Effects of antioxidant supplementation on postprandial oxidative stress and endothelial dysfunction: A single-blind, 15-day clinical trial in patients with untreated type 2 diabetes, subjects with impaired glucose tolerance, and healthy controls

Postprandial Metabolic and Oxidative Stress Responses to Grape Pomace Extract in Healthy Normal and Overweight/Obese Women: A Randomized, Double-Blind, Placebo-Controlled Crossover Study

Postprandial oxidative stress has been shown to promote atherosclerosis. Grape pomace (GP) is a source of similar-to-wine bioactive micro-constituents with known antioxidant properties. The aim of the present study was to evaluate metabolic and oxidative stress responses after the intake of grape pomace (GP) extract along with a high-fat meal, in normal and overweight healthy women. In a randomized, double-blind, placebo-controlled crossover study, 18 women were finally included, 11 with BMI < 25 kg/m2 and 7 with BMI > 25 kg/m2, and consumed a high-fat meal with placebo or GP extract capsules in two separate visits. Blood samples were collected before and 6 h after the consumption. Measurements included basic biochemical markers, uric acid (UA), protein carbonyls (PC), thiobarbituric acid substance (TBARS) levels, as well as superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities. At certain time points, the GP extract consumption in normal-weight women reduced UA, TBARS levels, and SOD activity, whereas it increased UA and reduced PC levels in overweight/obese women, compared to the placebo. GP-derived bioactive compounds may exert antioxidant actions during the postprandial state in healthy women, through different mechanisms according to their BMI status.

The Effect of N-Acetylcysteine and Ascorbic Acid-2-Phosphate Supplementation on Mesenchymal Stem Cell Function in B6.C-Lepob/J Type 2 Diabetic Mice

Diabetes is a complex multifactorial disorder associated with hyperglycemia, oxidative stress, and inflammation. The pathological microenvironment impairs mesenchymal stem cell (MSC) viability and dysregulates their proregenerative and immune-modulatory function causing maladaptive tissue damage. Targeting stem cells to protect them against impairment could thus delay the onset of complications and enhance the quality of life in diabetes mellitus patients. The aim of this study was to investigate the efficacy of N-acetylcysteine (NAC) and ascorbic-acid-2-phosphate (AAP) oral supplementation as preventative measure against MSC impairment. Healthy wild-type control (C57BL/6J) (male, n = 24) and obese diabetic (B6.C-Lep^ob/J) (ob/ob) (male, n = 24) mice received either placebo or antioxidant (NAC/AAP) supplementation for a period of 6 weeks. Metabolic parameters (weight and blood glucose) and the oxidative status (serum total serum antioxidant capacity, malondialdehyde) of animals were assessed. At the end of the 6-week supplementation period, bone marrow MSCs were isolated and their functionality (growth rate, viability, adipogenesis, and osteogenesis) assessed ex vivo. Real time quantitative polymerase chain reaction microarray analysis was also performed to assess the expression of 84 genes related to oxidative stress in MSCs. Despite no change in the metabolic profile, NAC/AAP supplementation improved the antioxidant status of diabetic animals and reduced lipid peroxidation, which is indicative of cellular damage. NAC/AAP also improved the population doubling time of MSCs (first 6-days postisolation) and significantly downregulated the expression of two genes (Nox1 and Rag2) associated with oxidative stress compared to placebo treatment. Taken together, this study has shown reduced oxidative stress and improvements in MSC function following in vivo antioxidant supplementation in healthy control and type 2 diabetic mice.

Does timing of phytonutrient intake influence the suppression of postprandial oxidative stress? A systematic literature review

BACKGROUND

Postprandial oxidative stress markers in blood are generated transiently from various tissues and cells following high-fat and/or high-carbohydrate (HFHC) meals, and may be suppressed by certain phytonutrients, such as polyphenols and carotenoids. However, the transient presence of phytonutrients in circulation suggests that timing of consumption, relative to the meal, could be important. This systematic review investigates the effect of timing of phytonutrient intake on blood markers of postprandial oxidative processes.

METHOD

EMBASE, Medline, Scopus and Web of Science were searched up to December 2020. Eligible studies met the criteria: 1) healthy human adults; 2) phytonutrient(s) consumed in solid form within 24 h of a HFHC meal; 3) postprandial measurements of oxidative stress or antioxidants in blood; and 4) controlled study design. Cohen's d effect sizes were calculated to compare studies.

RESULTS

Nine studies, involving 256 participants, were included. Phytonutrients were consumed either at the same time, 1 h before, or the day (>12 h) before a HFHC meal. Significant decreases in blood markers - plasma lipid hydroperoxides, plasma malondialdehyde, serum sNox2-dp, serum 8-iso-PGF2α, platelet p47phox phosphorylation, and Keap-1 and p47phox protein levels in mononuclear cells (MNCs) - were observed where the phytonutrient was consumed together with the challenge meal (n = 4). Lack of any effect on oxidative stress markers was observed where phytonutrients were consumed with (n = 1), 1 h before (n = 1), and the day before (n = 2) the HFHC meal.

CONCLUSION

Phytonutrients consumed with a HFHC meal significantly suppressed some markers of oxidative stress in blood. Although there were only a limited number of studies, it appears that suppression appeared effective at the time of peak phytonutrient concentration in plasma. However, further studies are required to confirm the observations and systematically optimise the effect of timing.

Pecan-enriched diets decrease postprandial lipid peroxidation and increase total antioxidant capacity in adults at-risk for cardiovascular disease

Pecans are a rich source of antioxidants, but the effect of regular consumption on post-meal responses is unknown. The objective of this study was to examine the impact of daily pecan consumption for 8 weeks on fasting and postprandial lipid peroxidation, total antioxidant capacity (TAC), and tocopherols in adults at higher risk for cardiovascular disease (CVD) (hypercholesterolemia or elevated adiposity). We hypothesized that daily pecan consumption would result in increased fasting γ-tocopherol, increased fasting and postprandial TAC, and decreased fasting and postprandial lipid peroxidation. This was a randomized, parallel, controlled trial with 3 treatments: two pecan groups and a nut free control (n = 16). The ADD group (n = 15) consumed pecans as part of a free-living diet, and the SUB group (n = 16) substituted the pecans for isocaloric foods from their habitual diet. At the pre- and post-intervention, a high saturated fat breakfast shake was consumed with postprandial blood draws over 2h. In the ADD and SUB groups, postprandial lipid peroxidation was suppressed (iAUC: 0.9 ± 1.3 to -2.9 ± 2.0 and 4.5 ± 1.7 to 0.7 ± 1.1 µM/2h, respectively; P <0.05) and TAC was elevated (iAUC: -240.8 ± 110.2 to 130.9 ± 131.7 and -227.6 ± 131.2 to 208.7 ± 145.7 µM Trolox Equivalents/2h, respectively; P <0.01) from pre- to post-intervention. Furthermore, there was an increase in γ-tocopherol from pre- to post-intervention within the ADD (1.4 ± 0.1 to 1.8 ± 0.1 µg/mL; P <0.001) and SUB groups (1.8 ± 0.2 to 2.1 ± 0.2 µg/mL; P <0.05). There were no changes in any variable within the control group. These findings suggest that daily pecan consumption protects against oxidative stress that occurs following a high-fat meal in adults at risk for CVD.

Effects of the Consumption of Low-Fat Cooked Ham with Reduced Salt Enriched with Antioxidants on the Improvement of Cardiovascular Health: A Randomized Clinical Trial

The aim of the study was to analyze how cardiovascular risk factors can be modified using nutritionally improved cooked ham enriched with a pool of antioxidants to influence relevant metabolic targets. Sixty-five untreated subjects (49.2% males, 50.8% females, mean age 40.92 ± 9.03 years) with total cholesterol level ≥180 mg/dL or LDL cholesterol ≥130 mg/dL participated in a 8-weeks randomized, double-blind controlled trial. Participant in the intervention group (51.5% males, 48.5% females, mean age 41.6 ± 9.8 years and mean BMI 25.1 ± 3.6 kg/m²) consumed cooked ham enriched with antioxidants (100 g/d) and controls (49.9% males, 53.1% females, mean age 40.2 ± 8.3 years and mean BMI 26.3 ± 3.2 kg/m²) received placebo. At 8 weeks, oxidized LDL decreased significantly between experimental and placebo groups (p < 0.036). Experimental group differences were also significant (p < 0.05). Similar findings in malondialdehyde, total cholesterol, high-sensitivity C-reactive protein, and interleukin 6 were observed in the intervention group. Significant between-group differences in these variables were also found, except for total cholesterol and interleukin 6. The effects on inflammation and oxidation support the direct action of these antioxidants on the etiopathogenic factors of atheromatous plaque. We also observed an improvement in the lipid profiles among the subjects.

