5-HIAA	5-Hydroxyindole-3-acetic acid
ACPA	Anti-citrullinated protein antibodies
ACR	American College of Rheumatology
AhR	Aryl hydrocarbon receptor
anti-CCP	Anti-cyclic citrullinated peptide antibodies
AUC	Area under the curve
bDMARDs	Biologic disease-modifying antirheumatic drugs
Breg	Regulatory B cell
BSH	Bile salt hydrolase
CA	Cholic acid
CCL	CC chemokine ligand
CCR	CC chemokine receptor
CD	Cluster of differentiation
CIA	Collagen-induced arthritis
CRP	C-reactive protein
csDMARDs	Conventional synthetic disease-modifying antirheumatic drugs
CXCL	CXC chemokine ligand
DAS28	Disease Activity Score in 28 joints
DC	Dendritic cell
DCA	Deoxycholic acid
DMARDs	Disease-modifying antirheumatic drugs
FLS	Fibroblast-like synoviocytes
FMT	Fecal microbiota transplantation
FOXK1	Forkhead box protein K1
Foxp3	Forkhead box protein P3
FXR	Farnesoid X receptor
GPBAR1/TGR5	G protein-coupled bile acid receptor 1
GPR	G protein-coupled receptor
HAQ-DI	Health Assessment Questionnaire-Disability Index
HDAC	Histone deacetylase
HIF-1α	Hypoxia-inducible factor 1-alpha
HLA	Human leukocyte antigen
H4R	Histamine H4 receptor
hs-CRP	High-sensitivity C-reactive protein
IAA	Indole-3-acetic acid
IAld	Indole-3-aldehyde
IDO1	Indoleamine 2,3-dioxygenase 1
IFN	Interferon
Ig	Immunoglobulin
IL	Interleukin
ILC	Innate lymphoid cell
IPA	Indole-3-propionic acid
ISAPP	International Scientific Association for Probiotics and Prebiotics
LCA	Lithocholic acid
LPS	Lipopolysaccharide
MTX	Methotrexate
NF-κB	Nuclear factor kappa B
NFATc1	Nuclear factor of activated T-cells, cytoplasmic 1
NOD	Nucleotide-binding oligomerization domain
PRR	Pattern recognition receptor
RA	Rheumatoid arthritis
RF	Rheumatoid factor
RORγt	RAR-related orphan receptor gamma t
SCFAs	Short-chain fatty acids
SIRT5	Sirtuin 5
SUCNR1	Succinate receptor 1
TAZ	Transcriptional coactivator with PDZ-binding motif
TDO	Tryptophan 2,3-dioxygenase
Tfh	T follicular helper cells
Tfh17	IL-17-producing T follicular helper cells
Tfr	T follicular regulatory cells
TGF-β	Transforming growth factor beta
Th1	Type 1 T helper cells
Th17	Type 17 T helper cells
TLR	Toll-like receptor
TMAO	Trimethylamine N-oxide
TNF-α	Tumor necrosis factor-alpha
TRAF6	TNF receptor associated factor 6
Treg	Regulatory T cell
tsDMARDs	Targeted synthetic disease-modifying antirheumatic drugs
UDCA	Ursodeoxycholic acid
VAS	Visual Analog Scale
VDR	Vitamin D receptor
VEGF	Vascular endothelial growth factor
YB-1	Y-box binding protein 1
7α-HSDH	7α-hydroxysteroid dehydrogenase