Clinical relevance of the oxidative stress concept

Dietary Implications of Polyunsaturated Fatty Acids during Pregnancy and in Neonates

Certain limitations exist for animals to modify fatty acid changes. Besides the role of arachidonic acid (AA), docosahexaenoic acid (DHA) and other 20-carbon long-chain polyunsaturated fatty acids (LCPUFAs) for the synthesis of inflammatory mediators as eicosanoids, different LCPUFAs have many other effects, including their abilities to regulate gene expression and downstream events. LCPUFAs are susceptible to autoxidation, which is prevented by the action of antioxidants in the form of enzymes like superoxide dismutases, catalases and peroxidases, as well as antioxidant compounds that protect against oxidation or repair the damage caused. Under normal conditions, the fetus needs both essential fatty acids (EFAs) and LCPUFAs, which are obtained from its mother by placental transfer. In early pregnancy, dietary derived fatty acids are accumulated in maternal adipose tissue. However, during late pregnancy, corresponding to the period of the highest fetal growth, maternal adipose tissue becomes catabolic and LCPUFAs are released into the circulation by adipose lipolytic activity. The released LCPUFAs are taken up by maternal liver to be esterified and released back to the circulation as triacylglycerides (TAGs) in very-low-density lipoprotein (VLDL) that become available to the placenta to be transferred to the fetus in the form of non-esterified fatty acids (NEFAs). An enhanced adipose tissue lipolysis is maintained around parturition and esterified LCPUFAs are diverted to mammary glands thanks to an increased activity of lipoprotein lipase for milk production. Throughout this process, LCPUFAs become available to the newborn during suckling. The important role of both DHA and AA for the development of the nervous system and for growth has motivated their dietary supplement during different postnatal stages. This has been especially important in preterm infants both because under normal conditions, the fetus acquires most of these fatty acids during late pregnancy, and because the immaturity of the enzyme systems for the synthesis of AA and DHA from their respective EFAs.

Compositional analyses of diverse phytochemicals and polar metabolites from different-colored potato (Solanum tubersum L.) tubers

Lipophilic bioactive compounds and hydrophilic primary metabolites from potato (solanum tubersum L.) tubers with different-colored flesh (white-, yellow-, red-, and purple) were characterized. The carotenoid content was relatively higher in red-colored potatoes, in which lutein was most plentiful. Among the other lipophilic compounds analyzed, including policosanols, tocopherols, and phytosterols, octacosanol was measured in the largest amount, followed by β-sitosterol, irrespective of color variations. Forty-three hydrophilics consisting of amino acids, organic acids, sugars, and sugar alcohols and 18 lipophilics were subjected to data-mining processes. The results of multivariate statistical analyses clearly distincted the different varieties and separated red-fleshed potatoes from other color-fleshed potatoes according to abundance of amino acids, sugars, and carotenoids. This study confirmed the metabolic association-related biochemical pathway between metabolite characteristic and color differences in potato tubers. These results can facilitate understanding the metabolic differences among diverse colored potatoes and provide fruitful information for genetic engineering of potato cultivars.

Metabolite profiling based on lipophilic compounds for quality assessment of perilla (Perilla frutescens) cultivars

Lipophilic compounds from Korean perilla ( Perilla frutescens ) seeds were characterized to determine the diversity among their phytochemicals and to analyze relationships between their contents. Twenty-four metabolites consisting of policosanol, phytosterol, tocopherol, and fatty acids were identified. The metabolite profiles were subjected to data mining processes, including principal component analysis (PCA), partial least-squares discriminate analysis (PLS-DA), and Pearson's correlation analysis. PLS-DA could distinguish between all cultivars except between Daesil and Daeyeup cultivars. Linolenic acid contents were positively correlated with β-sitosterol (r = 0.8367, P < 0.0001) and γ-tocopherol contents (r = 0. 7201, P < 0.001) among all perilla grains. The Daesil and Daeyeup cultivars appear to be good candidates for future breeding programs because they have simultaneously high linolenic acid, phytosterol, and tocopherol levels. These results demonstrate the use of metabolite profiling as a tool for assessing the quality of food.

