Dietary cheese whey protein protects rats against mild dextran sulfate sodium-induced colitis: Role of mucin and microbiota

Data from the literature suggest that the availability of the amino acids threonine, cysteine, or both, is limiting for mucin synthesis under conditions of chronic inflammatory bowel disease. Unlike casein, cheese whey protein is rich in these amino acids. The protective effect of cheese whey protein was examined using dextran sulfate sodium (DSS)-induced inflammation of the large intestine in rats that were fed a diet containing casein, cheese whey protein, or casein supplemented with threonine and cysteine. The clinical markers diarrhea and fecal blood were determined using biochemical assays, and gene expression of inflammation markers was used to quantify inflammation. The effect of dairy protein on mucin production was determined by gene expression of rat mucin 2 (MUC2) and by quantifying fecal mucin excretion. Fecal lactobacilli and bifidobacteria were determined using quantitative PCR. Dietary cheese whey protein reduced DSS-induced gene expression of the inflammation markers interleukin 1β, calprotectin, and inducible nitric oxide synthase, and diminished the clinical symptoms diarrhea and fecal blood loss. Moreover, cheese whey protein increased fecal mucin secretion without affecting gene expression of MUC2, suggesting enhanced mucin synthesis. In addition, cheese whey protein increased fecal lactobacilli and bifidobacteria counts. Supplementation of threonine and cysteine showed comparable effects. In conclusion, cheese whey protein protected rats against DSS-induced gut inflammation. This can most likely be explained by its threonine and cysteine content. Protection can be the result of both the stimulation of intestinal mucin synthesis and modification of microflora composition.     

核桃油对葡聚糖硫酸钠诱导小鼠结肠炎的影响

探讨核桃油(WO)对葡聚糖硫酸钠(DSS)诱导的小鼠结肠炎的保护作用。将昆明种小鼠随机分为4组,即正常对照组(Con)、DSS组、DSS+WO组和WO组,检测小鼠血清促炎因子、结肠组织抗氧化酶活性和Nod样受体蛋白-3(NLRP3)及相关mRNA的转录水平。结果表明:与Con组相比,DSS组小鼠血清白细胞介素1β(IL-1β)和IL-6含量,结肠NLRP3、半胱氨酸蛋白酶-1(Caspase-1)和IL-1βmRNA转录水平及NLRP3蛋白表达水平极显著增高(p <0.01),结肠超氧化物岐化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)和过氧化氢酶(CAT)活性极显著下降(p <0.01);与DSS组相比,DSS+WO组血清IL-1β和IL-6含量、结肠NLRP3和Caspase-1 mRNA转录水平及NLRP3蛋白表达水平极显著降低(p <0.01),结肠SOD、GSH-Px和CAT活性极显著增强(p <0.01)。核桃油通过增强结肠的抗氧化能力,并可能通过抑制NLRP3炎性小体通路基因的转录水平,降低相关炎性因子的表达水平,对DSS诱导的小鼠结肠炎发挥保护作用。     

Yogurt starter cultures of Streptococcus thermophilus and Lactobacillus bulgaricus ameliorate symptoms and modulate the immune response in a mouse model of dextran sulfate sodium-induced colitis

We investigated the yogurt starter cultures of Lactobacillus bulgaricus 151 and Streptococcus thermophilus MK-10 for their effect on the severity of experimental colitis, lymphocyte profile, and regulatory T-cell response. Colitis was induced in BALB/c mice via the administration of 3.5% dextran sulfate sodium salt (DSS) in drinking water for 6 d. Next, the mice were gavaged intragastrically with an active yogurt cultures (YC) mixture (～5 × 10⁹ cfu/mouse per day) or saline (vehicle) for 8 d. Mice receiving DSS or saline alone served as positive and negative controls, respectively. The length of the colon, disease activity index, histological scores, myeloperoxidase activity, epithelium-associated microbes, short-chain fatty acid profile, total IgA antibody-forming cells, CD3⁺CD8⁺, CD3⁺CD4⁺, CD3⁺CD4⁺CD25⁺, CD3⁺CD4⁺CD25⁺Foxp3⁺ T-cell subsets, and cytokine profiles (IL-2, IL-4, IL-6, IL-10, IL-17A, IFN-γ, and tumor necrosis factor) were examined after termination of the mice. Feeding mice with YC mixture reduced disease symptoms and modified intestinal microbiota and host inflammatory responsiveness to DSS. We observed limited weight loss and a decreased disease activity index score, lowered myeloperoxidase activity, and somewhat reduced damage of the intestine. The YC mixture upregulated the colon length, increased the amount and diversity of mucosa-associated microbes (enterobacteria, enterococci, and yeast), and decreased the concentration of putrefactive short-chain fatty acids in the cecal contents. It downregulated the input of cytotoxic CD3⁺CD8⁺ T cells and CD3⁺CD4⁺CD25⁺FoxP3⁺ regulatory T cells in Peyer's patches and enhanced CD3⁺CD4⁺CD25⁺ T cells in spleens and CD3⁺CD4⁺CD25⁺FoxP3⁺ cells in peripheral blood mononuclear cells. Simultaneously, IgA antibody-forming cells were downregulated in mesenteric lymph nodes (MLN) and enhanced in spleens (SPL). The cultures mostly enhanced the production of cytokines tested in MLN and SPL, except for IL-6, which was downregulated in MLN. Interleukin-2 and IL-4 were the most upregulated in MLN, whereas IL-10, IL-4, IL-2, IFN-γ, and tumor necrosis factor were most upregulated in SPL. In serum, the YC mixture downregulated IFN-γ and clearly increased IL-2. Based on these results, we recognize the high anti-inflammatory and immunomodulatory potential of the L. bulgaricus 151 and S. thermophilus MK-10 set. The strains possess the ability to modulate the intestinal mucosal and systemic immune system toward both IgA production and induction of regulatory T cells, shifting Th1/Th2 balance.     

