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Bäckström T, Doverskog M, Blackburn TP, Scharschmidt BF, Felipo V. Allopregnanolone and its antagonist modulate neuroinflammation and neurological impairment. Neurosci Biobehav Rev 2024; 161:105668. [PMID: 38608826 DOI: 10.1016/j.neubiorev.2024.105668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 03/18/2024] [Accepted: 04/07/2024] [Indexed: 04/14/2024]
Abstract
Neuroinflammation accompanies several brain disorders, either as a secondary consequence or as a primary cause and may contribute importantly to disease pathogenesis. Neurosteroids which act as Positive Steroid Allosteric GABA-A receptor Modulators (Steroid-PAM) appear to modulate neuroinflammation and their levels in the brain may vary because of increased or decreased local production or import from the systemic circulation. The increased synthesis of steroid-PAMs is possibly due to increased expression of the mitochondrial cholesterol transporting protein (TSPO) in neuroinflammatory tissue, and reduced production may be due to changes in the enzymatic activity. Microglia and astrocytes play an important role in neuroinflammation, and their production of inflammatory mediators can be both activated and inhibited by steroid-PAMs and GABA. What is surprising is the finding that both allopregnanolone, a steroid-PAM, and golexanolone, a novel GABA-A receptor modulating steroid antagonist (GAMSA), can inhibit microglia and astrocyte activation and normalize their function. This review focuses on the role of steroid-PAMs in neuroinflammation and their importance in new therapeutic approaches to CNS and liver disease.
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Affiliation(s)
| | | | | | | | - Vicente Felipo
- Laboratory of Neurobiology, Centro de Investigación Príncipe Felipe, Valencia, Spain
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Swiatek W, Parnell KM, Nickols GA, Scharschmidt BF, Rutter J. Validation of PAS Kinase, a Regulator of Hepatic Fatty Acid and Triglyceride Synthesis, as a Therapeutic Target for Nonalcoholic Steatohepatitis. Hepatol Commun 2020; 4:696-707. [PMID: 32363320 PMCID: PMC7193131 DOI: 10.1002/hep4.1498] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 02/12/2020] [Accepted: 02/15/2020] [Indexed: 12/29/2022] Open
Abstract
Hyperactivation of sterol regulatory element binding protein 1c (SREBP‐1c), which transcriptionally induces expression of enzymes responsible for de novo lipogenesis and triglyceride (TG) formation, is implicated in nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH) pathogenesis. Posttranslational SREBP‐1c maturation and activation is stimulated by the protein per–arnt–sim kinase (PASK). PASK‐knockout mice are phenotypically normal on a conventional diet but exhibit decreased hypertriglyceridemia, insulin resistance, and hepatic steatosis on a high‐fat diet. We investigated the effects of pharmacologic PASK inhibition using BioE‐1115, a selective and potent oral PASK inhibitor, in Zucker fatty (fa)/fa) rats, a genetic model of obesity, dyslipidemia, and insulin resistance, and in a dietary murine model of NAFLD/NASH. Female Zucker (fa/fa) rats and lean littermate (fa/+) controls received BioE‐1115 (3‐100 mg/kg/day) and/or omega‐3 fatty acids, and blood glucose, hemoglobin A1c, glucose tolerance, insulin, and serum TG were measured. C57BL/6J mice fed a high‐fat/high‐fructose diet (HF‐HFrD) were treated with BioE‐1115 (100 mg/kg/day) or vehicle. Body weight and fasting glucose were measured regularly; serum TG, body and organ weights, and liver TG and histology were assessed at sacrifice. Messenger RNA (mRNA) abundance of SREBP‐1c target genes was measured in both models. In Zucker rats, BioE‐1115 treatment produced significant dose‐dependent reductions in blood glucose, insulin, and TG (all greater than omega‐3 fatty acids) and dose dependently restored insulin sensitivity assessed by glucose tolerance testing. In HF‐HFrD mice, BioE‐1115 reduced body weight, liver weight, fasting blood glucose, serum TGs, hepatic TG, hepatic fibrosis, hepatocyte vacuolization, and bile duct hyperplasia. BioE‐1115 reduced SREBP‐1c target mRNA transcripts in both models. Conclusion: PASK inhibition mitigates many adverse metabolic consequences associated with an HF‐HFrD and reduces hepatic fat content and fibrosis. This suggests that inhibition of PASK is an attractive therapeutic strategy for NAFLD/NASH treatment.
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Affiliation(s)
- Wojciech Swiatek
- Department of Biochemistry University of Utah School of Medicine University of Utah Salt Lake City UT
| | | | | | | | - Jared Rutter
- Department of Biochemistry University of Utah School of Medicine University of Utah Salt Lake City UT.,Howard Hughes Medical Institute Salt Lake City UT
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Bajaj JS, Frederick RT, Bass NM, Ghabril M, Coyne K, Margolis MK, Santoro M, Coakley DF, Mokhtarani M, Jurek M, Scharschmidt BF. Overt hepatic encephalopathy: development of a novel clinician reported outcome tool and electronic caregiver diary. Metab Brain Dis 2016; 31:1081-93. [PMID: 27278222 DOI: 10.1007/s11011-016-9851-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Accepted: 06/01/2016] [Indexed: 12/22/2022]
Abstract
Clinical management and clinical trials of patients with overt hepatic encephalopathy (OHE) are compromised by lack of standardized and reproducible tools for its clinical diagnosis or for caregiver (CG) identification of OHE manifestations which merit medical evaluation. Using an iterative Delphi method, Steering Committee and international hepatologist panel, the West Haven (WH) scale was modified to develop and operationalize a clinician tool for OHE identification and grading (HE Grading Instrument, HEGI™). Major diagnostic criteria included disorientation to time, place, and person, asterixis, lethargy, and coma. Minimum HEGI requirements for OHE diagnosis included: (1) disorientation, or (2) presence of both lethargy and asterixis, or (3) coma. Inter- and intra-rater HEGI reproducibility were 97 % and 98 %, respectively. When applied to a phase II clinical trial population of 178 patients with 388 OHE episodes, HEGI demonstrated excellent concordance with investigator judgement. Additionally, a multi-stage study was conducted to develop a daily CG e-diary, based on OHE manifestations recognizable by CG including speech difficulties, unusual behavior, forgetfulness, confusion, disorientation and level of consciousness. The e-diary was designed for use on smart phone, laptop or desktop, utilized branching logic and skip patterns, incorporated automatic daily completion reminders and real time alerts to clinical sites to facilitate daily standardized CG input and was found to be user friendly and understandable. The HEGI and e-diary, which were developed using methodology accepted by regulatory authorities, are designed to facilitate the design and interpretation of clinical trials for OHE and improve outcomes for OHE patients in clinical practice.
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Affiliation(s)
- J S Bajaj
- Virginia Commonwealth University and McGuire VA Hospital, Richmond, VA, USA
| | - R T Frederick
- California Pacific Medical Center, San Francisco, CA, USA
| | - N M Bass
- University of California, San Francisco, CA, USA
| | - M Ghabril
- Indiana University, Indianapolis, IN, USA
| | | | - M K Margolis
- Patient-Centered Outcomes Research Institute, Washington, DC, USA
| | - M Santoro
- Horizon Pharma, 150 S Saunders Road, Lake Forest, IL, 60045, USA
| | - D F Coakley
- Horizon Pharma, 150 S Saunders Road, Lake Forest, IL, 60045, USA
| | - M Mokhtarani
- Horizon Pharma, 150 S Saunders Road, Lake Forest, IL, 60045, USA
| | - M Jurek
- Horizon Pharma, 150 S Saunders Road, Lake Forest, IL, 60045, USA
| | - B F Scharschmidt
- Horizon Pharma, 150 S Saunders Road, Lake Forest, IL, 60045, USA.
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Shchelochkov OA, Dickinson K, Scharschmidt BF, Lee B, Marino M, Le Mons C. Barriers to drug adherence in the treatment of urea cycle disorders: Assessment of patient, caregiver and provider perspectives. Mol Genet Metab Rep 2016; 8:43-7. [PMID: 27493880 PMCID: PMC4963256 DOI: 10.1016/j.ymgmr.2016.07.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 07/11/2016] [Indexed: 11/28/2022] Open
Abstract
Patients and families living with metabolic disorders face challenging dietary and drug treatment regimens. On the hypothesis that poor palatability, volume and frequency of drug/formula administration contribute to treatment non-adherence and hyperammonemic episodes, a survey was conducted of patient, caregiver (CG) and physician perspectives on treatments used in urea cycle disorders (UCD). Methods A paper and online survey assessed experience with UCD medications, medical foods and dietary supplements. Results 25 physicians, 52 adult patients and 114 CG responded. In 2009, the most common UCD-specific intervention reported by patients included sodium phenylbutyrate (60%), followed by l-citrulline (46%), amino acid medical foods (15%), l-arginine preparations (18%), and sodium benzoate (8%). Only 36% of patients reported experiencing no hyperammonemic episodes in the last 2 years. The most commonly reported cause of hyperammonemic episodes was infection or other acute illnesses, followed by dietary indiscretion, side effects of medications, and drug non-adherence. Most patients, caregivers and physicians (> 75%) ranked nitrogen-scavenging medications, l-citrulline, l-arginine, and medical foods as “effective” or “very effective.” Non-adherence was common (e.g. 18% of patients admitted to missing sodium phenylbutyrate “at least once a week” and “at least one a day”). Barriers to adherence included taste of medications, frequency of drug administration, number of pills, difficulty swallowing pills, side effects, forgetting to take medications, and high cost. Strategies to mitigate the gastrointestinal side effects of medications included the use of gastric tubes and acid reflux medications. Physicians indicated that 25% and 33% of pediatric and adult patients, respectively, were given less than the recommended dose of sodium phenylbutyrate due to concerns of tolerance, administration, and cost. Conclusions Despite positive views of their effectiveness, respondents found medications, medical foods and dietary supplements difficult to take and viewed adherence as inadequate, thus contributing to hyperammonemic episodes.
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Affiliation(s)
- Oleg A Shchelochkov
- Stead Department of Pediatrics, University of Iowa Hospitals and Clinics, Iowa City, IA, United States
| | | | | | - Brendan Lee
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Miguel Marino
- Oregon Health & Science University, Portland, OR, United States
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Vierling JM, Mokhtarani M, Brown RS, Mantry P, Rockey DC, Ghabril M, Rowell R, Jurek M, Coakley DF, Scharschmidt BF. Fasting Blood Ammonia Predicts Risk and Frequency of Hepatic Encephalopathy Episodes in Patients With Cirrhosis. Clin Gastroenterol Hepatol 2016; 14:903-906.e1. [PMID: 26707685 DOI: 10.1016/j.cgh.2015.11.018] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 11/12/2015] [Accepted: 11/25/2015] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS There is controversy over the use of measuring blood levels of ammonia (NH3) in the management of patients with overt hepatic encephalopathy (HE). METHODS We performed a retrospective analysis of data from a randomized, double-blind study of 178 patients with cirrhosis given glycerol phenylbutyrate (an NH3-lowering agent) or placebo for 16 weeks. Blood samples were collected at baseline and on study days 7 and 14 and NH3 levels were measured. The probabilities of having an HE episode, based on ammonia values, were modeled using binary logistic regression. A Cox proportional model was used to determine the risk of HE episodes in patients with baseline fasting NH3 levels ≤1.5-fold the upper limit of normal (ULN) versus patients with fasting NH3 levels >1.5-fold the ULN. RESULTS The risk and frequency of HE episodes and HE-related hospitalizations correlated with baseline (mean, 51 ± 6 μmol/L; ULN, 35 μmol/L) and on-study fasting levels of NH3, and increased sharply at levels >1.5-fold the ULN. Regardless of baseline level, NH3 exposure and the relative risk of HE episodes were decreased by glycerol phenylbutyrate. CONCLUSIONS In analysis of data from a phase 2 study of the effects of glycerol phenylbutyrate in patients with cirrhosis, we found that fasting levels of NH3 in blood can identify patients at risk for HE-related morbidity. Patients with HE might benefit from NH3-lowering therapy. ClinicalTrials.gov no: NCT 00999167.
