Increase In Glucose-6-phosphate Dehydrogenase Research Articles

Retinopathy of Prematurity and Glucose-6-Phosphate Dehydrogenase Activity: A Case-Control Study.

To determine whether red blood cell glucose-6-phosphate dehydrogenase (G6PD) activity is associated with retinopathy of prematurity (ROP). This case-control study was conducted in a Level-3 neonatal unit. Subjects were inborn boys with birth weight <2000g. "Cases" were consecutive subjects with ROP of any severity. "Controls" were consecutive unrelated subjects without ROP. Recipients of blood or exchange transfusions were excluded. Sixty cases (out of 98 screened) and 60 controls (out of 93 screened) were enrolled. G6PD activity (quantitative assay) as the candidate risk factor was evaluated. Sixty cases with 60 controls [mean (SD) gestation 28.80 (2.2) and 30.60 (2.2) wk respectively] were compared. "Cases" had a higher median (1st, 3rd quartile) G6PD activity compared to "controls" [7.39 (4.7, 11.5) vs. 6.28 (4.2,8.8) U/g Hb, p = 0.084]. G6PD activity was highest among ROP requiring treatment [8.68 (4.7, 12.3)] followed by ROP not requiring treatment [6.91 (4.4, 11.0)], followed by controls (plinear trend = 0.06). Gestation, birth weight, duration of oxygen, breastmilk feeding, and clinical sepsis were other variables associated with ROP on univariable analysis. On multivariable logistic regression, G6PD activity [Adjusted OR 1.14 (1.03, 1.25), p = 0.01] and gestation [Adjusted OR 0.74 (0.56, 0.97), p = 0.03] independently predicted ROP. C-statistic of the model was 0.76 (95% CI 0.67, 0.85). Higher G6PD activity was independently associated with ROP after adjusting for confounders. Each 1 U/g Hb increase in G6PD increased the odds of ROP by 14%. Severer forms of ROP were associated with higher levels of G6PD activity.

Cannabis sativa and/or melatonin do not alter brain lipid but alter oxidative mechanisms in female rats

BackgroundLipid profile and redox status play a role in brain (dys)functions. Cannabinoid and melatonergic systems operate in the brain and contribute to brain (patho)physiology, but their roles in the modulation of brain lipid and redox status are not well-known. We studied the effect of ethanol extract of Cannabis sativa (CS) and/or melatonin (M) on the lipid profile and anti-oxidant system of the rat brain.MethodsWe randomly divided twenty-four (24) female Wistar rats into 4 groups (n = 6 rats each). Group 1 (control) received distilled water mixed with DMSO. Groups II–IV received CS (2 mg/kg), M (4 mg/kg), and co-administration of CS and M (CS + M) respectively via oral gavage between 8:00 am and 10:00 am once daily for 14 days. Animals underwent 12-h fasting after the last day of treatment and sacrificed under ketamine anesthesia (20 mg/kg; i.m). The brain tissues were excised and homogenized for assay of the concentrations of the total cholesterol (TC), triacylglycerol (TG), high-density lipoprotein cholesterol (HDL-C), nitric oxide (NO), malondialdehyde (MDA), and the activities of glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), and acetylcholinesterase (AChE). One-way analysis of variance (ANOVA) was used to compare means across groups, followed by the least significant difference (LSD) post-hoc test.ResultsCS and/or M did not affect the lipid profile parameters. However, CS increased the G6PD (from 15.58 ± 1.09 to 21.02 ± 1.45 U/L; p = 0.047), GPx (from 10.47 ± 0.86 to 17.71 ± 1.04 U/L; p = 0.019), and SOD (from 0.81 ± 0.02 to 0.90 ± 0.01 μM; p = 0.007), but decreased NO (from 9.40 ± 0.51 to 6.75 ± 0.21 μM; p = 0.010) and had no effect on MDA (p = 0.905), CAT (p = 0.831), GR (p = 0.639), and AChE (p = 0.571) in comparison with the control group. M augmented the increase in G6PD (from 21.02 ± 1.45 U/L to 27.18 ± 1.81 U/L; p = 0.032) and decrease in NO (from 6.75 ± 0.21 to 4.86 ± 0.13 μM; p = 0.034) but abolished the increase in GPx (from 17.71 ± 1.04 to 8.59 ± 2.06 U/L; p = 0.006) and SOD (from 0.90 ± 0.01 to 0.70 ± 0.00 μM; p = 0.000) elicited by CS in the rat brain in comparison with the CS group.ConclusionsCS and M do not alter brain lipid profile. Our data support the contention that CS elicits an anti-oxidative effect on the brain tissue and that CS + M elicits a pro-oxidant effect in rat brain.

