Diabetes Hockerman Flashcards
Three Ps of diabetes
Polydipsia, polyuria, polyphagia
Mean age of T1DM diagnosis
12
How is type 1 diabetes characterized
-Autoimmune response that specifically targets pancreatic cells
-Glucose intolerance
-No functioning insulin-secreting pancreatic beta cells
-Dependency on insulin and a tendency towards ketoacidosis
-Family history is often negative
What percentage of beta cell mass must be lost in order for fasting blood glucose to increase from normal levels?
~70%
Which autoantigen is present in 99% of type 1 diabetics?
islet antigen 2 (IA-2)
57% of non-diabetics who have this antigen will develop type 1 diabetes
Consequences of lack of insulin
-Hyperglycemia - Decreased glucose uptake in cells where glucose uptake is insulin-dependent, decreased glycogen synthesis, increased conversion of amino acids to glucose
-Glucosuria - due to high blood glucose
-Hyperlipidemia - increased fatty acid mobilization from fat cells, increased fatty acid oxidation - ketoacidosis
-Uninhibited glucagon - increased glucagon levels in the presence of increased blood glucose levels
Complications caused by diabetes
-Cardiovascular - micro and macro angiopathies
-Neuropathy - increased blood glucose levels lead to increased utilization of the polyol pathway (aldose reductase), water accumulation in neurons/reduced protection from oxidative damage
-Nephropathy - renal vascular changes and changes in the glomerular basement membrane
-Ocular - cataracts, retinal microaneurysms and hemorrhage
-Increased susceptibility to infections
Current insulin therapy goals
-Keep average blood glucose levels below 150 mg/dL
-Prevent/delay onset of complications
-Increased risk of hypoglycemia
How does hyperglycemia covalently modify proteins?
Oxidation products of glucose react irreversibly with proteins to form advanced glycation end-products (AGE)
Complications caused by AGE
-Loss of normal protein function
-Acceleration of the aging process
-Theorized to account for many long-term complications of diabetes
Percentage of type 2 diabetics that are obese
80%
The typical age of onset for obese type 2 diabetics
Usually over 35
The typical age of onset for non-obese type 2 diabetics
-Often under 25
-Maturity onset diabetes of the young (MODY)
Cause of non-obese type 2 diabetes
Mutations in specific proteins
Cause of obese type 2 diabetes
Insulin resistance/decreased BCM
Mechanisms of cell damage initiated by hyperglycemia
-Polyol pathway
-Hexosamine pathway
-Protein kinase C pathway
-AGE pathway
Role of alpha subunits
-The regulatory unit of the receptor represses the catalytic activity of the beta subunit
-Repression is relieved by insulin binding
Role of beta subunits
-Contain the tyrosine kinase catalytic domains
-Autophosphorylation
How does the insulin membrane receptor stimulate glycolysis, glucose uptake, and lipogenesis?
-The receptor phosphorylates PI3K which activates PKB causing induction of glycolysis
-PI3K also converts PIP2 to PIP3 which recruits PDK1 also resulting in glycolysis
How does the insulin membrane receptor stimulate glucose uptake?
PI3K converts PIP2 to PIP3 which recruits PDK1 which is then able to activate aPKC which stimulates GLUT4 causing glucose uptake into skeletal muscles
How does the insulin membrane receptor stimulate lipogenesis and cell growth/proliferation?
-Phosphorylation of PI3K induces lipogenesis
-The receptor also activates MAPK which leads to lipogenesis and cell growth/proliferation
Effects of the insulin membrane receptor
-Increased glucose uptake
-Increased lipogenesis
-Increased glycolysis
-Increased glycogen synthesis
-Increased DNA + RNA synthesis (Cell growth/proliferation)
-Decreased gluconeogenesis
Insulin effects on the liver
Inhibition of:
-Glycogenolysis
-Ketogenesis
-Gluconeogenesis
Stimulation of:
-Glycogen synthesis
-Triglyceride synthesis
Insulin effect on skeletal muscle
Stimulation of:
-Glucose transport
-Amino acid transport