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CMBM Exam 2 > Fatty Acid Oxidation > Flashcards

Fatty Acid Oxidation Flashcards

1
Q

Canitine is synthesized from what amino acid?

A
  • lysine
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2
Q

Carnitine is synthesized in what organs?

A
  • liver and kidney

* not in skeletal or heart muscle

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3
Q

Carnitine uptake is mediated by what transporter?

A
  • OCTN2

* vitamin C required

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4
Q

OCTN2 transporter

A
  • mediates carnitine uptake into the cell
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5
Q

Hormone sensitive lipase in adipose tissue is activated by

A
  • glucagon induced phosphorylation
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6
Q

Each round of β-oxidation produces

A
  • 1 NADH
  • 1 FADH2
  • 1 acetyl-CoA
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7
Q

In muscle acyl CoA from beta oxidation is converted to

A
  • sent to TCA cycle to create:
    • 3 NADH
    • 1 FADH
    • 1 ATP
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8
Q

In liver acyl CoA from beta oxidation is converted to

A
  • ketone bodies
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9
Q

β-oxidation of saturated fatty acids occur in

A
  • primarily muscle and liver
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10
Q

fatty acyl CoA dehydrogenase enzymes

A
  • 4 are utilized in the mitochondrial matrix during beta oxidation
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11
Q

Medium Chain fatty acyl CoA dehydrogenase deficiency (MCADD) MOA

A
  • one of the most common inborn
    errors of fatty acid oxidation (1 in 12,000 birth in West and 1 in 40,000 worldwide)
  • autosomal recesive
  • MCFAs accumulate and cause damage to the tissues
  • damage liver and brain
  • severe hypoglycemia
  • misdiagnosis of Reye syndrome or Sudden Infant Death Syndrome (SIDS) is often made
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12
Q

Medium Chain fatty acyl CoA dehydrogenase deficiency (MCADD) symptoms

A
  • can be triggered once a baby has stopped receiving regular nightly feeds
  • vomiting, lethargy, frequently coma, and hypoglycemia which occurs due to tissues dependence on glucose for energy
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13
Q

Medium Chain fatty acyl CoA dehydrogenase deficiency (MCADD) diagnosis

A
  • Excessive urinary excretion of medium-chain dicarboxylic acids as well as their glycine and carnitine esters
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14
Q

Medium Chain fatty acyl CoA dehydrogenase deficiency (MCADD) treatments

A
  • high carbohydrate and MC acyl CoA derivatives
  • Human milk is particularly rich in LCFAs and infants with MCADD are treated by frequent feeding, avoidance of fasting, and carnitine supplementation
    • Deficiences in short and long chain fatty acyl dehydrogenases have similar clinical features
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15
Q

Hypoglycin

A
  • toxin found in unripe fruit of the Jamaican Ackee tree
  • inhibits both short and medium chain acyl CoA dehydrogenases
    • This inhibits β- oxidation and leads to nonketotic hypoglycemia.
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16
Q

Propionyl-CoA is converted to

A
  • succinyl-CoA

* through an ATP-dependent pathway and then enters the TCA cycle for further oxidation

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17
Q

Methylmalonyl-CoA mutase

A
  • vitamin B12 cofactor

- last part of the steps involved in converting propionyl CoA into succinyl CoA

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18
Q

Methylmalonic-aciduria

A
  • Defects in methylmalonyl-CoA mutase or deficiencies in vitamin B12 may lead to methylmalonic-aciduria
19
Q

Enoyl-CoA isomerase

A
  • isomerizes double bonds in UFAs so that oxidation can continue
    • Since UFAs are partially oxidized, less FADH2 and corresponding ATP is produced
    • oxidation of UFAs is essentially the same process as for saturated fats, except when a double bond is encountered
20
Q

Peroxisome

A
  • abundant in the liver and kidney
  • involved in a series of vital cellular reactions:
    • free radical detoxification
    • rid the cells of toxic peroxides
    • site of H2O2 production
    • α and β oxidations of fatty acids
      • where VLCFAs can only undergo preliminary beta oxidation
    • biosynthesis of bile acids, DHA, plasmalogens, hormones
    • helping the nervous system work properly
21
Q

