Glutathione Catabolism Research Articles

Identification of human circulating factors following remote ischemic conditioning (RIC): Potential impact on stroke

Remote ischemic conditioning (RIC) is a procedure consisting of short cycles of ischemia applied in a limb that activates endogenous protection in distant organs, such as the brain. Despite the promising outcomes of RIC, the biochemical factors governing inter-organ communication remain largely unexplored, particularly in humans. A pilot study on 20 healthy humans was performed to identify potential circulating biochemical factors involved in RIC signalling. Blood was collected before and immediately, 4 and 22 h after the end of RIC. To characterize the responses triggered by RIC, a combination of biochemical and proteomic analysis, along with functional in vitro tests in human cells, were performed.RIC did not alter the levels of nitric oxide, bilirubin and cell-free mitochondrial DNA. In contrast, carboxyhaemoglobin levels increased following RIC at all time points and young subset, suggesting endogenous production of carbon monoxide that is a cytoprotective gasotransmitter. Additionally, the levels of glutathione and cysteinylglycine bound to proteins also increased after RIC, while glutathione catabolism decreased. Plasma proteomic analysis identified overall 828 proteins. Several steps of statistical analysis (Student's t-test, repeated measures ANOVA, with Holm corrected pairwise p-values <0.05 threshold and fold change higher or lower than 100 %) leaded to the identification of 9 proteins with altered circulating levels in response to RIC at 4h and 22h. All 9 proteins are from extracellular space or exosomes, being involved in inflammation, angiogenesis or metabolism control. In addition, RIC-conditioned plasma from young subjects protected microglial cell culture against inflammatory stimuli, indicating an anti-inflammatory effect of RIC. Nevertheless, other functional tests in neurons or endothelial cells had no effect. Overall, we present some evidence for RIC-induced anti-inflammatory and antioxidant responses in healthy human subjects, in particular in young subjects. This study is a first step towards the disclosure of signalling factors involved in RIC-mediated inter-organ communication.

Mitochondrial respiratory function is preserved under cysteine starvation via glutathione catabolism in NSCLC

Cysteine metabolism occurs across cellular compartments to support diverse biological functions and prevent the induction of ferroptosis. Though the disruption of cytosolic cysteine metabolism is implicated in this form of cell death, it is unknown whether the substantial cysteine metabolism resident within the mitochondria is similarly pertinent to ferroptosis. Here, we show that despite the rapid depletion of intracellular cysteine upon loss of extracellular cystine, cysteine-dependent synthesis of Fe-S clusters persists in the mitochondria of lung cancer cells. This promotes a retention of respiratory function and a maintenance of the mitochondrial redox state. Under these limiting conditions, we find that glutathione catabolism by CHAC1 supports the mitochondrial cysteine pool to sustain the function of the Fe-S proteins critical to oxidative metabolism. We find that disrupting Fe-S cluster synthesis under cysteine restriction protects against the induction of ferroptosis, suggesting that the preservation of mitochondrial function is antagonistic to survival under starved conditions. Overall, our findings implicate mitochondrial cysteine metabolism in the induction of ferroptosis and reveal a mechanism of mitochondrial resilience in response to nutrient stress.

Abstract 436: Extracellular glutathione catabolism as an alternative cyst(e)ine source in cancer