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Affiliation(s)
| | | | | | - Parvez Mantry
- Liver Institute at Methodist Dallas Medical Center, Dallas, Texas
| | - Don C Rockey
- Medical University of South Carolina, Charleston, South Carolina
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Stuy M, Chen GF, Masonek JM, Scharschmidt BF. Refeeding syndrome in a young woman with argininosuccinate lyase deficiency. Mol Genet Metab Rep 2016; 4:6-8. [PMID: 26937403 PMCID: PMC4750572 DOI: 10.1016/j.ymgmr.2015.03.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
A severely chronically protein and calorie restricted young woman with argininosuccinate lyase deficiency developed transient refeeding syndrome (RFS) and hyperammonemia after modest diet liberalization following initiation of glycerol phenylbutyrate (GPB). The patient required IV supportive care and supplementation with potassium, magnesium and calcium. She is now doing well on GPB and an appropriate maintenance diet. Susceptibility to RFS should be considered in chronically nutritionally restricted patients with metabolic disorders after liberalization of diet.
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Affiliation(s)
- M Stuy
- Department of Medical and Molecular Genetics, Division of Clinical and Biochemical Genetics, Indiana University School of Medicine, Indianapolis, IN, United States
| | - G-F Chen
- Hyperion Therapeutics, Inc., Brisbane, CA, United States
| | - J M Masonek
- Hyperion Therapeutics, Inc., Brisbane, CA, United States
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Hook D, Diaz GA, Lee B, Bartley J, Longo N, Berquist W, Le Mons C, Rudolph-Angelich I, Porter M, Scharschmidt BF, Mokhtarani M. Protein and calorie intakes in adult and pediatric subjects with urea cycle disorders participating in clinical trials of glycerol phenylbutyrate. Mol Genet Metab Rep 2016; 6:34-40. [PMID: 27014577 PMCID: PMC4789342 DOI: 10.1016/j.ymgmr.2015.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 11/04/2015] [Indexed: 12/30/2022] Open
Abstract
Background Little prospectively collected data are available comparing the dietary intake of urea cycle disorder (UCD) patients to UCD treatment guidelines or to healthy individuals. Objective To examine the protein and calorie intakes of UCD subjects who participated in clinical trials of glycerol phenylbutyrate (GPB) and compare these data to published UCD dietary guidelines and nutritional surveys. Design Dietary data were recorded for 45 adult and 49 pediatric UCD subjects in metabolic control during participation in clinical trials of GPB. Protein and calorie intakes were compared to UCD treatment guidelines, average nutrient intakes of a healthy US population based on the National Health and Nutrition Examination Survey (NHANES) and Recommended Daily Allowances (RDA). Results In adults, mean protein intake was higher than UCD recommendations but lower than RDA and NHANES values, while calorie intake was lower than UCD recommendations, RDA and NHANES. In pediatric subjects, prescribed protein intake was higher than UCD guidelines, similar to RDA, and lower than NHANES data for all age groups, while calorie intake was at the lower end of the recommended UCD range and close to RDA and NHANES data. In pediatric subjects height, weight, and body mass index (BMI) Z-scores were within normal range (− 2 to 2). Conclusions Pediatric patients treated with phenylbutyrate derivatives exhibited normal height and weight. Protein and calorie intakes in adult and pediatric UCD subjects differed from UCD dietary guidelines, suggesting that these guidelines may need to be reconsidered.
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Affiliation(s)
- Debra Hook
- Miller Children's Hospital/Long Beach Medical Center, United States
| | - George A Diaz
- Mount Sinai School of Medicine, Department of Genetics and Genomic Sciences, Department of Pediatrics, United States
| | | | - James Bartley
- Miller Children's Hospital/Long Beach Medical Center, United States
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Lee B, Diaz GA, Rhead W, Lichter-Konecki U, Feigenbaum A, Berry SA, Le Mons C, Bartley J, Longo N, Nagamani SC, Berquist W, Gallagher RC, Harding CO, McCandless SE, Smith W, Schulze A, Marino M, Rowell R, Coakley DF, Mokhtarani M, Scharschmidt BF. Glutamine and hyperammonemic crises in patients with urea cycle disorders. Mol Genet Metab 2016; 117:27-32. [PMID: 26586473 PMCID: PMC4915945 DOI: 10.1016/j.ymgme.2015.11.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/10/2015] [Accepted: 11/10/2015] [Indexed: 12/30/2022]
Abstract
UNLABELLED Blood ammonia and glutamine levels are used as biomarkers of control in patients with urea cycle disorders (UCDs). This study was undertaken to evaluate glutamine variability and utility as a predictor of hyperammonemic crises (HACs) in UCD patients. METHODS The relationships between glutamine and ammonia levels and the incidence and timing of HACs were evaluated in over 100 adult and pediatric UCD patients who participated in clinical trials of glycerol phenylbutyrate. RESULTS The median (range) intra-subject 24-hour coefficient of variation for glutamine was 15% (8-29%) as compared with 56% (28%-154%) for ammonia, and the correlation coefficient between glutamine and concurrent ammonia levels varied from 0.17 to 0.29. Patients with baseline (fasting) glutamine values >900 μmol/L had higher baseline ammonia levels (mean [SD]: 39.6 [26.2]μmol/L) than patients with baseline glutamine ≤ 900 μmol/L (26.6 [18.0]μmol/L). Glutamine values >900 μmol/L during the study were associated with an approximately 2-fold higher HAC risk (odds ratio [OR]=1.98; p=0.173). However, glutamine lost predictive significance (OR=1.47; p=0.439) when concomitant ammonia was taken into account, whereas the predictive value of baseline ammonia ≥ 1.0 upper limit of normal (ULN) was highly statistically significant (OR=4.96; p=0.013). There was no significant effect of glutamine >900 μmol/L on time to first HAC crisis (hazard ratio [HR]=1.14; p=0.813), but there was a significant effect of baseline ammonia ≥ 1.0 ULN (HR=4.62; p=0.0011). CONCLUSIONS The findings in this UCD population suggest that glutamine is a weaker predictor of HACs than ammonia and that the utility of the predictive value of glutamine will need to take into account concurrent ammonia levels.
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Affiliation(s)
- B Lee
- Baylor College of Medicine, Houston, TX, USA.
| | - G A Diaz
- Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - W Rhead
- The Medical College of Wisconsin, Milwaukee, WI, USA
| | | | | | - S A Berry
- Univ. of Minnesota, Minneapolis, MN, USA
| | - C Le Mons
- National Urea Cycle Disorders Foundation, Pasadena, CA, USA
| | - J Bartley
- Miller Children's Hospital, Long Beach, CA, USA
| | - N Longo
- Univ. of UT, Salt Lake City, UT, USA
| | | | | | | | | | - S E McCandless
- Case Western Reserve Univ. Medical Center, Cleveland, OH, USA
| | - W Smith
- Maine Medical Ctr., Portland, ME, USA
| | - A Schulze
- The Hospital for Sick Children, Univ. of Toronto, Canada
| | - M Marino
- Oregon Health Sciences, Portland, OR, USA
| | - R Rowell
- MED Technical Consulting, Inc., Union City, CA, USA
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Nagamani SCS, Diaz GA, Rhead W, Berry SA, Le Mons C, Lichter-Konecki U, Bartley J, Feigenbaum A, Schulze A, Longo N, Berquist W, Gallagher R, Bartholomew D, Harding CO, Korson MS, McCandless SE, Smith W, Vockley J, Kronn D, Zori R, Cederbaum S, Merritt JL, Wong D, Coakley DF, Scharschmidt BF, Dickinson K, Marino M, Lee BH, Mokhtarani M. Self-reported treatment-associated symptoms among patients with urea cycle disorders participating in glycerol phenylbutyrate clinical trials. Mol Genet Metab 2015; 116:29-34. [PMID: 26296711 PMCID: PMC4804346 DOI: 10.1016/j.ymgme.2015.08.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Accepted: 08/03/2015] [Indexed: 11/19/2022]
Abstract
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.
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Affiliation(s)
- Sandesh C S Nagamani
- Baylor College of Medicine, One Baylor Plaza, Room R814, Houston, TX 77030, USA.
| | - George A Diaz
- Icahn School of Medicine at Mount Sinai, Department of Genetics and Genomic Sciences, Department of Pediatrics, 1428 Madison Avenue, New York, NY 10029, USA
| | - William Rhead
- The Medical College of Wisconsin, MS 716, 9000 W. Wisconsin Avenue, Milwaukee, WI 53226, USA
| | - Susan A Berry
- University of Minnesota, 420 Delaware St. SE, MMC 75, Minneapolis, MN 55455, USA
| | - Cynthia Le Mons
- National Urea Cycle Disorders Foundation, 75 S. Grand Ave, Pasadena, CA 91105, USA
| | | | - James Bartley
- Long Beach Memorial Hospital, 2801 Atlantic Avenue, Long Beach, CA 90806, USA
| | | | - Andreas Schulze
- The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G1X8, Canada
| | - Nicola Longo
- The University of Utah, Division of Medical Genetics, 2C412 SOM, 50 North Mario Capecchi Drive, Salt Lake City, UT 84132, USA
| | - William Berquist
- Stanford University, 750 Welch Road, #116, Palo Alto, CA 94305, USA
| | - Renata Gallagher
- UCSF School of Medicine, 550 16th Street, San Francisco, CA 94158, USA
| | - Dennis Bartholomew
- Nationwide Children's Hospital, 545 South 18th Street, TH485, Columbus, OH 43205, USA
| | - Cary O Harding
- Oregon Health & Science University, 3181 SW Sam Jackson Park Road, A036/B198, Mail code L103, Portland, OR 97239, USA
| | - Mark S Korson
- Tufts Medical Center, Floating Building, 3rd Floor, 800 Washington Street, Boston, MA 02111, USA
| | - Shawn E McCandless
- Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106, USA
| | - Wendy Smith
- Maine Medical Center, 1577 Congress Street, 2nd Floor, Portland, ME 04102, USA
| | - Jerry Vockley
- Children's Hospital of Pittsburgh, One Children's Hospital Drive, 4401 Penn Avenue, Rangos Floor 5, Pittsburgh, PA 15224, USA
| | - David Kronn
- Westchester Medical Center, 503 Grasslands Road, Valhalla, NY 10595, USA
| | - Robert Zori
- University of Florida, UFHSC Box 100296, Gainesville, FL 32610, USA
| | - Stephen Cederbaum
- University of California, Los Angeles, 10833 Le Conte Avenue CHS 32-225, Los Angeles, CA 90095, USA
| | - J Lawrence Merritt
- Seattle Children's Hospital, 4800 Sand Point Way NE M/S W-65945, Seattle, WA 98105, USA
| | - Derek Wong
- University of California, Los Angeles, 10833 Le Conte Avenue CHS 32-225, Los Angeles, CA 90095, USA
| | - Dion F Coakley
- Horizon Therapeutics Inc., 2000 Sierra Point Parkway Suite 400, Brisbane, CA 94005, USA
| | - Bruce F Scharschmidt
- Horizon Therapeutics Inc., 2000 Sierra Point Parkway Suite 400, Brisbane, CA 94005, USA
| | - Klara Dickinson
- Anthera Pharmaceuticals, 25801 Industrial Blvd. Suite B, Hayward, CA 94545, USA
| | - Miguel Marino
- Oregon Health & Science University, 3181 SW Sam Jackson Park Road, A036/B198, Mail code L103, Portland, OR 97239, USA
| | - Brendan H Lee
- Baylor College of Medicine, One Baylor Plaza, Room R814, Houston, TX 77030, USA
| | - Masoud Mokhtarani
- Horizon Therapeutics Inc., 2000 Sierra Point Parkway Suite 400, Brisbane, CA 94005, USA
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11
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Lee B, Diaz GA, Rhead W, Lichter-Konecki U, Feigenbaum A, Berry SA, Le Mons C, Bartley JA, Longo N, Nagamani SC, Berquist W, Gallagher R, Bartholomew D, Harding CO, Korson MS, McCandless SE, Smith W, Cederbaum S, Wong D, Merritt JL, Schulze A, Vockley J, Vockley G, Kronn D, Zori R, Summar M, Milikien DA, Marino M, Coakley DF, Mokhtarani M, Scharschmidt BF. Blood ammonia and glutamine as predictors of hyperammonemic crises in patients with urea cycle disorder. Genet Med 2014; 17:561-8. [PMID: 25503497 PMCID: PMC4465427 DOI: 10.1038/gim.2014.148] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Accepted: 09/17/2014] [Indexed: 11/18/2022] Open
Abstract
Purpose To examine predictors of ammonia exposure and hyperammonemic crises (HAC) in patients with urea cycle disorders (UCDs). Methods The relationships between fasting ammonia, daily ammonia exposure, and HACs were analyzed in >100 UCD patients. Results Fasting ammonia correlated strongly with daily ammonia exposure (r=0.764, p<0.001). For patients with fasting ammonia levels <0.5 ULN, 0.5 to <1.0 ULN, and ≥1.0 ULN, the probability of a normal average daily ammonia value was 87%, 60%, and 39%, respectively, and 10.3%, 14.1%, and 37.0% of these patients experienced ≥1 HAC over 12 months. Time to first HAC was shorter (p=0.008) and relative risk (4.5×; p=0.011) and rate (~5×, p=0.006) of HACs higher in patients with fasting ammonia ≥1.0 ULN vs. <0.5ULN; relative risk was even greater (20×; p=0.009) in patients ≥6 years. A 10 or 25 μmol/L increase in ammonia exposure increased the relative risk of a HAC by 50% and >200% (p<0.0001), respectively. The relationship between ammonia and HAC risk appeared independent of treatment, age, UCD subtype, dietary protein intake, or blood urea nitrogen. Fasting glutamine correlated weakly with AUC0-24 and was not a significant predictor of HACs. Conclusions Fasting ammonia correlates strongly and positively with daily ammonia exposure and with the risk and rate of HACs, suggesting that UCD patients may benefit from tight ammonia control.
