Endocrine Pancreas Physiology Flashcards
acinar cells
exocrine pancreas cells that produce and secrete digestive enzymes
islet of langerhans
endocrine pancreas cells; produces hormones
what are the cell types in the islet of langerhans and what do they secrete
a cells: glucagon
B cells: insulin
D cells: somatostatin
F cells: pancreatic polypeptide
what stimulates insulin secretion
high blood glucose
net effect of insulin & target tissues
decrease blood glucose
targets:
- liver
- muscle
- adipose
insulin effects in the liver
lowers hepatic glucose production
stimulates glycogenesis
inhibits glycogenolysis and gluconeogenesis
insulin effects in muscle
stimulates glucose uptake via GLUT4
stimulates AA uptake
stimulates protein synthesis
insulin effects in adipose tissue
stimulates glucose uptake via GLUT4
stimulates lipogenesis
inhibits fat mobilization
how is insulin secreted
Ca dependent activation
- glucose enters B cell through GLUT2 channels
- glucose gets converted to G6P then to ATP
- ATP causes K+ channels to close and Ca2+ channels to open
- Ca influxes into the cell and stimulates insulin release via exocytosis of secretory granules
ANS regulation of insulin secretion
B cells are innervated by both PNS and SNS
- cephalic phase - PNS predominates to increase insulin secretion during meal/fed state
- stress induced - SNS predominates to decrease insulin secretion (want high BG to make glucose available to brain)
what stimulates glucagon secretion
low blood glucose
amino acids (during high protein meal to prevent hypoglycemia from lack of carbohydrates)
net effects of glucagon & target tissues
increases blood glucose
targets:
- liver
- adipose
glucagon effects in the liver
increases hepatic glucose production
- stimulates glycogenolysis
- stimulates gluconeogenesis
glucagon effects in adipose
stimulates lipolysis and FFA efflux
effects of somatostatin
inhibits secretion of insulin and glucagon
can somatostatin be used as a treatment for diabetes
short half life makes it difficult
would need a long lasting, glucagon specific somatostatin to avoid inhibition of insulin
diabetes mellitus
failure to normally regulate blood glucose concentrations leading to hyperglycemia
what species is diabetes mellitus common in
dogs and cats
usually middle aged
clinical signs of diabetes mellitus
- hyperglycemia
- glucosuria
- PU/PD
- weight loss
- ketosis –> DKA
at what point (BG) do you start to see glucosuria
when blood glucose exceeds the renal transport capacity/threshold (>180; species variations)
what is the mechanism of PU/PD in diabetes
glucosuria –> osmotic diuresis –> water flows into renal tubules –> PU –> dehydration –> PD
what is the mechanism of ketosis in diabetes
inability of blood glucose to enter into tissues –> tissues rely on muscle and adipose for energy –> formation of ketone bodies –> acidifies the blood
how is a diagnosis of DM made
clinical signs
hyperglycemia +/- glucosuria
what are common complications associated with diabetes mellitus
- retinopathy (blindness/cataracts)
- nephropathy
- neuropathy
type I diabetes
“insulin dependent”
low/absent insulin production from pancreas
cause of type I diabetes
- autoimmune mediated destruction of B cells
- pancreatitis/isletitis
how to treat type I diabetes
exogenous insulin administration
want to avoid hypoglycemia
can monitor long term with fructosamine or HbA1c
what species is type I diabetes most common in
dogs
genetic predispositions: keeshonds, poodles, dachshunds, beagles
type II diabetes
“non-insulin dependent”
BOTH:
- insulin resistance
- impaired insulin secretion
requires both mechanisms because if it was only insulin resistance, the pancreas would produce more insulin to overcome the resistance
cause of type II diabetes
lifestyle/obesity leading to insulin resistance
risk factors:
- age (older)
- gender (male)
- neutering
- low activity
- corticosteroid administration
how to treat type II diabetes
lifestyle modification (diet weight loss)
later stages of disease become insulin dependent - requires exogenous insulin administration
what species is type II diabetes most common in
cats
what BG value is considered hypoglycemic
plasma glucose < 50-60 mg/dL
severe: <30 mg/dL
causes of hypoglycemia
- excess insulin in diabetic treatment (common)
- insulinoma
- prolonged fasting in young animals
- severe infections
- Addison’s disease (dec. corticosteroids)
- xylitol poisoning in dogs
clinical signs of hypoglycemia
hunger
drowsiness
dull mentation
palpitations
convulsions
coma
brain damage
