miR-146a regulates the crosstalk between intestinal epithelial cells, microbial components and inflammatory stimuli.

Regulation of miR-146a abundance and its role in intestinal inflammation and particularly in intestinal epithelial cells (IECs) has been poorly studied. Here we study the relationship between bacterial antigens and inflammatory stimuli, and miR-146a expression using IEC lines and models of colitis (trinitrobenzenesulfonic acid (TNBS), dextran sulfate sodium (DSS) and the CD4 + CD62L + T cell transfer model). Specific bacterial antigens and cytokines (LPS, flagelin and IL-1ß/TNF) stimulate miR-146a expression, while peptidoglycan, muramyldipeptide and CpG DNA have no effect. Overexpression of miR-146a by LPS depends on the activation of the TLR4/MyD88/NF-kB and Akt pathways. Accordingly, the induction of miR-146a is lower in TLR4, but not in TLR2 knock out mice in both basal and colitic conditions. miR-146a overexpression in IECs induces immune tolerance, inhibiting cytokine production (MCP-1 and GROα/IL-8) in response to LPS (IEC18) or IL-1ß (Caco-2). Intestinal inflammation induced by chemical damage to the epithelium (DSS and TNBS models) induces miR-146a, but no effect is observed in the lymphocyte transfer model. Finally, we found that miR-146a expression is upregulated in purified IECs from villi vs. crypts. Our results indicate that miR-146a is a key molecule in the interaction among IECs, inflammatory stimuli and the microbiota.

Human adipose tissue expresses intrinsic circadian rhythm in insulin sensitivity.

In humans, insulin sensitivity varies according to time of day, with decreased values in the evening and at night. Mechanisms responsible for the diurnal variation in insulin sensitivity are unclear. We investigated whether human adipose tissue (AT) expresses intrinsic circadian rhythms in insulin sensitivity that could contribute to this phenomenon. Subcutaneous and visceral AT biopsies were obtained from extremely obese participants (body mass index, 41.8 ± 6.3 kg/m(2); 46 ± 11 y) during gastric-bypass surgery. To assess the rhythm in insulin signaling, AKT phosphorylation was determined every 4 h over 24 h in vitro in response to different insulin concentrations (0, 1, 10, and 100 nM). Data revealed that subcutaneous AT exhibited robust circadian rhythms in insulin signaling (P < 0.00001). Insulin sensitivity reached its maximum (acrophase) around noon, being 54% higher than during midnight (P = 0.009). The amplitude of the rhythm was positively correlated with in vivo sleep duration (r = 0.53; P = 0.023) and negatively correlated with in vivo bedtime (r = -0.54; P = 0.020). No circadian rhythms were detected in visceral AT (P = 0.643). Here, we demonstrate the relevance of the time of the day for how sensitive AT is to the effects of insulin. Subcutaneous AT shows an endogenous circadian rhythm in insulin sensitivity that could provide an underlying mechanism for the daily rhythm in systemic insulin sensitivity.-Carrasco-Benso, M. P., Rivero-Gutierrez, B., Lopez-Minguez, J., Anzola, A., Diez-Noguera, A., Madrid, J. A., Lujan, J. A., Martínez-Augustin, O., Scheer, F. A. J. L., Garaulet, M. Human adipose tissue expresses intrinsic circadian rhythm in insulin sensitivity.

Fructooligosaccharides exert intestinal anti-inflammatory activity in the CD4+ CD62L+ T cell transfer model of colitis in C57BL/6J mice.

