Enhanced Store-Operated Ca2+ Signal of Small Intestinal Smooth Muscle Cells Accelerates Small Bowel Transit Speed in Type 1 Diabetic Mouse

Aims: The underlying mechanism of diabetic enteropathy, a common complication of type 1 diabetes, remains unclear. Store-operated Ca²⁺ entry (SOCE) is a ubiquitous type of Ca²⁺ influx involved in various cellular functions. Here, we show that SOCE-related stromal interaction molecule 1 (STIM1) and Orai1 participate in inappropriate cellular Ca²⁺ homeostasis, augmenting agonist-induced small intestinal smooth muscle contraction and small bowel transit speed in a mouse model of type 1 diabetes.

Methods and Results: We used small interfering (si)RNA to suppress STIM1 and Orai1 proteins, and employed intracellular Ca²⁺, small intestinal contraction and intestinal transit speed measurement to investigate the functional change. We found that SOCE activity and Orai1 and STIM1 expression levels of small intestinal smooth muscle were significantly increased in cells cultured in high glucose medium or in diabetic mice. Gastrointestinal transit speed and SOCE-mediated contractions were markedly increased in diabetic mice; Knocking down Orai1 or STIM1 with siRNA rescued both alterations in diabetic mice. However, the Orai1-large conductance Ca²⁺-activated K⁺ (BK_Ca) channel interaction was decreased in diabetic mice, and suppressing Orai1 expression or inhibiting the BK_Ca channel increased agonist-induced small intestinal contractions in normal mice.

Conclusion: We concluded that the increased SOCE caused by excessive STIM1 and Orai1 expression and decreased Orai1-BK_Ca interaction augmented small intestinal smooth muscle contraction and accelerated small bowel transit speed in diabetic mice. This finding demonstrates a pathological role for SOCE in diabetic enteropathy and provides a potential therapeutic target for diabetic enteropathy.

Small Bowel Transit and Altered Gut Microbiota in Patients With Liver Cirrhosis

Disturbance of the gut microbiota is common in liver cirrhosis (LC) patients, the underlying mechanisms of which are yet to be unfolded. This study aims to explore the relationship between small bowel transit (SBT) and gut microbiota in LC patients. Cross-sectional design was applied with 36 LC patients and 20 healthy controls (HCs). The gut microbiota was characterized by 16S rRNA gene sequencing. The Firmicutes/Bacteroidetes (F/B) ratio and the Microbial Dysbiosis index (MDI) were used to evaluate the severity of microbiota dysbiosis. The scintigraphy method was performed in patients to describe the objective values of SBT. Patients were then subdivided according to the Child–Pugh score (threshold = 5) or SBT value (threshold = 0.6) for microbiota analysis. LC patients were characterized by an altered gut microbiota; F/B ratios and MDI were higher than HC in both Child_5 (14.00 ± 14.69 vs. 2.86 ± 0.99, p < 0.01; 0.49 ± 0.80 vs. -0.47 ± 0.69, p < 0.01) and Child_5+ (15.81 ± 15.11 vs. 2.86±0.99, p < 0.01; 1.11 ± 1.05 vs. -0.47 ± 0.69, p < 0.01) sub-groups in patients. Difference in the gut microbiota between Child_ 5 and Child_5+ patients was inappreciable, but the SBT was relatively slower in Child_5+ patients (43 ± 26% vs. 80 ± 15%, p < 0.05). Compared with the Child–Pugh score indicators, SBT showed stronger associations with bacterial genera. A clear difference in the gut microbiota was observed between SBT_0.6- and SBT_0.6+ patients [Pr(>F) = 0.0068, pMANOVA], with higher F/B ratios and MDI in SBT_0.6- patients (19.71 ± 16.62 vs. 7.33 ± 6.65, p < 0.01; 1.02 ± 0.97 vs. 0.20 ± 0.58, p < 0.01). Similar results were observed between the SBT_0.6- and SBT_0.6+ sub-groups of patients with normal liver function and a Child–Pugh score of 5. SBT was negatively correlated with both the F/B ratio and MDI (r = -0.34, p < 0.05; r = -0.38, p < 0.05). Interestingly, an increased capacity for the inferred pathway “bacterial invasion of epithelial cells” in patients, was highly negatively correlated with SBT (r = -0.57, p < 0.01). The severity of microbiota dysbiosis in LC patients depends on SBT rather than Child–Pugh score. SBT per se might be significantly related to the gut microbiota abnormalities observed in patients with LC.