Inhibition of microsomal triglyceride transfer protein improves insulin sensitivity and reduces atherogenic risk in Zucker fatty rats

1. Insulin-resistant states are commonly associated with a significantly higher risk of atherosclerosis. Insulin resistance has also been correlated with enhanced very low-density lipoprotein (VLDL) production, which is exacerbated by increased intestinal lipid synthesis and insulin-stimulated de novo lipogenesis. Microsomal triglyceride transfer protein (MTP) catalyses the critical step in the synthesis and secretion of VLDL and chylomicrons. The purpose of the present study was to test the hypothesis that chronic inhibition of MTP with a small molecule inhibitor would improve insulin sensitivity and reduce atherogenic risk in a genetic model of diabetic dyslipidaemia. 2. The in vivo activity of BMS-201038, a potent inhibitor of MTP, was evaluated in a model of hypertriglyceridemia induced by Triton WR1339 and corn oil in Zucker fatty rats. Triglyceride secretion rate was significantly reduced by a single dose of BMS-201038 by 35% at 0.3 mg/kg and 47% at 1 mg/kg, respectively. 3. Another group of Zucker fatty rats was dosed orally with BMS-201038 (0.3 and 1 mg/kg) for 14 days. Serum levels of triglycerides were reduced by 71% and 87%, non-esterified free fatty acids were reduced by 33% and 40%, and low-density lipoproteins by 26% and 29%, by 0.3 mg/kg and 1 mg/kg dose of BMS-201038, respectively. These serum lipid changes were accompanied by significant improvements in glucose tolerance and insulin sensitivity. In addition, lipid peroxidation in liver was reduced by 59% and 61%, and superoxide dismutase activity was increased by 11% and 45% by 0.3 mg/kg and 1 mg/kg dose of BMS-201038, respectively. Similar beneficial changes were found in aorta as well. 4. The present study provides evidence that inhibition of MTP with a small molecule inhibitor significantly improves dyslipidaemia associated with insulin resistance and reduces the atherosclerotic risk.

Expression of heat shock proteins and nitrotyrosine in small arteries from patients with coronary heart disease

Heat shock proteins (HSPs) have been suggested to play an important role in the pathogenesis of cardiovascular disease; however, their levels in resistance arteries and their role as useful markers for endothelial dysfunction are not well known. In this paper we studied the levels of HSP90, HSP70, HSP60, HSP27, and of the oxidative stress marker nitrotyrosine (NT) in isolated small subcutaneous arteries from female and male patients with coronary heart disease (CHD) and compared them with healthy controls. HSPs and NT levels were analyzed by immunohistochemistry (IHC) with streptavidin-biotin complex and 3,3'-diaminobenzidine (DAB) staining. The results were assessed with a semi-quantitative method. The study showed lower levels of HSP90 in arteries from both male and female patients when compared to the healthy controls, while levels of HSP70 were lower only in male patients versus controls. The levels of HSP60 and HSP27 did not show any significant difference in either the male or the female groups. NT levels were higher in the arteries from female patients as compared to controls. In conclusion, the present study strengthens the concept that HSPs may play an important role in the pathogenesis of CHD, and that at least two of them, HSP70 and HSP90, may have useful applications as markers of vascular dysfunction in resistance arteries.

Oxidative stress and inflammation, a link between chronic kidney disease and cardiovascular disease

Patients with chronic kidney disease (CKD) show a high cardiovascular morbidity and mortality. This seems to be consequence of the cardiovascular risk factor clustering in CKD patients. Non traditional risk factors such as oxidative stress and inflammation are also far more prevalent in this population than in normal subjects. Renal disease is associated with a graded increase in oxidative stress markers even in early CKD. This could be consequence of an increase in reactive oxygen species as well as a decrease in antioxidant defence. This oxidative stress can accelerate renal injury progression. Inflammatory markers such as C reactive protein and cytokines increase with renal function deterioration suggesting that CKD is a low-grade inflammatory process. In fact, inflammation facilitates renal function deterioration. Several factors can be involved in triggering the inflammatory process including oxidative stress. Statin administration is accompanied by risk reduction in all major vascular events in patients with CKD that are considered high-risk patients. These beneficial effects seem to be consequence of not only their hypolipidemic effect but especially their pleitropic actions that involve modulation of oxidative stress and inflammation.

