Lecture 8 - Anemia Flashcards
Which vitamins and mineral are involved in RBC synthesis?
Folate
B12
Protein
Which vitamins and mineral are involved in hemoglobin ?
B6
Fe
Glycine
Protein
Which vitamins and mineral are involved in the maintenance of RBCs?
Vitamin E
-prevents free radicals from impacting the cell wall
Which vitamins and mineral are involved in clotting function?
Vitamin K
Ca
Protein
Eicosanoids
Which vitamins and mineral are involved in oncotic pressure?
Proteins
What is PLP?
Pyridoxal Phosphate
-an essential cofactor for delta aminolevulinic acid synthase (ALAS)
Where does PLP and ALAS come from?
From Krebs cycle
-substrate for reaction includes succinylcholine CoA& glycine
What does a deficiency win B6 lead to?
B6 required in the 1st step of heme synthesis in all tissues
-rxn occurs in the mitochondria
Deficiency of B6 or malabsorption will inhibit heme synthesis
-if your body doesn’t have enough B6 the body won’t start this process
Where is hemoglobin synthesized?
Liver and bone marrow
Why is vitamin C important?
increases bioavailability of non-heme Fe
-acts as a reducing agent to turn Fe3 to Fe2 to be absorbed better in the body
-Chelate remains soluble in the small intestine intestine improving absorption `
What is the effect of Vitamin C related too?
It is dose related
Why is vitamin E important?
Is a strong antioxidant which stabilizes membranes to prevent oxidative damage
- helps prolong RBC life
- helps reduce platelet aggregation and platelet adhesion to collagen
What is erythropoiesis?
Hematopoietic tissue in bone marrow produce RBC (red bone marrow)
What do erythroblasts require during their differentiation?
Folate and B12 for proliferation
What are folate and B12 important for?
Involved in DNA and RNA synthesis
Helps RBCs to form and split
What does a deficiency in Folate or B12 result in?
Deficiency inhibits purine and Thymidylate synthesis
- which causes cells to die early
- causes erythroblast apoptosis
What is Fe required for?
Hemoglobin synthesis
What is a deficiency in Fe result in?
Inhibits heme synthesis and RBC contain reduced amount of hemoglobin (hypochromic)
where does most of the Fe in your body go too?
80% Fe transported to bone marrow for heme synthesis
At what stage of the RBC does the bone marrow release it into the body?
Reticulocyte phase
What are the different kind of nutritional anemias you can have?
Microcytic, hypochromic: low hemoglobin levels, heme requires Fe, B6 (Vt C to enhance Fe absorption), glycine
Macrocytic: Immature RBC, cellular differentiation requires folate and B12
Normocytic, Normochromic: Anemia due to chronic disease
What does it mean to have Fe Deficiency?
Hypochromic mycrocytic
-Missing hemoglobin if you font have enough Fe you don’t have the hemoglobin to give it the colour
What does it mean when you have an anemia of chronic disease?
Related to inflammation of the body due to chronic conditions (small but norma in colour)
What do RBC look like when you have macrocytic/megaloblastic anemia?
Big and red RBC
-due to lack of folate and or B12 deficiency which affects DNA synthesis
What are the lab results of someone with Macrocytic or megaloblastic anemia?
Erythrocytes
- Increase mean cell hemoglobin (MCH)
- Increase mean cell volume
- Decrease RBC count
Decrease in Serum RBC[Folate], [B12], [Hgb], [Hct]
Increase Reticulocyte distribution widths (RDW)
What is RDW?
Reticulocyte distribution Width
Distribution of the size of the cells
-tells you that there is a variance in the RBC size
-doesnt say if its larger or smaller
What are scenarios when you have small or large RDW?
Small: cells are normal and are all the same size, there is little variance in size
Large:Micro/Macto anemia cause there is going to be different sized RBC
What does having microcytic or hypochromic anemia result in?
Fe deficiency
What do the labs look like for microcytic or hypochromic anemia?
Erythrocytes
- Decrease (MCV)(MCH)
- Increase RBC count
Decrease: Serum [Fe] [Ferritin][Hgb][Hct], Fe transferrin saturation
Increase: Serum [Transferrin] Total Fe binding Capacity, RDW
What is transferrin?
Transporter for Fe
What is the function of Fe?
Transport O2 as a component of Hgb or RBC
-also a component of myoglobin of muscles (stays in muscle)
Required for some runs involving energy formation
How many gs or Fe does out body have and where is it found within the body?
