Interrelationships of zinc with glucose and insulin metabolism in humans

ATSDR evaluation of the health effects of zinc and relevance to public health

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites, which have the greatest public health impact. These profiles comprehensively summarise toxicological and environmental information. This article constitutes the release of portions of the Toxicological Profile for Zinc. The primary purpose of this article is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective on the toxicology of zinc. It contains descriptions and evaluations of toxicological studies and epidemiological investigations, and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health. Toxicology and Industrial Health 2006; 22: 423-493.

Gene expression profiles analysis of the growing rat liver in response to different zinc status by cDNA microarray analysis

The effects of zinc on growing rats were characterized using the dietary zinc-deficient (ZD) and Zinc-overdose (ZO) models. Zinc deficiency had negative effects on the host final body weight and liver zinc content, whereas zinc overdose had positive effects. In order to identify the molecular changes in the liver responding to dietary zinc status, cDNA microarrays were used to analyze the expression pattern of 9753 genes in the livers of rats fed ZD and ZO diet for 6 wk, compared with zinc-adequate ZA. The mRNA levels for 62 genes were affected significantly by the ZD diet, whereas 66 gene transcriptions were markedly changed in the ZO diet. Those predominant gene products involved in nitrogen metabolism (glutaminase), carbohydrate metabolism (aldolase), lipid metabolism (stearoyl-CoA desaturase), growth (insulin-like growth factor-binding protein), transcription and translation (zinc-finger protein), immune (natural-killer cell), signal transduction (mitogen- activated protein kinase), and ion transportation (ATPase Na+/K+ transporting peptide) were clustered. In conclusion, a number of mammalian genes related to zinc in the liver were identified. The characterization of the genes and their products will allow a more comprehensive analysis of the role of zinc in metabolism. Furthermore, the mRNA identified could be useful in establishing the mechanisms of zinc in the pleiotropic metabolisms in vivo.

The Effect of Zinc supplementation on Ghrelin-Immunoreactive Cells and Lipid Parameters in Gastrointestinal Tissue of Streptozotocin-Induced Female Diabetic Rats

Zinc is an essential nutrient with a wide range of functions and closely involved in a variety of enzymatic processes of importance in glucose, protein and lipid metabolism. Ghrelin is the endogenous ligand of the G protein coupled growth hormone secretagogue receptor. The regulatory mechanism that explain the biosynthesis and secretion of ghrelin in the gastrointestinal tract has not been clarified. This study was undertaken to examine the effect of zinc supplementation on the streptozotocin (STZ)-induced diabetic rats, which exhibits ghrelin production and secretion, and lipid metabolism on the gastrointestinal tract. The animals were divided into four groups. Group I: Non-diabetic untreated animals. Group II: Zinc-treated non-diabetic rats. Group III: STZ-induced diabetic untreated animals. Group IV: Zinc-treated diabetic animals. Zinc sulfate was given to some of the experimental animals by gavage at a dose of 100 mg/kg body weight every day for 60 days. In the zinc-treated diabetic group, the blood glucose levels decreased and body weight increased as compared to the diabetic untreated group. Zinc supplementation to STZ-diabetic rats revealed the protective effect of zinc on lipids parameters such as total lipid, cholesterol, HDL-cholesterol and atherogenic index. There is no statistically change in ghrelin-immunoreactive cells in gastrointestinal tissue. But, it has found that zinc supplementation caused a significant reduction in densities of ghrelin-producing cells of fundic mucosa of zinc-treated diabetic animals as compared to untreated, non-diabetic controls. Zinc supplementation may contribute to prevent some complications of diabetic rats, biochemically.

Efeito da suplementação com zinco sobre a zincúria de pacientes com diabetes tipo 1

Neste estudo foi investigado o efeito da suplementação oral de zinco (Zn) em crianças e adolescentes com diabetes (DM), avaliando o controle metabólico da doença e concentrações de Zn na urina. A amostra foi constituída por 20 pacientes com DM tipo 1, os quais foram comparados com um grupo controle (n=17). O controle metabólico foi avaliado pela glicemia de jejum, glicosúria 24h e HbA1c. As concentrações de Zn foram investigadas na urina de 24h antes (T1) e após a suplementação (T2). Após a 1a coleta de dados dos pacientes com DM1 (T1), teve início a suplementação oral com Zn bis-glicina quelato sem sabor, por um período de 4 meses. As doses foram estabelecidas baseadas nas Dietary Reference Intakes. Os resultados evidenciaram um controle metabólico insatisfatório da doença, devido ao aumento da HbA1c de alguns pacientes, após a suplementação. A excreção urinária de Zn foi maior nos pacientes com DM1 e esteve correlacionado positivamente com o tempo de doença e HbA1c. A suplementação com Zn não corrigiu a heterogeneidade na variação circadiana da zincúria nos pacientes estudados, sugerindo que o controle metabólico inadequado no DM predispõe a distúrbios no metabolismo do Zn, independente da fonte, alimentar ou medicamentosa.

