Serum Phosphate Levels Research Articles

Early Hypophosphatemia as a Prognostic Marker in Acute Pancreatitis.

Acute pancreatitis (AP) is a complex disease representing a significant portion of gastrointestinal-related hospitalizations in the U.S. Understanding risk factors of AP might provide attractive therapeutic targets. We evaluated hypophosphatemia a prognostic marker in AP. We performed a retrospective review of electronic health records of patients with AP from 01/ 01/2012-12/31/2021 at Cedars-Sinai Medical Center with serum phosphate measured within 48 hours of admission. Multivariable logistic regression modeling was used to evaluate associations with ICU admission and AP severity. Multivariable log-linear modeling was employed to examine associations with length of stay (LOS). Of 1526 patients admitted for AP, 33% (499) had a serum phosphate level measured within 48 hours. Patients with hypophosphatemia were more likely to have ICU admission (adjusted odds ratio (AOR) = 4.57; 95% confidence interval (CI): 2.75-7.62; P < 0.001), have a longer hospital stay (log-LOS = 0.34; SE; 0.09; 95% CI: 0.17-0.52; P < 0.001), and have moderate or severe AP (AOR = 1.80; 95% CI: 1.16-2.80; P < 0.001) compared with those without hypophosphatemia. Serum phosphate is infrequently measured in patients with AP and shows promise as an early prognostic marker for outcomes of AP.

Circadian Regulation of Bone Remodeling.

Adult bones are continuously remodeled by the balance between bone resorption by osteoclasts and subsequent bone formation by osteoblasts. Many studies have provided molecular evidence that bone remodeling is under the control of circadian rhythms. Circadian fluctuations have been reported in the serum and urine levels of bone turnover markers, such as digested collagen fragments and bone alkaline phosphatase. Additionally, the expressions of over a quarter of all transcripts in bones show circadian rhythmicity, including the genes encoding master transcription factors for osteoblastogenesis and osteoclastogenesis, osteogenic cytokines, and signaling pathway proteins. Serum levels of calcium, phosphate, parathyroid hormone, and calcitonin also display circadian rhythmicity. Finally, osteoblast- and osteoclast-specific knockout mice targeting the core circadian regulator gene Bmal1 show disrupted bone remodeling, although the results have not always been consistent. Despite these studies, however, establishing a direct link between circadian rhythms and bone remodeling in vivo remains a major challenge. It is nearly impossible to repeatedly collect bone materials from human subjects while following circadian changes. In addition, the differences in circadian gene regulation between diurnal humans and nocturnal mice, the main model organism, remain unclear. Filling the knowledge gap in the circadian regulation of bone remodeling could reveal novel regulatory mechanisms underlying many bone disorders including osteoporosis, genetic diseases, and fracture healing. This is also an important question for the basic understanding of how cell differentiation progresses under the influence of cyclically fluctuating environments.

P075 What has parenteral iron got to do with rheumatology?