2-4g of elemental Fe
65% hemoglobin
10% Myoglobin
1-5% Enzymes
Remainder in blood/storage
-Bacteria love Fe so it has to be bound
How does Fe get transported and stored?
Transport= Transferrin
Storage= Ferritin
- liver
- bone marrow
- spleen
What are the 2 forms of Fe?
Heme- Fe in the porphyrin ring structure
-high bioavailability
Non heme- bound to components of food and have to be hydrolyzed, digested or solubilized prior to absorption
- mostly Fe3 (ferric)
- less bioavailability
- more subject to inhibitors
What are some inhibitors of non heme Fe absorption?
Polyphenols (coffee and tea) Oxalic Acid (spinach) Phytates (legumes) Ca Zn
How it Heme Fe absorbed and transported?
-Hydrolyzeed from global portion
-Remains soluble and absorbed intact across brush border by hem protein 1
-Proximal small intestine
0Heme hydrolized within mucosal cell into Ferrous Fe and protoporphyrin
How its non heme Fe absorbed and transported/
Hydrolyzed from components of food (Hal proteases)
Mostly Ferric Fe- remains soluble if acidic
Transported into mucosal cell via divalent mineral transporters (DMT-1)
-Zn, Mn share same transporter
What does the transferring transporter saturation depend on?
Rate of uptake
- binding serves to protect Fe from redox rxns
- carries Ferric (Fe3)
Where is most Fe stored?
Spleen and liver 60% as ferritin and hemosiderin
What is the turnover for Fe like?
20% absorption for heme
8% Absorption for nonheme
-amount of Fe absorbed cannot meet daily Fe requirements of body
-body is really good at conserving and recycling Fe from RBC
How do you lose Fe?
Stools due to cells, bile and blood loss
Gut due to gastritis, aspirin, infection, parasites, ulcers, cancer, hemorrhoids
What characteristics does one have to be Moree susceptible to Fe deficiency?
Decreased stomach acidity
Impaired Fe absorption
Blood donation
Intestinal parasitic infection
Why are kids and infant susceptible to Fe deficiency?
Cow milk is a poor source of Fe (very filling too)
Periods
Adolescent growth spurts - high demand in growth increases demand for everything to match
Can drugs impact Fe absorption ?
Yes, oral contraceptives and HRT
-reduces blood loss
Which groups of people have inadequate intake of Fe?
Elderly (reduced Hal and meant consumption)
Alcoholics
Vegetarians
Does being extremelyy active affect your Fe intake?
Yes, due to high wear and teat and Fe being used to repairs the body constantly
How common is Fe deficiency?
5-10% of women
> 50% of women have inadequate Fe stores in USA
1/3 pregnant women who do not take supplants have IDA
What is Fe deficiency?
An anemia: microcytic, hypochromic, with diminished O2 transport
Decreased performance during physical exertion
Long term deficiency results in permanent effects on development in children (fatigue, psychomotor performance, brain development)
What is Fe deficiency anemia?
Impaired adaptations to cold
Reduced immune functions
Increased lead absorption
Can lead to low birth weigh and preterm delivery
What can Fe toxicity be due to?
Accidental Fe overload (excessive ingestion of Fe supplements
Genetic Disorder (HH)
Absorbed Fe progressively deposited within joints and tissues
2 mutation found on chromosome, HFE gene
What is HH?
Hereditary hemochromatosis
- caucasian males ~20yo
- have increased absorption, maximally absorbing all Fe in body and depositing it elsewhere in the body when stores are full
How do you treat Fe toxicity?
Blood work (donating blood) and low Fe diet
What is the risk of excess Fe in population?
More Fe in the body can lead to more mutations leading to an increase in cancer
Indication of inflammation
Avoid alcohol if you have HH
What is the 1 stage when assessing Fe deficiency status?
[Fe Depletion]
Depletion of Fe stores (body can’t replace)
Plasma ferritin <12microg/L associate with ID
Inflammation/infection serum ferritin concentration rise unrelated to Fe stores
Confounded by chronic disease states (infection, inflammation, neoplastic& liver disease)
What is the 2nd stage when asses for Fe deficiency status?
[Fe deficiency] Transport Fe decreases Transferrin Saturation <16% (confounded) Plasma transferring increases 4mmol/L TIBC increases (confounded) Serum Fe <9mmol/L Increase erythrocyte protoporphyrin (precursor for hemoglobin molecules)
What is the 3rd stage when we asses for Fe deficiency?
[Fe deficiency Anemia]
Functioinal Fe limited
Hemoglobin women, pregnant, men= <120, 110, 130g/L
Mematocrit women, pregnant, men= <37%, 33% 40%
Decrease in MCV
Increase RDW
*plus all markers in stage 2
Do plant based milks have Fe?
