Kidney bone disease and mortality in CKD: revisiting the role of vitamin D, calcimimetics, alkaline phosphatase, and minerals

Recent progress towards the development of fluorescent probes for the detection of disease-related enzymes

Normal physiological functions as well as regulatory mechanisms for various pathological conditions depend on the activity of enzymes. Thus, determining the in vivo activity of enzymes is crucial for monitoring the physiological metabolism and diagnosis of diseases. Traditional enzyme detection methods are inefficient for in vivo detection, which have different limitations, such as high cost, laborious, and inevitable invasive procedures, low spatio-temporal resolution, weak anti-interference ability, and restricted scope of application. Because of its non-destructive nature, ultra-environmental sensitivity, and high spatiotemporal resolution, fluorescence imaging technology has emerged as a potent tool for the real-time visualization of live cells, thereby imaging the motility of proteins and intracellular signalling networks in tissues and cells and evaluating the binding and attraction of molecules. In the last few years, significant advancements have been achieved in detecting and imaging enzymes in biological systems. In this regard, the high sensitivity and unparalleled spatiotemporal resolution of fluorescent probes in association with confocal microscopy have garnered significant interest. In this review, we focus on providing a concise summary of the latest developments in the design of fluorogenic probes used for monitoring disease-associated enzymes and their application in biological imaging. We anticipate that this study will attract considerable attention among researchers in the relevant field, encouraging them to pursue advances in the development and application of fluorescent probes for the real-time monitoring of enzyme activity in live cells and in vivo models while ensuring excellent biocompatibility.

A comparative study of hormonal contraceptive use and vitamin D levels at Gondar Town 2023

Vitamin D deficiency is an emerging public health problem globally, with devastating health consequences. Some studies suggest that exogenous sex hormones, found in hormonal contraceptives, may enhance vitamin D levels. However, the reasons for this association are not fully understood, as women using hormonal contraception may have different lifestyle habits affecting their vitamin D status. Therefore, this study seeks to explore the relationship between hormonal contraceptive use and vitamin D levels. A Facility based comparative cross-sectional study was conducted in Gondar town from February to April 2023, involving a total of 162 women using three types of hormonal contraceptives (Norplant, DMPA, and COC) and 162 age and BMI-matched non-users as controls in a 1:1 ratio. Participants were selected using systematic random sampling. A semi-structured questionnaire was used to collected data regarding the socio-demographic, economic, obstetric, lifestyle, and clinical information. 5 milliliters of blood samples were collected from each participant for Laboratory analysis of serum vitamin D, calcium, and alkaline phosphates using a Beckman Coulter chemistry analyzer. Independent t-tests, ANOVA with post hoc Bonferroni test was used to compare statistics between the two groups, and logistic regression models to identify factors associated with Vitamin D deficiency. The mean serum Vitamin D levels of Norplant, DMPA, and COC users were 24.08 (± 5.17), 24.83 (± 5.52), and 31.90 (± 6.94) respectively; whereas control group has mean Vitamin D level of 22.00 (± 7.97). On the current study the prevalence of Vitamin D deficiency (< 20 ng/ml) among hormonal contraceptive users was found to be 21.6% (35/162), whereas 48.14% (78/162) of non-user controls had vitamin D deficiency. The odds of having Vitamin D deficiency was higher among participants who attained higher education, who never eat fish and have never been used vitamin D Supplements. However, the use of combined oral contraceptives (COC) shown to reduce the odd of having vitamin D deficiency by 90%. Similarly, individuals with normal and hypercalcemia state shown to have lower odd of having Vitamin D deficiency. Users of combined oral contraceptives (COC) had significantly higher mean serum Vitamin D levels compared to users of Norplant and DMPA, as well as non-users. The prevalence of Vitamin D deficiency was lower among COC users compared to non-users, highlighting a potential protective effect of COC use against Vitamin D deficiency.

Nutritional and Inflammatory Aspects of Low Parathyroid Hormone in Maintenance Hemodialysis Patients-A Longitudinal Study

BACKGROUND

Low serum parathyroid hormone (PTH) is an accepted marker for adynamic bone disease which is characterized by increased morbidity and mortality in maintenance hemodialysis (MHD) patients. In light of the known cross-sectional associations between PTH and malnutrition-inflammation syndrome, we aimed to examine the longitudinal associations between PTH with changes in nutritional and inflammatory parameters and clinical outcomes in MHD patients with low PTH.

METHODS

This historical prospective and longitudinal study analyzed a clinical database at a single hemodialysis center, containing the medical records of 459 MHD patients (mean age of 71.4 ± 12.9 years old, 171 women), treated between the years 2007-2020. Bone turnover, nutritional and inflammatory marker levels were recorded at 0, 6, 12, 18, 24, 30, and 36 months followed by a median of 24 additional months of clinical observations. According to previous use of vitamin D analogs and/or calcium-sensing receptor agonists, the study participants were divided into treatment-related and disease-related groups. A linear mixed effects model was adjusted for baseline demographics and clinical parameters.

RESULTS

Of 459 MHD patients, 81 (17.6%) had PTH lower than 150pg/mL. Among them, 30 patients had treatment-related and 51 had disease-related low PTH. At baseline, MHD patients with treatment-related low PTH had a higher rate of diabetes compared to the disease-related group. In a linear mixed effects model, increased PTH over time was associated with decreased levels of alkaline phosphatase and C-reactive protein and with increased hemoglobin and albumin, but not the geriatric nutritional risk index at 3-year follow-up. The survival rate did not differ between the groups, with the risk of hospitalizations due to fractures being higher (HR: 4.04 with 95% CI: 1.51-10.8) in the disease-related group. Statistical significance of this association was abolished after adding C-reactive protein or alkaline phosphatase to the multivariate models.

CONCLUSIONS

Low serum PTH in MHD patients behaves differently depending on its cause, with a higher risk of fractures in the disease-related group. This association is dependent on inflammation. Our results should be verified in larger epidemiological studies.

The Impact of COVID-19 Infection Control Measures on End-Stage Renal Disease Patients in a Community Hemodialysis Setting

INTRODUCTION

Several non-pharmaceutical infection control measures have been implemented at community-based hemodialysis centers to reduce the risk of Coronavirus Disease of 2019 (COVID-19) transmission, caused by the SARS-CoV-2 virus. However, there have been concerns that such measures may disrupt the routine and timely care required by patients, with adverse effects on their health outcomes. This cross-sectional study aims to determine the unintended consequences of COVID-19 infection control measures on hemodialysis patients.

METHODS

 Electronic medical records were extracted from patients enrolled in community-based hemodialysis centers in Singapore. A baseline group prior of patients consisted of those enrolled in 2017, which was three years prior to the SARS-CoV-2-related pandemic (n = 548). This was compared with the study group of patients enrolled in 2019 (n = 426), just before the COVID-19 pandemic started. Medical records for these two groups were extracted from January to July 2018 for the baseline group and from January to July 2020, respectively. Three regression models were built to study dialysis adherence, kidney disease biomarkers, and hospitalization episodes.

RESULTS

 There was no statistically significant difference in hospitalization and mortality outcomes, adherence to dialysis management, laboratory results for dialysis-related clearance, and anemia outcomes. There was a higher proportion of patients hospitalized for vascular access-related reasons in the study group as compared to the baseline group (OR 1.6, 95% CI: 1.10 to 2.29, P = 0.014). Patients in the study group had albumin levels 2.13% higher (95% CI: 0.88 to 3.39, P < 0.001) and alkaline phosphatase levels 7.3% lower (95% CI: 1.17 to 13.02, P = 0.020) than those in the baseline group.

CONCLUSIONS

 From this community-based hemodialysis study in Singapore, it was shown that the COVID-19 pandemic did not disrupt regular healthcare services for these patients. With strategies instituted for a coordinated health delivery workflow, ensuring sufficient capacity in the various healthcare delivery sites and overall pandemic preparedness, the patient clinical outcomes measures continued to be met with no adverse consequences noted. Some improvements in dialysis-related laboratory values and quality of care targets may be due to more stringent measures instituted to protect these vulnerable patients in the community.

A meta-analysis of the effects of clay mineral supplementation on alkaline phosphatase, broiler health, and performance

The crucial constraint in the broiler production sector is feed efficiency; many feed additives have been widely employed to increase broiler growth. Nonetheless, some of these substances exacerbate health and animal-based food product safety concerns. This meta-analysis examines the effect of clay minerals on alkaline phosphatase (ALP), broiler health, and performance. Metadata was constructed from 369 data items that were harvested from 86 studies. The addition of clay minerals was set as a fixed effect and the difference between experiments was established as a random effect. The metadata were fitted using a linear mixed model. Due to the presence of clay minerals, growth performance as assessed by body weight (BW), average daily gain (ADG), and performance efficiency index (PEI) increased significantly (P < 0.01). In the total period, the increases of BW, ADG, and PEI were 4.12 g, 0.0714 g/d, and 0.648, respectively, per unit of clay minerals added. Clay minerals did not affect blood serum parameters (e.g., ALP and calcium). The IgA and IgM concentrations in the jejunum and ileum were significantly greater (P < 0.01) in the starter phase. Among clay minerals, broilers fed diets with aluminosilicate, halloysite, kaolin, and zeolite consistently exhibited higher (P < 0.05) BW, ADG, PEI, and lower feed conversion ratio (P < 0.05) in the finisher phase. Aluminosilicate was the only clay that increased (P < 0.05) secretory IgA concentration in both jejunum and ileum. In conclusion, clay minerals could be used as a growth promoter, especially during the finisher phase, without adversely affecting feed intake, liver function, and mineral metabolism in broiler chickens. Aluminosilicate was superior in improving the mucosal immunity status of broiler chickens.

