Carbohadrate metabolism MBBS Follow respective lectures

1. Learning objectives
• Describe the effect of insulin on the process and
pathways that regulate blood glucose homeostasis
• Describe the effect of glucagon on metabolic
process in the liver and how this hormone functions
to regulate blood glucose homeostasis.
• Define the role of glucagon like peptide in
regulation 1 and 2 in regulation of glucose
homeostasis.
• Define the role of other hypoglycemic hormones in
regulation of glucose homeostasis.

2. • Compare and contrast type 1 and type 2 diabetes
mellitus.
• Recognize the clinical presentation of type 1
diabetes mellitus and discuss the diagnostic criteria.
• Describe the abnormalities in blood glucose
homeostasis in patient with type 1 diabetes &
discuss the metabolic derangements.

4. • The pancreas has two major types of tissues: the acini (secrete
digestive juices to duodenum) and the islets of Langerhans
(secrete insulin and glucagon directly into blood)
♦Alpha cells secrete glucagon
• elevates blood glucose concentrations
♦Beta cells secrete insulin
• reduces blood glucose concentrations
♦Delta cells secrete somatostatin
• slows the rate of food absorption and
digestive enzyme secretion
• Close interrelation among various cell types allow regulation of secretion of
some hormones by other hormones:
• insulin inhibits glucagon secretion, somatostatin inhibits insulin and
glucagon secretion

11. • ♦ Mechanism of Action of Insulin:
• The insulin receptor is a combination of 4 subunits held together
by disulfide linkages: two -subunits lying outside the cell
membrane and two -subunits protruding into the cell cytoplasm.
• When insulin binds to the -subunit in target
tissues, the -subunits in turn become activated.
• Activation of the -subunits triggers a series
• of reactions that draw the glucose transporter
to the cell membrane.
• Cells of various organ tissues like liver,
muscle, adipose are now able to increase
their uptake of glucose (w/in seconds after
insulin binds with its membrane).
• The cell membrane also becomes more
permeable to many amino acids.

12. • Summary: Metabolic Effects of Insulin
• Increases rate of glucose transport into target cell
• Increases rate of glucose utilization and ATP
formation
• Increases conversion of glucose to glycogen (liver,
skeletal muscle)
• Increases amino acid absorption and protein synthesis
• Increases triglyceride synthesis (adipose tissue)
• *DECREASES HIGH BLOOD GLUCOSE
LEVELS*
• (Insulin is anabolic hormone)

14. REGULATION OF BLOOD GLUCOSE

15. • Blood sugar is very finely regulated as it is
essential to have a continuous supply of
glucose to the brain
• FBS = 70-110 mg%
• RBS= 100-140 mg%
• Factors which regulate blood sugar are—
o Rate of supply of glucose to blood
o Rate of removal of glucose from blood

16. • Factors which contribute glucose is to blood
• Absorption from intestine
• Glycogenolysis
• Gluconeogenesis
• Glucose is obtained from other carbohydrates

17. • Factors which remove glucose from blood
• Hepatic glycogenesis
• Muscle glycogenesis
• Oxidation of glucose
• Lipogenesis
• Synthesis of non-essential amino acids

34. METABOLIC CHANGES IN TYPE1 DM

50. TYPE I DM
• ONSET- Usually during
childhood or puberty
• Symptoms develop rapidly
• Seen in undernourished
• Genetic predisposition-
moderate
• Beta cells are destroyed
eliminating the production
of insulin
TYPE II DM
• Frequently after the age of
35
• Symptoms develop
gradually
• Obesity is usually present
• Strong
Insulin resistance is combined
with inability to produce
appropriate amount of insulin

51. TYPE I DM
• Autoantibodies are
frequently found
• Ketosis- Common
• Acute Complication-
Ketoacidosis
• Response with oral
hypoglycemic-
Unresponsive
• Treatment– Only insulin
TYPE II DM
• Rare
• Rare
• Hyperosmolar non ketotic
coma
• Responsive
• Diet f/b exercise/ oral
hypoglycemic and if failure
occurs-- Insulin

54. • Maintaining Control
• Protect heart, nerves, blood vessels, eyes, and kidneys by controlling blood
glucose level.
• Maintain schedule for checking blood glucose level and taking insulin.
• Maintain well-balanced meal plan, exercise program, and healthy weight.
• How does exercise help?
•Most of the time muscle tissue depends on fatty acids for energy
• Under two conditions muscles use large amounts of glucose:
– During moderate or heavy exercise (muscle fibers become permeable to
glucose even in the absence of insulin– important in Type I)
– During the few hours after a meal (while pancreas is secreting more
insulin– important in Type II).
– Most of the glucose is stored as muscle glycogen.