Aldolase B suppresses hepatocellular carcinogenesis by inhibiting G6PD and pentose phosphate pathways.

Metabolic reprogramming is a core hallmark of cancer but it remains poorly defined in hepatocellular carcinogenesis (HCC). Here we show that hepatic aldolase B (Aldob) suppresses HCC by directly binding and inhibiting the rate-limiting enzyme in the pentose phosphate pathway, glucose-6-phosphate dehydrogenase (G6PD). A stage-dependent decrease of Aldob and increase of G6PD in human tumors are correlated with poor prognosis for patients with HCC. Global or liver-specific Aldob knockout promotes tumorigenesis in mice through enhancing G6PD activity and pentose phosphate pathway metabolism, whereas pharmacological inhibition or genetic knockdown of G6PD suppresses HCC. Consistently, restoration of Aldob in Aldob knockout mice attenuates tumorigenesis. We further demonstrate that Aldob potentiates p53-mediated inhibition of G6PD in an Aldob-G6PD-p53 complex. This scaffolding effect is independent of Aldob enzymatic activity. Together, our study reveals a new mode of metabolic reprogramming in HCC due to the loss of Aldob, suggesting a potential therapeutic strategy for HCC treatment.

Physiological and Molecular Osmotic Stress Responses in Three Durum Wheat (Triticum Turgidum ssp Durum) Genotypes

This study aims to investigate the activities and expression of enzymes of primary metabolism and relate these data with the growth performance of three different durum wheat genotypes (Maali; YT13; and ON66) under osmotic stress. Growth traits—including plant height, dry weight (DW) and relative water content (RWC)—were measured to classify genotypes depending on their tolerance to stress. Several enzymes were investigated: Ascorbate peroxidase (APX), Glutamine Synthetase (GS), Glutamine dehydrogenase (GDH), Glutamate synthase (GOGAT), Glucose 6-phosphate dehydrogenase (G6PDH), and Phosphoenolpyruvate Carboxylase (PEPC). The expression of the cytosolic and plastidic glutamine synthetase (TaGS1 and TaGS2), high affinity nitrate transporters (TaNRT2.3) and Glutamate dehydrogenase (TaGDH) were also detected by qRT-PCR. The results indicated different growth performances among genotypes, indicating Maali and YT13 as tolerant genotypes and ON66 as a drought-susceptible variety. Data showed a decrease in PEPC and increase in APX activities under osmotic stress; a slight decrease in GS activity was observed, together with an increase in G6PDH in all genotypes; GS and NRT2 expressions changed in a similar pattern in the different genotypes. Interestingly, Maali and YT13 showed higher transcript abundance for GDH under stress compared to ON66, suggesting the implication of GDH in protective phenomena upon osmotic stress.

Antioxidant SMe1EC2 modulates pentose phosphate pathway and glutathione-dependent enzyme activities in tissues of aged diabetic rats.

