Association between plasma gamma-glutamyltransferase fractions and metabolic syndrome among hypertensive patients

Among the risk factors associated to metabolic syndrome (MetS), hypertension shows the highest prevalence in Italy. We investigated the relationship between the newly identified serum γ-glutamyltransferase (GGT) fractions, b-s-m-f-GGT, and risk factors associated to MetS in hypertensive patients. A total of ninety-five consecutive hypertensive patients were enrolled. GGT fractions were analysed by gel-filtration chromatography, and hepatic steatosis was evaluated by ultrasound. MetS was diagnosed in 36% of patients. Considering the whole group, b-And f-GGT showed the highest positive correlation with BMI, glucose, triglycerides and insulin, and the highest negative correlation with HDL cholesterol. While both serum triglycerides and insulin were independently associated with b-GGT levels, only triglycerides were independently associated with f-GGT. The values of b-GGT activity increased with steatosis grade (g0 = 1.19; g2 = 3.29; ratio g2/g0 = 2.75, p < 0.0001 linear trend). Patients with MetS showed higher levels of b-GGT, m-GGT and f-GGT [median (25th-75th) U/L: 3.19 (1.50-6.59); 0.55 (0.26-0.81); 10.3 (9.1-13.6); respectively] as compared to subjects presenting with one or two MetS criteria [1.75 (0.95-2.85), p < 0.001; 0.33 (0.19-0.60), p < 0.05; 8.8 (7.0-10.6), p < 0.001]. Our data point to a potential role for b-And f-GGT fractions in identifying MetS patients among hypertensive subjects, thus providing a minimally invasive blood-based tool for MetS diagnosis

Mechanisms and targets of the modulatory action of S-nitrosoglutathione (GSNO) on inflammatory cytokines expression.

A number of experimental studies has documented that S-nitrosoglutathione (GSNO), the main endogenous low-molecular weight S-nitrosothiol, can exert modulatory effects on inflammatory processes, thus supporting its potential employment in medicine for the treatment of important disease conditions. At molecular level, GSNO effects have been shown to modulate the activity of a series of transcription factors (notably NF-jB, AP-1, CREB and others) as well as other components of signal transduction chains (e.g. IKK-b, caspase 1, calpain and others), resulting in the modulation of several cytokines and chemokines expression (TNFa, IL-1b, IFN-c, IL-4, IL-8, RANTES, MCP-1 and others). Results reported to date are however not univocal, and a single main mechanism of action for the observed anti-inflammatory effects of GSNO has not been identified. Conflicting observations can be explained by differences among the various cell types studies as to the relative abundance of enzymes in charge of GSNO metabolism (GSNO reductase, c-glutamyltransferase, protein disulfide isomerase and others), as well as by variables associated with the individual experimental models employed. Altogether anti-inflammatory properties of GSNO seem however to prevail, and exploration of the therapeutic potential of GSNO and analogues appears therefore warranted

Il ruolo delle mutazioni minori del gene HFE nelle iperferritinemie associate a sindrome dismetabolica