Decreased in vivo oxidative stress and decreased platelet activation following metformin treatment in newly diagnosed type 2 diabetic subjects

BACKGROUND

In type 2 diabetes, metformin reduces cardiovascular risk beyond the effect of glycaemic control. Since oxidative stress and the consequent enhanced platelet activation contribute to accelerated atherosclerosis in diabetes, we hypothesized that metformin could reduce oxidative stress in this condition.

METHODS

We randomized 26 newly diagnosed type 2 diabetic subjects to assume either metformin (M, n = 13) or gliclazide (G, n = 13) for 12 weeks. Drugs were titrated as needed to achieve good glycaemic control. Before and after treatment, we determined blood glucose, insulin, HbA(1c), vitamin A and E levels and 8-iso-PGF(2alpha) and 11-dehydro-thromboxane B(2) urinary excretion, an in vivo oxidative stress and a thromboxane-dependent platelet activation marker, respectively.

RESULTS

Notwithstanding a comparable improvement in metabolic control, 8-iso-PGF(2alpha) (M from 708 +/- 32 to 589 +/- 45 pg/mg cr, p < 0.001; G from 646 +/- 80 to 665 +/- 79, pg/mg cr, p = ns) and 11-dehydro-thromboxane B(2) (M from 2190 +/- 196 to 1753 +/- 150 pg/mg cr, p < 0.05; G from 2048 +/- 202 to 1923 +/- 223, pg/mg cr, p = ns) urinary excretion decreased after metformin but not after gliclazide treatment. After metformin, vitamin A and E levels significantly increased while they remained unchanged after gliclazide.

CONCLUSIONS

These data suggest that metformin could improve oxidative stress, preserve antioxidant function and restrain platelet activation in type 2 diabetes.

Oxidative stress markers in plasma and urine of prepubertal patients with type 1 diabetes mellitus

Markers of oxidative stress were studied in plasma and urine of prepubertal patients with type 1 diabetes mellitus (DM1) with less than 5 years of disease (n = 27). The results were compared to healthy, age- and sex-matched control children (n = 27). Oxidative stress parameters evaluated included advanced oxidation protein products (AOPP), total peroxyl radical-trapping antioxidant parameter (TRAP), and F2-isoprostanes (8-epi-prostaglandin-F2: 8-isoPGF2alpha). No statistically significant differences were found for any of the oxidative stress markers assessed between patients with DM1 and controls. In addition, weight, height, and routine metabolic tests, including creatininemia and cholesterol levels, were similar between the groups. The lack of significant differences between healthy controls and patients with DM1 suggests that treatment is able to counteract the increase in free radical production.

Composition, structure and absorption of milk lipids: a source of energy, fat-soluble nutrients and bioactive molecules

Milkfat is a remarkable source of energy, fat-soluble nutrients and bioactive lipids for mammals. The composition and content of lipids in milkfat vary widely among mammalian species. Milkfat is not only a source of bioactive lipid components, it also serves as an important delivery medium for nutrients, including the fat-soluble vitamins. Bioactive lipids in milk include triacylglycerides, diacylglycerides, saturated and polyunsaturated fatty acids, and phospholipids. Beneficial activities of milk lipids include anticancer, antimicrobial, anti-inflammatory, and immunosuppression properties. The major mammalian milk that is consumed by humans as a food commodity is that from bovine whose milkfat composition is distinct due to their diet and the presence of a rumen. As a result of these factors bovine milkfat is lower in polyunsaturated fatty acids and higher in saturated fatty acids than human milk, and the consequences of these differences are still being researched. The physical properties of bovine milkfat that result from its composition including its plasticity, make it a highly desirable commodity (butter) and food ingredient. Among the 12 major milk fatty acids, only three (lauric, myristic, and palmitic) have been associated with raising total cholesterol levels in plasma, but their individual effects are variable-both towards raising low-density lipoproteins and raising the level of beneficial high-density lipoproteins. The cholesterol-modifying response of individuals to consuming saturated fats is also variable, and therefore the composition, functions and biological properties of milkfat will need to be re-evaluated as the food marketplace moves increasingly towards more personalized diets.

