Systemic activation of glutamate dehydrogenase increases renal ammoniagenesis: implications for the hyperinsulinism/hyperammonemia syndrome

2010 ◽  
Vol 298 (6) ◽  
pp. E1219-E1225 ◽  
Author(s):  
Jason R. Treberg ◽  
Kathy A. Clow ◽  
Katie A. Greene ◽  
Margaret E. Brosnan ◽  
John T. Brosnan
Keyword(s):  
Skeletal Muscle ◽  
Carboxylic Acid ◽  
Glutamate Dehydrogenase ◽  
Glutamate Oxaloacetate Transaminase ◽  
Gain Of Function ◽  
Ammonia Metabolism ◽  
Allosteric Activator

The hyperinsulism/hyperammonemia (HI/HA) syndrome is caused by glutamate dehydrogenase (GDH) gain-of-function mutations that reduce the inhibition by GTP, consequently increasing the activity of GDH in vivo. The source of the hyperammonemia in the HI/HA syndrome remains unclear. We examined the effect of systemic activation of GDH on ammonia metabolism in the rat. 2-Aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) is a nonmetabolizable analog of the natural GDH allosteric activator leucine. A dose of 100 μmol BCH/100 g rat resulted in a mild systemic hyperammonemia. Using arterial-venous (A-V) differences, we exclude the liver, intestine, and skeletal muscle as major contributors to this BCH-induced hyperammonemia. However, renal ammonia output increased, as demonstrated by an increase in A-V difference for ammonia across the kidney in BCH-treated animals. Isolated renal cortical tubules incubated with BCH increased the rate of ammoniagenesis from glutamine by 40%. The flux through GDH increased more than twofold when BCH was added to renal mitochondria respiring on glutamine. The flux through glutaminase was not affected by BCH, whereas glutamate-oxaloacetate transaminase flux decreased when normalized to glutaminase flux. These data show that increased renal ammoniagenesis due to activation of GDH can explain the BCH-induced hyperammonemia. These results are discussed in relation to the organ source of the ammonia in the HI/HA syndrome as well as the role of GDH in regulating renal ammoniagenesis.

scholarly journals Study of Staphylococcus aureusPathogenic Genes by Transfer and Expression in the Less Virulent Organism Streptococcus gordonii

2001 ◽  
Vol 69 (2) ◽  
pp. 657-664 ◽  
Author(s):  
P. Stutzmann Meier ◽  
J. M. Entenza ◽  
P. Vaudaux ◽  
P. Francioli ◽  
M. P. Glauser ◽  
...  
Keyword(s):  
Single Gene ◽  
Individual Factors ◽  
Gene Products ◽  
Streptococcus Gordonii ◽  
Pathogenic Role ◽  
Gain Of Function ◽  
Function Strategy

ABSTRACT Because Staphylococcus aureus strains contain multiple virulence factors, studying their pathogenic role by single-gene inactivation generated equivocal results. To circumvent this problem, we have expressed specific S. aureus genes in the less virulent organism Streptococcus gordonii and tested the recombinants for a gain of function both in vitro and in vivo. Clumping factor A (ClfA) and coagulase were investigated. Both gene products were expressed functionally and with similar kinetics during growth by streptococci and staphylococci. ClfA-positive S. gordoniiwas more adherent to platelet-fibrin clots mimicking cardiac vegetations in vitro and more infective in rats with experimental endocarditis (P < 0.05). Moreover, deletingclfA from clfA-positive streptococcal transformants restored both the low in vitro adherence and the low in vivo infectivity of the parent. Coagulase-positive transformants, on the other hand, were neither more adherent nor more infective than the parent. Furthermore, coagulase did not increase the pathogenicity ofclfA-positive streptococci when both clfA andcoa genes were simultaneously expressed in an artificial minioperon in streptococci. These results definitively attribute a role for ClfA, but not coagulase, in S. aureus endovascular infections. This gain-of-function strategy might help solve the role of individual factors in the complex the S. aureus-host relationship.

