The putatively high-altitude adaptation of macaque monkeys: Evidence from the fecal metabolome and gut microbiome

Abstract

Animals living in high-altitude environments, such as the Tibetan Plateau, must face harsh environmental conditions (e.g., hypoxia, cold, and strong UV radiation). These animals' physiological adaptations (e.g., increased red cell production and turnover rate) might also be associated with the gut microbial response. Bilirubin is a component of red blood cell turnover or destruction and is excreted into the intestine and reduced to urobilinoids and/or urobilinogen by gut bacteria. Here, we found that the feces of macaques living in high-altitude regions look significantly browner (with a high concentration of stercobilin, a component from urobilinoids) than those living in low-altitude regions. We also found that gut microbes involved in urobilinogen reduction (e.g., beta-glucuronidase) were enriched in the high-altitude mammal population compared to the low-altitude population. Moreover, the spatial-temporal change in gut microbial function was more profound in the low-altitude macaques than in the high-altitude population, which might be attributed to profound changes in food resources in the low-altitude regions. Therefore, we conclude that a high-altitude environment's stress influences living animals and their symbiotic microbiota.

Keywords: adaptation; fecal color; gut microbiome; high altitude; primates; spatial–temporal changes.

FIGURE 1

The study sites for the low‐ and high‐altitude macaque populations.

FIGURE 2

The difference in the concentration of the fecal metabolites between the low‐ and high‐altitude samples. (a) The consistently significant changes in the concentration of the fecal metabolites between the low‐ and high‐altitude samples in each sampling season. Heatmap with z score conversion of the concentration. (b) The enrichment (May: high‐ vs. low‐altitude populations) of the KEGG pathways using the metabolome in the high‐altitude population. (c) The KEGG pathways' enrichment (August: low‐ vs. high‐ populations) using the metabolome in the low‐altitude population. The values in the legend are the p values. Aug, August; MML, Macaca mulatta littoralis living in the low‐altitude region; MMV, Macaca mulatta vestita living in the high‐altitude region.

FIGURE 3

The distribution of the 355 nonredundant MAGs (metagenomic assembled genomes) using 24 metagenomes. Phylogenetic analysis (using PhyloPhlAn [Segata et al., 2013]) of these 355 MAGs (coverage >80%, contamination rate < 10%). The panels in the center circle display the maximum‐likelihood trees created using the MAGs. The outer circle heatmap shows the relative abundance of each bin (MAG) in each macaque group or the gene numbers in each specific pathway. Aug, August; MML, Macaca mulatta littoralis living in the low‐altitude region; MMV, Macaca mulatta vestita living in the high‐altitude region.

FIGURE 4

The relative abundance of 20 MAGs harboring a high number of genes encoding putative enzymes involved in porphyrin and chlorophyll metabolism among each macaque group. Pairwise comparisons were based on the Kruskal–Wallis test (Bonferroni p‐value). Aug, August; MML, Macaca mulatta littoralis living in the low‐altitude region; MMV, Macaca mulatta vestita living in the high‐altitude region.

FIGURE 5

The relative abundance of genes coding for putative beta‐glucuronidase [EC 3.2.1.31], involved in reducing bilirubin beta‐diglucuronide to d‐urobilinogen using 24 metagenomes. Pairwise comparisons were based on the Kruskal–Wallis test (Bonferroni p‐value).

FIGURE 6

Putative gut microbial response to the high‐altitude environment using 24 metagenomes. (a) The relative abundance of four gut microbial species involved in bilirubin metabolism within each macaque group. Pairwise comparisons were based on the Kruskal–Wallis test (Bonferroni p‐value). (b) Linear discriminant analysis effect size was used to determine the significant difference (p < 0.05) in the relative abundance of KEGG pathways between low‐ and high‐altitude macaque populations in each sampling season. Aug, August; MML, Macaca mulatta littoralis living in the low‐altitude region; MMV, Macaca mulatta vestita living in the high‐altitude region.

FIGURE 7

The relative abundance and bacterial source of the target KEGG pathways associated with altitude adaptation using 24 metagenomes. Pairwise comparisons were based on the Kruskal–Wallis test (Bonferroni p‐value). Aug, August; MML, Macaca mulatta littoralis living in the low‐altitude region; MMV, Macaca mulatta vestita living in the high‐altitude region.

FIGURE 8

The PCoA ordination and adonis test (at 999 permutations with adjusted p‐value) based on the Bray–Curtis distance matrices in the macaque metagenomes based on (a) bacterial species; (b) KEGG function at the enzyme level; (c) CAZy glycoside hydrolase families; and (d) antibiotic resistance genes. Aug, August; MML, Macaca mulatta littoralis living in the low‐altitude region; MMV, Macaca mulatta vestita living in the high‐altitude region.