Assessment 3 Flashcards
Cystinuria
Defect in transport of cystine, lysine, arginine, ornithine
Poor absorption in kidneys/intstines
Cystine accumulates in urine (least soluble)
Treat w/ lots of water
Hartnup disease
Defect in transport of neutral AA (Ile, Leu, phe, Thr, Trp, Val)
Intestine and kidneys
D173N mutation
Lack of tryptophan, treat with try and niacin supplements
Cystinosis
Cannot transport cystine out of lysosome
Autosomal recessive, ESRD by 7-10yrs
Treat with cysteamine - reacts with cystine and end products leave lysosome
Pyruvate TA
Pyruvate –> Alanine
OAA TA
OAA –> Asp
a-KG TA
a-KG –> Glutamate
Alanine to Pyruvate
Transaminations all require…
Vitamin B6
Biosynthesis of Serine
3PG –> Phosphopyruvate –> phosphoserine –> Serine
Glycine synthesis
Serine –> Glycine
Serine hydroxymethyl transferase, creates N5/N10 methylene THF
Most stable THF?
N5 Methyl THF
All THF forms go towards that
Degradative reactions involving THF: Serine
Serine comes from 3PG which comes from Glucose
Glucose carbons —–> end up in THF compound
Degradative reactions involving THF: Formate
Make N10 formyl THF
Degradative reactions involving THF: Histidine degradation
Make N5-formimino THF
Biosynthetic reactions with THF
dUMP to TMP (N5/N10 methylene THF)
Glycine to Serine
Homocysteine –> methionine (N5 Methyl THF)
Purine biosynthesis (N10 formyl THF)
S Adenosylmethionine
Used in all methyl transferase reactions except homocysteine –> methionine
Phe –> Tyr
Enzyme: Phenylalanine hydroxylase
Cofactor: Tetrahydrobiopterin
AA degraded into which 7 families
Acetoacetyl-CoA Acetyl CoA Pyruvate a-KG Succinyl CoA Fumarate Oxaloacetate
Leucine degraded into…
Acetyl CoA
Leucine/Lysine degraded into…
Acetoacetyl-CoA –> Acetyle CoA
AA degradation cycle
Pyruvate –> Acetyl CoA + OAA –> Citrate –> aKG –> Succinyl CoA –> Fumarate –> Oxaloacetate
Ketogenic AA
Leucine
Lysine
Phenylalanine degradation
Phe –> Tyr –> x –> Homogentisic acid –> Fumorylacetoacetate –> Fumarate + Acetoacetate
Alcaptonuria
Buildup of homogentisic acid in urine
Black urine
Arthritis
Phenylketonuria
Cannot breakdown Phe:
Classical - no enzyme
Other - lack of THB
Buildup of TA product phenylpyruvate, phe, phenyllactate
Restrict Phe diet
Tyrosinemia Type I and II
Type I: Lack of fumarylacetoacetate hydrolase
Early death
Type II: Defect in tyrosineaminotransferase, buildup of Tyr
Treat both with low Phe and Tyr diet
Nitisinone
Treatment for Type 1 tyrosinemia
Blocks homogentisic acid production
Bilirubin production
Heme degraded –> biliverdin –> bilirubin –> Attached to albumin –> Carried in blood to liver
Bilirubin in hepatocytes
Albumin released, bilirubin enters hepatocytes –> Conjugated with glucoronic acid, water soluble –> excreted to bile and deconjugated by bacteria in intestines –> most leaves in feces
Hemochromatosis
Defect in HFE gene - excessive iron absorption
Excessive iron accumulation, especially in liver
Autosomal recessive
Hemosiderin (iron storage) deposition = damage to liver, pancreas, heart
Micronodular cirrhosis, diabetes, brown skin
Phlebotomy can be useful treatment
Wilson Disease
Copper accumulation - liver, brain, eye
ATP7B gene mutation (copper transporting ATPase) - Failure to incorporate copper into ceruloplasmin which takes copper to bile
Rare disease
Kayser Fleischer rings (copper in cornea)
Alpha-1 antitrypsin deficiency
Inhibitor of proteases, when not there –> tissue damage
Increase risk for hepatocellular carcinoma
Cirrhosis
Acute fatty liver of pregnancy
Very rare
Microvesicular steatosis