Improving Calcium Status of Women: Results of a Study of Bio-Availability of Calcium From Slaked Lime Fortified Rice

BACKGROUND

Fortification of rice with slaked lime is an acceptable and inexpensive way to combat calcium (Ca) deficiency. However, bioavailability of calcium after intake of slaked lime fortified rice is yet to be investigated.

OBJECTIVE

To measure the fractional absorption of Ca (FAC) from slaked lime fortified cooked rice.

DESIGN

We conducted an experimental study using stable isotopes of Ca to measure FAC during a single morning test meal containing rice fortified with slaked lime. Participants (n = 22) were given slaked lime fortified rice 3 times a day for 4 days. On the morning of the fifth day, the participants were served the same amount of rice as previous the 4 days at the breakfast test meal with an accurately measured amount of ⁴⁴Ca stable isotope oral tracer followed by an intravenous injection of ⁴²Ca. Urine was collected over the next 24 hours in 3 consecutive 8-hour pools. Fractional absorption of Ca was calculated from the measurement of the relative enrichment of the of each administered tracer ⁴⁴Ca and ⁴²Ca using inductively coupled plasma mass spectrometry.

RESULTS

The mean Ca concentration in the test meal was 879.5 ± 152.9 µg/g with a coefficient of variance (CV) of 17.2%. Although Ca absorption efficiency decreases with higher calcium intake, the total amount of calcium absorbed from test meal using FAC = 0.391 calculated from the third 8-hour urine pool was 69.0 (CV of 15.6) mg.

CONCLUSIONS

We showed that one-fifth of daily calcium recommendation for women of reproductive age could be met by ingesting ∼200 g cooked slake fortified rice.

The relationship between chronic kidney disease and denosumab-induced hypocalcemia in high-age osteoporotic patients

PURPOSE

A few studies have reported the safety of the treatment of elderly osteoporotic patients with chronic kidney disease (CKD) and the possibility of hypocalcemia. The aim of the present study was to examine the relationship between the incidence of hypocalcemia and the CKD stage in elderly osteoporotic patients treated with denosumab.

MATERIALS AND METHODS

This study was designed as a parallel-group comparison study between the denosumab-associated hypocalcemia (DAH) groups: the concentration of serum calcium was under 8.6 mg/dl and the normal calcium (NC) groups: the concentration of serum calcium was over 8.6 mg/dl. Fifty-two subjects over 70 years old were enrolled in this study, with 16 patients classified into the DAH group and 36 patients assigned to the NC group. All patients were further classified into two subgroups according to their age, into an around 75 years group to clarify the relevance of old age and an around 85 years group and also into a mild CKD group and a moderate CKD group by based on estimated glomerular filtration (eGFR). Serum calcium concentration, tartrate-resistant acid phosphatase (TRACP-5b), and type 1 procollagen N terminal propeptide (P1NP) were measured, and adverse drug reactions were evaluated.

RESULTS

The eGFR and serum calcium were significantly lower in the DAH group than in the NC group in the starting phase. Moreover, TRACP-5b was significantly higher in the DAH group than in the NC group in the starting phase. There were no significant differences in P1NP. The incidence of hypocalcemia was significantly higher in the around 85 groups than in the around 75 groups. The frequency of hypocalcemia was also significantly higher in the severe CKD group than in the mild CKD group.

CONCLUSION

Advanced age combined with low eGFR and low serum Ca status appear to be associated with the incidence of hypocalcemia when using denosumab for the treatment of osteoporosis.

Malnutrition-Inflammation Complex Syndrome With Associated Atherosclerosis and Chronic Kidney Disease: A Case Report

Patients with chronic kidney disease or on maintenance dialysis usually have secondary hyperparathyroidism. It is extremely rare for these patients to have hypoparathyroidism. It can be occasionally seen in patients on maintenance dialysis or after transplant if they have undergone parathyroidectomy for tertiary hyperparathyroidism or advanced secondary hyperparathyroidism. Also, the results of hypoparathyroidism on serum phosphorus in these patients have been infrequently reported in the literature. Here, we present a patient with chronic kidney disease stage 3 who presented with hypophosphatemia and hypoparathyroidism from the malnutrition-inflammation complex syndrome.

TNAP as a therapeutic target for cardiovascular calcification: a discussion of its pleiotropic functions in the body

Cardiovascular calcification (CVC) is associated with increased morbidity and mortality. It develops in several diseases and locations, such as in the tunica intima in atherosclerosis plaques, in the tunica media in type 2 diabetes and chronic kidney disease, and in aortic valves. In spite of the wide occurrence of CVC and its detrimental effects on cardiovascular diseases (CVD), no treatment is yet available. Most of CVC involve mechanisms similar to those occurring during endochondral and/or intramembranous ossification. Logically, since tissue-nonspecific alkaline phosphatase (TNAP) is the key-enzyme responsible for skeletal/dental mineralization, it is a promising target to limit CVC. Tools have recently been developed to inhibit its activity and preclinical studies conducted in animal models of vascular calcification already provided promising results. Nevertheless, as its name indicates, TNAP is ubiquitous and recent data indicate that it dephosphorylates different substrates in vivo to participate in other important physiological functions besides mineralization. For instance, TNAP is involved in the metabolism of pyridoxal phosphate and the production of neurotransmitters. TNAP has also been described as an anti-inflammatory enzyme able to dephosphorylate adenosine nucleotides and lipopolysaccharide. A better understanding of the full spectrum of TNAP's functions is needed to better characterize the effects of TNAP inhibition in diseases associated with CVC. In this review, after a brief description of the different types of CVC, we describe the newly uncovered additional functions of TNAP and discuss the expected consequences of its systemic inhibition in vivo.

The Novel Bone Alkaline Phosphatase Isoform B1x Is Associated with Improved 5-Year Survival in Chronic Kidney Disease

Circulating alkaline phosphatase (ALP) is an independent cardiovascular risk marker. Serum bone ALP (BALP) isoforms indicate bone turnover and comprise approximately 50% of total circulating ALP. In chronic kidney disease (CKD), mortality is highest in patients with increased ALP and BALP and low bone turnover. However, not all low bone turnover states are associated with increased mortality. Chronic inflammation and oxidative stress, features of protein energy wasting syndrome, induce cardiovascular BALP activity and fibro-calcification, while bone turnover is suppressed. Circulating BALP isoform B1x is associated with low ALP and low bone turnover and has been exclusively detected in CKD. We investigated the association of serum B1x with survival, abdominal aortic calcification (AAC) score, and aortic pulse wave velocity (PWV) in CKD. Serum ALP, BALP isoforms, parathyroid hormone (PTH), PWV, and AAC were measured repeatedly over 2 years in 68 prevalent dialysis patients. Mortality was assessed after 5 years. B1x was detected in 53 patients. A competing risk analysis revealed an association of B1x with improved 5-year survival; whereas, baseline PWV, but not AAC score, predicted mortality. However, PWV improved in 26 patients (53%), and B1x was associated with variation of PWV over time (p = 0.03). Patients with B1x had lower PTH and total ALP, suggesting an association with lower bone turnover. In conclusion, B1x is associated with time-varying PWV, lower circulating ALP, and improved survival in CKD, and thus may be an indicator of a reduced cardiovascular risk profile among patients with low bone turnover.

Association between serum alkaline phosphatase and renal outcome in patients with type 2 diabetes mellitus

This retrospective study included 299 patients with type 2 diabetes mellitus and biopsy-confirmed diabetic nephropathy (DN) to investigate the prognostic value of alkaline phosphatase (ALP) for renal outcome. Cox proportional hazards models were used to estimate the hazard ratios (HRs) for the serum ALP level on renal outcome, which was defined as end-stage renal disease (ESRD) or a 50% decline in estimated glomerular filtration rate (eGFR) from baseline. The median baseline ALP was 80 IU/L with an interquartile range of 64–97 IU/L. Serum ALP was negatively associated with eGFR but positively associated with proteinuria and renal interstitial fibrosis. During a median follow-up period of 23 months, ESRD or a 50% declined in the eGFR occurred in 156 (52.2%) patients. The highest quartile of ALP was significantly associated with poor renal outcome, as defined above (HR 2.38, 95% confidence interval [CI] 1.09–5.17), when adjusted for sociodemographics, baseline eGFR, proteinuria, liver function parameters, parathyroid hormone levels, and renal pathological findings. Each standard deviation higher in the natural log-transformed ALP was associated with a 25% increased risk for poor renal outcome. Additionally, there was a graded increase in the risk for poor renal outcome with higher ALP in patients with nephrotic-range proteinuria. However, no significant associations were observed between serum ALP levels and renal outcome in patients with non-nephrotic-range proteinuria. In conclusion, an elevated ALP level was independently associated with poor renal outcome in patients with type 2 diabetes mellitus and nephrotic-range proteinuria after multivariate adjustment.

Analyzing clinical characteristics of patients with different cumulative hemodialysis durations: a cross-sectional study

Background

The objective of this study was to examine the clinical characteristics of patients with different cumulative hemodialysis (HD) durations, so as to improve their survival rate.

Methods

In this cross-sectional study, we extracted background information and relevant clinical data from 145 patients who were undergoing maintenance HD three times a week at the Affiliated Hospital of Nantong University between January 1998 and January 2019. The study subjects were divided into four groups according to the duration of their HD: <5 years, 5–10 years, 10–15 years, and >15 years of HD. We collected the medical history and relevant clinical parameters for each subject, and measured the urea reduction ratio (URR), hemoglobin (Hb), serum calcium, phosphorus, parathyroid hormone (iPTH), and serum albumin (ALB) levels for each group.

Results

The average patient age was 52.06 ±  11.93 years old. The average patient age in the 10–15 years and >15 years groups was significantly lower than in the <5 years and 5–10 years groups (P = 0.002, P < 0.001, P = 0.012, and P = 0.0025, respectively). The most common cause of end-stage renal disease (ESRD) was chronic glomerulonephritis. We found no significant differences in URR, Hb, serum calcium, serum phosphorus, iPTH, and ALB levels.

