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Early RA patients had increased transthyretin levels in sera
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Transthyretin levels were significantly increased in the sera of patients with early rheumatoid arthritis, according to study results.
Researchers in China collected serum samples from 36 patients with early rheumatoid arthritis (ERA; disease course less than 6 months; mean age, 54 years; 24 women), 43 patients with late rheumatoid arthritis (LRA; disease course longer than 2 years; mean age, 56.5 years; 30 women), 40 patients with osteoarthritis (OA; mean age, 54.7 years; 25 women) and 40 healthy controls (mean age, 52.9 years; 25 women). ELISA was used to measure transthyretin (TTR) levels, and Western blot was utilized to detect serum TTR. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) then analyzed modified TTR.
Patients with ERA had significantly greater levels of serum TTR (502.46 ± 108.15 mg/L) compared with controls (424.98 ± 117.63 mg/L; P<.05). LRA patients also had higher levels of TTR than controls but were not statistically significant (P>.05). Differences between OA patients (363.90 ± 105.21 mg/L) and controls did not reach statistical significance (P>.05).
Western blot identified two protein bands corresponding to monomer and dimmer TTR. Each patient group had a similar proportion of TTR monomer. TTR dimmer proportion was lower in rheumatoid arthritis (RA) patients than controls, with LRA patients displaying a greater decrease (P<.05).
“By MALDI-TOF-MS, four major peaks were observed in sera corresponding to native TTR [13,749.86 ± 148 m/z), Sul-TTR [13,829.63 ± 2.76 m/z], Cys-TTR [13,870.70 ± 2.70 m/z], and Cysgly-TTR [13,927 + 5.77 m/z],” the researchers reported. Disease stages were varied with the proportion of modified TTR.
“We are the first to describe TTR and its modifications as possible serological markers for early diagnosis of RA,” the researchers concluded. “Four modified TTR were identified by RA by MALDI-TOF-MS, and the proportion of TTR isoforms varied with different disease stages. Thus TTR might be considered as a potential serological marker for early diagnosis of RA.
“Meanwhile, the role for TTR post-translational modification involved in RA pathogenesis should be further investigated.”
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