Smoking and development of type 2 diabetes in patients with decreased functional capacity

OBJECTIVE

Data regarding the possible contribution of cigarette smoking to development of type 2 diabetes are scarce and inconclusive. Patients with impaired functional capacity and diminished physical activity are prone to develop new diabetes. However, the role of smoking on diabetes incidence among these patients has not been specifically investigated. The present study was aimed to evaluate the association between cigarette smoking and development of type 2 diabetes in patients with coronary artery disease and decreased functional capacity over a 6.2-year follow-up period.

METHODS

The study sample comprised 630 nondiabetic patients aged 45-74 years, with a fasting blood glucose of <126 mg/dl and with impaired functional capacity (New York Heart Association functional class II and III). The sample was classified into two groups: 1) non smokers (never and past smokers pooled together)--552 patients and 2) current smokers--78 patients.

RESULTS

Smokers were younger but they had a relatively unfavorable lipid profile (with respect to apolipoproteins A, triglyceride and HDL-cholesterol levels). No significant differences between the groups were found for weight, body mass index, total cholesterol and blood pressure. During the follow-up, development of new diabetes was recorded in 98 patients: in 80 (14.5%) non smokers and in 18 (23.1%) smokers, p=0.05. Among the non smokers, there were no significant differences in diabetes incidence between 357 past smokers and 195 never smokers: respectively, 48 (13.4%) and 32 (16.4%), p=0.34. In addition, all-cause mortality among the smokers (23.1%) was significantly higher than in non smokers (12.7%), p=0.01. Multivariate analysis identified current smoking as an independent predictor of increased risk of new diabetes development with a hazard ratio of 1.94 (95% confidence interval 1.16-3.25).

CONCLUSIONS

Current smoking was associated with an independent two-fold increased risk for development of type 2 diabetes in patients with impaired functional capacity.

Dietary soy prevents brain Na+, K(+)-ATPase reduction in streptozotocin diabetic rats

The aim of this study was to investigate Na+, K(+)-ATPase activity in cerebral cortex, hippocampus and hypothalamus of diabetic rats. The action of dietary soy protein on the effect produced by diabetes on this activity was also tested. Forty-nine-day-old Wistar were divided into two groups: diabetes streptozotocin (50 mg/kg body weight) and control (citrate solution). Rats were sacrificed 56 days later. In other set of experiments, rats received a dietary with casein (control) from day 21 to the 49 of postnatal-age and were subjected to diabetes or received citrate (control). One week later, rats received a special dietary with soy protein with isoflavones or casein (control) from day 56 to the 105 of postnatal-age. Results showed that diabetic rats presented a reduction ( approximately 40%) of Na+, K(+)-ATPase activity in all structures studied. Pretreatment with soy protein prevented the inhibitory effects of diabetes on the enzyme activity. Assuming the possibility that these effects might also occur in the human condition, our findings may be relevant to explain, at least in part, the neurologic dysfunction associated with diabetes and might support a novel therapeutic strategy (soy protein) to slow the progression of neurodegeneration in this disorder.

Gamma-glutamyl transferase and metabolic risk factors for cardiovascular disease

OBJECTIVE

To elucidate the mechanism of the reported association between serum gamma-glutamyl transferase (GGT) activity and cardiovascular mortality.

METHODS

Cross-sectional analysis of the relationship between serum GGT activity and the risk factors for cardiovascular disease was performed.

PATIENTS AND MATERIALS

Middle-aged Japanese male personnel of the Self-Defense Forces who underwent retirement check-up.

RESULTS

Serum GGT activity was associated with total cholesterol, triglyceride, fasting plasma glucose, total homocysteine and systolic blood pressure. The association remained in the analysis adjusted for possible confounders including cigarette smoking, ethanol consumption and body mass index.

CONCLUSION

The observed association between serum GGT and cardiovascular risk factors may partly explain the reported relationship between serum GGT activity and cardiovascular disease. Serum GGT activity may be regarded as a marker of cardiovascular risk factors or oxidative stress rather than a mere indicator of excessive ethanol consumption or obesity.

