Midterm 3 - Lecture 18 Flashcards
What are the pancreatic hormones?
Insulin and glucagon
- synthesized from region known as the islets of Langerhans
- B-cell = insulin
- A-cell = glucagon
Molecular characteristics of insulin
51 aa protein hormone
What is insulin secreted by?
beta cells in pancreatic islets
What is the most important hormone in the regulation of glucose metabolism?
Insulin
- increases upon feeding and decreases in postabsorptive state
- insulin increases anabolic processes; CHO, protein and fat deposition
What is insulin induced by?
gastric inhibitory peptide (GIP) before blood glucose levels rise
What is the half-life of insulin in plasma?
5-8 minutes
What are 4 ways that insulin counteracts high blood glucose?
- increase glucose uptake by cells
- stimulate synthesis of glycogen/inhibit degradation
- increase consumption for ATP
- inhibit gluconeogenesis
Insulin increases glucose uptake in cells, increases glycogen synthesis, and decreases gluconeogenesis, what effect does this have on plasma concentration?
- decreases plasma concentration of glucose
- increases cell stores of glycogen
Insulin increases triglyceride synthesis and decreases lipolysis, what effect does this have on plasma concentration?
- decreases plasma concentration of FFA
- increases cell stores of triglycerides
Insulin increases aa uptake in many cell types and increases protein synthesis, what effect does this have on plasma concentration?
decreases plasma concentration of AA
How is insulin linked to a decrease in plasma concentration of glucose and an increase of cell stores of glycogen?
- increase glucose uptake in many cell types
- increases glycogen synthesis
- decreases gluconeogenesis
How is insulin linked to a decrease in plasma concentration of FFA and an increase in cell stores of triglycerides?
- increases triglyceride synthesis
- decreases lipolysis
How is insulin linked to a decrease in plasma concentration of AA?
- increases aa uptake in many cell types
- increases protein synthesis
What is glucagon secrete by?
- alpha cells in the pancreas
What hormone is secreted in response to low blood glucose? What effects does it have?
Glucagon
- stimulates glycogenolysis in the liver
- stimulates gluconeogenesis in the liver
- stimulates lipolysis in adipose through activation of hormone sensitive lipase
During a typical meal, what is glucagon and insulin secretion induced by?
- plasma aa (counteractive effects)
- insulin also induced by glucose, but glucagon is not
What is more important, the insulin to glucagon ration or the absolute amount of each?
insulin to glucagon ratio
How is the insulin to glucagon ratio affected if during absorption, postabsorption, and exercise?
absorptive: high
postabsorptive: low
exercise: low
Although insulin is low during exercise, why is glucose transported into muscle greater than during rest?
bc increased glucose transporters in cell membrane of skeletal muscle fibers
How is the insulin and glucagon ratio different in ruminants?
Relatively low and constant concentration of insulin and glucagon
- reflects the constant need for gluconeogenesis
What is the trademark of diabetes?
High blood glucose
- reduced entry into muscle and adipose
- increased glucose production by the liver
What is required for glucose uptake in most cells?
INSULIN
- exception of brain, RBC, hepatocytes and renal cortex
- cells can use fatty acids, ketones and aa for energy
Why is glucose in urine a trademark of diabetes?
- renal threshold for reabsorption surpassed
- increases water loss in urine = symptom of excessive urination and thirst
Type 1 diabetes
- beta cells fail to produce adequate insulin
- auto-immune
- patient must be given insulin
- common in dogs
Type 2 diabetes
- cellular actions of insulin hampered (insulin resistance)
- cats
What is insulin resistance (type 2 diabetes) induced by?
Inflammation
- makes cells less responsive to insulin
- initial response is to produce more insulin
