Altered gut microbial metabolism provides insights into cardiometabolic disease in zoo-housed western lowland gorillas
Cardiometabolic disease in zoo-housed great apes is a critical welfare and conservation issue. To better understand the root causes of this disease, from a microbiome perspective, we leveraged a comparative, international cohort that included metaOMIC analyses of fecal samples of zoo-housed western lowland gorillas (Gorilla gorilla gorilla) from multiple U.S. and European zoos, and free-range individuals from the Central African Republic. Regardless of health status, all zoo-housed gorillas appear to exhibit a microbially-rich gut and increased markers of active colonic fermentation, in contrast with gut metabolism more associated with processing lignified, plant-cell wall components in wild individuals; though these distinctions appear less pronounced in European zoos. However, predictive machine learning models found specific markers of cardiometabolic health status that distinguished affected from unaffected U.S. zoo-housed gorillas; specifically, metaOMIC association analyses show that cardiometabolic distress is associated with reduced fecal levels of the sulfur-containing amino acids - lysine and methionine, along with low abundance of microbial pathways linked to their generation; particularly, sulfate assimilation and reduction, and L-methionine and cysteine biosynthesis pathways. In contrast with healthy subjects, affected U.S. zoo-housed individuals also exhibited lower fecal butyrate and propionate, and reduced microbial metabolism of hexoses, despite the metabolite-rich environment that characterized all zoo-housed gorillas. Hence, we contemplate the possibility that cardiometabolic distress in U.S. zoo's gorillas is associated with altered gut microbial metabolism of specific dietary nutrients, drawing ecological and evolutionary parallels with cardiovascular disease in humans.