Its voluntary Fe fortification but if they do they have to do it to the same concentration as cow milk
How much Fe do we need?
For growth and UL 45mg
Men: 8mg
Women: 18mg
50+: 8mg
Pregnant: 27mg
What is the major cause of Fe deficiency in women men and children in developing countries?
Women: Diet or excess menstrual losses
Men: Suspect other factors (Disease)
Children: When giving Fe supplement, beware of feeding parasites
What are sources of folate?
Supplements and white wheat flour
(folic acid)
Legumes and leafy greens (naturally occurring, not stable, destroyed via cooking
What are the roles of Folate in the Body?
One carbon metabolism
- Universal methyl donor
- Uracil resides in transfer RNA
- deoxyuridylate to thymiidylate ini DNA synthesis
Amino acid synthesis
- Methionine (homocysteine)
- Serine/glycine interconversions
DNA/RNA synthesis
-Pyrimidines, purines
When do you need more folate?
Increased anabolic activity/periods of growth
If you are deficient in either Folate or B12 what is the result?
Megaloblastic anemia
How do you get megaloblastic anemia from a B12 deficient?
Methylfloate trap
- folate is metabolically unavailable for thymidylate formation
- Folate accumulates as 5-methyl tetrahydrofolate (inactive form) in absence of B12
What can not enough folate lead too?
Birth defects
Stroke
Anemia
What can too much folate lead to?
Masking B12 deficiency Presence of circulating unmetabolized folic acid Cognitive function Drug efficacy Epigenetic effects
What influences the absorption of folate?
Alcohol
Chrons
Tropical sprue
Celiac
Which groups are most at risk fro Folate deficiency?
Elderly (intake, lack of HCl)
Pregnant (Demand)
Alcoholics, smokers
Those taking the pill, anticonvulsants, depression meds
What does your blood look like and characteristics you have when you have a folate deficiency?
Megaloblastic anemia
Decreased white cells and decreased platelets
INtestinal function altered due to abnormal turnover of intestinal villa cells
Fatigue, weak, pallor, irritable, diarrhea, sore tongue, forgetfulness
What is the gestational risk of folate deficiency?
NTD Cleft lip/palate Heart defect LBW Preterm birth
What is the population risk of folate deficiency?
Stroke
Cancer
Megaloblastic anemia
What are the most common types of neural tube defects?
Spina bifida
Anencephaly (top and back of head)
-due to which part of the neural tube didn’t form properly
What are neural tube defects?
Congenital anomalies caused by failure of closure of the neural tube at 22-27 days after fertilization
1/1000or2000
-since fortification NTD declined 46% since 1998
What increases with what deficiency to increase the risk of CVD and stroke?
Homocysteine increases in patients with folate or vitamin B12 deficiencies
What studies showed an increase in CVD/stroke when you have a B12 or Folate deficiency?
Physicians Heart study
Framingham Heart study
NHANES II (2.9x increase in odds for stroke)
HOPE Study (Vitamin supplementation B6,12 and FA, decreased they but no evidence of reduced risk) -Didnt reduce heard disease which is the relation with homocysteine
What is a folate deficiency and its relation to cancer?
Deficiency leads to:
- Increased uracil incorporation in DNA (makes it more susceptible to oxidation)
- In vitro change suggestive of DNA & chromosomal damage
- Excess folate (leads to the development in breast, prostate and colon cancer)
What is the population strategy?
Mandatory food fortification effective 1998 for folate
- enriched white flour and bread (100gflour has 0.15 folic acid)
- Enriched pasta cornmeal (200mg FA/ 100g)
How much does the population strategy increase someone’s overall FA intake/day?
100micrograms/day
What is the risk of HIGH FA intake in the population?
Masking B12 deficiency Reduced response to Antifolate drug Immune infection Cognitive impairment Cancer
What is the risk of HIGH FA intake for the gestaition period?
Fetal programming :
- respiratory
- obesity
- Insulin sensitivity
What is the general intake of Folate in Canada?
Less than 1% had deficiency
40% showed [high]
22% women of child bearing age had concentrations below optimal for NTD risk reduciton
How does high FA mask B12 deficiency?
Prevents the anemica that normally develop when you are deficient in B12
-Folate cant Evers the hematological response in B12 patients but fails to prevent irreversible neurological changes associated its B12
How can you measure folate status?
