Alfredo Hager

Zinc as an essential micronutrient : A review

Zinc is one of the most important essential tracer metals of human nutrition, and its deficiency is a world nutritional problem. This work compiles past and present information about the role of zinc in human health.

Zinc and diabetes mellitus: is there a need of zinc supplementation in diabetes mellitus patients?

Diabetes mellitus is a group of metabolic disorders, the incidence of which varies widely throughout the world. The treatment of diabetes mellitus includes insulin, oral antidiabetic agents, and dietary regimens. Although the emphasis is on macronutrients intakes, there is strong evidence that there is an abnormal metabolism of several micronutrients in diabetic individuals. Zinc is one of the essential micronutrients of which status and metabolism is altered in this condition. This work is a short review about the close relation among zinc, glucose metabolism, and insulin physiology, as well as about the few experimental data about zinc absorption and zinc supplementation in diabetes mellitus patients.

Zinc Status and Immune System Relationship A Review

The essentiality of zinc for humans was first documented by Prasad in the 1960s. The main clinical manifestations associated with zinc deficiency are growth retardation, hypogonadism, diarrhea, and increased susceptibility to infectious diseases. Thus, in the past 25 yr, there was an increased interest of researchers in studying the role of zinc in human immunity. Although mechanistic research has been carried out using animal models, there are several studies in humans with similar results. This work is an attempt to review the information available in this field to understand the important role that zinc plays in the normal development and function of the immune system.

OXIDATIVE DAMAGE, PLASMA ANTIOXIDANT CAPACITY, AND GLUCEMIC CONTROL IN ELDERLY NIDDM PATIENTS

A study of oxidative damage was made in elderly noninsulin-dependent diabetes mellitus (NIDDM) patients. A statistically significant increase in glucose and fructosamine was found in fasting NIDDM patients, as well as an increase in the oxidation induced by tert-butyl hydroperoxide. The Total Reactive Antioxidant Potential (TRAP) of the plasma was much reduced (p < .02) and the uricemia was unchanged. The erythrocytes of diabetic patients show greater basal oxidation products (p < .05), and the susceptibility of the diabetic erythrocytes to oxidation injury was also shown to increase in the oxidation induced by t-BOOH (p < .05). Linear regression studies showed that TRAP was associated directly with uric acid (p < .05) and inversely with fructosamine and with glucose (p < .03 and p < .05 respectively) in patients with NIDDM, but not in the controls. The levels of fructosamine were found to be related to the basal damage of the red blood cells (direct correlation, p < .001). This study suggest an useful approach to diabetic oxidative stress for clinical settings.

Bioavailability, biodistribution, and toxicity of biozn-aas: a new zinc source. comparative studies in rats

Food fortification with a proper zinc compound is an economic and effective strategy to prevent zinc deficiency. BioZn-AAS, a zinc gluconate stabilized with glycine, was compared with zinc sulfate (reference standard), zinc hydroxide, and zinc gluconate, all of them labeled with (65)Zn. This preclinical study was performed on Sprague-Dawley rats of both sexes, and the administered dose was 85 microg/kg of zinc. Bioavailability studies showed that absorption of BioZn-AAS was not statistically different than absorption from other sources in female rats (25.65% +/- 2.20% for BioZn-AAS, 28.24% +/- 4. 60% for ZnSO(4), 24.91% +/- 4.02% for Zn[OH](2), and 25.51% +/- 2. 70% for Zn-gluconate). In the case of the male rats, absorption of BioZn-AAS (27.97% +/- 4.20%) was higher (P<0.05) than that from the other compounds (23.15% +/- 2.90% for ZnSO(4), 22.62% +/- 3.90% for Zn[OH](2), and 22.30% +/- 3.90% for Zn-gluconate). Biodistribution studies demonstrated that the zinc from BioZn-AAS followed the same metabolic pathway as zinc from the other sources. Toxicity studies were performed with 50 female and 50 male rats. The value of oral lethal dose 50 (LD(50)) was 2000 mg/kg for female rats and 1900 mg/kg for male rats. Therefore, we conclude that BioZn-AAS has adequate properties to be considered a proper zinc compound for food fortification or dietary supplementation.

A spectrophotometric method for the determination of hydroperoxides in liposomes.