The pentose phosphate pathway and glutathione-associated metabolism are the main antioxidant cellular defense systems. This study investigated the effects of the powerful antioxidant SMe1EC2 (2-ethoxycarbonyl-8-methoxy-2,3,4,4a,5,9b-hexahydro-1H-pyrido[4,3-b] indolinium dichloride) on pentose phosphate pathway (PPP) and glutathione-dependent enzyme activities in aged diabetic and aged matched control rats. Diabetes was induced by streptozotocin injection in rats aged 13–15 months. Diabetic and control rats were divided into two subgroups, one untreated and one treated with SMe1EC2 (10 mg/kg/day, orally) for 4 months. SMe1EC2 ameliorated body weight loss, but not hyperglycemia of aged diabetic rats. Diabetes resulted in decreased glucose-6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD) and glutathione-S-transferase (GST), yet in unchanged glutathione reductase (GR) in the liver of aged diabetic rats. In the liver of the aged control rats, SMe1EC2 did not affect G6PDH, 6PGDH and GR, but it inhibited GST. SMe1EC2 also failed to affect diabetes-induced decline in 6PGDH, it ameliorated G6PDH but produced further decline in GST in the liver of aged diabetic rats. In the kidney of aged rats, G6PDH and GST were found to be comparable among the groups, but diabetes up-regulated 6PGDH and GR; these alterations were prevented by SMe1EC2. In the heart of aged diabetic rats, while GST remained unchanged, the recorded increase in G6PD, 6PGD, GR was prevented by SMe1EC2. Furthermore, an unchanged GR and remarkable increases in G6PD, 6PGD and GST were found in the lung of the aged diabetic group. These alterations were completely prevented by SMe1EC2. The results suggest that in aged rats SMe1EC2 can ameliorate the response of the kidney, heart and lung but not that of the liver against diabetes-induced glucotoxicity by interfering with the activity of redox network enzymes.

Flaxseed Protects Against Diabetes-Induced Glucotoxicity by Modulating Pentose Phosphate Pathway and Glutathione-Dependent Enzyme Activities in Rats

ABSTRACTThis study investigated the effects of flaxseed (Linum usitatissimum L.) intake on general metabolism, pentose phosphate pathway (PPP) and glutathione-dependent enzymes in diabetic rats. Diabetes was induced by streptozotocin injection (40 mg/kg, i.p.) and the enzyme activities were determined spectrophotometrically. Diabetic and control rats were divided in two subgroups, one untreated, and one treated with flaxseed (0.714 g/kg body weight/day; orally) for 12 weeks. Flaxseed ameliorated decreased body weight (p < .05) and increased blood glucose (p < .001), triglyceride (p < .001), ALT (p < .001) and AST (p < .001) in diabetic rats. Diabetes resulted in increased glucose-6-phosphate dehydrogenase (G6PD) (p < .05) and decreased glutathione-S-transferase (GST) (p < .01), but unchanged 6-phosphogluconate dehydrogenase (6PGD) and glutathione reductase (GR) in the brain of rats. These alterations were partially improved by flaxseed in comparison to diabetic untreated group (p < .05). G6PD, 6PGD, GR were elevated (p < .001), while GST unchanged in the lung of diabetic untreated group compared to control. Flaxseed partially prevented the increase in 6PGD (p < .05) and GR (p < .01), but unaffected G6PD in the lung of diabetic rats. G6PD (p < .001), 6PGD (p < .05), GR (p < .001) were augmented, while GST showed a significant (p < .001) depletion in the pancreas of diabetic untreated rats compared to control. Diabetic alterations observed in pancreatic enzyme activities were significantly prevented by flaxseed. Furthermore, a remarkable decrease in 6PGD (p < .001) and an increase in G6PD (threefold of control) were found in the lens of diabetic untreated group that were completely prevented by flaxseed (p < .001). Flaxseed has beneficial effects against diabetes-induced glucotoxicity by modulating G6PD, 6PGD, GR and GST activities in tissues.

English

Aim: The effect of cigarette smoke on the aorta of Wistar rats was investigated for possible enzymatic destruction. Methods: Thirty six Wistar rats 200±10g were randomly grouped into 3 of 12 rats in each group. One group was exposed to cigarette smoke (Benson and Hedges containing 1.1mg nicotine) once daily at 18.00hours. The second group was exposed to smoke from cotton wool of equal weight as of the cigarette. The third group was the control and was not exposed to smoke. The animals had feeds and water ad libitum. The rats were sacrificed on 14th and 28th days, the aortae excised, homogenized in 0.2M sucrose and assayed for Glucose 6 Phosphate Dehydrogenase (G6PDH), Lactase Dehydrogenase (LDH) and Alkaline Phosphatase (ALP). Results: A significant decrease in ALP and LDH and an insignificant increase in G6PDH over a period of 14 days were observed. However, the activities of the three enzymes were significantly decreased over a period of 28 days. Conclusion: Exposure to cigarette smoke can affect certain enzymes of the wall of the descending aorta. Key words: Descending aorta, G6PDH, LDH, ALP

