Plasma levels of fibroblast growth factor-23 and mineral metabolism in diabetic and non-diabetic patients on chronic hemodialysis

Fibroblast growth factor 23 and calcium-phosphate metabolism in relation to cardiovascular risk factors in patients with type 1 diabetes

BACKGROUND

Cardiovascular disease (CVD) is the major cause of mortality in type 1 diabetes (T1D). The objective of this study is to evaluate fibroblast growth factor 23 (FGF23) and calcium-phosphate metabolism in relation to cardiovascular risk factors in adults with and without T1D.

METHODS

A case-control study was conducted using data from patients with T1D and age- and sex matched controls without T1D from the Lifelines Cohort Study.

RESULTS

We included 302 adults in the T1D group and 302 adults in the control group. Median age was 42 years. Median glycosylated hemoglobin (HbA1c) in the T1D group was 7.8%. FGF23 of all patients with T1D was not significantly different from controls. Females with T1D had significantly higher FGF23 than males with T1D (83.3 vs 69.3 U/mL, p = 0.002), this was not observed in controls. Serum phosphate, calcium, and alkaline phosphatase were higher and parathyroid hormone was lower in patients with T1D, compared to controls (all p < .001), all within normal range. In the T1D group, FGF23 was positively correlated with serum phosphate (p < .001), alkaline phosphatase (p = .01), and calcium (p = .030), these correlations were not observed in controls. Median FGF23 was significantly higher in current smokers than in nonsmokers with T1D (84.9 vs 73.5 U/mL, p < .05).

CONCLUSIONS

Serum calcium, phosphate, and alkaline phosphatase were higher in patients with T1D than in controls and were positively correlated to FGF23 in patients with T1D. Current smokers with T1D had higher FGF23 than nonsmokers with T1D. These findings may contribute to the increased risk of CVD in patients with T1D.

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.

Fibroblast Growth Factor 23 and Adverse Clinical Outcomes in Type 2 Diabetes: a Bitter-Sweet Symphony

PURPOSE OF REVIEW

Fibroblast growth factor 23 (FGF23) is a key phosphate-regulating hormone that has been associated with adverse outcomes in patients with chronic kidney disease (CKD). Emerging data suggest that FGF23 plays a specific role in type 2 diabetes, partly independent of kidney function. We aimed to summarize current literature on the associations between FGF23 and outcomes in patients with type 2 diabetes with or without CKD.

RECENT FINDINGS

Several cohort studies have shown strong associations between plasma FGF23 and cardiovascular outcomes in diabetic CKD. Moreover, recent data suggest that FGF23 are elevated and may also be a risk factor for cardiovascular disease and mortality in type 2 diabetes patients without CKD, although the magnitude of the association is smaller than in CKD patients. Diabetes-related factors may influence plasma FGF23 levels, and a higher FGF23 levels seem to contribute to a higher cardiovascular and mortality risk in patients with type 2 diabetes. Although this risk may be relevant in diabetic individuals with preserved kidney function, it is strongly accentuated in diabetic nephropathy. Future studies should clarify if FGF23 is merely a disease severity marker or a contributor to adverse outcomes in type 2 diabetes and establish if antidiabetic medication can modify FGF23 levels.

Hypomagnesemia is not an independent risk factor for mortality in Japanese maintenance hemodialysis patients

PURPOSE

It is unclear whether hypomagnesemia is an independent risk factor or innocent bystander for mortality in maintenance hemodialysis (MHD) patients. Thus, we studied associations between hypomagnesemia and all-cause as well as cardiovascular (CV) mortality in MHD patients.

METHODS

Baseline clinical characteristics and coronary artery calcium score (CACS) of 353 Japanese MHD patients were reviewed. Three-year survival rate and mortality risk factors were assessed.

