Bone mineral density assessment in patients with cystinuria.

BACKGROUND: Cystinuria is a rare genetic disease characterized by impaired tubular transport of cystine. Clinical features of cystinuria mainly include nephrolithiasis and its complications, although cystinuric patients may present with other comorbidities. There are currently no data on bone features of patients with cystinuria. Our aim is to characterize bone mineral density (BMD) in cystinuria. METHODS: Our study included adult cystinuric patients with estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m2 followed at 3 specialized outpatient clinics in Italy (Rome, Naples and Verona). Markers of bone turnover were analyzed in a centralized laboratory. Clinical, biochemical and dual-energy X-ray absorptiometry (DEXA) data were collected from September 2021 to December 2022. Linear regression models were used to evaluate statistically significant deviations from zero of Z-scores. RESULTS: Twenty-seven patients were included in the study. Mean (SD) age was 37 (15) years, 41% were women. Mean estimated glomerular filtration rate was 99 mL/min/1.73 m2. Serum parameters associated with bone turnover (parathyroid hormone, FGF23, calcium and phosphate) were all in the normal range, with only 4 patients showing mild hypophosphatemia. Prevalence of low bone mineral density, defined as Z-score ≤ - 2 at any site, was 15%. Average Z-scores were negative across most sites. CONCLUSIONS: Our study suggests that cystinuric patients have lower bone mineral density compared with individuals of the same sex and age, even when their kidney function is normal.

Sex differences in chronic kidney disease-related complications and mortality across levels of glomerular filtration rate.

BACKGROUND AND HYPOTHESIS: Chronic kidney disease (CKD) is a growing global health concern. Recent research has indicated sex disparities in CKD-related complications, yet the impact of sex differences on critical kidney function levels that trigger these complications and mortality remains inadequately documented. METHODS: We investigated sex-specific disparities in CKD-related complications and mortality according to eGFR levels. We analyzed NHANES data spanning from 1999 to 2018, including adult participants with an eGFR of 15-150 ml/min per 1.73m². The outcomes were CKD-related complications (hypertension, anaemia, CV diseases, acidosis, hyperphosphatemia, hyperparathyroidism) and all-cause and cause-specific mortality (CV mortality and non-CV mortality). Sex-stratified multivariable logistic and Cox regression models yielded odds ratios (ORs) and hazard ratios (HRs) for the relationship between eGFR categories and outcomes. Sex-stratified natural splines were used to explore the relationship between continuous eGFR and outcomes and identified eGFR thresholds of statistical significance. RESULTS: The study included 49 558 participants (50.3% women, 49.7% men). Multivariable logistic regression demonstrated a significant eGFR association with all CKD-related complications, exhibiting a linear trend across eGFR categories. Modelling eGFR as a natural spline revealed varied significance thresholds between sexes for anaemia and hyperparathyroidism. Additionally, the eGFR-hyperphosphatemia association was more pronounced in men. We observed substantial but not statistically significant differences between men and women in the thresholds of statistical significance for CV (significance appeared at a higher eGFR in men) and non-CV mortality (significance appeared at a higher eGFR in women). CONCLUSIONS: Research shows sex disparities in most CKD-related complications. Men develop anaemia and hyperparathyroidism earlier, women show steeper anaemia increase. Men have higher CV mortality risk. As eGFR decreased, men faced a higher risk of CV mortality at a higher eGFR threshold than women.

Circulating metabolites associated with kidney function decline and incident CKD: a multi-platform population-based study.