α-hydroxylase

A
  • adds a hydroxyl group to the α-carbon of phytanic
    acid, which then serves as a substrate for the remainder of the normal oxidative enzyme
  • In subsequent cycles of β-oxidation, acetyl- CoA and propionyl-CoA are released alternately
22
Q

Phytanic acid

A
  • branched fatty acid present in the tissues of ruminants and in dairy products and is, therefore, an important dietary component of fatty acid intake
23
Q

Refsum disease MOA

A
  • rare, autosomal disorder caused by a deficiency of α- hydroxylase
  • Phytanic acid accumulates in the tissues and serum in large quantities
24
Q

Refsum disease symptoms

A
  • symptoms are neurologic

* cerebellar ataxia, retinitis pigmentosa, nerve deafness and peripheral neuropathy

25
Q

Refsum disease treatment

A
  • dietary restrictions

* restriction of dairy products and ruminant meat from the diet can ameliorate the symptoms of this disease

26
Q

Zellweger syndrome MOA

A
  • congenital (autosomal recessive) disorder which results from reduction of peroxisome in the cells of liver, kidney, and brain
  • damages the white matter of the brain and also how the body metabolizes particular substances in the blood and organ tissues
27
Q

Zellweger syndrome symptoms

A
  • mental retardation
  • poor muscle tone
  • poor feeding
  • seizures
    • from abnormal brain and nervous system development
      ~ hearing and vision delay, or absent diminished, or absent reflexes
  • cysts in the liver affecting liver function
  • characteristic facial features
    • Head and face enlarged, high forehead, large anterior fontanelle (soft spot), malformed ear lobes,flat-looking face
  • Liver is enlarged with impaired function jaundice.
28
Q

Adrenoleukodystrophy MOA

A
  • Fatal demyelinating disease caused by mutations in the ABCD1 gene leading to an absent or non-functioning adrenoleukodystrophy protein (ALDP)
  • neurological disorder due to defective peroximal
    oxidation of VLCFAs
  • The most common peroxisomal disorder affecting males at early ages
29
Q

Adrenoleukodystrophy symptoms

A
  • accumulation of very long chain fatty acids (VLCFA) in tissues and plasma via inhibition of peroxisomal β-oxidation
  • Reduction in plasmalogens
  • Abnormalities in the white matter of the cerebrum
30
Q

Adrenoleukodystrophy protein (ALDP)

A
  • ATP-binding cassette transporter located in membranes of peroxisomes
  • Involved in degradation of very-long-chain-fatty acids (VLCFAs) in oligodendrocytes and microglia
  • Lack of the protein disrupts maintenance of myelin
31
Q

ω-oxidation of fatty acids

A
  • alternative / minor pathway of LCFA acid metabolism in endoplasmic reticulum of kidney and liver
  • can be induced by:
    • Failure of β-oxidation to proceed normally can result in increased ω-oxidation activity
    • lack of carnitine or carnitine palmitoyltransferase (CPT) activity preventing fatty acids from entering mitochondria leading to an accumulation of FAs in the cell
32
Q

Deficiencies in carnitine biochemistry

A
  • found in patients undergoing hemodialysis or exhibiting organic aciduria
  • Primary carnitine deficiency (systemic) present in 2 ways:
    • defective in endogeneous biosynthesis of carnitine
    • defect in the OCTN2 gene
33
Q

Primary carnitine deficiency symptoms

A
  • hypoketotic
  • hypoglycemic encephalopathy accompanied by hepatomegaly
  • elevated liver transaminases
  • hyperammonemia
  • often misdiagnosed as Reye syndrome or sudden infant death
  • Serious complications such as heart failure, liver problems, coma, and sudden unexpected death are also risk factors
34
Q

Myopathic carnitine deficiency MOA

A
  • defect in the muscle
    carnitine transporter
  • Severe reduction in muscle carnitine levels and normal liver and serum carnitine concentrations
  • restricted to muscle, with no renal leak of carnitine or signs of liver
    involvement
35
Q

Myopathic carnitine deficiency symptoms

A
  • deficiency can appear in the first years of life, but they may occur later during the second or third decade
  • proximal muscular weakness of varying degree
  • exercise intolerance
  • myalgia
36
Q

