HNFE 1004 Ch. 5 Lipids F2022 PDF

HNFE 1004 Lipids Dr. Angela Anderson Recommendations The 2020 Dietary Guidelines for Americans recommend that fat intake should be between 20-35% of Kcals There is no RDA Food and Nutrition Board recommends: Omega-6 – Men: 17 grams/day Women: 12 grams/day Omega-3 – Men 1.6 gra...

HNFE 1004 Lipids Dr. Angela Anderson Recommendations The 2020 Dietary Guidelines for Americans recommend that fat intake should be between 20-35% of Kcals There is no RDA Food and Nutrition Board recommends: Omega-6 – Men: 17 grams/day Women: 12 grams/day Omega-3 – Men 1.6 grams/day Women: 1.1 grams/day The AHA recommends that no more than 5-6% of Kcals come from saturated fats The AHA recommends limiting trans fats The AHA recommends that circulating cholesterol be reduced by limiting saturated and trans fats Lipids Provide 9 Kcal/g of energy We store fats in the body as TAGs in adipose tissue Released (lipolysis) & broken down (beta-oxidation) to be used as the primary energy source during fasted times of the day (3-5 hrs after a meal) Roles of Lipids in the body Providing energy, especially in a fasted state Storing energy for later as TAGs in adipose tissue, some in muscle Insulation & protection of the body Transports fat-soluble vitamins Phospholipids make up cell-membranes Cholesterol is important in cell membranes for baffling, building block of bile acids, precursor to hormones & vitamin D 2/3 of circulating cholesterol is from de novo synthesis Absorption of cholesterol from food ranges from 40-65% Fatty Acids – Simplest of all Lipids Classification Saturated: no carbon to carbon double bonds Solid @ room temp Unsaturated with one or more double bonds Liquid @ room temp One double bond – monounsaturated (MUFA) Two or more double bonds – polyunsaturated (PUFA) FA – free fatty acids  Fatty Acid Structure Saturated FA- no double bond Unsaturated FAs are typically in cisOmega-end Alpha-end configuration Affects molecular configuration trans – linear cis – folding or kinking configuration Food manufacturers used the process of hydrogenation to change a cis to a trans bond to decrease rancidity Other methods to decrease rancidity include- Vacuum packaging, inert gas, opaque packaging, dark colored glass, addition of vitamin C or E  Essential FAs C -18 (N) C - C- C -9 C -1 15 12 Omega-3 FA- alpha linolenic acid (ALA) Omega-6 FA- Linoleic acid PUFAs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Polyunsaturated Fatty Acids (PUFA) Omega-3 Family Omega-6 Family Alpha-linolenic acid Linoleic acid (Essential Fatty Acid) (Essential Fatty Acid) Docosahexaenoic Eicosapentaenoic Arachidonic acid acid acid (DHA) (EPA) Glycerolipids Mono-, di- and tri-esters of glycerol and FAs Most FAs in nature are found as glycerolipids (mainly TAG) 2 Monoacylglycerol (MAG) 2 Monoglyceride (MG) 1,2 Diacylglycerol (DAG) Triacylglycerol (TAG) 1,2 Diglyceride (DG) Triglyceride (TG)  Phospholipids Contain phosphate group Glycerol core structure cithin- can be sold as a dietary supplement & is used as an additive i ound in egg yolks, organ meats, nuts, & spinach Contains phosphatidylcholine Sterols / Steroids C-1 C D C-3 A B Cholesterol – most common example Attach LCFA here to create a cholesterol ester The precursor for a number of important sex and adrenal steroid hormones, bile salts, vitamin D… Also an important component of cell membranes Obtained from diet or synthesized from acetyl CoA units  Lipids Concept Map Lipid s 9kcal/ g Triglycerides – Sterols Phospholip main form of fat in ids – lipid diet and body (Cholesterol bilayer in (Glycerol + 3 fatty , vitamin D, cell acids) bile, membranes Saturate hormones) d fatty acid – no Unsaturate C=C d fatty acid Animal fats Coconut Monounsatura Polyunsaturat ted ed Essential oil Fatty Palm oil One C=C 2 or more Acids C=C Olive oil Omega-3 Corn oil (fish oils) Canola oil Sunflower oil Omega-6 Peanut oil (plant oils) Safflower oil Food sources- No fats found on My Plate Saturated FAs 40-60% of dairy & meat products 50% of fish products (but source of omega-3 FAs; also in chia seeds, walnuts, & flax seeds) Palm oil & coconut oil Unsaturated FAs Plant oils Corn, cottonseed, sunflower, soybean, & safflower- polyunsaturated (primary source of omega-6 FAs) Canola, olive & peanut- monounsaturated Flax seeds, walnuts, and oils from chia seeds, canola seeds, perilla seeds, & soybeans Phospholipids Wheat germ, peanuts, egg yolk, soy beans, & organ meats Cholesterol & plant sterols (phytosterols) Animal products- meats, eggs, whole milk Plant sterols- plant oils, nuts, seeds, beans, peas, lentils, & whole grains Found to lower cholesterol because they compete for the same absorption site in the SI Trans fats Found in processed foods, margarine, shortening as “partially hydrogenated” Ex. Partially hydrogenated soybean oil FDA bans Trans- fats Fats found in the MyPlate Food Groups Fish high in Omega-3s Dietary Guidelines & AHA recommend 2 servings of fatty fish per week Shown to decrease sudden cardiac death, coronary heart disease, & ischemic strokes Avoid/limit high mercury fish Shark, swordfish, king mackerel, tilefish, marlin, orange roughy, & bigeye (Ahi) tuna Cholesterol Maximum cholesterol dietary intake has been removed in favor of limiting saturated and trans fats Lipid digestion Lingual lipase begins to remove 1 FA from TAGs in the mouth Gastric lipase cleaves some more FAs off Pancreatic lipase continues the removal of FAs Can get access to TAGs only when lipid droplets are emulsified by bile Function of Bile Emulsifies lipid droplets Increases surface area of lipids so that enzymes can catabolize them Bile salts form micelles so that FAs can be absorbed by enterocytes 98% of bile salts are reabsorbed in the ileum, travel through the hepatic portal circulation back to the liver- enterohepatic circulation of bile TAG Digestion Overview Lipid absorption FAs, MAGs, cholesterol, fat soluble vitamins, & lysophosphatidylcholines are incorporated into micelles Enterocytes uptake the micelles (passive diffusion) and convert FAs, MAGs, cholesterol, & lysophosphatidylcholines back to TAGs, cholesterol esters, & phospholipids These are incorporated into chylomicrons which are excreted into the lymph via a lacteal Micelle Brush border Enterocyt es Fat Absorption into Enterocyte (Intestinal Mucosal Cell) FA and Cholesterol Transport Lipoprotein Lipase (LPL) Breaks down TAGs in the blood into FFAs to be absorbed by the cells Lipoprotein s Gropper and Smith “Advanced Nutrition and Human Metabolism” Very Low Density Lipoproteins (VLDL), Low Density Lipoproteins (LDL) & High Density Lipoproteins (HDL) VLDLs Made in the liver Major lipoprotein circulating in a fasted state Delivers TAGs to adipose tissue LDLs Formed from VLDL when the TAGs are gone Transports cholesterol for use by cells in the periphery—known as bad cholesterol Saturated fat has shown to increase LDLs HDLs Known as the good cholesterol transporter because removes cholesterol from peripheral cells and returns it to the liver where much converted to bile acids—known as reverse cholesterol transport or excreted Why do we study cholesterol? Serum cholesterol is positively correlated with coronary heart disease (CHD) and death- leading cause of death in Americans CHD Risk Positive Risk Factors: Smoking Hypertension (>130/80) Low HDL cholesterol (45, men; >55, women) Diabetes Sedentary High BMI Negative risk factor: HDL >60mg/dL 28 Atherosclerosis Initiation http://openi.nlm.nih.gov/detailedresult.php?img=2118281_jem2030813f01&req=4 High levels of circulating LDL allows for oxidation by ROS Oxidized-LDL is taken up by macrophages forming foam cells These foam cells aggregate to form a fatty streak 30 Atherosclerosis Progression http://exercisevascularcells.org/about.htm More foam cells aggregate leading to the incorporation of smooth muscle cells and collagen forming a fibrous plaque The fibrous plague could become necrotic and rupture or be injured and rupture Immune cells aggregate to repair the damage and consequently block the artery leading to an AMI 31 Where does cholesterol come from? Almost all tissues synthesize cholesterol The liver produces about 20% - biggest contributor Acetyl CoA is the building block Cholesterol production from diet and de novo synthesis is about 1g/day- used to make bile, vit. D, for membranes Daily recommended intake of cholesterol used to be 300mg/day Only half of this is absorbed So the majority of cholesterol in the body is made de novo Negative feedback loop on HMG-CoA Reductase- rate- limiting step Statins block HMG-CoA Reductase 32 Cholesterol and Exercise Meta-analysis including the results of 25 articles shows a modest increase in HDL with exercise Most effective in those with low BMI and high total cholesterol Exercise duration per session showed the strongest correlation for increased HDL “Effect of Aerobic Exercise Training on Serum Levels of High-Density Lipoprotein Cholesterol” (Kodame et al., 2007) 33 AHA Diet Recommendations for reduced cholesterol Plant Sterols and Cholesterol Foods rich in plant sterols Wheat germ, sesame sticks, pistachios, & sunflower seeds 2-5 g intake of plant sterols per day, has been shown to reduced total cholesterol 8-10% and LDL cholesterol 9-14% How to eat more plant sterols Swap butter for a spread enriched in plant sterols Swap full-fat yogurts for enriched yogurt or soy yogurt Drink milk enriched with plant sterols or soy milk Eat high fiber fruit, veggies, oats and beans Snack on nuts and seeds Drink enriched juices