Other Trace Minerals (Chromium, Manganese, Molybdenum) Flashcards
Cr supplements
2nd largest-selling mineral supplement in
the U.S.
Promises:
Weight loss with increased lean body mass and
decreased fat mass.
Improved control of blood glucose.
most stable form of Cr
Cr+3 in foods
Cr absorption
Absorption low (0.4-2.5%) – mechanism unclear
Dietary factors/ligands such as amino acids improve absorption by ↑
solubility, prevent olation (reaction of Cr with OH- in small intestine to form
polymers that precipitate out)
Cr supplements contain:
Inorganic Cr salt. e.g. Cr chloride, but likely not well absorbed unless with vitamin C
Organic Cr complex: (foods)
Cr-amino acids
Cr picolinate and Cr nicotinic acid are common
Function of Cr
Function: major = potentiate action of insulin
via Chromodulin (oligopeptide = GLY-CYS-ASP-GLU)
How:? (Fig. 13.22)
Cr is transported by transferrin
TfR used to get Cr-transferrin into cells
Cr + apochromodulin = chromodulin
which binds the insulin receptor -> amplifies the signal
insulin promotes
cellular uptake of glucose, storage of
energy (glucose as glycogen; fatty acids as fat),
muscle protein synthesis
**Cr added will only see change if person is inadequate
insulin inhibits
glycogen breakdown, gluconeogenesis,
lipolysis, protein degradation.
Chromium and Obesity?
Early evidence for body weight changes, as well as diabetes
control?
Well-controlled studies show:
no effects on strength, accretion of muscle, or fat loss
results on weight loss are minor and conflicting
Cr Sources
widespread
note: molasses, brewer’s yeast (beer), dark choc, tea, coffee
stainless steel equipment
lose Cr when processing sugar
Cr DRI
AI=
M: 35mch
F: 25mcg
No UL (Cr+6 industrial poison)
intake studies: intake of healthy individuals, balanced diets
Cr Deficiency
in humans rare
discovered in Canada, hospital patients showed symptoms of diabetes (wgt loss, neuropathy, impaired glucose tolerance)
Cr was added to feeding solution and now routinely added when intravenous nutrition used as complete food source
Manganese
Functions and mechanisms of action
Constituent of metalloenzymes – across many classes.
Bone, cartilage, and connective tissue synthesis
Urea synthesis
Amino acid/carbohydrate metabolism
Antioxidant roles
MnSOD – mitochondrial superoxide dismutase
Mn excretion
Mostly in bile
Like Cu, if a patient has problems in secreting bile
from the liver, we are very cautious about adding Mn
to an intravenous feeding.
Little in urine
Small amounts in sweat and skin desquamation
Mn Food sources
Whole grain cereals, nuts, and leafy vegetables
i.e. plant > animal sources
Digestion and absorption
Females may absorb greater amounts than M
Reasons unclear
Low < 5%; tightly regulated
Absorption poorly understood
Absorption throughout small intestine
Mn DRI
AI=
Men: 2.3 mg; women: 1.8 mg
Mn Deficiency
Very rare
From experimental study, deficiency signs are impaired
growth, skeletal defects, transient skin rash, altered lipid
and carbohydrate metabolism.
Mn Assessment of Nutriture
Plasma/serum/whole blood concentrations
Enzyme activity
Mn-SOD and arginase, but not good indicators
Mn toxicity
(of much interest)
Tolerable Upper Intake Level: 11 mg/day
Causes/Sources:
Airborne Mn - welders, battery manufacturers
High well water Mn – some southern US states
Liver failure
Neurotoxicity = current research
Cognitive and motor (Parkinson’s-like symptoms)
Mechanisms of neurotoxicity unknown
Molybdenum general functions
Mo, as molybdopterin, functions as co-factor in only 4
metalloenzyme functions
all catalyze oxidation-reduction reactions.
Mo is essential for enzyme activity.
4 enzymes Mo is in
- Sulfite oxidase
- Xanthine oxidoreductase
- Aldehyde oxidase
- Amidoxime reductase
sulfite oxidase
Sulfur metabolism – final step in oxidation of cysteine and methionine
sulfite to sulfate ->
Mo+6 regenerated to Mo+4 ->
2 Fe+3 regenerated to 2 Fe+2 <-
cytochrome C (ox) to cytochrome C (reduced) >
Xanthine oxidoreductase
Purine degradation
Converts hypoxanthine to xanthine, and converts
xanthine to uric acid.
aldehyde oxidase
Various roles – aldehyde oxidation
retinal -> retinoic acid
drug metabolism
Amidoxime reductase
physiological function is unknown
role in lipogenesis
reductive activation of N-hydroxylated prodrugs
Mo food sources
Legumes, meat, fish, poultry, and grains
Mo absorption
Poorly understood
~50-85%
Mo RDA
adults= 45mcg
Molybdenum Deficiency
No human report of Mo deficiency due to low dietary
intake.
One isolated report from an adult male on long-term
total parenteral nutrition
Assessment of Mo nutritional status
No validated indicators
Molybdenum – Toxicity and UL
UL= 2 mg
In cattle and sheep: high Mo intake causes secondary Cu deficiency
In Armenia, high soil Mo exposure in humans associated with aching joints, gout from high uric acid.
