The clinical significance of serum osteocalcin and N-terminal propeptide of type I collagen in predialysis patients with chronic renal failure

Relationship between serum level of miR-338-3p and miR-105-3p and bone metabolic markers in patients with diabetes nephropathy

OBJECTIVES

Diabetic nephropathy (DN) is one of the most common and serious complications of diabetes. The purpose of this study was to explore the relationship between serum microRNA-338-3p (miR-338-3p) and miR-105-3p and bone metabolic markers in patients with DN at different stages.

METHODS

A total of 153 patients diagnosed and treated in the Department of Nephrology from July 2020 to October 2021 were selected as the study objects. According to the staging criteria of diabetic nephropathy and 24-h urinary albumin quantitative level, the patients were divided into control group (35 cases), microalbuminuria group (37 cases), clinical stage albuminuria group (27 cases) and renal failure group (54 cases). Gene expressions were measured by real-time fluorescence quantitative PCR. The correlation was analyzed by Spearman. Serum miR-338-3p and miR-150-5p in the prediction of renal failure in DN was analyzed by ROC curve.

RESULTS

The levels of urinary albumin and serum creatinine were markedly increased with the increase of DN stage (p < 0.05). Compared with the microalbuminuria group, the expression levels of serum miR-383-3p, serum miR-105-3p, 25(OH)-D, BGP and PINP were obviously decreased, but the expression of parathyroid hormone (PTH) and type I collagen (β-CTX) was largely increased in clinical proteinuria group (p < 0.05). Compared with the clinical proteinuria group, the expression levels of serum miR-383-3p, serum miR-105-3p, 25(OH)-D, BGP and PINP were largely decreased, but the expression of PTH and β-CTX was obviously increased in the renal failure group (p < 0.05). Spearman correlation results showed that serum expressions of miR-383-3p and miR-105-3p were negatively correlated with PTH and β-CTX, and positively correlated with 25(OH)-D, BGP and PINP (p < 0.05). ROC curve analysis showed that the AUC of serum miR-338-3p and miR-150-5p was 0.896 with the specificity and sensitivity of 96.66% and 73.47%, which had certain predictive value for the occurrence of renal failure in DN.

CONCLUSIONS

The expression levels of serum miR-383-3p and miR-105-3p were significantly correlated with bone metabolism markers. The combined test can provide new ideas and insights for the clinical treatment of osteoporosis in DN.

Parathyroid hormone independently predicts fracture, vascular events, and death in patients with stage 3 and 4 chronic kidney disease

Doctors do not know whether treatment of high parathyroid hormone levels is linked to better outcomes in their patients with kidney disease. In this study, lower parathyroid hormone levels at baseline were linked to lower risk of fracture, vascular events, and death in people with kidney disease.

PURPOSE

Chronic kidney disease (CKD) affects ~ 20% of older adults, and secondary hyperparathyroidism (HPT) is a common condition in these patients. To what degree HPT predicts fractures, vascular events, and mortality in pre-dialysis CKD patients is debated. In stage 3 and 4 CKD patients, we assessed relationships between baseline serum PTH levels and subsequent 10-year probabilities of clinical fractures, vascular events, and death.

METHODS

We used Marshfield Clinic Health System electronic health records to analyze data from adult CKD patients receiving care between 1985 and 2013, and whose PTH was measured using a second-generation assay. Covariates included PTH, age, gender, tobacco use, vascular disease, diabetes, hypertension, hyperlipidemia, obesity, GFR, and use of osteoporosis medications.

RESULTS

Five thousand one hundred eight subjects had a mean age of 68 ± 17 years, 48% were men, and mean follow-up was 23 ± 10 years. Fractures, vascular events, and death occurred in 18%, 71%, and 56% of the cohort, respectively. In univariate and multivariate models, PTH was an independent predictor of fracture, vascular events, and death. The hazards of fracture, vascular events and death were minimized at a baseline PTH of 0, 69, and 58 pg/mL, respectively.

CONCLUSIONS

We found that among individuals with stage 3 and 4 CKD, PTH was an independent predictor of fractures, vascular events, and death. Additional epidemiologic studies are needed to confirm these findings. If a target PTH range can be confirmed, then randomized placebo-controlled trials will be needed to confirm that treating HPT reduces the risk of fracture, vascular events, and death.

