羟基类固醇硫酸基转移酶2B1调控肠道脂质吸收的作用及机制研究

Overproduction of intestinal apoB48-containning chylomicron is a most important reason of hyperlipidemia. Hyperlipidemia is highly correlated with acute cardiovascular events, insulin resistant states, metabolic syndrome, and so on. Inhibiting the intestinal lipoprotein production might be a new therapeutic strategy for the prevention and treatment of hyperlipidemia and its related metabolic disturbances. Hydroxysteroid sulfotransferase 2B1 (SULT2B1) is highly expressed in intestine, but the physiological and pathophysiological significances remain unknown. As a key nuclear transcriptional factor, HNF4a promotes intestinal fat absorption. It was reported that SULT2B1 could inhibit HNF4a activity. Our preliminary data showed that SULT2B1-/- mice were prone to get hyperlipidemia and metabolic disturbances upon high-fat diet feeding. The mRNA levels of chylomicron formation relative genes and the activity of HNF4a in intestine of SULT2B1-/- mice were higher than those of WT mice. Based on the previous results, we propose that SULT2B1 might transcriptionally inhibit chylomicron formation relative genes by suppressing HNF4a, and then reducing lipid absorption and metabolic syndrome progression. To clarify the hypothesis, we will utilize the intestine-specific SULT2B1 knockout (SULT2B1ΔIEC mice) to investigate the effect of intestinal SULT2B1 on chylomicron formation, lipid absorption, hyperlipidemia and metabolic disturbances upon high-fat diet feeding. We will also study the role of HNF4a in the effect of intestinal SULT2B1 on lipid absorption. The present project might elucidate the effect of SULT2B1 in intestinal lipoprotein production, hyperlipidemia and its related metabolic disturbances. A novel regulation pathway of lipid absorption might be provided.

肠道生成过量的乳糜微粒(CM)导致脂质吸收增加是血脂紊乱的重要原因。羟基类固醇硫酸基转移酶2B1(SULT2B1)催化胆固醇及其氧化衍生物的硫酸化反应，其高表达于小肠，但意义不明。核转录因子HNF4a促进肠道脂质吸收，有研究报道其活性可被SULT2B1抑制。我们前期发现SULT2B1-/-小鼠易出现血脂紊乱，其小肠CM生成基因转录水平和HNF4a活性增高。本项目提出：肠上皮细胞SULT2B1可通过抑制HNF4a活性而下调CM生成基因转录，最终抑制脂质吸收和维持血脂稳态。我们拟利用肠上皮细胞特异敲除SULT2B1小鼠明确肠上皮细胞SULT2B1对高脂喂养诱导的血脂异常及其相关代谢紊乱的影响，通过体内外实验研究肠上皮细胞SULT2B1对肠道CM合成和脂质吸收的作用，并探讨HNF4a在其中的作用。本项目将阐明SULT2B1调节肠脂质吸收和血脂稳态的作用和机制，将提出一条新的调节脂质吸收的通路。

抑制肠道过度吸收脂质是纠正血脂紊乱及与其密切相关的代谢性和心血管疾病的重要手段。羟基类固醇硫酸基转移酶2B1（SULT2B1）是参与胆固醇及其氧化衍生物硫酸化反应的关键酶。小肠组织表达极高丰度的SULT2B1，但其生理和病理生理学意义尚不清楚。我们给予SULT2B1flox/flox和SULT2B1∆IEC小鼠高脂高胆固醇饮食（D12108C，40 kcal%脂肪，1.25% 胆固醇）喂养12周后，于禁食（fasted）和禁食后再摄食（refed）取材，发现无论在fasted还是refed情况下，SULT2B1∆IEC小鼠血清总胆固醇、胆固醇酯和游离胆固醇水平均较SULT2B1flox/flox小鼠降低。取小鼠空肠上段抽提RNA，进行RNAseq分析。同时，我们发现相较SULT2B1flox/flox小鼠小肠类器官，SULT2B1∆IEC小鼠小肠类器官面积更小、出芽更少，增殖速度更慢，而SULT2B1的产物胆固醇硫酸酯（Cholesterol, CS）促进小肠类器官生长。提取上述小肠类器官的RNA进行RNAseq, 获得SULT2B1敲除后下调、给予CS后上调的基因，并将其与前述小鼠空肠上段组织RNAseq结果进行韦恩分析后，找到Apoc3这一重要的载脂蛋白基因可能是SULT2B1调控肠道脂质吸收的关键分子。文献报道Apoc3敲除能够显著降低血浆中总胆固醇水平、抗动脉粥样硬化。我们推测SULT2B1敲除后Apoc3的降低可能会延缓动脉粥样硬化的进展。因此，我们采用尾静脉注射AAV-PCSK9过表达腺相关病毒配合致动脉粥样饲料（D12109C，40 kcal%脂肪，1.25%胆固醇，0.5%胆酸）喂养的方法在SULT2B1flox/flox和SULT2B1∆IEC小鼠中建立动脉粥样硬化模型，三个月后取材发现，SULT2B1∆IEC小鼠主动脉弓部、直部及整个主动脉的粥样斑块面积均小于SULT2B1flox/flox小鼠。本项目研究了SULT2B1调节肠脂质吸收和血脂稳态及相关疾病的作用和机制，提出一条新的调节脂质吸收的通路。我们还研究发现，小肠的细胞增殖能力、线粒体形态和整体转录组谱在禁食和摄食后表现出显著的差异，而长期高脂喂养后该差异显著减小。通过一系列机制探讨，我们发现小肠上皮细胞的维生素A及活性其代谢产物维甲酸在此过程中发挥重要的调控作用。