8.2 Hormones that Affect Blood Sugar

Review

• What is the Endocrine System?

• What are the two types of hormones?

• How do they differ in terms of hormone-receptor interaction?

• Let’s go over the cyclic AMP signal transduction pathway (turn to page 375)

Hormones that control Blood Glucose Levels

• The pancreas contains islets of Langerhans that produce two hormones:– Alpha cells produce glucagon (increases blood

sugar levels)

– Beta cells produce insulin (reduces blood sugar levels)

Blood Sugar Homeostatic Feedback loop – Negative or Positive?

Eat a meal – Blood sugar levels rise

Normal Blood Sugar Level

Beta cells in pancreas release insulin into bloodstream

Body cells become permeable to glucose (glucose ENTERS cells)

Liver converts glucose into glycogen for storage

Blood sugar levels decrease

Blood Sugar Homeostatic Feedback loop – Negative or Positive?

Fasting leads to low blood sugar levels

Normal Blood Sugar Level

Alpha cells in pancreas release glucagon into bloodstream

Liver converts glycogen into glucose which is released into blood for energy

Blood sugar levels increase

Diabetes Mellitus

• Diabetes Mellitus can be broken down into three main types:– Type 1 = Juvenile-onset diabetes– Type 2 = adult-onset diabetes– Type 3 = gestational diabetes

Diabetes Mellitus

• Type 1 diabetes is caused by early degeneration of the beta cells in the pancreas

• This reduces the amount of insulin that is produced

• Individuals need to take regular injections of insulin

Diabetes Mellitus (contd.)• Type II diabetes is known as adult onset diabetes• Can develop as a result of poor diet and lack of

exercise (lifestyle related)• 90% of diabetic cases are type II diabetes

Diabetes Mellitus (contd.)

• Associated with “insulin-resistance” or decreased insulin production– Insulin resistance results from excessive insulin

circulating in the blood which causes the receptors for insulin on the cell surface to stop working or they are no longer produced

– Can be “autoimmune” whereby the body destroys the receptors for insulin, thinking that they are foreign agents

• No “cure” but treatment is available

Drugs used to Treat Type II Diabetes

• Alpha-glucosidase inhibitors– prevents the breakdown of starches, such as: bread, potatoes, &

pasta

– slows the rise in blood glucose levels after a meal

• Biguanides – reduce the amount of sugar produced by the liver & make muscle

tissue more sensitive to insulin so that sugar can be absorbed

• TDPP-4 inhibitors– help improve A1C without causing low blood sugar

(hypoglycemia)

More Drugs

• Sulfonylureas and meglitinides – stimulate the beta cells in the pancreas to

release more insulin

• Thiazolidinediones – help insulin work better in the muscle and fat– reduces liver’s sugar production

New Findings!

• Artificial Pancreas

– an implantable monitor and insulin pump monitors glucose levels and delivers insulin when needed

• Implantable glucose monitor

– An implanted cannula (sensor) in the stomach transmits blood glucose levels to receiver

• Glucose monitor contact lenses

– contact lenses change colour when concentration of glucose in tears change

Further Developments

• Stem Cell Research– stem cells derived from the

blood cells in umbilical cords – Used to create insulin-

producing cells that can be transplanted into patients

– (Diabetes Research Institute, 2010).

Watch this!

Adrenal Glands

• The adrenal glands are located above each kidney– Adrenal cortex

(surrounds the adrenal medulla)

– Adrenal medulla (inner gland)

Adrenal Hormones• Adrenal Medulla

– Produces epinephrine (adrenaline) and norepinephrine (or noradrenaline)

– Both are produced in times of stress – “fight or flight” response

– Causes blood sugar levels to rise

– Increases heart, breathing, and metabolic rate

– Blood vessels and iris in eye dilate – why?

Adrenal Hormones (contd.)

• Adrenal Cortex– Produces glucocorticoids, mineralocorticoids, and

the sex hormones– Glucocorticoids – increases blood amino acid

levels in response to stress so that they can be converted to glucose by the liver

– Mineralocorticoids – regulate salt-water balance (i.e. aldosterone increases sodium and water retention in kidneys)

– Both are stimulated by ACTH produced in the anterior pituitary

Let’s have some fun with this!

• Come up with a song or rap that describes the function of glucagon or insulin

Homework

• Do questions #1-3, 5,6 on p383