Both viable Bifidobacterium longum subsp. infantis B8762 and heat-killed cells alleviate the intestinal inflammation of DSS-induced IBD rats

Abstract

ABSTRACT In view of the safety concerns of probiotics, more and more attention is paid to the beneficial effects of dead probiotics cells. Herein, we investigated and compared the alleviation effects of viable Bifidobacterium longum subsp. infantis B8762 ( B. infantis B8762) and its heat-killed cells on dextran sodium sulfate (DSS)-induced inflammatory bowel disease (IBD) rats. Four groups of rats ( n = 12 per group) were included: normal control, DSS-induced colitis rats without bacterial administration (DSS), DSS-induced colitis rats with viable B. infantis B8762 administration (VB8762), and DSS-induced colitis rats with dead B. infantis B8762 administration (DB8762). Our results showed that both VB8762 and DB8762 administration exerted significant protective effects on DSS-induced IBD rats, as evidenced by a reduction in mortality, disease activity index score, body weight loss, as well as decreased histology score, which were companied by a significant decrease in serum pro-inflammatory factors compared with DSS group, and a stronger effect on modulating the fecal microbiota alpha-diversity and beta-diversity compared with DSS group. Additionally, the fecal metabolome results showed that both VB8762 and DB8762 interventions indeed altered the fecal metabolome profile and related metabolic pathways of DSS-induced IBD rats. Therefore, given the alleviation effects on colitis, the DB8762 can be confirmed to be a postbiotic. Overall, our findings suggested that VB8762 and DB8762 had similar ability to alleviate IBD although with some differences. Due to the minimal safety concern of postbiotics, we propose that the postbiotic DB8762 could be a promising alternative to probiotics to be applied in the prevention and treatment of IBDs. IMPORTANCE Inflammatory bowel disease (IBD) has emerged as a global disease because of the worldwide spread of western diets and lifestyles during industrialization. Up to now, many probiotic strains are used as a modulator of gut microbiota or an enhancer of gut barrier to alleviate or cure IBD. However, there are still many issues of using probiotics, which were needed to be concerned about, for instance, safety issues in certain groups like neonates and vulnerable populations, and the functional differences between viable and dead microorganisms. Therefore, it is of interest to investigate the beneficial effects of dead probiotics cells. The present study proved that both viable Bifidobacterium longum subsp. infantis B8762 and heat-killed cells could alleviate dextran sodium sulfate-induced colitis in rats. The findings help to support that some heat-killed probiotics cells can also exert relevant biological functions and can be used as a postbiotic.