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Face the Fats: The Biochemistry of Lipids by Nancy A. Rice Western Kentucky University 1.

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Presentation on theme: "Face the Fats: The Biochemistry of Lipids by Nancy A. Rice Western Kentucky University 1."— Presentation transcript:

1 Face the Fats: The Biochemistry of Lipids by Nancy A. Rice Western Kentucky University 1

2 Vytorin Pete was glad to finally be home. He’d been gone since 8 o’clock this morning - first to classes all day and then straight to his job at Dillard’s. Now it was 8 pm. He walked into his apartment and threw his backpack on the floor. Whew! He was tired and hungry! He found some hot pockets in the freezer and threw two in the microwave before he slumped on the couch and turned on the TV. Another one of those annoying drug company commercials! This one was about some drug called Vytorin TM. As the microwave beeped that his dinner was ready, Pete watched the commercial and laughed at all of the people who resembled what they ate. He wondered….do I look like a Hot Pocket? or search on Youtube for “Vytorin Ad” 2

3 As Pete wolfed down his dinner, he was curious. How much cholesterol was in a hot pocket anyway? He grabbed the box from the trash can and read the nutrition label on the back. 3

4 CQ#1: How much cholesterol was in Pete’s dinner? A.25 milligrams B.50 milligrams C.6 grams D.13 grams 4

5 Too young to have high cholesterol Whoa! After reading the package, Pete realized that only one hot pocket is considered a serving so he had eaten 620 calories for dinner! Not to mention 50 mg of cholesterol. Although he had no idea if this was high or not, he figured it couldn’t be too good or there wouldn’t be a need for a “Lean Pocket”! He decided to research cholesterol levels on the internet. He was not even sure what cholesterol was to begin with. He also wondered: what should a normal person’s cholesterol level be? Did he have high cholesterol? Nah, he reasoned. How could I? I’m too young. 5

6 Nutritional analysis of 3 common fast food meals Wendy’s 1.4 lb single with cheese –530 calories –27 g of total fat Medium french fries –420 calories –20 g of total fat Subway 6” turkey breast sandwich (no mayo or cheese) –280 calories –3.5 g total fat 2oz bag of Doritos –280 calories –14 g total fat 6 Steak n Shake Frisco Melt – 1173 calories – 93 g of total fat French fries – 211 calories – 10g total fat Vanilla shake – 654 calories – 21 g total fat 47 g total fat17.5 g total fat124 g total fat

7 CQ#2: What percent of your average daily food intake is fresh fruits and/or vegetables? A. 0% B. 10% C. 25 % D. 50% or greater 7

8 CQ#3: What percentage of your average daily food intake is lipids? 8 A. 0% B. 10% C. 25 % D. 50% or greater

9 Pete searched the internet… After a quick Google search, Pete found the following information: “ The American Heart Association and the United States Department of Agriculture recommend that you limit your fat intake to no more than 30% of your daily calories. Of that 30%, 10% or less of the fat calories should come from saturated fat. One gram of fat = 9 calories.” Fat? Saturated fat? Are these different than cholesterol? Pete kept searching…. 9

10 CQ#4: Pete normally consumes ~ 2000 calories per day. What % of his total daily caloric intake is coming from the two Hot Pockets? What % of his total daily calories is coming from the fat in his two Hot Pockets? A. ~ 30%; 5% B. ~ 30 %; 11% C. ~ 50 %; 20% D. ~ 60 %; 11% Is Pete meeting AHA recommended guidelines for fat consumption? (…limit your fat intake to no more than 30% of your daily calories…) 10

11 Cholesterol is a Lipid Lipids are the group of biological macromolecules that have a major hydrocarbon component and are mostly nonpolar and hydrophobic. Functionally, lipids are important in cell membrane structure and in energy production. There are three main families of lipids: –Steroids –Fats –Phospholipids 11

12 Steroids Typically have a core structure of four fused carbon rings Cholesterol is an example. Many hormones and vitamins are steroids. 12 Cholesterol