Serum/Plasma Folate
- most commonly performed test
- Poor indicator of the degree of folate deficiency
- Poor sensitivity (low plasma may reflect how dietary intake and provide little Information on tissue reserves
What affects the specificity of the Serum/Plasma Folate test?
Affected by an:
-Increase: liver damage, hemolysis
-Decrease; Alcohol, oral contraceptives, pregnancy, smoking
What is the limit off FA intake?
- intakes of 1mg/day are not likely to mask B12
- No evidence exists that 0.4mg/day of folate4 increased risk of masking B12 deficiency
What can high FA supplementation revers the effects off?
Anticonvulsant meds:
- phenyton (dilatin)
- Phenobarbital
- Pyrimidine
What is the Folate RBC test?
RBD [Folate] is more accurate and less variable than plasma folate as to the severity of folate deficiency
- not affected by short term influx
- $$$$
Is the RBC[Folate] test easy to measure? What does it measure?
More difficult to measure and $$$
-microbiological assay (gold standard)
Folate incorporated during erythropoiesis
- indicative of tissue folate stores
- not influenced by dietary intake
What is the sensitivity of the RBD [Folate] test?
- Reduction in tissue folate stores is reflected by RBC folate
- RBD [Folate] Reflects folate states at the time it was being synthesized
- Decreases more slowly than serum/[plasma folate in deficiency
What is the specificity in RBC [Folate]?
Not specific for folate deficiency - low values occur in B12 deficiency
Increases in Fe deficiency (magnitude and Etiology)
Elevated in liver disease and certain cancers
What is plasma homocysteine?
tHCY in plasma can serve as a marker for folate, B12 and B6 inadequacies
- High plasma tHCY almost always exists with B12/6 or Folate deficiency
- In the absence of B12/6 deficiency [homocysteine] can serve as functional test for folate status
What is the sensitivity and specificity of Homocysteine?
Sensitivity:
-more sensitive than fall in plasma folate to mark change in folate related physiology
Specificity:
-Mot specific for folate as affected by B12/6 also
What is the Leukocyte lobe count?
Tells you that you have a nutrient deficiency related to blood cells but cant distinguish which one
-earlier hematological sign for folate deficiency (physical sign in blood smear)
How many lobes do leukocytes have in general and how many makes it abnormal?
Usually have 3.2 lobes in a healthy individual
Greater than 3.5 lobes Is abnormal in later stages of folate deficiency
What happens to leukocytes in folate deficiency?
Hypersegmentation occurs resulting in an increased in number of n nuclear lobes
-also increase with B12 deficiency, uraemia, certain types of leukaemia
Following hypersegmentaiton, next change is an increase in size of RBC (increased MCV)
What is the sensitivity and specificity for leukocyte lobe count?
Sensitivity:
-no relationship between severity and degree of hypersegmentation
Specificity:
-Does not distinguish between folate and B12 deficiencies - occurs in other conditions
What is a dU?
Deoxyuridine suppression test
- folate status measurement
- not common
- Function indicator of folate status
What do you test in a dU?
Testing of bone marrow incorporation of radioactive substrate into RBC
Identifies which nutrient is deficient (B12 or folate) by seeing the incorporation of iridium into DNA strands
In folate deficiency what does it show the synthesis of in RBCs?
Megaloblasts
- abnormal precursors of RBCs, showing abnormal erythropoietic process
- reffered to as folate deficiency erythropoiesis
What are the DRIs for folate?
M/F 400micrograms/day
Pregnant 600micrograms/day
What is the upper limit for folic acid?
1000micrograms/day
-anything above that can mask B12 deficiency
What is Cyanocobalamin Pernicious Anemia?
Deficiency in B12
- megaloblastic anemia and nerve/brain damage
- Actual cause was defective parietal cells or lack of intrinsic factor (IF)
What are sources of B12?
B12 or cobalamin produced by micro organisms in plants
Animal products and meat alternatives
What are the DRIs for B12?
RDA
- Adults 2.4 micrograms/day
- 2.8 during pregnancy
What is the limiting factor for B12 absorption?
Intrinsic Factor
-we can only absorb so much
What are the 2 forms of B12?
Methylcobalamin
-involved in carbon metabolism
5-Deoxyadenosylcobalamin
-MG pathway
Both contain cobalt
What is the function of B12 in the body?
DNA synthesis
Folate absorption
Myelin Synthesis
Enzymatic Rxns
What are the 3 rxns that B12 is involved in?
Homocysteine-> methionine
-methionine synthase where b12 is a cofactor
Methylmalonic Acid -> Succinyl CoA
-Energy pathway by methylmalonyl CoA mutase
Methyltetrahydrofolate-> tetrahydrofolate
How is B12 absorbed and metabolized?
