1. Hormonal Control of Nutrient Metabolism and Storage
Dr. Mujeeb Ahmed Shaikh
Assistant Professor
AlMaarefa College

2. Learning Objectives
Describe the effect of insulin on glucose, fat, and protein metabolism.
Explain what is meant by counter-regulatory hormones, and describe the actions of glucagon, amylin, somatostatin, gut-derived hormones, epinephrine, growth hormone, and the adrenal cortical hormones in the regulation of blood glucose levels.

3. Nutrient Metabolism and Storage
The body uses glucose, fatty acids, and other substrates as fuel to satisfy its energy needs.

4. Glucose Metabolism and Storage
The brain and nervous system rely almost exclusively on glucose as a fuel source.
Other tissue can use fatty acids & ketone bodies
Body tissues obtain glucose from the blood.
In normal person the fasting blood glucose levels are tightly regulated between 80 and 90 mg/dL (4.4 and5.0 mmol/L).

5. After meal 2/3 of the glucose is removed from the blood & stored in liver as glycogen.
Between meals, the liver releases glucose as a means of maintaining the blood glucose within its normal range.
Extra glucose - glycogen / fats.
After muscle & liver get saturated the extra glucose used for FA & triglyceride synthesis.

6. Between meals, the liver releases glucose as a means of maintaining the blood glucose within its normal range.
The liver synthesizes glucose from amino acids, glycerol, and lactic acid in a process called gluconeogenesis.

7. Glucose Regulating Hormones
The hormonal control of blood glucose resides largely within the endocrine pancreas.
The pancreas is made up of two major tissue types: the acini and the islets of Langerhans.
Acini – digestive juices into duodenum
islets of Langerhans - secrete hormones into the blood.

9. Islet cells Alpha cells – Glucagon Beta cells – insulin & amylin
Delta cells - Somatostatin.
PP cells - pancreatic polypeptide

10. Endocrine pancreas: Islets of Langerhans Alpha Beta cells Delta cells
PP cells
cells
Insulin
Pancreatic
Glucagon
Somatostatin
and amylin
polypeptide

11. Functions of Pancreatic Hormones
Glucagon: causes cells to release stored food into the blood
Insulin: allows cells to take up glucose from the blood
Amylin: slows glucose absorption in small intestine; suppresses glucagon secretion
Somatostatin: decreases GI activity; suppresses glucagon and insulin secretion

12. Anabolism and Catabolism
available foodstuffs
Anabolism
stored foodstuffs
(in blood)
Insulin,
(in cells)
anabolic
steroids
glucose
glycogen
Catabolism
amino acids
proteins
glucagon,
epinephrine,
free fatty acids
cortisol
triglycerides
liver can convert amino acids
and free fatty acids into
ketones

13. Insulin and Glucagon Are the Main Controls
available foodstuffs
Anabolism
stored foodstuffs
(in blood)
Insulin ,
(in cells)
anabolic
steroids
glucose
glycogen
Catabolism
amino acids
proteins
Glucagon ,
epinephrine,
free fatty acids
triglycerides
cortisol
liver can convert amino acids
and free fatty acids into
ketones

14. Insulin
Insulin is the only hormone known to have a direct effect in lowering blood glucose levels.
The actions of insulin are threefold:
it promotes glucose uptake by target cells and provides for glucose storage as glycogen,
it prevents fat and glycogen breakdown, and
It inhibits gluconeogenesis and increases protein synthesis
Insulin acts to promote
fat storage by increasing the transport of glucose into fat cells
It also facilitates triglyceride synthesis from glucose in cells and inhibits the intracellular breakdown of stored triglycerides.

15. Insulin also inhibits protein break-down and increases protein synthesis by increasing the active transport of amino acids into body cells, and it inhibits gluconeogenesis, or the building of glucose from new sources, mainly amino acids.

16. Metabolic Effects of Insulin
Protein
Glycogen
Glucose-P
Pyruvate
CO2
Ketoacids
Liver
Glucose
Glucose
Free fatty
acids
Amino
acids
Adipose
tissue
Muscle
Plasma
Stimulate 
Glucose
Free fatty acids
Ketoacids
Amino acids
Inhibit

17. Approximate Rates of Insulin Secretion at Different Blood Glucose Levels
100%
Insulin Response
( )
50% 40 80
120
160
200
240
Plasma glucose (mg/dl)

18. Insulin
α - chain
β - chain
Proinsulin
Active insulin
C - Peptide

19. The C-peptide chains can be measured clinically, and this measurement can be used to study beta cell function (i.e., persons with type 2diabetes with very little or no remaining beta cell function will have very low or nonexistent levels of C-peptide in their blood, and thus will likely need insulin replacement for treatment).

20. Insulin vs Blood Glucose
Increase blood glucose
Increased insulin secretion

21. Secretion of insulin occurs in a pulsatile fashion
Secretion of insulin occurs in a pulsatile fashion. After exposure to glucose, which is a nutrient secretagogue, a First-phase release of stored preformed insulin occurs, followed by a second-phase release of newly synthesized insulin.
Serum insulin levels begin to rise within minutes after a meal, reach a peak in approximately 3 to 5 minutes, and then return to baseline levels within 2 to 3 hours.
Insulin has a half-life of approximately 15 minutes once it is released into the general circulation.

