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The unexpected relationship between the endurance of a horse and its intestinal microbiota? Indeed, some bacteria in the intestinal microbiota directly influence energy metabolism, in particular that of the mitochondria¹ which are real energy producing factories for cells. That is the conclusion of an original study carried out by scientists from INRAE, in partnership with the National Veterinary School at Alfort and the University of Evry. At the origin of their questions, horses capable of running races at speeds between 100 and 160 km in approximately 8h, which is for humans the equivalent of a race up Mont Blanc, a real physical feat! Studies in genomics and statistics have improved our understanding of energy metabolism in these horse athletes.

To understand how these horses succeed in having such endurance, scientists looked for a link between the intestinal microbiota and the mitochondria of blood cells. For this, they took samples from blood and manure from 20 horses, before and just after a race. Genetic and metabolic analyses of blood and manure show that a real dialogue exists between the intestinal microbiota of the horse and blood cell mitochondria. The microbiota makes fatty acides such as butyrate², that enter the blood. These fatty acids act both as fuel for the mitochondria but also as messengers. They "know" when an intense effort is being made: they adjust energy production by using butyrate for example, which delays muscle fatigue, hypoglycemia and reduces inflammation.

This work is a pioneer in the study of the relationship between the microbiota and mitochondria, explored here on an original model for energy metabolism in endurance race horses. Even though the precise mechanisms for molecular communication implicated must still be studied in detial, these first results improve our understanding of energy metabolism during a prolonged effort. They offer ways to preserve the welfare of horses and facilitate endurance effort by adapting the diet to favor an optimal intestinal microbiota.

1* Mitochondria are comptments in most animal cells, in charge of producing energy to ensure cell function and in the end organ function.
2* Butyrate is a fatty acid with antiinflammaotry properties produced and exported by bacteria.