The Impact of Normal Range of Serum Phosphorus on the Incidence of End-Stage Renal Disease by A Propensity Score Analysis

Chronic ACLD Knees with Early Developmental Cartilage Lesions Exhibited Increased Posterior Tibial Translation during Level Walking

OBJECTIVE

Early articular cartilage lesion (CL) is a vital sign in the onset of posttraumatic knee osteoarthritis (PTOA) in patients with anterior cruciate ligament deficiency (ACLD). Researchers have suggested that altered kinematics could accelerate CLs and, therefore, lead to the onset of PTOA. However, little is known about whether specific knee kinematics exist that lead to early CL in chronic ACLD knees. Level walking is the most frequent and relevant in vivo activity, which greatly impacts knee health. We hypothesized that the knee kinematics during level walking in chronic ACLD knees with early tibiofemoral CL would significantly differ from those of chronic ACLD knees without early tibiofemoral CL.

METHODS

Thirty patients with a chronic ACLD history, including 18 subjects with CLs and 12 subjects without CLs, and 35 healthy control subjects were recruited for the study from July 2020 to August 2022. The knee kinematic data during level walking were collected using a three-dimensional motion analysis system. The kinematic differences between groups were compared using statistical parametric mapping with one dimension for One-Way ANOVA. The cartilage statuses of the ACLD knees were assessed via MRI examination. The CLs distribution of subjects was evaluated using a modified Noyes scale and analyzed by chi-square tests.

RESULTS

ACLD knees with CLs had significantly greater posterior tibial translation (7.7-8.0mm, 12%-18% gait cycle GC, p = 0.014) compared to ACLD knees without CLs during level walking. ACLD knees with CLs had greater posterior tibial translation (4.6-5.5mm, 0%-23% GC, p < 0.001; 5.8-8.0mm, 86%-100% GC, p < 0.001) than healthy controls during level walking. In the group of ACLD knees with CLs, CL is mainly located in the back of the tibia plateau and front of load bearing area of the medial femoral condyle (p < 0.05).

CONCLUSION

Chronic anterior cruciate ligament deficient knees with cartilage lesions have increased posterior tibial translation compared to anterior cruciate ligament deficient knees without cartilage lesions and healthy subjects. The posterior tibial translation may play an important role in knee cartilage degeneration in ACLD knees. The increased posterior tibial translation and cartilage lesion characteristics may improve our understanding of the role of knee kinematics in cartilage degeneration and could be a helpful potential reference for anterior cruciate ligament deficient therapy, such as physical training to improve abnormal kinematic behavior.

The association of normal-range serum phosphorus with immunoglobulin A nephropathy progression: a retrospective cohort study

PURPOSE

The relationship between serum phosphorus and immunoglobulin A (IgA) nephropathy progression remains uncertain, especially normal-range serum phosphorus. Therefore, we herein examined the relationship between the normal-range serum phosphorus and the progression of IgA nephropathy.

METHODS

One hundred sixty-two patients with primary IgA nephropathy were divided into three groups according to tertiles of baseline serum phosphorus (first tertile: 0.73-1.04 mmol/L; second tertile: 1.04-1.21 mmol/L; third tertile: 1.21-1.60 mmol/L). Estimated glomerular filtration rate (eGFR) was calculated using the chronic kidney disease epidemiology collaboration. The composite outcome was defined as a decrease of at least 50% in eGFR from baseline or end-stage kidney disease (ESKD). The association of serum phosphorus with IgA nephropathy progression was estimated using Cox proportional hazards models, adjusting for potential confounders.

RESULTS

During a median 16 month follow-up period, 15 patients reached a composite outcome. In the crude Cox proportional hazard model, baseline serum phosphorus as a continuous variable was associated with increased risk for adverse renal outcomes [hazard ratio (HR) = 63.510, 95% confidence interval (CI) = 3.953-1020.284, P = 0.003], and the high tertile of serum phosphorus group had an increased risk of the composite outcome by using the low tertile group as the reference (HR = 11.895, 95% CI = 1.522-92.993, P = 0.018). After adjustment for traditional risk factors, the high tertile of serum phosphorus group was significantly related to IgA nephropathy progression compared with the low tertile group (HR = 9.424, 95% CI = 1.019-87.165, P = 0.048).

CONCLUSIONS

Relatively higher serum phosphorus levels within the normal range were significantly associated with the progression of IgA nephropathy.