Conclusion

A prolonged HD duration was related to a younger mean age at the start of HD treatment. The leading cause of ESRD was chronic glomerulonephritis. We predominantly found diabetic nephropathy in the group with a duration of <5 years cumulative HD. Most of the indexes related to hemodialysis almost satisfied the recommended values in these patients.

Low serum parathyroid hormone is a risk factor for peritonitis episodes in incident peritoneal dialysis patients: a retrospective study

BACKGROUND

Serum parathyroid hormone (PTH) levels have been reported to be associated with infectious mortality in peritoneal dialysis (PD) patients. Peritonitis is the most common and fatal infectious complication, resulting in technique failure, hospital admission and mortality. Whether PTH is associated with peritonitis episodes remains unclear.

METHODS

We examined the association of PTH levels and peritonitis incidence in a 7-year cohort of 270 incident PD patients who were maintained on dialysis between January 2012 and December 2018 using Cox proportional hazard regression analyses. Patients were categorized into three groups by serum PTH levels as follows: low-PTH group, PTH < 150 pg/mL; middle-PTH group, PTH 150-300 pg/mL; high-PTH group, PTH > 300 pg/mL.

RESULTS

During a median follow-up of 29.5 (interquartile range 16-49) months, the incidence rate of peritonitis was 0.10 episodes per patient-year. Gram-positive organisms were the most common causative microorganisms (36.2%), and higher percentage of Gram-negative organisms was noted in patients with low PTH levels. Low PTH levels were associated with older age, higher eGFR, higher hemoglobin, calcium levels and lower phosphate, alkaline phosphatase levels. After multivariate adjustment, lower PTH levels were identified as an independent risk factor for peritonitis episodes [hazard ratio 1.643, 95% confidence interval 1.014-2.663, P = 0.044].

CONCLUSIONS

Low PTH levels are independently associated with peritonitis in incident PD patients.

Artificial intelligence enabled applications in kidney disease

Artificial intelligence (AI) is considered as the next natural progression of traditional statistical techniques. Advances in analytical methods and infrastructure enable AI to be applied in health care. While AI applications are relatively common in fields like ophthalmology and cardiology, its use is scarcely reported in nephrology. We present the current status of AI in research toward kidney disease and discuss future pathways for AI. The clinical applications of AI in progression to end-stage kidney disease and dialysis can be broadly subdivided into three main topics: (a) predicting events in the future such as mortality and hospitalization; (b) providing treatment and decision aids such as automating drug prescription; and (c) identifying patterns such as phenotypical clusters and arteriovenous fistula aneurysm. At present, the use of prediction models in treating patients with kidney disease is still in its infancy and further evidence is needed to identify its relative value. Policies and regulations need to be addressed before implementing AI solutions at the point of care in clinics. AI is not anticipated to replace the nephrologists' medical decision-making, but instead assist them in providing optimal personalized care for their patients.

Parathyroid Hormone Serum Levels and Mortality among Hemodialysis Patients in the Gulf Cooperation Council Countries: Results from the DOPPS (2012-2018)

BACKGROUND

The prospective Dialysis Outcomes and Practice Patterns Study (DOPPS) has collected data since 2012 in all six Gulf Cooperation Council (GCC) countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and United Arab Emirates). We report the relationship of PTH with mortality in this largest GCC cohort of patients on hemodialysis studied to date.

METHODS

Data were from randomly selected national samples of hemodialysis facilities in GCC-DOPPS phases 5 and 6 (2012-2018). PTH descriptive findings and case mix-adjusted PTH/mortality Cox regression analyses were based on 1825 and 1422 randomly selected patients on hemodialysis, respectively.

RESULTS

Mean patient age was 55 years (median dialysis vintage, 2.1 years). Median PTH ranged from 259 pg/ml (UAE) to 437 pg/ml (Kuwait), with 22% having PTH <150 pg/ml, 24% with PTH of 150-300 pg/ml, 34% with PTH 301-700 pg/ml, and 20% with PTH >700 pg/ml. Patients with PTH >700 pg/ml were younger; on dialysis longer; less likely to be diabetic; have urine >200 ml/d; be prescribed 3.5 mEq/L dialysate calcium; had higher mean serum creatinine and phosphate levels; lower white blood cell counts; and more likely to be prescribed cinacalcet, phosphate binders, or IV vitamin D. A U-shaped PTH/mortality relationship was observed with more than two- and 1.5-fold higher adjusted HR of death at PTH >700 pg/ml and <300 pg/ml, respectively, compared with PTH of 301-450 pg/ml.

CONCLUSIONS

Secondary hyperparathyroidism is highly prevalent among GCC patients on hemodialysis, with a strong U-shaped PTH/mortality relationship seen at PTH <300 and >450 pg/ml. Future studies are encouraged for further understanding this PTH/mortality pattern in relationship to unique aspects of the GCC hemodialysis population.

Hemodialysis patients with low serum parathyroid hormone levels have a poorer prognosis than those with secondary hyperparathyroidism

BACKGROUND

Low serum parathyroid hormone (PTH) level and secondary hyperparathyroidism (SHPT) are very common in hemodialysis patients. However, the outcomes of patients with low PTH level or SHPT have not been carefully compared. Therefore, in the present study, we compared the outcomes of hemodialysis patients with low PTH level or SHPT.

METHODS

This was a multi-center, prospective, cohort study of 647 patients. The patients were recruited between 1 September 2016 and 1 January 2017 and followed until 31 December 2018. The participants were allocated to a low PTH group [serum intact PTH (iPTH) concentration < 60 pg/ml] and an SHPT group (iPTH ⩾ 600 pg/ml) according to their mean iPTH concentration across the entire observation period, and the outcomes were compared between these groups. The primary outcome was a composite outcome, which comprised all-cause mortality, non-fatal acute myocardial infarction, non-fatal acute stroke, and acute heart failure.

RESULTS

A total of 197 hemodialysis patients were allocated to the two groups: 87 with low PTH level and 110 with SHPT; 450 patients with time-averaged iPTH concentrations of 60-600 pg/ml were excluded. Kaplan-Meier analysis of the composite endpoint revealed a significant difference between participants with low PTH level and those with SHPT (p = 0.002). Cox multiple regression showed that participants with low PTH level had a higher incidence of the composite endpoint than those with SHPT (relative risk: 1.337, 95% confidence interval: 1.059-1.688).

CONCLUSION

Hemodialysis patients with low PTH level had a higher incidence of mortality and non-fatal cardiovascular events than those with SHPT, irrespective of whether the participants were age-matched.

Parathyroid Hormone Serum Levels and Mortality among Hemodialysis Patients in the Gulf Cooperation Council Countries: Results from the DOPPS (2012–2018)

Background

The prospective Dialysis Outcomes and Practice Patterns Study (DOPPS) has collected data since 2012 in all six Gulf Cooperation Council (GCC) countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and United Arab Emirates). We report the relationship of PTH with mortality in this largest GCC cohort of patients on hemodialysis studied to date.

Methods

Data were from randomly selected national samples of hemodialysis facilities in GCC-DOPPS phases 5 and 6 (2012–2018). PTH descriptive findings and case mix–adjusted PTH/mortality Cox regression analyses were based on 1825 and 1422 randomly selected patients on hemodialysis, respectively.

Results

Mean patient age was 55 years (median dialysis vintage, 2.1 years). Median PTH ranged from 259 pg/ml (UAE) to 437 pg/ml (Kuwait), with 22% having PTH <150 pg/ml, 24% with PTH of 150–300 pg/ml, 34% with PTH 301–700 pg/ml, and 20% with PTH >700 pg/ml. Patients with PTH >700 pg/ml were younger; on dialysis longer; less likely to be diabetic; have urine >200 ml/d; be prescribed 3.5 mEq/L dialysate calcium; had higher mean serum creatinine and phosphate levels; lower white blood cell counts; and more likely to be prescribed cinacalcet, phosphate binders, or IV vitamin D. A U-shaped PTH/mortality relationship was observed with more than two- and 1.5-fold higher adjusted HR of death at PTH >700 pg/ml and <300 pg/ml, respectively, compared with PTH of 301–450 pg/ml.

Conclusions

Secondary hyperparathyroidism is highly prevalent among GCC patients on hemodialysis, with a strong U-shaped PTH/mortality relationship seen at PTH <300 and >450 pg/ml. Future studies are encouraged for further understanding this PTH/mortality pattern in relationship to unique aspects of the GCC hemodialysis population.

PF-06869206 is a selective inhibitor of renal Pi transport: evidence from in vitro and in vivo studies

Plasma phosphate (P_i) levels are tightly controlled, and elevated plasma P_i levels are associated with an increased risk of cardiovascular complications and death. Two renal transport proteins mediate the majority of P_i reabsorption: Na⁺-phosphate cotransporters Npt2a and Npt2c, with Npt2a accounting for 70-80% of P_i reabsorption. The aim of the present study was to determine the in vitro effects of a novel Npt2a inhibitor (PF-06869206) in opossum kidney (OK) cells as well as determine its selectivity in vivo in Npt2a knockout (Npt2a^-/-) mice. In OK cells, Npt2a inhibitor caused dose-dependent reductions of Na⁺-dependent P_i uptake (IC₅₀: ~1.4 μmol/L), whereas the unselective Npt2 inhibitor phosphonoformic acid (PFA) resulted in an ~20% stronger inhibition of P_i uptake. The dose-dependent inhibitory effects were present after 24 h of incubation with both low- and high-P_i media. Michaelis-Menten kinetics in OK cells identified an ~2.4-fold higher K_m for P_i in response to Npt2a inhibition with no significant change in apparent V_max. Higher parathyroid hormone concentrations decreased P_i uptake equivalent to the maximal inhibitory effect of Npt2a inhibitor. In vivo, the Npt2a inhibitor induced a dose-dependent increase in urinary P_i excretion in wild-type mice (ED₅₀: ~23 mg/kg), which was completely absent in Npt2a^-/- mice, alongside a lack of decrease in plasma P_i. Of note, the Npt2a inhibitor-induced dose-dependent increase in urinary Na⁺ excretion was still present in Npt2a^-/- mice, a response possibly mediated by an off-target acute inhibitory effect of the Npt2a inhibitor on open probability of the epithelial Na⁺ channel in the cortical collecting duct.

