Metabolism 2 Study guide Exam 2 1 Explain the DRI The goal of the DRI is to prevent chronic diseases not to prevent defiencys The focus is now on malnutrition from over nutrition DRI started in 1835 with lemons on ships Then first RDA was in 1949 with the focus to prevent defiency in the military Changed because it was too broad focus on healthy people and too many fat unhealthy people Now have EAR RDA AI and UP 2 What are vitamins and difference between fat and water soluble They are micronutrients that must be supplied from the diet Needed for normal function and their absence cause certain symptoms with each one The body can make some but not in appreciable amounts Fat soluble is obviously soluble in fat stored in the body in large amounts so it s not required every day Since it s stored defiency takes a long time to occur Most have precursors and only higher organisms need them Can be toxic at low amounts but still way higher than the UL Water soluble are stored minimally excreted in the urine so defiency can happen much faster Absorbed into blood since water soluble and both simple and complex organisms need Since they aren t really stored they are only toxic at mega doses 100x DRI Folate 1 What is the synthesis 2 How is it absorbed It s made from 9 different precursors such as PABA glutamic acide Pterdine The body can make all except Pterdine acid It must be absorbed as a monoglutamate form so the polyglutamate is hydrolyzed with a conjugase The conjugase is also Zinc dependent so you need Zinc to absorb Folic acid Some foods have conjugase inhibitors though like oranges cabbage lentin Then it is reduced in the liver to its active form THF Minimal storage of 11 28 mg 3 What are the functions It is use in one carbon transfers in the synthesis of the purines and pyridimes Nucleic acids and in some AA metabolism such as the glycine serin but the important one is the methionine regeneration Green leafy veggies oranges yeast It is destroyed with cooking 50 95 4 What are the sources 5 What is the defiency The risk groups are those that prolonging the cooking Alcoholics pregnant and lactating women are also at risk And some intestinal diseases such as Celiac disease Some drugs also interfere with the absorption such as methotrexate in chemo some antimicrobials and Dilantin an anticonvulsant The defiency causes megaloblastic RBC large and immature 6 How to assess and what is the DRI There are 2 ways You can check the RBC folate level but this only shows long term You can check the plasma folate levels it will be as 5 methyl THF The DRI is 400 ug and 600 ug in pregnant women Expressed in DFE 1ug folate 1 7ug synthetic folate and synthetic has better bioavailability Also learn the whole Folate Cobalamin Methionine reaction Cobalamin 1 What is its active form 2 How is it absorbed They forms are also known as corrinoids and they are multiple forms They all has 4 rings surrounding the cobalamin The two active forms are 5 deoxyadenosylcobalamin which has 4 deoxys and methylcobalamin which has 4 methyls All the other forms can also be converted into these This vitamin has the most complicated absorption So first the pepsin releases the cobalamin from its ring and the cobalamin bounds to an R protein and then travels to the small intestine In the first part the duodenum the R protein is hydrolyzed and then the cobalamin binds then something called Intrinsic Factor which is made in the stomach Now it gets absorbed in the ileum where the receptors are Once the cobalamin is in the blood it then binds to either Transcobalmin 1 2 or 3 Although 2 is the most common one And then it is stored in the liver mostly and some in the muscles Stored better than most water soluble vitamins so defiency take several years to occur Bacteria in the intestinal also can make a little 3 What are the functions Works with folate in that whole methione reaction Also in DNA synthesis and myelin synthesis for the neurons 4 What is the defiency It rarely occurs in the diet mostly in some absorption problem This is easy to see when you look at how many molecules are involved in its absorption Those that can t make the Intrinsic Factor since as patients with gastrectomys or impaired mucosa are at risk Or they have a lower surface area for absorption with a blind loop or ilealitis Pancreatis and parasites don t help either Of course alcoholics and elderly also Defiency always occurs in stages So first you get low serum Trancoblamin 2 levels Then you get low RBC levels Then you get lower DNA synthesis greater homocysteine levels these are bad Anemia and neuropathy And finally you get Pernicious Anemia which is characterized by appearance of megaloblastic RBC s and GI abnormalities 5 What are the sources Animal in animal products About 30 is destroyed in cooking 6 What is the DRI It is 2 4 2 6 ug daily Zinc 1 Main properties Most of the Zinc is in the muscles and bone but it is not available there It is a catalytic structural and regulatory mineral 2 Absorption and transport Needs to be hydrolyzed obviously and animal sources oysters are the best are better absorbed It enters the brush border and then the cytosol then binds to metallothionein Zinc pool To enhance If deficient like all nutritients Pregnant lactating Human milk better absorption To inhibit Phytate oxalate fiber High dose of Ca Fe if supplemented Cu supplementation Excreted In poop 3 Functions Catalytic polymerase Structural Lots of enzymes such as carbonic anhydrase in acid base balance DNA It stabilizes biomembranes and helps proteins fold up Regulatory Gene expression stimulator of the trans acting factors 4 Deficiency Mild is slower growth impaired immune function and wound healing dermatitis sore throat Severe is all of the above and anorexia from loss of taste dwarfism hypogonadism and night blindness Acrodermatitis Enteropathica is an inherited disease where the body does not produce the enzyme to shuttle zinc across the intestine Treated with large oral doses cause some will leak in It is rare but it does occur when food is prepared in galvanized containers or when zinc is inhaled High doses interfere with Fe and Cu absorption Serum levels can be used WBC best light dark test metallothionen and serum zinc metallothionen decreases in deficiency Risk groups are anorexia poor food choices low protein diets and strict vegetarians 5 Toxicity 6 How to assess Copper 1 Main functions It is in the body as two forms Cu cupro Cu cupri and there are two
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