PURPOSE: Fructooligosaccharides (FOS) are used as functional foods due to their prebiotic effects. Intestinal anti-inflammatory activity has been established in most, but not all, studies in animal models of colitis, using mainly chemically induced inflammation. Our goal was to test the effect of FOS (degree of polymerization 2-8) in the chronic, lymphocyte-driven CD4+ CD62L+ T cell transfer model of colitis. METHODS: Colitis was induced by transfer of CD4+ CD62L+ T cells to C57BL/6J Rag1(-/-) mice. FOS (75 mg day(-1)) was administered by gavage as a post-treatment. Three groups were established: non-colitic (NC), colitic control (C, CD4+ CD62L+ transferred mice treated with vehicle) and colitic+FOS (C+FOS, similar but treated with FOS). Mice were killed after 13 days. RESULTS: Treatment of mice with FOS ameliorated colitis, as evidenced by an increase in body weight, a lesser myeloperoxidase and alkaline phosphatase activities, a lower secretion of proinflammatory cytokines by mesenteric lymph node cells ex vivo (IFN-γ, IL-17, and TNF-α), and a higher colonic expression of occludin (C+FOS vs. C, p < 0.05). Increased relative abundance of lactic acid bacteria was observed in FOS-treated mice (p < 0.05). CONCLUSIONS: FOS exert intestinal anti-inflammatory activity in T lymphocyte-dependent colitis, suggesting it may be useful in the management of inflammatory bowel disease in appropriate conditions.

Nondigestible oligosaccharides exert nonprebiotic effects on intestinal epithelial cells enhancing the immune response via activation of TLR4-NFκB.

SCOPE: Prebiotic effects of non absorbable glucids depend mainly on digestion by the colonic microbiota. Our aim was to assess nonprebiotic, direct effects of 4 prebiotics, namely fructooligosaccharides, inulin, galactooligosaccharides, and goat's milk oligosaccharides on intestinal epithelial cells. METHODS AND RESULTS: Prebiotics were tested in intestinal epithelial cell 18 (IEC18), HT29, and Caco-2 cells. Cytokine secretion was measured by ELISA and modulated with pharmacological probes and gene silencing. Prebiotics induced the production of growth-related oncogene, (GROα), monocyte chemoattractant protein 1 (MCP-1), and macrophage inflammatory protein 2 (MIP2) in IEC18 cells, with an efficacy that was 50-80% that of LPS. Prebiotics did not change RANTES expression, which was robustly induced by LPS in IEC18 cells. Cytokine secretion was suppressed by Bay11-7082, an inhibitor of IκB-α phosphorylation. The response was markedly decreased by Myd88 or TLR4 gene knockdown. Prebiotics also elicited cytokine production in HT29 but not in Caco-2 cells, consistent with reduced and vestigial expression of TLR4 in these cell lines, respectively. Prebiotic-induced MCP-1 secretion was reduced also in colonic explants from TLR4 KO mice compared with the controls. CONCLUSIONS: We conclude that prebiotics are TLR4 ligands in intestinal epithelial cells and that this may be a relevant mechanism for their in vivo effects.

Active hexose-correlated compound and Bifidobacterium longum BB536 exert symbiotic effects in experimental colitis.

PURPOSE: Active hexose-correlated compound (AHCC) is a commercial extract obtained from Basidiomycetes under controlled conditions, yielding a 74 % content in oligosaccharides, especially α-glucans. AHCC has a number of therapeutic effects, including intestinal anti-inflammatory activity. Bifidobacterium longum BB536 is a probiotic with potential health-promoting effect at the gut level. The purpose of the present study was to evaluate the possibility of synergism between AHCC, which is believed to act as a prebiotic, and B. longum BB536. METHODS: We used the trinitrobenzene sulfonic acid model (TNBS) of colitis in rats. AHCC (100 or 500 mg kg(-1)) and B. longum BB536 (5 × 10(6) CFU rat(-1) day(-1)) were administered together or separately for 7 days prior to colitis induction and then for another 7 days and compared with control (noncolitic) and TNBS rats. RESULTS: The results show that both treatments had intestinal anti-inflammatory activity separately, which was enhanced when used in combination, as shown by changes in body weight gain, colonic weight to length ratio, myeloperoxydase activity and iNOS expression. Interestingly, the association of AHCC 100 mg kg(-1) + B. longum BB536 showed the highest anti-inflammatory activity. CONCLUSIONS: Our data provide a preclinical experimental basis for the synergistic effect of AHCC and B. longum BB536 on inflammatory bowel disease.