Plasma concentrations of vitamin A and E and risk of dysglycemia in first-trimester pregnant Saudi women

BACKGROUND

Existing evidence suggest that low concentrations of vitamin A and E may have a contribution to the development of diabetes complications; however, data regarding the status of vitamin A and E among individuals with prediabetes are lacking. This study aimed to examine the association of plasma concentrations of vitamin A and E with the glycemic control status among first trimester pregnant Saudi women.

METHODS

In this cross-sectional study, 1102 first trimester pregnant Saudi women were recruited from antenatal clinics. Sociodemographic and anthropometric information were collected, and laboratory analyses of blood glycated hemoglobin (A1C) and plasma vitamins A and E were performed. Subjects were classified as normoglycemic, prediabetic, or undiagnosed diabetic. Multinomial regression models adjusted for age estimated the adjusted odds ratios (aORs) and [95% confidence intervals (CIs)].

RESULTS

Among the sample, 78.8% (n = 868) had normal glycemic control, while 19.1% (n = 211) had prediabetes and 2.1% (n = 23) had undiagnosed diabetes. Plasma concentrations of vitamin A and E of prediabetic participants were at a level midway between that of normoglycemic and diabetic participants (p < 0.01). Compared to subjects with normoglycemic status, those with higher concentrations of vitamin A and E had lower odds of being prediabetic (aOR = 0.27 [0.21-0.35] and aOR = 0.95 [0.94-0.96], respectively) or diabetic (aOR = 0.18 [0.13-0.24] and aOR = 0.93 [0.92-0.94], respectively).

CONCLUSIONS

Our findings indicate a possible contribution of vitamins A and E to the progression of prediabetes to diabetes. Future longitudinal studies are needed to elucidate the association between the antioxidant status and dysglycemia. Clinicians should monitor the glycemic and the antioxidant status closely and provide dietary guidance where needed.

Serum Lycopene Levels in Patients with Diabetic Retinopathy

Purpose.

Accumulating evidence indicates that oxidative stress may play an important role in the pathogenesis of type 2 diabetes and its complications. Lycopene, a very potent antioxidant of carotenoids, has received considerable scientific interest in recent years for its potential role in the prevention of oxidative stress-related chronic diseases. This study was undertaken to investigate whether the serum levels of lycopene are altered between type 2 diabetic patients with and without diabetic retinopathy.

Methods.

A total of 71 patients with type 2 diabetes were analyzed and compared with 23 nondiabetic healthy controls. Serum lycopene concentrations were assayed using high-performance liquid chromatography.

Results.

Lycopene level was found to be significantly lower in diabetic patients than in controls (p=0.021). In the diabetic group, subjects with proliferative diabetic retinopathy had significantly lower lycopene levels than subjects without diabetic retinopathy or with nonproliferative diabetic retinopathy. In the analysis of correlations, hemoglobin A1c were negatively correlated with lycopene (r=–0.345, p=0.007) after multivariate adjustment. A stepwise linear multiple regression model revealed that age and hemoglobin A1c were significant determinants of lycopene.

Conclusions.

Our findings show that measuring serum lycopene is a novel convenient method for evaluating oxidative damage. Diabetic patients, especially those with advanced diabetic retinopathy, had significantly lower serum lycopene levels; this suggests that lycopene may be helpful for the diagnosis, severity, and therapeutic evaluation of diabetic retinopathy.

Low-density lipoprotein oxidation biomarkers in human health and disease and effects of bioactive compounds

Based on the significance of oxidized low-density lipoprotein (LDL) in health and disease, this review focuses on human studies addressing oxidation of LDL, including three lines of biomarkers, (i) ex vivo LDL resistance to oxidation, a "challenge test" model, (ii) circulating oxidized LDL, indicating the "current in vivo status", and (iii) autoantibodies against oxidized LDL as fingerprints of an immune response to oxidized LDL, along with circulating oxysterols and 4-hydroxynonenal as biomarkers of lipid peroxidation. Lipid peroxidation and oxidized LDL are hallmarks in the development of various metabolic, cardiovascular and other diseases. Changes further occur across life stages from infancy to older age as well as in athletes and smokers. Given their responsiveness to targeted nutritional interventions, markers of LDL oxidation have been employed in a rapidly growing number of human studies for more than 2 decades. There is growing interest in foods, which, besides providing energy and nutrients, exert beneficial effects on human health, such as protection of DNA, proteins and lipids from oxidative damage. Any health claim, however, needs to be substantiated by supportive evidence derived from human studies, using reliable biomarkers to demonstrate such beneficial effects. A large body of evidence has accumulated, demonstrating protection of LDL from oxidation by bioactive food compounds, including vitamins, other micronutrients and secondary plant ingredients, which will facilitate the selection of oxidation biomarkers for future human intervention studies and health claim support.

Redox theory of aging: implications for health and disease

Genetics ultimately defines an individual, yet the phenotype of an adult is extensively determined by the sequence of lifelong exposures, termed the exposome. The redox theory of aging recognizes that animals evolved within an oxygen-rich environment, which created a critical redox interface between an organism and its environment. Advances in redox biology show that redox elements are present throughout metabolic and structural systems and operate as functional networks to support the genome in adaptation to environmental resources and challenges during lifespan. These principles emphasize that physical and functional phenotypes of an adult are determined by gene-environment interactions from early life onward. The principles highlight the critical nature of cumulative exposure memories in defining changes in resilience progressively during life. Both plasma glutathione and cysteine systems become oxidized with aging, and the recent finding that cystine to glutathione ratio in human plasma predicts death in coronary artery disease (CAD) patients suggests this could provide a way to measure resilience of redox networks in aging and disease. The emerging concepts of cumulative gene-environment interactions warrant focused efforts to elucidate central mechanisms by which exposure memory governs health and etiology, onset and progression of disease.

Pre-Clinical Study for the Antidiabetic Potential of Selenium Nanoparticles

This research was delineated to explore the efficacy of selenium nanoparticles delivered in liposomes (L-Se) in the mitigation of type-2 diabetes mellitus. Adult female Wistar rats were assigned into four groups: group I, the normal control group in which the rats received normal saline solution orally; group II, the diabetic control group in which the rats were injected intraperitoneally with a single dose of streptozotocin (STZ) for induction of diabetes; group III, the metformin (Met)-treated group in which the diabetic rats were treated orally with Met; and group IV, the L-Se-treated group in which the diabetic rats were treated orally with L-Se. All treatments were delivered for 21 days. Blood and pancreas tissue samples were obtained for biochemical analysis, immunohistochemical examinations, and histopathological investigation. The L-Se-treated group showed significant drop in serum glucose and pancreatic malondialdehyde (MDA), nitric oxide (NO), tumor necrosis factor-α (TNF-α), and prostaglandin F2α (PGF2α) levels associated with significant rise in serum insulin and pancreatic glutathione, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) values, in addition to significant improvement in the immunohistochemical indices (insulin and glucagon). Aforementioned results are appreciated by the histopathological findings of pancreatic tissue. In conclusion, our data have brought about compelling evidence favoring the antidiabetic potency of elemental selenium nanoparticles delivered in liposomes through preservation of pancreatic β cell integrity with consequent increment of insulin secretion and in turn glucose depletion, repression of oxidative stress, potentiation of the antioxidant defense system, and inhibition of pancreatic inflammation.

