421 Exam 2 Ppt 4

Front 1

where is calcium located in the body?

Back 1

99% found within the bones

1% found in extracellular fluids, intracellular structures, cell membranes

Front 2

serum calcium exists in three fractions:

Back 2

protein bound: physiologically inactive

ionized: physiologically active, functions intracellularly (better indicator of calcium tatus)

complexed: complexed with small negative ion (such as citrate, lactate, phosphate), biologic role uncertain; albumin carries calcium in the blood (low albumin, low serum calcium)

Front 3

what is the appropriate biochemical indicator for calcium?

Back 3

there are none presently

largely due to the fact that calcium concentration in the body fluids is tightly controlled, little/none association between calcium intake and serum calcium concentrations

urinary tends to be better than blood (more responsive to high/low intake) - still not great indicator

Front 4

what are low serum calcium concentrations indicative of?

Back 4

metabolic issue, rather than low of high intake of calcium (although special considerations for TPN patients - calcium is going straight into the blood)

Front 5

factors that can influence urinary calcium concentrations

Back 5

hypercalcemia - increased serum calcium

time of day - increased urinary calcium concentration during the day

diet - increased protein, increased urinary calcium

Front 6

zinc functions

Back 6

zinc is a cofactor for numerous enzymes

involved in many metabolic processes such as: protein synthesis, wound healing, immune function, tissue growth, tissue maintenance

Front 7

where is zinc stored in the body?

Back 7

there is no reserve (storage) for zinc in the body; concentration is maintained by both conservation and redistribution of tissue zinc

Front 8

are static measures, like serum zinc, reliable?

Back 8

they are available but interpretation is complicated by body's homeostatic control of zinc status and other factors that are unrelated to zinc status (stress, infection, inflammation) so serum zinc is NOT a reliable indicator of dietary zinc intake or whole body zinc status

Front 9

what is a more reliable statis indicator of zinc status

Back 9

metallothionen may be an indicator (a little better than serum zinc); it is a static measurement; metallothionen is a protein found in the liver, pancreas, and kidney that binds zinc and copper

tissue metallothionen concentrations are often proportional to zinc status (if both serum zinc and serum metallothionen are low, zinc deficiency is likely)

need both serum zinc and metallothionen to determine deficiency

Front 10

what is another way to evaluate zinc?

Back 10

hair zinc concentration - reflects zinc status over past several months

gold standard in non-industrialized countries but in our country it can be contaminated by all sorts of things (must follow proper methods if used)

Front 11

limitations to hair zinc concentration:

Back 11

its susceptibility to contamination from exogenous sources

non-nutritional factors that affect assessment: hair dye, shampoos, pregnancy, age

Front 12

vitamin A status is grouped into 5 categories:

Back 12

deficient, marginal, adequate, excessive, toxic

Front 13

assessment of vitamin A involves ____ measures and ____ measures

Back 13

static (serum vitamin A) and functional (dose response test, dark adaptation) measures

functional tests usually used in research settings

Front 14

serum vitamin A (retinol)

Back 14

most common measure of vitamin A status

typically 95% of serum vitamin A is in the form of retinol, bound to retinol binding protein (other 5% is unbound free retinyl esters)

serum measures are predictive for vitamin A status when reserves are either deficiency or excessive (good at assessing at the extremes)

there are guidelines generated from NHANES data for interpretation of serum vitamin A

best clinical method

Front 15

what to remember when interpreting serum vitamin A

Back 15

serum vitamin A concentrations may be within expected range despite low concentrations of vitamin A in the liver

Front 16

relative dose response procedure

Back 16

fasting blood sample taken

vitamin A administered orally as retinyl palmitate

blood sample taken 5 hours later

typically done in developing countries, not done clinically

Front 17

modified dose response procedure

Back 17

dehydroretinol, a naturally occurring form of vitamin A that is not found in the diet is administered

only one blood sample taken at 5 hours

can tell all levels of stores

Front 18

relative dose response/modified dose response principle:

Back 18

if stores of retinol are high, plasma retinol concentration is not affected much by oral administration

if stores of retinol are low, plasma retinol concentration will increase rapidly from oral administration

best research methods

Front 19

direct measure of liver stores

Back 19

measurement of liver concentration of vitamin A can be used to assess status

best method

Front 20

dark adaptation principle

Back 20

vitamin A plays a large role in visual function

when light strikes rhodopsin, the molecule will split into opsin and a trans-isomer of retinol, which generates a visual response - rhodopsin is then reformed

during this process, some retinol is lost and replaced by vitamin A

with vitamin A deficiency, less rhodopsin is formed and eye fails to adapt to low light levels after exposure to bright light

measure rhodopsin and rate of generation

Front 21

serum vitamin C

Back 21

most commonly used test to assess Vitamin C status

highly related to recent dietary intake of Vitamin C

factors that affect serum vitamin C: smoking, gender

Front 22

what better represents cellular and total body pool of Vitamin C

Back 22

Vitamin C concentration in poly- and mono- morphonuclear leukocytes

Front 23

what is the best test to assess vitamin D status and why?

