Characterization of Novel Pathogenic Variants Causing Pyridox(am)ine 5′-Phosphate Oxidase-Dependent Epilepsy

Several variants of the enzyme pyridox(am)ine 5′-phosphate oxidase (PNPO), responsible for a rare form of vitamin B6-dependent neonatal epileptic encephalopathy known as PNPO deficiency (PNPOD), have been reported. However, only a few of them have been characterised with respect to their structural and functional properties, despite the fact that the knowledge of how variants affect the enzyme may clarify the disease mechanism and improve treatment. Here, we report the characterisation of the catalytic, allosteric and structural properties of recombinantly expressed D33V, R161C, P213S, and E50K variants, among which D33V (present in approximately 10% of affected patients) is one of the more common variants responsible for PNPOD. The D33V and E50K variants have only mildly altered catalytic properties. In particular, the E50K variant, given that it has been found on the same chromosome with other known pathogenic variants, may be considered non-pathogenic. The P213S variant has lower thermal stability and reduced capability to bind the FMN cofactor. The variant involving Arg161 (R161C) largely decreases the affinity for the pyridoxine 5′-phosphate substrate and completely abolishes the allosteric feedback inhibition exerted by the pyridoxal 5′-phosphate product.

Influence of Serum Biochemistry on Bone and Kidney Phenotypes in Subjects With Symptomatic Primary Hyperparathyroidism

OBJECTIVETo analyze the abnormalities in serum parathormone (PTH)-25-hydroxy-vitamin D (25-OHD) axis and calcium phosphate homeostasis in symptomatic PHPT patients having bone disease, nephrolithiasis and impaired renal function (IRF) at diagnosis. METHODSConsecutive adults (>18 years) with diagnosed symptomatic PHPT were enrolled in the retrospective study. Relevant clinical, biochemical and imaging parameters were recorded.RESULTSAdult patients with symptomatic PHPT were identified (N=60, age 45.2±14.4 years, 45 females). Predominant phenotypes were bone disease (osteoporosis and/or clinical fractures, n=42, 70%) and nephrolithiasis (n=24, 40%). Compared to patients with nephrolithiasis only (subgroup C, n=7) and simultaneous bone disease/nephrolithiasis (subgroup D, n=17), patients with isolated bone disease phenotype (subgroup B, n=25) had significantly higher alkaline phosphatase (AlP) and lower 25-OHD levels at presentation. Patient subgroups with nephrolithiasis had higher serum calcium levels and lower effective glomerular filtration rate (eGFR) at presentation. PTH was not significantly different among these subgroups. Patients with IRF (eGFR <60 ml/min per 1.73 m2, n=17) in our cohort had significantly higher serum calcium, phosphate, PTH levels and nephrolithiasis rates. Presence of nephrolithiasis, higher calcium x phosphate product (IRF: 36.2 ± 10.7 versus no IRF: 26.2 ± 5.7 mg2/dl2) and increased PTH levels were independently associated with IRF at diagnosis.CONCLUSIONSWhile PHPT patients with isolated bone disease were found to have lower 25-OHD and higher AlP levels independent of PTH levels; PTH was found to be an independent predictor of impaired renal function at diagnosis.

Estimation of Serum Vitamin D2, Growth Hormone, Alkaline Phosphatase and Calcium Phosphate Product in Patients with End Stage Renal Disease

INTRODUCTION The chronic kidney disease (CKD) patient's calcium phosphate product, alkaline phosphatase (ALP), vitamin-D2 and human growth hormone (hGH) are altered under haemodialysis. This study aimed to evaluate these biochemical variables in conjunction with haemoglobin and blood pressure to find out their association in End Stage Renal Disease (ESRD) patients. MATERIAL AND METHODS This cross-sectional study comprised of 104 patients with ESRD undergoing haemodialysis. The estimated glomerular filtration rate (eGFR) was calculated by Cockcroft-Gault (CG) equation and calcium, phosphorus, ALP were measured by fully automated analyzer whereas vitamin-D2 and hGH were measured by sandwich and competitive enzyme linked immune sorbent assay (ELISA) techniques. RESULTS The mean age of patients was 53.12 ±16.37 years comprising 68% male. The hypovitaminosis D was 57.7% deficiency and 23.1% insufficiency states whereas hGH insufficiency was 22.1%. The calcium phosphate product was found to be increased in only 39.9% cases. The increased ALP level was observed in 64.4% cases. There was statistically significant association between hGH and Hb status (p=0.03). The significant difference in mean sodium and Ca×P of ESRD cases was observed with hypertension status (p=0.03 and p=0.01) respectively. Moreover, the significant difference in mean eGFR and hGH was observed with haemoglobin status (p=0.0001and p=0.01) respectively. CONCLUSION Increased level of ALP and hypovitaminosis-D was very common in ESRD patients undergoing dialysis with less prevalence of hGH insufficiency and calcium phosphate product increment. The anaemia and hypertension status can be pre-existing condition with ESRD which are cumbersome to control if not monitor in these patients.

