Comparison of selective M3 and nonselective muscarinic receptor antagonists on gastrointestinal transit and bowel habits in humans

Deciphering antidiarrheal effects of Meda pata (Litsea glutinosa (Lour.) C.B.Rob.) leaf extract in chemical-induced models of albino rats

ETHNOPHARMACOLOGICAL RELEVANCE

Diarrhea is one of the leading causes of preventable death in developing countries, mainly caused by bacterial infections and traditional therapies are very common in diarrheal incidences. Meda Pata (Litsea glutionsa) has a long history of use as traditional medicine for diarrhea, dysentery, and spasm in Bangladesh, India, and some other Asian countries.

AIM OF THE STUDY

This research reports the antidiarrheal effects of Meda Pata (Litsea glutinosa leaf extract, LGLEx) in animal models. The work has been supported by in silico molecular docking study to verify the effects.

MATERIALS AND METHODS

The antidiarrheal effect of LGLEx was investigated in castor oil-induced diarrhea, magnesium sulfate-induced diarrhea, and gastrointestinal motility test models. Antidiarrheal effects were supported by a molecular docking study through an interaction between LGLEx's GC-MS analyzed imidazole-containing compounds and muscarinic acetylcholine receptor (PDB: 4U14) and 5-HT3 receptor (PDB: 5AIN).

RESULTS

LGLEx potentially reduced the diarrheal incidences in in vivo assays reducing gastrointestinal motility. The maximum diarrheal inhibition was obtained in the castor oil-induced model (62.63%) and and BaSO₄-induced model (73.14%), which were statistically significant (P < 0.05) when compared to the reference drug loperamide. In the castor-oil and BaSO4-induced models, peristaltic movement was reduced by 25.96% and 32.17%, respectively. Biochemical markers particularly IgE, C-reactive proteins, and serum electrolytes were significantly (P < 0.0) restored in treated groups. A Molecular docking analysis revealed that two compounds (1-Ethyl-2-hydroxymethylimidazole and 1,6-Anhydro-beta-D-glucofuranose demonstrated the highest binding affinity with target receptors muscarinic acetylcholine receptor (PDB: 4U14) and 5-HT3 receptor (PDB: 5AIN) confirming their drug likeliness. The findings indicate a high potential antidiarrheal impact that warrants further investigation for its therapeutic application.

Review article: An analysis of the pharmacological rationale for selecting drugs to inhibit vomiting or increase gastric emptying during treatment of gastroparesis

BACKGROUND

Drugs which can inhibit nausea/vomiting and/or increase gastric emptying are used to treat gastroparesis, mostly 'off-label'. Within each category, they act at different targets and modulate different physiological mechanisms.

AIMS

Address the questions: In gastroparesis, why should blocking one pathway causing vomiting, be more appropriate than another? Why might increasing gastric emptying via one mechanism be more appropriate than another?

METHODS

Drugs used clinically were identified via consensus opinions and reviews, excluding the poorly characterised. Their pharmacology was defined, mapped to mechanisms influencing vomiting and gastric emptying, and rationale developed for therapeutic use.

RESULTS

Vomiting: Rationale for 5-HT₃ , D₂ , H₁ or muscarinic antagonists, and mirtazapine, amitriptyline, nortriptyline, are poor. Arguments for inhibiting central consequences of vagal afferent transmission by NK₁ antagonism are complicated by doubts over effects on nausea. Gastric emptying: Confusion emerges because of side-effects of drugs increasing gastric emptying: Metoclopramide (5-HT₄ agonist, D₂ and 5-HT₃ antagonist; also blocks some emetic stimuli and causes tardive dyskinesia) and Erythromycin (high-efficacy motilin agonist, requiring low doses to minimise side-effects). Limited trials with selective 5-HT₄ agonists indicate variable efficacy.

CONCLUSIONS

Several drug classes inhibiting vomiting have no scientific rationale. NK₁ antagonism has rationale but complicated by limited efficacy against nausea. Studies must resolve variable efficacy of selective 5-HT₄ agonists and apparent superiority over motilin agonists. Overall, lack of robust activity indicates a need for novel approaches targeting nausea (e.g., modulating gastric pacemaker or vagal activity, use of receptor agonists or new targets such as GDF15) and objective assessments of nausea.

