Faculty Bibliography

Cystinuria, a genetic disorder of cystine transport, is characterized by excessive excretion of cystine in the urine and recurrent cystine stones in the kidneys and, to a lesser extent, in the bladder. Males generally are more severely affected than females. The disorder may lead to chronic kidney disease in many patients. The cystine transporter (b^0,+) is a heterodimer consisting of the rBAT (encoded by SLC3A1) and b^0,+AT (encoded by SLC7A9) subunits joined by a disulfide bridge. The molecular basis of cystinuria is known in great detail, and this information is now being used to define genotype-phenotype correlations. Current treatments for cystinuria include increased fluid intake to increase cystine solubility and the administration of thiol drugs for more severe cases. These drugs, however, have poor patient compliance due to adverse effects. Thus, there is a need to reduce or eliminate the risks associated with therapy for cystinuria. Four mouse models for cystinuria have been described and these models provide a resource for evaluating the safety and efficacy of new therapies for cystinuria. We are evaluating a new approach for the treatment of cystine stones based on the inhibition of cystine crystal growth by cystine analogs. Our ongoing studies indicate that cystine diamides are effective in preventing cystine stone formation in the Slc3a1 knockout mouse model for cystinuria. In addition to crystal growth, crystal aggregation is required for stone formation. Male and female mice with cystinuria have comparable levels of crystalluria, but very few female mice form stones. The identification of factors that inhibit cystine crystal aggregation in female mice may provide insight into the gender difference in disease severity in patients with cystinuria.

PURPOSE/OBJECTIVE:The purpose of the study was to assess the differences in the concentration and function of urinary proteins between patients with cystine stones (CYS) and healthy controls (HC). We postulated that CYS and HC groups would demonstrate different proteomic profiles. METHODS:A pilot study was performed comparing urinary proteomes of 10 patients with CYS and 10 age- and gender-matched HC, using liquid chromatography-mass spectrometry. Proteins which met the selection criteria (i) ≥ 2 unique peptide identifications; (ii) ≥ twofold difference in protein abundance; and (iii) ≤ 0.05 p value for the Fisher's Exact Test were analyzed using Gene Ontology classifications. RESULTS:Of the 2097 proteins identified by proteomic analysis, 398 proteins were significantly different between CYS and HC. Of those, 191 were involved in transport processes and 61 in inflammatory responses. The majority were vesicle-mediated transport proteins (78.5%), and 1/3 of them were down-regulated; of those, 12 proteins were involved in endosomal transport (including 6 charged multivesicular body proteins (CHMP) and 3 vacuolar sorting-associated proteins) and 9 in transmembrane transport. Myosin-2 and two actin-related proteins were significantly up-regulated in the vesicle-mediated transport group. CONCLUSION/CONCLUSIONS:We provide proteomic evidence of impaired endocytosis, dysregulation of actin and myosin cytoskeleton, and inflammation in CYS. Endosomal transport proteins were down-regulated mainly through defective CHMP. These findings may contribute to further understanding of the pathogenesis of CYS, potentially affecting its management.

Objective/UNASSIGNED:Lesinurad (LESU) is a selective urate reabsorption inhibitor approved at 200 mg daily for use with a xanthine oxidase inhibitor (XOI) to treat hyperuricaemia in gout patients failing to achieve target serum urate on XOI. The aim of the study was to investigate the long-term safety of LESU + XOI therapy. Methods/UNASSIGNED:Safety data were pooled from three 12-month phase III (core) trials evaluating LESU 200 and 400 mg/day combined with an XOI (LESU200+XOI and LESU400+XOI), and two 12-month extension studies using descriptive statistics. To adjust for treatment duration, treatment-emergent adverse events (TEAEs) were expressed as exposure-adjusted incidence rates (patients with events per 100 person-years). Results/UNASSIGNED:In the core studies, exposure-adjusted incidence rates for total and total renal-related TEAEs were comparable for XOI alone and LESU200+XOI but higher with LESU400+XOI. Exposure-adjusted incidence rates for serum creatinine (sCr) elevations ⩾1.5×baseline were 2.9, 7.3 and 18.7, respectively. Resolution (sCr ⩽1.2×baseline) occurred in 75-90% of all events, with 66-75% occurring without any study medication interruption. Major adverse cardiovascular events were 3, 4 and 9 with XOI, LESU200+XOI and LESU400+XOI, respectively. Longer exposure in core+extension studies did not increase rates for any safety signals. Conclusion/UNASSIGNED:At the approved dose of 200 mg once-daily combined with an XOI, LESU did not increase renal, cardiovascular or other adverse events compared with XOI alone, except for sCr elevations. With extended exposure in the core+extension studies, the safety profile was consistent with that observed in the core studies, and no new safety concerns were identified.