The Impact of Medical Nutrition Intervention on the Management of Hyperphosphatemia in Hemodialysis Patients with Stage 5 Chronic Kidney Disease: A Case Series

The treatment and interdisciplinary management of patients with chronic kidney disease (CKD) continue to improve long-term outcomes. The medical nutrition intervention's role is to establish a healthy diet plan for kidney protection, reach blood pressure and blood glucose goals, and prevent or delay health problems caused by kidney disease. Our study aims to report the effects of medical nutrition therapy-substituting foods rich in phosphorus-containing additives with ones low in phosphates content on phosphatemia and phosphate binders drug prescription in stage 5 CKD patients with hemodialysis. Thus, 18 adults with high phosphatemia levels (over 5.5 mg/dL) were monitored at a single center. Everyone received standard personalized diets to replace processed foods with phosphorus additives according to their comorbidities and treatment with prosphate binder drugs. Clinical laboratory data, including dialysis protocol, calcemia, and phosphatemia, were evaluated at the beginning of the study, after 30 and 60 days. A food survey was assessed at baseline and after 60 days. The results did not show significant differences between serum phosphate levels between the first and second measurements; thus, the phosphate binders' initial doses did not change. After 2 months, phosphate levels decreased considerably (from 7.322 mg/dL to 5.368 mg/dL); therefore, phosphate binder doses were diminished. In conclusion, medical nutrition intervention in patients with hemodialysis significantly reduced serum phosphate concentrations after 60 days. Restricting the intake of processed foods containing phosphorus additives-in particularized diets adapted to each patient's comorbidities-and receiving phosphate binders represented substantial steps to decrease phosphatemia levels. The best results were significantly associated with life expectancy; at the same time, they showed a negative correlation with the dialysis period and participants' age.

Upslope walking increases anterior tibial translation deficiency in patients with generalized joint hypermobility

BACKGROUND

Generalized joint hypermobility (GJH) is a highly prevalent disease that frequently affects the knee joint. The current literature has conflicting results about whether patients with GJH had knee kinematics deficiency during gait. This could be because most of the testing environment (level walking) was gentle and low-demanding for patients when studying their knee kinematics. With a high-demanding knee function and sagittal firm structure requirement, upslope walking was thought to stimulate sagittal knee kinematics deficiency in patients with GJH.

RESEARCH QUESTIONS

However, only little investigation reported whether upslope walking could stimulate knee kinematic deficiency or not. We hypothesize that upslope walking can increase sagittal knee kinematic deficiency between GJH subjects and healthy controls.

METHODS

A three-dimensional motion analysis was conducted to explore whether upslope walking could stimulate sagittal knee kinematic deficiency in patients with GJH. A total of 44 patients with GJH and 44 healthy controls were recruited. Subjects walked on both level and upslope (15%) conditions when the kinematic data were collected. SPM1D analysis was taken to explore the differences between groups.

RESULTS

Our results showed that upslope walking could significantly increase knee flexion angle and anterior tibial translation in both GJH patients and healthy controls (p < 0.05). The increments of anterior tibial translation (values in upslope walking minus values in level walking) of GJH patients were greater than those of healthy controls (magnitude varying from 2.5 to 2.9 mm during 0-3% gait cycles (GC), p = 0.034; 1.4-2.9 mm during 93-100%GC, p = 0.012).

SIGNIFICANCES

The findings partially confirmed our hypothesis and suggested that upslope walking could increase anterior tibial translation deficiency in patients with GJH. Upslope walking may be a practical motion task in studying the weakness of knee kinematics of GJH subjects for researchers and scholars. Patients with GJH may face a more challenging knee kinematic environment than healthy controls in up-sloped activities.

Association between Serum Inorganic Phosphorus Levels and Adverse Outcomes in Chronic Kidney Disease: The Fukushima CKD Cohort Study

