Patients with insulin-dependent diabetes or coronary heart disease following rehabilitation express serum fractalkine levels similar to those in healthy control subjects

Chemokines in Prediabetes and Type 2 Diabetes: A Meta-Analysis

Background

A growing number of studies found inconsistent results on the role of chemokines in the progression of type 2 diabetes (T2DM) and prediabetes (PDM). The purpose of this meta-analysis was to summarize the results of previous studies on the association between the chemokines system and T2DM/PDM.

Methods

We searched in the databases, PubMed, Web of Science, Embase and Cochrane Library, for eligible studies published not later than March 1, 2020. Data extraction was performed independently by 2 reviewers, on a standardized, prepiloted form. Group differences in chemokines concentrations were summarized using the standardized mean difference (SMD) with a 95% confidence interval (CI), calculated by performing a meta-analysis using the random-effects model.

Results

We identified 98 relevant studies that investigated the association between 32 different chemokines and T2DM/PDM. Altogether, these studies involved 14,708 patients and 14,574 controls. Results showed that the concentrations of CCL1, CCL2, CCL4, CCL5, CCL11, CXCL8, CXCL10 and CX3CL1 in the T2DM patients were significantly higher than that in the controls, while no difference in these concentrations was found between the PDM patients and controls.

Conclusion

Progression of T2DM may be associated with elevated concentrations of chemokines.

Meta-Analysis Registration

PROSPERO, identifier CRD42019148305.

Fractalkine in obstructive sleep apnea patients

BACKGROUND

Obstructive sleep apnea (OSA) is the most common sleep disorder affecting 2-4 % of the adult population. In addition to several potential mechanisms, inflammation is one of the suggested etiological factors in OSA. Fractalkine/CX3CL1 which is detected in activated or stressed endothelium, smooth muscle cells, skeletal muscle cells, macrophages, neurons, and hepatocytes is an inflammatory marker and attracts attention of sleep specialists in OSA pathogenesis. In this study, we had two goals. The first one was to investigate the role of fractalkine in OSA pathogenesis while the second one was to detect the impact of OSA treatment with positive airway pressure (PAP) on serum fractalkine levels.

METHOD

This study included 34 patients (6 females, 28 males) diagnosed as OSA and 20 healthy controls (4 females, 16 males). Initial serum fractalkine levels of both groups were first evaluated in order to demonstrate any potential relation of OSA with fractalkine. Subsequently, serum fractalkine levels of the OSA patients were evaluated following 1 week of PAP treatment to demonstrate the impact of PAP treatment on serum fractalkine levels.

RESULTS

Although there was no significant difference between OSA patients and healthy controls by means of plasma fractalkine levels (p, 0.67) statistically, plasma fractalkine levels significantly decreased in OSA patients after 1 week of PAP treatment (p, 0.001).

CONCLUSION

This study showed that fractalkine, a potential mediator of chronic inflammation, was not sensitive in diagnosing OSA but might be an indicator of the success of OSA treatment.

Circulating fractalkine levels predict the development of the metabolic syndrome

The fractalkine/CX3CR1 axis plays an important role in regulating glucose and lipid metabolism. However, the role of fractalkine in metabolic disorders remains to be fully elucidated. We selected 887 Chinese (40-65 years old) at baseline, with a subgroup of 459 participants examined again 2 years later. The relationship of serum fractalkine levels with the metabolic syndrome (MetS) and its components was investigated. At baseline, participants with MetS had higher fractalkine concentrations than their counterparts without MetS (P < 0.001). At the 2-year follow-up, participants in the highest quartile of baseline fractalkine exhibited higher values for body mass index, waist circumference, waist-to-hip ratio, body fat percentage, glucose, insulin, total cholesterol, triglycerides (TG), and homeostasis model assessment of insulin resistance (HOMA-IR) and lower value for high density lipoprotein-cholesterol (HDL-c) (all P < 0.05). Among 390 participants without MetS at baseline, 45 developed it at year 2. Even after multiple adjustments for visceral adipose tissue area, HOMA-IR, C-reactive protein (CRP), or TG and HDL-c, baseline fractalkine predicted the development of MetS (OR = 7.18, 95%CI: 2.28-18.59). In conclusion, circulating fractalkine predicts the development of the MetS independently of central obesity, CRP, insulin resistance, and dyslipidemia.

Chemokines and atherosclerosis: focus on the CX3CL1/CX3CR1 pathway

Atherosclerosis is currently considered an inflammatory disease. Much attention has been focused on the potential role of inflammatory mediators as prognostic/diagnostic markers or therapeutic targets of atherosclerotic cardiovascular disease. CX3CL1 (or fractalkine) is a structurally and functionally unique chemokine with a well documented role in atherosclerosis. In its membrane bound form it promotes the firm adhesion of rolling leucocytes onto the vessel wall, while in its soluble form it serves as a potent chemoattractant for CX3CR1-expressing cells. Additionally, CX3CL1 exerts cytotoxic effects on the endothelium as well as anti-apoptotic and proliferative effects on vascular cells, affecting the context and stability of the atherosclerotic plaque. Studies on animal models have shown that the blockade of the CX3CL1/CX3CR1 pathway ameliorates the severity of atherosclerosis, while genetic epidemiology has confirmed that a genetically-defined less active CX3CL1/CX3CR1 pathway is associated with a reduced risk of atherosclerotic disease in humans. Although several studies support an important pathogenic role of CX3CL1/CX3CR1 in atherogenesis and plaque destabilization, this does not necessarily suggest that this pathway is a suitable therapeutic target or that CX3CL1 can serve as a prognostic/diagnostic biomarker. Further studies on the CX3CL1/CX3CR1 chemokine pathway are clearly warranted to justify the clinical relevance of its role in atherosclerosis.

Fractalkine and its receptor (CX3CR1) in patients with stable coronary artery disease and diabetes mellitus

BACKGROUND

Fractalkine and its receptor CX3CR1 are associated with atherosclerosis. In vitro studies have shown increased expression of fractalkine in endothelial and vascular smooth muscle cells when stimulated with a high concentration of glucose. Increased serum levels of fractalkine have been shown in patients with type 2 diabetes mellitus (T2DM) and also in unstable coronary artery disease (CAD) patients. We investigated whether CAD patients with T2DM or metabolic syndrome have increased circulating and gene expression levels of fractalkine compared to CAD patients without these conditions.

METHODS

Serum levels of fractalkine were analyzed by the enzyme-linked immunosorbent assay (ELISA) method in 1001 patients with angiographically verified CAD, of which 200 had T2DM and 244 had metabolic syndrome. All patients were taking aspirin as an antithrombotic treatment. Gene expression of fractalkine and CX3CR1 in circulating leukocytes was explored in a subset of patients (n=168).

RESULTS

We found no significant difference in circulating levels of fractalkine in patients with T2DM [653 (556, 775) pg/mL] compared to patients without T2DM [646 (553, 761) pg/mL], p=0.50. There was also no difference between patients with and without metabolic syndrome (p=0.60). Fractalkine was not expressed in circulating leukocytes, and CX3CR1 was not expressed differently between any of the groups (p=0.13 and p=0.32, respectively). Smokers had lower fractalkine levels (p<0.001), and patients on angiotensin II receptor blockers had higher levels (p=0.047) compared to nonaffected patients.

CONCLUSIONS

In the present CAD population, no differences in circulating levels of fractalkine or expression levels of CX3CR1 were observed between patients with and without T2DM, or with and without metabolic syndrome, which may be related to their underlying disease.