Post-prandial systemic 8-isoprostane increases after consumption of moderate and high-fat meals in insufficiently active males

A single high-fat meal (HFM) leads to an increase in triglycerides and oxidative stress. Oxidative stress can be assessed via 8-isoprostane generation, which is associated with the development of asthma and cardiovascular disease. No previous research has investigated whether airway and systemic 8-isoprostane increases postprandially in nonasthmatic participants according to the energy and fat content of a meal. Our purpose was to assess airway and systemic 8-isoprostane after a HFM and a true-to-life moderate-fat meal (MFM). We hypothesized that airway and systemic 8-isoprostane would increase after a HFM and a MFM, with the greatest increase in the HFM condition. Eight nonasthmatic men (25.8±6.9years) completed the HFM and MFM trials in a randomized crossover design. After a 10-hour fast, participants consumed either a HFM (71.13kJ/kg body mass, 60% fat, 23% CHO) or a MFM (35.56kJ/kg body mass, 30% fat, 52% CHO). Exhaled breath condensate to assess airway 8-isoprostane was collected at baseline and at 3 and 6hours postmeal. Venous blood samples were collected at baseline and hourly until 6hours postmeal to assess triglycerides, and every 3hours for systemic 8-isoprostane. Airway 8-isoprostane responses were not significant as a main effect of time (P=.072), between conditions (P=.365), or between time and condition (P=.319) postmeal. Systemic 8-isoprostane increased over time (P<.001), but not between conditions (P=.124) or between time and condition (P=.649) postmeal. Triglyceride incremental area under the curve was different in the HFM compared to the MFM condition (P=.013). After a HFM and a MFM, 8-isoprostane increases systemically; however, airway 8-isoprostane does not change.

Administration of tauroursodeoxycholic acid prevents endothelial dysfunction caused by an oral glucose load

Postprandial hyperglycaemia leads to a transient impairment in endothelial function; however, the mechanisms remain largely unknown. Previous work in cell culture models demonstrate that high glucose results in endoplasmic reticulum (ER) stress and, in animal studies, ER stress has been implicated as a cause of endothelial dysfunction. In the present study, we tested the hypothesis that acute oral administration of tauroursodeoxycholic acid (TUDCA, 1500 mg), a chemical chaperone known to alleviate ER stress, would prevent hyperglycaemia-induced endothelial dysfunction. In 12 young healthy subjects (seven men, five women), brachial artery flow-mediated dilation (FMD) was assessed at baseline, and at 60 and 120 min after an oral glucose challenge. Subjects were tested on two separate visits in a single-blind randomized cross-over design: after oral ingestion of TUDCA or placebo capsules. FMD was reduced from baseline during hyperglycaemia under the placebo condition (-32% at 60 min and -28% at 120 min post oral glucose load; P<0.05 from baseline) but not under the TUDCA condition (-4% at 60 min and +0.3% at 120 min post oral glucose load; P>0.05 from baseline). Postprandial plasma glucose and insulin were not altered by TUDCA ingestion. Plasma oxidative stress markers 3-nitrotyrosine and thiobarbituric acid reactive substance (TBARS) remained unaltered throughout the oral glucose challenge in both conditions. These results suggest that hyperglycaemia-induced endothelial dysfunction can be mitigated by oral administration of TUDCA, thus supporting the hypothesis that ER stress may contribute to endothelial dysfunction during postprandial hyperglycaemia.

The Protective Effect of Antioxidants Consumption on Diabetes and Vascular Complications

Obesity and diabetes is generally accompanied by a chronic state of oxidative stress, disequilibrium in the redox balance, implicated in the development and progression of complications such as micro- and macro-angiopathies. Disorders in the inner layer of blood vessels, the endothelium, play an early and critical role in the development of these complications. Blunted endothelium-dependent relaxation and/or contractions are quietly associated to oxidative stress. Thus, preserving endothelial function and oxidative stress seems to be an optimization strategy in the prevention of vascular complications associated with diabetes. Diet is a major lifestyle factor that can greatly influence the incidence and the progression of type 2 diabetes and cardiovascular complications. The notion that foods not only provide basic nutrition but can also prevent diseases and ensure good health and longevity is now attained greater prominence. Some dietary and lifestyle modifications associated to antioxidative supply could be an effective prophylactic means to fight against oxidative stress in diabesity and complications. A significant benefit of phytochemicals (polyphenols in wine, grape, teas), vitamins (ascorbate, tocopherol), minerals (selenium, magnesium), and fruits and vegetables in foods is thought to be capable of scavenging free radicals, lowering the incidence of chronic diseases. In this review, we discuss the role of oxidative stress in diabetes and complications, highlight the endothelial dysfunction, and examine the impact of antioxidant foods, plants, fruits, and vegetables, currently used medication with antioxidant properties, in relation to the development and progression of diabetes and cardiovascular complications.

l-Arginine Supplementation Alleviates Postprandial Endothelial Dysfunction When Baseline Fasting Plasma Arginine Concentration Is Low: A Randomized Controlled Trial in Healthy Overweight Adults with Cardiometabolic Risk Factors

BACKGROUND

Vascular endothelial dysfunction, the hallmark of early atherosclerosis, is induced transiently by a high-fat meal. High doses of free l-arginine supplements reduce fasting endothelial dysfunction.

OBJECTIVE

We sought to determine the effects of a low dose of a sustained-release (SR) l-arginine supplement on postprandial endothelial function in healthy overweight adults with cardiometabolic risk factors and to investigate whether this effect may vary by baseline arginine status.

METHODS

In a randomized, double-blind, 2-period crossover, placebo-controlled trial (4-wk treatment, 4-wk washout), we compared the effects of 1.5 g SR-l-arginine 3 times/d (4.5 g/d) with placebo in 33 healthy overweight adults [body mass index (BMI, in kg/m(2)): 25 to >30] with the hypertriglyceridemic waist (HTW) phenotype [plasma triglycerides > 150 mg/dL; waist circumference > 94 cm (men) or > 80 cm (women)]. The main outcome variable tested was postprandial endothelial function after a high-fat meal (900 kcal), as evaluated by use of flow-mediated dilation (FMD) and Framingham reactive hyperemia index (fRHI), after each treatment. By use of subgroup analysis, we determined whether the effect was related to the baseline plasma arginine concentration.

RESULTS

In the total population, the effects of SR-arginine supplementation on postprandial endothelial function were mixed and largely varied with baseline fasting arginine concentration (P-interaction < 0.05). In the lower half of the population (below the median of 78.2 μmol arginine/L plasma), but not the upper half, SR-arginine supplementation attenuated the postprandial decrease in both FMD (29% decrease with SR-arginine compared with 50% decrease with placebo) and fRHI (5% increase with SR-arginine compared with 49% decrease with placebo), resulting in significantly higher mean ± SEM values with SR-arginine (FMD: 4.0% ± 0.40%; fRHI: 0.41 ± 0.069) than placebo (FMD: 2.9% ± 0.31%; fRHI: 0.21 ± 0.060) at the end of the postprandial period (P < 0.05).

CONCLUSIONS

Supplementation with low-dose SR-arginine alleviates postprandial endothelial dysfunction in healthy HTW adults when the baseline plasma arginine concentration is relatively low. The benefits of arginine supplementation may be linked to a lower ability to mobilize endogenous arginine for nitric oxide synthesis during a postprandial challenge. This trial was registered at clinicaltrials.gov as NCT02354794.

Markers of Antioxidant Defense in Patients with Type 2 Diabetes

Aims. Diabetes is considered a state of increased oxidative stress. This study evaluates blood concentrations of selected markers of antioxidant defense in patients with type 2 diabetes. Methods. The study included 80 type 2 diabetes patients and 79 apparently healthy controls. Measured markers included ferric reducing ability of plasma (FRAP), reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione reductase (GR), γ-glutamyltransferase (GGT) and uric acid serum, and plasma and/or hemolysate levels. Results. FRAP, uric acid, CRP, and GGT levels were significantly higher in patients with diabetes. Plasma and hemolysate GR was significantly higher whereas GPx activity was significantly lower in patients with diabetes. There were no significant differences in antioxidant defense markers between patients with and without chronic diabetes complications. Fasting serum glucose correlated with plasma GPx, plasma and hemolysate GR, FRAP, and serum GGT, and HbA1c correlated with serum GGT. Only FRAP and serum uric acid were significantly higher in obese (BMI > 30 kg/m²) patients with diabetes than in nonobese patients. Conclusions. Some components of antioxidant defense such as GR, uric acid, and GGT are increased in patients with type 2 diabetes. However, the whole system cannot compensate for an enhanced production of ROS as reflected by the trend toward decreased erythrocytes GSH.

Effect of Fresh Royal Jelly Ingestion on Glycemic Response in Patients With Type 2 Diabetes

BACKGROUND

Type 2 diabetes is the fourth major public health problem worldwide. Royal Jelly (RJ) insulin-like activity and blood glucose modulating properties have been reported in animal and healthy volunteers.

OBJECTIVES

This study aimed to investigate the effect of a single dose of fresh RJ as a complementary therapy on glycemic response in patients with type 2 diabetes.