Oxidized LDL and lipids as risk factors for ischemic heart disease in type 2 diabetes

Background. Abnormal lipid profile is an important risk factor in the development of macrovascular atherosclerotic complications in patients with type 2 diabetes mellitus (T2D). Factors that contribute to endothelial cell dysfunction associated with the initiation of atherosclerosis include oxidative stress. The aim of this study was to investigate the relationship between lipid profile and oxidative stress in type 2 diabetics with and without ischemic heart disease (IHD). Methods. We studied 80 patients with T2D, 40 with IHD (group A1) and 40 without IHD (group A2). We also studied 51 non-diabetics, 31 with IHD (group B1), and 20 without IHD (group B2 - control group). Lipid profile was estimated by the total cholesterol, HDL cholesterol, LDL cholesterol, the level of triglyceride (Tg), lipoproteina a (Lp a), Apo A I, A II, B 100 and E. To evaluate the oxidative status we measured circulating oxidized LDL (ox LDL), erythrocyte antioxidative enzyme activity: superoxide dismutase (E-SOD), glutathione peroxidase (E-GPX), as well as the total antioxidative serum activity (TAS). Inflammatory reaction was estimated by C-reactive protein (CRP) and fibrinogen. Results. No significant difference was found in the lipid profile in groups A1, A2 and B1, but the group B2 had the lowest one. Lp a level was significantly higher in group B1 comparing to other groups (p < 0.05). There was no significant difference in the level of ox LDL between the groups. In diabetics, ox LDL positively correlated with the total cholesterol, LDL cholesterol, non HDL cholesterol, Apo B 100 and the relations between LDL/HDL and Tg/HDL (p < 0.001), as well as with Tg and fibrinogen (p < 0.05). In group B1, ox LDL positively correlated with total cholesterol, Tg (p < 0.01), LDL, and non HDL cholesterol (p < 0.05) and significantly with Apo B 100 (p < 0.001). There was no significant difference in the antioxidant enzyme activities between the groups of diabetics (A1 and A2), but fibrinogen was higher in the group with IHD (group A1, p < 0.05). Group B1 had lower ESOD activity than the groups A1 and A2 (p < 0.05), but CRP was higher (p < 0.05). There were no significant correlations between oxLDL and CRP in groups A1 and A2, but it was statistically significant in the group B1 (p < 0.05). Conclusion. In this study we demonstrated the increased oxidative stress in diabetics compared to non-diabetics regardless of the presence of IHD. Fibrinogen, but not CRP, was higher in diabetics with IHD, compared to diabetics without IHD. The increased oxidative stress, the reduced antioxidative activity E-SOD, and the higher level of CRP were found in non-diabetics with IHD compared to non-diabetics without IHD.

In vitro and ex vivo antioxidant activities of labetalol on rabbit neutrophil respiratory burst

The beta-adrenoreceptor blocker labetalol has demonstrated important antioxidant properties in vitro that inhibit superoxide anion production during normal leukocyte oxidative metabolism. This study investigated the in vitro and ex vivo effects of labetalol on respiratory burst in rabbit neutrophils. The production of superoxide anions was examined in activated purified rabbit neutrophils after intravenous administration of labetalol (4.0 mg/kg of body weight). At a concentration up to 200 mg/L, labetalol did not demonstrate any cytotoxic effects on neutrophils, as determined by enzyme lactate dehydrogenase activity. In the cell-free system, labetalol demonstrated no significant activity, but in formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated rabbit neutrophils, labetalol demonstrated concentration-dependent antioxidant activity. The in vitro 50% inhibitory concentration (IC50) with the fMLP stimulus was 16.5+/-0.21 mg/L in the rabbit neutrophils and 13.2+/-0.16 mg/L in the human neutrophils. In the fMLP-stimulated rabbit polymorphonuclear leukocytes, labetalol demonstrated its peak inhibitory activity (47%) 3 hours after administration. The mechanism by which labetalol acts in the treatment of hypertension may occur from an interaction in the signaling pathway of protein kinase C activation. The antioxidant properties demonstrated in this mechanism contribute to the drug's antihypertensive action and thus, may reduce the risk of injuries inflicted by reactive oxygen species involved in the pathogenesis of hypertension.

