CPPS303 XIAO Lecture 2 Intestinal Lipid Metabolism March_12_2025 (1)

Question 1

What territory do we acknowledge we are on?

Answer 1

Treaty 6 Territory and the Homeland of the Métis.

Question 2

Who is the instructor for CPPS 303?

Answer 2

Changting Xiao, PhD.

Question 3

What is the primary textbook for the course?

Answer 3

Medical Physiology, Boron & Boulpaep, 3rd edition.

Question 4

What will be covered in the lectures?

Answer 4

Specialized features of and integrated coordination among organs that regulate metabolic and energy homeostasis.

Question 5

What are the key components of lipid metabolism discussed?

Answer 5

• Triacylglycerol synthesis
• Chylomicron synthesis, secretion, transport
• Cytoplasmic lipid droplet metabolism

Question 6

What leads to the development of metabolic diseases?

Answer 6

Dietary lipid overload.

Question 7

What enzymes are involved in triacylglycerol digestion?

Answer 7

• Lingual lipase
• Gastric lipase
• Pancreatic lipase

Question 8

What are the digestion products of triacylglycerol?

Answer 8

• Fatty acids
• Monoacylglycerol

Question 9

What type of transport is used for fatty acid uptake?

Answer 9

• Passive diffusion
• Facilitated transport (CD36, FATP4)

Question 10

Where does re-esterification of fatty acids occur?

Answer 10

At the endoplasmic reticulum (ER).

Question 11

What are the metabolic fates of lipids in enterocytes?

Answer 11

• Chylomicron synthesis and secretion
• Beta-oxidation in mitochondria
• Storage as cytoplasmic lipid droplets
• Synthesis of other complex lipids

Question 12

What are the components of chylomicrons?

Answer 12

• TAGs
• Phospholipids
• Cholesteryl esters
• Cholesterol
• Apolipoproteins (B48, AI, A4)

Question 13

What is the diameter range of chylomicrons?

Answer 13

~250 nm (75-1200 nm).

Question 14

What is the function of the lymphatic system in lipid transport?

Answer 14

Transporting chylomicrons and preventing backflow.

Question 15

What are cytoplasmic lipid droplets (CLD) associated with?

Answer 15

Transient lipid storage and dynamic changes during feeding and fasting.

Question 16

What are the cholesterol transporters mentioned?

Answer 16

• NPC1L1 (Niemann-Pick C1-like 1)
• SR-BI (scavenger receptor class B type I)

Question 17

What is transintestinal cholesterol excretion (TICE)?

Answer 17

Cholesterol derived from plasma is taken up by enterocytes and excreted to the intestinal lumen.

Question 18

What is the role of ABCG5 and ABCG8 in cholesterol transport?

Answer 18

Mediating cholesterol efflux back into the lumen and exclusion of plant sterols.

Question 19

Fill in the blank: Dietary lipids are digested by ______ enzymes.

Answer 19

pancreatic

Question 20

True or False: Chylomicrons are too large to enter capillary blood vessels.

Answer 20

True

Question 21

What is the primary pathway for the re-esterification of digested lipids in enterocytes?

Answer 21

MAG pathway (major, ~80%).

Question 22

What happens to mature chylomicrons after exocytosis?

Answer 22

They are transported by the lymphatic system.

Question 23

What is the impact of feeding on cytoplasmic lipid droplets?

Answer 23

Increase in number and size with fat ingestion.

Question 24

What is the primary role of apolipoprotein B-48?

Answer 24

Structural protein in chylomicron particles.

Question 25

What are stored cytoplasmic lipid droplets?

Answer 25

Structures that store lipids within cells ## Footnote Cytoplasmic lipid droplets serve as reservoirs for energy and lipid metabolism.

Question 26

What is chylomicron assembly?

Answer 26

The process of forming chylomicrons from lipids and apoB48 ## Footnote Chylomicrons are lipoproteins that transport dietary lipids from the intestines.

Question 27

What proteins are involved in the transport of pre-chylomicrons?

Answer 27

MTP (Microsomal Triglyceride Transfer Protein) ## Footnote MTP is essential for the assembly and secretion of chylomicrons.

Question 28

How are mature chylomicrons discharged?

Answer 28

By exocytosis ## Footnote This process allows chylomicrons to enter the lymphatic system for transport.

Question 29

What system transports chylomicrons after they are discharged?

Answer 29

The lymphatic system ## Footnote Chylomicrons are transported through lymphatic vessels before entering the bloodstream.

Question 30

What is pharmacotherapy targeted to in the context of diet-induced obesity?

Answer 30

Specific molecules involved in the absorptive process ## Footnote Molecules include luminal lipases, bile acids, NPC1L1, MGAT2, DGAT1, and MTP.

Question 31

Fill in the blank: Digestion and absorption of dietary fats involves _______.

Answer 31

[Triacylglycerol metabolism] ## Footnote This includes the breakdown and absorption of dietary fats in the intestine.

Question 32

What is TAG re-synthesis?

Answer 32

The process of reconstructing triacylglycerols in intestinal enterocytes ## Footnote This occurs primarily at the endoplasmic reticulum (ER).

Question 33

What is the role of cytoplasmic lipid droplet metabolism?

Answer 33

Transient storage of lipids ## Footnote This process is crucial for managing lipid availability in cells.

Question 34

What is the primary function of cholesterol uptake and transport?

Answer 34

To facilitate the absorption and distribution of cholesterol in the body ## Footnote Cholesterol is essential for cell membrane structure and function.

Question 35

True or False: Chylomicrons are the only transport mechanism for dietary lipids.

Answer 35

False ## Footnote Other mechanisms and lipoproteins also play roles in lipid transport.