B12 binds intrinsic factor (glycoprotein-> B12 absorption limited by capacity of IF
-absorption on receptor sites in ileum
How is B12 transported?
Trans cobalamin II
Where is the storage of B12?
Stored in Liver in these forms:
Doxyadenosyl cobalamin 65-75%
Hydroxycobalamin 20-30%
Methylcobalamiine 1-5%
How does one get B12 deficiency?
Genetic- polymorphism, deficiency in receptors
Pharmacological- H2 receptor inhibitor, PPIs
Infection and Parasites- H pylori, tropical sprue
Disease- Celiac, Chrones
Age (Lack HCl)
Social (Religion)
Dietary (vegetarian)
Lifestyle (Obesity, Chronic alcoholabuse)
What are the clinical signs and symptoms of B12 deficiency?
Fatigue Generalized weakness Indigestion Pallow Diarrhea Smooth beefy red tongue (atrophic glossitis)
What is a secondary effect of vitamin B12?
Demyelination affected Spinal cord, brain, optic nerve and peripheral nerves may all be affected
- start to feel tingles in the feet and hands first
- confounding cause diabetes causes numbness and tingling
What are the cerebral signs of B12 deficiency affecting the nervous system?
Irritability Apathy Marked Confusion Depression Memorry Loss Psychosis Optic neuropathy
What are the ways in which to test for B12?
Serum B12
Leukocyte lobe count
Holo transcobalamin (transporter for B12)
Methylmalonic Acid (MMA)
(distinct molecule related to the energy pathway)
Schilling test (radioactive IF)
Serum Homocysteine
What is the serum B12 test?
Serum B12 + CBC
-reflects B12 intake and body stores
Classical Findings: Megaloblastic anemia- identical to folate deficiency
what is the sensitivity and specificity of B12?
Sensitivity: Stores only reflected when low
Specificity: B12 Levels measured are directly affected by serum binding proteins
What does serum B12 have decreased levels in?
Elderly Pregnancy Fe/Folate deficiency Cancer Medications Malabsorption Gastrectomy/ileum resection
What is the holo transcobalamin II test?
Circulating transport protein delivers B12 tro receptors
Early and sensitive measure of B12 deficiency
- short 1/2 life
- Amount of B12 attached to holoTCII drops but no drop in serum B12
- Decrease with deficiency
B12 rapidly depleted from holo transcobalamin II with low fit B status
What is the specificity of holo transcobalamin II test?
More specific than tHYC
What is the MMA test?
Serum of plasma methylmalonic acid (Functional test)
MMA may be an early indicator of deficiency
Useful to identify individuals with deficiency even if subclinical (only seeing reduced functions)
-elevated in B12 deficiency but not with folate or B6 deficiency
When does myelin damage occur?
Doesn’t occur until we area talking about deficiency
How sensitive if MMA test?
More sensitive and specific indicator of B12 deficiency than Serum B12
What is the Shilling test?
Older test for B12
- Newer tests to detect pernicious anemia
- Newer is better and cheaper
What does Serological assays measure?
B12 deficiency by measuring intrinsic factor using antibodies
-is presence of IF antibodies then you have pernicious anemia
What does gastrin measure?
Endocrine regulatory. peptide secreted by stomach, attempt to increase Hal secretion by stomach
-if gastrin increases you have pernicious anemia
How do you treat B12 deficiency?
Supplementation
-usually oral, then if it doesn’t start to correct in 3 months then injection
What are the advantages of oral supplementation?
Save money
Avoid painful injection
Avoid repeated patients visits
What dosage is required to correct neurological deficits?
1000microgram/day to help improve and correct neurological deficits
After someone is on oral B12 supplements for 3 months, what should the checkup tests be?
Serum B12
CBC
Is the masking of Vitamin B12 really something to worry about?
Prevalence of inadequacy under estimated due to erroneous belief that deficiency unlikely except among strict vegetarians or patient with pernicious anemia
- adults: 5% severe, 14-16% marginal
- 70+: 6% severe, >20% marginal
Out of the different types of vegetarians, who ones have the most B12?
Omnivores
LOV+Fish
LOV
Vegan
What % of Canadas population is B12 deficiency?
4.6%
20% marginal B12 status
94.9% had normal tHcy
What are the B12 concentration in breast milk like?
B12 concentrations in breast milk DO reflect maternal status
How much FA do prenatal supplements need to have?
More than 200 micrograms of FA