Protein-energy wasting (PEW) is a major diet-related complication in hemodialysis (HD) patients. Nutrient-based dietary guidelines emphasize animal-based protein foods for preventing and managing PEW in HD patients. Although dietary protein intake is important for protein anabolism, other dietary factors contribute to PEW. In this article, we examine the diet-related etiologies of PEW in HD patients, and discuss how they may be affected differently by animal- and plant-based protein foods. In general, animal foods are superior sources of protein, but may contribute more to metabolic derangements that cause PEW. Given the potential mixed effects of animal-based protein foods on PEW, human research studies are needed to determine the impact of liberalizing the diet to allow plant-based protein foods on protein status.

IMPORTANCE:The World Trade Center (WTC) attacks on September 11, 2001, created an unprecedented environmental exposure to known and suspected carcinogens suggested to increase the risk of multiple myeloma. Multiple myeloma is consistently preceded by the precursor states of monoclonal gammopathy of undetermined significance (MGUS) and light-chain MGUS, detectable in peripheral blood. OBJECTIVE:To characterize WTC-exposed firefighters with a diagnosis of multiple myeloma and to conduct a screening study for MGUS and light-chain MGUS. DESIGN, SETTING, AND PARTICIPANTS:Case series of multiple myeloma in firefighters diagnosed between September 11, 2001, and July 1, 2017, together with a seroprevalence study of MGUS in serum samples collected from Fire Department of the City of New York (FDNY) firefighters between December 2013 and October 2015. Participants included all WTC-exposed FDNY white, male firefighters with a confirmed physician diagnosis of multiple myeloma (n = 16) and WTC-exposed FDNY white male firefighters older than 50 years with available serum samples (n = 781). EXPOSURES:WTC exposure defined as rescue and/or recovery work at the WTC site between September 11, 2001, and July 25, 2002. MAIN OUTCOMES AND MEASURES:Multiple myeloma case information, and age-adjusted and age-specific prevalence rates for overall MGUS (ie, MGUS and light-chain MGUS), MGUS, and light-chain MGUS. RESULTS:Sixteen WTC-exposed white male firefighters received a diagnosis of multiple myeloma after September 11, 2001; median age at diagnosis was 57 years (interquartile range, 50-68 years). Serum/urine monoclonal protein isotype/free light-chain data were available for 14 cases; 7 (50%) had light-chain multiple myeloma. In a subset of 7 patients, myeloma cells were assessed for CD20 expression; 5 (71%) were CD20 positive. In the screening study, we assayed peripheral blood from 781 WTC-exposed firefighters. The age-standardized prevalence rate of MGUS and light-chain MGUS combined was 7.63 per 100 persons (95% CI, 5.45-9.81), 1.8-fold higher than rates from the Olmsted County, Minnesota, white male reference population (relative rate, 1.76; 95% CI, 1.34-2.29). The age-standardized prevalence rate of light-chain MGUS was more than 3-fold higher than in the same reference population (relative rate, 3.13; 95% CI, 1.99-4.93). CONCLUSIONS AND RELEVANCE:Environmental exposure to the WTC disaster site is associated with myeloma precursor disease (MGUS and light-chain MGUS) and may be a risk factor for the development of multiple myeloma at an earlier age, particularly the light-chain subtype.

Background: Cystinuria is an inherited kidney stone disorder caused by mutations to the SLC3A1 and SLC7A9 genes. While most cases are due to biallelic mutations to either gene, monoallelic and digenic families have been described, with overall considerable disease variability. Nevertheless, clear genotype/phenotype correlations have not been described to date.
Method(s): A next generation sequencing (NGS) panel consisting of 90 known and candidate kidney stone genes was developed and validated. A total of 49 unrelated, genetically unscreened individuals with a clinical diagnosis of cystinuria were analyzed using this panel. Preliminary correlations with phenotype were made with the genic groups.
Result(s): The baseline mean (SD) characteristics of the cohort were: age at diagnosis = 19.6y (12.5), number of stones = 5.8 (6.6), cystine excretion = 939.9mg (323.6), eGFR = 82.1ml/min/1.73m² (24.5), with age at last follow up = 43.8y (14). A total of 34 patients (69.4%) had biallelic SLC3A1 and 11 (22.4%) biallelic SLC7A9 mutations. One SLC3A1 and two SLC7A9 cases had a single detected mutation, and one case had no mutations detected. Large rearrangements, detected by LOG2 ratio analysis of the sequence data and confirmed by Multiplex Ligation-dependent Probe Amplification (MLPA), accounted for 31.9% of all SLC3A1 mutations, mainly the common ex5-9 duplication. Other common mutations were the SLC3A1 missense change p.Met467Thr (21.7% alleles) and the nonsense mutation p.Arg270* (18.8%), while for SLC7A9 the missense mutation p.Gly105Arg accounted for 29.2% of pathogenic alleles. Ten novel mutations were identified for each gene. The only detected correlation with genotype was with baseline mean stone number, SLC3A1 = 7.1 (7.1), SLC7A9 = 2.0 (2.1; p=0.05) in this cohort.
Conclusion(s): This analysis shows the utility of a panel-based NGS approach in cystinuria populations and more broadly in patients with suspected monogenic stone disease. Other genetic and/or environmental factors likely also contribute to the observed phenotypic variability

