Pathophysiology of the Endocrine Pancreas Flashcards
what do beta cells secrete?
insulin
amylin
what percentage of the islet cells are beta cells?
60-70%
what do delta cells secrete?
somatostatin
what is the half-life of insulin?
3-5 minutes
insulin is secreted at a constant basal level, and in a __________________ in response to increased blood glucose levels
bolus or spike
what does insulin stimulate in hepatocytes?
glycogen storage
is insulin required for glucose uptake in hepatocytes?
no: primarily use GLUT2 transporter
where is somatostatin produced?
hypothalamus
stomach
intestine
pancreatic delta cells
what does gastrin stimulate?
production of hydrochloric acid by parietal cells
what is diabetes insipidus?
polyuria due to decreased ADH response or ADH deficiency
what percentage of beta cells must be lost for clinical diabetes mellitus?
> 90%
what does insulin resistance in the peripheral tissues cause?
decreased glucose uptake in response to insulin
what happens with beta cells in type II/non-insulin dependent diabetes mellitus?
may be abnormal: beta cell exhaustion
may be overcome to some extent by increased secretion of insulin
what are the clinical signs associated with diabetes mellitus?
polyuria/polydipsia
weight loss despite good appetite or polyphagia
hepatomegaly due to hepatic lipidosis
cataracts, more common in dogs than cats
dehydration
halitosis
what are the consistent laboratory findings with diabetes mellitus?
hyperglycemia: marked and persistent
glucosuria
what are some complications of diabetes mellitus?
ketoacidosis
cataract formation
hypokalemia/hyperkalemia
immune dysfunction
microvascular complications
urinary tract infections
what type of acidosis do increased ketones cause?
titration-type
high anion gap
______________ precedes ketonemia
ketonuria
intracellular _____________ causes water influx by osmotic effect in diabetic cataracts
sorbitol
chronic high levels of glucose lead to _________________________________________________
glycosylation of proteins in blood and tissues
what type of diabetes mellitus do most dogs with diabetes mellitus have?
type I/insulin dependent
what type of diabetes mellitus is usually the one in cats?
type II
~80%
which cats have a higher incidence of diabetes mellitus?
neutered males
burmese, russian blue, abyssinian, norwegian forest
what are some possible predisposing factors for feline diabetes mellitus?
glucose transport abnormalities
leptin resistance
reduced adiponectin
beta cell dysfunction
islet amyloidosis (not proven- only in humans)
obese cats have reduced expression of _________ in muscle and adipose tissue
GLUT4
what is leptin secreted by?
adipose tissue
with positive energy balance, melanocortin 4 receptor (MC4R) is stimulated by alpha-melanocyte stimulating hormone (alpha-MSH), _______________________
increasing satiety
what is acromegaly caused by?
hypersomatotropism
excess growth hormone
what does increased growth hormone case with insulin?
insulin resistance
is diabetes mellitus common in ferrets?
no, uncommon
what does cortisol cause in skeletal muscle?
insulin resistance
what does cortisol cause in adipose tissue?
increased insulin sensitivity
who is gestational diabetes described in?
dogs
what causes gestational diabetes?
increased progesterone and growth hormone secreted in pregnancy or diestrus
the amount of glycosylated protein can be measured to evaluate ___________________________
long-term blood glucose levels
type II (insulin resistance) in horses may occur with ________________________________________
pituitary pars intermedia dysfunction (PPID)
what do horses with equine metabolic syndrome have an increased tendency for?
obesity
laminitis
what happens in equine metabolic syndrome with adipose tissue?
obesity or accumulation of fat in focal areas
true/false: glucose is usually within reference interval with equine metabolic syndrome
true
in equine metabolic syndrome, what are the insulin and glucose levels?
high insulin
normal or slightly elevated blood glucose
equine metabolic syndrome horses exhibit an __________________ insulin response to carbohydrates
exaggerated
avian diabetes mellitus may be secondary to increased _____________
glucagon
do birds usually have higher baseline glucose than mammals?
yes
what are some more common differentials for hypoglycemia?
excess insulin
malabsorption
artifactual/maldigestion
what does the exocrine pancreas do?
produces digestive enzymes
secrete into the intestinal lumen via pancreatic duct
what do F (PP) cells secrete?
pancreatic polypeptide
what do epsilon cells secrete?
ghrelin
what degrades insulin?
insulinase
insulysin
liver and kidneys
what is removed to make active insulin?
