#2985 Gut microbiome-dependent systemic alterations in experimental chronic kidney disease
Authors: Yarritu Alex , Anders Wibke , Thiele Arne , Holle Johannes Benjamin , Szijarto Istvan Andras , Rauch Ariana , Bartolomaeus Hendrik , Wilck Nicola 
Published: May 2024

Abstract

Background and Aims
Patients diagnosed with Chronic Kidney Disease (CKD) undergo a notable decline in both quality of life and life expectancy, primarily attributable to the heightened prevalence of cardiovascular diseases (CVD). These conditions not only contribute to the initiation of CKD but are also a consequence of inflammation associated with CKD. Despite optimal kidney replacement therapies, irreversible alterations of the CV system may persist. The responsible mechanisms in CKD leading to CVD are incompletely understood. CKD is characterized by gut microbial dysbiosis, with a significant proportion of uremic toxins suspected to have microbial origin. We hypothesize that the gut microbiota promotes inflammation and CV risk in states of impaired kidney function.

Method
Experimental CKD was induced in 129sv mice by 5/6 nephrectomy. Prior to nephrectomy, mice were assigned to receive either glucose (Ctrl) or a non-absorptive antibiotic cocktail (comprising Ampicillin, Metronidazole, Neomycin, and Vancomycin, Abx) via the drinking water to deplete their microbiomes throughout the 13-week study period. Ctrl and Abx-treated Sham-operated mice served as controls. Plasma, feces, and urine specimens were systematically collected at diverse time intervals, facilitating the longitudinal exploration of metabolite dynamics and CKD progression through an untargeted Nuclear Magnetic Resonance (NMR) approach. Simultaneously, echocardiography assessments were conducted at identical time points to assess cardiac function.

Results
Abx-treated CKD mice displayed improved kidney function, demonstrated by significantly reduced levels of plasma Cystatin C (0.2913 ± 0.1850 mg/L) compared to Ctrl (0.9133 ± 0.6616 mg/L)(p = 0.0256). Hearts from Abx-treated CKD mice exhibited significantly less remodeling, independent of their blood pressure (radiotelemetry measurements). The ratio of left ventricular (LV) mass to tibia length was 4.858 ± 0.3453 in the Abx-treated group compared to Ctrl (8.198 ± 0.3542) (p &lt; 0.0001). Sirius red stained hearts revealed significantly less fibrosis in Abx-treated CKD mice (5.784 ± 5.465%) compared to Ctrl (11.98 ± 3.741%) (p = 0.0218). The cardiac expression of several damage-associated genes (Npbb, Ctgf, and Ngal) portrayed the same trend. To elucidate the interplay between the microbiome and the immune system underlying these observed effects, we provide a comprehensive atlas of the immune landscape in different organs (blood, spleen, heart, intestine), along with a catalogue of gut-derived metabolites, shedding light on the systemic alterations induced by microbiome-dependent mechanisms in CKD.

Conclusion
Our findings suggest that microbiome-dependent mechanisms drive kidney function decline and cardiac remodeling in experimental CKD. These results underscore the interplay between microbial alterations, metabolite dynamics, immune response, and cardiovascular complications in the context of CKD.