Comparison of a high-carbohydrate and a high-monounsaturated fat, olive oil-rich diet on the susceptibility of LDL to oxidative modification in subjects with Type 2 diabetes mellitus

AIMS

To compare the effects of a high-carbohydrate (CHO) diet and a high-monounsaturated fatty acid (MUFA) diet on LDL oxidative resistance in free-living individuals with Type 2 diabetes mellitus.

METHODS

Twenty-two men and women out-patients with Type 2 diabetes, with mean age 61 years and in fair metabolic control (HbA1c<8.0%), were enrolled at a university hospital lipid clinic in a randomized, crossover feeding trial comparing two isocaloric diets for 6 weeks each: CHO (fat, 28% energy) and MUFA (fat, 40% energy) based on virgin olive oil. Outcome measurements were changes in LDL susceptibility to oxidation, body weight, glycaemic control, and lipoprotein profiles.

RESULTS

Planned and observed diets were well matched. Participants preferred the MUFA diet over the CHO diet. The lag time of conjugated diene formation during Cu2+-induced LDL oxidation was similar after the CHO and MUFA diets (36.4 +/- 12.2 min and 36.0 +/- 13.7 min, respectively). Body weight, glycaemic control, total triglycerides, and total, LDL- and HDL-cholesterol levels also were similar after the two diets. Compared with the CHO diet, the MUFA diet lowered VLDL-cholesterol by 35% (P=0.023) and VLDL triglyceride by 16% (P=0.016).

CONCLUSIONS

Natural food-based high-CHO and high-MUFA diets have similar effects on LDL oxidative resistance and metabolic control in subjects with Type 2 diabetes. A MUFA diet is a good alternative to high-CHO diets for nutrition therapy of diabetes because it also has a beneficial effect on the lipid profile and superior patient acceptance.

Vitamin C as an antioxidant: evaluation of its role in disease prevention

Vitamin C in humans must be ingested for survival. Vitamin C is an electron donor, and this property accounts for all its known functions. As an electron donor, vitamin C is a potent water-soluble antioxidant in humans. Antioxidant effects of vitamin C have been demonstrated in many experiments in vitro. Human diseases such as atherosclerosis and cancer might occur in part from oxidant damage to tissues. Oxidation of lipids, proteins and DNA results in specific oxidation products that can be measured in the laboratory. While these biomarkers of oxidation have been measured in humans, such assays have not yet been validated or standardized, and the relationship of oxidant markers to human disease conditions is not clear. Epidemiological studies show that diets high in fruits and vegetables are associated with lower risk of cardiovascular disease, stroke and cancer, and with increased longevity. Whether these protective effects are directly attributable to vitamin C is not known. Intervention studies with vitamin C have shown no change in markers of oxidation or clinical benefit. Dose concentration studies of vitamin C in healthy people showed a sigmoidal relationship between oral dose and plasma and tissue vitamin C concentrations. Hence, optimal dosing is critical to intervention studies using vitamin C. Ideally, future studies of antioxidant actions of vitamin C should target selected patient groups. These groups should be known to have increased oxidative damage as assessed by a reliable biomarker or should have high morbidity and mortality due to diseases thought to be caused or exacerbated by oxidant damage.

Effects of vitamin E on cardiovascular and microvascular outcomes in high-risk patients with diabetes: results of the HOPE study and MICRO-HOPE substudy

OBJECTIVES

Experimental and observational studies suggest that vitamin E may reduce the risk of cardiovascular (CV) events and of microvascular complications in people with diabetes. However, data from randomized clinical trials are limited. Therefore, we evaluated the effects of vitamin E supplementation on major CV outcomes and on the development of nephropathy in people with diabetes.

