[Basal insulin levels in a Zulia State population in Venezuela]

This study examines the basal insulin levels in a population from Zulia state (Venezuela). A total of 1703 subjects (1175 women and 528 men) from five different sanitary regions (Maracaibo, La Guajira, Perijá, Sur del Lago de Maracaibo, y Costa Oriental del Lago de Maracaibo) were studied. Weight, height, waist and hip circumferences, and blood pressure were determined. A blood sample was taken after a 12-h overnight fast to determine serum glucose, triglycerides, total cholesterol and HDL-C using enzymatic methods and insulin by radioimmunoassay. According to ATP III criteria two groups were established: a group without metabolic abnormalities (138 subjects) and a group with some metabolic abnormalities 84.8% of subjects of the non metabolic alteration groups and 80.4% of the group with some metabolic alteration were of mixed race. Non metabolic altered lean subjects (BMI <25 Kg/m2) had the lowest (p < 0.0001) basal insulin levels compared to the ones with overweight from the same group and the obese with metabolic abnormalities. This study proposes to consider a cutoff basal insulin levels of 13 microU/mL for women and 11 microU/mL for men, over 20 years of age, in the Zulia state region of Venezuela.

The acute-phase response of the liver in relation to thyroid hormone-induced redox signaling

Recently, we reported that 3,3',5-triiodothyronine (T3) induces the expression of redox-sensitive genes as a nongenomic mechanism of T3 action. In this study, we show that T3 administration to rats (daily doses of 0.1 mg/kg ip for 3 consecutive days) induced a calorigenic response and liver glutathione depletion as an indication of oxidative stress, with higher levels of interleukin (IL)-6 in serum (ELISA) and hepatic STAT3 DNA binding (EMSA), which were maximal at 48-72 h after treatment. Under these conditions, the protein expression of the acute-phase proteins haptoglobin and beta-fibrinogen is significantly augmented, a change that is suppressed by pretreatment with alpha-tocopherol (100 mg/kg ip) or gadolinium chloride (10 mg/kg iv) before T3. It is concluded that T3 administration induces the acute-phase response in rat liver by a redox mechanism triggered at the Kupffer cell level, in association with IL-6 release and activation of the STAT3 cascade, a response that may contribute to reestablishing homeostasis in the liver and extrahepatic tissues exhibiting oxidative stress.

Thyroid hormone-induced oxidative stress in rodents and humans: a comparative view and relation to redox regulation of gene expression

Thyroid hormone (3,3',5-triiodothyronine, T(3)) exerts significant actions on energy metabolism, with mitochondria being the major target for its calorigenic effects. Acceleration of O(2) consumption by T(3) leads to an enhanced generation of reactive oxygen and nitrogen species in target tissues, with a higher consumption of cellular antioxidants and inactivation of antioxidant enzymes, thus inducing oxidative stress. This redox imbalance occurring in rodent liver and extrahepatic tissues with a calorigenic response, as well as in hyperthyroid patients, is further enhanced by an increased respiratory burst activity in Kupffer cells, which may activate redox-sensitive transcription factors such as NF-kappaB thus up-regulating gene expression. T(3) elicits an 80-fold increase in the serum levels of tumor necrosis factor-alpha (TNF-alpha), which is abolished by pretreatment with the antioxidants alpha-tocopherol and N-acetylcysteine, the Kupffer-cell inactivator GdCl(3), or an antisense oligonucleotide against TNF-alpha. In addition, T(3) treatment activates hepatic NF-kappaB, a response that is (i) inhibited by antioxidants and GdCl(3) and (ii) accompanied by induced mRNA expression of the NF-kappaB-responsive genes for TNF-alpha and interleukin (IL)-10. T(3) also increases the hepatic levels of mRNA for IL-1alpha and those of IL-1alpha in serum. Up-regulation of liver iNOS expression is also achieved by T(3), through a cascade initiated by TNF-alpha and involving IkappaB-alpha phosphorylation and NF-kappaB activation. In conclusion, T(3)-induced oxidative stress in the liver enhances the DNA-binding of NF-kappaB and the NF-kappaB-dependent expression of cytokines and iNOS by actions primarily exerted at the Kupffer cell level.

