Glucose homeostasis, insulin secretion, and islet phospholipids in mice
PANCREAS AS AN ENDOCRINE GLAND - 2 · Control of Insulin secretion •Increased Blood Glucose...
Transcript of PANCREAS AS AN ENDOCRINE GLAND - 2 · Control of Insulin secretion •Increased Blood Glucose...
PANCREAS AS AN ENDOCRINE GLAND - 2
Dr. Sumera Gul
Associate Professor
Department of Physiology
Learning objectives
At the end of the lecture the students should be able to:
• Explain the mechanism of secretion of Insulin
• Discuss the factors affecting the secretion of Insulin
• Explain the relationship of insulin in switching between carbohydrate and lipid metabolism
Insulin
• Cell?
• Type?
• Receptor location?
• Receptor type?
• Mechanism of action?
Insulin
• Cell? B cell of Islet of Langerhans
• Type? peptide
• Receptor location? Cell membrane
• Receptor type? Enzyme linked receptor
• Mechanism of action? Activation of tyrosine kinases and IRS
Secretion of Insulin
Control of Insulin secretion• Increased Blood Glucose Stimulates Insulin
Secretion.
• At the normal fasting level of blood glucose of 80 to 90 mg/100 ml, the rate of insulin secretion is minimal on the order of 25 ng/min/kg of body weight.
Control of Insulin secretion
• 1. The concentration of insulin in plasma increases almost 10-fold within 3 to 5 minutes after acute elevation of the blood glucose.
• This increase in insulin concentration decreases about halfway back toward normal in another 5 to 10 minutes.
• 2. Beginning at about 15 minutes, insulin secretion rises a second time and reaches a new plateau in 2 to 3 hours
• Amino acids:
• The most potent of these amino acids are arginine and lysine.
• Amino acids strongly potentiate the glucose stimulus for insulin secretion.
Effect of Amino Acids
• Gastrin,
• Secretin,
• Cholecystokinin,
• Glucagon like peptide–1 (GLP-1),
• Glucose-dependent insulinotropic peptide (GIP)
Effect of Gastrointestinal hormones
Incretins
GLP-1 and GIP,
they enhance the rate of insulin release from the pancreatic beta cells in presence of glucose
inhibit glucagon secretion from the alpha cells
Effect of Gastrointestinal hormones
• Other hormones that either directly increase insulin secretion or potentiate the glucose stimulus for insulin secretion
• Include:
• Glucagon, • growth hormone,• cortisol, • progesterone and estrogen.
• Parasympathetic stimulation increase insulin secretion during hyperglycemic conditions
• Sympathetic nerve stimulation may increase glucagon secretion and decrease insulin secretion during hypoglycemia
Control of Insulin secretion
Witch between CHO and Fat metabolism
Hyperglycemia
Insulin secretion
And use of Glucose
Decreased glucose levels
Glucagon
Lipolysis
Spare glucose
utilization
Witch between CHO and Fat metabolism
Prolonged Hypoglycemia
GH
Cortisol
Use of Fats
Spare glucose
utilization
Increases Blood
glucose
Witch between CHO and Fat metabolism
Stress
Fear
Severe Hypoglycemia
Epinephrine
Lipolysis
Glycogenolysis
Increases Blood glucose