Glucose-6-phosphate dehydrogenase deficiency

Hospital-based surveillance of severe paediatric malaria in two malaria transmission ecological zones of Burkina Faso

BACKGROUND

In the current context of tailoring interventions to maximize impact, it is important that current data of clinical epidemiology guide public health programmes and health workers in the management of severe disease. This study aimed at describing the burden of severe malaria at hospital level in two areas with distinct malaria transmission intensity.

METHODS

A hospital-based surveillance was established in two regional hospitals located in two areas exposed to different malaria transmission. Data on paediatric severe malaria admissions were recorded using standardized methods from August 2017 to August 2018 with an interruption during the dry season from April to June 2018.

RESULTS

In total, 921 children with severe malaria cases were enrolled in the study. The mean age was 33.9 (± 1.3) and 36.8 (± 1.6) months in lower malaria transmission (LMT) and higher malaria transmission (HMT) areas (p = 0.15), respectively. The geometric mean of asexual P. falciparum density was significantly higher in the LMT area compared to the HMT area: 22,861 trophozoites/µL (95% CI 17,009.2-30,726.8) vs 11,291.9 trophozoites/µL (95% CI 8577.9-14,864.5). Among enrolled cases, coma was present in 70 (9.2%) participants. 196 patients (21.8%) presented with two or more convulsions episodes prior to admission. Severe anaemia was present in 448 children (49.2%). Other clinical features recorded included 184 (19.9%) cases of lethargy, 99 (10.7%) children with incoercible vomiting, 80 (8.9%) patients with haemoglobinuria, 43 (4.8%) children with severe hypoglycaemia, 37 (4.0%) cases where child was unable to drink/suck, 11 (1.2%) cases of patients with circulatory collapse/shock, and 8 cases (0.9%) of abnormal bleeding (epistaxis). The adjusted odds of presenting with coma, respiratory distress, haemoglobinuria, circulatory collapse/shock and hypoglycaemia were significantly higher (respectively 6.5 (95%CI 3.4-12.1); 1.8 (95%CI 1.0-3.2); 2.7 (95%CI 1.6-4.3); 5.9 (95%CI 1.3-27.9); 1.9 (95%CI 1.0-3.6)) in children living in the HMT area compared to those residing in the LMT area. Overall, forty-four children died during hospitalization (case fatality rate 5.0%) with the highest fatalities in children admitted with respiratory distress (26.0%) and those with hypoglycaemia (25.0%).

CONCLUSION

The study showed that children in the HMT area have a higher risk of presenting with coma, shock/dehydration, haemoglobinuria, hypoglycaemia, and respiratory distress. Case-fatality rate is higher among patients with respiratory distress or hypoglycaemia. Hospital surveillance provides a reliable and sustainable means to monitor the clinical presentation of severe malaria and tailor the training needs and resources allocation for case management.

G6PD deficiency: imbalance of functional dichotomy contributing to the severity of COVID-19

Human COVID-19 has affected more than 491 million people worldwide. It has caused over 6.1 million deaths and has especially perpetrated a high number of casualties among the elderly and those with comorbid illnesses. COVID-19 triggers a pro-oxidant response, leading to the production of reactive oxygen species (ROS) as a common innate defense mechanism. However, ROS are regulated by a key enzyme called G6PD via the production of reduced nicotinamide adenine dinucleotide phosphate (NADPH), which controls the generation and removal of ROS in a tissue-specific manner. Therefore, a deficiency of G6PD can lead to the dysregulation of ROS, which causes a severe inflammatory response in COVID-19 patients. This report highlights the G6PD dichotomy in the regulation of ROS and inflammatory responses, as well as its deficiency in severity among COVID-19 patients.