22. Mechanism of Glucose Stimulated Insulin Secretion

23. Factors Affecting Insulin Secretion
Stimulators
Inhibitors
Glucose
Mannose
Galactose
Amino acids
Arginine
Lysine
Leucine
Alanine
Free fatty acids, Keto acids
Glucagon (direct and indirect effects)
Gastro intestinal hormones
Glucagon like peptide 1 (GLP-1)
Glucose dependant Insulinotropic
Peptide (GIP)
Secretin
Fasting
Exercise
Somatostatin
Neural influences
Sympathetic activity-
-adrenergic stimulation
norepinephrine, epinephrine)
Neural influences
Vagal activity (acetylcholine)
b-adrenergic stimulation
Drugs like Sulfonylurea

24. Processing of Proinsulin and C-Peptide
Connecting peptide
HOOC
NH2 20 1 S 1 S 15
A-chain 5 10
B-chain S 30 5 S S S 25
Proinsulin 10 20 15
C-Peptide S S 20
NH2
COOH 1 5 S 10 15 S
Insulin
A-chain S S
NH2
COOH 1 5 10 15 20 25 30
B-chain

25. The Insulin Receptor & Mechanisms of Insulin Action

26. Insulin Receptors

27. Cell membranes are impermeable to glucose, they require a special carrier, called a glucose transporter, to move glucose from the blood into the cell.
GLUT 1, GLUT 2, GLUT 3, GLUT 4.
GLUT-4 is the insulin-dependent glucose transporter for skeletal muscle and adipose tissue

28. GLUT-2 is the major transporter of glucose into beta cells and liver cells. It has a low affinity for glucose and acts as a transporter only when plasma glucose levels are relatively high, such as after a meal.
GLUT-1 is present in all tissues. It does not require the actions of insulin and is important in transport of glucose into cells of the nervous system.

29. Glucagon
A polypeptide molecule produced by the alpha cells of the islets of Langerhans, maintains blood glucose between meals and during periods of fasting.
Glucagon produces an increase in blood glucose.
Initiate breakdown of glycogen between meals
Gluconeogenesis
Makes fatty acids available for use as energy

30. Factors Affecting Glucagon Secretion
Stimulation
Inhibition
Hypoglycemia
Amino acids
Arginine
Alanine
Gastrointestinal hormones
Cholecystokinin (CCK)
Gastrin
Fasting
Exercise
Neural influences
Vagal activity-acetylcholine
Sympathetic activity-
-adrenergic stimulation
(norepinephrine, epinephrine)
Glucose
Somatostatin
Insulin (direct effect)
Gastrointestinal hormones
Secretin
Glucagon-like peptide-1 (GLP-1)
Free fatty acids
Ketoacids
Neural influences
a-adrenergic stimulation

31. Approximate Rates of Insulin & Glucagon Secretion at Different Blood Glucose Levels
100%
100%
Insulin Response
( )
Glucagon Response
( )
50%
50% 40 80
120
160
200
240
Plasma glucose (mg/dl)

32. Amylin, Somatostatin, and Gut-Derived Hormones
A polypeptide that is co secreted with insulin from the beta cells.
Plasma levels of amylin increase in response to nutritional stimuli to produce inhibition of gastric emptying and glucagon secretion.
he less soluble and insoluble forms, which may cause degeneration of the beta cells and contribute to the pathogenesis of overt diabetes

33. Somatostatin
Its a polypeptide hormone containing only 14 amino acids that has an extremely short half-life.
Secreted by the delta cells acts locally in the islets of Langerhans to inhibit the release of insulin and glucagon.
It also decreases gastrointestinal activity after ingestion of food.
Almost all factors related to ingestion of food stimulate somatostatin secretion.

34. Incretins
Several gut derived hormones have been identified as having what is termed an incretin effect, meaning that they increase insulin release after an oral nutrient load.
The two hormones that account for about 90% of the incretin effect are glucagon like peptide-1, which is released from L cells in the distal small bowel, and glucose-dependent insulinotropic polypeptide, which is released by K cells in the upper gut (mainly the jejunum).

35. Counter regulatory Hormones
They counteract the storage functions of insulin in regulating blood glucose levels during periods of fasting, exercise, and other situations that either limit glucose intake or deplete glucose stores.
The catecholamines,
Growth hormone, and
Glucocorticoids.

36. Epinephrine
helps to maintain blood glucose levels during periods of stress.
Glycogenolysis in the liver
Inhibits insulin release
Increasing the breakdown of muscle glycogen stores.
A direct lipolytic effect on adipose cells,

37. Growth Hormone Increases protein synthesis
Mobilizes fatty acids from adipose tissue, and antagonizes the effects of insulin.
Chronic hypersecretion of growth hormone, as occurs in acromegaly, can lead to glucose intolerance and the development of diabetes mellitus.

38. Glucocorticoid Hormones
Gluconeogenesis by the liver
Hypoglycemia is a potent stimulus for cortisol secretion.
In predisposed persons, the prolonged elevation of glucocorticoid hormones can lead to hyperglycemia and the development of diabetes mellitus.

39. (Liver Hepatic Glucose Output)
Hormonal Interactions in the Maintenance of Blood Glucose Concentration
Glucose
Production
(Liver Hepatic Glucose Output)
(-)
(+)
(+)
Glucagon
Epinephrine
Glucocorticoids
Growth Hormone
Blood Glucose
Insulin
(+)
(-)
Glucose
Consumption
(Skeletal Muscle and
Adipose Tissue)

40. Hormonal Effects on FFA Production in Adipose Tissue
Epinephrine
Insulin
Triglycerides
Fatty Acids
Insulin + +
Hormone
Sensitive
Lipase
-Glycerol-P _
glucose _
Growth hormone
Cortisol
Epinephrine
glycerol
FFA