Plasma levels of guanylins are reduced in patients with Crohn's disease.

Background: Guanylin (GN) and uroguanylin (UGN) are endogenous ligands for the intestinal receptor guanylate cyclase C (GC-C), an important regulator of intestinal fluid homeostasis. Gene expression and protein levels of GN are suppressed in inflamed intestinal tissue from patients with inflammatory bowel disease (IBD), but knowledge about plasma levels of guanylins in these conditions is sparse. We aimed to investigate the fasting plasma levels of the prohormones proGN and proUGN in patients with Crohn's Disease (CD) and relate these to levels found in persons with other diarrheal conditions, as well as persons with normal bowel habits.Methods: Plasma from patients with CD, patients with Familial GUCY2C Diarrheal Disease (FGDS), diarrhea-predominant irritable bowel syndrome (IBS-D) and healthy controls (HC) was analyzed using ELISA assays.Results: Significantly lower fasting plasma levels of proguanylins were found in CD and FGDS patients, compared to HC. In CD patients, plasma proGN levels correlated negatively with Harvey Bradshaw Index and with number of stools/24 h.Conclusion: Our data indicate that diarrhea may be a determinant for levels of proGN in plasma, and should be further explored in studies of different diarrheal disorders.

Gastrointestinal transit and contractility in diabetic constipation: A wireless motility capsule study on diabetes patients and healthy controls.

BACKGROUND: Diabetic constipation is traditionally attributed to slow colonic transit, despite limited evidence. More than half of patients find treatment unsatisfactory. To improve treatment, there is a need for better diagnostic understanding of the condition. OBJECTIVE: In this wireless motility capsule study, we aimed to investigate gastrointestinal transit and contractility in diabetes patients with and without constipation, and in healthy controls. METHODS: We prospectively included type 1 or type 2 diabetes patients with gastrointestinal symptoms. Based on the Gastrointestinal Symptom Rating Scale we distinguished into two groups: with constipation and without constipation. Non-diabetic controls were asymptomatic. All were examined with wireless motility capsule, determining transit times and contractility parameters. RESULTS: 57 patients (42 women, 46 with type 1 diabetes) and 26 healthy controls (14 women) were included. We found no difference in transit times between diabetes patients with and without constipation. Compared to healthy controls (35:55, h:min), whole-gut transit was slower in both diabetes patients with constipation (66:15, p = 0.03) and without constipation (71:16, p < 0.001). Small bowel motility index correlated rs  = -0.32 (p = 0.01) with constipation symptoms. CONCLUSIONS: Diabetes patients with constipation had similar transit times as those without constipation. Both groups had slower whole-gut transit than healthy controls. Constipation was associated with reduced small bowel, but not colonic contractility. Our results imply that other mechanisms than slow colonic transit may be more important in the pathogenesis of diabetic constipation.

Comparison of pre-analytical conditions for quantification of serotonin in platelet-poor plasma.

BACKGROUND: Reported concentrations of serotonin in platelet-poor plasma (PPP) in healthy subjects vary widely due to different pre-analytical procedures. AIM: To examine how different pre-analytical conditions affect the measured concentration of serotonin in PPP. METHOD: Six pre-analytical protocols were compared for preparation of PPP from EDTA whole blood for quantification of serotonin from nine healthy individuals. Three combinations of centrifugation with a mild centrifugation of gel-free EDTA tubes followed by a stronger centrifugation were compared to single-stage centrifugation of EDTA tubes with separator gel and heat shock treatment of blood prior to centrifugation. All samples were analysed using the same enzyme linked immunosorbent assay (ELISA) method. RESULTS: Findings show that two consecutive centrifugations; first a mild centrifugation at 100 or 200×g followed by centrifugation at 4500 or 14500×g resulted in the lowest serotonin concentration in PPP. CONCLUSION: Two successive centrifugations to produce PPP for serotonin analysis; first a mild centrifugation to avoid mechanical stress on the platelets, and next a stronger centrifugation to remove platelets, is superior to the use of gel tubes and heat shock treatment.

Prolonged intestinal transit and diarrhea in patients with an activating GUCY2C mutation.

INTRODUCTION: Increased intestinal hydration by activation of the epithelial enzyme linked receptor guanylate cyclase C (GC-C) is a pharmacological principle for treating constipation. Activating mutations in the GUCY2C gene encoding GC-C cause Familial GUCY2C diarrhea syndrome (FGDS) which has been diagnosed with severe dysmotility. AIM: To investigate gut motility and hormones before and after a meal in FGDS patients and compare with healthy controls (HC). SUBJECTS AND METHODS: Bristol stool chart and stool frequency was assessed. Before and after a meal occlusive and non-occlusive contractions were obtained using ultrasound. A wireless motility capsule (WMC) recorded gut transit time, pH, contractions and pressure. Plasma levels of selected gut hormones were measured at different time points. RESULTS: The FGDS patients had 4 (range 1-10) loose stools/day and prolonged total gut transit time compared to HC, 55.5 h vs 28.5 h, respectively,with significantly increased colon transit time. In FGDS patients, pH in duodenum, small bowel and colon was increased and the number of contractions and the intraluminal pressure were significantly decreased, measured by WMC. Ultrasound showed in small bowel increased number of non-occlusive contractions in the FGDS patients. Serotonin (5-HT) plasma levels in the HC peaked 30 min after the meal, while the FGDS patients had no response. CONCLUSION: Despite having diarrhea, the FGDS patients have prolonged transit time through the gut compared to HC, particularly in colon. The reduced number of intestinal contractions and lack of 5-HT release after a meal in FGDS patients surprisingly resemble colonic motility disturbances seen in patients with constipation.

Guanylate Cyclase C Activation Shapes the Intestinal Microbiota in Patients with Familial Diarrhea and Increased Susceptibility for Crohn's Disease.

BACKGROUND: With 25% prevalence of Crohn's disease, Familial GUCY2C diarrhea syndrome (FGDS) is a monogenic disorder potentially suited to study initiating factors in inflammatory bowel disease (IBD). We aimed to characterize the impact of an activating GUCY2C mutation on the gut microbiota in patients with FGDS controlling for Crohn's disease status and to determine whether changes share features with those observed in unrelated patients with IBD. METHODS: Bacterial DNA from fecal samples collected from patients with FGDS (N = 20), healthy relatives (N = 11), unrelated healthy individuals (N = 263), and IBD controls (N = 46) was subjected to sequencing of the V3-V4 region of the 16S rRNA gene to determine gut microbiota composition. Food frequency questionnaires were obtained from patients with FGDS and their relatives. RESULTS: Compared with healthy controls, FGDS displayed prominent changes in many microbial lineages including increase in Enterobacteriaceae, loss of Bifidobacterium and Faecalibacterium prausnitzii but an unchanged intraindividual (alpha) diversity. The depletion of F. prausnitzii is in line with what is typically observed in Crohn's disease. There was no significant difference in the dietary profile between the patients and related controls. The gut microbiota in related and unrelated healthy controls was also similar, suggesting that diet and familial factors do not explain the gut microbiota alterations in FGDS. CONCLUSIONS: The findings support that the activating mutation in GUCY2C creates an intestinal environment with a major influence on the microbiota, which could contribute to the increased susceptibility to IBD in patients with FGDS.