Glucose-6-phosphate Dehydrogenase Levels Research Articles

Significance of Low Levels of Glucose-6-Phosphate Dehydrogenase Levels in Pregnancy

AbstractAbstract 5165 Purpose of the study:To characterize the significance of Glucose-6- Phosphate Dehydrogenase (G6PD) levels measured in pregnancy. Case series and results:We saw 3 patients referred to Hematology clinic over the past 1 year. The G6PD levels were measured in pregnancy by the obstetrician while working up the anemia (Table 1). They did not have any evidence of hemolysis during the time of workup and it is unclear as to why the G6PD levels were sent. The G6PD levels were found to be low and all 3 patients had iron deficiency anemia, that improved with iron supplementation. There was no evidence of pregnancy induced hypertension, urinary tract infections, or infections during pregnancy. All the pregnancies were uneventful resulting in healthy babies and the G6PD levels normalized after the delivery in all the patients. We did a literature search to see the significance of such an association and if there were any recommendations for further testing in these individuals.Table:1G6PD – in pregnancy (5.0–15.0 U/g HB)Hemoglobin (d) g/dLFerritin (e) (10–291 ng/mL)G6PD post pregnancyHemoglobin (f) g/dL (post pregnancy)Subject A3.4 (6 mos)a10.39.3Adequate (6 mos)b13.8Subject B3.3 (6 mos)a1128.5Intermediate (10 days)C Adequate (6 mos)b12.7Subject C4.3 (7 mos)a1114.8Adequate (3 mos)b13.4a:months of pregnancy at which G6PD was measured.b:months post pregnancy G6PD was measured.c:subject B had G6PD level checked by screening method 10 days post pregnancy that was reported as Intermediate, and the quantitative analysis showed a level of 3. 6 [4. 6 – 13. 5 U/g HB]. G6PD normalized on subsequent testing 6 months post pregnancy.d/e:Hemoglobin and ferritin were checked at the time of measuring G6PD level during pregnancy.f:Hemoglobin checked after delivery at the time of measuring G6PD level. Discussion:G6PD deficiency is one of the most common inherited red cell disorders transmitted in an X-linked recessive fashion affecting approximately 400 million people worldwide. In the United States, black males are most commonly affected, with a prevalence of approximately 10 percent. Acute hemolysis is caused by infection, ingestion of fava beans, or exposure to an oxidative drug. G6PD catalyzes nicotinamide adenine dinucleotide phosphate (NADP) to its reduced form, NADPH, in the pentose phosphate pathway. NADPH protects cells from oxidative damage. G6pd deficiency predisposes cells to increased oxidative damage predisposing to hemolysis. G6PD deficiency in pregnancy may manifest as increased urinary tract infections, preeclamsia, neonatal jaundice, hydrops fetalis and still birth. Vergnes et al. [Lancet 1968] reported that low erythrocyte G6PD levels were found in 25% of women in early pregnancy and in up to 65% of women in late pregnancy. In their study G6PD levels normalized after delivery. The reason for this decrease is unclear. Pregnancy is shown to cause increased oxidative stress, alteration in neutrophil G6PD trafficking [ Kindzelskii et al. J Clin Invest 2002] though it is unclear if any of these mechanisms are implicated in the decreased levels of G6PD during pregnancy. Conclusions:There are no clear guidelines for the subsequent testing and management of low levels of G6PD diagnosed in the setting of pregnancy. Evidence based guidelines would be helpful towards identifying the subset of patients with true G6PD deficiency. Disclosures:No relevant conflicts of interest to declare.

Şizofreni hastalarında kanda glukoz-6-fosfat dehidrogenaz aktivitesi ve element düzeyleri / Elements levels and glucose-6-phosphate dehydrogenase activity in blood of patients with schizophrenia

