Elevated plasma fractalkine levels are associated with higher levels of IL-6, Apo-B, LDL-C and insulin, but not with body composition in a large female twin sample

Physical exercise is associated with a reduction in plasma levels of fractalkine, TGF-β1, eotaxin-1 and IL-6 in younger adults with mobility disability

Mobility disability (MD) refers to substantial limitations in life activities that arise because of movement impairments. Although MD is most prevalent in older individuals, it can also affect younger adults. Increasing evidence suggests that inflammation can drive the development of MD and may need to be targeted for MD prevention. Physical exercise has anti-inflammatory properties and has been associated with MD prevention. However, no studies to date have examined whether exercise interventions affect the peripheral inflammatory status in younger adults with MD. To this end, we used blood samples from young and middle-aged adults with MD (N = 38; median age = 34 years) who participated in a 12-week intervention that included aerobic and resistance exercise training. A pre-post assessment of inflammatory biomarkers was conducted in plasma from two timepoints, i.e., before the exercise trial and at follow-up (3–7 days after the last exercise session). We successfully measured 15 inflammatory biomarkers and found that exercise was associated with a significant reduction in levels of soluble fractalkine, transforming growth factor beta 1 (TGF-β1), eotaxin-1 and interleukin (IL) 6 (corrected α = 0.004). We also found significant male-specific effects of exercise on (i) increasing IL-16 and (ii) decreasing vascular endothelial growth factor-A (VEGF-A). In line with our results, previous studies have also found that exercise can reduce levels of TGF-β1, eotaxin-1 and IL-6. However, our finding that exercise reduces plasma levels of fractalkine in younger adults with MD, as well as the sex-dependent findings, have not been previously reported and warrant replication in larger cohorts. Given the suggested role of inflammation in promoting MD development, our study provides additional support for the use of physical exercise as a treatment modality for MD.

Impact of Vitamin D Supplementation on Inflammatory Markers' Levels in Obese Patients

In view of research suggesting a possible beneficial impact of vitamin D on systemic inflammatory response, the authors decided to investigate an influence of vitamin D supplementation on serum levels of certain inflammatory markers in obese patients. The current study included such biomarkers as interleukin-6 (IL-6), pituitary adenylate cyclase-activating peptide (PACAP), advanced oxidation protein products (AOPP), C-X3-C Motif Chemokine Ligand 1 (CX3CL1), monocyte chemoattractant protein-1 (MCP-1), and nitric oxide (NO). The measurements were performed with the ELISA method before and after 3-month-long supplementation of 2000 IU of vitamin D orally. The results showed that the therapy did not induce any statistically significant changes in serum levels of MCP-1, IL-6, CX3CL1, and PACAP. The supplementation was related to a significant increase in measurements of NO and AOPP levels, although the correlation analysis between vitamin D concentration after its supplementation and the concentration of the molecular parameters did not show significant relation. In conclusion, our study seems to contradict certain aspects of findings available in the literature regarding the vitamin D’s impact.

Novel insights into the pathological mechanisms of metabolic related dyslipidemia

Due to the technological advances, it has been well-established that obesity is strongly correlated with various health problems. Among these problems, dyslipidemia is one of the most important concomitant symptoms under obese status which is the main driving force behind the pathological progression of cardio-metabolic disorder diseases. Importantly, the type of dyslipidemia, arising from concerted action of obesity, has been identified as "metabolic related dyslipidemia", which is characterized by increased circulating levels of Low density lipoprotein cholesterol (LDL-C), Triglycerides (TG) accompanied by lower circulating levels of High density lipoprotein cholesterol (HDL-C). On the other hand, the metabolic related dyslipidemia is being verified as a vital link between obesity and hypertension, diabetes mellitus, and Cardiovascular disease (CVD). In this review, we summarized the current understanding of metabolic related dyslipidemia and the potential mechanisms which lead to the pathogenesis of obesity. Meanwhile, we also summarized the emerging results which focused on several novel lipid bio-markers in metabolic related dyslipidemia, such as pro-protein convertase subtilisin/kexin type 9 (PCSK9) and sphingosine-1-phosphate (S1P), and their potential use as biomarkers of metabolic related dyslipidemia.

Pathology of metabolically-related dyslipidemia

It is well established that overweight/obesity is closely associated with multiple health problems. Among these, dyslipidemia is the most important and main driving force behind pathologic development of cardio-metabolic disorders such as diabetes mellitus, atherosclerotic-related cardiovascular disease and hypertension. Notably, a subtype of dyslipidemia, metabolic related dyslipidemia, is now recognized as a vital link between obesity and multiple different cardiovascular diseases. This condition is characterized by increased low density lipoprotein cholesterol (LDL-C) and triglyceride (TG) and very low density lipoprotein cholesterol (VLDL-C) as well as decreased high density lipoprotein cholesterol (HDL-C) in serum. In this review, we summarize the current understanding of metabolic related dyslipidemia and the potential mechanisms which lead to the pathogenesis of obesity/overweight. We focus on several novel lipid biomarkers such as pro-protein convertase subtilisin/kexin type 9 (PCSK9) and sphingosine-1-phosphate (S1P) and their potential use as biomarkers of metabolic related dyslipidemia.