Objective Although an association between serum inorganic phosphorus levels and a poor prognosis has been noted in dialysis patients, these associations have been insufficiently reported in non-dialysis-dependent chronic kidney disease (NDD-CKD) patients. This study attempted to determine the association between serum inorganic phosphorus levels and adverse outcomes in Japanese NDD-CKD patients. Methods We investigated the relationships between serum inorganic phosphorus levels and adverse outcomes, such as kidney events, cardiovascular events, and all-cause death, in Japanese NDD-CKD patients using longitudinal data from the Fukushima CKD Cohort Study with a median follow-up period of 2.8 years. The study evaluated 822 patients with NDD-CKD enrolled between June 2012 and July 2014. A kidney event was defined as a combination of doubling of the baseline serum creatinine or end-stage renal disease. Cox regression was performed to analyze the relationships of the quartile of the serum inorganic phosphorus with kidney events, cardiovascular events, and all-cause death. Results The frequency of kidney events per 1,000 person-years exhibited a U-shaped distribution based on serum inorganic phosphorus levels, with these levels not significantly associated with an increased risk of cardiovascular events and all-cause death. A multivariable Cox regression analysis showed an increased risk of kidney events for the highest quartile of the serum inorganic phosphorus levels (≥3.7 mg/dL) versus the second quartile (2.9-3.2 mg/dL, hazard ratio, 3.30; 95% confidence interval, 1.50-7.28; p=0.003). There were no significant associations between the serum calcium levels and adverse outcomes. Conclusion Serum inorganic phosphorus levels were associated with an increased risk of CKD progression in Japanese NDD-CKD patients.

Postdialysis serum phosphate equilibrium in hemodialysis patients on a controlled diet and no binders

BACKGROUND

Studies evaluating the change in serum phosphate post hemodialysis (HD) demonstrate an initial decline during dialysis but a rebound post dialysis. However, previous studies were done on usual diet and phosphate binders, with limited number of blood draws, confounding conclusions. We determined serum phosphate reduction, rebound, and equilibrium over 48 h in HD patients consuming a controlled, low phosphorus diet without binders.

METHODS

Serum phosphate (mg/dL) was analyzed before and after a HD treatment and frequently during the ensuing 48 h intradialytic period in the clinical research unit. Thirteen subjects were enrolled and had been off phosphate binders for 10 days and consumed a standardized low phosphate (900 mg/day) diet for 3 weeks prior to the assessments. Linear regression was used to determine relationships between the pre-HD serum phosphate, decline post-HD (post-HD drop); and a 48 h area under curve (AUC) using the trapezoidal method as a measure of overall phosphate levels from the end of dialysis to 48 h post dialysis. Repeated Measures ANOVA with Dunnett's posthoc test was used to determine rebound.

RESULTS

Five of 13 subjects returned to >90% of their pre-HD serum phosphate within the first 24 h post-HD, and serum phosphate was 94 ± 0.11% (range 63%-113%) by 48 h after the completion of HD. The 48 h AUC of serum phosphate during the interdialytic period was correlated with both pre dialysis phosphorus (r = 0.85; p = 0.0002) and the pre-post drop in serum phosphate during dialysis (r = 0.69; p = 0.0085). In contrast, the net ultrafiltration was not related to the 48 h AUC of serum phosphorus (r = 0.20; p = 0.51).

CONCLUSIONS

In hemodialysis patients on standard low phosphorus diet and no phosphate binders, the interdialytic serum phosphorus level, assessed as AUC, is determined by the pre dialysis phosphorus and net-change in serum phosphorus during the dialysis treatment, but not the ultrafiltration volume [Correction added on 25 January, after first online publication: In the last sentence of the Abstract, the word "potassium" has been replaced with "phosphorus" to improve accuracy.].

Association between serum phosphate and mortality in critically ill patients: a large retrospective cohort study

OBJECTIVES

This research aims to explore the impact of serum phosphate on the mortality of critically ill patients.

DESIGN

A retrospective large cohort study.

SETTING

Our data were extracted from a publicly accessible database named 'Multiparameter Intelligent Monitoring in Intensive Care Database III'.

PARTICIPANTS

27 131 patients were included by clear definitions of selection and exclusion criteria.

INTERVENTIONS

We used initial phosphate at admission as a design variable. Patients were divided into six groups with different serum phosphate levels and five groups at different intensive care unit (ICU) departments.

PRIMARY AND SECONDARY OUTCOMES

28-day and 90-day mortality were primary outcomes. All-cause mortality and length of stay ICU were secondary outcomes.

RESULTS

Patients with very-high-normal serum phosphate, hypophosphataemia and hyperphosphataemia had worse outcomes. And the relationship between serum phosphate and the probability of 28-day or 90-day mortality had a linear relationship. After adjustment for potential confounders, hypophosphataemia and hyperphosphataemia were not significantly associated with 28-day or 90-day mortality. Nevertheless, at the medical ICU, hyperphosphataemia was associated with increased 28-day or 90-day mortality (HR=0.64, 95% CI 0.48 to 0.84, p=0.0017; HR=0.72, 95% CI 0.57 to 0.91, p=0.0067, respectively), using group 2 (≥2.5 mg/dL and <3.0 mg/dL) as the reference group.