Fetus causes inherited metabolic disorder in mother
Adult Polycystic kidney disease
Mutation in gene encodinc polycystin-1 (transmembrane glycoprotein)
Loss of function of stress response on ciliary membranes = abnormal fluid filled cysts
Familial hypercholesterolemia
Mutation in gene encoding LDL receptor on hepatocytes
Increased blood cholesterol
Heterozygotes have 1/2 LDL receptors, homozygotes have none
Gilbert syndrome
Fluctuating hyperbilirubinemia in response to stress, fasting, exercise
UGT1A1 mutation
Bilirubin conjugator
UGT1A1
Bilirubin transport proteins
Albumin/bilirubin transporter: OATP2
Conjugated bilirubin tranporter: MRP2
Control points for bilirubin clearance
- Uptake
- Conjugation
- Secretion
CAR agonist
Increases bilirubin metabolism and clearance
Unconjugated hyperbilirubinemia
Increased production - hemolysis
Decreased uptake - OATP2
Impaired conjugation
Crigler-Najjar type I vs type II
Type 1: No UGT1A1 activity, high levels of bilirubinemia
Kernicterus
Type II: Reduced UGT1A1 activity, usually benign
Indinavir and UGT1A1
Huge increase in bilirubinemia with Gilbert syndrome
Inhibits UGT1A1
Kernicterus treatment
Expose to light, photoisomerization of Bilirubin
Dubin Johnson Syndrome
MRP2 mutation
Cannot excrete conjugated bilirubin
Black livers - lipofuscin melanin complex
Rotor syndrome
Conjugated bilirubin secreted back into blood (MRP3) cannot be taken back into hepatocyte
OARP1B1/3 defect
Bilirubin and inflammation
Heme oxygenase suppresses inflammation
Activated leukocytes upregulate HO = increased bilirubin = slow inflammation
Neurotransmitters developed from tyrosine
Dopamine
Norepinephrine
Epinephrine
Need B6 and THB
Serotonin
Derived from tryptophan
B6 and THB
GABA
Derived from glutamate
Histamine
Derived from histidine
B6
Homocystinemia/uria
Buildup of homocysteine
Optic lens issues, osteoporosis, mental retardation
B6 can lower levels in 50% of cases (lower affinity of B6 by enzyme)
Defective enzymes that can lead to homocystinemia
- Cystathionine beta synthase (Homocysteine –> Cystathionine)
- N5/N10 methylene THF reductase (N5/N10 methylene THF –> N5 methyl THF)
- Methionine synthase (N5 methyl THF –> THF and Homocysteine –> Methionine)
Elevated homocysteine effects
Decrease endothelial growth
Increase smooth muscle cell proliferation - can exacerbate atherosclerosis
Block coagulation cascade –> clots/thrombosis
Homocysteinemia treatment
Vit supplements: B6, folic acid, B12
Neural tube defects and homocysteine
Does not have direct effect
But can monitor levels of functional folate by checking homocysteine levels
Increased homocysteine = decreased functional folate
Vit B12
Obtain from milk/meat, absorbed via intrinsic factor
Methyl cobalamin: Used Methionine synthase reaction
Adenosyl cobalamin: Methly malonyl coa –> succinyl coa
B12 deficiency - neurological problems
Lack of B12 = lack of methionine = lack of SAM
SAM needed for DNA methylation
Betaine pathway
Choline –> Betaine –> Dimethylglycine
Homocystein –> methionine in final step
Branched chain amino acid metabolism, step 1 and 2
- Transamination, B6 required
2. Branched chain alpha keto acid DH
Isoleucine metabolism final product
Succinyl CoA + Acetyl CoA
Ketogenic and Glucogenic
Leucine metabolism final products
Acetyl CoA
Ketogenic only
Valine metabolism final products
Succinyl CoA
Glucogenic
Maple syrup urine disease
Defect in branched chain alpha keto acid DH
Buildup of branched chain amino acids
Glycine metabolism pathways
- Glycine Serine
