Fetuin-A and arterial stiffness in patients with normal kidney function

Evaluation of the Correlation between the rs4918 Polymorphism of AHSG Gene and Coronary Artery Calcification in Patients with Coronary Artery Disease

Objectives: Fetuin-A is a circulating calcification inhibitor that prevents coronary artery calcification (CAC) by increasing calcium phosphate solubility and inhibiting VSMC differentiation and apoptosis. In this study, we investigated the correlation between rs4918 and CAC in patients with coronary artery disease (CAD). Methods: Forty-two healthy individuals and eighty-one CAD patients were recruited in the present study. The CAC score (CACS) was measured by CT angiography and the genotype analysis of rs4918 single-nucleotide polymorphism SNP was performed by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Results: The CACS was significantly higher in CAD patients compared to healthy individuals (p < 0.001); however, there was no significant difference between the mean CACS in the presence and absence of rs4918 (p = 0.792). The mean calcium score of the left main coronary artery (LMCA) was significantly lower in carriers of the rs4918 allele (p = 0.036). The frequency of rs4918 SNP was almost similar in the control group and CAD patients (p = 0.846). Conclusions: in patients with CAD, we found no significant association between rs4918 SNP and CACS, indicating that carriers of this allele are not at increased risk of developing cardiovascular diseases compared with those without.

The association between fetuin-A and testosterone levels and markers of arterial stiffness in Saudi subjects with type 2 diabetes mellitus

BACKGROUND

Inconsistent results have been described regarding the part of fetuin-A and testosterone in arterial stiffness in type 2 diabetes mellitus (T2DM).

AIM

To look into the links of serum fetuin-A and testosterone levels with brachial-Ankle pulse wave velocity (baPWV), a marker of arteriosclerosis and common carotid intima media thickness (ccIMT), a marker of early atherosclerosis, in diabetic Saudi men patients.

SUBJECTS AND METHODS

One hundred and fifty adult male patients with T2DM and 60 non-diabetic control subjects were enrolled from different Saudi Arabia Taif hospitals. Biochemical analysis, anthropometric measurements, blood pressure, baPWV and ccIMT were investigated.

RESULTS

Stepwise regression in diabetic patients revealed that the most important predictor of ba-PWV was serum fetuin-A followed by serum glucose and the most important predictor of ccIMT was serum fetuin-A followed by serum HDL then serum triglycerides.

CONCLUSIONS

Only fetuin-A levels not testosterone are negatively associated with early markers of atherosclerosis.

Serum and Aqueous Humor Levels of Fetuin-A in Pseudoexfoliation Syndrome

PURPOSE

To evaluate serum and aqueous humor levels of fetuin-A in patients with pseudoexfoliation syndrome (PEXS) in comparison with those of age- and sex-matched healthy subjects.

MATERIALS AND METHODS

This prospective study included 25 patients with PEXS and 25 control subjects who were undergoing cataract surgery without any systemic or ocular disease. Aqueous humor and serum fetuin-A levels were measured with enzyme-linked immunosorbent assay method.

RESULTS

The mean age of the PEXS group (14 males, 11 females, n = 25) was 57.7 ± 6.9 years, and the control group (13 males, 12 females, n = 25) was 58.1 ± 5.7 years. There was no difference between the groups in terms of age (p = 0.77) and sex (p = 0.83). The mean serum fetuin-A level of the PEXS group did not differ from that of the control group (p = 0.53). The mean aqueous humor level of the PEXS group was significantly higher than that of the control group (p = 0.032). There were no significant correlations between aqueous humor and serum fetuin-A levels among patients with PEXS and control group (p > 0.05).

CONCLUSIONS

Increased levels of fetuin-A in aqueous humor of patients with PEXS may show the local effect of fetuin-A on the anterior segment. With considering the wide range of possible biological functions of fetuin-A in the pathogenesis of PEXS, further studies are needed to clarify the clinical relevance of these findings.