High FGF23 levels are associated with impaired trabecular bone microarchitecture in patients with osteoporosis

This cross-sectional study examined the associations between c-terminal FGF23 levels, laboratory markers of bone metabolism and bone microarchitecture in 82 patients with osteoporosis. Higher FGF23 levels were associated with impaired trabecular but not cortical bone microarchitecture, and this was confirmed after adjusting for confounding variables such as age or BMI.

INTRODUCTION

Fibroblast growth factor 23 (FGF23) is an endocrine hormone-regulating phosphate and vitamin D metabolism. While its mode of action is well understood in diseases such as hereditary forms of rickets or tumor-induced osteomalacia, the interpretation of FGF23 levels in patients with osteoporosis with regard to bone microarchitecture is less clear.

METHODS

C-terminal FGF23 levels and bone turnover markers were assessed in 82 patients with osteoporosis (i.e., DXA T-score ≤ - 2.5 at the lumbar spine or total hip). Bone microarchitecture was measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius and tibia. Data were analyzed in a cross-sectional design using correlation and regression models.

RESULTS

We found a significant negative logarithmic correlation between FGF23 levels and trabecular but not cortical bone microarchitecture at both skeletal sites. Furthermore, using a multiple linear regression model, we confirmed FGF23 as a predictor for reduced trabecular parameters even when adjusting for confounding factors such as age, BMI, phosphate, bone-specific alkaline phosphatase, vitamin D3, and PTH.

CONCLUSIONS

Taken together, high FGF23 levels are associated with impaired trabecular bone microarchitecture in osteoporosis patients, and this association seems to occur after adjustment of confounding variables including phosphate and vitamin D. Future longitudinal studies are now needed to validate our findings and investigate FGF23 in relation to fracture risk.

Serum sclerostin levels are positively related to bone mineral density in peritoneal dialysis patients: a cross-sectional study

Background

Sclerostin, an antagonist of the Wingless-type mouse mammary tumor virus integration site (Wnt) pathway that regulates bone metabolism, is a potential contributor of chronic kidney disease (CKD)–mineral and bone disorder (MBD), which has various forms of presentation, from osteoporosis to vascular calcification. The positive association of sclerostin with bone mineral density (BMD) has been demonstrated in CKD and hemodialysis (HD) patients but not in peritoneal dialysis (PD) patients. This study assessed the association between sclerostin and BMD in PD patients.

Methods

Eighty-nine PD patients were enrolled; their sera were collected for measurement of sclerostin and other CKD–MBD-related markers. BMD was also assessed simultaneously. We examined the relationship between sclerostin and each parameter through Spearman correlation analysis and by comparing group data between patients with above- and below-median sclerostin levels. Univariate and multiple logistic regression models were employed to define the most predictive of sclerostin levels in the above-median category.

Results

Bivariate analysis revealed that sclerostin was correlated with spine BMD (r = 0.271, P = 0.011), spine BMD T-score (r = 0.274, P = 0.010), spine BMD Z-score (r = 0.237, P = 0.027), and intact parathyroid hormone (PTH; r = − 0.357, P < 0.001) after adjustments for age and sex. High BMD, old age, male sex, increased weight and height, diabetes, and high osteocalcin and uric acid levels were observed in patients with high serum sclerostin levels and an inverse relation was noticed between PTH and sclerostin. Univariate logistic regression analysis demonstrated that BMD is positively correlated with above-median sclerostin levels (odds ratio [OR] = 65.61, P = 0.002); the correlation was retained even after multivariate adjustment (OR = 121.5, P = 0.007).

Conclusions

For the first time, this study demonstrated a positive association between serum sclerostin levels and BMD in the PD population.

Bone turnover markers are associated with bone density, but not with fracture in end stage kidney disease: a cross-sectional study

BACKGROUND

Fracture risk is increased in chronic kidney disease (CKD), but assessment of bone fragility remains controversial in these patients. This study investigated the associations between bone turnover markers, bone mineral density (BMD), and prevalent fragility fracture in a cohort of kidney transplantation candidates.

METHODS

Volumetric BMD of spine and hip was measured by quantitative computed tomography. Parathyroid hormone (PTH), bone-specific alkaline phosphatase, procollagen type-1 N-terminal propeptide, tartrate resistant alkaline phosphatase, and C- and N-terminal telopeptides of type 1 collagen were analyzed from fasting morning blood samples. Fragility fractures included prevalent vertebral fractures and previous low-trauma clinical fractures.

