Lubiprostone: a chloride channel activator

Pharmacologic Treatment of Chronic Constipation

Chronic constipation is a common disease that can impair the quality of life, with a prevalence of 14% globally and 16.5% in South Korea. Straining, hard stools, the sensation of incomplete evacuation, the sensation of anorectal blockage, and manual maneuvers to facilitate defecation are the related symptoms of chronic constipation. On the other hand, medications commonly referred to as laxatives are the essentials of treatment for constipation compared to non-pharmacological treatment, such as lifestyle modifications, biofeedback, or surgery. Unfortunately, there is still an unmet need to determine if pharmacological treatment for constipation is being administered appropriately. Therefore, there are many disadvantages as to whether the indications and side effects of laxatives are adequately considered and prescribed as the primary treatment modality for constipation in a real clinical situation in Korea. Laxatives are generally recommended as the next step for patients in whom organic causes have been excluded and have not responded to initial non-pharmacologic therapies such as dietary fiber intake and exercise. Laxatives can be classified as bulk-forming laxatives, osmotic laxatives, stimulant laxatives, and other novel laxatives. On the other hand, there are distinct mechanisms underlying constipation, and appropriate administration is the most decisive. Therefore, the present investigators prepared this review to discuss appropriate pharmacological strategies for chronic constipation in Korea. Moreover, this paper also includes suggestions for appropriate pharmacological treatment options for special patient populations.

Constipation in Patients With Chronic Kidney Disease

Constipation is a frequent symptom in patients with chronic kidney disease (CKD). This review outlines the mechanisms and management of constipation in patients with CKD from a physician's perspective. Common causes of constipation in patients with CKD include concomitant medications, low dietary fiber intake, water-restricted diet, lack of physical activity, altered gut microbiota, and reduced gastrointestinal motility. Constipation has a negative impact on overall health, and, in particular, the presence of constipation has been associated with worsening kidney function and increased risk of developing advanced stages of CKD. Although lifestyle and dietary modifications may not always be practical for patients with CKD, they are recommended because they are beneficial as they lower mortality in patients with CKD. The use of laxatives containing magnesium salts, bulking agents, and osmotic laxatives may have insufficient efficacy and may be associated with adverse effects. In contrast, lactulose and lubiprostone have been shown to exhibit reno-protective effects. Linaclotide and plecanatide have very limited systemic absorption and appear safe in patients with CKD. Tenapanor reduces paracellular intestinal phosphate absorption in addition to blocking sodium uptake by enterocytes, and provides additional benefit in patients patients with CKD who have hyperphosphatemia and constipation. Prucalopride leads to improvements in bowel function and constipation-related symptoms in cases in which response to conventional laxatives are inadequate. However, the dose of prucalopride should be reduced to 1 mg once daily for patients with CKD. In conclusion, there are important advances on the impact and treatment of constipation in patients with CKD.

Lubiprostone plus polyethylene glycol electrolyte lavage solution (PEG-ELS) versus PEG-ELS for bowel preparation in chronic constipation: a randomized controlled trial

Colonoscopy is considered the standard procedure for early detection and prevention of colorectal cancer. Adequate bowel cleansing is an important determinant of the efficacy of colonoscopy screening. Currently, there is no standard method of bowel preparation for patients with chronic constipation. The aim was to access the rate of adequate bowel cleansing achieved using split-dose polyethylene glycol electrolyte lavage solution (PEG-ELS) plus lubiprostone in comparison with split-dose PEG-ELS alone. A single-centre, endoscopist-blinded, randomized controlled trial was conducted. Seventy-eight constipated patients aged 18-75 years who were indicated for colonoscopy in the gastroenterology unit of Srinagarind Hospital, Khon Kaen University, between February 2020 and February 2021 were randomly allocated to receive either split-dose PEG-ELS in combination with lubiprostone (N = 39) or split-dose PEG-ELS alone (N = 39) before colonoscopy. Adequate bowel cleansing was defined as an Ottawa bowel preparation score ≤ 7. The rate of adequate bowel cleansing was comparable between the PEG-ELS plus lubiprostone group and the PEG-ELS alone group (50% vs. 52.9%, p value = 0.81) with a relative risk of 1.13 (95% CI = 0.43-2.91). There were no significant differences in adenoma detection rate (41.2% vs. 35.3%, p value = 0.62), adverse events, acceptance, compliance, or patient satisfaction between the 2 groups. No additional benefit to successful bowel preparation was achieved by the combination of lubiprostone and PEG-ELS in chronic constipation patients undergoing colonoscopy.

Alleviation of cholestatic liver injury and intestinal permeability by lubiprostone treatment in bile duct ligated rats: role of intestinal FXR and tight junction proteins claudin-1, claudin-2, and occludin

Gut barrier disintegrity and endotoxin translocation to the liver and systemic circulation are serious clinical complications associated with the stoppage of intestinal bile flow. There is no precise pharmacological option to prevent increased intestinal permeability after bile duct ligation (BDL). Lubiprostone, a chloride channel-2 agonist, has been shown to accelerate restoration of epithelial barrier dysfunction caused by injury, but the exact mechanisms underlying the beneficial effects of lubiprostone on intestine barrier integrity remain unknown. Here, we assessed the beneficial effect of lubiprostone on cholestasis caused by BDL and relevant mechanisms. Male rats were subjected to BDL for 21 days. Seven days after BDL induction, lubiprostone was administered twice daily (10 µg/kg of body weight). Intestinal permeability was assessed through measurements of serum lipopolysaccharide (LPS) concentration. Real-time PCR was conducted to assess expression of intestinal claudin-1 occludin and FXR genes, which are important in preserving the intestinal epithelial barrier integrity, as well as claudin-2 being involved in a leaky gut barrier. Histopathological alterations were also monitored for liver injury. Lubiprostone significantly decreased BDL-induced systemic LPS elevation in rats. BDL induced a significant reduction in FXR, occludin, and claudin-1 genes expression, while increased claudin-2 expression in rat colon. Treatment with lubiprostone significantly restored expression of these genes to the control values. BDL also increased the level of hepatic enzymes ALT, ALP, AST, and total bilirubin, while lubiprostone could preserve the hepatic enzymes and total bilirubin in the treated BDL rats. Lubiprostone also caused a significant reduction in BDL-induced liver fibrosis and intestinal damage in rats. Our results suggest that lubiprostone favorably prevents BDL-induced alterations in intestinal epithelial barrier integrity possibly via modulating intestinal FXRs and tight junction gene expression.

Evaluation and management of irritable bowel syndrome

ABSTRACT

Irritable bowel syndrome (IBS) is a common diagnosis that providers encounter in primary and specialty care. IBS is characterized by chronic abdominal pain and altered bowel habits. The American College of Gastroenterology recently released an updated guideline for the evaluation and management of patients with IBS. According to the guideline, it remains important to confirm diagnosis based on criteria and lack of alarm signs; IBS should not be a diagnosis of exclusion. Management should be focused on addressing altered bowel habits and global symptoms using a multidisciplinary approach.

The Role of Ion Channels in Functional Gastrointestinal Disorders (FGID): Evidence of Channelopathies and Potential Avenues for Future Research and Therapeutic Targets

Several gastrointestinal (GI) tract abnormalities, including visceral hypersensitivity, motility, and intestinal permeability alterations, have been implicated in functional GI disorders (FGIDs). Ion channels play a crucial role in all the functions mentioned above. Hormones and natural molecules modulate these channels and represent targets of drugs and bacterial toxins. Mutations and abnormal functional expression of ion channel subunits can lead to diseases called channelopathies. These channelopathies in gastroenterology are gaining a strong interest, and the evidence of co-relationships is increasing. In this review, we describe the correlation status between channelopathies and FGIDs. Different findings are available. Among others, mutations in the ABCC7/CFTR gene have been described as a cause of constipation and diarrhea. Mutations of the SCN5A gene are instead associated with irritable bowel syndrome. In contrast, mutations of the TRPV1 and TRPA genes of the transient receptor potential (TRP) superfamily manifest hypersensitivity and visceral pain in sensory nerves. Recently, mice and humans affected by Cantu syndrome (CS), which is associated with the mutations of the KCNJ8 and ABCC9 genes encoding for the Kir6.1 and SUR2 subunits, showed dysfunction of contractility throughout the intestine and death in the mice after the weaning on solid food. The discovery of a correlation between channelopathies and FIGD opens new avenues for discovering new direct drug targets for specific channelopathies, leading to significant implications for diagnosing and treating functional GI diseases.