Serum fetuin-A levels and abdominal aortic calcification in healthy men - The STRAMBO study

Vascular calcification results from an imbalance between increased extracellular levels of calcium and phosphate, reduced solubility, and low levels of calcification inhibitors in blood or the vascular wall. Fetuin-A is a major circulating calcification inhibitor. Rodent models of fetuin-A deficit indicate its calcification inhibiting potential. Clinical studies suggest its role as a biomarker in vascular disease. This cross-sectional study was performed in a cohort of 974 men aged ≥ 40 years (average 68 years) consisting of men holding health insurance cover with Mutuelle des Travailleurs de la Région Lyonnaise. Abdominal aortic calcification (AAC) was assessed semi-quantitatively on lateral dual energy X-ray absorptiometry (DXA) spine scans. Serum fetuin-A was measured by an immunoassay. After adjustment for confounders (age, lifestyle, body composition, health status, treatment, glomerular filtration rate [GFR], hormones, and cytokines), prevalence of severe AAC (AAC score>4) decreased with increasing fetuin-A levels (OR=0.68 per SD increase, 95% CI: 0.54-0.84, p<0.001). After adjustment for confounders, low fetuin-A and hypertension were each associated with higher odds of AAC>4. Coexistence of low serum fetuin-A levels and heavy smoking, elevated fibroblast growth factor 23 levels or low serum dickkopf-1 levels were associated with higher odds of AAC>4. Similar results were obtained for 789 men with GFR>60 mL/min/1.73 m(2). Similar results were obtained when severe AAC was defined as AAC score >3 or AAC>5. Thus, lower serum fetuin-A levels are associated with severe AAC, suggesting that poor calcification inhibitory potential contributes to vascular calcification, independently of renal impairment.

Genetic determinants of arterial stiffness

Stiffness of large arteries (called arteriosclerosis) is an independent predictor of cardiovascular morbidity and mortality. Although previous studies have shown that arterial stiffness is moderately heritable, genetic factors contributing to arterial stiffness are largely unknown. In this paper, we reviewed the available literature on genetic variants that are potentially related to arterial stiffness. Most variants have shown mixed depictions of their association with arterial stiffness across multiple studies. Various methods to measure arterial stiffness at different arterial sites can contribute to these inconsistent results. In addition, studies in patient populations with hypertension or atherosclerosis may overestimate the impact of genetic variants on arterial stiffness. Future studies are recommended to standardize current measures of arterial stiffness in different age groups. Studies conducted in normal healthy subjects may also provide better opportunities to find novel genetic variants of arterial stiffness.

Maternal plasma fetuin-A concentration is lower in patients who subsequently developed preterm preeclampsia than in uncomplicated pregnancy: a longitudinal study

Objective: Fetuin-A is a negative acute phase protein reactant that acts as a mediator for lipotoxicity, leading to insulin resistance. Intravascular inflammation and insulin resistance have been implicated in the mechanisms of disease responsible for preeclampsia (PE). Maternal plasma concentrations of fetuin-A at the time of diagnosis of preterm PE are lower than in control patients with a normal pregnancy outcome. However, it is unknown if the changes in maternal plasma fetuin-A concentrations precede the clinical diagnosis of the disease. We conducted a longitudinal study to determine whether patients who subsequently developed PE had a different profile of maternal plasma concentrations of fetuin-A as a function of gestational age (GA) than those with uncomplicated pregnancies. Methods: A longitudinal case-control study was performed and included 200 singleton pregnancies in the following groups: (1) patients with uncomplicated pregnancies who delivered appropriate for gestational age (AGA) neonates (n = 160); and (2) patients who subsequently developed PE (n = 40). Longitudinal samples were collected at each prenatal visit and scheduled at 4-week intervals from the first or early second trimester until delivery. Plasma fetuin-A concentrations were determined by ELISA. Analysis was performed using mixed-effects models. Results: The profiles of maternal plasma concentrations of fetuin-A differ between PE and uncomplicated pregnancies. Forward analysis indicated that the rate of increase of plasma fetuin-A concentration in patients who subsequently developed PE was lower at the beginning of pregnancy (p = 0.001), yet increased faster mid-pregnancy (p = 0.0017) and reached the same concentration level as controls by 26 weeks. The rate of decrease was higher towards the end of pregnancy in patients with PE than in uncomplicated pregnancies (p = 0.002). The mean maternal plasma fetuin-A concentration was significantly lower in patients with preterm PE at the time of clinical diagnosis than in women with uncomplicated pregnancies (p < 0.05). In contrast, there were no significant differences in maternal plasma fetuin-A concentration in patients who developed PE at term. Conclusions: (1) The profile of maternal plasma concentrations of fetuin-A over time (GA) in patients who develop PE is different from that of normal pregnant women; (2) the rate of change of maternal plasma concentrations of fetuin-A is positive (increases over time) in the midtrimester of normal pregnancy, and negative (decreases over time) in patients who subsequently develop PE; (3) at the time of diagnosis, the maternal plasma fetuin-A concentration is lower in patients with preterm PE than in those with a normal pregnancy outcome; however, such differences were not demonstrable in patients with term PE.