Abstract Background/Aims A 39 year-old female had been experiencing a six-month history of insidious onset migratory joint and bone pain, stiffness, malaise and over the last four months proximal muscle weakness. There had been partial relief with the use of non-steroidal anti-inflammatory medication. Past medical history included severe menorrhagia secondary to fibroids with a haemoglobin of 50g/dl on a handful of occasions, requiring x3 iron infusions (Ferric Carboxymaltose (FCM)1000mg) over a two year period. The last two infusions were provided three months apart. After each infusion, profound fatigue ensued. A blood test demonstrated an elevated ALP 301 (RR 30-130 U/L), reduced phosphate 0.48 (RR 0.8-1.5mmol/L) and mildly reduced 25OH vitamin D 44 (RR 50-140nmol/L). Corrected calcium was low-normal 2.29 (RR 2.2-2.6mmol/L) as was PTH 4.62 (RR 1.6-6.9pmol/L). A CTCAP excluded malignancy. Methods The patient had been treated with Cholecalciferol 1000iu and Dipyridamole 100mg daily with weekly blood test monitoring for six weeks prior to review in the metabolic bone clinic. Dipyridamole aided biochemical and symptomatic improvement. Further tests returned with an elevated FGF23 252 (RR 0-100 RU/ml), a normal Urine phosphate/Creatinine 1.6 and TmP/GFR ratio (suggesting the FGF23 effect on the kidney was not severe or its effects inhibited by Dipyridamole). ALP had reduced slightly to 269, PTH was elevated at 10.81 (RR 1.95-8.49micromol/L) and 1,25 Dihydroxy Vit D 182 (RR43-144 pmol/L). Results The patient was diagnosed with Parenteral iron triggered hypophosphatemia osteomalacia (6H-syndrome). A delayed diagnosis and referral resulted from unfamiliarity of side-effects of parenteral iron, especially Ferric Carboxymaltose, which has an alert on the GOV.UK website. The patient discontinued IV iron and was placed on oral Ferrous Gluconate 300mg daily. In retrospect, bone and joint pain was likely the result of enthesial pain and pseudofractures. In patients with diagnostic uncertainty, an isotope bone scan would be beneficial in assessing the extent of such pseudofractures. Hypophosphatemia is common following FCM (≥1/100 to &amp;lt; 1/10), and often self-limiting and asymptomatic. However, sustained hypophosphatemia (from recurrent infusions) can result in osteomalacia. Both anaemia and certain iron preparations can cause an elevation in FGF23 leading to increased urinary phosphate excretion. Dipyridamole has anti-phosphaturic effects by inhibiting FGF23. Conclusion It is advised in such patients to monitor serum phosphate levels at two- and five-weeks post infusion and to re-evaluate therapy with FCM in patients with persistent hypophosphatemia. It is common for symptoms, imaging, and biochemistry (FGF23 and ALP) to remain elevated/positive several months after diagnosis. This case highlights the need to ask about iron infusions in the drug history in patients presenting with hypophosphatemia and to be aware that musculoskeletal pain following iron infusions can be a sign of osteomalacia which will need investigating. Rarely, proximal muscle weakness can occur following the above iron preparation. Disclosure K.M. Achilleos: None. V. Rajagopal: None. C. Adams: None. G. Clunie: None.

Preclinical development of EXT608, an investigational parathyroid hormone derivative with extended half-life for the treatment of hypoparathyroidism.

Hypoparathyroidism, a deficiency of parathyroid hormone (PTH), results in hypocalcemia, hyperphosphatemia, and hypercalciuria. The disease is poorly controlled by calcium and vitamin D supplements or native PTH(1-84) replacement therapy. A version of PTH is being developed using D-VITylation technology, whereby vitamin D is conjugated to a therapeutic peptide, which confers a long plasma half-life by virtue of binding to the abundant vitamin D binding protein (DBP). D-VITylation of PTH caused no reduction in activity at the PTHR1 receptor, and resulted in a plasma elimination half-life of 7-15h in rats and 24-32h in cynomolgus monkeys. Analysis of steady-state pharmacokinetics as a function of dose showed flat profiles with smaller peak:trough ratios at low doses, indicative of slower subcutaneous absorption. In thyroparathyroidectomized (TPTx) rats, PTH(1-34)-vitamin D conjugates restored serum calcium and phosphate levels into the normal range over the 24h dosing period, and increased bone turnover markers and reduced bone mineral density. Urinary calcium was initially elevated, but normalized by the end of treatment on day 27. In healthy monkeys, a single dose of PTH(1-34)-vitamin D conjugates elevated serum calcium levels above the normal range for a period of 24-48h while simultaneously reducing urinary calcium. Therefore, the lead compound, EXT608, is a promising candidate as a therapeutic that can truly mimic the endogenous activity of PTH and warrants further study in patients with hypoparathyroidism.

The Effect of Unadjusted Mineral Supplementation on Bone Health of Preterm Infants Fed Fortified Human Milk: An Exploratory Analysis

