Fatty Acids

Structure

• amphipathic hydrocarbon chain (saturated or unsaturated)

Function

• serves as main energy source

Location

• Stored in adipose tissue
• Transported on albumin or free (lipoproteins)

Palmitic Acid

C16:0

Stearic Acid

C18:0

Oleic Acid

C18:1 (9)

Linoleic Acid

C18:2 (9,12)

• makes Omega 6
• essential in diet

Linolenic Acid

C18:3 (9,12,15)

• makes Omega 3
• essential in diet

Arachidonic Acid

C20:4 (5,8,11,14)

• precursor for many steroids/hormones

Hormone-sensitive lipase

Stimulation: epinephrine, glucagon  Inhibition: Insulin, glucose

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Fates of Glycerol

From adipose -> liver

1. glycerol kinase: converts to glycerol phosphate and stored as TAG in liver
2. glycerol phosphate dehydrogenase: converts to DHAP to enter glycolysis

Fates of Fatty Acids

1. Diffuse to bloodstream -> associate with albumin
2. Diffuse to cells to become activated
3. Undergo β-oxidation

Beta Oxidation (location/products)

Location: mitochondrial matrix of peripheral tissues

Produces:

• FADH2 (2 ATP)
• NADH   (3 ATP)
• Acetyl CoA  (12 ATP)

Carnitine Shuttle

Inhibited: malonyl Co-A; acetyl CoA/CoA ratio

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Carnitine acetyltransferase I

Replaces S-CoA with carnitine in cytosol -> will shuttle to mito. matrix

Carnitine acyltransferase II

Removes carnitine to regenerate acyl-CoA in the matrix

Sources of carnitine

Dietary: meat, fish, dairy

Endogenous synthesis: liver and kidney

Secondary carnitine deficiency

1. Decreased carnitine synthesis due to liver disease
2. Restricted vegetarian diet
3. High metabolic requirements (pregnancy, severe infections, trauma)
4. Patients with hemodialysis

CPT-I Deficiency

1. Mostly affects liver
2. Cannot synthesize glucose during fasting
3. Hypoketotic hypoglycemia

CPT-II deficiency

1. Affects cardiac and skeletal muscle (cramping and weakness)
2. Carnitine not regenerated
3. Fat droplets appear in muscle tissue

Treatments for CPT deficiency

1. Avoid prolonged fasting
2. Diet with only medium-chain length FAs
3. Administer oral carnitine (rotten fish smell)

Beta Oxidation

cycle repeats: (n/2)-1 = nadh, fadh #; (n/2) = acetyl-CoA

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