Pharmacokinetics and Bioequivalence of the Lubiprostone Capsule in Healthy Chinese Subjects

A pharmacokinetic (PK) study and a bioequivalence (BE) study were conducted to investigate the PK characteristics and safety of lubiprostone in healthy Chinese subjects and to evaluate the BE between the test and the reference drugs. The PK study consisted of a fasting state cohort (a single dose of 24 µg of lubiprostone), a 2-period crossover fasting and fed state cohort (a single dose of 48 µg of lubiprostone), and a multiple-dose cohort (24 µg of lubiprostone twice daily). The BE study was a single-dose, 2-treatment, 4-period, replicated crossover study. The plasma concentration of 15-OH-lubiprostone (M3) was measured by high-performance liquid chromatography-tandem mass spectrometry. The PK parameters were calculated using the noncompartment model with Phoenix WinNonlin. After a single dose of 24 ug of lubiprostone, the main PK parameters of M3 were 49.2 pg/mL, 74.0 h/pg/mL, and 1.1 hours for maximum plasma concentration (C_max ), area under the plasma concentration time curve from time 0 to the last time point, and t_1/2 , respectively. The main PK parameters of M3 showed dose-proportional characteristics in the dose range of 24-48 µg. Food affects the PK parameters of M3. Compared to the fasting state, time to maximum plasma concentration was delayed, C_max decreased slightly, while AUC increased significantly under the fed state. The test and reference products had similar PK parameters and were bioequivalent in the fed state.

Cost of Constipation: A New Look With a Focus on New Medications

GOAL

The study was designed to assess drug costs for constipation therapy and to relate costs to markers of functional status.

BACKGROUND

Secretagogues have been introduced as new agents for the treatment of constipation. Previously published modeling studies suggested that improved productivity lowers the indirect disease burden and balances the higher drug costs.

STUDY

Data were abstracted from the publicly available Medical Expenditure Panel Survey to identify adults with a functional gastrointestinal disorder who received a prescription for laxatives or secretagogues covering >2 days. Demographic data, recorded health care utilization and cost, and markers of functional status were extracted for the years from 2005 to 2017 to determine differences between participants treated with secretagogues or laxatives.

RESULTS

The cohort of 2006 persons was female predominant [67.8%; age: 56.9 (55.8-57.9) years] and spent $92.89 (75.68-110.10) for medications treating constipation. The use of secretagogues (10.3% of the cohort) was the best independent predictor of constipation treatment costs. Using quality of life measures, perceived limitations in activities or work, and absenteeism, there was no difference between participants receiving laxatives and those taking secretagogues.

CONCLUSION

Using survey data designed to be representative of the United States population, the study identified secretagogues as a key cost factor in drug treatment of constipation. The results do not support models suggesting improved role functioning offsets these higher direct expenditures. While prospective comparative studies are needed to more definitively correlate costs with direct or indirect benefits of different agents, limiting the use of more expensive medications to otherwise refractory cases may help to reign in the spiraling health care costs in this country.

ACG Clinical Guideline: Management of Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a highly prevalent, chronic disorder that significantly reduces patients' quality of life. Advances in diagnostic testing and in therapeutic options for patients with IBS led to the development of this first-ever American College of Gastroenterology clinical guideline for the management of IBS using Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Twenty-five clinically important questions were assessed after a comprehensive literature search; 9 questions focused on diagnostic testing; 16 questions focused on therapeutic options. Consensus was obtained using a modified Delphi approach, and based on GRADE methodology, we endorse the following: We suggest that a positive diagnostic strategy as compared to a diagnostic strategy of exclusion be used to improve time to initiating appropriate therapy. We suggest that serologic testing be performed to rule out celiac disease in patients with IBS and diarrhea symptoms. We suggest that fecal calprotectin be checked in patients with suspected IBS and diarrhea symptoms to rule out inflammatory bowel disease. We recommend a limited trial of a low fermentable oligosaccharides, disacchardies, monosaccharides, polyols (FODMAP) diet in patients with IBS to improve global symptoms. We recommend the use of chloride channel activators and guanylate cyclase activators to treat global IBS with constipation symptoms. We recommend the use of rifaximin to treat global IBS with diarrhea symptoms. We suggest that gut-directed psychotherapy be used to treat global IBS symptoms. Additional statements and information regarding diagnostic strategies, specific drugs, doses, and duration of therapy can be found in the guideline.

Uncontrolled, Open-Label Pre-Dinner Administration of Elobixibat in Japanese Adults with Chronic Constipation: A Retrospective Chart Review

BACKGROUND

Elobixibat has been approved as a new therapeutic drug for chronic constipation. Only the pharmacological efficacy and safety profile of pre-breakfast administration of elobixibat had been previously demonstrated.

OBJECTIVE

We evaluated the efficacy and safety profile of pre-dinner administration of elobixibat in patients with functional constipation in a retrospective observational study.

METHODS

Patients aged 20 years or older diagnosed with functional constipation by the Rome IV criteria from June 1, 2018, to January 17, 2019. The evaluation time points were at the start and 1, 2, 4, and 8 weeks after treatment. The primary end point was frequency of spontaneous bowel movements per week. The secondary end points were changes in Bristol Stool Form Scale score, onset time required for spontaneous defecation after administration, percent of patients with spontaneous defecation within 24 hours and 48 hours after the first administration, improvement of abdominal pain or abdominal bloating evaluated by a visual analog scale, and total score and each subscore of the Japanese-Translated Version of Patient Assessment of Constipation Quality of Life Questionnaire.

RESULTS

Pre-dinner administration of elobixibat was associated with significantly increased frequency of spontaneous bowel movements and improved Bristol Stool Form Scale score at 1, 2, 4, and 8 weeks after treatment. The mean onset time until spontaneous defecation after treatment was 4 to 5 hours, which was earlier than that by conventional constipation treatment drugs and almost constant within an individual during the treatment period. Spontaneous defecation was achieved by 85.4% within 24 hours and 90.2% within 48 hours after the first administration. Elobixibat also improved patients' quality of life, which was evaluated by the Japanese-Translated Version of Patient Assessment of Constipation Quality of Life Questionnaire without adverse events.

CONCLUSIONS

Pre-dinner administration of elobixibat improved constipation, abdominal pain and bloating, and patient quality of life by management of fixed defecation. (Curr Ther Res Clin Exp. 2020; 81:XXX-XXX).

A meta-analysis of randomized controlled trials of the addition of lubiprostone to bowel preparation before colonoscopy

AIM

Adequate bowel preparation is essential to the quality of colonoscopy. We performed a meta-analysis to determine the efficacy and safety of the addition of lubiprostone to the bowel preparation process prior to colonoscopy.

METHODS

Online databases, namely, PubMed, MEDLINE and Cochrane Library, were searched for randomized controlled trials that assessed the additive effect of lubiprostone on the quality of colon preparation in patients undergoing colonoscopy. Each included study was evaluated by the Jadad score to assess the quality of the study. The primary outcome was bowel preparation efficacy, defined as the proportion of patients with an excellent or poor preparation. The secondary outcomes included the length of the colonoscopy, polyp detection, and any adverse effects.

RESULTS

In total, 5 articles published between 2008 and 2016 fulfilled the selection criteria. The addition of lubiprostone to the bowel cleansing process significantly increased the proportion of patients with an excellent preparation (risk ratio [RR] = 1.68, 95% confidence interval (CI): 1.40-2.02, P < .00001) but did not decrease the procedural time or increase the polyp detection rate (mean difference = -0.52, 95% CI: -3.74-2.69, P = .75; RR = 1.16, 95% CI: 0.96-1.42, P = .13, respectively). There was no significant difference in the proportion of patients with any adverse events.

