A matter of fat: insulin resistance and oxidative stress

BACKGROUND

Obesity is linked to insulin resistance (IR), which can lead to type 2 diabetes mellitus. Oxidative stress present in early obesity may favor the progression to comorbid conditions.

OBJECTIVE

To examine the relationship between oxidative stress biomarkers and the severity of IR in a group of obese children.

METHODS

Forty obese children with a body mass index (BMI) Z-score ≥ 2 were divided into two groups using the median obtained for the homeostasis model assessment of IR (HOMA-IR). Anthropometric parameters (including body fat composition by bioelectrical impedance) and biochemical parameters were assessed. The following biomarkers of oxidative stress were measured: malondialdehyde (MDA), carbonyl groups (CG), reduced glutathione, oxidized low-density lipoprotein, and vitamin E. Comparisons were adjusted for gender and Tanner stage.

RESULTS

Children with high values of HOMA-IR were more likely to have high body fat percentage and waist circumferences. However, the BMI Z-score did not correlate to the level of IR. Children with higher values of HOMA-IR presented increased levels of markers of oxidative stress in lipids (MDA, p = 0.005) and proteins (CG, p = 0.015). Moreover, MDA increased with increasing levels of HOMA-IR (r = 0.50, p = 0.002), suggesting that lipoperoxidation increases as IR worsens. In a multivariate regression model, only HOMA-IR was predictive of MDA values, irrespective of adiposity parameters and other metabolic risk factors (r2 = 0.22, p = 0.002).

CONCLUSIONS

Oxidative stress increases in obese children according to the severity of IR, which could be linked to the development of comorbidities.

Elevated advanced oxidation protein products (AOPPs) indicate metabolic risk in severely obese children

BACKGROUND AND AIMS

The assessment of oxidative stress may aid in the identification of subsequent metabolic risk in obese children. The objective of this study was to determine whether the plasma level of advanced oxidation protein products, analyzed with a recently proposed modified assay that involves a delipidation step (mAOPPs), was related to metabolic risk factors (MRFs) in severely obese children.

METHODS AND RESULTS

The plasma levels of mAOPPs were determined by spectrophotometry in 54 severely obese and 44 healthy children. We also measured lipid peroxidation biomarkers (thiobarbituric acid-reactive substances, malondialdehyde, and 8-isoprotane F(2α)) and sulfhydryl groups, a marker of antioxidant defense. Protein oxidation and lipid peroxidation markers were higher and sulfhydryl levels were lower in obese children compared with controls. Taking metabolic risk into account, obese children were subdivided according to the cutoff point (53.2 μmol/L) obtained for their mAOPPs values from the ROC curve. Anthropometric measures and the existence of hypertension did not differ between groups. The presence of dyslipidemia and insulin resistance was significantly higher in the group with higher mAOPPs levels. The highest levels of mAOPPs were found in the children with ≥3 MRFs. The level of mAOPPs was positively correlated with triglycerides and negatively correlated with high-density lipoprotein cholesterol. There was no correlation of this marker of protein oxidation with biomarkers of lipid peroxidation.

CONCLUSION

The determination of mAOPPs in delipidated plasma is an easy way to evaluate protein oxidation. It may be useful in severely obese children for better cardiovascular risk assessment.

Oxidant mechanisms in childhood obesity: the link between inflammation and oxidative stress

Evidence of obesity-induced oxidative stress in adults has emerged in the past several years, and similar evidence has been demonstrated in children more recently. The reactive species of oxygen or nitrogen can chemically alter all major classes of biomolecules by modifying their structure and function. Organisms have developed mechanisms to protect biomolecules from the deleterious effects of free radicals. These include the enzymes superoxide dismutase, catalase, and glutathione peroxidase, as well as water and lipid-soluble antioxidants, such as glutathione, ascorbate (vitamin C), α-tocopherol (vitamin E), and β-carotene. Obesity creates oxidant conditions that favor the development of comorbid diseases. Energy imbalances lead to the storage of excess energy in adipocytes, resulting in both hypertrophy and hyperplasia. These processes are associated with abnormalities of adipocyte function, particularly mitochondrial stress and disrupted endoplasmic reticulum function. In this sense, oxidative stress can also be induced by adipocyte associated inflammatory macrophages. There is a close link among obesity, a state of chronic low-level inflammation, and oxidative stress. In addition, the dysregulation of adipocytokines, which are secreted by adipose tissue and promoted by oxidative stress, act synergistically in obesity-related metabolic abnormalities. Adipocytokines link the local and systemic inflammation responses in the context of obesity. It is thought that the evaluation of oxidative status may allow for the identification of patients at an increased risk of complications. Decreasing the levels of chronic inflammation and oxidative stress in childhood may decrease cardiovascular morbidity and mortality in adulthood.