PATIENTS AND METHODS

In this randomized clinical trial, 40 patients with type 2 diabetes were assigned into the RJ (n = 20) and placebo (n = 20) groups and received either 10 g fresh RJ or placebo after overnight fasting. Serum glucose, insulin and C-peptide concentrations were determined at 0, 60, 120 minutes after the intervention. Independent t-tests and repeated measures ANOVA were used to analyze data.

RESULTS

The mean serum glucose levels were significantly decreased in RJ and placebo groups; however, mean serum level was different but not statistically. (P = 0.77). One hour after RJ ingestion the mean serum insulin concentrations were increased and after 2 hours it was decreased insignificantly (P = 0.54, P = 0.20). The mean C-peptide concentrations were significantly increased after 1 and 2 hours of RJ ingestion; however, in the placebo group we observed a slight but insignificant reduction at the time of 1 and 2 hours in the mean C-peptide serum levels (P = 0.40). Moreover, there was no significant difference in none of the glycemic control parameters between both studied groups (P > 0.05).

CONCLUSIONS

It seems that RJ does not appear to have significant immediate effects on glycemic factors in patients with type 2 diabetes. However, further studies with larger sample sizes and different doses of RJ are needed to achieve more precise results.

Does Supplementation with Royal Jelly Improve Oxidative Stress and Insulin Resistance in Type 2 Diabetic Patients?

BACKGROUND

Animal studies have shown antioxidant effects of Royal Jelly (RJ) and its effect on insulin resistance as the most common complication of Type 2 diabetes. This study was conducted to determine the effect of RJ intake on serum total antioxidant capacity, Malondialdehyde and insulin resistance in T2DM.

METHODS

In this randomized controlled trial, forty-six type 2 diabetic patients, aged 25-65 years, with BMI of 20-30 kg/m(2), and HbA1c of 6-8% were included. The patients were randomly assigned to receive 1000 mg of RJ supplement or placebo, 3 times daily for 8 weeks. HOMA-IR, anthropometric measurements, fasting blood glucose, serum insulin, total antioxidant capacity and malondialdehyde level were measured.

RESULTS

In comparison with placebo, HOMA-IR decreased (P=0.015) while serum total antioxidant capacity increased significantly in RJ group (P=0.016). No significant difference was detected for serum insulin and MDA in two groups.

CONCLUSIONS

RJ intake may have favorable effects on serum TAC and HOMA-IR in diabetic patients.

Prevention of diabetes-induced cardiovascular complications upon treatment with antioxidants

Oxidative stress is considered to play an important role in the pathogenesis of diabetes-induced cardiovascular disease (CVD), which is invariably associated with abnormal blood lipid profile, insulin resistance and metabolic syndrome. Stress, smoking, high saturated fat intake as well as low fruit and vegetable intakes have been shown to increase oxidative stress and hyperlipidemia, which increase the predisposition of diabetic subjects to atherosclerosis, stroke and coronary heart disease. The oxidation of low-density lipoprotein by oxidative stress is essential for the development of atherosclerosis, and the reduction in oxidative stress as well as blood glucose and cholesterol is considered critical for the prevention of diabetes-induced CVD. Although epidemiological studies have demonstrated that vitamin C and vitamin E decrease the incidence of coronary heart disease, different clinical trials have failed to support the beneficial effect of these antioxidants. Nonetheless, it has been suggested that natural forms of these vitamins may be more efficacious than synthetic vitamins, and this may explain the inconsistencies in results. Antioxidants, N-acetyl-L-cysteine and resveratrol, have also been shown to attenuate the diabetes-induced cardiovascular complications. It has been indicated that the antioxidant therapy may be effective in a prevention strategy rather than as a treatment for CVD. The evidence presented here supports the view that cardiovascular complications in diabetes may be induced by oxidative stress and appropriate antioxidant therapy may be promising for attenuating the progression of diabetes-induced CVD.

Vitamin D and L-cysteine levels correlate positively with GSH and negatively with insulin resistance levels in the blood of type 2 diabetic patients

Background/Objectives:

Vitamin D, L-cysteine (LC) and glutathione (GSH) levels are lower in the blood of diabetic patients. This study examined the hypothesis that the levels of vitamin D and LC correlate with those of GSH in the blood of type 2 diabetic patients (T2D), and that vitamin D and LC upregulate glutamate–cysteine ligase (GCLC), which catalyzes GSH biosynthesis, in cultured monocytes.

Subjects/Methods:

Fasting blood was obtained after written informed consent from T2D (n=79) and healthy controls (n=22). U937 monocytes were pretreated with 1,25 (OH)₂ vitamin D (0–25 nM) or LC (0–500 μM) for 24 h and then exposed to control or high glucose (25 mM) for 4 h.

Results:

Plasma levels of vitamin D, LC, GSH and GCLC protein were significantly lower in T2D versus those in age-matched healthy controls. Multiple linear regression analyses and adjustment for body weight showed a significant positive correlation between plasma levels of vitamin D (r=0.26, P=0.05) and LC (r=0.81, P=0.001) and that of GSH, and between LC and vitamin D (r=0.27, P=0.045) levels. Plasma levels of GSH (r=−0.34, P=0.01) and LC (r=−0.33, r=0.01) showed a negative correlation with triglyceride levels. Vitamin D correlated inversely with HbA_1C (−0.30, P=0.01) and homeostatic model assessment insulin resistance (r=−0.31, P=0.03), which showed a significant positive correlation with triglycerides (r=0.44, P=0.001) in T2D. Cell culture studies demonstrate that supplementation with vitamin D and LC significantly increased GCLC expression and GSH formation in control and high-glucose-treated monocytes.

Conclusions:

This study suggests a positive relationship between the concentrations of the micronutrients vitamin D and LC and that of GSH. Some of the beneficial effects of vitamin D and LC supplementation may be mediated by an increase in the levels of GSH and a decrease in triglyceride levels in T2D patients.

Effects of royal jelly supplementation on glycemic control and oxidative stress factors in type 2 diabetic female: a randomized clinical trial

OBJECTIVE

It has been proposed that royal jelly has antioxidant properties and may improve oxidative stress and glycemic control. Therefore, we investigated the effects of royal jelly supplementation in diabetic females.

METHODS

In this pilot, parallel design randomized clinical trial, 50 female volunteers with type 2 diabetes were randomly allocated to the supplemented (25, cases) and placebo (25, cases) groups, based on random block procedure produced by Random Allocation Software, given a daily dose of 1,000 mg royal jelly soft gel or placebo, respectively, for 8 weeks. Before and after intervention, glycemic control indices, antioxidant and oxidative stress factors were measured.

RESULTS

After royal jelly supplementation, the mean fasting blood glucose decreased remarkably (163.05±42.51 mg/dL vs. 149.68±42.7 mg/dL). Royal jelly supplementation resulted in significant reduction in the mean serum glycosylated hemoglobin levels (8.67%±2.24% vs. 7.05%±1.45%, P=0.001) and significant elevation in the mean insulin concentration (70.28±29.16 pmol/L vs. 86.46±27.50 pmol/L, P=0.01). Supplementation significantly increased erythrocyte superoxidase dismutase and glutathione peroxidase activities and decreased malondialdehyde levels (P<0.05). At the end of study, the mean total antioxidant capacity elevated insignificantly in both groups.

CONCLUSIONS

On the basis of our findings, it seems that royal jelly supplementation may be beneficial in controlling diabetes outcomes. Further studies with larger sample size are warranted.

Diabetes mellitus-associated vascular impairment: novel circulating biomarkers and therapeutic approaches

It is widely accepted that diabetes mellitus (DM) impairs endothelial nitric oxide synthase activity as well as enhances the production of reactive oxygen species, thus resulting in diminished nitric oxide bioavailability and the consequent pro-atherogenetic alterations. Important biomarkers of the vasculature are related to endothelial dysfunction, to inflammatory and coagulation processes, and to oxidative stress in DM. Several therapeutic strategies might exert favorable effects on the vasculature of diabetic patients, such as insulin analogues, antihypertensive agents, statins, and hypoglycemic agents, whereas in spite of the prominent role of oxidative stress in diabetes, antioxidant therapy remains controversial. The use of specific biomarkers related to vascular function could be a useful therapeutic approach in such patients.

Influence of acute coffee consumption on postprandial oxidative stress

Background:

Coffee has been reported to be rich in antioxidants, with both acute and chronic consumption leading to enhanced blood antioxidant capacity. High-fat feeding is known to result in excess production of reactive oxygen and nitrogen species, promoting a condition of postprandial oxidative stress.