RESULTS

Median (interquartile range) age, dialysis vintage, serum magnesium (Mg), serum albumin and CACS of the subjects were 68 (60-78) years, 75 (32-151) months, 2.4 (2.2-2.7) mg/dl, 3.6 (3.3-3.8) g/dl, and 1181 (278-3190), respectively. During the 3-year period, 91 patients died. Kaplan-Meier overall 3-year survival rates were 59.0% in in patients with Mg < 2.4 mg/dl (n = 136) and 82.3% in patients with Mg ≥ 2.4 mg/dl (n = 217), (P < 0.0001). In Cox regression models not incorporating serum albumin, Mg < 2.4 mg/dl was significantly associated with 3-year all-cause death, independent of age, dialysis vintage, average ultrafiltration, Log (CACS + 1), warfarin use, serum potassium, high-sensitivity C-reactive protein (hsCRP), phosphate, uric acid, and intact parathyroid hormone [Hazard ratio (HR) 95% confidence interval (CI): 2.82 (1.31-6.29), P = 0.0078], and CV death, independent of age, dialysis vintage, Log (CACS + 1), warfarin use, serum hsCRP, and uric acid [HR (95% CI): 4.47 (1.45-16.76), P = 0.0086]. Nevertheless, associations of Mg < 2.4 mg/dl with all-cause and CV mortality were all absent in models that included serum albumin.

CONCLUSIONS

Hypomagnesemia is not an independent risk factor for mortality but is associated with malnutrition in MHD patients.

Addition of Novel Biomarkers for Predicting All-Cause and Cardiovascular Mortality in Prevalent Hemodialysis Patients

Novel biomarkers might improve the prediction of mortality in hemodialysis (HD) patients. We simultaneously measured the levels of conventional and novel biomarkers [serum N-terminal pro-brain natriuretic peptide (NT-proBNP), intact fibroblast growth factor-23 (FGF23), β2-microglobulin (β2MG), cystatin C, and high-sensitivity C-reactive protein (hsCRP)] in 307 prevalent Japanese HD patients. There were 66 all-cause deaths, and 25 cardiovascular (CV) deaths during 2 years, which were assessed using Cox models and concordance (C)-statistics. The addition of NT-proBNP alone (P < 0.05) or NT-proBNP, hsCRP, and β2MG as a panel (C-statistics: 0.834 vs. 0.776, P < 0.01) to a conventional risk model composed of age, diabetes, and the serum albumin level significantly improved the prediction of 2-year all-cause mortality, and the addition of NT-proBNP and hsCRP as a panel to a conventional risk model composed of age significantly improved the prediction of 2-year CV mortality (P < 0.05) in Japanese prevalent HD patients. Neither FGF23 nor cystatin C improved mortality prediction.

Relationship of fibroblast growth factor 23 and fetuin--A to coronary atherosclerosis

BACKGROUND

Serum fibroblast growth factor 23 (FGF-23) and fetuin-A are established predictors of morbidity and mortality due to cardiovascular disease. The objective of the present study is to evaluate the relationship between coronary artery disease (CAD) and serum concentrations of FGF-23 and fetuin-A.

METHODS

A total of 383 subjects who underwent coronary computed tomography angiography (CCTA) were included in the study. CCTA detected CAD in 208 patients; the rest of the patients had no detectable CAD.

RESULTS

Serum FGF-23 and fetuin-A levels were significantly increased in CAD patients compared to non-CAD patients (26.6±21.1pg/mL vs. 17.9±16.1pg/mL, p=0.001 and 826±350mg/L vs. 595±300mg/L, p<0.001, respectively). Serum FGF-23, fetuin-A, low-density lipoprotein (LDL)-cholesterol, and uric acid values were elevated in non-diabetic patients with CAD when compared to those without CAD. FGF-23, and fetuin-A were not significantly different in diabetic patients with CAD when compared to those without CAD. Using multivariate logistic regression analysis, we found that age, hypertension, LDL-Cholesterol, high-density lipoprotein (HDL)-Cholesterol, hs-CRP, uric acid, FGF-23 and fetuin-A levels were independently associated with the presence of CAD.

CONCLUSION

FGF-23 and fetuin-A were positively correlated with coronary atherosclerosis Similar trends were seen among diabetic patients, but this did not reach statistical significance. FGF-23 and fetuin-A could be used as novel risk markers of cardiovascular disease.

Fibroblast growth factor-23 levels are associated with vascular calcifications in peritoneal dialysis patients

BACKGROUND

The aim of the study was to assess the relationship between fibroblast growth factor-23 (FGF-23) and vascular calcifications (VC) in peritoneal dialysis (PD) patients.

METHODS

A cross-sectional study was performed in 55 PD patients who underwent pelvic X-ray to assess for VC. Patients with and without linear calcifications were recorded.