Background: Investigation of circulating metabolites associated with kidney function and chronic kidney disease (CKD) risk could enhance our understanding of underlying pathways and identify new biomarkers for kidney function. Methods: We selected participants from the population-based Rotterdam Study with data on circulating metabolites and estimated glomerular filtration rate based on serum creatinine (eGFRcreat) available at the same time point. Data on eGFR based on serum cystatin C (eGFRcys) and urine albumin-to-creatinine ratio (ACR) were also included. CKD was defined as eGFRcreat <60 ml/min per 1.73 m2. Data on circulating metabolites (ntotal = 1381) was obtained from the Nightingale and Metabolon platform. Linear regression, linear mixed, and Cox proportional-hazards regression analyses were conducted to study the associations between metabolites and kidney function. We performed bidirectional two-sample Mendelian randomization analyses to investigate causality of the identified associations. Results: We included 3337 and 1540 participants with data from Nightingale and Metabolon, respectively. A total of 1381 metabolites (243 from Nightingale and 1138 from Metabolon) were included in the analyses. A large number of metabolites were significantly associated with eGFRcreat, eGFRcys, ACR, and CKD, including 16 metabolites that were associated with all four outcomes. Among these, C-glycosyltryptophan (HR 1.50, 95%CI 1.31;1.71) and X-12026 (HR 1.46, 95%CI 1.26;1.68) were most strongly associated with CKD risk. We revealed sex differences in the associations of 11-ketoetiocholanolone glucuronide and 11-beta-glucuronide with the kidney function assessments. No causal associations between the identified metabolites and kidney function were observed. Conclusion: Our study indicates that several circulating metabolites are associated with kidney function which are likely to have potential as biomarkers, rather than as molecules involved in the pathophysiology of kidney function decline.

Determinants of renal papillary appearance in kidney stone formers: An in-depth examination.

OBJECTIVES: The aim of this study is to investi-gate the association between the urinary metabolic milieu and kidney stone recurrence with a validated papillary evaluation score (PPLA). MATERIALS AND METHODS: We prospectively enrolled 30 stone for-mers who underwent retrograde intrarenal surgery procedures. Visual inspection of the accessible renal papillae was performed to calculate PPLA score, based on the characterization of ductal plugging, surface pitting, loss of papillary contour and Randall's plaque extension. Stone compositions, 24h urine collections and kidney stone events during follow-up were collected. Relative supersaturation ratios (RSS) for calcium oxalate (CaOx), brushite and uric acid were calculated using EQUIL-2. PPLA score > 3 was defined as high. RESULTS: Median follow-up period was 11 months (5, 34). PPLA score was inversely correlated with BMI (OR 0.59, 95% CI 0.38, 0.91, p = 0.018), type 2 diabetes (OR 0.04, 95% CI 0.003, 0.58, p = 0.018) and history of recurrent kidney stones (OR 0.17, 95%CI 0.04, 0.75, p = 0.019). The associations between PPLA score, diabetes and BMI were not confirmed after excluding patients with uric acid stones. Higher PPLA score was associated with lower odds of new kidney stone events during follow-up (OR 0.15, 95% CI 0.02, 1.00, p = 0.05). No other significant correla-tions were found. CONCLUSIONS: Our results confirm the lack of efficacy of PPLA score in phenotyping patients affected by kidney stone disease or in predicting the risk of stone recurrence. Larger, long-term studies need to be performed to clarify the role of PPLA on the risk of stone recurrence.

The role of urinary supersaturations for lithogenic salts in the progression of autosomal dominant polycystic kidney disease.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is associated with significant risk of forming kidney stones, especially those made of calcium oxalate and uric acid, compared with the general population. Since crystals are able to activate the inflammasome and lead to cell injury, crystalluria might worsen ADPKD natural history, acting as a third hit. METHODS: The Bern ADPKD registry is a prospective observational cohort study. Height-adjusted total kidney volume (ht-TKV) was measured at baseline and every 3 years. Twenty-four hour urinary solute excretions collected at baseline and eGFR measurements over time were included in this analysis. Twenty-four hour urinary supersaturations (SS) for calcium oxalate, calcium phosphate and uric acid were calculated using EQUIL-2. Linear regression models were used to assess linear and non-linear associations between slopes of ht-TKV and eGFR with SSs and 24 h urinary solute excretions. RESULTS: Seventy-seven participants (mean age 45.0 [SD 12.9] years, eGFR 76.4 [28.3] mL/min/1.73 m2) were included, with a median follow-up of 4 years. The median slopes of ht-TKV and eGFR were 3.9 percent/year and 2.9 mL/min/1.73 m2/year, respectively. SS for uric acid showed a direct, linear association (p value for linearity 0.035) with ht-TKV slope. When analyzing individual components, urinary uric acid, ammonium, magnesium and sulfate were all directly associated with ht-TKV slope. Urinary sulfate was also directly associated with eGFR slope. CONCLUSIONS: Uric acid supersaturation and several other urinary components are identified as predictors of cyst growth in patients with ADPKD. Future studies with a dedicated design are needed to investigate the pathophysiological mechanisms underlying these associations.

