WK7 - Endocrine Regulation of Metabolism Flashcards
(40 cards)
What is glucose used for?
How is it stored?
What is it synthesized from?
- used for ATP synthesis
- stored as glycogen or triglyceride
- synthesized from precursors (glycerol, lactate, amino acids)
What is fat used for?
How is it stored?
- used for ATP synthesis (oxidative metabolism)
- stored as triglyceride (TAG)
What is amino acids used for?
- used for glucose production (gluconeogenesis)
- used for the synthesis of protein
What hormones are responsible for regulation of fuel metabolism?
- insulin
- glucagon
- epinephrine/norepinephrine
- cortisol
- growth hormone
The pancreas is divided functionally in 2 parts. What are they?
- Exocrine pancreas
- digestive enzymes secreted into intestine - Endocrine pancreas
- hormones secreted into blood
How is the endocrine pancreas organized?
- clusters of cells called Islets (~1000-5000 cells/islet)
- comprise 1-3% of the adult pancreas and contain multiple cell types
- beta-cell comprise 60-80% of the islet
What are the cell types of the pancreatic islet?
alpha cells - glucagon
beta cells - insulin
What is the site of production of insulin?
- produced by beta-cells of the pancreatic islet
What type of hormone is insulin?
peptide hormone - encoded by the insulin gene
What stimulates the secretion of insulin?
Insulin are secreted in response to nutrients and hormones
- secreted from pancreatic beta-cells in fed state
- stimuli for secretion: glucose, amino acids, fatty acids, other hormones
What are the target tissues of insulin?
All cells express insulin receptors.
Insulin regulates metabolically active tissues:
- liver
- skeletal muscle
- heart
- adipose tissue
- brain
- pancreas
What happens in the absence of insulin?
Without insulin:
- cells cannot take up and utilize glucose
- fuels is mobilized not stored
Result:
- excess nutrients are circulate in the blood but they cannot be used as fuel source
Describe the effects of insulin on fuel metabolism.
- The overall effect of insulin is to promote the utilization of glucose and the storage of surplus fuel in times of “feast” - Insulin is an ANABOLIC hormone
- decrease lipolysis (in adipose tissue)
- decrease gluconeogenesis (in hepatocyte)
- decrease glycogenolysis (in liver and muscle)
- increase glycogen synthesis (in liver and muscle)
- increase glucose uptake/breakdown (in all tissues)
- increase TAG synthesis and storage (in adipose tissue)
- increase protein synthesis (in muscle)
Overall effect: promote the utilization of glucose and the storage of surplus fuel
What is seen in untreated diabetes?
- high blood glucose levels
- increase fatty acids in blood because unable to store triclycerides; therefore increase in triglyceride levels
Recall: excess nutrients circulate in blood but cannot be used as fuel source
Which hormones allow us to use stored energy reserves and mobilize fuel in times of fasting or “famine”?
Fast:
- glucagon
- epinephrine/norepinephrine
Slow:
- cortisol
- growth hormone
What is the site of production of glucagon?
alpha-cells of the pancreas
What type of hormone is glucagon?
peptide hormone - encoded by the glucagon gene
What are the targets of glucagon?
- liver
- adipose tissue
What are the effects of glucagon?
- increase gluconeogenesis (in hepatocyte
- increase glycogenolysis (in liver and muscle)
- increase lipolysis of TAG (in adipose tissue)
- decrease glycogen synthesis (in liver and muscle)
Overall effect: mobilization of fuel
What stimulates the release of glucagon?
released when blood glucose and insulin is low
What is the site of production of epinephrine?
EPI - produced by cells of the adrenal medulla
What type (or what is the derivative) of hormone is epinephrine?
Derivative of tyrosine
What are the targets of epinephrine?
acts on liver, adipose tissue and skeletal muscle
When is epinephrine released?
- for ‘fight or flight’ response
- released when blood glucose levels are low