Causal relationship between body mass index and fetuin-A level in the asian population: a bidirectional Mendelian randomization study

OBJECTIVE

Fetuin-A is associated with body mass index (BMI) as well as components of the metabolic syndrome. However, it is unclear if fetuin-A affects BMI or the other way around. We therefore assessed the causal association between fetuin-A and BMI or vice versa, utilizing a bidirectional Mendelian randomization approach.

DESIGN AND METHODS

This was a study of 2558 subjects from the Electricity Generating Authority of Thailand (EGAT) cohort. Two polymorphisms, that is, rs2248690 in the alpha2-Hereman-Schmid glycoprotein (AHSG) gene and rs9939609 in the fat mass and obesity-associated (FTO) gene were genotyped. Bidirectional causal models were constructed using a two-stage least-square instrumental variable (IV) regression. First, rs2248690 locus was used as the instrumental variable for the effect of circulating fetuin-A on BMI, and then, the FTO rs9939609 locus was used as the instrumental variable for the effect of BMI on circulating fetuin-A.

RESULTS

Among the 2558 subjects, the prevalence of the minor AHSG (T) and FTO (A) alleles was 17.9% and 22.1%, respectively. The AHSG rs2248690 locus was highly related to serum fetuin-A levels (P < 0.001). Likewise, the FTO rs9939609 locus and BMI were highly associated (P < 0.001). Mendelian randomization analyses showed that circulating fetuin-A, instrumented by the AHSG rs2248690 locus, was associated with BMI (coefficient = 2.26; 95% CI: 0.39, 4.12). In contrast, BMI, instrumented by the FTO rs9939609 locus, was not associated with circulating fetuin-A (coefficient = 0.0007; 95% CI: -0.0242, 0.0256).

CONCLUSION

Our findings suggest a causal association leading from circulating fetuin-A to BMI. There was no evidence of reverse causality from BMI to fetuin-A.

Associations of serum fetuin-A levels with insulin resistance and vascular complications in patients with type 2 diabetes

OBJECTIVE

We examined the relationship between serum fetuin-A, insulin resistance (IR), metabolic syndrome (MS) and vascular complications including cardiac autonomic neuropathy (CAN) in patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 172 T2DM patients were recruited and evaluated for diabetic microangiopathies (nephropathy, retinopathy and peripheral neuropathy) including CAN. Serum fetuin-A levels were measured by enzyme-linked immunosorbent assay (ELISA), and the IR was assessed by the index of homeostasis model [homeostasis model assessment-insulin resistance (HOMA-IR)]. Atherosclerotic burden was assessed by ankle-brachial index (ABI) and brachial-ankle pulse wave velocity (baPWV).

RESULTS

Serum fetuin-A levels showed significant positive correlations with HOMA-IR (r = 0.196, p = 0.022), and the mean levels of HOMA-IR were significantly increased progressively across fetuin-A tertiles (p for trend = 0.044). Serum fetuin-A showed significant positive correlations with baPWV, systolic blood pressure (BP), total cholesterol, triglycerides, serum fasting c-peptide and negative correlations with ABI. Serum fetuin-A levels were also negatively correlated with serum adiponectin and positively correlated with serum tumour necrosis factor-α (TNF-α). The mean levels of serum fetuin-A were not significantly different according to the presence of each microangiopathies including CAN. Also, the mean levels of serum fetuin-A were not different between patients with MS and without MS.

CONCLUSIONS

This present study showed that levels of serum fetuin-A are significantly associated with IR and arterial stiffness assessed by baPWV, while there are no associations with each microangiopathies in patients with T2DM.