[Serum insulin, leptin and growth hormone levels are associated with body mass index and obesity index in adolescents]

Leptin, insulin and growth hormone levels seem to regulate body composition, fat distribution and fat mass. The purpose of this study was to determine the relationship among insulin, leptin and growth hormone levels in a group of adolescents. Ninety five adolescents (31 boys and 64 girls) between 13 and 18 y. of age were studied. A medical and nutritional history was made which included body mass index (BMI) and subcutaneous skinfolds measurements. Basal levels of glucose, triglycerides, total cholesterol, HDL-C, LDL-C, VLDL-C, leptin, insulin and growth hormone were determined. The leptin and insulin levels were positively associated with body mass index (BMI) and obesity index (OBI). Insulin, leptin and obesity markers were negatively associated with growth hormone level. Fifty two percent of the adolescents with BMI = 21.09 kg/m2 were considered metabolically obese because they had elevated levels of insulin (18.68 +/- 1.52 vs. 10.08 +/- 0.38 microU/ml), HOMA IR (3.34 +/- 0.24 vs. 1.76 +/- 0.07), leptin (16.30 +/- 1.24 vs. 8.11 +/- 1.32 ng./dl) and triglycerides (78.56 +/- 4.38 vs. 64.39 +/- 5.48 mg/dl) and lower levels of HDL-C (39.09 +/- 1.27 vs. 43.30 +/- 2.38 mg/dl), compared with normal group. The same alterations were observed in the obese group, in which significative decrease in growth hormone level was added. We conclude that hyperinsulinemia, hyperleptinemia and low growth hormone levels, may be established as risk factors related to obesity markers, lipid alterations and insulin resistance that can lead to an early development of Type II diabetes and cardiovascular disease.

Increased immunohistochemical expression of thrombomodulin at placental perivascular myofibroblast in severe preeclampsia (PE)

The presence of pro-coagulant and anti-coagulant components of the placental vascular endothelium and syncytiotrophoblast are essential for homeostasis. Vascular endothelium prevents blood clot formation in vivo by involving a cell surface thrombin-binding glycoprotein, thrombomodulin (TM), that activates plasma anti-coagulant protein C. The TM levels increase during pregnancy, but the fibrinolytic capacity diminishes. Since vascular lesions with placental coagulation disorders can be associated with preeclampsia (PE), we hypothesized that TM expression in the stem villous vasculature and syncytiotrophoblast of the placenta are impaired in PE. Plasma and placental tissue samples were collected from PE (n=12) and normotensive pregnant patients (n=11). Patient's gestational age was 35.7+/-1.2 (normotensive) and 30.6+/-1.5 weeks (PE). Blood samples were drawn 30 min before delivery. Serum PAI-1 and PAI-2 antigens were determined by enzyme-linked immunoabsorbent assay (ELISA). A monoclonal antibody specific for TM was used for immunohistochemical tissue staining (ABC) and the staining was quantified by semi quantitative scores. Results show no intensity differences at the apical syncytiotrophoblast between the two groups. However, in preeclamptic placenta, TM expression diminished in the endothelium of the stem villi arteries and increased in the perivascular and stromal myofibroblats in cases of severe PE. TM changes were associated with an increased PAI-1/PAI-2 ratio. It is suggested that in severe PE, the decreased placental blood flow may be due to structural and functional impairment of the endothelium of the stem villi vessels and the surrounding perivascular and stromal myofibroblast, by increasing TM expression which may modulate fetal blow flow in the villous tree.

Scientific management of Mediterranean coastal zone: a hybrid ocean forecasting system for oil spill and search and rescue operations

The oil spill from Prestige tanker showed the importance of scientifically based protocols to minimize the impacts on the environment. In this work, we describe a new forecasting system to predict oil spill trajectories and their potential impacts on the coastal zone. The system is formed of three main interconnected modules that address different capabilities: (1) an operational circulation sub-system that includes nested models at different scales, data collection with near-real time assimilation, new tools for initialization or assimilation based on genetic algorithms and feature-oriented strategic sampling; (2) an oil spill coastal sub-system that allows simulation of the trajectories and fate of spilled oil together with evaluation of coastal zone vulnerability using environmental sensitivity indexes; (3) a risk management sub-system for decision support based on GIS technology. The system is applied to the Mediterranean Sea where surface currents are highly variable in space and time, and interactions between local, sub-basin and basin scale increase the non-linear interactions effects which need to be adequately resolved at each one of the intervening scales. Besides the Mediterranean Sea is a complex reduced scale ocean representing a real scientific and technological challenge for operational oceanography and particularly for oil spill response and search and rescue operations.

