The hepatic function of cholesterol sulfotransferase 2B1b (SULT2B1b)in energy met

说明(申请人提供)：胆固醇磺基转移酶SULT2B1b是一种胞质磺基转移酶，以其磺化胆固醇和氧化甾醇的活性而闻名。代谢综合征，通常表现为肥胖和胰岛素抵抗的2型糖尿病，是一个主要的健康问题。糖脂代谢紊乱在肥胖和2型糖尿病的发病机制中起着重要作用。虽然SULT2B1b在胆固醇硫化反应中的催化活性已被证明，但SULT2B1b及其酶促副产物胆固醇硫酸盐(CS)在能量代谢和代谢综合征中的作用仍很不清楚。我们的初步结果表明：1)SULT2B1b在肥胖小鼠中被诱导，并在从禁食状态向饮食状态的过渡过程中被诱导；2)SULT2B1b和CS抑制肝细胞的糖异生；3)SULT2B1b和CS特异性地抑制HNF4α的糖异生活性；4)CS处理抑制了HNF4α的乙酰化并改善了胰岛素敏感性；5)转基因过表达SULT2B1b改善了HNF4模型的代谢功能；6)瘦素是SULT2B1b代谢受益的潜在效应因子；7)SULT2B1b抑制了乙酰辅酶A合成酶2的表达，减少了HNF4α的乙酰化，并导致HNF4的核排斥；8)下调HNF4α的α表达可取消CS对体外糖异生的抑制作用；9)SULT2B1b是潜在的HNF4α靶基因，为糖异生负反馈调控提供了可能的机制。根据我们的初步数据，我们假设胆固醇磺基转移酶SULT2B1b在抑制糖异生和减轻代谢性疾病方面具有以前未被认识到的作用。从机理上讲，SULT2B1b的代谢优势可能是通过其酶促副产物胆固醇硫酸盐(CS)和靶向糖异生转录因子HNF4α的乙酰化和核转位实现的。我们还假设SULT2B1是一个HNF4α靶基因，这代表了一种负反馈机制来限制HNF4α的糖异生活性。我们预计瘦素可能是SULT2B1b改善代谢功能的潜在效应者。通过使用肝脏特异性SULT2B1b转基因小鼠，结合肥胖症和2型糖尿病的HFD和ob/ob模型，我们提出了三个特定的目标来检验我们的假设：1)确定肝脏特异性的SULT2B1b过表达是否抑制肥胖和2型糖尿病的ob/ob模型；2)确定SULT2B1b和CS抑制糖异生的分子机制；以及3)确定HNF4α诱导SULT2B1b是否代表糖异生负反馈调节的潜在机制。据我们所知，这项研究是首次尝试全面评价SULT2B1b及其酶促副产物CS在体内能量代谢中的内生和肝功能。这项研究的结果可能确立SULT2B1b作为新的治疗靶点，CS作为治疗代谢性疾病的治疗剂。

DESCRIPTION (provided by applicant): The cholesterol sulfotransferase SULT2B1b is a cytosolic sulfotransferase best known for its activity in sulfonating cholesterol and oxysterols. Metabolic syndrome, often manifested as obesity and insulin resistant type 2 diabetes, is a major health concern. The dysregulation of glucose and lipid metabolism plays an important pathogenic role in obesity and type 2 diabetes. Although the activity of SULT2B1b in catalyzing the sulfation of cholesterol has been documented, the role of SULT2B1b and its enzymatic byproduct cholesterol sulfate (CS) in energy metabolism and metabolic syndrome remains largely unknown. Our preliminary results showed that: 1) SULT2B1b was induced in obese mice and during the transition from the fasted to the fed state; 2) SULT2B1b and CS inhibited gluconeogenesis in hepatic cells; 3) SULT2B1b and CS specifically inhibited the gluconeogenic activity of HNF4α; 4) Treatment with CS inhibited gluconeogenesis and improved insulin sensitivity in both HFD and ob/ob models; 5) Transgenic overexpression of SULT2B1b improved metabolic functions in the HFD model; 6) Leptin is a potential effector for the metabolic benefit of SULT2B1b; 7) SULT2B1b and CS suppressed the expression of acetyl-coenzyme A synthetase 2 (Acss2), decreased the acetylation of HNF4α, and caused the nuclear exclusion of HNF4α; whereas a forced expression of Acss2 abolished the inhibitory effect of CS on HNF4α; 8) Down-regulation of HNF4α abolished the inhibitory effect of CS on gluconeogenesis in vitro; and 9) SULT2B1b is a potential HNF4α target gene, providing a possible mechanism of negative feedback regulation of gluconeogenesis. Based on our preliminary data, we hypothesize that the cholesterol sulfotransferase SULT2B1b has a previously unrecognized role in inhibiting gluconeogenesis and alleviating metabolic disease. Mechanistically, the metabolic benefit of SULT2B1b may have been achieved through its enzymatic byproduct cholesterol sulfate (CS) and by targeting the acetylation and nuclear translocation of the gluconeogenic transcriptional factor HNF4α. We also hypothesize that the SULT2B1 is a HNF4α target gene, which represents a negative feedback mechanism to limit the gluconeogenic activity of HNF4α. We anticipate that leptin is a potential effector of SULT2B1b in improving metabolic functions. By using the liver-specific SULT2B1b transgenic mice, in conjunction with HFD and ob/ob models of obesity and type 2 diabetes, we propose three Specific Aims to test our hypotheses: 1) To determine whether the liver-specific overexpression of SULT2B1b inhibits the ob/ob model of obesity and type 2 diabetes; 2) To determine the molecular mechanism by which SULT2B1b and CS inhibit gluconeogenesis; and 3) To determine whether the induction of SULT2B1b by HNF4α represents a potential mechanism of negative feedback regulation of gluconeogenesis. To our knowledge, this study represents the first attempt to comprehensively evaluate the endobiotic and hepatic function of SULT2B1b and its enzymatic byproduct CS in energy metabolism in vivo. Results from this study may establish SULT2B1b as a novel therapeutic target and CS as a therapeutic agent to manage metabolic disease.