[MORPHOGENETIC PROTEINS--FIBROBLAST GROWTH FACTOR AND KLOTHO, IN THE SERA OF PATIENTS WITH CHRONIC RENAL DISEASE]

The aim of the study was to evaluate the role of morphogenetic proteins--fibroblast growth factor-23 (FGF-23) and extracellular form (alpha) of Klotho protein, present in the sera of patients with chronic renal disease (CRD) as markers of cardiovascular risk. The study included 130 patients (64 men and 66 women) with stage I-VD CRD. The patients'age was 20-65 (mean 41 ± 6.7) years. 30 of them had chronic glomerulonephritis, 23 chronic tubulointerstitial nephritis, 28 hypertensive nephrosclerosis, 22 polycystic kidneys, 27 type 2 diabetes mellitus. Inclusion and exclusion criteria were standardfor clinical studies of CRD patients. Control group contained 30 healthy volunteers matched for age and sex. The patients were uniformly distributed by stages of CRD in terms of age and sex (18-20 per group). All of them were followed up during 1 year Standard clinical and laboratory examination was supplemented by the measurement of the parathyroid hormone (PTH), Ca and P levels. Serum FGF-23 and Klotho levels were determined by ELISA before and 1 year after onset of the study. Blood pressure including brachial (peripheral) and aortic (central) one as swell as the pulse wave velocity was measured by a Sphygocorr apparatus (Australia). Other studies included ECG, EchoCG, and X-ray of abdominal aorta in the lateral projection using the Kaupilla method. Comparison of FGF-23 and Klotho levels in patients at different stages of CRD revealed their decrease with decreasing glomerular filtration rate that started before (at IIIA stage) a rise in the serum P and PTG levels (IV-V stage). Negative relationship was documented between the Klotho level and the degree of cardiac calcinosis estimated from a semi-quantitative scale (r = 0.64; p < 0.01). Serum FGF-23 significantly correlated wiht myocardial remodeling (r = 0.612; p < 0.01). Multiple regression analysis showed that patients with elevated FGF-23 and P levels, high central systolic pressure and pulse wave velocity had greater left ventricular myocardium mass. ROC-analysis demonstrated that FGF-23 level over 412 pg/ml is indicative of left ventricular hypertrophy with sensitivity 80% and specificity 76%. Patients undergoing hemodialysis who died within 1 year after the onset of the treatment had a higher FGF-23 level than survivals on hemodialysis. The risk of death during the first year on hemodialysis correlated with the FGF-23 level (r = 0.564, p < 0.01). ROC-analysis showed that Klotho levels below 387 pg/ml suggested an increased risk of myocardiym calcification with sensitivity 80% and specificity 75%. It is concluded that morphogenetic proteins, fibroblast growth factor and Klotho, not only play an important role in mineral metabolism in patients with CRD but also produce pleiotropic effects on the development of cardiovascular complications (via involvement in cardiac and vascular calcification and remodeling). It provides a basis for the use of these proteins as early markers of cardiovascular risk in CRD patients.

The changes of serum sKlotho and NGAL levels and their correlation in type 2 diabetes mellitus patients with different stages of urinary albumin

OBJECTIVE

To investigate the changes of serum anti-aging protein Klotho and neutrophil gelatinase-associated lipocalin (NGAL) levels and their correlation in type 2 diabetes mellitus (T2DM) patients at different stages of diabetic kidney disease (DKD) determined by urinary albuminuria.

METHODS

462 cases with T2DM were divided into three groups: normoalbuminuric [N-UAlb; urinary albumin to creatinine ratio (UACR) < 30 mg/g, n=180], microalbuminuric [M-UAlb; UACR 30-300 mg/g, n = 158], macroalbuminuric [L-UAlb; UACR > 300 mg/g, n = 124]. The levels of serum soluble-Klotho (sKlotho), NGAL, 8-isoprostane prostaglandin F2α (8-iso-PGF2α), monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1) were determined by enzyme-linked immunosorbent assay (ELISA) in all cases and 160 control subjects.

RESULTS

Compared with control, serum sKlotho levels were significantly decreased (P < 0.001), and serum NGAL levels increased significantly (P < 0.001) in T2DM patients. Furthermore, serum sKlotho and NGAL levels were significantly negatively correlated (P < 0.001). Serum sKlotho levels negatively correlated with UACR, TG, CHO, LDL, 8-Iso-PGF2α, MCP-1, TNF-α, TGF-β1 (P < 0.001), but positively correlated with LDL (P < 0.001). Serum NGAL levels positively correlated with UACR, 8-Iso-PGF2α, MCP-1, TNF-α, TGF-β1 (P < 0.001). In addition, serum NGAL levels and LDL were significantly positively correlated (P = 0.005), and HDL was significantly negatively correlated (P < 0.001).

CONCLUSION

Serum Klotho and NGAL levels may become new biomarkers of the early diagnosis of DKD in T2DM. Klotho may participate in the development of DKD pathological mechanism such as oxidative stress related to inflammation, renal fibrosis, lipid metabolic disorders, modulating the pathological process of diabetic kidney tissue. NGAL may play a part in these mechanisms.

Active vitamin D and accelerated progression of aortic stiffness in hemodialysis patients: a longitudinal observational study

BACKGROUND

We hypothesized that high-dose active vitamin D therapy in the form of alphacalcidol (α-calcidol), used to treat secondary hyperparathyroidism in chronic kidney disease, could lead to vascular calcification and accelerated progression of aortic stiffness.