Methods:

We tested the hypothesis that coffee intake following a high-fat meal would attenuate the typical increase in blood oxidative stress during the acute postprandial period. On 3 different occasions, 16 men and women consumed a high-fat milk shake followed by either 16 ounces of caffeinated or decaffeinated coffee or bottled water. Blood samples were collected before and at 2 and 4 hours following intake of the milk shake and analyzed for triglycerides (TAG), malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and Trolox equivalent antioxidant capacity (TEAC).

Results:

Values for TAG and MDA (P < 0.001), as well as for H₂O₂ (P < 0.001), increased significantly following milk shake consumption, with values higher at 4 hours compared with 2 hours post consumption for TAG and H₂O₂ (P < 0.05). TEAC was unaffected by the milk shake consumption. Coffee had no impact on TAG, MDA, H₂O₂, or TEAC, with no condition or interaction effects noted for any variable (P > 0.05).

Conclusions:

Acute coffee consumption following a high-fat milk shake has no impact on postprandial oxidative stress.

The role of oxidative stress in postprandial endothelial dysfunction

Endothelial dysfunction is a turning point in the initiation and development of atherosclerosis and its complications and is predictive of future cardiovascular events. Ingestion of high-carbohydrate or high-fat meals often results in postprandial hyperglycaemia and/or hypertriacylglycerolaemia that may lead to a transient impairment in endothelial function. The present review will discuss human studies evaluating the impact of high-carbohydrate and high-fat challenges on postprandial endothelial function as well as the potential role of oxidative stress in such postprandial metabolic alterations. Moreover, the present review will differentiate the postprandial endothelial and oxidative impact of meals rich in varying fatty acid types.

Reactive oxygen species and the cardiovascular system

Ever since the discovery of free radicals, many hypotheses on the deleterious actions of reactive oxygen species (ROS) have been proposed. However, increasing evidence advocates the necessity of ROS for cellular homeostasis. ROS are generated as inherent by-products of aerobic metabolism and are tightly controlled by antioxidants. Conversely, when produced in excess or when antioxidants are depleted, ROS can inflict damage to lipids, proteins, and DNA. Such a state of oxidative stress is associated with many pathological conditions and closely correlated to oxygen consumption. Although the deleterious effects of ROS can potentially be reduced by restoring the imbalance between production and clearance of ROS through administration of antioxidants (AOs), the dosage and type of AOs should be tailored to the location and nature of oxidative stress. This paper describes several pathways of ROS signaling in cellular homeostasis. Further, we review the function of ROS in cardiovascular pathology and the effects of AOs on cardiovascular outcomes with emphasis on the so-called oxidative paradox.

Reactive oxygen and nitrogen species in pathogenesis of vascular complications of diabetes

Macrovascular and microvascular diseases are currently the principal causes of morbidity and mortality in subjects with diabetes. Disorders of the physiological signaling functions of reactive oxygen species (superoxide and hydrogen peroxide) and reactive nitrogen species (nitric oxide and peroxynitrite) are important features of diabetes. In the absence of an appropriate compensation by the endogenous antioxidant defense network, increased oxidative stress leads to the activation of stress-sensitive intracellular signaling pathways and the formation of gene products that cause cellular damage and contribute to the vascular complications of diabetes. It has recently been suggested that diabetic subjects with vascular complications may have a defective cellular antioxidant response against the oxidative stress generated by hyperglycemia. This raises the concept that antioxidant therapy may be of great benefit to these subjects. Although our understanding of how hyperglycemia-induced oxidative stress ultimately leads to tissue damage has advanced considerably in recent years, effective therapeutic strategies to prevent or delay the development of this damage remain limited. Thus, further investigation of therapeutic interventions to prevent or delay the progression of diabetic vascular complications is needed.

Plasma metabolomics and proteomics profiling after a postprandial challenge reveal subtle diet effects on human metabolic status

We introduce the metabolomics and proteomics based Postprandial Challenge Test (PCT) to quantify the postprandial response of multiple metabolic processes in humans in a standardized manner. The PCT comprised consumption of a standardized 500 ml dairy shake containing respectively 59, 30 and 12 energy percent lipids, carbohydrates and protein. During a 6 h time course after PCT 145 plasma metabolites, 79 proteins and 7 clinical chemistry parameters were quantified. Multiple processes related to metabolism, oxidation and inflammation reacted to the PCT, as demonstrated by changes of 106 metabolites, 31 proteins and 5 clinical chemistry parameters. The PCT was applied in a dietary intervention study to evaluate if the PCT would reveal additional metabolic changes compared to non-perturbed conditions. The study consisted of a 5-week intervention with a supplement mix of anti-inflammatory compounds in a crossover design with 36 overweight subjects. Of the 231 quantified parameters, 31 had different responses over time between treated and control groups, revealing differences in amino acid metabolism, oxidative stress, inflammation and endocrine metabolism. The results showed that the acute, short term metabolic responses to the PCT were different in subjects on the supplement mix compared to the controls. The PCT provided additional metabolic changes related to the dietary intervention not observed in non-perturbed conditions. Thus, a metabolomics based quantification of a standardized perturbation of metabolic homeostasis is more informative on metabolic status and subtle health effects induced by (dietary) interventions than quantification of the homeostatic situation. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11306-011-0320-5) contains supplementary material, which is available to authorized users.

Effects of acute ingestion of different fats on oxidative stress and inflammation in overweight and obese adults

Background

Studies show that obese individuals have prolonged elevations in postprandial lipemia and an exacerbated inflammatory response to high fat meals, which can increase risk for cardiovascular diseases. As epidemiological studies indicate an association between type of fat and circulating inflammatory markers, the purpose of this study was to investigate the acute effect of different fat sources on inflammation and oxidative stress in overweight and obese individuals.

Methods

Eleven overweight and obese subjects consumed three high fat milkshakes rich in monounsaturated fat (MFA), saturated fat (SFA), or long-chain omega 3 polyunsaturated fat (O3FA) in random order. Blood samples collected at baseline, 1, 2, 4, and 6 hours postprandial were analyzed for markers of inflammation (soluble intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), tumor necrosis factor- α (TNF-α), and C-reactive protein (CRP)), oxidative stress (8-epi-prostaglandin-F2α (8-epi) and nuclear factor-κB (NF-κB)), and metabolic factors (glucose, insulin, non-esterified free fatty acids, and triglycerides (TG)).

Results

O3FA enhanced NF-kB activation compared to SFA, but did not increase any inflammatory factors measured. Conversely, SFA led to higher ICAM-1 levels than MFA (p = 0.051), while MFA increased TG more than SFA (p < 0.05). CRP increased while TNF-α and 8-epi decreased with no difference between treatments.

Conclusions

While most of the inflammatory factors measured had modest or no change following the meal, ICAM-1 and NF-κB responded differently by meal type. These results are provocative and suggest that type of fat in meals may differentially influence postprandial inflammation and endothelial activation.

Effect of vitamin C supplementation on postprandial oxidative stress and lipid profile in type 2 diabetic patients

Diabetes mellitus is one of the most wide spread endocrine disorders and an important developing health problem in the world. Cardiovascular disease is a common complication of type 2 diabetes. Several risk factors for coronary heart disease cosegregate in type 2 diabetes, including hyperglycemia, hyperlipaemia, increases production of free radical and decrease in antioxidant defense system. In this study we evaluated the effect of vitamin C supplementation on fasting and postprandial oxidative stress and lipid profile in type 2 diabetic patients. 30 patients with type 2 diabetes from Nader Kazemi Clinic, Shiraz, Iran were randomly divided into 2 groups; vitamin C treatment group (1000 mg d(-1)) and placebo group from May to September 2010. Fasting and postprandial lipid profile and Malondialdehyde (MDA) level were measured at the beginning of the study and after six weeks of supplementation. Data analysis was carried out using Mann-Whitney U test with p < 0.05 being significant by SPSS software version 16.The result of the study showed a significantly decrease in fasting (p = 0.006) and postprandial MDA (p < 0.001) in vitamin C group compare to placebo group but not in lipid profile. This study suggests that vitamin C supplementation can decrease fasting and postprandial oxidative stress and may prevent diabetes complication.

Reduction in generation of reactive oxygen species and endothelial dysfunction during postprandial state

BACKGROUND AND AIMS

To characterise changes in generation of cellular reactive oxygen species (ROS) in healthy males during the postprandial state, and to analyse the influence of the postprandial state on endothelial ROS generation and endothelial dysfunction.

