Aging-associated cardiac dysfunction and leaky gut in heterozygous Akap1 knockout mice
Authors: Paolillo R , Boccella N , Coretti L , D'Apice S , Lama A , Avvediemnto M , Mollica M.P , Mattace Raso G , Esposito G , Lembo F , Perrino C 
Published: November 2020

Abstract

Background
Mitochondrial A-kinase anchoring proteins (mitoAKAPs) encoded by the Akap1 gene are crucially involved in multiple cellular processes, including cardiomyocyte survival and function. There is a correlation between ROS production, intestinal permeability and the composition of the intestinal microbiota, especially during aging. Whether Akap1 deletion affects microbiota composition, intestinal function during senescence is currently unknown.

Purpose
The purpose of the study was to shed light into the complex interplay between gut permeability and microbiota composition, cardiac function and aging in adult (6-month-old, 6m) and old (24-month-old, 24m) Akap 1 wild type (Akap1+/+) or Akap1 heterozygous knockout mice (Akap1+/−).

Methods
Cardiac function was non-invasively analyzed by echocardiography in adult and old, Akap1+/+ and Akap1+/− mice. Colon, serum and feces samples were collected after sacrifice in 6m and 24m mice of either genotype. Intestinal barrier permeability was evaluated in colon samples by Occludin (Ocln) and Tight junction protein ZO-1 (Tjp1) mRNA expression analysis. Systemic inflammation was measured by Tumor Necrosis Factor-alpha (TNF-alpha), Lipopolysaccharide (LPS), Interleukin-10 (IL-10) and Interleukin-1 (IL-1) circulating levels. Microbial DNA was extracted from feces samples and gut microbiota composition was evaluated by Illumina Mi-Seq analysis. Bioinformatic analyses were carried out to identify intestinal populations.

Results
Akap1 partial deletion accelerated the progression of cardiac dysfunction in 24m mice as demonstrated by a significant reduction of fractional shortening in Akap1+/− 24m mice compared to Akap1+/+ 24m (Figure 1A). Colon permeability was impaired in Akap1+/− 24m as shown by reduced Ocln expression (Figure 1B), while circulating TNF-alpha was increased in Akap1+/− 24m (Figure 1C). Next, we analyzed the differences in abundance of all 2042 Operational Taxonomic Units (OTUs) between age-matched Akap1+/+ and Akap1+/−. We identified 10 OTUs differently represented in Akap1+/+ and Akap1+/− 6m mice, while a bigger set of bacterial OTUs (19) were different between Akap1+/+ and Akap1+/− 24m mice. LDA scores of differentially microbiome abundant taxa in Akap1+/+ and Akap1+/− 24m (Figure 1D) showed different assortment in Clostridiales family (Ruminococcus torques specie), Porphyromonadaceae family (Barseniella intestinihominis specie) and Lachnospiraceae genus (Blautia producta specie), bacterial species that have been previously identified in patients with heart failure and involved in anti-inflammatory mechanisms.

Conclusions
mitoAKAPs play a crucial role in the maintenance of cardiac function and intestinal barrier during aging, since Akap1 partial deletion promotes gut permeability, bacteria translocation and systemic inflammation associated with systolic 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.