HLA class II and response to interferon-beta in multiple sclerosis

OBJECTIVE

To study the relationship between human leucocyte antigen (HLA) genotype and clinical response to interferon-beta (IFN-beta).

METHODS

We analysed the HLA class II genotypes of 96 multiple sclerosis (MS) patients treated with IFN-beta. The patients were classified as responders or non-responders according to clinical criteria: one or more relapses or a sustained increase after 1 year treatment compared with the year prior to IFN-beta therapy of > or = 0.5 points on the Expanded Disability Status Scale (EDSS).

RESULTS

There were 66 (69%) responders and 30 (31%) non-responders. Baseline clinical characteristics were similar. We found no association between HLA class II alleles and clinical response to IFN-beta.

CONCLUSIONS

HLA genotype does not appear to influence the clinical response to IFN-beta in MS patients.

Screening test for preeclampsia through assessment of uteroplacental blood flow and biochemical markers of oxidative stress and endothelial dysfunction

OBJECTIVE

This study was undertaken to evaluate whether screening through a uterine artery (UtA) Doppler and biochemical markers of oxidative stress and endothelial dysfunction predict preeclampsia.

STUDY DESIGN

UtA Doppler was performed at 11 to 14 and 22 to 25 weeks on 1447 asymptomatic pregnant women. Oxidative stress, endothelial dysfunction, and antiangiogenic state were assessed in women who later developed preeclampsia and normotensive controls.

RESULTS

There was a significantly increased of UtA pulsatility index (PI), plasma levels of soluble fms-like tyrosine kinase 1 (sFlt1), PAI-1/PAI-2 ratio, and F-2 isoprostane in women who subsequently developed preeclampsia compared with control pregnancies. Multivariate logistic regression showed that increased UtA PI performed at 23 weeks was the best predictor for preeclampsia.

CONCLUSION

This study demonstrates early changes in markers of impaired placentation, antiangiogenic state, oxidative stress, and endothelial dysfunction suggesting that these derangements may play a role in the pathogenesis of preeclampsia. Our data point to UtA as the best test to predict preeclampsia at 23 weeks of gestation.

Redox up-regulated expression of rat liver manganese superoxide dismutase and Bcl-2 by thyroid hormone is associated with inhibitor of kappaB-alpha phosphorylation and nuclear factor-kappaB activation

Recently, we demonstrated that 3,3',5-triiodothyronine (T3) induces oxidative stress in rat liver, with enhancement in the DNA binding of nuclear factor-kappaB (NF-kappaB) and the NF-kappaB-dependent expression of tumor necrosis factor-alpha (TNF-alpha). In this study, we show that T3 administration (daily doses of 0.1 mg/kg i.p. for three consecutive days) elicited a calorigenic response and higher liver O2 consumption rates, with increased serum levels of TNF-alpha (ELISA), liver inhibitor of kappaB (IkappaB-alpha) phosphorylation (Western blot analysis), and hepatic NF-kappaB DNA binding (EMSA) at 56-72 h after treatment. Within this time interval, liver manganese superoxide dismutase (MnSOD) activity and the protein expression of MnSOD and Bcl-2 are enhanced. These changes are abrogated by the administration of alpha-tocopherol (100 mg/kg i.p.) prior to T3. It is concluded that T3 treatment leads to the redox upregulation of MnSOD and Bcl-2 in rat liver, in association with TNF-alpha release and activation of the IkappaB-alpha kinase/NF-kappaB cascade, which may constitute a protective mechanism against free radical toxicity involving cell death signaling.

Redox regulation of thyroid hormone-induced Kupffer cell-dependent IkappaB-alpha phosphorylation in relation to inducible nitric oxide synthase expression

