TABLE 1.

Roles of ghrelin in degenerative musculoskeletal disorders.

Disease	Signal pathway	Roles in disease	References
OP	MAPK/PI3K	Promoting osteoblast proliferation and differentiation and inhibiting apoptosis	[57], [58]
	GHSR/ERK and GHSR/PI3K/AKT	Inhibiting apoptosis in MC3T3‐E1 cells	[59]
	GH‐IGF‐I axis	Increasing BMD	[60]
OA	JAK2/STAT3/IRF‐1	Suppressing the expression of MMPs and ADAMTs and inhibiting degradation of human chondrocyte aggregates and Col II	[61], [62]
	NF‐κB	Antagonizing exaggerated catabolism in degenerative chondrocytes	[63]
	AKT	Suppressing the disorganized anabolism	[63]
Sarcopenia	p38/C/EBPβ	Inhibiting myostatin activation	[64]
	PI3Kβ, mTORC2, and p38	Inhibiting dexamethasone‐induced skeletal muscle atrophy and atrogene expression	[34]
IVDD	NF‐κB	Inhibiting the role of IL‐1β in NP cell proliferation and apoptosis	[65]
	AKT	Promoting anabolism in NP cells	[65]

Abbreviations: ADAMTs, a disintegrin and metalloproteinase with thrombospondin motifs; AKT, protein kinase B; BMD, bone mineral density; ERK, extracellular regulated protein kinase; GH, growth hormone; GHSR, growth hormone secretagogue receptor; IGF, insulin‐like growth factors; IL‐1β, interleukin‐1β; IRF‐1, interferon regulatory factor‐1; IVDD, intervertebral disc degeneration; MAPK, mitogen‐activated protein kinase; MMPs, matrix metalloproteinases; mTORC2, mammalian target of rapamycin complex 2; NP, nucleus pulposus; OA, osteoarthritis; OP, osteoporosis; PI3K, phosphoinositide 3‐kinase; PI3Kβ, phosphoinositide 3‐Kinase β.