RESULTS

The fracture prevalence was 18% in 157 adult kidney transplant candidates. Fractured patients had reduced BMD and Z-score at both spine and hip. Levels of bone turnover markers were significantly higher in patients on maintenance dialysis than in pre-dialysis patients; but did not differ between patients with and without fracture. There were strong, positive correlations between PTH and all bone turnover markers. PTH was negatively associated with Z-score at lumbar spine and total hip; in contrast, bone turnover markers were only negatively associated with total hip Z-score.

CONCLUSIONS

Bone turnover markers were negatively associated with bone density, but not associated with prevalent fracture in kidney transplantation candidates. The role of bone turnover markers in assessing bone fragility in CKD will require further investigation.

TRIAL REGISTRATION

This study was registered at ClinicalTrials.gov with identifier NCT01344434 .

Use of CTX-I and PINP as bone turnover markers: National Bone Health Alliance recommendations to standardize sample handling and patient preparation to reduce pre-analytical variability

The National Bone Health Alliance (NBHA) recommends standardized sample handling and patient preparation for C-terminal telopeptide of type I collagen (CTX-I) and N-terminal propeptide of type I procollagen (PINP) measurements to reduce pre-analytical variability. Controllable and uncontrollable patient-related factors are reviewed to facilitate interpretation and minimize pre-analytical variability.

INTRODUCTION

The IOF and the International Federation of Clinical Chemistry (IFCC) Bone Marker Standards Working Group have identified PINP and CTX-I in blood to be the reference markers of bone turnover for the fracture risk prediction and monitoring of osteoporosis treatment. Although used in clinical research for many years, bone turnover markers (BTM) have not been widely adopted in clinical practice primarily due to their poor within-subject and between-lab reproducibility. The NBHA Bone Turnover Marker Project team aim to reduce pre-analytical variability of CTX-I and PINP measurements through standardized sample handling and patient preparation.

METHODS

Recommendations for sample handling and patient preparations were made based on review of available publications and pragmatic considerations to reduce pre-analytical variability. Controllable and un-controllable patient-related factors were reviewed to facilitate interpretation and sample collection.

RESULTS

Samples for CTX-I must be collected consistently in the morning hours in the fasted state. EDTA plasma is preferred for CTX-I for its greater sample stability. Sample collection conditions for PINP are less critical as PINP has minimal circadian variability and is not affected by food intake. Sample stability limits should be observed. The uncontrollable aspects (age, sex, pregnancy, immobility, recent fracture, co-morbidities, anti-osteoporotic drugs, other medications) should be considered in BTM interpretation.

CONCLUSION

Adopting standardized sample handling and patient preparation procedures will significantly reduce controllable pre-analytical variability. The successful adoption of such recommendations necessitates the close collaboration of various stakeholders at the global stage, including the laboratories, the medical community, the reagent manufacturers and the regulatory agencies.

Rapid cortical bone loss in patients with chronic kidney disease

Chronic kidney disease (CKD) patients may have high rates of bone loss and fractures, but microarchitectural and biochemical mechanisms of bone loss in CKD patients have not been fully described. In this longitudinal study of 53 patients with CKD Stages 2 to 5D, we used dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HRpQCT), and biochemical markers of bone metabolism to elucidate effects of CKD on the skeleton. Median follow-up was 1.5 years (range 0.9 to 4.3 years); bone changes were annualized and compared with baseline. By DXA, there were significant declines in areal bone mineral density (BMD) of the total hip and ultradistal radius: -1.3% (95% confidence interval [CI] -2.1 to -0.6) and -2.4% (95% CI -4.0 to -0.9), respectively. By HRpQCT at the distal radius, there were significant declines in cortical area, density, and thickness and increases in porosity: -2.9% (95% CI -3.7 to -2.2), -1.3% (95% CI -1.6 to -0.6), -2.8% (95% CI -3.6 to -1.9), and +4.2% (95% CI 2.0 to 6.4), respectively. Radius trabecular area increased significantly: +0.4% (95% CI 0.2 to 0.6), without significant changes in trabecular density or microarchitecture. Elevated time-averaged levels of parathyroid hormone (PTH) and bone turnover markers predicted cortical deterioration. Higher levels of serum 25-hydroxyvitamin D predicted decreases in trabecular network heterogeneity. These data suggest that significant cortical loss occurs with CKD, which is mediated by hyperparathyroidism and elevated turnover. Future investigations are required to determine whether these cortical losses can be attenuated by treatments that reduce PTH levels and remodeling rates.