Biochemical/metabolic changes associated with hepatocellular carcinoma development in mice

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related mortality after lung and stomach cancers. This work was undertaken to investigate some of the biochemical mediators/pathways associated with or implicated in the pathogenesis of HCC. Male albino mice were classified into two groups: normal control group and HCC group. Early stage HCC was induced by injection of diethylnitrosamine (DEN) i.p. 200 mg/kg as a single dose, and after 2 weeks, the mice were given i.p. injection of thioacetamide (TAA) 100 mg/kg twice per week for 4 weeks. Mice were left for further 2 weeks without any treatment, after which, mice were sacrificed; blood and liver samples were collected. Serum was used for determination of activities of glucose-6-phosphate dehydrogenase (G6PDH) and aldolase as well as levels of insulin-like growth factor-1 (IGF-1) and epithelial cadherin (E-cadherin). One portion of the liver was used for histopathological examination and immunohistochemical staining of the tumor suppressor p53 protein. Another portion of the liver was used for determination of citrate synthase activity. Induction of HCC in mice resulted in significant increase in G6PDH and aldolase activities, and E-cadherin level, but significant decrease in IGF-1. HCC mice group showed moderate expression of p53 protein. These results suggest that the molecular pathogenesis of HCC in mice involves reduction of serum level of IGF-1 and increased serum level of E-cadherin accompanied by dysregulation of p53 protein expression. HCC was also associated with reprogrammed metabolic profile shifted toward increased glycolysis and lipogenesis.

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

ELICITATION OF THE PROLINE-LINKED PENTOSE PHOSPHATE PATHWAY METABOLITES AND ANTIOXIDANT ENZYME RESPONSE BY ASCORBIC ACID IN DARK GERMINATED FAVA BEAN SPROUTS

ABSTRACT Elicitation by ascorbic acid stimulated higher phenolic content in late stages of germination and higher antioxidant activity during early and late germination in fava bean sprouts. The high free radical scavenging-linked antioxidant activity on day 1 coincided with high levo-dihydroxy phenylalanine and total phenolics. A positive correlation between the stimulation of phenolic synthesis and glucose-6-phosphate dehydrogenase (G6PDH) activity was also observed, indicating its likely role in carbohydrate mobilization. Improved guaiacol peroxidase (GPX) activity in response to elicitation indicated the likely polymerization of soluble phenolics. Higher GPX, superoxide dismutase and catalase linked antioxidant enzyme response correlated to increase in proline and phenolics. A proline-linked stimulation likely provided nicotinamide adenine dinucleotidephosphate from pentose phosphate pathway (PPP) as indicated by an increase in G6PDH, the first committed step of PPP, which then supported phenolic synthesis and antioxidant enzyme response. PRACTICAL APPLICATIONS This research indicates that ascorbic acid is an effective elicitor of the pentose phosphate pathway (PPP) in dark germinated fava bean sprouts. It increases synthesis of health-relevant phenolics and levo-dihydroxy phenylalanine relevant to Parkinson's disease management. The stimulation of PPPwas linked to accumulation of free proline thereby supporting the proline-linked pentose phosphate pathway model. It provides an understanding of the role of phenolic antioxidants on redox modulation in the cell by being effective free radical scavengers and also by inducing the antioxidant enzyme responses through providing the reducing equivalents required for their activity. This knowledge can be used as a biochemical strategy to design seed sprouts for functional food applications.

