Juan José Hicks

METFORMIN, ARTERIAL FUNCTION, INTIMA-MEDIA THICKNESS AND NITROXIDATION IN METABOLIC SYNDROME: THE MEFISTO STUDY

1 Metabolic syndrome (MS) is one of the greatest public health problems in Mexico, where more than 75% of adults in urban populations are overweight or obese. Metabolic syndrome has several comorbidities, which result in a high cardiometabolic risk. 2 Some of the vasopathogenic phenomena in MS are caused by nitroxidant stress, secondary to cardiometabolic dysfunction. 3 The action of metformin to diminish or control MS remains a matter of debate. 4 In the present study, 60 patients with at least three diagnostic criteria for MS were divided into two groups. Both groups received similar dietary counselling, but one group was given 850 mg metformin daily. 5 The variables assessed were body mass index, waist circumference, systolic and diastolic blood pressures (SBP and DBP, respectively), total cholesterol (TC), high‐ and low‐density lipoprotein–cholesterol, triglycerides (TG), fasting glucose, nitroxidant metabolites (free carbonyls, malondialdehyde, dityrosines and advanced oxidative protein products (AOPP)), nitric oxide (NO), carotid vascular stiffness, carotid intima–media thickness (IMT) and C‐reactive protein (CRP). 6 After 1 year follow up, both groups reported weight loss, as well as decreases in waist circumference, SBP and DBP. 7 Patients on metformin exhibited reductions in TC and IMT and there were marked changes in nitroxidation: levels of carbonyls, dityrosines and AOPP were reduced, whereas those of NO were increased, indicating better endothelial function. In addition, in patients given metformin, CRP levels decreased. 8 In conclusion, metformin has a considerable beneficial effect on nitroxidation, endothelial function and IMT in patients with MS.

Airborne particulate matter PM2.5 from Mexico City affects the generation of reactive oxygen species by blood neutrophils from asthmatics: an in vitro approach

BackgroundThe Mexico City Metropolitan Area is densely populated, and toxic air pollutants are generated and concentrated at a higher rate because of its geographic characteristics. It is well known that exposure to particulate matter, especially to fine and ultra-fine particles, enhances the risk of cardio-respiratory diseases, especially in populations susceptible to oxidative stress. The aim of this study was to evaluate the effect of fine particles on the respiratory burst of circulating neutrophils from asthmatic patients living in Mexico City.MethodsIn total, 6 subjects diagnosed with mild asthma and 11 healthy volunteers were asked to participate. Neutrophils were isolated from peripheral venous blood and incubated with fine particles, and the generation of reactive oxygen species was recorded by chemiluminescence. We also measured plasma lipoperoxidation susceptibility and plasma myeloperoxidase and paraoxonase activities by spectrophotometry.ResultsAsthmatic patients showed significantly lower plasma paraoxonase activity, higher susceptibility to plasma lipoperoxidation and an increase in myeloperoxidase activity that differed significantly from the control group. In the presence of fine particles, neutrophils from asthmatic patients showed an increased tendency to generate reactive oxygen species after stimulation with fine particles (PM2.5).ConclusionThese findings suggest that asthmatic patients have higher oxidation of plasmatic lipids due to reduced antioxidant defense. Furthermore, fine particles tended to increase the respiratory burst of blood human neutrophils from the asthmatic group.On the whole, increased myeloperoxidase activity and susceptibility to lipoperoxidation with a concomitant decrease in paraoxonase activity in asthmatic patients could favor lung infection and hence disrupt the control of asthmatic crises.

Pro-oxidating properties of melatonin in the in vitro interaction with the singlet oxygen.