CONCLUSIONS

Patients with very-high-normal serum phosphate also had worse outcomes, it might be necessary to re-evaluate the definitions of the normal reference range for serum phosphate. Hypophosphataemia and hyperphosphataemia are not the independent risk factors of 28-day or 90-day ICU mortality, which leads us to consider whether phosphate monitoring is not a necessary measure in critically ill patients. But hyperphosphataemia was associated with increased 28-day or 90-day mortality at the medical ICU, which emphasises the potential importance of early diagnosis and treatment of hyperphosphataemia for the patients who were admitted to the medical ICU.

Dietary Phosphorus as a Marker of Mineral Metabolism and Progression of Diabetic Kidney Disease

Phosphorus is an essential nutrient that is critically important in the control of cell and tissue function and body homeostasis. Phosphorus excess may result in severe adverse medical consequences. The most apparent is an impact on cardiovascular (CV) disease, mainly through the ability of phosphate to change the phenotype of vascular smooth muscle cells and its contribution to pathologic vascular, valvular and other soft tissue calcification. Chronic kidney disease (CKD) is the most prevalent chronic disease manifesting with the persistent derangement of phosphate homeostasis. Diabetes and resulting diabetic kidney disease (DKD) remain the leading causes of CKD and end-stage kidney disease (ESRD) worldwide. Mineral and bone disorders of CKD (CKD-MBD), profound derangement of mineral metabolism, develop in the course of the disease and adversely impact on bone health and the CV system. In this review we aimed to discuss the data concerning CKD-MBD in patients with diabetes and to analyze the possible link between hyperphosphatemia, certain biomarkers of CKD-MBD and high dietary phosphate intake on prognosis in patients with diabetes and DKD. We also attempted to clarify if hyperphosphatemia and high phosphorus intake may impact the onset and progression of DKD. Careful analysis of the available literature brings us to the conclusion that, as for today, no clear recommendations based on the firm clinical data can be provided in terms of phosphorus intake aiming to prevent the incidence or progression of diabetic kidney disease.

Association between serum phosphorus and mortality in NHANES 2003-2006: the effect of gender and renal function

BACKGROUND

The impact of high serum phosphorus in the general population is still debated. Studies are heterogeneous, most lack an adjustment for parathyroid hormone, vitamin D and phosphorus intake and the effect might differ by gender and renal function. We investigated the association between serum phosphorus and mortality in American adults.

METHODS

We prospectively analyzed 5698 non-pregnant and non-CKD adults from the National Health and Nutrition Examination Survey (NHANES) 2003-2006. Serum phosphorus and potential confounders including parathyroid hormone, 25(OH)vitamin D and phosphorus intake were evaluated. All-cause, cardiovascular- and cancer-related deaths were recorded through December 31st, 2015. Sex-specific terciles of serum phosphorus were used to fit adjusted Cox proportional hazard models for mortality. Analysis was stratified by gender and renal function.

RESULTS

A total of 590 deaths were recorded over a median follow-up of 81 months. Women showed higher serum phosphorus than men. The adjusted hazard ratio (HR) for all-cause mortality was 1.35 (95% CI 1.08-1.58) (p = 0.033) for the third tercile (versus second tercile). This increased risk was present in participants with estimated glomerular filtration rate (eGFR) below 90 ml/min/1.73 m² but not above, although interaction was not significant (p = 0.12). Interaction by gender, phosphorus intake, PTH and fasting time was also not detected. For cardiovascular and cancer mortality, the adjusted HR was 0.81 (95% CI 0.33-2.00) (p = NS) and 1.45 (95% CI 0.77-2.72) (p = NS), respectively.

CONCLUSIONS

We demonstrated that the highest tercile of serum phosphorus is associated with increased all-cause mortality, irrespective of PTH, 25(OH)vitamin D or phosphorus intake. This association may differ by gender and renal function, but larger studies testing for effect modification are needed.