13 Fats and Fatty Acids A fat, also known as a triacylglycerol or triglyceride, is a glycerol linked to three fatty acids. Condensation reactions between glycerol hydroxyl groups and fatty acid carboxyl groups form ester linkages joining the two subunits. Fatty acids can be either saturated or unsaturated. 13

14 Saturated and Unsaturated Fatty Acids Fats that have no double bonds in the hydrocarbon chain are “saturated” with hydrogens and are very linear, e.g. animal fats. Fats that have a double bond are called unsaturated and have “kinks” in the hydrocarbon chain, e.g. plant oils. Unsaturated fats can be either monounsaturated as shown or polyunsaturated (more than one double bond). Unsaturated fats are generally healthier than saturated fats. 14

15 CQ#5: Which of the following is the best explanation for why vegetable oils are liquid at room temperature? A. Vegetable oils are saturated fatty acids that do not pack together efficiently and therefore have a low melting point. B. Vegetable oils are saturated fatty acids that pack together very efficiently and therefore have a low melting point. C. Vegetable oils are unsaturated fatty acids that do not pack together efficiently and therefore have a low melting point. D. Vegetable oils are unsaturated fatty acids that pack together very efficiently and therefore have a low melting point. 15

16 Phospholipids Phospholipids consist of a 3-carbon glycerol linked to a negatively charged phosphate group, and two fatty acids. Phospholipids are a major component of cell membranes due to their amphipathic nature. Amphipathic molecules have a nonpolar region (hydrophobic) and a polar region (hydrophilic). 16

17 CQ#6: Which of these best describes the term phospholipid? A.A polar lipid molecule that fully interacts with water. B. A nonpolar lipid molecule that is made amphipathic by the addition of a phosphate. C. A nonpolar lipid molecule that is made polar by the addition of a phosphate. D. A polar lipid molecule that fully repels water. 17

18 Pete was beginning to understand a little bit about cholesterol and fats. But he still didn’t understand: why were they so unhealthy? And if they are unhealthy, why do we even need cholesterol and fat? In small groups, develop an answer. What would you tell Pete? 18

19 Pete learned that your body needs some cholesterol. In addition to being a component of cell membranes, cholesterol is also used to make hormones, vitamin D, and substances that help you digest foods. Your liver makes all the cholesterol your body needs. And excess cholesterol and fat in our bodies is dangerous. It often means you are overweight, and it can damage your vascular system. The amount of cholesterol a person produces varies depending upon their genetic makeup. 19

20 Since cholesterol is hydrophobic (water fearing) and blood is hydrophilic (water loving), the two do not mix. Cholesterol is carried through the bloodstream in protein packages called lipoproteins, made up of lipid on the inside and protein on the outside. Two kinds of lipoproteins carry cholesterol throughout your body High density lipoproteins (HDL) - Low density lipoproteins (LDL)

21 LDL and HDL continued…. LDL cholesterol is sometimes called bad cholesterol. –High LDL cholesterol leads to a buildup of cholesterol in arteries. The higher the LDL level in your blood, the greater chance you have of getting heart disease. HDL cholesterol is sometimes called good cholesterol. –HDL carries cholesterol from other parts of your body back to your liver. The liver removes the cholesterol from your body. The higher your HDL cholesterol level, the lower your chance of getting heart disease. 21

22 Hyperlipidemia can lead to disease When there is too much cholesterol /LDL in your body (because of diet and the rate at which the cholesterol is processed) it is deposited in arteries, including those of the heart, which can lead to narrowing of the arteries and heart disease. Studies of people with heart disease have shown that lowering cholesterol/LDL reduces the risk for dying from heart disease, having a heart attack, or needing heart bypass surgery or angioplasty. 22

23 Pete was beginning to get the idea. Low cholesterol/LDL levels in your blood help keep you healthy by preventing heart attacks and strokes. Therefore, maybe eating foods that are low in cholesterol may ultimately be able to lower your risk for these diseases. But what would a normal blood cholesterol level be? 23

