Transverse aortic constriction impairs intestinal barrier integrity, promotes inflammation and alterations in gut microbiota composition
Authors: Paolillo R , Boccella N , Coretti L , D'Apice S , Lama A , Schiattarella G.G , Mollica M.P , Mattace Raso G , Esposito G , Lembo F , Perrino C 
Published: November 2020

Abstract

Background
Microbiota composition plays an important role in the pathophysiology of heart failure (HF). Reduced cardiac output can disrupt intestinal barrier function and promote systemic inflammation through bacterial translocation. Several gut and cardiac pathological conditions are reciprocally linked at multiple levels and through different, still largely undefined mechanisms.

Purpose
We analyzed the effects of Transverse aortic constriction (TAC) on aortic pressures, gut barrier integrity, systemic inflammation and gut microbiota composition.

Methods
TAC was induced in C57BL6 mice of either sex. Sham-operated (Sham) mice were used as controls. After one-week (1w) and four weeks (4w), mice have been anesthetized, cardiac function and abdominal aortic blood flow were analyzed. Colon, serum and feces samples were collected after sacrifice. Intestinal barrier integrity was evaluated in colon samples by Tight junction protein ZO-1 (Tjp1) and Occludin (Ocln) mRNA analysis. Circulating levels of Tumor Necrosis Factor-alpha (TNF-alpha), Lipopolysaccharide (LPS), Interleukin-10 and Interleukin-1 were measured. Microbial DNA was extracted from feces samples and gut microbiota composition was evaluated by Illumina Mi-Seq analysis.

Results
TAC induced left ventricular hypertrophy and systolic dysfunction. Abdominal aortic blood flow was significantly reduced in TAC mice compared to sham (Figure 1A). Decreased intestinal perfusion in TAC mice was associated to a prompt and strong weakening of intestinal barrier integrity and long-lasting decrease of colonic anti-inflammatory cytokine levels, as shown by reduced mRNA expression of interleukin-10 (IL-10) and Occludin (Ocln) (Figure 1B). Serum levels of lipopolysaccharide (LPS) were increased after TAC surgery and significant increases of circulating proinflammatory cytokines tumor necrosis factor-a (TNF-a) were detected in TAC mice (Figure 1C). High-resolution approach was used to obtain bacterial species assignment of key genera with significant differences among groups. After TAC, significant increases of Bifidobacterium, Lactobacillus and Turicibacter, whereas the genus Oscillospira was significantly less (Figure 1D). Butyrate-producing bacteria are considered relevant colonizers of the gastrointestinal tract being butyrate important in anti-inflammation and maintaining intestinal barrier integrity. Oscillospira genus members have been described as butyrate producers. Notably, in old patients with heart failure and in animal models of hypertension, increase in lactate-producing Lactobacillus was found.

Conclusions
These data indicate a remodeling of specific bacterial species abundance within identified key genera starting soon after TAC, designating a clear effect of the treatment on microbiota profiles and, possibly, on microbiota functionality. Gut dysbiosis may represent an element to be considered in the development or progression of cardiac dysfunction.
Figure 1

Funding Acknowledgement
Type of funding source: Other. Main funding source(s): CP was supported by Ministero dell'Istruzione, Università e Ricerca Scientifica grant (2015583WMX) and Programma STAR grant by Federico II University and Compagnia di San Paolo. RP was supported by a research grant provided by the Cardiopath PhD program. LC was supported by 2018-2019 Postdoctoral Fellowship Grants provided by Fondazione Umberto Veronesi.