A multicenter study to evaluate pain characteristics in osteogenesis imperfecta.

The objective was to describe pain characteristics and treatments used in individuals with varying severity of osteogenesis imperfecta (OI) and investigate pain-associated variables. This work was derived from a multicenter, longitudinal, observational, natural history study of OI conducted at 12 clinical sites of the NIH Rare Diseases Clinical Research Network's Brittle Bone Disorders Consortium. Children and adults with a clinical, biochemical, or molecular diagnosis of OI were enrolled in the study. We did a cross-sectional analysis of chronic pain prevalence, characteristics, and treatments used for pain relief and longitudinal analysis to find the predictors of chronic pain. We included 861 individuals with OI, in 41.8% chronic pain was present, with similar frequency across OI types. Back pain was the most frequent location. Nonsteroidal anti-inflammatory drugs followed by bisphosphonates were the most common treatment used. Participants with chronic pain missed more days from school or work/year and performed worse in all mobility metrics than participants without chronic pain. The variables more significantly associated with chronic pain were age, sex, positive history of rodding surgery, scoliosis, other medical problems, assistive devices, lower standardized height, and higher body mass index. The predictors of chronic pain for all OI types were age, use of a wheelchair, and the number of fractures/year. Chronic pain is prevalent in OI across all OI types, affects mobility, and interferes with participation. Multiple covariates were associated with chronic pain.

Biomarkers for liver disease in urea cycle disorders.

BACKGROUND: Urea cycle disorders (UCDs) are among the most common inborn errors of liver metabolism. As therapies for hyperammonemia associated with urea cycle dysfunction have improved, chronic complications, such as liver disease, have become increasingly apparent in individuals with UCDs. Liver disease in UCDs may be associated with hepatic inflammation, hepatic fibrosis, portal hypertension, liver cancer and even liver failure. However, except for monitoring serum aminotransferases, there are no clear guidelines for screening and/or monitoring individuals with UCDs for liver disease. Thus, we systematically evaluated the potential utility of several non-invasive biomarkers for liver fibrosis in UCDs. METHODS: We evaluated grey-scale ultrasonography, liver stiffness obtained from shear wave elastography (SWE), and various serum biomarkers for hepatic fibrosis and necroinflammation, in a cohort of 28 children and adults with various UCDs. RESULTS: Overall, we demonstrate a high burden of liver disease in our participants with 46% of participants having abnormal grey-scale ultrasound pattern of the liver parenchyma, and 52% of individuals having increased liver stiffness. The analysis of serum biomarkers revealed that 32% of participants had elevated FibroTest™ score, a marker for hepatic fibrosis, and 25% of participants had increased ActiTest™ score, a marker for necroinflammation. Interestingly, liver stiffness did not correlate with ultrasound appearance or FibroTest™. CONCLUSION: Overall, our results demonstrate the high overall burden of liver disease in UCDs and highlights the need for further studies exploring new tools for identifying and monitoring individuals with UCDs who are at risk for this complication. TRIAL REGISTRATION: This study has been registered in ClinicalTrials.gov (NCT03721367).

Acid-Induced Downregulation of ASS1 Contributes to the Maintenance of Intracellular pH in Cancer.

Downregulation of the urea cycle enzyme argininosuccinate synthase (ASS1) by either promoter methylation or by HIF1α is associated with increased metastasis and poor prognosis in multiple cancers. We have previously shown that in normoxic conditions, ASS1 downregulation facilitates cancer cell proliferation by increasing aspartate availability for pyrimidine synthesis by the enzyme complex CAD. Here we report that in hypoxia, ASS1 expression in cancerous cells is downregulated further by HIF1α-mediated induction of miR-224-5p, making the cells more invasive and dependent on upstream substrates of ASS1 for survival. ASS1 was downregulated under acidic conditions, and ASS1-depleted cancer cells maintained a higher intracellular pH (pHi), depended less on extracellular glutamine, and displayed higher glutathione levels. Depletion of substrates of urea cycle enzymes in ASS1-deficient cancers decreased cancer cell survival. Thus, ASS1 levels in cancer are differentially regulated in various environmental conditions to metabolically benefit cancer progression. Understanding these alterations may help uncover specific context-dependent cancer vulnerabilities that may be targeted for therapeutic purposes. SIGNIFICANCE: Cancer cells in an acidic or hypoxic environment downregulate the expression of the urea cycle enzyme ASS1, which provides them with a redox and pH advantage, resulting in better survival.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/3/518/F1.large.jpg.

