Alterations in the Gut Microbiome Can Elicit Hypertension in WKY Rats

Introduction Gut dysbiosis or an unhealthy change in the gut microbiota (bacteria) is linked to a number of pathological conditions including gastrointestinal disorders, type II diabetes, and obesity. Although an association between gut dysbiosis and hypertension has been reported, a direct cause and effect relationship has not been established. We tested the hypothesis that hypertension could be induced in a normotensive strain of rats (WKY) or attenuated in a hypertensive strain of rats [spontaneously hypertensive rats (SHR)] by exchanging the gut microbiota between the WKY and SHR rats. Methods Cecal contents from 20 wk SHR rats were pooled; similarly, cecal contents from 9 wk WKY rats were pooled. Each of the pooled samples was diluted 1:20 in buffer, thoroughly mixed, and centrifuged to remove the particulate matter. The supernatants from each of the samples were aliquoted and frozen to use for inoculating recipient rats. Three week old recipient WKY and SHR rats were gavaged daily with an antibiotic cocktail [ampicillin, gentamycin, metronidazole, neomycin (all 3mg/day) and vancomycin (1.5 mg/day) in 1 ml buffer] for 10 consecutive days. The purpose of the antibiotics was to reduce the native microbiota load with the idea of allowing easier colonization of gavaged microbiota. Two days after the last antibiotic administration, 0.75 ml of the cecal supernatant was gavaged into the recipient rats daily for four consecutive days and weekly thereafter. Cecal supernatant from the SHR donors was gavaged into WKY and SHR rats. In a similar manner, cecal supernatant from the WKY donor pool was gavaged into WKY and SHR rats (n=7/group). Group designation are indicated in the following example: “WKY g‐SHR” represents WKY rats gavaged with cecal contents from SHR rats. Fecal pellets were collected weekly for identification of the microbiota (down to the genus level) by sequencing the 16s ribosomal RNA gene. Systolic blood pressure (SBP) was measured weekly using tail‐cuff plethysmography. Results Prior to cecal gavages (age = 4 wks), SBP (~143 mmHg) was similar in SHR and WKY rats. Although the SBP for SHR g‐WKY tended to be 12–17 mmHg less that SHR g‐SHR at ages between 10 and 16 wks, the differences were not significant. For example, at 12 wks of age, SBP for SHR g‐SHR was 202 ± 6 mmHg while the SBP for SHR g‐WKY rats was 185 ± 7 mmHg (p=0.118). However, in WKY rats, there was a significant donor effect (p=0.02, 2‐way RM ANOVA) with SBP running 15–25 mmHg higher in WKY g‐SHR than WKY g‐WKY ( Figure ). At 12 wks of age the SBP was 182 ± 8 and 156 ± 8 mmHg in WKY g‐SHR and WKY g‐SHR respectively (p=0.02). Summary and Conclusion Although altering the gut microbiota in SHR had no significant effects on SBP, we did find that inoculating WKY rats with SHR microbiota significantly increased SBP. Therefore, the gavage contents, presumably microbiota, were responsible for increasing SBP in WKY rats. We conclude that the contents of the gut can directly affect systemic blood pressure. Support or Funding Information R01NS080531; S. Adnan is a fellow in the APS Undergraduate Summer Research Program.