CONCLUSION

The addition of lubiprostone to the bowel preparation regimen prior to colonoscopy is effective and safe.

Efficacy and Safety of Lubiprostone in Patients with Opioid-Induced Constipation: Phase 3 Study Results and Pooled Analysis of the Effect of Concomitant Methadone Use on Clinical Outcomes

Objective

The efficacy and safety of oral lubiprostone for relieving symptoms of opioid-induced constipation (OIC) in patients with chronic noncancer pain were evaluated in a randomized, double-blind, placebo-controlled study. These data were also pooled with those from two similar phase 3 studies to explore the effects of methadone on treatment response.

Methods

In the primary study, adults with OIC (fewer than three spontaneous bowel movements [SBMs] per week) were randomized to receive lubiprostone 24 mcg or placebo twice daily for 12 weeks. The primary end point was a change from baseline in the frequency of SBMs at week 8 in patients without a prior dose reduction. For the pooled analysis, the efficacy of lubiprostone was compared with placebo in patients receiving methadone or nonmethadone opioids. Responders were defined as patients with nine or more weeks of nonmissing SBM data who had one or more additional SBMs per week from baseline for each week that data were available and three or more SBMs per week for nine or more weeks.

Results

In the primary study, the change from baseline at week 8 in SBM frequency was similar in the lubiprostone and placebo groups (P = 0.842). In the pooled analysis, the response rate was significantly higher with lubiprostone treatment vs placebo for patients receiving nonmethadone opioids (P = 0.002) but was similar between lubiprostone treatment and placebo in patients receiving methadone (P = 0.692). The safety profile of lubiprostone was unaffected by methadone use.

Conclusions

The phase 3 study did not meet its primary efficacy end point. However, analysis of pooled data from all phase 3 studies in the OIC clinical development program, stratified by methadone opioid usage, confirmed that lubiprostone is effective for treatment of OIC in patients taking nonmethadone opioids; no safety concerns were identified based on the type of opioid used.

Efficacy of Lubiprostone for the Treatment of Opioid-Induced Constipation, Analyzed by Opioid Class

Objectives

To examine the efficacy and safety of lubiprostone for the treatment of opioid-induced constipation (OIC) in patients by opioid class received.

Design

Data were pooled from three phase III, randomized, double-blind, placebo-controlled studies.

Subjects/Setting

Adults with chronic noncancer pain receiving opioid therapy for 30 or more days and diagnosed with OIC.

Methods

Overall mean change from baseline in spontaneous bowel movement (SBM) frequency, overall treatment response (≥1 SBM/week improvement over baseline SBM frequency in all treatment weeks with available data and ≥3 SBMs/week for ≥9 of the 12 weeks of treatment), and OIC-related symptoms were examined in patients taking opioids. Data were pooled and analyzed by opioid group.

Results

In patients receiving phenanthrene opioids (e.g., oxycodone; N = 1,159), lubiprostone significantly increased overall mean changes in SBM frequency from baseline (P = 0.0001), increased overall response rate (P = 0.0024), and improved OIC symptoms (P ≤ 0.0229) vs placebo. Patients receiving phenylpiperidine opioids (e.g., fentanyl; N = 137) had significant improvement in SBM frequency (P = 0.0129) and favorable trends in response rates (21.4% vs 9.8%; P = 0.0723) and OIC symptoms vs placebo. Efficacy was not observed in overall analyses of patients receiving diphenylheptane opioids (e.g., methadone), although an increase in SBM frequency was observed in patients who received a morphine-equivalent daily dose of 200 or fewer mg, suggesting a dose-dependent negative interference of this opioid class on lubiprostone effects. For all groups, the lubiprostone adverse event profile was similar; the most common treatment-emergent adverse events were nausea and diarrhea.

Conclusions

In patients using commonly prescribed opioids, lubiprostone is effective and generally well tolerated for the treatment of OIC.

Canadian Association of Gastroenterology Clinical Practice Guideline for the Management of Irritable Bowel Syndrome (IBS)

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal (GI) disorders, affecting about 10% of the general population globally. The aim of this consensus was to develop guidelines for the management of IBS.

METHODS

A systematic literature search identified studies on the management of IBS. The quality of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development and Evaluation (GRADE) approach. Statements were developed through an iterative online platform and then finalized and voted on by a multidisciplinary group of clinicians and a patient.

RESULTS

Consensus was reached on 28 of 31 statements. Irritable bowel syndrome is diagnosed based on symptoms; serological testing is suggested to exclude celiac disease, but routine testing for C-reactive protein (CRP), fecal calprotectin or food allergies is not recommended. A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, polyols (FODMAP) diet is suggested, while a gluten-free diet is not. Psyllium, but not wheat bran, supplementation may help reduce symptoms. Alternative therapies such as peppermint oil and probiotics are suggested, while herbal therapies and acupuncture are not. Cognitive behavioural therapy and hypnotherapy are suggested psychological therapies. Among the suggested or recommended pharmacological therapies are antispasmodics, certain antidepressants, eluxadoline, lubiprostone, and linaclotide. Loperamide, cholestyramine and osmotic laxatives are not recommended for overall IBS symptoms. The nature of the IBS symptoms (diarrhea-predominant or constipation-predominant) should be considered in the choice of pharmacological treatments.

CONCLUSIONS

Patients with IBS may benefit from a multipronged, individualized approach to treatment, including dietary modifications, psychological and pharmacological therapies.

Lubiprostone in the treatment of chronic idiopathic constipation: an update on health-related quality of life and patient-reported outcomes

Chronic idiopathic constipation, if inadequately treated, can be bothersome with a detrimental effect on patients’ quality of life (QOL). This may also result in frequent health care visits, increasing the burden of this ailment’s medical cost. Management strategies, focused on lifestyle changes, include increased exercise, a high-fiber diet, and toilet training. Pharmacologic options include fiber supplementation, laxatives, serotonergic agents, and prosecretory agents such as lubiprostone. In this review, we were able to conclude that lubiprostone, when used for chronic idiopathic constipation, has a significantly beneficial effect on both patients’ symptoms and their QOL. In multiple randomized controlled trials, it has been found to have increased the number of spontaneous bowel movements at different time endpoints. Corresponding improvements were also observed for abdominal bloating, discomfort, stool frequency, and straining symptoms among patients.

Gut microbiota, hypertension and chronic kidney disease: Recent advances

A large number of different microbial species populates intestine. Extensive research has studied the entire microbial population and their genes (microbiome) by using metagenomics, metatranscriptomics and metabolomic analysis. Studies suggest that the imbalances of the microbial community causes alterations in the intestinal homeostasis, leading to repercussions on other systems: metabolic, nervous, cardiovascular, immune. These studies have also shown that alterations in the structure and function of the gut microbiota play a key role in the pathogenesis and complications of Hypertension (HTN) and Chronic Kidney Disease (CKD). Increased blood pressure (BP) and CKD are two leading risk factors for cardiovascular disease and their treatment represents a challenge for the clinicians. In this Review, we discuss mechanisms whereby gut microbiota (GM) and its metabolites act on downstream cellular targets to contribute to the pathogenesis of HTN and CKD, and potential therapeutic implications.

Analysis of Nausea in Clinical Studies of Lubiprostone for the Treatment of Constipation Disorders

BACKGROUND

Lubiprostone is a ClC-2 chloride channel activator approved for the treatment of chronic idiopathic constipation (CIC) and opioid-induced constipation (OIC) in adults and irritable bowel syndrome with constipation (IBS-C) in women. Lubiprostone is generally well tolerated, with nausea being the most common adverse event.

AIMS

To characterize nausea with lubiprostone using pooled results from clinical studies in patients with CIC, OIC, or IBS-C.

METHODS

Data from three 3- and 4-week placebo-controlled studies and three long-term open-label studies were pooled for the CIC analysis. The OIC and IBS-C analyses each used pooled data from three 12-week placebo-controlled studies and one 36-week open-label extension study.

