L11: Metabolism and Obesity

Question 1

Cholesterol balance related to _____________ and _______________

Answer 1

Cholesterol balance related to dietary cholesterol ingestion and synthesis by the liver

Question 2

Fate of Absorbed Amino Acids?

Question 3

Fate of Absorbed Fats?

Answer 3

Chylomicrons (dietary lipids)-> Fatty Acids -> + a-glycerol phosphate -> Triglycerides in adipose tissue

Cholesterol balance related to dietary cholesterol ingestion and synthesis by the liver

Question 4

Fate of Absorbed Glucose?

Answer 4

In Demand: Glucose tranported to Cells e.g. muscle -> ATP & energy

When in excess the liver converts Glucose to:

• Glycogen (Stored)
• a-Glycerol Phosphate + Fatty Acids (Transported via VLDL to Adipose)-> Triglyceride Stored in Adipose cells

Question 5

Glycogenolysis in Liver/Muscles?

Answer 5

Glycogens stores in Liver

• Glucose-6 phosphatase able to convert glycogen => glucose
• Rapid Release of Glucose (within seconds of sympathetic stimulation)
• Function to maintain blood glucose
• Short-lived- only lasts a few hours

Glycogen stores in Muscles

• NO Glucose-6 phosphatase
• Slower release of ATP, Lactate and Pyruvate (Lactate and Pyruvate can be used to make glucose (Cori Cycle)

Question 6

Process in the liver that converts lactate (released from muscles via glycogenolysis) to glucose which is then returned to the muscle to meet metabolic demand in times of extreme exertion?

Answer 6

Cori Cycle

NOT SUSTAINABLE: Requires more ATP in Liver than ATP released from glycolysis in muscle. Only done in short term under extreme exertion

Question 7

Process of Lipolysis (Beta Oxidation) in Starvaton?

Answer 7

Question 8

Energy Sources in Post-Absorptive State?

Answer 8

Glycogenolysis

Cori cycle

Lipolysis

Protein Catabolism

Gluconeogenesis

Question 9

During high rates of fatty acid oxidation, primarily in the liver, large amounts of _______________ are generated. These exceed the capacity of the TCA cycle, and one result is the synthesis of __________________

Answer 9

During high rates of fatty acid oxidation, primarily in the liver, large amounts of Acetyl-CoA are generated. These exceed the capacity of the TCA cycle, and one result is the synthesis of ketone bodies, or ketogenesis

Question 10

Ketone Bodies: (_________, _____________, ______________)

• __________ abnormal constituents of blood
• Produced by ___________ – exported to other tissues

Tissues: ____________ and _____________________ used in skeletal muscles to produce ATP (Heart uses for energy preferentially to glucose)

Symptoms:

• Patients w/ severe ketoacidosis have “acetone breath” (Common in ________________)
• Accumulation of ketone bodies only a problem when produced at rate faster than _________________ can handle

Answer 10

Ketone Bodies: (Acetoacetate, b-hydroxybutyrate, acetone)

• NOT abnormal constituents of blood
• Produced by mitochondria in the liver – exported to other tissues

Tissues: Acetoacetate and b-hydroxybutyrate used in skeletal muscles to produce ATP- Heart uses these 2 for energy preferentially to glucose

Symptoms:

• Patients w/ severe ketoacidosis have “acetone breath” (Common in Type 1 Diabetes)
• Accumulation of ketone bodies only a problem when produced at rate faster than blood buffer can handle

Question 11

Response to Starvation. When does death occur?

Answer 11

Increase Glucose

• First from Glycogenolysis – Liver & Skeletal muscle (Glycogen is used up in 1-2 days)
• Then Gluconeogenesis (from Amino acids, glycerol, and lactate (Cori cycle))

Fatty Acids Metabolism: During high rates of fatty acid oxidation, primarily in the liver, large amounts of Acetyl-CoA are generated. These exceed the capacity of the TCA cycle, and one result is the synthesis of ketone bodies (ketogenesis)

Amino Acid Catabolism (Deanimation):

• => Glucogenic AA metabolism (Kreb’s cycle)
• => Ketogenic AA metabolism (Acetyl-CoA)

Death occurs after 4 weeks when body mass is 50% (Temperature and blood glucose only fall at the end)

Question 12

Basal power output of a man at rest?

Answer 12

Basal power output of a man at rest is approximately 100W

Question 13

How to calculate the BMR using indirect calorimetry?

Answer 13

RQ = CO2 eliminated / O2 consumed

Question 14

Factors Affecting Metabolic Rate?

Answer 14

Question 15

How to calculate BMI/Ranges of it?

Answer 15

Question 16

What percentage contribution does genetics make to obesity?

Answer 16

70-75% based on Swedish twin studies

Question 17

De-Novo Lipogenesis (Glucose vs. Fructose)?

Answer 17

Generation of new fats in response to sugars varies greatly:

• Glucose: Low contributor to denovolipogenesis
• Fructose: Significant denovolipogenesis

Question 18

Leptin vs. Grehlin?

Answer 18

Leptin: ob gene encodes a protein which was made by adipocytes

• Excites satiety center of the hypothalamus and acts as adipostat (negative feedback stabilizes % body fat)

Grehnlin: Orexigenic agent - Stimulates hunger and opposes Leptin

• Promotes growth hormone release
• Targets the hypothalamus (plus others incl GIT)
• Role in gastric motiliy