523 MITOAKAP PLAY A ROLE IN THE PROGRESSION TOWARDS HEART FAILURE MODULATING GUT INTEGRITY AND COMPOSITION DURING AGING
Authors: D´apice Stefania , Paolillo Roberta , Coretti Lorena , Lama Adriano , Iole Danila , Polese Pina , Pentella Tommaso , Raso Giuseppina Mattace , Mollica Mariapina , Lembo Francesca , Esposito Giovanni , Perrino Cinzia 
Published: December 2022

Abstract

Background
Mitochondrial A-kinase anchoring proteins (mitoAKAP) encoded by the Akap1 gene promote Protein Kinase A mitochondrial targeting, regulating mitochondrial structure and function, reactive oxygen species production and cardiomyocyte survival. Whether mitoAKAP levels play a role in cardiac aging, gut barrier integrity and gut microbiota composition is currently unknown.

Purpose
The aim of this study was to highlight the complex interplay between cardiac dysfunction, gut barrier integrity, gut microbiota composition and aging in young (6-month-old, 6m) and old (24-month-old, 24m) wild type (wt) and Akap1 heterozygous mice (Akap1+/-).

Methods
Cardiac function was noninvasively analyzed by echocardiography in 6m and 24m wt and Akap1+/- mice. Gut microbial DNA was extracted and gut microbiota composition was analyzed by Illumina Mi-Seq analysis. Bioinformatics analysis was carried out to identify major intestinal populations. Alpha diversity within each sample was determined, and then analyzed according to genotype and age; then, inter-sample diversity was determined. For each dataset, we used UniFrac to calculate the differences between microbial communities based on phylogenetic distance between taxa sets in a phylogenetic tree. Bioinformatics analyses were performed using the analysis of similarities (ANOSIM). To evaluate the role of mitoAKAPs in intestinal permeability, we analyzed intestinal junction proteins expression levels in colon samples of all groups. Variance analysis was performed to determine significance among the groups.

Results
Partial loss of Akap1 accelerated the progression of cardiac dysfunction in 24m mice, as demonstrated by a significantly lower % fractional shortening (%FS) compared to 24m wt mice (%FS, wt 6m: 60±3; Akap1-/+ 6m: 58±5; wt 24m: 49±6*; Akap1-/+ 24m: 39±12*§; *p&lt;0.05 vs. wt 6m; §p&lt;0.05 vs. wt 24m). In 24m Akap1+/- mice, aging was associated to enhanced colon permeability, as shown by reduced levels of Ocln and Tjp1 mRNA expression. A principal coordinate analysis of fecal samples based on their unweighted UniFrac distances revealed that samples from Akap1+/- 24m mice cluster apart from wt 24m samples, suggesting that Akap1+/- 24m mice exhibit a different assortment of microbial communities. This observation was supported by ANOSIM R statistic that revealed significant differences in gut microbiota composition between wt and Akap1+/- 24m mice (ANOSIM R=0.475, P=0.023), while no significant differences in bacterial assortment were identified between wt and Akap1+/- 6m mice. We analyzed the differences in abundance of all 2,042 Operational Taxonomic Units (OTUs) between age-matched wt and Akap1+/-. We identified 10 OTUs differently represented in wt and Akap1+/- 6m mice, while a bigger set of bacterial OTUs (19) were different between wt and Akap1+/-24m mice. Consistent with previous results in patients with heart failure, we identified Clostridiales, Blautia producta and R. Torques among differently regulated species. These results are in accordance with previous data on patients with heart failure (HF).

Conclusion
Partial Akap1 deletion plays an important role in the progression toward HF and modulates colon permeability and gut microbiota composition during aging. This work highlights the complex interplay between gut microbiota and development of cardiac dysfunction, and characterization of these processes might lead to the development of new diagnostic and therapeutic approaches for cardiac dysfunction.