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Molecular Genetics and Metabolism Nov 2017Glycerol phenylbutyrate (GPB) is approved in the US for the management of patients 2months of age and older with urea cycle disorders (UCDs) that cannot be managed with...
INTRODUCTION
Glycerol phenylbutyrate (GPB) is approved in the US for the management of patients 2months of age and older with urea cycle disorders (UCDs) that cannot be managed with protein restriction and/or amino acid supplementation alone. Limited data exist on the use of nitrogen conjugation agents in very young patients.
METHODS
Seventeen patients (15 previously on other nitrogen scavengers) with all types of UCDs aged 2months to 2years were switched to, or started, GPB. Retrospective data up to 12months pre-switch and prospective data during initiation of therapy were used as baseline measures. The primary efficacy endpoint of the integrated analysis was the successful transition to GPB with controlled ammonia (<100μmol/L and no clinical symptoms). Secondary endpoints included glutamine and levels of other amino acids. Safety endpoints included adverse events, hyperammonemic crises (HACs), and growth and development.
RESULTS
82% and 53% of patients completed 3 and 6months of therapy, respectively (mean 8.85months, range 6days-18.4months). Patients transitioned to GPB maintained excellent control of ammonia and glutamine levels. There were 36 HACs in 11 patients before GPB and 11 in 7 patients while on GPB, with a reduction from 2.98 to 0.88 episodes per year. Adverse events occurring in at least 10% of patients while on GPB were neutropenia, vomiting, diarrhea, pyrexia, hypophagia, cough, nasal congestion, rhinorrhea, rash/papule.
CONCLUSION
GPB was safe and effective in UCD patients aged 2months to 2years. GPB use was associated with good short- and long-term control of ammonia and glutamine levels, and the annualized frequency of hyperammonemic crises was lower during the study than before the study. There was no evidence for any previously unknown toxicity of GPB.
Topics: Ammonia; Child, Preschool; Cough; Disease Management; Drug-Related Side Effects and Adverse Reactions; Female; Fever; Glutamine; Glycerol; Humans; Infant; Male; Neutropenia; Phenylbutyrates; Prospective Studies; Retrospective Studies; Urea Cycle Disorders, Inborn
PubMed: 28916119
DOI: 10.1016/j.ymgme.2017.09.002 -
Nature Communications Sep 2018Heterozygous de novo mutations in the neuronal protein Munc18-1 are linked to epilepsies, intellectual disability, movement disorders, and neurodegeneration. These...
Heterozygous de novo mutations in the neuronal protein Munc18-1 are linked to epilepsies, intellectual disability, movement disorders, and neurodegeneration. These devastating diseases have a poor prognosis and no known cure, due to lack of understanding of the underlying disease mechanism. To determine how mutations in Munc18-1 cause disease, we use newly generated S. cerevisiae strains, C. elegans models, and conditional Munc18-1 knockout mouse neurons expressing wild-type or mutant Munc18-1, as well as in vitro studies. We find that at least five disease-linked missense mutations of Munc18-1 result in destabilization and aggregation of the mutant protein. Aggregates of mutant Munc18-1 incorporate wild-type Munc18-1, depleting functional Munc18-1 levels beyond hemizygous levels. We demonstrate that the three chemical chaperones 4-phenylbutyrate, sorbitol, and trehalose reverse the deficits caused by mutations in Munc18-1 in vitro and in vivo in multiple models, offering a novel strategy for the treatment of varied encephalopathies.
Topics: Animals; Brain Diseases; Caenorhabditis elegans Proteins; Cell Line, Tumor; Cells, Cultured; HEK293 Cells; Humans; Mice, Knockout; Munc18 Proteins; Mutation, Missense; Neurons; Organic Chemicals; Phenylbutyrates; Protein Aggregates; Protein Aggregation, Pathological; Saccharomyces cerevisiae Proteins; Sorbitol; Trehalose
PubMed: 30266908
DOI: 10.1038/s41467-018-06507-4 -
FASEB Journal : Official Publication of... Sep 2019Healthy cardiomyocytes are electrically coupled at the intercalated discs by gap junctions. In infarcted hearts, adverse gap-junctional remodeling occurs in the border...
