Biochem FA - p65-72 Nutrition

Question 1

Fat soluble vitamins? Absorption dependent on what?

Answer 1

A, D, E, K Absorption dependent on gut and pancreas.

Question 2

What can cause fat-soluble deficiencies?

Answer 2

Malabsorption syndromes with steatorrhea (eg, cystic fibrosis and celiac disease) or mineral oil intake

Question 3

Water soluble vitamins?

Answer 3

B1 (thiamine: TPP) B2 (riboflavin: FAD, FMN) B3 (niacin: NAD+) B5 (pantothenic acid: CoA) B6 (pyridoxine: PLP) B7 (biotin) B9 (folate) B12 (cobalamin) C (ascorbic acid)

Question 4

What water soluble vitamins are not easily washed out?

Answer 4

B12 and B9 (folate) B12 stored in liver for ~ 3–4 years. B9 stored in liver for ~ 3–4 months.

Question 5

Result of B-complex deficiencies?

Answer 5

B-complex deficiencies often result in dermatitis, glossitis, and diarrhea.

Question 6

VITAMIN A AKA? Function?

Answer 6

AKA retinol Antioxidant; constituent of visual pigments (retinal); essential for normal differentiation of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells); prevents squamous metaplasia.

Used to treat measles and acute promyelocytic leukemia (APL).

Retinol is vitamin A, so think retin-A (used topically for wrinkles and Acne). Found in liver and leafy vegetables. Use oral isotretinoin to treat severe cystic acne. Use all-trans retinoic acid to treat acute promyelocytic leukemia.

Question 7

VITAMIN A Deficiency leads to..?

Answer 7

Night blindness (nyctalopia); dry, scaly skin (xerosis cutis); corneal squamous metaplasia Ž Bitot spots (keratin debris; foamy appearance on conjunctiva A ); corneal degeneration (keratomalacia); immunosuppression.

Question 8

VITAMIN A Excess leads to..?

Answer 8

Acute toxicity—nausea, vomiting, vertigo, and blurred vision. Chronic toxicity—alopecia, dry skin (eg, scaliness), hepatic toxicity and enlargement, arthralgias, and idiopathic intracranial hypertension. Teratogenic (cleft palate, cardiac abnormalities), therefore a ⊝ pregnancy test and two forms of contraception are required before isotretinoin (vitamin A derivative) is prescribed. Isotretinoin is teratogenic.

Question 9

VITAMIN B1 AKA? Function?

Answer 9

AKA thiamine In thiamine pyrophosphate (TPP), a cofactor for several dehydrogenase enzyme reactions: ƒƒ Branched-chain ketoacid dehydrogenase ƒƒ α-ketoglutarate dehydrogenase (TCA cycle) ƒƒ Pyruvate dehydrogenase (links glycolysis to TCA cycle) ƒƒ Transketolase (HMP shunt) (Be APT)

Question 10

Wernicke-Korsakoff Syndrome

Answer 10

confusion, ophthalmoplegia, ataxia (classic triad) + confabulation, personality change, memory loss (permanent). Damage to medial dorsal nucleus of thalamus, mammillary bodies.

Question 11

VITAMIN B1 Deficiency leads to..?

Answer 11

Impaired glucose breakdown –> ATP depletion worsened by glucose infusion; highly aerobic tissues (eg, brain, heart) are affected first. In alcoholic or malnourished patients, give thiamine before dextrose to dec risk of precipitating Wernicke encephalopathy. Diagnosis made by inc in RBC transketolase activity following vitamin B1 administration.

Question 12

Dry beriberi? Wet beriberi?

Answer 12

Dry beriberi—polyneuropathy, symmetrical muscle wasting. Wet beriberi—high-output cardiac failure (dilated cardiomyopathy), edema. Ber1Ber1

Question 13

VITAMIN B2 AKA? Function?

Answer 13

AKA riboflavin Component of flavins FAD and FMN, used as cofactors in redox reactions, eg, the succinate dehydrogenase reaction in the TCA cycle. FAD and FMN are derived from riboFlavin (B2 ≈ 2 ATP).

Question 14

VITAMIN B2 Deficiency leads to..?

