Abstract 192: High Fat Diet Promotes Haplotype Dependent Differential Transcriptional Regulation of the Human Angiotensinogen Gene
Angiotensinogen (AGT) is the only known precursor to angiotensin II. Systemic renin angiotensin aldosterone system (RAAS) is activated in human and experimental models of obesity. RAAS activation in obesity is linked to the development of cardiovascular pathophysiologies. We have identified polymorphisms in 2.5 Kb promoter of human angiotensinogen gene (hAGT) that forms two haplotype (Hap) blocks: -6A/G (-1670A/G, -1562C/T, -1561T/C) and -217A/G (-532T/C, -793A/G, -1074T/C,& -1178G/A). Hap -6A/-217A (Hap -6A) is associated with human hypertension whereas, Hap -6G/-217G (Hap -6G) reduces cardiovascular risk. Here, we examine high fat diet-mediated allele-specific transcriptional regulation of the hAGT gene in adipose tissue, in vivo, in transgenic (TG) mice engineered with either haplotype of the hAGT gene. Twelve-week-old male TG mice with Hap –6A or –6G were fed normal diet (10% kcal as fat) and high fat diet (60% kcal as fat) for 10 weeks. Using Q - RT PCR and western blot we show increased hAGT expression in adipose tissue of the Hap -6A-TG mice after high fat diet than control diet (Hap -6A-0.68±0.04 vs. Hap -6G- 0.33±0.03 A.U., p<0.05). ChIP assay shows greater chromatin binding of GR, MR, CEBPβ and STAT3 transcriptional factors (Hap -6A- 0.80±0.04 vs. Hap -6G- 0.26±0.06 A.U., p<0.05) to the hAGT transgenes in Hap -6A TG mice after high fat diet. No significant change was observed in the endogenous mouse AGT gene. In addition, after high fat diet, change ([[Unable to Display Character: ∆]]) in inflammatory and redox markers was significantly (p<0.05) greater in TG mice with Hap I including, IL1 (4.6±0.8 vs. 2.1±0.49 fold), IL6 (4.0±0.69 vs. 2.1±0.2 fold) and NOX1 (8.3±0.4 vs. 2.5±0.6 fold). This is accompanied by reduction in levels of antioxidant defenses (SOD1: 0.97±0.0 vs. 1.4±0.1 fold; HO1: 0.77±0.1 vs. 1.3±0.2 fold) & activation of MAPK14 and ERK1/2 signaling. Taken together, our results show that SNPs in the hAGT Hap -6A favor high fat diet induced binding of transcriptional factors GR, MR, CEBP-β and STAT3 that lead to elevated expression of the hAGT in expanded mass of the adipose tissue. This also activates the RAAS with pathophysiological implications including, phosphorylation of kinases such as MAPK14 and ERK2, increase in tissue pro-inflammatory and oxidative stress molecules.
Author Disclosures: A. Rana: None. N. Puri: None. S. Jain: None. A. Kumar: None.
- © 2015 by American Heart Association, Inc.