Healthy cardiomyocytes are electrically coupled at the intercalated discs by gap junctions. In infarcted hearts, adverse gap-junctional remodeling occurs in the border zone, where cardiomyocytes are chemically and electrically influenced by myofibroblasts. The physical movement of these contacts remains unquantified. Using scanning ion conductance microscopy, we show that intercellular contacts between cardiomyocytes and myofibroblasts are highly dynamic, mainly owing to the edge dynamics (lamellipodia) of the myofibroblasts. Decreasing the amount of functional connexin-43 (Cx43) at the membrane through Cx43 silencing, suppression of Cx43 trafficking, or hypoxia-induced Cx43 internalization attenuates heterocellular contact dynamism. However, we found decreased dynamism and stabilized membrane contacts when cellular coupling was strengthened using 4-phenylbutyrate (4PB). Fluorescent-dye transfer between cells showed that the extent of functional coupling between the 2 cell types correlated with contact dynamism. Intercellular calcein transfer from myofibroblasts to cardiomyocytes is reduced after myofibroblast-specific Cx43 down-regulation. Conversely, 4PB-treated myofibroblasts increased their functional coupling to cardiomyocytes. Consistent with lamellipodia-mediated contacts, latrunculin-B decreases dynamism, lowers physical communication between heterocellular pairs, and reduces Cx43 intensity in contact regions. Our data show that heterocellular cardiomyocyte-myofibroblast contacts exhibit high dynamism. Therefore, Cx43 is a potential target for prevention of aberrant cardiomyocyte coupling and myofibroblast proliferation in the infarct border zone.-Schultz, F., Swiatlowska, P., Alvarez-Laviada, A., Sanchez-Alonso, J. L., Song, Q., de Vries, A. A. F., Pijnappels, D. A., Ongstad, E., Braga, V. M. M., Entcheva, E., Gourdie, R. G., Miragoli, M., Gorelik, J. Cardiomyocyte-myofibroblast contact dynamism is modulated by connexin-43.
Topics: Animals; Antineoplastic Agents; Cell Adhesion; Cell Communication; Cell Movement; Cells, Cultured; Connexin 43; Gap Junctions; Male; Myocytes, Cardiac; Myofibroblasts; Phenylbutyrates; Rats; Rats, Sprague-Dawley
PubMed: 31253057
DOI: 10.1096/fj.201802740RR -
Bioengineered Feb 2022Rifampin (RFP), a first-line anti-tuberculosis drug, often induces cholestatic liver injury and hyperbilirubinemia which limits its clinical use. Multidrug...
Rifampin (RFP), a first-line anti-tuberculosis drug, often induces cholestatic liver injury and hyperbilirubinemia which limits its clinical use. Multidrug resistance-associated protein 2 (MRP2) localizes to the hepatocyte apical membrane and plays a pivotal role in the biliary excretion of bilirubin glucuronides. RFP is discovered to reduce MRP2 expression in liver cells. 4-Phenylbutyrate (4-PBA), a drug used to treat ornithine transcarbamylase deficiency (DILI), is reported to alleviate RFP-induced liver cell injury. However, the underlying mechanism still remains unclear. In the current study, we discovered that RFP induced HepG2 cell viability reduction, apoptosis and MRP2 ubiquitination degradation. Administration of 4-PBA alleviated the effect of RFP on HepG2 cell viability reduction, apoptosis and MRP2 ubiquitination degradation. In mechanism, 4-PBA suppressed RPF-caused intracellular Ca disorder and endoplasmic reticulum (ER) stress, as well as the increases of Clathrin and adapter protein 2 (AP2). ER stress marker protein C/EBP homologous protein took part in the modulation of AP2 and clathrin. Besides, 4-PBA reduced the serum bilirubin level in RFP-induced cholestasis mouse model, along with raised the MRP2 expression in liver tissues. These findings indicated that 4-PBA could alleviate RFP-induced cholestatic liver injury and thereby decreased serum total bilirubin concentration via inhibiting ER stress and ubiquitination degradation of MRP2, which provides new insights into the mechanism of 4-PBA in the treatment of RFP-induced cholestasis and liver damage.
