Table 2.

Overview of metabolic changes in OA chondrocytes.

Metabolic Signaling Pathway	Alteration in OA	Relationship with Metabolism	Ref.
Nicotinamide adenine dinucleotide pathway
NAMPT	Increase	Produce NAD+	[55]
SIRT1	Decrease	Consume NAD+	[72]
PARP1	Controversial	Consume NAD+	[45,70]
MAPK and mTOR pathway
p38	Increase	Upregulate GLUT1, activate p38/cAMP/CREB/MMP13 axis	[73]
PKC	Increase	Upregulate GLUT1, regulate glycosaminoglycan synthesis	[74]
AKT	Increase	Upregulate glycolytic enzymes and glucose transporters	[75]
HIFs pathway
HIF-1α	Increase	Increase glycolysis and reduce mitochondrial respiration	[76,77]
AMPK pathway
AMPK	Decrease	Decrease ATP production and increase ATP consumption	[78]
PTEN/PI3K/AKT pathway
PTEN	Increase	Reduce proteoglycan synthesis, glycolysis and mitochondrial respiration	[79]

Abbreviations: OA: Osteoarthritis; NAMPT: Nicotinamide phosphoribosyltransferase; SIRT1: Sirtuin 1; PARP1: Poly(ADP-ribose) polymerase 1; PKC: Protein kinase C; AKT: Protein kinase B; HIF-1α: Hypoxia-inducible factor 1α; AMPK: AMP-activated protein kinase; mTOR: Mammalian target of rapamycin; ATP: Adenosine triphosphate; NAD⁺: Nicotinamide adenine dinucleotide; GLUT1: Glucose transporter 1; cAMP: Cyclic adenosine monophosphate; CREB: Response element binding protein; MMP13: Matrix metalloproteinase 13.