RAS inhibitors and renal and general mortality in patients with heart failure supported by left ventricular assist devices: a registry study.

BACKGROUND: The aim of our study was to analyze the association between renin-angiotensin system inhibitor (RASi) therapy and renal outcomes and mortality in patients with heart failure (HF) supported by left ventricular assist device (LVAD) using a large, nationwide prospective cohort. To date, no studies have comprehensively analyzed the association between RASi and renal outcomes and mortality in patients with HF supported by LVAD. METHODS: We performed a retrospective observational study on LVAD patients in the Interagency Registry for Mechanically Assisted Circulatory Support. The main outcome was a composite of renal event and all-cause mortality. Secondary outcomes were the individual components of the composite outcome. A renal event was defined as a composite of doubling serum creatinine, eGFR decrease ≥ 40%, or need for dialysis. The exposure of interest was RASi therapy, updated during follow-up. Cox regression models adjusted for potential confounders were used to estimate the association between time-updated RASi therapy and the outcomes of interest. RESULTS: The analysis included 6448 patients. During a median follow-up of 12.7 months (IQR 19.8 months), 1632 patients developed the composite outcome. RASi therapy was associated with a lower risk of developing the composite outcome (HR 0.61, 95% CI 0.55, 0.68, P < 0.001). A significant association was confirmed between RASi therapy and renal outcomes (HR 0.74, 95% CI 0.61, 0.89, P = 0.002) and all-cause mortality (HR 0.56, 95% CI 0.50, 0.63, P < 0.001). CONCLUSIONS: Our data suggest a beneficial role of RASi therapy on renal function and all-cause mortality in patients with HF supported by LVAD.

Unravelling the Complex Relationship between Diet and Nephrolithiasis: The Role of Nutrigenomics and Nutrigenetics.

Nephrolithiasis is an increasingly prevalent condition, especially in high income countries, and is associated with high morbidity. Extraordinary progress in genetics made the identification of genetic forms of nephrolithiasis possible. These genetic diseases are usually rare and do not account for the most common forms of nephrolithiasis that are the result of several factors such as environment, dietary habits, and predisposing genes. This knowledge has shaped what we classify as nephrolithiasis, a condition that is now recognized as systemic. How and to what extent all these factors interact with one another and end in kidney stone formation, growth, and recurrence is not completely understood. Two new research fields have recently been trying to give some answers: nutrigenomics and nutrigenetics. These fields have the aim of understanding the intricate diet/genome interface that influences gene expression regulation mainly through epigenetic mechanisms and results in specific medical conditions such as cancer, metabolic syndrome, and cardiovascular diseases. Epigenetics seems to play a crucial role and could represent the link between environmental factors, that we are constantly exposed to, and risk factors for nephrolithiasis. In this systematic review, we summarize all the available evidence of proven or hypothesized epigenetic mechanisms related to nephrolithiasis.

Trajectories of Kidney Function in Patients with ATTRv Treated with Gene Silencers.

Hereditary transthyretin amyloidosis (ATTRv; v for "variant") is the most common form of hereditary amyloidosis, with an autosomal dominant inheritance and a variable penetrance. This disease has a significant variability in clinical presentation and multiorgan involvement. While kidney involvement in early-onset ATTRv has been reported in one-third of patients, in late-onset ATTRv it has generally been considered rare. In the present study, we describe trajectories of kidney function over time before and after treatment with gene silencing therapies in a cohort of 17 ATTRv patients with different mutations, coming from Italy (nine subjects treated with inotersen and eight patients treated with patisiran). The analysis of estimated glomerular filtration rate (eGFR) slopes revealed that the average change in eGFR was 0.01 mL/min/1.73 m2 per month before initiation and -0.23 mL/min/1.73 m2 per month during follow-up for inotersen and -0.62 mL/min/1.73 m2 per month before initiation and -0.20 mL/min/1.73 m2 per month during follow-up for patisiran. In conclusion, we did not observe any significant difference either between the two groups of treatment or within-group before and after therapy, so gene-silencing therapies may be considered safe for renal function in ATTRv and are not associated with a worsening of eGFR slope.