Topics: Animals; Apoptosis; Chemical and Drug Induced Liver Injury, Chronic; Cytoprotection; Endoplasmic Reticulum Stress; Hep G2 Cells; Hepatocytes; Humans; Liver; Male; Mice; Mice, Inbred ICR; Multidrug Resistance-Associated Protein 2; Phenylbutyrates; Protective Agents; Rifampin; Signal Transduction; Ubiquitination
PubMed: 35045794
DOI: 10.1080/21655979.2021.2024970 -
Biochimica Et Biophysica Acta.... Nov 2020Aging impairs the mitochondrial electron transport chain (ETC), especially in interfibrillar mitochondria (IFM). Mitochondria are in close contact with the endoplasmic...
Aging impairs the mitochondrial electron transport chain (ETC), especially in interfibrillar mitochondria (IFM). Mitochondria are in close contact with the endoplasmic reticulum (ER). Induction of ER stress leads to ETC injury in adult heart mitochondria. We asked if ER stress contributes to the mitochondrial dysfunction during aging. Subsarcolemmal mitochondria (SSM) and IFM were isolated from 3, 18, and 24 mo. C57Bl/6 mouse hearts. ER stress progressively increased with age, especially in 24 mo. mice that manifest mitochondrial dysfunction. OXPHOS was decreased in 24 mo. IFM oxidizing complex I and complex IV substrates. Proteomic analysis showed that the content of multiple complex I subunits was decreased in IFM from 24 mo. hearts, but remained unchanged in in 18 mo. IFM without a decrease in OXPHOS. Feeding 24 mo. old mice with 4-phenylbutyrate (4-PBA) for two weeks attenuated the ER stress and improved mitochondrial function. These results indicate that ER stress contributes to the mitochondrial dysfunction in aged hearts. Attenuation of ER stress is a potential approach to improve mitochondrial function in aged hearts.
Topics: Aging; Animals; Electron Transport Complex I; Endoplasmic Reticulum Stress; Hydrogen Peroxide; Male; Mice; Mice, Inbred C57BL; Mitochondria, Heart; Models, Biological; Myocardium; Oxidative Phosphorylation; Phenylbutyrates; Real-Time Polymerase Chain Reaction
PubMed: 32698045
DOI: 10.1016/j.bbadis.2020.165899 -
Epilepsia Jan 2024γ-Aminobutyric acid type A (GABA ) receptor subunit gene mutations are major causes of various epilepsy syndromes, including severe kinds such as Dravet syndrome....
4-Phenylbutyrate promoted wild-type γ-aminobutyric acid type A receptor trafficking, reduced endoplasmic reticulum stress, and mitigated seizures in Gabrg2 mice associated with Dravet syndrome.
OBJECTIVE
γ-Aminobutyric acid type A (GABA ) receptor subunit gene mutations are major causes of various epilepsy syndromes, including severe kinds such as Dravet syndrome. Although the GABA receptor is a major target for antiseizure medications, treating GABA receptor mutations with receptor channel modulators is ineffective. Here, we determined the effect of a novel treatment with 4-phenylbutyrate (PBA) in Gabrg2 knockin mice associated with Dravet syndrome.
METHODS
We used biochemistry in conjunction with differential tagging of the wild-type and the mutant alleles, live brain slice surface biotinylation, microsome isolation, patch-clamp whole-cell recordings, and video-monitoring synchronized electroencephalographic (EEG) recordings in Gabrg2 mice to determine the effect of PBA in vitro with recombinant GABA receptors and in vivo with knockin mice.
RESULTS
We found that PBA reduced the mutant γ2(Q390X) subunit protein aggregates, enhanced the wild-type GABA receptor subunits' trafficking, and increased the membrane expression of the wild-type receptors. PBA increased the current amplitude of GABA-evoked current in human embryonic kidney 293T cells and the neurons bearing the γ2(Q390X) subunit protein. PBA also proved to reduce endoplasmic reticulum (ER) stress caused by the mutant γ2(Q390X) subunit protein, as well as mitigating seizures and EEG abnormalities in the Gabrg2 mice.