METHODS

We conducted an observational study in 85 patients on chronic hemodialysis, among which 70 were taking a weekly dose of α-calcidol of <2 µg and 15 were taking a weekly dose of ≥2 µg (pharmacological dose). Parathyroid hormone, 25-hydroxyvitamin D, fibroblast growth factor 23, and α-klotho were determined. Aortic stiffness was assessed by determination of carotid-femoral pulse wave velocity (cf-PWV) at baseline and after a mean follow-up of 1.2 years. A multivariable regression model was used to evaluate the impact of pharmacological dose of α-calcidol on the progression of aortic stiffness.

RESULTS

At baseline, clinical, biological, and hemodynamic parameters were similar. At follow-up, cf-PWV increased more in patients with pharmacological dose of α-calcidol (0.583±2.291 m/s vs. 1.948±1.475 m/s; P = 0.04). After adjustment for changes in mean blood pressure and duration of follow-up, pharmacological dose of α-calcidol was associated with a higher rate of progression of cf-PWV (0.969 m/s; 95% confidence interval = 0.111-1.827; P = 0.03), and this association persisted after further adjustments for parameters of mineral metabolism.

CONCLUSIONS

In this study, pharmacological dose of α-calcidol was associated with accelerated progression of aortic stiffness. This study suggest that the vascular safety of active vitamin D posology may need to be specifically addressed in the treatment of chronic kidney disease-related bone mineral disorder.

Association between decreased klotho blood levels and organic growth hormone deficiency in children with growth impairment

Objective

Klotho is an aging-modulating protein expressed mainly in the kidneys and choroid plexus, which can also be shed, released into the circulation and act as a hormone. Klotho deficient mice are smaller compared to their wild-type counterparts and their somatotropes show marked atrophy and reduced number of secretory granules. Recent data also indicated an association between klotho levels and growth hormone (GH) levels in acromegaly. We aimed to study the association between klotho levels and GH deficiency (GHD) in children with growth impairment.

Design

Prospective study comprising 99 children and adolescents (aged 9.0±3.7 years, 49 male) undergoing GH stimulation tests for short stature (height-SDS = −2.1±0.6). Klotho serum levels were measured using an α-klotho ELISA kit.

Results

Klotho levels were significantly lower (p<0.001) among children with organic GHD (n = 11, 727±273 pg/ml) compared to both GH sufficient participants (n = 59, 1497±754 pg/ml) and those with idiopathic GHD (n = 29, 1645±778 pg/ml). The difference between GHS children and children with idiopathic GHD was not significant. Klotho levels positively correlated with IGF-1- standard deviation scores (SDS) (R = 0.45, p<0.001), but were not associated with gender, pubertal status, age or anthropometric measurements.

Conclusions

We have shown, for the first time, an association between low serum klotho levels and organic GHD. If validated by additional studies, serum klotho may serve as novel biomarker of organic GHD.

Fibroblast growth factor 23 and Klotho serum levels in healthy children

Data for fibroblast growth factor 23 (FGF23) and particularly for Klotho in healthy children are limited. We aimed to investigate the relationship between FGF23 and Klotho with age and TmP/GFR and to evaluate parameters that might affect FGF23 and Klotho. In 159 healthy children (82 boys) with a mean±SD age of 8.78±3.47years we measured FGF23 (intact FGF23/iFGF23 and C-terminal FGF23/cFGF23) and soluble aKlotho serum levels by ELISA. Mean±SD value for cFGF23, was 51.14±12.79 RU/ml whereas median (range) values for iFGF23 and Klotho were 35 (8.8, 120) pg/ml and 1945 (372, 5866) pg/ml respectively. Neither FGF23 nor Klotho were significantly associated with age. Pubertal children had higher Klotho than prepubertal (p<0.05), and girls had higher levels of cFGF23 (p<0.05) and Klotho (p<0.001) than boys. Serum phosphate and TmP/GFR were positively associated with cFGF23 (p<0.01 and p<0.001), iFGF23 (p<0.05 and p<0.001) and Klotho (p<0.05 and p<0.01). Klotho was positively correlated with IGF-I (p<0.0001) and 1,25 (OH)2 vitamin D (p<0.05). In this study we provide data on cFGF23, iFGF23, and Klotho measured simultaneously in healthy children. The positive association of serum phosphate and TmP/GFR with FGF23 and Klotho suggests that they have a counterregulatory effect on phosphate homeostasis. The strong association of Klotho with IGF-I could indicate a role of Klotho in linear growth through phosphate regulation, but further studies are required.

α-Klotho is an acute phase protein and altered by restraint stress in mice

OBJECTIVE

To identify whether α-Klotho is a kind of acute phase protein and alternation in the level of protein and mRNA under restraint stress.

METHOD

48 mice were divided into three groups of 16: 1h, 10h and 20 h treat time group. Each group included restraint stress and control subgroup with same number animals (n = 8). ELISA was utilized in the assay of serum α-Klotho and corticosterone, RT-PCR was occupied in the detection of the expression of α-Klotho mRNA in renal tissue.

RESULT

α-Klotho protein concentration of control group 1h, 10h and 20 h was 757.71 ± 333.93 pg/ml, 687.38 ± 342.79 pg/ml and 912.90 ± 337.8 pg/ml, respectively. While the concentration of restraint stress group 1h, 10h and 20 h was 726.40 ± 342.79 pg/ml, 1261.54 ± 442.71 pg/ml, and 1696.18 ± 404.11 pg/ml. There was no significant difference among 1h, 10h and 20 h control groups (P > 0.05) as well as 1h treat time subgroup. Compared with respective control group, the difference of restraint stress group in 10h and 20 h treat time group was significant (P < 0.05). The expression of α-Klotho mRNA was slightly downregulated even when the mice underwent a 1 hour restraint stress, though without significance (p > 0.05). Prominent fold change, 2.02 and 2.46, happened in 10h and 20 h restraint group with significance (P < 0.05 and P < 0.01), respectively.