Abstract Glutathione (GSH) is the most abundant antioxidant in the human body and plays essential roles in physiology and disease. Unchecked oxidative stress is involved in tumor initiation and progression. Paradoxically, clinical and laboratory data show that ROS-scavenging molecules such as glutathione not only fail to impede tumor growth but, in many cases, accelerate it. Still, preliminary data from our lab show that genetically ablating tumors’ ability to synthesize GSH does not affect their growth. This finding suggests that the favorable influence of glutathione on tumor growth may arise from external sources. Yet, the mechanism cancer cells employ to take advantage of extracellular glutathione in this context is unknown. Here, we show that γ-glutamyl-transpeptidase 1 (GGT1), an enzyme that localizes on the outer side of the cell’s membrane, can break down extracellular GSH, yielding glutamate and the dipeptide cysteinylglycine. Cysteinylglycine can be further metabolized, generating cysteine and glycine to the cells. We found that the addition of exogenous GSH, as well as cysteinylglycine, can mitigate cell death, proliferation arrest, and oxidative stress caused by cystine depletion. The overexpression of human GGT1 in cancer cells significantly reduces the amount of glutathione needed to rescue cell fitness. Accordingly, pharmacologic inhibition of GGT1 activity prevented GSH's ability to rescue cell proliferation. Moreover, an unbiased pharmacological screening revealed that GGT1-mediated cysteine acquisition renders cancer cells resistant to inhibitors of cystine uptake and utilization, supporting the role of GGT1 as a source of cyst(e)ine. Our findings reveal that cancer cells can access cysteine, a vital yet scarce amino acid, through GGT1's ability to break down glutathione, which is present in remarkably high concentrations within the tumor microenvironment. Although the downstream proteins involved in the transport and utilization of GSH breakdown products are yet to be identified, we anticipate this pathway has the potential to uncover novel therapeutic avenues for cancer treatment by targeting alternative pathways of nutrient acquisition that are potentially implicated in cancer progression and therapy resistance. Citation Format: Fabio Hecht, Marco Zocchi, Emily Tuttle, Gloria Asantewaa, TashJaé Scales, Fatemeh Alimohammadi, Nathan Ward, Gina DeNicola, Isaac Harris. Extracellular glutathione catabolism as an alternative cyst(e)ine source in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 436.

Isotope tracing reveals bacterial catabolism of host-derived glutathione during Helicobacter pylori infection.

Mammalian cells synthesize the antioxidant glutathione (GSH) to shield cellular biomolecules from oxidative damage. Certain bacteria, including the gastric pathogen Helicobacter pylori, can perturb host GSH homeostasis. H. pylori infection significantly decreases GSH levels in host tissues, which has been attributed to the accumulation of reactive oxygen species in infected cells. However, the precise mechanism of H. pylori-induced GSH depletion remains unknown, and tools for studying this process during infection are limited. We developed an isotope-tracing approach to quantitatively monitor host-derived GSH in H. pylori-infected cells by mass spectrometry. Using this method, we determined that H. pylori catabolizes reduced GSH from gastric cells using γ-glutamyl transpeptidase (gGT), an enzyme that hydrolyzes GSH to glutamate and cysteinylglycine (Cys-Gly). gGT is an established virulence factor with immunomodulatory properties that is required for H. pylori colonization in vivo. We found that H. pylori internalizes Cys-Gly in a gGT-dependent manner and that Cys-Gly production during H. pylori infection is coupled to the depletion of intracellular GSH from infected cells. Consistent with bacterial catabolism of host GSH, levels of oxidized GSH did not increase during H. pylori infection, and exogenous antioxidants were unable to restore the GSH content of infected cells. Altogether, our results indicate that H. pylori-induced GSH depletion proceeds via an oxidation-independent mechanism driven by the bacterial enzyme gGT, which fortifies bacterial acquisition of nutrients from the host. Additionally, our work establishes a method for tracking the metabolic fate of host-derived GSH during infection.

