Lipids

Chapter 6

Chapter 6 Learning Objectives• Describe how lipids are named and classified based

upon features such as composition and bonding.• Describe how the physical and chemical properties

of lipids are influenced by features such as composition and bonding.

• Identify the sources, functions and dietary recommendations for various lipids important to humans (i.e. essential & non-essential FA, saturated & nonsaturated FA, cholesterol, trans fat.)

• Describe the structure and function of mono, di-, triglycerides, phospholipids, cholesterol and lipids such as LDL and HDL that circulate in the body.

Chapter 6 Learning Objectives (Continued)

• Describe how the various lipids consumed are digested, transported, metabolized,stored and removed from storage.

• Outline the recommendations for dietary intake and food sources of the various types of lipids.

• Discuss the causes (etiology), course and treatment of cardiovascular disease and the relationship between diet and known risk factors.

Fatty Acid Structure

Fatty Acids Can Take Several Forms

Fatty Acids Can Have Different Chain Lengths

Saturated and Unsaturated Fatty Acids

Cis versus Trans Fatty Acids

What Are Lipids?

• Other naming systems– Alpha (α) naming system• Types and positions of double bonds relative to

carboxylic acid (α) end– Omega (ω) naming system• Where the first double bond is located relative to the

methyl (ω) end• Does not distinguish cis or trans configuration or

location of double bonds– Common names

Names and Food Sources of Some Important Fatty Acids in the Body

Which Fatty Acids Do We Need, and Where Do They Come From?

• Two essential fatty acids– Linoleic acid• 18 carbons, two cis double bonds• ω-6 fatty acid

– Linolenic acid• 18 carbons, three cis double bonds• ω-3 fatty acid

Essential Fatty Acids

Which Fatty Acids Do We Need, and Where Do They Come From?

• Converting linoleic and linolenic acids– Building blocks for longer fatty acids • Elongation• Desaturation

– Linoleic acid• Arachadonic acid

– Linolenic acid• Eicosapentaenoic acid (EPA)

– Docosahexaenoic acid (DHA)

Which Fatty Acids Do We Need, and Where Do They Come From?

• Metabolism of essential fatty acids– Eicosanoids• Chemical messengers• Prostaglandins • ω-3 and ω-6 eicosanoids have opposing actions• Dietary influence

• Essential fatty acid deficiency – Signs and symptoms

Metabolism of the Essential Fatty Acids

Which Fatty Acids Do We Need, and Where Do They Come From?

• Conditionally essential fatty acids– Infancy• Arachodonic acid and DHA

• Dietary sources – Essential fatty acid sources – EPA and DHA sources– SFAs– PUFAs– MUFAs

Distribution of Fatty Acid Classes in Commonly Consumed Lipids

Mono-, Di-, and Triglycerides: What’s the Difference?

• Number of fatty acids attached to glycerol backbone– Ester linkages – Mixture of fatty acid

types– Hydrophobic

A Triglyceride Molecule

Mono-, Di-, and Triglycerides: What’s the Difference?

• Triglyceride roles in the body– Energy source • Lipolysis • Lipases

– Lipoprotein lipase– Hormone-sensitive lipase

• Ketones

Mono-, Di-, and Triglycerides: What’s the Difference?

• Triglyceride roles in the body– Storage of excess energy • Adipose tissue – adipocytes

– Subcutaneous and visceral adipose tissue

• Insulin– Lipogenesis

• Advantages of triglyceride storage

– Insulation– Protection

What Are Phospholipids and Sterols?

• Phospholipids– Phosphate-containing polar head group– Amphipathic • Hydrophilic – polar head group• Hydrophobic – fatty acids

– Major component of cell membranes– Food sources• Phosphatidylcholine

A Phospholipid Molecule

What Are Phospholipids and Sterols?

• Phospholipids– Cell membranes– Cellular metabolism– Eicosanoid production– Carriers of hydrophobic substances

A Cell Membrane Consists of a Phospholipid Bilayer, Proteins & Cholesterol

What Are Phospholipids and Sterols?

• Sterols – Multi-ring structures • Free• Bound

– Sterol ester

– Cholesterol • Bile acids, membranes, steroid hormones

– Cholesteryl ester• Membranes, carriers for fatty acids in blood

Structures of a Sterol, Cholesterol, and a Cholesteryl Ester

What Are Phospholipids and Sterols?

• Sources of cholesterol– Synthesis in the body• Influence of dietary

factors – Dietary sources –Medications

• Phytosterols & phytostanols

How Are Dietary Lipids Digested?

• Goal of triglyceride digestion• Mouth– Lingual lipase

• Stomach– Gastrin stimulates release of gastric lipase

Overview of Triglyceride Digestion

How Are Dietary Lipids Digested?

• Small intestine– Phase 1: Micelle formation• Release of cholecystokinin (CCK)

– Gallbladder contracts and releases bile

• Emulsification – Ester linkages more accessible to digestive enzymes – Micelles

Emulsification of Lipids in the Small Intestine

How Are Dietary Lipids Digested?

• Small intestine– Phase II: Digestion of triglycerides• Release of secretin and CCK• Release of pancreatic lipase

– Completes triglyceride digestion

How Are Dietary Lipids Digested?

• Small intestine– Digestion of phospholipids and cholesteryl esters• Micelles

– Phospholipids• Phospholipase A2

– Fatty acid and lysophospholipid

– Cholesteryl esters• Bile salt-dependent cholesteryl ester hydrolase

Phospholipid and Cholesteryl Ester Digestion

How Are Dietary Lipids Absorbed and Circulated in the Body?