Polyamines are increased in obese children and are related to markers of oxidative/nitrosative stress and angiogenesis

CONTEXT

Polyamines (putrescine, spermidine, and spermine) are polycationic amines derived from arginine, which is the precursor of nitric oxide (NO). Due to the close relationship between the metabolism of polyamines and NO metabolism, the alteration in polyamine homeostasis can affect the NO bioavailability at the endothelium.

OBJECTIVES

The objective of the study was to test the hypothesis that childhood obesity is associated with a significant modification of blood polyamines and to investigate the presence of correlation between these molecules, circulating markers of oxidative and nitrosative stress, and endothelial dysfunction.

DESIGN AND SETTING

This was an observational analytical case-control study conducted at one tertiary care center.

PATIENTS AND METHODS

The study was performed with 102 children aged 7-14 yr (60 obese, 42 nonobese). Blood polyamines were measured by HPLC. Metabolites of the NO pathway, oxidative stress parameters, inflammatory markers, adhesion molecules, and adipocytokines were also determined.

RESULTS

Polyamine levels were significantly higher in obese children. Among them, spermine was the polyamine with the more discriminatory power, taking into account the obesity. In all children, spermine levels were related to biomarkers of oxidative/nitrosative stress, inflammation, and leptin and to adhesion molecules, soluble E-selectin, and soluble intercellular adhesion molecule-1. Only in obese children was there a positive correlation with vascular endothelial growth factor and a negative correlation with 3'-nitrotyrosine levels.

CONCLUSIONS

Polyamine levels are increased in childhood obesity and correlated to markers of oxidative/nitrosative stress and angiogenesis. This finding implicates polyamine metabolism in the complications of obesity. Their potential utility as a clinical tool remains to be elucidated.

Effect of a Diet Supplemented with alpha-Tocopherol and beta-Carotene on ATP and Antioxidant Levels after Hepatic Ischemia-Reperfusion

Ischemia-reperfusion injury associated with liver transplantation remains a serious complication in clinical practice. In the present study the effect of intake of α-tocopherol or β-carotene to limit liver injury by oxidative stress in ischemia and reperfusion was explored. Wistar rats were fed with diets enriched with α-tocopherol (20 mg/day) or β-carotene (3 mg/day) for 21 days. After 21 days, their livers were subjected to 15 and 30 min of ischemia and afterwards were reperfused for 60 min. The recovery of levels of ATP during reperfusion was better in the group of rats whose diets were supplemented with α-tocopherol or β-carotene than in the group control. The supplementation of the diet induced changes in the profile of enzymatic antioxidants. The supplementation with α-tocopherol and β-carotene resulted in a decreased of superoxide dismutase during the ischemia and a recovery was observed after reperfusion. Not changes were observed for the enzymes catalase and glutathione peroxidase and glutathione but their values were higher to those of the group control. In conclusion, the supplementation with α-tocopherol and β-carotene improve the antioxidant and energetic state of liver after ischemia and reperfusion injury.

Oxidative markers in children with severe obesity following low-calorie diets supplemented with mandarin juice

AIM

 To evaluate the effect of supplementing a hypocaloric diet with mandarin juice, a food with a high content of antioxidants (vitamin C, flavonoids and carotenoids), on biomarkers of oxidant/antioxidant status of severe obese children.

METHODS

 Forty obese children were randomized into two groups pair-wise in a 4-week controlled intervention study. Both groups followed a hypocaloric diet. One group received additionally a supplementation of 500mL of 100% mandarin juice daily. Clinical data, anthropometry, dietary intake and fasting blood samples were collected at baseline and after the intervention. Lipid peroxidation was assessed by circulating levels of malondialdehyde, and protein oxidation was determined by the concentration of plasma carbonyl groups. The antioxidant defence was evaluated by red cell-reduced glutathione and plasma levels of α-tocopherol and vitamin C.

RESULTS

 The supplemented group experienced a decrease in the levels of malondialdehyde (-9.6%, p =0.014) and carbonyl groups (-36.1%, p =0.006) and an increase in antioxidants (α-tocopherol +16.1%, p=0.006, glutathione +36.1%, p < 0.0001, and vitamin C + 94.6%, p < 0.0001).

CONCLUSION

  The mandarin juice consumption with a reduced calorie diet positively affects the antioxidant defence and produces a decrease in biomarkers of oxidative stress in obese children.

