Impact of the Uncoupling Protein 1 on Cardiovascular Risk in Patients with Rheumatoid Arthritis

Figures

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  Figure 1. UCP1 transcription in adipose tissue associates with high serum levels of IL-6 and overweight. UCP1 transcription was analyzed by quantitative PCR in subcutaneous adipose tissue of 111 female patients with rheumatoid arthritis, among those 89 patients were UCP1 positive and 22 patients were UCP1-negative. (A) DAS28, (B) Erythrocyte sedimentation rate (ESR), Serum levels of (C) IL6, (D) IL1beta, (E) IL9, (F) IFNg, (G) Body mass index (BMI), (H) Frequency of overweight (BMI > 25 kg/m2). (I) Patient groups based on BMI and serum levels of IL6. BMI > 25 kg/m2 and IL6 > 1 pg/mL indicated high groups. Open circles indicate UCP1 negative cases. (J) The group combined high IL6 and BMI had significantly increased expression of UCP1. Boxplots show median, inter-quartile range and range. Statistical analysis was performed using non-parametric Mann–Whitney statistics and p-value < 0.05 are indicated.

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  Figure 2. Activation of UCP1 transcription down-stream of IL6 signaling. UCP1+ patients with high BMI and high IL6 (HiHiU+, n = 39) are compared to UCP1-negative patients (others, n = 69) by serum levels of leptin (A), resistin (B), visfatin (C); mRNA expression in adipose tissue of leptin (D), STAT3 (E), resistin (F), and ABCA1 (G). (H) Correlation between serum levels of adipokines and transcription of ABCA1 (open bars) and UCP1 (filled bars). mRNA expression of (I) UCP1 and (J) ABCA1 in adipose cells stimulated in vitro with IL6 +/− Tocilizumab. Boxplots show median, inter-quartile range and range. Statistical analysis was performed using the Mann–Whitney statistics. Correlations were performed with Spearman correlation and compared using Fisher r-to-z transformation (* p < 0.05, ** p < 0.01).

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  Figure 3. Inhibition of IL6 receptor signaling increases serum IL6 levels and UCP1 transcription. Comparison of UCP1 positive patients with rheumatoid arthritis treated with methotrexate monotherapy (MTX, n = 45), TNFa inhibitors (TNFi, n = 28), conventional antirheumatic drugs (cDMARD, n=17), and IL6 receptor inhibitor tocilizumab (Toci, n = 18). (A) Transcription of UCP1 in adipose tissue of (B) Serum levels of IL6. (C) Body mass index (BMI). Female RA patients were grouped by UCP1 transcription into high UCP1 with high BMI and IL6 (HiHiU+, n = 39), tocilizumab-treated patients with high UCP1 (TociU+, n = 16) and the remaining UCP1-negative patients (others, n = 69). (D) Serum levels of IL6, (E) erythrocyte sedimentation rate (ESR), (F) disease activity score (DAS28). Serum levels of (G) IFNg, (H) IL9, (I) IL10, and (J) IL4. Boxplots show median, inter-quartile range and range. Statistical analysis was performed using non-parametric Kruskal–Wallis statistics with post hoc analysis.

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  Figure 4. Unfavorable metabolic profile and increased cardiovascular risk despite high transcription of UCP1 female RA patients were grouped by UCP1 transcription into high UCP1 with high BMI and IL6 (HiHiU+, n = 39), tocilizumab-treated patients with high UCP1 (TociU+, n = 16) and the remaining UCP1-negative patients (others, n = 69). (A) Plasma glucose, (B) HOMA-IR, (C) total cholesterol (TC), (D) low-density lipids (LDL), (E) high-density lipids (HDL), (F) triglycerides (TG). (G) Triglycerides-to-HDL ratio. (H) mRNA expression of ABCA1. (I) Correlation of UCP1 and ABCA1 with inflammation and metabolic markers in RA patients (n = 111) and in tocilizumab-treated patients (n = 18). Analyses were done with Spearman’s correlation test and compared using Fisher r-to-z transformation (* p < 0.05, ** p < 0.01, *** p < 0.001). (J) Cardiovascular risk was estimated by Pocock’s score, (K) Framingham score. (L) Frequency of previous and diabetes mellitus (DM) and cardiovascular (CV) events in the groups and development of new events (nDM and nCV) at 5 years follow-up. Odds ratio (OR) was calculated between the groups’ HiHiU+ and others.