• Absorption occurs two ways– Enter enterocytes unassisted• Short- and medium-chain fatty acids

– Packaged in micelles • More hydrophobic compounds

Absorption & Circulation of Lipids in the Small Intestine

How Are Dietary Lipids Absorbed and Circulated in the Body?

• Circulation occurs two ways– Albumin• Short- and medium-chain fatty acids

– Chylomicrons • Released into lymph• Lipoprotein lipase• Chylomicron remnants

– Broken down to be reused or recycled

The Lipoproteins

What Is the Role of Other Lipoproteins in Lipid Transport & Delivery?

• Liver– Central command center– Recycling center

• Lipoproteins – Transport lipids in the blood – Apoproteins – Density • Lipid is less dense than protein

The Origins and Major Functions of Lipoproteins

What Is the Role of Other Lipoproteins in Lipid Transport & Delivery?

• VLDLs– Similarities with chylomicrons– Differences from chylomicrons– Primary function

• IDLs– Denser form of VLDL

What Is the Role of Other Lipoproteins in Lipid Transport & Delivery?

• LDLs– LDL receptors on cell membranes – Importance of cholesterol• Eicosanoids and immune factors

– Plaque – Diet and LDL cholesterol• SFAs and trans fatty acids

What Is the Role of Other Lipoproteins in Lipid Transport & Delivery?

• HDLs– Lowest lipid-to-protein ratio– Reverse cholesterol transport • Cardiovascular disease

– Diet and HDL cholesterol • Carbohydrates• MUFA• Alcohol

What Is the Relationship Between Lipid Intake & Health?

• Obesity– Excess lipid intake – Increased risk for many diseases

• Cardiovascular disease– Total dietary lipid intake• Types of dietary lipids

– Genetics • Cancer – Recommendations

What Are the Dietary Recommendations for Lipids?

• Essential fatty acids – DRIs• AIs

• Omega-3 fatty acids– Fish intake

• Saturated fat intake – Dietary guidelines

What Are the Dietary Recommendations for Lipids?

• Trans fatty acids– Minimize intakes • Commercially produced trans fatty acids

• Cholesterol – No DRIs– Therapeutic Lifestyle Change (TLC) diet

• Total lipid intake– AMDRs

Nutrition Matters

Nutrition and Cardiovascular Disease

How Does Cardiovascular Disease Develop?

• Slowing or obstruction of blood flow– Heart– Other parts of the body

• Atherosclerosis – Narrowing and hardening of blood vessels– Heart disease– Stroke – Other complications

Causes of Cardiovascular Disease

http://www.youtube.com/watch?v=mCYAOeEe6-w&feature=related

How Does Cardiovascular Disease Develop?

• Atherosclerosis and CVD– Plaque accumulates • Fatty acids, cholesterol, foam cells, cellular waste,

calcium, and other substances

– Chronic inflammation• C-reactive protein (CRP)

How Does Cardiovascular Disease Develop?

• Heart disease– Type of CVD– Angina pectoris• Chest pain

– Heart attack • Damage• Signs and symptoms for each sex

Diagnosing Heart Disease

Surgically Treating Heart Disease

How Does Cardiovascular Disease Develop?

• Stroke– Brain is deprived of oxygen and nutrients– Transient ischemic attacks (TIAs• Warning signs

– Treatment• Type and location of stroke

What Are the Risk Factors for Cardiovascular Disease?

• Nonmodifiable risk factors– Age, sex, genetics, prior stroke or heart attack, low

birth weight• Modifiable risk factors– Smoking, diabetes, stress, excessive alcohol intake– Hypertension

What Are the Risk Factors for Cardiovascular Disease?

• Modifiable risk factors– Elevated blood lipids • Hyperlipidemia

– LDLs– HDLs

• Antioxidants • Cholesterol ratio

Reference Values for Blood Lipids

What Are the Risk Factors for Cardiovascular Disease?

• Modifiable risk factors– Obesity• Apple-shaped

– Physical inactivity• Independent risk factor for CVD• Recommended activity levels

– Diabetes • Either type• Controlling blood glucose levels

How Does Nutrition Influence Cardiovascular Risk?

• Control of hypertension – Sodium or salt intake – Essential dietary

minerals• Potassium, calcium, and

magnesium –DASH diet

How Does Nutrition Influence Cardiovascular Risk?

• Controlling blood lipid levels– Low-carbohydrate diets• Short-term weight loss

– Dietary lipids • Saturated and trans fatty acids

– Monounsaturated and omega-3 fatty acids • Sources

– Alcohol

How Does Nutrition Influence Cardiovascular Risk?

• Other dietary factors– B vitamins• Folate, vitamin B6, and vitamin B12

– Homocysteine

– Dietary antioxidants – Functional foods• Phytochemicals• Zoonutrients

• Dietary patterns

Examples of Heart-Healthy Functional Foods & Their Biologically Active Components

Hydrogenation, protects against oxidation thereby prolonging shelf life.It also alters the

texture from liquid to solid.

Example: margarine or shortening

This process allows margarine to be separable, pie crust to be flaky.

Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning

Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning

High-Fat Foods and Heart Disease

High-Fat Foods and Heart Disease

The Mediterranean Diet

• Traditionally– Low in saturated fat– Very low in trans fat– Rich in unsaturated fat– Rich in complex carbohydrate and fiber– Rich in nutrients and phytochemicals

• Benefits for heart disease risk