Prucalopride: the evidence for its use in the treatment of chronic constipation

Introduction:

Chronic constipation is a common condition that is difficult to treat. Existing options for the treatment of patients with different subgroups of constipation are limited. A new efficacious and safe drug is needed to limit the frequently observed adverse effects induced by laxatives, to improve general wellbeing and quality of life, and to provide an alternative for enemas or even resectional surgery in patients in whom stimulant laxatives cause disabling adverse effects or fail to increase bowel movement frequency.

Aims:

The purpose of this article is to assess the current evidence supporting the use of the selective and high affinity serotonin-4 (5-HT₄) receptor agonist prucalopride in the management of chronic constipation.

Evidence review:

There are now convincing data from phase II and multicenter phase III randomized, double-blind, placebo-controlled trials that prucalopride treatment results in a clinically meaningful increase in the number of spontaneous complete bowel movements, a reduction of perceived severity of symptoms and improved disease-related quality of life in a significant proportion of patients. There is a rapid onset of the effect and the improvement is maintained for at least 12 weeks.

Prucalopride in a dose of up to 4 mg per day appeared generally well tolerated and devoid of serious cardiac events. Adverse events, most frequently headache and nausea, are usually mild or moderate and occur mainly during the first days of treatment. Prucalopride should be used with prudence and with careful assessment of the benefit-risk ratio until more clinical and electrophysiologic data become available, because relatively few patients have been exposed to the drug for long periods of time.

Place in therapy:

Prucalopride 1–2 mg once daily may be given to patients suffering from chronic constipation for whom laxatives do not provide adequate relief of their symptoms. Patients with severe constipation and slow transit, who frequently develop tolerance to stimulant laxatives, are also eligible for prucalopride treatment.

HLA-DQ genotype is associated with accelerated small bowel transit in patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND

Colonic transit (CT) is accelerated in 46% of patients with diarrhea-predominant irritable bowel syndrome (IBS-D). Improvement in IBS-D with gluten withdrawal is associated with human leukocyte antigen (HLA)-DQ2 positivity; the mechanism of improvement is unclear.

OBJECTIVE

To determine if HLA-DQ2-positive or HLA-DQ8-positive patients with IBS-D have faster small bowel (SB) or CT than HLA-DQ2-negative and HLA-DQ8-negative patients.

MATERIALS AND METHODS

Among 94 patients with IBS-D, who previously provided DNA samples, 64 had undergone validated measurements of CT [geometric center at 24 h (GC24)]; 50 of the patients also had measurement of gastric emptying (GE) and 54 of SB transit (colonic filling at 6 h). HLA-DQ status was determined by tag single nucleotide polymorphism approach. Associations of colonic filling at 6 h and GC24 with HLA-DQ2 and HLA-DQ8 status were assessed using analysis of covariance, adjusting for BMI.

RESULTS

Mean age was 40.8±1.6 years; 98.5% were females. In 60 of the 64 patients, celiac disease was excluded by serology or histology. There were no significant differences in age or BMI among the different HLA-DQ groups. Independently, patients positive for HLA-DQ2 had numerically greater colonic filling at 6 h compared with HLA-DQ2-negative (P=0.065), and those positive for HLA-DQ8 had greater colonic filling at 6 h compared with HLA-DQ8-negative patients (P=0.021). Gastric emptying was not associated with HLA-DQ2 and HLA-DQ8 status. Patients positive for both HLA-DQ2 and HLA-DQ8 had greater colonic filling at 6 h (P=0.013) and numerically higher, but not significant, GC24 (P=0.38) compared with HLA-DQ2-negative and HLA-DQ8-negative patients.

CONCLUSION

Patients with IBS-D positive for HLA-DQ8 or for both HLA-DQ2 and HLA-DQ8 have faster SB transit. The mechanism of the accelerated SB transit and the effect of gluten withdrawal on SB function in IBS-D deserve further investigation.