RESULTS

The populations included the following numbers of patients: CIC, 316 (placebo) and 1113 (lubiprostone 24 mcg twice daily [BID]); OIC, 652 (placebo) and 889 (lubiprostone 24 mcg BID); and IBS-C, 435 (placebo) and 1011 (lubiprostone 8 mcg BID). The incidence of nausea in lubiprostone-treated patients ranged from 11.4 to 31.1%, with the highest incidence in patients with CIC. Among patients with any nausea, most reported only mild or moderate severity (96.5-99.1% across indications) and only one event (83.6-88.7%); most events occurred within the first 5 days of treatment.

CONCLUSIONS

Nausea was the most common adverse event following the treatment with lubiprostone. Event rates varied by indication and dose, and the majority of nausea adverse events were mild to moderate in severity. Nausea events predominantly occurred early in the treatment period in all of the pooled study populations.

Research and progress on ClC‑2 (Review)

Chloride channel 2 (ClC-2) is one of the nine mammalian members of the ClC family. The present review discusses the molecular properties of ClC‑2, including CLCN2, ClC‑2 promoter and the structural properties of ClC‑2 protein; physiological properties; functional properties, including the regulation of cell volume. The effects of ClC‑2 on the digestive, respiratory, circulatory, nervous and optical systems are also discussed, in addition to the mechanisms involved in the regulation of ClC‑2. The review then discusses the diseases associated with ClC‑2, including degeneration of the retina, Sjögren's syndrome, age‑related cataracts, degeneration of the testes, azoospermia, lung cancer, constipation, repair of impaired intestinal mucosa barrier, leukemia, cystic fibrosis, leukoencephalopathy, epilepsy and diabetes mellitus. It was concluded that future investigations of ClC‑2 are likely to be focused on developing specific drugs, activators and inhibitors regulating the expression of ClC‑2 to treat diseases associated with ClC‑2. The determination of CLCN2 is required to prevent and treat several diseases associated with ClC‑2.

Mashiningan Improves Opioid-Induced Constipation in Rats by Activating Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channel

Opioid receptor stimulants are analgesics used in patients with and without cancer; however, they often cause constipation, resulting in poor adherence and deterioration of the quality of life. Hence, suitable treatments for constipation are required. In this study, we investigated the pharmacological mechanisms of action of mashiningan (MNG), a Kampo medicine used to treat constipation, and evaluated the effect of MNG on opioid-induced constipation in rats. MNG (100 or 300 mg/kg) was orally administered to normal or codeine phosphate (CPH)-induced constipation in rats, and its effect was evaluated on the basis of fecal counts, characteristics, and weight. Small intestinal fluid secretion was measured after treatment with MNG alone or coadministration with a cystic fibrosis transmembrane conductance regulator (CFTR)-specific inhibitor (CFTRinh-172). The effects of MNG on the CFTR and type-2 chloride channel were determined using patch-clamp or short-circuit current experiments, respectively. MNG increased the fecal weight and proportion of soft feces in normal rats. CPH-induced constipation in rats decreased fecal counts and weight, whereas MNG prevented these effects and increased the proportion of soft feces. MNG increased the electronic chloride current, and this effect was inhibited by the CFTRinh-172 in the CFTR assay. Furthermore, MNG increased small intestinal fluid secretion, and this effect was abolished by coadministration with the CFTRinh-172. MNG improved opioid-induced constipation in rats, and this improvement may have been mediated by increasing intestinal fluid secretion via CFTR chloride channel activation. Therefore, MNG is expected as a medicine of the treatment of constipation in patients taking opioids.

Chemotherapy-Induced Constipation and Diarrhea: Pathophysiology, Current and Emerging Treatments

Gastrointestinal (GI) side-effects of chemotherapy are a debilitating and often overlooked clinical hurdle in cancer management. Chemotherapy-induced constipation (CIC) and Diarrhea (CID) present a constant challenge in the efficient and tolerable treatment of cancer and are amongst the primary contributors to dose reductions, delays and cessation of treatment. Although prevalence of CIC is hard to estimate, it is believed to affect approximately 16% of cancer patients, whilst incidence of CID has been estimated to be as high as 80%. Despite this, the underlying mechanisms of both CID and CIC remain unclear, but are believed to result from a combination of intersecting mechanisms including inflammation, secretory dysfunctions, GI dysmotility and alterations in GI innervation. Current treatments for CIC and CID aim to reduce the severity of symptoms rather than combating the pathophysiological mechanisms of dysfunction, and often result in worsening of already chronic GI symptoms or trigger the onset of a plethora of other side-effects including respiratory depression, uneven heartbeat, seizures, and neurotoxicity. Emerging treatments including those targeting the enteric nervous system present promising avenues to alleviate CID and CIC. Identification of potential targets for novel therapies to alleviate chemotherapy-induced toxicity is essential to improve clinical outcomes and quality of life amongst cancer sufferers.

Addition of Lubiprostone to polyethylene glycol(PEG) enhances the quality & efficacy of colonoscopy preparation: a randomized, double-blind, placebo controlled trial

Background

Adequate bowel preparation is an essential prerequisite for complete mucosal visualization during colonoscopy. Polyethylene glycol (PEG) solutions are commonly used. However the large volume of the solution is often poorly tolerated. Addition of Lubiprostone (LB) could improve the adequacy of standard PEG preparation & reduce requirement. The aims to assess adequacy of PEG preparation with addition of single dose LB (24mcg) vs placebo and efficacy of reduced dose PEG + LB compared with full dose PEG + LB.

Methods

Single center prospective double blind randomized controlled trial. Part I: 442 patients for colonoscopy randomized to receive placebo (GrA) or single dose of LB (GrB) prior to PEG preparation. Quality of bowel preparation graded 0–9 according to Boston Bowel Preparation Scale (BBPS). BBPS-9: excellent and BBPS 0–4: repeat procedure.

Part II: 146 patients randomized to receive LB + 1.5 L PEG (GrC; 75) or LB + 1 L PEG (GrD; 71). BBPS score compared with GrB (2 L PEG).

Results

Part I: 442 patients (221 GrA & 221 Gr B). LB resulted in significant improvement in total BBPS (7.44 + 0.14 vs. 6.36 + 0.16, p < 0.0001). 66.5 % Gr B vs 38 % Gr A had excellent prep; 42.5 % GrB vs 24 % GrA had adequate prep. Repeat procedure needed 9.5 % Gr B vs 16.7 % Gr A (P < 0.01).

Part II: No difference in BBPS scores with lower doses (Gr C&D) compared to standard (GrB) (Mean BBPS 7.44 + 0.14 GrA,7.30 + 0.25 GrC;7.25 + 0.26 GrD;p >0.05).

Conclusion

Single dose LB prior to PEG significantly enhanced bowel preparation compared to PEG alone. There was no significant difference in quality of preparation with lower doses of PEG when combined with LB.

Trial registration

The study protocol was approved by institutional review board and the trial was registered on March 22, 2011 with clinicaltrials.gov (NCT01324284).

Constipation in Elderly Patients with Noncancer Pain: Focus on Opioid-Induced Constipation

Constipation is a common and often debilitating condition in the elderly, which may be caused by underlying disease conditions, structural abnormalities in the bowel, and a variety of medications such as anticholinergics, antidepressants, and opiates. In this review, we focus on opioid-induced constipation (OIC), which is often underrecognized and undertreated in the elderly. When opioid therapy is initiated, healthcare providers are encouraged to evaluate risk factors for the development of constipation as part of a thorough patient history. To this end, the patient assessment should include the use of validated instruments, such as the Bristol Stool Scale and Bowel Function Index, to confirm the diagnosis and provide a basis for evaluating treatment outcomes. Healthcare providers should use a stepwise approach to the treatment of OIC in the elderly. Conventional laxatives are a first-line option and considered well tolerated with short-term use as needed; however, evidence is lacking to support their effectiveness in OIC. Moreover, because of the risk of adverse events and other considerations, such as chewing difficulties and swallowing disorders, conventional oral laxatives may be inappropriate for the treatment of OIC in the elderly. Thus, the availability of new pharmacologic agents such as the peripherally acting µ-opioid receptor antagonists methylnaltrexone and naloxegol, which target the underlying causes of OIC, and the secretagogue lubiprostone may provide more effective treatment options for elderly patients with OIC.