RESULTS

Fifteen patients (27.3%) had linear calcifications on pelvic X-ray. FGF-23 levels were higher in patients with VC (299.5 (30.4-2,410.0) vs. 74.4 (14.8-1,030) pg/ml, p < 0.01). Diabetic patients had lower FGF-23 values (43.2 (14.9-134.0) vs. 103.5 (14.8-2,410) pg/ml, p < 0.01). Patients with residual renal function (RRF) had lower FGF-23 levels (70.6 (14.8-513) vs. 179.5 (30.4-2,410) pg/ml, p = 0.06); however, this did not reach statistical significance. FGF-23 levels, age, creatinine, Ca, dialysis duration and HbA1c were positively correlated with VC, whereas RRF, Ca intake and ALP were negatively associated. Multivariate logistic analysis confirmed FGF-23 levels, age, dialysis duration and RRF to be associated with VC.

CONCLUSIONS

FGF-23 levels are associated with VC in PD patients. Further studies are needed to clarify whether it is simply a marker or a potential factor. It may prove to be an important therapeutic target for VC management.

Fibroblast growth factor-23 and calcium phosphate product in young chronic kidney disease patients: a cross-sectional study

Background

Fibroblast growth factor-23 (FGF-23), a novel marker of bone disease in chronic kidney disease (CKD) has been shown to correlate with vascular calcifications. We aimed to describe the effect of the calcium phosphate product (Ca*P) on FGF-23 concentrations in children and young adults without confounding cardiovascular disease.

Methods

Pediatric and young adult patients with CKD stages I-V were recruited in this cross sectional study to measure FGF-23, cystatin C, vitamin D-metabolites and other serum markers of bone metabolism. FGF-23 levels were determined with an enzyme-linked immunosorbent assay. The association between FGF-23 and (Ca*P) was assessed using non-parametric methods. Patients were divided into two age groups, less than 13 years of age and greater than 13 years of age.

Results

This cross-sectional study measured serum FGF-23, in 81 patients (42 females, 51.9%) at London Health Sciences Centre, aged 2 to 25 years, with various stages of CKD (Cystatin C estimated glomerular filtration rate, eGFR=10.7-213.0 ml/min). For the whole entire group of patients, FGF-23 levels were found to correlate significantly with age (Spearman r= 0.26, p=0.0198), Cystatin C eGFR (Spearman r=−0.40 p=0.0002), CKD stage (Spearman r=0.457, p<0.0001), PTH (Spearman r=0.330, p=0.0039), ionized calcium (Spearman r=−0.330, p=0.0049), CysC (Spearman r= 0.404, p=0.0002) and 1,25-dihydroxyvitamin D (Spearman r=−0.345, p=0.0034) concentrations. No significant correlation was found between FGF-23 levels and calcium phosphate product (Spearman r= 0.164, p=0.142). Upon classification of patients into two age groups, less than 13 years of age and more than 13 years of age, correlational results differed significantly. FGF-23 correlated with CysC eGFR( Spearman r= −0.633, p<0.0001), CKD stage (Spearman r=0.731, p<0.0001), phosphate (Spearman r= 0.557, p<0.0001), calcium phosphate product (Spearman r=0.534, p<0.0001), 125(OH)2 Vit D (Spearman r=−0.631, p<0.0001), PTH (Spearman r= 0.475, p=0.0017) and ionized calcium (Spearman r= −0.503, p=0.0015) only in the older group. The relationship between FGF-23 and Ca*P for the older group could be expressed by the exponential model FGF-23= 38.15 e^0.4625Ca*P.

Conclusion

Abnormal values of FGF-23 in adolescents and young adults with CKD correlate with Ca* P in the absence of vascular calcifications, and may serve as a biomarker for the risk of cardiovascular calcifications.

Factors related to nephrotic-range proteinuria in late-stage chronic kidney disease patients with diabetes mellitus

PURPOSE

Diabetic nephropathy and proteinuria are important risk factors for both end-stage renal disease and cardiovascular events. The present study aimed to identify the factors associated with nephrotic-range proteinuria in patients with advanced diabetic nephropathy.

METHODS

This cross-sectional study enrolled 386 diabetic patients with chronic kidney disease (CKD) stages 3-5, from our outpatient Department of Nephrology. Urinary protein-to-creatinine ratio was recorded. Additionally, other laboratory parameters, body mass index, blood pressure, comorbidities, and medications were also reviewed.