Background: Kidney stones represent a disease of worldwide prevalence with significant public health implications. About 60-80% of stones are composed of calcium oxalate (CaOx); hyperoxaluria is a major risk factor for CaOx stones. Oxalate is an endproduct of mammalian digestion and as with urea, must be excreted. We obtain oxalate from diet, or from endogenous production. Certain intestinal bacteria have the ability to degrade oxalate, protecting against oxalate nephropathy, including nephrolithiasis. To understand the role of the gut microbiome in oxalate metabolism, we compared conventional mice with germ-free mice (that lack a microbiota). In addition to the stress of endogenous oxalate production, we challenged groups with dietary and metabolic (via hydroxyproline (Hyp) supplementation) oxalate loads.
Method(s): Conventional (CO) and germ-free (GF) mice were fed normal chow diets supplemented with either 1% Oxalate (Ox), 1% Hydroxyproline (Hyp) or were unsupplemented (NC) for 6 weeks (n=3-4/mice group). After 6 weeks, we obtained 48-hour urine collections for measurement of the oxalate/creatinine ratio (Uox/cr).
Result(s): In CO mice, Uox/cr increased with the Ox diet compared with NC (0.57 + 0.17 vs 0.16 + 0.05, p= 0.03 by Student's t test), but not with the Hyp diet (0.14 +0.03 vs 0.16 +0.05, p=ns). However, in germ-free mice, both dietary Hyp and Ox led to increased Uox/ cr compared to NC diet (0.50 +/- 0.04, 0.85 +/- 0.11, vs. 0.31+/- 0.06, p<0.05 by ANOVA, respectively). Uox/Cr was lower in CO mice than GF mice when receiving Hyp (p=0.01, by Student's t test), Ox (p=0.06), and NC diets (0.06).
Conclusion(s): In conclusion, oxalate excretion was higher in the germ-free than in the conventional mice under all three dietary conditions (Ox, Hyp, NC), providing direct evidence that the normal gut microbiome plays a protective (symbiotic) role in oxalate metabolism. With the metabolic stress of the Hyp diet, the CO mice but not the germfree mice could compensate. Since mice are not colonized with O. formigenes, this work indicates that other members of their microbiota have the functional capacity to alter oxalate metabolism

Background: CSF have lower HRQoL compared to US Standard Population. We have shown previously that HRQoL results need to be controlled for the last stone event and comorbidities. We now show the first longitudinal HRQoL domain profiles for baseline and two yearly follow-ups.
Method(s): CSF were enrolled from the RKSC registry. HRQoL was measured with the generic non-disease specific SF-36v2. Results were calculated as norm-based scores (NBS) based on US Standard Population (Domain score mean = 50). We selected 3 stone frequency groups (SFG): low (stone-free during observation period), medium (minimum of one stone event between 31-365 days) and high (stone event always present within 30 days of the survey), and compared the groups' HRQoL at baseline and second follow-up.
Result(s): We scored 386 surveys. 78 participants (32 males and 46 females) were compared at baseline and 2 follow-up assessments. Mean age was 45 years (male 44/ female 46). Repeated measure ANOVA showed no difference within each SFG over time (Fig 1). However, domain scores were significantly different between SFG's (p<0.05) at each time point, with low>medium>high stone frequency. Whether surgical intervention was required, and type, were not predictors of HRQoL outcomes. Better HRQoL tracked with lower cystine excretion per liter on 24h urine collections; lower cystine capacity and higher citrate doses were underpowered (NS).
Conclusion(s): CSF with high stone event rates experience worse HRQoL over time, while CSF with no stone events achieved better HRQoL than US standard. Clinnical data suggest that the high SFG is undertreated