Chemico-Biological Profiling of Blumea lacera (Burm.f.) DC. (Family: Asteraceae) Provides New Insights as a Potential Source of Antioxidant, Cytotoxic, Antimicrobial, and Antidiarrheal Agents

Blumea lacera (Burm.f.) DC., popular for its traditional use in different diseases, was employed in phytochemical and biological investigations. The chemical studies led to the isolation of acyclic diterpene-phytol (1) along with two fatty acids-linolenic acid (2) and oleic acid (3). All the structures were determined by ¹H NMR spectroscopic analysis and first time reported from this plant. Different fractions of crude methanol extract were subjected to antioxidant, cytotoxicity, antimicrobial, and antidiarrheal assays. The molecular docking studies have been implemented using PyRx, UCSF Chimera, Discovery Studio, and online tools. In addition, The ADME/T analysis and PASS prediction were implemented by using PASS online tools. In the molecular docking study of antioxidant, cytotoxicity, antimicrobial, and antidiarrheal activity, the compounds showed strong binding affinity ranging from −4.5 to −6.2 kcal/mol. Again, all three isolated compounds met the preconditions of Lipinski's five rules for drug discovery. In DPPH free radical scavenging assay, the pet-ether and chloroform soluble fraction showed noteworthy antioxidant activity sowing promising IC₅₀ values (10.76 μg/ml and 11.77 μg/ml, respectively), compared to the standard (6.05 μg/ml) with a total phenolic content range of 7.33–40.33 mg of GAE/gm. The pet-ether soluble fraction revealed substantial cytotoxicity showing an LC₅₀ value of 1.03 μg/ml, compared to the standard (0.93 μg/ml). Besides, ethyl acetate soluble fraction showed moderate activity against both Gram-positive and Gram-negative bacteria, while both ethyl acetate and pet-ether soluble fraction showed excellent dose-dependent antidiarrheal activity.

Neurotransmitter Dysfunction in Irritable Bowel Syndrome: Emerging Approaches for Management

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder whose aetiology is still unknown. Most hypotheses point out the gut-brain axis as a key factor for IBS. The axis is composed of different anatomic and functional structures intercommunicated through neurotransmitters. However, the implications of key neurotransmitters such as norepinephrine, serotonin, glutamate, GABA or acetylcholine in IBS are poorly studied. The aim of this review is to evaluate the current evidence about neurotransmitter dysfunction in IBS and explore the potential therapeutic approaches. IBS patients with altered colorectal motility show augmented norepinephrine and acetylcholine levels in plasma and an increased sensitivity of central serotonin receptors. A decrease of colonic mucosal serotonin transporter and a downregulation of α2 adrenoceptors are also correlated with visceral hypersensitivity and an increase of 5-hydroxyindole acetic acid levels, enhanced expression of high affinity choline transporter and lower levels of GABA. Given these neurotransmitter dysfunctions, novel pharmacological approaches such as 5-HT₃ receptor antagonists and 5-HT₄ receptor agonists are being explored for IBS management, for their antiemetic and prokinetic effects. GABA-analogous medications are being considered to reduce visceral pain. Moreover, agonists and antagonists of muscarinic receptors are under clinical trials. Targeting neurotransmitter dysfunction could provide promising new approaches for IBS management.

Clinical features and disturbances of gastrointestinal transit in patients with rapid gastric emptying

AIMS

Some patients with upper gastrointestinal symptoms have rapid gastric emptying (GE). We aimed to compare patients with normal and rapid GE and to identify phenotypes among patients with rapid GE.

METHODS

Among 2798 patients who underwent GE scintigraphy, we compared patients with normal and rapid GE and separately, patients with rapid GE at 1 hour (GE1), 2 hours (GE2), or both (GE12).

RESULTS

In 2798 patients, GE was normal (74%), delayed (18%), or rapid (8%). Among 211 patients with rapid GE, patterns were rapid GE1 (48%), 2 hours (17%), or 1 and 2 hours (35%); 42 (20%) had diseases that explain rapid GE. A combination of upper and lower gastrointestinal symptoms (54%) was more common that isolated upper (17%) or lower (28%) gastrointestinal symptoms (P < .001). Constipation was more prevalent in patients with rapid GE 2 (72%) than rapid GE 1 (47%) or rapid GE12 hours (67%) (P < .05). Among 179 diabetes mellitus (DM) patients, 15% had rapid GE, which was not associated with the DM phenotype. By multivariable analysis, insulin therapy (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.15-0.88), and weight loss (OR, 0.10; 95% CI, 0.01-0.78) were associated with a lower risk of rapid than normal GE in DM.