Emerging functions of adipokines in linking the development of obesity and cardiovascular diseases

Increasing evidence shows that obesity is the critical factor in shaping cardio-metabolic phenotypes. However, the pathogenic mechanisms remain incompletely clarified. According to the published reports, adipose tissue communicates with several diverse organs, such as heart, lungs, and kidneys through the secretion of various cytokines named adipokines. The adipocytes isolated from obese mice or humans are dysfunctional with aberrant production of pro-inflammatory adipokines, which subsequently induce both acute and chronic inflammatory reaction and facilitate the process of cardio-metabolic disorder complications. Furthermore, the microenvironment within adipose tissue under obese status also influence the secretion of adipokines. Recently, given that several important adipokines have been completely researched and causally involved in various diseases, we could make a conclusion that adipokines play an essential role in modulating the development of cardio-metabolic disorder diseases, whereas several novel adipokines continue to be explored and elucidated. In the present review, we summarized the current knowledge of the microenvironment of adipose tissue and the published mechanisms whereby adipocytes affects obesity and cardiovascular diseases. On the other hand, we also provide the evidence to elucidate the functions of adipokines in controlling and regulating the inflammatory reactions which contribute to obesity and cardiovascular disease.

Increased fractalkine and vascular dysfunction in obesity and in type 2 diabetes. Effects of oral antidiabetic treatment

Activation of fractalkine and other chemokines plays an important role in atherogenesis and, in conjunction with endothelial dysfunction, promotes premature vascular damage in obesity and diabetes. We hypothesized that increased circulating fractalkine coexists with impaired vasomotor function in metabolically healthy or unhealthy obesity, and that treatment with antidiabetic drugs may impact these abnormalities in type 2 diabetes. Compared to lean subjects, in both obese groups the vasodilator responses to acetylcholine and sodium nitroprusside were impaired (both P < .001); ET_A-receptor blockade resulted in greater vasodilation (both P < .001); and plasma levels of fractalkine, E-selectin and monocyte chemoattractant protein (MCP)-1 were increased (all P < .05). In diabetic patients, oral antidiabetic drugs (glyburide, metformin or pioglitazone) reduced circulating levels fractalkine and E-selectin (both P < .05), without affecting vascular responses (all P > .05). Our findings indicate that insulin resistant states are associated with elevated atherogenic chemokines and impaired vascular reactivity. Antidiabetic treatment results in lower circulating fractalkine, which may provide cardiovascular benefits.

Fractalkine: an inflammatory chemokine elevated in subjects with polycystic ovary syndrome

PURPOSE

Fractalkine (FKN) is an inflammatory chemokine related to reproductive system and glucose metabolism. There is a link between FKN and steroidogenesis as FKN induces progesterone synthesis. Polycystic ovary syndrome (PCOS) is a common reproductive and metabolic disorder associated with low progesterone production and insulin resistance. We aimed to explore whether women with PCOS have any difference in FKN levels compared to women without PCOS. We also focused on determination of any association between FKN levels and hormonal-metabolic parameters in women with PCOS.

METHODS

The current research was designed as a case-control study. Eighty subjects with PCOS and 80 age- and body mass index (BMI)-matched subjects with normal menstrual cycle were taken into the study. We measured circulating FKN levels via ELISA methods.

RESULTS

Circulating FKN levels were higher in women with PCOS than controls (1.93 ± 0.61 vs. 1.22 ± 0.33 ng/ml, P< 0.001). FKN levels showed a positive correlation with body mass index (BMI), insulin resistance, inflammatory marker hs-CRP, total testosterone, and free-androgen index (FAI), whereas it showed a negative correlation with sex hormone-binding protein in women with PCOS. Linear regression analyses revealed that the link of FKN with BMI, insulin resistance, hs-CRP, and FAI was independent. Binary logistic regression analysis showed that the risk of having PCOS was associated with high levels of FKN.

CONCLUSIONS

Increased FKN levels related to insulin resistance, inflammation and androgens in women with PCOS. FKN may have an inter-related role in different pathophysiologic pathways of PCOS.

Initial effects of inflammation-related cytokines and signaling pathways on the pathogenesis of post-traumatic osteoarthritis

The main pathological change in post-traumatic osteoarthritis (PTOA) is cartilage degeneration, which is closely related to inflammation and oxidative stress. Inflammation can cause degeneration of articular cartilage. Cartilage degeneration can also stimulate the progression of inflammation. It has been found that inflammatory cytokines can participate in the pathological process of cartilage degeneration through multiple signaling pathways, mainly mitogen-activated protein kinase, nuclear transcription factor kappa B, and Wnt–β-catenin signal transduction pathways. This review aimed at exploring the relationship between PTOA and inflammation-related cytokines by introducing the role of proinflammatory cytokines in chondrocyte destruction and extracellular matrix degradation.

