Minerals Flashcards
Folate (B9)
- precursor of tetrahydrofolate, coenzyme involved in generating precursors for DNA and protein synthesis
- hemopoietic B vitamin
Deficiency:
- neural tube defects in newborns of deficient mothers
- macrocytic anemia
- hyperhomocysteinemia (cardiovascular risk)
Suspectible:
- pregnancy
- elderly
- alcoholics
- patients with certain long term drug treatments
- people with genetic polymorphisms in folate metabolism
Folate supplementation
- inadequate folate early in pregnancy appears to be associated with neural tube defects. Mothers may have inadequate folate without symptoms
- demand very high in pregnancy and lactation
- grain products enriched in folate have lowered the risk
- defiency inhibits DNA synthesis by decreasing availability or purines and dTMP
- anticonvulsant drugs and oral contraceptives may also interfere with absorption of folates
Cobalamine (B12)
function:
- coenzyme in methionine synthesis and in conversion of methylmalonyl CoA to succinyl CoA
- needed in folate metabolism
- can be stored very effectively but deficiencies come from lack of absorption due to deficiency in intrinsic factor
Deficiency:
-pernicious anemia (megaloblastic anemia with demyelination)
Susceptible:
-elderly, patients with malabsorption diseases, long- term vegetarians
Megablastic anemia
- large size of RBCs in presence of folate/vitamin B12 deficiency
- arises from a deficiency in nucleotides, leading to decreased DNA and RNA synthesis. Cells increase in size without dividing, and large immature RBCs do not carry sufficient oxygen
- pernicious anemia refers specifically to a B12 deficent anemia arising from lack of intrinsic factor
Minerals
- inorganic compounds critical for human physiology
- many minerals are enzyme cofators, but they can also play structural roles in proteins or on their own
- categorized as macrominerals and microminerals based on level required (doesn’t correlate with importance)
- often work in parallel with vitamins, so supplements often contain both
Cobalamine and cobalt
- cobalamine contains a cobalt
- B12 in food must be released from protein by acid hydrolysis in the stomach. It then must bind to intrinsic factor to be absorbed in the ileum
Mineral classification
- Macrominerals:
- Potassium, Sodium, Chloride, Calcium, Phosphorus, Sulfur, Magnesium
- 100-200 mg/day
Microminerals:
- Iron, Copper, Zinc, Chromium, Iodine, Manganese, Selenium, Molybdenum, Fluoride, Boron
- lower 100 mg/day
Calcium
Function:
- major component of bone
- signaling
- coagulation
- muscle contractions
- neurotransmission
Deficiency:
mild- muscle cramps, osteoporosis
severe- rickets
Susceptible groups:
-children, adult women, elderly
Where does calcium come from and go?
- 98% of calcium is in bone and teeth
- hydroxyapatite is the basic mineral component of bones and teeth
- bone is the body’s calcium reservoir: bone releases Ca2+ if serum levels of insufficient
- 2% of calcium in rest of the body
- low serum calcium signals enhance intestinal absorption and stimulate bone resorption
Osteoporosis
- osteoporotic bone from calcium deficiency is porous
- calcium intake during period when bone is reaching maximum density (age 10-35) is important to prevent osteoporosis
- even higher levels of calcium intake are required to maintain bone mass in postmenopausal women (exercise also helps main bone density)
Magnesium
Functions:
- essential for many enzymes useing MgATP as substrate (usually transporters)
- present at high levels in bone
Deficiency:
-weakness, tremors, cardiac arrhythmia
Susceptible groups:
-alcoholics, patients taking diuretics or experiences severe vomiting and diarrhea
Phosphorus
Functions:
- most present in phosphates
- Major component of bone (hydroxyapatite)
- constituent of nucleic acids, membrane lipids
- required in all energy-producing reactions
Deficiency:
rare- can result in rickets, muscle weakness and breakdown, seizure
-quite abundant in food supply
Iron
Function
- O2/CO2 transport in hemoglobin
- oxidative phosphorylation
- cofactor in several nonheme iron proteins and cytochromes (redox properties of iron are important
- best sources are meat, dried legumes and fruit and iron enriched cereal products
Defiency:
-microcytic hypchromic anemia, decreased immunity
Susceptible:
-common in children and menstruating women, pregnant women, and elderly
Iron absorption and distribution
- reduction of Fe3+ and Fe2+ is promoted by vitamin C in diet (Vitamin C deficiency causes mild anemia)
- Low pH in stomach helps release Fe3+ from ligands and make it bioavailable
- uptake of iron in mucosal cells of small intestine is regulated in response to iron-deficient or overload states
- iron is carefully escorted both in circulation and in cells because of the potential for inadvertent redox damage
Major barriers to absorption
1) release of Fe3+ from food
2) availability of reducing agent to convert Fe3+ to Fe 2_
- although spinach does contain iron, it is so tightly chelated that it cannot be readily absorbed.