Background: In standard fortification of human milk (HM), the HM macronutrient content is assumed, and a fixed amount of a multinutrient fortifier is added to achieve recommended nutrient intakes. In target fortification, the HM macronutrient content is regularly measured, guiding the addition of modular macronutrient supplements to the fortified HM, to achieve the nutritional targets more precisely. Objective: The study aimed to investigate whether this addition of modular supplements, unaccompanied by mineral supplementation, predispose to metabolic bone disease (MBD). Methods: This is a secondary analysis of a larger study of infants born with &lt;33 weeks gestational age. Fortifications based on the assumed (Group 1) or measured (Group 2) of the HM macronutrient content were compared, using low serum phosphate levels as an indicator of MBD, and length growth as a surrogate of bone growth. Results: Eighty-four infants were included, 35 in Group 1 and 49 in Group 2. During the exposure period, infants of Group 2 received higher mean fat (6.1 vs. 5.3 g/kg/day, P &lt; 0.001) and carbohydrate (13.0 vs. 11.7 g/kg/day, P &lt; 0.001) intakes; in addition, they exhibited lower mean serum phosphate (5.5 vs. 6.0 mg/dL, P = 0.022) and faster mean length velocity (1.06 vs. 0.89 cm/week, P = 0.003). Conclusions: These findings suggest that feeding fortified HM with extra fat and carbohydrate content, unaccompanied by mineral supplementation, promotes increased bone growth, as indicated by accelerated length growth, but with insufficiently mineralized osteoid, indicated by low serum phosphate levels. Intervention studies using direct biomarkers of bone mass content and mineral density are necessary to corroborate our findings.

The effect of parathyroid hormone lowering by etelcalcetide therapy on calcification propensity and calciprotein particles in hemodialysis patients.

This study investigated whether parathyroid hormone (PTH) lowering with etelcalcetide, and the consequent effects on mineral and bone metabolism, could improve serum calcification propensity (T50 time) and decrease calciprotein particle (CPP) load in hemodialysis patients with secondary hyperparathyroidism. In this single-arm, prospective, dose-escalation proof-of-principle study, hemodialysis patients received etelcalcetide at 2.5mg/dialysis session with increments of 2.5mg every 4 weeks to a maximum dose of 15mg three times a week or until a pre-specified safety endpoint was reached, followed by an 8-week wash-out phase. Out of 36 patients recruited (81% male, 62±13 years), 16 patients completed the study per protocol with a mean maximum tolerated dose of etelcalcetide of 9.5±2.9mg/dialysis session. With escalating doses of etelcalcetide, PTH and serum calcium levels significantly decreased (P<0.0001). While there was no significant change in T50 times or serum phosphate levels, etelcalcetide did yield significant and consistent reductions in serum levels of endogenous calciprotein monomers [-35.4 (-44.4 to -26.5)%, P<0.0001], primary [-22.4 (-34.5 to -10.3)%, P<0.01] and secondary CPP [-29.1 (-45.7 to -12.4)%, P<0.01], an effect that was reversed after therapy withdrawal. Serum levels of osteoclastic markers significantly decreased with escalating doses of etelcalcetide, while levels of the osteoblastic marker remained stable. Lowering of PTH with etelcalcetide did not result in statistically significant changes in T50. By contrast, homogenous reductions in serum levels of calciprotein monomers, primary and secondary CPP were observed.

Hypophosphatemia and Type-2 Diabetes Mellitus: A Review

Type-2 diabetes is a global public health crisis that threatens the economies of all nations, particularly developing countries. Type-2 diabetes mellitus has been suggested to be the most common endocrine disorder associated with several metabolic disturbances including changes in serum calcium, zinc, magnesium, or phosphate. Moreover, those who have poor glycemic control and longtime diabetes mellitus are more likely to decrease the blood phosphate level. Low serum phosphate level may be associated with morbidity and mortality from cardiovascular disease in these patients. So, the findings of this study may suggest that serum phosphate is an important screening parameter in type-2 diabetic patients especially who have poor glycemic control and longtime diabetes mellitus. Eastern Med Coll J. July 2023; 8 (2): 45-50

Exploring the association between serum phosphate levels and mortality in patients hospitalized with infectious diseases: a nationwide study.

The purpose of this study was to examine associations of serum phosphate levels with mortality, target organ damage and length of hospital stay in adults with infectious diseases hospitalized outside of the intensive care unit. This nationwide retrospective cohort study comprised patients admitted with infections, to medical and surgical departments in eight tertiary hospitals during 2001-2020. The main exposure variable was the first serum phosphate levels at admission (up to 1 week). The analysis included multivariable logistic regression models and quantile regression. Of 126,088 patients (49% males, mean age: 69.3 years), 24,809 (19.7%) had decreased phosphate levels, 92,730 (73.5%) normal phosphate levels, and 8,549 (6.8%) elevated phosphate levels on admission. Overall- and in-hospital mortality rates were highest among those with hyperphosphatemia (74.5 and 16.4%, respectively), followed by those with normophosphatemia (57.0 and 6.6%), and lastly the hypophosphatemia group (48.7 and 5.6%); p < 0.001 for all. After adjusting for confounders, the lowest predicted mortality rate was observed in the normophosphatemia group. In the multivariable model, hyperphosphatemia conferred a higher probability of target organ damage (OR [95% CI]: 2.43 [2.06-2.86]), while moderate hypophosphatemia conferred a lower probability (OR [95% CI]: 0.73 [0.65-0.82]), compared to normal phosphate levels and extreme hypophosphatemia showed a non-significant association (OR [95% CI]: 0.87 [0.57-1.28]). The associations were independent of renal failure. In a multivariable model, hyperphosphatemia was associated with a slight increase of 0.33 days in length of stay compared to normal phosphate levels. A J-shaped relation was found between phosphate levels and prognosis in patients hospitalized with infectious diseases, regardless of their renal function.