CONCLUSION

α-Klotho is a kind of acute phase protein. The serum α-Klotho protein is promoted while the α-Klotho mRNA is downregulated under the constraint stress.

Soluble α-klotho as a novel biomarker in the early stage of nephropathy in patients with type 2 diabetes

Objective

Although α-klotho is known as an anti-aging, antioxidant, and cardio-renal protective protein, the clinical implications of soluble α-klotho levels in patients with diabetes have not been evaluated. Therefore, this study evaluated whether plasma and urinary α-klotho levels are associated with albuminuria in kidney disease in diabetes.

Research Design and Methods

A total of 147 patients with type 2 diabetes and 25 healthy control subjects were enrolled. The plasma and urine concentrations of α-klotho were analyzed by enzyme-linked immunosorbent assay.

Results

Plasma α-klotho (572.4 pg/mL [95% CI, 541.9–604.6 pg/mL] vs. 476.9 pg/mL [95% CI, 416.9–545.5 pg/mL]) and urinary α-klotho levels (59.8 pg/mg creatinine [95% CI, 43.6–82.0 pg/mg creatinine] vs. 21.0 pg/mg creatinine [95% CI, 9.7–45.6 pg/mg creatinine]) were significantly higher in diabetic patients than non-diabetic controls. Among diabetic patients, plasma α-klotho concentration was inversely associated with albuminuria stages (normoalbuminuria, 612.6 pg/mL [95% CI, 568.9–659.6 pg/mL], microalbuminuria, 551.8 pg/mL [95% CI, 500.5–608.3 pg/mL], and macroalbuminuria, 505.7 pg/mL [95% CI, 439.7–581.7 pg/mL] (p for trend  = 0.0081), while urinary α-klotho levels were remained constantly high with increasing urinary albumin excretion.

Conclusions

Soluble α-klotho levels in plasma and urine may be novel and useful early markers of diabetic renal injury.

Prognostic value and link to atrial fibrillation of soluble Klotho and FGF23 in hemodialysis patients

Deranged calcium-phosphate metabolism contributes to the burden of morbidity and mortality in dialysis patients. This study aimed to assess the association of the phosphaturic hormone fibroblast growth factor 23 (FGF23) and soluble Klotho with all-cause mortality. We measured soluble Klotho and FGF23 levels at enrolment and two weeks later in 239 prevalent hemodialysis patients. The primary hypothesis was that low Klotho and high FGF23 are associated with increased mortality. The association between Klotho and atrial fibrillation (AF) at baseline was explored as secondary outcome. AF was defined as presence of paroxysmal, persistent or permanent AF. During a median follow-up of 924 days, 59 (25%) patients died from any cause. Lower Klotho levels were not associated with mortality in a multivariable adjusted analysis when examined either on a continuous scale (HR 1.25 per SD increase, 95% CI 0.84–1.86) or in tertiles, with tertile 1 as the reference category (HR for tertile two 0.65, 95% CI 0.26–1.64; HR for tertile three 2.18, 95% CI 0.91–2.23). Higher Klotho levels were associated with the absence of AF in a muItivariable logistic regression analysis (OR 0.66 per SD increase, 95% CI 0.41–1.00). Higher FGF23 levels were associated with mortality risk in a multivariable adjusted analysis when examined either on a continuous scale (HR 1.45 per SD increase, 95% CI 1.05–1.99) or in tertiles, with the tertile 1 as the reference category (HR for tertile two 1.63, 95% CI 0.64–4.14; HR for tertile three 3.91, 95% CI 1.28–12.20). FGF23 but not Klotho levels are associated with mortality in hemodialysis patients. Klotho may be protective against AF.

Associations of FGF-23 and sKlotho with cardiovascular outcomes among patients with CKD stages 2-4

BACKGROUND AND OBJECTIVES

CKD-mineral and bone disorders (CKD-MBD) measures contribute to cardiovascular morbidity in patients with CKD. Among these, fibroblast growth factor (FGF)-23 and its coreceptor Klotho may exert direct effects on vascular and myocardial tissues. Klotho exists in a membrane-bound and a soluble form (sKlotho). Recent experimental evidence suggests sKlotho has vasculoprotective functions.

DESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTS

Traditional and novel CKD-MBD variables were measured among 444 patients with CKD stages 2-4 recruited between September 2008 and November 2012 into the ongoing CARE FOR HOMe study. Across tertiles of baseline sKlotho and FGF-23, the incidence of two distinct combined end points was analyzed: (1) the first occurrence of an atherosclerotic event or death from any cause and (2) the time until hospital admission for decompensated heart failure or death from any cause.

RESULTS

Patients were followed for 2.6 (interquartile range, 1.4-3.6) years. sKlotho tertiles predicted neither atherosclerotic events/death (fully adjusted Cox regression analysis: hazard ratio [HR] for third versus first sKlotho tertile, 0.75 [95% confidence interval (95% CI), 0.43-1.30]; P=0.30) nor the occurrence of decompensated heart failure/death (HR for third versus first sKlotho tertile, 0.81 [95% CI, 0.39-1.66]; P=0.56). In contrast, patients in the highest FGF-23 tertile had higher risk for both end points in univariate analysis. Adjustment for kidney function attenuated the association between FGF-23 and atherosclerotic events/death (HR for third versus first FGF-23 tertile, 1.23 [95% CI, 0.58-2.61]; P=0.59), whereas the association between FGF-23 and decompensated heart failure/death remained significant after adjustment for confounders (HR for third versus first FGF-23 tertile, 4.51 [95% CI, 1.33-15.21]; P=0.02).

CONCLUSIONS

In this prospective observational study of limited sample size, sKlotho was not significantly related to cardiovascular outcomes. FGF-23 was significantly associated with future decompensated heart failure but not incident atherosclerotic events.

