Diet-induced alteration of intestinal stem cell identity and lineage allocation underlies obesity and pre-diabetes in mice

Excess nutrient uptake and altered hormone secretion in the gut contribute to a systemic energy imbalance causing obesity and increased risk for type 2 diabetes (T2D) and colorectal cancer. This functional maladaptation is thought to emerge at the level of the intestinal stem cells (ISCs). But, how an obesogenic diet affects ISC identity and fate decisions is not well understood. Here, we study the intestinal responses to an obesogenic diet in mice by combining single-cell profiling of more than 27,000 small intestinal crypt cells with genetic lineage labelling and tracing of ISC fate decisions and in situ metabolomics. We find that an obesogenic diet induces ISC and progenitor hyperproliferation, but also enhances ISC differentiation and cell turnover. Furthermore, the regional identity of ISCs and enterocytes is reprogrammed from a distal to a proximal phenotype and enterocyte zonation is altered to adapt cell function to nutrient availability. Single-cell resolution of the enteroendocrine lineage shows an increase in endocrine progenitors and peptidergic enteroendocrine cell (EEC) types and a decrease in serotonergic EEC types. Mechanistically, we can link increased fatty acid synthesis, Ppar signalling and the Insr/Igf1r/Akt pathway to ISC dysfunction, hyperproliferation and impaired endocrine differentiation. In summary, our work describes key molecular mechanisms of diet-induced intestinal maladaptation in mice that promote obesity, and, thus, underlie the pathogenesis of the metabolic syndrome and associated complications. We performed Affymetrix microarray analysis on FACS purified intestinal crypt cells expressing different levels of Foxa2-Venus Fusion (FVF) protein (FVF-negative, FVF-low, FVF-high) isolated mice fed a high-fat-high-sugar or control diet.

肠道内过量营养摄取与激素分泌异常会引发全身性能量失衡，进而导致肥胖，并增加2型糖尿病（Type 2 Diabetes, T2D）与结直肠癌的患病风险。这种功能性适应不良被认为起源于肠道干细胞（Intestinal Stem Cells, ISCs）层面，但目前对于致肥胖饮食如何影响肠道干细胞的身份特征与命运决定仍不甚明晰。本研究结合对超过27000个小肠隐窝细胞的单细胞图谱分析、肠道干细胞命运决定的遗传谱系标记与追踪技术，以及原位代谢组学方法，探究了小鼠体内肠道对致肥胖饮食的响应机制。研究发现，致肥胖饮食可诱导肠道干细胞与祖细胞过度增殖，同时增强肠道干细胞的分化能力与细胞更新速率；此外，肠道干细胞与肠上皮细胞的区域身份特征被重编程，从远端表型转向近端表型，且肠上皮细胞的分区模式发生改变，以适配细胞功能对营养可利用性的需求。对肠内分泌谱系的单细胞分辨率分析显示，内分泌祖细胞与肽能肠内分泌细胞（Peptidergic Enteroendocrine Cell, EEC）类型的占比上升，而血清素能肠内分泌细胞类型的占比下降。从机制层面而言，本研究可将脂肪酸合成增强、过氧化物酶体增殖物激活受体（Peroxisome Proliferator-Activated Receptor, Ppar）信号通路，以及胰岛素受体/胰岛素样生长因子1受体/Akt（Insulin Receptor/Insulin-like Growth Factor 1 Receptor/Akt, Insr/Igf1r/Akt）信号通路与肠道干细胞功能异常、过度增殖以及内分泌分化受损关联起来。综上，本研究阐明了小鼠体内饮食诱导的肠道适应不良的关键分子机制，该机制可促进肥胖发生，进而成为代谢综合征及其相关并发症的发病基础。我们对从喂食高脂高糖饮食或对照饮食的小鼠体内分离得到的、表达不同水平Foxa2-Venus融合蛋白（Foxa2-Venus Fusion, FVF）的荧光激活细胞分选（Fluorescence-Activated Cell Sorting, FACS）纯化肠道隐窝细胞进行了Affymetrix基因芯片分析，这些细胞包括FVF阴性、FVF低表达与FVF高表达三个亚群。