manganese molybdenum flouride reviewer

8/12/2019 Manganese Molybdenum Flouride Reviewer

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Manganese Molybdenum Flouride

A. Manganese

Manganese Content of Foods

Whole grains,dried fruits, nuts,

leafy vegetables

Manganese Absorption

1 to 14% Probably low-capacity, high affinity, active transport mechanism Absorbed in the Mn+2state

Factors influencing absorption

Low molecular weight ligands such as citrate and histidine improveabsorption

Fiber, phytate, oxalate, iron, copper either precipitate it or compete withit for absorption

Manganese Transport & storage

Free or bound as Mn2+to alpha-2 macroglobulin, albumin, beta globulin,gamma

globulin Oxidized to Mn+3 and complexed totransferrintissues Accumulates in mitochondria in Mn+2or Mn+3hydrate or as Mn+3(PO4)2

precipitate

Found in all tissues throughout the bodyManganese Functions & mechanisms of action (enzyme activator or part of a

metalloenzyme)

Mn can function as enzyme activator (usually non-specific) for a severalclasses of enzymes

Transferases Mn is specific to glycosyl transferase transfer of a sugarmoeity from UDP to an acceptor

Hydrolases Prolidase (dipeptidase for collagen degradation)andarginase in urea cycle

Lyases activates PEPCK that converts oxaloacetate tophosphoenolpyruvate - gluconeogenesis

Oxido-reductases Superoxide dismutase (SOD) is a Mn dependentmetalloenzyme in mitochondria free radical scavenger

Ligases/synthetases Pyruvate carboxylase (4 Mn atoms) convertspyruvate to oxaloacetate (Mg can substitute here)

Manganese Other roles

-Modulator of second messenger pathways via cAMP

Manganese Interactions with other nutrients

-Iron (competes for absorption); possibly calcium, zinc


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Manganese Excretion

Mostly in bile - >90% Little in urine Sweat, skin desquamation

Manganese Adequate Intake

Men: 2.3 mg; women: 1.8 mgPregnancy: 2 mg; lactation: 2.6 mg

Deficiency

rarely develops unless deliberated omitted from diet

Toxicity

Liver failure (because route of excretion), neonatal TPN

Miners who inhale Mn dust

UL = 11 mgManganese

Assessment of nutriture

Mononuclear blood cell/plasma/ serum/whole blood concentrations

Enzyme activity

Lymphocyte Mn-SOD

Blood arginase activity

B. Molybdenum

Molybdenum Sources

Influenced by soil content Found in legumes, meat, fish, poultry, grains

Absorption, transport, & storage

Thought to be passive absorption Thought to travel in blood as molybdate (MoO42+ Most found in liver, kidneys, bone

Molybdenum Functions & mechanisms of action

catalyze oxidation-reduction reactions

Sulfite oxidase Aldehyde oxidase Xanthine dehydrogenase & xanthine oxidase


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Xanthine Oxidase

Iron-sulfur centers (non-heme), FAD, molybdopterin (oxosulfido form) Intestine, thyroid and others

Characteristics of Xanthine Enzymes

Iron-sulfur centers (non-heme), FAD, molybdopterin (oxosulfido form) Location of enzymes:

o Dehydrogenase - Liver, lungs, kidneys, intestineo Oxidase Intestine, thyroid, otherso Aldehyde oxidase liver

Aldehyde oxidase is similar to dehydrogenase and uses oxygen aselectron acceptor

Dehydrogenase formOxidase form

o Oxidation of sulhydryl group or proteolysis of portion of enzyme Dehydrogenase and oxidase forms hydroxylate purines, pteridines,

pyrimidines, other ringed nitrogen compounds

Little clinical evidence of Mo deficiency deficiency Reperfussion injury excess xanthine oxidase activity

Molybdenum Interactions with other nutrients

Tungsten antagonizes Mo Sulfur & copper Ruminants - High intake S or Mo depresses Cu uptake

