Ghaffarzadegan Tannaz, Marungruang Nittaya, Fåk Frida, Nyman Margareta
Food for Health Science Centre, Lund University, Lund, Sweden.
PLoS One. 2016 Jun 17;11(6):e0157427. doi: 10.1371/journal.pone.0157427. eCollection 2016.
Bile acids (BAs) act as signaling molecules in various physiological processes, and are related to colonic microbiota composition as well as to different types of dietary fat and fiber. This study investigated whether guar gum and pectin-two fibers with distinct functional characteristics-affect BA profiles, microbiota composition, and gut metabolites in rats. Low- (LM) or high-methoxylated (HM) pectin, and low-, medium-, or high-molecular-weight (MW) guar gum were administered to rats that were fed either low- or high-fat diets. Cecal BAs, short-chain fatty acids (SCFA) and microbiota composition, and plasma lipopolysaccharide-binding protein (LBP) levels were analyzed, by using novel methodologies based on gas chromatography (BAs and SCFAs) and 16S rRNA gene sequencing on the Illumina MiSeq platform. Strong correlations were observed between cecal BA and SCFA levels, microbiota composition, and portal plasma LBP levels in rats on a high-fat diet. Notably, guar gum consumption with medium-MW increased the cecal amounts of cholic-, chenodeoxycholic-, and ursodeoxycholic acids as well as α-, β-, and ω-muricholic acids to a greater extent than other types of guar gum or the fiber-free control diet. In contrast, the amounts of cecal deoxycholic- and hyodeoxycholic acid were reduced with all types of guar gum independent of chain length. Differences in BA composition between pectin groups were less obvious, but cecal levels of α- and ω-muricholic acids were higher in rats fed LM as compared to HM pectin or the control diet. The inflammatory marker LBP was downregulated in rats fed medium-MW guar gum and HM pectin; these two fibers decreased the cecal abundance of Oscillospira and an unclassified genus in Ruminococcaceae, and increased that of an unclassified family in RF32. These results indicate that the molecular properties of guar gum and pectin are important for their ability to modulate cecal BA formation, gut microbiota composition, and high-fat diet induced inflammation.
胆汁酸（BAs）在各种生理过程中充当信号分子，并且与结肠微生物群组成以及不同类型的膳食脂肪和纤维有关。本研究调查了瓜尔胶和果胶这两种具有不同功能特性的纤维是否会影响大鼠的胆汁酸谱、微生物群组成和肠道代谢产物。将低甲氧基化（LM）或高甲氧基化（HM）果胶，以及低、中、或高分子量（MW）瓜尔胶给予喂食低脂或高脂饮食的大鼠。采用基于气相色谱法（用于胆汁酸和短链脂肪酸）和Illumina MiSeq平台上的16S rRNA基因测序的新方法，分析盲肠胆汁酸、短链脂肪酸（SCFA）和微生物群组成，以及血浆脂多糖结合蛋白（LBP）水平。在高脂饮食的大鼠中，观察到盲肠胆汁酸和短链脂肪酸水平、微生物群组成与门静脉血浆LBP水平之间存在强相关性。值得注意的是，与其他类型的瓜尔胶或无纤维对照饮食相比，食用中等分子量的瓜尔胶会更大程度地增加盲肠中胆酸、鹅去氧胆酸和熊去氧胆酸以及α-、β-和ω-鼠胆酸的含量。相反，所有类型的瓜尔胶，无论链长如何，都会降低盲肠中脱氧胆酸和猪去氧胆酸的含量。果胶组之间胆汁酸组成的差异不太明显，但与喂食HM果胶或对照饮食的大鼠相比，喂食LM果胶的大鼠盲肠中α-和ω-鼠胆酸水平更高。在喂食中等分子量瓜尔胶和HM果胶的大鼠中，炎症标志物LBP被下调；这两种纤维降低了瘤胃菌科中未分类属和颤螺菌属的盲肠丰度，并增加了RF32中未分类科的丰度。这些结果表明，瓜尔胶和果胶的分子特性对于它们调节盲肠胆汁酸形成、肠道微生物群组成以及高脂饮食诱导的炎症的能力很重要。
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