Opioid-induced constipation

Opioid-induced constipation (OIC) is a very troublesome, difficult to manage and a nearly universal complication of chronic opioid use to control pain associated with advanced illness. Some studies have reported that OIC is so intolerable in some patients that they skip their opioid medications and bear pain instead of OIC. Laxatives have commonly been used as a prophylaxis and treatment of OIC but they are frequently ineffective because the commonly available laxatives do not target the underlying mechanism of OIC, which is the blockade of peripheral mu-receptors. Recently, there have been a number of advances in the treatment of OIC, which any physician involved with opioid-prescribing discipline should be aware of. This review will update the new options and strategies available for treating OIC along with the relevant clinical trials. Finally, this review also provides a recommendation on the preferred way to approach a patient with OIC in the modern era as well as highlight on the importance of doctor-patient communication in this setting.

Definition, diagnosis and treatment strategies for opioid-induced bowel dysfunction–Recommendations of the Nordic Working Group

Background and aims

Opioid-induced bowel dysfunction (OIBD) is an increasing problem due to the common use of opioids for pain worldwide. It manifests with different symptoms, such as dry mouth, gastro-oesophageal reflux, vomiting, bloating, abdominal pain, anorexia, hard stools, constipation and incomplete evacuation. Opioid-induced constipation (OIC) is one of its many symptoms and probably the most prevalent. The current review describes the pathophysiology, clinical implications and treatment of OIBD.

Methods

The Nordic Working Group was formed to provide input for Scandinavian specialists in multiple, relevant areas. Seven main topics with associated statements were defined. The working plan provided a structured format for systematic reviews and included instructions on how to evaluate the level of evidence according to the GRADE guidelines. The quality of evidence supporting the different statements was rated as high, moderate or low. At a second meeting, the group discussed and voted on each section with recommendations (weak and strong) for the statements.

Results

The literature review supported the fact that opioid receptors are expressed throughout the gastrointestinal tract. When blocked by exogenous opioids, there are changes in motility, secretion and absorption of fluids, and sphincter function that are reflected in clinical symptoms. The group supported a recent consensus statement for OIC, which takes into account the change in bowel habits for at least one week rather than focusing on the frequency of bowel movements. Many patients with pain receive opioid therapy and concomitant constipation is associated with increased morbidity and utilization of healthcare resources. Opioid treatment for acute postoperative pain will prolong the postoperative ileus and should also be considered in this context. There are no available tools to assess OIBD, but many rating scales have been developed to assess constipation, and a few specifically address OIC. A clinical treatment strategy for OIBD/OIC was proposed and presented in a flowchart. First-line treatment of OIC is conventional laxatives, lifestyle changes, tapering the opioid dosage and alternative analgesics. Whilst opioid rotation may also improve symptoms, these remain unalleviated in a substantial proportion of patients. Should conventional treatment fail, mechanism-based treatment with opioid antagonists should be considered, and they show advantages over laxatives. It should not be overlooked that many reasons for constipation other than OIBD exist, which should be taken into consideration in the individual patient.

Conclusion and implications

It is the belief of this Nordic Working Group that increased awareness of adverse effects and OIBD, particularly OIC, will lead to better pain treatment in patients on opioid therapy. Subsequently, optimised therapy will improve quality of life and, from a socio-economic perspective, may also reduce costs associated with hospitalisation, sick leave and early retirement in these patients.

ClC-2 regulation of intestinal barrier function: Translation of basic science to therapeutic target

The ClC-2 chloride channel is a member of the voltage-gated chloride channel family. ClC-2 is involved in various physiological processes, including fluid transport and secretion, regulation of cell volume and pH, maintaining the membrane potential of the cell, cell-to-cell communication, and tissue homeostasis. Recently, our laboratory has accumulated evidence indicating a critical role of ClC-2 in the regulation of intestinal barrier function by altering inter-epithelial tight junction composition. This review will detail the role of ClC-2 in intestinal barrier function during intestinal disorders, including experimental ischemia/reperfusion injury and dextran sodium sulfate (DSS)-induced inflammatory bowel disease. Details of pharmacological manipulation of ClC-2 via prostone agonists will also be provided in an effort to show the potential therapeutic relevance of ClC-2 regulation, particularly during intestinal barrier disruption.

Current developments in pharmacological therapeutics for chronic constipation

Chronic constipation is a common gastrointestinal disease severely affecting the patient׳s quality of life. The traditional treatment of constipation is the use of laxatives. Recently, several new drugs including lubiprostone, linaclotide and prucalopride have been approved for treatment of chronic constipation. However, a significant unmet medical need still remains, particularly among those patients achieving poor results by current therapies. The 5-HT4 receptor modulators velusetrag and naronapride, the guanylate cyclase C agonist plecanatide and the ileal bile acid transporter inhibitor elobixibat are recognized as the most promising drugs under investigation. Herein, we give a comprehensive review on the pharmacological therapeutics for the treatment of chronic constipation, with the purpose of reflecting the drug development trends in this field.

A randomized, placebo-controlled trial of lubiprostone for opioid-induced constipation in chronic noncancer pain

OBJECTIVES

This multicenter, phase 3 trial evaluated oral lubiprostone for constipation associated with non-methadone opioids in patients with chronic noncancer-related pain.

METHODS

Adults with opioid-induced constipation (OIC; <3 spontaneous bowel movements [SBMs] per week) were randomized 1:1 to double-blind lubiprostone 24 μg or placebo twice daily for 12 weeks. The primary end point was the overall SBM response rate. Responders had at least moderate response (≥1 SBM improvement over baseline frequency) in all treatment weeks with available observed data, as well as full response (≥3 SBMs per week) for at least 9 of the 12 treatment weeks.

RESULTS

In total, 431 patients were randomized; 212 each received lubiprostone and placebo, and 7 were not treated. Overall, the SBM response rate was significantly higher for patients treated with lubiprostone vs. placebo (27.1 vs. 18.9%, respectively; P=0.030). Overall mean change from baseline in SBM frequency was significantly greater with lubiprostone vs. placebo (3.2 vs. 2.4, respectively; P=0.001). The median time to first SBM was significantly shorter with lubiprostone vs. placebo (23.5 vs. 37.7 h, respectively; P=0.004). Compared with placebo, the patients treated with lubiprostone exhibited significant improvements in straining (P=0.004), stool consistency (P<0.001), and constipation severity (P=0.010). No significant differences were observed in quality-of-life measures or the use of rescue medication; however, the percentage of patients who used rescue medication was consistently lower in the lubiprostone group than in the placebo group at months 1 (34.9 vs. 37.7%), 2 (23.4 vs. 26.6%), and 3 (20.5 vs. 22.0%). Adverse events (AEs) >5% were diarrhea, nausea, vomiting, and abdominal pain (lubiprostone: 11.3, 9.9, 4.2, and 7.1%, respectively; placebo, 3.8, 4.7, 5.2, and 0%, respectively). None of the serious AEs (lubiprostone, 3.3%; placebo, 2.8%) were related to lubiprostone.

CONCLUSIONS

Lubiprostone significantly improved symptoms of OIC and was well tolerated in patients with chronic noncancer pain.

ClC-1 chloride channels: state-of-the-art research and future challenges

The voltage-dependent ClC-1 chloride channel belongs to the CLC channel/transporter family. It is a homodimer comprising two individual pores which can operate independently or simultaneously according to two gating modes, the fast and the slow gate of the channel. ClC-1 is preferentially expressed in the skeletal muscle fibers where the presence of an efficient Cl(-) homeostasis is crucial for the correct membrane repolarization and propagation of action potential. As a consequence, mutations in the CLCN1 gene cause dominant and recessive forms of myotonia congenita (MC), a rare skeletal muscle channelopathy caused by abnormal membrane excitation, and clinically characterized by muscle stiffness and various degrees of transitory weakness. Elucidation of the mechanistic link between the genetic defects and the disease pathogenesis is still incomplete and, at this time, there is no specific treatment for MC. Still controversial is the subcellular localization pattern of ClC-1 channels in skeletal muscle as well as its modulation by some intracellular factors. The expression of ClC-1 in other tissues such as in brain and heart and the possible assembly of ClC-1/ClC-2 heterodimers further expand the physiological properties of ClC-1 and its involvement in diseases. A recent de novo CLCN1 truncation mutation in a patient with generalized epilepsy indeed postulates an unexpected role of this channel in the control of neuronal network excitability. This review summarizes the most relevant and state-of-the-art research on ClC-1 chloride channels physiology and associated diseases.