Renal effect of severe hypoxia evaluated By NGAL measurements: An in vivo and in vitro study.

PURPOSE: To investigate possible renal damage in healthy men exposed to extreme hypobaric hypoxia, using urinary Neutrophil Gelatinase-Associated Lipocalin (NGAL) concentration as biomarker. The value of NGAL as a biomarker of proximal tubular cell damage under hypoxic conditions was also tested in vitro experiments. METHODS: NGAL was assayed in a cohort of air cadets (n = 16) exposed to hypobaric hypoxia in a hypobaric chamber during their training program. In all subjects, urine creatinine (Cr) and urinary NGAL levels were measured immediately before, 3, and 24 h after hypobaric environment exposure. Three in vitro experiments using proximal tubular cell cultures were also performed to measure NGAL gene expression, NGAL secretion in the culture medium and to evaluate apoptosis under two cycles of hypoxia and reoxygenation. RESULTS: In the in vivo study, geometric means of urinary NGAL/Cr ratio measured 24 h after hypobaric hypoxia in the hypobaric chamber were significantly lower than baseline values (13.4 vs 25.9 ng/mg, p = 0.01). In cell cultures, hypoxia down-regulated NGAL gene expression without significantly changing NGAL secretion in the culture medium. Hypoxia significantly increased the percentage of apoptotic/necrotic cells, especially after the second hypoxia-reoxygenation cycle. CONCLUSIONS: Exposure to hypobaric-hypoxic environments does not cause significant and irreversible renal tubular injury in vivo and in vitro, except than in a late stage. The hypoxic insult does not seem to be mirrored by an increase of urinary NGAL in healthy men nor of NGAL gene expression in HK-2 cell culture or secretion in the culture medium in the in vitro conditions reported in the present study.

Urinary metabolic profile and stone composition in kidney stone formers with and without heart disease.

OBJECTIVE: Kidney stone disease seems to be associated with an increased risk of incident cardiovascular outcomes; the aim of this study is to identify differences in 24-h urine excretory profiles and stone composition among stone formers with and without cardiovascular disease (CVD). METHODS: Data from patients attending the Department of Renal Medicine's metabolic stone clinic from 1995 to 2012 were reviewed. The sample was divided according to the presence or absence of CVD (myocardial infarction, angina, coronary revascularization, or surgery for calcified heart valves). Univariable and multivariable regression models, adjusted for age, sex, BMI, hypertension, diabetes, eGFR, plasma bicarbonate and potential renal acid load of foods were used to investigate differences across groups. RESULTS: 1826 patients had available data for 24-h urine analysis. Among these, 108 (5.9%) had a history of CVD. Those with CVD were older, have higher prevalence of hypertension and diabetes and lower eGFR. Univariable analysis showed that patients with CVD had significantly lower 24-h urinary excretions for citrate (2.4 vs 2.6 mmol/24 h, p = 0.04), magnesium (3.9 vs 4.2 mmol/24 h, p = 0.03) and urinary pH (6.1 vs 6.2, p = 0.02). After adjustment for confounders, differences in urinary citrate and magnesium excretions remained significant. No differences in the probability of stone formation or stone compositions were found. CONCLUSIONS: Stone formers with CVD have lower renal alkali excretion, possibly suggesting higher acid retention in stone formers with cardiovascular comorbidities. Randomized clinical trials including medications and a controlled diet design are needed to confirm the results presented here.

Cystinuria: an update on pathophysiology, genetics, and clinical management.