Association Between Serum Fetuin-A levels, Carotid Artery Stiffness, and Intima–Media Thickness in Patients With Normotensive Obstructive Sleep Apnea Syndrome

Increased carotid intima–media thickness (cIMT) and stiffness, reflecting subclinical atherosclerosis, are associated with obstructive sleep apnea syndrome (OSAS). The relationship between serum fetuin-A, which inhibits ectopic calcification, and atherosclerosis is unclear. Therefore, we investigated the association between serum fetuin-A levels and carotid artery stiffness and cIMT in patients with normotensive OSAS (n = 50) and non-OSAS controls (n = 38). Compared with controls, there were lower fetuin-A levels (59.4 ± 6.5 vs 68.2 ± 5.8 ng/mL, P = .029), higher mean cIMT (0.73 ± 0.2 vs 0.63 ± 0.3 mm, P < .001), and greater stiffness (β) index (7.45 ± 0.9 vs 5.2 ± 0.7, P = .001) in the OSAS group. The cIMT and stiffness (β) index were inversely correlated with fetuin-A levels ( r = −.324, P = .033; r = −.466, P < .001, respectively) and positively correlated with apnea hypopnea index ( r = .498, P < .001; r = .422, P = .001, respectively) in the OSAS group. Decreased serum fetuin-A levels were associated with subclinical carotid atherosclerosis in patients with normotensive OSAS.

Associations of fetuin-A and osteoprotegerin with arterial stiffness and early atherosclerosis in chronic hemodialysis patients

BACKGROUND

Cardiovascular morbidity and mortality remains excessive in patients with chronic kidney disease. The association of vascular changes with regulators of extraosseous calcification in this patient population is still under investigation. The aim of the present study was to investigate the associations of the calcification inhibitor fetuin-A, and the anti-osteoclastic factor osteoprotegerin (OPG) with vascular pathology in chronic hemodialysis patients.

METHODS

In this cross-sectional study including 81 stable chronic hemodialysis patients, we measured carotid-to-femoral pulse wave velocity (cfPWV) with applanation tonometry, reflecting arterial stiffness, and common carotid intima-media thickness (ccIMT), a surrogate of early atherosclerosis, as well as serum levels of fetuin-A and OPG. Co-morbidities, traditional cardiovascular risk factors, inflammatory markers and mineral-bone disease serology parameters were also recorded.

RESULTS

cfPWV correlated inversely with fetuin-A (r=-0.355, p=0.001) and positively with OPG (r=0.584, p<0.001). In multilinear regression analysis including age, gender, diabetes, cardiovascular disease, hypertension, pulse pressure, LDL, logCRP, both fetuin-A and OPG were independently associated with cfPWV (p=0.024 and p=0.041 respectively). ccIMT was negatively associated with fetuin-A (r=-0.312, p=0.005) and positively with OPG (r=0.521, p<0.0001); however these associations lost statistical significance after adjustment for age.

CONCLUSION

In chronic hemodialysis patients both fetuin-A and OPG levels are independently associated with arterial stiffness but not with early atherosclerotic vascular changes.

Fetuin-A and the cardiovascular system

Fetuin was first isolated from bovine serum in 1944. It is now most commonly known as either fetuin-A or alpha-2-HS-glycoprotein (AHSG), the protein product of Ahsg gene. A prominent feature of this protein is the functional diversity exerted in human physiology and pathophysiology. Fetuin-A plays a role in bone metabolism, metabolic disorders such as insulin resistance and diabetes mellitus (DM), and central nervous system (CNS) disorders such as ischemic stroke (IS) and neurodegenerative diseases. In addition, emerging evidence suggests involvement of fetuin-A in the cardiovascular system. However, there are many discordant findings on the associations between fetuin-A and vascular diseases. In other words, it is unknown whether fetuin-A is an exacerbating or a protective factor in the cardiovascular system. One reason for the seemingly inconsistent behavior is the dual functionality of fetuin-A in vascular diseases where it can act as an atherogenic factor or as a vascular calcification inhibitor. In addition, the existence of confounding factors such as DM and renal dysfunction can veil the primary association between fetuin-A and clinical parameters. Considering these issues, we discuss the role of fetuin-A for atherosclerosis and vascular calcification in this review.