Effect of Anabolic Steroid Nandrolone Decanoate on the Properties of Certain Enzymes in the Heart, Liver, and Muscle of Rats, and their Effect on Rats' Cardiac Electrophysiology

Nandrolone decanoate (ND) is an anabolic steroid, modified to enhance anabolic rather than androgenic actions. The physiological effects of ND treatment are often used in various aspects of medical practice. In this investigation we have tried to establish whether a single, high dose of ND (20 mg/kg) would cause any anabolic effects. Moreover, we have attempted to correlate the eventual effects with changes in the activity and kinetic properties of anabolic- and bioenergetic-involved enzymes in different tissues of rats, along with the rats' ECG parameters. The body and liver weights of the rats were unchanged, but heart weight had increased 10 days after ND injection. Electrocardiographic data showed a small prolongation of the QRS complex 3, 6, and 10 days after ND treatment. It was established that ND causes activation of glucose-6-phosphate and 6-phosphogluconate dehydrogenases, malic enzyme, and NADP-linked isocitrate dehydrogenase in rat hearts. Moreover, 6-phosphogluconate dehydrogenase from the hearts of ND-treated rats showed higher affinity to its substrate, in comparison with control. Activation of transketolase by ND in the liver was accompanied by inhibition of glucose-6-phosphate and 6-phosphogluconate dehydrogenases. We observed an increase of glucose 6-phosphate dehydrogenase and NAD-linked malate dehydrogenase in the muscle of ND treated rats. It may be concluded that ND in a single high dose exhibits cardiotrophic action, especially towards the increase of heart dehydrogenases activity which generates NADPH and supplies ribose phosphate for the biosynthesis of nucleotides and nucleic acids. On the other hand, ND may cause activation of ATP synthesis in muscle by enhanced malate-aspartate shuttle action.

Effects of lead nitrate on the activity of metabolic enzymes during early developmental stages of the African catfish, Clarias gariepinus (Burchell, 1822)

Glucose-6-phosphate dehydrogenase (G6PDH), lactate dehydrogenase (LDH) and pyruvate kinase (PK) are key metabolic enzymes. G6PDH has been used as a biomarker of pollution-induced carcinogenesis in fish. LDH has been used as marker of lesions in toxicology and clinical chemistry, and PK catalyses the conversion of phosphoenol pyruvate to pyruvate, with regeneration of ATP. The effect of different concentrations of lead nitrate on the activity of these enzymes in two different early ontogenetic stages (embryonic and free embryonic stage) of the African catfish Clarias gariepinus was investigated. Embryo homogenates were used for measurements of G6PDH, LDH and PK activity spectrophotometrically at 340 nm and 25°C. The ontogenetic variations of the three enzymes during early ontogeny, from the 30 h to the 168 h post-fertilisation stage (PFS) (beginning of exogenous feeding), were studied. There was a significant decrease in activities of all three enzymes from 30 h-PFS to 96 h-PFS, followed by a significant increase in G6PDH and LDH. PK showed insignificant fluctuations in activity. Different patterns of enzyme activities were recorded due to exposure to different lead nitrate concentrations (100 μg/l, 300 μg/l and 500 μg/l). In the pre-hatching stage (30 h-PFS) the activity of the three enzymes increased at exposure to 100 μg/l lead nitrate and then decreased with increasing dose. In the post-hatching stages (48 h-PFS–168 h-PFS) G6PDH activity increased and LDH activity decreased with increasing lead concentrations. Unlike G6PDH and LDH, the PK enzyme fluctuated during the post-hatching stages and did not reveal a specific trend of response (increase or decrease) with increasing lead concentrations. Therefore, the measurement of G6PDH and LDH activities, but not PK activity, could be useful biomarkers of intoxication to reveal the embryotoxic potential of lead nitrate in fish embryos. The post-hatching stages of the African catfish are more sensitive than the pre-hatching stage (30 h-PFS) is, probably due to the protective capacity provided by the hardened chorion. The interaction and the main effects of age and lead doses were found to be highly significant, referring to the great impact of lead on these enzyme systems with increasing early development.