Antixoxidant Supplements versus Health Benefits of Brief/Intermittent Exposure to Potentially Toxic Physical or Chemical Agents

Although antioxidants can act locally to react with an oxidant, oral administration of "antioxidants" is quite useless in treating oxidative stress in tissues. Furthermore, it does not make sense to consider a vitamin as an antioxidant, but vitamin B3 leads to the in vivo formation of compounds that are essential for reducing this stress. A rigorous treatment of the subject indicates that to deal with oxidative stress, the most direct approach is to enhance the innate antioxidant mechanisms. The question is whether this is possible through daily activities. Diets can contain the necessary components for these mechanisms or may induce the expression of the genes involved in them. Another possibility is that pro-oxidant molecules in food increase the sensitivity and power of the detoxification pathways. This option is based on well-known DNA repair mechanisms after exposure to radiation (even from the Sun), or strong evidence of induction of antioxidant capacity after exposure to powerful pro-oxidants such as H₂O₂. More experimental work is required to test whether some molecules in food can increase the expression of antioxidant enzymes and/or improve antioxidant mechanisms. Identifying effective molecules to achieve such antioxidant power is critical to the food and nutraceutical industries. The potential of diet-based interventions to combat oxidative stress must be viewed from a new perspective.

Structure activity relationship in β-carboline derived anti-malarial agents

Malaria, even though an avoidable and treatable disease, can be fatal if ignored. Artemisinin Combination Therapy (ACT) and RTS, S/AS01 vaccine (Mosquirix™) are the only modest means available with humans to overcome malaria, a lethal affliction wreaking havoc across the globe. Employment of ACT is associated with problems such as 'Artemisinin Resistance' and the 'Hypnozoite conundrum' that hinder the complete eradication of malaria. In this view, the natural products specifically comprising β-carboline scaffold have shown good antiplasmodial responses against different strains of malaria. Taking these observations forward, researchers have performed structure-activity relationship (SAR) studies around three different β-carboline skeletons (tetrahydro β-carbolines, dihydro β-carbolines, β-carbolines) to design new β-carboline derived heterocyclic structures or modified naturally occurring derivatives. In addition, different approaches such as dimerization and linkage to other moieties have also been adopted to enhance the antimalarial activity. The present review describes a comprehensive SAR study encapsulating various natural and synthetic β-carbolines to elaborate upon the utility of these skeletons in designing drugs to subdue this deadly disease.

Medical genetics and genomic medicine in Nigeria

Medical genetics and genomic medicine in Nigeria.

A trade off between catalytic activity and protein stability determines the clinical manifestations of glucose-6-phosphate dehydrogenase (G6PD) deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common polymorphism and enzymopathy in humans, affecting approximately 400 million people worldwide. It is responsible for various clinical manifestations, including favism, hemolytic anemia, chronic non-spherocytic hemolytic anemia, spontaneous abortion, and neonatal hyperbilirubinemia. Understanding the molecular mechanisms underlying the severity of G6PD deficiency is of great importance but that of many G6PD variants are still unknown. In this study, we report the construction, expression, purification, and biochemical characterization in terms of kinetic properties and stability of five clinical G6PD variants-G6PD Bangkok, G6PD Bangkok noi, G6PD Songklanagarind, G6PD Canton+Bangkok noi, and G6PD Union+Viangchan. G6PD Bangkok and G6PD Canton+Bangkok noi showed a complete loss of catalytic activity and moderate reduction in thermal stability when compared with the native G6PD. G6PD Bangkok noi and G6PD Union+Viangchan showed a significant reduction in catalytic efficiency, whereas G6PD Songklanagarind showed a catalytic activity comparable to the wild-type enzyme. The Union+Viangchan mutation showed a remarkable effect on the global stability of the enzyme. In addition, our results indicate that the location of mutations in G6PD variants affects their catalytic activity, stability, and structure. Hence, our results provide a molecular explanation for clinical manifestations observed in individuals with G6PD deficiency.

