Increased leptin levels in patients with rheumatoid arthritis: a meta-analysis

Adipokines in Rheumatoid Arthritis: Emerging Biomarkers and Therapeutic Targets

Rheumatoid arthritis (RA) is a chronic inflammatory disease manifested by joint involvement, extra-articular manifestations, and general symptoms. Adipose tissue, previously perceived as an inert energy storage organ, has been recognised as a significant contributor to RA pathophysiology. Adipokines modulate immune responses, inflammation, and metabolic pathways in RA. Although most adipokines have a pro-inflammatory and aggravating effect on RA, some could counteract this pathological process. The coexistence of RA and sarcopenic obesity (SO) has gained attention due to its impact on disease severity and outcomes. Sarcopenic obesity further contributes to the inflammatory milieu and metabolic disturbances. Recent research has highlighted the intricate crosstalk between adipose tissue and skeletal muscle, suggesting potential interactions between these tissues in RA. This review summarizes the roles of adipokines in RA, particularly in inflammation, immune modulation, and joint destruction. In addition, it explores the emerging role of adipomyokines, specifically irisin and myostatin, in the pathogenesis of RA and their potential as therapeutic targets. We discuss the therapeutic implications of targeting adipokines and adipomyokines in RA management and highlight the challenges and future directions for research in this field.

The Influence of Adipokines on Radiographic Damage in Inflammatory Rheumatic Diseases

Inflammatory rheumatic diseases (IRDs) are complex immune-mediated diseases that are characterized by chronic inflammation of the joints. Rheumatoid arthritis (RA) and spondyloarthritis (SpA), including axial SpA (ax SpA) and psoriatic arthritis (PsA), are the most common forms of IRD. Both RA and ax SpA are characterized by a chronic course with progressive structural modifications, namely, cartilage damage and bone erosions in RA and osteoproliferative changes with spinal ossifications in ax SpA. The adipose tissue is involved in the pathophysiology of IRDs via the release of several proteins, namely, adipokines. Several adipokines with pro-inflammatory effects have been identified, such as leptin, adiponectin, visfatin and resistin. In this review, we discuss the role that adipokines may play in the structural modifications of the peripheral joints and/or axial skeleton. In RA, the role of leptin in structural damage remains controversial, while adiponectin and its high-molecular-weight isoform are known to have an influence on the development of bone erosions and radiographic progression. Resistin also appears to be a potent detrimental adipokine for the joints in RA. In ax SpA, visfatin seems to be an attractive candidate for radiographic progression, while leptin and adiponectin have negative effects on radiographic progression.

Improved outcomes in rheumatoid arthritis with obesity after a weight loss intervention: randomized trial

OBJECTIVE

To examine whether a weight loss intervention programme improves RA disease activity and/or musculoskeletal ultrasound synovitis measures in obese RA patients.

METHODS

We conducted a proof-of-concept, 12-week, single-blind, randomized controlled trial of obese RA patients (BMI ≥ 30) with 28-joint DAS (DAS28)  ≥ 3.2 and with evidence of power Doppler synovitis. Forty patients were randomized to the diet intervention (n = 20) or control group (n = 20). Diet intervention consisted of a hypocaloric diet of 1000-1500 kcal/day and high protein meal replacements. Co-primary outcomes included change in DAS28 and power Doppler ultrasound (PDUS)-34. Clinical disease activity, imaging, biomarkers, adipokines and patient-reported outcomes were monitored throughout the trial. Recruitment terminated early. All analyses were based on intent-to-treat for a significance level of 0.05.

RESULTS

The diet intervention group lost an average 9.5 kg/patient, while the control group lost 0.5 kg (P < 0.001). Routine Assessment of Patient Index Data 3 (RAPID3) improved, serum leptin decreased and serum adiponectin increased significantly within the diet group and between the groups (all P < 0.03). DAS28 decreased, 5.2 to 4.2, within the diet group (P < 0.001; -0.51 [95% CI -1.01, 0.00], P = 0.056, between groups). HAQ-Disability Index (HAQ-DI) improved significantly within the diet group (P < 0.04; P = 0.065 between group). Ultrasound measures and the multi-biomarker disease activity score did not differ between groups (PDUS-34 -2.0 [95% CI -7.00, 3.1], P = 0.46 between groups).