Racial differences in utilization and outcomes of hemodialysis access in the Unites States

OBJECTIVE

To evaluate patterns of use and outcomes of arteriovenous fistulas and prosthetic grafts within racial categories in a large population based cohort of hemodialysis (HD) patients in the United States.

METHODS

A retrospective analysis of white, black, and Hispanic patients in the prospectively maintained United States Renal Database System who had an autogenous fistula or prosthetic graft placed for HD access between January 2007 and December 2014 was performed. Analysis of variance, χ2, t-tests, Kaplan-Meier, log-rank tests, multivariable logistic, and Cox regression analyses were used to evaluate maturation, patency, infection, and mortality.

RESULTS

This study of 359,942 patients, composed of 285,781 autogenous fistulas (79.4%) and 74,161 prosthetic grafts (20.6%) placed in 213,877 white (59.4%), 115,727 black (32.2%), and 30,338 Hispanic (8.4%) patients. There was a 11% increase in the risk-adjusted odds of HD catheter use as bridge to autogenous fistula placement in blacks (adjusted odds ratio, 1.11; 95% confidence interval [CI], 1.08-1.14; P < .001) and a 9% increase in Hispanics (adjusted odds ratio, 1.09; 95% CI, 1.05-1.14; P < .001) compared with whites. Fistula maturation for HD access for whites vs blacks vs Hispanics was 77.0% vs 76.3% vs 77.8% (P = .35). After adjusting for covariates, fistula maturation was higher for blacks (adjusted hazard ratio, 1.09; 95% CI, 1.06-1.13; P < .001) and Hispanics (adjusted hazard ratio, 1.13; 95% CI, 1.06-1.20; P < .001) compared with whites. There was no significant difference in prosthetic graft maturation for blacks and Hispanics compared with whites. Primary, primary-assisted, and secondary patency were highest for Hispanic and least for black autogenous fistula recipients. Primary, primary-assisted, and secondary patency was also highest for Hispanic patients who received prosthetic grafts. Prosthetic grafts were associated with a decrease in patency and patient survival compared with fistulas in all racial categories. Mortality was lower for blacks and Hispanics relative to white patients. Initiation of HD with a catheter and conversion to autogenous fistula was associated with decrease in patency and patient survival compared with initiation with a fistula in all racial groups.

CONCLUSIONS

Autogenous fistulas are associated with better patency and patient survival compared with prosthetic grafts for all races studied. The use of HD catheter before fistula placement is more prevalent in Hispanic and black patients and is associated with worse patency and patient survival irrespective of race. Fistula and graft patency is highest for Hispanic patients. Patient survival is higher for Hispanic and black patients relative to whites. These associations suggest potential benefit with initiation of HD via autogenous fistula and minimizing temporizing catheter use, irrespective of race.

Oxidation of parathyroid hormone

Parathyroid hormone (PTH) is the key hormone regulating calcium homeostasis and, as such, is an important diagnostic and prognostic marker. Although the measurement of PTH has greatly improved over the past few decades, oxidation status thereof is unaccounted for in currently used assays. PTH can be oxidized on methionine residues located at amino acid positions 8 and 18. This is a relevant post-translational modification as, due to refolding of the molecule, it results in the decreased ability to activate the PTH1 receptor. Although this loss of activity after oxidation was observed as early as 1934, only recently a method was developed to measure and distinguish non-oxidized PTH (n-oxPTH) from oxidized PTH. This method creates exciting possibilities for studying more specifically the role of n-oxPTH in physiology and pathology. Therefore, it can now be explored what the clinical implications of measuring n-oxPTH will be. Herein, we review the available evidence of the effect of oxidation on the biological activity of PTH. We also discuss studies examining the mechanism of PTH oxidation in vivo and efforts to stabilize synthetic PTH ex vivo for therapeutic applications. Lastly, the available studies regarding the clinical significance of n-oxPTH are evaluated and future directions discussed.

Digital radiography as an alternative method in the evaluation of bone density in uremic rats

INTRODUCTION

Digital radiography (DRx) may provide a suitable alternative to investigate mineral and bone disorder (MBD) and loss of bone density (BD) in rodent models of chronic kidney disease (CKD). The objective of this study was to use DRx to evaluate BD in CKD rats, and to evaluate the correlation between DRx findings and serum MBD markers and bone histomorphometry.

METHODS

Uremia was induced by feeding Wistar rats an adenine-enriched diet (0.75% for 4 weeks/0.10% for 3 weeks); outcomes were compared to a control group at experimental weeks 3, 4, and 7. The following biochemical markers were measured: creatinine clearance (CrC), phosphate (P), calcium (Ca), fractional excretion of P (FeP), alkaline phosphatase (ALP), fibroblast growth factor-23 (FGF-23), and parathyroid hormone (PTH). DRx imaging was performed and histomorphometry analysis was conducted using the left femur.

RESULTS

As expected, at week 7, uremic rats presented with reduced CrC and higher levels of P, FeP, and ALP compared to controls. DRx confirmed the lower BD in uremic animals (0.57±0.07 vs. 0.68 ± 0.06 a.u.; p = 0.016) compared to controls at the end of week 7, when MBD was more prominent. A severe form of high-turnover bone disease accompanied these biochemical changes. BD measured on DRx correlated to P (r=-0.81; p = 0.002), ALP (r = -0.69, p = 0.01), PTH (r = -0.83, p = 0.01), OS/BS (r = -0.70; p = 0.02), and ObS/BS (r = -0.70; p = 0.02).

CONCLUSION

BD quantified by DRx was associated with the typical complications of MBD in CKD and showed to be viable in the evaluation of bone alterations in CKD.

Exploring the putative interactions between chronic kidney disease and chronic periodontitis

Chronic kidney disease (CKD) and chronic periodontitis (CP) are both common diseases, which are found disproportionately comorbid with each other and have been reported to have a detrimental effect on the progression of each respective disease. They have an overlap in risk factors and both are a source of systemic inflammation along with a wide selection of immunological and non-specific effects that can affect the body over the lifespan of the conditions. Previous studies have investigated the directionality of the relationship between these two diseases; however, there is a lack of literature that has examined how these diseases may be interacting at the localized and systemic level. This review discusses how oral microorganisms have the ability to translocate and have distal effects and provides evidence for microbial involvement in a systemic disease. Furthermore, it summarizes the reported local and systemic effects of CKD and CP and discusses how the interaction of these effects may be responsible for directionality associations reported.

Low parathyroid hormone level predicts infection-related mortality in incident dialysis patients: a prospective cohort study

BACKGROUND/AIMS

Parathyroid hormone (PTH) is an important factor influencing immunologic dysfunction, but the effect of PTH level on infection-related outcomes remains unclear in incident dialysis.

METHODS

We evaluated a multicenter prospective cohort study of 1,771 incident dialysis patients (1,260 hemodialysis and 511 peritoneal dialysis) in Korea. Patients were divided into three groups based on serum intact PTH (iPTH) level. The primary outcomes were all-cause and infection-related mortality and multivariate Cox regression analysis was performed to evaluate the role of iPTH in all-cause and infection-related mortality.

RESULTS

During the follow-up period of 27.3 months, 175 patients (9.9%) died, and infection-related death represented 20% of all-cause mortality. Both all-cause mortality and infection-related mortality rates (p < 0.001 and p = 0.003, by logrank) were markedly higher in patients with serum iPTH < 150 pg/mL than in the other groups. Multivariate Cox regression analysis revealed that patients with serum iPTH < 150 pg/mL remained at higher risk for infection-related mortality than patients in the target range of 150 ≤ iPTH < 300 pg/mL, after adjusting for confounding variables (hazard ratio [HR], 2.52; 95% confidence interval, 1.06 to 5.99; p = 0.04). The HR of infection-related mortality in patients with serum iPTH < 150 pg/mL was significantly higher in patients with low serum phosphorus, low Ca × P product, low serum alkaline phosphatase and those older than 65 years.

CONCLUSION

Low serum iPTH level is an independent predictor of infection-related mortality in incident dialysis patients.

The roles of calcium-sensing receptor (CaSR) in heavy metals-induced nephrotoxicity

The kidney is a vital organ responsible for regulating water, electrolyte and acid-base balance as well as eliminating toxic substances from the blood in the body. Exposure of humans to heavy metals in their natural and occupational environments, foods, water, and drugs has serious implications on the kidney's health. The accumulation of heavy metals in the kidney has been linked to acute or chronic renal injury, kidney stones or even renal cancer, at the expense of expensive treatment options. Therefore, unearthing novel biomarkers and potential therapeutic agents or targets against kidney injury for efficient treatment are imperative. The calcium-sensing receptor (CaSR), a G-protein-coupled receptor (GPCR) is typically expressed in the parathyroid glands and renal tubules. It modulates parathyroid hormone secretion according to the serum calcium (Ca²⁺) concentration. In the kidney, it modulates electrolyte and water excretion by regulating the function of diverse tubular segments. Notably, CaSR lowers passive and active Ca²⁺ reabsorption in distal tubules, which facilitates phosphate reabsorption in proximal tubules and stimulates proton and water excretion in collecting ducts. Moreover, at the cellular level, modulation of the CaSR regulates cytosolic Ca²⁺ levels, reactive oxygen species (ROS) generation and the mitogen-activated protein kinase (MAPK) signaling cascades as well as autophagy and the suppression of apoptosis, an effect predominantly triggered by heavy metals. In this regard, we present a review on the CaSR at the cellular level and its potential as a therapeutic target for the development of new and efficient drugs against heavy metals-induced nephrotoxicity.