Gender dependence of serum soluble Klotho in acromegaly

OBJECTIVES

In acromegaly, disease activity is biochemically assessed by growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels. However, they are often discrepant, as several factors including gender influence their relationship. We recently found excessively high serum levels of soluble Klotho (sKl) in acromegalic patients, which depended on GH to a comparable extent as IGF-1. To further elucidate the relationship between GH and sKl, we examined the effect of gender on sKl in patients with untreated acromegaly.

PATIENTS AND DESIGN

We determined GH, IGF-1 and sKl in sera of 62 consecutive patients with newly diagnosed acromegaly (31 females/31 males, aged 20-85 years).

RESULTS

For their given GH excess at presentation with acromegaly, females had lower IGF-1 (490 ± 33 vs 604 ± 33 ng/ml, P = 0·02), but higher sKl [5171 ± 590 vs 3439 ± 431 pg/ml (mean ± SE), P = 0·02] levels than males. In multiple regression analysis, IGF-1 was closely associated with logGH (estimate 139, SE 47, P = 0·005) and BMI (estimate 14·2, SE 4·8, P = 0·005). sKl was closely associated with logGH (estimate 3088, SE 652, P = 0·0001) and gender (estimate 2034, SE 612, P = 0·002), and to a lesser extent with BMI (estimate 174, SE 66, P = 0·01).

CONCLUSIONS

For a given GH status, sKl concentrations are higher and IGF-1 concentrations are lower in women than in men. GH is the strongest predictor for both sKl and IGF-1, but gender needs to be considered when using these parameters for monitoring acromegalic patients.

Left ventricular mass progression despite stable blood pressure and kidney function in stage 3 chronic kidney disease

BACKGROUND/AIMS

Progressive chronic kidney disease (CKD) is associated with worsening cardiovascular (CV) risk not explained by traditional risk factors. Left ventricular (LV) hypertrophy (LVH) is an important CV risk factor, but its progression has not been documented in early CKD. We explored whether progression of LVH in early CKD would occur despite stable kidney function.

METHODS

We conducted a post hoc analysis of a 12-month study of lanthanum carbonate in stage 3 CKD, which included longitudinal assessments of CV biomarkers. Primary outcome for the analysis was the change in LV mass (LVM) indexed to height in meters(2.7) (LVM/Ht(2.7)). Secondary outcomes were changes in blood pressure (BP), pulse-wave velocity, LV systolic/diastolic function, fibroblast growth factor 23 (FGF23), klotho, and estimated glomerular filtration rate (eGFR).

RESULTS

Thirty-one of 38 original subjects had sufficient data for analysis. LVM/Ht(2.7) increased (47 ± 13 vs. 53 ± 13 g/m(2.7), p = 0.006) over 12 months despite stable BP, stable eGFR and normal LV systolic function. Vascular stiffness and LV diastolic dysfunction persisted throughout the study. Klotho levels decreased (748 ± 289 to 536 ± 410 pg/ml, p = 0.03) but were unrelated to changes in LVM/Ht(2.7). The change in FGF23/klotho ratio was strongly correlated with changes in LVM/Ht(2.7) (r2 = 0.582, p = 0.03).

CONCLUSION

Subjects with stage 3 CKD exhibited increasing LVM, persistent LV diastolic dysfunction and vascular stiffness despite stable kidney function, BP and LV systolic function. Abnormal FGF23 signaling due to reduced klotho expression may be associated with increasing LVM.

Acute and long term mineral metabolism adaptation in living kidney donors: a prospective study

BACKGROUND

Living kidney donors (LKDs) experience an abrupt decline in glomerular filtration rate (GFR). Mineral metabolism adaptations in early CKD are still debated and not well studied in LKDs. We prospectively studied acute and long term mineral metabolism adaptation of LKDs.

METHODS

From May 2010 to December 2012, we included 27 adult LKDs. Their mineral parameters and renal function were repeatedly measured at days 0, 1, 2, 3, 180 and 360 after donation. We also measured in uninephrectomized rats' Klotho in the remnant kidney and FGF23 circulating levels.

RESULTS

In the first days after nephrectomy, LKDs experience transient dilution hypocalcemia and secondary hyperparathyroidism. Urinary phosphate reabsorption decreases in spite of an abrupt decline in circulating FGF23 and Klotho. In a more chronic stage, at days 180 and 360 after donation, LKDs have lower GFR and 1,25(OH)2D compared to pre-donation levels, with unchanged 25(OH)D. PTH levels increase, resulting in decreased plasma phosphate levels and renal tubular reabsorption of phosphate. In comparison to pre-donation, FGF23 levels are not significantly changed whereas circulating Klotho levels are lower than pre-donation but higher than immediately post-donation. In uninephrectomized rats, Klotho kidney expression increases after three weeks, whereas circulating FGF23 levels are unchanged.

CONCLUSION

From six months after kidney donation, LKDs develop secondary hyperparathyroidism related to a decrease in 1,25(OH)2D, and decreased plasma phosphate levels. FGF23 levels do not rise in LKDs. Middle term mineral metabolism adaptations to decreased eGFR in donors include decrease in 1,25(OH)2D and increase in PTH and fractional excretion of phosphate resulting in lowered plasma phosphate levels, independently of FGF23. These adaptations differ from those described in CKD patients.

Soluble α-klotho and its relation to kidney function and fibroblast growth factor-23

CONTEXT

Relations between fibroblast growth factor-23 (FGF-23), soluble α-klotho (s-α-klotho), and kidney function in chronic kidney disease (CKD) are still unclear. Especially the role of s-α-klotho requires further study.

OBJECTIVES

Our objectives were to analyze the relation of s-α-klotho to estimated glomerular filtration rate (eGFR), FGF-23, and other parameters of calcium-phosphate metabolism and to investigate the response of s-α-klotho to cholecalciferol.