scholarly journals Recent advances in understanding the role of FOXO3

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 1372 ◽  
Author(s):  
Renae J. Stefanetti ◽  
Sarah Voisin ◽  
Aaron Russell ◽  
Séverine Lamon
Keyword(s):  
Cell Cycle ◽  
Skeletal Muscle ◽  
Protein Turnover ◽  
Genetic Basis ◽  
The Body ◽  
Biological Processes ◽  
Forkhead Box ◽  
Protein Pool

The forkhead box O3 (FOXO3, or FKHRL1) protein is a member of the FOXO subclass of transcription factors. FOXO proteins were originally identified as regulators of insulin-related genes; however, they are now established regulators of genes involved in vital biological processes, including substrate metabolism, protein turnover, cell survival, and cell death. FOXO3 is one of the rare genes that have been consistently linked to longevity in in vivo models. This review provides an update of the most recent research pertaining to the role of FOXO3 in (i) the regulation of protein turnover in skeletal muscle, the largest protein pool of the body, and (ii) the genetic basis of longevity. Finally, it examines (iii) the role of microRNAs in the regulation of FOXO3 and its impact on the regulation of the cell cycle.

scholarly journals FGF-2–dependent signaling activated in aged human skeletal muscle promotes intramuscular adipogenesis

2021 ◽  
Vol 118 (37) ◽  
pp. e2021013118 ◽  
Author(s):  
Sebastian Mathes ◽  
Alexandra Fahrner ◽  
Umesh Ghoshdastider ◽  
Hannes A. Rüdiger ◽  
Michael Leunig ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Transcriptional Activation ◽  
Human Skeletal Muscle ◽  
Muscle Growth ◽  
Muscle Cells ◽  
Adeno Associated Virus ◽  
Adult Skeletal Muscle

Aged skeletal muscle is markedly affected by fatty muscle infiltration, and strategies to reduce the occurrence of intramuscular adipocytes are urgently needed. Here, we show that fibroblast growth factor-2 (FGF-2) not only stimulates muscle growth but also promotes intramuscular adipogenesis. Using multiple screening assays upstream and downstream of microRNA (miR)-29a signaling, we located the secreted protein and adipogenic inhibitor SPARC to an FGF-2 signaling pathway that is conserved between skeletal muscle cells from mice and humans and that is activated in skeletal muscle of aged mice and humans. FGF-2 induces the miR-29a/SPARC axis through transcriptional activation of FRA-1, which binds and activates an evolutionary conserved AP-1 site element proximal in the miR-29a promoter. Genetic deletions in muscle cells and adeno-associated virus–mediated overexpression of FGF-2 or SPARC in mouse skeletal muscle revealed that this axis regulates differentiation of fibro/adipogenic progenitors in vitro and intramuscular adipose tissue (IMAT) formation in vivo. Skeletal muscle from human donors aged >75 y versus <55 y showed activation of FGF-2–dependent signaling and increased IMAT. Thus, our data highlights a disparate role of FGF-2 in adult skeletal muscle and reveals a pathway to combat fat accumulation in aged human skeletal muscle.

scholarly journals 2-(3-Hydroxy-5-phosphonooxymethyl-2-methyl-4-pyridyl)-1,3-thiazolidine-4-carboxylic Acid, Novel Metabolite of Pyridoxal 5′-Phosphate and Cysteine Is Present in Human Plasma—Chromatographic Investigations

2020 ◽  
Vol 21 (10) ◽  
pp. 3548 ◽  
Author(s):  
Justyna Piechocka ◽  
Monika Wrońska ◽  
Iwona E. Głowacka ◽  
Rafał Głowacki
Keyword(s):  
Carboxylic Acid ◽  
Human Plasma ◽  
Vitamin B6 ◽  
Active Form ◽  
Aqueous Environment ◽  
Breast Cancer Patients ◽  
Limit Of Quantification ◽  
Apparently Healthy

