Feed-Fast Cycle

1
Feed-Fast Cycle
2
CONNECTION OF PATHWAYS

1. ATP is the universal currency of energy
2. ATP is generated by oxidation of glucose, fatty
   acids, and amino acids common intermediate -gt
   acetyl CoA electron carrier -gt NADH and FADH2
3. NADPH is major electron donor in reductive
   biosynthesis
4. Biomolecules are constructed from a small set of
   building blocks
5. Synthesis and degradation pathways almost always
   separated -gt Compartmentation !!!

3
METABOLIC PROFILE OF ORGANS
4
THE LIVER AS CENTRAL PLAYER

• Blood from intestine travels via hepatic portal
  to liver 1st
• Liver ideally placed to regulate fuel passage
  elsewhere

Hepatic Artery
5
KEY JUNCTIONS BETWEEN PATHWAYS
6
FIVE PHASES OF GLUCOSE HOMEOSTASIS

• Absorptive, post-absorptive, and early starvation
  occur sequentially over 2 days.
• Intermediate, and prolonged starvation are over
  38 subsequent days and beyond

7
POSTABSORPTIVE STATE
INSULIN SECRETION STIMULATED BY GLUCOSE UPTAKE
8
POSTABSORPTIVE STATE -gt AFTER A MEAL
9
(No Transcript)
10
METABOLIC PROFILE OF ADIPOSITE TISSUE
Triacylglycerols are stored in tissue -gt
enormous reservoir of metabolic fuel -gt needs
glucose to synthesis TAG -gt glucose level
determines if fatty acids are released into blood
11
METABOLIC PROFILE OF MUSCLES
Major fuels are glucose, fatty acids, and ketone
bodies -gt has a large storage of glycogen -gt
glucose is preferred fuel for burst of
activity -gt production of lactate (anaerobe)
12
METABOLIC PROFILE OF BRAIN
Glucose is fuel for human brain -gt ketone
bodies can replace glucose
13
(No Transcript)
14
MOBILIZATION AT STARVATION
Also at not treated diabetes
15
(No Transcript)
16
EARLY FASTING STATE
Blood-glucose level drops after several hours
after the meal - gt decrease in insulin
secretion -gt rise in glucagon secretion Low
blood-glucose level -gt stimulates glucagon
secretion of a-cells of the pancreas Glucagon -gt
signals starved state -gt mobilizes glycogen
stores (break down) -gt inhibits glycogen
synthesis -gt main target organ is liver -gt
inhibits fatty acid synthesis -gt stimulates
gluconeogenesis in liver -gt large amount of
glucose in liver released to blood stream -gt
maintain blood-glucose level Muscle Liver use
fatty acids as fuel when blood-glucose level drops
17
EARLY FASTING STATE -gt DURING THE NIGHT
18
LIVER FUNCTION IN THE FASTING STATE
19
PROLONGED STARVATION
FIRST PRIORITY -gt provide sufficient glucose to
brain and other tissues that are dependent on
it SECOND PRIORITY -gt preserve protein -gt shift
from utilization of glucose to utilization of
fatty acids ketone bodies -gt mobilization of
TAG in adipose tissues gluconeogenesis by liver
-gt muscle shift from glucose to fatty acids as
fuel AFTER 3 DAYS OF STARVATION -gt liver forms
large amounts of ketone bodies -gt brain and heart
start to use ketone bodies as fuel AFTER SEVERAL
WEEKS OF STARVATION -gt ketone bodies major fuel
of brain AFTER DEPLETION OF TAG STORES -gt
proteins degradation accelerates -gt death due to
loss of heart, liver, and kidney function
20
PROLONGED STARVATION
21
(No Transcript)
22
Summary Glucose Homeostasis During Fasting
23
THANKS