PATIENTS, DESIGN, AND SETTING

Twenty-four CKD (stage 1-5) patients participated in this 8-week randomized controlled trial (vitamin D and chronic renal insufficiency).

INTERVENTIONS

Interventions included 40 000 IU cholecalciferol or placebo weekly.

MAIN OUTCOME MEASURE

S-α-klotho was determined by ELISA with antihuman klotho antibodies 67G3 and 91F1.

RESULTS

For all patients, s-α-klotho concentrations did not differ between CKD stages. When patients were subdivided based on FGF-23 concentrations, a positive association of s-α-klotho with eGFR became apparent in patients with lower than median FGF-23 concentrations but not in those above median value. Patients with s-α-klotho below 204 pg/mL showed higher age, lower phosphate clearance, and lower bone-specific alkaline phosphatase compared with patients with higher s-α-klotho. Treatment with cholecalciferol significantly increased 1,25-dihydroxyvitamin D. The increase of FGF-23 had only borderline significance. There was no significant effect of high-dose cholecalciferol administration for 8 weeks on plasma s-α-klotho.

CONCLUSIONS

CKD patients with s-α-klotho below 204 pg/mL had higher age, lower phosphate clearance, and lower bone-specific alkaline phosphatase. An association of s-α-klotho with eGFR was observed only in the presence of close to normal, but not high, FGF-23 concentrations. Cholecalciferol treatment did not change s-α-klotho concentrations.

Impact of parathyroidectomy on serum FGF23 and soluble Klotho in hemodialysis patients with severe secondary hyperparathyroidism

CONTEXT

Klotho is a transmembrane protein that functions as a coreceptor for fibroblast growth factor 23 (FGF23). Klotho is cleaved and released into the circulation; however, the main site of production, physiological role, and regulation of soluble Klotho in humans are largely unknown.

OBJECTIVE

The aim of this study was to determine the impact of parathyroidectomy (PTx) on serum FGF23 and soluble Klotho levels in patients with severe secondary hyperparathyroidism.

DESIGN AND SETTING

This was a prospective, single-arm trial conducted at Tokai University School of Medicine.

PATIENTS

Thirteen hemodialysis patients with severe secondary hyperparathyroidism who were candidates for PTx participated in the study.

INTERVENTIONS

All patients underwent total PTx with forearm autotransplantation.

MAIN OUTCOME MEASURES

We evaluated changes in serum FGF23 and soluble Klotho levels for 90 days after PTx. Other biochemical parameters related to mineral and bone metabolism were also assessed.

RESULTS

At baseline, serum FGF23 levels were markedly elevated, whereas serum soluble Klotho levels were modestly decreased. PTx resulted in a marked, progressive decline in serum FGF23 levels together with significant reductions in serum calcium, phosphorus, and intact PTH levels. The serum soluble Klotho levels were reduced 13% from baseline on the day after PTx; however, these levels then increased progressively, reaching 34% above the postoperative values.

CONCLUSIONS

Our results suggest that the parathyroid gland is not the major site of soluble Klotho production in patients with end-stage renal disease, and the production of Klotho by other organ(s) is affected by alterations in mineral metabolism or medications taken after PTx.

[Mineral metabolism in patients on chronic peritoneal dialysis]

INTRODUCTION

Children with chronic kidney disease (CKD) and receiving peritoneal dialysis (PD) have disorders of mineral metabolism that impact their growth, survival and cardiovascular functions. New molecular markers offer a better understanding of the pathophysiology of this disease.

OBJECTIVE

To characterize some components of mineral metabolism, with emphasis on FGF23/Klotho and cardiovascular functions (CV) of these patients.

PATIENTS AND METHOD

Prospective observational cohort study.

EXCLUSION CRITERIA

serum 25 (OH) vitamin D < 20 ng/ml, peritonitis within the last two months and active nephrotic syndrome. Calcemia, phosphemia, parathyroid hormone (PTH), 25 (OH) vitD3, 1.25 (OH) vitD3, FGF23 and Klotho in plasma were measured. FGF23 and Klotho were quantified in healthy children as a control group. Echocardiography was performed calculating the left ventricular mass index (LVMI). Descriptive statistics analysis, Pearson correlation coefficient for association among variables and multivariate analysis were conducted.

RESULTS

33 patients, 16 males, aged between 1.2 and 13.4 years were included. Age of onset for PD: 7.3 ± 5.0 years, time receiving PD: 13.5 ± 14.5 months. The plasma concentration of 25 (OH) vitD3 was 34.2 ± 6.3 pg/ml. Calcemia and phosphemia values were 9.8 ± 0.71 and 5.4 ± 1.0 mg/dl respectively. PTH was 333 ± 287 pg/ml. FGF23 in plasma was 225.7 ± 354.3 pg/ml and Klotho 131.6 ± 72 pg/ml, and in the controls ( n = 16 ), it was 11.9 ± 7.2 pg/ml and 320 ± 119 pg/ml, respectively. The residual and total dose of dialysis (KtV) was 1.6 ± 1.3 and 2.9 ± 1.6, respectively. FGF23 levels significantly correlated with calcium (p < 0.001, r = 0.85), and inversely with residual KtV, showing no relationship with phosphemia. Klotho level correlated negatively with residual KtV and also, it showed a negative association with chronological age and age at onset of PD. LVMI > 38 g/m² was confirmed in 20/28 patients.

CONCLUSIONS

The values of FGF23, and PTH are elevated in children with CKD on PD. Klotho levels in CKD patients are lower than control children. A strong association of calcemia with FGF23 and PTH is reported. Residual renal function is inversely associated with FGF23 and Klotho. A high incidence of left ventricular hypertrophy was found evidencing a cardiovascular compromise in these patients.