Discriminants of prevalent fractures in chronic kidney disease

Patients with chronic kidney disease (CKD) have higher rates of fracture than the general population. Increased bone remodeling, leading to microarchitectural deterioration and increased fragility, may accompany declining kidney function, but there are no reliable methods to identify patients at increased risk for fracture. In this cross-sectional study of 82 patients with predialysis CKD, high-resolution imaging revealed that the 23 patients with current fractures had significantly lower areal density at the femoral neck; total, cortical, and trabecular volumetric bone density; cortical area and thickness; and trabecular thickness. Compared with levels in the lowest tertile, higher levels of osteocalcin, procollagen type-1 N-terminal propeptide, and tartrate-resistant acid phosphatase 5b were associated with higher odds of fracture, even after adjustment for femoral neck T-score. Discrimination of fracture prevalence was best with a femoral neck T-score of -2.0 or less and a value in the upper two tertiles for osteocalcin, procollagen type-1 N-terminal propeptide, or tartrate-resistant acid phosphatase 5b; these values corresponded to the upper half of the normal premenopausal reference range. In summary, these cross-sectional data suggest that measurement of bone turnover markers may increase the diagnostic accuracy of densitometry to identify patients with CKD at high risk for fracture.

Assessment of bone microarchitecture in chronic kidney disease: a comparison of 2D bone texture analysis and high-resolution peripheral quantitative computed tomography at the radius and tibia

Bone microarchitecture can be studied noninvasively using high-resolution peripheral quantitative computed tomography (HR-pQCT). However, this technique is not widely available, so more simple techniques may be useful. BMA is a new 2D high-resolution digital X-ray device, allowing for bone texture analysis with a fractal parameter (H(mean)). The aims of this study were (1) to evaluate the reproducibility of BMA at two novel sites (radius and tibia) in addition to the conventional site (calcaneus), (2) to compare the results obtained with BMA at all of those sites, and (3) to study the relationship between H(mean) and trabecular microarchitecture measured with an in vivo 3D device (HR-pQCT) at the distal tibia and radius. BMA measurements were performed at three sites (calcaneus, distal tibia, and radius) in 14 healthy volunteers to measure the short-term reproducibility and in a group of 77 patients with chronic kidney disease to compare BMA results to HR-pQCT results. The coefficient of variation of H(mean) was 1.2, 2.1, and 4.7% at the calcaneus, radius, and tibia, respectively. We found significant associations between trabecular volumetric bone mineral density and microarchitectural variables measured by HR-pQCT and H(mean) at the three sites (e.g., Pearson correlation between radial trabecular number and radial H(mean) r = 0.472, P < 0.001). This study demonstrated a significant but moderate relationship between 2D bone texture and 3D trabecular microarchitecture. BMA is a new reproducible technique with few technical constraints. Thus, it may represent an interesting tool for evaluating bone structure, in association with biological parameters and DXA.

Vitamin D receptor gene, biochemical bone markers and bone mineral density in Mexican women on dialysis

BACKGROUND

The influence of the Bsm1 polymorphism of the vitamin D receptor (VDR) gene on mineral and bone disorders in chronic kidney disease (CKD) is still under discussion. The aim of this study was to analyse the relationship between VDR polymorphism, bone mineral density (BMD), biochemical bone markers and clinical factors in women on peritoneal dialysis (PD) and haemodialysis (HD).

METHODS

In a cross-sectional study, 197 women (42 +/- 10 years; 25% with diabetes mellitus (DM); body mass index (BMI) 25.26 +/- 4.77 kg/m(2)) treated by PD (72%) or HD (28%) underwent measurements of BMD (measured at the calcaneus by quantitative ultrasound; expressed as T- and Z-scores) and plasma total calcium (tCa), intact parathyroid hormone 1-84 (iPTH), phosphorus, albumin, glucose, osteoprotegerin (OPG), fetuin-A, intact osteocalcin-49 and N-MID fragment 1-43 aa (N-MID osteocalcin) N-terminal propeptide of type 1 procollagen (PINP) and C-terminal telopeptide-beta aspartic acid (BCL). DNA was extracted from peripheral blood. PCR products were digested with Bsm1 to analyse VDR polymorphism.