METHODS AND RESULTS

Seventeen healthy subjects were recruited. Blood samples were collected in the fasting state and 2, 4, 6 and 8h after liquid-meal intake (composition: 25% fat, 55% dextromaltose and 14% protein), providing 40 gfat m(-2) body surface. Plasma lipids, apolipoproteins, glucose and insulin were measured during this period. Peripheral blood mononuclear cells (PBMCs) were isolated by density-gradient centrifugation. The influence of postprandial state on intracellular ROS generation was measured by two different methods in PBMCs and in a human immortalised endothelial cell line (ECV 304). Artery flow-mediated vasodilation (FMD) was used to evaluate the endothelial function, and oxygen consumption by PBMCs was measured. Reduced ROS generation was observed in all methods and cells during the postprandial period. FMD was impaired 8h after meal intake (23±6 vs. 13±2, P<0.05 vs. baseline). The consumption of oxygen was reduced in PBMCs (-14% into 2h, P<0.05 vs. baseline and -27% after 4h, P<0.01 vs. baseline). ROS generation was correlated with plasma lipids, insulin, apolipoproteins and oxygen consumption.

CONCLUSIONS

In contrast to the previously reported elevation of postprandial oxidative stress, this study shows reduced ROS generation in PBMCs and in ECV 304. Data obtained in both cellular models suggest the existence of a protective response against plasma postprandial oxidative stress.

Exacerbated postprandial oxidative stress induced by the acute intake of a lipid meal compared to isoenergetically administered carbohydrate, protein, and mixed meals in young, healthy men

OBJECTIVE

To compare the oxidative stress response following isocaloric consumption of a lipid, carbohydrate, protein, and mixed meal.

DESIGN

Ten young (27.3 ± 7.0 years), healthy (body mass index = 24.9 ± 4.0 kg·m(-2)) men consumed isocaloric test meals on 4 separate days, separated by 1 week, in a random-order crossover design. Blood samples were collected premeal and at 1, 2, 4, and 6 hours postmeal and assayed for various markers of oxidative stress, as well as triglycerides (TAG) and glucose. Total area under the curve (AUC) was calculated for each variable, and a 4 × 5 analysis of variance (ANOVA) was used to further analyze data.

RESULTS

Significant meal effects were noted for hydrogen peroxide AUC (p = 0.004), with values higher for the lipid meal compared with all other meals (p < 0.05). Contrasts revealed greater AUC for TAG (p = 0.05), malondialdehyde (p = 0.002), and nitrate/nitrite (p = 0.02) for the lipid meal compared with the protein meal. With regard to the ANOVA, oxidative stress values were highest for the lipid meal and increased from 2-6 hours postmeal following lipid ingestion (p < 0.05). No other meals resulted in a significant increase in oxidative stress (p > 0.05).

CONCLUSIONS

These data indicate that when controlling for total dietary energy, a lipid meal results in the greatest increase in postprandial oxidative stress in a sample of young, healthy men.

Cellular and molecular mechanisms of vascular injury in diabetes--part II: cellular mechanisms and therapeutic targets

Although the mechanisms by which insulin-resistance and hyperglycemia lead to cardiovascular disease are still incompletely understood, all mechanisms apparently converge on the vessel wall and the endothelium as a common disease target. Endothelial cells play a crucial role in vascular homeostasis, providing a functional barrier and modulating several signals involved in vasomotion, as well as antiplatelet, anti-inflammatory, anti-proliferative, and anti-oxidant properties of the vessel wall. Endothelial cell dysfunction occurs early in diabetes and insulin resistance states. Since atherosclerosis may result from an imbalance between the magnitude of vascular injury and the capacity of repair, a role has been recently postulated for a defective mobilization of vascular progenitors, including endothelial progenitor cells, in the pathogenesis of vascular disease. Here we summarize the evidence for such an occurrence. We also here highlight how new insights into pathways of vascular damage in diabetes may indicate new targets for preventive and treatment strategies.

A 21 day Daniel Fast improves selected biomarkers of antioxidant status and oxidative stress in men and women

BACKGROUND

Dietary modification via both caloric and nutrient restriction is associated with multiple health benefits, some of which are related to an improvement in antioxidant status and a decrease in the production of reactive oxygen species. The Daniel Fast is based on the Biblical book of Daniel, is commonly partaken for 21 days, and involves food intake in accordance with a stringent vegan diet. The purpose of the present study was to determine the effect of a 21 day Daniel Fast on biomarkers of antioxidant status and oxidative stress.

METHODS

43 subjects (13 men; 30 women; 35 ± 1 yrs; range: 20-62 yrs) completed a 21 day Daniel Fast following the guidelines provided by investigators. Subjects reported to the lab in a 12 hour post-absorptive state both pre fast (day 1) and post fast (day 22). At each visit, blood was collected for determination of malondialdehyde (MDA), hydrogen peroxide (H2O2), nitrate/nitrite (NOx), Trolox Equivalent Antioxidant Capacity (TEAC), and Oxygen Radical Absorbance Capacity (ORAC). Subjects recorded dietary intake during the 7 day period immediately prior to the fast and during the final 7 days of the fast.

RESULTS

A decrease was noted in MDA (0.66 ± 0.0.03 vs. 0.56 ± 0.02 μmol L-1; p = 0.004), while H2O2 demonstrated a trend for lowering (4.42 ± 0.32 vs. 3.78 ± 0.21 μmol L-1; p = 0.074). Both NOx (18.79 ± 1.92 vs. 26.97 ± 2.40 μmol L-1; p = 0.003) and TEAC (0.47 ± 0.01 vs. 0.51 ± 0.01 mmol L-1; p = 0.001) increased from pre to post fast, while ORAC was unchanged (5243 ± 103 vs. 5249 ± 183 μmol L-1 TE; p = 0.974). As expected, multiple differences in dietary intake were noted (p < 0.05), including a reduction in total calorie intake (2185 ± 94 vs. 1722 ± 85).

CONCLUSION

Modification of dietary intake in accordance with the Daniel Fast is associated with an improvement in selected biomarkers of antioxidant status and oxidative stress, including metabolites of nitric oxide (i.e., NOx).

Relative bioavailability of generic and branded acetylcysteine effervescent tablets: A single-dose, open-label, randomized-sequence, two-period crossover study in fasting healthy Chinese male volunteers

BACKGROUND

Acetylcysteine may be used as a muco- lytic agent for the treatment of chronic bronchitis, chronic obstructive pulmonary disease, and other pulmonary diseases complicated by the production of viscous mucus. However, little is known of its pharmacokinetic properties when given orally in healthy volunteers, particularly in a Chinese Han population. This study was conducted to provide support for the marketing of a generic product in China.

OBJECTIVE

The purpose of this study was to compare the pharmacokinetics and relative bioavailability of a generic test formulation and a branded reference formulation of acetylcysteine in fasting healthy Chinese male volunteers.

METHODS

A single-dose, open-label, randomized-sequence, 2-period crossover design with a 7-day washout period between doses was used in this study. Healthy Chinese male nonsmokers aged 18 to 40 years with a body mass index (BMI) of 19 to 25 kg/m(2) were selected. Eligible volunteers were randomly assigned to receive acetylcysteine 600 mg PO as either the test formulation (3 tablets of 200 mg each) or reference formulation (1 tablet of 600 mg) under fasting conditions. A total of 15 serial blood samples were collected over a 24-hour interval, and total plasma acetylcysteine concentrations were analyzed by a validated liquid chromatography-isotopic dilution mass spectrometry method. Pharmacokinetic parameters (C(max), T(max), t(½) AUC(0-t), and AUC(0-∞) were calculated and analyzed statistically. The 2 formulations were considered bioequivalent if the 90% CIs of the log-transformed ratios (test/reference) of C(max) and AUC were within the predetermined bioequivalence ranges (70%-143% for C(max); 80%-125% for AUC), as established by the State Food and Drug Administration of China. Tolerability was determined by vital signs, clinical laboratory tests, 12-lead ECGs, physical examinations, and interviews with the subjects about adverse events (AEs).

RESULTS

A total of 24 healthy Chinese Han male volunteers were enrolled in and completed the study (mean [SD] age, 25.0 [2.4] years; height, 173.0 [5.6] cm; weight, 65.9 [6.4] kg; BMI, 22.0 [1.7] kg/m(2)). No formulation, period, or sequence effects were observed. The 90% CIs for the log-transformed C(max), AUC(0-t), and AUC(0-∞) were 89.7% to 103.8%, 86.7% to 101.7%, and 87.7% to 102.4%, respectively, which met the predetermined criteria for assuming bioequivalence. Two subjects (8.3%) experienced 2 mild AEs (increase in total bile acid and prolongation of the QT interval), which were not considered to be related to study drug administration.