CONCLUSION

Obese RA patients on the diet intervention achieved weight loss. There were significant between group improvements for RAPID3, adiponectin and leptin levels, and positive trends for DAS28 and HAQ-DI. Longer-term, larger weight loss studies are needed to validate these findings, and will allow for further investigative work to improve the clinical management of obese RA patients.

TRIAL REGISTRATION

ClinicalTrials.gov, https://clinicaltrials.gov, NCT02881307.

The Involvement of Glucose and Lipid Metabolism Alteration in Rheumatoid Arthritis and Its Clinical Implication

Obviously, immune cells like T cells and macrophages play a major role in rheumatoid arthritis (RA). On one hand, the breakdown of immune homeostasis directly induces systemic inflammation; on the other hand, these cells initiate and perpetuate synovitis and tissue damages through the interaction with fibroblast-like synoviocytes (FLS). In recent years, the pathological link between metabolic disorders and immune imbalance has received increasing attention. High energy demand of immune cells leads to the accumulation of metabolic byproducts and inflammatory mediators. They act on various metabolism-sensitive signal pathways as well as relevant transcription factors, such as HIF-1α, and STATs. These molecular events will impact RA-related effectors like circulating immune cells and joint-resident cells in return, allowing the continuous progression of systemic inflammation, arthritic manifestations, and life-threatening complications. In other words, metabolic complications are secondary pathological factors for the progression of RA. Therefore, the status of energy metabolism may be an important indicator to evaluate RA severity, and in-depth explorations of the mechanisms underlying the mystery of how RA-related metabolic disorders develop will provide useful clues to further clarify the etiology of RA, and inspire the discovery of new anti-rheumatic targets. This article reviews the latest research progress on the interactions between immune and metabolism systems in the context of RA. Great importance is attached to the changes in certain pathways controlling both immune and metabolism functions during RA progression.

Emerging role of leptin in joint inflammation and destruction

Rheumatoid arthritis (RA) is an autoimmune disease characterized by tumor-like hyperplasia and inflammation of the synovium, which causes synovial cell invasion into the bone and cartilage. In RA pathogenesis, various molecules in effector cells (i.e., immune cells and mesenchymal cells) are dysregulated by genetic and environmental factors. Consistent with the early stages of RA, these pathogenic cells cooperate and activate each other directly by cell-to-cell contact or indirectly via humoral factors. Recently, growing evidence has revealed essential role of adipokines, which are multifunctional signal transduction molecules, in the immune system. In this review, we summarize the current understanding of the cross-talk between leptin, one of the most well-known and best-characterized adipokines, and osteoimmunology. Furthermore, we discuss the contribution of leptin to the pathogenesis of RA and its potential mechanisms.

Mini-Review: The Contribution of Adipokines to Joint Inflammation in Inflammatory Rheumatic Diseases

Inflammatory rheumatic diseases (IRD) are complex disorders characterized by chronic inflammation of the joints and related skeletal structures. The most common forms of IRD are rheumatoid arthritis (RA) and spondyloarthritis (SpA), including axial SpA (axSpA) and psoriatic arthritis (PsA). Obesity is a frequent comorbidity in RA and PsA, and to a lesser extend in axial SpA. The association between obesity and IRD may be explained by the release from fat tissue of several bioactive proteins, namely adipokines. Adipokines are involved in the regulation of various processes such as lipid or glucose metabolism, but also inflammation. Adipokines are interrelated with the immune system, with both innate and adaptive immune cell connections. Several adipokines with pro-inflammatory effects have been identified such as leptin, visfatin or resistin. Conversely, adiponectin and more specifically its low molecular weight isoform, is considered to have antiinflammatory properties. In this review, we discuss the contribution of adipokines to the joint inflammation of IRD, the relation they have with immune pathways of these diseases, their links with the structural impact on peripheral joints and/or axial skeleton, and also the influence they may have on the cardiometabolic risk of IRD.