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Affiliation(s)
- Brendan Lee
- 1] Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA [2] Howard Hughes Medical Institute, Chevy Chase, Maryland, USA
| | - George A Diaz
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - William Rhead
- The Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | | | - Annette Feigenbaum
- The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Susan A Berry
- University of Minnesota, Minneapolis, Minnesota, USA
| | - Cindy Le Mons
- National Urea Cycle Disorders Foundation, Pasadena, California, USA
| | | | | | - Sandesh C Nagamani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | | | | | | | - Cary O Harding
- Oregon Health & Science University, Portland, Oregon, USA
| | | | - Shawn E McCandless
- University Hospitals Case Medical Center and Case Western Reserve University, Cleveland, Ohio, USA
| | | | | | - Derek Wong
- University of California, Los Angeles, Los Angeles, California, USA
| | | | - Andreas Schulze
- The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | | | | | - David Kronn
- Westchester Medical Center, Westchester, New York, USA
| | - Roberto Zori
- University of Florida, Gainesville, Florida, USA
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Shchelochkov OA, Lee BH, Scharschmidt BF, Dickinson KA, Herberich E, Hawkins S, Smith J, Le Mons C. Assessment of barriers to drug adherence in the treatment of urea cycle disorders in North America. Clin Biochem 2014. [DOI: 10.1016/j.clinbiochem.2014.07.085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Berry SA, Lichter-Konecki U, Diaz GA, McCandless SE, Rhead W, Smith W, Lemons C, Nagamani SCS, Coakley DF, Mokhtarani M, Scharschmidt BF, Lee B. Glycerol phenylbutyrate treatment in children with urea cycle disorders: pooled analysis of short and long-term ammonia control and outcomes. Mol Genet Metab 2014; 112:17-24. [PMID: 24630270 PMCID: PMC4382922 DOI: 10.1016/j.ymgme.2014.02.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 02/06/2014] [Accepted: 02/09/2014] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To evaluate glycerol phenylbutyrate (GPB) in the treatment of pediatric patients with urea cycle disorders (UCDs). STUDY DESIGN UCD patients (n=26) ages 2months through 17years were treated with GPB and sodium phenylbutyrate (NaPBA) in two short-term, open-label crossover studies, which compared 24-hour ammonia exposure (AUC0-24) and glutamine levels during equivalent steady-state dosing of GPB and sodium phenylbutyrate (NaPBA). These 26 patients plus an additional 23 patients also received GPB in one of three 12-month, open label extension studies, which assessed long-term ammonia control, hyperammonemic (HA) crises, amino acid levels, and patient growth. RESULTS Mean ammonia exposure on GPB was non-inferior to NaPBA in each of the individual crossover studies. In the pooled analyses, it was significantly lower on GPB vs. NaPBA (mean [SD] AUC0-24: 627 [302] vs. 872 [516] μmol/L; p=0.008) with significantly fewer abnormal values (15% on GPB vs. 35% on NaPBA; p=0.02). Mean ammonia levels remained within the normal range during 12months of GPB dosing and, when compared with the 12months preceding enrollment, a smaller percentage of patients (24.5% vs. 42.9%) experienced fewer (17 vs. 38) HA crises. Glutamine levels tended to be lower with GPB than with NaPBA during short-term dosing (mean [SD]: 660.8 [164.4] vs. 710.0 [158.7] μmol/L; p=0.114) and mean glutamine and branched chain amino acid levels, as well as other essential amino acids, remained within the normal range during 12months of GPB dosing. Mean height and weight Z-scores were within normal range at baseline and did not change significantly during 12months of GPB treatment. CONCLUSIONS Dosing with GPB was associated with 24-hour ammonia exposure that was non-inferior to that during dosing with NaPBA in individual studies and significantly lower in the pooled analysis. Long-term GPB dosing was associated with normal levels of glutamine and essential amino acids, including branched chain amino acids, age-appropriate growth and fewer HA crises as compared with the 12month period preceding enrollment.
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Affiliation(s)
| | | | - George A Diaz
- Icahn School of Medicine at Mount Sinai, Department of Genetics and Genomic Sciences, Department of Pediatrics, New York, NY, USA
| | | | - William Rhead
- The Medical College of Wisconsin, Milwaukee, WI, USA
| | | | - Cynthia Lemons
- National Urea Cycle Disorders Foundation, 75 S. Grand Ave., Pasadena, CA 91105, USA
| | | | | | | | | | - Brendan Lee
- Baylor College of Medicine, Houston, TX, USA
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Rockey DC, Vierling JM, Mantry P, Ghabril M, Brown RS, Alexeeva O, Zupanets IA, Grinevich V, Baranovsky A, Dudar L, Fadieienko G, Kharchenko N, Klaryts'ka I, Morozov V, Grewal P, McCashland T, Reddy KG, Reddy KR, Syplyviy V, Bass NM, Dickinson K, Norris C, Coakley D, Mokhtarani M, Scharschmidt BF. Randomized, double-blind, controlled study of glycerol phenylbutyrate in hepatic encephalopathy. Hepatology 2014; 59:1073-83. [PMID: 23847109 PMCID: PMC4237123 DOI: 10.1002/hep.26611] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 06/22/2013] [Indexed: 12/19/2022]
Abstract
UNLABELLED Glycerol phenylbutyrate (GPB) lowers ammonia by providing an alternate pathway to urea for waste nitrogen excretion in the form of phenylacetyl glutamine, which is excreted in urine. This randomized, double-blind, placebo-controlled phase II trial enrolled 178 patients with cirrhosis, including 59 already taking rifaximin, who had experienced two or more hepatic encephalopathy (HE) events in the previous 6 months. The primary endpoint was the proportion of patients with HE events. Other endpoints included the time to first event, total number of events, HE hospitalizations, symptomatic days, and safety. GPB, at 6 mL orally twice-daily, significantly reduced the proportion of patients who experienced an HE event (21% versus 36%; P=0.02), time to first event (hazard ratio [HR]=0.56; P<0.05), as well as total events (35 versus 57; P=0.04), and was associated with fewer HE hospitalizations (13 versus 25; P=0.06). Among patients not on rifaximin at enrollment, GPB reduced the proportion of patients with an HE event (10% versus 32%; P<0.01), time to first event (HR=0.29; P<0.01), and total events (7 versus 31; P<0.01). Plasma ammonia was significantly lower in patients on GPB and correlated with HE events when measured either at baseline or during the study. A similar proportion of patients in the GPB (79%) and placebo groups (76%) experienced adverse events. CONCLUSION GPB reduced HE events as well as ammonia in patients with cirrhosis and HE and its safety profile was similar to placebo. The findings implicate ammonia in the pathogenesis of HE and suggest that GPB has therapeutic potential in this population. (Clinicaltrials.gov, NCT00999167).
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Affiliation(s)
| | | | - Parvez Mantry
- Liver Institute at Methodist Dallas Medical CenterDallas, TX
| | | | | | - Olga Alexeeva
- Nizhny Novgorod Regional HospitalNizhny Novgorod, Russia
| | | | | | | | - Larysa Dudar
- O.O. Bogomolets, National Medical UniversityKiev, Ukraine
| | - Galyna Fadieienko
- State Institution “L.T. Malaya Institute of Therapy of NAMS of Ukraine,”Kharkiv, Ukraine
| | - Nataliya Kharchenko
- National Medical Academy of Postgraduate Education; Kiev City Clinical Hospital #8Kiev, Ukraine
| | - Iryna Klaryts'ka
- Crimean Republican Institution “M.O. Semashko Clinical Hospital,”Simferopol, Ukraine
| | | | - Priya Grewal
- Icahn School of Medicine at Mt. SinaiNew York, NY
| | | | | | | | | | - Nathan M Bass
- University of California San FranciscoSan Francisco, CA
| | | | | | - Dion Coakley
- Hyperion Therapeutics, Inc.South San Francisco, CA
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Mokhtarani M, Diaz GA, Rhead W, Berry SA, Lichter-Konecki U, Feigenbaum A, Schulze A, Longo N, Bartley J, Berquist W, Gallagher R, Smith W, McCandless SE, Harding C, Rockey DC, Vierling JM, Mantry P, Ghabril M, Brown RS, Dickinson K, Moors T, Norris C, Coakley D, Milikien DA, Nagamani SC, Lemons C, Lee B, Scharschmidt BF. Elevated phenylacetic acid levels do not correlate with adverse events in patients with urea cycle disorders or hepatic encephalopathy and can be predicted based on the plasma PAA to PAGN ratio. Mol Genet Metab 2013; 110:446-53. [PMID: 24144944 PMCID: PMC4108288 DOI: 10.1016/j.ymgme.2013.09.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 09/29/2013] [Indexed: 10/26/2022]
Abstract
BACKGROUND Phenylacetic acid (PAA) is the active moiety in sodium phenylbutyrate (NaPBA) and glycerol phenylbutyrate (GPB, HPN-100). Both are approved for treatment of urea cycle disorders (UCDs) - rare genetic disorders characterized by hyperammonemia. PAA is conjugated with glutamine in the liver to form phenylacetyleglutamine (PAGN), which is excreted in urine. PAA plasma levels ≥ 500 μg/dL have been reported to be associated with reversible neurological adverse events (AEs) in cancer patients receiving PAA intravenously. Therefore, we have investigated the relationship between PAA levels and neurological AEs in patients treated with these PAA pro-drugs as well as approaches to identifying patients most likely to experience high PAA levels. METHODS The relationship between nervous system AEs, PAA levels and the ratio of plasma PAA to PAGN were examined in 4683 blood samples taken serially from: [1] healthy adults [2], UCD patients of ≥ 2 months of age, and [3] patients with cirrhosis and hepatic encephalopathy (HE). The plasma ratio of PAA to PAGN was analyzed with respect to its utility in identifying patients at risk of high PAA values. RESULTS Only 0.2% (11) of 4683 samples exceeded 500 μg/ml. There was no relationship between neurological AEs and PAA levels in UCD or HE patients, but transient AEs including headache and nausea that correlated with PAA levels were observed in healthy adults. Irrespective of population, a curvilinear relationship was observed between PAA levels and the plasma PAA:PAGN ratio, and a ratio>2.5 (both in μg/mL) in a random blood draw identified patients at risk for PAA levels>500 μg/ml. CONCLUSIONS The presence of a relationship between PAA levels and reversible AEs in healthy adults but not in UCD or HE patients may reflect intrinsic differences among the populations and/or metabolic adaptation with continued dosing. The plasma PAA:PAGN ratio is a functional measure of the rate of PAA metabolism and represents a useful dosing biomarker.
