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Increased circulatory levels of fractalkine (CX3CL1) are associated with inflammatory chemokines and cytokines in individuals with type-2 diabetes.

ABSTRACT: BACKGROUND:Fractalkine (CX3CL1) is involved in the development of numerous inflammatory conditions including metabolic diseases. However, changes in the circulatory fractalkine levels in type-2 diabetes (T2D) and their relationship with inflammatory chemokines/cytokines remain unclear. The aim of the study was to determine the T2D-associated modulations in plasma fractalkine levels and investigate their relationship with circulatory chemokines/cytokines. METHODS:A total of 47 plasma samples were collected from 23 T2D and 24 non-diabetic individuals selected over a wide range of body mass index (BMI). Clinical metabolic parameters were determined using standard commercial kits. Fractalkine and chemokines/cytokines were measured using Luminex X-MAP® technology. C-reactive protein (CRP) was measured by ELISA. The data were compared using unpaired t-test and the dependence between two variables was assessed by Pearson's correlation coefficient (r). RESULTS:Plasma fractalkine levels were significantly higher (P?=?0.005) in T2D patients (166?±?14.22 pg/ml) as compared with non-diabetics (118?±?8.90 pg/ml). In T2D patients, plasma fractalkine levels correlated positively (P???0.05) with inflammatory chemokines/cytokines including CCL3 (r?=?0.52), CCL4 (r?=?0.85), CCL11 (r?=?0.51), CXCL1 (r?=?0.67), G-CSF (r?=?0.91), IFN-?2 (r?=?0.97), IL-17A (r?=?0.79), IL-1? (r?=?0.97), IL-12P70 (r?=?0.90), TNF-? (r?=?0.58), and IL-6 (r?=?0.60). In non-diabetic individuals, fractalkine levels correlated (P???0.05) with those of CCL4 (r?=?0.49), IL-1? (r?=?0.73), IL-12P70 (r?=?0.41), and TNF-? (r?=?0.50). Notably, plasma fractalkine levels in T2D patients associated with systemic inflammation (CRP) (r?=?0.65, P?=?0.02). CONCLUSIONS:The altered plasma fractalkine levels associate differentially with inflammatory chemokines/cytokines in T2D patients which may have implications for T2D immunopathogenesis.

SUBMITTER: Sindhu S

PROVIDER: S-EPMC5379731 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Increased circulatory levels of fractalkine (CX3CL1) are associated with inflammatory chemokines and cytokines in individuals with type-2 diabetes.

Sindhu Sardar S Akhter Nadeem N Arefanian Hossein H Al-Roub Areej Abu AA Ali Shamsha S Wilson Ajit A Al-Hubail Asma A Al-Beloushi Shaima S Al-Zanki Saad S Ahmad Rasheed R

Journal of diabetes and metabolic disorders 20170404

<h4>Background</h4>Fractalkine (CX3CL1) is involved in the development of numerous inflammatory conditions including metabolic diseases. However, changes in the circulatory fractalkine levels in type-2 diabetes (T2D) and their relationship with inflammatory chemokines/cytokines remain unclear. The aim of the study was to determine the T2D-associated modulations in plasma fractalkine levels and investigate their relationship with circulatory chemokines/cytokines.<h4>Methods</h4>A total of 47 plas ...[more]

PMID: 28396851

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Project description:BackgroundFractalkine (CX3CL1) promotes migration and adhesion of lymphocytes and monocytes to inflamed tissues. Prior studies show a role for CX3CL1 in atherosclerosis. The relationship between inflammatory cytokines, cholesterol, and CX3CL1 levels in human subjects without known coronary artery disease is not well characterized. The goal of our study was to assess baseline CX3CL1 levels, and after modulation of cholesterol levels by statins to determine if CX3CL1 is linked to cholesterol levels or inflammatory stimuli.MethodsWe performed a blinded, randomized hypothesis generating study in human subjects without known coronary artery disease treated sequentially with three statins of differing potencies. Fractalkine (CX3CL1), GM-CSF, VEGF-A, other chemokines, and lipid levels were measured. Mechanistic studies of CX3CL1 induction by LDL cholesterol and TNFα in cultured human endothelial cells were performed using real-time PCR.ResultsTherapy with statins reduced total and LDL cholesterol levels as expected. CX3CL1 levels were significantly reduced from no statin control levels (89.9 ± 18.5 pg/mL) after treatment with atorvastatin (60.0 ± 7.8 pg/mL), pravastatin (54.2 ± 7.0 pg/mL) and rosuvastatin (65.6 ± 7.3 pg/mL) (χ (2)(2) = 17.4, p ≤ 0.001). Cholesterol is not a known regulator of CX3CL1. We found GM-CSF (r(2) = 0.524; p < 0.005) and VEGF-A (r(2) = 0.4; p < 0.005) levels were highly and positively correlated with CX3CL1. Total (r(2) = 0.086) and LDL cholesterol (r(2) = 0.059) levels weakly correlated with CX3CL1 levels. Finally, we tested whether LDL cholesterol could induce CX3CL1, GM-CSF, and VEGF-A in human endothelial cells, versus TNFα. LDL cholesterol alone resulted in small, non-significant increases in CX3CL1 and GM-CSF, while TNFα resulted in > 10-fold induction.ConclusionsOur findings suggest that while statins suppress CX3CL1 levels, inflammatory cytokines may be the major regulator of CX3CL1 levels rather than cholesterol itself. Additional studies in a larger patient population are needed to confirm these findings, determine if CX3CL1 levels reflect inflammation levels, and potentially add to standard risk factors in prediction of atherosclerotic disease events.

