Identification of metabolite profiles during gout flare in a prospective gout cohort: glutamine and histidine as anti-inflammatory metabolites

 

Charles Leroy, Phd Student ; Nghia Pham, Md; François Brial, Phd; Brenda Kischkel, Phd; Gwénaëlle Jayat ; Elena Ishow, Phd; Christèle Combes, Phd; Leo Joosten, Phd; Augustin Latourte,md,phd; Pascale Richette, Md, Phd; Hang-Korng Ea, Md, Phd

 

Affiliation(s):

Inserm U1132 Hôpital Lariboisiere

 

 

 

Background: Gout due to the presence of monosodium urate crystals (MSU) which occurs after chronic hyperuricemia is responsible for recurrent inflammatory flares. Gout inflammation is driven by IL-1β release after interaction of MSU crystals with immune cells. Gout flare is characterized by a self-limited inflammatory reaction. The mechanisms of crystal-induced inflammation initiation remain unclear. We recently observed the increase of several inflammatory biomarkers including TNFSF14 and IL-6 during gout flare in a prospective gout cohort (GOUTROS).

Objectives: Our objective is to analyze and identify metabolites associated with gout flare and resolution in a prospective gout cohort.

Methods: Plasmas were collected from 71 patients (5 females and 66 males) during gout flare (T1) and after the flare (T2) and analyzed by Nuclear Magnetic Resonance (NMR) based metabolomic. A total of 146 parameters (115 Lipoproteins and 41 Metabolites) were quantified using a targeted approach. Glutamine and glutamate were measured in the synovial fluid of patients suffering from osteoarthritis (OA), gout and calcium pyrophosphate deposition disease by colorimetric dosage (Sigma). THP-1 monocytes were primed by PMA (phorbol 12- myristate 13-acetate) and stimulated by synthetic MSU crystal in the presence or not of metabolite (glutamine or histidine) supplementation.

Results: Plasmas analysis by NMR identified 17 metabolites with different abondance during gout flare (T1) and flare resolution (T2): 6 metabolites (Glyc,GlycA,GlycB,Glyc/SPC,H2FC,Acetoacetic acid) were increased during the flare and 11 decreased (Histidine, H4TG, Glycine, Alanine, H4PL, H4A1, H4A2, Methionine, Glutamine, Lysine, H4CH) (figure 1A). Correlation analysis showed a strong association between these metabolites and CRP. Especially, glutamine and histidine abondance was negatively correlated with CRP, TNFSF14 and IL-6 (figure 1B), hinting for a potential role in inflammation regulation. Synovial fluid dosage of glutamine and glutamate level revealed that patients suffering from crystal driven inflammation had lower glutamine/glutamate ratios compared to mechanical osteoarthritis (OA) synovial fluid (figure 2A-C). In vitro, supplementation of THP1 cells with 20mM of glutamine significantly reduced IL-1β concentration after MSU stimulation (figure 2D). Histidine supplementation shows a tendency to decrease IL-1β concentration after MSU stimulation (figure 2E).

Conclusion: Among the 17 metabolites associated with gout flare, the abondance of glutamine and histidine was diminished during the inflammation phase. These 2 metabolites possessed anti-inflammatory properties. Further studies are ongoing to identify how these metabolites reduce IL-1β production.