The molecular mechanism of how hepatocytes maintain cholesterol homeostasis has become much more transparent with the discovery of sterol regulatory element binding proteins (SREBPs) in recent years. These membrane pr...The molecular mechanism of how hepatocytes maintain cholesterol homeostasis has become much more transparent with the discovery of sterol regulatory element binding proteins (SREBPs) in recent years. These membrane proteins aremembers of the basic helix-loop-helix-leucine zipper (bHLHZip) family of transcription factors. They activate the expression of at least 30 genes involved in the synthesis of cholesterol and lipids. SREBPs are synthesized as precursor proteins in the endoplasmic reticulum (ER), where they form a complex with another protein, SREBP cleavage activating protein (SCAP). The SCAP molecule contains a sterol sensory domain. In the presence of high cellular sterol concentrations SCAP confines SREBP to the ER. With low cellular concentrations, SCAP escorts SREBP to activation in the Golgi. There, SREBP undergoes two proteolytic cleavage steps to release the mature, biologically active transcription factor, nuclear SREBP (nSREBP). nSREBP translocates to the nucleus and binds to sterol response elements (SRE) in the promoter/enhancer regions of target genes. Additional transcription factors are required to activate transcription of these genes. Three different SREBPs are known, SREBPs-1a, -1c and -2. SREBP-1a and -1c are isoforms produced from a single gene by alternate splicing. SREBP-2 is encoded by a different gene and does not display any isoforms. It appears that SREBPs alone, in the sequence described above, can exert complete control over cholesterol synthesis, whereas many additional factors (hormones, cytokines, etc.) are required for complete control of lipid metabolism. Medicinal manipulation of the SREBP/SCAP system is expected to prove highly beneficial in the management of cholesterol-related disease.展开更多
OBJECTIVE: To study the mechanism of Dangfei Liganning capsule(当飞利肝宁胶囊) in the treatment of rats with metabolic associated fatty liver disease(MAFLD). METHODS: Totally 48 specific pathogen free SpragueDawley ma...OBJECTIVE: To study the mechanism of Dangfei Liganning capsule(当飞利肝宁胶囊) in the treatment of rats with metabolic associated fatty liver disease(MAFLD). METHODS: Totally 48 specific pathogen free SpragueDawley male rats were randomly divided into normal Group, model group, Dangfei Liganning high, moderate, and low-dose groups and Essentiale group which were fed with high fat diet for 8 weeks, and gavage and molding were carried out simultaneously. Dangfei Liganning high, middle and low-dose group were given 0.27, 0.135 and 0.0675 g·kg-1·d-1 respectively by gavage, Essentiale group was given 0.123 g·kg-1·d-1 by gavage, the same amount of distilled water was given by gavage in the normal group and the model group. The rats were weighed at the 0th week, 2nd week, 4th week, 6th week and 8th weekend respectively. The rats were sacrificed at the end of the 8th week. Serum levels of alanine aminotransferase(ALT), alanine aminotransferase(AST),triglyceride(TG), total cholesterol(CHO), high-density lipoprotein cholesterol(HDL-C), low-density lipoprotein (LDL-C), total protein(TP), albumin(Alb), globulin(GLB), total bilirubin(TBIL), direct bilirubin(DBIL), tumor necrosis factor-α(TNF-α) and interleukin-6(IL-6) were measured. The levels of liver tumor necrosis factor-α(TNF-α), interleukin-6(IL-6) and liver pathology [hematoxylin and eosin(HE) staining, oil red O staining] were detected. The expression levels of liver X receptor α(LXRα), steroid regulatory element binding protein-1(SREBP-1) and fatty acid synthase(FAS) were detected by immunohistochemistry, Western blot and reverse transcription-polymerase chain reaction reverse transcription-polymerase chain reaction. RESULTS: From the beginning to the 8th week, the growth rate of body weight in the Dangfei Liganning highdose group was slower than all other groups. There was no significant difference in ALB level in all groups(P > 0.05). Compared with the model group, the levels of ALT, AST, LDL-C, TG, CHO, TP, GLB, TBIL, DBIL, IL-6, TNF-α were