Relationship Between Insulin Sensitivity and β-Cell Secretion in Nondiabetic Subjects with Rheumatoid Arthritis

Understanding the Role of the Complement System in Insulin Resistance and Metabolic Syndrome in Patients With Rheumatoid Arthritis

OBJECTIVE

The complement system has been associated with the etiopathogenesis of rheumatoid arthritis (RA). Insulin resistance (IR) and metabolic syndrome (MetS) are prevalent among patients with RA. The aim of this study was to explore the relationship between a comprehensive evaluation of the complement system and IR, as well as MetS, in patients with RA.

METHODS

A total of 339 nondiabetic patients with RA were recruited. Functional assays of the 3 complement pathways were assessed. Additionally, serum levels of the following individual components of the complement system were measured: C1q (classical); lectin (lectin); C2, C4, and C4b (classical lectin); factor D and properdin (alternative); C3 and C3a (common); C5, C5a, and C9 (terminal); as well as the factor I and C1 inhibitor regulators. IR and β cell function indices were calculated using the homeostatic model assessment. Criteria for MetS were applied. Multivariable linear regression analysis was performed to investigate the association between the complement system and IR in patients with RA.

RESULTS

Many elements of the upstream and common complement pathways, but not the functional tests of the 3 routes, correlated positively with higher levels of IR and β cell function. However, after multivariable adjustment for factors associated with IR, these relationships were lost. Conversely, the presence of MetS in patients with RA maintained a relationship with higher levels of C1q, C4, C3, properdin, and factor I after adjusting for confounders.

CONCLUSION

There is a positive correlation between the complement system and MetS among nondiabetic patients with RA. This association is independent of traditional IR factors.

Malondialdehyde Serum Levels in a Full Characterized Series of 430 Rheumatoid Arthritis Patients

Background. Oxidative stress has been involved in the pathogenesis of rheumatoid arthritis (RA). The serum malondialdehyde (MDA) level is a reliable biomarker of oxidative stress status. In the present work, we aimed to analyze how a comprehensive characterization of the disease characteristics in RA, including a lipid profile, insulin resistance, and subclinical atherosclerosis, relates to serum MDA levels. Methods. In a cross-sectional study that included 430 RA patients, serum MDA levels were evaluated. Multivariable analysis was performed to examine the relationship of MDA with disease activity scores and disease characteristics, including subclinical carotid atherosclerosis, a comprehensive lipid molecule profile, and indices of insulin resistance and beta cell function indices. Results. The erythrocyte sedimentation rate (ESR) showed a significant and positive relationship with MDA. However, this did not occur for other acute phase reactants such as C-reactive protein or interleukin-6. Although the DAS28-ESR score (Disease Activity Score in 28 joints) had a positive and significant association with MDA serum levels, other disease activity scores that do not use the erythrocyte sedimentation rate in their formula did not show a significant relationship with MDA. Other disease characteristics, such as disease duration and the existence of rheumatoid factor and antibodies against citrullinated protein, were not related to serum MDA levels. This also occurred for lipid profiles, insulin resistance indices, and subclinical carotid atherosclerosis, for which no associations with circulating MDA were found. Conclusions. The disease characteristics are not related to circulating MDA levels in patients with RA.

The Ratio of Monocytes to HDL-Cholesterol Is Associated with Cardiovascular Risk and Insulin Resistance in Patients with Rheumatoid Arthritis

The monocytes to high-density lipoprotein (HDL)-cholesterol ratio (MHR) indicates inflammation based on the anti-inflammatory properties of HDL-cholesterol as well as the pro-inflammatory effect of monocytes. Several studies have investigated MHR in various disorders, specifically in cardiovascular diseases. Consequently, MHR has been significantly associated with cardiovascular and all-cause mortality in the general population, regardless of established risk factors. However, its role in the augmented risk of cardiovascular disease found in rheumatoid arthritis (RA) has not been studied to date. This is a cross-sectional study that encompassed 430 patients with RA and 208 controls matched by sex and age. Complete blood cell count and complete lipid profile were evaluated. Multivariable analysis was made to analyze the relationship between MHR and RA disease and features subclinical carotid atherosclerosis, and traditional CV factors including insulin resistance and beta cell function indices. MHR values did not differ between controls and patients after multivariable adjustment (12 ± 6 vs. 11 ± 6, p = 0.18). No relationship between this ratio and the characteristics of the disease was found excluding ESR, which showed a significant and positive association with MHR after adjustment for covariates. MHR significantly correlated with Systematic Coronary Risk Evaluation-2 (SCORE2) cardiovascular risk algorithm, and insulin resistance and beta cell function parameters after adjustment. In conclusion, MHR does not differ between patients with RA and controls. The relationship of this biomarker with disease-related data is poor. However, MHR is highly and positively related to cardiovascular risk and insulin resistance in RA.