CONCLUSIONS

Eight percent of patients undergoing scintigraphy had rapid GE, which is most frequently associated with upper and lower gastrointestinal symptoms; constipation is common. Insulin therapy and weight loss were associated with a lower risk of rapid than normal GE in DM patients.

Desmethylbellidifolin From Gentianella acuta Ameliorate TNBS-Induced Ulcerative Colitis Through Antispasmodic Effect and Anti-Inflammation

Desmethylbellidifolin (DMB) is a natural xanthone extracted from Gentianella acuta, which is used as the antidiarrhea drug in traditional Mongolian medicines. It remains unknown whether DMB can ameliorate ulcerative colitis (UC). In this study, trinitrobenzenesulfonic acid (TNBS)-induced colitis rats were treated with G. acuta extract (GAE) or DMB for 10 days. Body weight, food and water intake, rectal bleeding score, diarrhea score, and histopathological parameters were measured. Rat colon were collected to determine myeloperoxidase, nitric oxide levels, and inflammatory cytokines expression. In addition, the role of DMB on lipopolysaccharide stimulated RAW264.7 cell inflammatory response and intestine smooth muscle contraction was determined. The results showed that GAE and DMB treatment could significantly alleviate TNBS-induced UC. Colon morphological alteration, nitric oxide level, and inflammatory cytokines level, such as nitric oxide synthase, interleukin-6, tumor necrosis factor-α, and cyclooxygenase-2, were decreased. In addition, DMB attenuated lipopolysaccharide-induced nitric oxide release and proinflammatory cytokine expression in RAW264.7 cells. In isolated mice intestinal tissue, DMB also reduced the intestine smooth muscle spontaneous contraction and inhibited KCl, acetylcholine, BaCl₂, or histamine-induced intestine smooth muscle active tension, while the active frequency was unaffected. Our results demonstrated that GAE and its active constituent DMB could inhibit TNBS-induced UC, reducing inflammatory response and alleviate colon muscle spasm, suggesting that DMB may be a good candidate for subsequent development as a multitargeting drug for UC treatment.

Choosing an Animal Model for the Study of Functional Dyspepsia

Functional dyspepsia (FD) is a common functional gastrointestinal disorder with pain or discomfort in the upper abdomen as the main characteristic. The prevalence of FD worldwide varies between 5% and 11%. This condition adversely affects attendance and productivity in the workplace. Emerging evidence is beginning to unravel the pathophysiologies of FD, and new data on treatment are helping to guide evidence-based practice. In order to better understand the pathophysiologies of FD and explore better treatment options, various kinds of animal models of FD have been developed. However, it is unclear which of these models most closely mimic the human disease. This review provides a comprehensive overview of the currently available animal models of FD in relationship to the clinical features of the disease. The rationales, methods, merits, and disadvantages for modelling specific symptoms of FD are discussed in detail.

Systemic Absorption of Cyclopentolate and Adverse Events After Retinopathy of Prematurity Exams

PURPOSE

Preterm infants undergoing Retinopathy of Prematurity Eye Exams (ROPEE) may experience adverse events, possibly from systemic absorption of cyclopentolate. The purpose of this study was to analyze the association between adverse events and drug levels found in neonates undergoing ROPEE.

MATERIALS AND METHODS

25 infants were randomized into two groups during routine ROP screening: 5 infants for blood collection before mydriatic drops and 20 for blood collection 1 h after eye drops. Blood was collected onto dried blood spot cards, extracted, and analyzed for cyclopentolate and phenylephrine using liquid chromatography and mass spectrometry. Relationships between drug levels and adverse events were assessed.

RESULTS

Cyclopentolate (range 6-53 ng/ml) was observed in 15 of 18 infants, while phenylephrine was not detected. Levels of cyclopentolate were significantly higher in infants who were on oxygen (p = 0.01). There was a significant association between cyclopentolate levels and gastric residuals in tube-fed infants not receiving oxygen (p = 0.01).

CONCLUSIONS

Cyclopentolate levels varied among preterm infants after ROPEE. Cyclopentolate was positively associated with increased gastric residuals. Underlying medical conditions requiring oxygen administration may affect absorption and metabolism of cyclopentolate. There is a need to predict infants at risk for high blood levels of cyclopentolate in order to prevent or treat adverse events after ROPEE.

