Abstract

Background: Oxygen and inflammation levels in the gut have emerged as important factors in liver disease progression. Intestinal hypoxia, caused by altered blood flow and impaired oxygen delivery, triggers inflammation, and disrupts the intestinal barrier, leading to bacterial translocation and could encourage dysbiosis with facultative anaerobes. Bacterial translocation and their products reach the liver, promoting inflammation, oxidative stress, and liver damage. However, the relationship between oxygen response, gut inflammation, and liver disease progression in cirrhosis patients remains largely unknown and are the focus of this study.

Methods: Twelve age-balanced men, including healthy control (54±3 yrs), compensated (55±4 yrs, MELD 7) , and decompensated cirrhosis (56±5 yrs, MELD 11, prior HE on lactulose) underwent EGD & prepped colonoscopy on the same day with pinch biopsies taken from the duodenum (DUOD) and ascending colon (ASCEND). Total RNA was isolated using Trizol. Gene profiles were analyzed with the NanoString nCounter®. Differentially expressed genes (DEGs) between groups were identified using Rosalind. Gene Ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed.

Results: Bioinformatic analysis revealed significantly upregulated expression of key inflammation-related genes [mitogen-activated protein kinase kinase 2 (MAP2K2), signal transducer and activator of transcription 3 (STAT3) and thioredoxin (TXN)], along with downregulated expression of genes associated with reactive oxygen response (ROS) [Ferredoxin 1 (FDX1), Metal Regulatory Transcription Factor 1 (MTF1)] in both DUOD and ASCEND of cirrhosis subjects compared to healthy controls. Furthermore, decompensated patients exhibited increased expression of inflammation-related genes [MAP2K1, Nuclear Factor Kappa B Subunit 1 (NFKB1) and Interleukin 6 (IL6)] and decreased ROS-related genes [Epidermal Growth Factor Receptor (EGFR) and NADH: Ubiquinone Oxidoreductase Subunit A12 (NDUFA12)] compared to compensated patients. The GO and KEGG analysis highlighted that, in compensated patients, DEGs were most associated with increase in ‘aerobic respiration’, ‘response to hypoxia’, ‘oxidative phosphorylation’, ‘chemical carcinogenesis - reactive oxygen species’ and decrease in 'response to oxidative stress', ‘cellular respiration’, ‘inflammatory response’. Similar trends were observed in decompensated patients, with more significant changes.

Conclusion: We found alteration in oxygen consumption-related gene expression across small and large intestine in humans with cirrhosis, which increases with progression of disease. This could promote the growth of potential anaerobic pathobionts in the gut and could be relevant in understanding the interplay between gut oxygen levels, inflammation, and liver disease in liver cirrhosis.