Table 2.

Metabolites altered in ON and OP.

Category	Metabolites	Variation Trend	Reference
Amino Acids	glutamine	↓ *	Wang et al. [33]
		↑ *	Zhao et al. [45]
		↑	You et al. [46]
		↑	Miyamoto et al. [40,47]
	hydroxyproline	↑	Wang et al. [33]
		↑	Miyamoto et al. (2017) [40]
		↓	Deng et al. [41]
		↑	Miyamoto et al. (2018) [47]
	gly-gly	↓	Miyamoto et al. (2017) [40]
		↓	Kou et al. [43]
		↓	Miyamoto et al. (2018) [47]
	cystine	↓	Miyamoto et al. (2017) [40]
		↓	Zhao et al. [45]
		↓	Miyamoto et al. (2018) [47]
	taurine	↓	Pontes et al. [35]
		↑	Zhao et al. [45]
		↓	Yu et al. [37]
Lipid Metabolites	PC	↑	Aleidi et al. [34]
		↑	Cao et al. [42]
		↑	Kou et al. [43]
	LPC	↑	Wang et al. [33]
		↓	Deng et al. [41]
		↓	Cao et al. [42]
		↑	Kou et al. [43]
		↑	Miyamoto et al. (2018) [47]
	SM	↓	Cao et al. [42]
		↓	Kou et al. [43]
Carbohydrate Metabolites	glucose	↓	Kou et al. [43]
		↓	You et al. [46]
Other Metabolites	lactate	↑	Kou et al. [43]
		↑	Pontes et al. [35]
		↓	You et al. [46]
	succinic	↑	Deng et al. [41]
		↑	Zhao et al. [45]
		↑	Yu et al. [37]

* ↑: Increased expression; ↓: Decreased expression.