Pharmacological agents currently in clinical trials for disorders in neurogastroenterology

Esophageal, gastrointestinal, and colonic diseases resulting from disorders of the motor and sensory functions represent almost half the patients presenting to gastroenterologists. There have been significant advances in understanding the mechanisms of these disorders, through basic and translational research, and in targeting the receptors or mediators involved, through clinical trials involving biomarkers and patient responses. These advances have led to relief of patients' symptoms and improved quality of life, although there are still significant unmet needs. This article reviews the pipeline of medications in development for esophageal sensorimotor disorders, gastroparesis, chronic diarrhea, chronic constipation (including opioid-induced constipation), and visceral pain.

A randomised controlled study of the effect of cholinesterase inhibition on colon function in patients with diabetes mellitus and constipation

OBJECTIVES

Chronic constipation in diabetes mellitus is associated with colonic motor dysfunction and is managed with laxatives. Cholinesterase inhibitors increase colonic motility. This study evaluated the effects of a cholinesterase inhibitor on gastrointestinal and colonic transit and bowel function in diabetic patients with constipation.

DESIGN

After a 9-day baseline period, 30 patients (mean ± SEM age 50 ± 2 years) with diabetes mellitus (18 type 1, 12 type 2) and chronic constipation without defaecatory disorder were randomised to oral placebo or pyridostigmine, starting with 60 mg three times a day, increasing by 60 mg every third day up to the maximum tolerated dose or 120 mg three times a day; this dose was maintained for 7 days. Gastrointestinal and colonic transit (assessed by scintigraphy) and bowel function were evaluated at baseline and the final 3 and 7 days of treatment, respectively. Treatment effects were compared using analysis of covariance, with gender, body mass index and baseline colonic transit as covariates.

RESULTS

19 patients (63%) had moderate or severe autonomic dysfunction; 16 (53%) had diabetic retinopathy. 14 of 16 patients randomised to pyridostigmine tolerated 360 mg daily; two patients took 180 mg daily. Compared with placebo (mean ± SEM 1.98 ± 0.17 (baseline), 1.84 ± 0.16 (treatment)), pyridostigmine accelerated (1.96 ± 0.18 (baseline), 2.45 ± 0.2 units (treatment), p<0.01) overall colonic transit at 24 h, but not gastric emptying or small-intestinal transit. Treatment effects on stool frequency, consistency and ease of passage were significant (p ≤ 0.04). Cholinergic side effects were somewhat more common with pyridostigmine (p=0.14) than with placebo.

CONCLUSIONS

Cholinesterase inhibition with oral pyridostigmine accelerates colonic transit and improves bowel function in diabetic patients with chronic constipation.

Differential effects of selective and non-selective muscarinic antagonists on gastrointestinal transit and bowel function in healthy women

BACKGROUND

The gastrointestinal effects of antimuscarinic drugs used to treat overactive bladder may be related to the selectivity of these agents for M(3) -muscarinic receptor subtypes. We compared the effects of non-selective (fesoterodine) and M(3)-selective (solifenacin) antimuscarinics on gastrointestinal transit in healthy women.

METHODS

Gastric emptying (GE), small-intestinal transit (colonic filling at 6 h), colonic transit [geometric center at 24 h (GC24; primary endpoint) and 48 h (GC48)], and bowel habits were assessed by scintigraphy and bowel diaries before and after randomization to fesoterodine 8 mg, solifenacin 10 mg, or placebo (2 : 2 : 1) for 14 days. An interim analysis to finalize sample size was conducted.

KEY RESULTS

After 60 subjects [placebo (n = 12), fesoterodine (n = 25), solifenacin (n = 23)] completed the study, the study was terminated due to a prespecified criterion (sample size ≥ 452.5 needed to provide ≥ 80% power to demonstrate superiority of fesoterodine over solifenacin in GC24). Compared with baseline, (i) placebo delayed small-intestinal, but not colonic, transit, (ii) fesoterodine significantly increased GE t(1/2) vs placebo (17.0 min; P = 0.027), and (iii) fesoterodine and solifenacin delayed small-intestinal (-36.8% and -21.8%, respectively, P < 0.001 vs placebo) and colonic transit (GC24: -0.44 and -0.49, respectively, P < 0.05 vs placebo; GC48: -0.25 and -0.65, respectively, P > 0.05 vs placebo). Solifenacin increased stool hardness from baseline (P = 0.010 for difference vs fesoterodine); stool frequency was comparable.

CONCLUSIONS & INFERENCES

In healthy women, fesoterodine had greater effects on small-intestinal transit and solifenacin had greater effects on colonic transit; the latter finding may explain why solifenacin, but not fesoterodine, increased stool hardness.