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Background: Patients with irritable bowel syndrome (IBS) often show psychological disorders, including somatization, usually driven by an altered gut–brain axis. These changes are also accompanied by modifications in the circulating levels of vitamin D (VD) and neurotransmitters such as serotonin (5‐HT) and brain‐derived neurotrophic factor (BDNF). The present study aimed to evaluate the relationship between gastrointestinal (GI) symptoms and circulating levels of VD, 5‐HT, and BDNF in IBS patients with diarrhea (IBS‐D) categorized according to somatization. Methods: Fifty‐three IBS‐D patients were recruited and profiled for GI symptoms by validated questionnaires. The fasting serum concentrations of VD, 5‐HT, and BDNF were assessed. The health of the intestinal barrier, minimal inflammation, and dysbiosis was also evaluated. Key Results: Thirty patients showed high somatization scores, IBS‐D(S+), and 23 low somatization scores, IBS‐D(S‐). IBS‐D(S+) patients reported higher "Abdominal pain" and the "Abdominal pain duration in days" scores, lower serum VD levels and increased 5‐HT and BDNF concentrations than IBS‐D(S‐). Besides, in IBS‐D(S+) patients, the GI symptoms correlated with 5HT, BDNF, and VD concentrations. These parameters were associated with impaired small intestinal permeability and increased inflammation markers. Conclusions and Inferences: These data support the multifactorial IBS pathogenesis in which organic and psychological factors interact. An active role by VD, 5‐HT, and BDNF in affecting the clinical and biochemical profiles in IBS‐D(S+) patients may be conceivable. Therefore, the routine VD estimation and the assay of circulating levels of 5‐HT and BDNF could be considered a new approach for managing these patients. [ABSTRACT FROM AUTHOR]

Functional probiotics may prevent Helicobacter pylori infection, and some evidence suggests that they also possess antitumor properties. Lactobacillus brevis (CD2) is a functional Lactobacillus strain with peculiar biochemical features, essentially related to the activity of arginine deiminase . This enzyme catalyzes the catabolism of arginine and affects the biosynthesis of polyamines (putrescine, spermidine, and spermine). Polyamines are polycations found in high concentrations in both normal and neoplastic cells. Our aims were: 1, to assess whether oral administration of L. brevis (CD2) affects H. pylori survival in the human gastric mucosa; 2, to evaluate the effects of L. brevis (CD2) on polyamine biosynthesis in gastric biopsies from H. pylori-positive patients. For 3 weeks before endoscopy, 22 H. pylori-positive dyspeptic patients randomly received (ratio 1 : 1) high oral doses of L. brevis (CD2) or placebo. Before and after treatment, H. pylori infection was determined by urea breath test (UBT). In gastric biopsies, ornithine decarboxylase activity and polyamine levels were, respectively, evaluated by a radiometric technique and high-pressure liquid chromatography (HPLC). L. brevis (CD2) treatment did not eradicate H. pylori. However, a reduction in the UBT delta values occurred, suggesting a decrease in intragastric bacterial load. Significantly, L. brevis (CD2) induced a decrease in gastric ornithine decarboxylase activity and polyamine levels. Our data support the hypothesis that L. brevis (CD2) treatment decreases H. pylori colonization, thus reducing polyamine biosynthesis. Alternatively, the arginine deiminase activity following L. brevis (CD2) administration might cause arginine deficiency, preventing polyamine generation from gastric cells. [ABSTRACT FROM AUTHOR]