Lecture 45 11/29/23

Question 1

What are the characteristics of brain metabolism?

Answer 1

-normally uses glucose
-can use lactate and ketones in some areas
-certain parts of the brain always require glucose

Question 2

What are the characteristics of skeletal muscle metabolism?

Answer 2

-can use glucose, fatty acids, ketones, or branched chain amino acids
-preference is for free fatty acids
-stores energy as glycogen and intramyocellular lipid

Question 3

What are the characteristics of cardiac muscle metabolism?

Answer 3

-utilizes mostly fatty acids
-has high carnitine requirement

Question 4

What are the characteristics of liver metabolism?

Answer 4

-regulatory role
-monitors nutrient uptake
-takes up glucose to store as glycogen
-takes up lactate, amino acids, and glycerol for conversion to glucose-6-phosphate
-stores glucose-6-phosphate as glycogen or uses it for glucose production
-takes up fatty acids for reesterification or ketone production

Question 5

What are the characteristics of kidney metabolism?

Answer 5

-performs gluconeogenesis
-uses most of its produced glucose for its own functioning

Question 6

What are the characteristics of intestinal tract metabolism?

Answer 6

-uses 20% of body’s resting oxygen composition
-major fuel sources are glutamate and glutamine
-colonocytes use the short chain fatty acid butyrate as fuel

Question 7

What are the characteristics of adipose tissue metabolism?

Answer 7

-store and release fatty acids
-triglycerides are hydrolyzed and stored in adipocytes in a fed state
-stored triglycerides, free fatty acids, and glycerol are released during starvation

Question 8

Which tissues can only use glucose?

Answer 8

-red blood cells
-retina
-renal medulla

Question 9

What happens in tissues that can only use glucose?

Answer 9

-glucose metabolism produces lactate
-lactate is returned to liver to participate in Cori cycle
-Cori cycle converts lactate into glucose

Question 10

What happens to glucose in the absorptive phase?

Answer 10

-glucose levels rise
-insulin is released
-hepatic glycogenesis is stimulated
-excess glucose goes into peripheral circulation

Question 11

Why are free fatty acid levels low during the absorptive phase?

Answer 11

they are immediately packaged into other compounds following a meal

Question 12

What happens to protein in the absorptive phase?

Answer 12

-no purely storage form
-dietary protein must be used for protein synthesis or catabolized

Question 13

What happens to fat in the absorptive phase?

Answer 13

majority is deposited into adipose tissue, liver, or muscle

Question 14

What happens to glucose in the post-absorptive phase?

Answer 14

-glucose levels fall
-decreased insulin secretion
-increased glucagon secretion
-glycogenolysis releases glucose

Question 15

How does insulin level impact fat stores?

Answer 15

-high insulin levels prevent lipolysis in adipose tissue
-low insulin levels cause the release of free fatty acids

Question 16

What are the characteristics of gluconeogenesis in the post-absorptive phase?

Answer 16

-begins after 24 hours of fasting
-tissues that have to use glucose contribute lactate for recycling through the Cori cycle
-kidneys increase gluconeogenesis function

Question 17

What are the characteristics of ketones in the post-absorptive phase?

Answer 17

-fatty acids are converted to ketones in the liver
-many tissues can use the ketones in place of glucose

Question 18

What are the characteristics of simple starvation?

Answer 18

-body initially utilizes liver glycogen stores
-mixture of muscle protein and fat used after glycogen
-metabolism eventually slows down after a day or two and shifts to using stored fat for energy

Question 19

What are the characteristics of stress starvation?

Answer 19

-disease leads to alterations in cytokines and hormones
-metabolic rate and gluconeogenesis increase
-body dramatically increases protein catabolism to produce glucose

Question 20

What are the consequences of stress starvation?

Answer 20

-slowed wound healing
-impaired immune function
-decreased strength and mobility
-poorer prognosis