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Affiliation(s)
- M Mokhtarani
- Hyperion Therapeutics, 601 Gateway Blvd., Suite 200, South San Francisco, CA 94080, USA.
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Monteleone JPR, Mokhtarani M, Diaz GA, Rhead W, Lichter-Konecki U, Berry SA, Lemons C, Dickinson K, Coakley D, Lee B, Scharschmidt BF. Population pharmacokinetic modeling and dosing simulations of nitrogen-scavenging compounds: disposition of glycerol phenylbutyrate and sodium phenylbutyrate in adult and pediatric patients with urea cycle disorders. J Clin Pharmacol 2013; 53:699-710. [PMID: 23775211 DOI: 10.1002/jcph.92] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 03/12/2013] [Indexed: 11/08/2022]
Abstract
Sodium phenylbutyrate and glycerol phenylbutyrate mediate waste nitrogen excretion in the form of urinary phenylacetylglutamine (PAGN) in patients with urea cycle disorders (UCDs); rare genetic disorders characterized by impaired urea synthesis and hyperammonemia. Sodium phenylbutyrate is approved for UCD treatment; the development of glycerol phenylbutyrate afforded the opportunity to characterize the pharmacokinetics (PK) of both compounds. A population PK model was developed using data from four Phase II/III trials that collectively enrolled patients ages 2 months to 72 years. Dose simulations were performed with particular attention to phenylacetic acid (PAA), which has been associated with adverse events in non-UCD populations. The final model described metabolite levels in plasma and urine for both drugs and was characterized by (a) partial presystemic metabolism of phenylbutyric acid (PBA) to PAA and/or PAGN, (b) slower PBA absorption and greater presystemic conversion with glycerol phenylbutyrate, (c) similar systemic disposition with saturable conversion of PAA to PAGN for both drugs, and (d) body surface area (BSA) as a significant covariate accounting for age-related PK differences. Dose simulations demonstrated similar PAA exposure following mole-equivalent PBA dosing of both drugs and greater PAA exposure in younger patients based on BSA.
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17
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Smith W, Diaz GA, Lichter-Konecki U, Berry SA, Harding CO, McCandless SE, LeMons C, Mauney J, Dickinson K, Coakley DF, Moors TL, Mokhtarani M, Mokhtarani M, Scharschmidt BF, Lee B. Ammonia control in children ages 2 months through 5 years with urea cycle disorders: comparison of sodium phenylbutyrate and glycerol phenylbutyrate. J Pediatr 2013; 162:1228-34, 1234.e1. [PMID: 23324524 PMCID: PMC4017326 DOI: 10.1016/j.jpeds.2012.11.084] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 10/02/2012] [Accepted: 11/29/2012] [Indexed: 11/16/2022]
Abstract
OBJECTIVES To examine ammonia levels, pharmacokinetics, and safety of glycerol phenylbutyrate (GPB; also referred to as HPN-100) and sodium phenylbutyrate (NaPBA) in young children with urea cycle disorders (UCDs). STUDY DESIGN This open label switch-over study enrolled patients ages 29 days to under 6 years taking NaPBA. Patients underwent 24-hour blood and urine sampling on NaPBA and again on a phenylbutyric acid-equimolar dose of GPB and completed questionnaires regarding signs and symptoms associated with NaPBA and/or their UCD. RESULTS Fifteen patients (8 argininosuccinate lyase deficiency, 3 argininosuccinic acid synthetase deficiency, 3 ornithine transcarbamylase deficiency, 1 arginase deficiency) ages 2 months through 5 years enrolled in and completed the study. Daily ammonia exposure (24-hour area under the curve) was lower on GPB and met predefined noninferiority criteria (ratio of means 0.79; 95% CI 0.593-1.055; P=.03 Wilcoxon; 0.07 t test). Six patients experienced mild adverse events on GPB; there were no serious adverse events or significant laboratory changes. Liver tests and argininosuccinic acid levels among patients with argininosuccinate lyase deficiency were unchanged or improved on GPB. Eleven of 15 patients reported 35 symptoms on day 1; 23 of these 35 symptoms improved or resolved on GPB. Mean systemic exposure to phenylbutyric acid, phenylacetic acid, and phenylacetylglutamine (PAGN) were similar and phenylacetic acid exposure tended to be higher in the youngest children on both drugs. Urinary PAGN concentration was greater on morning voids and varied less over 24 hours on GPB versus NaPBA. CONCLUSIONS GPB results in more evenly distributed urinary output of PAGN over 24 hours were associated with fewer symptoms and offers ammonia control comparable with that observed with NaPBA in young children with UCDs.
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Affiliation(s)
- W Smith
- Maine Medical Center, 1577 Congress Street, 2nd Floor, Portland, ME 04102
| | - GA Diaz
- Mount Sinai School of Medicine, Department of Genetics and Genomic Sciences, Department of Pediatrics, 1428 Madison Avenue, New York, NY 10029
| | - U Lichter-Konecki
- Children’s National Medical Center, Division of Genetics and Metabolism, 111 Michigan Avenue NW #1950, Washington, DC 20010
| | - SA Berry
- University of Minnesota, 420 Delaware St. SE, MMC 75, Minneapolis, MN 55455
| | - CO Harding
- Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, A036/B198, Mailcode L103, Portland, OR 97239
| | - SE McCandless
- University Hospitals Case Medical Center and Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106
| | - C LeMons
- National Urea Cycle Disorders Foundation, 75 South Grand Avenue, Pasadena, CA 91105
| | - J Mauney
- Chiltern, 2520 Independence Blvd., Ste. 202, Wilmington NC
| | - K Dickinson
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - DF Coakley
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - TL Moors
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - M Mokhtarani
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - M Mokhtarani
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - BF Scharschmidt
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080
| | - B Lee
- Baylor College of Medicine, One Baylor Plaza, Room R814, Houston, TX 77030,Howard Hughes Medical Institute, One Baylor Plaza, Room R814, Houston, TX 77030
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18
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Diaz GA, Krivitzky LS, Mokhtarani M, Rhead W, Bartley J, Feigenbaum A, Longo N, Berquist W, Berry SA, Gallagher R, Lichter-Konecki U, Bartholomew D, Harding CO, Cederbaum S, McCandless SE, Smith W, Vockley G, Bart SA, Korson MS, Kronn D, Zori R, Merritt JL, C S Nagamani S, Mauney J, Lemons C, Dickinson K, Moors TL, Coakley DF, Scharschmidt BF, Lee B. Ammonia control and neurocognitive outcome among urea cycle disorder patients treated with glycerol phenylbutyrate. Hepatology 2013; 57:2171-9. [PMID: 22961727 PMCID: PMC3557606 DOI: 10.1002/hep.26058] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 08/15/2012] [Indexed: 02/02/2023]
Abstract
UNLABELLED Glycerol phenylbutyrate is under development for treatment of urea cycle disorders (UCDs), rare inherited metabolic disorders manifested by hyperammonemia and neurological impairment. We report the results of a pivotal Phase 3, randomized, double-blind, crossover trial comparing ammonia control, assessed as 24-hour area under the curve (NH3 -AUC0-24hr ), and pharmacokinetics during treatment with glycerol phenylbutyrate versus sodium phenylbutyrate (NaPBA) in adult UCD patients and the combined results of four studies involving short- and long-term glycerol phenylbutyrate treatment of UCD patients ages 6 and above. Glycerol phenylbutyrate was noninferior to NaPBA with respect to ammonia control in the pivotal study, with mean (standard deviation, SD) NH3 -AUC0-24hr of 866 (661) versus 977 (865) μmol·h/L for glycerol phenylbutyrate and NaPBA, respectively. Among 65 adult and pediatric patients completing three similarly designed short-term comparisons of glycerol phenylbutyrate versus NaPBA, NH3 -AUC0-24hr was directionally lower on glycerol phenylbutyrate in each study, similar among all subgroups, and significantly lower (P < 0.05) in the pooled analysis, as was plasma glutamine. The 24-hour ammonia profiles were consistent with the slow-release behavior of glycerol phenylbutyrate and better overnight ammonia control. During 12 months of open-label glycerol phenylbutyrate treatment, average ammonia was normal in adult and pediatric patients and executive function among pediatric patients, including behavioral regulation, goal setting, planning, and self-monitoring, was significantly improved. CONCLUSION Glycerol phenylbutyrate exhibits favorable pharmacokinetics and ammonia control relative to NaPBA in UCD patients, and long-term glycerol phenylbutyrate treatment in pediatric UCD patients was associated with improved executive function (ClinicalTrials.gov NCT00551200, NCT00947544, NCT00992459, NCT00947297). (HEPATOLOGY 2012).