Re-evaluation of serum leptin and adiponectin concentrations normalized by body fat mass in patients with rheumatoid arthritis

Leptin and adiponectin are produced mainly in adipocytes and classified as adipocytokines because of their possible involvement in inflammation and immunity. The aim of this study was to elucidate the relationships of these adipocytokines with the disease activities of RA. We examined leptin and adiponectin concentrations and inflammatory markers such as metalloproteinase-3 (MMP-3) in 136 patients with rheumatoid arthritis (RA) (26 males and 110 females, 69.6 ± 9.3 years) and 78 controls (36 males and 42 females, 66.7 ± 15.0 years). Serum leptin and adiponectin concentrations correlated positively (r = 0.565, P < 0.001) and negatively (r = –0.331, P < 0.001) to the amount of body fat, respectively. Serum leptin and adiponectin concentrations normalized by body fat mass were significantly higher in RA than those in controls [leptin, 1.24 (median) ng/mL/kg fat in RA vs. 0.76 ng/mL/kg fat in controls; adiponectin, 0.74 μg/mL/kg fat in RA vs. 0.44 μg/mL/kg fat in controls]. Normalized adiponectin concentrations correlated positively not only to the degree of bone destruction in Steinbrocker classification but also to serum MMP-3 concentrations. Normalized leptin concentrations did not correlate to the degree of bone destruction. We conclude that adiponectin but not leptin may be involved in joint damage in RA.

Tocilizumab Increases Body Weight and Serum Adipokine Levels in Patients with Rheumatoid Arthritis Independently of Their Treatment Response: a Retrospective Cohort Study

BACKGROUND

Causes of weight change after tocilizumab treatment are unclear. We aimed to investigate the effects of tocilizumab treatment on body weight and serum adipokine levels in patients with rheumatoid arthritis (RA).

METHODS

In this retrospective cohort study, we evaluated weight changes in patients with RA who received methotrexate (Cohort I) or tocilizumab with methotrexate (Cohorts II and III) for 24 weeks. Adipokine concentrations at baseline and 24 weeks were analyzed in Cohorts I and III. Cohorts I and II received tocilizumab therapy for an additional 48 weeks, during which weight changes were monitored (24-72 weeks).

RESULTS

No significant weight change occurred after 24 weeks of methotrexate treatment (mean difference, -0.2 kg; P = 0.630), but was observed after 24 weeks of tocilizumab treatment (mean difference, +0.9 kg; P = 0.010). Weight changed regardless of the treatment response in both treatment groups. The leptin-adiponectin ratio (P = 0.015) and levels of adiponectin (P < 0.001), leptin (P < 0.001), and resistin (P = 0.003) increased significantly after 24 weeks of tocilizumab, but not methotrexate treatment. After 24, 48 and 72 weeks of tocilizumab treatment in Cohort II, mean (95% confidence interval [CI]) weight changes from baseline were +0.7 (0.0-1.4), +1.2 (0.4-2.0) and +1.1 (0.2-2.0) kg, respectively, and mean (95% CI) percent weight changes from baseline were +1.3% (0.1%-2.6%), +2.2% (0.7%-3.6%), and +2.0% (0.4%-3.7%) at 24, 48, and 72 weeks, respectively.

CONCLUSION

Weight and the leptin-adiponectin ratio increased after tocilizumab treatment. Given that cardiovascular (CV) risk factors may deteriorate in patients with RA who receive tocilizumab, further studies are required to determine the effects of weight gain on CV outcomes in these patients.

Effects of Tocilizumab, an Anti-Interleukin-6 Receptor Antibody, on Serum Lipid and Adipokine Levels in Patients with Rheumatoid Arthritis