A STUDY OF CORRELATION BETWEEN GAMMA GLUTAMYL TRANSFERASE AND METABOLIC SYNDROME

CONTEXT:The metabolic syndrome ( Syndrome X, or insulin resistance syndrome) is a combination of several risk factors that contribute to atherosclerotic cardiovascular disease (ASCVD). Elevated blood pressure, triglycerides, hyperglycemia, waist circumference and low HDL- cholesterol are all symptoms of accelerated dyslipidemic atherogenesis. Glutamyl transferase (GGT) has long been thought to be a biomarker for hepatic and biliary illness and alcoholic related disease. GGT is required for the extracellular catabolism of glutathione, which is the most important thiol antioxidant in humans.It co localizes with oxidised low density lipoprotein (LDL) and foam cells in the atheromatous core of coronary plaques. GGT can be a proinammatory sign. GGT was found to be a prognostic marker for Metabolic syndrome, CVD, and heart failure .AIM: Study of Gamma glutamyltransferase in metabolic syndrome patients. MATERIALS AD METHODS: A sample size of 100 patients admitted in medicine and other departments in nri general hospital are included in study Qualitative data was expressed in frequencies and percentages a STASTISTICAL ANALYSIS: nd Quantitative data in mean and standard deviation. Non parametric statistics i.e. Chisquare test was used to nd the signicant association between the two qualitative variables. Independent t test and ANOVA were used to nd the statistical signicance between quantitative variables. Pearson correlation coefcient was used to nd correlation between two variables. p value of &lt;0.05was considered statistically signicant. CONCLUSION: It should be highlighted that elevated levels of GGT are not the only hepatic biomarker of hepatic steatosis, as evidenced by ndings from several research. lines of evidence point to a link between high GGT levels in the blood and the metabolic syndrome. As a result, higher GGT levels are associated with increased insulin resistance and a higher risk of type 2 diabetes .

An unexpected role for leucyl aminopeptidase in UV tolerance revealed by a genome-wide fitness assessment in a model cyanobacterium

UV radiation (UVR) has significant physiological effects on organisms living at or near the Earth's surface, yet the full suite of genes required for fitness of a photosynthetic organism in a UVR-rich environment remains unknown. This study reports a genome-wide fitness assessment of the genes that affect UVR tolerance under environmentally relevant UVR dosages in the model cyanobacterium Synechococcus elongatus PCC 7942. Our results highlight the importance of specific genes that encode proteins involved in DNA repair, glutathione synthesis, and the assembly and maintenance of photosystem II, as well as genes that encode hypothetical proteins and others without an obvious connection to canonical methods of UVR tolerance. Disruption of a gene that encodes a leucyl aminopeptidase (LAP) conferred the greatest UVR-specific decrease in fitness. Enzymatic assays demonstrated a strong pH-dependent affinity of the LAP for the dipeptide cysteinyl-glycine, suggesting an involvement in glutathione catabolism as a function of night-time cytosolic pH level. A low differential expression of the LAP gene under acute UVR exposure suggests that its relative importance would be overlooked in transcript-dependent screens. Subsequent experiments revealed a similar UVR-sensitivity phenotype in LAP knockouts of other organisms, indicating conservation of the functional role of LAPs in UVR tolerance.

Modulation of Subcellular Redox Homeostasis with Trialkylphosphines

Redox homeostasis is essential for cell function and its disruption is associated with multiple pathologies. Redox balance is largely regulated by the relative concentrations of reduced (GSH) and oxidized (GSSG) glutathione. In eukaryotic cells, this ratio is different in each cell compartment. There is a lack of chemical probes able to modulate GSH/GSSG in order to study the impact of redox stress in an organelle specific manner. Here, we highlight the importance of trialkylphosphines to induce reductive stress and how it can be targeted to a specific organelle. Our probe is selectively activated by endogenous nitroreductases, and releases tributylphosphine to trigger redox stress in mitochondria. Mechanistic studies revealed that the induced stress activates a cellular response orchestrated by transcription factor ATF4, which upregulates genes involved in glutathione catabolism.

Glutathione catabolism by Enterobacteriaceae species to hydrogen sulphide adversely affects the viability of host systems in the presence of 5'fluorodeoxyuridine.

Reduced glutathione (GSH) plays an essential role in relieving oxidative insult from the generation of free radicals via normal physiological processes. However, GSH can be exploited by bacteria as a signalling molecule for the regulation of virulence. We describe findings arising from a serendipitous observation that when GSH and Escherichia coli were incubated with 5′fluorodeoxyuridine (FUdR)‐synchronised populations of Caenorhabditis elegans, the nematodes underwent rapid death. Death was mediated by the production of hydrogen sulphide mainly through the action of tnaA, a tryptophanase‐encoding gene in E. coli. Other Enterobacteriaceae species possess similar cysteine desulfhydrases that can catabolise l‐cysteine‐containing compounds to hydrogen sulphide and mediate nematode killing when worms had been pre‐treated with FUdR. When colonic epithelial cell lines were infected, hydrogen sulphide produced by these bacteria in the presence of GSH was also able to inhibit ATP synthesis in these cells particularly when cells had been treated with FUdR. Therefore, bacterial production of hydrogen sulphide could act in concert with a commonly used genotoxic cancer drug to exert host cell impairment. Hydrogen sulphide also increases bacterial adhesion to the intestinal cells. These findings could have implications for patients undergoing chemotherapy using FUdR analogues that could result in intestinal damage.