- the second requirement is often satisfied by vitamin C
-hepidin signals iron sufficiency and prevents export of Fe2+ from duodenal mucosal cell by downregulating the exporter
Characteristics of iron-deficient anemia
- microcytic anemia- small, pale, red blood cells
- less hemoglobin is produced, and RBCs undergo more cell divisions in bone marrow waiting for hemoglobin synthesis
- patient symptoms: fatigue, pallor, weakness, dizziness
Iron toxicity
- chemical properties as redox agents- if not localized properly they can catalyze product of ROS
- also one transition metal can replace another at an enzyme’s active site, compromising an enzyme’s activity
- Long term: Hemochromatosis
- iron overload leads to iron deposits in multiple tissues. Leads to compromised liver, pancreatic, and cardiac function
- ultimately can compromise mitochondrial function leading to lactic acidosis
Acute: iron overdose in children
-most common cause of death due to toxicity in children under 6 comes from consumption of adult iron supplements
Copper
Functions:
- assists iron absorption through ceruloplasmin
- cofactor for enzymes required in collagen synthesis, fatty acid metabolism, and elimination of ROS
Deficiency:
-quite rare, symptoms include anemia, hypercholesterolemia fragility of large arteries, bone demineralization, demyelination
Susceptibility
-those with genetic Menkes syndrome or consuming excessive zinc
Menkes’ disease
-iron deficiency disorder that comes from inherited mutations in a Cu- transporting ATPase ATP7A
Wilson’s disease
- mutation in ATP7B, a relative ATP7A, but results in copper overload
- copper is not sequestered properly, and accumulates in liver with severe liver and nervous system symptoms. Results in liver failure and liver cancer
Zinc
function:
- cofactor for over 300 metalloenzymes
- plays a structural role in many proteins (Zn finger domains)
Deficiency:
-poor wound healing, dermatitis, reduced taste acuity, poor growth and impaired sexual development in children
Suspectible groups: alcoholics, elderly, people with malabsorption or kidney disease
Chromium
- function:
- component of chromodulin- facilitates insulin binding to its receptor
deficiency:
-impaired glucose tolerance (from reduced insulin effectiveness)
susceptible populations:
-those with impaired glucose tolerance, but Cr3+ hasn’t yet proven helpful in treatment of type 2 diabetics
Iodine
- function:
- incorporated into triodothyronine (T3) and thyroxine (T4)
- regulates basal metabolic rate
Deficiency:
- goiter-enlarged thyroid gland (low I stimulates increased thyroid stimulating hormone)
- hyperthyroidism or hypothyroidism
Saltwater fish is an excellent dietary source of iodine
Selenium
Function
- component of antioxidant enzymes (glutathione peroxidase)
- component of deiodinase enzymes involved in T3 and T4 metabolism
Deficiency:
-Keshan disease (in areas with little selenium in soil)- cardiomyopathy and cretinism
Manganese
- part of arginase, pyruvate carboxylase, superoxidase dismutase
Molybedum
-xanthene oxidase
Fluoride
-incorportated into bones and teeth, strengthening them
Boron
-involved in bone formation
Sulfur
-component of amino acids and used in certain post- translational modifications
Most common vitamin and nutrient deficiencies in the general population
- Children: iron and calcium
- Teenagers- calcium and magnesium, possibly vitamin A, C and B6
- Women- iron, calcium, magnesium, vitamin B6, folate
- Elderly- Vitamins B6, B12, D, possiblly zinc and chromium
- Alcoholics- susceptibile to multiple deficiencies, but especially folate, B6, and thiamine
-there are Drug-nutrient interactions that should be considered
