Comparison of muscle metabolomics between two Chinese horse breeds

Abstract

With their enormous muscle mass and athletic ability, horses are well-positioned as model organisms for understanding muscle metabolism. There are two different types of horse breeds—Guanzhong (GZ) horses, an athletic breed with a larger body height (~148.7 cm), and the Ningqiang pony (NQ) horses, a lower height breed generally used for ornamental purposes—both inhabited in the same region of China with obvious differences in muscle content. The main objective of this study was to evaluate the breed-specific mechanisms controlling muscle metabolism. In this study, we observed muscle glycogen, enzyme activities, and LC–MS/MS untargeted metabolomics in the gluteus medius muscle of six, each of GZ and NQ horses, to explore differentiated metabolites that are related to the development of two muscles. As expected, the glycogen content, citrate synthase, and hexokinase activity of muscle were significantly higher in GZ horses. To alleviate the false positive rate, we used both MS1 and MS2 ions for metabolite classification and differential analysis. As a result, a total of 51,535 MS1 and 541 MS2 metabolites were identified, and these metabolites can separate these two groups from each other. Notably, 40% of these metabolites were clustered into lipids and lipid-like molecules. Furthermore, 13 significant metabolites were differentially detected between GZ and NQ horses (fold change [FC] value ≥ 2, variable important in projection value ≥1, and Q value ≤ 0.05). They are primarily clustered into glutathione metabolism (GSH, p = 0.01), taurine, and hypotaurine metabolism (p < 0.05) pathways. Seven of the 13 metabolites were also found in thoroughbred racing horses, suggesting that metabolites related to antioxidants, amino acids, and lipids played a key role in the development of skeleton muscle in horses. Those metabolites related to muscle development shed a light on racing horses' routine maintenance and improvement of athletic performance.

Baselining physiological parameters in three muscles across three equine breeds. What can we learn from the horse?

“…It is known that carnitine is essential for the shuttling of fatty acids from the cytosol into the mitochondria ( Buechler and Lowenstein, 1990 ; Hoppel, 2003 ) ( Figure 7 ). Finally, in an equine study comparing Guanzhong horses, which have athletic tall bodies, and Ningqiang pony horses, which have an agile but strong body that allows them to transport heavy goods in the mountains, the SCAC propionylcarnitine appeared in higher concentrations in the GM of the pony draft horses, which was attributed to the differences in muscle development between these two breeds ( Meng et al, 2023 ). Interestingly, both in healthy untrained humans and endurance horses, such as Arabian and Standardbred horses, SCACs are the most abundant carnitine metabolites in blood, particularly acetylcarnitine ( Bene et al, 2005 ; Westermann et al, 2008 ; Adams et al, 2009 ; van der Kolk et al, 2020 ).…”