CONCLUSIONS

This single-dose study of acetylcysteine 600 mg PO found that the 3 tablets of the generic test formulation and 1 tablet of the branded reference formulation met the regulatory criteria for assuming bioequivalence in these fasting healthy Chinese male volunteers. Both formulations were generally well tolerated.

Mechanisms of vascular complications in prediabetes

Although the state of prediabetes is defined by its role as a diabetes risk factor, it also carries a significant risk of cardiovascular disease, independent of progression to diabetes. Typical diabetic microvascular complications also occur, albeit at low rates, in prediabetes. There is evidence that both glucose-related and glucose-independent mechanisms contribute to these vascular complications. Effective preventive strategies will likely require control of glycemia, as well as other metabolic risk factors. This article reviews some of the proposed mechanisms for the vascular complications of the prediabetic state.

Systemic oxidative stress is increased to a greater degree in young, obese women following consumption of a high fat meal

High fat meals induce oxidative stress, which is associated with the pathogenesis of disease. Obese individuals have elevated resting biomarkers of oxidative stress compared to non-obese. We compared blood oxidative stress biomarkers in obese (n = 14; 30 ± 2 years; BMI 35 ± 1 kg•m⁻²) and non-obese (n = 16; 24 ± 2 years; BMI 23 ± 1 kg•m⁻²) women, in response to a high fat meal. Blood samples were collected pre-meal (fasted), and at 1, 2, 4 and 6 hours post meal, and assayed for trolox equivalent antioxidant capacity (TEAC), xanthine oxidase activity (XO), hydrogen peroxide (H₂O₂), malondialdehyde (MDA), triglycerides (TAG), and glucose. An obesity status effect was noted for all variables (p < 0.001; MDA p = 0.05), with obese women having higher values than non-obese, except for TEAC, for which values were lower. Time main effects were noted for all variables (p ≤ 0.01) except for TEAC and glucose, with XO, H₂O₂, MDA and TAG increasing following feeding with a peak response at the four or six hour post feeding time point. While values tended to decline by six hours post feeding in the non-obese women (agreeing with previous studies), they were maintained (MDA) or continued to increase (XO, H₂O₂ and TAG) in the obese women. While no interaction effects were noted (p > 0.05), contrasts revealed greater values in obese compared to non-obese women for XO, H₂O₂, MDA, TAG and glucose, and lower values for TEAC at times from 1–6 hours post feeding (p ≤ 0.03). We conclude that young, obese women experience a similar pattern of increase in blood oxidative stress biomarkers in response to a high fat meal, as compared to non-obese women. However, the overall oxidative stress is greater in obese women, and values appear to remain elevated for longer periods of time post feeding. These data provide insight into another potential mechanism related to obesity-mediated morbidity.

Postprandial oxidative stress in response to dextrose and lipid meals of differing size

We have recently noted that ingestion of dietary lipid (in the form of heavy whipping cream) leads to greater oxidative stress than dietary carbohydrate (in the form of dextrose), when consumed in isocaloric amounts.

Objective

In the present investigation we attempted to replicate our work and also to determine the oxidative stress response to dextrose and lipid meals of two different kilocalorie (kcal) amounts.

Design

Nine young (22 ± 2 years), healthy men consumed in a random order, cross-over design one of four meals/drinks: dextrose at 75 g (300 kcals), dextrose at 150 g (600 kcals), lipid at 33 g (300 kcals), lipid at 66 g (600 kcals). Blood samples were collected Pre meal, and at 30 min, 60 min, 120 min, and 180 min post meal. Samples were assayed for glucose, triglycerides (TAG), malondialdehyde (MDA), and hydrogen peroxide (H₂O₂). Area under the curve (AUC) was calculated for each variable, and a 4 × 5 ANOVA was utilized to further analyze data.

Results

A meal × time effect (p = 0.0002) and a time effect was noted for glucose (p < 0.0001; 30 min > Pre, 1 hr, 2 hr, and 3 hr). The dextrose meals primarily contributed to this time effect. No other effects were noted for glucose (p > 0.05). A meal effect was noted for TAG (p = 0.01; 66 g lipid meal > 75 g and 150 g dextrose meals). No other effects were noted for TAG (p > 0.05). An AUC effect was noted for MDA (p = 0.04; 66 g lipid meal > 75 g and 150 g dextrose meals). A meal × time effect (p = 0.02) and a meal effect was noted for MDA (p = 0.004; 66 g lipid meal > 75 g and 150 g dextrose meals). No time effect was noted for MDA (p = 0.72). An AUC effect was noted for H₂O₂ (p = 0.0001; 66 g lipid meal > 33 g lipid meal and 75 g and 150 g dextrose meals). A meal × time effect (p = 0.0002), a meal effect (p < 0.0001; 66 g lipid meal > 33 g lipid meal and 75 g and 150 g dextrose meals), and a time effect was noted for H₂O₂ (p < 0.0001; 2 hr > Pre, 30 min, and 1 hr; 3 hr > Pre). The time effect for H₂O₂ was primarily influenced by the 66 g lipid meal.

Conclusions

These data indicate that 1) minimal oxidative stress is observed following ingestion of dextrose loads of either 75 g or 150 g, or a lipid load of 33 g and 2) lipid ingestion at 66 g leads to greater oxidative stress than lipid at 33 g or dextrose at either 75 g or 150 g. Hence, in a sample of young and healthy men, only 66 g of lipid (taken in the form of heavy whipping cream) leads to a significant increase in blood oxidative stress, as measured by MDA and H₂O₂.

Asymmetric dimethylarginine as a mediator of vascular dysfunction and a marker of cardiovascular disease and mortality: an intriguing interaction with diabetes mellitus

Asymmetric dimethylarginine (ADMA) has evolved as an important regulator of nitric oxide (NO) synthesis in recent years. Elevated levels of ADMA have been reported in many conditions associated with a high cardiovascular risk. Moreover, ADMA is a biomarker for major cardiovascular events and mortality in cohorts with high, intermediate and low overall cardiovascular risk. Discrepant data have been reported on cardiovascular risk in people with and without diabetes mellitus, and the association of ADMA with diabetes mellitus per se has also remained controversial, possibly relating to type and stage of diabetes. Clinical and experimental data suggest that there is a multifaceted link between ADMA and insulin metabolism and action on one hand, and ADMA and glucose utilisation on the other. This interplay may be regulated by the enzyme involved in the metabolic degradation of ADMA, dimethylarginine dimethylaminohydrolase (DDAH). Recent data from prospective clinical studies suggest that whilst ADMA may be a marker for total mortality in patients without diabetes, elevated ADMA may exert beneficial effects in patients with diabetes. In this respect, ADMA could serve as a re-coupling agent overcoming endothelial nitric oxide synthase (eNOS) uncoupling in patients with diabetes. Anticipated advances in clinical and experimental investigation will help us to better understand this complex interrelationship between diabetes, eNOS, DDAH and ADMA.

Postprandial lipaemia, oxidative stress and endothelial function: a review

AIMS

Postprandial lipaemia-induced endothelial dysfunction is felt to be mediated by increases in oxidative stress. In this review, we have examined the cross-sectional relationships found among these three variables.

METHODS

We found 20 studies conducted by 16 independent investigative teams through a Medline search from 1980 to 2008; studies were required to report correlations between at least two of the three variables of interest in studies of humans. This review is divided into (i) discussions on the biomarkers and other measures of postprandial lipaemia, oxidative stress and endothelial function; (ii) associations reported among the three variables; and (iii) other considerations including alternative intervention studies.

RESULTS

Triglycerides and free fatty acids are robust and well-standardised biomarkers of lipaemia. Measures of oxidative stress ranged from electron spin techniques to measures of lipid peroxidation and are limited by lack of standardisation. Brachial artery flow-mediated dilatation is the most commonly used measure of endothelial function. The associations between postprandial lipaemia and oxidative stress and between postprandial lipaemia and endothelial function are strong and consistent. However, the association between postprandial oxidative stress and endothelial function appears weak, at least using current approaches to measurement of oxidative stress.