New factors of cardiometabolic risk in severely obese children: influence of pubertal status

The aim of this prospective study was to evaluate the utility of new biochemical markers to assess cardiometabolic risk in severely obese children and adolescents. A total of 107 subjects aged 7 to 14 years, were clinically assessed and anthropometric measures and percentage of fat mass by single frequency bioimpedance analysis were recorded. Of these, 44 were non-overweight and 63 severely obese (body mass index Z-score>2.5) which were stratified by Tanner stages. To estimate the metabolic risk the following variables were considered for analysis: Waist circumference/height>0.5, fasting glucose>100 mg/dL, triglycerides>110 mg/dL, HDL-C<40 mg/dL, and systolic or diastolic blood pressure>95th percentile for age and gender. Fasting insulinemia, apoprotein A1 and B, high-sensitive C-reactive protein, alanine aminotransferase, homocysteine, and folic and uric acids were determined. In severely obese children, metabolic risk was present more frequently in mid puberty. The normalized anthropometric parameters with respect to 50th percentile for age and gender did not differ in the presence of metabolic risk. Insulin resistance was an independent determinant of metabolic risk, adjusted by Tanner stages. Elevated high-sensitive C-reactive protein was noted without any effect of metabolic risk or pubertal stage. Homocysteine, apoprotein B, and alanine aminotransferase values increased with metabolic risk and were not influenced by puberty. Although insulin resistance remains the main factor influencing metabolic risk, biochemical markers as homocysteine, apoprotein B, and alanine aminotransferase, may be useful for identifying severe obese pubertal subjects particularly prone to comorbidities.

Oxidant/antioxidant status in obese children compared to pediatric patients with type 1 diabetes mellitus

BACKGROUND

Type 1 diabetes (T1D) mellitus and obesity are recognized risk factors for cardiovascular disease (CVD). A common mechanism underlying an increased risk for endothelial dysfunction in these two metabolic diseases is oxidative stress.

OBJECTIVE

To evaluate and compare the oxidant/antioxidant defense systems in children affected with T1D or obesity in order to determine the importance of oxidative stress before the emergence of complications.

SUBJECTS

Children with T1D (n = 20) or obesity (n = 22), without comorbidities, and age- and sex-matched controls (n = 16).

METHODS

We assessed lipid peroxidation by circulating levels of lipoperoxides and malondialdehyde, as well as protein oxidation by the concentration of plasma carbonyl groups. The endogenous antioxidative defense system was evaluated by the red cell glutathione peroxidase and reduced glutathione. The serum levels of alpha-tocopherol and beta-carotene were determined to assess exogenous antioxidants.

RESULTS

Lipid peroxidation was significantly higher in both T1D and obese children when compared with control children. However, T1D patients showed a more elevated level, because their malondialdehyde values were significantly increased with respect to obese children. Protein oxidation was present in both groups of children and did not differ between them. With respect to obese children, the glutathione peroxidase activity and exogenous antioxidants were decreased in T1D patients.

CONCLUSION

Oxidative stress is present in both children with T1D and obesity, although it is more pronounced in the former. Obese children may suffer an additional oxidative stress in the case of developing impaired glucose metabolism.

Effect of beer consumption on levels of complex I and complex IV liver and heart mitochondrial enzymes and coenzymes Q9 and Q10 in adriamycin-treated rats

BACKGROUND

There is increasing evidence indicating that the dietary intake of food with high antioxidant capacity may protect mitochondria from damage and exert positive effects on different pathogenic processes.

AIM OF THE STUDY

The present study was designed to evaluate the possible protective effect of alcohol-free beer intake on chain components dysfunction of liver and heart mitochondria, and to compare with the effect of alcohol beer intake.

METHODS

The study was carried out in rat heart and liver mitochondria by inducing with Adriamycin the dysfunction of the respiratory chain. Heart and liver mitochondria were isolated from rats and subjected to oxidative stress with two doses of Adriamycin (5 mg/Kg) 7 days from the beginning of consumption of both alcohol-free and alcohol beer during 31 days. Complexes I and IV and the levels of coenzymes Q(9) and Q(10) were evaluated and compared with a control group.

RESULTS

Liver and heart mitochondria isolated from rats treated with Adryamicin showed a decrease in levels of complex I and complex IV enzymatic activity and in levels of coenzymes Q(9) and Q(10). Beer intake for itself does not affect any of the studied parameters. Therefore, the consumption of both alcohol and alcohol-free beer by rats treated with Adriamycin prevents the inhibition of enzymatic activities of complexes I and IV and the oxidation of coenzymes Q(9) and Q(10) in rat heart and liver mitochondria.

CONCLUSIONS

These results indicate that alcohol-free beer prevents adriamycin-induced damage to mitochondrial chain components and, therefore, helps to prevent mitochondrial dysfunction.