Cystinuria is the most common genetic cause of nephrolithiasis in children. It is considered a heritable aminoaciduria as the genetic defect affects the reabsorption of cystine and three other amino acids (ornithine, lysine, and arginine) in the renal proximal tubule. Patients affected by this condition have elevated excretion of cystine in the urine, and because of this amino acid's low solubility at normal urine pH, patients tend to form cystine calculi. To date, two genes have been identified as disease-causative: SLC3A1 and SLC7A9, encoding for the two subunits of the heterodimeric transporter. The clinical features of this condition are solely related to nephrolithiasis. The diagnosis is usually made during infancy or adolescence, but cases of late diagnosis are common. The goal of therapy is to reduce excretion and increase the solubility of cystine, through both modifications of dietary habits and pharmacological treatment. However, therapeutic interventions are not always sufficient, and patients often have to undergo several surgical procedures during their lives to treat recurrent nephrolithiasis. The goal of this literature review is to synthesize the available evidence on diagnosis and management of patients affected by cystinuria in order to provide physicians with a practical tool that can be used in daily clinical practice. This review also aims to shed some light on new therapy directions with the aim of ameliorating kidney outcomes while improving adherence to treatment and quality of life of cystinuric patients.

Renal Involvement in Hereditary Transthyretin Amyloidosis: An Italian Single-Centre Experience.

OBJECTIVE: Hereditary transthyretin amyloidosis (ATTRv) represents a diagnostic challenge considering the great variability of clinical presentation and multiorgan involvement. In the present study, we report the prevalence of kidney involvement and kidney function over time in a cohort of ATTRv patients with different transthyretin gene mutations. PATIENTS AND METHODS: For this study, we systematically collected data from all patients with a diagnosis of ATTRv followed at the Neurology Unit of Fondazione Policlinico Universitario A. Gemelli IRCCS. Kidney involvement was defined as presence of estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 obtained with CKD-EPI equation, abnormal urinary protein excretion (UPE) (>150 mg/24 h) and/or albuminuria > 30 mg/24 h (or mg/g creatinine). The analysis included data from 46 patients with 122 measurements of serum creatinine. RESULTS: Among the 46 patients included in the analysis, kidney involvement was present in 37%, with 15% showing reduced eGFR and 22% abnormal UPE (63% of patients with available UPE data). No single predictor was associated with either eGFR values or its slope over time. CONCLUSIONS: Kidney involvement is quite common in patients with ATTRv regardless of the underlying genetic variant. In particular, abnormal UPE appears to be a common feature of the disease.

Biological Effects of XyloCore, a Glucose Sparing PD Solution, on Mesothelial Cells: Focus on Mesothelial-Mesenchymal Transition, Inflammation and Angiogenesis.

Glucose-based solutions remain the most used osmotic agents in peritoneal dialysis (PD), but unavoidably they contribute to the loss of peritoneal filtration capacity. Here, we evaluated at a molecular level the effects of XyloCore, a new PD solution with a low glucose content, in mesothelial and endothelial cells. Cell viability, integrity of mesothelial and endothelial cell membrane, activation of mesothelial and endothelial to mesenchymal transition programs, inflammation, and angiogenesis were evaluated by several techniques. Results showed that XyloCore preserves mesothelial and endothelial cell viability and membrane integrity. Moreover XyloCore, unlike glucose-based solutions, does not exert pro-fibrotic, -inflammatory, and -angiogenic effects. Overall, the in vitro evidence suggests that XyloCore could represent a potential biocompatible solution promising better outcomes in clinical practice.

The European Rare Kidney Disease Registry (ERKReg): objectives, design and initial results.

BACKGROUND: The European Rare Kidney Disease Reference Network (ERKNet) recently established ERKReg, a Web-based registry for all patients with rare kidney diseases. The main objectives of this core registry are to generate epidemiological information, identify current patient cohort for clinical research, explore diagnostic and therapeutic management practices, and monitor treatment performance and patient's outcomes. The registry has a modular design that allows to integrate comprehensive disease-specific registries as extensions to the core database. The diagnosis (Orphacode) and diagnostic information (clinical, imaging, histopathological, biochemical, immunological and genetic) are recorded. Anthropometric, kidney function, and disease-specific management and outcome items informing a set of 61 key performance indicators (KPIs) are obtained annually. Data quality is ensured by automated plausibility checks upon data entry and regular offline database checks prompting queries. Centre KPI statistics and benchmarking are calculated automatically. RESULTS: Within the first 24 months since its launch, 7607 patients were enrolled to the registry at 45 pediatric and 12 specialized adult nephrology units from 21 countries. A kidney disease diagnosis had been established in 97.1% of these patients at time of enrolment. While 199 individual disease entities were reported by Orphacode, 50% of the cohort could be classified with 11, 80% with 43 and 95% with 92 codes. Two kidney diagnoses were assigned in 6.5% of patients; 5.9% suffered from syndromic disease. Whereas glomerulopathies (54.8%) and ciliopathies including autosomal dominant polycystic kidney disease (ADPKD) (31.5%) were the predominant disease groups among adults, the pediatric disease spectrum encompassed congenital anomalies of the kidney and urinary tract (CAKUT) (33.7%), glomerulopathies (30.7%), ciliopathies (14.0%), tubulopathies (9.2%), thrombotic microangiopathies (5.6%), and metabolic nephropathies (4.1%). Genetically confirmed diagnoses were reported in 24% of all pediatric and 12% adult patients, whereas glomerulopathies had been confirmed by kidney biopsy in 80.4% adult versus 38.5% pediatric glomerulopathy cases. CONCLUSIONS: ERKReg is a rapidly growing source of epidemiological information and patient cohorts for clinical research, and an innovative tool to monitor management quality and patient outcomes.