Background: Behavioral methods enhance the effectiveness of lifestyle interventions, but are often resource intensive. Although mobile health (mHealth) technology can help create lower input interventions, their feasibility, acceptability and efficacy have not been adequately evaluated in hemodialysis (HD) patients.
Method(s): Maintenance HD patients with persistent hyperphosphatemia (n=40) were randomized to receive: (1) educational (Edu) videos (EDU), (2) Edu + mobile selfmonitoring (SM) with MyNetDiary (MON), or (3) Edu + SM + social cognitive theory (SCT)-based behavioral counseling videos (SCT) over a 12-week period with videos for each group delivered using iPads. Serum phosphorus concentrations (sPO4) were measured at baseline, 12 and 24 weeks, and a 5-point Likert scale survey on the mHealth technology was completed at 24-weeks. Two participants in the EDU group with no follow-up sPO4 measurements were excluded; missing sPO4 measurements at 12-and 24-weeks were imputed by carrying forward the most recent sPO4 values.
Result(s): At the end of the intervention phase (12-weeks), there was a non-significant trend towards greater decreases in sPO4 in the MON (-0.5+/-1.6 mg/dL, p=0.32) and SCT (-0.3+/-2.1 mg/dL, p=0.56) groups compared to the EDU group (+0.2+/-1.4 mg/dL), but these differences had mostly disappeared by the end of the monitoring phase (24-weeks) (EDU +0.1+/-1.2 mg/dL, MON -0.1+/-1.9 mg/dL, SCT -0.1+/-2.1 mg/dL). Most participants agreed or strongly agreed that the iPads were convenient (64%), and SM helped them stay motivated (68%), take binders (61%), and limit phosphorus intake (68%). Relatively few participants reported that they agreed or strongly agreed that they sometimes "got lost" maneuvering the iPad programs (24%), felt that SM wasn't worthwhile (16%), or would have preferred face-to-face meetings offsite (4%).
Conclusion(s): Many HD patients are willing, able and report benefits of engaging in technology-supported behavioral interventions involving SM and SCT. Although these programs are easy to disseminate with limited resources once developed, any benefits for phosphorus management in HD patients may last only as long as the intervention is active

Background: About 60-80% of kidney stones are composed of calcium oxalate (CaOx); idiopathic CaOx kidney stones (CaOPx), primary hyperoxaluria (PH) and enteric hyperoxaluria (EH) are diseases predisposing to stones. Oxalobacter formigenes (Oxf) is a human gut commensal that depends on oxalate for its carbon and energy, and may be protective against CaOx stones. We hypothesize that the microbiome community structure differs between patients with CaOx, PH, EH and normal subjects (NS). We also expect that Oxf isolates from PH patients will result in further reduction in urinary oxalate when compared to Oxf reference strain CC13, in a germ-free (GF) mouse model.
Method(s): We collected fecal specimens from 34 subjects (mean age: 39.1 +/- 11.9 years) with PH (n=6), CaOPx (n=10), EH (n= 5) and NS (n=13) in a cross-sectional observational study, and tested fecal samples from the groups by: 1)16S rRNA sequencing to determine the microbiome community structure, 2)PCR and qPCR for Oxf colonization and, 3) culturing in high oxalate selective media for indication of Oxf presence and subsequent isolation. We isolated Oxf from 4 PH (Oxf PH) subjects. We gavaged a growing culture of PH Oxf (n=6), Oxf reference strain CC13 (Oxf CC13) (n=5), and sham (n=6) into adult C5B6 GF mice, observing them for 4 weeks. We collected urine from mice for 48 hours before sacrifice to be tested for oxalate and creatinine (Uox/cr).
Result(s): Oxf was detected in 6 (46%) of 13 NS, 1 (10%) of 10 CaOPx, 0 (0%)of 4 EH, and 5 (83%) of 6 PH. Microbiome analysis revealed that the 4 groups differed in beta diversity, based on Bray-Curtis dissimilarity (p=0.08). Alpha diversity analysis trended toward lower Shannon and phylogenetic diversity index in the CaOPx and EH subjects compared to PH and NS. Introducing the PH Oxf to GF mice led to lower Uox/cr than in uninoculated controls (0.68 +/- 0.14, and 2.26 +/-0.49, respectively, p=0.04 by Mann-Whitney U test), but not significantly different from the Oxf CC13-innoculated mice (0.68 +/- 0.14, and 0.91 +/-0.24, respectively, p=0.26 by Mann-Whitney U test).
Conclusion(s): These studies provide evidence of differences in Oxf colonization rates and in microbiome composition in patients with CaOx stones and show the functional capacity of a PH Oxf strain to ameliorate hyperoxaluria. Studies to expand these patient groups are on-going