Back 23

total 25 (OH) D level in blood

ingested and cutaneously produced vitamin D is rapidly converted to 25 (OH) D, but in serum only a fraction of 25 (OH) D is converted to its active metabolite 1, 25 (OH) 2D

Front 24

what is the method of choice for assessing Vitamin E status?

Back 24

plasma tocopherol but if available, then the ratio of alpha tocopherol to total plasma lipids because tocopherols are transported on the lipoproteins in the blood

ratios usually used in research setting

Front 25

what are two methods to assess biotin status?

Back 25

urinary biotin excretion - better indicator - static

urinary 3-hydroxyisovalerate excretion - biotin is needed in two amino acid reactions and in deficiency will produce 3-hydroxyisovalerate - functional indicator

Front 26

what is the most common way to measure vitamin B6?

Back 26

plasma PLP (pyroxidal 5'-phosphate)

PLP accounts for 70-90% of total B6 in plasma

fasting concentration is most accurate

Front 27

what is vitamin B6 composed of?

Back 27

pyridoxine (PN)

pyridoxal (PL)

pyridoxamine (PM)

within the liver, erythrocytes, and other tissues these compounds are phosphorylated into PLP and PMP

Front 28

factors affecting plasma PLP concentration

Back 28

asthma, coronary heart disease, pregnancy

these conditions decrease PLP but not due to vitamin B6 deficiency

Front 29

what are three other methods to evaluate vitamin B6 status?

Back 29

urinary 4-pyridoxic acid (4-PA) - major urinary metabolite of B6 and is indicative of recent B6 intake

functional tests: tryptophan load test, methionine load test (vitamin B6 is responsible for the metabolism of these amino acids)

Front 30

serum folate and what affects it

Back 30

indicates recent dietary intake but does not correlate well with tissue stores

non-nutritional factors affecting folate: acute renal failure, active liver disease, RBC hemolysis

Front 31

what is the best measure of depleted tissue stores of folate?

Back 31

erythrocyte folate - correlates well with liver stores and total body stores

reflects folate intake for the life of the RBC (120 days)

less influenced by dietary folate

Front 32

what is the most common way to measure vitamin B12 and what are factors that affect this measurement

Back 32

serum Vitamin B12 - however, serum levels are maintained at the expense of tissue stores

factors that affect serum B12: leukemias and lymphomas, active liver disease

Front 33

what is a functional way to assess vitamin B12

Back 33

methylmalonic acid (MMA) - B12 is needed for the conversion of MMA to succinyl CoA

MMA increases in B12 deficiency, but not folate deficiency

best to use MMA test in combination with serum B12 to assess B12 status

Front 34

what are the different groups for Vitamin K

Back 34

Vitamin K1: phylloquinone, phytonadione

K2: menaquinone or MKs

K3: menadione (synthetic form not used in humans)

Front 35

how do you assess vitamin K status

Back 35

phylloquinone and menaquinoes are the most commonly measured, K1 more so because it is the primary source of dietary vitamin K

serum K1 reflects recent intake and responds to changes in dietary intake within 24 hours

vitamin K is variable in the diet, one serum may not reflect normal dietary intake

Front 36

a classical measure of vitamin K deficiency can be

Back 36

increased prothrombin time - time it takes your blood to clot (vitamin K is needed to turn proteins into substances that will clot your blood)

this test is no longer used much

Front 37

other proteins that can be used to assess Vitamin K status?

Back 37

osteocalcin and matrix Gla protein (both depend on Vitamin K for carboxylation of glutamyl residues)

Front 38

all possible ways to assess vitamin K status

Back 38

blood phylloquinone concentration (most common - clinical)

prothrombin time (not used anymore)

factor VII activity (not used anymore)

urinary gamma-carboxyglutamyl residues (research)

undercarboxylated prothrombin (research)

under gamma-carboxylated osteocalcin (research)

Front 39

three methods to indicate iodine status

Back 39

urinary iodine concentration (most used)

the goiter rate

blood concentrations of thyroid stimulating hormone and thyroglobulin

Front 40

which method can assess iodine over days

Back 40

urinary iodine is a sensitive indicator of recent intake (days)

spot urinary iodine concentrations are highly variable from day-to-day and should not be used to classify iodine status of individuals

Front 41

which method can assess iodine over weeks/months?

Back 41

thyroglobulin shows an intermediate response (weeks to months)

Front 42

which method can assess iodine over months/years?

Back 42

changes in the goiter rate reflect long term-iodine nutrition