Objective: Japanese Brown (JBR) cattle, especially the Kochi (Tosa) pedigree (JBRT), is a local breed of moderately marbled beef. Despite the increasing demand, the interbreed differences in muscle metabolites from the highly-marbled Japanese Black (JBL) beef remain poorly understood. We aimed to determine flavorrelated metabolites and postmortem metabolisms characteristic to JBRT beef in comparison with JBL beef.Methods: Lean portions of the longissimus thoracis (LT, loin) muscle from four JBRT cattle were collected at 0, 1, and 14 d postmortem. The muscle metabolomic profiles were analyzed using capillary electrophoresis time-of-flight mass spectrometry. The difference in postmortem metabolisms and aged muscle metabolites were analyzed by statistical and bioinformatic analyses between JBRT (n = 12) and JBL cattle (n = 6).Results: A total of 240 metabolite annotations were obtained from the detected signals of the JBRT muscle samples. Principal component analysis separated the beef samples into three different aging point groups.According to metabolite set enrichment analysis (MSEA), postmortem metabolic changes were associated with the metabolism of pyrimidine, nicotinate and nicotinamide, purine, pyruvate, thiamine, amino sugar, and fatty acid; citric acid cycle; and pentose phosphate pathway as well as various amino acids and mitochondrial fatty acid metabolism. The aged JBRT beef showed higher ultimate pH and lower lactate content than aged JBL beef, suggesting the lower glycolytic activity in postmortem JBRT muscle. JBRT beef was distinguished from JBL beef by significantly different compounds, including choline, amino acids, uridine monophosphate, inosine 5′-monophosphate, fructose 1,6-diphosphate, and betaine, suggesting interbreed differences in the accumulation of nucleotide monophosphate, glutathione metabolism, and phospholipid metabolism. Conclusion:Glycolysis, purine metabolism, fatty acid catabolism, and protein degradation were the most common pathways in beef during postmortem aging. The differentially expressed metabolites and the relevant metabolisms in JBRT beef may contribute to the development of a characteristic flavor.

Injured neurons in the mammalian central nervous system (CNS) possess a very limited ability to regenerate axons under physiological conditions. This is in marked contrast with peripheral axons, which can regrow and establish functional connections even after the formation of lesions. The absence of regeneration in the CNS is caused by an inhibitory influence of the environment of the injured axons and the lack of intrinsic factors that enable regeneration in the peripheral nervous system (PNS) (He & Jin, 2016;Hilton & Bradke, 2017;Liu et al., 2011). Fundamentally similar processes are thought to be important for developmental axon growth and axonal