Disruption of mitochondrial redox homeostasis by enzymatic activation of a trialkylphosphine probe.

Redox homeostasis is essential for cell function and its disruption is associated with multiple pathologies. Redox balance is largely regulated by the relative concentrations of reduced and oxidized glutathione. In eukaryotic cells, this ratio is different in each cell compartment, and disruption of the mitochondrial redox balance has been specifically linked to metabolic diseases. Here, we report a probe that is selectively activated by endogenous nitroreductases, and releases tributylphosphine to trigger redox stress in mitochondria. Mechanistic studies revealed that, counterintuitively, release of a reducing agent in mitochondria rapidly induced oxidative stress through accumulation of superoxide. This response is mediated by glutathione, suggesting a link between reductive and oxidative stress. Furthermore, mitochondrial redox stress activates a cellular response orchestrated by transcription factor ATF4, which upregulates genes involved in glutathione catabolism.

Ген гамма-глутамилциклотрансферазы - ключевого фермента катаболизма глутатиона и предрасположенность к ишемическому инсульту: анализ ассоциаций с болезнью и функциональное аннотирование ДНК-полиморфизмов

Генетико-эпидемиологическими исследованиями установлено, что полиморфные варианты генов ферментов антиоксидантной системы являются значимыми предикторами риска развития и тяжести проявления ишемического инсульта (ИИ). Целью настоящего исследования было изучение ассоциации трех частых однонуклеотидных полиморфизмов (SNP) rs38420, rs4270 и rs6462210 гена гамма-глутамилциклотрансферазы (GGCT) - ключевого фермента катаболизма глутатиона с риском развития ИИ и функциональное аннотирование этих SNPs. Материалом для исследования послужили образцы ДНК 1288 неродственных индивидов славянского происхождения, в том числе 600 пациентов с диагнозом ИИ и 688 относительно здоровых добровольцев. Генотипирование полиморфных вариантов гена GGCT осуществлялось с использованием технологии iPLEX на генетическом анализаторе MassARRAY-4. Функциональное аннотирование SNPs осуществлялось биоинформатическими методами с использованием различных онлайн-инструментов и баз данных. Установлена ассоциация генотипа TT SNP rs6462210 с пониженным риском развития ишемического инсульта (OR=0,36 95%CI 0,15-0,85, p=0,01). Биоинформатический анализ регуляторного потенциала исследованных полиморфных вариантов показал, что их фенотипические эффекты проявляются ослаблением транскрипционной активности гена GGCT преимущественно в клетках крови и артериях, главным образом, в результате химических модификаций хроматина. У полиморфизма rs4270, находящегося в тесном неравновесии по сцеплению с SNP rs6462210 (D’=0,966, p&lt;0,01), обнаружен участок связывания c микроРНК hsa-miR-1246, способной блокировать экспрессию GGCT, тем самым, способствуя снижению образования L-цистеина - предшественника глутатиона. В результате исследования впервые показано, что вариабельность гена GGCT может вносить вклад в развитие ИИ. Экспериментальные исследования по оценке регуляторного потенциала полиморфных вариантов гена GGCT потребуются для патофизиологической интерпретации выявленных ассоциаций. Genetic epidemiological studies have established that polymorphisms of the genes encoding antioxidant defense enzymes represent meaningful predictors for the risk and severity of ischemic stroke (IS). The aim of this study was to investigate associations of IS with three common single nucleotide polymorphisms (SNPs) such as rs38420, rs4270 and rs6462210 in gamma-glutamylcyclotransferase (GGCT) gene, a key enzyme of glutathione catabolism. DNA samples obtained from 1288 unrelated individuals of Slavic origin, including 600 patients with IS and 688 healthy volunteers were included in the study. Genotyping of the GGCT polymorphisms was done using an iPLEX-based technology by the MassARRAY-4 system. Functional annotation of SNPs was performed using numerous online bioinformatics tools and resources. We found an association between genotype T/T rs6462210 and a decreased risk of ischemic stroke (OR = 0.36 95% CI 0.15-0.85, p=0.01). The haplotype rs38420A-rs4270T-rs6462210C showed a clear tendency in association with decreased disease risk (p=0.057). Bioinformatics analysis showed that the phenotypic effects of the SNPs are characterized by a weak transcriptional activity of the GGCT gene mainly in blood cells and arteries as a result of chemical modifications of chromatin. For the rs4270 polymorphism, which is in close linkage disequilibrium with SNP rs6462210 (D’=0.966, p&lt;0.01), we found a binding site for miRNA hsa-miR-1246 which is capable to block the GGCT expression, thereby reducing the formation of L-cysteine, a precursor of glutathione. The study showed for the first time that GGCT gene may contribute to the development of ischemic stroke. Experimental studies focusing on the regulatory potential of GGCT gene polymorphisms are required for the pathophysiological interpretation of the identified associations.

