1 Zinc Metabolism 2 Study Guide 2 1 What is the RDA and where is it found The RDA for zinc in men is 8 mg day and in women it is 18 mg day It is found in seafood meats eggs and dairy whole grains and in vegetables It can also be in the endogenous form of carboxypeptidase 2 Absorption and transport Like all other food zinc has to by hydrolyzed out of the food in digestion with HCl Once hydrolyzed it is absorbed in the jejunum best at around 12 60 Before absorption zinc has to bind to a protein called metallothionein this does not serve as a transporter but more as a zinc pool This is required Animal products are absorbed best The two transporters are called Nramp2 and DC MT1 Phytate fiber and oxalates decrease the absorption of it There are many interactions with other minerals for zinc calcium decreases its absorption at high does iron decreases it and so does copper The reason will be gone over in the copper section Citric acid increases the absorption rate since an acidic environment will help hydrolyze the zinc faster so it is available faster to absorb Amino acids also enhance the absorbtion Once it is in the enterocyte it can either be used there stored there or transported elsewhere If stored there it is stored with metallothionein if transported out then four different transporters can be used ZnT 1 through ZnT 4 3 Functions Zinc is a catalytic structural and regulatory mineral As a catalyst it is involved in many reactions most notably the carbonic anhydrase in respiration Co2 H2o H HCO3 and with alkaline phosphatase It is used with Tony Berardi 2 alcohol dehydrogenase superoxide dismutase and as carboxypeptidase in protein digestion Structurally it stabilizes the membranes of the cell and help in the folding of polypeptides into functional proteins and for tissue growth and bone formation along with immunity It has various roles in carbohydrate metabolism BMR taste and other transporter proteins Regulatory is it has a role in gene expression 4 What are some nutrient interactions that it has There are many interactions with other minerals for zinc calcium decreases its absorption at high doses iron decreases it and so does copper The reason will be gone over in the copper section 5 Deficiency There are two levels of deficiency sore throat Mild deficiency has slower growth impaired immune function and wound healing dermatitis Severe is all of the above and anorexia from loss of taste dwarfism hypogonadism and night blindness Know the differences like with dwarfism and hypogonadism Acrodermatitis Enteropathica is an inherited disease where the body does not produce the enzyme to shuttle zinc across the intestine It is treated with large oral doses because some will still leak in despite the lack of the enzyme Everyone who is at risk for deficiency should be common sense alcoholics are at risk for every deficiency and any one where getting nutrients will be a problem burn patient those on TPN tube feeding surgery 6 Toxicity 7 How to assess status It is rare but it does occur when food is prepared in galvanized containers or when zinc is inhaled Very high doses will interfere with iron and copper metabolism and therefore lead to anemia The patient will present nausea vomiting and cramps Tony Berardi A WBC test is the best to assess the zinc status For functional tests we have a light dark test taste acuity and a zinc tolerance It might be best to use a combo of serum zinc and the metallothionen as it will decrease when deficient Remember that this is that zinc pool 3 Copper 1 What is the RDA and where is it found The RDA is 900 ug day for both men and women and it found in organ meats legumes nuts and seeds It is in the body as two forms Cu cuprous Cu cupri 2 How is it absorbed and transported Range from 12 to 50 depending on intake if you need a lot your body will absorb more With a low intake it will be absorbed active transport taking energy and a high intake will make it passive transport Think of the concentration gradient If you are trying to absorb a small amount you must have a larger amount in your body so it will have to move against its concentration gradient And as usual it has to be freed from the proteins via HCl and proteases Now to things that inhibit it Zinc The reason for this is because as we know zinc needs to bind to the metallothionein shown as MT first but copper has a higher affinity to it for some reason So the copper will displace the zinc from the MT and get trapped in it If are zinc intake is higher than the RDA it will make more MT as a result more MT means more copper will bind to it and not be absorbed Sulfur fiber vitamin C and phytates also inhibit it Once in the blood copper travels on the proteins albumin and transcuprein It is excreted via bile through the intestine Somewhat in sweat 3 What are the functions Copper acts oxidize ferric to ferrous Going back to iron iron has two forms ferric iron and ferrous iron It is readily absorbed as ferric but it can only bind to transferrin to travel in the body as ferrous so it must be oxidized Copper picks up an electron from the ferric oxidizing it to ferrous This is why a copper deficiency will lead to anemia copper is required for iron function It does this through the enzyme ceruloplasmin Tony Berardi 4 expression neurotransmitters Superoxide dismutase depends on copper also along with amine oxidases cytochrome C oxidase and tyrosine metabolism It is connected to immune and nervous function and gene Its other functions are in various oxidases that act as either free radicals or catabolizes 4 Is there a deficiency with copper and how can you assess it You can simply look at ones plasma levels or their serum ceruloplasmin to assess status Deficiency is rare but it will cause hypochromatic anemia a lowered immune function osteopenia and myocardial diseases Wilson s disease is a genetic disease that leads to copper excess with impaired excretion It is caused by a mutation in the ATP 7B gene Is rare with 200x normal intake and retarded people that eat pennies It will lead to nausea 5 Toxicity liver and kidney disease Iron 1 What is Iron and where is it stored When you think of iron think of hemoglobin and oxygen transport The average adult has 2 5mg 3 5mg at any moment in their body mostly in the form of hemoglobin and myoglobin There is an iron pool in the body that the body always has access to in the form of ferritin how iron is stored in the body So it is used for hemoglobin synthesis which is
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