.

METHODS: Animals were randomly divided into three groups, and intragastrically administered 0-4 °C saline (ice-cold group) or 15-20 °C saline (saline control group) daily for 14 d, or were left untreated (blank control group). Stools were collected 3-24 h after treatment to record the wet and dry weights and the stool form. Intestinal propulsion experiments were carried out and defecation time was measured for six days continuously after suspending treatments. The expressions of PGP9.5 were detected by immunohistochemistry.

RESULTS: Based on the percentage of stool weight changes compared with baseline (before irritation) in 9-14 d, stool weight changes were classified into three levels. Each level shows a different body state, which is state I (no change: plus or minus 5%), state II (slightly decreased: 5%-15%) and state III (decreased: 15%-25%). In state III, between day 9-14, the stool weights decreased by 15%-25% compared with the baseline, and changed at a rate > 10% compared with blank control values, and the stools became small and dry. Additionally, intestinal functions degenerated in these animals, and PGP9.5-positive expression markedly decreased in jejunum, ileum and proximal colon myenteric plexus.

CONCLUSION: Irritation with ice-cold saline is a stable, repeatable method in building constipation model in mice for exploring the pathogenesis and treatment options of constipation, and the change of stool weight and size may serve as a useful tool to judge a constipation model success or not.

Molecular characterization of eluxadoline as a potential ligand targeting mu-delta opioid receptor heteromers

Eluxadoline, an orally active mixed μ opioid receptor (μOR) agonist δ opioid receptor (δOR) antagonist developed for the treatment of diarrhea-predominant irritable bowel syndrome, normalizes gastrointestinal (GI) transit and defecation under conditions of novel environment stress or post-inflammatory altered GI function. Furthermore, compared to loperamide, which is used to treat non-specific diarrhea, the effects of eluxadoline on GI transit occur over a wider dosage range. However, the mechanisms of action of eluxadoline are unclear. In this study, we compared the ability of eluxadoline and loperamide to activate G-protein- and β-arrestin-mediated signaling at μOR homomers or μOR-δOR heteromers in heterologous cells. We also examined the ability of both compounds to reduce castor oil induced diarrhea in wild type (WT) and mice lacking δOR. We find that eluxadoline is more potent than loperamide in eliciting G-protein activity and β-arrestin recruitment in μOR expressing cells. However, in cells expressing μOR-δOR heteromers, the potency of eluxadoline is higher, but its maximal effect is lower than that of loperamide. Moreover, in these cells the signaling mediated by eluxadoline but not loperamide is reduced by μOR-δOR heteromer-selective antibodies. We find that in castor oil-induced diarrhea eluxadoline is more efficacious compared to loperamide in WT mice, and δOR appears to play a role in this process. Taken together these results indicate that eluxadoline behaves as a potent μOR agonist in the absence of δOR, while in the presence of δOR eluxadoline's effects are mediated through the μOR-δOR heteromer.

A review of the clinical manifestations, pathophysiology and management of opioid bowel dysfunction and narcotic bowel syndrome

Opioids are widely used for the treatment of malignant and non-malignant pains. These medications are accompanied by adverse effects, in particular gastrointestinal symptoms known as opioid bowel dysfunction (OBD). The most common symptom of OBD is refractory constipation that is usually stable regardless of the use of laxatives. Narcotic bowel syndrome (NBS) is a subset of OBD described as ambiguous chronic pain aggravated by continual or increased opioid use for pain relief. Pathophysiology of these disorders are not definitely disentangled. Some challenging hypothesis have been posed leading to specific management in order to mitigate the adverse effects. This article is a review of the literature on the prevalence, pathophysiology and management of OBD and NBS.

Physiology, signaling, and pharmacology of opioid receptors and their ligands in the gastrointestinal tract: current concepts and future perspectives

Opioid receptors are widely distributed in the human body and are crucially involved in numerous physiological processes. These include pain signaling in the central and the peripheral nervous system, reproduction, growth, respiration, and immunological response. Opioid receptors additionally play a major role in the gastrointestinal (GI) tract in physiological and pathophysiological conditions. This review discusses the physiology and pharmacology of the opioid system in the GI tract. We additionally focus on GI disorders and malfunctions, where pathophysiology involves the endogenous opioid system, such as opioid-induced bowel dysfunction, opioid-induced constipation or abdominal pain. Based on recent reports in the field of pharmacology and medicinal chemistry, we will also discuss the opportunities of targeting the opioid system, suggesting future treatment options for functional disorders and inflammatory states of the GI tract.