- Glycine cleavage enzyme = CO2, N5/N10, NH4
- Oxidase to Glyoxylate, transaminate back to Glycine
Primary Oxaluria type 1
Lack of glycine transaminase
Buildup of Glyoxylate and subsequently oxalate kidney stones
Non ketotic hyperglycinemia
Glycine cleavage enzyme defect
Elevated glycine in CSF and plasma –> Neurological defects because glycine is inhibitory neurotransmitter
Heme synthesis
Succinyl CoA + Glycine –> delta aminolivulenic acid –> x2 –> Porphobiliniogen –> Heme
Lead poisoning
Inhibits heme synthesis
Affects Aminolevulinic acid Dehydratase
Porphyria
Class of defects in heme biosynthesis
Photophobia, eat rare meats
AST/ALT ratio in NAFLD
AST/ALT less than 1
AST/ALT ratio in alcoholic liver disease
AST/ALT >1
NASH vs hepatic steatosis
NASH has fibrosis, not to extent of cirrhosis
Hepatic steatosis has fatty droplets only
Ballooning degeneration
NASH
Cells swell and fill with fluid, nuclei in center
Cirrhosis
Extensive fibrosis around regenerating nodules
Large web of fibrosis and noticeable cell damage
Collagen deposition in Space of Disse = blockage of hepatocytes to blood
Mechanisms of death in cirrhosis
Liver failure
Portal hypertension
Hepatocellular carcinoma
Alcoholic liver disease
Cirrhosis preceded by hepatic steatosis and alcoholic hepatitis
Mallory bodies surrounding hepatocytes
Alcohol metabolizing enzymes create more NADH and H = more lipid synthesis = fatty droplets
Hyperdynamic circulation
Portal hypertension = body response to dilate arteries = BP Drop = more salt/water retained = even more edema
Ascites
Fluid in peritoneal cavity
Hypoalbuminemia, hyperdynamic circulation
NAFLD
Due to hyperlipidemia, obesity etc
Steatosis more common than NASH
NAFLD lab findings
AST/ALT
NAFLD guidelines
Weight loss reduced hepatic steatosis
Loss of body weight helps steatosis but need more for necroinflammation improvement
Exercise may help
NASH treatment?
Vitamin E
Intrahepatic cholestasis vs extrahepatic
Intrahepatic: Defective bile secretion or intrahepatic bile duct disease
Extrahepatic: Mechanical obstruction or injury of large bile ducts outside of liver
Cholestasis clinical features
Jaundice
Pruritis
Malabsorption
Cholestasis lab findings
Elevated ALP, GGT, 5NT
Elevated conjugated bilirubin
Secondary biliary cirrhosis
Prolonged obstruction of extrahepatic biliary tree
Fibrosis of liver –> cirrhosis
Intrahepatic cholestasis histology
Centrilolobular
Intracellular and canalicular
Hepatocyte necrosis
Extrahepatic cholestasis histology
Bile duct/bile plugs
Edema and acute inflammation of portal tracts
Cholelithiasis
Gall stones
Can be asymptomatic
Cholesterol (80%) and pigment stones
4 F’s of gall stones
Female
Forties
Fat
Fertile
Biliary colic
Severe RUQ pain post prandial
Fatty food intolerance
Acute cholesytitis
Murphys sign
Palpable gall bladder
Elevated ALP and leukocytosis
Acute cholecystitis complications
Gangrenous cholecystitis
Emphysematous
Stone in bile duct
Gall bladder hydrops
Acute cholecystitis treatment
Early cholestectomy
Intraoperative cholangiogram to rule out common bile duct stones
Electrolytes/fluid
Choledocolithiasis
Stones in biliary tree
Obstruction can lead to ascending cholangitis - bacterial infection of bile ducts
Acute Cholangitis
Bacterial infection of biliary tree
Inflammation aggravated
E. coli, Clostriidium, Enterobacter
Charcot triad
Abdominal pain, fever, jaundice
Reynolds Pentad
Charcot triad + hypotension, altered menta status
Clinical features of acute cholangitis
Charcot triad
Reynolds Pentad
Elevated WBC