Objectives: Glucose-6-phosphate dehydrogenase (G6PD) is the rate limiting enzyme of the hexose monophosphate cascade which plays role in the synthesis of nucleotide, reduced glutathion, fatty acid and cholesterol precursors. At the same time, it is an important enzyme for neuronal development during and after fetal life and for neurotransmitters. Serum elements are necessary for neuronal development and synthesis and activity of enzymes and hormones. The aim of this study was to compare serum levels of some elements and G6PD enzyme activity in schizophrenic patients with those in healthy individuals. Methods: This study involved blood serum analysis of 32 schizophrenia patients and 32 age- and sex-matched healthy controls. Copper, zinc, iron, magnesium levels were determined with a double lighted, deuterium sourced, background proof reading fire atomic spectrophotometer and in order to determine aluminum and manganese levels, a graphite tube atomizer spectroscope was used. G6PD enzyme activity was analyzed by the Glock and Mclean Method. Results: This analysis revealed higher levels of G6PD activity, copper, iron, magnesium and aluminum in schizophrenia patients compared to controls, whereas zinc and manganese levels showed a decreasing trend on the contrary. Discussion: The higher levels of G6PD activity in schizophrenic patients is not consistent with the literature in general. It is considered that results on G6PD and element levels may be explained as the effects of specific hormones, antipsychotic medications, or by schizophrenia itself. Conclusion: The elements we investigated and G6PD are important for the antioxidant system. Thus changing levels of elements in patients with schizophrenia may lead to disturbed functions of antioxidant enzymes and G6PD. Further researches on this subject conducted with larger and drug naive patient groups are needed.

Increase of Energy Balance Significantly Alters Major Lipogenic Gene Expression in Lactation Ewes

The objective of the present study was to examine changes observed in the expression of cytosolic NADP isocitrate dehydrogenase (ICDH) and glucose 6-phosphate dehydrogenase (G6PD) genes, the major implicated genes in ruminant lipogenesis in terms of produce NADPH, during the early post-weaning period in dairy ewes in respect to energy intake, and to further correlate the noted changes with their respective enzymatic activities. A total of 21 subcutaneous adipose tissue samples were obtained from seven lactating (2nd lactation period) dairy ewes of the Chios breed. Adipose tissue samples were taken from the tail head region at weeks 1, 2, and 4 after weaning (45 days after parturition). Dairy ewes were in negative energy balance during weeks 1 and 2 after weaning and they moved into a strong positive energy balance at week 4 after weaning. Expression of ICDH and G6PD genes and their respective enzymatic activity was determined. Results showed that both genes’ expression and enzymatic activities were significantly minimal at week 1 after weaning, reaching a maximum level at week 4 after weaning (P < 0.05). A 3.5-fold and a 5-fold increase of G6PD and ICDH mRNA levels were observed, respectively. Concerning their respective enzymatic activities, a 5.5-fold and 2-fold increase was noted, respectively. A positive correlation was found between ICDH and G6PD gene expression (P < 0.001) indicating a synchronized response to energy intake changes. Almost similar changes were observed for enzymatic activities, rendering these enzymes as potential biochemical markers of ovine lipogenesis

Antiparasitic Therapy

Parasitic diseases affect more than 2 billion people globally and cause substantial morbidity and mortality, particularly among the world's poorest people. This overview focuses on the treatment of the major protozoan and helminth infections in humans. Recent developments in antiparasitic therapy include the expansion of artemisinin-based therapies for malaria, new drugs for soil-transmitted helminths and intestinal protozoa, expansion of the indications for antiparasitic drug treatment in patients with Chagas disease, and the use of combination therapy for leishmaniasis and human African trypanosomiasis.

Modulation of antioxidant status and lipid peroxidation in erythrocyte by dietary supplementation during heat stress in buffaloes

The aim of this study was to determine the ameliorative effect of dietary supplementation on heat stress induced oxidative stress in buffalo erythrocytes. Experiments were performed on eight adult buffaloes of either sex divided in two groups of four animals each viz. group I (control), group II (supplemented with sodium bicarbonate, potassium carbonate and ascorbic acid). Animals were exposed to hot dry (40 °C, ambient humidity) and hot humid (37 °C, 70% relative humidity) conditions for 4 h daily for 5 days in psychrometric chamber. Activities catalase (CAT), superoxide dismutase (SOD) and glucose 6 phosphate dehydrogenase (G6PD) and levels of reduced glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) were significantly ( P < 0.05) increased after exposure to heat stress in both groups under hot dry as well as hot humid conditions. Supplemented group showed significant ( P < 0.05) fall in CAT, SOD and G6PD activities and levels of GSH and TBARS. The results indicate that supplementation of ascorbate along with salts (sodium bicarbonate, potassium carbonate) was effective in reducing heat stress in buffaloes.