Answer 14

Cheilosis (inflammation of lips, scaling and fissures at the corners of the mouth), Corneal vascularization. The 2 C’s of B2

Question 15

VITAMIN B3 AKA? Function?

Answer 15

AKA niacin Constituent of NAD+, NADP+ (used in redox reactions). Derived from tryptophan. Synthesis requires vitamins B2 and B6. - Need FAD and PLP to make NAD Used to treat dyslipidemia; lowers levels of VLDL and raises levels of HDL. NAD derived from Niacin (B3 ≈ 3 ATP).

Question 16

VITAMIN B3 Deficiency leads to..?

Answer 16

Glossitis. Severe deficiency leads to pellagra, which can also be caused by Hartnup disease, malignant carcinoid syndrome (increased tryptophan metabolism), and isoniazid (low vitamin B6).

Question 17

Symptoms of pellagra

Answer 17

Symptoms of pellagra: Diarrhea, Dementia (also hallucinations), Dermatitis (C3/C4 dermatome circumferential “broad collar” rash [Casal necklace], hyperpigmentation of sunexposed limbs A ). The 3 D’s of B3

Question 18

Hartnup disease

Answer 18

Autosomal Recessive. Deficiency of neutral amino acid (eg, tryptophan) transporters in proximal renal tubular cells and on enterocytes –> neutral aminoaciduria and decreased absorption from the gut –> decreased tryptophan for conversion to niacin –> pellagra-like symptoms.

Treat with high-protein diet and nicotinic acid. Deficiency of vitamin B3 –> pellagra.

Question 19

VITAMIN B3 Excess leads to..?

Answer 19

Facial flushing (induced by prostaglandin, not histamine; can avoid by taking aspirin with niacin), hyperglycemia, hyperuricemia. Excess of vitamin B3 Ž podagra.

Question 20

VITAMIN B5 AKA? Function?

Answer 20

AKA pantothenic acid Essential component of coenzyme A (CoA, a cofactor for acyl transfers) and fatty acid synthase. B5 is “pento”thenic acid

Question 21

VITAMIN B5 Deficiency leads to..?

Answer 21

Dermatitis, enteritis, alopecia, adrenal insufficiency BLAKE works at Pentagon (pantothenic acid) Bald adrenaL coA sKin issues (dermatitis) Enteritis

Question 22

VITAMIN B6 AKA? Function?

Answer 22

AKA pyridoxine Vitamin B6

1. glycogen phosphorylase.
2. De - decarboxylation reactions
3. Tri - a cofactor used in transamination (eg, ALT and AST),
4. 4 products - Synthesis of cystathionine, heme, niacin, histamine
5. 5 Neurotransmitters - serotonin, epinephrine, norepinephrine (NE), dopamine, and GABA.
6. Converted to pyridoxal phosphate (PLP),

Question 23

VITAMIN B6 Deficiency leads to..?

Answer 23

Convulsions, hyperirritability, peripheral neuropathy (deficiency inducible by isoniazid and oral contraceptives), sideroblastic anemia (due to impaired hemoglobin synthesis and iron excess).

Question 24

VITAMIN B7 AKA? Function?

Answer 24

AKA biotin Cofactor for carboxylation enzymes (which add a 1-carbon group): - Pyruvate carboxylase: pyruvate (3C) –> oxaloacetate (4C) - Acetyl-CoA carboxylase: acetyl-CoA (2C) –> malonyl-CoA (3C) - Propionyl-CoA carboxylase: propionyl-CoA (3C) –> methylmalonyl-CoA (4C)

Question 25

VITAMIN B7 Deficiency leads to..?

Answer 25

Dermatitis, enteritis, alopecia. Caused by long-term antibiotic use or excessive ingestion of raw egg whites. “*Avid*in in egg whites *avid*ly binds biotin” that’s fucking stupid let’s think of something better. Relatively rare.

Question 26

VITAMIN B9 AKA? Function?

Answer 26

AKA folate Converted to tetrahydrofolic acid (THF), a coenzyme for 1-carbon transfer/methylation reactions. Important for the synthesis of nitrogenous bases in DNA and RNA.

Question 27

VITAMIN B9 Sources? Storage?

Answer 27

Found in leafy green vegetables. Absorbed in jejunum. Folate from foliage. Small reserve pool stored primarily in the liver.