In an aqueous system, the oxidation of the erythrocyte membrane by the singlet oxygen formed during the photoactivation of the rose bengal coloring was examined. The effects of the singlet oxygen on lipids and proteins were studied through the simultaneous quantification of peroxidation products, lipoperoxides and carbonyl groups, the oxidation of protein SH groups and the activity of the glyceraldehyde 3-phosphate dehydrogenase (G3PD) associated with the erythrocyte membrane. The antioxidant activity of melatonin was tested and compared to that of two antioxidants in extreme cases of hydrosolubility, ascorbate and beta-carotene, with the purpose of comparing the protective ability of melatonin against singlet oxygen. The results show the expected effect even at low (0.125-0.75 mM; 0.015-0.90 mM, respectively) for ascorbate and beta-carotene, antioxidants known to possess important antioxidant qualities against singlet oxygen. It is shown that melatonin, under the conditions described, and at the concentrations at which the other two compounds are efficacious, not only confers little antioxidant protection, but that a pro-oxidant tendency was proven both on lipids and proteins, as well as on G3PD enzymatic activity. The results show that the antioxidant protective effect that melatonin can exert on biological systems is probably not by a direct interaction with oxidant species, but probably, as has been previously proposed, through the regulation of antioxidant defense systems. The formation of secondary oxidation products, such as melatonin-derived endoperoxides, may explain the evidence found on pro-oxidant qualities of this molecule.

Inhibition of human sperm motility by calcium and zinc ions

Abstract Calcium and zinc chloride were effective in impairing the motility and viability of human spermatozoa at high molar concentrations. The effect of these ions on several enzymatic activities and on oxygen uptake was measured in order to explain the mechanism by which immobilization was produced. The possibility of using these salts in fertility regulation is suggested.

Uterine glutathione reductase activity: modulation by estrogens and progesterone.

The aim of this study was to determine whether glutathione reductase activity in uterine tissue is regulated by sex hormones. In spayed rats uterine glutathione reductase was significantly increased by exogenous estrogen (P< 0.01), progesterone (P< 0.01) or estrogen plus progesterone (P<0.01). When enzyme activity is expressed per mg protein, daily administration of estrogen or progesterone induces a progressive increase of this enzyme between 24 to 48 h or 24 to 72 h of treatment, respectively. Whereas the combination of both steroids causes an earlier and higher increase in glutathione reductase activity at 24 h of treatment. Estradiol singly or in combination with progesterone induced the highest protein concentration in the uterus. Whereas uterine DNA concentration is only significantly affected by estradiol. Our results suggest that uterine glutathione reductase is regulated by estradiol and progesterone and may be involved in maintaining levels of reduced glutathione in the uterus. This compound may be required for control of the redox state of thiol groups and in detoxification reactions involving H2O2 and electrophylic substances. The antioxidant action of estrogens is partially due to the stimulation of glutathione reductase.

Inhibition of implantation by intraluminal administration of concanavalin A in mice

Important characteristics of endometrial implantation sites are the changes of polarity and molecular composition of the cellular surface. For this reason the masking of surface carbohydrates could lead to an inhibition of the recognition by the blastocyst of the endometrial implantation site. Considering the impact of lectins on carbohydrates, we decided to utilize the intraluminal administration (5 microliter) of different concentrations of concanavalin A (15-60 microgram) in pregnant female mice in the preimplantation phase. An inhibition of 100% of implantation wqs obtained with concentrations of 30 and 60 microgram of the lectin administered on days 3 and 4 of the pregnancy (P less than 0.001). Less important effects were observed on administering 15 or 20 microgram of the lectin (73 and 87% of inhibition) and on utilizing the different doses on days 1 and 2 of the pregnancy. Thus, we conclude that the egg must recognize certain molecules of the endometrial surface (alpha-D-mannopyranose and alpha-D-glucopyranose) in order to implant and that the making of these sites potentially constitutes a new contraceptive approach.

Cyclic-amp receptors in the human spermatozoa membrane

Abstract The binding properties of cyclic-AMP to human spermatozoa were studied. Incubation of whole human spermatozoa and of head and tail fractions with 14 C-cyclic AMP induced the binding of 7.8 ± 0.86 pmoles of the nucleotide per 5 × 10 7 sperm cells showing an intrinsic association constant of 15 × 10 −8 M. No significant inhibition of cyclic-AMP binding was caused by the addition of one hundred fold excess of AMP. However, when the excess AMP reached a thousand fold a slight but significant reduction (10%) was observed. These values were not modified by using sperm homogenates instead of intact sperm cells, which suggested that cyclic-AMP binding is to surface membranes and not to protein released from broken or damaged sperm. Binding was found to be unrelated with pH, between 6 to 8, but depended on the temperature of the incubation medium, showing a maximum at 20°C. The blocking of membrane sulfhydryl groups significantly inhibited (48%) cyclic-AMP binding to sperm cells.