RESULTS

The Z-score of BMD was -1.1 +/- 1.03. According to the values of osteopenia (T-score = -1.0), patients with higher BMD were younger, had lower frequency of amenorrhoea and diabetes and had higher serum creatinine and fetuin levels as well as lower levels of PINP. In a stepwise multivariate logistics analysis, osteopenia was associated with presence of genotype BB+Bb (OR = 3.26, P < or = 0.003) and age (OR = 0.95, P = 0.050). According to the B allele, bb: n = 126 (64%) and BB+Bb: n = 71(36%), group bb had significantly higher mean Z-scores (-0.97 +/- 1.0 vs -1.3+/-0.92; P < or = 0.021).

CONCLUSIONS

The high frequency of osteopenia observed in female CKD patients on dialysis is associated with age and genetic predisposition as revealed by its association to the Bsm1 VDR polymorphism.

Optimizing bone health in chronic kidney disease

Phosphocalcic metabolism disorders often complicate chronic kidney disease (CKD) and worsen as kidney function declines, with a consequence on bone structural integrity. The risk of fracture exceeds that of the normal population in both patients with pre-dialysis CKD and end-stage renal disease (ESRD). The increasing incidence of CKD, the high mortality rate induced by hip fracture, the decreased quality of life and economic burden of fragility fracture make the renal bone disorders a major problem of public health around the world. Optimizing bone health in CKD patients should be a priority. Bone biopsy is invasive. Dual-energy X-ray absorptiometry, commonly used to screen individuals at risk of fragility fracture in the general population, is not adequate to assess advanced CKD because it does not discriminate fracture status in this population. New non-invasive three-dimensional high-resolution imaging techniques, distinguishing trabecular and cortical bone, appear to be promising in the assessment of bone strength and might improve bone fracture prediction in this population. Therapeutic intervention in the chronic kidney disease-mineral and bone disorders (CKD-MBD) should begin early in the course of CKD to maintain serum concentration of biological parameters involved in mineral metabolism in the normal recommended ranges, prevent the development of parathyroid hyperplasia, prevent extra-skeletal calcifications and preserve skeletal health. In this paper, we review studies of mineral and bone disorders in patients with CKD and ESRD, the utility of current techniques to assess bone health and the preventive and therapeutic strategies for managing CKD-MBD.

Clinical significance of bone alkaline phosphatase isoforms, including the novel B1x isoform, in mild to moderate chronic kidney disease

BACKGROUND

Mineral bone disorder (MBD) is a common complication of chronic kidney disease (CKD) even during the early stages. Bone alkaline phosphatase (BALP) is a marker of bone formation and plays a pivotal role in the mineralization process. Three BALP isoforms (B/I, B1 and B2) have been identified in healthy individuals and a fourth isoform (B1x) has been discovered in serum from dialysis patients. We investigated these BALP isoforms, type I procollagen intact amino-terminal propeptide (PINP), carboxy-terminal telopeptide of type I collagen (CTX) and tartrate-resistant acid phosphatase isoform 5b (TRACP5b), as well as bone mineral density (BMD) in predialysis CKD patients.

METHODS

PINP, CTX, TRACP5b and BALP isoforms were analysed in serum from 46 patients within CKD stages 3-5. BMD was determined by dual-energy x-ray absorptiometry.

RESULTS

PINP, TRACP5b and the BALP isoforms, B/I, B1 and B2, were independent predictors of total hip BMD in all patients. Furthermore, B/I predicted osteopaenia in the hip and in the distal 1/3 of the radius in CKD stage 3. The B1x isoform was detected in nine patients (20%), who had lower GFR, higher phosphate and calcium x phosphate product.

CONCLUSION

We found an association of BALP isoforms and other markers of bone turnover with total hip BMD, which predominantly comprises trabecular bone. The association of the new BALP isoform B1x with risk factors for vascular calcification leads us to hypothesize a possible role for B1x in this process. The significance of the BALP isoforms in CKD remains to be further explored in experimental and clinical settings in conjunction with bone histomorphometry.