Detailed functional analysis of two clinical glucose-6-phosphate dehydrogenase (G6PD) variants, G6PDViangchan and G6PDViangchan+Mahidol: Decreased stability and catalytic efficiency contribute to the clinical phenotype

Deficiency of glucose-6-phosphate dehydrogenase (G6PD) is an X-linked hereditary genetic defect that is the most common polymorphism and enzymopathy in humans. To investigate functional properties of two clinical variants, G6PDViangchan and G6PDViangchan+Mahidol, these two mutants were created by overlap-extension PCR, expressed in Escherichia coli and purified to homogeneity. We describe an overexpression and purification method to obtain substantial amounts of functionally active protein. The KM for G6P of the two variants was comparable to the KM of the native enzyme, whereas the KM for NADP(+) was increased 5-fold for G6PDViangchan and 8-fold for G6PDViangchan+Mahidol when compared with the native enzyme. Additionally, kcat of the mutant enzymes was markedly reduced, resulting in a 10- and 18-fold reduction in catalytic efficiency for NADP(+) catalysis for G6PDViangchan and G6PDViangchan+Mahidol, respectively. Furthermore, the two variants demonstrated significant reduction in thermostability, but similar susceptibility to trypsin digestion, when compared with the wild-type enzyme. The presence of NADP(+) is shown to improve the stability of G6PD enzymes. This is the first report indicating that protein instability and reduced catalytic efficiency are responsible for the reduced catalytic activity of G6PDViangchan and G6PDViangchan+Mahidol and, as a consequence, contribute to the clinical phenotypes of these two clinical variants.

Brain glucose-6-phosphate dehydrogenase protects against endogenous oxidative DNA damage and neurodegeneration in aged mice

Glucose-6-phosphate dehydrogenase (G6PD) protects the embryo from endogenous and xenobiotic-enhanced oxidative DNA damage and embryopathies. Here we show in aged mice that G6PD similarly protects against endogenous reactive oxygen species (ROS)-mediated neurodegeneration. In G6PD-normal (G6PD(+/+)) and heterozygous (G6PD(+/def)) and homozygous (G6PD(def/def)) G6PD-deficient male and female mice at about 2 years of age, oxidative DNA damage in various brain regions was assessed by 8-oxo-2'-deoxyguanosine formation using high-performance liquid chromatography and immunohistochemistry. Morphological changes in brain sections were assessed by H&E staining. DNA oxidation was increased in G6PD(def/def) mice in the cortex (p < 0.02), hippocampus (p < 0.01) and cerebellum (p < 0.006) compared to G6PD(+/+) mice, and was localized to distinct cell types. Histologically, in G6PD(+/def) mice, enhanced regionally and cellularly specific neurodegenerative changes were observed in those brain regions exhibiting elevated DNA oxidation, with a 53% reduction in the Purkinje cell count. These results show G6PD is important in protecting against the neurodegenerative effects of endogenous ROS in aging, and suggest that common hereditary G6PD deficiencies may constitute a risk factor for some neurodegenerative diseases.

Haemoglobinuria among children with severe malaria attending tertiary care in Ibadan, Nigeria

Background

Haemoglobinuria is one of the manifestations of severe malaria and results from severe intravascular haemolysis. Glucose-6-phosphate dehydrogenase (G6PD) deficiency has been implicated in its aetiology. Haemoglobinuria may be associated with severe anaemia and, less frequently, acute renal failure.

Methods

A prospective case-control study was carried out to determine the incidence of haemoglobinuria as confirmed by dipstick urinalysis, microscopy and spectrophotometric measurement, among children with severe malaria. A total of 251 children presenting at the Children’s Emergency Ward with severe malaria were recruited over a period of 21 months. The G6PD status and the outcomes of severe malaria in children with and without haemoglobinuria was studied with respect to renal failure, the recurrence of haemoglobinuria and blood pressure changes over a three-month follow-up period.