Question 28

VITAMIN B9 Deficiency leads to..?

Answer 28

Macrocytic, megaloblastic anemia; hypersegmented polymorphonuclear cells (PMNs); glossitis; no neurologic symptoms (as opposed to vitamin B12 deficiency).

Question 29

VITAMIN B9 Labs show..?

Answer 29

Increased homocysteine, normal methylmalonic acid levels.

Question 30

VITAMIN B9 Causes of deficiency

Answer 30

Seen in alcoholism and pregnancy. Deficiency can be caused by several drugs (eg, phenytoin, sulfonamides, methotrexate).

Question 31

VITAMIN B9 Supplemented in pregnancy HOW AND WHY ? (bonus) What can folate supplementation mask?

Answer 31

Supplemental maternal folic acid at least 1 month prior to conception and during early pregnancy to DECREASE risk of neural tube defects. Give vitamin B9 for the 9 months of pregnancy. Folate supplementation can mask the hematologic symptoms of B12 deficiency, but not the neurologic symptoms.

Question 32

VITAMIN B12 AKA? Function?

Answer 32

AKA cobalamin Cofactor for methionine synthase (transfers CH3 groups as methylcobalamin) and methylmalonyl-CoA mutase. Important for DNA synthesis.

Question 33

VITAMIN B12 Sources? Synthesized by? Storage?

Answer 33

Found in animal products. Synthesized only by microorganisms. Very large reserve pool (several years) stored primarily in the liver.

Question 34

VITAMIN B12 Deficiency leads to..?

Answer 34

Macrocytic, megaloblastic anemia hypersegmented PMNs paresthesias and subacute combined degeneration (degeneration of dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts) due to abnormal myelin. Associated with high serum homocysteine and methylmalonic acid levels, along with 2° folate deficiency. Prolonged deficiency –> irreversible nerve damage.

Question 35

VITAMIN B12 Causes of deficiency

Answer 35

Deficiency caused by:

• malabsorption (eg, sprue, enteritis, Diphyllobothrium latum, achlorhydria, bacterial overgrowth, alcohol excess)
• lack of intrinsic factor (eg, pernicious anemia, gastric bypass surgery)
• absence of terminal ileum (surgical resection, eg, for Crohn disease)
• certain drugs (eg, metformin) insufficient intake (eg, veganism).

Question 36

VITAMIN C AKA? Function?

Answer 36

AKA ascorbic acid

• Antioxidant
• Facilitates iron absorption by reducing it to Fe2+ state.
• Necessary for hydroxylation of proline and lysine in collagen synthesis.
• Necessary for dopamine β-hydroxylase, which converts dopamine to NE.
• Ancillary treatment for methemoglobinemia by reducing Fe3+ to Fe2+.

Question 37

VITAMIN C Deficiency leads to..?

Answer 37

Scurvy—swollen gums, easy bruising, petechiae, hemarthrosis, anemia, poor wound healing, perifollicular and subperiosteal hemorrhages, “corkscrew” hair. Weakened immune response. Vitamin C deficiency causes sCurvy due to a Collagen synthesis defect.

Question 38

VITAMIN C Excess leads to..?

Answer 38

• Nausea, vomiting, diarrhea, fatigue,
• calcium oxalate nephrolithiasis.
• Can increase iron toxicity in predisposed individuals by increasing dietary iron absorption (ie, can worsen hereditary hemochromatosis or transfusion-related iron overload).

Question 39

VITAMIN D D3 AKA? Sources? D2 AKA? Sources? Both converted to..? Where?

Answer 39

D3 (cholecalciferol) from exposure of skin (stratum basale) to sun, ingestion of fish, milk, plants. D2 (ergocalciferol) from ingestion of plants, fungi, yeasts. Both converted to 25-OH D3 (storage form) in liver and to the active form 1,25-(OH)2 D3 (calcitriol) in kidney.

Question 40

VITAMIN D Function?

Answer 40

^ intestinal absorption of Ca2+ and PO4^3–. ^ bone mineralization at low levels. ^ bone resorption at higher levels.

Question 41

VITAMIN D Regulation?

Answer 41

^ PTH, low Ca2+, low PO4^3– –> 1,25-(OH)2D3 production.