Urea Cycle Dysregulation Generates Clinically Relevant Genomic and Biochemical Signatures.

The urea cycle (UC) is the main pathway by which mammals dispose of waste nitrogen. We find that specific alterations in the expression of most UC enzymes occur in many tumors, leading to a general metabolic hallmark termed "UC dysregulation" (UCD). UCD elicits nitrogen diversion toward carbamoyl-phosphate synthetase2, aspartate transcarbamylase, and dihydrooratase (CAD) activation and enhances pyrimidine synthesis, resulting in detectable changes in nitrogen metabolites in both patient tumors and their bio-fluids. The accompanying excess of pyrimidine versus purine nucleotides results in a genomic signature consisting of transversion mutations at the DNA, RNA, and protein levels. This mutational bias is associated with increased numbers of hydrophobic tumor antigens and a better response to immune checkpoint inhibitors independent of mutational load. Taken together, our findings demonstrate that UCD is a common feature of tumors that profoundly affects carcinogenesis, mutagenesis, and immunotherapy response.

Induction of Nitric-Oxide Metabolism in Enterocytes Alleviates Colitis and Inflammation-Associated Colon Cancer.

Nitric oxide (NO) plays an established role in numerous physiological and pathological processes, but the specific cellular sources of NO in disease pathogenesis remain unclear, preventing the implementation of NO-related therapy. Argininosuccinate lyase (ASL) is the only enzyme able to produce arginine, the substrate for NO generation by nitric oxide synthase (NOS) isoforms. Here, we generated cell-specific conditional ASL knockout mice in combination with genetic and chemical colitis models. We demonstrate that NO derived from enterocytes alleviates colitis by decreasing macrophage infiltration and tissue damage, whereas immune cell-derived NO is associated with macrophage activation, resulting in increased severity of inflammation. We find that induction of endogenous NO production by enterocytes with supplements that upregulate ASL expression and complement its substrates results in improved epithelial integrity and alleviation of colitis and of inflammation-associated colon cancer.

Neuroimaging findings of extensive sphenoethmoidal dysplasia in NF1.

Whereas isolated sphenoid wing dysplasia (SWD) is a well-known clinical feature in neurofibromatosis 1 (NF1), extensive cranial defects involving multiple bones have been rarely reported in this disorder. In this report, we describe the clinical course of a 20-year-old male with NF1 and an extensive cranial bone dysplasia. The large sphenoethmoidal defect was associated with transethmoidal and orbital cephalocele as well as inferolateral herniation of the frontal lobe. In spite of the large defect, the individual did not have any symptoms or complications resulting from the osteopathy. We review the current knowledge of the pathogenesis and management of cranial bone dysplasia in NF1.

Generalized metabolic bone disease and fracture risk in Rothmund-Thomson syndrome.