Results

It was found that the incidence of haemoglobinuria among children with severe malaria is 19.1%. Children <5 years constituted 76.8% of all the study patients. Patients with haemoglobinuria had median age of 52.5 months, which was significantly higher than 35 months in patients without haemoglobinuria (p=0.001). Although, haemaglobinuria was commoner among boys (54.2%) than girls (45.8%), the difference was not statistically significant. There were no significant differences between children with and without haemoglobinuria regarding their nutritional status or parasite densities. Among the clinical features of the study patients, only jaundice was significantly associated with haemoglobinuria (p=0.0001). Renal failure occurred in three out of 48 children with haemoglobinuria and in none of the 203 without. There was not recurrence of haemoglobinuria in the follow-up period. At discharge, blood pressure was elevated in six children (one previously haemoglobinuric), but all returned to normal within the follow-up period.

Conclusions

Haemoglobinuria was a prominent feature of severe malaria and it was significantly associated with jaundice at presentation. Haemoglobinuria was commoner in older children than younger children but not related to sex. G6PD deficiency was not an independent predictor of the occurrence or outcome of haemoglobinuria. Blood pressure was not affected by haemoglobinuria on admission nor during follow-up.

Life and Death of Glucose-6-Phosphate Dehydrogenase (G6PD) Deficient Erythrocytes - Role of Redox Stress and Band 3 Modifications

SUMMARY

G6PD catalyzes the first, pace-making reaction of pentosephosphate cycle (PPC) which produces NADPH. NADPH maintains glutathione and thiol groups of proteins and enzymes in the reduced state which is essential for protection against oxidative stress. Individuals affected by G6PD deficiency are unable to regenerate reduced glutathione (GSH) and are undefended against oxidative stress. G6PD deficiency accelerates normal senescence and enhances the precocious removal of chronologically young, yet biologically old cells. The term hemolytic anemia is misleading because RBCs do not lyse but are removed by phagocytosis. Acute hemolysis by fava bean ingestion in G6PD deficient individuals (favism) is described being the best-studied natural model of oxidant damage. It bears strong analogies to hemolysis by oxidant drugs or chemicals. Membrane alterations observed in vivo during favism are superimposable to changes in senescent RBCs. In summary, RBC membranes isolated from favic patients contained elevated amounts of complexes between IgG and the complement fragment C3b/C3c and were prone to vesiculation. Anti-band 3 IgG reacted to aggregated band 3-complement complexes. In favism extensive clustering of band 3 and membrane deposition of hemichromes were also observed. Severely damaged RBCs isolated from early crises had extensive membrane cross-bonding and very low GSH levels and were phagocytosed 10-fold more intensely compared to normal RBCs.

A comparative study of the lateral geniculate body of rat (Rattus norvegicus), bat (Eidolon helvum) and pangolin (Manis tricuspis)

In this study, the lateral geniculate bodies (LGB) of rats, bats and pangolins were compared using histological and quantitative histochemical parameters to observe possible modifications that enable these mammals to cope with their habitation particularly with respect to their diet. The study was conducted using ten adult Wistar rats, ten fruit bats and eight pangolins comprising of both sexes. After being sacrificed by cervical dislocation, their skulls were opened using bone forceps to expose the brains. The lateral geniculate bodies were excised from each brain tissue, homogenized and homogenate studied spectrophotometrically for the activities of lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G-6-PDH), acid phosphatase (ACP), alkaline phosphatase (ALP) and acetylcholinesterase (AChE). The LGB tissue samples meant for histological studies were fixed in 10% formol calcium and processed for paraffin wax embedding. Serial sections of 3?m thickness were stained with Hematoxylin and Eosin (H &amp; E) and Cresyl fast violet (CFV) stains. The stained tissues were studied under the light microscope. Application of one-way ANOVA statistical method showed that there were significant differences (p&lt;0.05) in the activities of LDH, G-6-PDH, ACP, ALP and AChE of the LGB of the three mammals as revealed in the quantitative histochemistry of these enzymes and markers. Histological observations revealed no observable differences in the relative distribution of neurons and their supporting glial cells within the LGB of the three mammalian species. The comparison of the differences observed in the histological and the quantitative histochemical activities in these mammalian species revealed a variation in the visual perception and their individual peculiarities in relation to their mode and pattern of living.