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Affiliation(s)
- George A Diaz
- Mount Sinai School of Medicine, Department of Genetics and Genomic Sciences, Department of Pediatrics, New York, NY, USA
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Ghabril M, Zupanets IA, Vierling J, Mantry P, Rockey D, Wolf D, O'Shea R, Dickinson K, Gillaspy H, Norris C, Coakley DF, Mokhtarani M, Scharschmidt BF. Glycerol Phenylbutyrate in Patients With Cirrhosis and Episodic Hepatic Encephalopathy: A Pilot Study of Safety and Effect on Venous Ammonia Concentration. Clin Pharmacol Drug Dev 2013; 2:278-84. [DOI: 10.1002/cpdd.18] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 01/30/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Marwan Ghabril
- Indiana University School of Medicine; Indianapolis, IN; USA
| | | | | | - Parvez Mantry
- Liver Institute at Methodist Dallas Medical Center; Dallas, TX; USA
| | - Don Rockey
- University of Texas; Southwestern, Dallas, TX; USA
| | - David Wolf
- New York Medical College; Valhalla, NY; USA
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20
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Mokhtarani M, Diaz GA, Rhead W, Lichter-Konecki U, Bartley J, Feigenbaum A, Longo N, Berquist W, Berry SA, Gallagher R, Bartholomew D, Harding CO, Korson MS, McCandless SE, Smith W, Vockley J, Bart S, Kronn D, Zori R, Cederbaum S, Dorrani N, Merritt JL, Sreenath-Nagamani S, Summar M, Lemons C, Dickinson K, Coakley DF, Moors TL, Lee B, Scharschmidt BF. Urinary phenylacetylglutamine as dosing biomarker for patients with urea cycle disorders. Mol Genet Metab 2012; 107:308-14. [PMID: 22958974 PMCID: PMC3608516 DOI: 10.1016/j.ymgme.2012.08.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 08/07/2012] [Accepted: 08/07/2012] [Indexed: 11/22/2022]
Abstract
UNLABELLED We have analyzed pharmacokinetic data for glycerol phenylbutyrate (also GT4P or HPN-100) and sodium phenylbutyrate with respect to possible dosing biomarkers in patients with urea cycle disorders (UCD). STUDY DESIGN These analyses are based on over 3000 urine and plasma data points from 54 adult and 11 pediatric UCD patients (ages 6-17) who participated in three clinical studies comparing ammonia control and pharmacokinetics during steady state treatment with glycerol phenylbutyrate or sodium phenylbutyrate. All patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate or sodium phenylbutyrate in a cross over fashion and underwent 24-hour blood samples and urine sampling for phenylbutyric acid, phenylacetic acid and phenylacetylglutamine. RESULTS Patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate ranging from 1.5 to 31.8 g/day and of sodium phenylbutyrate ranging from 1.3 to 31.7 g/day. Plasma metabolite levels varied widely, with average fluctuation indices ranging from 1979% to 5690% for phenylbutyric acid, 843% to 3931% for phenylacetic acid, and 881% to 1434% for phenylacetylglutamine. Mean percent recovery of phenylbutyric acid as urinary phenylacetylglutamine was 66.4 and 69.0 for pediatric patients and 68.7 and 71.4 for adult patients on glycerol phenylbutyrate and sodium phenylbutyrate, respectively. The correlation with dose was strongest for urinary phenylacetylglutamine excretion, either as morning spot urine (r = 0.730, p < 0.001) or as total 24-hour excretion (r = 0.791 p<0.001), followed by plasma phenylacetylglutamine AUC(24-hour), plasma phenylacetic acid AUC(24-hour) and phenylbutyric acid AUC(24-hour). Plasma phenylacetic acid levels in adult and pediatric patients did not show a consistent relationship with either urinary phenylacetylglutamine or ammonia control. CONCLUSION The findings are collectively consistent with substantial yet variable pre-systemic (1st pass) conversion of phenylbutyric acid to phenylacetic acid and/or phenylacetylglutamine. The variability of blood metabolite levels during the day, their weaker correlation with dose, the need for multiple blood samples to capture trough and peak, and the inconsistency between phenylacetic acid and urinary phenylacetylglutamine as a marker of waste nitrogen scavenging limit the utility of plasma levels for therapeutic monitoring. By contrast, 24-hour urinary phenylacetylglutamine and morning spot urine phenylacetylglutamine correlate strongly with dose and appear to be clinically useful non-invasive biomarkers for compliance and therapeutic monitoring.
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Affiliation(s)
- M Mokhtarani
- Hyperion Therapeutics, 601 Gateway Blvd, Suite 200, South San Francisco, CA 94080, USA.
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Lee B, Rhead W, Diaz GA, Scharschmidt BF, Mian A, Shchelochkov O, Marier JF, Beliveau M, Mauney J, Dickinson K, Martinez A, Gargosky S, Mokhtarani M, Berry SA. Phase 2 comparison of a novel ammonia scavenging agent with sodium phenylbutyrate in patients with urea cycle disorders: safety, pharmacokinetics and ammonia control. Mol Genet Metab 2010; 100:221-8. [PMID: 20382058 PMCID: PMC2905228 DOI: 10.1016/j.ymgme.2010.03.014] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 03/18/2010] [Accepted: 03/18/2010] [Indexed: 11/23/2022]
Abstract
UNLABELLED Glycerol phenylbutyrate (glyceryl tri (4-phenylbutyrate)) (GPB) is being studied as an alternative to sodium phenylbutyrate (NaPBA) for the treatment of urea cycle disorders (UCDs). This phase 2 study explored the hypothesis that GPB offers similar safety and ammonia control as NaPBA, which is currently approved as adjunctive therapy in the chronic management of UCDs, and examined correlates of 24-h blood ammonia. METHODS An open-label, fixed sequence switch-over study was conducted in adult UCD patients taking maintenance NaPBA. Blood ammonia and blood and urine metabolites were compared after 7 days (steady state) of TID dosing on either drug, both dosed to deliver the same amount of phenylbutyric acid (PBA). RESULTS Ten subjects completed the study. Adverse events were comparable for the two drugs; 2 subjects experienced hyperammonemic events on NaPBA while none occurred on GPB. Ammonia values on GPB were approximately 30% lower than on NaPBA (time-normalized AUC=26.2 vs. 38.4 micromol/L; Cmax=56.3 vs. 79.1 micromol/L; not statistically significant), and GPB achieved non-inferiority to NaPBA with respect to ammonia (time-normalized AUC) by post hoc analysis. Systemic exposure (AUC(0-24)) to PBA on GPB was 27% lower than on NaPBA (540 vs. 739 microgh/mL), whereas exposure to phenylacetic acid (PAA) (575 vs. 596 microg h/mL) and phenylacetylglutamine (PAGN) (1098 vs. 1133 microg h/mL) were similar. Urinary PAGN excretion accounted for approximately 54% of PBA administered for both NaPBA and GPB; other metabolites accounted for <1%. Intact GPB was generally undetectable in blood and urine. Blood ammonia correlated strongly and inversely with urinary PAGN (r=-0.82; p<0.0001) but weakly or not at all with blood metabolite levels. CONCLUSIONS Safety and ammonia control with GPB appear at least equal to NaPBA. Urinary PAGN, which is stoichiometrically related to nitrogen scavenging, may be a useful biomarker for both dose selection and adjustment for optimal control of venous ammonia.
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Affiliation(s)
- Brendan Lee
- Baylor College of Medicine, Houston, TX, USA.
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22
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MCGuire BM, Zupanets IA, Lowe ME, Xiao X, Syplyviy VA, Monteleone J, Gargosky S, Dickinson K, Martinez A, Mokhtarani M, Scharschmidt BF. Pharmacology and safety of glycerol phenylbutyrate in healthy adults and adults with cirrhosis. Hepatology 2010; 51:2077-85. [PMID: 20512995 PMCID: PMC3733097 DOI: 10.1002/hep.23589] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
UNLABELLED Phenylbutyric acid (PBA), which is approved for treatment of urea cycle disorders (UCDs) as sodium phenylbutyrate (NaPBA), mediates waste nitrogen excretion via combination of PBA-derived phenylacetic acid with glutamine to form phenylactylglutamine (PAGN) that is excreted in urine. Glycerol phenylbutyrate (GPB), a liquid triglyceride pro-drug of PBA, containing no sodium and having favorable palatability, is being studied for treatment of hepatic encephalopathy (HE). In vitro and clinical studies have been performed to assess GPB digestion, safety, and pharmacology in healthy adults and individuals with cirrhosis. GPB hydrolysis was measured in vitro by way of pH titration. Twenty-four healthy adults underwent single-dose administration of GPB and NaPBA and eight healthy adults and 24 cirrhotic subjects underwent single-day and multiple-day dosing of GPB, with metabolites measured in blood and urine. Simulations were performed to assess GPB dosing at higher levels. GPB was hydrolyzed by human pancreatic triglyceride lipase, pancreatic lipase-related protein 2, and carboxyl-ester lipase. Clinical safety was satisfactory. Compared with NaPBA, peak metabolite blood levels with GPB occurred later and were lower; urinary PAGN excretion was similar but took longer. Steady state was achieved within 4 days for both NaPBA and GPB; intact GPB was not detected in blood or urine. Cirrhotic subjects converted GPB to PAGN similarly to healthy adults. Simulations suggest that GPB can be administered safely to cirrhotic subjects at levels equivalent to the highest approved NaPBA dose for UCDs. CONCLUSION GPB exhibits delayed release characteristics, presumably reflecting gradual PBA release by pancreatic lipases, and is well tolerated in adults with cirrhosis, suggesting that further clinical testing for HE is warranted.
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Affiliation(s)
| | - Igor A. Zupanets
- National University of Pharmacy and Kharkiv National Medical University, Kharkiv, Ukraine
| | - Mark E. Lowe
- Division of Pediatric Gastroenterology, Hepatology, and Nutrition, University of Pittsburgh, Pittsburgh, PA
| | - Xunjun Xiao
- Division of Pediatric Gastroenterology, Hepatology, and Nutrition, University of Pittsburgh, Pittsburgh, PA
| | - Vasyliy A. Syplyviy
- National University of Pharmacy and Kharkiv National Medical University, Kharkiv, Ukraine
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23
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Malfertheiner P, Schultze V, Rosenkranz B, Kaufmann SHE, Ulrichs T, Novicki D, Norelli F, Contorni M, Peppoloni S, Berti D, Tornese D, Ganju J, Palla E, Rappuoli R, Scharschmidt BF, Del Giudice G. Safety and immunogenicity of an intramuscular Helicobacter pylori vaccine in noninfected volunteers: a phase I study. Gastroenterology 2008; 135:787-95. [PMID: 18619971 DOI: 10.1053/j.gastro.2008.05.054] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 05/12/2008] [Accepted: 05/21/2008] [Indexed: 02/06/2023]
Abstract
INTRODUCTION Helicobacter pylori infection is among the most common human infections and the major risk factor for peptic disease and gastric cancer. Immunization with vaccines containing the H pylori vacuolating cytotoxin A (VacA), cytotoxin-associated antigen (CagA), and neutrophil-activating protein (NAP), alone or in combination, have been shown to prevent experimental infection in animals. AIM We sought to study the safety and immunogenicity of a vaccine consisting of recombinant VacA, CagA, and NAP given intramuscularly with aluminium hydroxide as an adjuvant to noninfected healthy subjects. METHODS This controlled, single-blind Phase I study randomized 57 H pylori-negative volunteers into 7 study arms exploring 2 dosages (10 and 25 microg) of each antigen and 3 schedules (0, 1, 2 weeks; 0, 1, 2 months; and 0, 1, 4 months) versus alum controls. All participants were followed for 5 months. Thirty-six subjects received a booster vaccination 18-24 months after the completion of the primary vaccination. RESULTS Local and systemic adverse reactions were mild and similar in placebo and vaccine recipients on the monthly schedules. All subjects responded to 1 or 2 of the antigens and 86% of all vaccines mounted immunoglobulin G antibody responses to all 3 antigens. Vaccinees exhibited an antigen-specific cellular response. Vaccination 18-24 months later elicited anamnestic antibody and cellular responses. CONCLUSIONS This intramuscular H pylori vaccine demonstrated satisfactory safety and immunogenicity, produced antigen-specific T-cell memory, and, therefore, warrants further clinical study.
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Affiliation(s)
- Peter Malfertheiner
- Otto-von-Guericke Universitaet, Department of Gastroenterology, Hepatology and Infectious Diseases, Magdeburg, Germany
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24
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Insel PA, Kornfeld S, Majerus PW, Marks AR, Marks PA, Relman AS, Scharschmidt BF, Stossel TP, Varki AP, Weiss SJ, Wilson JD. Blasts from the past. J Clin Invest 2004; 114:1017-33. [PMID: 15489944 PMCID: PMC522273 DOI: 10.1172/jci23321] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
With this issue of the JCI, we celebrate the 80th anniversary of the Journal. While 80 years is not a century, we still feel it is important to honor what the JCI has meant to the biomedical research community for 8 decades. To illustrate why the JCI is the leading general-interest translational research journal edited by and for biomedical researchers, we have asked former JCI editors-in-chief to reflect on some of the major scientific advances reported in the pages of the Journal during their tenures.