24 Lipoprotein Profile Cholesterol levels are measured in milligrams (mg) of cholesterol per deciliter (dL) of blood. Desirable or optimal levels for adults with or without existing heart disease are: –Total cholesterol: Less than 200 mg/dL. –Low Density Lipoprotein (LDL) cholesterol: Less than 100 mg/dL. –High Density Lipoprotein (HDL): 40 mg/dL or higher. –Triglycerides: Less than 150 mg/dL. The National Cholesterol Education Program recommends that healthy adults over 20 years of age have their cholesterol levels checked once every 5 years. 24

25 Pete heads to the campus health center… Pete decided he better check out his own lipid profile. He went to the campus health center after fasting all night and had his blood drawn. A few days later the doctor called with his results. 25

26 CQ#7: Review Pete’s lipid profile results below. What should Pete know? A. Pete has acceptable cholesterol levels. B. Pete has borderline high cholesterol and high LDL levels; however the fact that his HDL is elevated is a benefit to him. C. Pete has high cholesterol and HDL levels yet the fact that his LDL is elevated is a benefit to him. Total cholesterol: mg/dl HDL: 55 mg/dl LDL: 122 mg/dl Triglycerides:125 mg/dl 26

27 Pete was surprised. He was young, relatively active (he walked to class everyday at least), was only a little overweight, and he thought he ate pretty well. But apparently his body did not think so. His doctor suggested three things to help lower his blood cholesterol: –Reduce the amount of saturated fat and cholesterol in his diet. –Lose some weight. Losing weight can help lower your LDL and total cholesterol levels, as well as raise your HDL and lower your triglyceride levels. –Be physically active for at least 30 minutes most, if not all, days. 27

28 So if KFC already cooks their chicken in vegetable oil, what’s the problem? “Ok, doc. No more burgers and fries. But I don’t get it. I’ve been reading a lot on the internet and I know that oil, like corn oil, is not saturated. It’s unsaturated. So why are things cooked in margarine also bad? Isn’t margarine made from corn oil?” “Yes, you’re right, Pete,” his doctor said. “There is another type of bad fat out there. It’s called a trans fat. Lots of trans fats exist in products like margarine.” 28

29 CQ#8: Trans fats _____ A. Are essential. B. Are antioxidants. C. Have trans double bonds. D. Are present in all foods. E. Are in transition from unsaturated to saturated fats. 29

30 CQ#9: Trans fats are formed when: A. Liquid fat is chemically changed to solid fat. B. Solid fat is chemically changed to liquid fat. C. Liquid fat is refrigerated. D. Solid fat is melted. 30

31 Trans Fats – The Double Whammy Trans fats come from adding hydrogen to vegetable oil (unsaturated fats) through a process called hydrogenation. “Partially hydrogenated” oils may contain higher levels of trans fats. Trans fats are more solid than oils. Trans fats increase the shelf life of foods. Unlike other fats, trans fats both raise your "bad" (LDL) cholesterol and lower your "good" (HDL) cholesterol. 31

32 CQ#10: Which of these does not contain trans fats? A. Fast-food french fries B. Grilled hamburger C. Store-bought cookies D. Frozen chicken nuggets 32

33 CQ#11: What does trans-fat-free mean on food labels? A. Less than 1.5g per serving B. Less than 1g per serving C. Less than 0.5g per serving D. 0g per serving 33

34 FDA recommendations for labeling trans fats In January 2006, all food labels were required to list saturated fat and cholesterol amounts AND trans fat content. Foods with 0.5 g or less / serving are considered “trans fat free.” –From the FDA: If the ingredient list includes the words “shortening,” “partially hydrogenated vegetable oil” or “hydrogenated vegetable oil,” the food contains trans fat. Because ingredients are listed in descending order of predominance, smaller amounts are present when the ingredient is close to the end of the list. 34

35 Ban the Trans Fats! Many cities and several states have lobbied to ban trans fats from restaurants –Tiburon, CA, was first. –New York City was second. For more information see –http://www.bantransfats.com/ 35

36 Resolution Wow! Pete never knew that food could be so complicated. But now it all makes sense. He didn’t think he ate a lot of high cholesterol foods, but he did eat a lot of processed snacks and fast food – cookies, french fries – foods with high trans fat content. Pete decided it was time to really start paying more attention to what he ate, especially with regard to fats and cholesterol, and to exercise. It’s never to early to “Face the Fats.” 36