Bone imaging and chronic kidney disease: will high-resolution peripheral tomography improve bone evaluation and therapeutic management?

Bone damage because of chronic kidney disease (CKD) represents a daily challenge for nephrologists. The impact of CKD on bone health may be immediate (serum phosphocalcic disturbances) or delayed (bone fractures and vascular calcifications). Histomorphometry remains the gold standard to evaluate bone, but it is rarely performed in clinical practice. Areal measurement of bone mineral density by dual x-ray absorptiometry is routinely performed to evaluate bone mass. However, this technique presents some limitations. In 2000, the United States National Institutes of Health defined new "quality" criteria for the diagnosis of osteoporosis in addition to decreased bone mass. Bone strength actually integrates two concepts: bone quantity and bone quality (i.e., microarchitectural organization, bone turnover, bone material properties such as mineralization, collagen traits, and microdamage) that cannot be evaluated by dual x-ray absorptiometry. New three-dimensional, noninvasive bone-imaging techniques have thus been developed, e.g., high-resolution peripheral quantitative computed tomography. High-resolution peripheral quantitative computed tomography allows evaluation of both volumetric density and microarchitecture in different compartments of bone, at the distal radius and tibia. High-resolution peripheral quantitative computed tomography may be useful in predicting fractures and assessing bone preventive or therapeutic strategies in CKD patients. It should be evaluated in long-term, longitudinal follow-ups.

Chronic kidney disease and bone fracture: a growing concern

Susceptibility to fracture is increased across the spectrum of chronic kidney disease (CKD). Moreover, fracture in patients with end-stage kidney disease (ESKD) results in significant excess mortality. The incidence and prevalence of CKD and ESKD are predicted to increase markedly over the coming decades in conjunction with the aging of the population. Given the high prevalence of both osteoporosis and CKD in older adults, it is of the utmost public health relevance to be able to assess fracture risk in this population. Dual-energy X-ray absorptiometry (DXA), which provides an areal measurement of bone mineral density (aBMD), is the clinical standard to predict fracture in individuals with postmenopausal or age-related osteoporosis. Unfortunately, DXA does not discriminate fracture status in patients with ESKD. This may be, in part, because excess parathyroid hormone (PTH) secretion may accompany declining kidney function. Chronic exposure to high PTH levels preferentially causes cortical bone loss, which may be partially offset by periosteal expansion. DXA can neither reliably detect changes in bone volume nor distinguish between trabecular and cortical bone. In addition, DXA measurements may be low, normal, or high in each of the major forms of renal osteodystrophy (ROD). Moreover, postmenopausal or age-related osteoporosis may also affect patients with CKD and ESKD. Currently, transiliac crest bone biopsy is the gold standard to diagnose ROD and osteoporosis in patients with significant kidney dysfunction. However, bone biopsy is an invasive procedure that requires time-consuming analyses. Therefore, there is great interest in developing non-invasive high-resolution imaging techniques that can improve fracture risk prediction for patients with CKD. In this paper, we review studies of fracture risk in the setting of ESKD and CKD, the pathophysiology of increased fracture risk in patients with kidney dysfunction, the utility of various imaging modalities in predicting fracture across the spectrum of CKD, and studies evaluating the use of bisphosphonates in patients with CKD.

Bone mass, biochemical markers and growth in children with chronic kidney disease: a 1-year prospective study

AIM

This study was designed to investigate bone mineral density (BMD), growth parameters and biochemical markers in children with chronic kidney disease (CKD).

METHODS

Sixteen patients, 4-18 years, with CKD were prospectively followed for 1 year. Auxological data, body composition, BMD by dual-energy X-ray absorptiometry, bone age, bone turnover markers, vitamin D, parathyroid hormone (PTH), leptin, osteoprotegerin, insulin-like growth factor-I (IGF-I) and IGF binding protein-3 were measured. A questionnaire regarding bone health and diet was also performed.

RESULTS

Delayed bone age was observed (n = 11) and the BMD Z-scores for total body were below zero in seven patients. However, total body BMD (TBBMD) increased in 12 patients. Most patients had increased osteocalcin and carboxy-terminal telopeptide of type I collagen, but normal alkaline phosphatase, type I procollagen intact amino-terminal propeptide and tartrate-resistant acid phosphatase 5b. Ten patients had increased PTH. Most children had normal levels of leptin, osteoprotegerin, IGF-I and IGFBP-3. Leptin, at baseline, correlated with differences in TBBMD over 1 year.