It is well-established that aminothiols, to which cysteine (Cys) belongs, are highly reactive towards aldehydes in an aqueous environment, forming substituted thiazolidine carboxylic acids. This report provides evidence that formation of the product containing a thiazolidine ring through non-enzymatic condensation of Cys and an active form of vitamin B6 pyridoxal 5′-phosphate (PLP) occurs in vivo in humans. To prove this point, a new method, based on a gas chromatography coupled with mass spectrometry (GC-MS), has been designed to identify and quantify Cys and PLP adduct, 2-(3-hydroxy-5-phosphonooxymethyl-2-methyl-4-pyridyl)-1,3-thiazolidine-4-carboxylic acid (HPPTCA) in human plasma. The GC-MS assay relies on sample deproteinization by ultrafiltration over cut-off membranes and preconcentration by drying under vacuum, followed by treatment of the residue with derivatization mixture containing anhydrous pyridine, N-trimethylsilyl-N-methyl trifluoroacetamide (MSTFA) and trimethylchlorosilane (TMCS). The method quantifies HPPTCA in a linear range from 1 to 20 µmol L−1, where the lowest standard on the calibration curve refers to the limit of quantification (LOQ). The validity of the method was demonstrated. Furthermore, the method was successfully applied to plasma samples donated by apparently healthy volunteers and breast cancer patients. The GC-MS assay provides a new tool that will hopefully facilitate studies on the role of HPPTCA in living systems.

scholarly journals Inositol 1,4-bisphosphate is an allosteric activator of muscle-type 6-phosphofructo-1-kinase

1989 ◽  
Vol 259 (2) ◽  
pp. 463-470 ◽  
Author(s):  
G W Mayr
Keyword(s):  
Inositol Phosphates ◽  
Head Group ◽  
Muscle Type ◽  
Allosteric Effectors ◽  
Fructose 1,6 Bisphosphate ◽  
Regulatory Properties ◽  
Allosteric Activator

The allosteric effects of various inositol biphosphate (InsP2) isomers and other inositol phosphates, of glycerophosphoinositol phosphates (GroPInsPx) and of phosphoinositides (PtdInsPx) on muscle-type 6-phosphofructo-1-kinase (PFK) were investigated. The binding of these substances to PFK was indirectly estimated by their ability to stabilize the tetrameric enzyme. At near-physiological concentrations of other allosteric effectors, muscle PFK was activated AMP-dependently by Ins(1,4)P2 (Ka = 43 microM), Ins(2,4)P2 (Ka = 70 microM) and GroPIns4P (Ka = 20 microM). These compounds activated PFK by a mechanism similar to that established for activating hexose bisphosphates. Indirect binding experiments indicated minimal Kd,app. values of about 5 microM for the binding of Ins(1,4)P2 in the presence of 0.1 mM-AMP at pH 7.4. This apparent affinity was comparable with that of fructose 1,6-bisphosphate and glucose 1,6-bisphosphate at identical conditions. The enzyme was also found to interact specifically with PtdIns4P (Kd,app. = 37 microM), the inositol phospholipid carrying Ins(1,4)P2 as its head group. The regulatory behaviour of muscle-type PFK in vitro and the concentrations of Ins(1,4)P2 in vivo (between 4 and greater than 50 nmol/g wet wt. of tissue) are consistent with the hypothesis that there is a functional interaction in vivo. Furthermore, a role of PtdIns4P in membrane compartmentation of PFK is suggested. Comparative experiments with liver PFK indicate that these regulatory properties may be relatively specific for the muscle isoform. Unlike muscle PFK, the liver isoform was slightly activated by sub-micromolar concentrations of Ins(1,4,5)P3.

scholarly journals Anti-Inflammatory and Antinociceptive Activities of Anthraquinone-2-Carboxylic Acid

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Jae Gwang Park ◽  
Seung Cheol Kim ◽  
Yun Hwan Kim ◽  
Woo Seok Yang ◽  
Yong Kim ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Molecular Mechanisms ◽  
Interleukin 1 ◽  
Nuclear Factor ◽  
Experimental Conditions ◽  
Gene Assay ◽  
Anti Inflammatory ◽  
Gastric Irritation