Impact of Dialysis Vintage and Renal Biomarkers on Mortality in Dialysis-Dependent Patients With Critical Limb Ischemia Undergoing Revascularization

Purpose: Revascularization of both endovascular therapy (EVT) and surgical reconstruction improve clinical outcomes of patients with critical limb ischemia (CLI); however, treatment of dialysis-dependent patients with CLI is still challenging. This study aimed to investigate the impact of dialysis-related parameters on the risk of mortality in dialysis-dependent patients undergoing revascularization for CLI. Materials and Methods: We retrospectively identified 274 dialysis-dependent patients with CLI (196 males; mean age 71 years), who underwent revascularization, from the clinical database of the surgical reconstruction vs peripheral intervention in patients with critical limb ischemia (SPINACH) study, which was a prospective, multicenter, observational study. Of these patients, 175 patients underwent EVT and 99 patients received surgical reconstruction. The current study evaluated the impact of dialysis vintage and renal biomarkers on the mortality rate of dialysis-dependent patients with CLI undergoing revascularization. Results: During a mean follow-up period of 1.7 ± 1.1 years, 147 deaths were observed. The 3-year overall survival rate and its standard error were estimated to be 40.5% ± 8.1% using the Kaplan-Meier method. A Cox proportional hazard analysis revealed that dialysis vintage ≥4 years, serum creatinine levels <4.7 mg/dL, serum urea nitrogen ≥88 mg/dL, and calcium-phosphate product ≥62.6 mg2/dL2 were independent risk factors for mortality after adjustment for the detailed mortality risk score developed in the SPINACH study. Adding these parameters to the original mortality risk score slightly, but not significantly, increased the area under the time-dependent receiver operating characteristics curve from 0.74 (95% CI, 0.67 to 0.81) to 0.77 (0.71 to 0.84) (p=0.084), whereas continuous net reclassification improvement reached 0.75 (0.12 to 0.90) (p=0.027). Conclusion: We found that long dialysis vintage, low serum creatinine, high serum urea nitrogen, and high calcium-phosphate product were independently associated with the increased risk of mortality in dialysis-dependent patients with CLI undergoing revascularization.

Bone metabolic disorder and its contributing factors in patients with chronic kidney disease; a three-year cohort study

Introduction: The prevalence of bone mineral disorder is best known in end-stage renal disease (ESRD) patients, but less data is available for the earlier stages. Objectives: We aimed to compare the prevalence of bone metabolic disorder at all stages of chronic kidney disease (CKD) and assess its contribution to CKD progression and patients’ outcome. Patients and Methods: In a retrospective cohort study, CKD patients who were under treatment for three years were selected from a nephrology clinic in Tehran, Iran. Patients’ demographic and laboratory data, as well as the outcome of their treatment were gathered and analyzed. Results: In 473 patients with an average age of 61.5, 60.1% were at stage III, 35.8% were at stage IV, and 4.1% were at stage V of CKD. There was a significant relationship between CKD stage and serum phosphate, calcium-phosphate product, and systolic blood pressure (SBP). Furthermore, the patients’ outcome was significantly related to advanced stages of CKD, higher first phosphate level, diabetes mellitus in medical history, and higher stages of SBP. By multiple Cox regression analysis, after adjustment for glomerular filtration rate (GFR), the first serum phosphate level, and the calcium-phosphate product did not contribute to the undesirable outcome. Conclusion: Although bone metabolic disorder is more frequently seen in advanced stages of chronic kidney disease, these changes can be seen even in earlier stages of the disease. The influence of phosphate abnormality in the patients’ outcome should be studied more in earlier stages for better control.

A high serum phosphate and calcium-phosphate product is associated with cerebral small vascular disease in patients with stroke; a real world study.

