Selenium-Enriched Lactobacillus Plantarum Alleviate of High Alkalinity-Induced Microbiota-Gut-Blood Systems Affect by Improving Gut Microbiota

Abstract

High alkalinity is the most important limiting factor in carbonate-type saline-alkali water aquaculture, and fish growth is slow and survival is low in high alkaline environments. Selenium-enriched(Se-enriched) Lactobacillus plantarum(L. plantarum) have antioxidant and anti-inflammatory properties and can regulate the balance of gut flora. However, the physiological regulatory mechanism of Se-enriched L. plantarum on common carp under high alkalinity stress is still unclear. In the present study, 360 common carp were randomly divided into groups C, A25 and FXA25, and fed for 56 days. High alkalinity stress induces growth inhibition in common carp. Histopathology showed atrophy of intestinal villi, and damage to intestinal microvilli and tight junction complexes. Serological parameters showed ammonia and LPS content in serum were significantly increased. Gut microbial disruption under high alkalinity stress, increased the abundance of Bacteroidota (LPS-producing bacteria), Providencia sp(ammonia-producing bacteria) and Vibrio(pathogenic bacteria), significant decrease the expression of the tight junction proteins ZO-1 and Occludin, disrupting the gut barrier. However, Se-enriched L. plantarum were able to decreased the abundance of Vibrio, increase the expression of tight junction proteins ZO-1 and Occludin, and alleviate intestinal damage caused by high alkalinity, while reducing the content of LPS and ammonia in serum. In addition, metabolomic analysis of serum revealed that high alkalinity stress activated Autophagy-animal, Glucocorticoid and meneralocorticoid receptor agonists/antagonists, ABC transporters, Phosphatidylinositol signaling system, and mTOR signaling pathway, and significantly reduced creatine content. Se-enriched L. plantarum treatment significantly increased creatine content to alleviate the effects of high alkalinity stress. In summary, this study found that Se-enriched L. plantarum can alleviate the harm of high alkalinity to common carp by regulating the balance of intestinal microbiota, improving intestinal barrier function, reducing harmful substances from entering the bloodstream, and increasing the content of creatine. This study revealed the physiological regulatory mechanism of Se-enriched L. plantarum in alleviating high alkalinity stress, and provided ideas and theoretical basis for the protection of high alkalinity poisoning of fish in saline-alkali waters.

Keywords: Se-enriched L. plantarum, High alkalinity, Gut microbial, Tight junction protein, LPS