Mechanism of inulin in colic and gut microbiota of captive Asian elephant

Abstract

Background: Gut microbiota have a complex role on the survivability, digestive physiology, production, and growth performance in animals. Recent studies have emphasized the effects of prebiotics therapy on the gut disease, but the relationship between elephant gut-related diseases and prebiotics remains elusive. Here, a case study was undertaken to evaluate the mechanism of inulin treatment in colic in Asian elephant (Elephas maximus Linnaeus).

Methods: Fecal samples were collected from a sick elephant and four healthy elephants. Analysis of microbial profile was carried out by 16S rRNA sequencing, and the short chain fatty acids were tested by gas chromatography. The physiological function of "inulin-microbiota" of elephant was verified in mice by fecal microbial transplantation (FMT). The expression of related proteins was determined by Western blotting and qPCR.

Results: (1) Eating inulin can cure gut colic of the sick elephant and changed gut microbiota. (2) It was found that "inulin microbiota" from the post-treatment elephants can promote the proliferation of intestinal cells, increase the utilization of short chain fatty acids (SCFAs), maintain intestinal barrier, and reduce the inflammation in mice. (3) The mechanism was inulin-gut microbiota-SCFAs-immune barrier.

Conclusions: Inulin contributed to rehabilitate the gut microbiota and gut immune barrier of the elephant with colic. This provides reasonable verification for using prebiotics to treat the colic in captive elephants. Prebiotics will foresure play an increasingly important role in disease prevention and treatment of captive animals in the future. Video Abstract.

Keywords: Asian elephants (Elephas maximus Linnaeus); Colic; Gut microbiota; Inulin.

Fig. 1

Inulin altered the gut microbiota of the sick Asian elephant. A Elephant fecal photos before and after treatment. B Alpha diversity (Shannon) of bacterial communities across groups. C PCoA plot based on Bray–Curtis distance metrics in different groups (ANOSIM). D Abundance represented as the proportions of ASVs classified at the phylum rank. E Relative abundance of specific genus significantly altered by inulin. F Cluster heatmap showing the proportions of ASVs classified at the genus rank. G Differential bacterial taxonomy selected by LEfSe analysis with LDA score > 4. Con: control group of 4 healthy elephants; Pre-inulin: before inulin treatment of the sick elephant; Post-inulin: after inulin treatment of the sick elephant. Data are means ± SEM

Fig. 2

“Inulin-microbiota” affects energy metabolism in mice by FMT. A Pattern of fecal transplantation. B Changes of the body weight with time of transplantation (repeated measures ANOVA). C Changes of food intake with time of transplantation (repeated measures ANOVA). D Percentage of initial body weights. E Weight of WAT. F Five hours fasting glucose. G Weight of the colon. H Colon histopathologic appearance by H&E staining. Scale bars, 500 μm. Visualization of PCNA-positive cells in proximal colon by staining. Scale bars, 100 μm. I Colon villus length. J PCNA-positive cells per villus. Control: mice gavaged with mice fecal microbiota, Pre-FMT: mice gavaged with fecal microbiota from elephant before inulin treatment; Post-FMT: mice gavaged with fecal microbiota from elephant after inulin treatment. Data are means ± SEM. *P < 0.05, **P < 0.01, and ***P < 0.001

Fig. 3

“Inulin-microbiota” affects immunity and nutrient transports in mice by FMT. A The mRNA was extracted from hypothalamus to analyze the expression of NPY, POMC, AgRP, and CART. B, C Quantitation of TH and BDNF in hypothalamus. D Quantitation of CXCL1, TNF-a, and IL-6 in white adipose tissue (WAT). E The relative expression of Occludin and Claudin-2 in the colon was analyzed by RT-PCR. F, G The relative expression of MCT1 and FFAR2 in the colon was analyzed by Western blotting. H Concentration of three short-chain fatty acids. Control: mice gavaged with mice fecal microbiota; Pre-FMT: mice gavaged with fecal microbiota from elephant before inulin treatment; Post-FMT: mice gavaged with fecal microbiota from elephant after inulin treatment. Data are means ± SEM. *P < 0.05, **P < 0.01, and ***P < 0.001

Fig. 4

Changes of gut microbiota in mice after FMT. A Alpha diversity (Chao1) of bacterial communities across groups. B PCoA plot based on Bray–Curtis distance metrics in different groups. C Relative abundance of specific genus significantly altered by FMT. D Cluster heatmap showing the proportions of ASVs classified at the genus rank. E Correlation analysis between genus abundance and physiological indexes (Spearman). Control: mice gavaged with mice fecal microbiota; Pre-FMT: mice gavaged with fecal microbiota from elephant before inulin treatment; Post-FMT: mice gavaged with fecal microbiota from elephant after inulin treatment. Data are means ± SEM. *P < 0.05, **P < 0.01, and ***P < 0.001