Oral administration of engineered probiotic prevents gut dysbiosis in type 1 diabetes and alleviates diabetic retinopathy (DR)

Abstract

Purpose : Previously, we showed that ACE2 deficiency in Akita mice, a type 1 diabetes model, modulates the gut microbiome and results in gut barrier disruption, bacterial translocation into the circulation, and increases in retinal vascular permeability (Duan et al Cir Res 2019). These defects were associated with depletion of circulating angiogenic cells (CACs; CD45⁺/FLK1⁺/CD133⁺) in the intestine and loss of their vascular reparative function. Exogenous administration of CACs restored gut barrier integrity and corrected retinal vascular permeability. Here, we investigate whether oral administration of engineered probiotics expressing human ACE2 could prevent gut dysbiosis and development of DR.

Methods : Akita and ACE2^-/Y-Akita mice were gavaged with Lactobacillus paracasei bacteria expressing human ACE2 (ACE2-LP) (10¹⁰ CFU in PBS; 3X/week) for 9 months and euthanized. Gut permeability was assessed using ELISA, immunohistochemistry and retinal function by ERG. Microbial load in the circulation was assessed by measuring peptidoglycan (PGN), zonulin, and fatty acid binding protein-2 (FABP-2) levels.

Results : Oral administration of ACE2-LP bacteria prevented gut dysbiosis and maintained gut barrier integrity as assessed by decreases in the levels of zonulin (ng/mL) in Akita (19.16; p<0.05) and ACE2^-/y-Akita (19.75) compared with untreated Akita (39.84) and ACE2^-/y-Akita (37.53) mice. Similar reductions were observed in FABP2 and PGN levels. In the intestine, effect of ACE2-LP treatment was associated with increased levels of CACs in Akita (1.921%; p<0.01) and ACE2^-/y-Akita (2.058%; p<0.02) compared with untreated Akita (0.809%) and ACE2^-/y-Akita (0.207%) mice. Under both conditions, retinal function was significantly better in ACE2-LP treated Akita (scotopic a wave; p<0.002, b wave; p<0.01, and photopic b wave; p<0.02) and ACE2^-/y-Akita (scotopic a wave; p<0.02, b wave; p<0.01, and photopic b wave; ns) mice compared with untreated Akita and ACE2^-/y-Akita mice. Acellular capillary formation was significantly less in the ACE2-LP-treated Akita (p<0.0001) and ACE2^-/y-Akita mice (p<0.03) compared with untreated Akita and ACE2^-/y-Akita mice.

Conclusions : Our preclinical studies suggest that engineered probiotics delivering ACE2 may represent a novel therapeutic strategy for treatment of DR.

This is a 2020 ARVO Annual Meeting abstract.