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25
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Neves FAR, Cavalieri RR, Simeoni LA, Gardner DG, Baxter JD, Scharschmidt BF, Lomri N, Ribeiro RCJ. Thyroid hormone export varies among primary cells and appears to differ from hormone uptake. Endocrinology 2002; 143:476-83. [PMID: 11796501 DOI: 10.1210/endo.143.2.8631] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We characterized T3 efflux in primary cultures of cells derived from human placenta, neonatal rat cardiac myocytes, and rat inner medullary collecting ducts (IMCD). The T3 efflux rate was highest in placenta cells, followed by ventriculocytes, atriocytes, and IMCD cells. Verapamil reversibly blocked [125I]T3 efflux in these cells in a manner that correlated with their T3 efflux rate. Thus, verapamil inhibition of [125I]T3 efflux in placenta cells led to a 432% increase in the [125I]T3 content compared with 33% increase in IMCD cells. Several unlabeled iodothyronines, but not TRIAC, differentially blocked [125I]T3 efflux such as (T4 > T3 > rT3 = D-T3 > D-T4) in placenta cells and (T4 > rT3 = D-T4 = T3 > D-T3) in ventriculocytes, suggesting tissue-specific differences in the carriers/transporters responsible for T3 efflux. This hypothesis draws further support from the fact that D-T3 inhibited [125I]T3 efflux in placenta cells, but not in ventriculocytes. TRIAC did not affect T3 efflux in ventriculocytes or placenta cells, but it greatly inhibited [125I]T3 uptake in these cells, suggesting that [125I]T3 uptake and efflux mechanisms are distinct and appear to be mediated by distinct carrier/transporter proteins. Collectively, these data suggest that differences in thyroid hormone transport in target cells may provide an important mechanism for regulating hormone action in a tissue-specific fashion.
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Affiliation(s)
- Francisco A R Neves
- Department of Pharmaceutical Sciences, University of Brasília, Brasília, DF 70910-900, Brazil
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26
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Cavalieri RR, Simeoni LA, Park SW, Baxter JD, Scharschmidt BF, Ribeiro RC, Lomri N. Thyroid hormone export in rat FRTL-5 thyroid cells and mouse NIH-3T3 cells is carrier-mediated, verapamil-sensitive, and stereospecific. Endocrinology 1999; 140:4948-54. [PMID: 10537118 DOI: 10.1210/endo.140.11.7127] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Export of L-T3 out of the cell is one factor governing the cellular T3 content and response. We previously observed in liver-derived cells that T3 export was inhibited by verapamil, suggesting that it is due to either ATP-binding cassette/multidrug resistance (MDR1/mdr1b) or multidrug resistance-related (MRP1/mrp1) proteins. To test this hypothesis we measured T3 export in FRTL-5, NIH-3T3, and rat hepatoma (HTC) cells that varied in expression of these proteins. FRTL-5 and NIH-3T3 cells were found to contain a T3 efflux mechanism that is verapamil inhibitable, saturable, and stereospecific. By contrast, T3 efflux in HTC cells was slow and unaffected by verapamil. Neither FRTL-5 nor NIH-3T3 cells express mdrlb, but all three cell types express mrpl, as assessed by immunoblotting. Overexpression of MDR1 in NIH-3T3 cells did not enhance verapamil-inhibitable T3 efflux. Photoaffinity labeling of FRTL-5 and NIH-3T3 cells with [125I]L-T3 revealed a labeled 90- to 100-kDa protein that was not present in HTC cells. Verapamil and excess nonradioactive L-T3, but not D-T3, inhibited labeling of this protein. The lack of correlation between T3 efflux and MDR1 and mrpl expression and the finding of a photoaffinity-labeled putative transport protein smaller than MDR1 or mrp1 protein (approximately 170 kDa) suggest that a novel protein is involved in the transport of T3 out of cells.
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Affiliation(s)
- R R Cavalieri
- Nuclear Medicine Research Laboratory, Veterans Administration Medical Center, San Francisco, California, USA
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27
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Wolkoff AW, Suchy FJ, Moseley RH, Meier PJ, Gollan JL, Freimer N, Fitz JG, Boyer JL, Berk PD, Scharschmidt BF. Advances in hepatic transport: molecular mechanisms, genetic disorders, and treatment. A summary of the 1998 AASLD single topic conference. Hepatology 1998; 28:1713-9. [PMID: 9828241 DOI: 10.1002/hep.510280637] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- A W Wolkoff
- Albert Einstein College of Medicine, Bronx, NY, USA.
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28
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Bull LN, van Eijk MJ, Pawlikowska L, DeYoung JA, Juijn JA, Liao M, Klomp LW, Lomri N, Berger R, Scharschmidt BF, Knisely AS, Houwen RH, Freimer NB. A gene encoding a P-type ATPase mutated in two forms of hereditary cholestasis. Nat Genet 1998; 18:219-24. [PMID: 9500542 DOI: 10.1038/ng0398-219] [Citation(s) in RCA: 487] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cholestasis, or impaired bile flow, is an important but poorly understood manifestation of liver disease. Two clinically distinct forms of inherited cholestasis, benign recurrent intrahepatic cholestasis (BRIC) and progressive familial intrahepatic cholestasis type 1 (PFIC1), were previously mapped to 18q21. Haplotype analysis narrowed the candidate region for both diseases to the same interval of less than 1 cM, in which we identified a gene mutated in BRIC and PFIC1 patients. This gene (called FIC1) is the first identified human member of a recently described subfamily of P-type ATPases; ATP-dependent aminophospholipid transport is the previously described function of members of this subfamily. FIC1 is expressed in several epithelial tissues and, surprisingly, more strongly in small intestine than in liver. Its protein product is likely to play an essential role in enterohepatic circulation of bile acids; further characterization of FIC1 will facilitate understanding of normal bile formation and cholestasis.
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Affiliation(s)
- L N Bull
- Department of Psychiatry and Liver Center, University of California San Francisco, 94143, USA
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29
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Abstract
With major advances in biomedical science over the last 2 decades, the possibility of treating human disease at a genetic level has become a tantalizing possibility. As a result, a growing number of investigators are focusing on the development of techniques to deliver therapeutic genes into cells. The liver has been a model organ in the development of this gene transfer technology. This review focuses on the attributes and limitations of the current gene delivery systems that have been explored in the context of liver disease and highlights the obstacles that must be addressed before hepatic gene therapy becomes a clinical reality.
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Affiliation(s)
- T J Davern
- Department of Medicine, University of California, San Francisco 94143-0538, USA
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30
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Roman RM, Wang Y, Lidofsky SD, Feranchak AP, Lomri N, Scharschmidt BF, Fitz JG. Hepatocellular ATP-binding cassette protein expression enhances ATP release and autocrine regulation of cell volume. J Biol Chem 1997; 272:21970-6. [PMID: 9268333 DOI: 10.1074/jbc.272.35.21970] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In a model liver cell line, recovery from swelling is mediated by a sensitive autocrine pathway involving conductive release of ATP, P2 receptor stimulation, and opening of membrane Cl- channels (Wang, Y., Roman, R. M., Lidofsky, S. D., and Fitz, J. G. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 12020-12025). However, the mechanisms coupling changes in cell volume to ATP release are not known. Based on evidence that certain ATP-binding cassette (ABC) proteins may function as ATP channels or channel regulators, we evaluated the potential role of ABC proteins by comparing ATP release and volume regulation in rat HTC and HTC-R hepatoma cells, the latter of which overexpress Mdr proteins. In both cell types, Cl- current activation (ICl-swell) and volume recovery following swelling were dependent on conductive ATP efflux. The rate of volume recovery was approximately 6-fold faster in HTC-R cells compared with HTC cells. This effect is likely due to enhanced ABC protein-dependent ATP release since (i) ICl-swell and cell volume recovery were eliminated by inhibition of P-glycoprotein transport (20 microM verapamil and 15 microM cyclosporin A); (ii) swelling-induced Cl- current density was similar in both cell types (approximately -50 pA/pF; not significant); and (iii) ATP conductance measured by whole-cell techniques was increased approximately 3-fold in HTC-R cells compared with HTC cells. Moreover, HTC-R cells exhibited enhanced survival during hypotonic stress. By modulating ATP release, hepatic ABC proteins may play a key role in the cellular pathways coupling changes in cell volume to ion permeability and secretion.
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Affiliation(s)
- R M Roman
- Division of Gastroenterology, Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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31
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Luther TT, Hammerman P, Rahmaoui CM, Lee PP, Sela-Herman S, Matula GS, Ananthanarayanan M, Suchy FJ, Cavalieri RR, Lomri N, Scharschmidt BF. Evidence for an ATP-dependent bile acid transport protein other than the canalicular liver ecto-ATPase in rats. Gastroenterology 1997; 113:249-54. [PMID: 9207285 DOI: 10.1016/s0016-5085(97)70102-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND & AIMS Canalicular secretion is rate limiting in overall blood-to-bile transport of bile acids. Studies using transfected cells have implicated the canalicular ecto-adenosine triphosphatase (ecto-ATPase) in adenosine triphosphate (ATP)-dependent bile acid transport. However, the structural features of this ecto-ATPase are not those anticipated for an in-to-out ATP-dependent transporter. The aim of this study was to explore the possible existence of an ATP-dependent bile acid transport mechanism distinct from ecto-ATPase. METHODS Bile acid transport activity and ecto-ATPase expression were analyzed in primary rat hepatocytes, rat hepatoma HTC cells, and specially adapted HTC (HTC-R) cells using plasma membrane vesicles and Northern blot, slot blot, ribonuclease protection assay, and Western blot analyses. RESULTS Plasma membranes isolated from HTC-R cells exhibited ATP-dependent taurocholate transport, which was many-fold greater than that in HTC cells. Hepatocytes showed the highest transport rates. Protein and RNA analyses showed very low expression of ecto-ATPase in HTC and HTC-R cells compared with hepatocytes. There was no difference between the two cell types at both the RNA and protein level. CONCLUSIONS These findings show the presence in HTC-R cells and, apparently in hepatocytes, of one or more proteins other than the ecto-ATPase that mediate ATP-dependent transport of bile acids.
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Affiliation(s)
- T T Luther
- Department of Medicine, University of California, San Francisco 94143-0538, USA
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32
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Ribeiro RC, Cavalieri RR, Lomri N, Rahmaoui CM, Baxter JD, Scharschmidt BF. Thyroid hormone export regulates cellular hormone content and response. J Biol Chem 1996; 271:17147-51. [PMID: 8663353 DOI: 10.1074/jbc.271.29.17147] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Actions of thyroid hormones (THs) are determined by intracellular free hormone concentration. Here we report that enhanced TH extrusion via a saturable, cold-sensitive mechanism lowers intracellular TH and causes TH resistance in hepatoma cells. Since these cells overexpress multidrug resistance P-glycoproteins and TH extrusion and resistance are blunted by verapamil, P-glycoproteins may mediate this resistance. Verapamil-inhibitable TH efflux was also found in primary hepatocytes, cardiocytes, and fibroblasts. These findings demonstrate that TH extrusion can modulate TH availability and action in mammalian cells.
