Metabolic effects of glycine supplementation in captive cheetahs (Acinonyx jubatus)

Abstract

Cheetahs are a vulnerable species and their conservation is of global importance. In captivity, cheetahs are prone to a wide range of gastrointestinal diseases that are believed to be linked to the diets they receive in captivity. In the wild, cheetahs eat whole carcass diets rich in collagen. This is not always feasible in captive settings resulting in most facilities feeding their cheetahs only raw muscle meat, which has lower collagen concentrations. Glycine is a simple amino acid that has many physiological functions in mammals, most notably its role on collagen biosynthesis, where it is the most abundant amino acid present. Anecdotal evidence showed that dietary glycine supplementation may improve gastritis. Thus, this study aimed to determine the effect of glycine supplementation on the metabolism of the cheetah. Ten healthy male and female captive cheetahs housed at Cango Wildlife Ranch in Oudtshoorn, Western Cape were fed either a meat only or glycine supplemented meat diet for four weeks, followed by a 4 week cross-over. Body measurements, urine and blood samples were collected at baseline, four weeks (diet 1) and eight weeks (diet 2). Haematology, serum biochemistry and untargeted 1H nuclear magnetic resonance analysis was performed followed by the appropriate spectra, data and statistical analyses. The glycine diet resulted in a decreased serum albumin, alkaline phosphatase and total calcium concentration and an increased eosinophils and basophils count compared to the baseline or control diet. Body weight also decreased on the glycine diet which may be due to shifts in energy metabolism when glycine was supplemented. A total of 151 and 60 metabolites were identified in the urine and serum, respectively, in the 10 cheetahs. After data reduction, 10 and 7 metabolites were highlighted as important contributors towards the metabolome differences between the diet groups. The important metabolites identified in urine were dimethyl sulphone, proline, fructose, dimethylamine, trimethylamine, pyroglutamic acid, 1,3-diaminopropane, dihydrothymine, methylmalonic acid and pimelic acid. The metabolites identified in serum were glutamic acid, threonine, α-aminobutyric acid, glucose-6-phosphate, ethanolamine, methionine and propionic acid. These metabolites play various metabolic roles including energy production, immune function, protein and collagen biosynthesis or as products of gut microbiome fermentation. The collagen rich diet fed prior to the study, which was reflected in the baseline samples, had a more profound effect on the identified metabolites compared to the glycine supplemented diet. However, glycine supplementation did influence these pathways and had a direct effect on threonine and methionine related pathways. Specifically that of threonine sparing, pyrimidine biosynthesis and decreasing the production of bacterial fermentation products which may prove to be extremely beneficial in improving gastrointestinal health. This indicates the importance of this simple amino acid in whole body metabolism of cheetahs, especially when dietary collagen is limited. Glycine supplementation may be a simple method to improve the gastrointestinal and overall health of captive cheetahs and future studies should use targeted approaches to further understand the roles of the identified metabolites.