FGF23 as a Potential Pathophysiological Factor in Peripheral Arterial Disease Associated with Chronic Kidney Disease.

Fibroblast growth factor 23 (FGF23) levels are often elevated in chronic kidney disease (CKD). FGF23 and inflammation are common characteristics in CKD, and both are associated with worse disease progression and the occurrence of complications. The existence of an interaction between FGF23 and inflammation has been suggested, each of which influences the expression and activity of the other, leading to a vicious feedback loop with adverse outcomes, including cardiovascular disease and mortality. In this work, we determined circulating FGF23 levels in a group of patients with CKD stages 3 and 4 subjected to elective femoral endarterectomy due to established peripheral artery disease (PAD), a condition resulting from an athero-inflammatory process, and we studied its associations with different inflammatory markers and mediators. We evaluated its association with serum tumor necrosis factor (TNF)α, interleukin (IL) 6, and IL10, as well as with the gene expression levels of these parameters and A disintegrin and metalloproteinase domain-containing protein (ADAM) 17 in femoral vascular tissue and peripheral blood circulating cells (PBCCs). We also analyzed its association with serum concentrations of C-reactive protein (CRP), the systemic immune inflammation index (SII), and the neutrophil-to-lymphocyte ratio (NLR). Finally, we determined the vascular immunoreactivity of protein TNFα in a subgroup of patients. FGF23 concentrations were independently associated with circulating and PBCC mRNA levels of TNFα. Worst kidney function and diabetes were also found to be contributing to FGF23 levels. Patients with higher levels of FGF23 also had greater vascular immunoreactivity for TNFα.

Klotho inversely relates with carotid intima- media thickness in atherosclerotic patients with normal renal function (eGFR ≥60 mL/min/1.73m2): a proof-of-concept study.

Introduction: Klotho protein is predominantly expressed in the kidneys and has also been detected in vascular tissue and peripheral blood circulating cells to a lesser extent. Carotid artery intima-media thickness (CIMT) burden, a marker of subclinical atherosclerosis, has been associated with reductions in circulating Klotho levels in chronic kidney disease patients, who show reduced levels of this protein at all stages of the disease. However, the contribution of serum Klotho and its expression levels in peripheral blood circulating cells and in the carotid artery wall on the CIMT in the absence of kidney impairment has not yet been evaluated. Methods: We conducted a single-center study in 35 atherosclerotic patients with preserved kidney function (eGFR≥60 mL/min/1.73m2) subjected to elective carotid surgery. Serum levels of Klotho and cytokines TNFa, IL6 and IL10 were determined by ELISA and transcripts encoding for Klotho (KL), TNF, IL6 and IL10 from vascular segments were measured by qRT-PCR. Klotho protein expression in the intima-media and adventitia areas was analyzed using immunohistochemistry. Results: APatients with higher values of CIMT showed reduced Klotho levels in serum (430.8 [357.7-592.9] vs. 667.8 [632.5-712.9] pg/mL; p<0.001), mRNA expression in blood circulating cells and carotid artery wall (2.92 [2.06-4.8] vs. 3.69 [2.42-7.13] log.a.u., p=0.015; 0.41 [0.16-0.59] vs. 0.79 [0.37-1.4] log.a.u., p=0.013, respectively) and immunoreactivity in the intimal-medial area of the carotids (4.23 [4.15-4.27] vs. 4.49 [4.28-4.63] log µm2 p=0.008). CIMT was inversely related with Klotho levels in serum (r= -0.717, p<0.001), blood mRNA expression (r=-0.426, p=0.011), and with carotid artery mRNA and immunoreactivity levels (r= -0.45, p=0.07; r= -0.455, p= 0.006, respectively). Multivariate analysis showed that serum Klotho, together with the gene expression levels of tumor necrosis factor TNFa in blood circulating cells, were independent determinants of CIMT values (adjusted R2 = 0.593, p<0.001). Discussion: The results of this study in subjects with eGFR≥60mL/min/1.73m2 show that patients with carotid artery atherosclerosis and higher values of CIMT present reduced soluble Klotho levels, as well as decreased KL mRNA expression in peripheral blood circulating cells and Klotho protein levels in the intima-media of the carotid artery wall.

Klotho expression in peripheral blood circulating cells is associated with vascular and systemic inflammation in atherosclerotic vascular disease.