RESEARCH DESIGN AND METHODS

The Heart Outcomes Prevention Evaluation (HOPE) trial is a randomized clinical trial with a 2 x 2 factorial design, which evaluated the effects of vitamin E and of ramipril in patients at high risk for CV events. Patients were eligible for the study if they were 55 years or older and if they had CV disease or diabetes with at least one additional coronary risk factor. The study was designed to recruit a large number of people with diabetes, and the analyses of the effects of vitamin E in this group were preplanned. Patients were randomly allocated to daily treatment with 400 IU vitamin E and with 10 mg ramipril or their respective placebos and were followed for an average of 4.5 years. The primary study outcome was the composite of myocardial infarction, stroke, or CV death. Secondary outcomes included total mortality, hospitalizations for heart failure, hospitalizations for unstable angina, revascularizations, and overt nephropathy.

RESULTS

There were 3,654 people with diabetes. Vitamin E had a neutral effect on the primary study outcome (relative risk = 1.03, 95% CI 0.88-1.21; P = 0.70), on each component of the composite primary outcome, and on all predefined secondary outcomes.

CONCLUSIONS

The daily administration of 400 IU vitamin E for an average of 4.5 years to middle-aged and elderly people with diabetes and CV disease and/or additional coronary risk factor(s) has no effect on CV outcomes or nephropathy.

Oxidative stress impairs insulin but not platelet-derived growth factor signalling in 3T3-L1 adipocytes

Activation of phosphatidylinositol 3-kinase (PI 3-kinase) is a common event in both insulin and platelet-derived growth factor (PDGF) signalling, but only insulin activates this enzyme in the high-speed pellet (HSP), and induces GLUT4 translocation. Recently, we have demonstrated that exposure of 3T3-L1 adipocytes to oxidative stress impairs insulin-stimulated GLUT4 translocation and glucose transport, associated with impaired PI 3-kinase translocation and activation in the HSP [Tirosh, Potashnik, Bashan and Rudich (1999) J. Biol. Chem. 274, 10595-10602]. In this study the effect of a 2 h exposure to approximately 30 microM H(2)O(2) on insulin versus PDGF-BB signalling and metabolic effects was compared. PDGF-stimulated p85-associated PI 3-kinase activity in total cell lysates, as well as co-precipitation of the PDGF receptor, were unaffected by oxidative stress. Additionally, the increase in p85 association with the plasma-membrane lawns by PDGF remained intact following oxidation, whereas the insulin effect was decreased. PDGF significantly increased protein kinase B (PKB) activity in early differentiated cells, and that of p70 S6-kinase in both early and fully differentiated 3T3-L1 adipocytes. Following oxidation the effect of PDGF on PKB and p70 S6-kinase activation remained intact, whereas significant inhibition of insulin-stimulated activation of those enzymes was observed. In accordance, in both early and fully differentiated cells, oxidative stress completely blunted insulin- but not PDGF-stimulated protein synthesis. In conclusion, oxidative stress impairs insulin, but not PDGF, signalling and metabolic actions in both early and fully differentiated 3T3-L1 adipocytes. This emphasizes compartment-specific activation of PI 3-kinase as an oxidation-sensitive step specifically leading to insulin resistance.

Aldehyde analysis by high performance liquid chromatography/tandem mass spectrometry

This paper describes the development of a high performance liquid chromatography/tandem mass spectrometric (MS/MS) procedure for the specific qualitative and quantitative analysis of lipid aldehydes in biological matrices. A derivatisation method, which results in molecules that exhibit a common product ion on MS/MS, permits informative precursor ion scans, at high sensitivity. This has been applied to the examination of plasma in order to examine the production of aldehydes consequent on in vitro lipid oxidation. Quantitative analysis of target molecules using multiple reaction monitoring has been developed to permit quantitation in the same matrices.

Alpha-lipoic acid: a multifunctional antioxidant that improves insulin sensitivity in patients with type 2 diabetes

Alpha-Lipoic acid (LA) is a disulfide compound that is produced in small quantities in cells, and functions naturally as a co-enzyme in the pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase mitochondrial enzyme complexes. In pharmacological doses, LA is a multifunctional antioxidant. LA has been used in Germany for over 30 years for the treatment of diabetes-induced neuropathy. In patients with type 2 diabetes, recent studies have reported that intravenous (i.v.) infusion of LA increases insulin-mediated glucose disposal, whereas oral administration of LA has only marginal effects. If the limitations of oral therapy can be overcome, LA could emerge as a safe and effective adjunctive antidiabetic agent with insulin sensitizing activity.