Patients with rheumatoid arthritis (RA) are at increased risk of cardiovascular disease. Dyslipidemia is a known adverse effect of tocilizumab (TCZ), an anti-interleukin-6 receptor antibody used in RA treatment. We aimed to assess the effect of TCZ on lipid profile and adipokine levels in RA patients. Height, weight, disease activity scores, lipid profile and atherogenic indices (AI), leptin, adiponectin, resistin, interleukin-6, and high-sensitivity C-reactive protein (CRP) were measured before and four months after initiation of TCZ in 40 RA patients and 40 healthy controls. Following TCZ treatment, total cholesterol, high density lipoprotein (HDL), and triglycerides were significantly elevated, but no significant changes in weight, body mass index (BMI), low density lipoprotein (LDL), and AI were observed. Compared with controls, significantly higher adiponectin levels were measured in the RA group at baseline. Following TCZ treatment, resistin levels and the leptin-to-adiponectin ratio increased, adiponectin levels decreased, and leptin levels remained unchanged. No correlation was found between the change in adipokine serum levels and changes in the disease activity indices, nor the lipid profile. In conclusion, the changes observed suggest a protective role for TCZ on the metabolic and cardiovascular burden associated with RA, but does not provide a mechanistic explanation for this phenomenon.

Leptin as an obesity marker in rheumatoid arthritis

The determination of excess of body fat mass provides a more suitable determinant of obesity in rheumatoid arthritis patients; however, body mass index (BMI) may not be accurate for the quantification of adiposity. To identify a marker of excess adiposity in women with rheumatoid arthritis (RA) using different methods for fat mass evaluation. A cross-sectional study was conducted in adult female patients with RA. Disease activity was assessed by DAS28-ESR, and obesity was determined by waist circumference (WC), BMI and dual-energy X-ray absorptiometry (DXA). The Human Bone Metabolism kit (Merck Millipore, Darmstadt, Alemanha) was used to determine the plasma levels of leptin, TNF-α, IL-6, and IL-1β by quantification of serum proteins by technical microspheres (LUMINEX, TX, USA). Adiponectin was measured by enzyme-linked immunosorbent assay sandwich kit (R&D Systems, Minneapolis, MN, USA). Eighty-nine female patients, median age of 55.4 (± 11.6) years, and median disease duration of 16.4 (± 14.9) years were included. The frequency of obesity was 33.7% according to BMI, 89.9% with WC, and 56.1% with DXA. The median serum leptin concentration was the only marker that correlated with body fat percentage according to the three methods. This correlation was positive and not influenced by DAS28, C-reactive protein, erythrocyte sedimentation rate, or inflammatory cytokines levels (IL-6, TNF-α, IL-1β). Analysis of ROC curves determined the cut-off point of 10.3 ng/mL of leptin as an obesity marker, with a sensitivity of 96.43% and a specificity of 23.81%. Serum leptin correlates positively with fat mass and is potentially useful in excess fat mass determination in clinical practice.

Leptin Upregulates Peripheral CD4+CXCR5+ICOS+ T Cells via Increased IL-6 in Rheumatoid Arthritis Patients

CD4⁺CXCR5⁺ICOS⁺ T cells, known as Tfh (T Follicular helper) cells, are required for antibody production. Abnormal production and differentiation of Tfh cells are involved in many autoimmune diseases, including rheumatoid arthritis (RA). Leptin has the property of modulating immune system. Here, we explored the effect of leptin on CD4⁺CXCR5⁺ICOS⁺ T cells production in RA patients. Serum leptin levels were measured by enzyme-linked immunosorbent assay (ELISA). Peripheral blood mononuclear cells (PBMC) stimulated with CD3/CD28 were cultured in the presence and absence of leptin and with or without anti-IL-6 receptor (anti-IL-6R), anti-IL-21R, and anti-IL-12R antibody respectively. IL-6, IL-21, and IL-12 levels were determined by ELISA. Bcl-6 was detected by reverse transcription-polymerase chain reaction. STAT1, pSTAT1, STAT3, and pSTAT3 were examined by western blot. We found that leptin levels were higher in RA patients than healthy controls. Leptin-stimulated RA PBMC upregulated CD4⁺CXCR5⁺ICOS⁺ T cells, along with increased IL-6, IL-21, and IL-12.CD4⁺CXCR5⁺ICOS⁺ T cells, Bcl-6 mRNA expression, pSTAT1, and pSTAT3 obviously declined when anti-IL-6R antibody was added into leptin-treated RA PBMC, which suggested that leptin upregulated RA CD4⁺CXCR5⁺ICOS⁺ T cells via increased IL-6 by activation of STAT1 and STAT3. We presented an innovative mechanism on how leptin participated in RA pathogenesis.