significantly decreased and HDL-C were significantly increased in Dangfei Liganning high-dose group(P < 0.01, < 0.05). HE and oil red O staining showed that the fatty lesions in rat liver were alleviated, while the expressions of LXRα, SREBP-1, FAS m RNA and protein were significantly decreased(P < 0.01). CONCLUSIONS: Dangfei Liganning capsule can slow down the increase of body weight of MAFLD rats, reduce the levels of transaminase, Lipid and inflammatory factors in MAFLD rats, promote the synthesis of liver protein and bile metabolism, and improve the liver fatty lesion of MAFLD rats, among which the Dangfei Liganning highdose group is more effective. The mechanism of action may be through blocking LXR-SREBP-1-FAS signal pathway.展开更多
Background Sterol regulatory element binding protein （SREBP）-2 plays a key role in lipid homeostasis by stimulating gene expression of cholesterol biosynthetic pathways. The insulin-like growth factor binding prote...Background Sterol regulatory element binding protein （SREBP）-2 plays a key role in lipid homeostasis by stimulating gene expression of cholesterol biosynthetic pathways. The insulin-like growth factor binding protein （IGFBP） family regulates growth and metabolism, especially bone cell metabolism, and correlates with osteonecrosis. However, association of their gene polymorphisms with risk of avascular necrosis of the femoral head （ANFH） has rarely been reported. We determined whether SREBP-2 and IGFBP-3 gene polymorphisms were associated with increased ANFH risk in the Chinese population. Methods Two single nucleotide polymorphisms of SREBP2 gene, rs2267439 and rs2267443, and one of IGFBP-3 gene, rs2453839, were selected and genotyped in 49 ANFH patients and 42 control individuals by direct sequencing assay. Results The frequencies of rs2267439 TT and rs2267443 GA of SREBP2 and rs2453839 TT and CT of IGFBP-3 in the ANFH group showed increased and decreased tendencies （against normal control group）, respectively. Interaction analysis of genes revealed that the frequency of carrying rs2267439 TT and rs2267443 GA genotypes of SREBF-2 in ANFH patients was significantly higher than in the control group （P 〈0.05）. Association analysis between polymorphisms and clinical phenotype demonstrated that the disease course in ANFH patients with the rs2453839 TT genotype of IGFBP-3 was significantly shorter than that of CT＋CC carriers （P 〈0.01）. CT＋CC genotype frequency in patients with stage Ill/IV bilateral hip lesions was significantly higher than in those with stage Ill/IV unilateral lesions and stage II/111 bilateral lesions （P 〈0.05-0.02）. Conclusions Our results suggested that interaction of SREBP-2 gene polymorphisms and the relationship between the polymorphisms and clinical phenotype of IGFBP-3 were closely related to increased ANFH risk in the Chinese population. The most significant finding was that the CT＋CC genotype carriers of IGFBP-3 rs2453839 were highly associated with the development of ANFH.展开更多
固醇调节元件结合蛋白1(Sterol regulatory element-binding protein 1,SREBP-1)是重要的核转录因子之一,能调控内源性胆固醇、脂肪酸、甘油三酯和磷脂合成所需酶的表达,以维持血脂动态平衡。研究表明,SREBP-1及其靶基因网络的异常可引...固醇调节元件结合蛋白1(Sterol regulatory element-binding protein 1,SREBP-1)是重要的核转录因子之一,能调控内源性胆固醇、脂肪酸、甘油三酯和磷脂合成所需酶的表达,以维持血脂动态平衡。研究表明,SREBP-1及其靶基因网络的异常可引起胰岛素抵抗、Ⅱ型糖尿病、心功能紊乱、血管并发症和肝脂肪变等一系列代谢性疾病。近年高通量组学技术的发展极大扩展了对SREBP-1靶基因及其转录调控模式的了解。文章对SREBP-1蛋白结构、活化过程、DNA结合位点及其调控的靶基因等方面的研究进展进行了综述,并着重介绍了基于组学数据的转录调控网络的构建,这将有助于更好的认识SREBP-1在脂类代谢中的作用,为深入探讨脂质代谢性疾病的治疗提供新线索。展开更多
文摘The molecular mechanism of how hepatocytes maintain cholesterol homeostasis has become much more transparent with the discovery of sterol regulatory element binding proteins (SREBPs) in recent years. These membrane proteins aremembers of the basic helix-loop-helix-leucine zipper (bHLHZip) family of transcription factors. They activate the expression of at least 30 genes involved in the synthesis of cholesterol and lipids. SREBPs are synthesized as precursor proteins in the endoplasmic reticulum (ER), where they form a complex with another protein, SREBP cleavage activating protein (SCAP). The SCAP molecule contains a sterol sensory domain. In the presence of high cellular sterol concentrations SCAP confines SREBP to the