Ricardo A. Caro

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.

The role of zinc in the growth and development of children

This review concerns the importance of zinc in growth, development, and cognitive function in children and the deleterious consequences of its deficiency on childrens health. Possible strategies to overcome zinc deficiency and the results of some supplementation trials are discussed.

Effect of probiotics and functional foods and their use in different diseases

The use of functional foods (probiotics and prebiotics) has been demonstrated to be effective for the treatment or control of several diseases. Further well designed trials to examine the effects of different probiotic components are required. It is important to establish separate functions and to gain further insight into the underlying mechanisms that include competitive exclusion and modification of colonic microflora. For a very long time Russians have used kefir for the treatment of a wide range of illnesses. This paper attempts to review the use of probiotic and functional foods in different diseases, with a special emphasis on kefir.

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.

Fortification Strategies to Combat Zinc and Iron Deficiency

Food fortification is an important strategy to combat iron and zinc deficiency. This review covers the basic concepts of food fortification, as well as its advantages and disadvantages. The main characteristics of the most common zinc and iron compounds used in this procedure are also analyzed.

Experimental evidence pointing to the bidirectional interaction between the immune system and the thyroid axis.

Among the many examples of neuroendocrine-immune system interactions the relationship between the thyroid axis and the immune function has yet to be clearly established. Here we studied the influence of thyroid hormones on the course of an alloimmune response. Murine T(3) and T(4) levels were found to be increased a few days after the immunization of mice with allogeneic lymphoid cells. Besides in vivo treatment with T(4) was shown to increase alloantibody titers during the early stages of alloimmunization and to enforce lymphoid proliferation in vitro in a mixed lymphocyte reaction. Conversely, lowering thyroid hormone seric levels by propylthiouracil treatment, negatively modulates the humoral and cellular alloimmune responses. The evidence here points to the existence of a bidirectional communication between both systems. The possibility that the antigenic challenge would increase the thyroid gland activity thus leading to a positive modulatory action upon the immune response is also discussed.

Induction of mammary tumors in rat by intraperitoneal injection of NMU: histopathology and estral cycle influence

In order to obtain an experimental model we induced mammary tumors in female Sprague-Dawley rats. The carcinogen N-nitroso-N-methylurea (NMU) was injected intraperitoneally (i.p.) at doses of 50 mg/kg body weight when animals were 50, 80 and 110 days old. Tumor sizes were measured with a caliper and their growth parameters and histopathological properties were tested. For 100 rats, 88.4% of developed lesions were ductal carcinomas, histologically classified as 52.8% cribiform variety, 30.6% solid carcinoma. Metastases in liver, spleen and lung were present. Other primary tumors were detected with low incidence. The influence of the rat estrous cycle during the first exposure to intraperitoneal NMU injection was studied. The latency period in estrus, proestrus and diestrus was 82 +/- 15, 77 +/- 18 and 79 +/- 18 days, respectively. Tumor incidence was significantly higher in estrus (95.2%) than proestrus (71.4%) or diestrus (77.4), (P < 0.01). Mean number or tumors per animal was similar among the three groups (4.4 +/- 3.2, 3.8 +/- 3.6, 3.2 +/- 1.8). The procedure described appears to be the simplest method for inducing experimental mammary tumors in rats.

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.

Hormone Dependence of Mammary Tumors Induced in Rats by Intraperitoneal NMU Injection

The purpose of this work was to determine the hormone dependence of mammary tumors induced in Sprague-Dawley rats by three intraperitoneal injections of N-nitroso-N-methylurea at 50, 80, and 110 days of age. Two experimental designs were carried out: (a) Ten days before the first NMU injection, 130 rats were divided into 13 batches and randomly assigned to the following treatments: control, ovariectomy (OVX), tamoxifen (TAM), bromocriptine (BROM), haloperidol (HAL), estradiol (E2), progesterone (Pg), OVX + BROM, TAM + BROM, OVX + HAL, TAM + HAL, OVX + TAM, and E2 + BROM. After 150 days of treatment the following growth parameters were determined: latency period (LP), mean tumor number per rat (n/t), and tumor incidence (TI). LP was significantly increased (p < 0.05) only by Pg and TAM + BROM. The n/t was significantly decreased (p < 0.05) by all treatments except HAL. TI was significantly reduced by OVX, TAM, BROM, and their combinations, (b) Rats bearing ip-NMU-induced mammary tumors were divided into 7 batches and assigned to the following treatments: control, OVX, TAM, BROM, HAL, OVX + BROM, and TAM + BROM. Tumor growth was assessed up to 60 days of treatment; only OVX, TAM and their combination with BROM were able to produce tumor regression. These results support the essential role of E2 and prolactin in the promotion stage of carcinogenesis. However, for established tumors, growth becomes more independent from hormone influence, in particular from prolactin deprivation. We conclude that this model seems suitable for studying the mechanisms underlying the evasion of hormonal control of tumor growth.

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.