The transcriptional regulation of the human angiotensinogen gene after high-fat diet is haplotype-dependent: Novel insights into the gene-regulatory networks and implications for human hypertension

Abstract

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.

FGF23-Mediated Activation of Local RAAS Promotes Cardiac Hypertrophy and Fibrosis

“…The inductions of AGT , REN, ACE and AT1R on transcriptional level were shown to be mediated by the transcription factor activator protein 1 (AP-1), e.g., via activation of ERK1/2 [62,63,64,65]. In addition, the induction of AGT was further linked to activation of signal transducer and activator of transcription 3 (Stat3), glucocorticoid receptor, and CCAAT/enhancer-binding protein beta (CEBP-β) [66]. Interestingly, in atrial fibrillation, FGF23 mediated profibrotic response via Stat3 and Smad pathways in cardiac fibroblasts [67], and CEBP-β was significantly upregulated in myocardial tissue of patients on dialysis, which showed enhanced LVH and LV fibrosis [31].…”

A systems biology approach identifies the role of dysregulated PRDM6 in the development of hypertension

“…sgRNAs were designed to delete the 52 bp region encompassing rs13359291 and independent deletion lines were verified as previously described ( Supplemental Table 13 ). PROMO, an in silico motif finder tool, predicts rs13359291 to be a putative binding site for CEBP β and α ( Figure 4A and Table 4 ), which are known regulators of the renin-angiotensin-aldosterone system (RAAS) ( 22 , 23 ). Using RT-qPCR we found a significant downregulation in PRDM6 mRNA expression in the CRISPR-Cas9-deleted cells compared with WT cells ( Figure 4B ).…”

A polymorphism in intron I of the human angiotensinogen gene (hAGT) affects binding by HNF3 and hAGT expression and increases blood pressure in mice

“…5). It is important to note that a T/G SNP at Ϫ1074 in the promoter of the hAGT gene also alters binding of HNF3␤ (27). Surprisingly, both variants, ϩ1164A and Ϫ1074T, belong to the risk haplotype of the hAGT gene and show increased binding with HNF3␤.…”