A modification of the Asakawa-Matsushita iodometric assay method for the determination of the content of lipid hydroperoxides was developed which permits the simultaneous processing of many samples of high lipid content. The method has the advantages of simplicity as well as good reproducibility, so it is not necessary to process standards with each determination. Our technique exceeds the sensitivity attained with other spectrophotometric determinations reported in the literature. The method requires the total elimination of water from the samples, and this was accomplished using an azeotropic mixture of ethanol:water of 96:4. The results obtained with liposomes indicate that the method is applicable to biological material limited to small volume samples, ranging 5-50 microliters. We want to emphasize that this method permits the study of the peroxidation process as function of time.

ESR study of order and dynamics in lecithin liposomes with high cholesterol content

Abstract Previous studies have shown that increasing amounts of cholesterol in phosphatidyl choline liposomes (involving cholesterol/lecithin ratios up to 1), produce an increase in order and a decrease in mobility of the phospholipids in the bilayer. The present work focuses on the order and dynamics of the phospholipids in soybean and egg yolk liposomes with cholesterol/lecithin (chol/lec) ratios as high as 2. The influence of cholesterol on the order parameter and correlation times of 5-, 12- and 16-doxyl stearic acid probes, is analyzed for both types of liposomes. The order parameter increases continuously with the increase of the amount of cholesterol although the correlation time at first increases, then it levels off at a chol/lec ratio of 1, and thereafter shows a small, gradual decrease up to a ratio of 2. A statistical model of cholesterol substitution on the lecithin lattice was employed to explain the correlation time results.

99mTc-ENS, a new radiopharmaceutical for aerial lung scintigraphy : Comparative studies in rats

Abstract The biological behavior of 99m Tc-labeled exogenous natural surfactant ( 99m Tc-ENS) was studied and compared to 99m Tc-diethylenetriaminepentaacetate ( 99m Tc-DTPA) and 99m TcO 4 − . The labeling yield percentages for 99m Tc-DTPA and 99m Tc-ENS were higher than 95%. Biodistribution studies performed after aerosolization showed that the percentage of activity concentration in lungs for 99m Tc-ENS was 98.7 ± 1.3%, for 99m Tc-DTPA 77.8 ± 20.6%, and 22.4 ± 7.5% in the case of 99m TcO 4 − . These results suggest that this new radiopharmaceutical shows an optimal lung concentration, and therefore it can be considered for clinical trials.

Stability study of lecithin liposomes during storage using ESR

Abstract The technique of electron spin resonance is employed to study the stability of liposomes by measuring the decay of the encapsulated volume as a function of the incubation time. This volume at first remained constant, next it decreased to 50% of its initial value in a characteristic time t 50% , then it decreased further to a final residual value. The characteristic time varied from 1.2 to 23 days, it was larger for egg yolk than for soybean samples, and for both materials it increased with the lysolecithin to lecithin ratio. The oxidation damage associated with the appearance of hydroperoxides increased with the incubation time, and was twice as large for unilamilar vesicles than it was for multilamilar vesicles. The oxidative decay was three times faster for soybean than for egg yolk samples, but the amount of oxidative damage after the time t 50% was only 10–15% greater for the soybean case. The studies were carried out using the Tempone nitroxide radical ion, and the broadening agent tris(oxalato)chromate(III).

99mTc-ENS ventilation scintigraphy : Preliminary study in human volunteers

Exogenous natural surfactant (ENS) labeled with (99m)Tc ((99m)Tc-ENS, 900-1110 MBq), a new radiopharmaceutical for ventilation scintigraphy, was nebulized during 3 min to five volunteers. For comparative purposes, (99m)Tc-diethylenetriamine pentaacetic acid (DTPA) was studied in the same way. (99m)Tc-ENS images were of at least the same quality as (99m)Tc-DTPA images. However, in smoking volunteers, the (99m)Tc-DTPA images show some areas that seemed to be not well-ventilated, although these areas appeared well-ventilated when the study was performed with (99m)Tc-ENS. These results suggest that (99m)Tc-ENS can be used for ventilation scintigraphy to allow the observation of some areas that cannot been visualized using (99m)Tc-DTPA as ventilation agent.