Study findings raise possibility of therapies to target equine obesity

As hind-gut fermenters, the intestinal microbiota plays a critical role in cellulose fermentation and energy production in horses.
As hind-gut fermenters, the intestinal microbiota plays a critical role in cellulose fermentation and energy production in horses.

Therapies that target the make-up of the microbial community living in the hindgut of horses could be developed to tackle obesity, researchers suggest.

Scientists from Texas A&M University say their research has identified important differences in energy metabolism between obese and non-obese horses.

Michelle Coleman and her colleagues, writing in the open-access journal PLOS ONE, note that obesity among horses is of growing concern, with a reported prevalence of 31% in Britain.

Obesity increases the risk of insulin problems and the chances of developing the painful and damaging hoof condition laminitis.

The combination of obesity, insulin dysregulation and laminitis are components of equine metabolic syndrome (EMS).

However, current diagnostic tests for EMS do not adequately assess the disordered physiological processes behind it, which limits the ability to diagnose, manage, and prevent it.

They noted that, in people, the gastrointestinal microbiota – the community of micro-organisims in the gut – has been shown to be a crucial factor in the development of metabolic diseases such as obesity and type 2 diabetes.

“The gastrointestinal microbiota of horses is naturally highly diverse and variable in composition,” they said.

“As hind-gut fermenters, the intestinal microbiota plays a critical role in cellulose fermentation and energy production in horses.

“Although the microbial composition of the microbiota is important, the metabolites (metabolic byproducts) of these organisms are a major mechanism influencing the health of the host.”

The study team used 40 horses in central Texas for their study. Half were obese while the others were healthy and of normal weight.

They set out to learn more about the community of micro-organisms (microbiome) and the metabolites in their dung, as well as drawing blood to evaluate their lipid (fat) profiles.

The researchers found important differences between the obese horses and the controls in all three areas.

“The lipid profile observed in horses closely resembles the lipid profile of obese humans,” they observed.

In particular, there were significant differences in metabolites of the mitochondrial tricarboxylic acid cycle and circulating free fatty acids. The tricarboxylic acid cycle is the second stage of the three-stage cellular respiration cycle.

“These results indicate that the host and bacterial metabolism should be considered important in obese horses.”

Further studies were needed, they said, to substantiate the validity of these results from their proof-of-concept study.

Further work might confirm whether the differences seen in overweight horses might serve as biomarkers and lead to therapeutic interventions for obesity and its consequences.

They said further work is needed to learn more about the association between the bacterial communities identified in the dung and the metabolic byproducts found.

“Given some of the similarities observed in this study of horses with what is known about humans, the potential exists that information gleaned from studying the relationship of the microbiota, intestinal metabolome, and host metabolism in horses could be relevant to human health.”

The full study team comprised Coleman, Canaan Whitfield-Cargile and Noah Cohen, all with Texas A&M University; and Rodolfo Madrigal, with Loomis Basin Equine Medical Center in Penryn, California.

Coleman MC, Whitfield-Cargile CM, Madrigal RG, Cohen ND (2019) Comparison of the microbiome, metabolome, and lipidome of obese and non-obese horses. PLoS ONE 14(4): e0215918.

The study, published under a Creative Commons License, can be read here

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