Jonas Cederberg

Reactive oxygen species cause diabetes-induced decrease in renal oxygen tension

Aims/hypothesisAugmented formation of reactive oxygen species (ROS) induced by hyperglycaemia has been suggested to contribute to the development of diabetic nephropathy. This study was designed to evaluate the influence of streptozotocin (STZ)-induced diabetes mellitus, as well as the effects of preventing excessive ROS formation by α-tocopherol treatment, on regional renal blood flow, oxygen tension and oxygen consumption in anaesthetized Wistar Furth rats.MethodsNon-diabetic and STZ-diabetic rats were investigated after 4 weeks with or without dietary treatment with the radical scavenger DL-α-tocopherol (vitamin E, 5%). A laser-Doppler technique was used to measure regional renal blood flow, whilst oxygen tension and consumption were measured using Clark-type microelectrodes.ResultsRenal oxygen tension, but not renal blood flow, was lower throughout the renal parenchyma of diabetic rats when compared to non-diabetic control rats. The decrease in oxygen tension was most pronounced in the renal medulla. Renal cellular oxygen consumption was markedly increased in diabetic rats, predominantly in the medullary region. Diabetes increased lipid peroxidation and protein carbonylation in the renal medulla. Treatment with α-tocopherol throughout the course of diabetes prevented diabetes-induced disturbances in oxidative stress, oxygen tension and consumption. The diabetic animals had a renal hypertrophy and a glomerular hyperfiltration, which were unaffected by α-tocopherol treatment.Conclusions/interpretationWe conclude that oxidative stress occurs in kidneys of diabetic rats predominantly in the medullary region and relates to augmented oxygen consumption and impaired oxygen tension in the tissue.

Combined Treatment with Vitamin E and Vitamin C Decreases Oxidative Stress and Improves Fetal Outcome in Experimental Diabetic Pregnancy

The aim was to investigate whether dietary supplementation of a combination of the two antioxidants, vitamin E and vitamin C, would protect the fetus in diabetic rat pregnancy at a lower dose than previously used. Normal and streptozotocin-induced diabetic rats were mated and given standard food or food supplemented with either 0.5% vitamin E + 1% vitamin C or 2% vitamin E + 4% vitamin C. At gestational d 20, gross morphology and weights of fetuses were evaluated. Vitamins E and C and thiobarbituric acid reactive substances were measured in maternal and fetal compartments. In addition, protein carbonylation was estimated in fetal liver. Maternal diabetes increased the rate of malformation and resorption in the offspring. High-dose antioxidant supplementation decreased fetal dysmorphogenesis to near normal levels. The low-dose group showed malformations and resorptions at an intermediate rate between the untreated and the high-dose groups. Thiobarbituric acid reactive substances were increased in fetal livers of diabetic rats and reduced to normal levels already by low-dose antioxidative treatment. Protein carbonylation rate was also increased in fetal liver of diabetic rats; it was normalized by high-dose treatment but only partially reduced by low-dose antioxidants. We conclude that combined antioxidative treatment with vitamins E and C decreases fetal malformation rate and diminishes oxygen radical-related tissue damage. However, no synergistic effect between the two antioxidants was noted, a result that may influence future attempts to design antiteratogenic treatments in diabetic pregnancy. Oxidatively modified proteins may be teratogenically important mediators in diabetic embryopathy.

Congenital Malformations in Offspring of Diabetic Mothers—Animal and Human Studies

The disturbed embryo-fetal development in diabetic pregnancy has been extensively investigated in experimental [1,2] and clinical [3,4] studies. The research focus has shifted during the last decades due to the successively improved clinical treatment of diabetic pregnancy [5–8]. Thus, in the early days of insulin therapy the offspring faced a significant risk of both intrauterine and perinatal mortality, as well as markedly increased risk for postnatal morbidity [9]. At present, almost eighty years after the introduction of insulin therapy, when the rate of most previous complications has been reduced, the incidence of congenital malformation remains increased [10] and constitutes a major threat to the health of the offspring of the diabetic woman [11–20]. The magnitude of the expected risk for congenital malformation varies from a doubling to 5-6 times that of non-diabetic gestation [6,21–37], and congenital malformations are commonly regarded as a major cause of mortality and morbidity in the offspring of diabetic pregnancy [10,27,29,38–41]. The continued risk for fetal malformation justifies future intensified clinical and experimental research efforts. Clinical investigations have reported increased incidences of congenital malformation both in type-1 [3,10,21,42], and type-2 [18,25,33,39,43,44] diabetic pregnancies. The offspring of women with gestational diabetes show increased rate of congenital malformations [16,18,45–49], however, in these studies there may be a proportion of pregnant women with undiagnosed type-1 or type-2 diabetes contributing to the high rate of fetal dysmorphogenesis. Also, clinical studies have indicated that the risk for congenital malformations is dependent on the blood glucose regulation during the peri-conception period and the first trimester [35,50–55], in particular during the first seven weeks of pregnancy [56]. Experimental studies have suggested that the major teratogen in diabetic pregnancy is hyperglycemia [57–60], although other diabetes-related factors may also influence the fetal outcome, e.g. increased levels of ketone bodies [61–70], triglycerides [71,72], and branched chain amino acids [72,73]. Several teratological pathways in the embryonic tissues have emerged, such as alterations in the metabolism of inositol [74–79], arachidonic acid/prostaglandins [74,80,81] and reactive oxygen species [73,82–84]. The embryonic formation of sorbitol [75,76,78,85,86], glycated proteins [87–89], and the maternal and fetal genotypes [90–94] are also suggested to influence the complex teratological events in diabetic pregnancy. The cell biological details and interplay of these factors and pathways will be the subject for future research efforts in the field of diabetic embryopathy.