Development of a Biomarker Panel to Distinguish Risk of Progressive Chronic Kidney Disease

Chronic kidney disease (CKD) patients typically progress to kidney failure, but the rate of progression differs per patient or may not occur at all. Current CKD screening methods are sub-optimal at predicting progressive kidney function decline. This investigation develops a model for predicting progressive CKD based on a panel of biomarkers representing the pathophysiological processes of CKD, kidney function, and common CKD comorbidities. Two patient cohorts are utilised: The CKD Queensland Registry (n = 418), termed the Biomarker Discovery cohort; and the CKD Biobank (n = 62), termed the Predictive Model cohort. Progression status is assigned with a composite outcome of a ≥30% decline in eGFR from baseline, initiation of dialysis, or kidney transplantation. Baseline biomarker measurements are compared between progressive and non-progressive patients via logistic regression. In the Biomarker Discovery cohort, 13 biomarkers differed significantly between progressive and non-progressive patients, while 10 differed in the Predictive Model cohort. From this, a predictive model, based on a biomarker panel of serum creatinine, osteopontin, tryptase, urea, and eGFR, was calculated via linear discriminant analysis. This model has an accuracy of 84.3% when predicting future progressive CKD at baseline, greater than eGFR (66.1%), sCr (67.7%), albuminuria (53.2%), or albumin-creatinine ratio (53.2%).

Severe chronic kidney disease environment reduced calcium-sensing receptor expression in parathyroid glands of adenine-induced rats even without high phosphorus diet

Background

Chronic kidney disease (CKD) disrupts mineral homeostasis and its main underlying cause is secondary hyperparathyroidism (SHPT). We previously reported that calcium-sensing receptor (CaSR) mRNA and protein expression in parathyroid glands (PTGs) significantly decreased in a CKD rat model induced by a 5/6 nephrectomy that were fed a high phosphorus diet. However, there was a significant difference in the severity of CKD between high phosphorus and adequate phosphorus diet groups. Thus, it was unclear whether CKD environment or the high phosphorus diet influenced CaSR expression, and the underlying mechanism remains largely unknown.

Methods

CKD was induced in rats with 0.75% adenine-containing diet. CKD and control rats were maintained for 5 days and 2 weeks on diets with 0.7% or 1.3% phosphorus. For gene expression analysis, quantitative real-time polymerase chain reaction was performed with TaqMan probes. Protein expression was analyzed by immunohistochemistry.

Results

PTG CaSR expression significantly decreased in the presence of a severe CKD environment, even without the high phosphate load. Ki67 expressing cells in PTGs were significantly higher only in the CKD rats fed a high phosphorus diet. Furthermore, among the many genes that could affect CaSR expression, only vitamin D receptor (VDR) and glial cells missing 2 (Gcm2) showed significant changes. Moreover, Gcm2 was significantly reduced at an early stage without significant changes in serum calcium, phosphorus and 1,25(OH)₂ vitamin D, and there was no significant reduction in CaSR and VDR expressions. Then, significantly elevated Ki67-positive cell numbers were also only observed in the early CKD PTGs with high-phosphorus diets.

Conclusions

Our data suggest that the cause of the decreased PTG CaSR expression is the reduction in VDR and Gcm2 expression; Gcm2 may play a role in the onset and progression of SHPT.

Sevelamer Use in End-Stage Kidney Disease (ESKD) Patients Associates with Poor Vitamin K Status and High Levels of Gut-Derived Uremic Toxins: A Drug-Bug Interaction?

Gut microbial metabolism is not only an important source of uremic toxins but may also help to maintain the vitamin K stores of the host. We hypothesized that sevelamer therapy, a commonly used phosphate binder in patients with end-stage kidney disease (ESKD), associates with a disturbed gut microbial metabolism. Important representatives of gut-derived uremic toxins, including indoxyl sulfate (IndS), p-Cresyl sulfate (pCS), trimethylamine N-oxide (TMAO), phenylacetylglutamine (PAG) and non-phosphorylated, uncarboxylated matrix-Gla protein (dp-ucMGP; a marker of vitamin K status), were analyzed in blood samples from 423 patients (65% males, median age 54 years) with ESKD. Demographics and laboratory data were extracted from electronic files. Sevelamer users (n = 172, 41%) were characterized by higher phosphate, IndS, TMAO, PAG and dp-ucMGP levels compared to non-users. Sevelamer was significantly associated with increased IndS, PAG and dp-ucMGP levels, independent of age, sex, calcium-containing phosphate binder, cohort, phosphate, creatinine and dialysis vintage. High dp-ucMGP levels, reflecting vitamin K deficiency, were independently and positively associated with PAG and TMAO levels. Sevelamer therapy associates with an unfavorable gut microbial metabolism pattern. Although the observational design precludes causal inference, present findings implicate a disturbed microbial metabolism and vitamin K deficiency as potential trade-offs of sevelamer therapy.