Serum phosphate levels and the development of sepsis associated acute kidney injury: evidence from two independent databases.

We aimed to investigate the association between serum phosphate levels and the risk for developing sepsis associated acute kidney injury (SAKI). Septic patients from the Medical Information Mart for Intensive Care IV (MIMIC IV) and the eICU Collaborative Research Database (eICU-CRD) were enrolled. Restricted cubic spline (RCS) was used to visualize the relationship between phosphate levels and the risk of SAKI. Patients were divided into four categories based on their serum phosphate levels. Logistic regression analysis, receiver operating characteristic (ROC) curve and subgroup analysis were performed to evaluate the predictive value of serum phosphate for SAKI. A total of 9,244 and 2,124 patients from the MIMIC IV and eICU-CRD database were included in the final analysis. RCS curve revealed a non-linear correlation between phosphate levels and the risk of SAKI (p for non-linearity <0.05). Each 1 mg/dL increase in phosphate levels was associated with a 1.51 to 1.64-fold increased risk of SAKI (OR 2.51-2.64, p < 0.001) in the MIMIC IV cohort and a 0.29 to 0.38-fold increased risk (OR 1.29-1.38, p < 0.001) in the eICU-CRD cohort. Compared to the normal-low category, hyperphosphatemia and normal-high category were independently associated with an increased risk of SAKI, while hypophosphatemia was independently associated with a decreased risk in the MIMIC IV cohort. A similar trend was observed in the eICU-CRD cohort, but statistical significance disappeared in the hypophosphatemia category and the adjusted model of normal high category. These finding was consistent in subgroup analysis. Elevated serum phosphate, even within the normal range, is an independent risk factor for developing SAKI in septic patients. Abnormal change in serum phosphate levels may be a novel biomarker for early prediction of SAKI occurrence.

Renal hyperparathyroidism- a risk factor in the development of encapsulating peritoneal sclerosis.

Encapsulating peritoneal sclerosis (EPS) is a rare complication of prolonged peritoneal dialysis (PD) exposure, characterised by peritoneal thickening, calcification, and fibrosis ultimately presenting with life-threatening bowel obstruction. The presence or role of peritoneal calcification in the pathogenesis of EPS is poorly characterised. We hypothesise that significantly aberrant bone mineral metabolism in patients on PD can cause peritoneal calcification which may trigger the development of EPS. We compared the temporal evolution of bone mineral markers during PD in EPS patients with non-EPS long-term PD controls. Linear mixed model and logistic regression analysis were used to compare four-monthly serum levels of calcium, phosphate, parathyroid hormone, and alkaline phosphatase (ALP) over the duration of PD exposure in 46 EPS and 46 controls (PD, non-EPS) patients. EPS patients had higher mean calcium (2.51 vs. 2.41 mmol/L) and ALP (248.00 vs. 111.13 IU/L) levels compared with controls (p=0.01 and p<0.001 respectively, maximum likelihood estimation). Logistic regression analysis demonstrated that high serum calcium and phosphate levels during PD were associated with a 4.5 and 2.9 fold increase in the risk of developing EPS respectively. High levels of calcium and phosphate in patients on PD were identified to be risk factors for EPS development. Possible reasons for this may be an imbalance of pro-calcifying factors and calcification inhibitors promoting peritoneal calcification which increases peritoneal stiffness. Mechanical alterations may trigger, unregulated fibrosis and subsequent development of EPS. Improved management of secondary hyperparathyroidism during PD may ultimately diminish the EPS risk.