Serum fetuin-A in metabolic and inflammatory pathways in patients with myocardial infarction

BACKGROUND

Although multifunctional glycoprotein α2HS-glycoprotein/human fetuin-A (AHSG) is involved in atherosclerosis, it is not clear whether high or low concentrations are more important. We studied the correlation of serum AHSG with adiponectin, leptin, resistin, C-reactive protein (CRP) and tumour necrosis factor-α (TNF-α) to see whether its metabolic effects or its involvement in subclinical inflammation are dominant in patients with established coronary disease.

MATERIALS AND METHODS

In this cross-sectional study, AHSG concentration was determined in sera of 171 patients (age: 62 ± 6 years, mean ± SD) with previous myocardial STEMI infarction and normal renal function and 81 age-matched healthy controls by radial immunodiffusion. Results  Patients had increased AHSG levels (673 ± 103 vs. 619 ± 96 mg L(-1), P < 0·001) compared to controls. Obese and diabetic patients had higher AHSG concentration than those with normal BMI or without diabetes but even the latter group had elevated AHSG levels (667 ± 101 mg L(-1), n = 88) compared to controls (P = 0·002). Serum AHSG correlated negatively with adiponectin (r = -0·236, P = 0·006) even after adjusting for BMI (r = -0·177, P = 0·043). AHSG determined adiponectin levels independently from BMI, age and other adipocytokines (P = 0·014). The correlation between leptin and AHSG (r = 0·321, P = 0·021) weakened following adjustment for BMI (r = 0·209, P = 0·072). Serum AHSG did not correlate significantly with CRP, resistin and TNF-α concentrations. BMI and resistin but not AHSG determined TNF-α levels independently.

CONCLUSIONS

AHSG is elevated in sera of patients with previous myocardial infarction. Association with adipokines favours the concept that AHSG is involved in atherosclerosis more likely through metabolic pathways (insulin resistance, obesity and adipocyte dysfunction) than by inflammation in patients with post-myocardial infarction.

β2-microglobulin, a novel biomarker of peripheral arterial disease, independently predicts aortic stiffness in these patients

Arterial stiffness is a prominent feature of vascular ageing and strongly predicts cardiovascular and total mortality. The β2-microglobulin, (β2M) a newly identified biomarker of peripheral arterial disease (PAD), is related to renal insufficiency, inflammatory and neoplastic diseases, but may also play a role in vascular dysfunction. However, the relationship between arterial stiffness and β2M has not been previously studied in patients with atherosclerosis. In the present study we examined a possible association between β2M and arterial stiffness in patients with PAD and in healthy subjects. Plasma β2M levels and parameters of arterial stiffness such as aortic pulse wave velocity (aPWV) and augmentation index (AIx) were measured in 66 patients with PAD and in 66 apparently healthy subjects. Plasma levels of β2M, aPWV and AIx were significantly increased in patients with PAD compared with controls (1858.1 ± 472.8 vs 1554.5 ± 277.9 μg/L, p < 0.001; 9.9 ± 2.2 m/s vs 7.6 ± 1.6 m/s, p < 0.001; 28 ± 8 vs 14 ± 11%, p < 0.001; respectively). There existed significant correlation between aPWV and β2M for the patient group (R = 0.47; p < 0.001), but not for the controls (R = 0.14; p = 0.26). In multivariate analysis, β2M remained independently associated with aPWV, fetuin-A, age and glomerular filtration rate in patients (R(2) = 0.5, p < 0.001). We found no relationship between β2M and AIx in either group. We demonstrated that among patients with PAD elevated plasma β2M levels were associated with higher aortic stiffness irrespective of cardiovascular disease risk factors. These data suggest that β2M may influence the pathogenesis of aortic stiffness in atherosclerosis.

Poor agreement between commercial ELISAs for plasma fetuin-A: An effect of protein glycosylation?

BACKGROUND

Fetuin-A is a circulating inhibitor of ectopic calcification. Low plasma levels have been associated in some studies with increased vascular calcification, aortic stiffness and mortality in patients with Chronic Kidney Disease (CKD). However, there are other studies examining the association of fetuin-A with vascular parameters and mortality, which do not show these associations. These conflicting data may be explained by methodological differences.