C peptide
what might C peptide do?
activation of Na/K ATPase and nitric oxide synthase
may be used to evaluate endogenous insulin secretion
what does increased intracellular glucose concentration of glucose in the beta cells cause?
membrane depolarization and influx of extracellular calcium and exoxytosis of insulin containing granules
diffuses in through GLUT2
where does insulin bind to?
insulin receptor-kinases and insulin receptor substrate proteins
where are Na/glucose cotransporters found?
enterocytes and renal tubules
use Na gradient created by Na/K ATPase
where are GLUT1 transporters found?
most cells
red blood cells
where are GLUT2 transporters found?
high expression liver, renal tubules, small intestine, beta cells
where are GLUT3 transporters found?
neurons/brain
where are GLUT4 transporters found?
striated and cardiac muscle and adipose tissue
regulated by insulin
what are the effects of amylin?
decrease glucagon secretion
decreases gastric emptying
increases satiety
what does pancreatic polypeptide do?
inhibits gall bladder contraction and exocrine pancreatic enzyme secretion
acts to antagonize cholecystokinin
may act as satiety factor
what does somatostatin act to inhibit the release of?
growth hormone
thyroid-stimulating hormone
insulin
glucagon
gastrin
vasoactive intestinal peptide
exocrine pancreatic enzymes
prolactin
gastrin is not normally secreted by the endocrine pancreas, but may be secreted by ____________________
islet neoplasia
what are some diseases of the pancreatic islets?
metabolic disease
neoplasia
what might lesions in the pancreas manifest histologically as with type one diabetes mellitus?
inflammatory infiltrates in islets
lack of visible islets
islet cell degeneration/vacuolation
what are some causes of diabetes-like syndrome (damage pancreas or induce insulin resistant due to another disease)?
diabetogenic hormones or drugs
pancreatitis or pancreatic neoplasia
what are some microvascular complications of diabetes mellitus?
diabetic retinopathy
neuropathy
nephropathy
how are ketones formed?
fatty acids being broken down produce acetyl CoA
insufficient Kreb’s cycle intermediates so don’t use up
acetyl CoA forms ketones
what can be measured to evaluate chronic hyperglycemia?
fructosamine
glycosylated Hb measurement`
what might glycosylation do?
interfere with antibody-antigen binding
development of microvascular disease and neuropathy
what dog breeds are more likely to get canine diabetes mellitus?
australian terrier
miniature and standard schnauzer
samoyed
bichon frise
fox terrier
beagle
miniature and toy poodles
keeshond
what do obese cats have reduced expression of?
GLUT4 in muscle and adipose tissue
where is the melanocortin 4 receptor mainly expressed?
hypothalamus
what does adiponectin do with insulin?
enhances sensitivity
how can chronic high glucose levels reduce the number of beta cells?
overstimulation
induction of apoptosis and inflammation
amyloidosis may occur
what are some other endocrinopathies that may present like diabetes mellitus in cats?
hypersomatrotropism/acromegaly
hyperadrenocorticism
what does hypersomatotropism/acromegaly cause with glucose?
glucosuria and hyperglycemia
production of insulin-like growth factor-1 is increased by _____________________________
high growth hormone levels
what are the effects of cortisol on glycemia?
insulin resistance in skeletal muscle tissue
increased insulin sensitivity in adipose tissue
liver: increases gluconeogenesis
pancreas: stimulates glucagon release and inhibits insulin releease
does a urine ketone dipstick detect beta-hydroxybutyrate?
no
what happens in equine metabolic syndrome with insulin?
resistance/dysregulation
where do horses accumulate fat with equine metabolic syndrome?
nuchal ligament
behind shoulders
tail base
prepuce or mammary gland
what are the clinical findings with equine metabolic syndrome?
hypertriglyceridemia
increased insulin levels
hyperleptinemia/leptin resistance
what response to equine metabolic disease horses have to carbohydrates?
exaggerated
what might avian diabetes mellitus be due to?
increased glucagon production
type 1 with chronic pancreatitis
what is the most common islet cell neoplasm in veterinary medicine?
insulinoma