Increased platelet and erythrocyte arginase activity in chronic obstructive pulmonary disease associated with tobacco or wood smoke exposure.

Background Chronic obstructive pulmonary disease (COPD) is an inflammatory disease that is characterized by a progressive and irreversible decline in lung function and is caused primarily by chronic exposure to tobacco and to wood smoke. It is linked to oxidative stress and to an up-regulation of airway arginases and is also associated with alterations in platelets and erythrocytes. In the present study, arginase activity was studied in platelets and erythrocytes of 2 groups of COPD patients: 31 tobacco ex-smokers and 27 patients who had been exposed to wood smoke. A total of 15 healthy controls were also included. Methods Plasma, platelets, and erythrocytes were obtained from the blood samples. Levels of the oxidative stress biomarkers, carbonyls and malondialdehyde, were measured in the plasma, and arginase activity was quantified in platelets and erythrocytes. Results In both groups of COPD patients, an increase in the oxidative stress biomarkers was found. Platelet arginase activity in both COPD groups was 2-fold higher than that in the control group. In the erythrocytes, the arginase activity increased 1.7-fold over the control only in the wood smoke-induced COPD group. Discussion and Conclusions These results suggest that the increase in arginase activity in platelets and erythrocytes participates in the alteration in nitric oxide metabolism in COPD patients and that there may be some differences between the tobacco smoke- and wood smoke-induced COPD.

Oxidation by reactive oxygen species (ROS) alters the structure of human insulin and decreases the insulin-dependent D-glucose-C14 utilization by human adipose tissue.

The formation of dityrosine of human insulin oxidized by metal-catalyzed oxidation system (H2O2/Cu) was estimated by fluorescent methods. The oxidation of tyrosine and phenylalanine residues present on the insulin molecule was evident after 2 minutes of in vitro oxidation due to the formation of protein-bound dityrosine. The success of oxidative protein modification was followed until available aromatic residues were consumed (60 minutes), measured by their emission at 405 nm. The structural and chemical changes on insulin molecule are related to the loss of biological activity as assessed by measuring the increase of U-14C-glucose utilization by human adipose tissue in a radiorespirometry system. The oxidation of glucose (14CO2 production) of the adipose cells was increased 35 % (301 +/- 119 to 407 +/- 182 cpm/mg in dry weight. P < 0.05) in presence of 0.1 IU and 69 % (301 +/- 119 to 510 +/- 266 cpm/dry weight. P < 0.05) for 1.0 IU of insulin. The recombinant human insulin oxidized for 5 minutes only increased the glucose oxidation by 25 %. In conclusion, these observations show that dityrosine formation and other oxidative chemical changes of insulin due to its in vitro oxidation decrease and can abolish its biological activity.

Comparative Glycolytic Metabolism of Sperm from Normal, Asthenospermic, and Oligoasthenospermic Men *

The glycolysis of spermatozoa from normal, asthenospermic, and oligoasthen ospermic men was studied using a respirometry technique to measure glucose utilization by the production of 14CO2 from glucose 14C (U-L). Lactate and pyruvate were measured by a spectrophotometric method using DNA as reference. Human spermatozoa preferred glucose to fructose as the glycolytic substrate when concentrations of these hexoses did not exceed normal concentrations in the blood. Spermatozoa from oligoasthenospermic men produced an average of 3.5 times more 14CO2 (345, 457 dpm/mg DNA/hour) than did spermatozoa from asthenospermic (88,837 dpm/mg DNA/hour) and normal men (96,595 dpm/mg DNA/hour). They also formed four times more lactate (9.63 mumoles/mg DNA/hour) than spermatozoa from normal men (2.33 mumoles/mg DNA/hour) and 6.4 times more pyruvate (2.90 mumoles/mg DNA/hour compared to 0.45 mumoles/mg DNA/hour). Spermatozoa from asthenospermic men formed amounts of lactate (3.01 mumoles/mg DNA/hour) and pyruvate (0.63 mumoles/mg DNA/hour) similar to those produced by spermatozoa from normal men.