Transcript glucosehomeostasis3

17 September 2010
• 1QQ # 5
• Glucose Homeostasis
– Source, targets, actions, negative feedback loops for
• Insulin
• Glucagon
• Epinephrine
– A case study in glucose homeostasis
• Endocrinology: Begin Chapter 11 p 315-346
• Next week in lab: Reading a Research Paper
– Scan the Androstenedione paper before coming to lab.
1QQ # 5a
1. Which of the following are true during the absorptive
phase? (Circle all correct responses.)
a) Amino acids are released from muscle tissue.
b) The liver converts glucose to a-ketoacids.
c) Muscle cells generate glycogen from glucose
d) Excess amino acids are converted to triglycerides in
the liver.
e) As plasma glucose levels rise, so does the secretion
of insulin.
f) The main fuel molecules for most cells are fatty acids
and ketones.
g) GLUT-4 transporters are inserted into the cell
membranes of adipocytes.
1 a b c d e
f
g
1QQ # 5b
1. Which of the following are true during the post
absorptive phase? (Circle all correct responses.)
a) Amino acids are released from muscle tissue.
b) The liver converts glucose to a-ketoacids.
c) Muscle cells generate glycogen from glucose
d) Excess amino acids are converted to triglycerides in
the liver.
e) As plasma glucose levels rise, so does the secretion
of insulin.
f) The main fuel molecules for most cells are fatty acids
and ketones.
g) GLUT-4 transporters are inserted into the cell
membranes of adipocytes.
1 a b c d e
f
g
Recognize and
distinguish between
hyposecretion and
hyporesponsiveness
GLUT-4
Activates some enzymes, inactivates others
↑ plasma glucose →↑insulin secretion→↑glucose uptake into cells →↓ plasma glucose
Diabetes mellitus:
T1DM =beta cells fail to produce adequate insulin (5%)
T2DM = target cells “resistant” (less responsive) to insulin
Hyperglycemia
Diagram of Kidney and renal “handling” of glucose
Filtration
Reabsorption
Transport maximum (Tm)
Explain how hyperglycemia
Can result in glucose in the
urine, and the consequences
thereof.
Analogy of
Exceeding Transport
Maximum:
YouTube of Lucy at
Candy Factory
Identify sensors,
afferent pathway,
integrator,
efferent pathway,
effectors
Fig. 16.07
How is insulin secretion
affected if plasma
glucose is lower than
set point?
Which cell types have
insulin receptors?
Stimulatory
actions of
insulin in
green
Inhibitory
actions of
insulin in
dashed red
Graph your daily caloric intake
over a 48 hour period
Plasma
Glucose
Calories
consumed
100
65
6am
Noon
6pm
MN
6am
Noon
6pm
MN
6am
Overlay INSULIN SECRETION on the graph
Overlay GLUCAGON SECRETION on the graph
Noon
Absorptive Phase
Post-Absorptive Phase
Thinking
about food
Factors that influence Insulin Secretion
?
FF
WHY?
The Integrator
integrates multiple
inputs
FF
Glucose
uptake,
Storage,
Lipogenesis
Another
hormone that
regulates
plasma glucose
concentration
Glucagon prevails
during postabsorptive phase
Transition from
absorptive to postabsorptive phase?
Fig. 16.10
EPI, yet another horomone in
glucose homeostasis, effects
opposite of Insulin
Don’t fret about
receptors, afferent
pathway, and
integrator for this
feedback loop.
Glucose-counterregulatory
controls
(oppose effects of insulin)
Glucagon
Epinephrine
Cortisol (permissive effect)
Growth hormone (permissive effect)
Who
Cares?
A Case Study
• On our website at
• http://webs.wofford.edu/davisgr/bio342/oggt.htm
A Case Study of Glucose Homeostasis
A 35 year old male presented with the following complaints: frequent severe
headaches upon awakening at 4:30 am, blurred vision, and fatigue due to excessive
stress at work. The patient complained of routine 16 hr workdays followed by a
midnight snack of breakfast cereal.
An OGTT was ordered and provided the following results:
During the second hour of the OGTT, the patient exhibited anxiety, paleness, hunger,
tremulousness, and cold sweat. No additional tests were ordered. The patient was
instructed to replace the midnight snack of cereal with a protein-rich snack.
Oral Glucose Tolerance Test
• Overnight fast, no
beverages other than water
• Fasting blood sample
• Ingest 75 grams glucose
• Blood samples every 0.5
hours for 3-5 hours
• Plot plasma glucose
concentration over time
• Compare curves
60
Stress,
Emergency
(fight or flight)
Effect on
Alpha Cells
Effect on
Beta cells
The Answer to the Problem?
• Rationale for substituting protein
for carbohydrate midnight snack?