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder characterized by poikiloderma, small stature, sparse hair, skeletal abnormalities, increased risk of osteosarcoma, and decreased bone mass. To date, there has not been a comprehensive evaluation of the prevalence and extent of metabolic bone disease in RTS. Furthermore, the mechanisms that result in this phenotype are largely unknown. In this report, we provide a detailed evaluation of 29 individuals with RTS with respect to their metabolic bone status including bone mineral density, calcium kinetics studies, and markers of bone remodeling. We show that individuals with RTS have decreased areal bone mineral density. Additionally, we demonstrate that the presence of pathogenic variants in RECQL4 and low bone mineral density correlate with the history of increased risk of fractures. Using a RECQL4-deficient mouse model that recapitulates skeletal abnormalities seen in individuals with RTS, we demonstrate that generalized skeletal involvement is likely due to decreased osteogenesis. Our findings are clinically relevant as they may help in the risk stratification of patients with RTS and also in the identification of individuals who may benefit from additional surveillance and management of metabolic bone disease.

A metabolic link between the urea cycle and cancer cell proliferation.

Clinical observations in citrullinemia type I, an inborn error of metabolism, led us to explore the benefits of somatic ASS1 silencing in cancer. We found that downregulation of ASS1 results in preferential utilization of its substrate, aspartate, for pyrimidine synthesis to support cell proliferation. Reducing aspartate availability for pyrimidine synthesis restricted cancerous proliferation.

Human recombinant arginase enzyme reduces plasma arginine in mouse models of arginase deficiency.

Arginase deficiency is caused by deficiency of arginase 1 (ARG1), a urea cycle enzyme that converts arginine to ornithine. Clinical features of arginase deficiency include elevated plasma arginine levels, spastic diplegia, intellectual disability, seizures and growth deficiency. Unlike other urea cycle disorders, recurrent hyperammonemia is typically less severe in this disorder. Normalization of plasma arginine levels is the consensus treatment goal, because elevations of arginine and its metabolites are suspected to contribute to the neurologic features. Using data from patients enrolled in a natural history study conducted by the Urea Cycle Disorders Consortium, we found that 97% of plasma arginine levels in subjects with arginase deficiency were above the normal range despite conventional treatment. Recently, arginine-degrading enzymes have been used to deplete arginine as a therapeutic strategy in cancer. We tested whether one of these enzymes, a pegylated human recombinant arginase 1 (AEB1102), reduces plasma arginine in murine models of arginase deficiency. In neonatal and adult mice with arginase deficiency, AEB1102 reduced the plasma arginine after single and repeated doses. However, survival did not improve likely, because this pegylated enzyme does not enter hepatocytes and does not improve hyperammonemia that accounts for lethality. Although murine models required dosing every 48 h, studies in cynomolgus monkeys indicate that less frequent dosing may be possible in patients. Given that elevated plasma arginine rather than hyperammonemia is the major treatment challenge, we propose that AEB1102 may have therapeutic potential as an arginine-reducing agent in patients with arginase deficiency.

Self-reported treatment-associated symptoms among patients with urea cycle disorders participating in glycerol phenylbutyrate clinical trials.

BACKGROUND: Health care outcomes have been increasingly assessed through health-related quality of life (HRQoL) measures. While the introduction of nitrogen-scavenging medications has improved survival in patients with urea cycle disorders (UCDs), they are often associated with side effects that may affect patient compliance and outcomes. METHODS: Symptoms commonly associated with nitrogen-scavenging medications were evaluated in 100 adult and pediatric participants using a non-validated UCD-specific questionnaire. Patients or their caregivers responded to a pre-defined list of symptoms known to be associated with the use of these medications. Responses were collected at baseline (while patients were receiving sodium phenylbutyrate [NaPBA]) and during treatment with glycerol phenylbutyrate (GPB). RESULTS: After 3 months of GPB dosing, there were significant reductions in the proportion of patients with treatment-associated symptoms (69% vs. 46%; p<0.0001), the number of symptoms per patient (2.5 vs. 1.1; p<0.0001), and frequency of the more commonly reported individual symptoms such as body odor, abdominal pain, nausea, burning sensation in mouth, vomiting, and heartburn (p<0.05). The reduction in symptoms was observed in both pediatric and adult patients. The presence or absence of symptoms or change in severity did not correlate with plasma ammonia levels or NaPBA dose. CONCLUSIONS: The reduction in symptoms following 3 months of open-label GPB dosing was similar in pediatric and adult patients and may be related to chemical structure and intrinsic characteristics of the product rather than its effect on ammonia control.