Role of parathyroid hormone in anorexia on maintenance hemodialysis patients

BACKGROUND AND AIM

Anorexia, which is a common condition in patients on hemodialysis (HD), is characterized by impaired appetite, a subjective condition that hinders anorexia diagnosis. Anorexia is frequently associated with protein energy wasting and inflammation, increasing morbidity and mortality risk. The aim of the study was to evaluate the association between appetite and nutritional, inflammatory, hormonal, and dietary intake parameters in patients on maintenance HD.

METHODS

Cross-sectional study with clinical, laboratory, and anthropometric parameters, body composition, muscle function, and dietary intake assessment. To evaluate appetite, a three simple questions questionnaire previously validated was used. After appetite classification, the sample was dichotomized in "normal appetite" and "impaired appetite" and compared. Multiple logistic regression was used to identify association between variables and outcome.

RESULTS

125 patients on HD were included, aged 60.6 ± 14.12 years old, median HD vintage 35.5 months. In dichotomized sample, 78.4% patients showed "normal appetite", and 21.6% "impaired appetite". "Impaired appetite" was independently associated with increased serum PTH (OR 1.001; 95% CI 1.000-1.002; p = 0.03), low zinc intake (OR 0.860; 95% CI 0.746-0.991; p = 0.03) and lower urea serum (OR 0.982; 95% CI 0.965-0.999; p = 0.04). Both groups showed insufficient dietary intake.

CONCLUSIONS

Appetite was independently associated with increased serum of PTH, low serum concentration of urea, and low zinc intake which may infer association of appetite with mineral bone disease, protein intake and zinc deficiency.

Effect of extended hours dialysis on markers of chronic kidney disease-mineral and bone disorder in the ACTIVE Dialysis study

Background

Chronic Kidney Disease - Mineral and Bone Disorder (CKD-MBD) is a significant cause of morbidity among haemodialysis patients and is associated with pathological changes in phosphate, calcium and parathyroid hormone (PTH). In the ACTIVE Dialysis study, extended hours dialysis reduced serum phosphate but did not cause important changes in PTH or serum calcium. This secondary analysis aimed to determine if changes in associated therapies may have influenced these findings and to identify differences between patient subgroups.

Methods

The ACTIVE Dialysis study randomised 200 participants to extended hours haemodialysis (≥24 h/week) or conventional haemodialysis (≤18 h/week) for 12 months. Mean differences between treatment arms in serum phosphate, calcium and PTH; and among key subgroups (high vs. low baseline phosphate/PTH, region, time on dialysis, dialysis setting and frequency) were examined using mixed linear regression.

Results

Phosphate binder use was reduced with extended hours (− 0.83 tablets per day [95% CI -1.61, − 0.04; p = 0.04]), but no differences in type of phosphate binder, use of vitamin D, dose of cinacalcet or dialysate calcium were observed. In adjusted analysis, extended hours were associated with lower phosphate (− 0.219 mmol/L [− 0.314, − 0.124; P < 0.001]), higher calcium (0.046 mmol/L [0.007, 0.086; P = 0.021]) and no change in PTH (0.025 pmol/L [− 0.107, 0.157; P = 0.713]). The reduction in phosphate with extended hours was greater in those with higher baseline PTH and dialysing at home.

Conclusion

Extended hours haemodialysis independently reduced serum phosphate levels with minimal change in serum calcium and PTH levels. With a few exceptions, these results were consistent across patient subgroups.

Trial registration

Clinicaltrials.gov NCT00649298. Registered 1 April 2008.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1438-3) contains supplementary material, which is available to authorized users.

Association of ORAI1 Genetic Polymorphism with Serum Calcium and Phosphorus Levels in Non-dialysis Chronic Kidney Disease Patients: A Case-control Study

Background

As chronic kidney disease (CKD) is a silent killer, it is now a global concern to find out the possible causes by genetic and biological markers. In the earlier stages of CKD, serum calcium and phosphorus levels fall down later on turned into hypercalcemia and hyperphosphatemia contributing high mortality in CKD. This study aimed to examine the serum calcium and phosphorus levels in non-dialysis CKD patients and healthy controls to find out their association with ORAI1 genetic polymorphism.

Methods

The present study recruited 96 non-dialysis CKD patients and 100 control subjects matched by age, gender, and body mass index (BMI). Measurement of serum calcium levels was performed with atomic absorption spectrophotometer (HITACHI, 170-30) and phosphorus levels were determined by UV VIS spectrophotometer (Analytik Jena SPEKOL 2000). PCR-RFLP technique was applied to determine the genetic polymorphism of ORAI1 (rs12313273 and rs6486795) gene.

Results

The mean values of serum calcium and phosphorus levels were 2.53 ± 0.50 mg/dL and 3.77 ± 0.42 mg/dL for the patient group and 3.67 ± 2.37 mg/dL and 13.66 ± 6.34 mg/dL for the control group, respectively. We observed significantly reduced serum calcium and phosphorus levels in non-dialysis CKD patients compared with control subjects (p < 0.001). No significant polymorphism of ORAI1 (rs12313273 and rs6486795) was found with declined serum calcium and phosphorus levels.

Conclusions

The present study suggested that there is no linear correlation between ORAI1 genetic polymorphism with serum calcium and phosphorus levels in non-dialysis CKD patients.

Exercise Alleviates Osteoporosis in Rats with Mild Chronic Kidney Disease by Decreasing Sclerostin Production

Chronic kidney disease–mineral bone disorder (CKD–MBD), comprising mineral, hormonal, and bone metabolic imbalance, is a major CKD-related issue; it causes osteoporosis prevalence in CKD patients. Osteocyte-derived sclerostin inhibits the osteogenic Wnt/β-catenin signaling pathway; its levels rise when kidney function declines. Exercise modulates the physiological functions of osteocytes, potentially altering sclerostin production. It may aid bone and mineral electrolyte homeostasis in CKD. Mild CKD was induced in rats by partial nephrectomy. They were divided into: sham (no CKD), CKD, and CKD + exercise (8 weeks of treadmill running) groups. Micro-CT scanning demonstrated that the CKD + exercise-group rats had a higher bone mineral density (BMD) of the spine and femoral metaphysis and higher femoral trabecular bone volume than the CKD-group rats. Bone formation rates were not significantly different. The CKD + exercise-group rats had lower serum sclerostin (157.1 ± 21.1 vs 309 ± 38.1 pg/mL, p < 0.05) and CTX-1 (bone resorption marker) levels. Immunohistochemistry revealed higher tibial β-catenin concentrations in the CKD + exercise-group rats. Serum FGF-23, intact parathyroid hormone (iPTH), alkaline phosphatase (ALP), calcium, and phosphate levels showed no significant differences between these groups. Thus, exercise improves BMD and bone microstructure in mild CKD by inhibiting sclerostin production, but does not alter serum minerals.

Hypophosphatemic Rickets

Hypophosphatemic rickets, mostly of the X-linked dominant form caused by pathogenic variants of the PHEX gene, poses therapeutic challenges with consequences for growth and bone development and portends a high risk of fractions and poor bone healing, dental problems and nephrolithiasis/nephrocalcinosis. Conventional treatment consists of PO4 supplements and calcitriol requiring monitoring for treatment-emergent adverse effects. FGF23 measurement, where available, has implications for the differential diagnosis of hypophosphatemia syndromes and, potentially, treatment monitoring. Newer therapeutic modalities include calcium sensing receptor modulation (cinacalcet) and biological molecules targeting FGF23 or its receptors. Their long-term effects must be compared with those of conventional treatments.

Serum alkaline phosphatase and the risk of coronary heart disease, stroke and all-cause mortality: Tehran Lipid and Glucose Study

OBJECTIVES

To investigate the association of alkaline phosphatase (ALP) levels with the risk of the composite end point of cardiovascular disease (CVD), and all-cause mortality as well as each of them separately.

DESIGN

Prospective cohort study.

SETTING

Within the framework of the Tehran Lipid and Glucose Study (TLGS) cohort, participants were followed from baseline examination (1999-2001) until March 2014.

PARTICIPANTS

A total of 2578 participants, aged ≥30 years free of prevalent CVD at baseline examination.

PRIMARY OUTCOME

The main outcome measures were composite end point of coronary heart disease (CHD), stroke, all-cause mortality and each per se.

RESULTS

During a median follow-up of 11.3 years, 369, 68, 420, 170 and 495 participants experienced CHD, stroke, CVD, all-cause mortality and the composite outcome, respectively. In the multivariable Cox regression models, the adjusted HRs (95% CI) for mentioned events per one SD increase in ALP level after full adjustment were 1.11 (1.01 to 1.22), 1.20 (0.97 to 1.49, p=0.058), 1.10 (1.01 to 1.21), 1.16 (1.01 to 1.33) and 1.11 (1.02 to 1.21), respectively. Furthermore, participants with ALP levels in the highest tertile had significant adjusted HRs (95% CI) for stroke (1.88 (1.00 to 3.61)), CVD (1.30 (1.01 to 1.68)) and composite outcome (1.27 (1.00 to 1.61)). The cut-off value of ALP ≥199 IU/L for predicting composite outcome was derived using Youden's index, based on which this cut-off point was associated with significant risk of 80%, 26%, 43% and 26% for incident stroke, CVD, all-cause mortality and composite outcome. Additionally, no improvement was seen in the predictive ability of traditional risk factors models after adding ALP values, considering the levels of Akaike information criterion, C-index and Net Reclassification Index.