METHODS

We compared plasma fetuin-A measurements made with two widely-used commercial fetuin-A ELISA kits (Biovendor, Modrice, Czech Republic; Epitope Diagnostics Inc., San Diego, US) in samples from patients with and without CKD. We evaluated the effect of differences in fetuin-A glycosylation status on assay specificity.

RESULTS

Deming regression analysis showed poor agreement between methods (for CKD cohort: y=-0.05+2.52x, S(y|x)=0.099g/L, R(2)=0.694). The Epitope Diagnostics kit demonstrated significant positive bias and greater specificity for deglycosylated fetuin-A relative to the Biovendor assay.

CONCLUSION

The apparently contradictory nature of reports of the association of fetuin-A with biological variables may reflect differences in the specificity of different ELISA methods for glycosylated plasma fetuin-A.

Fetuin-A gene polymorphism in patients with calcium oxalate stone disease

OBJECTIVES

To evaluate the association of fetuin-A polymorphisms with calcium oxalate nephrolithiasis. Fetuin-A is a circulating calcium-regulatory glycoprotein that inhibits extraosseous calcification.

METHODS

Fetuin-A c.742C > T and c.766C > G polymorphisms were investigated in 103 patients with calcium oxalate nephrolithiasis and 73 age- and gender-matched healthy volunteers, using polymerase chain reaction-restriction fragment length polymorphism techniques. Additionally, we compared serum fetuin-A levels in the 2 groups.

RESULTS

A statistically significant difference was observed between the control and patient groups (chi(2) test, P = .003) for the genotype of fetuin-A c.766C > G polymorphism. The odds ratio (95% confidence interval) for the CG genotype in those at risk of stone disease was 4.2 (1.73-10.28). The frequency distribution for fetuin-A c.742C > T polymorphism was not statistically different in stone patients and controls (P = .77). Serum mean fetuin-A concentration was significantly lower in the patients (710.38 +/- 156.42 microg/mL) than in the controls (810.89 +/- 173.43 microg/mL, P = .0001). In the patient group (but not in the control group), subjects carrying fetuin-A genotype 1 had significantly higher serum fetuin-A concentrations than the group carrying fetuin-A genotype 2-1 (P = .001).

CONCLUSIONS

These results reveal that the patients with fetuin-A c.766C > G gene polymorphism may be at higher risk for renal calcium oxalate stone formation.

Association between carotid diameter and the advanced glycation end product N-epsilon-carboxymethyllysine (CML)

Background

N^ε-Carboxymethyllysine (CML) is the major non-cross linking advanced glycation end product (AGE). CML is elevated in diabetic patients and apparent in atherosclerotic lesions. AGEs are associated with hypertension and arterial stiffness potentially by qualitative changes of elastic fibers. We investigated whether CML affects carotid and aortic properties in normoglycemic subjects.

Methods

Hundred-two subjects (age 48.2 ± 11.3 years) of the FLEMENGHO study were stratified according to the median of the plasma CML level (200.8 ng/ml; 25^th percentile: 181.6 ng/ml, 75^th percentile: 226.1 ng/ml) into "high CML" versus "low CML" as determined by ELISA. Local carotid artery properties, carotid intima media thickness (IMT), aortic pulse wave velocity (PWV), blood pressure and fetuin-A were analyzed. In 26 patients after carotidectomy, CML was visualized using immunohistochemistry.

Results

According to the CML median, groups were similar for anthropometric and biochemical data. Carotid diameter was enlarged in the "high" CML group (485.7 ± 122.2 versus 421.2 ± 133.2 μm; P < 0.05), in particular in participants with elevated blood pressure and with "high" CML ("low" CML: 377.9 ± 122.2 μm and "high" CML: 514.5 ± 151.6 μm; P < 0.001). CML was associated fetuin-A as marker of vascular inflammation in the whole cohort (r = 0.28; P < 0.01) and with carotid diameter in hypertensive subjects (r = 0.42; P < 0.01). CML level had no effect on aortic stiffness. CML was detected in the subendothelial space of human carotid arteries.

Conclusion

In normoglycemic subjects CML was associated with carotid diameter without adaptive changes of elastic properties and with fetuin-A as vascular inflammation marker, in particular in subjects with elevated blood pressure. This may suggest qualitative changes of elastic fibers resulting in a defective mechanotransduction, in particular as CML is present in human carotid arteries.