Rana Anita, Jain Sudhir, Puri Nitin, Kaw Meenakshi, Sirianni Natalie, Eren Deniz, Mopidevi Brahma Raju, Kumar Ashok
Department of Physiology and Pharmacology, University Of Toledo Medical Centre, Toledo, Ohio, United States of America.
Department of Pathology, New York Medical College, Valhalla, New York, United States of America.
PLoS One. 2017 May 3;12(5):e0176373. doi: 10.1371/journal.pone.0176373. eCollection 2017.
Single nucleotide polymorphisms (SNPs) in the human angiotensinogen (hAGT) gene may modulate its transcription and affect the regulation of blood pressure via activation of the renin-angiotensin aldosterone system (RAAS). In this regard, we have identified polymorphisms in the 2.5 Kb promoter of the hAGT gene that form two haplotype (Hap) blocks: -6A/G (-1670A/G, -1562C/T, -1561T/C) and -217A/G (-532T/C, -793A/G, -1074T/C & -1178G/A). hAGT gene with Hap -6A/-217A (Hap I) is associated with increased blood pressure whereas, Hap -6G/-217G (Hap II) is associated with normal blood pressure in human subjects. Since RAAS over activity contributes to hypertension in obesity, we have made transgenic mice (TG) containing either Hap I or Hap II of the hAGT gene to understand the role of obesity on its transcriptional regulation. Although, a high-fat diet (60% Kcal from fat, 12 weeks) elevates hAGT and mAGT regardless of haplotype, this effect is significantly (p<0.05) accentuated in Hap I mice, in both adipose and liver tissues. Chromatin Immuno- precipitation (ChIP) assay shows an increased binding of transcription factors including, GR, CEBPβ and STAT3 to the chromatin of the Hap I TG mice after high-fat diet as compared to Hap II TG mice (p<0.05). Differential plasma levels of hAGT in Hap II and I mice, after high-fat diet, further corroborate the variable transcriptional regulation of the hAGT, governed by gene-haplotypes. Taken together, our results show that SNPs in the Hap-I of the hAGT gene promote high-fat diet-induced binding of transcription factors GR, CEBP-β and STAT3, which lead to elevated expression of the hAGT gene in hepatic and adipose tissues.
人类血管紧张素原（hAGT）基因中的单核苷酸多态性（SNP）可能会调节其转录，并通过激活肾素-血管紧张素-醛固酮系统（RAAS）影响血压调节。在这方面，我们在hAGT基因的2.5 Kb启动子中鉴定出多态性，形成了两个单倍型（Hap）块：-6A/G（-1670A/G、-1562C/T、-1561T/C）和-217A/G（-532T/C、-793A/G、-1074T/C和-1178G/A）。携带Hap -6A/-217A（单倍型I）的hAGT基因与血压升高有关，而携带Hap -6G/-217G（单倍型II）的hAGT基因在人类受试者中与正常血压有关。由于RAAS过度活跃会导致肥胖相关的高血压，我们制备了携带hAGT基因单倍型I或单倍型II的转基因小鼠（TG），以了解肥胖对其转录调控的作用。尽管高脂饮食（脂肪提供60%的千卡热量，持续12周）会升高hAGT和小鼠血管紧张素原（mAGT），且与单倍型无关，但在脂肪组织和肝脏组织中，这种效应在单倍型I小鼠中显著增强（p<0.05）。染色质免疫沉淀（ChIP）分析表明，与单倍型II转基因小鼠相比，高脂饮食后，单倍型I转基因小鼠的染色质上包括糖皮质激素受体（GR）、CCAAT增强子结合蛋白β（CEBPβ）和信号转导和转录激活因子3（STAT3）在内的转录因子结合增加（p<0.05）。高脂饮食后，单倍型II和单倍型I小鼠血浆中hAGT水平的差异进一步证实了由基因单倍型控制的hAGT可变转录调控。综上所述，我们的结果表明，hAGT基因单倍型I中的SNP促进了高脂饮食诱导的转录因子GR、CEBP-β和STAT3的结合，从而导致hAGT基因在肝脏和脂肪组织中的表达升高。