37 Postscript Are all partially hydrogenated products bad? NO! Recent changes in the food industry with regard to processing of oils results in partially hydrogenated products with minimal trans fat content. A recent publication in Ann Nutr Metab 2009; 54 (Suppl.1):15-24 states that: “…margarines and cooking products, and to a lesser extent dressings, have been adapted to contain less trans fatty acids (TFA), less saturated fatty acids (SFA) and more essential (polyunsaturated, PUFA) fatty acids…By blending vegetable oils rich in the essential PUFAs  -linolenic acid (  -3) or linoleic acid (  -6), margarines and dressings with both essential fatty acids present in significant quantities can be realized. In addition, full hydrogenation and fat rearrangement have enabled the production of cost- effective margarines virtually devoid of TFA and low in SFA. Dietary surveys indicate that vegetable oils, soft margarines and dressings are indeed often important sources of essential fatty acids in people's diets, whilst providing negligible amounts of TFA and contributing modestly to SFA intakes. “ 37

38 Statin Drugs (optional slide) Statin drugs inhibit the enzyme HMG-CoA reductase This is an enzyme in the synthesis pathway of cholesterol Statins also increase cholesterol uptake from the bloodstream by resulting in more LDL receptor expression Vytorin is actually a combination drug made of simvastatin and ezetimibe, (Zetia) which prevents cholesterol absorption from the digestive tract. 38

39 Image Credits Slides 3, 4 and 9 – right Description: Image of the nutritional data from a cheeseburger Hot Pockets. Slide 7 – lower right Description: Fruits and vegetables Source: Wikimedia commons Link: Permission: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation Slide 8 – lower right Description: Oils Source: National Institutes of Health Link: Permission: Open source free access; work of U.S. Federal government under the terms of Title 17, Chapter 1, Section 105, of the U.S. Code. Slide 12 – right Description: Molecular structure of cortisol and Vitamin D Source: Wikimedia Commons Link: Permission: This image of a simple structural formula is ineligible for copyright and therefore in the public domain, because it consists entirely of information that is common property and contains no original authorship. Slide 12 – right (lower) Description: Cell membrane structure Source; Wikimedia Commons Link: Permission: This image has been released into the public domain by its author, LadyofHats. 39

40 Slide 13 – right Description: Molecular structure of a triglyceride backbone Source: Wikimedia Commons Link: Permission: This image has been released into the public domain by its author Slide 14 – right top Description: Space filling model of myristic acid Source: Wikimedia commons Link: Permission: image has been released into the public domain by its author Slide 14 – right middle Description: Molecular structure of myristic acid Source: Wikimedia commons Link: Permission: This image is ineligible for copyright and therefore in the public domain, because it consists entirely of information that is common property and contains no original authorship Slide 14 – right middle Description: Space filling model of oleic acid Source: Wikimedia commons Link: Permission: This image has been released into the public domain by its author Slide 14 – right bottom Description: Molecular structure of oleic acid Source: Wikimedia Commons Link: Permission: This image has been released into the public domain by its author Slide 16 – right (left hand side) Description: Molecular structure of phosphatidylcholine Source: Wikimedia commons Link: Permission: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation 40

41 Slide 16 – right (right hand side) Description: Structure of phospholipids in solution Source: Wikimedia commons Link: Permission: This image has been released into the public domain by its author, LadyofHats. Slide 20 – right Description: lipoprotein structure Source: "lipoprotein." The Oxford Dictionary of Sports Science. Oxford University Press, 1998, 2006, Answers.com 21 Jul Link: Permission: Slide 22 – right Description: Artherosclerosis Source: National Heart Lung Blood Institute of the NIH Link: Permission: Open source free access; work of U.S. Federal government under the terms of Title 17, Chapter 1, Section 105, of the U.S. Code. Slide 30 – right Description: Krispy Kreme donuts Source: Wikimedia Link: Permission; Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation Slide 38 – right Description: HMG-CoA reductase pathway (cholesterol) Source: Wikimedia Link Permission: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation 41


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