Intestinal proteases mediate digestion and immune signalling, while increased gut proteolytic activity disrupts the intestinal barrier and generates visceral hypersensitivity, which is common in ...irritable bowel syndrome (IBS). However, the mechanisms controlling protease function are unclear. Here we show that members of the gut microbiota suppress intestinal proteolytic activity through production of unconjugated bilirubin. This occurs via microbial β-glucuronidase-mediated conversion of bilirubin conjugates. Metagenomic analysis of faecal samples from patients with post-infection IBS (n = 52) revealed an altered gut microbiota composition, in particular a reduction in Alistipes taxa, and high gut proteolytic activity driven by specific host serine proteases compared with controls. Germ-free mice showed 10-fold higher proteolytic activity compared with conventional mice. Colonization with microbiota samples from high proteolytic activity IBS patients failed to suppress proteolytic activity in germ-free mice, but suppression of proteolytic activity was achieved with colonization using microbiota from healthy donors. High proteolytic activity mice had higher intestinal permeability, a higher relative abundance of Bacteroides and a reduction in Alistipes taxa compared with low proteolytic activity mice. High proteolytic activity IBS patients had lower fecal β-glucuronidase activity and end-products of bilirubin deconjugation. Mice treated with unconjugated bilirubin and β-glucuronidase-overexpressing E. coli significantly reduced proteolytic activity, while inhibitors of microbial β-glucuronidases increased proteolytic activity. Together, these data define a disease-relevant mechanism of host-microbial interaction that maintains protease homoeostasis in the gut.
Intestinal pseudo-obstruction is characterized by impaired transit and luminal dilation in the absence of mechanical obstruction. Our study aims to describe the clinical, radiographic, and ...physiological findings in pseudo-obstruction associated with systemic sclerosis (SSc), amyloidosis, and paraneoplastic syndrome.
A retrospective cohort of patients evaluated at our institution between January 1, 2008, and August 1, 2018, was assembled. Clinical, imaging, and physiological characteristics were abstracted from electronic medical records.
We identified 100 cases of pseudo-obstruction (55 SSc, 27 amyloidosis, and 18 paraneoplastic). Female population predominance was seen in SSc (71%) vs male population in amyloidosis (74%). Most common symptom was abdominal bloating in all 3 groups. Vomiting was more common in SSc than amyloidosis (73% vs 46%, P = 0.02). Diarrhea was more common in amyloidosis and SSc compared with paraneoplastic (81% and 67% vs 28%, P < 0.01). Weight loss (>5%) was more common in SSc compared with amyloidosis and paraneoplastic (78% vs 31% and 17%, P < 0.0001). Only small bowel dilation was seen in 79%, 40%, and 44% and only large bowel dilation in 2%, 44%, and 44% of patients in SSc, amyloidosis, and paraneoplastic, respectively. Five of 8 SSc patients had myopathic and 3 of 5 paraneoplastic had neuropathic involvement on gastroduodenal manometry.
SSc-associated pseudo-obstruction demonstrates female population predominance and presents with vomiting, diarrhea, and weight loss. Amyloidosis-associated pseudo-obstruction shows male population predominance. Small bowel is more commonly involved than large bowel on both imaging and transit studies in SSc. Myopathic involvement was more common in SSc, contrary to neuropathic in paraneoplastic syndrome.
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