DISCUSSION AND CONCLUSIONS

These observations are consistent with the proposed concept that oxidative stress mediates the adverse effects of postprandial lipaemia on endothelial function; they are limited by the difficulties in measuring oxidative stress. Efforts directed at optimising and standardising the measurement of oxidative stress will be of value in future works in this area.

Protection from olanzapine-induced metabolic toxicity in mice by acetaminophen and tetrahydroindenoindole

OBJECTIVE

In mice and in humans, treatment with the second-generation antipsychotic drug olanzapine (OLZ) produces excessive weight gain, adiposity and secondary metabolic complications, including loss of glucose and insulin homeostasis. In mice consuming a high-fat (HF) diet, a similar phenotype develops, which is inhibited by the analgesic acetaminophen (APAP) and by the antioxidant tetrahydroindenoindole (THII). Therefore, we examined the ability of APAP and THII to prevent metabolic changes in mice receiving OLZ.

DESIGN AND MEASUREMENT

C57BL/6J mice received either a normal diet or a HF diet, and were administered daily dosages of OLZ (3 mg kg(-1) body weight), alone or with APAP (30 mg kg(-1) body weight) or THII (4.5 mg kg(-1) body weight), for 10 weeks. Parameters of body composition and metabolism, including glucose and insulin homeostasis and oxidative stress, were examined.

RESULTS

OLZ treatment doubled the HF diet-induced increases in body weight and percent body fat. These increases were partially prevented by both APAP and THII, although food consumption was constant in all groups. The THII protection was associated with an increase in whole body and mitochondrial respiration. OLZ also exacerbated, and both APAP and THII prevented, HF diet-induced loss of glucose tolerance and insulin resistance. As increased body fat promotes insulin resistance by a pathway involving oxidative stress, we evaluated production of reactive oxygen and lipid peroxidation in white adipose tissue (WAT). HF diet caused an increase in lipid peroxidation, NADPH-dependent O(2) uptake and H(2)O(2) production, which were further exacerbated by OLZ. APAP, THII and the NADPH oxidase inhibitor, diphenyleneiodonium chloride, each abolished oxidative stress in WAT.

CONCLUSIONS

We conclude that both APAP and THII intervene in the development of obesity and metabolic complications associated with OLZ treatment.

Effect of oral acetyl L-carnitine arginate on resting and postprandial blood biomarkers in pre-diabetics

Background

Resting and postprandial oxidative stress is elevated in those with metabolic disorders such as diabetes. Antioxidant supplementation may attenuate the rise in oxidative stress following feeding. Therefore we sought to determine the effects of acetyl L-carnitine arginate (ALCA) on resting and postprandial biomarkers of glucose and lipid metabolism, as well as oxidative stress.

Methods

Twenty-nine pre-diabetic men and women were randomly assigned to either 3 g·day^-1 of ALCA (n = 14; 31 ± 3 yrs) or placebo (n = 15; 35 ± 3 yrs) in a double-blind design, to consume for eight weeks. Fasting blood samples were taken from subjects both pre and post intervention. After each fasting sample was obtained, subjects consumed a high fat, high carbohydrate meal and additional blood samples were taken at 1, 2, 4, and 6 hours post meal. Samples were analyzed for a variety of metabolic variables (e.g., glucose, HbA1c, lipid panel, C-reactive protein, nitrate/nitrite, and several markers of oxidative stress). Area under the curve (AUC) was calculated for each variable measured post meal, both pre and post intervention.

Results

ALCA, but not placebo, resulted in an increase in nitrate/nitrite (25.4 ± 1.9 to 30.1 ± 2.8 μmol·L^-1) from pre to post intervention, with post intervention values greater compared to placebo (p = 0.01). No other changes of statistical significance were noted (p > 0.05), although ALCA resulted in slight improvements in glucose (109 ± 5 to 103 ± 5 mg·dL^-1), HbA1c (6.6 ± 1.1 to 6.2 ± 1.2%), and HOMA-IR (3.3 ± 1.3 to 2.9 ± 1.2). AUC postprandial data were not statistically different between ALCA and placebo for any variable (p > 0.05). However, nitrate/nitrite demonstrated a moderate effect size (r = 0.35) for increase from pre (139.50 ± 18.35 μmol·L^-1·6 hr^-1) to post (172.40 ± 21.75 μmol·L^-1·6 hr^-1) intervention with ALCA, and the magnitude of decrease following feeding was not as pronounced as with placebo.

Conclusion

Supplementation with ALCA results in an increase in resting nitrate/nitrite in pre-diabetics, without any statistically significant change in other metabolic or oxidative stress variables measured at rest or post meal.

Post-challenge hyperglycemia in older adults is associated with increased cardiovascular risk profile

CONTEXT

Post-challenge hyperglycemia (PCH) is common in older adults and is associated with increased cardiovascular disease (CVD) risk and total mortality. However, PCH is rarely recognized in clinical settings, and the glycemic exposure and CVD risk profile of elderly individuals with PCH has not been defined.

OBJECTIVE

The aim of the study was to characterize metabolic and CVD risk profile of elderly subjects with PCH and to determine the effect of acute postprandial metabolic changes on vascular biomarkers.

DESIGN

We conducted a cross-sectional study with a standard meal challenge protocol.

PARTICIPANTS

Older adults with normal glucose tolerance (n = 30) or PCH (fasting glucose <126 mg/dl and 2-h glucose >or=170 mg/dl; n = 28) participated in the study.

MAIN OUTCOME MEASURES

We assessed fasting and postprandial levels of glucose, insulin, lipids, high sensitivity C-reactive protein, plasminogen activator inhibitor-1, and adiponectin and endothelial function using reactive hyperemia peripheral arterial tonometry.

RESULTS

Normal glucose tolerance and PCH subjects were matched for age, sex, body mass index, and ethnicity. Fasting glucose (102 +/- 3 vs. 93 +/- 2 mg/dl; P < 0.001) and glycosylated hemoglobin (5.7 vs. 5.4%; P = 0.01) were modestly higher in the PCH group, which was also more insulin resistant (homeostasis model assessment for insulin resistance, 7.0 +/- 1.3 vs. 4.1 +/- 0.6; P = 0.03). Fasting high sensitivity C-reactive protein was higher (2.6 +/- 0.5 vs. 1.3 +/- 0.2 mg/dl; P = 0.05), and adiponectin was lower (11.6 +/- 1.6 vs. 14.0 +/- 1.3 microg/ml; P = 0.03) in subjects with PCH. Peak and 6-h postprandial area under the curve glucose, insulin, and lipids were higher in PCH subjects, who also had higher fasting and postprandial levels of plasminogen activator inhibitor-1. Reactive hyperemia peripheral arterial tonometry declined postprandially only in PCH.

CONCLUSIONS

Older adults with PCH experience significant fasting and postprandial metabolic dysregulation, which is accompanied by a proatherosclerotic and prothrombotic vascular profile.

The role of exercise in minimizing postprandial oxidative stress in cigarette smokers

Cigarette smoking continues to pose a significant health burden on society. Two well-described mechanistic links associating smoking with morbidity and mortality include elevated blood lipids and increased oxidative stress. These variables have traditionally been measured while an individual is fasting, but evidence suggests that postprandial lipemia and oxidative stress provide more important information concerning susceptibility to disease, in particular cardiovascular disease. Cigarette smokers have elevated levels of biomarkers of oxidative stress at rest and experience impaired postprandial lipid and glucose metabolism. We have confirmed these findings while noting an exaggerated oxidative stress response to high-fat feeding. Smoking cessation is without question the best approach to minimizing smoking-induced ill health and disease, but success rates among those who attempt to quit are dismal. Other means to decrease a smoker's susceptibility to oxidative stress-related disease are needed. We propose that exercise may aid in attenuating postprandial oxidative stress, and we do so in 3 distinct ways. First, exercise stimulates an increase in endogenous antioxidant enzyme activity. Second, exercise improves blood triglyceride clearance via a reduced chylomicron-triglyceride half-life and an enhanced lipoprotein lipase activity. Third, exercise improves blood glucose clearance via an enhanced glucose 4 transport protein translocation and protein content, as well as insulin-insulin receptor binding and postreceptor signaling. Improvements in antioxidant status, as well as lipid and glucose processing, may aid greatly in minimizing feeding-induced oxidative stress in smokers. If so, and in accordance with the recent joint initiative of the American College of Sports Medicine and the American Medical Association, exercise may be viewed as a "medicine" for cigarette smokers at increased risk for postprandial oxidative stress. Research into this area may provide insight into the potential benefits of exercise for this purpose.