Association of plasma soluble α-klotho with pro-endothelin-1 in patients with type 2 diabetes

OBJECTIVES

To study the relationship between plasma soluble klotho (sKlotho) and pro-endothelin-1 (proET-1) in patients with type 2 diabetes (T2DM).

SUBJECTS AND METHODS

In this cross-sectional study, we recruited 175 T2DM subjects and 56 non-diabetic controls. Plasma sKlotho, proET-1 and extracellular superoxide dismutase (SOD) were measured by ELISA and ILMA, respectively.

RESULTS

Plasma sKlotho level in patients with T2DM was lower compared to that in non-diabetic controls (416.8±148.1 vs. 494.6±134.3 pg/ml, p=0.001) and showed significant interaction with diabetes status in its association with proET-1. Plasma sKlotho was inversely correlated with proET-1 in T2DM (Rho=-0.410, p<0.0001) but not in non-diabetic controls (Rho=0.091, p=0.505). Multivariable linear regression models revealed that sKlotho was independently associated with proET-1 after adjustment for renal filtration function, albuminuria, diabetes duration, HbA1c, systolic and diastolic blood pressure.

CONCLUSIONS

Plasma sKlotho was associated with proET-1 independent of renal function in patients with T2DM.

Early chronic kidney disease-mineral bone disorder stimulates vascular calcification

The chronic kidney disease-mineral and bone disorder (CKD-MBD) syndrome is an extremely important complication of kidney diseases. Here we tested whether CKD-MBD causes vascular calcification in early kidney failure by developing a mouse model of early CKD in a background of atherosclerosis-stimulated arterial calcification. CKD equivalent in glomerular filtration reduction to human CKD stage 2 stimulated early vascular calcification and inhibited the tissue expression of α-klotho (klotho) in the aorta. In addition, osteoblast transition in the aorta was stimulated by early CKD as shown by the expression of the critical transcription factor Runx2. The ligand associated with the klotho-fibroblast growth factor receptor complex, FGF23, was found to be expressed in the vascular media of sham-operated mice. Its expression was decreased in early CKD. Increased circulating levels of the osteocyte-secreted proteins, FGF23, and sclerostin may have been related to increased circulating klotho levels. Finally, we observed low-turnover bone disease with a reduction in bone formation rates more than bone resorption. Thus, the CKD-MBD, characterized by cardiovascular risk factors, vascular calcification, increased circulating klotho, FGF23 and sclerostin levels, and low-turnover renal osteodystrophy, was established in early CKD. Early CKD caused a reduction of vascular klotho, stimulated vascular osteoblastic transition, increased osteocytic secreted proteins, and inhibited skeletal modeling producing the CKD-MBD.

[Significance of the morphogenetic proteins FGF-23 and Klotho as predictors of prognosis of chronic kidney disease]

AIM

To study the role of the morphogenetic proteins FGF-23 and Klotho in the progression of chronic kidney disease (CKD) and in the development of cardiovascular events, inflammation, protein-energy deficiency, and other complications.

SUBJECTS AND METHODS

Examinations were made in 70 patients with Stages I-VD CKD: 41 with chronic glomerulonephritis (including 10 with nephritis in the presence of diffuse connective tissue diseases), 22 with tubulointerstitial nephritis, and 7 with hypertensive nephrosclerosis. There were a total of 30 men and 40 women whose age was 20 to 84 years; the mean age at the study inclusion was 41 +/- 6.7 years. The serum levels of FGF-23 (Human FGF-23 ELISA kit using monoclonal antibodies to complete molecule of FGF-23) and Klotho (Human alpha-K1 ELISA using anti-Klotho antibodies) were investigated in all the 70 patients with CKD.

RESULTS

The sera of all the examinees with CKD showed elevated FGF-23 and decreased Klotho levels, the magnitude of a change in which increased from Stage I to VD. In patients with different stages of CKD, the increase in FGF-23 levels, as glomerular filtration rate reduced, outstripped that in the serum levels of phosphorus and intact parathyroid hormone. There was a strong correlation of the serum level of the morphogenetic proteins, Klotho in particular, with proteinuria, C-reactive protein level, protein-energy deficiency, indicating the pleiotropic effects of these proteins. There was also a strong correlation between serum Klotho and ferritin levels and transferrin saturation percentage, which suggests that Klotho may be involved in iron regulation.

CONCLUSION

The results of the investigation lend credence to the experimental and clinical findings that the serum levels of the morphogenetic proteins FGF-23 (an increase) and Klotho (a decrease) are early markers for progressive CKD and that their changes begin just in Stage III CKD and progress as renal failure worsens.

Changes chemopreventive markers in colorectal cancer development after inulin supplementation

BACKGROUND

Natural dietary compounds such as prebiotics modulate microbial composition and could prevent the colon cancer development as potential chemopreventive agent.

OBJECTIVES

Effect of prebiotic-inulin on biochemical, microbial and chemopreventive markers were examined in Sprague-Dawley rats during experimental chemically dimethylhydrazine induced colon cancer development.

METHODS

Rats were divided to 3 groups: control group (CG), group with dimethylhydrazine (DMH) and group with DMH and prebiotic (DMH+PRE). The efficacy of the prebiotic inulin (PRE) on the activities of β-glucuronidase, short chain fatty acids (SCFAs), counts of coliforms and lactobacilli, immunoreactivity of cyclooxygenase-2 (COX-2), transcription nuclear factor kappa beta (NFκB) and inducible nitric oxide synthase (iNOS) in colon tissue were examined.

RESULTS

Inulin significantly decreased coliforms counts (p<0.01), increased lactobacilli counts (p<0.001), and decreased activity of β-glucuronidase (p<0.01) in fresh caecal digesta. Butyric and propionic acids concentrations were increased after inulin supplementation in comparison to DMH group. Application of inulin decreased immunoreactivity and numbers of COX-2, NFκB and iNOS positive cells in colon tissue in comparison to DMH group.

