Background: The Goto-Kakizaki (GK) rat, developed from repeated inbreeding of glucose-intolerant Wistar rats, has been widely used to explore the development of spontaneous type-2 diabetes mellitus (T2DM). However, the gastric microbiota of GK and Wistar rats are still unclear. This study aimed to understand the gastric microbiota characteristics of GK rats by comparing it with non-diabetic Wistar rats.
Materials and Methods: Male Wistar rats and GK rats were housed in specific pathogen-free (SPF) environment for 12 weeks with free access to sterilized food and water. Body weight and random blood glucose (BG) levels were determined. At the end of the experiment, the gastric contents of the rats were collected for the identification of gastric microbiota using 16S rRNA gene sequencing.
Results: The richness of gastric microbiota in GK rats was similar to that of Wistar rats (P > 0.05). The results of Shannon, Simpson, beta diversity indices, and ANOSIM analysis showed that alpha and beta diversity of gastric microbiota in GK rats were significantly lower than that of Wistar rats (P < 0.01). Firmicutes (96.0%), Proteobacteria (1.9%) and Cyanobacteria (0.8%) were the dominant gastric microbiota in GK rats accounting for 72.9%, 14.7% and 10.9%, respectively. Linear discriminant analysis effect size (LEfSe)  revealed  that phylum Firmicutes and four genera (Anaerovibrio, Collinsella, Prevotellaceae _UCG_001 , and Lactobacillus ) were significantly abundant in the stomachs of GK rats. In contrast, seven genera (unidentified_Chloroplast, Porphyromonas, Neisseria, Rubrobacter, Veillonella, Lachnospiraceae_UCG_005 , and unidentified_Erysipelotrichaceae ) were significantly abundant in the stomachs of Wistar rats. Blood glucose was positively correlated with Anaerobibrio  and Lactobacillus , and negatively correlated with four genera (Porphyromonas, Rubrobacter, Lachnospiraceae _UCG_005 , and unidentified_Erysipelotrichaceae ). In addition, chemoheterotrophy and fermentation were the most important functions of gastric microbiota.
Conclusion: The gastric microbiota of GK rats with spontaneous T2DM showed the typical characteristics of low diversity and significant enrichment of Firmicutes phylum and four genera (Anaerovibrio, Collinsella, Prevotellaceae _UCG_001 , and Lactobacillus ) compared with gastric microbiota of Wistar rats.
Keywords: gastric microbiota, type-2 diabetes mellitus, GK rat, wistar rat, 16S rRNA gene sequencing