Pancreaticoduodenectomy model demonstrates a fundamental role of dysfunctional ß cells in predicting diabetes.

BACKGROUNDThe appearance of hyperglycemia is due to insulin resistance, functional deficits in the secretion of insulin, and a reduction of ß cell mass. There is a long-standing debate as to the relative contribution of these factors to clinically manifesting ß cell dysfunction. The aim of this study was to verify the acute effect of one of these factors, the reduction of ß cell mass, on the subsequent development of hyperglycemia.METHODSTo pursue this aim, nondiabetic patients, scheduled for identical pancreaticoduodenectomy surgery, underwent oral glucose tolerance tests (OGTT) and hyperglycemic clamp (HC) procedures, followed by arginine stimulation before and after surgery. Based on postsurgery OGTT, subjects were divided into 3 groups depending on glucose tolerance: normal glucose tolerance (post-NGT), impaired glucose tolerance (post-IGT), or having diabetes mellitus (post-DM).RESULTSAt baseline, the 3 groups showed similar fasting glucose and insulin levels; however, examining the various parameters, we found that reduced first-phase insulin secretion, reduced glucose sensitivity, and rate sensitivity were predictors of eventual postsurgery development of IGT and diabetes.CONCLUSIONDespite comparable functional mass and fasting glucose and insulin levels at baseline and the very same 50% mass reduction, only reduced first-phase insulin secretion and glucose sensitivity predicted the appearance of hyperglycemia. These functional alterations could be pivotal to the pathogenesis of type 2 diabetes (T2DM).TRIAL REGISTRATIONClinicalTrials.gov NCT02175459.FUNDINGUniversità Cattolica del Sacro Cuore; Italian Ministry of Education, University and Research; European Foundation for the Study of Diabetes.

Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) detection as a rapid and convenient screening test for cystinuria.

BACKGROUND: Cystinuria is an inborn congenital disorder characterised by a defective cystine metabolism resulting in the formation of cystine stones. The Brand's test, used for diagnosis, requires dangerous substances, so has been replaced with high-performance liquid chromatography with fluorimetric detection (HPLC-FL). However, this technique requires the use of complex equipment. Infrared spectroscopy, universally used for stone analysis, recently was employed to detect insoluble cystine in urine. The aim of this study is to evaluate Infrared Spectroscopy combined with chemometric analysis as screening method to identify those patients requiring confirmation by HPLC-FL analysis. METHODS: We examined 24 h urine specimens from 57 patients. The quantitative analysis was performed by HPLC-FL. The infrared spectroscopic urine sediment analysis was performed with an ATR accessory (ATR-FTIR). Urine is centrifuged, the supernatant is discarded, and the sediment is dried on to the ATR prism surface. Statistical analysis was performed using a custom-made software developed in MATLAB environment. RESULTS: The HPLC-FL determination showed a normal excretion of cystine in 49 samples and an abnormal excretion in the remaining 8 samples. The ATR-FTIR analysis combined with a statistical approach gives a sensitivity of 1.0 and a specificity of 0.82 were obtained. CONCLUSIONS: The introduction of the ATR-FTIR technique in our clinical laboratory setting may reduce time and cost analysis for diagnosis of cystinuria.