Assessing Postoperative Phosphate and Calcium/Phosphate Ratio as Surrogates for Parathyroid Hormone Following Total Thyroidectomy.

Evaluate utility of postoperative phosphate and calcium/phosphate ratio (Ca/P) as surrogates for parathyroid hormone (PTH) following total thyroidectomy. Retrospective cohort study. Tertiary care hospital. We retrospectively reviewed patients 18 years or older who underwent total thyroidectomy in a tertiary care hospital by a single surgeon from 2015 through 2021. Patients with incomplete data, pre-existing hypoparathyroidism, vitamin D deficiency, or renal failure were excluded. All patients had PTH drawn within 4 hours of surgery and serum calcium, albumin, and phosphate levels on postoperative Day 1. Corrected calcium was used to calculate a Ca/P. Receiver operating characteristic (ROC) curves were generated to compare phosphate level or Ca/P with PTH. Each possible surrogate was assessed relative to PTH cutoffs of less than 5, 10, 15, and 20 pg/mL. A good screening test was defined as having an area under the curve (AUC) greater than 0.8. A total of 185 patients underwent total thyroidectomy with 1 fellowship-trained otolaryngologist. Most patients were female (62%), median age 48 years. Most surgeries were performed for cancer (68%). Six (3.2%) patients required IV calcium supplementation and 2 (1.1%) required readmission for symptomatic hypocalcemia. ROC curves comparing phosphate and Ca/P to PTH at the listed cutoffs demonstrated AUC ranging from 0.55 to 0.66 and 0.61 to 0.79, respectively. None met the threshold for a good screening test. Postoperative phosphate and Ca/P ratio are not surrogates for PTH levels following total thyroidectomy. More research is needed to identify cost-effective strategies for postoperative calcium monitoring in patients undergoing total thyroidectomy. Retrospective cohort study.

Acquired Forms of Fibroblast Growth Factor 23-Related Hypophosphatemic Osteomalacia.

Fibroblast growth factor 23 (FGF23) is a pivotal humoral factor for the regulation of serum phosphate levels and was first identified in patients with autosomal dominant hypophosphatemic rickets and tumor-induced osteomalacia (TIO), the most common form of acquired FGF23-related hypophosphatemic rickets/osteomalacia (FGF23rHR). After the identification of FGF23, many other inherited and acquired forms of FGF23rHR were reported. In this review article, the detailed features of each acquired FGF23rHR are discussed, including TIO, ectopic FGF23 syndrome with malignancy, fibrous dysplasia/McCune-Albright syndrome, Schimmelpenning-Feuerstein-Mims syndrome/cutaneous skeletal hypophosphatemia syndrome, intravenous iron preparation-induced FGF23rHR, alcohol consumption-induced FGF23rHR, and post-kidney transplantation hypophosphatemia. Then, an approach for the differential diagnosis and therapeutic options for each disorder are concisely introduced. Currently, the majority of endocrinologists might only consider TIO when encountering patients with acquired FGF23rHR; an adequate differential diagnosis can reduce medical costs and invasive procedures such as positron emission tomography/computed tomography and venous sampling to identify FGF23-producing tumors. Furthermore, some acquired FGF23rHRs, such as intravenous iron preparation/alcohol consumption-induced FGF23rHR, require only cessation of drugs or alcohol to achieve full recovery from osteomalacia.

Lanthanum Hydroxide and Chronic Kidney Disease Mineral and Bone Disorder: A Rat Model.

To investigate the pharmacological effects and molecular mechanisms of lanthanum hydroxide(LH) on ectopic mineralization of soft tissue and abnormal bone in rats with acute kidney injury(AKI). Wistar rats were modeled by 5/6 nephrectomy. After the operation, the rats were divided into different groups, the biochemical indexes of serum collected at different times. LH was administered by intragastric tube at doses of 0.4, 0.2, and 0.1g/kg, respectively. Rats were sacrificed in the 16th week after LH treatment. Observation of pathological changes in tissues were made by specific staining. Western Blot, Real-Time Quantitative PCR, and immunohistochemistry techniques were used to detect the impact on pathway-related proteins. Compared with the control group (no LH administered), the serum phosphate level of the LH group was significantly reduced (p<0.01), calcification of the thoracic aorta was reduced (p<0.05, p<0.01) (Serum biochemical tests before dosing and during drug treatment cycles), renal fibrosis was improved (p<0.01), nuclear entry of nuclear factor kappa-B (NF-κB) was reduced (p<0.01), and the expression of the smooth muscle protein 22α (SM22α) was significantly increased (p<0.01). The expression of osteogenic marker genes was decreased. In addition, compared with the controls, the receptor activator for nuclear factor-κB ligand/osteoprotegerin (RANKL/OPG) ratio of the femur in the model group was increased (p<0.05). LH can inhibit the occurrence and development of vascular calcification and bone abnormalities in AKI rats by inhibiting the NF-κB and RANKL/OPG signaling pathways.

