Lipid Metabolism I - Lipid Metabolism 1 Reading: Gropper...

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Lipid Metabolism 1 Reading: Gropper 4 th ed, Ch 6, pp. 138–147, 151–153 Gropper 5 th ed, Ch 5, pp. 144–154, 157–161
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2 Objectives for today: Review lipid absorption and digestion Lipid transport Catabolism of triglycerides and fatty acids
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3 Lipid Metabolism
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4 Dietary lipids: sources Animal Meat, poultry, fish, eggs Lard, tallow Milk, cheese, cream, butter Plant Nuts, avocados Peanuts and soybeans Vegetable oils Shortening and margarine
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5 Dietary lipids: saturation Fatty acids: Saturated (SFA) Unsaturated (UFA) Monounsaturated (MUFA) Polyunsaturated (PUFA) Animal fats have low P/S ratio Vegetable fats have high P/S ratio Lower melting point (except coconut oil) Adipose and red blood cell membrane P/S ratio reflects diet Useful for compliance in research studies
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6 Dietary lipids: sterols Animal: cholesterol, cholesteryl esters Plant: phytosterols Compete for incorporation into micelles and displace cholesterol Inhibit cholesterol absorption Used in margarine and spreads
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7 Lipid Absorption 2.0 Lipid digestion products diffuse into the enterocytes— the micelles themselves DO NOT enter the cells Free fatty acids are reesterified to make triglycerides, phosphatides, and cholesteryl esters rapid metabolism maintains concentration gradient for diffusion from intestinal lumen Short-chain free fatty acids (<10-12 carbons) diffuse directly into the blood
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8 Intestinal mucosal cell Endoplasmic reticulum HDL Lymphatics FA-albumin Lysophosphatidylcholine (direct absorption) Monoacylglycerols Free fatty acids Glucose Glycerol Micellar particles Cholesterol LYSPC CHYLO Apoprotein FA-CoA CE Short-chain FFA PC TG Albumin MG CHOL a-GP Portal circulation Fig. 6-16, p. 139
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9 Chylomicrons Transport exogenous lipids to tissues Are made in enterocytes (contrast with micelles) Resynthesized lipids and fat-soluble vitamins are collected in the endoplasmic reticulum as large fat particles Covered by monolayer of polar phospholipids Receive a layer of protein on surface (apoprotein) Go to the Golgi apparatus, where carbohydrate is attached to the protein Released into the lymphatic circulation slowly and eventually blood (but NOT via hepatic portal vein) Blood levels peak at 0.5–3 hr, but may take up to 14 hr TAG-laden chylomicrons causes ‘milky’ look Other lipoproteins are added in circulation
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10 Lipoprotein lipase (extrahepatic) Found in endothelial cells lining capillary walls adipose tissue, skeletal, and cardiac muscle Hydrolyzes lipids to free fatty acids and glycerols which are absorbed by cells Activated by apoC-2 on lipoproteins (VLDL and Chylomicrons)
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This note was uploaded on 11/25/2011 for the course NTR 342 taught by Professor Tillman during the Spring '09 term at University of Texas at Austin.

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Lipid Metabolism I - Lipid Metabolism 1 Reading: Gropper...

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