Involvement of Serum Leptin, Adiponectin Concentrations in RA Joint Damage

In patients with rheumatoid arthritis (RA), both serum leptin and adiponectin concentrations normalized by body fat mass are elevated. Serum adiponectin levels, but not serum leptin levels, however, may be involved in the joint damage associated with the disease. Results of the analysis were published in the journal Scientific Reports.

The investigators sought to elucidate the relationship of these adipocytokines—that is, leptin and adiponectin, which have shown possible involvement in inflammation and immunity—with the disease activities observed among patients with RA. A cross-sectional, controlled clinical study on the subject was conducted in Japan. Leptin and adiponectin concentrations, as well as such inflammatory markers as metalloproteinase-3 (MMP-3), were evaluated in 136 individuals with RA, 110 of whom were females and 26 of whom were males, as well as in 78 controls without RA, 42 of whom were females and 36 of whom were males. The average age of the patients with RA was 69.6±9.3 years, compared with 66.7±15.0 years in the controls. Participants with RA were individuals who had been visiting the outpatient clinic at one of several hospitals in Japan, whereas controls without RA included those who had such orthopedic issues as joint pain due to osteoarthritis or osteoporosis.

Results of the study demonstrated that serum leptin and adiponectin concentrations correlated positively (r= 0.565; P <.001) and negatively (r= –0.331; P <.001) with the amount of body fat, respectively. Further, serum leptin and adiponectin levels that were normalized by body fat mass were significantly higher among patients with RA compared with controls (leptin: 1.24 ng/mL/kg fat in RA vs 0.76 ng/mL/kg fat in controls; P <.001 and adiponectin: 0.74 ng/mL/kg fat in RA vs 0.44 ng/mL/kg fat in controls; P <.001).

Additionally, normalized adiponectin concentrations correlated positively not only with the degree of bone destruction (per Steinbrocker classification), but also with serum MMP-3 concentrations. Normalized leptin levels, however, did not correlate with the degree of bone destruction.

With respect to inflammatory markers, serum concentrations of C-reactive protein (CRP) in patients with RA were significantly higher than CRP levels in controls (median, 0.11 mg/dL vs 0.08 mg/dL, respectively; P =.007). Moreover, serum concentrations of MMP-3 were also significantly higher in individuals with RA than in controls (median, 66.1 ng/mL vs 31.8 ng/mL, respectively; P <.001).

The investigators concluded that the results of this study may help to shed some light on the involvement of leptin and adiponectin in the pathogenesis of RA.

Reference

Chihara K, Hattori N, Ichikawa N, Matsuda T, Saito T. Re-evaluation of serum leptin and adiponectin concentrations normalized by body fat mass in patients with rheumatoid arthritis. Sci Rep. 2020;10(1):15932. doi:10.1038/s41598-020-73068-2