Glucose homeostasis

1. PHYSIOLOGY

2. PRAPAREDBY GROUP
2
Question

3. • Introduction
• Sources of glucose
• Phases of glucose homeostasis
• Hormones in glucose homeostasis
Insulin
Glucagon
Overview

5. Glucose homeostasis
• A process that
• Controls glucose metabolism and
• Maintains normal blood glucose level in the body
• Glucose is a major source of body’s energy
• The liver plays a key role in maintaining blood glucose
level
• It is tightly controlled as the brain constantly needs
glucose
• Severe hypoglycemia can cause coma and death
• Chronic hyperglycemia results in glycation of proteins,
endothelial dysfunction and diabetes mellitus

6. Sources of glucose

7. Sources of glucose
Cookies Dessert

8. ANALYZE THE SITUATION
Cookies(C) + deserts(D)= simplified sugar
simplified sugar is a form of carbohydrate
carbohydrate is degraded to form glucose….
this implies that any time we eat cookies, desserts(carbohydrate) our
blood glucose or blood sugar,(B) level goes up…mathematically,
 C ,D B

9. SECTION 2
HOW THEN DOES THE BODY DEAL WITH THE SUDDEN
INCREASE IN BLOOD GLUCOSE CONCENTRATION?

10. Phases of glucose homeostasis
•Five phases:
In well-fed state:
Phase I
In fasting:
Phase II (Glycogenolysis)
Phase III (Gluconeogenesis)
Phase IV (Glucose, ketone bodies oxidation)
Phase V (Fatty acid (FA), KB oxidation)

11. Phase I (Well-fed state)
• Glucose is mainly supplied by dietary CHOs
• Liver removes about 70% of glucose load after a CHO meal
• All body tissues use dietary glucose for energy in this phase
• Some glucose is converted to glycogen for storage in the liver
(glycogenesis)

12. Phase I (Well-fed state)
• Excess glucose is converted to fatty acids and triglycerides in the
liver
• These are transported via VLDL (very low density lipoproteins) to
adipose tissue for storage
• Gluconeogenesis is inhibited in this phase
• Cori and glucose-alanine cycles are inhibited

13. Hormones and glucose homeostasis

14. Insulin
• Plays a major role in glucose homeostasis
• Synthesized by the β-cells of islets of Langerhans of pancreas
• A small protein composed of two chains
• Rise in blood glucose level stimulates insulin secretion
• Promotes entry of glucose into cells

15. Insulin actions

16. Mechanism of action
• The insulin receptor is present on the plasma
membrane of cell
• Composed of
• α-subunit (extracellular)
• β-subunit (cytoplasmic)
• Binding of insulin to α-subunit causes
phosphorylation of β-subunit
• This activates the receptor
• The activated receptor then phosphorylates
intracellular proteins generating a biological response

18. Insulin and CHO metabolism
Promotes glucose uptake into cell:
• Glucose is diffused into cells through hexose
transporters such as GLUT4
• GLUT4 is present in cytoplasmic vesicles
• Insulin binding to its receptor causes vesicles to
diffuse into plasma membrane
• GLUT4 is inserted into the membrane
• Allowing glucose transport into the cell
• Brain and liver have non-insulin dependent glucose
transporter

20. Insulin and CHO metabolism
• Stimulates glycogen synthesis
• Decreases blood glucose levels
• Increases glycolysis
• Stimulates protein synthesis
• Insulin deficiency causes diabetes mellitus
• Hyperinsulinemia is due to insulin resistance in:
• Diabetes mellitus or
• Metabolic syndrome

21. Glucagon
• A peptide hormone secreted by α-cells
of pancreatic islets
• Secreted in response to hypoglycemia
• Increases glucose levels
• Stimulates glycogenolysis
• Activates hepatic gluconeogenesis

23. Comparison between effect of Insulin and glucagon

25. What then Happens when the hormones
cant regulate blood glucose levels??
Inability of the pancreas to control glucose levels will result in:
Hyperglycemia(blood sugar levels remain too high the body suppresses
appetite over the short term.
Long-term hyperglycemia causes many of the long-term health problems
including heart disease, eye, kidney, and nerve damage.
A major sign/symptom of diabetes, defined as blood glucose over 140
mg/dL.

26. Diabetes Mellitus

28. hypoglycemia
• Low blood sugar:
If blood sugar levels drop too low, a potentially fatal condition called
hypoglycemia (below 40 mg/dl) develops.
Symptoms may include lethargy, impaired mental functioning;
irritability; shaking, twitching, weakness in arm and leg muscles;
pale complexion; sweating; paranoid or aggressive mentality and
loss of consciousness.

29. Insulin Resistance
Insulin resistance is generally regarded as a pathological condition in
which cells fail to respond to the normal actions of the hormone insulin.

30. Summary
• In normal person, the blood glucose concentration is usually
between 80 -90mg/100ml of blood in the fasting person
• the concentration increases to 120 -140 during the first hour after
meal, but feedback systems for control of blood glucose return the
glucose concentration rapidly back to the control level.
• when the blood glucose rises to a high concentration after a meal '
the rate of insulin secretion is also increases and glucose
concentration rapidly back to the normal.

31. Summary
If the blood sugar level drops below the norm, for example between
meals, or after fasting, then the alpha cells of the Islets of Langerhans
detect this change and respond by secreting glucagon
Doctors and health workers advises that a healthy eating plan that
limits sugar intake and is balanced by an appropriate level of exercise
can help control blood glucose levels hence preventing diabetes and
other related diseases.