Trace Elements

1
Trace Elements

• Reed A Berger MD
• Visiting Clinical Professor in Nutrition

2
Trace Elements

• -a naturally occurring, homogeneous, inorganic
  substance required in humans in amounts less than
  100 mg/day

3
Copper

• -found in the liver, brain, heart, kidneys, and
  muscle
• -about 90 of copper in the plasma is in the form
  of ceruloplasmin
• -the rest is bound to albumin, transcuprein, and
  AAs

4
Functions

• -component of many enzymes
• -oxidation of Fe prior to transport in the plasma
  
• -cross-linking of collagen
• -mitochondrial energy production, protection from
  oxidants, etc

5
Absorption, Transport, Excretion

• -some absorption from the stomach, but most in
  the small intestine
• -absorption variesit decreases with increased
  intake

6
Metabolism

• -for short term transport to the liver copper is
  carried primarily by albumin
• -copper-albumin complex acts as a temporary
  storage site for copper
• -in the liver, metallothionein is the storage
  site
• -ceruloplasmin is the storage site in the plasma
  and cells

7

• -secreted from the liver as a component of bile
• -once in the GI tract, it becomes part of the
  bodys pool and is reabsorbed or excreted
  depending on the bodys need
• -biliary excretion increases in response to
  copper overload
• -small amts of copper are present in the urine,
  sweat, and menstrual blood
• -can be conserved by the kidney for reabsorption

8

• -unabsorbed copper is in the feces
• -in high levels, zinc can induce copper
  deficiency by stimulating intestinal cells to
  produce more metallothionein which binds copper
  more avidly than zinc and then is exfoliated with
  the intestinal cells
• -fiber and phytate do not adversely effect copper
  absorption

9
RDA and Sources

• -see handout

10
Deficiency

• -decrease in serum copper and ceruloplasmin
  levels are seen
• -neutropenia, leukopenia,bone demineralization
• -subperiosteal hemorrhages, hair and skin
  depigmentation, defective elastin formation
• -failure of erythropoiesis, cerebral and
  cerebellar degenerationgtgtgtdeath

11

• -neutropenia, leukopenia are the best early
  indicators in children
• -because it is stored in the liver, deficiency
  takes a long time to develop
• -bone changes such as osteoporosis, soft tissue
  calcification can occur with prolonged TPN

12
Menkes disease

• -sex-linked recessive defect that results in
  copper malabsorption, increased urinary loss, and
  abnormal intracellular copper distribution
• -affected infants retarded growth, defective
  keratinization and pigmentation of hair,
  hypothermia, degenerative changes of the aorta,
  mental deterioration, abnormalities of the
  metaphyses of long bones
• -all of the above is due to interference with
  collagen and elastin cross-linking

13
Menkes contd

• -there is accumulation of copper in the
  intestinal mucosa even though copper and
  ceruloplasmin levels are very low
• -transient improvement with parenteral copper

14

• -decreased plasma copper levels are also seen
  in malabsorptive diseases, celiac sprue, tropical
  sprue, protein-losing enteropathies, and
  nephrotic syndrome

15
Toxicity

• -increased copper levels seen during pregnancy
  and in women on OCPs, those with acute and
  chronic infections, pts with liver disease
• -any liver disease that interferes with bile
  excretion (primary biliary cirrhosis) and
  mechanical obstruction causes increases in liver
  copper
• -Wilsons disease accumulation of excessive
  copper in the body tissue as the result of a
  genetic deficiency in the liver synthesis of
  ceruloplasmin

16
Iodine

• -body normally has 20-30 mg of iodine and more
  than 75 is in the thyroid gland
• -the rest is in the mammary gland, gastric
  mucosa, and blood
• -its only function is related to thyroid hormone

17
Absorption and Excretion

• -iodine is absorbed in the form of iodide
• -occurs both as free and protein-bound iodine in
  circulation
• -iodine is stored in the thyroid where it is used
  for the synthesis of T3 and T4
• -the hormone is degraded in target cells and in
  the liver and the iodine is conserved if needed
• -excretion is primarily via urine
• -small amts from bile are excreted in the feces

18
Deficiency

• -goiterenlargement of the thyroid gland
• -deficiency may be absolutein areas of
  deficiency, or relativeadolescence, pregnancy,
  lactation
• -goiters are more prevalent in women and with
  increased age

19

• -goitrogens occurring naturally in foods can
  cause goiter by blocking absorption or
  utilization of iodine (cabbage, turnips, peanuts,
  soybeans)
• -severe deficiency during gestation and early
  postnatal growth cretinismmental deficiency,
  spastic diplegia, quadriplegia, deaf mutism,
  dysarthria, shuffling gait, short stature,
  hypothyroidism

20
Toxicity

• -iodine has wide margin of safety
• -goiter usually occurs with excess intakegtneed

21
Chromium--Functions

• -required for normal lipid and CHO metabolism and
  for the fxn of insulin
• -?can supplementation raise HDL

22
Absorption and Excretion

• -10-25 absorption in its trivalent form
• -amount absorbed remains constant at dietary
  intakes gt40 ug (micrograms) at which point
  excretion in urine is proportional to intake
• -increased intake of simple sugar, strenuous
  exercise, or physical trauma also increase
  urinary excretion
• -both chromium and Fe are carried by Tf, however
  albumin can also assume this role

23
Deficiency

• -altered CHO metabolism, impaired glucose
  tolerance, glycosuria, fasting hyperglycemia,
  increased insulin levels and decreased insulin
  binding
• -impaired growth, peripheral neuropathy, negative
  nitrogen balance
• -increased chromium losses in stress
• -hyperglycemia and wt loss reverse with IV
  supplementation in TPN

24
Cobalt

• -most stored with vitamin B12
• -component of B12cobalamin
• -essential for maturation of RBCs and normal
  function of all cells

25
Absorption and Excretion

• -shared with Fe
• -absorption is increased in pts with deficient Fe
  intake, portal cirrhosis with Fe overload, and
  hemochromatosis
• -excretion is mainly thru the urine
• -small amts in feces, hair, sweat

26
Sources and Intakes

• -microorganisms are able to synthesize B12
• -humans must obtain B12 and cobalt from animal
  foods such as organ and muscle meat
• -takes a long time to become deficienthappens
  in vegetarians

27
Deficiency

• -related to vit B12 deficiency
• -macrocytic anemia
• -genetic defect pernicious anemia
• -tx massive doses
• -more in the vitamin lecture

28
Toxicity

• -polycythemia
• -hyperplasia of BM
• -reticulocytosis
• -increased blood volume

29
Selenium

• -glutathione peroxidase
• -acts with other antioxidants and free radical
  scavengers
• -overlaps with vit E for antioxidant effects
• -fxn with vit E to protect cell and organelle
  membranes from oxidative damage

30
Absorption and Excretion

• -upper segment of the small intestine
• -increased absorption with deficiency
• -status is measured by measuring selenium or
  glutathione peroxidase in plasma, platelets, and
  RBCs or selenium levels in whole blood or urine
• -RBC selenium is an indicator of long-term status

31
Deficiency

• -rare
• -Keshan Dz or Kashin-Beck Dz
• -long term TPN, cancer, CF

32
Molybendum

• -relationship with copper and sulfate
• -cofactor of many enzymes involved in the
  catabolism of sulfur AA, purines and pyridines
• -Toxicity gout-like syndrome, reproductive SEs
• -Deficiency increased risk with co-existing
  copper deficiency, TPN

33
Silicon, Vanadium, Arsenic, Boron

• -see handouts
• -will not be on the exam!!!