CONCLUSION

Inulin suppressed expression observed markers, which play an important role in carcinogenesis and in the inflammatory process, which predisposes to the use of inulin in the prevention or treatment of inflammatory bowel disease (Tab. 1, Fig. 2, Ref. 17).

Association between circulating fibroblast growth factor 23, α-Klotho, and the left ventricular ejection fraction and left ventricular mass in cardiology inpatients

Background

Fibroblast growth factor 23 (FGF23), with its co-receptor Klotho, plays a crucial role in phosphate metabolism. Several recent studies suggested that circulating FGF23 and α-Klotho concentrations might be related to cardiovascular abnormalities in patients with advanced renal failure.

Purpose

Using data from 100 cardiology inpatients who were not undergoing chronic hemodialysis, the association of circulating levels of FGF23, α-Klotho, and other calcium-phosphate metabolism-related parameters with the left ventricular ejection fraction (LVEF) and left ventricular mass (LVM) was analyzed.

Methods and Results

LVEF was measured using the modified Simpson method for apical 4-chamber LV images and the LVM index (LVMI) was calculated by dividing the LVM by body surface area. Univariate analysis showed that log transformed FGF23, but not that of α-Klotho, was significantly associated with LVEF and LVMI with a standardized beta of −0.35 (P<0.001) and 0.26 (P<0.05), respectively. After adjusting for age, sex, estimated glomerular filtration rate, and serum concentrations of intact parathyroid hormone, and 25-hydroxyvitamin D as covariates into the statistical model, log-transformed FGF23 was found to be a statistically positive predictor for decreased left ventricular function and left ventricular hypertrophy.

Conclusions

In cardiology department inpatients, circulating FGF23 concentrations were found to be associated with the left ventricular mass and LVEF independent of renal function and other calcium-phosphate metabolism-related parameters. Whether modulation of circulating FGF23 levels would improve cardiac outcome in such a high risk population awaits further investigation.

Infection and smoking are associated with decreased plasma concentration of the anti-aging protein, α-klotho

OBJECTIVE

The objective of this study was to determine whether maternal plasma concentrations of soluble α-klotho are different between women with microbial invasion of the intra-amniotic cavity (MIAC) and those without MIAC among preterm labor and intact membranes (PTL) or preterm prelabor rupture of membranes (pPROM).

METHODS

A cross-sectional study was conducted to include women in the following groups: i) PTL with MIAC (n=14); ii) PTL without MIAC (n=79); iii) pPROM with MIAC (n=30); and iv) pPROM without MIAC (n=33). MIAC was defined as a positive amniotic fluid culture for microorganisms (aerobic/anaerobic bacteria or genital mycoplasmas). Amniotic fluid samples were obtained within 48 h of maternal blood collection. Plasma concentration of soluble α-klotho was determined by ELISA.

RESULTS

i) The median plasma concentration (pg/mL) of soluble α-klotho was significantly lower in patients with MIAC than in those without MIAC (787.0 vs. 1117.8; P<0.001). ii) Among patients with PTL, those with MIAC had a lower median plasma concentration (pg/mL) of soluble α-klotho than those without MIAC (787.0 vs. 1138.9; P=0.007). iii) Among patients with pPROM, those with MIAC had a lower median plasma concentration (pg/mL) of soluble α-klotho than those without MIAC (766.4 vs. 1001.6; P=0.045). iv) There was no significant difference in the median plasma concentration of soluble α-klotho between PPROM without MIAC and PTL without MIAC (1001.6 pg/mL vs. 1138.9 pg/mL, respectively; P=0.5). v) After adjustment for potential confounders (maternal age, tobacco use, gestational age at venipuncture), soluble α-klotho remained significantly associated with MIAC (P=0.02); and vi) Among patients without MIAC, smoking was significantly associated with a lower median plasma concentration soluble α-klotho than in non-smokers (794.2 pg/mL vs. 1382.0 pg/mL, respectively; P<0.001); however, this difference was not observed in patients with MIAC.

CONCLUSIONS

Intra-amniotic infection occurring at preterm gestations (regardless of membrane status) was associated with a decrease in maternal plasma concentrations of soluble α-klotho. Moreover, among patients without infection, the plasma concentration of α-klotho was lower in smokers.

The impact of nephrectomy and renal transplantation on serum levels of soluble Klotho protein

BACKGROUND

Klotho, a single-pass transmembrane protein primarily expressed in the kidneys, parathyroid glands, and choroid plexus of the brain, has a short cytoplasmic tail and a long extracellular domain, which can be cleaved and released as a soluble form. However, information regarding the origins and kinetics of soluble serum Klotho remains poorly understood. We evaluated serial changes in serum Klotho levels among living donors before and after retroperitoneoscopic nephrectomy as well as in their renal transplant recipients.

METHODS

The levels of soluble Klotho in serum obtained from 10 living donors and their renal transplant recipients were determined using a sandwich enzyme-linked immunosorbent assay system.

RESULTS

Serum soluble Klotho was detectable in all subjects. The baseline serum Klotho concentrations in the living donors ranged from 726.4 to 1417.1 pg/mL (median, 909.8 pg/mL; interquartile ranges [IR], 754.8-1132.4), whereas that in the concomitant renal transplant recipients ranged from 397.5 to 1047.2 pg/mL (median, 613.0 pg/mL; IR, 445.9-750.8; P = .003). The levels of soluble serum Klotho measured 5 days after retroperitoneoscopic nephrectomy (median, 619.0 pg/mL; IR, 544.6-688.5; P = .001) were significantly lower than the baseline values. Among the renal transplant recipients, no significant changes in serum Klotho levels were observed during the observation period.

