CBL 7: The Thirsty Dog

List the hormones involved in glucose homeostasis

insulin, glucagon, adrenaline, GH, progesterone, glucocorticoids

What is the stimulus for insulin secretion?

high BGL (hyperglycaemia)

What cell produces insulin?

pancreatic beta cells

What receptor does insulin signal through?

insulin receptor (RTK)

What impact does insulin have on blood glucose concentration?

decreases it

How does insulin cause a decrease in glucose concentration?

stimulates glucose uptake by cells

What is the stimulus for glucagon secretion?

low BGL (hypoglycaemia)

What type of cell produces glucagon?

pancreatic alpha cells

What is glucagon’s receptor?

cell membrane; G protein

What impact does glucagon have on glucose concentration?

increases

How does glucagon cause an increase in glucose concentration?

glycogen is converted to glucose (glycogenolysis)

What is the stimulus for adrenaline release?

sympathetic nervous system

What type of cell produces adrenaline?

adrenal gland medulla (chromaffin cells)

What are adrenaline’s receptors?

cell membrane adrenoreceptors; G protein

What impact does adrenaline have on glucose concentration?

increases

How does adrenaline cause glucose concentration to increase?

stimulates liver to release glucose (also gluconeogenesis, glycogenolysis, increased lipolysis)

What does GH stand for?

growth hormone

What type of cell is GH produced by?

cells in pars distalis (somatotropes) in pituitary gland

What is the stimulus for GH release?

GHRH

What is GH’s receptor?

cell membrane; tyrosine kinase

What impact does GH have on glucose concentration?

increases

What does GH cause that causes glucose concentration to increase?

reduced insulin sensitivity & liver to release insulin-like growth factor (IGF-1)

What type of cell is progesterone produced by?

granulosa cells in ovary (and adrenal cortex)

What stimulates release of progesterone?

FSH/LH

What is progesterone’s receptor?

nuclear receptor affecting transcription

What impact does progesterone have on glucose concentration?

increases

How does progesterone cause an increase in glucose concentration?

increases production of GH

What cell type are glucocorticoids produced by?

adrenal gland cortex

What is the stimulus for glucocorticoid release?

ACTH

What is glucocorticoid’s receptors?

nuclear receptor that affects transcription

What impact do glucocorticoids have on glucose concentration?

increase

How do glucocorticoids increase glucose concentration?

gluconeogenesis and insulin resistance

Describe the gross appearance/shape of a dog pancreas

yellowish, soft, V-shaped gland

Where is the pancreas located in the dog?

dorsally in the abdominal cavity caudal to the liver (and closely associated with the duodenum)

How many lobes does a dog pancreas have and what are they called?

2 (right and left)

Where is the right lobe of the pancreas located?

in mesoduodenum

Where is the left lobe of the pancreas located?

near stomach and spleen

Where do the ducts of the pancreas open into?

duodenum

Give 3 examples of metabolic disturbances in diabetes mellitus

dehydration

hypovolemia

elevated liver enzymes

What are the clinical signs of dehydration in dogs?

lethargy, panting, loss of skin elasticity, dry sticky gums, lack of appetite and energy

Hypervolemia

excess fluid

What are the clinical signs of hypovolemia in dogs?

tachycardia, pale mucous membranes, hypotension, weak peripheral pulses

What are the clinical signs of having elevated liver enzymes in dogs?

diarrhoea, neurological signs, reduced appetite

How would you differentiate between stress-induced hyperglycaemia and true hyperglycaemia?

if stress-induced, fructosamine concentrations are normal

Why may glucose be detected in urine in animals with diabetes mellitus?

insulin can’t keep up with high BGL so excess of glucose will end up in urine

glucosuria

presence of glucose in urine

osmotic diuresis

increased urine flow caused by excessive amounts of nonreabsorbed solute within the renal tubules

Why can hyperglycaemia result in polyuria?

not all of glucose can be filtered out of the urine so glucose left in urine causes more water to be drawn into urine via osmosis

What is fructosamine?

a glycosylated protein (glucose + protein)

What does fructosamine do?

reflect glucose levels over last 2-3 weeks

List other common causes of PUPD in dogs

hyperadrenocorticism, kidney diseases, liver diseases, pyometra

What does normal daily water intake depend on?

breed, age, diet, activity levels, climate and medical conditions/treatments

What time should a urine sample be collected?

AM or after fasting

How should urine samples be collected?

off the floor or free catch

What storage vessel should be used to obtain a urine sample?

sterile container (e.g. glass red-top tube)

How should urine be stored before analysis?

refrigerated and brought to clinic as soon as possible

How should a blood sample of glucose be handled prior to analysis?

centrifuge, remove serum and store in fridge at 2-8 degrees

List possible complications of diabetes mellitus

hypoglycaemia, diabetic ketoacidosis, urinary tract infection, diabetic neuropathy, cataracts

hypoglycaemia

low blood sugar level

diabetic ketoacidosis

overproduction of ketones

Diabetes mellitus

absolute/relative insulin deficiency

diabetes insipidus

lack of ADH production/release

Type 1 diabetes (insulin-dependent)

inability to produce or secrete insulin

Type 2 diabetes

when the body does not respond to the insulin it produces

In what species is diabetes mellitus commonly diagnosed?

dogs and cats

What is the most common cause of PUPD in horses?

PPID

What is PPID?

pituitary pars intermedia dysfunction (Equine Cushing’s)

PUPD

polyuria and polydipsia

What advice should be given regarding disposal of medical waste in the home environment?

empty containers should be taken for incineration, don’t dispose of waste with domestic rubbish, or drain or toilet

How can the environmental impact of medical waste be minimised?

separate different materials before disposal

Outline the basis treatment of diabetes mellitus

insulin by injection

When are insulin injections normally given?

twice daily around food time

Where do you perform a subcutaneous injection in a dog?

scruff of neck

How is the digital environment helpful for owners with diabetic pets?

easy, instant access to info about their animal

What costs should be considered when managing a dog with diabetes mellitus?

check-ups, emergency care, insulin, syringes and needles, blood glucose monitoring, prescription diets, pet insurance

What impact can caring for an animal with diabetes mellitus have on the owner?

responsibility, commitment, time, money