Glutathione catabolism by Treponema denticola impacts its pathogenic potential

Treponema denticola is a spirochete that is etiologic for periodontal diseases. This bacterium is one of two periodontal pathogens that have been shown to have a complete three step enzymatic pathway (GTSP) that catabolizes glutathione to H2S. This pathway may contribute to the tissue pathology seen in periodontitis since diseased periodontal pockets have lower glutathione levels than healthy sites with a concomitant increase in H2S concentration. In order to be able to demonstrate that glutathione catabolism by the GTSP is critical for the pathogenic potential of T. denticola, allelic replacement mutagenesis was used to make a deletion mutant (Δggt) in the gene encoding the first enzyme in the GTSP. The mutant cannot produce H2S from glutathione since it lacks gamma-glutamyltransferase (GGT) activity. The hemolytic and hemoxidation activities of wild type T. denticola plus glutathione are reduced to background levels with the Δggt mutant and the mutant has lost the ability to grow aerobically when incubated with glutathione. The Δggt bacteria with glutathione cause less cell death in human gingival fibroblasts (hGFs) in vitro than do wild type T. denticola and the levels of hGF death correlate with the amounts of H2S produced. Importantly, the mutant spirochetes plus glutathione make significantly smaller lesions than wild type bacteria plus glutathione in a mouse back lesion model that assesses soft tissue destruction, a major symptom of periodontal diseases. Our results are the first to prove that T. denticola thiol-compound catabolism by its gamma-glutamyltransferase can play a significant role in the in the types of host tissue damage seen in periodontitis.

Hubungan kadar serum gamma-glutamyl transferase dengan profil lipid pada Diabetes Melitus-Tipe 2 (DM-2) terkontrol dan tidak terkontrol di Rumah Sakit Umum Pusat Haji, Adam Malik Medan, Indonesia

Background: Diabetes mellitus is a group of metabolic diseases with characteristics of hyperglycemia that occur due to impaired insulin secretion, insulin work, or both whereas also impaired lipid peroxidation caused by oxidative stress. Gamma-glutamyl transferase (GGT) is an enzyme on the surface of the cell membrane that is responsible for the catabolism of glutathione which acts as a marker of oxidative stress. This study aims to determine the relationship of serum GGT levels with lipid profiles in controlled and uncontrolled type 2 DM.Method: A cross-sectional study was conducted at H. Adam Malik General Hospital Medan from September - November 2018 among 60 patients with type 2 DM grouped according to HbA1c &lt;7% controlled and HbA1C &gt; 7% uncontrolled. GGT levels and lipid profiles examined using enzymatic calorimetry and HbA1c with Immunoturbidimetry method. The relationship of serum GGT levels with lipid profiles in controlled DM-2 was tested using the Pearson correlation test whereas controlled DM-2 correlation test using the Spearman's correlation test using SPSS version 21 for Windows.Results: Most of respondents were males with HbA1C levels &lt;7% (53.3%) and HbA1C ≥ 7% (60.0%). There was no difference in the mean age and serum GGT levels between uncontrolled DM-2 or controlled DM-2 group (P = 0.260 and P = 0.520, respectively). There was no association between serum GGT levels and lipid profiles in the controlled type 2 DM group and uncontrolled type 2 DM. (r=P&gt; 0.05).Conclusion: There is no significant relationship between serum GGT levels and lipid profiles in controlled and uncontrolled type 2 DM groups.