High Serum Phosphate Level as a Risk Factor to Determine Renal Prognosis in Autosomal Dominant Polycystic Kidney Disease: A Retrospective Study

Background: Serum phosphate levels, which are associated with the progression of renal dysfunction in chronic kidney disease, in patients with autosomal dominant polycystic kidney disease (ADPKD) are lower than those in patients with other kidney diseases. However, their role in ADPKD remains unclear. This study aimed to determine whether serum phosphate levels could have an association with renal prognoses among patients with ADPKD. Methods: In total, 55 patients with PKD1 or PKD2 mutations but not undergoing dialysis were evaluated. Data regarding serum phosphate levels were collected, and Cox regression analyses were used to calculate hazard ratios (HRs) with renal replacement therapy as the endpoint. Results: The median (quartile 1; quartile 3) serum phosphate concentration was 3.4 (3.1; 3.9) mg/dL, and the estimated glomerular filtration rate (eGFR) was 39.5 (17.6; 65.7) mL/min/1.73 m². The multivariate analysis that included age, PKD1 mutation, eGFR, urinary protein excretion, hyperuricemia, and serum phosphate determined that eGFR (HR, 0.82; 95% confidence interval (CI), 0.74-0.90; p < 0.0001) and serum phosphate (HR, 6.78; 95% CI, 1.94-34.02; p = 0.0021) were independently associated with renal replacement therapy. Conclusions: We found that serum phosphate levels were significantly associated with poor renal prognoses in patients with ADPKD.

Potential interaction of inflammatory hyperemia and hyperphosphatemia in tumorigenesis

The present article proposes that the association of inflammation with cancer is potentially mediated by the interaction of inflammatory hyperemia and hyperphosphatemia. Hyperemia increases blood flow rate and blood volume, and hyperphosphatemia is caused by elevated serum levels of dysregulated inorganic phosphate. It is hypothesized that the interaction of inflammatory hyperemia and hyperphosphatemia circulates increased amounts of inorganic phosphate to the tumor microenvironment, where increased uptake of inorganic phosphate through sodium-phosphate cotransporters is sequestered in cells. Elevated levels of intracellular phosphorus increase biosynthesis of ribosomal RNA, leading to increased protein synthesis that supports tumor growth. The present article also proposes that the interaction of inflammatory hyperemia and hyperphosphatemia may help explain a chemopreventive mechanism associated with NSAIDs.

Hyperphosphatemia and risks of acute kidney injury, end-stage renal disease, and mortality in hospitalized patients

BACKGROUND

Hyperphosphatemia is associated with vascular calcification and bone mineral disorders and is a major concern among patients with chronic kidney disease (CKD). However, the relationship between hyperphosphatemia and renal outcome in non-CKD patients has not been studied. Furthermore, the clinical implications of hyperphosphatemia in relation to the risks of acute kidney injury (AKI), end-stage renal disease (ESRD), and mortality after hospitalization remain unresolved.

METHODS

A total of 20,686 patients (aged ≥18 years) admitted to Seoul National University Bundang Hospital from January 2013 to December 2013 were retrospectively reviewed. Patients were divided into quartiles according to serum phosphorus level at the time of admission. The odds ratios (ORs) for AKI and hazard ratios (HRs) for ESRD and all-cause mortality were calculated after adjustment of multiple covariates.

RESULTS

AKI developed in 2319 patients (11.2%), with higher ORs for patients in the third and fourth quartiles (1.4 [1.24-1.68] and 2.8 [2.44-3.22], respectively) compared with the first quartile group. During a median follow-up period of 4.0 years, 183 patients (0.88%) developed ESRD and 3675 patients (17.8%) died. Patients in the fourth quartile had higher risks of ESRD and mortality than patients in the first quartile (HRs, 2.3 [1.46-3.75] and 1.4 [1.22-1.49], respectively). These trends remained consistent in patients with an estimated glomerular filtration rate > 60 ml/min/1.73 m².

CONCLUSIONS

Hyperphosphatemia is related to the risks of AKI, ESRD, and mortality, and it may therefore be necessary to monitor serum phosphorus level in hospitalized patients, irrespective of kidney function.

Relative hypophosphatemia early after transplantation is a predictor of good kidney graft function

BACKGROUND

Phosphate level is a potent independent risk factor for cardiovascular disease and mortality in patients with chronic kidney disease. The association between hypophosphatemia and kidney function in kidney transplant patients is uncertain.

