Probiotic Kefir Antihypertensive Effects in Spontaneously Hypertensive Rats Involves Central and Peripheral Mechanisms

Abstract

Gut microbiota dysbiosis has been associated with hypertension. Long‐term use of probiotics have been shown to decrease blood pressure, improve baroreflex, and ameliorate endothelial dysfunction in Spontaneously Hypertensive Rats (SHR). Yet, the mechanisms are not well understood. We aimed to evaluate peripheral and centrally mediated mechanisms by which the probiotic kefir promotes beneficial effects in SHRs. We used Wistar Kyoto (WKY) and SHR male rats, divided into: WKY and SHR treated with vehicle, and SHR treated with milk fermented by the kefir grains (5%; SHR‐Kefir; oral gavage, daily/9 weeks). We evaluated blood pressure by tail cuff method weekly. The effects of kefir were evaluated on gut anatomy (histological analysis of the small intestine), gut microbiota composition (microbiological analysis of the feces), and endotoxin levels (Lipopolysaccharide (LPS) content analyzed in serum). Within the paraventricular nucleus of the hypothalamus (PVN), we evaluated microglia activation and tyrosine hydroxylase (TH) protein expression via immunofluorescence. TH mRNA levels were analyzed via real time PCR. SHR‐Kefir presented a lower mean blood pressure (151.9±2.9mmHg) compared to SHR (173.1±2.41mmHg, P<0.0001 n=6). Basal gut microbiota composition in SHRs differed from that observed for WKY, suggesting dysbiosis. Treatment with kefir restored the normal gut microbiota composition profile of Lactobacillus, Staphylococcus, Brucella and Bifidobacterium spp. The number of Paneth cells/crypt was decreased in SHR (1.66±0.06) compared to WKY (2.40±0.08 p<0.0004), an effect which was normalized with kefir treatment (SHR‐Kefir:2.23±0.15). An increase in LPS serum content in SHR (0.71±0.02) compared to WKY (0.54±0.04 EU/mL p<0.01), suggesting increased intestinal permeability during hypertension, was reversed in SHR‐Kefir (0.54±0.01). Within the PVN, microglia density was used as an indication of microglia activation. We found increased microglia activation in SHR (9.47±0.61) compared to WKY (6.87±0.68 p<0.07), which was normalized in SHR‐Kefir rats (4.77±0.55, arbitrary units [AU]). TH protein overexpression observed in SHRs was reduced with treatment of probiotic (WKY: 5.25±0.58; SHR: 13.68±0.81 and SHR‐Kefir: 8.42±0.55, AU p<0.0001). The mRNA expression of TH within the PVN (punches) was increased in SHR by 47%. Kefir treatment decreased mRNA TH expression (WKY: 1.21±0.45; SHR: 1.79±0.50; SHR‐Kefir: 1.30±0.27 fold change). Our data shows that kefir treatment in SHRs restores gut microbiota composition and intestinal structure, diminishes levels of serum endotoxin, reduces neuroinflammation, and balances levels of tyrosine hydroxylase within the hypothalamus. Altogether, our data suggests that kefir antihypertensive‐associated mechanisms involves gut microbiota–brain axis communication during hypertension.Support or Funding InformationThis work was funded by CAPES PDSE 88881.133261/2016‐01 to MAS. VCB is funded by AHA 14SDG20400015.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.