Direct interactions between ENaC gamma subunit and ClCN2 in cystic fibrosis epithelial cells

Cystic fibrosis (CF) is a lethal disease caused by mutations in the chloride channel CFTR gene. The disease is characterized by decreased chloride secretion and unregulated sodium absorption through the epithelial sodium channel (ENaC) in the airway epithelium and other affected organs. We hypothesize that a non‐CFTR alternative chloride channel ClCN2 can be activated to negatively regulate ENaC in CF epithelial cell cultures. We identified a novel interaction between ClCN2 and the ENaCγ subunit in CF airway epithelial cells and show that the upregulation of ClCN2 leads to decreased expression of ENaCγ via a K63 ubiquitination mechanism. These regulatory effects of ClCN2 on ENaCγ appear to be dependent on the CBS‐1 domain located within the c‐terminus of ClCN2, which is necessary for the targeting of ClCN2 to the apical surface. In sum, these results suggest the ability of ClCN2 to negatively regulate sodium absorption through ENaC, supporting its role as a therapeutic target for the treatment of CF.

Cystic Fibrosis is caused by mutations in the chloride channel CFTR gene which secondarily increases sodium reabsorption in the airways. ClCN2 is an epithelial chloride channel in the airways that can be activated in CF. We show an interaction between ClCN2 and the epithelial sodium channel subunit gamma that affects subunit expression and targeting to the plasma membrane.

Gut microbial and short-chain fatty acid profiles in adults with chronic constipation before and after treatment with lubiprostone

Identifying specific gut microorganisms associated with chronic constipation may be useful for diagnostic and therapeutic purposes. The objective of this study was to evaluate whether or not the gut microbial community of constipated subjects had specific microbial signatures and to assess the effects of lubiprostone treatment on the gut microbial community. Stool diaries, breath H2 and CH4 levels, and stool samples were collected from ten healthy subjects and nine patients meeting the Rome III criteria for chronic functional constipation. Constipated subjects received lubiprostone for four weeks, during which stool diaries were maintained. Stool samples were evaluated for gut microbial communities using pyrosequencing and quantitative real-time PCR (qPCR) targeting 16S-rRNA gene, along with concentrations of short-chain fatty acids (SCFAs) using high-performance liquid chromatography. Prior to treatment, gut microbial profiles were similar between constipated subjects and healthy subjects, while iso-butyrate levels were significantly higher in constipated subjects compared with healthy subjects. Despite increases in stool frequency and improvements in consistency after lubiprostone treatment, gut microbial profiles and community diversity after treatment showed no significant change compared to before treatment. While we did not observe a significant difference in either breath methane or archaeal abundance between the stool samples of healthy and constipated subjects, we confirmed a strong correlation between archaeal abundance measured by qPCR and the amount of methane gas exhaled in the fasting breath. Butyrate levels, however, were significantly higher in the stool samples of constipated subjects after lubiprostone treatment, suggesting that lubiprostone treatment had an effect on the net accumulation of SCFAs in the gut. In conclusion, lubiprostone treatment improved constipation symptoms and increased levels of butyrate without substantial modification of the gut microbial structure.

Management of constipation in Parkinson's disease

INTRODUCTION

Constipation is a frequent non-motor feature of Parkinson's disease (PD). It is the most common gastrointestinal symptom of the disease and it can precede motor symptoms by as much as 20 years. Constipation can produce discomfort and affect activities of daily living, productivity and quality of life, thus warranting early diagnosis and treatment.

AREAS COVERED

In this review, the safety and efficacy of traditional and novel strategies for constipation management will be discussed. A treatment algorithm for constipation in PD will be presented.

EXPERT OPINION

Polyethylene glycol and lubiprostone are first-line compounds recommended by evidence-based medicine guidelines for the treatment of constipation due to slow colonic transit in PD. Management of constipation secondary to defecatory dysfunction due to pelvic floor dyssynergia can be done by levodopa or apomorphine injections, botulinum toxin type A injection into the puborectalis muscle, and nonpharmacological interventions, like biofeedback therapy or functional magnetic stimulation, which showed some benefit in PD patients with constipation, but in general more extensive studies are warranted.

Alteration of the Intestinal Environment by Lubiprostone Is Associated with Amelioration of Adenine-Induced CKD

The accumulation of uremic toxins is involved in the progression of CKD. Various uremic toxins are derived from gut microbiota, and an imbalance of gut microbiota or dysbiosis is related to renal failure. However, the pathophysiologic mechanisms underlying the relationship between the gut microbiota and renal failure are still obscure. Using an adenine-induced renal failure mouse model, we evaluated the effects of the ClC-2 chloride channel activator lubiprostone (commonly used for the treatment of constipation) on CKD. Oral administration of lubiprostone (500 µg/kg per day) changed the fecal and intestinal properties in mice with renal failure. Additionally, lubiprostone treatment reduced the elevated BUN and protected against tubulointerstitial damage, renal fibrosis, and inflammation. Gut microbiome analysis of 16S rRNA genes in the renal failure mice showed that lubiprostone treatment altered their microbial composition, especially the recovery of the levels of the Lactobacillaceae family and Prevotella genus, which were significantly reduced in the renal failure mice. Furthermore, capillary electrophoresis-mass spectrometry-based metabolome analysis showed that lubiprostone treatment decreased the plasma level of uremic toxins, such as indoxyl sulfate and hippurate, which are derived from gut microbiota, and a more recently discovered uremic toxin, trans-aconitate. These results suggest that lubiprostone ameliorates the progression of CKD and the accumulation of uremic toxins by improving the gut microbiota and intestinal environment.

Stimulation of Mucin, Mucus, and Viscosity during Lubiprostone in Patients with Chronic Constipation may Potentially Lead to Increase of Lubrication

Objectives:

The purpose of this clinical trial was to explore whether lubiprostone increases the rate of mucus and mucin secretion and its viscosity in chronic constipation (CC) patients. The secretion of chloride (CS) into the gastrointestinal tract lumen is pivotal in the body's ability to process non-digestible food components. CS sets the optimal rate of hydration for non-digestible food components, their fluidity, and their adequate propulsion along the alimentary tract. Chloride is also instrumental in the secretion of alimentary tract mucus, and the formation of a gel-like, viscous mucus-buffer layer. This layer acts as the first line and vanguard of the mucosal barrier. This barrier is essential in mucosal lubrication and protection. Lubiprostone, a novel chloride channel stimulator ClC-2, is currently approved for the treatment of CC. Its impact on mucus, mucus secretion, and viscosity is not established.

Methods:

A double-blind, crossover trial was approved by the IRBs at the Kansas University Medical Center (Kansas City, KS) (study site) and at the Texas Tech University HSC (El Paso, TX) (analysis site). The study included 20 patients (17 females (F); mean age: 37 years) with symptoms of CC diagnosed according to the Rome III criteria. Patients were randomized to 1 week of therapy with lubiprostone or placebo followed by a 1 week washout and 1 week of the alternative therapy. Gastric juice was collected basally and during stimulation with pentagastrin (6 μg/kg body weight subcutaneously) at the end of weeks 1 and 3. Pentagastrin stimulation mimics food stimulation. The mucus content in gastric juice was assessed gravimetrically. The mucin content was measured after its purification using ultracentrifugation. The viscosity of the gastric secretion was measured using a digital viscometer.