METHODS

In total, 90 kidney transplant recipients were divided into two groups: one group of patients with hypophosphatemia and the other group without hypophosphatemia. The recipients with hypophosphatemia were identified as having less than or equal to the lowest quartile of serum phosphate levels at 1-, 3-, and 12-month post-transplant. The cumulative kidney survival rates were calculated for each group using the Kaplan-Meier method, and the adjusted hazard ratio (HR) was calculated using the Cox regression model.

RESULTS

The mean age of patients was 47 years and the median follow-up period was 58 months. During the follow-up period, the following results were demonstrated in 90 transplant patients: graft loss (n = 6), mortality (n = 3). According to the Kaplan-Meier analysis results, the patients with hypophosphatemia demonstrated a significantly lower risk of 30% decline in eGFR compared to those without hypophosphatemia at 1- and 3-month post-transplant, but not at 12-month post-transplant. After adjusting for confounding factors, hypophosphatemia at 1- and 3-month post-transplant was an independent predictor of good kidney survival (HR 0.31, 95% CI 0.10-0.82 and HR 0.31, 95% CI 0.07-0.92, respectively).

CONCLUSIONS

Our findings suggest that hypophosphatemia during the first 3 months after kidney transplantation was associated with better kidney survival.

A Body Mass Index-Based Cross-Classification Approach for the Assessment of Prognostic Factors in Chronic Kidney Disease Progression

Background/Aims: Cross-classification analyses are rarely reported. We investigated the prognostic factors for chronic kidney disease (CKD) progression using a body mass index (BMI)-based cross-classification approach. Methods: Patients’ renal outcome (≥50% decline in the estimated glomerular filtration rate or end-stage renal disease) in each subcohort was examined. Results: The number of prognostic factors identified in the multivariate Cox analysis was smaller in the “BMI ≥25, female” and CKD stage 3 subcohorts than in other subcohorts. Prognostic factors identified in the “BMI ≥25, CKD stage 3” subcohort only comprised albuminuria and male sex, and those in the “BMI ≥25, female” subcohort only comprised albuminuria, hyperphosphatemia, and anemia. Albuminuria, kidney impairment, male sex, hyperphosphatemia, anemia, and increased pulse pressure × heart rate product (PP × HR; pulsatile stress) were stable renal prognostic factors in almost all subcohorts. On the other hand, the prognostic value of increased BMI, younger age, hypoalbuminemia, increased intact parathyroid hormone, and decreased estimated 24-h urinary potassium excretion (e24hUK) differed according to subcohort. BMI was positively associated with CKD progression in the “BMI ≥25, age ≥65 years” and “BMI ≥25, CKD stages 4–5” subcohorts, whereas it was negatively associated with CKD progression in the “BMI <25, diabetes mellitus” subcohort. PP × HR was independently associated with CKD progression in the “BMI <25, CKD stage 3” subcohort, which had relatively few identified renal prognostic factors. Decreased e24hUK was a renal prognostic factor for CKD progression in the “BMI <25, CKD stages 4–5” subcohort, while no significant factors were observed in the “BMI ≥25, CKD stages 4–5” subcohort. Conclusion: A BMI-based cross-classification approach, which provides more comprehensive findings than that in previous approaches, is expected to be an effective method for evaluating renal prognostic factors in patients with CKD who are affected by multiple risk factors.

Phosphate binding by sucroferric oxyhydroxide ameliorates renal injury in the remnant kidney model

Recent clinical studies indicate that the disturbed phosphate metabolism in chronic kidney disease (CKD) may facilitate kidney injury; nonetheless, the causal role of phosphate in CKD progression remains to be elucidated. Here, we show that intestinal phosphate binding by sucroferric oxyhydroxide (SF) ameliorates renal injury in the rat remnant kidney model. Sprague-Dawley rats received 5/6 nephrectomy (RK) and had a normal chow or the same diet containing SF (RK + SF). RK rats showed increased plasma FGF23 and phosphate levels, which were suppressed by SF administration. Of note, albuminuria in RK rats was significantly ameliorated by SF at both 4 and 8 weeks. SF also attenuated glomerulosclerosis and tubulointerstitial injury. Moreover, several different approaches confirmed the protective effects on podocytes, explaining the attenuation of glomerulosclerosis and albuminuria observed in this study. As a possible mechanism, we found that SF attenuated renal inflammation and fibrosis in RK rats. Interestingly, von Kossa staining of the kidney revealed calcium phosphate deposition in neither RK nor RK + SF rats; however, plasma levels of calciprotein particles were significantly reduced by SF. These data indicate that latent positive phosphate balance accelerates CKD progression from early stages, even when overt ectopic calcification is absent.