Secondary carnitine deficiency MOA

A
  • decrease of carnitine levels in plasma or tissues which are caused by other metabolic disorders
    • Inadequate intake (eg, due to fad diets, lack of access, vegetarians)
    • Deficiencies in mitochondrial mobilizing enzymes (eg, CAT1 or CAT2)
    • Decreased endogenous synthesis of carnitine due to a severe liver disorder
    • Excess loss of carnitine due to diarrhea, diuresis, or hemodialysis
    • hereditary disorder in which carnitine leaks from renal tubules
    • Increased requirements for carnitine when ketosis is present or demand for fat oxidation is high (eg, during a critical illness such as sepsis or major burns; after major surgery of the GI tract)
    • Decreased muscle carnitine levels due to mitochondrial impairment (eg, due to use of zidovudine or AZT)
37
Q

Secondary carnitine deficiency treatment

A
  • Avoidance of fasting and strenuous exercise
  • Dietary interventions, based on cause
  • Carnitine deficiency due to inadequate dietary intake, increased requirements, excess losses, decreased synthesis, or (sometimes) enzyme deficiencies can be treated by:
    • In some cases oral L-carnitine may help
    • Consuming uncooked cornstarch at bedtime prevents early morning
      hypoglycemia
    • Some patients require supplementation with medium-chain triglycerides and essential fatty acids
    • Patients with a fatty acid oxidation disorder require a high-carbohydrate, low-fat diet
38
Q

Deficiencies in Acyl-CoA Dehydrogenases MOA

A
  • group of inherited diseases that impair β-oxidation result from deficiencies in acyl-CoA dehydrogenases
  • The enzymes affected may belong to one of four categories:
    • very long-chain acyl-CoA dehydrogenase (VLCADD)
    • long-chain acyl-CoA dehydrogenase (LCADD)
    • medium-chain acyl-CoA dehydrogenase (MCADD)
    • short-chain acyl-CoA dehydrogenase (SCADD)
39
Q

Long-term alcohol consumption can inhibit

A
  • mitochondrial fatty acid oxidation
  • promotes the deposition of esterified fatty acids in the liver
    • No β-oxidation of FAs
    • Fat deposition in the liver
40
Q

Gaucher disease MOA

A
  • Autosomal recessive, mutation in gene encoding glucocerebrosidase
    • lysosomal enzyme that breaks down glucocerebroside (GBA) into glucose and ceramide
  • Defect leads to accumulation of GBA in macrophages, and subsequent enlargement of macrophages known as “Gaucher cells”
    • accumulate most commonly in the spleen, liver, and bone marrow
  • Gaucher cells may also be found in lungs, skin, eyes, kidney, heart, and in the nervous system
  • In the spleen, accumulation of Gaucher cells leads to enlargement of spleen, and activation of red blood cell (RBC) metabolism
    • RBCs break down faster than pruduced; anemia
  • most common genetic lysosomal storage disorder
  • Type 1 does not affect the nervous system. In contrast, type 2 and 3 are rare and neuronopathic
  • high case in Ashkenazi jews
41
Q

Gaucher disease symptoms

A
  • Some individuals may experience no symptoms.
  • Generalized lack of energy and stamina due to anemia.
  • Type 1 is most common (99% of the cases)
  • Extensive and progressive brain damage (types 2 and 3)
  • Increased tendency for bleeding and bruising
  • Enlarged spleen and liver (hepatoslienomegaly)
  • Accumulation in bone marrow and loss of bone density
  • Low blood platelets
42
Q

Disorders Associated with Abnormal Sphingolipid Metabolism

A
  • Tay-Sachs disease
  • Sandhoff-Jatzkewitz disease
  • Fabry’s disease
  • Sulfatide lipdosis
  • Krabbe’s disease
  • Gaucher disease
  • Niemann-Pick disease
  • GM1 gangliosidosis
43
Q

Disorders Associated with Abnormal Sphingolipid Metabolism symptoms

A
  • mental retardation in all

- early mortality in some

CMBM Exam 2 (13 decks)

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