Thyroid hormone-induced calorigenesis promotes oxidative stress in the liver with higher respiratory burst activity in Kupffer cells, which could increase the expression of redox-sensitive genes. Our aim was to test the hypothesis that L-3,3',5-triiodothyronine (T3) triggers inducible nitric oxide synthase (iNOS) expression in rat liver by upstream mechanisms involving the inhibitor of kappa (Ikappa) kinase activation. T3 administration (daily doses of 0.1 mg/kg for three consecutive days) induced a calorigenic response, with maximal increases in the content of hepatic thiobarbituric acid reactants or protein carbonyls and NOS activity at 48-72 h after treatment, compared to control values. In this time interval, the serum levels of tumor necrosis factor-alpha (TNF-alpha; ELISA) are enhanced, concomitantly with higher liver IkappaB-alpha phaphosphorylation (Western blot analysis), NF-kappaB DNA binding (electrophoretic mobility shift assay), and iNOS mRNA expression (reverse transcription-polymerase chain reaction). These changes and the increase in hepatic NOS activity are abolished by the administration of either alpha-tocopherol (100 mg/kg) or the Kupffer cell inactivator gadolinium chloride (10 mg/kg) prior to T3. It is concluded that T3-induced oxidative stress triggers the redox upregulation of liver iNOS expression through a cascade initiated by TNF-a produced by Kupffer cells and involving Ikappa-alpha phosphorylation and NF-kappaB activation, a response that may represent a defense mechanism by protecting the liver from cytokine-mediated lethality and ROS toxicity.

Chronic iron overload enhances inducible nitric oxide synthase expression in rat liver

Iron is an essential micronutrient promoting oxidative stress in the liver of overloaded animals and human, which may trigger the expression of redox-sensitive genes. We have tested the hypothesis that chronic iron overload (CIO) enhances inducible nitric oxide synthase (iNOS) expression in rat liver by extracellular signal-regulated kinase (ERK1/2) and NF-kappaB activation. CIO (diet enriched with 3%(wt/wt) carbonyl-iron for 12 weeks) increased liver protein carbonylation and decreased reduced glutathione (GSH) content and the GSH/GSSG ratio after 6 weeks, parameters that are normalized after 8-12 weeks of treatment. These changes are paralleled by higher phosphorylated-ERK1/2 to non-phosphorylated-ERK1/2 ratios at 6 and 8 weeks, increased NF-kappaB DNA binding to the iNOS gene promoter at 8-12 weeks, and higher iNOS mRNA expression and activity at 8 and 12 weeks. It is concluded that CIO triggers liver oxidative stress at early times, with upregulation of iNOS expression involving the ERK/NF-kappaB pathway at later times, a finding that may represent a hepatoprotective mechanism against CIO toxicity in addition to the recovery of GSH homeostasis.

Pathophysiological basis for the prophylaxis of preeclampsia through early supplementation with antioxidant vitamins

Preeclampsia (PE) is a multisystem disorder that remains a major cause of maternal and foetal morbidity and death. To date, no treatment has been found that prevents the development of the disease. Endothelial dysfunction is considered to underlie its clinical manifestations, such as maternal hypertension, proteinuria, and edema; however, the precise biochemical pathways involved remain unclear. A current hypothesis invokes the occurrence of oxidative stress as pathogenically important, as suggested by the fact that in PE, the placental and circulating levels of lipid peroxidation products (F2-isoprostanes and malondialdehyde [MDA]) are increased and endothelial cells are activated. A potential mechanism for endothelial dysfunction may occur via nuclear transcription factor kappa B (NF-kappaB) activation by oxidative stress. Alternatively, the idea that the antiangiogenic placental soluble fms-like tyrosine kinase 1 factor (sFlt1) is involved in the pathogenesis of this disease is just emerging; however, other pathophysiological events seem to precede its increased production. This review is focused on evidence providing a pathophysiological basis for the beneficial effect of early antioxidant therapy in the prevention of PE, mainly supported by the biological effects of vitamins C and E.

Prevalence and risk factors associated with the metabolic syndrome and dyslipidemia in White, Black, Amerindian and Mixed Hispanics in Zulia State, Venezuela

