The gut microbiota plays a central role in plasma metabolite changes in hypertension
Authors: Cheema M. Umar , Pluznick Jennifer L. 
Published: June 2021

Metabolites produced by the gut microbiota are absorbed into the bloodstream of the host, where they can then act as signaling molecules which modulate host physiology. These byproducts of gut microbial metabolism have been attributed to both positive (short chain fatty acid) and negative (p‐cresol sulfate, indoxyl sulfate) effects on host health. Moreover, changes in the gut microbiota (known as “dysbiosis”) have been associated with pathophysiological conditions including obesity, chronic kidney disease, diabetes and irritable bowel syndrome. Recent work from our lab and others has shown that gut microbial metabolites also play a role in blood pressure regulation. In this study, we hypothesized that hypertension would alter gut microbial metabolite production, and that an unbiased screen for changes in gut microbial metabolites would allow us to identify novel microbial metabolites. To pursue this, six week old C57BL/6 conventional (mice with gut microbiota; conv, n=6) and germ‐free (mice without gut microbiota; GF, n=6) mice were infused with angiotensin‐II (AngII) for 4 weeks (400ng.kg−1.min−1; Alzet 1004). In parallel control groups, conv (n=6) and GF (n=6) mice received saline via minipumps. Our primary goal was to identify metabolites which were differentially regulated in conventional mice treated with AngII, but not in GF mice, indicating that these metabolites are microbial in origin. Following minipump implantation, animals were housed singly to prevent cross‐contamination of microbiota. At the end of fourth week, feces and blood were collected. Both plasma and feces samples were processed and analyzed by using Liquid Chromatography‐Tandem Mass Spectroscopy (LC‐MS/MS) for metabolite detection (Metabolon). In plasma, we identified 4 metabolites which were significantly upregulated with AngII treatment in conv mice (p<0.05 ANOVA, q value<0.2); none of these 4 metabolites were upregulated with AngII in GF mice. These upregulated metabolites were 4‐ethylphenylsulfate (benzoate metabolism), p‐cresol sulfate (benzoate metabolism, known uremic toxin), p‐cresol glucuronide (tyrosine metabolism), and spermidine (polyamine metabolism). These changes were not mirrored by changes in fecal levels of the metabolites. Similarly, we identified 8 metabolites which were downregulated in conv mice with AngII treatment (p<0.05 ANOVA, q value<0.2); none of these metabolites were also downregulated in GF mice treated with AngII. The downregulated metabolites include indoleacetate (tryptophan metabolism), N,N,N‐trimethyl‐5‐aminovalerate (lysine metabolism), and gentisate (tyrosine metabolism). For some of the downregulated metabolites (4/8), these changes were mirrored by changes in fecal metabolites. Intriguingly, some of the changes in plasma metabolites were sex‐specific, occurring in only males (downregulation of mannose and ferulic acid 4‐sulfate) or females (upregulation of 4‐ethylphenylsulfate and p‐cresol glucuronide). Finally, 16S sequencing revealed clear changes in the conv mice microbiome with AngII treatment, including sex dependent shifts. In summary, these studies demonstrate that gut microbiota are a primary regulator of metabolite changes in hypertension.Support or Funding InformationFunding: AHAThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.