CONCLUSION

Our data regarding soluble serum Klotho levels obtained from living donors support the idea that the kidneys are a major source of soluble serum Klotho in human subjects without a deterioration of renal function. In recipients, concomitant acute kidney injuries and immunosuppressive protocols might modulate the release of soluble Klotho from the grafts into the circulation.

Serum soluble Klotho protein level is associated with residual diuresis in incident peritoneal dialysis patients

AIM

Active vitamin D (1,25-dihydroxyvitamin D₃), PTH, fibroblast growth factor-23 (FGF-23) and Klotho protein are key regulators of phosphate metabolism. Hyperphosphatemia and increased FGF-23 level in patients with end-stage renal disease are associated with increased morbidity and mortality. The relationships among key regulators of phosphate metabolism are still being investigated. FGF-23, the humoral factor involved in phosphate metabolism, is strongly associated with serum phosphorus level. Klotho, a transmembrane protein expressed primarily in renal tubules, functions as an obligatory co-receptor for FGF-23. The soluble form of Klotho, produced by the shedding of the transmembrane protein, is detectable in body fluids. The purpose of the study was to assess if serum soluble alpha-Klotho level was related to phosphate metabolism parameters and residual renal function (RRF) in incident peritoneal dialysis (PD) patients.

METHODS

Thirty-five clinically stable patients 4 to 6 weeks after the onset of PD were included in the study. For each patient, clinical and laboratory data were reviewed. Serum phosphorus concentration, urinary and peritoneal phosphate clearance, serum FGF-23 and soluble Klotho protein concentrations were determined.

RESULTS

Serum soluble alpha-Klotho was strongly negatively correlated with 24-hour diuresis (Rs = -0.55, p = 0.004) and renal phosphate clearance (Rs = -0.40, p = 0.049), but not with RRF.

CONCLUSIONS

Serum soluble Klotho protein concentration is inversely related to residual diuresis and renal phosphate clearance in incident PD patients.

Soluble α-klotho: a novel serum biomarker for the activity of GH-producing pituitary adenomas

OBJECTIVE

Klotho is a lifespan-influencing gene expressed mainly in the kidneys. Soluble α-Klotho (αKL) is released into the circulation. In this study, we present baseline αKL serum levels of patients with acromegaly compared with controls with other pituitary adenomas and assess changes following transsphenoidal surgery.

DESIGN

Prospective controlled study.

METHODS

We measured soluble αKL (sandwich ELISA) and IGF1 (RIA) in sera of 14 patients (eight females and six males) with active acromegaly and in 22 control patients (13 females and nine males) operated for non-GH-producing pituitary adenomas. Immunohistochemical staining for Klotho was performed in resected adenomas and in normal pituitary tissue samples.

RESULTS

Soluble αKL was high in the acromegaly group preoperatively (median 4217 pg/ml, interquartile range (IQR) 1812-6623 pg/ml) and declined after surgery during early follow-up (2-6 days; median 645 pg/ml, IQR 550-1303 pg/ml) (P<0.001) and during late follow-up (2-3 months post-operatively; median 902 pg/ml, IQR 497-1340 pg/ml; P<0.001). In controls, preoperative soluble αKL was significantly lower than in acromegalics, 532 pg/ml (400-677 pg/ml; P<0.001). Following surgery, soluble αKL remained low during early and late follow-up - changes over time within the control group were not statistically significant. These results were independent of age, sex and kidney function. Klotho staining was equal or slightly decreased in GH-positive adenomas compared with controls.

CONCLUSION

High soluble αKL serum levels were specific to GH-producing adenomas and decreased rapidly following adenoma removal. Thus, soluble αKL appears to be a new specific and sensitive biomarker reflecting disease activity in acromegaly. Similar Klotho staining patterns in controls and acromegalics suggest that the rise in serum αKL is caused by systemic actions of pituitary GH rather than due to increased expression of Klotho by the pituitary (adenoma).

Umbilical cord levels of sclerostin, placental weight, and birth weight are predictors of total bone mineral content in neonates

CONTEXT

During pregnancy, changes occur in the maternal calcium homeostasis to fulfill fetal demand. We hypothesized that the fibroblast growth factor 23 (FGF23) system and Wnt signaling pathway are important for normal skeletal development in the offspring.

AIMS

Circulating α-klotho, FGF23, sclerostin, and 25-hydroxyvitamin D (25(OH)D) at the fetal and maternal sides of the placenta were measured to investigate associations with newborn bone mass independent of maternal BMI, calcium and phosphate levels, placental weight, and birth weight.

METHODS

In a prospective cohort of healthy pregnant women, the total body bone mineral content (BMC) in 202 newborns was measured by dual-energy X-ray absorptiometry. Maternal circulating levels of the biomarkers were measured at gestational weeks 30-32 and in umbilical cord plasma (UCP) at birth.

RESULTS

Mean α-klotho and sclerostin concentrations in the UCP were significantly higher than maternal levels (3004 vs 1077  pg/ml; P<0.001 and 629 vs 346  pg/ml; P<0.001 respectively), and mean 25(OH)D was lower (31 vs 45  nmol/l; P<0.001). The UCP and maternal FGF23 levels were similar. No significant effects of maternal biomarkers on BMC were found in regression analyses. Among UCP biomarkers, only UCP sclerostin was significantly associated with BMC in univariate analyses, and the effect remained significant after adjustment for birth weight and other confounders.

CONCLUSIONS

We found that UCP sclerostin levels, birth weight, and placental weight were significant predictors of neonatal BMC but found no evidence for a main role of maternal levels of α-klotho, FGF23, sclerostin, or 25(OH)D nor of UCP levels of α-klotho, FGF23, or 25(OH)D.