Blue cures blue but be cautious

Methemoglobinemia is a disorder characterized by the presence of >1% methemoglobin (metHb) in the blood. Spontaneous formation of methemoglobin is normally counteracted by protective enzyme systems, for example, nicotinamide adenine dinucleotide phosphate (NADPH) methemoglobin reductase. Methemoglobinemia is treated with supplemental oxygen and methylene blue (1–2 mg/kg) administered slow intravenously, which acts by providing an artificial electron acceptor for NADPH methemoglobin reductase. But known or suspected glucose-6-phosphate dehydrogenase (G6PD) deficiency is a relative contraindication to the use of methylene blue because G6PD is the key enzyme in the formation of NADPH through pentose phosphate pathway and G6PD-deficient individuals generate insufficient NADPH to efficiently reduce methylene blue to leukomethylene blue, which is necessary for the activation of the NADPH-dependent methemoglobin reductase system. So, we should be careful using methylene blue in methemoglobinemia patient before G6PD levels.

16-Bromoepiandrosterone, an activator of the mammalian immune system, inhibits glucose 6-phosphate dehydrogenase from Trypanosoma cruzi and is toxic to these parasites grown in culture

Glucose 6-phosphate dehydrogenase (G6PDH) catalyzes the first step of the pentose-phosphate pathway which supplies cells with ribose 5-phosphate (R5P) and NADPH. R5P is the precursor for the biosynthesis of nucleotides while NADPH is the cofactor of several dehydrogenases acting in a broad range of biosynthetic processes and in the maintenance of the cellular redox state. RNA interference-mediated reduction of G6PDH levels in bloodstream-form Trypanosoma brucei validated this enzyme as a drug target against Human African Trypanosomiasis. Dehydroepiandrosterone (DHEA), a human steroidal pro-hormone and its derivative 16α-bromoepiandrosterone (16BrEA) are uncompetitive inhibitors of mammalian G6PDH. Such steroids are also known to enhance the immune response in a broad range of animal infection models. It is noteworthy that the administration of DHEA to rats infected by Trypanosoma cruzi, the causative agent of Human American Trypanosomiasis (also known as Chagas’ disease), reduces blood parasite levels at both acute and chronic infection stages. In the present work, we investigated the in vitro effect of DHEA derivatives on the proliferation of T. cruzi epimastigotes and their inhibitory effect on a recombinant form of the parasite’s G6PDH ( TcG6PDH). Our results show that DHEA and its derivative epiandrosterone (EA) are uncompetitive inhibitors of TcG6PDH, with K i values of 21.5 ± 0.5 and 4.8 ± 0.3 μM, respectively. Results from quantitative inhibition assays indicate 16BrEA as a potent inhibitor of TcG6PDH with an IC 50 of 86 ± 8 nM and those from in vitro cell viability assays confirm its toxicity for T. cruzi epimastigotes, with a LD 50 of 12 ± 8 μM. In summary, we demonstrated that, in addition to host immune response enhancement, 16BrEA has a direct effect on parasite viability, most likely as a consequence of TcG6PDH inhibition.

