Functional metabolic capacity of pig colonocytes is differentially modulated by fermentable fibre and poorly...

The intestine is a highly metabolic organ that relies on energy production within the intestinal cells to sustain its functions. In the colon, intestinal cell metabolic function could be affected positively and negatively by microbiota-derived metabolites. Protein fermentation metabolites are known to negatively impact intestinal metabolic function, while fibre fermentation metabolites are generally thought beneficial. We aimed to investigate whether proteins of different digestibility in the absence and presence of fibres impact the energy metabolism of colonocytes, with potentially adverse health effects. We fed 32, 9-week-old boars one of four experimental diets for 14 days in a 2 × 2 factorial arrangement. Whey and collagen were added as a well and a poorly digestible protein source, respectively, and fibre was either included at 5% or 23%. We examined the effects of the diets on the flux of fermentation metabolites in colon digesta and assessed the impact of the diets on functional metabolic capacity of isolated colonocytes using the Seahorse XF analyzer. Feeding the poorly digestible protein source collagen indeed increased nitrogen flow into the colon by 135% compared to the well-digestible whey-protein source. Feeding high fermentable fibre increased colonic fluxes of both fibre-derived metabolites acetate, propionate, butyrate and caproate, but also increased flux of protein-derived metabolites ammonia, isobutyrate, isovalerate, valerate and isocaproate. To analyse the impact of the diets and the induced differential metabolic composition of the intestinal lumen on functional metabolic capacity of the intestine, we used extracellular flux analysis on freshly isolated pig colonocytes. Colonocytes isolated from high fermentable fibre-fed pigs in the whey-protein diet, but not in the collagen-protein diet, had a reduced mitochondrial capacity, as indicated by a 35% reduction of maximal respiration (interaction P < 0.05) and a 20% reduction of spare respiratory capacity (interaction P < 0.05). Colonocytes from high fermentable fibre-fed pigs had a 37% decreased glycolytic activity compared to the colonocytes isolated from the low fermentable fibre-fed pigs (P < 0.001). This indicated that different diets, and in particular different protein sources and fibre levels, differentially affect colonic epithelial cell metabolism in pigs. Especially, high fermentable fibre lowered both colonocyte mitochondrial and glycolytic metabolism, indicating that high-fibre intake in pigs could lower colonocyte energetic status. Because the metabolic capacity of colonocytes is tightly linked with their functionality, assessment of intestinal cell metabolic capacity may be a valuable tool for future research.