CONCLUSION

Independent associations between ALP levels and the risks of CVD and mortality events were shown, despite the fact that adding the data of ALP to known risk factors did not improve the prediction of these events.

NUTRITIONAL OR ACTIVE VITAMIN D FOR THE CORRECTION OF MINERAL METABOLISM ABNORMALITIES IN NON-DIALYSIS CHRONIC KIDNEY DISEASE PATIENTS?

CONTEXT

Benefits of vitamin D therapies in chronic kidney disease (CKD) are debated.

OBJECTIVE

To compare the effects of medium-term native (VitD) and active (VDRA) vitamin D on parameters of mineral metabolism and arterial function in non-dialysis CKD.

DESIGN

Open-label, active comparator, randomized study.

SUBJECTS AND METHODS

Forty-eight adult patients, vitamin D naïve, CKD stage 3 to 5 with increased parathyroid hormone (iPTH) were randomized to receive either oral cholecalciferol 1000UI/day (n=24) or paricalcitol 1mcg/day (n=24) for 6 months. Median changes at end of study vs. baseline in serum calcidiol, iPTH, total alkaline phosphatase (ALP), and cardio-ankle vascular index (CAVI) were the efficacy parameters.

RESULTS

Higher increase in calcidiol (15.5 [95%CI 13.3; 17.2] vs. 0.4 [95%CI -6.1; 3.7]ng/mL, p<0.001) were found in VitD group. Conversely, the decline of iPTH (-35.2 [95%CI -83; 9] vs. 13.3 [95%CI -8.1; 35]pg/mL, p=0.008) and ALP (-34 [95%CI -58; -11] vs. -10 [95%CI -23; -2]U/L, p=0.02) were greater after paricalcitol. More subjects experienced iPTH decrease in VDRA group (71% vs. 39%, p=0.03). The variation in CAVI and the incidence of hypercalcemia and hyperphosphatemia were similar.

CONCLUSIONS

It seems that secondary hyperparathyroidism was more efficiently treated by VDRA, whereas cholecalciferol better corrected the calcidiol deficiency in non-dialysis CKD.

Parathyroidectomy in the Management of Secondary Hyperparathyroidism

Secondary hyperparathyroidism develops in CKD due to a combination of vitamin D deficiency, hypocalcemia, and hyperphosphatemia, and it exists in nearly all patients at the time of dialysis initiation. There is insufficient data on whether to prefer vitamin D analogs compared with calcimimetics, but the available evidence suggests advantages with combination therapy. Calcium derangements, patient adherence, side effects, and cost limit the use of these agents. When parathyroid hormone level persists >800 pg/ml for >6 months, despite exhaustive medical interventions, monoclonal proliferation with nodular hyperplasia is likely present along with decreased expression of vitamin D and calcium-sensing receptors. Hence, surgical parathyroidectomy should be considered, especially if concomitant disorders exist, such as persistent hypercalcemia or hyperphosphatemia, tissue or vascular calcification including calciphylaxis, and/or worsening osteodystrophy. Parathyroidectomy is associated with 15%-57% greater survival in patients on dialysis, and it also improves hypercalcemia, hyperphosphatemia, tissue calcification, bone mineral density, and health-related quality of life. The parathyroidectomy rate in the United States declined to approximately seven per 1000 dialysis patient-years between 2002 and 2011 despite an increase in average parathyroid hormone levels, reflecting calcimimetics introduction and uncertainty regarding optimal parathyroid hormone targets. Hospitalization rates are 39% higher in the first postoperative year. Hungry bone syndrome occurs in approximately 25% of patients on dialysis, and profound hypocalcemia requires high doses of oral and intravenous calcium along with calcitriol supplementation. Total parathyroidectomy with autotransplantation carries a higher risk of permanent hypocalcemia, whereas risk of hyperparathyroidism recurrence is higher with subtotal parathyroidectomy. Given favorable long-term outcomes from observational parathyroidectomy cohorts, despite surgical risk and postoperative challenges, it is reasonable to consider parathyroidectomy in more patients with medically refractory secondary hyperparathyroidism.

Prognostic value of bone- and vascular-derived molecular biomarkers in hemodialysis and renal transplant patients: a systematic review and meta-analysis

Background

Patients undergoing hemodialysis and kidney graft recipients are high-risk populations for cardiovascular and all-cause mortality. Fibroblast growth factor 23 (FGF23), osteoprotegerin (OPG), RANK ligand, osteopontin (OPN), Klotho protein and bone morphogenetic protein-7 (BMP-7) are bone- and vascular-derived molecular biomarkers that have been shown to be associated with cardiovascular surrogate end points; however, currently available data on the prognostic value of these biomarkers is inconsistent. The aim of the present study was to conduct a systematic review and meta-analysis in order to summarize the available evidence on the association of molecular biomarkers with mortality in individuals undergoing hemodialysis and renal transplant patients.

Methods

Two databases (MEDLINE and Embase) were systematically searched. Studies were eligible if the association of biomarker and mortality was reported as time-to-event data [hazard Ratio (HR)] or as effect size with a fixed time of follow-up [odds Ratio (OR)]. Abstracted HRs were converted onto a standard scale of effect and combined using a random effects model.

Results

From a total of 1170 studies identified in initial searches, 21 met the inclusion criteria. In hemodialysis patients, comparing the lower third with the upper third of baseline FGF23 distribution, pooled HRs (95% confidence intervals) were 1.94 (1.47, 2.56) for all-cause mortality and 2.4 (1.64, 3.51) for cardiovascular mortality. For the same comparison of baseline OPG distribution, pooled HRs were 1.8 (0.95, 3.39) for all-cause mortality and 2.53 (1.29, 4.94) for cardiovascular mortality. Reported risk estimates of RANK ligand, OPN, Klotho protein and BMP-7 were not suitable for pooling; however, only Klotho protein was significantly related to mortality. For kidney graft recipients, four studies that investigated the relationship of FGF23 and OPG with mortality were identified, all of which reported a significant association.

Conclusions

In hemodialysis patients, FGF23 is a predictor of all-cause and cardiovascular mortality, whereas the predictive value of OPG is restricted to cardiovascular mortality. Further studies are needed in order to gain insight into the prognostic value of these biomarkers in renal transplant recipients.

Osteoporosis, bone mineral density and CKD-MBD complex (I): Diagnostic considerations

Osteoporosis (OP) and chronic kidney disease (CKD) independently influence bone and cardiovascular health. A considerable number of patients with CKD, especially those with stages 3a to 5D, have a significantly reduced bone mineral density leading to a high risk of fracture and a significant increase in associated morbidity and mortality. Independently of classic OP related to age and/or gender, the mechanical properties of bone are also affected by inherent risk factors for CKD ("uraemic OP"). In the first part of this review, we will analyse the general concepts regarding bone mineral density, OP and fractures, which have been largely undervalued until now by nephrologists due to the lack of evidence and diagnostic difficulties in the context of CKD. It has now been proven that a reduced bone mineral density is highly predictive of fracture risk in CKD patients, although it does not allow a distinction to be made between the causes which generate it (hyperparathyroidism, adynamic bone disease and/or senile osteoporosis, etc.). Therefore, in the second part, we will analyse the therapeutic indications in different CKD stages. In any case, the individual assessment of factors which represent a higher or lower risk of fracture, the quantification of this risk (i.e. using tools such as FRAX^®) and the potential indications for densitometry in patients with CKD could represent an important first step pending new clinical guidelines based on randomised studies which do not exclude CKD patients, all the while avoiding therapeutic nihilism in an area of growing importance.

Positioning novel biologicals in CKD-mineral and bone disorders

Renal osteodystrophy (ROD), the histologic bone lesions of chronic kidney disease (CKD), is now included in a wider syndrome with laboratory abnormalities of mineral metabolism and extra-skeletal calcifications or CKD-mineral and bone disorders (CKD-MBD), to highlight the increased burden of mortality. Aging people, frequently identified as early CKD, could suffer from either the classical age-related osteoporosis (OP) or ROD. Distinguishing between these two bone diseases may not be easy without bone biopsy. In any case, besides classical therapies for ROD, nephrologists are now challenged by the possibility of using new drugs developed for OP. Importantly, while therapies for ROD mostly aim at controlling parathyroid secretion with bone effects regarded as indirect, new drugs for OP directly modulate bone cells activity. Thus, their action could be useful in specific types of ROD. Parathyroid hormone therapy, which is anabolic in OP, could be useful in renal patients with low turnover bone disease. Denosumab, the monoclonal antibody against receptor activator of NF-κB ligand (RANK-L) that inhibits osteoclast activity and proliferation, could be beneficial in cases with high turnover bone. Use of romosozumab, the monoclonal antibody against sclerostin, which both stimulates osteoblasts and inhibits osteoclasts, could allow both anabolic and anti-resorptive effects. However, we should not forget the systemic role now attributed to CKD-MBD. In fact, therapies targeting bone cells activity could also result in unpredicted extra-bone effects and affect cardiovascular outcomes. In conclusion, the new biologicals established for OP could be useful in renal patients with either OP or ROD. In addition, their potential non-bone effects warrant investigation.