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Affiliation(s)
- R C Ribeiro
- Department of Medicine, University of California, San Francisco, California 94143-0540, USA
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33
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Hagenbuch B, Scharschmidt BF, Meier PJ. Effect of antisense oligonucleotides on the expression of hepatocellular bile acid and organic anion uptake systems in Xenopus laevis oocytes. Biochem J 1996; 316 ( Pt 3):901-4. [PMID: 8670169 PMCID: PMC1217435 DOI: 10.1042/bj3160901] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A Na(+)-dependent bile acid (Na+/taurocholate co-transporting polypeptide; Ntcp) and a Na(+)-independent bromosulphophthalein (BSP)/bile acid uptake system (organic-anion-transporting polypeptide; oatp) have been cloned from rat liver by using functional expression cloning in Xenopus laevis oocytes. To evaluate the extent to which these cloned transporters could account for overall hepatic bile acid and BSP uptake, we used antisense oligonucleotides to inhibit the expression of Ntcp and oatp in Xenopus laevis oocytes injected with total rat liver mRNA. An Ntcp-specific antisense oligonucleotide co-injected with total rat liver mRNA blocked the expression of Na(+)-dependent taurocholate uptake by approx. 95%. In contrast, an oatp-specific antisense oligonucleotide when co-injected with total rat liver mRNA had no effect on the expression of Na(+)-dependent taurocholate uptake, but it blocked Na(+)-independent uptake of taurocholate by approx. 80% and of BSP by 50%. Assuming similar expression of hepatocellular bile acid and organic anion transporters in Xenopus laevis oocytes, these results indicate that Ntcp and oatp respectively represent the major, if not the only, Na(+)-dependent and Na(+)-independent taurocholate uptake systems in rat liver. By contrast, the cloned oatp accounts for only half of BSP transport, suggesting that there must be additional, non-bile acid transporting organic anion uptake systems in rat liver.
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Affiliation(s)
- B Hagenbuch
- Department of Medicine, University Hospital, Zürich, Switzerland
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34
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Abstract
The interest of mammalian biologists in ATP-binding cassette (ABC) proteins is relatively recent. However, ABC proteins are widespread in distribution and have long been known to play an important transport role in prokaryotes. The review includes a brief overview of the structure, regulation, and varied functions of ABC proteins in different cell types as well as a synopsis of the emerging role of ABC proteins in human biology and disease. The review then focuses on the established (canalicular secretion of organic cations by the multidrug resistance, or MDR 1, gene product; ductular secretion of fluid and electrolytes mediated by CFTR), probable (biliary phospholipid secretion by the MDR 2 gene product; secretion of non-bile acid organic anions by the multidrug resistance protein, or MRP), and possible (bile acid secretion; biliary secretion of the signaling molecule, ATP; hormone transport) roles of known and novel ABC proteins in hepatobiliary secretion.
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Affiliation(s)
- N Lomri
- Department of Medicine, University of California, San Francisco, 94143-0538, USA
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35
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36
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Affiliation(s)
- B F Scharschmidt
- Department of Medicine, University of California, San Francisco, USA
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37
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Brown RS, Lomri N, De Voss J, Rahmaoui CM, Xie MH, Hua T, Lidofsky SD, Scharschmidt BF. Enhanced secretion of glycocholic acid in a specially adapted cell line is associated with overexpression of apparently novel ATP-binding cassette proteins. Proc Natl Acad Sci U S A 1995; 92:5421-5. [PMID: 7777523 PMCID: PMC41706 DOI: 10.1073/pnas.92.12.5421] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Secretion of anionic endo- and xenobiotics is essential for the survival of animal and plant cells; however, the underlying molecular mechanisms remain uncertain. To better understand one such model system--i.e., secretion of bile acids by the liver--we utilized a strategy analogous to that employed to identify the multidrug resistance (mdr) genes. We synthesized the methyl ester of glycocholic acid (GCE), which readily enters cells, where it is hydrolyzed to yield glycocholic acid, a naturally occurring bile acid. The rat hepatoma-derived HTC cell line gradually acquired resistance to GCE concentrations 20-fold higher than those which inhibited growth of naive cells, yet intracellular accumulation of radiolabel in resistant cells exposed to [14C]GCE averaged approximately 25% of that in nonresistant cells. As compared with nonresistant cells, resistant cells also exhibited (i) cross-resistance to colchicine, a known mdr substrate, but not to other noxious substances transported by hepatocytes; (ii) increased abundance on Northern blot of mRNA species up to 7-10 kb recognized by a probe for highly conserved nucleotide-binding domain (NBD) sequences of ATP-binding cassette (ABC) proteins; (iii) increased abundance, as measured by RNase protection assay, of mRNA fragments homologous to a NBD cRNA probe; and (iv) dramatic overexpression, as measured by Western blotting and immunofluorescence, of a group of 150- to 200-kDa plasma membrane proteins recognized by a monoclonal antibody against a region flanking the highly conserved NBD of mdr/P-glycoproteins. Finally, Xenopus laevis oocytes injected with mRNA from resistant cells and incubated with [14C]GCE secreted radiolabel more rapidly than did control oocytes. Enhanced secretion of glycocholic acid in this cell line is associated with overexpression of ABC/mdr-related proteins, some of which are apparently novel and are likely to include a bile acid transport protein.
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Affiliation(s)
- R S Brown
- Department of Medicine, University of California, San Francisco 94143, USA
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38
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Wright TL, Hollander H, Pu X, Held MJ, Lipson P, Quan S, Polito A, Thaler MM, Bacchetti P, Scharschmidt BF. Hepatitis C in HIV-infected patients with and without AIDS: prevalence and relationship to patient survival. Hepatology 1994. [PMID: 7927246 DOI: 10.1002/hep.1840200508] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Limited information is available about the prevalence of hepatitis C virus in patients with human immunodeficiency virus in relation to specific risk factors or about the influence of hepatitis C virus coinfection on survival. This retrospective study addressed these questions. METHODS The study population consisted of 512 predominantly non-intravenous drug-using male homosexuals, 224 of whom had AIDS. Samples positive for hepatitis C virus antibody by second-generation enzyme immunoassay were further tested by means of strip immunoblot assay, and for hepatitis C virus RNA by means of polymerase chain reaction amplification. A randomly selected set of enzyme immunoassay-negative samples was also tested for hepatitis C virus RNA and, if hepatitis C virus RNA positive, by a second-generation recombinant immunoblot assay. RESULTS The prevalence of hepatitis C virus infection unaccounted for by intravenous drug use or transfusion was 11.7% by enzyme immunoassay, and 87% of sera positive by enzyme immunoassay were also positive by second-generation recombinant immunoblot assay or hepatitis C virus RNA analysis. Hepatitis C virus RNA was detectable in 53% of enzyme immunoassay-positive samples but in only about 1% of enzyme immunoassay-negative samples. Hepatitis C virus coinfection did not influence survival of HIV-infected patients with or without manifestations of AIDS. CONCLUSIONS Hepatitis C virus infection in nontransfused, non-intravenous drug-using patients with HIV infection is several times more prevalent than in volunteer blood donors, suggesting homosexual transmission of hepatitis C virus. About half of patients seropositive for hepatitis C virus antibody have detectable hepatitis C virus RNA, and serologically occult hepatitis C virus viremia is rare. Hepatitis C virus coinfection does not appear to adversely influence survival.
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Affiliation(s)
- T L Wright
- Department of Medicine, University of California, San Francisco 94121
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Scharschmidt BF, DeAmicis A, Bacchetti P, Held MJ. Chance, concurrence, and clustering. Analysis of reviewers' recommendations on 1,000 submissions to the Journal of Clinical Investigation. J Clin Invest 1994; 93:1877-80. [PMID: 8182120 PMCID: PMC294293 DOI: 10.1172/jci117177] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Affiliation(s)
- B F Scharschmidt
- Department of Medicine, School of Medicine, University of California, San Francisco 94143
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Scharschmidt BF. Nurturing creativity: young Turks and young minds. J Clin Invest 1993; 92:1597-601. [PMID: 8408612 PMCID: PMC288314 DOI: 10.1172/jci116741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Affiliation(s)
- B F Scharschmidt
- Division of Gastroenterology, University of California, San Francisco 94143
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Lidofsky SD, Xie MH, Sostman A, Scharschmidt BF, Fitz JG. Vasopressin increases cytosolic sodium concentration in hepatocytes and activates calcium influx through cation-selective channels. J Biol Chem 1993; 268:14632-6. [PMID: 7686902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
A variety of hormonal agonists activate transmembrane Na+ and Ca2+ flux in hepatocytes, but the responsible mechanisms are poorly understood. We employed microfluorimetric and patch clamp recording techniques in hepatocytes to determine the effect of the hormone vasopressin on cytosolic Na+ concentration ([Na+]i) and to identify the transmembrane Na+ transport pathways activated by this agonist. Under basal conditions, [Na+]i, measured using the Na(+)-sensitive fluorophore sodium-binding benzofuran isophthalate, averaged 12.1 +/- 1.6 mM. Exposure to vasopressin rapidly increased [Na+]i by 8.3 +/- 0.9 mM. This increase was attributable to activation of Na+ influx. It occurred in the absence of solutes co-transported with Na+ and was not associated with activation of Na+/H+ antiport. In cell-attached membrane patches, vasopressin activated ion channels that carried inward positive current at the resting membrane potential. Further characterization in excised membrane patches revealed two classes of ion channels, with conductances of 16.0 +/- 2.8 and 30.9 +/- 3.1 picosiemens, respectively. Single channel currents reversed near 0 mV, and ion substitution studies demonstrated that each channel type was permeable to Na+, Ca2+, and K+ but not Cl-. These observations in hepatocytes indicate that vasopressin increases [Na+]i and activates cation-selective channels, which likely accounts for vasopressin-activated Na+ and Ca2+ influx.
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Affiliation(s)
- S D Lidofsky
- Department of Medicine and Liver Center, University of California, San Francisco 94143-0538
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Abstract
Hepatocytes possess several mechanisms for membrane acid-base transport, which work in concert to maintain intracellular pH (pHi) in a narrow physiological range, despite metabolic processes that produce and consume substantial quantities of H+ and HCO3-.Na(+)-H+ and Cl(-)-HCO3- exchangers contribute to recovery from intracellular acidosis and alkalosis, respectively, but are largely inoperative at physiological values of pHi. Recent studies indicate that hepatocytes also possess a mechanism for coupled transport of Na+ and HCO3- across the basolateral membrane. This appears to be the dominant pathway for membrane acid-base transport operative under basal conditions, mediates influx of Na+ and HCO3-, and is an important contributor to recovery from intracellular acidosis. In this review, the properties of hepatic Na(+)-HCO3- cotransport are described with emphasis on its effects on pHi and Na+ homeostasis and on the possible role of membrane potential difference as a signal modulating the rate of HCO3- influx and pHi of hepatocytes through effects on this transporter.