Serum level of gamma-glutamyl transferase as a biomarker for predicting stenosis severity in patients with coronary artery disease

BackgroundGamma glutamyl transferase (GGT) is associated with pathogenesis of various diseases such as coronary artery disease (CAD). GGT activity displays an essential role in the catabolism of glutathione which is reported as a major antioxidant. The aim of this study was to explore the association of GGT activity with obstruction severity of artery in 500 CAD patients. ResultsOur finding showed a significant association between serum GGT activity and CAD patients. In particular, the level of GGT in patients who had ≥50% obstruction was higher, compared to healthy and patients with less than 50% obstruction in their coronary arteries (the level of GGT in patients with at least one (1 SVD), two (2VD), three (3VD) coronary artery obstruction were 55.6±9.7, 71.7±12.7 and 84.7±13.4, while these values in patients with negative angio or control group were 28±10 and 17±4.6). Furthermore, the activity of this marker was associated with increased the risk of CAD (Odd ratio of GGT in 3VD group: 2, 95%CI: 1.8–2.3), which was also related with HDL-C. Of note, the level of GGT was enhanced progressively with increasing the obstruction severity of arteries. ConclusionWe demonstrate the prognostic value of serum level of GGT as a biomarker for predicting obstruction severity in patients with CAD.

Gamma-glutamyltransferase activity in exosomes as a potential marker for prostate cancer

BackgroundExosomes or extracellular vesicles have the potential as a diagnostic marker for various diseases including cancer. In order to identify novel exosomal markers for prostate cancer (PC), we performed proteomic analysis of exosomes isolated from PC cell lines and examined the usefulness of the marker in patients.MethodsExosomes isolated by differential centrifugation from the culture medium of androgen-dependent LNCaP prostate cancer cell line and its sublines of partially androgen-independent C4, androgen-independent C4–2 and bone metastatic C4–2B were subjected to iTRAQ-based proteomic analysis. Exosomes were also isolated by immunocapture and separated by size exclusion chromatography and density gradient centrifugation. Protein expression was determined by Western blot analysis. GGT activity was measured using a fluorescent probe, γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG). Immunohistochemical analysis of tissues was performed using anti-GGT1 antibody.ResultsAmong proteins upregulated in C4–2 and C4–2B cells than in LNCaP cells, we focused on gamma-glutamyltransferase 1 (GGT1), a cell-surface enzyme that regulates the catabolism of extracellular glutathione. The levels of both GGT1 large and small subunits were elevated in exosomes isolated from C4–2 and C4–2B cells by differential centrifugation and by immunocapture with anti-CD9 or -prostate-specific membrane antigen (PSMA) antibody. In cell lysates and exosomes, GGT1 expression correlated with GGT activity. Size exclusion chromatography of human serum demonstrated the presence of GGT activity and GGT1 subunits in fractions positive for CD9. Density gradient centrifugation revealed the co-presence of GGT1 subunits with CD9 in exosomes isolated by differential centrifugation from human serum. Since GGT activity correlated with GGT1 expression in serum exosomes isolated by differential centrifugation, we measured serum exosomal GGT activity in patients. Unexpectedly, we found that serum exosomal GGT activity was significantly higher in PC patients than in benign prostatic hyperplasia (BPH) patients. In support of this finding, immunohistochemical analysis showed increased GGT1 expression in PC tissues compared with BPH tissues.ConclusionsOur results suggest that serum exosomal GGT activity could be a useful biomarker for PC.