Molecular characterization of glucose-6-phosphate dehydrogenase deficiency in Pakistani population

INTRODUCTION

Glucose-6-phosphate dehydrogenase (G6PD; E.C. 1.1.1.49) deficiency is the commonest inborn error of metabolism with more than 140 genetic variants. The incidence of G6PD deficiency is 2-9% in Pakistan, but G6PD variants were never studied comprehensively. We therefore designed this study to describe the frequency of G6PD variants and their associated enzyme activities in Pakistan.

METHODS

Patients diagnosed with G6PD deficiency were enrolled. RFLP-PCR was utilized to identify common mutations previously reported from Asian countries. Where mutational analysis failed, amplification of 9-12 exons with subsequent gene sequencing was performed. G6PD enzyme activity was assessed through the quantitative enzyme assay.

RESULTS

Two hundred and seventy-six G6PD-deficient subjects (237 male and 39 women) were investigated. G6PD Mediterranean (563C-T) was the most common genetic variant (n=216 or 78%). G6PD Chatham (1003A-G) and G6PD Orissa (131C-G) were observed in 14 (5%) and two (0.7%) subjects respectively. A novel mutation 973 G-A with a predicated amino acid change of asp325asn was identified in exon 9. This was named G6PD Karachi after the place of origin of proband. Polymorphism in position 1311C/T was uniformly observed with all variants. Forty-three or 17% of DNA samples remained uncharacterized. Very low levels of G6PD enzyme activity was observed with 563C-T mutation.

CONCLUSION

We concluded that 563C-T was the commonest G6PD variant, while 1003A-G and 131C-G were less-frequent genetic variants of G6PD in Pakistani population. A novel genetic variant 973G-A was also identified. Very low levels of G6PD enzyme activity was seen with G6PD 563C-T. Mutational analysis failed in a significant proportion of samples warranting further work.

Glucose-6-phosphate dehydrogenase laboratory assay: How, when, and why?

Glucose 6-phosphate dehydrogenase (G6PD) deficiency is the most common defect of red blood cells. Although some different laboratory techniques or methods are employed for the biochemical screening, a strict relationship between biochemists, clinicians, and molecular biologists is necessary for a definitive diagnosis. This article represents an overview on the current laboratory tests finalized to the screening or to the definitive diagnosis of G6PD-deficiency, underlying the problems regarding the biochemical and molecular identification of heterozygote females other than those regarding the standardization of the clinical and laboratory diagnostic procedures. Finally, this review is aimed to give a flow-chart for the complete diagnostic approach of G6PD-deficiency.

Coexistence of five G6PD variants indicates ethnic complexity of Phuket islanders, Southern Thailand

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzymopathy in humans. The prevalence of G6PD deficiency and its molecular basis were studied in Phuket islanders, Southern Thailand. A total of 345 volunteers (123 males and 222 females) were recruited in this study. Infection with Plasmodium falciparum or Plasmodium vivax was not detected in any of these subjects by polymerase chain reaction (PCR)-based diagnosis. G6PD-deficient individuals were identified with the WST-8/1-methoxy PMS method. The molecular basis of G6PD deficiency was investigated by PCR-direct sequencing procedures or PCR-restriction enzyme fragment length polymorphism assays. The numbers of individuals showing severe and mild G6PD deficiency were 14 and 21, respectively. A high prevalence of G6PD deficiency was observed in subjects with Moken (15.4%) or Thai (15.5%) ethnic background. G6PD Mahidol (487G>A) (n=14), G6PD Viangchan (871G>A) (n=11), G6PD Gaohe (95A>G) (n=2), G6PD Kaiping (1388G>A) (n=1), and G6PD Kerala-Kalyan (949G>A) (n=1) were identified. The results suggest that several groups of people of the Asian Continent, such as Burmese, Laotian or Cambodian, Thai and Chinese, participated in the establishment of the ethnic identity of the current ethnic groups of Phuket Island.