1,25-(OH)2D3 feedback inhibits its own production. ^
PTH –> Ca2+ reabsorption and low PO4^3– reabsorption in the kidney.

Question 42

VITAMIN D Deficiency leads to..?

Answer 42

Rickets in children (deformity, such as genu varum “bowlegs” A ), osteomalacia in adults (bone pain and muscle weakness), hypocalcemic tetany.

Question 43

VITAMIN D Causes of deficiency? Exacerbation of deficiency?

Answer 43

Caused by malabsorption,  sun exposure, poor diet, chronic kidney disease (CKD), advanced liver disease. Deficiency is exacerbated by pigmented skin, premature birth. Give oral vitamin D to breastfed infants.

Question 44

VITAMIN D Excess leads to..?

Answer 44

Hypercalcemia, hypercalciuria, loss of appetite, stupor. Seen in granulomatous diseases (^ activation of vitamin D by epithelioid macrophages).

Question 45

VITAMIN E AKA? Function?

Answer 45

AKA tocopherol, tocotrienol Antioxidant (protects RBCs and membranes from free radical damage).

Question 46

VITAMIN E Deficiency leads to..?

Answer 46

Hemolytic anemia, acanthocytosis, muscle weakness, demyelination of posterior columns ( position and vibration sensation) and spinocerebellar tract (ataxia).

Question 47

VITAMIN E Neurological presentation similar to ____ but without..?

Answer 47

Neurologic presentation may appear similar to vitamin B12 deficiency, but without megaloblastic anemia, hypersegmented neutrophils, or ^ serum methylmalonic acid levels.

Question 48

VITAMIN E Excess leads to..?

Answer 48

Risk of enterocolitis in infants. High-dose supplementation may alter metabolism of vitamin K –> enhanced anticoagulant effects of warfarin.

Question 49

VITAMIN K AKA? Function? Synthesis?

Answer 49

AKA phytomenadione, phylloquinone, phytonadione, menaquinone Activated by epoxide reductase to the reduced form, which is a cofactor for the γ-carboxylation of glutamic acid residues on various proteins required for blood clotting. Synthesized by intestinal flora.

Question 50

VITAMIN K Clotting factors? Inhibited by..?

Answer 50

K is for Koagulation. Necessary for the maturation of clotting factors II, VII, IX, X, and proteins C and S. Warfarin inhibits vitamin K–dependent synthesis of these factors and proteins.

Question 51

VITAMIN K Deficiency leads to..? (bonus) Why give Vitamin K injection to neonates at birth?

Answer 51

Neonatal hemorrhage with ^ PT and ^ aPTT but normal bleeding time (neonates have sterile intestines and are unable to synthesize vitamin K). Can also occur after prolonged use of broad-spectrum antibiotics. Not in breast milk; neonates are given vitamin K injection at birth to prevent hemorrhagic disease of the newborn.

Question 52

ZINC Function?

Answer 52

Mineral essential for the activity of 100+ enzymes. Important in the formation of zinc fingers (transcription factor motif).

Question 53

ZINC Deficiency leads to..?

Answer 53

• Delayed wound healing,
• suppressed immunity, male hypogonadism,
• decreased adult hair (axillary, facial, pubic),
• dysgeusia, anosmia.
• Associated with acrodermatitis enteropathica (defect in intestinal zinc absorption).
• May predispose to alcoholic cirrhosis.

Question 54

What protein malnutrition causes skin lesions, edema, and liver malfunction?

Answer 54

Kwashiorkor Protein malnutrition resulting in skin lesions, edema due to decreased plasma oncotic pressure, liver malfunction (fatty change due to decreased apolipoprotein synthesis). Clinical picture is small child with swollen abdomen

Question 55

Causes of Kwashiorkor

Answer 55

Kwashiorkor results from protein-deficient MEALS: Malnutrition Edema Anemia Liver (fatty) Skin lesions (eg, hyperkeratosis, dyspigmentation) Get it? MEALS? like they don’t have enough food? and it’s also the mnemonic? so fucking clever 8^)

Question 56

What malnutrition syndrome results in skin lesions and liver malfunction, but no edema?

Answer 56

Marasmus Malnutrition not causing edema. Diet is deficient in calories, but no nutrients are entirely absent. *M*arasmus results in *M*uscle wasting.