硫酸葡聚糖对低离子强度下罗非鱼肌球蛋白热变性聚集的抑制及其机制

以罗非鱼背部白肉为原料提取肌球蛋白,分析在低离子强度(1,50,150 mmol/L KCl)下,硫酸葡聚糖(dextran sulfate,DS)的添加对热处理(40～80℃,1℃/min)过程中肌球蛋白(2.0mg/mL)溶解度和分子结构的影响,探讨DS对肌球蛋白热变性聚集的抑制效果及机理。结果表明,在1mmol/L KCl条件下,肌球蛋白溶解度极低,热处理后分子头部聚集,尾部交联;在50,150mmol/L KCl条件下,肌球蛋白纤丝逐渐解离变粗,热处理后丝状体消失,头部聚集,溶解度、α-螺旋含量明显下降。添加0.4mg/mL DS后,热处理过程中体系浊度、溶解度和α-螺旋含量无明显变化,与未添加DS的体系相比,相同温度条件下肌球蛋白的溶解度明显增大(P0.05),表面电势升高。DS与肌球蛋白分子间强的静电相互作用能有效抑制低离子强度下肌球蛋白的热变性聚集。     

Protective effect of Lactobacillus fermentum CQPC04 on dextran sulfate sodium–induced colitis in mice is associated with modulation of the nuclear factor-κB signaling pathway

Colitis severely affects the quality of life of patients, and lactic acid bacteria have been reported to be able to improve or treat colitis. In this study, we selected a strain of Lactobacillus fermentum (CQPC04) with good resistance in vitro to evaluate its effect on improvement in mice with dextran sulfate sodium (DSS)–induced colitis. We analyzed the effects of L. fermentum CQPC04 on mice with colitis macroscopically via colon length and histopathology. We also used conventional biochemical and ELISA kits, real-time quantitative PCR (RT-qPCR), and Western blotting to analyze microscopically the effects of L. fermentum CQPC04 on related oxidant indices and pro- and anti-inflammatory cytokines in serum and colon tissue of mice. The results indicated that L. fermentum CQPC04 notably increased colon length and ameliorated pathological damage of colon tissue in colitic mice. Serum indices showed that L. fermentum CQPC04 increased the enzyme activity of total superoxide dismutase (T-SOD) and catalase (CAT) and decreased the content of malondialdehyde (MDA) and the activity of myeloperoxidase (MPO). In addition, it inhibited the release of the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), IFN-γ, IL-1β, IL-6, and IL-12, and increased the release of the anti-inflammatory cytokine IL-10 in serum. The RT-qPCR experiments confirmed that L. fermentum CQPC04 downregulated the expression of pro-inflammatory cytokine nuclear factor-κB-p65 (NF-κBp65), NF-κB inhibitor-α (IκB-α), TNF-α, IFN-γ, IL-1β, IL-6, cyclooxygenase 2 (COX-2), and inducible nitric oxide synthase (iNOS), and upregulated the expression of IL-10 in colon tissue. Western blot analysis indicated that L. fermentum CQPC04 significantly reduced expression of NF-κBp65, TNF-α, IL-1β, COX-2, and iNOS in mouse colon tissues, and increased expression of IκB-α and superoxide dismutase 2 (SOD2). Thus, L. fermentum CQPC04 could effectively alleviate the symptoms of DSS-induced colitis mice and is a potential probiotic for human experiments.