Differentially expressed miR-3680-5p is associated with parathyroid hormone regulation in peritoneal dialysis patients

Mineral and bone disorder (MBD) is observed universally in patients with chronic kidney disease (CKD). Detrimental MBD-related skeletal changes include increased prevalence of fracture, cardiovascular disease, and mortality. MicroRNAs (miRNAs) have been identified as useful biomarkers in various diseases, and the aim of this study was to identify miRNAs associated with parathyroid hormone level in peritoneal dialysis (PD) patients. Fifty-two PD patients were enrolled and grouped by their intact parathyroid hormone (iPTH) level; 11 patients had low iPTH (<150 pg/mL) and 41 patients had high iPTH (≥150 pg/mL). Total RNA was extracted from whole blood samples. Total RNA from 15 patients (7 and 8 patients in the low and high iPTH groups, respectively) underwent miRNA microarray analysis, and three differentially upregulated (>2-fold change) miRNAs previously associated with human disease were selected for real-time quantitative PCR (qPCR) analysis. Interaction analyses between miRNAs and genes were performed by using TargetScan and the KEGG pathway database. Microarray results revealed 165 miRNAs were differentially expressed between patients with high iPTH levels and low iPTH levels. Of those miRNAs, 81 were upregulated and 84 were downregulated in patients with high iPTH levels. Expression levels of miR-1299, miR-3680-5p, and miR-548b-5p (previously associated with human disease) in 52 patients were analyzed by using qPCR. MiR-3680-5p was differentially expressed in low and high iPTH patients (P < 0.05). The predicted target genes of miR-3680-5p were USP6, USP32, USP46, and DLT, which are involved in the ubiquitin proteolysis pathway. This pathway has roles in PTH and parathyroid hormone related protein degradation and proteolysis. The mechanisms involved in the associations among low PTH, adynamic bone disease, miR-3680-5p, and the target genes should be explored further in order to elucidate their roles in CKD-MBD development.

Analysis of the kinetics of the parathyroid hormone, and of associated patient outcomes, in a cohort of haemodialysis patients

Background

Observational studies have recently associated a decrease in serum parathyroid hormone (PTH) level with a higher rate of mortality among hemodialysis (HD) patients. Decreases in PTH level can result from medical intervention (MPD) and surgical parathyroidectomy (PTX), or may occur spontaneously, usually associated with an underlying malnutrition-inflammation syndrome (SPD). The aim of our study was to prospectively identify the incidence of decreases in PTH level in a cohort of HD patients and the frequency distribution of the different causes (MPD, PTX and SPD), as well as to evaluate the survival outcomes for each PTH group (MPD, PTX and SPD) compared to patients who did not experience a PTH decrease over the first 36 months of the study (NPD).

Methods

The 197 patients receiving HD at our center in January 2010, and meeting our eligibility criteria, were enrolled in our prospective study, and were observed for a period of 60 months. A decrease in PTH level >50 % between two successive PTH measurements obtained within an interval <3 months was defined as a significant event. MPD referred to a decrease in PTH due to an increased oral calcium intake, increased dialysate calcium concentration (DCC), increased alfacalcidol use, or use of cinacalcet therapy. A surgical 7/8 PTX was performed in young patients or in patients in whom cinacalcet therapy failed. SPD referred to a decrease in PTH related to a medical or surgical event. Baseline characteristics among patients in each group (MPD, PTX, SPD, and NPD) were evaluated using Fisher’s exact test. The 60-month survival was evaluated using Kaplan-Meier and Cox multivariable proportional hazards models. Univariate and multivariate Cox analyzes were used identify variables with mortality. The relative risk of mortality was expressed as a hazard ratio (HR).

Results

The distribution of the 197 patients forming our four study groups was 34 % in the NPD group, 35 % in the SPD group, 25 % in the MSD group and 6 % in the PTX group. Among patients in the SPD group, the main acute comorbid conditions were peripheral vascular and cardiac complications, sepsis, fractures, and cancers with an increase in serum CRP level (from 14.3 ± 18 to 132 ± 90 mg/L) and a decrease in serum albumin (from 33 ± 4.5 to 28.6 ± 4 g/L). In the MPD group, the main therapeutic change was an increase in DCC, either independently or in association with cinacalcet therapy. The median survival rate among patients was 10 months for SPD, compared to 22 months among patients in the MPD group (p < 0.001). Using multivariable Cox model and taking the NPD group as reference, the risk of mortality was lower among patients in the MPD group (HR, 0.42[0.2-0.87] p = 0.01), with survival being comparable for the SPD and NPD groups (HR, 1.3 [0.75-2.2]). No mortality was observed in the PTX group.

Conclusion

The poor outcomes associated with SPD, related to acute comorbid conditions, should not lead to undertreat secondary hyperparathyroidism whose appropriate medical or surgical therapies are associated with better outcomes.

Low serum intact parathyroid hormone level is an independent risk factor for overall mortality and major adverse cardiac and cerebrovascular events in incident dialysis patients

Abnormal bone dynamics is a major risk factor for cardiovascular disease in patients with chronic kidney disease. The level of serum intact parathyroid hormone (iPTH) is widely used as a bone dynamic marker. We investigated the effect of the mean level of serum iPTH on overall mortality and cardiovascular outcomes in incident dialysis patients.

PURPOSE

Chronic kidney disease-mineral bone disorder (CKD-MBD) is a major risk factor for cardiovascular disease (CVD) in patients with end-stage renal disease (ESRD). CKD-MBD is classified as low- or high-turnover bone disease according to the bone dynamics; both are related to vascular calcification in ESRD. To evaluate the prognostic value of abnormal serum parathyroid hormone (PTH) levels on ESRD patients, we investigated the effects of time-averaged serum intact PTH (TA-iPTH) levels on overall mortality and major adverse cardiac and cerebrovascular events (MACCEs) in incident dialysis patients.

METHODS

Four hundred thirteen patients who started dialysis between January 2009 and September 2013 at Yonsei University Health System were enrolled. The patients were divided into three groups according to TA-iPTH levels during the 12 months after the initiation of dialysis: group 1, <65 pg/ml; group 2, 65-300 pg/ml; and group 3, >300 pg/ml. Cox regression analyses were performed to determine the prognostic value of TA-iPTH for overall mortality and MACCEs.

RESULTS

The mean age of the patients was 57 ± 15 years, and 222 patients (54 %) were men. During the median follow-up of 40.8 ± 29.3 months, 49 patients (12 %) died, and MACCEs occurred in 55 patients (13 %). The multivariate Cox regression analyses demonstrated that a low TA-iPTH level was an independent risk factor for both overall mortality (group 2 as reference; group 1: hazard ratio (HR) = 2.06, 95 % confidence interval (CI) = 1.11-3.83, P = 0.023) and MACCEs (HR = 1.82, 95 % CI = 1.04-3.20, P = 0.036) in incident dialysis patients after adjustment for confounding factors.

CONCLUSION

Low serum TA-iPTH is a useful clinical marker of both overall mortality and MACCEs in patients undergoing incident dialysis, mediated by vascular calcification.

The Relation Between Variability of Intact Parathyroid Hormone, Calcium, and Cardiac Mortality in Hemodialysis Patients

Chronic kidney disease-mineral and bone disorder (CKD-BMD) is a condition known to be associated with cardiovascular disease and mortality in hemodialysis (HD) patients. The relation between calcium (Ca), phosphorus (P), and intact parathyroid hormone (iPTH) variability in HD patients and cardiac mortality is unknown. The purpose of this study was to assess the relation between variability in these parameters and cardiac mortality. Baseline demographic and biochemical parameters of 218 HD patients together with Ca values corrected with albumin and P values measured on a monthly basis and iPTH levels measured at 3-monthly intervals were recorded over 2 years. Standard deviation (SD) and smoothness index (SI) for each parameter were calculated to assess Ca, P, and iPTH variability. The relations between all parameters and cardiac mortality were then analyzed. Cardiac mortality was observed in 38 patients in the 2-year study period. Nonsurviving patients' ages, systolic and diastolic blood pressure (DBP), high sensitivity C-reactive protein (HsCRP) levels, mean iPTH, and SD iPTH were significantly higher than those of surviving patients, while albumin levels, SI iPTH and SI Ca were significantly lower. Age, low albumin, high DBP, SI iPTH, and SI Ca were identified as independent predictors of cardiac mortality at multivariate analysis. Our study shows that Ca and iPTH variability affect cardiac mortality independently of mean and baseline values. When supported by further studies, the relation between Ca and iPTH variability and cardiac mortality in HD patients can lead to a new perspective in terms of prognosis and treatment planning.

Successful Conversion From Parenteral Paricalcitol to Pulse Oral Calcitriol for the Management of Secondary Hyperparathyroidism in Hemodialysis Patients

OBJECTIVE

The management of hyperparathyroidism in hemodialysis patients involves the administration of phosphate binders, vitamin D receptor activators, and calcimimetics. Intravenous paricalcitol has been preferred over oral calcitriol as it may cause less hypercalcemia and hyperphosphatemia. However, there is little data looking at the efficacy and tolerability of oral calcitriol in the calcimimetic era particularly in a real practice-based experience. The University of California, Irvine free-standing dialysis center converted from routine intravenous paricalcitol to oral calcitriol due to pharmacy purchasing preferences. We report the efficacy, safety, and cost of such a change.

SUBJECTS

Ninety-three preconversion intravenous paricalcitol and 91 postconversion oral calcitriol.

INTERVENTION

Conversion to in-center, pulse, oral calcitriol (0.25 mcg = 1 mcg paricalcitol) 3 times a week from intravenous paricalcitol. Additional dose adjustments were made by the nephrologists based on clinical indications.

MAIN OUTCOME MEASURE

Five-month average serum calcium, phosphorous, and intact parathyroid hormone levels and cardiovascular events pretransition and posttransition.

RESULTS

There were 93 patients on intravenous paricalcitol between April 2013 and August 2013, of which 74 converted to oral calcitriol and were included in the postconversion group evaluated between October 2013 and February 2014. An additional 17 new patients had initiated calcitriol such that 91 patients were on oral therapy in the postconversion period. Sevelamer use increased from 41 (44.1%) patients preconversion to 48 (52.7%) postconversion, whereas calcium acetate use significantly dropped from 62 (66.7%) to 46 (50.5%) (P = .026). Cinacalcet use dropped slightly from 37 (39.7%) patients preconversion to 35 (38.4%) postconversion. Average serum calcium, phosphorus, and intact parathyroid hormone levels remained unchanged after conversion. Percent of values within Kidney Disease Outcome Quality Initiative guidelines were similarly maintained. Estimated vitamin D cost savings were $564 per person/year. No increase in the incidence of cardiovascular events was observed.