Study of Glucose-6-phosphate Dehydrogenase (G6PD) Status in Preeclampsia

Background: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is one of the common enzymopathy and may be one of the risk factor for complicated pregnancy. Objectives : To measure erythrocyte G6PD level in pregnant women with preeclampsia in order to observe this enzyme status and also to measure Hb, TC of RBC, serum bilirubin, reticulocyte count to observe hemolytic status. In addition, to correlate this enzyme level with all these hematological parameters in order to find out any relationships among them. Methods: This cross sectional study was carried out in the Department of Physiology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Shahbag, Dhaka from January to December 2008. For this, 30 pregnant women with preeclampsia, age ranged from 20 to 34 years during their third trimester (>24th weeks) were studied (group B). They were selected from the Obstetric and Gynae Out Patient Department (OPD) of BSMMU and Bangladesh Medical College Hospital (BMCH) of Dhaka City. For comparison age matched 30 apparently normal pregnant women of the same gestational age (control group - group A) were also studied. They were selected by personal contact. Erythrocyte G6PD level was measured by Spectrophotometric method using kit of Randox. Serum bilirubin, hemoglobin concentration, total count of RBC and reticulocyte count were measured by standard laboratory techniques. For statistical analysis ANOVA, independent sample t test, Chi-square test and Pearson's correlation coefficient test were performed by using SPSS for windows version-12 as applicable. Results: In this study, erythrocyte G6PD level was significantly lower in preeclampsia in comparison to that of control but their percentages of involvement was not statistically significant. In addition, hemoglobin concentration and RBC count were significantly lower and serum bilirubin and reticulicyte count were significantly higher in the study group than those of control group. On the other hand, erythrocyte G6PD level was positively correlated with hemoglobin concentration and total count of RBC while negatively correlated with serum bilirubin and reticulocyte count and all these relationships were statistically significant in the study group. Conclusion: Therefore, this study revealed that presence of G6PD deficiency associated with hemolysis in preeclampsia may act as a contributory factor for the development of this complicated pregnancy. Key words: G6PD; preeclampsia DOI: 10.3329/bsmmuj.v2i2.4758 BSMMU J 2009; 2(2): 56-60

Unexpected glucose‐6‐phosphate dehydrogenase deficiency

A 50-year-old man with refractory intestinal T-cell lymphoma was started on combination chemotherapy (ifosfamide, methotrexate, l-asparaginase, etoposide, dexamethasone). Cotrimoxazole was commenced for pneumocystis prophylaxis after a normal glucose-6-phosphate dehydrogenase (G6PD) spot fluorescence screen [>4·5 iu/g haemoglobin (Hb)]. Initial tumour shrinkage was accompanied by renal impairment (creatinine 393 μmol/l, normal 67–109) and hyperuricaemia (1259 μmol/l, normal 260–530), and rasburicase (4·5 mg × 1 dose) was given for tumour lysis. Despite a dramatic fall in uric acid level (55 μmol/l), anaemia suddenly occurred (Hb fell from 113 g/l to 59 g/l), followed by hypotension and oliguria. Biochemical screening showed raised unconjugated bilirubin (41 μmol/l, normal <6) and lactate dehydrogenase (798 iu/l, normal 118–211). Intravascular haemolysis was confirmed by raised methaemalbumin (14·3 mg/l, normal <01·0) levels and haemoglobinuria. A peripheral blood film showed bite cells and abundant hemi-ghost cells (left), classical for oxidative haemolysis. The patient survived with transfusion, haemodialysis and supportive treatment, with complete renal recovery. A repeat G6PD enzyme assay on his stored blood sample showed a marginal G6PD level of 5·5 iu/g Hb, which lies within the range expected for female heterozygotes. His four brothers were all G6PD deficient (0·21–1·24 iu/g Hb). Using allele-specific polymerase chain reaction, a G6PD Kaiping allele (nt 1388 G→A) was detected in the patient and all siblings. Surprisingly the patient also carried a second normal G6PD allele, suggesting extra X chromosome material. On further questioning, the patient volunteered a history of azoospermia and bilateral absent vas deferens. There were no other abnormal features suggestive of Klinefelter syndrome. Karyotype analysis on stimulated peripheral blood lymphocytes and fluorescence in situ hybridization with an X whole chromosome painting probe (Oncor Inc., Gaithersburg, MD, USA) confirmed the presence of extra X chromosome material on the Y-chromosome (right, red arrow) in all 20 metaphases analysed: 46, XY.ish add(Y)(p11)(wcpX+). Hence the patient was an occult carrier of extra X chromosome material and a heterozygous carrier of G6PD deficiency. Deficiency of G6PD is the commonest red cell enzymopathy world-wide. It affects 4·8% of all Southern Chinese males, and is screened for at birth and before the commencement of oxidative medications. In female heterozygotes, random lyonization of the X chromosomes results in a mixture of normal and G6PD deficient red cells. The resultant average enzyme levels usually lie within the normal range. However female heterozygotes for G6PD deficiency can still suffer haemolysis as a result of skewed lyonization because of age, haemopoietic transplantation or clonal haemopoiesis. Without mandatory screening, this can cause unexpected severe haemolysis. Our case showed that a simple fluorescent screen might still be insufficient. Severe oxidative stresses because of a combination of drugs (cotrimoxazole and rasburicase) could still cause en masse destruction of the G6PD deficient subpopulation, resulting in life-threatening intravascular haemolysis. Hence, a quantitative enzyme level assay is a better option in areas endemic for G6PD deficiency.

