Evidence for a link between gut microbiota and hypertension in the Dahl rat. Physiol Genomics 47: 187-197, 2015. First published March 31, 2015 doi:10.1152/physiolgenomics.00136.2014.-The gut microbiota plays a critical role in maintaining physiological homeostasis. This study was designed to evaluate whether gut microbial composition affects hypertension. 16S rRNA genes obtained from cecal samples of Dahl salt-sensitive (S) and Dahl salt-resistant (R) rats were sequenced. Bacteria of the phylum Bacteroidetes were higher in the S rats compared with the R rats. Furthermore, the family S24-7 of the phylum Bacteroidetes and the family Veillonellaceae of the phylum Firmicutes were higher in the S rats compared with the R rats. Analyses of the various phylogenetic groups of cecal microbiota revealed significant differences between S and R rats. Both strains were maintained on a high-salt diet, administered antibiotics for ablation of microbiota, transplanted with S or R rat cecal contents, and monitored for blood pressure (BP). Systolic BP of the R rats remained unaltered irrespective of S or R rat cecal transplantation. Surprisingly, compared with the S rats given S rat cecal content, systolic BP of the S rats given a single bolus of cecal content from R rats was consistently and significantly elevated during the rest of their life, and they had a shorter lifespan. A lower level of fecal bacteria of the family Veillonellaceae and increased plasma acetate and heptanoate were features associated with the increased BP observed in the S rats given R rat microbiota compared with the S rats given S rat microbiota. These data demonstrate a link between microbial content and BP regulation and, because the S and R rats differ in their genomic composition, provide the necessary basis to further examine the relationship between the host genome and microbiome in the context of BP regulation in the Dahl rats. gut; microbial; SCFA; metabolic; metabolomics THE MAINTENANCE OF blood pressure (BP) homeostasis is a complex process that is carefully orchestrated by a variety of genetic and environmental factors and studied extensively in rat models (2, 5, 11, 15-17, 19, 21-23, 26, 42-44, 50). Dietary salt is one of the prominent environmental factors influencing the development and progression of salt-sensitive hypertension (13,14,24,57). As the consumed salt is transported through the gastrointestinal tract, one of the anatomical sites through which it is absorbed, in addition to the small intestine and the colon, is the cecum. The functions of the cecum are to absorb fluids and salts that remain after completion of intestinal digestion and absorption and to mix its contents with a lubricating substance, mucus. The cecum is also an "anerobic fermentor" as it houses a large number of bacteria that aid in digestion of undigested material in the stomach and small intestine. This is accomplished by a fermentative process that helps in breaking down fibers for their survival (33).In recent years, there is ample evidence in the literature ...

Acute subcutaneous administration of Angiotensin II (Ang II) causes a rise in blood pressure in diabetic Wistar rats. Diabetes was induced using streptozotocin (70 mg/kg, i.v.). Chronic administration of pomegranate juice (PJ) extract (100 mg/kg and 300 mg/kg; p.o. for 4 weeks) obtained from Punica granatum (punicaceae) fruits reduced the mean arterial blood pressure and vascular reactivity changes to various catecholamines and also reversed the biochemical changes induced by diabetes and Ang II. PJ treatment also caused a significant decrease in levels of thiobarbituric acid reactive substances (TBARS) in kidney and pancreas while activities of enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GSH) showed significant elevation. The cumulative concentration response curve (CCRC) of Ang II was shifted towards right in rats treated with PJ using isolated strip of ascending colon. In histopathological examination, PJ treatment prevented the tubular degenerative changes induced by diabetes. The results suggest that the PJ extract could prevent the development of high blood pressure induced by Ang II in diabetic rats probably by combating the oxidative stress induced by diabetes and Ang II and by inhibiting ACE activity. In conclusion, PJ has antihypertensive action in Ang II diabetic model.

G-protein coupled estrogen receptor, Gper1, has been implicated in cardiovascular disease, but its mechanistic role in blood pressure control is poorly understood. Here we demonstrate that genetically salt-sensitive hypertensive rats with complete genomic excision of Gper1 by a multiplexed gRNA CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas9 (CRISPR Associated Protein) approach, present with lower blood pressure, which was accompanied by altered microbiota, different levels of circulating short chain fatty acids, and improved vascular relaxation. Microbiotal transplantation from hypertensive Gper1+/+ rats reversed the cardiovascular protective effect exerted by the genomic deletion of Gper1. Thus, this study reveals a role for Gper1 in promoting microbiotal alterations that contribute to cardiovascular pathology. However, the exact mechanism by which Gper1 regulates BP is still unknown. Our results indicate that the function of Gper1 is contextually dependent on the microbiome, whereby, contemplation of using Gper1 as a target for therapy of cardiovascular disease requires caution.

Multiple GWAS studies have reported strong association of cardiac QT-interval to a region on HSA17. Interestingly, a rat locus homologous to this region is also linked to QT-intervals. The high resolution positional mapping study located the rat QT-interval locus to a <42.5kb region on RNO10. This region contained no variants in protein-coding sequences, but a prominent contiguous 19bp indel polymorphism was noted within a novel predicted long non-coding RNA (lncRNA), which we named as Rffl-lnc1. To assess the candidacy of this novel lncRNA on QT-interval, targeted CRISPR/Cas9 based genome-engineering approaches were applied on the rat strains used to map this locus. Targeted disruption of the rat Rffl-lnc1 locus caused aberrant, short QT-intervals and elevated blood pressure. Further, to specifically examine the significance of the 19bp polymorphism within the Rffl-lnc1 locus, a CRISPR/Cas9 based targeted knock-in rescue model was constructed by inserting the 19bp into the strain which contained the deletion polymorphism. The knock-in alleles successfully rescued the aberrant QT-interval and blood pressure phenotypes. Further studies revealed that the 19bp polymorphism was necessary and sufficient to recapitulate the phenotypic effect of the previously mapped <42.5kb rat locus. To our knowledge, this study is the first demonstration of a combination of both CRISPR/Cas9 based targeted disruption as well as CRISPR/Cas9 based targeted knock-in rescue approaches applied for a mammalian positional cloning study, which defines the quantitative trait nucleotides (QTNs) within a rat long non-coding RNA as being important for the pleiotropic regulation of both cardiac QT-intervals and blood pressure.

High blood pressure is a common cause of chronic kidney disease. Since CD40, a member of the tumor necrosis factor receptor family, has been linked to the progression of kidney disease in ischemic nephropathy, we studied the role of Cd40 in the development of hypertensive renal disease. The Cd40 gene was mutated in the Dahl S genetically hypertensive rat with renal disease by targeted-gene disruption using zinc-finger nuclease technology. These rats were then given low (0.3%) and high (2%) salt diets and compared. The resultant Cd40 mutants had significantly reduced levels of both urinary protein excretion (41.8 ± 3.1 mg/24hours vs. 103.7 ± 4.3 mg/24hours) and plasma creatinine (0.36 ± 0.05 mg/dL vs. 1.15 ± 0.19 mg/dL), with significantly higher creatinine clearance compared to the control S rats (3.04 ± 0.48 ml/minute vs. 0.93 ± 0.15 ml/minute) indicating renoprotection was conferred by mutation of the Cd40 locus. Furthermore, the Cd40 mutants had a significant attenuation in renal fibrosis, which persisted on the high salt diet. However, there was no difference in systolic blood pressure between the control and Cd40 mutant rats. Thus, these data serve as the first evidence for a direct link between Cd40 and hypertensive nephropathy. Hence, renal fibrosis is one of the underlying mechanisms by which Cd40 plays a crucial role in the development of hypertensive renal disease.