Adult presentation of X-linked Conradi-Hünermann-Happle syndrome.

Conradi-Hünermann-Happle syndrome, or X-linked dominant chondrodysplasia punctata type 2 (CDPX2), is a genodermatosis caused by mutations in EBP. While typically lethal in males, females with CDPX2 generally manifest by infancy or childhood with variable features including congenital ichthyosiform erythroderma, chondrodysplasia punctata, asymmetric shortening of the long bones, and cataracts. We present a 36-year-old female with short stature, rhizomelic and asymmetric limb shortening, severe scoliosis, a sectorial cataract, and no family history of CDPX2. Whole exome sequencing (WES) revealed a p.Arg63del mutation in EBP, and biochemical studies confirmed a diagnosis of CDPX2. Short stature in combination with ichthyosis or alopecia, cataracts, and limb shortening in an adult should prompt consideration of a diagnosis of CDPX2. As in many genetic syndromes, the hallmark features of CDPX2 in pediatric patients are not readily identifiable in adults. This demonstrates the utility of WES as a diagnostic tool in the evaluation of adults with genetic disorders.

Branched-chain amino acid metabolism: from rare Mendelian diseases to more common disorders.

Branched-chain amino acid (BCAA) metabolism plays a central role in the pathophysiology of both rare inborn errors of metabolism and the more common multifactorial diseases. Although deficiency of the branched-chain ketoacid dehydrogenase (BCKDC) and associated elevations in the BCAAs and their ketoacids have been recognized as the cause of maple syrup urine disease (MSUD) for decades, treatment options for this disorder have been limited to dietary interventions. In recent years, the discovery of improved leucine tolerance after liver transplantation has resulted in a new therapeutic strategy for this disorder. Likewise, targeting the regulation of the BCKDC activity may be an alternative potential treatment strategy for MSUD. The regulation of the BCKDC by the branched-chain ketoacid dehydrogenase kinase has also been implicated in a new inborn error of metabolism characterized by autism, intellectual disability and seizures. Finally, there is a growing body of literature implicating BCAA metabolism in more common disorders such as the metabolic syndrome, cancer and hepatic disease. This review surveys the knowledge acquired on the topic over the past 50 years and focuses on recent developments in the field of BCAA metabolism.

The practice of adult genetics: a 7-year experience from a single center.

The purpose of our study is to familiarize the reader with genetic disorders commonly seen in adults and identify challenges and barriers that limit provision of services. We conducted a retrospective chart analysis of patients seen in the adult Genetics clinics from January 2004 to December 2010 in a metropolitan medical center consisting of an academic private clinic and a county hospital clinic. During the study period, a total of 1,552 patients (n = 1,108 private clinic patients; n = 444 county clinic patients) were evaluated and managed. Of these, 790 and 280 were new patient visits at the private clinic and county clinic, respectively. Approximately 35% (374/1,070) of new patients were seen for cancer-related indications, while neurological indications accounted for approximately 14% (153/1,070) in both clinics. Cardiology-related indications accounted for approximately 13% (145/1,070) of patients, followed closely by chromosomal and syndromic indications for which almost 9% (96/1,070) of new patients were seen. Approximately 8% (90/1,070) of new patients were seen for musculoskeletal indications. We saw increased clinic growth during the study period and found that the most common indications for referral are: (1) Personal/family history of cancer (2) neurological (3) cardiovascular (CV) (4) chromosomal/syndromic and (5) musculoskeletal. A number of challenges were identified, including coordination of services, feasibility of testing, and an overall higher complexity of care with increased clinic scheduling time requirements. Through this review, we demonstrate the demand for adult genetics services and propose some guidelines to address the challenges of management in the adult genetics patient population.