ER. With low cellular concentrations, SCAP escorts SREBP to activation in the Golgi. There, SREBP undergoes two proteolytic cleavage steps to release the mature, biologically active transcription factor, nuclear SREBP (nSREBP). nSREBP translocates to the nucleus and binds to sterol response elements (SRE) in the promoter/enhancer regions of target genes. Additional transcription factors are required to activate transcription of these genes. Three different SREBPs are known, SREBPs-1a, -1c and -2. SREBP-1a and -1c are isoforms produced from a single gene by alternate splicing. SREBP-2 is encoded by a different gene and does not display any isoforms. It appears that SREBPs alone, in the sequence described above, can exert complete control over cholesterol synthesis, whereas many additional factors (hormones, cytokines, etc.) are required for complete control of lipid metabolism. Medicinal manipulation of the SREBP/SCAP system is expected to prove highly beneficial in the management of cholesterol-related disease.
基金Supported by Capital Health Development Research Project:Assessment of the Efficacy of BIEJIAJIANWAN Pill in Patients with Chronic Hepatitis B Cirrhosis/Fibrosis (CD2018-2-2173)Beijing Municipal Administration of Hospitals Incubating Program:Clinical Observation on the Treatment of Nonalcoholic Fatty Liver Disease by Invigorating the Spleen,Soothing the Liver,Activating Blood Circulation and Resolving Phlegm (PZ2019011)。
文摘OBJECTIVE: To study the mechanism of Dangfei Liganning capsule(当飞利肝宁胶囊) in the treatment of rats with metabolic associated fatty liver disease(MAFLD). METHODS: Totally 48 specific pathogen free SpragueDawley male rats were randomly divided into normal Group, model group, Dangfei Liganning high, moderate, and low-dose groups and Essentiale group which were fed with high fat diet for 8 weeks, and gavage and molding were carried out simultaneously. Dangfei Liganning high, middle and low-dose group were given 0.27, 0.135 and 0.0675 g·kg-1·d-1 respectively by gavage, Essentiale group was given 0.123 g·kg-1·d-1 by gavage, the same amount of distilled water was given by gavage in the normal group and the model group. The rats were weighed at the 0th week, 2nd week, 4th week, 6th week and 8th weekend respectively. The rats were sacrificed at the end of the 8th week. Serum levels of alanine aminotransferase(ALT), alanine aminotransferase(AST),triglyceride(TG), total cholesterol(CHO), high-density lipoprotein cholesterol(HDL-C), low-density lipoprotein (LDL-C), total protein(TP), albumin(Alb), globulin(GLB), total bilirubin(TBIL), direct bilirubin(DBIL), tumor necrosis factor-α(TNF-α) and interleukin-6(IL-6) were measured. The levels of liver tumor necrosis factor-α(TNF-α), interleukin-6(IL-6) and liver pathology [hematoxylin and eosin(HE) staining, oil red O staining] were detected. The expression levels of liver X receptor α(LXRα), steroid regulatory element binding protein-1(SREBP-1) and fatty acid synthase(FAS) were detected by immunohistochemistry, Western blot and reverse transcription-polymerase chain reaction reverse transcription-polymerase chain reaction. RESULTS: From the beginning to the 8th week, the growth rate of body weight in the Dangfei Liganning highdose group was slower than all other groups. There was no significant difference in ALB level in all groups(P > 0.05). Compared with the model group, the levels of ALT, AST, LDL-C, TG, CHO, TP, GLB, TBIL, DBIL, IL-6, TNF-α were significantly decreased and HDL-C were significantly increased in Dangfei Liganning high-dose group(P < 0.01, < 0.05). HE and oil red O staining showed that the fatty lesions in rat liver were alleviated, while the expressions of LXRα, SREBP-1, FAS m RNA and protein were significantly decreased(P < 0.01). CONCLUSIONS: Dangfei Liganning capsule can slow down the increase of body weight of MAFLD rats, reduce the levels of transaminase, Lipid and inflammatory factors in MAFLD rats, promote the synthesis of liver protein and bile metabolism, and improve the liver fatty lesion of MAFLD rats, among which the Dangfei Liganning highdose group is more effective. The mechanism of action may be through blocking LXR-SREBP-1-FAS signal pathway.