CONCLUSIONS

Only seven (44%) had negative Z-scores and TBBMD increased over 1 year. Bone markers at baseline did not predict the longitudinal changes in BMD.

Annual change in bone mineral density in predialysis patients with chronic renal failure: significance of a decrease in serum 1,25-dihydroxy-vitamin D

Bone disease occurs in the predialysis phase of chronic renal failure (CRF). The aim of this study was to examine how a decrease in renal function affects annual bone mineral density (BMD) changes in predialysis CRF patients and to examine the factors that affect BMD. The BMD of the distal radius in 53 predialysis CRF patients (age, 61.3 +/- 10.8 years; serum creatinine 2.7 +/- 1.2 mg/dl) was measured by peripheral quantitative computed tomography (pQCT) twice with a 1-year interval. The total BMD of the radius significantly decreased over a year (P < 0.001), and both trabecular and cortical BMD showed a significant decrease. Significant positive correlations with BMD changes were found for estimated creatinine clearance (r = 0.375, P < 0.01) and baseline serum 1,25(OH)(2)D (r = 0.434, P < 0.005), indicating that BMD decreased to a greater extent with larger reductions in creatinine clearance and serum 1,25(OH)(2)D. Of several bone metabolic markers examined, baseline serum osteocalcin was significantly positively correlated with annual BMD changes (r = -0.276, P < 0.05). Multiple regression analysis showed that baseline serum 1,25(OH)(2)D (beta = 0.434) was a significant predictor of decreases in total and trabecular BMD (R (2) = 0.188, P < 0.01; and R (2) = 0.207, P < 0.01), independent of other confounding factors. These results indicate that BMD decreases as renal function deteriorates in predialysis CRF patients, and that osteocalcin is a clinically useful marker associated with the decrease in BMD. The serum 1,25(OH)(2)D level is the principal factor affecting BMD of the radius, suggesting that supplementation with an active form of vitamin D is of importance for predialysis CRF patients.

Serum Levels of 1–84 and 7–84 Parathyroid Hormone in Predialysis Patients with Chronic Renal Failure Measured by the Intact and Bio-PTH Assay

BACKGROUND

The intact parathyroid hormone (PTH) assay detects both PTH(1-84) and the PTH(7-84)-like fragment, which is reported to be an antagonist of the biological action of PTH(1-84). It is debatable which of the two assays is clinically more useful, the intact or bio-PTH assay, the latter of which only detects PTH(1-84). It is also unknown whether serum levels of the PTH(7-84)-like fragment have clinical significance.

METHODS

Serum PTH concentrations in 104 predialysis patients with chronic renal failure (CRF; serum creatinine 3.53 +/- 1.93; 62 males and 42 females; 61.0 +/- 11.5 years old) were measured using both the intact and bio-PTH assays, and the concentration of the PTH(7-84)-like fragment was calculated by subtracting bio-PTH from intact PTH. Three bone formation and three bone resorption markers were measured simultaneously.

RESULTS

The PTH values measured using the two assays were strongly positively correlated (r = 0.959, p < 0.0001), and were also significantly positively correlated with the three bone formation and three bone resorption markers to a similar degree. The PTH(7-84)-like fragment was significantly positively correlated with both the intact and bio-PTH (r = 0.855, p < 0.0001 for intact PTH; r = 0.672, p < 0.0001 for bio-PTH), and was also significantly positively correlated with each of the six bone metabolism markers. There is no significant relationship between the bio-PTH/PTH(7-84)-like fragment ratio and clinical parameters including bone metabolic markers.

CONCLUSION

From the strong relationship between the two assays, and the similar degree of the relationship between each PTH assay and each of the six bone metabolism markers, it is considered that the bio-PTH and intact PTH assays have similar clinical significance in predialysis CRF patients. Serum levels of the PTH(7-84)-like fragment seem to increase as serum PTH(1-84) increases. The results suggest that the serum PTH(7-84)-like fragment has little specific clinical effect on bone metabolism, even when assessed by the ratio of bio-PTH/PTH(7-84)-like fragment.