Project description:BackgroundCardiometabolic disease is a major cause of morbidity and mortality in persons with chronic kidney disease (CKD). Fractalkine (CX3CL1) is a potential mediator of both atherosclerosis and metabolic disease. Studies of the relationship of CX3CL1 with risk of cardiovascular disease (CVD) events and metabolic traits are lacking, particularly in the high-risk setting of CKD.Study designCross-sectional and longitudinal observational analysis.Setting & participantsAdults with CKD from 7 US sites participating in the Chronic Renal Insufficiency Cohort (CRIC) Study.PredictorQuartiles of plasma CX3CL1 levels at baseline.OutcomesBaseline estimated glomerular filtration rate from a creatinine and cystatin C-based equation, prevalent and incident CVD, diabetes, metabolic syndrome and its criteria, homeostatic model assessment of insulin resistance, hemoglobin A1c level, myocardial infarction, all-cause mortality, and the composite outcome of myocardial infarction/all-cause mortality.ResultsAmong 3,687 participants, baseline CX3CL1 levels were associated positively with several CVD risk factors and metabolic traits, lower estimated glomerular filtration rate, and higher levels of inflammatory cytokines, as well as prevalent CVD (OR, 1.09; 95% CI, 1.01-1.19; P=0.03). Higher CX3CL1 level also was associated with prevalent diabetes (OR, 1.26; 95% CI, 1.16-1.38; P<0.001) in adjusted models. During a mean follow-up of 6 years, there were 352 deaths, 176 myocardial infarctions, and 484 composite outcomes. In fully adjusted models, 1-SD higher CX3CL1 level increased the hazard for all-cause mortality (1.11; 95% CI, 1.00-1.22; P=0.02) and the composite outcome (1.09; 95% CI, 1.00-1.19; P=0.04).LimitationsStudy design did not allow evaluation of changes over time, correlation with progression of phenotypes, or determination of causality of effect.ConclusionsCirculating CX3CL1 level may contribute to both atherosclerotic CVD and diabetes in a CKD cohort. Further studies are required to establish mechanisms through which CX3CL1 affects the pathogenesis of atherosclerosis and diabetes.

Project description:ObjectiveWe have previously shown the existence of a muscle-pancreas intercommunication axis in which CX3CL1 (fractalkine), a CX3C chemokine produced by skeletal muscle cells, could be implicated. It has recently been shown that the fractalkine system modulates murine β-cell function. However, the impact of CX3CL1 on human islet cells especially regarding a protective role against cytokine-induced apoptosis remains to be investigated.MethodsGene expression was determined using RNA sequencing in human islets, sorted β- and non-β-cells. Glucose-stimulated insulin secretion (GSIS) and glucagon secretion from human islets was measured following 24 h exposure to 1-50 ng/ml CX3CL1. GSIS and specific protein phosphorylation were measured in rat sorted β-cells exposed to CX3CL1 for 48 h alone or in the presence of TNFα (20 ng/ml). Rat and human β-cell apoptosis (TUNEL) and rat β-cell proliferation (BrdU incorporation) were assessed after 24 h treatment with increasing concentrations of CX3CL1.ResultsBoth CX3CL1 and its receptor CX3CR1 are expressed in human islets. However, CX3CL1 is more expressed in non-β-cells than in β-cells while its receptor is more expressed in β-cells. CX3CL1 decreased human (but not rat) β-cell apoptosis. CX3CL1 inhibited human islet glucagon secretion stimulated by low glucose but did not impact human islet and rat sorted β-cell GSIS. However, CX3CL1 completely prevented the adverse effect of TNFα on GSIS and on molecular mechanisms involved in insulin granule trafficking by restoring the phosphorylation (Akt, AS160, paxillin) and expression (IRS2, ICAM-1, Sorcin, PCSK1) of key proteins involved in these processes.ConclusionsWe demonstrate for the first time that human islets express and secrete CX3CL1 and CX3CL1 impacts them by decreasing glucagon secretion without affecting insulin secretion. Moreover, CX3CL1 decreases basal apoptosis of human β-cells. We further demonstrate that CX3CL1 protects β-cells from the adverse effects of TNFα on their function by restoring the expression and phosphorylation of key proteins of the insulin secretion pathway.

Dataset Information

Increased circulatory levels of fractalkine (CX3CL1) are associated with inflammatory chemokines and cytokines in individuals with type-2 diabetes.

Publications

Increased circulatory levels of fractalkine (CX3CL1) are associated with inflammatory chemokines and cytokines in individuals with type-2 diabetes.

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