Effects of dietary glucose supplementation on the fasted plasma metabolome in cats and dogs

The study objective was to evaluate nutritional metabolomics in support of companion animal nutrition. The specific purpose was to identify metabolites that differed significantly (q-value < 0.05) in the 23 h fasted plasma metabolome of healthy adult female neutered cats (n = 14) and dogs (n = 14) following 2 weeks adaptation to a single batch of diet, nutritionally complete for both species, with and without dietary glucose supplementation (3.85 % w/w). The study consisted of a two-way, crossover design with samples from individual animals on days 14, 16 and 18 of each diet. Metabolic profiling consistently identified 219 metabolites from cats and 216 metabolites from dogs. Fasted plasma glucose did not change significantly with diet in either species whilst 41 % of cat and 20 % of dog metabolites did change significantly. In general, the two species responded similarly and provided data interpretable within the context of insulin-regulated responses to glucose, for example decreased fatty acid oxidation, increased uptake of branched chain amino acids into muscle, and in cats, decreased glucogenic amino acid catabolism. Other responses, such as increased 1 carbon pool intermediates in cats, were consistent with known nutritional differences between cats and dogs and interpretable within the context of energy metabolism. Data also indicated inter-individual variability and diet-dependent changes in digestion and absorption, providing insights for future study designs. In this proof-of-principle study it was concluded that metabolomics can provide data interpretable to a well-characterised area of nutrition and metabolism and also provide novel insights into metabolic adaptations with relevance to companion animal nutrition.