Increased rate of lipid peroxidation and protein carbonylation in experimental diabetic pregnancy.

Aims/hypothesis. Maternal Type I (insulin-dependent) diabetes mellitus is associated with an increased risk for fetal malformations and spontaneous abortions. Although the pathogenic mechanism is not fully understood, reactive oxygen species have been shown to contribute to the pathogenesis in experimental studies. By measuring 8-iso-PGF2α and protein carbonyls, radical oxygen damage to lipids and proteins can be estimated. The aim of this study was to investigate the status of lipid peroxidation and protein carbonylation in mothers and fetuses in experimental diabetic pregnancy. Methods. Non-pregnant and pregnant rats with and without streptozotocin-induced diabetes were studied after 4 weeks of diabetes or at gestational day 19, respectively. Gross morphology of the offspring was studied and 24 h urine, plasma, amniotic fluid, maternal and fetal livers were collected. Concentrations of 8-iso-PGF2α, 15-keto-DH-PGF2α and other oxidative stress variables were measured. Results. Malformation and resorption rates were increased in diabetic litters, whereas fetal weights were decreased in the control rats. There were no statistically significant differences in maternal plasma concentrations of 8-iso-PGF2α, but plasma protein carbonyl content was increased in the diabetic groups. Pregnancy increased 24 h urinary excretion of 8-iso-PGF2α in diabetic rats but not in the control rats. There was no difference in the amniotic fluid concentration of 8-iso-PGF2α between the normal and the diabetic group. However, in the diabetic group there was a correlation between the uterine horn concentration of 8-iso-PGF2α and the percentage of resorptions. Conclusions/interpretation. In diabetic pregnancy, both diabetes and pregnancy are promoting oxygen radical damage. Fetal oxidative stress markers do not clearly reflect fetal morphology. [Diabetologia (2001) 44: 766–774]

Vitamin E reduces lipid peroxidation in experimental hepatotoxicity in rats.

Background and aims Lipid peroxidation is believed to be involved in the pathophysiology of a number of diseases and in the process of aging. This study investigates the effects of dietary supplementation with vitamin E (20 g/kg diet of all-rac-α-tocopheryl succinate for 3 weeks) on both non-enzymatic and enzymatic lipid peroxidation in experimental rats with carbon tetrachloride (CCl4)-induced hepatotoxicity (2.5 mL/kg body). Methods Plasma, urine and liver samples from control rats (n = 6), CCl4-treated rats (n = 6), and rats supplemented with vitamin E prior to CCl4 treatment (n = 8) were collected. Non-enzymatic lipid peroxidation induced by free radicals was investigated by measurement of a major F2-iso-prostane, 8-iso-prostaglandin F2α (8-iso-PGF2α). Cyclooxygenase-catalyzed enzymatic lipid peroxidation was measured with a major PGF2α metabolite, 15-kto-13,14-dihydro-prostaglandin F2α (15-K-DH-PGF2α). Malondialdehyde and antioxidants in plasma were also quantified. Results CCl4 treatment alone resulted in significantly higher levels of plasma, urinary and liver 8-iso-PGF2α, and of plasma and urinary 15-K-DH-PGF2α compared to controls. Rats supplemented with vitamin E prior to CCl4 treatment had significantly lower levels of urinary and liver 8-iso-PGF2α, urinary 15-K-DH-PGF2α, and plasma malondialdehyde than rats treated with CCl4 alone. However, plasma 8-iso-PGF2α and plasma 15-K-DH-PGF2α were not affected by vitamin E supplementation. Conclusion Thus, both non-enzymatic and enzymatic lipid peroxidation during experimental hepatic oxidative injury were suppressed by dietary vitamin E supplementation in rats.

Pathogenesis of Diabetes-Induced Congenital Malformations

Abstract The increased rate of fetal malformation in diabetic pregnancy represents both a clinical problem and a research challenge. In recent years, experimental and clinical studies have given insight into the teratological mechanisms and generated suggestions for improved future treatment regimens. The teratological role of disturbances in the metabolism of inositol, prostaglandins, and reactive oxygen species has been particularly highlighted, and the beneficial effect of dietary addition of inositol, arachidonic acid and antioxidants has been elucidated in experimental work. Changes in gene expression and induction of apoptosis in embryos exposed to a diabetic environment have been investigated and assigned roles in the teratogenic processes. The diabetic environment appears to simultaneously induce alterations in several interrelated teratological pathways. The complex pathogenesis of diabetic embryopathy has started to unravel, and future research efforts will utilize both clinical intervention studies and experimental work that aim to characterize the human applicability and the cell biological components of the discovered teratological mechanisms.