Inhibition of Trypanosoma brucei glucose-6-phosphate dehydrogenase by human steroids and their effects on the viability of cultured parasites

Dehydroepiandrosterone (DHEA) is known as an intermediate in the synthesis of mammalian steroids and a potent uncompetitive inhibitor of mammalian glucose-6-phosphate dehydrogenase (G6PDH), but not the enzyme from plants and lower eukaryotes. G6PDH catalyzes the first step of the pentose-phosphate pathway supplying cells with ribose 5-phosphate, a precursor of nucleic acid synthesis, and NADPH for biosynthetic processes and protection against oxidative stress. In this paper we demonstrate that also G6PDH of the protozoan parasite Trypanosoma brucei is uncompetitively inhibited by DHEA and epiandrosterone (EA), with K i values in the lower micromolar range. A viability assay confirmed the toxic effect of both steroids on cultured T. brucei bloodstream form cells. Additionally, RNAi mediated reduction of the G6PDH level in T. brucei bloodstream forms validated this enzyme as a drug target against Human African Trypanosomiasis. Together these findings show that inhibition of G6PDH by DHEA derivatives may lead to the development of a new class of anti-trypanosomatid compounds.

Comparison of a semiquantitative and a quantitative method for neonatal screening of glucose 6-phosphate dehydrogenase deficiency with subsequent confirmation by allelic discrimination assays

Glucose 6-phosphate dehydrogenase (G6PD) deficiency is a X-linked disorder causing neonatal jaundice and haemolysis on oxidative stress. We compared the currently used fluorescent spot test (FST) against a quantitative assay (OSMMR2000-D) and molecular testing methods for screening and identification of G6PD deficient neonates. A total of 1371 cord blood samples were tested using the semiquantitative FST and quantitative G6PD assay. Positive FST samples were subjected to allelic discrimination assays for G6PD Viangchan, Mediterranean, Canton and Kaiping, which encompass over 75% of the G6PD mutations detected in our population. Positive FST results were seen in 86 (6.3%) of the samples tested. Mean G6PD level using the quantitative assay was 15.3 U/g haemoglobin (Hgb) with 60% and 20% enzyme activity 9.2 and 3.1 U/g Hgb, respectively. Twenty-one of the 86 samples detected as positive by FST had activity above 9.2 U/g Hgb, 10 of which were identified as harbouring one of the four mutations tested. The quantitative assay used in this study, using cord blood samples may cause false negative results if limits are established as proposed. We propose that the FST remains an effective screening tool for G6PD deficiency and can be supplemented by rapid real time molecular identification methods for confirmation.

G6PD enzyme activity in normal term neonates and adults using OSMMR-D kit with HB normalisation

Background Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common cause of neonatal jaundice in South East Asia. Screening of cord blood for G6PD deficiency by the semiquantitative fluorescent spot test can miss cases of partial G6PD deficiency. Enzymes quantitation using colorimetric method is relatively simple, and able to quantitate the level of the enzymes. We evaluated the method of enzyme quantitation using OSMMR-D kit with haemoglobin (Hb) normalisation and established the normal range of G6PD activity for the normal term neonates and adults. Methods The blood sample was mixed with 75 µL of elution buffer in a well of microplate. The microplate was slowly warmed to 37°C. After incubation for 8 min, the microplate was read at 405 nm for Hb evaluation. Then, colour reagent mixture (OSMMR-D kit, Greece) was added and the microplate was read again at 550 nm at 0 min, then at 10 min. The results are directly expressed in U/g Hb. Blood samples from a total of 106 neonates and 281 adults (aged between 15 and 59 years) were randomly selected for enzyme quantitation. Results All cases showing bright activity with fluorescent spot test demonstrated normal level of G6PD activity with mean of 12.43 U/g Hb for neonates and 9.35 U/g Hb for adults. There was no significant difference in the mean normal G6PD activity between the two racial groups (Malays and Chinese) as well as between the genders. The reference range for normal G6PD activity is 10.15–14.71 U/g Hb for neonates and 6.75–11.95 U/g Hb for adults. Conclusions This study has established the normal range for the G6PD level in normal term neonates and adults. The quantitation of G6PD enzymes using OSMMR-D kit with Hb normalisation was simple since the Hb was analysed simultaneously and the results were reproducible with CV of less than 5%.