Relationship between leptin concentrations and disease activity in patients with rheumatoid arthritis

BACKGROUND AND OBJECTIVE

Multiple studies have found a direct relationship between leptin concentrations and disease activity in rheumatoid arthritis.

PATIENTS AND METHODS

We studied 77 patients with the diagnosis of rheumatoid arthritis; the leptin determination was through an enzyme immunoassay. Disease activity was assessed by the DAS-28 CRP. A multivariate logistic regression model was used to determine the association between significant variables and leptin concentrations.

RESULTS

40.3% of the patients were in remission, 41.6% were mildly active, 11.7% were moderately active and 6.5% were severely active. The results show an independent association between higher concentrations of leptin and disease activity (OR 1.7; 95% CI 1.4-3.2; p .03), the number of swollen joints (OR 4.6; 95% CI 1.7-8.3; p .000), the number of painful joints (OR 3.4; 95% CI 1.6-4.6; p .000), and the presence of metabolic syndrome (OR 1.3; 95% IC 1.2-1,9; p .045).

CONCLUSION

The data suggest that serum leptin is elevated in patients with active RA.

Baseline adiponectin and leptin levels in predicting an increased risk of disease activity in rheumatoid arthritis: A meta-analysis and systematic review

To determine the pathogenic role of adipokines, such as adiponectin and leptin, in rheumatoid arthritis (RA) by investigating whether serum levels of these adipokines correlated with disease activity in RA patients. Medline, Cochrane, EMBASE and Google Scholar were searched for studies published until 5 November 2015 reporting serum levels of leptin and adiponectin and measures of disease activity including DAS scores and radiographic progression scores (such as total change in SHS scores and number of erosions). Secondary outcomes included pain scores, functional status and health questionnaires. Only randomized controlled trials, cohort studies, or two-armed prospective or retrospective studies were included. A χ²-based test of homogeneity was performed using Cochran's Q statistic and I². A total of 917 predominantly female participants (average age range, 39-56 years) from six prospective cohort studies were included for assessment. A fixed-effects analysis was applied for leptin levels due to lack of heterogeneity among the studies (Q = 4.4364; I²=32.38). A random-effects analysis was applied to serum levels of adiponectin because of significant heterogeneity between studies (Q = 4.444, I²=77.50%). Serum leptin levels were higher in RA patients with high disease activity (pooled SMD: 0.53, 95% CI: 0.24-0.82); however, serum adiponectin levels did not correlate with RA disease activity (pooled OR: 1.38, 95% CI: 0.77-2.47). The meta-analysis provides an additional factor to determine high disease activity index in RA, that is, serum leptin levels, which can be of benefit when choosing treatment strategies.

Plasma/Serum Leptin Levels in Patients with Ankylosing Spondylitis: A Systematic Review and Meta-analysis

BACKGROUND AND AIMS

Leptin is an adipokine that has several effects on metabolism and immune system in patients with ankylosing spondylitis (AS). The present investigations of the relationship between plasma/serum leptin levels and AS are contradictory. To derive a more precise estimation on the plasma/serum leptin levels in AS patients and related factors, a meta-analysis was performed.

METHODS

Published literature that compares plasma/serum leptin levels between AS group and control group from PubMed, Embase, Cochrane Library and other databases were searched. The study quality was assessed by the Newcastle-Ottawa scale. Pooled standardized mean difference (SMD) with its 95% confidence interval (CI) was calculated by fixed-effects or random-effect model analyses. Statistical heterogeneity within studies was examined by the Q statistic.

RESULTS

A total of eight studies including 391 AS patients and 293 healthy controls were finally included in the meta-analysis. No significant differences in plasma/serum leptin levels was found between AS patients and healthy controls when all studies were pooled into the meta-analysis (pooled SMD = 0.384, 95% CI = -1.522 to 0.753). Meanwhile, subgroup analyses by gender also showed no significant differences in plasma/serum leptin levels between case group and controls.

CONCLUSION

There is no significant difference in plasma/serum leptin levels between AS patients and controls.