Glutathione in the human brain: Review of its roles and measurement by magnetic resonance spectroscopy

We review the transport, synthesis and catabolism of glutathione in the brain as well as its compartmentation and biochemistry in different brain cells. The major reactions involving glutathione are reviewed and the factors limiting its availability in brain cells are discussed. We also describe and critique current methods for measuring glutathione in the human brain using magnetic resonance spectroscopy, and review the literature on glutathione measurements in healthy brains and in neurological, psychiatric, neurodegenerative and neurodevelopmental conditions In summary: Healthy human brain glutathione concentration is ∼1–2 mM, but it varies by brain region, with evidence of gender differences and age effects; in neurological disease glutathione appears reduced in multiple sclerosis, motor neurone disease and epilepsy, while being increased in meningiomas; in psychiatric disease the picture is complex and confounded by methodological differences, regional effects, length of disease and drug-treatment. Both increases and decreases in glutathione have been reported in depression and schizophrenia. In Alzheimer's disease and mild cognitive impairment there is evidence for a decrease in glutathione compared to age-matched healthy controls. Improved methods to measure glutathione in vivo will provide better precision in glutathione determination and help resolve the complex biochemistry of this molecule in health and disease.

GAMMA-GLUTAMYL TRANSFERASE AS AN INDICATOR OF OBESITY: A CROSS-SECTIONAL STUDY

ABSTRACTObjective: Obesity, characterized by an increase in excessive fat accumulation, represents a social problem worldwide and has been recognizedas a major underlying factor in the pathogenesis of several diseases. Gamma-glutamyl transferase (GGT) is a cell-surface protein contributing tothe extracellular catabolism of glutathione. Elevated GGT is strongly associated with obesity and excess deposition of fat in the liver, termed nonalcoholicfatty liver disease, which is thought to cause hepatic insulin resistance and contribute to the development of systemic insulin resistanceand hyperinsulinemia. Therefore, we have investigated the serum GGT levels in obese individuals and the correlation of serum GGT with bodymass index (BMI) and waist circumference.Methods: The study was carried out in 100 obese patients and 100 non-obese individuals.Results: Patients with obesity showed a significant increase in GGT levels when compared to the control group. The mean levels of BMI, WC, totalcholesterol, triglycerides, low-density lipoprotein-cholesterol (LDL-c), very LDL-cholesterol, total protein, and aspartate aminotransferase werefound to be significantly elevated in the obese individuals compared to controls. The mean levels of high-density lipoprotein-cholesterol showed asignificant decrease in the obese participants.Conclusion: Elevated liver enzymes, although in normal ranges, especially at upper quartiles as observed in our study, may play a central role inearly diagnosis of fat overflow to the liver. The findings of our study suggest that serum GGT levels may be a simple and reliable marker of visceral fataccumulation.Keywords: Diabetes mellitus, Gamma-glutamyl transferase, Insulin resistance, Metabolic syndrome, Obesity.

Gamma-glutamyltransferase-friend or foe within?

Gamma-glutamyltransferase (GGT) is a liver enzyme, which is located on the plasma membranes of most cells and organ tissues, but more commonly in hepatocytes, and is routinely used in clinical practice to help indicate liver injury and as a marker of excessive alcohol consumption. Among the liver enzymes, important advances have especially been made in understanding the physiological functions of GGT. The primary role of GGT is the extracellular catabolism of glutathione, the major thiol antioxidant in mammalian cells, which plays a relevant role in protecting cells against oxidants produced during normal metabolism; GGT, therefore, plays an important role in cellular defence. Beyond its physiological functions, circulating serum GGT has been linked to a remarkable array of chronic conditions and diseases, which include nonalcoholic fatty liver disease, vascular and nonvascular diseases and mortality outcomes. This review summarizes the available epidemiological and genetic evidence for the associations between GGT and these adverse outcomes, the postulated biologic mechanisms underlying these associations, outlines areas of outstanding uncertainty and the implications for clinical practice.

Role of γ-glutamyltranspeptidase in the pathogenesis of Helicobacter suis and Helicobacter pylori infections.