Apolipoprotein C-III is linked to the insulin resistance and beta-cell dysfunction that are present in rheumatoid arthritis

Background

Insulin resistance and beta-cell dysfunction are manifestations of rheumatoid arthritis (RA). Apolipoprotein C-III (ApoC3) has been associated with such insulin resistance and beta-cell dysfunction in the general population. Our purpose was to study whether ApoC3 is also related to the insulin resistance and beta-cell dysfunction that are present in patients with RA.

Methods

Three hundred thirty-eight non-diabetic patients with RA who had a glycemia lower than 110 mg/dl were recruited. Insulin, C-peptide, and ApoC3 were assessed. Insulin resistance and beta-cell function were calculated using the Homeostasis Model Assessment (HOMA2) indices. A multivariable regression analysis was performed to study the relationship of ApoC3 with those molecules and indices adjusting for classic factors associated with insulin resistance that included glucocorticoids.

Results

ApoC3 was related to significant higher levels of circulating insulin (beta coef. 0.37 [95%CI 0.01–0.73] µU/ml, p = 0.044) and C-peptide (beta coef. 0.13 [95%CI 0.05–0.22] ng/ml, p = 0.003), and higher insulin resistance —HOMA2-IR— (beta coef. 0.05 [95%CI 0.00–0.09], p = 0.041) and beta-cell dysfunction —HOMA2-%B— (beta coef. 2.94 [95%CI 0.07–5.80], p = 0.044) indices. This was found after a fully multivariable analysis that included, among others, prednisone intake and the classic factors associated with carbohydrate metabolism such as triglycerides, waist circumference, and obesity.

Conclusion

ApoC3, insulin resistance, and beta-cell dysfunction are independently associated in patients RA.

High prevalence of undiagnosed impaired glucose tolerance in patients with rheumatoid arthritis

Objectives

Although the risk of diabetes mellitus has been recognised in rheumatoid arthritis, undiagnosed dysglycaemia remained under-reported. The study aimed to determine the prevalence and associated factors of dysglycaemia among patients with rheumatoid arthritis, utilising the oral glucose tolerance test.

Methods

This cross-sectional study involved patients with rheumatoid arthritis, aged ⩾30 years. Following an oral glucose tolerance test, they were divided into two: dysglycaemia and normoglycaemia. Demographic and laboratory parameters were compared using logistic regression analyses.

Results

There were 35.5% (55/155) patients with dysglycaemia (including 25.8% impaired glucose tolerance, 7.1% diabetes mellitus and 1.9% with both impaired fasting glucose and impaired glucose tolerance). Patients with dysglycaemia were heavier (65.5 ± 12.3 versus 60.7 ± 10.6 kg, p = 0.01), had wider waist (89.0 ± 12.5 versus 83.1 ± 9.6 cm, p < 0.01), lower high-density lipoprotein cholesterol (1.4 ± 0.3 versus 1.5 ± 0.4 mmol/L, p = 0.02), higher triglyceride (1.3 (0.9-1.8) versus 0.9 (0.8-1.2) mmol/L, p < 0.01) and intercellular adhesion molecule-1 (361.79 (290.38-481.84) versus 315.92 (251.45-407.93) ng/mL, p = 0.01). History of smoking (odds ratio: 5.70, confidence interval: 1.27-25.7), elevated triglyceride (odds ratio: 2.87, confidence interval: 1.33-6.22) and intercellular adhesion molecule-1 (odds ratio: 1.003, confidence interval: 1.001-1.006) were significantly associated with dysglycaemia.