Association of serum phosphate, calcium and alkaline phosphatase with risk of incident fractures in healthy older adults.

Aging increases fracture risk through bone loss and microarchitecture deterioration due to an age-related imbalance in bone resorption and formation during bone remodelling. We examined the associations between levels of phosphate, calcium, and alkaline phosphatase, and fracture risk in initially-healthy older individuals. A post-hoc analysis of the Aspirin in Reducing Events in the Elderly (ASPREE) trial recruited 16,703 Australian participants aged ≥70 years and 2,411 US participants aged ≥65 years. Analyses were conducted on ASPREE-Fracture substudy participants from Australia with serum calcium, phosphate, and alkaline phosphatase measurement. Fracture data were collected post-randomization. Cox regression was used to calculate hazard ratios (HR) and 95% confidence intervals (CIs). Phosphate, calcium, and alkaline phosphatase were analysed in deciles (D1-D10), with deciles 4-7 (31-70%) as the reference category. Restricted cubic spline curves were used to identify nonlinear associations. Of the 9915 participants, 907 (9·2%) persons had incident fractures recorded over 3·9 (SD 1·4) years. In the fully adjusted model, males in the top decile (D10) of phosphate had 78% higher risk of incident fracture (HR 1·78, 95% CI 1·25-2·54). No such association was observed for females (HR 1·09, 95% CI 0·83-1·44). The population attributable fraction in men within the D10 phosphate category is 6·9%. This result confirms that, high-normal serum phosphate levels are associated with increased fracture risk in older men.

Effect of early serum phosphate disorder on in-hospital and 28-day mortality in sepsis patients: a retrospective study based on MIMIC-IV database

BackgroundThis study aims to assess the influence of early serum phosphate fluctuation on the short-term prognosis of sepsis patients.MethodsThis retrospective study used the Medical Information Mart for Intensive Care IV database to analyze serum phosphate levels in sepsis patients within 3 days of ICU admission. According to the absolute value of delta serum phosphate (the maximum value minus the minimum value of serum phosphorus measured within three days), the patients were divided into four groups, 0–1.3, 1.4–2.0, 2.1–3.1, and ≥ 3.2 mg/dl. Meanwhile, the direction of delta serum phosphate was compared. With the serum phosphate change group of 0–1.3 mg/dl as the reference group, the relationship between delta serum phosphate and in-hospital mortality and 28-day mortality was analyzed by multivariate Logistics regression analysis.ResultsThe study involved 1375 sepsis patients. Serum phosphate changes (0–1.3, 1.4–2.0, 2.1–3.1, and ≥ 3.2 mg/dl) correlated with in-hospital and 28-day mortality variations (p = 0.005, p = 0.008). Much higher serum phosphate fluctuation elevated in-hospital and 28-day mortality. Compared to the 0–1.3 mg/dl change group, adjusted odds ratios (OR) in other groups for in-hospital mortality were 1.25 (0.86–1.81), 1.28 (0.88–1.86), and 1.63 (1.10–2.43), and for 28-day mortality were 1.21 (0.86–1.72), 1.10 (0.77–1.57), and 1.49 (1.03–2.19). Under the trend of increasing serum phosphate, the ORs of in-hospital mortality and 28-day mortality in ≥ 3.2 mg/dl group were 2.52 and 2.01, respectively.ConclusionIn conclude, the delta serum phosphate ≥ 3.2 mg/dl was associated with in-hospital mortality and 28-day mortality in patients with sepsis.

Reinforcement Learning and PK-PD Models Integration to Personalize the Adaptive Dosing Protocol of Erdafitinib in Patients with Metastatic Urothelial Carcinoma.