Anthraquinone compounds are one of the abundant polyphenols found in fruits, vegetables, and herbs. However, thein vivoanti-inflammatory activity and molecular mechanisms of anthraquinones have not been fully elucidated. We investigated the activity of anthraquinones using acute inflammatory and nociceptive experimental conditions. Anthraquinone-2-carboxylic acid (9,10-dihydro-9,10-dioxo-2-anthracenecarboxylic acid, AQCA), one of the major anthraquinones identified from Brazilian taheebo, ameliorated various inflammatory and algesic symptoms in EtOH/HCl- and acetylsalicylic acid- (ASA-) induced gastritis, arachidonic acid-induced edema, and acetic acid-induced abdominal writhing without displaying toxic profiles in body and organ weight, gastric irritation, or serum parameters. In addition, AQCA suppressed the expression of inflammatory genes such as cyclooxygenase- (COX-) 2 in stomach tissues and lipopolysaccharide- (LPS-) treated RAW264.7 cells. According to reporter gene assay and immunoblotting analyses, AQCA inhibited activation of the nuclear factor- (NF-)κB and activator protein- (AP-) 1 pathways by suppression of upstream signaling involving interleukin-1 receptor-associated kinase 4 (IRAK1), p38, Src, and spleen tyrosine kinase (Syk). Our data strongly suggest that anthraquinones such as AQCA act as potent anti-inflammatory and antinociceptive componentsin vivo, thus contributing to the immune regulatory role of fruits and herbs.

Role of Interleukin-6 in Skeletal Muscle Protein Breakdown and Cathepsin Activity in vivo

1996 ◽  
Vol 28 (5) ◽  
pp. 361-366 ◽  
Author(s):  
J. Fujita ◽  
T. Tsujinaka ◽  
C. Ebisui ◽  
M. Yano ◽  
H. Shiozaki ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Interleukin 6 ◽  
Muscle Protein ◽  
Protein Breakdown ◽  
Skeletal Muscle Protein ◽  
Muscle Protein Breakdown ◽  
Cathepsin Activity

scholarly journals Circular RNA hsa_circ_0001829 promotes gastric cancer progression through miR-155-5p/SMAD2 axis

2020 ◽  
Vol 39 (1) ◽  
Author(s):  
Qiuling Niu ◽  
Zhijie Dong ◽  
Min Liang ◽  
Yuanwei Luo ◽  
Hai Lin ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Cell Lines ◽  
Cancer Progression ◽  
Cell Cycle Progression ◽  
Luciferase Assay ◽  
Migration And Invasion ◽  
Circular Rnas ◽  
Gain Of Function

Abstract Background Accumulating evidences have shown that circular RNAs (circRNAs) play important roles in regulating the pathogenesis of cancer. However, the role of circRNAs in gastric cancer (GC) remains largely unclear. Methods In this study, we identified a novel upregulated circRNA, hsa_circ_0001829, in chemically induced malignant transformed human gastric epithelial cells using RNA-seq. Subsequent qRT-PCR and ISH assays were performed to detect the expression level of hsa_circ_0001829 in GC cell lines and tissues. Functional roles of hsa_circ_0001829 in GC were then explored by loss- and gain-of- function assays. Bioinformatic prediction and luciferase assay were used to investigate potential mechanisms of hsa_circ_0001829. Finally, the mice xenograft and metastasis models were constructed to assess the function of hsa_circ_0001829 in vivo. Results We found that hsa_circ_0001829 was significantly upregulated in GC tissues and cell lines. Loss- and gain-of- function assays showed that hsa_circ_0001829 promotes GC cells proliferation, migration and invasion, and the affected cell cycle progression and apoptosis rates may account for the effect of hsa_circ_0001829 on GC proliferation. In addition, bioinformatic prediction and luciferase assay showed that hsa_circ_0001829 acts as a molecular sponge for miR-155-5p and that SMAD2 was a target gene of miR-155-5p; moreover, hsa_circ_0001829 sponges miR-155-5p to regulate SMAD2 expression and hsa_circ_0001829 promotes GC progression through the miR-155-5p–SMAD2 pathway. Finally, suppression of hsa_circ_0001829 expression inhibited tumor growth and aggressiveness in vivo. Conclusion Taken together, our findings firstly demonstrated a novel oncogenic role of hsa_circ_0001829 in GC progression through miR-155-5p–SMAD2 axis, and our study may offer novel biomarkers and therapeutic targets for GC.

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