Chapter 16 ( Lipid Mobilization And Catabolism ) Flashcards
Mechanism of Niacin in ttt of hyperlipidemia ?
Inhibit HSL in adipose tissue , with fewer fatty acids entering the liver , both VLDL and its product LDL will be lower in serum
What is the main enzyme responsible for fatty acid entry into mitochondria ? Its control ?
Carnitine acyltransferase-1
Inhibited by Malony-CoA
Insulin indirectly inhibit Beta oxidation by ativating acetyl-CoA carboxylase and increasing the malonyl-CoA concentration in the cytoplasm
Glucagon reverse this process
MCAD deficiency ? Features ? Ttt ? Prevention ?
Autosomal Recessive with variable expression Features : Fasting hypoglycemia Low or absent ketones Lethargy , coma , death Diagnosis : Dicarboxylic acidemia Dicarboxylic aciduria C8-C10 acyl canitines in blood Ttt : IV glucose Prevention : frequent feeding , high carbohydrate , low fat diet
Myopathic CAT/CPT deficiency ? Features ?
Autosomal Recessive with late onset
Features :
Muscle aches , weakness
Myoglobinuria
Provoked by prolonged exercise especially after fasting, cold or associated stress
Diagnosis :
Muscle biopsy shows elevated muscle triglycerides detected as lipid droplets in the cytoplasm
Ttt : cease muscle activity and give glucose
How to differentiated myopathic CAT deficiency from McArdle disease ?
Myopathic CAT deficiency : oil red O stain positive or Sudan black positive under microscope
McArdle disease : PAS positive material under microscope
Ackee fruit in Jamaica mechanism and features ?
Mechanism : contain toxin called Hypoglycin that acts as inhibitor of fatty acyl-CoA dehydrogenase
Features : jamaican vomiting and sever hypoglycemia of sudden onset followed by convulsions , coma , death
The 2 important enzymes in Propionic acid pathway ?
1- Propionyl-CoA carboxylase ( ATP, Biotin , CO2 )
2- Methymalonyl-CoA mutase ( vit B12 )
How to differentiate between Vit B12 and folate deficiency ?
In Vit B12 there is Methylmalonic aciduria
How acetoacetate is activated in extrahepatic sites ( muscle , renal cortex , brain ) ?
Thiopharase converts it to Acetoacetyl-CoA
Major enzymes of Ketogenesis ?
HMG-CoA synthase
HMG-CoA lyase
Why can’t liver metabolizes ketone bodies ?
Because it lacks Thiophorase ( acetoacetyl-CoA transferase )
Why urinary nitroprusside test can dramatically underestimate ketoacidosis and its resolution during ttt ?
As it detects only acetoacetate and doesn’t detect Beta-hydroxybutyrate , and in diabetics and alcoholics the ratio between them shifts and Beta-hydroxybutyrate predominates
Tay-Sachs defect ? Accumulating substrate ? Symptoms ?
Defect : Hexosaminidase A deficiency Substate accumulating in inclusion body : Ganglioside GM2 Symptoms : Cherry red spots in macula Psychomotor retardation Blindness Startle reflex Death < 2 years
Gaucher disease defect ? Substrate accumulating ? Symptoms ?
Defect : Glucocerebrosidase deficiency Substrate accumulating : glucocerebroside Symptoms : Crumble paper inclusions Hepatosplenomegaly Erosions of bones and fractures Pancytopenia or thrombocytopenia
Niemann-Pick disease defect ? Substrate accumulating ? Symptoms ?
Defect : Sphingomyelinase Substrate accumulating : Sphingomyelin Symptoms : cherry red spot in macula Foamy macrophages with zebra bodies Hepatosplenomegaly Microcephaly , mental retardation Early death