Helicobacter (H.) suis can colonize the stomach of pigs as well as humans, causing chronic gastritis and other gastric pathological changes including gastric ulceration and mucosa-associated lymphoid tissue (MALT) lymphoma. Recently, a virulence factor of H. suis, γ-glutamyl transpeptidase (GGT), has been demonstrated to play an important role in the induction of human gastric epithelial cell death and modulation of lymphocyte proliferation depending on glutamine and glutathione catabolism. In the present study, the relevance of GGT in the pathogenesis of H. suis infection was studied in mouse and Mongolian gerbil models. In addition, the relative importance of H. suis GGT was compared with that of the H. pylori GGT. A significant and different contribution of the GGT of H. suis and H. pylori was seen in terms of bacterial colonization, inflammation and the evoked immune response. In contrast to H. pyloriΔggt strains, H. suisΔggt strains were capable of colonizing the stomach at levels comparable to WT strains, although they induced significantly less overall gastric inflammation in mice. This was characterized by lower numbers of T and B cells, and a lower level of epithelial cell proliferation. In general, compared to WT strain infection, ggt mutant strains of H. suis triggered lower levels of Th1 and Th17 signature cytokine expression. A pronounced upregulation of B-lymphocyte chemoattractant CXCL13 was observed, both in animals infected with WT and ggt mutant strains of H. suis. Interestingly, H. suis GGT was shown to affect the glutamine metabolism of gastric epithelium through downregulation of the glutamine transporter ASCT2.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0163-6) contains supplementary material, which is available to authorized users.

Gamma glutamyl transferase activity is Independently associated with oxidative stress rather than SYNTAX score

Background. Gamma glutamyl transferase (GGT) is involved in the pathophysiologic process of coronary atherosclerosis. GGT activity plays a role in the catabolism of glutathione which is known as one of the major antioxidants. However, there is a lack of research on direct examination of relevance between serum GGT activity with systemic oxidative stress. Objectives. We aimed to investigate the relationship between GGT activity with systemic oxidative stress markers and the extent and complexity of coronary artery disease (CAD) assessed with SYNTAX score in stable CAD. Methods. Measurements were obtained from 359 patients with stable CAD (Mean age = 57.7 ± 10.1 years). The patients were divided into two groups according to the median GGT level (GGT < median group < 22 and GGT > median group ≥ 22). Angiography was performed and SYNTAX score was calculated in all patients. Oxidative stress markers (total oxidant status [TOS], total antioxidant capacity [TAC] and oxidative stress index [OSI]) were measured in all patients. Results. While SYNTAX score and oxidative stress markers such as TOS and OSI have been increased, TAC was decreased in GGT > median group compared with GGT < median group (p < 0.05, for all). GGT activity was independently associated with diabetes (β = 0.106, p = 0.015) and OSI (β = 0.556, p < 0.001) in multiple linear regression analysis. However, the independent association between GGT activity and SYNTAX score was not found in present study (β = 0.063, p = 0.238). Conclusion. In stable CAD, increased GGT activity within the normal range is associated with increased oxidative stress rather than increased extent and complexity of CAD.

Serum gamma-glutamyl transferase levels and in-hospital mortality in patients with acute heart failure

Acute heart failure (AHF) is a major cause of hospitalisation, morbidity and mortality worldwide. Gamma-glutamyl transferase (GGT) is an enzyme responsible for the extracellular catabolism of antioxidant glutathione and a potential risk indicator of cardiac mortality. Limited data exists on the prognostic value of circulating levels of GGT in patients hospitalized due to AHF. To study the association between baseline GGT activity and in-hospital mortality in AHF patients. The study cohort consisted of 183 AHF patients with left ventricular ejection fraction (LVEF) < 50%. The primary endpoint was in-hospital mortality. Patients were divided into two groups according to in-hospital mortality. The relationship between GGT activity and in-hospital mortality was tested using logistic regression models, adjusting for clinical characteristics and echocardiographic findings. After adjustment for possible confounders, GGT level was significantly related (OR 1.056, 95% CI 1.018-1.096, p = 0.04) to in-hospital mortality. Elevated GGT activity is an independent predictor of short-term mortality in patients with AHF and reduced LVEF.