Endogenous opiates and behavior: 2012

This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Opioid μ-receptors as new target for insulin resistance

Type-2 diabetes is one of the fastest growing public health problems worldwide resulting from both environmental and genetic factors. Activation of μ-opioid receptor (MOR) could result in reversal of the impairment of insulin-stimulated glucose disposal in genetically obese Zucker rats via exercise training. This improvement of insulin resistance was associated with an elevation of circulating β-endorphin to ameliorate the post-receptor insulin signaling cascade, including downstream effectors of the phosphatidylinositol 3-kinase (PI3-kinase) signaling pathway. In insulin resistant rats, Loperamide treatment effected on the insulin receptor substrate (IRS)-1/PI3-kinase/Akt signaling cascade and subsequent insulin-stimulated glucose transport trafficking on skeletal muscle, which were all suppressed by MOR antagonism. In addition, induction of insulin resistance by the intake of high fructose is more rapid in MOR knockout mice than in wild-type mice. Improvements in insulin sensitivity through the peripheral MOR activation overcoming defects related to the post-receptor in IRS-1-associated PI3-kinase step have been defined. Opioid receptor activation, especially of the μ-subtype, may provide merits in the amelioration of defective insulin action. Atypical zeta (ζ) isoform of protein kinase C serves as a factor that integrates with peripheral MOR pathway and insulin signals for glucose utilization. The developments call new insights into the chemical compounds and/or herbal products that might enhance opioid peptide secretion and/or stimulate MOR in peripheral insulin-sensitive tissues to serve as potential agents or adjuvants for helping the glucose metabolism. In the present review, we update these topics and discuss the concept of targeting peripheral MOR pathway for the treatment of insulin resistance.

Effect of thienorphine on intestinal transit and isolated guinea-pig ileum contraction

AIM: To evaluate the effect of thienorphine on small intestinal transit in vivo and on guinea-pig ileum (GPI) contraction in vitro.

METHODS: The effects of thienorphine on intestinal transit were examined in mice and in isolated GPI. Buprenorphine and morphine served as controls. The distance traveled by the head of the charchol and the total length of the intestine were measured in vivo. Gastrointestinal transit was expressed as a percentage of the distance traveled by the head of the marker relative to the total length of the small intestine. The isolated GPI preparations were connected to an isotonic force transducer and equilibrated for at least 1 h before exposure to drugs. Acetylcholine was used for muscle stimulation.

RESULTS: Thienorphine (0.005-1.0 mg/kg, ig) or buprenorphine (0.005-1.0 mg/kg, sc) dose-dependently significantly inhibited gut transit compared with saline. Thienorphine inhibited gut transit less than buprenorphine. The maximum inhibition by thienorphine on the intestinal transit was 50%-60%, whereas the maximum inhibition by morphine on gut transit was about 100%. Thienorphine also exhibited less inhibition on acetylcholine-induced contraction of GPI, with a maximum inhibition of 65%, compared with 93% inhibition by buprenorphine and 100% inhibition by morphine. Thienorphine induced a concentration-dependent decrease in the basal tonus of spontaneous movement of the GPI, the effect of which was weaker than that with buprenorphine. The duration of the effect of thienorphine on the GPI was longer than that with buprenorphine.

CONCLUSION: Thienorphine had less influence, but a longer duration of action on GPI contraction and moderately inhibited intestinal transit.

Role of antidiarrhoeal drugs as adjunctive therapies for acute diarrhoea in children

Acute diarrhoea is a leading cause of child mortality in developing countries. Principal pathogens include Escherichia coli, rotaviruses, and noroviruses. 90% of diarrhoeal deaths are attributable to inadequate sanitation. Acute diarrhoea is the second leading cause of overall childhood mortality and accounts for 18% of deaths among children under five. In 2004 an estimated 1.5 million children died from diarrhoea, with 80% of deaths occurring before the age of two. Treatment goals are to prevent dehydration and nutritional damage and to reduce duration and severity of diarrhoeal episodes. The recommended therapeutic regimen is to provide oral rehydration solutions (ORS) and to continue feeding. Although ORS effectively mitigates dehydration, it has no effect on the duration, severity, or frequency of diarrhoeal episodes. Adjuvant therapy with micronutrients, probiotics, or antidiarrhoeal agents may thus be useful. The WHO recommends the use of zinc tablets in association with ORS. The ESPGHAN/ESPID treatment guidelines consider the use of racecadotril, diosmectite, or probiotics as possible adjunctive therapy to ORS. Only racecadotril and diosmectite reduce stool output, but no treatment has yet been shown to reduce hospitalisation rate or mortality. Appropriate management with validated treatments may help reduce the health and economic burden of acute diarrhoea in children worldwide.

Opioid/naloxone prolonged release combinations for opioid induced constipation

I read with great interest the recent article by Chen et al in a recent issue of your esteemed journal. The article is highly thought provoking. One emerging therapeutic alternative for opioid induced constipation is the emergence of opioid/naloxone prolonged release combinations. For instance, naloxone when administered in a 1:2 ratio with oxycodone reverses the inhibitory effect of oxycodone on the gastrointestinal tract. The advantage of oxycodone/naloxone prolonged release (OXN) is that while its anti-nociceptive efficacy is equivalent to that of oxycodone prolonged release (OXC), it significantly decreases the “Bowel Function Index” thereby ameliorating symptoms of opioid induced constipation to a large extent. Schutter et al in a recent study have reported a decrease in the bowel function index from 38.2 to 15.1. Similarly, Löwenstein et al in another recent study have reported that following a month of therapy, complete spontaneous bowel movements per week is increased from one in OXC therapy to three in OXN therapy.