BIBC 120 Lecture Notes - Lecture 20: Trans Fat, Ldl Receptor, Peroxisome Proliferator-Activated Receptor
24 May 2018
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Week 7.3
1) Trans fatty acids
• small amt occurs naturally but not a health risk
• hydrogenation of Unsat. FA in vegetable oil converts them to SFAs and produces
large amt of trans fatty acids as a byproduct; do pose health risk
• Consumption of trans-fats in processed foods increases risk for cardiovascular
disease
• Risk assessed by disease occurrence and by effect on LDL/HDL
• 1990s, the average American consumed 4 – 6 grams of trans-fats per day.
i. 2006 – FDA mandates listing trans-fat content on food labels
ii. 2008 – California bans trans-fats from restaurants
iii. Consumption dropped to approx. 1 gram per day in 2012.
• Trans-fats still used to maintain semi-solid consistency in frostings and
shortenings
• Hydrogenated and partially hydrogenated vegetable oils
• makes it more spreadable, more heat stable
• trans FA occur as a byproduct of this reaction
i. Still used in some deep-fat frying
ii. 2013 - FDA began the process of banning all trans-fats from processed
foods
2) ω- ad ω-6 Fatty Acids READ 225-228
• counting from methyl end have 1st double bond at C3 or C6
• Essential Fatty Acids: linoleic acid (w-6 18:2) and linolenic acid (w-3 18:3)
i. Huas lack the Δ- desaturase ad Δ-15 desaturase enzymes required
to make these fatty acids. (delta counting from carbonyl end)
ii. L L sources: vegetable oils, seeds, nuts
• linoleic acid with delta5 desaturase, elongation; delta 6desaturase, with AcCoA
→ arachidonic acid (w-6 20:4) →eicosanoids (signaling molecules in
inflammation) i.e. prostaglandins, thromboxanes, leukotrienes
i. arachidonic acid found in meat, eggs
• linolenic acid with delta5 desaturase, elongation; delta 6desaturase, with AcCoA
→EPH (w-3 20:5) with desaturation and elongation→ DHA (w-3 22:6)
i. both EPH and DHA are important for making phospholipids (esp. in
nervous system); conditionally essential in infants (rapid growth of
nervous system)
ii. EPH/DHA found in fish
• AI for lioleic/lioleic acid do’t eed to ko
How do dietary fatty acids affect serum cholesterol (LDL vs. HDL) and the risk for heart disease?
- consumption of w-3s: 45% decrease in risk for heart diseases going from lowest fifth →
highest fifth
- PPAR nuclear receptors play an important role; nuclear receptors: transcription factors that
binds hydrophobic ligands and then regulate gene expression
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