Dietary Changes Involving Bifidobacterium longum and Other Nutrients Delays Chronic Kidney Disease Progression

BACKGROUND

Recent studies suggest that prebiotic and/or probiotic treatments ameliorate kidney function in humans and animals by improving the gut environment. However, the gut microbiota and kidney disease interactions remain to be determined. This study investigated whether synbiotics modulate the gut microbiota and ameliorate kidney function using a rat model of chronic kidney disease (CKD). As uremic toxins are associated with CKD-related mineral and bone disorder, the secondary aim was to evaluate the relationship between synbiotics and secondary hyperparathyroidism (SHPT).

METHODS

5/6 nephrectomy (Nx) rats were developed as the CKD model. Sham-operated (sham) rats were used as the control. To investigate the effectiveness of prebiotics (glutamine, dietary fiber, and oligosaccharide) and probiotics (Bifidobacterium longum strain; GFOB diet), rats were randomly assigned to 4 groups: Nx group fed the GFOB diet (n = 10); Nx group fed the control (CON) diet (n = 10); sham group fed the GFOB diet (n = 5); and sham group fed the control diet (n = 5). Blood, feces, and kidney samples were collected and analyzed.

RESULTS

Serum creatinine (Cre) and blood urea nitrogen in the Nx GFOB group were significantly lower than those in the Nx CON group. Serum indoxyl sulfate in the Nx GFOB group was lower than that in the Nx CON group, and significantly correlated with serum Cre. Inorganic phosphorus and intact parathyroid hormone in the Nx GFOB group were significantly lower than those in the Nx CON group.

CONCLUSION

Improving the gut environment using synbiotics ameliorated kidney function and might be a pharmacological treatment for SHPT without any serious adverse events.

Machine Learning to Compare Frequent Medical Problems of African American and Caucasian Diabetic Kidney Patients

Objectives

End-stage renal disease (ESRD), which is primarily a consequence of diabetes mellitus, shows an exemplary health disparity between African American and Caucasian patients in the United States. Because diabetic chronic kidney disease (CKD) patients of these two groups show differences in their medical problems, the markers leading to ESRD are also expected to differ. The purpose of this study was, therefore, to compare their medical complications at various levels of kidney function and to identify markers that can be used to predict ESRD.

Methods

The data of type 2 diabetic patients was obtained from the 2012 Cerner database, which totaled 1,038,499 records. The data was then filtered to include only African American and Caucasian outpatients with estimated glomerular filtration rates (eGFR), leaving 4,623 records. A priori machine learning was used to discover frequently appearing medical problems within the filtered data. CKD is defined as abnormalities of kidney structure, present for >3 months.

Results

This study found that African Americans have much higher rates of CKD-related medical problems than Caucasians for all five stages, and prominent markers leading to ESRD were discovered only for the African American group. These markers are high glucose, high systolic blood pressure (BP), obesity, alcohol/drug use, and low hematocrit. Additionally, the roles of systolic BP and diastolic BP vary depending on the CKD stage.

Conclusions

This research discovered frequently appearing medical problems across five stages of CKD and further showed that many of the markers reported in previous studies are more applicable to African American patients than Caucasian patients.

The role of phosphate in kidney disease

The importance of phosphate homeostasis in chronic kidney disease (CKD) has been recognized for decades, but novel insights - which are frequently relevant to everyday clinical practice - continue to emerge. Epidemiological data consistently indicate an association between hyperphosphataemia and poor clinical outcomes. Moreover, compelling evidence suggests direct toxicity of increased phosphate concentrations. Importantly, serum phosphate concentration has a circadian rhythm that must be considered when interpreting patient phosphate levels. Detailed understanding of dietary sources of phosphate, including food additives, can enable phosphate restriction without risking protein malnutrition. Dietary counselling provides an often underestimated opportunity to target the increasing exposure to dietary phosphate of both the general population and patients with CKD. In patients with secondary hyperparathyroidism, bone can be an important source of serum phosphate, and adequate appreciation of this fact should impact treatment. Dietary and pharmotherapeutic interventions are efficacious strategies to lower phosphate intake and serum concentration. However, strong evidence that targeting serum phosphate improves patient outcomes is currently lacking. Future studies are, therefore, required to investigate the effects of modern dietary and pharmacological interventions on clinically meaningful end points.