Zinc helps against infection by tapping brakes in immune response
New research suggests that zinc helps control infections by gently tapping the brakes on the immune response in a way that prevents out-of-control inflammation that can be damaging and even deadly.
Scientists determined in human cell culture and animal studies that a protein lures zinc into key cells that are first-responders against infection. The zinc then interacts with a process that is vital to the fight against infection and by doing so helps balance the immune response.
This study revealed for the first time that zinc homes in on this pathway and helps shut it down, effectively ensuring that the immune response does not spiral out of control. The team led by Ohio State University researchers also found that if there is not enough zinc available at the time of infection, the consequences include excessive inflammation.
In this research, zinc’s activity was studied in the context of sepsis, a devastating systemic response to infection that is a common cause of death in intensive-care unit patients. But scientists say these findings might also help explain why taking zinc tablets at the start of a common cold appears to help stem the effects of the illness.
“We do believe that to some extent, these findings are going to be applicable to other important areas of disease beyond sepsis,” said Daren Knoell, senior author of the study and a professor of pharmacy and internal medicine at Ohio State. “Without zinc on board to begin with, it could increase vulnerability to infection. But our work is focused on what happens once you get an infection – if you are deficient in zinc you are at a disadvantage because your defense system is amplified, and inappropriately so.
“The benefit to health is explicit: Zinc is beneficial because it stops the action of a protein, ultimately preventing excess inflammation.”
Study says Zinc helps us fight virus and infection
Researchers at the University of Florida Center for Nutritional Sciences find that zinc boosts immunity and could help fight viral and bacterial infection. The study, published in the August 2009 print issue of the Journal of Leukocyte Biology suggests that zinc could be developed to treat antibiotic resistant infections because it stimulates activation of immune enhancing T-cells needed to fight viruses and infection.
Study co-author, Robert Cousins, PhD says, “It has been shown that zinc supplementation significantly reduces the duration and severity of childhood diarrhea, lower respiratory infections, and incidence of malaria in zinc-deficient children. Age-related declines in immune function have also been related to zinc deficiency in the elderly”. The study shows that zinc boosts immune function by activating (T cells) that can help destroy viruses and bacteria.
While this study and previous work linking zinc deficiency to inflammation might suggest that supplementation could help very sick ICU patients, it’s still too early to make that leap.
“I think the question is whom to give zinc to, if anybody at all. We predict that not everybody in the ICU with sepsis needs zinc, but I anticipate that a proportion of them would,” Knoell said. “Zinc is a critical element that we get from our diet, but we do not think we can give zinc and fix everything. Usually, if there is zinc deficiency, we would expect to see other nutrient deficiencies, too.”
Zinc and infection
Zinc is necessary for the normal functioning of all living systems. In microbes and mammals vital biological roles of zinc include the presence of this metal in metalloenzymes and membrane stabilization. In addition, zinc may bind nonspecifically to sulfhydryl, histidine, or other moieties on membranes, enzymes, or other proteins and alter their activity. Serum levels of zinc decrease sharply in many infections. Levels slightly below normal seem to be associated with optimal phagocytic function, and low concentrations of zinc may decrease microbial virulence. Brief decreases in serum levels appear to have no detrimental effect on host immunity and may act as a protective measure by decreasing the ability of indigenous or infecting microbes to thrive. However, prolonged zinc deficiency in mammals is associated with depressed T-cell function but near normal B-cell function. More work is needed for better understanding of zinc-related biochemistry and for determining the relationship between zinc status and susceptibility to infection in mammals.
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PMID: 6338570 [PubMed - indexed for MEDLINE]
Sugarman B.
Zinc deficiency affects about 2 billion people worldwide, including an estimated 40 percent of the elderly in the United States – who are also among the most likely Americans to end up in an ICU.
The research is published in the journal Cell Reports.
Dietary zinc deficiency is widespread in developing countries and is often aggravated by intercurrent acute and chronic infections.
Recent studies have demonstrated that zinc supplementation of apparently well-nourished children can significantly reduce morbidity and mortality and shorten the time to recovery from common infectious diseases.
Zinc is a key micronutrient that is present in all organs, tissues and body fluids. After iron, it is the second most abundant trace element in the body and mediates a wide variety of physiological functions. It is a necessary component of numerous metalloproteins, including those important for DNA replication and cell division, and is crucial for maintaining immunological integrity, predominantly cellular immunity and antioxidant activity. Because of its role in maintaining cell integrity and immunity, it is considered to play a key role in cells that have a rapid turnover and a critical role in the control and prevention of infections. Despite these functions, the body does not store zinc and requires a constant dietary intake. Zinc is more abundant and easily absorbed from red meat and animal proteins, but can also be obtained from seafood, dairy products, cereals and nuts. Most vegetables, however, are not good sources of zinc owing to the presence of phytate, a component of plants that chelates zinc and prevents its absorption.
Diets that are low in animal protein and rich in phytate thus contribute to the high prevalence of zinc deficiency in developing countries.
This review describes the effect that zinc deficiency and replenishment has in common acute infectious diseases in developing countries, namely acute respiratory infections, diarrhoea and malaria, and its potential role in diseases associated with impaired cellular immunity, namely tuberculosis, lepromatous leprosy and leishmaniasis.
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LUIS E. CUEVAS & AI KOYANAGI
Liverpool School of Tropical Medicine, Liverpool, UK
Knoell’s lab previously showed that zinc-deficient mice developed overwhelming inflammation in response to sepsis compared to mice on a normal diet. Zinc supplementation improved outcomes in the zinc-deficient mice.