| Inflammatory bowel disease(IBD) is a relapsing, chronic intestinal inflammation, and is not medically curable. The IBD incidence continues to rise in recent years. It is urgent and important to find effectively alternative treatments. Lactic acid bacteria(LAB) have received increasing attention in recent decades as commercial probiotics and showed many beneficial functions. Conjugated linoleic acid(CLA) is one of its metabolites which presents strong anti-inflammatory benefits. In hence, we hypothesize that LAB with CLA production ability might exert anti-inflammatory effects in vivo via CLA generation. In this study, the effects of LAB with different CLA conversion ability on DSS-induced colitis in mice were investigated, and the mechanisms were discussed from the perspective of CLA. This study established the foundation for usage of CLA-producing LAB in the treatment of intestinal inflammation, and improved the cross-talk between CLA-producing LAB and intestinal health. The main results of this study are as follow:1. The inflammatory indexes such as DAI, colon length, colonic histopathologic damage and MPO activity, were investigated to explore the effects of CLA-producing LAB on the symptoms of DSS-induced colitis. L. plantarum ZS2058 and B. breve CCFM683 with the highest CLA conversion rate significantly inhibited the increase of DAI, colon shortening, colonic histopathologic damage and MPO activity, however, L. plantarum ST-III and B. longum CCFM645, which could not generate CLA, did not show any improvement on the symptoms of colitis. The improvement effects of L. plantarum and Bifidobacteria on colitis were positively correlated with their ability of CLA production, indicating that CLA is an key factor in their anti-inflammatory effects.2. The m RNA expression of cytokines(TNF-α, IL-1β, IL-6, IL-10) and PPARγ were investigated via RT-q PCR analysis to compare the effects of different treatments on colonic cytokines and PPARγ in colitis mice. LAB could improve the colonic immune disorder at different levels, which illustrated that the capacity of LAB on immune-regulation is universal. The efficient CLA producer L. plantarum ZS2058 significantly attenuated the expression of proinflammatory cytokines(TNF-α, IL-1β, IL-6), and up-regulated the expression of colonic anti-inflammatory cytokine IL-10, balanced the immune response, however, L. plantarum ST-III, which could not produce CLA, did not exhibit those properties. Furthermore, the regulation of L. plantarum ZS2058 and L. plantarum ST-III on the expression of PPARγ were positively correlated with their CLA production abilities. Therefore, L. plantarum ZS2058 improving immune disorder in colitis mice maybe via CLA production, which up-regulated the expression of PPARγ and inhibited the expression of proinflammatory cytokines.3. The integrity of colonic mucus layer was investigated by alcian blue staining, as well as the m RNA expression of intestinal barrier-related genes were detected by RT-q PCR to analyze the effects of CLA-producing LAB on intestinal barrier. The protection effects on mucus layer and regulation of tight junction-related genes by L. plantarum and Bifidobacteria were apparently correlated with their abilities of CLA generation. The positive control, CLA, significantly up-regulated MUC2, Claudin 3, ZO-1, and E-cadherin 1. These results indicated that CLA produced by LAB in vivo could be involved in the regulation of intestinal barrier.4. The fatty acid profiles in colonic contents, blood and liver were analyzed, and CLA concentration in colonic contents were significantly increased by nearly 2.38- and 4.62- fold in the L. plantarum ZS2058 and B. breve CCFM683 feeding groups, respectively. Therefore, the results further validate our hypothesis that CLA-production LAB might exert antiinflammatory effects by generating CLA in vivo. |
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