Influence of dietary lipids on the erythrocyte antioxidant status of hypercholesterolaemic children

The aim of this work was to examine the effect of dietary lipid intakes on the biomarkers of red cell antioxidant status in hypercholesterolaemic children. The study population included 34 children (18 boys and 16 girls) with cholesterol levels > or =5.2 mmol/l and 16 normolipidaemic children (9 boys and 7 girls) between 6 and 12 years of age. The status of the erythrocyte antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and reduced glutathione (GSH) were estimated spectrophotometrically. Dietary intake was assessed by 24-h recall and seven-day records. The hypercholesterolaemic children showed a decreased activity of antioxidant enzymes in relation to the control group. There was a negative correlation between energy intake and the activity of antioxidant enzymes (SOD and CAT) and GSH levels. Cholesterol intake was inversely correlated with CAT and GPx activity and GSH levels. The intake of polyunsaturated fat was positively correlated with the GPx activity. A decrease in the fat content of the diet for 6 months was proposed and 15 children followed the diet strictly. The activities of antioxidant enzymes in these children were significantly higher after the low-fat diet; the greatest increment was noted in the activity of GPx (91% with respect to the initial values), SOD was increased by 44% and CAT by 70%. We conclude that the intake of dietary lipids can modulate the antioxidant defence system, and an excess of energy and cholesterol has a negative influence on the antioxidant enzymes.

Defatted milled grape seed protects adriamycin-treated hepatocytes against oxidative damage

Defatted milled grape seed (DMGS) is a wine by-product obtained from the oil extraction of the grape seed that contains different types of phenolic compounds. The present study was designed to evaluate the possible protective effect of DMGS on toxicity induced by adriamycin (ADR) in isolated rat hepatocytes. The study was carried out by examining the results of lactate dehydrogenase (LDH) release to estimate cytotoxicity; the thiobarbituric acid reactant substances (TBARS) and carbonyl group levels were measured as biomarkers of oxidative stress and ATP and GSH levels as estimation of intracellular effect. The results showed that DMGS extract protects the cellular membrane from oxidative damage and consequently prevents protein and lipid oxidation. The levels of ATP and GSH changes for the ADR toxicity were restored to control value in the presence of DMGS extract. The experimental results suggest that this wine by-product may be used to decrease oxidative stress.

Anti-rat liver microsomal and cytosolic antibodies in hepatitis C virus infection

In order to assess the frequency of autoimmunity markers in hepatitis C virus infection, 229 RIBA 2 HCV positive individuals were tested by ELISA and Immunoblot assay using as antigen rat liver microsomal and cytosolic proteins. Twenty-one out of 229 individuals (9%) showed anti-rat liver microsome antibodies by ELISA, but the titre was low (1:100 to 1:1,600). In Immunoblot, only 5 of these 21 ELISA positive sera recognized also rat liver microsomal proteins (MW between 30 to 64 kDa). Antibodies against rat liver cytosolic proteins were found by ELISA in 14 out of 229 individuals (6%). Three of them showed a reactivity in Immunoblot to 42 kDa or 55 kDA proteins. In conclusion, HCV infection could induce an autoimmune response against rat liver microsomal and cytosolic proteins in a small number of subjects; the titre of antibodies being lower and the pattern of reactivity different in respect to patients with autoimmune hepatitis.

Clinical and immunological heterogeneity of anti-liver-kidney microsome antibody-positive autoimmune hepatitis in children

A group of children with autoimmune hepatitis is characterized by the presence in their sera of anti-liver-kidney microsome antibody (LKMA) as defined by immunofluorescence. Immunoblot analysis of the sera of 21 such children using rat-liver microsome total proteins as antigen allowed separation into three groups--group 1, whose sera recognized a 50 kDa protein; group 2, whose sera recognized a 66 kDa protein; and group 3, whose sera recognized both proteins. Patients with the anti-66-kDa reactivity more often displayed an acute onset of the disease, less signs of portal hypertension, better sensitivity to immunosuppressive therapy, and less tendency to relapse. They also displayed a lower titer of anti-rat-liver microsome antibody in enzyme-linked immunosorbent assay (ELISA) and a serum reactivity with a rat-liver cytosolic protein. These results (a) indicate that the LKMA-positive autoimmune hepatitis of children is heterogeneous from both clinical and immunological view points, (b) suggest that children with anti-66-kDa reactivity could have a less severe disease than children with the 50-kDa reactivity, and (c) indicate that immunoblot analysis should be added to ELISA and immunofluorescence studies to achieve better characterization of these patients.