Oxidative injury and enzymic antioxidant misbalance in schizophrenics with positive, negative and cognitive symptoms

With its hallucinations, delusions, thought disorder, and cognitive deficits, schizophrenia affects the most basic human processes of perception, emotion, and judgment. Evidence increasingly suggests that schizophrenia is a subtle disorder of brain development and plasticity and oxidative injury contributes largely to pathophysiology of schizophrenia, indicated by the increased lipid peroxidation products in plasma and altered levels of enzymatic antioxidants in schizophrenic patients. However, the status of antioxidants and the extent of lipid peroxidation in erythrocytes have not been investigated so far in schizophrenia patients with different symptoms. In the present study, in order to examine the antioxidant status and lipid peroxidation in the schizophrenics with positive, negative and cognitive symptoms, the activities of three free radical scavenging enzymes glutathione transferase (GST), glucose-6-phosphate dehydrogenase (G6PD), ceruloplasmin ferroxidase (Cp) and the level of thiobarbituric acid-reactive substances (TBARS) as an index of lipid peroxidation were analyzed. Results showed that there was a significant increase in GST activity in all the schizophrenics when compared to normal and it was observed that there was a significant decrease in erythrocyte, G6PD and ceruloplasmin ferroxidase levels in patients with schizophrenia, when compared to controls. Schizophrenics with positive symptomology were found to have pronounced decrease in the activities of Cp ferroxidase and statistically more significant decrease in G6PD levels were found in patients with negative symptoms. Further a significant rise in oxidative stress and decreased secondary enzymic antioxidant status was observed in the chronic stage of schizophrenics as compared to those in acute condition. The study showed that the level of malondialdehyde was increased in schizophrenics with positive (163%), negative (137%) and cognitive (132%) symptoms compared to control groups .The increased activities of antioxidant enzymes may be a compensatory regulation in response to increased oxidative stress. The decreased concentrations of the antioxidants status support the hypothesis that lipid peroxidation is an important causative factor in the pathogenesis of schizophrenia. These data reveal that antioxidant defense mechanisms might be impaired in schizophrenic patients. Understanding these basic pathologic processes may yield novel targets for the development of more effective treatments. Keywords: Schizophrenia, symptoms, secondary antioxidant enzymes, malondialdehyde (MDA), oxidative stress

Cimetidine and dapsone‐mediated methaemoglobinaemia

I read with interest the case report from Choi et al. [1] relating to dapsone-mediated methaemoglobinaemia. The role of cimetidine in partially attenuating the haematological side-effects of dapsone does not appear to have been discussed in the anaesthesia literature. I wish to suggest the possible therapeutic benefit of peri-operative administration of cimetidine in patients receiving dapsone. The oxidative metabolism of dapsone leads to its toxicity. The majority of dapsone undergoes reversible acetylation in liver followed by elimination as N-hydroxylamine and to a lesser degree monoacetylated hydroxylamine. Dapsone N- hydroxylation is responsible for the haematological side-effects such as methaemoglobinaemia and haemolysis. Dapsone hydroxylamine depletes glutathione within glucose-6-phosphate dehydrogenase (G6PD)-deficient cells. The nitroso derivative then causes peroxidation reactions, leading to rapid haemolysis. Doses of 100 mg or less in normal healthy persons and 50 mg or less in G6PD-deficient individuals do not cause haemolysis [2]. A maximum dose of 150–300 mg a day, in divided doses, is recommended to minimise the risk of methaemoglobinaemia [3]. Cimetidine, an H2-recector antagonist, competes with dapsone for cytochrome P 450 enzymes. Thus cimetidine may be used as a selective inhibitor of N-hydroxylation and decrease the quantity of methaemoglobinaemia produced by dapsone [3, 4]. Cimetidine 400 mg three times daily has been shown to lead to a significant (> 25%) and sustained fall in methaemoglobin in patients on chronic dapsone therapy [5]. This dose appears to be well tolerated and not associated with adverse effects. The peri-operative use of cimetidine is likely to benefit patients by increasing the clinical safety margin, minimising the incidence and severity of methaemoglobinaemia and, possibly, avoiding the complications associated with treatment modalities such as methylene blue or ascorbic acid [6]. The mean elimination half-life of dapsone is about 20–30 h. Sulphones are retained in the circulation for long periods because of intestinal re-absorption from bile, requiring periodic interruption of treatment in dermatological diseases [2]. It is imperative to discontinue dapsone at least 4–7 days pre-operatively in patients listed for elective surgery. Furthermore, the G6PD level should be checked in all patients receiving dapsone therapy to identify patients at risk of peri-operative methaemoglobinaemia.