Rumen sulfur metabolites replace O2 on Mo New Mo form binds Cu

Manganese, zinc, iron, lead, ascorbic acid, methionine, cysteine, protein shown to affect Mo availability but mechanism not yet shown

Molybdenum Excretion

Mostly as molybdate in urine Small amounts in bile, sweat, hair

Molybdenum Recommended Dietary Allowance

Adults: 45g

Pregnancy/lactation: 50g


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Molybdenum Deficiency

Diet rich in antagonistic substances (e.g.sulfate, Cu, tungstate) Low Mo intakes associated with cancer of esophagus in China

Toxicity

UL = 2 mg

Assessment of nutriture

No validated indicators although plasma and tissue levels appear to be

comparable

C. Fluoride

Fluoride Sources

Fluoridated water In US, 1 ppm (1 mg/liter)

Provides about 0.24 mg/cup3.4 mg/day Some grains(legumes), some marine fish Tea Leaves accumulate the element in high amounts

Fluoride Digestion, absorption, transport, & storage

In water or toothpaste, rapid absorption In food, protein-bound F hydrolyzed Calcium in diet forms precipitates with F Thought to be absorbed by passive diffusion (rapid in stomach - exists as

HF at low pH)

Transported as ionic F or hydrofluoric acid, or bound (nonionic/organic) Most found in bones & teeth

Fluoride Functions & mechanisms of action

Promotes mineral precipitation from amorphous solutions of Ca & phosphate -

formation of apatite

F can replace hydroxide ions in apatite (1:20-40); resulting apatite more

resistant to acid

Matrix protein high affinity for F - May stimulate nucleation and deposition of

calcium in the matrix (rather than be part of it)

Topical F appears to decrease production of acid by oral bacteria

Fluoride and Tooth Decay

Role in prevention of cavities:

Secreted in saliva Aids in synthesis of fluorapatite crystals Increases remineralization of new tooth lesions Increases mineral concentrations in plaque that help mineralization and

remineralization

Fluorapatite is more resistant to acid erosion

Inhibits bacterial growthStimulates osteoblasts to make new bone?- needs further studies.


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Relationship Among Caries Experience, Dental Fluorosis, and Fluoride

Concentration of Drinking Water

DRI, NAP, 1997

Fluoridation is ControversialCheng et al, 2007

Fluoride Effects on Caprine Osteoblasts

Qu et al, 2008

Osteoblasts isolated from embryonic caprine calvaria Incubation experiments with graded levels of fluoride

Measured osteoblast proliferation, alkaline phosphatase activity, and apoptosis Low doses of fluoride increases proliferation and mineralization; high

doses are detrimental

Fluoride Interactions with other nutrients

Aluminum, calcium, magnesium, chloride all reduce F uptake Phosphate and sulfate increase uptake

Fluoride Excretion

Mostly in urine (inversely related to pH because of HF availability at low pH),

also feces sweat

Fluoride Adequate Intake

Men: 4 mg; women: 3 mg

American Dental Association recommends fluoridation of water at 1-2 ppm

Fluoride UL

10 mg/d for children >8 years and adults

1.3 mg/d for children 1-3 years

Fluoride Deficiencycan possibly decrease growth in test animals but not well documented. There is

also No evidence on growth for humans. HOWEVER, good evidence it reduces

tooth decay

Toxicity of Fluoride

Chronic toxicityo Mottling or weakening of the teeth in children (2-8 mg F/kg BW)o Skeletal fluorosis

Acute toxicityo nausea, vomiting, diarrhea, acidosis, cardiac abnormalities

Preventiono Limit toothpaste to pea size for childreno Prevent multiple uses of fluoride


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Fluoride Assessment of nutriture

o Plasma or urine concentrations normal range 0.01 0.2g F-/ml plasma or0.2 1.1 mg F-ml urine

o Ion-specific electrode potentiometry

manganese molybdenum flouride reviewer

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