Cardiovascular disease is the leading cause of death worldwide. New therapeutic strategies are aimed to modulate the athero-inflammatory process that partially orchestrates underlying vascular damage. Peripheral blood circulating cells include different immune cells with a central role in the development of the atherogenic inflammatory response. The anti-aging protein α-Klotho has been related to protective effects against CVD. KL is expressed in monocytes, macrophages, and lymphocytes where it exerts anti-inflammatory effects. In this work, we analyse the relationships of the levels of inflammatory markers with the expression of the KL gene in PBCCs and with the serum levels of soluble KL in atherosclerotic vascular disease. For this, we conducted a cross-sectional single-center case-control study including a study group of 76 CVD patients and a control group of 16 cadaveric organ donors without medical antecedent or study indicating CVD. Vascular artery fragments and whole blood and serum samples were obtained during elective or organ retrieval surgery. Serum levels of sKL, TNFα and IL10, and gene expression levels of KL, TNF, IL10, NFKB1, DNMT1, and DNMT3A in PBCCs were measured. In these cells, we also determined KL promoter methylation percentage. Histological and immunohistochemical analyses were employed to visualize atherosclerotic lesions and to measure IL10 and TNFα levels in vascular fragments. Patients with CVD presented higher values of proinflammatory markers both at systemic and in the vasculature and in the PBCCs, compared to the control group. In PBCCs, CVD patients also presented lower gene expression levels of KL gene (56.4% difference, P < 0.001), higher gene expression levels of DNMT1 and DNMT3A (P < 0.0001, for both) and a higher methylation status of in the promoter region of KL (34.1 ± 4.1% vs. 14.6 ± 3.4%, P < 0.01). In PBCCs and vasculature, KL gene expression correlated inversely with pro-inflammatory markers and directly with anti-inflammatory markers. sKL serum levels presented similar associations with the expression levels of pro- and anti-inflammatory markers in PBCCs. The differences in KL expression levels in PBCCs and in serum sKL levels with respect to control group was even greater in those CVD patients with macroscopically observable atheromatous plaques. We conclude that promoter methylation-mediated downregulation of KL gene expression in PBCCs is associated with the pro-inflammatory status in atherosclerotic vascular disease.

Association between serum levels of Klotho and inflammatory cytokines in cardiovascular disease: a case-control study.

Decrease in soluble anti-aging Klotho protein levels is associated to cardiovascular disease (CVD). Diverse studies have shown a bidirectional relationship between Klotho and inflammation, a risk factor for the development of CVD. In this work we aimed to evaluate the association between Klotho and inflammatory cytokines levels in the context of human CVD.The study included 110 patients with established CVD and preserved renal function, and a control group of 22 individuals without previous history of cardiovascular events. Serum Klotho and IL10 levels were significantly lower in the CVD group. Inflammatory status, marked by the TNFα/IL10 ratio and the C-reactive protein (CRP) levels, was significantly increased in the group of patients with established CVD. Soluble Klotho levels were directly correlated with eGFR (r=0.217) and IL10 (r=0.209) and inversely correlated with age (r=-0.261), CRP (r=-0.203), and TNFα/IL10 (r=-0.219). This association with TNFα/IL10 remained significant in age-matched subgroups. Multiple logistic regression analysis showed that age, smoking and the neutrophil-to-lymphocyte ratio (NLR) constituted risk factors for the presence of CVD, while Klotho was a protective factor.In conclusion, in patients with established CVD, the reduction in soluble Klotho is associated with a pro-inflammatory status marked by lower IL10 concentrations and higher TNFα/IL10 ratio and CRP levels.

Soluble levels and endogenous vascular gene expression of KLOTHO are related to inflammation in human atherosclerotic disease.

Atherosclerosis is a chronic inflammatory disorder affecting the artery wall. Klotho, an anti-aging factor expressed in the vessel walls that participates in the maintenance of vascular homeostasis, can be down-regulated by inflammation. In this proof-of-concept work we seek to characterize the arterial KLOTHO expression in the vascular wall, as well as the serum concentration of this protein, in a group of patients with clinical atherosclerotic disease. In addition, we aim to analyze the relationship between Klotho and inflammation. Vascular samples were obtained from 27 patients with atherosclerotic disease under an elective vascular surgery procedure, and from 11 control subjects (cadaveric organ donation programme). qRT-PCR was performed to analyze the gene expression of KLOTHO, TNF-α, IL-6, and IL-10 Serum levels of soluble KLOTHO were measured by ELISA. As compared with control subjects, serum concentrations and vascular expression of Klotho were lower in patients with atherosclerotic vascular disease, whereas inflammatory status was significantly higher. There was a negative and significant correlation between inflammatory parameters and Klotho. After controlling for the effect of other variables, partial correlation showed a direct relationship between vascular KLOTHO gene expression and IL-10 mRNA levels, whereas there was a negative association with serum LDL concentrations and vascular TNF-α expression. Our study indicates an inverse interrelationship between inflammation and Klotho in atherosclerosis. Further studies are necessary to elucidate whether the inflammatory state causes Klotho deficiency or, on the contrary, reduction of Klotho could be responsible for greater inflammation, and finally, to investigate the potential clinical relevance of this association.