Results:

In comparison with placebo, the volume of gastric secretion in patients with CC during administration of lubiprostone increased significantly by 50% (86.3 vs. 57.5 ml/h) (P<0.001) in basal conditions and increased by 25% (210.0 vs. 167.6 ml/h) (P=0.024) during stimulation with pentagastrin. The rate of gastric mucus secretion during therapy with lubiprostone was 91% higher (257.3 vs. 135 mg/h) (P=0.001) in basal conditions and 28% higher (348.1 vs. 270.8 mg/h) (NS) in stimulated conditions, although the latter was not statistically significant. The rate of gastric mucin secretion during lubiprostone therapy was 85% higher (98.4 vs. 65.5 mg/h) (P=0.011) in basal conditions and 38% (98.3 vs. 71.7 mg/h) (NS) higher in stimulated conditions. In basal conditions, the viscosity of gastric secretion during administration of lubiprostone increased by 240% at the lowest (P<0.001) and by 106% at the highest shear rate (P<0.001). In stimulated conditions, it increased by 226% (P<0.01) at the lowest shear rate and by 67% (P<0.01) at the highest shear rate.

Conclusions:

The significantly higher content of gastric mucus and mucin during therapy in basal conditions with lubiprostone in patients with CC suggests and supports the potentially leading role of lubiprostone and ClC-2 stimulation in their secretion. This increased stimulation results in profoundly increased viscosity, which in turn facilitates and/or accelerates the transit and evacuation of non-digestible food components. Although increases in mucus and mucin were observed in stimulated conditions, neither increase was statistically significant. Based on this experiment, we hypothesize that, in CC patients, the significantly increased rate of mucus and its major component, mucin secretion, during lubiprostone administration may partially explain its clinical effectiveness and also have additional clinically important effects. We propose that since the increased mucus production enhances the protective quality of the mucosal barrier, it also boosts its potential to withstand luminal aggressive components such as acid/pepsin duet, Helicobacter pylori and/or nonsteroidal anti-inflammatory drugs/aspirin, or a combination of all. Further trials are needed to test this hypothesis. As this was crossover clinical trial, the patients serve as their own controls. No interaction was found with body mass index (BMI) and treatment. The observed relationships of BMI and mucus and mucin secretions and gastric juice volume are important considerations in the design of future trials, particularly if a crossover design is not used.

Diets for constipation

Chronic constipation is a very common disease in children. Successful treatment of constipation can be achieved not only with medication but also with lifestyle changes, including a proper diet. Diets including fruits, fluids, and probiotics are good for constipation. Some dietary components are helpful for constipation, and some are harmful. In this study, we present diets related to constipation from the literature, and propose some perspectives regarding diets related to constipation.

Effects of lubiprostone on pacemaker activity of interstitial cells of cajal from the mouse colon

Lubiprostone is a chloride (Cl^-) channel activator derived from prostaglandin E₁ and used for managing constipation. In addition, lubiprostone affects the activity of gastrointestinal smooth muscles. Interstitial cells of Cajal (ICCs) are pacemaker cells that generate slow-wave activity in smooth muscles. We studied the effects of lubiprostone on the pacemaker potentials of colonic ICCs. We used the whole-cell patch-clamp technique to determine the pacemaker activity in cultured colonic ICCs obtained from mice. Lubiprostone hyperpolarized the membrane and inhibited the generation of pacemaker potentials. Prostanoid EP₁, EP₂, EP₃, and EP₄ antagonists (SC-19220, PF-04418948, 6-methoxypyridine-2-boronc acid N-phenyldiethanolamine ester, and GW627368, respectively) did not block the response to lubiprostone. _L-NG-nitroarginine methyl ester (_L-NAME, an inhibitor of nitric oxide synthase) and 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, an inhibitor of guanylate cyclase) did not block the response to lubiprostone. In addition, tetraethylammonium (TEA, a voltage-dependent potassium [K⁺] channel blocker) and apamin (a calcium [Ca²⁺]-dependent K⁺ channel blocker) did not block the response to lubiprostone. However, glibenclamide (an ATP-sensitive K⁺ channel blocker) blocked the response to lubiprostone. Similar to lubiprostone, pinacidil (an opener of ATP-sensitive K⁺ channel) hyperpolarized the membrane and inhibited the generation of pacemaker potentials, and these effects were inhibited by glibenclamide. These results suggest that lubiprostone can modulate the pacemaker potentials of colonic ICCs via activation of ATP-sensitive K⁺ channel through a prostanoid EP receptor-independent mechanism.

Recent advances in pharmacological treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a highly prevalent functional disorder that reduces patients’ quality of life. It is a chronic disorder characterized by abdominal pain or discomfort associated with disordered defecation in the absence of identifiable structural or biochemical abnormalities. IBS imposes a significant economic burden to the healthcare system. Alteration in neurohumoral mechanisms and psychological factors, bacterial overgrowth, genetic factors, gut motility, visceral hypersensitivity, and immune system factors are currently believed to influence the pathogenesis of IBS. It is possible that there is an interaction of one or more of these etiologic factors leading to heterogeneous symptoms of IBS. IBS treatment is predicated upon the patient’s most bothersome symptoms. Despite the wide range of medications and the high prevalence of the disease, to date no completely effective remedy is available. This article reviews the literature from January 2008 to July 2013 on the subject of IBS peripherally acting pharmacological treatment. Drugs are categorized according to their administration for IBS-C, IBS-D or abdominal pain predominant IBS.

A randomized study of lubiprostone for opioid-induced constipation in patients with chronic noncancer pain

Objective

To evaluate the efficacy and safety of oral lubiprostone for relieving symptoms of opioid-induced constipation (OIC) in patients with chronic noncancer pain.

Design

Prospective, randomized, double-blind, placebo-controlled trial.

Setting

Seventy-nine US and Canadian centers.

Subjects

Patients aged ≥18 years with OIC, defined as <3 spontaneous bowel movements (SBMs) per week.

Methods

Patients received lubiprostone 24 mcg or placebo twice daily for 12 weeks. The primary endpoint was change from baseline in SBM frequency at week 8.

Results

Among randomized patients (N = 418; lubiprostone, N = 210; placebo, N = 208), most completed the study (lubiprostone, 67.1%; placebo, 69.7%). The safety and efficacy (intent-to-treat) populations included 414 (lubiprostone, N = 208; placebo, N = 206) and 413 (lubiprostone, N = 209; placebo, N = 204) patients, respectively. The mean (standard deviation) age was 50.4 (10.9) years; most patients were female (64.4%) and white (77.7%). Changes from baseline in SBM frequency rates were significantly higher at week 8 (P = 0.005) and overall (P = 0.004) in patients treated with lubiprostone compared with placebo. Pairwise comparisons showed significantly greater overall improvement for abdominal discomfort (P = 0.047), straining (P < 0.001), constipation severity (P = 0.007), and stool consistency (P < 0.001) with lubiprostone compared with placebo. Moreover, patients rated the effectiveness of lubiprostone as significantly (P < 0.05) better than placebo for 11 of 12 weeks. The most common treatment-related adverse events (AEs) with lubiprostone and placebo were nausea (16.8% vs 5.8%, respectively), diarrhea (9.6% vs 2.9%), and abdominal distention (8.2% vs 2.4%). No lubiprostone-related serious AEs occurred.

Conclusion

Lubiprostone effectively relieved OIC and associated signs and symptoms and was well tolerated in patients with chronic noncancer pain (http://clinicaltrials.gov/ct2/show/NCT00595946).

Lubiprostone for the treatment of functional constipation in children

OBJECTIVES

Pediatric functional constipation is common; effective, easily administered treatment options are limited. Lubiprostone is an oral chloride channel protein-2 activator that stimulates gastrointestinal fluid secretion, softens stools, and facilitates bowel movements (BMs). We evaluated the safety and effectiveness of lubiprostone in children and adolescents with functional constipation.

METHODS

Patients ≥12 kg, 17 years or younger, and with <3 spontaneous BMs (SBMs; ie, BMs that did not occur within 24 hours of rescue medication use) per week were enrolled at 22 US general pediatric and pediatric gastroenterology centers (January 2007-October 2008). Patients received 4 weeks of open-label lubiprostone at doses of 12 μg once daily (QD), 12 μg twice daily (BID), or 24 μg BID based on age and weight. The primary endpoint was SBM frequency during week 1 versus baseline.