RESULTS

The mean age of the patients was 65.1 ± 11.6 years. Among patients with CKD stage 3 and 4, the odds ratio (OR) for nephrotic-range proteinuria in relation with systolic blood pressure significantly increased starting from 121 mmHg (OR 7.04 and 11.79 for systolic blood pressure of 121-140 and ≥141 mmHg, respectively, in comparison with systolic blood pressure below 121 mmHg). In addition, serum phosphorus ≥4.7 mg/dl was associated with significantly higher risk (OR 15.45) for severe proteinuria, compared with a phosphorus level ≤2.6 mg/dl. Finally, hypertriglyceridemia ≥241 mg/dl was also associated with higher OR for severe proteinuria, compared with a triglyceride level ≤200 mg/dl. Similar associations were found in patients with CKD stage 5.

CONCLUSIONS

Higher systolic blood pressure, serum phosphorus, and triglyceride levels are associated with nephrotic-range proteinuria in patients with diabetic nephropathy and CKD stage 3-5. Further studies should clarify whether a reduction in serum phosphorus would lead to a decrease in proteinuria in these patients.

Fibroblast growth factor-23 helps explain the biphasic cardiovascular effects of vitamin D in chronic kidney disease

Hypovitaminosis D is highly prevalent in chronic kidney disease (CKD). Recently, vitamin D has sparked widespread interest because of its potential favorable benefits on cardiovascular disease (CVD). Evidence from clinical studies and animal models supports the existence of biphasic cardiovascular effects of vitamin D, in which lower doses suppress CVD and higher doses stimulate CVD. However, the mechanism for the different effects remains unclear. Fibroblast growth factor-23 (FGF-23) is a recently identified member of the FGF family, and thought to be actively involved in renal phosphate and vitamin D homeostasis. More specifically, Vitamin D stimulates FGF-23 secretion and is inhibited by increased FGF-23. Given this background, we hypothesize that FGF-23 may provide a unique tool to explain the biphasic cardiovascular effects of vitamin D in CKD. The data presented in this review support the hypothesis that FGF-23 may be linked with the high cardiovascular risk in CKD through accelerating the onset of vascular calcification, secondary hyperparathyroidism, left ventricular hypertrophy and endothelial dysfunction. Therefore, modulation of FGF-23 may become a potential therapeutic target to lowing cardiovascular risk in CKD. Several clinical interventions, including decreased phosphate intake, phosphate binders, cinacalcet plus concurrent low-dose vitamin D, C-terminal tail of FGF-23 and renal transplantation, have been employed to manipulate FGF-23.

Earlier onset and greater severity of disordered mineral metabolism in diabetic patients with chronic kidney disease

OBJECTIVE

Disordered mineral metabolism is a common complication of chronic kidney disease (CKD) and a novel risk factor for CKD progression, cardiovascular disease, and mortality. Although diabetes is the leading cause of CKD and is associated with worse clinical outcomes than other etiologies, few studies have evaluated mineral metabolism in CKD according to diabetes status.

RESEARCH DESIGN AND METHODS

Using the Chronic Renal Insufficiency Cohort Study, we tested the hypothesis that diabetes is independently associated with lower serum calcium and higher serum phosphate, parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF23).

RESULTS

Compared with participants without diabetes (n = 1,936), those with diabetes (n = 1,820) were more likely to have lower estimated glomerular filtration rate (eGFR), lower serum albumin, and higher urinary protein excretion (all P < 0.001). Unadjusted serum phosphate, PTH, and FGF23 levels were higher and calcium was lower among those with compared with those without diabetes (all P < 0.001). After multivariate adjustment, diabetes remained a significant predictor of serum phosphate, PTH, and FGF23 but not calcium. The eGFR cut point at which 50% of participants met criteria for secondary hyperparathyroidism or elevated FGF23 was higher in participants with diabetes compared with those without (PTH: eGFR 30-39 vs. 20-29, P < 0.001; FGF23: eGFR 50-59 vs. 40-49, P < 0.001).

CONCLUSIONS

Disordered mineral metabolism begins earlier in the course of CKD and is more severe among CKD patients with compared with those without diabetes. Future studies should explore mechanisms for these differences and whether they contribute to excess risks of adverse clinical outcomes among diabetic patients with CKD.