CONCLUSIONS

We conclude that in-center distributed pulse oral calcitriol may be an effective, safe, and economical treatment option for the management of hyperparathyroidism in hemodialysis patients.

αKlotho and Chronic Kidney Disease

Alpha-Klotho (αKlotho) protein is encoded by the gene, Klotho, and functions as a coreceptor for endocrine fibroblast growth factor-23. The extracellular domain of αKlotho is cleaved by secretases and released into the circulation where it is called soluble αKlotho. Soluble αKlotho in the circulation starts to decline in chronic kidney disease (CKD) stage 2 and urinary αKlotho in even earlier CKD stage 1. Therefore soluble αKlotho is an early and sensitive marker of decline in kidney function. Preclinical data from numerous animal experiments support αKlotho deficiency as a pathogenic factor for CKD progression and extrarenal CKD complications including cardiac and vascular disease, hyperparathyroidism, and disturbed mineral metabolism. αKlotho deficiency induces cell senescence and renders cells susceptible to apoptosis induced by a variety of cellular insults including oxidative stress. αKlotho deficiency also leads to defective autophagy and angiogenesis and promotes fibrosis in the kidney and heart. Most importantly, prevention of αKlotho decline, upregulation of endogenous αKlotho production, or direct supplementation of soluble αKlotho are all associated with attenuation of renal fibrosis, retardation of CKD progression, improvement of mineral metabolism, amelioration of cardiac function and morphometry, and alleviation of vascular calcification in CKD. Therefore in rodents, αKlotho is not only a diagnostic and prognostic marker for CKD but the enhancement of endogenous or supplement of exogenous αKlotho are promising therapeutic strategies to prevent, retard, and decrease the comorbidity burden of CKD.

The role of 99mTc-MIBI SPECT-CT in reoperation therapy of persistent hyperparathyroidism patients

To compare the role of 99mTc-MIBI SPECT-CT image and US in reoperation of persistent secondary hyperparathyroidism patients. A total of 8 persistent secondary hyperparathyroidism patients underwent parathyroidectomy. The sensitivity and accuracy of US and 99mTc-MIBI images before operation were determined. 9 of 14 surgical resection tissues from 8 persistent secondary hyperparathyroidism patients were confirmed to parathyroid hyperplasia. The results showed that the sensitivities were 77.8% and 100%, respectively, for US and 99mTc-MIBI SPECT-CT images. And the accuracies of US and 99mTc-MIBI dual time planar image and SPECT-CT were 50%, 78.6%, respectively. There was significantly difference between two procedures (P=0.021). The superior and inferior localization of glands were both detected by the ultrasound and scintigraphy. Two ectopic parathyroidism nodules were found by 99mTc-MIBI SPECT-CT imaging, while US provided no consistent findings. There was no significantly difference between two procedures (P=0.3). Although two cases of them were not confirmed by pathology, the iPTH of them (800 and 1429 respectively) were much higher than other four cases (<400) pg/ml. PTX is a safe and effective treatment for the patients with persistent SHPT. 99mTc-MIBI planar and SPECT-CT imaging may provide more helps for clinician’s localization the hyperparathyroidism glands accurately.

Disturbances in Bone Largely Predict Aortic Calcification in an Alternative Rat Model Developed to Study Both Vascular and Bone Pathology in Chronic Kidney Disease

Because current rat models used to study chronic kidney disease (CKD)-related vascular calcification show consistent but excessive vascular calcification and chaotic, immeasurable, bone mineralization due to excessive bone turnover, they are not suited to study the bone-vascular axis in one and the same animal. Because vascular calcification and bone mineralization are closely related to each other, an animal model in which both pathologies can be studied concomitantly is highly needed. CKD-related vascular calcification in rats was induced by a 0.25% adenine/low vitamin K diet. To follow vascular calcification and bone pathology over time, rats were killed at weeks 4, 8, 10, 11, and 12. Both static and dynamic bone parameters were measured. Vascular calcification was quantified by histomorphometry and measurement of the arterial calcium content. Stable, severe CKD was induced along with hyperphosphatemia, hypocalcemia as well as increased serum PTH and FGF23. Calcification in the aorta and peripheral arteries was present from week 8 of CKD onward. Four and 8 weeks after CKD, static and dynamic bone parameters were measurable in all animals, thereby presenting typical features of hyperparathyroid bone disease. Multiple regression analysis showed that the eroded perimeter and mineral apposition rate in the bone were strong predictors for aortic calcification. This rat model presents a stable CKD, moderate vascular calcification, and quantifiable bone pathology after 8 weeks of CKD and is the first model that lends itself to study these main complications simultaneously in CKD in mechanistic and intervention studies.

A new player in chronic kidney disease mineral and bone disorder: tenascin-C

AIMS

Chronic kidney disease-mineral and bone disorder (CKD-MBD) is a condition frequently observed in CKD. The search for a reliable and easy to use biomarker in the diagnosis of CKD-MBD is continuing. Tenascin-C (TN-C) is an important extracellular (ECM) protein synthesized by osteoblasts during bone growth and morphogenesis. The purpose of this study was to assess the relation between inflammation and MBD and TN-C in HD patients and to identify a new marker that can be used to help diagnose CKD-MBD.

MATERIALS AND METHODS

136 HD patients and 22 healthy controls were enrolled in this cross-sectional, observational multicenter study. Once patients' demographic and biochemical parameters had been recorded, peripheral blood samples were collected for TN-C measurement before the mid-week HD session. The relationship between TN-C levels and demographic and biochemical parameters was then assessed.

RESULTS

TN-C levels were significantly higher in the HD patient than in the control group (P&lt;.001). Intact parathormone (iPTH) affected TN-C levels in the HD patient group. TN-C levels was significantly higher in both the high (&gt;300 pg/ml) and low iPTH groups (&lt;150 pg/ml) compared to the 150-300 pg/ml iPTH group (P&lt;.001, &lt;.001 respectively).

CONCLUSIONS

This study showed, for the first time in the literature, high levels of TN-C in the low and high iPTH groups and that this elevation was associated with iPTH. We think that if our study is supported by further research, TN-C can be a biomarker capable of use in diagnosing CKD-MBD.

Association of aspartate aminotransferase with mortality in hemodialysis patients

BACKGROUND

Liver disease is a common comorbid condition in maintenance hemodialysis (MHD) patients and may be associated with poor survival. The relationship between aspartate aminotransferase (AST) and survival has not yet been addressed in these patients. We hypothesized that higher AST level is associated with higher death risk in MHD patients.

METHODS

A 5-year (January 2007-December 2011) cohort of 109 718 MHD patients was studied in the USA in dialysis clinics where AST was measured in at least 50% of all outpatients in the baseline calendar quarter. Survival models were adjusted for demographic variables, and available clinical and laboratory surrogates of malnutrition-inflammation complex, and cubic survival splines were plotted.

RESULTS

A linear association existed between baseline serum AST levels and mortality. Increasing AST of >20 IU/L was incrementally and almost linearly associated with higher death risk at all levels of adjustment. In fully adjusted models, AST levels of ≥40 IU/L were associated with the highest risk of mortality (hazard ratio: 1.46, 95% CI: 1.38-1.54). Low AST levels (<15 IU/L) were associated with increased death risk only in fully adjusted models examining hepatitis C virus-positive patients.

CONCLUSIONS

Higher AST level of >20 IU/L is incrementally associated with higher mortality in MHD patients whereas AST in the 15-20 IU/L range is associated with the greatest survival. These findings suggest that the assessment of liver function and improving liver disease may confer survival benefit to MHD patients.

Acetazolamide sensitive tissue calcification and aging of klotho-hypomorphic mice

Klotho, a protein expressed mainly in the kidney, is required for the inhibitory effect of FGF23 on renal 1,25(OH)2D3 formation. Klotho counteracts vascular calcification and diverse age-related disorders. Klotho-hypomorphic mice (kl/kl) suffer from severe vascular calcification and rapid aging. The calcification is at least in part caused by excessive 1,25(OH)2D3, Ca(2+), and phosphate concentrations in blood, which trigger osteogenic signaling including upregulation of alkaline phosphatase (Alpl). As precipitation of calcium and phosphate is fostered by alkaline pH, extracellular acidosis could counteract tissue calcification. In order to induce acidosis, acetazolamide was added to drinking water (0.8 g/l) of kl/kl and wild-type mice. As a result, acetazolamide treatment of kl/kl mice partially reversed the growth deficit, tripled the life span, almost completely reversed the calcifications in trachea, lung, kidney, stomach, intestine, and vascular tissues, the excessive aortic alkaline phosphatase mRNA levels and the plasma concentrations of osteoprotegerin, osteopontin as well as fetuin-A, without significantly decreasing FGF23, 1,25(OH)2D3, Ca(2+), and phosphate plasma concentrations. In primary human aortic smooth muscle cells, acidotic environment prevented phosphate-induced alkaline phosphatase mRNA expression. The present study reveals a completely novel effect of acetazolamide, i.e., interference with osteoinductive signaling and tissue calcification in kl/kl mice.

KEY MESSAGES

Klotho deficient (kl/kl) mice suffer from hyperphosphatemia with dramatic tissue calcification. Acetazolamide (ACM) treatment partially reversed the growth deficit of kl/kl mice. In kl/kl mice, ACM reversed tissue calcification despite continued hyperphosphatemia. ACM tripled the life span of kl/kl mice. In human aortic smooth muscle cells, low extracellular pH prevented osteogenic signaling.