Conclusions

Prevalence of undiagnosed dysglycaemia, particularly impaired glucose tolerance, was high in these patients with rheumatoid arthritis, using a 75-g oral glucose tolerance test, which was not associated with disease activity or corticosteroid use. Those with high triglyceride, history of smoking and elevated intercellular adhesion molecule-1 were the two significant predictors for dysglycaemia in our patients with rheumatoid arthritis. Oral glucose tolerance test could be an important laboratory investigation for dysglycaemia in these high-risk patients.

Insulin Signaling in Arthritis

Inflammatory arthritis is burdened by an increased risk of metabolic disorders. Cytokines and other mediators in inflammatory diseases lead to insulin resistance, diabetes and hyperlipidemia. Accumulating evidence in the field of immunometabolism suggests that the cause-effect relationship between arthritis and metabolic abnormalities might be bidirectional. Indeed, the immune response can be modulated by various factors such as environmental agents, bacterial products and hormones. Insulin is produced by pancreatic cells and regulates glucose, fat metabolism and cell growth. The action of insulin is mediated through the insulin receptor (IR), localized on the cellular membrane of hepatocytes, myocytes and adipocytes but also on the surface of T cells, macrophages, and dendritic cells. In murine models, the absence of IR in T-cells coincided with reduced cytokine production, proliferation, and migration. In macrophages, defective insulin signaling resulted in enhanced glycolysis affecting the responses to pathogens. In this review, we focalize on the bidirectional cause-effect relationship between impaired insulin signaling and arthritis analyzing how insulin signaling may be involved in the aberrant immune response implicated in arthritis and how inflammatory mediators affect insulin signaling. Finally, the effect of glucose-lowering agents on arthritis was summarized.

Impact of disease activity on impaired glucose metabolism in patients with rheumatoid arthritis

Objective

To explore glucose metabolism in rheumatoid arthritis (RA) and its association with insulin resistance (IR) risk factors and disease activity indicators, including matrix metalloproteinase-3 (MMP3).

Methods

This single-center study included 127 non-diabetic subjects: 90 RA patients and 37 matched controls. IR-related risk factors, disease activity (DAS28-ESR/CRP), concentrations of inflammation markers, MMP3, glucose, specific insulin, and C-peptide (a marker of β-cell secretion) were determined. Homeostasis Model Assessment was used to establish insulin resistance (HOMA2-IR) and sensitivity (HOMA2-%S). Associations of HOMA2 indices with IR-related risk factors, inflammation markers, and RA activity were tested using multiple regression analyses.

Results

RA patients had significantly increased HOMA2-IR index than controls. In the RA group, multivariate analysis revealed DAS28-ESR, DAS28-CRP, tender joint counts, patient’s global assessment, and MMP3 level as significant positive predictors for HOMA2-IR (β = 0.206, P = 0.014; β = 0.192, P = 0.009; β = 0.121, P = 0.005; β = 0.148, P = 0.007; β = 0.075, P = 0.025, respectively), and reciprocal negative for HOMA2-%S index. According to the value of the coefficient of determination (R²), DAS28-ESR ≥ 5.1 has the largest proportion of variation in both HOMA2-IR indices. DAS28-ESR ≥ 5.1 and ESR were independent predictors for increased C-peptide concentration (β = 0.090, P = 0.022; β = 0.133, P = 0.022). Despite comparability regarding all IR-related risk factors, patients with DAS28-ESR ≥ 5.1 had higher HOMA2-IR than controls [1.7 (1.2–2.5) vs. 1.2 (0.8–1.4), P = 0.000]. There was no difference between patients with DAS28-ESR < 5.1 and controls [1.3 (0.9–1.9) vs. 1.2 (0.8–1.4), P = 0.375].

Conclusions

RA activity is an independent risk factor for impaired glucose metabolism. DAS28-ESR ≥ 5.1 was the main contributor to this metabolic disturbance, followed by MMP3 concentration, outweighing the impact of classic IR-related risk factors.