Serum leptin and serum leptin/serum leptin receptor ratio imbalance in obese rheumatoid arthritis patients positive for anti-cyclic citrullinated peptide antibodies

Introduction

Leptin has a prominent role in the development and maintenance of acute and chronic inflammatory states such as rheumatoid arthritis (RA) and obesity. Nevertheless, the association of serum leptin (sLep) and soluble leptin receptor (sLepR) in RA pathogenesis has not been clarified. The purpose of this study was to evaluate the association of sLep, sLepR and leptin production indexes such as sLep/fat mass ratio with clinical activity and biomarkers and anti-cyclic citrullinated peptide (anti-CCP) antibodies in RA compared with body mass index (BMI) matched control subjects.

Methods

We included 64 RA patients and 66 controls matched for age, gender and BMI. Subjects were evaluated for BMI, fat mass distribution, sLep, sLepR, sLep/fat mass ratio and sLepR/fat mass ratio. Patients were evaluated for clinical activity and anti-CCP antibodies.

Results

We found two or three fold increased sLep levels, sLep/sLepR ratio and sLep/fat mass ratio in obese anti-CCP positive RA patients vs. controls. Partial correlations showed that anti-CCP antibodies were correlated with sLep/fat mass ratio (partial r = 0.347, P = 0.033) after adjustment for age, subcutaneous adipose tissue and fat mass.

Conclusions

In preobese and obese RA patients there is and increased production of sLep according to anti-CCP positivity. This phenomenon suggests there is an additive effect of chronic inflammation resulting from RA and obesity in which leptin favors the humoral response against citrullinated proteins. In summary, the data observed in our study suggests sLep could be a surrogate marker of chronicity and humoral immunity in RA in the presence of obesity.

The role of leptin in the pathophysiology of rheumatoid arthritis

The past 20 years of research on leptin has provided important insights into its role in rheumatoid arthritis (RA). Leptin is one of the different adipokines produced by the adipose tissue that influences the endocrine system, energy homeostasis and the immune response in several ways. Leptin is known to have predominantly pro-inflammatory effects, especially in the setting of chronic inflammation. Animal models of arthritis have illustrated well the participation of leptin in the inflammatory response within the joints. In patients with RA, numerous studies have evaluated the concentrations of leptin in the bloodstream and/or the joint cavity, showing higher levels compared to control populations. Leptin has also been found to correlate with clinical or biological measurements of disease activity of RA. Conversely, the relationship between serum leptin and joint structural damage is less evident. Leptin may also promote the development of atherosclerosis in RA and may contribute to the cardiovascular consequences of the metabolic syndrome that coexists with RA. Indeed, leptin could be a link between inflammation, metabolic risk factors and cardiovascular diseases in RA. Finally, due to abnormal body composition phenotypes with an increased prevalence of obesity in RA, the therapeutic response to traditional DMARDs and/or biological agents may be attenuated. This review discusses the multiple interplays that have been described between leptin and the clinical, radiographic and therapeutic aspects of RA.

Serum leptin levels in pemphigus: a case control study

BACKGROUND

Pemphigus is an autoimmune blistering disease mediated by autoantibodies directed against keratinocyte adhesion molecules. Leptin, an adipocyte-derived hormone, plays a role in immune responses and promotes autoimmunity.

OBJECTIVES

This study was conducted to determine whether serum leptin levels are altered in pemphigus patients and whether there is any correlation between leptin levels and the severity of disease.

METHODS

This study included 47 newly diagnosed patients with pemphigus and 43 age- and sex-matched healthy controls. Clinical characteristics and pemphigus area and activity score (PAAS) were assessed. Serum leptin levels (ng/mL) were measured by a commercial enzyme-linked immunosorbent assay (ELISA).

RESULTS

Patients did not differ significantly in serum leptin levels from healthy controls (median (range): 10.8 (0.1-110) ng/mL versus 12 (0.5-69.9) ng/mL and P = 0.53). There was no significant association between serum leptin concentrations and severity of disease measured by PAAS (r s = 0.06, P = 0.70).

CONCLUSION

The results suggest that pemphigus does not have a direct influence on serum leptin levels and the pathogenesis of pemphigus seems to be not dependent on the connection with adipose tissue.