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Affiliation(s)
- J G Fitz
- Duke University Medical Center, Durham, North Carolina 27710
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Lidofsky SD, Fitz JG, Weisiger RA, Scharschmidt BF. Hepatic taurocholate uptake is electrogenic and influenced by transmembrane potential difference. Am J Physiol 1993; 264:G478-85. [PMID: 8460701 DOI: 10.1152/ajpgi.1993.264.3.g478] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Uptake of the bile acid taurocholate by hepatocytes is coupled to Na+ influx. The stoichiometry of uptake, however, is uncertain, as is the influence of the transmembrane electrical potential difference (PD) on this process. In this study, we examined the relationship between taurocholate extraction and PD (measured using intracellular microelectrodes) in perfused liver, and we measured taurocholate-induced transport current in cultured hepatocytes using patch-clamp recording techniques. In the perfused liver under basal conditions, PD averaged -28.4 +/- 0.6 (SE) mV, and extraction of 1, 50, and 300 microM taurocholate was 0.95 +/- 0.02, 0.98 +/- 0.01, and 0.41 +/- 0.03, respectively. When the Na+ chemical gradient was decreased by replacing perfusate Na+ with choline, the membrane depolarized to -17.2 +/- 1.1 mV, and taurocholate extraction markedly decreased at all taurocholate concentrations (P < 0.01). When perfusate Na+ concentration was held constant at 137 mM, membrane depolarization induced by substitution of gluconate for perfusate Cl- (-17.9 +/- 0.6 mV) or Cl- for nitrate (-10.3 +/- 2.1 mV) significantly decreased extraction of 300 microM taurocholate. Abrupt exposure to taurocholate produced a concentration-dependent membrane depolarization in the presence of Na+, but not in its absence (P < 0.001). In cultured hepatocytes, exposure to 100 microM taurocholate produced an inward current of -0.056 +/- 0.016 pA/pF at a holding potential of -40 mV. This current was Na+ dependent, and it increased twofold as holding potential was changed from -20 to -50 mV.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S D Lidofsky
- Department of Medicine, University of California, San Francisco 94143
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Scharschmidt BF, Held MJ, Hollander HH, Read AE, Lavine JE, Veereman G, McGuire RF, Thaler MM. Hepatitis B in patients with HIV infection: relationship to AIDS and patient survival. Ann Intern Med 1992; 117:837-8. [PMID: 1416559 DOI: 10.7326/0003-4819-117-10-837] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- B F Scharschmidt
- Gastroenterology Division, University of California, San Francisco 94143-0538
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Lidofsky SD, Bass NM, Prager MC, Washington DE, Read AE, Wright TL, Ascher NL, Roberts JP, Scharschmidt BF, Lake JR. Intracranial pressure monitoring and liver transplantation for fulminant hepatic failure. Hepatology 1992; 16:1-7. [PMID: 1618463 DOI: 10.1002/hep.1840160102] [Citation(s) in RCA: 199] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cerebral edema and intracranial hypertension, commonly present in fulminant hepatic failure, may lead to brainstem herniation and limit the survival of comatose patients awaiting liver transplantation before a donor organ becomes available. Also, they are likely responsible for postoperative neurological morbidity and mortality. Although intracranial pressure monitoring has been proposed to aid clinical decision making in this setting, its use in the prevention of brainstem herniation preoperatively, in the selection of patients for liver transplantation who have the potential for neurological recovery and in the maintenance of cerebral perfusion during liver transplantation has not been examined in detail. To address these issues, we established a protocol for intracranial pressure monitoring in comatose patients with fulminant hepatic failure as part of their preoperative and intraoperative management. Twenty adults and three children underwent intracranial pressure monitoring. Ten patients required preoperative medical therapy with mannitol, barbiturates or both for a rise in intracranial pressure above 25 mm Hg. Four patients had a sustained lowering of intracranial pressure, three of whom survived hospitalization. Six patients had intracranial hypertension refractory to medical management, were removed from a waiting list for a donor organ and died with brainstem herniation. Of the remaining 17 patients, 3 died of other causes while awaiting a donor organ, 2 recovered spontaneously without neurological sequelae and 12 underwent liver transplantation. All but one patient undergoing liver transplantation had transient intraoperative intracranial hypertension develop, requiring medical treatment. The 12 patients who had transplants recovered neurologically and were discharged from the hospital.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S D Lidofsky
- Department of Medicine, University of California, San Francisco 94143
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Fitz JG, Lidofsky SD, Xie MH, Scharschmidt BF. Transmembrane electrical potential difference regulates Na+/HCO3- cotransport and intracellular pH in hepatocytes. Proc Natl Acad Sci U S A 1992; 89:4197-201. [PMID: 1570347 PMCID: PMC525660 DOI: 10.1073/pnas.89.9.4197] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We have examined the hypothesis that a regulatory interplay between pH-regulated plasma membrane K+ conductance (gK+) and electrogenic Na+/HCO3- cotransport contributes importantly to regulation of intracellular pH (pHi) in hepatocytes. In individual cells, membrane depolarization produced by transient exposure to 50 mM K+ caused a reversible increase in pHi in the presence, but not absence, of HCO3-, consistent with voltage-dependent HCO3- influx. In the absence of HCO3-, intracellular alkalinization and acidification produced by NH4Cl exposure and withdrawal produced membrane hyperpolarization and depolarization, respectively, as expected for pHi-induced changes in gK+. By contrast, in the presence of HCO3-, NH4Cl exposure and withdrawal produced a decrease in apparent buffering capacity and changes in membrane potential difference consistent with compensatory regulation of electrogenic Na+/HCO3- cotransport. Moreover, the rate of pHi and potential difference recovery was several-fold greater in the presence as compared with the absence of HCO3-. Finally, continuous exposure to 10% CO2 in the presence of HCO3- produced intracellular acidification, and the rate of pHi recovery from intracellular acidosis was inhibited by Ba2+, which blocks pHi-induced changes in gK+, and by 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid, which inhibits Na+/HCO3- cotransport. These findings suggest that in hepatocytes, changes in transmembrane electrical potential difference, mediated by pH-sensitive gK+, play a central role in regulation of pHi through effects on electrogenic Na+/HCO3- cotransport.
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Affiliation(s)
- J G Fitz
- Department of Medicine, University of California, San Francisco 94143
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Fitz JG, Lidofsky SD, Xie MH, Cochran M, Scharschmidt BF. Plasma membrane H(+)-HCO3- transport in rat hepatocytes: a principal role for Na(+)-coupled HCO3- transport. Am J Physiol 1991; 261:G803-9. [PMID: 1659220 DOI: 10.1152/ajpgi.1991.261.5.g803] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Na(+)-coupled HCO3- transport has been demonstrated in the basolateral membrane of hepatocytes, but there is uncertainty regarding its stoichiometry or capacity compared with other mechanisms of H(+)-HCO3- transport. After preincubation in medium free of Na+, either in the presence or absence of HCO3(-)-CO2, rat hepatocytes in primary culture were reexposed to Na+ or HCO3(-)-CO2 alone or in combination. Transporter electrogenicity was assessed by measuring membrane potential difference (PD), and the relative capacities of Na(+)-coupled HCO3- transport, Cl(-)-HCO3- exchange, and Na(+)-H+ exchange were assessed by measuring the magnitude and rate of change of intracellular pH (pHi) using BCECF. In the absence of Na+, exposure to HCO3- alone had no consistent effect on PD or pHi. In the absence of HCO3-, reexposure to Na+ depolarized cells by 3 +/- 1 mV and caused an amiloride-inhibitable increase in pHi of 0.031 +/- 0.02 units/min. In the presence of HCO3-, reexposure to Na+ hyperpolarized cells by -14 +/- 5 mV and increased pHi at a rate of 0.133 +/- 0.11 units/min; both the hyperpolarization and alkalinization were inhibited by SITS but unaffected by amiloride. These changes in PD indicate that Na(+)-coupled HCO3- transport is electrogenic, consistent with coupling of more than one HCO3- to each Na+. Furthermore, SITS-inhibitable Na(+)-dependent alkalinization exceeds amiloride-inhibitable Na(+)-dependent alkalinization by an order of magnitude, suggesting that the transport capacity of Na(+)-coupled HCO3- transport exceeds that of Na(+)-H+ exchange.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J G Fitz
- Department of Medicine, University of California, San Francisco 94143
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Fitz JG, Lidofsky SD, Weisiger RA, Xie MH, Cochran M, Grotmol T, Scharschmidt BF. HCO3(-)-coupled Na+ influx is a major determinant of Na+ turnover and Na+/K+ pump activity in rat hepatocytes. J Membr Biol 1991; 122:1-10. [PMID: 1875399 DOI: 10.1007/bf01872734] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Recent studies in hepatocytes indicate that Na(+)-coupled HCO3- transport contributes importantly to regulation of intracellular pH and membrane HCO3- transport. However, the direction of net coupled Na+ and HCO3- movement and the effect of HCO3- on Na+ turnover and Na+/K+ pump activity are not known. In these studies, the effect of HCO3- on Na+ influx and turnover were measured in primary rat hepatocyte cultures with 22Na+, and [Na+]i was measured in single hepatocytes using the Na(+)-sensitive fluorochrome SBFI. Na+/K+ pump activity was measured in intact perfused rat liver and hepatocyte monolayers as Na(+)-dependent or ouabain-suppressible 86Rb uptake, and was measured in single hepatocytes as the effect of transient pump inhibition by removal of extracellular K+ on membrane potential difference (PD) and [Na+]i. In hepatocyte monolayers, HCO3- increased 22Na+ entry and turnover rates by 50-65%, without measurably altering 22Na+ pool size or cell volume, and HCO3- also increased Na+/K+ pump activity by 70%. In single cells, exposure to HCO3- produced an abrupt and sustained rise in [Na+]i from approximately 8 to 12 mM. Na+/K+ pump activity assessed in single cells by PD excursions during transient K+ removal increased congruent to 2.5-fold in the presence of HCO3-, and the rise in [Na+]i produced by inhibition of the Na+/K+ pump was similarly increased congruent to 2.5-fold in the presence of HCO3-. In intact perfused rat liver, HCO3- increased both Na+/K+ pump activity and O2 consumption. These findings indicate that, in hepatocytes, net coupled Na+ and HCO3- movement is inward and represents a major determinant of Na+ influx and Na+/K+ pump activity. About half of hepatic Na+/K+ pump activity appears dedicated to recycling Na+ entering in conjunction with HCO3- to maintain [Na+]i within the physiologic range.
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Affiliation(s)
- J G Fitz
- Department of Medicine and Liver Center, University of California, San Francisco
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Lidofsky SD, Xie MH, Scharschmidt BF. Na(+)-Ca2+ exchange in cultured rat hepatocytes: evidence against a role in cytosolic Ca2+ regulation or signaling. Am J Physiol 1990; 259:G56-61. [PMID: 2372064 DOI: 10.1152/ajpgi.1990.259.1.g56] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Plasma membrane Na(+)-Ca2+ exchange contributes importantly to the regulation of cytosolic Ca2+ concentration ([Ca2+]i) in excitable cells. Despite extensive study in excitable tissues, the role of this transporter in the regulation of [Ca2+]i in hepatocytes is unknown, and conflicting information has been reported regarding the presence of Na(+)-Ca2+ exchange in hepatocyte plasma membrane vesicles. We have therefore assessed the role of Na(+)-dependent Ca2+ transport in the regulation of [Ca2+]i in rat hepatocytes in primary culture under basal conditions and after exposure to vasopressin, a hormone that elevates [Ca2+]i. Ca2+ efflux, measured using 45Ca, did not differ in the presence or absence of extracellular Na+, either under basal conditions or in response to vasopressin. [Ca2+]i, measured using the Ca2(+)-sensitive dye fura-2, was not altered by transient or prolonged exposure to Na(+)-free media or by exposure to ouabain in concentrations sufficient to produce a five-fold elevation in intracellular Na+ concentration. The [Ca2+]i response to vasopressin was also unaffected by Na+ removal or ouabain. By contrast, in cultured rat cardiac myocytes, cells that possess Na(+)-Ca2+ exchange, transient or prolonged Na+ removal as well as ouabain exposure produced greater than fivefold increases in [Ca2+]i compared with controls. We conclude that Na(+)-Ca2+ exchange does not contribute to the regulation of [Ca2+]i in hepatocytes.
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Affiliation(s)
- S D Lidofsky
- Department of Medicine, University of California, San Francisco 94143
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Scharschmidt BF. Something Old, Something New, Something Blue. J Clin Invest 1990. [DOI: 10.1172/jci114396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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