The effect of anti-TNF treatment on body composition and insulin resistance in patients with rheumatoid arthritis

Given the link between systemic inflammation, body composition and insulin resistance (IR), anti-inflammatory therapy may improve IR and body composition in inflammatory joint diseases. This study assesses the IR and beta cell function in rheumatoid arthritis (RA) patients with active disease compared to osteoarthritis (OA) patients and investigates the effect of anti-TNF treatment on IR, beta cell function and body composition in RA. 28 Consecutive RA patients starting anti-TNF treatment (adalimumab), and 28 age, and sex-matched patients with OA were followed for 6 months. Exclusion criteria were use of statins, corticosteroids, and cardiovascular or endocrine co-morbidity. Pancreatic beta cell function and IR, using the homeostasis model assessment (HOMA2), and body composition, using dual-energy X-ray absorptiometry (DXA) were measured at baseline and 6 months. At baseline, IR [1.5 (1.1–1.8) vs. 0.7 (0.6–0.9), 100/%S] and beta cell function (133% vs. 102%) were significantly (p < 0.05) higher in RA patients with active disease as compared to OA patients. After 6 months of anti-TNF treatment, IR [1.5 (1.1–1.8) to 1.4 (1.1–1.7), p = 0.17] slightly improved and beta cell function [133% (115–151) to 118% (109–130), p <0.05] significantly improved. Improvement in IR and beta cell function was most pronounced in RA patients with highest decrease in CRP and ESR. Our observations indicate that IR and increased beta cell function are more common in RA patients with active disease. Anti-TNF reduced IR and beta cell function especially in RA patients with highest decrease in systemic inflammation and this effect was not explained by changes in body composition.

Insulin resistance in non-diabetes patients with spondyloarthritis

Objectives: Insulin resistance (IR) constitutes a major underlying abnormality driving cardiovascular disease in the general population and has been linked to inflammatory diseases. In this study, we aimed to determine the prevalence of IR in patients with spondyloarthritis (SpA) and whether IR can be explained by disease-related features in such cases. Method: The study included 577 subjects: 306 patients diagnosed with SpA according to Assessment of SpondyloArthritis international Society criteria and 271 controls. Insulin and C-peptide serum levels, IR and β-cell function (%B) indices by homoeostatic model assessment (HOMA2), and lipid profiles were assessed in patients and controls. A multivariable regression analysis was performed to evaluate the differences in IR indices between patients and controls and to determine how IR is associated with disease-related characteristics in SpA patients. Results: HOMA2-%B and HOMA2-IR scores, both calculated with insulin or C-peptide, had significantly higher values in SpA patients compared to controls in multivariable analysis adjusted for age, gender, traditional IR-related factors, and glucocorticoid intake. Disease activity, functional status, and metrological SpA indices were positively related to IR, but only in univariable analysis. Disease duration and positivity for human leucocyte antigen-B27 were independently associated with a higher HOMA2-%B after multivariable analysis. Conclusion: Patients with SpA have an increased IR compared to controls. SpA disease-related data are independently associated with β-cell dysfunction.

Higher Prevalence and Degree of Insulin Resistance in Patients With Rheumatoid Arthritis Than in Patients With Systemic Lupus Erythematosus

OBJECTIVE

Since insulin resistance (IR) is highly prevalent in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), we aimed to determine whether differences in IR exist between the two conditions.

METHODS

We conducted a cross-sectional study comprising 413 subjects without diabetes (186 with SLE and 227 with RA). Glucose, insulin, and C-peptide serum levels, as well as IR by the homeostatic model assessment (HOMA2) were studied. A multivariable regression analysis was performed to evaluate the differences in IR indexes between patients with SLE and RA, as well as to determine if IR risk factors or disease-related characteristics are differentially associated with IR in both populations.

RESULTS

The insulin:C-peptide molar ratio was upregulated in patients with RA compared to patients with SLE (β 0.009, 95% CI 0.005-0.014, P < 0.001) after multivariable analysis. HOMA2 indexes related to insulin sensitivity (HOMA2-%S) were found to be lower (β -27, 95% CI -46 to -9, P = 0.004) and β cell function (HOMA2-%B) showed higher IR indexes (β 38, 95% CI 23-52, P < 0.001) in RA than in SLE patients after multivariable analysis. Patients with RA more often fulfilled the definition of IR than those with SLE (OR 2.15, 95% CI 1.25-3.69, P = 0.005). The size effect of IR factors on IR indexes was found to be equal in both diseases.

CONCLUSION

IR sensitivity is lower and β cell function is higher in RA than in SLE patients. The fact that traditional IR factors have an equal effect on IR in both SLE and RA supports the contention that these differences are related to the diseases themselves.