基金This work was supported by grants from the National Natural Science Foundation of China （ No. 81173047 and No. 31371161 ） and the Natural Science Foundation of Hunan （No. 12JJ5068）.
文摘Background Sterol regulatory element binding protein （SREBP）-2 plays a key role in lipid homeostasis by stimulating gene expression of cholesterol biosynthetic pathways. The insulin-like growth factor binding protein （IGFBP） family regulates growth and metabolism, especially bone cell metabolism, and correlates with osteonecrosis. However, association of their gene polymorphisms with risk of avascular necrosis of the femoral head （ANFH） has rarely been reported. We determined whether SREBP-2 and IGFBP-3 gene polymorphisms were associated with increased ANFH risk in the Chinese population. Methods Two single nucleotide polymorphisms of SREBP2 gene, rs2267439 and rs2267443, and one of IGFBP-3 gene, rs2453839, were selected and genotyped in 49 ANFH patients and 42 control individuals by direct sequencing assay. Results The frequencies of rs2267439 TT and rs2267443 GA of SREBP2 and rs2453839 TT and CT of IGFBP-3 in the ANFH group showed increased and decreased tendencies （against normal control group）, respectively. Interaction analysis of genes revealed that the frequency of carrying rs2267439 TT and rs2267443 GA genotypes of SREBF-2 in ANFH patients was significantly higher than in the control group （P 〈0.05）. Association analysis between polymorphisms and clinical phenotype demonstrated that the disease course in ANFH patients with the rs2453839 TT genotype of IGFBP-3 was significantly shorter than that of CT＋CC carriers （P 〈0.01）. CT＋CC genotype frequency in patients with stage Ill/IV bilateral hip lesions was significantly higher than in those with stage Ill/IV unilateral lesions and stage II/111 bilateral lesions （P 〈0.05-0.02）. Conclusions Our results suggested that interaction of SREBP-2 gene polymorphisms and the relationship between the polymorphisms and clinical phenotype of IGFBP-3 were closely related to increased ANFH risk in the Chinese population. The most significant finding was that the CT＋CC genotype carriers of IGFBP-3 rs2453839 were highly associated with the development of ANFH.
文摘固醇调节元件结合蛋白1(Sterol regulatory element-binding protein 1,SREBP-1)是重要的核转录因子之一,能调控内源性胆固醇、脂肪酸、甘油三酯和磷脂合成所需酶的表达,以维持血脂动态平衡。研究表明,SREBP-1及其靶基因网络的异常可引起胰岛素抵抗、Ⅱ型糖尿病、心功能紊乱、血管并发症和肝脂肪变等一系列代谢性疾病。近年高通量组学技术的发展极大扩展了对SREBP-1靶基因及其转录调控模式的了解。文章对SREBP-1蛋白结构、活化过程、DNA结合位点及其调控的靶基因等方面的研究进展进行了综述,并着重介绍了基于组学数据的转录调控网络的构建,这将有助于更好的认识SREBP-1在脂类代谢中的作用,为深入探讨脂质代谢性疾病的治疗提供新线索。