Quantitative genetics of circulating Dickkopf-related protein 1 (DKK1) in community-based sample of UK twins

Dickkopf-related protein 1 (DKK1) is a major inhibitor of Wnt signalling pathway but also plays an important role in bone formation. Its circulating levels appear to correlate significantly with plasma levels of inflammatory factors, fractalkine and IL-6. This study, using a large sample of UK twins, showed that the variation of each of these factors and correlation between them was explained by the genetic factors, and indicated possible association with DKK1 gene variants.

INTRODUCTION

DKK1 is involved in the development of several inflammatory conditions related to bone and joint degradation. Our objectives were to explore the genetic contribution (heritability) to circulating DKK1 variation and its correlation with other inflammatory cytokines, interleukin 6 (IL-6) and fractalkine, and to test whether the DKK1 heritability could be attributable to single nucleotide polymorphisms (SNPs) mapped to DKK1, IL-6 and FRCT genes.

METHODS

The study included a large community-based sample of 4939 women drawn from the general UK population. Plasma samples were analysed for circulating levels of DKK1, IL-6 and fractalkine (FRCT); 65 SNPs of DKK1, IL-6 and FRCT candidate genes, with MAF >0.1, were examined. We applied variance component analysis to evaluate contribution of putative genetic (including above SNPs) and environmental factors to variation of DKK1, and its correlation with IL-6 and FRCT.

RESULTS

Putative genetic factors explained 42.2 ± 2 % of the total variation of circulating DKK1 levels, and were also significant for fractalkine and IL-6 variations. Most importantly, we report significant phenotypic (0.208 ± 0.006-0.459 ± 0.007) and genetic (0.338 ± 0.069-0.617 ± 0.033) correlations between these molecules. We found evidence suggestive of association between the DKK1 and its structural genes variants.

CONCLUSIONS

Circulating DKK1 levels correlated significantly with levels of IL-6 and FRCT, known risk factors for several inflammatory processes suggesting a potential role of DKK1 in inflammation and tissue injury. Our results suggest the contribution of genetic factors in inter-individual variation of DKK1 levels in human population. However, further studies are required to determine genetic polymorphisms affecting DKK1 variation and its correlation with IL-6 and FRCT.

Genetic Variants of CD40 Gene Are Associated with Coronary Artery Disease and Blood Lipid Levels

Objectives. The present study aimed to evaluate the effect of CD40 and CXCR4 genes polymorphisms on CAD susceptibility and the blood lipid levels and history of cardiovascular risk factors in a Chinese Han population. Materials and Methods. A total of 583 unrelated patients with CAD and 540 controls were recruited. Two tag SNPs (rs4239702 and rs1535045) at the CD40 locus and one tag SNP (rs2228014) at the CXCR4 locus were genotyped using the SEQUENOM Mass-ARRAY system. Results. After adjusting the risk factors, the frequency of rs1535045-T allele was also higher in patients than controls. Haplotype analysis showed that the rs4239702(C)-rs1535045(T) haplotype was associated with CAD. People with rs4239702-TT genotype had higher blood lipid levels in case group while it was not in the control group. History of cardiovascular risk factors showed no association for the three SNPs in case group and control group. Conclusions. rs1535045 in CD40 gene is likely to be associated with CAD in the Chinese Han population. rs4239702(C)-rs1535045(T) haplotype was associated with CAD. Only in CAD patients, the blood lipid level of patients with rs4239702-TT genotype was higher than other patients. CXCR4 gene may not relate to CAD.

Fractalkine (CX3CL1), GM-CSF and VEGF-a levels are reduced by statins in adult patients

BACKGROUND

Fractalkine (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.

METHODS

We 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.

RESULTS

Therapy 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.

CONCLUSIONS

Our 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.

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.

Fractalkine signaling in regulation of insulin secretion

Fractalkine is a chemokine, which has been shown to play important roles in metabolic disease in both animal models and humans. Fractalkine is a key player in the accumulation of atherosclerotic plaques, and fractalkine receptor (CX3CR1) mutations have been implicated in obesity. Serum fractalkine levels have been found to be elevated in type 2 diabetic patients, but the role of fractalkine signaling on the pancreatic β cell was unclear. Recently published findings in April 2013 issue of the journal Cell by Lee and Olefsky et al. have implicated fractalkine in β-cell insulin secretion. They demonstrate that Cx3cr1 knockout mice have impaired glucose tolerance resulting from decreased insulin secretion. In addition, fractalkine administration improved glucose tolerance and induced insulin secretion. This modulation of insulin secretion was proposed to result from an increase in intracellular calcium and potentiation of insulin secretion, which occurs in a Gαi and MEK-dependent manner. They also found that Cx3cr1 knockout animals had transcriptional repression of genes important for β-cell function, specifically NeuroD, via induction of ICER-1. One important issue that remains unresolved is how CX3CR1 signaling regulates the potentiation of calcium influx and the distal events in insulin exocytosis. Finally, testing the effects of fractalkine treatment on proliferation and survival in vivo during regenerative conditions would be critical to determine the potential use of this chemokine in diabetes. While these exciting results open the possibility for new therapeutics, there are some concerns about a potential risk for exacerbation of atherosclerosis.