Bile Acids

本研究旨在阐明富含原花青素的葡萄多酚提取物对胆汁的调节作用。 酸(BA)向法尼醇X受体(FXR)传递信号，从而改善葡萄糖代谢。使用肠道- 特异性(FXRΔIE)和肝脏特异性(FXRΔL)FXR基因敲除小鼠和衍生的回肠类器官，我们将调查 GP诱导的血糖改善是否是由于抑制了肠道和/或肝脏的FXR信号。我们 还将确定全科医生是否直接隔离二次胆汁酸(SBAs)或间接导致它们的耗尽。 食用富含多酚的食物与降低患慢性病的风险有关；然而，许多饮食 多酚的吸收能力很差，这引发了人们对其作用机制的质疑(S)。新陈代谢优势 多酚很可能是由肠道微生物区系的变化驱动的。先前的研究表明，GPs可以改善血糖 高脂饮食(HFD)喂养的野生型(WT)小鼠的代谢由于GP诱导的肠道微生物区系的变化 与体重减轻、代谢性内毒素血症(即较低的血清脂多糖)、 组织炎症，以及紧密连接蛋白表达增加。我们最近的数据显示，全科医生 补充剂对糖尿病db/db小鼠高血糖的缓解作用与肥胖、肠道屏障的变化无关 正直和炎症。相反，GP诱导的db/db小鼠肠道微生物区系的变化促进了BA 抑制肠道FXR活性和FXR反应通路的特征。选择性肠道抑制 FXR与改善糖代谢和减少神经酰胺合成有关 服用降糖药，二甲双胍。二甲双胍改变肠道微生物区系和BA池，减少神经酰胺 肝脏糖异生标志物的产生和降低的表达[Sun等人，2018年]。的双重对抗性 肝脏和肠道中的FXR可能促进胆汁淤积[Kong等，2012]，因此区分组织特异性 GP对FXR活性的影响是重要的。16S rRNA V4扩增序列分析表明，GP补充剂 与继发性BA(SBAS)代谢有关的耗竭的属伴随着血清的急剧下降 SBAs和初级BA(Pbas)的增加。补充GPS的小鼠的肠道和肝脏组织有： 1)降低FXR活性标志物SHP和Fgf15的基因表达；2)降低Smpd3的表达， Cers4和Sptlc2、FXR对神经酰胺合成至关重要的反应基因；以及3)增加了 Cyp7a1，一种负责合成PBA的酶。用肠道有机化合物来区分直接影响 BAS对肠道FXR激活和神经酰胺合成的影响及GP诱导的BA谱拮抗作用 到肠道FXR。我们建议1)研究补充GP对FXRΔIE和FXRΔL的血糖调节作用 为了揭示GP是否对肝脏FXR信号机制具有拮抗作用，并区分GP是否具有 在回肠内隔离SBAs对FXR有激动剂作用。2)用FXR∆IE提取的回肠有机化合物测定 肠道FXR对GP介导的神经酰胺生物合成调控的需求和3)直接决定 从添加了GP的小鼠身上收集的回肠内容物厌氧培养是否缺乏产生SBAs的能力。

This proposal aims to elucidate how proanthocyanidin-rich extracts of grape polyphenols (GPs) modulate bile acid (BA) signaling to farnesoid X-receptor (FXR) resulting in improved glucose metabolism. Using intestine- specific (FxrΔIE) and liver-specific (FxrΔL) FXR knockout mice and derived ileal organoids, we will investigate whether GP-induced glycemic improvements are due to inhibition of intestinal and/or hepatic FXR signaling. We will also determine if GPs directly sequester secondary bile acids (SBAs) or indirectly leads to their depletion. Consumption of polyphenol-rich foods is associated with reduced risk of chronic disease; however, many dietary polyphenols are poorly absorbed raising questions about their mechanism(s) of action. Metabolic benefits of polyphenols are likely driven by changes in the gut microbiota. Prior work showed that GPs improved glucose metabolism in high-fat diet (HFD)-fed wild type (WT) mice due to GP-induced changes in the gut microbiota that correlated with attenuated body weight, metabolic endotoxemia (i.e. lower serum lipopolysaccharide (LPS)), tissue inflammation, as well as increased tight junction protein expression. Our recent data showed that GP supplementation mitigated hyperglycemia in diabetic db/db mice independent of changes in obesity, gut barrier integrity, and inflammation. Rather, GP-induced changes in the gut microbiota of db/db mice promoted a BA profile that suppressed intestinal FXR activity and FXR responsive pathways. Selective inhibition of intestinal FXR has been correlated with improved glucose metabolism and decreased ceramide synthesis in mice treated with antidiabetic drug, metformin. Metformin altered the gut microbiota and BA pool, reduced ceramide production, and lowered expression of hepatic gluconeogenic markers [Sun et al., 2018]. Dual antagonism of FXR in liver and intestine may promote cholestasis [Kong et al., 2012], therefore differentiating tissue specific effects of GPs on FXR activity is important. 16S rRNA V4 amplicon sequencing showed that GP supplementation depleted genera implicated in secondary BA (SBAs) metabolism concomitant with a dramatic decrease in serum SBAs and an increase in primary BAs (PBAs). Intestinal and liver tissues of mice supplemented with GPs had: 1) decreased gene expression of Shp and Fgf15, markers of FXR activity; 2) lowered expression of Smpd3, Cers4, and Sptlc2 , FXR responsive genes critical for ceramide synthesis; and 3) increased expression of Cyp7a1, an enzyme responsible for PBA synthesis. Gut organoids were used to differentiate the direct effects of BAs on intestinal FXR activation and ceramide synthesis and revealed GP-induced a BA profile antagonistic to intestinal FXR. We propose to 1) investigate glucoregulatory effect of GP supplementation in FxrΔIE and FxrΔL to uncover if GPs are antagonistic to liver FXR signaling mechanisms and distinguish the ability of GPs to sequester SBAs agonistic to FXR within the ileum. 2) Use ileal gut organoids derived from FXR∆IE to determine the requirement of intestinal FXR for GP-mediated regulation of ceramide biosynthesis and 3) directly determine whether anaerobic cultures of ileal content collected from GP supplemented mice lack ability to produce SBAs.