Studies have highlighted the association between insulin resistance (IR) and several cardiovascular (CV) risk factors, including hypertension (HTN), obesity, dyslipidemia (i.e. high triglyceride and low HDL-cholesterol) and glucose intolerance, in a cluster known as the metabolic syndrome (MS). There are few data on the frequency of the MS and dyslipidemia in developing countries, and none in South America. To estimate the prevalence of the MS and its components in Zulia State, Venezuela, and to establish associated demographic and clinical factors, we evaluated 3108 Hispanic men and women aged 20 years or older from a cross-sectional survey of a random representative sample from each health district in Zulia State, Venezuela (1999-2001). Prevalence of the MS and dyslipidemia was defined according to the National Cholesterol Education Program (NCEP)/Adult Treatment Panel III (ATP III) criteria. The age-adjusted prevalence of MS and dyslipidemia was 31.2% and 24.1%, respectively, with higher rates in men than in women. Prevalence rates increased with age and with the degree of obesity. MS prevalence was lower in Amerindian (17.%) compared to Black (27.2%), White (33.3%) and Mixed (37.4%) men, but no differences were found among women. Overall, low HDL-cholesterol (65.3%), abdominal obesity (42.9%) and HTN (38.1%) were the most frequent MS components. After adjusting for age, sex and race groups, family history of diabetes, obesity and HTN were associated with the MS. Sedentary lifestyle also increased the risk of MS, event after adjusting for the same covariates, obesity and the degree of IR. These results suggest that MS is found in approximately one-third of the Venezuelan adult population in Zulia State, with higher prevalence in men related to the presence of dyslipidemia. Lifestyle interventions in MS subjects are needed in Venezuela to halt the burden of CV disease and diabetes.

Checkpoint kinase 1 (CHK1) protein and mRNA expression is downregulated in aggressive variants of human lymphoid neoplasms

CHK1: gene encodes for a serine/threonine kinase involved in the regulation of cell cycle progression and DNA damage checkpoints. To determine the role of CHK1 in the pathogenesis of lymphoid neoplasms and its relationship to other DNA damage response genes, we have analyzed the gene status, protein, and mRNA expression in a series of tumors and nonneoplastic lymphoid tissues. CHK1 protein and mRNA expression levels were very low in both reactive tissues and resting lymphoid cells, whereas tumor samples showed a variable pattern of expression related to their proliferative activity. However, seven aggressive tumors showed a dissociate pattern of extremely low or negative protein expression in spite of a high proliferative activity. Four of these tumors were diffuse large B-cell lymphomas (DLCLs) with concordant reduced levels of mRNA, whereas one blastoid mantle cell lymphoma (B-MCL) and two DLCLs had relatively normal levels of mRNA. No gene mutations, deletions, or hypermethylation of the promoter region were detected in any of these cases. In all these tumors ATM, CHK2, and p53 genes were wild type. These findings suggest that CHK1 inactivation in NHLs occurs by loss of protein expression in a subset of aggressive variants alternatively to ATM, CHK2, and p53 alterations.

Azathioprine and methotrexate in multiple sclerosis

Evidence for the effectiveness of immunosuppressive agents in MS is scanty. There are few good quality trials; most have methodological limitations, such as a small sample size and short duration. Moreover, there is no consistency in treatment regimes, patient groups or outcome measures and the clinical benefits remain unclear. Although azathioprine appears to reduce the relapse rate in MS patients, its effect on disability progression has not been demonstrated. Methotrexate may alter the course of disease favourably in patients with progressive MS, but the evidence is again sparse.

[Treatment with tacrolimus in autoimmune diseases]

Tacrolimus is an immunosuppressive drug used most successfully as a primary drug to suppress the rejection of transplants. Tacrolimus may also be useful as a novel therapy for autoimmune disease. There are various reports in the bibliography about the use of tacrolimus in the treatment of some autoimmune diseases: inflammatory bowel disease, autoimmune hepatitis, cutaneous, neurologic, renal, endocrine or eye disease. In this review of more than 130 papers, we discuss the rationale for the use of tacrolimus in autoimmune disease and report the clinical experience with the drug in the management of a variety of autoimmune diseases. But, although there are a lot questions that require future research (dose, duration of treatment, when to begin tacrolimus treatment, how to monitor it, etc.), there is also wide experience with tacrolimus in the treatment of this type of disease.

The effect of expression levels on codon usage in Plasmodium falciparum

The usage of alternative synonymous codons in the completely sequenced, extremely A+T-rich parasite Plasmodium falciparum was studied. Confirming previous studies obtained with less than 3% of the total genes recently described, we found that A- and U-ending triplets predominate but translational selection increases the frequency of a subset of codons in highly expressed genes. However, some new results come from the analysis of the complete sequence. First, there is more variation in GC3 than previously described; second, the effect of natural selection acting at the level of translation has been analysed with real expression data at 4 different stages and third, we found that highly expressed proteins increment the frequency of energetically less expensive amino acids. The implications of these results are discussed.

DQB1*0602 allele shows a strong association with multiple sclerosis in patients in Malaga, Spain

BACKGROUND

The human leukocyte antigen (HLA) class II DR2 haplotype (DRB1*1501, DQA1*0102, DQB1*0602) has been associated with multiple sclerosis (MS) in all ethnic groups and very strongly in Caucasians.