Protective effects of antioxidant micronutrients (vitamin E, zinc and selenium) in type 2 diabetes mellitus

Type 2 diabetes (T2D) is a major cause of vascular complications affecting heart, kidney, retina and peripheral nerves. Hyperglycaemia leads to oxidative stress that plays an important role in vascular degenerative lesions observed in diabetes. In this Review we consider whether vitamin E, zinc or selenium are involved in the pathogenesis of diabetes. Concerning vitamin E, major epidemiological studies do not give the expected results in preventing cardiovascular outcomes. The mechanisms of free radical overproduction in diabetes could explain these results. Superoxide anion overproduction originates from mitochondria; in these conditions antioxidant enzymes are more relevant to reduce oxygen species than vitamin E. Zinc has numerous targets to modulate insulin activity, including its antioxidant capacity. Zinc status is decreased in most T2D patients. The effect of zinc supplementation on antioxidant status is raised when complications are associated. Selenium is a major antioxidant trace element and is the co-factor of glutathione peroxidase (Se GSHpx). Low Se GSHpx activity, observed in diabetic patients, is associated with thrombosis and cardiovascular complications.

Zinc

The use of zinc in metal alloys and medicinal lotions dates back before the time of Christ. Currently, most of the commercial production of zinc involves the galvanizing of iron and the manufacture of brass. Some studies support the use of zinc gluconate lozenges to treat the common cold, but there are insufficient data at this time to recommend the routine use of these lozenges. Zinc is an essential co-factor in a variety of cellular processes including DNA synthesis, behavioral responses, reproduction, bone formation, growth, and wound healing. Zinc is a relatively common metal with an average concentration of 50 mg/kg soil and a range of 10-300 mg/kg soil. Meat, seafood, dairy products, nuts, legumes, and whole grains contain relatively high concentrations of zinc. The mobility of zinc in anaerobic environments is poor and therefore severe zinc contamination occurs primarily near points sources of zinc release. The recommended daily allowance for adults is 15 mg zinc. The ingestion of 1-2 g zinc sulfate produces emesis. Zinc compounds can produce irritation and corrosion of the gastrointestinal tract, along with acute renal tubular necrosis and interstitial nephritis. Inhalation of high concentrations of zinc chloride from smoke bombs detonated in closed spaces may cause chemical pneumonitis and adult respiratory distress syndrome. In the occupational setting inhalation of fumes from zinc oxide is the most common cause of metal fume fever (fatigue, chills, fever, myalgias, cough, dyspnea, leukocytosis, thirst, metallic taste, salivation). Zinc compounds are not suspected carcinogens. Treatment of zinc toxicity is supportive. Calcium disodium ethylenediaminetetraacetate (CaNa2EDTA) is the chelator of choice based on case reports that demonstrate normalization of zinc concentrations, but there are few clinical data to confirm the efficacy of this agent.

Alterações metabólicas e funcionais do zinco em diabetes mellitus

O objetivo desta revisão foi relatar as alterações metabólicas e fisiológicas do zinco na presença do diabetes mellitus. O zinco é componente de várias enzimas e participa de vias metabólicas que envolvem a síntese de proteínas, metabolismo de carboidratos, de lipídeos e de ácidos nucléicos. Este mineral tem sido relacionado com a interação entre hormônios e seus receptores, e com melhoras no estímulo pós receptor. Estudos in vitro apontam que a insulina pode se complexar com o zinco melhorando a solubilidade e estocagem deste hormônio nas células beta do pâncreas. Em diabetes mellitus experimental, tem sido detectado alterações na concentração e na distribuição de zinco nos tecidos, assim como hiperzincúria logo após a indução da doença. Em pacientes com diabetes do tipo 1 ou tipo 2, as avaliações bioquímicas têm demonstrado concentrações de zinco no plasma inversamente proporcionais ao tempo de duração da doença, baixos valores em células sangüíneas, assim como hiperzincúria logo após a indução da doença. O mau controle metabólico nestes pacientes pode estar associado à depleção intracelular de zinco, predispondo a alterações no estado nutricional deste mineral. O conhecimento das funções do zinco no metabolismo de nutrientes, no crescimento, no sistema imunológico e nos tecidos oculares tem gerado especulações em relação ao envolvimento da deficiência deste micronutriente na gênese de algumas complicações da doença.