La ferritina sierica elevata, o la iperferritinemia, è un riscontro comune agli esami del sangue di routine e spesso richiede ulteriori valutazioni. Nella quasi totalità dei casi, l’iperferritinemia non si associa a sovraccarico marziale e non sempre è possibile determinarne le cause (circa 1 caso su 3 rimane inspiegato). Nella seguente tesi abbiamo studiato casi di iperferritinemia associati a mutazioni minori del gene HFE (ovvero mutazioni caratterizzate da bassa penetranza per emocromatosi) o caratterizzati dall’assenza di cause genetiche evidenti, sia in donatori di sangue che in pazienti già avviati a salassoterapia. Lo scopo del nostro studio retrospettivo è stato quello di: A) verificare la prevalenza della mutazione minore (H63D) del gene HFE nei soggetti con iperferritinemia (sia nei donatori di sangue sia nei pazienti seguiti dall’ambulatorio trasfusionale per salassoterapia); B) valutare eventuali differenze nelle frequenze genotipiche tra donatori e pazienti e tra aree geografiche (Marche- Toscana); C) indagare il ruolo della mutazione HFE minore (H63D) nella manifestazione fenotipica dell’ iperferritinemia e D) nello sviluppo di alterazioni metaboliche sistemiche e steatosiche a livello epatico. Nei gruppi di soggetti con iperferritinemia da noi presi in esame, abbiamo riscontrato le seguenti frequenze alleliche della variante H63D: 25% nei donatori marchigiani; 42,6% - 59,4% nei pazienti marchigiani; 32,6% nei pazienti seguiti a Pisa. I soggetti con mutazioni minori del gene HFE mostravano, rispetto ai controlli: valori più elevati di colesterolo, glicemia e alanino aminotransferasi (ALT); percentuali più alte di alterazioni compatibili con sindrome metabolica; percentuali più elevate di ALT> 40 U/l e alterazioni epatiche di carattere steatosico. Nonostante i numerosi studi sull’argomento, molti aspetti delle iperferritinemie dismetaboliche (DIOS: dysmetabolic iron overload syndrome) associate o meno a NAFLD (non-alcoholic fatty liver disease), sono tuttora discussi e, in particolare per quanto riguarda il ruolo della variante H63D del gene HFE, molti risultati sono contraddittori. Nei soggetti con iperferritinemia da noi presi in esame, la presenza della mutazione H63D risulta associata a maggior rischio di steatosi epatica (OR 4,995), indipendentemente dai valori di saturazione di transferrina (quindi indipendentemente dalla presenza o meno di un sovraccarico marziale dimostrabile biochimicamente)

Effects of membrane gamma-glutamyltranspeptidase activity on expression, redox status and activation of EGFR in prostate cancer cells

Regulation of signal transduction systems by redox-sensing mechanisms is now considered as a general means of overall control on cellular “traditional” signalling, based on protein phosphorylation/dephosphorylation equilibrium. Different redox alterations of thiols in cysteine residues of a protein can induce different functional states, thus acting as a fine post-translational modification. At present, available data mostly extrapolate from model systems employing an exogenous source of prooxidants (e.g., various concentrations of hydrogen peroxide). A novel redox factor of enzymatic nature is gamma-glutamyltranspeptidase (GGT), an ectoenzyme in charge of glutathione catabolism and expressed in a wide range of human epithelial cells as well as cancer cells. Indeed, one of the roles of GGT-dependent production of prooxidants, is modulation of redox status of cell surface protein thiols, as previously described for TNFR1 (tumor necrosis factor 1). Consequently, the present study aims to verify the effects of GGT activity on redox status and function of another transmembrane receptor, i.e. EGFR (epidermal growth factor receptor). Although present in normal cells, EGFR is overexpressed in a variety of tumor cell lines and is currently an important target of cancer therapy. However, despite available data indicate that EGFR expression is generally associated to unfavorable prognosis, much is still to be clarified with respects to other mechanisms concurring with EGFR expression in determining EGFR signalling output. Indeed, one of such mechanisms might consist in redox phenomena. Consistently, our preliminary results show that GGT determines a more oxidized status of the EGFR and this, in turn, also provokes an aberrant reduced phosphorylation of the tyr-1068 residue of the receptor. This can prevent the ubiquitinylation and degradation of EGFR, wich may be sorted to the nucleus instead, where it is known to activate signalling pathways implicated in tumorigenesis and resistance to DNA damaging radiation and alkylating anti-cancer agents. Indeed, in our model system, GGT seems to enhance the localization of the receptor in the perinuclear compartment. Moreover, our data demonstrate that the basal expression of the EGFR is reduced under the prooxidant effect of GGT. These findings may imply that an endogenous source of hydrogen peroxide can shift the balance of the EGFR signalling network acting on several levels, e.g. the receptor trafficking and down-regulation. A better understanding of such processes may be crucial to unravel mechanisms underlaying cancer progression and treatment resistance and may also define new therapeutic targets