AIM

To investigate the possible HLA class II (DRB1, DQA1 and DQB1) associations with MS in Malaga, southern Spain.

METHODS

We analysed the HLA class II sub-regions DRB1, DQA1 and DQB1 by polymerase chain reaction (PCR) and sequence-specific oligonucleotide probe hybridization (PCR/SSO) for DRB1 and DQB1 and with sequence-specific primers (PCR/SSP) for DRB1 subtypes and DQA1. Possible HLA class II associations with clinical MS characteristics were investigated in 149 subjects with and 160 without MS.

RESULTS

Associations were detected between MS and the HLA class II alleles DRB1*1501 (45.6 % vs. 21.3%, p=0.001), DQA1*0102 (44% vs. 29.4%, p=0.001) and DQB1*0602 (45% vs. 20.6%, p=0.001). The DR2 haplotype (DRB1*1501, DQA1*0102, DQB1*0602) was associated with MS (43.6 % vs. 20%, p=0.002). DQB1*0602 was the only allele that maintained an association with MS in a logistic regression model. No HLA class II alleles or genotypes were significantly associated with any clinical characteristics of MS.

CONCLUSIONS

Our results confirm the positive association of the DR2 haplotype with MS, particularly the allele DQB1*0602, in the population studied. DR4 was not associated with the disease in Malaga. HLA class II alleles or haplotypes were not associated with clinical or demographic characteristics, or clinical form or severity of MS.

Effects of acute gamma-hexachlorocyclohexane intoxication in relation to the redox regulation of nuclear factor-kappaB, cytokine gene expression, and liver injury in the rat

gamma-Hexachlorocyclohexane-induced hepatotoxicity is associated with oxidative stress. We tested the hypothesis that gamma-hexachlorocyclohexane triggers the redox activation of nuclear factor-kappaB (NF-kappaB), leading to proinflammatory cytokine expression. Liver NF-kappaB activation (electrophoretic mobility shift assay), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1alpha (IL-1alpha) mRNA expression (reverse transcription-polymerase chain reaction), and their serum levels (enzyme-linked immunosorbent assay) were measured at different times after gamma-hexachlorocyclohexane treatment (50 mg/kg). The relationship between these and hepatic O(2) uptake, glutathione and protein carbonyl levels, and sinusoidal lactate dehydrogenase (LDH) efflux in liver perfusion studies was determined. gamma-Hexachlorocyclohexane increased liver NF-kappaB DNA binding at 14-22 h after treatment, concomitantly with significant glutathione depletion and an increase in the rate of O(2) consumption, the content of protein carbonyls, and the sinusoidal LDH efflux. In these conditions, the expression of TNF-alpha and IL-1alpha is enhanced, with maximal increases in their respective mRNA content and serum levels of the cytokines being elicited at 18 h after gamma-hexachlorocyclohexane treatment. All these changes are suppressed by the administration of alpha-tocopherol (100 mg/kg) or the Kupffer cell inactivator gadolinium chloride (10 mg/kg) prior to gamma-hexachlorocyclohexane. gamma-Hexachlorocyclohexane-induced TNF-alpha levels in serum are suppressed by pretreatment with an antisense oligonucleotide (ASO TJU-2755; daily doses of 10 mg/kg for 2 days) targeting the primary transcript for the cytokine, whereas those of IL-1alpha are not modified. It is concluded that gamma-hexachlorocyclohexane-induced liver oxidative stress triggers the DNA binding activity of NF-kappaB, with the consequent increase in the expression of NF-kappaB-dependent genes for TNF-alpha and for IL-1alpha, factors that may mediate the hepatotoxicity of the insecticide.