The integration of pharmacokinetic-pharmacodynamic (PK-PD) modeling and simulations with artificial intelligence/machine learning algorithms is one of the most attractive areas of the pharmacometric research. These hybrid techniques are currently under investigation to perform several tasks, among which precision dosing. In this scenario, this paper presents and evaluates a new framework embedding PK-PD models into a reinforcement learning (RL) algorithm, Q-learning (QL), to personalize pharmacological treatment. Each patient is represented with a set of PK-PD parameters and has a personal QL agent which optimizes the individual treatment. In the training phase, leveraging PK-PD simulations, the QL agent assesses different actions, defined consistently with the clinical knowledge to consider only plausible dose-adjustments, in order to find the optimal rules. The proposed framework was evaluated to optimize the erdafitinib treatment in patients with metastatic urothelial carcinoma. This drug was approved by the US Food and Drug Administration (FDA) with a dose-adaptive protocol based on monitoring the levels of serum phosphate, which represent a biomarker of both treatment efficacy and toxicity. To evaluate the flexibility of the methodology, a heterogeneous virtual population of 141 patients was generated using an erdafitinib population PK (PopPK)-PD literature model. For each patient, treatment response was simulated by using both QL-optimized protocol and the clinical one. QL agents outperform the approved dose-adaptive rules, increasing more than 10% the efficacy and the safety of treatment at each end point. Results confirm the great potentialities of the integration of PopPK-PD models and RL algorithms to optimize precision dosing tasks.

Regulation of FGF23 Production in Osteocytes.

FGF23 is a bone-derived hormone working to reduce serum phosphate level. This review focuses on recent findings regarding regulatory mechanisms of FGF23 expression in osteocytes, FGF23 levels, and activities. Circulatory FGF23 levels reflecting FGF23 biological activities can be regulated by both FGF23 expression and posttranslational modification of FGF23 protein. O-linked glycosylation and phosphorylation of FGF23 protein as well as enzymes that can cleave FGF23 protein are involved in the posttranslational modification. However, precise mechanisms of FGF23 protein processing are not clear. Several extracellular factors have been shown to affect FGF23 levels in kidney injuries. Contribution of these factors may be different depending on the causes and stages of kidney injury. FGF23 activities are regulated by complex mechanisms involving transcriptional and posttranslational modulations. There still remain several questions regarding the regulatory mechanisms of FGF23 expression and FGF23 processing.

Diagnostic pitfalls and therapeutic challenges of hypercalcaemia in chronic kidney disease: a case report and a narrative review

BackgroundEvaluation of hypercalcaemia in a patient with chronic kidney disease (CKD) is challenging, especially in low-resource settings. Hormone assays should be interpreted with caution as CKD affects both parathyroid hormone (PTH) and vitamin D. Therapies such as bisphosphonates are contraindicated in CKD, while fluid resuscitation can lead to volume overload. We report the diagnostic workup of a patient with stage V CKD who presented with symptomatic hypercalcaemia and discuss the diagnostic pitfalls and therapeutic challenges.Case presentationA 72-year-old Sri Lankan woman with stage V, non-oliguric CKD presented with a 2-week history of worsening lassitude, increased thirst and constipation. She was clinically euvolemic and did not have signs of uraemia. Bilateral lung fields had occasional coarse crepitations. The rest of the physical examination was normal. Her serum creatinine level was similar to her baseline (4.7 mg/dl, eGFR 9 ml/min). She was found to have a high serum calcium (14.3 mg/dl) and phosphate (5.0 mg/dl) levels. Her PTH level was 24.1 pg/ml (15–68), and she was deficient in 25-hydroxycholecalciferol (9 mg/ml (30–100)). She was not on calcium or vitamin D supplementation. Disseminated tuberculosis was diagnosed after detecting granulomata in the lungs and abdomen in the contrast-enhanced computed tomography (CECT) and mycobacterial DNA in sputum. She was hydrated with 0.9% NaCl with meticulous use of frusemide. The effect of frusemide waned off by the 10th day, requiring haemodialysis to control the hypercalcaemia. Vitamin D was replaced intramuscularly with 200,000 IU, after which the calcium levels increased. She was treated with IV pamidronate 30 mg, and the calcium levels started reducing drastically. Antituberculous therapy (ATT) was initiated 7 days after pamidronate treatment. The calcium levels normalised 2 days after ATT and sustained beyond 2 months.ConclusionInterpretation of PTH and phosphate levels should be done with caution when evaluating hypercalcaemia in patients with advanced chronic kidney disease. First- and second-generation assays detect PTH fragments which accumulate in CKD, leading to false positives. Hypophosphataemic effects of PTH/PTHrP can be masked by accumulation of phosphate in CKD. Bisphosphonates might have a role in treating calcitriol-induced hypercalcaemia, although this needs further evaluation.