Human αB-Crystallin Mutation Causes Oxido-Reductive Stress and Protein Aggregation Cardiomyopathy in Mice

The autosomal dominant mutation in the human alphaB-crystallin gene inducing a R120G amino acid exchange causes a multisystem, protein aggregation disease including cardiomyopathy. The pathogenesis of cardiomyopathy in this mutant (hR120GCryAB) is poorly understood. Here, we show that transgenic mice overexpressing cardiac-specific hR120GCryAB recapitulate the cardiomyopathy in humans and find that the mice are under reductive stress. The myopathic hearts show an increased recycling of oxidized glutathione (GSSG) to reduced glutathione (GSH), which is due to the augmented expression and enzymatic activities of glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase, and glutathione peroxidase. The intercross of hR120GCryAB cardiomyopathic animals with mice with reduced G6PD levels rescues the progeny from cardiac hypertrophy and protein aggregation. These findings demonstrate that dysregulation of G6PD activity is necessary and sufficient for maladaptive reductive stress and suggest a novel therapeutic target for abrogating R120GCryAB cardiomyopathy and heart failure in humans.

G6PD deficiency from lyonization after hematopoietic stem cell transplantation from female heterozygous donors

To determine whether during hematopoietic stem cell transplantation (HSCT), X-chromosome inactivation (lyonization) of donor HSC might change after engraftment in recipients, the glucose-6-phosphate dehydrogenase (G6PD) gene of 180 female donors was genotyped by PCR/allele-specific primer extension, and MALDI-TOF mass spectrometry/Sequenom MassARRAY analysis. X-inactivation was determined by semiquantitative PCR for the HUMARA gene before/after HpaII digestion. X-inactivation was preserved in most cases post-HSCT, although altered skewing of lyonization might occur to either of the X-chromosomes. Among pre-HSCT clinicopathologic parameters analyzed, only recipient gender significantly affected skewing. Seven donors with normal G6PD biochemically but heterozygous for G6PD mutants were identified. Owing to lyonization changes, some donor-recipient pairs showed significantly different G6PD levels. In one donor-recipient pair, extreme lyonization affecting the wild-type G6PD allele occurred, causing biochemical G6PD deficiency in the recipient. In HSCT from asymptomatic female donors heterozygous for X-linked recessive disorders, altered lyonization might cause clinical diseases in the recipients.

Glucose-6-Phosphate Dehydrogenase Deficiency in Retinal Vein Occlusion

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is one of the most common human genetic abnormalities, with a high prevalence in Sardinia, Italy. Evidence indicates that G6PD-deficient patients are protected against ischemic heart and cerebrovascular disease. The purpose of this study was to assess the frequency of G6PD deficiency in Sardinian patients with retinal vein occlusion (RVO) and to ascertain whether the deficiency may offer protection against RVO. Erythrocyte G6PD levels were measured in 448 consecutive RVO patients: 194 with central RVO (CRVO) and 254 with branch RVO (BRVO). Age- and sex-matched subjects (n = 896) who were undergoing cataract surgery and had no history of RVO served as the control. Multiple logistic regression models were used to investigate the association between G6PD deficiency and RVO, CRVO, or BRVO. G6PD deficiency was found in 21 (4.7%) patients with RVO, 7 (3.6%) with CRVO, 14 (5.5%) with BRVO, and 107 (11.9%) control subjects. Differences between cases and controls were statistically significant (P < 0.005). Multiple conditional logistic regression analysis, including as covariates G6PD deficiency, hypertension, diabetes, and hypercholesterolemia, revealed that G6PD deficiency was significantly associated with decreased risk of development of RVO, CRVO, or BRVO. After adjustment for hypertension, diabetes, and hypercholesterolemia, the association between G6PD deficiency and RVO, CRVO, or BRVO remained statistically significant. Similar results were obtained after adjustment for systolic or diastolic blood pressure, plasma glucose, and cholesterol levels. However, when the patients with CRVO or BRVO were categorized by gender, a significant association was found only in the women. The frequency of G6PD deficiency in patients with RVO was significantly lower than expected. The results suggest that G6PD-deficient patients have a significantly decreased risk of development of RVO in the Sardinian population.