Effects of gamma-hexachlorocyclohexane and L-3,3',5-triiodothyronine on rat liver cytochrome P4502E1-dependent activity and content in relation to microsomal superoxide radical generation

Liver microsomal cytochrome P4502E1-dependent p-nitrophenol (PNP) hydroxylation and expression of cytochrome P4502E1 were studied in rats subjected to gamma-hexachlorocyclohexane (HCCH) or L-3,3,5-triiodothyronine (T3) administration as a possible mechanism contributing to superoxide radical (O2.-) generation. HCCH treatment (a single dose of 40 mg/kg body wt) produced a 43% increase in the content of total cytochrome P450, whereas T3 (daily doses of 0.1 mg/kg body wt for two consecutive days) led to a 37% decrease. NADPH-dependent O2.- generation was elevated by HCCH and T3, expressed as either per mg of protein or per nmol of cytochrome P450, with a 135% enhancement in the O2.- production/superoxide dismutase (SOD) activity ratios being observed in both conditions. This was partly due to depression of SOD activity. Concomitantly, the molecular activity of NADPH-cytochrome p450 reductase was enhanced by 90 and 69% by HCCH and T3, respectively. In these conditions, microsomal PNP hydroxylation showed increases of 58 and 45% in HCCH- and T3-treated rats over control values, respectively, with a parallel 31% (HCCH) and 41% (T3) enhancement in the content of cytochrome P4502E1 assessed by western immunoblotting. We conclude that HCCH and T3 enhance the expression and activity of cytochrome P4502E1 and that of NADPH-cytochrome P450 reductase in rat liver, regardless of the changes in total cytochrome P450 content, representing major contributory mechanisms to microsomal NADPH-dependent O2.- generation.

[Levels of apoproteins B, A1 and CIII as markers for cardiovascular risk in lean and obese adolescents]

Cardiovascular disease is a significant health problem affecting the adult population. Because atherosclerosis may begin in childhood, the aim of the present study was to identify biochemical markers for cardiovascular risk at an early stage of life. We studied 79 adolescents (48 girls and 31 boys) whose ages ranged from 13 to 17 years. A medical history (including pubertal stage by Tanner) was obtained from each subject. Anthropometric assessment was established by height, weight, body mass index (BMI), waist and hip circumferences, skinfolds, centrality index and obesity index. After a 12-h fast, basal blood glucose levels, total cholesterol, triglycerides, LDL-C and HDL-C were determined by enzymatic methods, mean basal insulin levels by radio immunoassays and apo A1, B, CIII by turbidimetric immunoassays. According to the BMI and taking 25 Kg/m2 as the cutoff value, 35% of the girls and 16% of the boys were obese. Eighty-five percent of the girls and 58% of the boys were hyperinsulinemic (basal insulin > 12 uU/ml). Circumferences, skinfolds, centrality and obesity index were higher (p < 0.05) in boys than in girls. In both, boys and girls, basal insulin levels were higher than the cutoff insulin value for our lab (>12 microU/ml), with the girls having higher insulin levels than the boys. Apo A1 was negatively associated with the obesity index and positively with HDL-C. Apo B was related to total cholesterol and LDL-C. Apo CIII was associated with basal insulin levels, triglycerides and VLDL-C. Our results suggest that apo CIII might be a good marker for higher insulin levels, insulin resistance and cardiovascular risk in adolescents.

Effects of acute lindane intoxication and thyroid hormone administration in relation to nuclear factor-κB activation, tumor necrosis factor-α expression, and Kupffer cell function in the rat

Nuclear factor-kappaB (NF-kappaB) DNA binding, tumor necrosis factor-alpha (TNF-alpha) expression, and parameters related to liver oxidative stress and Kupffer cell function were assessed in control rats and in animals given 3,3',5-triiodothyronine (T3) (0.1 mg T3/kg) and/or lindane (50 mg/kg; 4 h after T3). Liver NF-kappaB DNA binding and serum TNF-alpha levels were enhanced by the combined T3-lindane administration after 16-22 h, effects that were lower than those elicited by the separate treatments and coincided with increased hepatic TNF-alpha mRNA levels. Thyroid calorigenesis occurred independently of lindane, whereas T3, lindane and T3-lindane groups showed liver glutathione (GSH) depletion, with higher protein carbonyl levels in lindane and T3-lindane groups. Carbon-induced O2 consumption/carbon uptake ratios were not altered by T3 or lindane compared to controls, whereas combined T3-lindane administration elicited a 92% diminution with enhancement in the sinusoidal efflux of lactate dehydrogenase (LDH). In conclusion, depression of T3- or lindane-induced liver NF-kappaB activation and TNF-alpha expression occurred after their combined treatment, effects that correlate with the impairment of the respiratory burst activity of Kupffer cells and exacerbation of liver injury.