SIGNIFICANCE
This research has unveiled a promising and innovative approach for treating epilepsy linked to GABA receptor mutations through an unconventional antiseizure mechanism. Rather than directly modulating the affected mutant channel, PBA facilitates the folding and transportation of wild-type receptor subunits to the cell membrane and synapse. Combining these findings with our previous study, which demonstrated PBA's efficacy in restoring GABA transporter 1 (encoded by SLC6A1) function, we propose that PBA holds significant potential for a wide range of genetic epilepsies. Its ability to target shared molecular pathways involving mutant protein ER retention and impaired protein membrane trafficking suggests broad application in treating such conditions.
Topics: Mice; Humans; Animals; Receptors, GABA-A; Receptors, GABA; Epilepsies, Myoclonic; Seizures; Epilepsy; gamma-Aminobutyric Acid; Endoplasmic Reticulum Stress; Phenylbutyrates
PubMed: 37746768
DOI: 10.1111/epi.17779 -
International Journal of Molecular... Jul 2021There are two types of cytochrome P450 enzymes in nature, namely, the monooxygenases and the peroxygenases. Both enzyme classes participate in substrate biodegradation...
There are two types of cytochrome P450 enzymes in nature, namely, the monooxygenases and the peroxygenases. Both enzyme classes participate in substrate biodegradation or biosynthesis reactions in nature, but the P450 monooxygenases use dioxygen, while the peroxygenases take HO in their catalytic cycle instead. By contrast to the P450 monooxygenases, the P450 peroxygenases do not require an external redox partner to deliver electrons during the catalytic cycle, and also no external proton source is needed. Therefore, they are fully self-sufficient, which affords them opportunities in biotechnological applications. One specific P450 peroxygenase, namely, P450 OleT, reacts with long-chain linear fatty acids through oxidative decarboxylation to form hydrocarbons and, as such, has been implicated as a suitable source for the biosynthesis of biofuels. Unfortunately, the reactions were shown to produce a considerable amount of side products originating from C and C hydroxylation and desaturation. These product distributions were found to be strongly dependent on whether the substrate had substituents on the C and/or C atoms. To understand the bifurcation pathways of substrate activation by P450 OleT leading to decarboxylation, C hydroxylation, C hydroxylation and C-C desaturation, we performed a computational study using 3-phenylpropionate and 2-phenylbutyrate as substrates. We set up large cluster models containing the heme, the substrate and the key features of the substrate binding pocket and calculated (using density functional theory) the pathways leading to the four possible products. This work predicts that the two substrates will react with different reaction rates due to accessibility differences of the substrates to the active oxidant, and, as a consequence, these two substrates will also generate different products. This work explains how the substrate binding pocket of P450 OleT guides a reaction to a chemoselectivity.
Topics: Cytochrome P-450 Enzyme System; Fatty Acids; Models, Chemical; Phenylbutyrates; Phenylpropionates
PubMed: 34281222
DOI: 10.3390/ijms22137172 -
Leukemia Research Nov 2011
Topics: Animals; Enzyme Inhibitors; Female; Human T-lymphotropic virus 1; Humans; Leukemia-Lymphoma, Adult T-Cell; Phenylbutyrates
PubMed: 21868093
DOI: 10.1016/j.leukres.2011.07.036 -
American Journal of Physiology.... Nov 2007To determine whether circulating citrulline can be manipulated in vivo in humans, and, if so, whether citrulline availability affects the levels of related amino acids,...