Glucose metabolism during embryogenesis of the hard tick Boophilus microplus

Glucose metabolism plays an essential role in the physiology and development of almost all living organisms. In the present study we investigated glucose metabolism during the embryogenesis of the hard tick Boophilus microplus. An increase in glucose and glycogen content during the embryonic development of B. microplus was detected and shown to be due to the high enzyme activity of both gluconeogenesis and glycolytic pathways. Glucose 6-phosphate (G-6P), formed by hexokinase, is driven mainly to pentose-phosphate pathway, producing fundamental substrates for cellular biosynthesis. We detected an increase in glucose 6-phosphate dehydrogenase and pyruvate kinase activities after embryo cellularization. Accumulation of key metabolites such as glycogen and glucose was monitored and revealed that glycogen content decreases from day 1 up to day 6, as the early events of embryogenesis take place, and increases after the formation of embryo cellular blastoderm on day 6. Glucose and guanine (a sub-product of amino acids degradation in arachnids) accumulate almost concomitantly. The activity of phosphoenolpyruvate carboxykinase was increased after embryo cellularization. Taken together these data indicate that glycogen and glucose, formed during B. microplus embryogenesis after blastoderm formation, are produced by intense gluconeogenesis.

Protective effects of the antioxidant Ginkgo biloba extract and the protease inhibitor aprotinin against Leiurus quinquestriatus venom-induced tissue damage in rats

Oxidative stress and proteases have been implicated in several diseases and extensive evidence indicates that antioxidants and protease inhibitors help prevent organ functional damage. Leiurus quinquestriatus (LQQ) scorpion venom causes cellular injuries that may lead to multiple organ failure. Thus, the capability of the antioxidant "natural standardized extract of Gingko biloba leaves (Gin, EGb 761)" and the non-selective protease inhibitor, aprotinin, in ameliorating venom-induced biochemical alterations indicative of cellular injury and oxidative stress was studied to determine their effectiveness in protecting rats from venom-evoked cellular damages. Thus, in this study, rats were treated with LQQ venom (0.3mg.kg-1, subcutaneously) alone or after Gin (150mg.kg-1, orally, daily for 2 weeks before venom) and/or aprotinin (Apr, 46000 KIU.kg-1, intraperitoneally, 30 min before venom). Control groups were injected with saline or treatment modalities. Lungs and hearts were excised after decapitating rats (n=8/group) 60 min after venom injection and the following activities were measured: reduced glutathione (GSH), malondialdehyde (MDA) - an index of lipid peroxidation, glutathione peroxidase (GPx), glucose-6-phosphate dehydrogenase (G6PD), and lactate dehydrogenase (LDH). Our findings demonstrate that LQQ venomsignificantly elevated GSH (p<0.05 vs. control), MDA (p<0.05), G6PD (p<0.05), and LDH activities (p<0.001) in hearts of envenomed rats. The venom also elevated MDA (p<0.05 vs. control) and reduced GSH and GPx (p<0.05) in the lungs of envenomed rats. In general, pretreatment with EGb761 attenuated LQQ venom-evoked increases in GSH (p<0.05 vs. venom), MDA in rat hearts and lungs (p<0.05 vs. venom), plus LDH in the heart (p<0.01). Aprotinin alone significantly reduced the venom-elicited increase in G6PD and LDH activities and the decrease in GPx levels (p<0.05). In general, these protective effects of EGb761 on GSH, MDA (p<0.01 vs. venom) and LDH (p<0.001) in the heart and/or lung were potentiated when combined with aprotinin. We concluded that the effectiveness of EGb761 and Apr in ameliorating venom-evoked biochemical changes indicative of necrosis and free radical generation point out the involvement of oxidative stress and proteases in venom-evoked cellular damages seen in this study in isolated rat hearts and lungs.