Polymorphisms in candidate genes for type 2 diabetes mellitus in a Mexican population with metabolic syndrome findings

The metabolic or insulin resistance syndrome, characterized by hypertension, dyslipidemia, glucose intolerance and hyperinsulinemia, may have genetic determinants. The insulin gene (INS), insulin receptor gene (INSR) and insulin receptor substrate 1 gene (IRS1) have been proposed as candidate genes. We examined eight polymorphisms in these genes in 163 individuals from Yucatan, Mexico; this population has a high prevalence of obesity, type 2 diabetes mellitus and dyslipidemia. Subjects were evaluated for body mass index (BMI) and blood pressure. Blood samples were collected to determine glucose, insulin, triglycerides and cholesterol levels, as well as for DNA isolation. Restriction fragment length polymorphisms in INS, INSR and IRS1 were identified by polymerase chain reaction and digestion with selected restriction enzymes. Among the eight polymorphisms analyzed, the PstI polymorphism in INS was significantly associated with hypertriglyceridemia and with the presence of at least one abnormality related to the metabolic syndrome (P=0.007 and 0.004, respectively). The MaeIII polymorphism in INS was associated with fasting hyperinsulinemia (P=0.045). In multilocus analyses including both INS polymorphisms, significant associations were seen with hypertriglyceridemia (P=0.006), hypercholesterolemia (P=0.031) and with presence of at least one metabolic abnormality (P=0.009). None of the polymorphisms in INSR or IRS1 was associated with any of these traits. These findings suggest that the insulin gene may be an important determinant of metabolic syndrome, and particularly of dyslipidemia, in this population.

Oxidative stress-mediated hepatotoxicity of iron and copper: role of Kupffer cells

Iron- or copper-mediated catalysis leads to the generation of reactive oxygen species (ROS) that can attack biomolecules directly, with the consequent enhancement in membrane lipid peroxidation, DNA damage, and protein oxidation. Reactive nitrogen species (RNS) can also be formed, leading to nitration of aromatic structures in addition to the oxidative deterioration of cellular components. Kupffer cells, the resident macrophages of the liver, play significant roles in immunomodulation, phagocytosis, and biochemical attack. Upon stimulation, liver macrophages release biologically active products related to cell injury, namely, ROS, RNS, and both immunomodulatory and fibrogenic cytokines, with production of chemokines and adhesion molecules by other cells of the liver sinusoid. Iron and copper alter the functional status of Kupffer cells by enhancing their respiratory burst activity without modifying particle phagocytosis. This effect is probably due to extra O2 equivalents used in the oxidation of biomolecules and/or in the activating action of iron/copper on nitric oxide synthase, in addition to those employed by NADPH oxidase activity. Changes in gene expression of Kupffer cells may also be accomplished by iron and copper through modulation of the activity of transcription factors such as NF-kappaB, which signals the production of cytotoxic, proinflammatory, or fibrogenic mediators. Thus, iron/copper-induced hepatotoxicity is a multifactorial phenomenon underlying actions due to the generation of ROS and RNS that may alter essential biomolecules with loss of their biological functions, modulate gene expression of Kupffer cells with production of cytotoxic mediators, or both.

Thyroid hormone-induced oxidative stress triggers nuclear factor-kappaB activation and cytokine gene expression in rat liver

Nuclear factor-kappaB (NF-kappaB) is a redox-sensitive factor responsible for the transcriptional activation of cytokine-encoding genes. In this study, we show that 3,3,5-triiodothyronine (T(3)) administration to rats activates hepatic NF-kappaB, as assessed by electrophoretic mobility shift assay. This response coincides with the onset of calorigenesis and enhancement in hepatic respiration, and is suppressed by the antioxidants alpha-tocopherol and N-acetylcysteine or by the Kupffer cell inactivator gadolinium chloride. Livers from hyperthyroid rats with enhanced NF-kappaB DNA-binding activity show induced mRNA expression of the NF-kappaB-responsive genes for tumor necrosis factor-alpha (TNF-alpha) and interleukin- (IL-) 10, as evidenced by reverse transcription-polymerase chain reaction assay, which is correlated with increases in the serum levels of the cytokines. T(3) also increased the hepatic levels of mRNA for IL-1alpha and those of IL-1alpha in serum, with a time profile closely related to that of TNF-alpha. It is concluded that T(3)-induced oxidative stress enhances the DNA-binding activity of NF-kappaB and the NF-kappaB-dependent expression of TNF-alpha and IL-10 genes.