Cerebral small vessel disease (CSVD) is a slowly progress disease, often accompanied by stroke, and result in dementia, depression, cognitive impairment, etc. It had already known that calcium and phosphorus metabolism (CPM) disorders were associated with vascular related adverse events. Serum Ca, P, Ca×P are the most commonly used indicators of CPM in clinical. The risk factors of CSVD and the relationship of serum Ca, P, Ca×P and CSVD in stroke patients who do not have CPM disorders are still obscure. We enrolled 488 CSVD patients in a cohort from a consecutive hospital-based stroke registry, and further sub-grouped them into lacunes, white matter hyperintensities (WMHs), cerebral microbleeds (CMBs), and matched them to 140 stroke patients without CSVD as controls. CSVD patients had higher levels of serum Ca, P, Ca×P. We developed 2 predictive models and nomograms (incorporating age, hypertension, P or Ca×P, respectively) for CSVD patients. The prediction and calibration power were good. Area under the curve (AUC) was 0.855, 0.851, respectively. P value of Hosmer-Lemeshow goodness of fit (H-L) test was 0.689, 0.698, respectively. P and Ca×P were positive correlated with CSVD, with OR 3720.401 (646.665-21404.249), 1.294 (1.222-1.370), respectively. We further validated the models in lacunes, WMHs, and CMBs, and found models were still valid in these 3 subtypes. In summary, a high serum P or Ca×P are associated with an increased risk of CSVD in stroke patients who without CPM disorders.

Cutaneous manifestations of end-stage renal disease

Objectives: (1) To study the dermatological manifestations in patients with end-stage renal disease (ESRD) of diverse etiology and (2) to compare the dermatological manifestations in patients on conservative treatment and those receiving hemodialysis. Materials and Methods: One hundred patients with ESRD who attended the nephrology/dermatology department of a tertiary care center were examined for dermatological manifestations. Results: All the 100 patients evaluated had at least one cutaneous manifestation. Pallor was the most common cutaneous finding in our study (64%). Xerosis was observed in 61% and pruritus in 46%. Other common findings included diffuse hyperpigmentation (22%) and cutaneous infections (20%). Specific changes noted were acquired perforating dermatoses (7%) and nephrogenic systemic fibrosis (2%). Nail, oral mucosa, and hair were affected in 61%, 54%, and 29% cases, respectively. No significant association was noted between dermatological manifestations and modality of treatment. Comparison of serum calcium, serum phosphorus, and calcium-phosphate product was done with pruritus and a significant association was noted between pruritus and the serum levels of phosphate and calcium-phosphate product. Limitations: Small sample size and the single center study design were the major limitations. Conclusion: Dermatological manifestations are common among patients with ESRD. Early diagnosis and prompt management of the dermatological diseases may improve the quality of life of the affected.

Associations of serum sclerostin and Dickkopf-related protein-1 proteins with future cardiovascular events and mortality in haemodialysis patients: a prospective cohort study

Background Sclerostin and Dickkopf-related protein-1 (Dkk-1) proteins are inhibitors of the canonical Wnt/β-catenin bone pathway. Sclerostin but not Dkk-1 is associated with increased arterial stiffness. This study examined the prognostic significance of sclerostin and Dkk-1 levels for cardiovascular outcomes and mortality in haemodialysis (HD) patients. Methods Serum sclerostin and Dkk-1 levels were measured with enzyme-linked immunosorbent assay in 80 HD patients that were followed-up for a median of 45 months. Factors that could interfere with the association of sclerostin and Dkk-1 with outcomes [including carotid–femoral pulse wave velocity (PWV), parathyroid hormone (PTH), calcium–phosphate product and others] were assessed at baseline. The primary endpoint was a combination of all-cause death, non-fatal myocardial infarction, non-fatal stroke, coronary revascularization, hospitalization for decompensated heart failure and new-onset atrial fibrillation. Secondary endpoints included cardiovascular and all-cause mortality. Results Cumulative freedom from the primary endpoint was significantly lower for higher tertiles of sclerostin (77.8, 69.2 and 40.7%; Tertiles 1–3, respectively; log-rank P = 0.004). The risk for the primary outcome gradually increased for higher sclerostin tertiles [Tertile 3: hazard ratio (HR) = 3.847, 95% confidence interval (CI) 1.502–9.851]. No significant association was evident between sclerostin and all-cause mortality, whereas higher sclerostin levels presented a trend towards higher risk for cardiovascular mortality. Dkk-1 levels exhibited no association with the risk of the primary or secondary endpoints. In stepwise Cox regression modelled analysis, sclerostin levels were associated with the primary outcome, independently of PTH, calcium–phosphate product, serum albumin, C-reactive protein and PWV levels (HR = 2.921, 95% CI 1.401–6.090; P = 0.004). Conclusions High sclerostin levels are associated with lower cumulative freedom and higher risk for a composite endpoint of cardiovascular events and mortality. Dkk-1 exhibited no association with the future risk of adverse outcomes.