Prevalence of intracranial artery calcification in hemodialysis patients--a case-control study

BACKGROUND

Intracranial artery calcification has been reported to be an independent risk factor for ischemic stroke. Also, existence of a positive correlation has been reported between the presence of arterial calcification and that of ischemic changes in the area supplied by such arteries. While intracranial artery calcification has frequently been observed on computed tomographic (CT) images of the brain in hemodialysis patients, its prevalence has not been reported previously. We investigated our hemodialysis outpatients to determine the prevalence of intracranial artery calcification in these patients in comparison with that in healthy controls.

METHODS

Brain CT examinations were performed in 107 patients under maintenance hemodialysis therapy. For comparison, 43 representatives of the general population who underwent a brain CT examination as part of a health checkup were also studied as control subjects.

RESULTS

Intracranial calcifications were more frequently found among hemodialysis patients (87.9%) than among control subjects (53.5%, P = 0.0003), and the prevalences of calcification in each of the intracranial arteries in the two groups were as follows: vertebral artery (65.5% vs. 25.6%, P = 0.0002), internal carotid artery (62.1% vs. 18.6%, P < 0.0001), basilar artery (34.5% vs. 34.9%, ns), anterior cerebral artery (0 vs. 2.3%, ns), middle cerebral artery (24.1% vs. 20.9%, ns), and posterior cerebral artery (5.2% vs. 4.7%, ns).

CONCLUSIONS

A much higher rate of intracranial artery calcification was observed in hemodialysis patients than in the general population, and the most frequently involved sites of calcification in these patients were the relatively large intracranial arteries.

Serum fibroblast growth factor-23 levels and progression of aortic arch calcification in non-diabetic patients on chronic hemodialysis

AIM

Vascular calcification is a cause of cardiovascular death in hemodialysis (HD) patients. The aim of the present study was to evaluate the relationship between the progression of aortic arch calcification (AoAC) and serum fibroblast growth factor (FGF)-23.

METHODS

The enrolled study subjects were 127 (83 men and 44 women) HD patients. Calcification of the aortic arch was semiquantitatively estimated with a score (AoACS) on plain chest radiology. Change in AoACS (ΔAoACS) was obtained by subtracting the baseline AoACS value from the follow-up AoACS value. The second assessment was performed from 5 years after the first determination.

RESULTS

The percentage of male gender in non-progressors (58.5%) was lesser than in regressors (60.0%) and progressors (74.6%). In addition, the dialysis duration in regressors (14.1±5.1 years) was shorter than in non-progressors (19.5±7.0 years) and progressors (16.8±7.5 years). Interestingly, the serum FGF-23 level in regressors (39225.5±9247.9 pg/mL) was significantly higher than in non-progressors (12896.5±26323.5 pg/mL) and progressors (14062.4±18456.8 pg/mL). Multi-ple regression analyses showed male gender (β value=0.969, F=5.092, p=0.0192), serum levels of albumin (β value=-1.395, F=4.541, p=0.0296) and log FGF-23 (β value=-0.001, F=7.273, p=0.0115) to be significant independent determinants of ΔAoACS.

CONCLUSION

Changes in AoAC evaluated by using a simple chest radiograph are associated with serum FGF-23 levels. Excess accumulation of FGF-23 in serum may enable to inhibit the calcification process in vessel walls in chronic HD patients.

Fibroblast growth factor (FGF)-23 and fetuin-A in calcified carotid atheroma

AIMS

Human atheroma calcification occurs secondary to repetitive injury/remodelling of the vessel wall and might be initiated by adherence of mineral-loaded fetuin-A whether or not professional matrix mineralizing cells are present. The aim was to investigate the contribution of fibroblast growth factor (FGF)-23 to ectopic mineralization.

METHODS AND RESULTS

Serial sections of formalin-fixed paraffin-embedded human carotid atheroma (n = 54) were investigated with respect to (i) size and distribution of calcific deposits, (ii) indicators of chondrogenic/osteogenic transformation, and (iii) expression of fetuin-A and FGF-23. All specimens were calcified and SOX-9, collagen type II, cathepsin-K, fetuin-A and FGF-23 expression was seen in 46, 53, 53, 54 and 48 specimens, respectively. The intracellular detection of FGF-23 (45/48) indicates local synthesis. Whereas fetuin-A expression was seen also within areas of vascular smooth muscle actin-positive cells adjacent to calcific deposits, FGF-23 expression was apparently restricted to the mineralization-prone areas. Both local expression and FGF-23 serum concentrations were significantly associated with the degree of atheroma calcification.