Study on the Antioxidant Status of Vitiligo Patients of Different Age Groups in Baroda

One of the major hypotheses in the pathogenesis of vitiligo is the oxidative stress hypothesis. Pollution plays a major role in the production of free radicals. Gujarat, a highly industrialized state in India has a high prevalence of vitiligo patients. No previous studies were done on the age-dependent antioxidant status of vitiligo patients in Baroda city, Gujarat. Blood samples were collected from vitiligo patients of different age groups (5-15, 16-25, 26-35, 36-45 yr) and from age matched healthy volunteers. Antioxidant enzymes in blood such as catalase, superoxide dismutase, glutathione peroxidase and non-enzymatic antioxidants such as reduced glutathione and plasma vitamin E were estimated. Lipid peroxidation levels in erythrocytes and the reducing equivalent system, i.e. glucose-6-phosphate dehydrogenase were also measured. Significant increase in superoxide dismutase activity and lipid peroxidation levels in erythrocytes was observed in all age groups of vitiligo patients as compared with age-matched healthy controls, wherein an increase of 55% (P < 0.02) was observed in superoxide dismutase activity and lipid peroxidation levels in 36-45 yr age group. Whole blood glutathione levels, erythrocyte glutathione peroxidase and glucose-6-phosphate dehydrogenase activity were decreased significantly, whereas erythrocyte catalase activity and plasma vitamin E levels were not different in vitiligo patients as compared with age-matched healthy controls. No specific age group showed a significant difference. This is the first report on the age-dependent antioxidant status of vitiligo patients in Baroda. The disease affects individuals of any age group as shown in this study and systemic oxidative stress might precipitate the pathogenesis of vitiligo in susceptible patients.

Onset of maternal arterial blood flow and placental oxidative stress. A possible factor in human early pregnancy failure

The aim was to measure changes in the oxygen tension within the human placenta associated with onset of the maternal arterial circulation at the end of the first trimester of pregnancy, and the impact on placental tissues. Using a multiparameter probe we established that the oxygen tension rises steeply from <20 mmHg at 8 weeks of gestation to >50 mmHg at 12 weeks. This rise coincides with morphological changes in the uterine arteries that allow free flow of maternal blood into the placenta, and is associated with increases in the mRNA concentrations and activities of the antioxidant enzymes catalase, glutathione peroxidase, and manganese and copper/zinc superoxide dismutase within placental tissues. Between 8 to 9 weeks there is a sharp peak of expression of the inducible form of heat shock protein 70, formation of nitrotyrosine residues, and derangement of the mitochondrial cristae within the syncytiotrophoblast. We conclude that a burst of oxidative stress occurs in the normal placenta as the maternal circulation is established. We speculate that this may serve a physiological role in stimulating normal placental differentiation, but may also be a factor in the pathogenesis of pre-eclampsia and early pregnancy failure if antioxidant defenses are depleted.

An embryoprotective role for glucose-6-phosphate dehydrogenase in developmental oxidative stress and chemical teratogenesis

The primary recognized health risk from common deficiencies in glucose-6-phosphate dehydrogenase (G6PD), a cytoprotective enzyme for oxidative stress, is red blood cell hemolysis. Here we show that litters from untreated pregnant mutant mice with a hereditary G6PD deficiency had increased prenatal (fetal resorptions) and postnatal death. When treated with the anticonvulsant drug phenytoin, a human teratogen that is commonly used in pregnant women and causes embryonic oxidative stress, G6PD-deficient dams had higher embryonic DNA oxidation and more fetal death and birth defects. The reported G6PD gene mutation was confirmed and used to genotype fetal resorptions, which were primarily G6PD deficient. This is the first evidence that G6PD is a developmentally critical cytoprotective enzyme for both endogenous and xenobiotic-initiated embryopathic oxidative stress and DNA damage. G6PD deficiencies accordingly may have a broader biological relevance as important determinants of infertility, in utero and postnatal death, and teratogenesis.