Nrf2 is involved in the effect of tanshinone IIA on intracellular redox status in human aortic smooth muscle cells

Tanshinone IIA is the major antioxidant component in the traditional Chinese medicine Salvia miltiorrhiza. Transcription factor nuclear-factor-E2-related factor (Nrf2) regulates a battery of antioxidant response element (ARE)-regulated genes. The aim of this study was to determine the effect of tanshinone IIA on Nrf2 activation and intracellular redox status in human aortic smooth muscle cells. Tanshinone IIA potentiated tumor necrosis factor α (TNF-α)-mediated nuclear accumulation of Nrf2 and expression of ARE-related genes, while it reversed TNF-α-induced down-regulation of intracellular glutathione (GSH), NADPH and glucose 6-phosphate dehydrogenase (G6PDH) levels. Specific silence of Nrf2 by siRNA down-regulated tanshinone IIA-induced Nrf2 activation and increased of intracellular GSH, NADPH and G6PDH levels. Tanshinone IIA-induced Nrf2 activation was association with activation of ERK and PKB, which was prevented by treatment with PD098059 or wortmannin. Tanshinone IIA attenuated TNF-α, angiotensin II, H2O2-mediated reactive oxygen species (ROS) production. These results demonstrated that tanshinone IIA-induced Nrf2 activation is the major regulatory pathway of cytoprotective gene expression against oxidative stress via ERK and PKB signaling pathways.

Glucose-6-Phosphate Dehydrogenase Deficiency in Female Octogenarians, Nanogenarians, and Centenarians

Age-related skewing of X-chromosome inactivation leading to glucose-6-phosphate dehydrogenase (G6PD) deficiency in elderly women in a population with prevalent G6PD gene mutations was investigated. G6PD activity was measured biochemically. G6PD mutations were detected by polymerase chain reaction (PCR) and allele-specific extension, and analyzed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and Sequenom MassARRAY. X-chromosome inactivation was quantified by semiquantitative PCR for the HUMARA gene, before and after HpaII digestion. In 173 women (median age: 90 years; range, 80-107 years), 18 heterozygotes for G6PD mutations were identified. Three heterozygotes were G6PD deficient, owing to skewed X-chromosome inactivation affecting the wild-type allele. Fifteen heterozygotes, with skewing apparently affecting the mutant alleles, had normal but significantly lower G6PD levels. At 1.73%, G6PD deficiency was significantly more frequent than expected from population screening at birth. Due to skewed X-chromosome inactivation, elderly women in populations with prevalent G6PD mutations are at risk of G6PD deficiency.

Elevation of glucose 6-phosphate dehydrogenase activity increases xylitol production in recombinant Saccharomyces cerevisiae

To increase the NAD(P)H-dependent xylitol production in recombinant Saccharomyces cerevisiae harboring the xylose reductase gene from Pichia stipitis, the activity of glucose 6-phosphate dehydrogenase (G6PDH) encoded by the ZWF1 gene was amplified to increase the metabolic flux toward the pentose phosphate pathway and NADPH regeneration. Compared with the control strain, the specific G6PDH activity was enhanced approximately 6.0-fold by overexpression of the ZWF1 gene. Amplification in the G6PDH activity clearly improved the NAD(P)H-dependent xylitol production in the recombinant S. cerevisiae strain. With the aid of an elevated G6PDH level, maximum xylitol concentration of 86 g/l was achieved with productivity of 2.0 g/l h in the glucose-limited fed-batch cultivation, corresponding to 25% improvement in volumetric xylitol productivity compared with the recombinant S. cerevisiae strain containing the xylose reductase gene only.