CONCLUSIONS

Besides the induction of bone islets and subsequent mineral deposition, severe remodelling of the vessel wall is sufficient to create a mineralizable fetuin-A-attracting microenvironment. FGF-23 might contribute to the formation of proper mineral, i.e. control local phosphate concentration.

Fibroblast growth factor-23 is associated with C-reactive protein, serum phosphate and bone mineral density in chronic kidney disease

We investigated the association between fibroblast growth factor-23 (FGF-23) and (1) the biochemical parameters implicated in chronic kidney disorder (CKD)-bone and mineral disorder (CKD-MBD) and (2) bone mineral density (BMD) in patients with CKD 1-4. C-reactive protein (CRP) and serum phosphate correlated with FGF-23. A significant association was seen between FGF-23 and BMD at the hip.

INTRODUCTION

Circulating FGF-23 is elevated in CKD, although the primary stimulus remains unclear. Moreover, it is still unknown whether increase in FGF-23 has a biological effect on bone metabolism. The aim of the study was to investigate the association of FGF-23 with (1) the biochemical parameters linked with CKD-bone and mineral disorder (CKD-MBD) and (2) bone mineral density in CKD.

METHODS

We studied 145 patients (74 M, 71 F) aged (mean [SD]) 53 [14] years with CKD 1-4. Serum calcium, phosphate, parathyroid hormone, FGF-23, 25 (OH) vitamin D, 1, 25 (OH)(2) vitamin D, bone turnover markers, CRP were determined. BMD was measured at the lumbar spine, femoral neck (FN), forearm, and total hip (TH). Multivariate analysis was undertaken to explore the association between (1) the biochemical variables and FGF-23 and (2) FGF-23 and BMD.

RESULTS

Elevations in FGF-23 occurred in CKD stage 3 compared to CKD stage 1/2, although no significant differences in serum phosphate were observed. Serum phosphate (p<0.001), CRP (p<0.001) and diabetes mellitus (p<0.05) were associated with FGF-23. BMD Z-score was significantly lower at the TH and FN in CKD 4 (p<0.05). A significant association was seen between BMI, FGF-23, bone specific alkaline phosphatase and BMD at the TH (p<0.05).

CONCLUSIONS

The data suggest that FGF-23 may be associated with parameters implicated in the complications of CKD. Longitudinal studies are required for further clinical evaluation.

FGF-23 as a predictor of renal outcome in diabetic nephropathy

BACKGROUND AND OBJECTIVES

Fibroblast growth factor 23 (FGF-23) has emerged as a new factor in mineral metabolism in chronic kidney disease (CKD). An important regulator of phosphorus homeostasis, FGF-23 has been shown to independently predict CKD progression in nondiabetic renal disease. We analyzed the relation between FGF-23 and renal outcome in diabetic nephropathy (DN).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

DN patients participating in a clinical trial (enalapril+placebo versus enalapril+losartan) had baseline data collected and were followed until June 2009 or until the primary outcome was reached. Four patients were lost to follow-up. The composite primary outcome was defined as death, doubling of serum creatinine, and/or dialysis need.

RESULTS

At baseline, serum FGF-23 showed a significant association with serum creatinine, intact parathyroid hormone, proteinuria, urinary fractional excretion of phosphate, male sex, and race. Interestingly, FGF-23 was not related to calcium, phosphorus, 25OH-vitamin D, or 24-hour urinary phosphorus. Mean follow-up time was 30.7±10 months. Cox regression showed that FGF-23 was an independent predictor of the primary outcome, even after adjustment for creatinine clearance and intact parathyroid hormone (10 pg/ml FGF-23 increase = hazard ratio, 1.09; 95% CI, 1.01 to 1.16, P=0.02). Finally, Kaplan-Meier analysis showed a significantly higher risk of the primary outcome in patients with FGF-23 values of >70 pg/ml.

CONCLUSIONS

FGF-23 is a significant independent predictor of renal outcome in patients with macroalbuminuric DN. Further studies should clarify whether this relation is causal and whether FGF-23 should be a new therapeutic target for CKD prevention.