RESULTS

Of 127 enrolled patients, 124 were treated and analyzed (12 μg QD, n = 27; 12 μg BID, n = 65; 24 μg BID, n = 32), and 109 completed the study. The mean age of treated patients was 10.2 years (range 3-17 years); 65 were boys. Mean SBM frequency significantly increased compared with baseline at week 1 (3.1 vs. 1.5 SBMs/week, P < 0.0001). SBM frequency was improved significantly from baseline overall (P < 0.0001) and for individual dose groups (P ≤ 0.0062) during weeks 2, 3, and 4. Common (≥5%) adverse events included nausea (18.5%), vomiting (12.1%), diarrhea (8.1%), abdominal pain (7.3%), and headache (5.6%). Two patients experienced serious adverse events (unrelated abdominal pain; unrelated sickle cell crisis).

CONCLUSIONS

Lubiprostone was efficacious and well tolerated in children and adolescents with functional constipation.

Discovery of bufadienolides as a novel class of ClC-3 chloride channel activators with antitumor activities

ClC-3 chloride (Cl(-)) channel has been shown to be involved in cell proliferation, cell cycle, and cell migration processes. Herein, we found that a series of bufadienolides isolated from toad venom were a novel class of ClC-3 Cl(-) channel activators with antitumor activities. Bufalin, which has the most potent antitumor activity, and 15β-acetyloxybufalin, which has no antitumor activity, were chosen as representative compounds to investigate the role of the ClC-3 Cl(-) channel. It was found that bufalin rapidly elicited activation of the ClC-3 Cl(-) channel and subsequently induced apoptosis through inhibition of the PI3K/Akt/mTOR pathway. The PI3K/Akt/mTOR pathway was attenuated by pretreatment with Cl(-) channel blockers [tamoxifen and 5-nitro-2-(3-phenylpropylamino)benzoic acid, NPPB] or ClC-3 small interfereing RNA. In summary, we discovered that activation of the ClC-3 Cl(-) channel, which subsequently induced inhibition of the PI3K/Akt/mTOR signaling pathway, was involved in the antitumor activities of bufadienolides.

Novel amino-carbonitrile-pyrazole identified in a small molecule screen activates wild-type and ΔF508 cystic fibrosis transmembrane conductance regulator in the absence of a cAMP agonist

Cystic fibrosis (CF) is caused by loss-of-function mutations in the CF transmembrane conductance regulator (CFTR) Cl⁻ channel. We developed a phenotype-based high-throughput screen to identify small-molecule activators of human airway epithelial Ca²⁺-activated Cl⁻ channels (CaCCs) for CF therapy. Unexpectedly, screening of ∼110,000 synthetic small molecules revealed an amino-carbonitrile-pyrazole, C(act)-A1, that activated CFTR but not CaCC Cl⁻ conductance. C(act)-A1 produced large and sustained CFTR Cl⁻ currents in CFTR-expressing Fisher rat thyroid (FRT) cells and in primary cultures of human bronchial epithelial (HBE) cells, without increasing intracellular cAMP and in the absence of a cAMP agonist. C(act)-A1 produced linear whole-cell currents. C(act)-A1 also activated ΔF508-CFTR Cl⁻ currents in low temperature-rescued ΔF508-CFTR-expressing FRT cells and CF-HBE cells (from homozygous ΔF508 patients) in the absence of a cAMP agonist, and showed additive effects with forskolin. In contrast, N-(2,4-di-tert-butyl-5-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide (VX-770) and genistein produced little or no ΔF508-CFTR Cl⁻ current in the absence of a cAMP agonist. In FRT cells expressing G551D-CFTR and in CF nasal polyp epithelial cells (from a heterozygous G551D/Y1092X-CFTR patient), C(act)-A1 produced little Cl⁻ current by itself but showed synergy with forskolin. The amino-carbonitrile-pyrazole C(act)-A1 identified here is unique among prior CFTR-activating compounds, as it strongly activated wild-type and ΔF508-CFTR in the absence of a cAMP agonist. Increasing ΔF508-CFTR Cl⁻ conductance by an "activator," as defined by activation in the absence of cAMP stimulation, provides a novel strategy for CF therapy that is different from that of a "potentiator," which requires cAMP elevation.

Lubiprostone decreases mouse colonic inner mucus layer thickness and alters intestinal microbiota

BACKGROUND

Lubiprostone has been used to treat constipation through its effects to stimulate Cl(-) secretion, resulting in water and electrolyte secretion.

AIM

Potential associated changes in intestinal mucus and the colonizing bacteria (microbiome) have not been studied. As mucus obstructions may play a role in cystic fibrosis, the hypothesis that lubiprostone alters intestinal mucus and the microbiome was investigated.

METHODS

Ion transport studies were performed ex vivo. For mucus and microbiome studies, mice were gavaged daily with lubiprostone or vehicle. Mucin from intestinal sections was analyzed in Carnoy's fixed tissues stained with Alcian blue. Microbiome composition was analyzed by 16S rRNA gene-based sequencing.

RESULTS

Lubiprostone stimulated short circuit current in all mouse intestinal segments after both serosal and mucosal additions, albeit at lower concentrations in the latter. Current was Cl-dependent and blocked by mucosal diphenylcarboxylic acid, serosal bumetanide, and serosal Ba(++). The CFTR inhibitor CFTRinh172 had a marginal effect. Mucus near epithelial cells (inner layer mucus) was not present in the small intestine of any mice. Proximal colon inner mucus layer was thicker in ∆F/∆F compared with +/∆F and +/+ mice. Lubiprostone decreased inner mucus layer thickness in both proximal and distal colon of all mice. Furthermore, lubiprostone altered the intestinal microbiome by increasing abundance of Lactobacillus and Alistipes.

CONCLUSIONS

Lubiprostone activates non-CFTR Cl(-) secretion and alters the colonic inner mucus layer, which is associated with changes in the composition of the enteric microbiome.

Colonic motility-promoting agents for treatment of chronic constipation

Chronic constipation (CC) is one of the most common functional gastroin testinal disorders. Possible etiologies for CC include alterations in gastrointestinal motility and secretion. Research efforts in CC have led to the identification of multifactorial and often overlapping etiologies including abnormalities in myenteric neurons, alterations in neurotransmitters and their receptors, and incoordination of the muscles of the pelvic floor or anorectum. In this article, we review the safety and efficacy of colonic motility-promoting agents, such as 5-HT modulators, motilin agonists, chloride-channel activators, opioid antagonists, uroguanylin and GC-2C receptor agonists, in the management of CC.

Dual activation of CFTR and CLCN2 by lubiprostone in murine nasal epithelia

Multiple sodium and chloride channels on the apical surface of nasal epithelial cells contribute to periciliary fluid homeostasis, a function that is disrupted in patients with cystic fibrosis (CF). Among these channels is the chloride channel CLCN2, which has been studied as a potential alternative chloride efflux pathway in the absence of CFTR. The object of the present study was to use the nasal potential difference test (NPD) to quantify CLCN2 function in an epithelial-directed TetOn CLCN2 transgenic mouse model (TGN-K18rtTA-hCLCN2) by using the putative CLCN2 pharmacological agonist lubiprostone and peptide inhibitor GaTx2. Lubiprostone significantly increased chloride transport in the CLCN2-overexpressing mice following activation of the transgene by doxycycline. This response to lubiprostone was significantly inhibited by GaTx2 after CLCN2 activation in TGN-CLCN2 mice. Cftr(-/-) and Clc2(-/-) mice showed hyperpolarization indicative of chloride efflux in response to lubiprostone, which was fully inhibited by GaTx2 and CFTR inhibitor 172 + GlyH-101, respectively. Our study reveals lubiprostone as a pharmacological activator of both CFTR and CLCN2. Overexpression and activation of CLCN2 leads to improved mouse NPD readings, suggesting it is available as an alternative pathway for epithelial chloride secretion in murine airways. The utilization of CLCN2 as an alternative chloride efflux channel could provide clinical benefit to patients with CF, especially if the pharmacological activator is administered as an aerosol.