To determine whether circulating citrulline can be manipulated in vivo in humans, and, if so, whether citrulline availability affects the levels of related amino acids, nitric oxide, urinary citrulline, and urea nitrogen, 10 healthy volunteers were studied on 3 separate days: 1) under baseline conditions; 2) after a 24-h treatment with phenylbutyrate (0.36 g.kg(-1).day(-1)), a glutamine "trapping" agent; and 3) during oral L-citrulline supplementation (0.18 g.kg(-1).day(-1)), in randomized order. Plasma, erythrocyte (RBC), and urinary citrulline concentrations were determined by gas chromatography-mass spectrometry at 3-h intervals between 1100 and 2000 on each study day. Regardless of treatment, RBC citrulline was lower than plasma citrulline, with an RBC-to-plasma ratio of 0.60 +/- 0.04, and urinary citrulline excretion accounted for <1% of the citrulline load filtered by kidney. Phenylbutyrate induced an approximately 7% drop in plasma glutamine (P = 0.013), and 18 +/- 14% (P < 0.0001) and 19 +/- 17% (P < 0.01) declines in plasma and urine citrulline, respectively, with no alteration in RBC citrulline. Oral L-citrulline administration was associated with 1) a rise in plasma, urine, and RBC citrulline (39 +/- 4 vs. 225 +/- 44 micromol/l, 0.9 +/- 0.3 vs. 6.2 +/- 3.8 micromol/mmol creatinine, and 23 +/- 1 vs. 52 +/- 9 micromol/l, respectively); and 2) a doubling in plasma arginine level, without altering blood urea or urinary urea nitrogen excretion, and thus enhanced nitrogen balance. We conclude that 1) depletion of glutamine, the main precursor of citrulline, depletes plasma citrulline; 2) oral citrulline can be used to enhance systemic citrulline and arginine availability, because citrulline is bioavailable and very little citrulline is lost in urine; and 3) further studies are warranted to determine the mechanisms by which citrulline may enhance nitrogen balance in vivo in humans.
Topics: Adult; Amino Acids; Biological Availability; Citrulline; Dietary Supplements; Erythrocytes; Humans; Kinetics; Male; Phenylbutyrates; Reference Values
PubMed: 17901164
DOI: 10.1152/ajpgi.00289.2007 -
Molecular Genetics and Metabolism Aug 2019Glycerol phenylbutyrate (GPB) is currently approved for use in the US and Europe for patients of all ages with urea cycle disorders (UCD) who cannot be managed with...
INTRODUCTION
Glycerol phenylbutyrate (GPB) is currently approved for use in the US and Europe for patients of all ages with urea cycle disorders (UCD) who cannot be managed with protein restriction and/or amino acid supplementation alone. Currently available data on GPB is limited to 12 months exposure. Here, we present long-term experience with GPB.
METHODS
This was an open-label, long-term safety study of GPB conducted in the US (17 sites) and Canada (1 site) monitoring the use of GPB in UCD patients who had previously completed 12 months of treatment in the previous safety extension studies. Ninety patients completed the previous studies with 88 of these continuing into the long-term evaluation. The duration of therapy was open ended until GPB was commercially available. The primary endpoint was the rate of adverse events (AEs). Secondary endpoints were venous ammonia levels, number and causes of hyperammonemic crises (HACs) and neuropsychological testing.
RESULTS
A total of 45 pediatric patients between the ages of 1 to 17 years (median 7 years) and 43 adult patients between the ages of 19 and 61 years (median 30 years) were enrolled. The treatment emergent adverse events (TEAE) reported in ≥10% of adult or pediatric patients were consistent with the TEAEs reported in the previous safety extension studies with no increase in the overall incidence of TEAEs and no new TEAEs that indicated a new safety signal. Mean ammonia levels remained stable and below the adult upper limit of normal (<35 µmol/L) through 24 months of treatment in both the pediatric and adult population. Over time, glutamine levels decreased in the overall population. The mean annualized rate of HACs (0.29) established in the previously reported 12-month follow-up study was maintained with continued GPB exposure.
CONCLUSION
Following the completion of 12-month follow-up studies with GPB treatment, UCD patients were followed for an additional median of 1.85 (range 0 to 5.86) years in the present study with continued maintenance of ammonia control, similar rates of adverse events, and no new adverse events identified.
Topics: Adolescent; Adult; Canada; Child; Child, Preschool; Disease Management; Female; Follow-Up Studies; Glycerol; Humans; Hyperammonemia; Infant; Male; Middle Aged; Neuropsychological Tests; Phenylbutyrates; United States; Urea Cycle Disorders, Inborn; Young Adult
PubMed: 31326288
DOI: 10.1016/j.ymgme.2019.07.004