ACTION OFCAPPARIS DECIDUAAGAINST ALLOXAN-INDUCED OXIDATIVE STRESS AND DIABETES IN RAT TISSUES

Alloxan-induced diabetic rats were treated with insulin (i.p.) or withCapparis deciduapowder as a hypoglycaemic agent mixed with diet. The effect was assessed on lipid peroxidation (LPO) and the antioxidant defense system in rat tissues. The increased levels of blood glucose in diabetes produce superoxide anions and hydroxyl radicals in the presence of transition metal ions which cause oxidative damage to cell membranes. The heart tissue showed an increased lipid peroxidation (LPO) in diabetic rats while no significant change was observed in the liver and kidney. The treatment withC. decidualowered LPO in these tissues even more effectively than insulin-treated rats. The superoxide dismutase (SOD) activity increased in the heart and kidneys in the diabetic group of rats probably to increase dismutation of superoxide anions. However, treatment withC. deciduadecreased SOD activity in the liver and kidney and was comparable to control rats. Catalase (CAT) activity was not significantly affected in any of the tissues in diabetic and insulin-treated animals, however, CAT activity markedly increased in tissues withC. deciduatreatment. Total and Se-dependent glutathione peroxidase (GSH-Px) in the heart was markedly lowered in diabetic rats which recovered with insulin as well as with C. decidua treatment. The increase in GSH-Px and CAT activity withC. deciduatreatment may lower H2O2toxicity and reduce oxidative stress in diabetes. However, glutathione (GSH) content in the heart and kidney and glutathione reductase (GSH-R) activity in all the tissues studied increased in diabetic rats while treatment with insulin lowered GSH content and GSH-R activity in these tissues. The treatment withC. deciduaalso decreased GSH-R activity in the kidney and heart which resulted in the decrease in GSH content in these tissues. The changes such as the increase in kidney and heart SOD may be an adaptive response in order to neutralize superoxide anions. The increase in GSH content and GSH-R activity in the tissue are in response to neutralize superoxide anions and to counteract oxidative stress in diabetes. GlutathioneS-transferase (GST) was not significantly affected in diabetic rat tissue, however, heart GST increased with antidiabetic treatments. The increase in glucose-6-phosphate dehydrogenase (G6PDH) in the kidney and heart of diabetic rats subsequently decreased withC. deciduatreatment. The increase in G6PDH in tissues may increase NADPH generation required for GSH-R activity and GSH production. It is suggested that these changes initially counteract the oxidative stress in diabetes, however, a gradual decrease in the antioxidative process may be one of the factors which results in chronic diabetes. The data indicate thatC. deciduamay have potential use as an antidiabetic agent and in lowering oxidative stress in diabetes.

Malic enzyme and glucose 6-phosphate dehydrogenase gene expression increases in rat liver cirrhogenesis.

The cirrhogenic ability of thioacetamide has been used to induce a model of chronic generalized liver disease that resembles the preneoplastic state of human fibrosis. Malic enzyme (ME) and glucose-6-phosphate dehydrogenase (G6PDH) are two cytosolic NADPH-generating enzymes; their activities significantly increased in liver when macronodular cirrhosis was induced by long-term thioacetamide administration to rats. The progressive increase in G6PDH and ME activities during the cirrhogenic process is parallel to the induction in gene expression of both enzymes detected by the increase in their mRNAs. These data indicate that NADPH-consuming mechanisms such as the microsomal oxidizing system and the maintenance of the cell redox state could be involved. A relationship between the extent of G6PD and ME gene expression and oxidative stress generated by the oxidative metabolism of thioacetamide is proposed as the hepatic concentration of malondialdehyde, a metabolite derived from lipid peroxidation, underwent a progressive and significant enhancement during thioacetamide-induced cirrhogenesis. These results led us to suggest that the enhanced activities of G6PDH and ME might be related to microsomal mechanisms of detoxification as well as to the maintenance of the cellular redox state. Furthermore, the noticeable increase in the hepatocyte population involved in DNA replication parallel to G6PDH activity suggests that G6PDH, through ribose-5-phosphate, might also be involved in the processes of DNA synthesis and repair.

Involvement of different ion channels in osteoblasts' and osteocytes' early responses to mechanical strain.

The involvement of functional ion channels in previously documented early responses of osteocytes and osteoblasts to mechanical strain in bone tissue was investigated in explants of rat ulnae by the use of ion channel blockers. Gadolinium chloride (a blocker of stretch/shear-sensitive cation channels) elevated basal prostaglandin (PG) E2 and prostacyclin (PGI2) release and osteocyte glucose-6-phosphate dehydrogenase (G6PD) activity, but was associated with a reduction in basal nitric oxide (NO) production. Gadolinium abolished loading-related increases in the release of PGI2 and NO and osteocyte G6PD activity. Gadolinium also reduced the loading-related release of PGE2 assumed to originate from osteoblasts and the magnitude of loading-related increases in G6PD activity in these cells. Nifedipine (a blocker of L-type voltage-dependent calcium channels) had no effect on basal levels of prostanoid or NO release, or G6PD activity in osteocytes or osteoblasts, and did not affect loading-related release of PGI2 or increase in osteocyte G6PD. However, nifedipine prevented loading-related increases in PGE2 and NO release and osteoblast G6PD activity. These results are consistent with osteocytes' response to bone loading requiring activatable ion channels sensitive to gadolinium, but not those sensitive to nifedipine. In osteoblasts, the early responses to bone loading appear to be associated with ion channels sensitive to gadolinium and nifedipine; however, the nifedipine-sensitive channels seem to have the dominant effect.