Influence of hydroxyurea on tubular phosphate handling in sickle cell nephropathy

ObjectiveThis study aims to evaluate the markers of tubular phosphate handling in adults with sickle cell anemia (SCA) and the influence of hydroxyurea (HU), the degree of anemia and Hb F concentration on these markers. MethodsEighty-eight steady state SCA patients in outpatient follow-up in Fortaleza, Ceara, Brazil and 31 healthy individuals were included in this study. Vitamin D (25OHD) was measured by enzyme-bound fluorescence assay, intact parathyroid hormone (iPTH) by electrochemiluminescence, and serum and urinary phosphate and creatinine by colorimetric methods. Details of Hb F and HU use were obtained from clinical records. Tubular reabsorption of phosphate (TRP) and maximum tubular reabsorption of phosphate (MTRP) were calculated. SCA patients were stratified according to the use of HU, degree of anemia and percentage of Hb F. The significance level was set for p-values <0.05. ResultsCompared to controls the 25OHD level (25 ± 11 vs. 30 ± 9 pg/mL) was lower in SCA, while serum phosphate and MTRP were higher (3.86 ± 0.94 vs. 3.46 ± 0.72 and 3.6 ± 1.21 vs. 3.21 ± 0.53, respectively). There was no significant difference in iPTH, TRP and phosphaturia. Serum phosphate showed correlation with TRP (r = 0.32; p-value = 0.008) and MTRP (r = 0.9; p-value <0.001) in SCA. Patients taking HU, especially those with Hb F >10 % presented reduced serum phosphate levels, and TRP and MTRP rates. Those with mild anemia presented reduced serum phosphate levels and MTRP rates. ConclusionSerum phosphate levels and renal phosphate reabsorption rate were increased in SCA. HU use, high Hb F concentration and total Hb were associated with better control of tubular phosphate handling markers.

Relationship of the bone phenotype of the Klotho mutant mouse model of accelerated aging to changes in skeletal architecture that occur with chronological aging.

Due to the relatively long life span of rodent models, in order to expediate the identification of novel therapeutics of age related diseases, mouse models of accelerated aging have been developed. In this study we examined skeletal changes in the male and female Klotho mutant (kl/kl) mice and in male and female chronically aged mice to determine whether the accelerated aging bone phenotype of the kl/kl mouse reflects changes in skeletal architecture that occur with chronological aging. 2, 6 and 20-23 month old C57BL/6 mice were obtained from the National Institute of Aging aged rodent colony and wildtype and kl/kl mice were generated as previously described by M. Kuro-o. Microcomputed tomography analysis was performed ex vivo to examine trabecular and cortical parameters from the proximal metaphyseal and mid-diaphyseal areas, respectively. Serum calcium and phosphate were analyzed using a colorimetric assay. The expression of duodenal Trpv6, which codes for TRPV6, a vitamin D regulated epithelial calcium channel whose expression reflects intestinal calcium absorptive efficiency, was analyzed by quantitative real-time PCR. Trabecular bone volume (BV/TV) and trabecular number decreased continuously with age in males and females. In contrast to aging mice, an increase in trabecular bone volume and trabecular number was observed in both male and female kl/kl mice. Cortical thickness decreased with advancing age and also decreased in male and female kl/kl mice. Serum calcium and phosphate levels were significantly increased in kl/kl mice but did not change with age. Aging resulted in a decline in Trpv6 expression. In the kl/kl mice duodenal Trpv6 was significantly increased. Our findings reflect differences in bone architecture as well as differences in calcium and phosphate homeostasis and expression of Trpv6 between the kl/kl mutant mouse model of accelerated aging and chronological aging. Although the Klotho deficient mouse has provided a new understanding of the regulation of mineral homeostasis and bone metabolism, our findings suggest that changes in bone architecture in the kl/kl mouse reflect in part systemic disturbances that differ from pathophysiological changes that occur with age including dysregulation of calcium homeostasis that contributes to age related bone loss.