Effect of hepatocyte growth factor/scatter factor on lipogenesis in adult rat hepatocytes in primary culture.

Hepatocyte growth factor (HGF)/scatter factor is known to be the most potent mitogen for hepatocytes. In this paper, we report that lipogenesis in primary cultured rat hepatocytes treated with 10 ng/ml of recombinant human HGF (rhHGF) for 24 h was stimulated, as measured by the incorporation of 3H2O into long-chain fatty acids, to more than twice as much as the control. Insulin (0.1 microM) was more effective than rhHGF but rhHGF did not show an additive or synergistic effect when added to insulin. We also showed that treatment with rhHGF increased the activities of glucose-6-phosphate dehydrogenase (G6PDH) and malic enzyme, key enzymes which supply NADPH for lipogenesis, and acetyl-CoA carboxylase, the rate-limiting enzyme of lipogenesis. The increase in G6PDH and acetyl-CoA carboxylase activities was accompanied by increases in the levels of mRNA for the enzymes. These results suggest that HGF is involved in liver regeneration not only by stimulation of cell proliferation but also by acceleration of differentiation of hepatocytes.

Early loading-related changes in the activity of glucose 6-phosphate dehydrogenase and alkaline phosphatase in osteocytes and periosteal osteoblasts in rat fibulae in vivo.

The tibiae and fibulae of 14-week-old rats were subjected to a single 5 minutes period of cyclic longitudinal loading at 1 Hz. The activity of the enzymes glucose 6-phosphate dehydrogenase (G6PD) and alkaline phosphatase (ALP) in osteocytes and periosteal osteoblasts was measured immediately and 24 h after loading. In osteocytes G6PD activity was increased immediately after loading but returned to control values 24 h later. There was no detectable ALP activity in these cells regardless of loading history. In periosteal osteoblasts G6PD activity was raised immediately after loading and remained higher than controls 24 h later. ALP activity in periosteal cells was unaffected immediately after loading but 24 h later was substantially increased. These findings are consistent with osteocytes and periosteal cells both being immediately responsive to periods of intermittent loading in their adjacent matrices. In both cell types an early feature of this response is an increase in G6PD activity. In osteocytes this response is short-lived, suggesting that it is an early biochemical change associated with strain perception that does not progress to matrix synthesis. The increase in G6PD activity with unaffected ALP levels in periosteal cells immediately after loading is consistent with a similar response. In these cells the increase in G6PD accompanied by increased ALP levels 24 h after loading suggests that the loading-related response progresses to new bone formation.

Intestinal metaplasia and altered enzyme expression in propylnitrosamine-induced Syrian hamster cholangiocellular and gallbladder lesions

Intrahepatic bile duct and gallbladder preneoplastic and neoplastic lesions induced in Syrian golden hamsters by propylnitrosamine treatment were investigated for the presence of polysaccharides and assayed immunohistochemically for expression of the enzymes glucose-6-phosphate dehydrogenase (G6PD) and glutathione-S-transferase (GST) molecular forms. On the basis of an increase in G6PD and the GST-placental form, a sequence of altered cell populations ranging from simple ductular proliferation through dysplasia and cholangiofibroma to cholangiocellular carcinoma could be established, the latter three lesions being characterized by marked increase in polysaccharide production. While similar goblet cell (intestinal) metaplasia and increased polysaccharide storage were also evident in carcinogen-induced gallbladder lesions G6PD and GST-P expression was decreased when compared with control epithelium.