Lecture 29- Glucose Metabolism, Energy Balance and Obesity 2 Flashcards
Describe the brain pituitary thyroid axis…
CHR neurons preside in the PVN.
They project to the medial eminence
Highly fenestrated release hormone into blood
Thyrotropes release thyroid hormone (they don’t directly produce,
They release TSH that acts on the thyroid, this where it is actually
Released in form T3 and T4 (number relates to number of iodine’s)
Which of the thyroid forms (T3 or T4) is the metabolic active form?
t4= Triiodothyronine
Means it is the one that has the most effect in the body
What is the intracellular effect of thyroid hormones?
T4 in the cytoplasm is converted to T3 which passes into the nucleus
T3 acts on a nucleus receptor and binds to act on DNA in the nucleus
This has an effect on proteins and growth as results in an increase or decrease in messenger RNA
What is the biggest effect of high thyroid levels?
High oxygen consumption/ high metabolic rate
Look at the slide that shows effect of thyroid hormone to link it all together…
Look at slides
What diseases are caused by hypothyroidism?
- Goiter: less prevalent these days cause have iodine in salt. Thyroid tries to produce hormones in absence of iodine= thyroid grows as working so hard
- Hashimoto= autoimmune disease that attacks the thyroid and destroys it. Decrease in thyroid tissue, can’t produce hormone, metabolic weight, have no energy, gain weight Need to give hormones instead of just iodine to solve.
What disease is characterized by Hyperthyroidism? Is this usually an environmental effect?
Graves= enlarged eyes cos produce antibodies that attack tissue behind the eye and swells. Produce antibody that binds to receptor for TSH, so stimulate thyroid to produce more T3 and T4. Only autoimmune condition that does not destroy the tissue, could be ‘reversed’
-Typically genetic not enviromental
If someone has low levels of TSH what disease are they likely to have?
Grave’s disease and have lots of negative feedback
How precise is our management of body weight? Why is this so impressive?
- The difference between consumed and spent energy equals an accuracy of 99.8%!
- Amazing that we keep this balance when how much we eat/ our energy intake is so variable every single day
- Our brain is more precise at counting calories than food labels (usually around 25% off)
What is the chance of losing body weight after being obese?
Less than 1% (very low) as the brain has such tight control
What two factors does the body mass index take into account? What is normal?
weight (kgs)/ height (m)
Normal= 20-25
Average= 27 in US (obesity pandemic is at large)
How does fructose play a role in obesity?
Added fructose:
- Softdrinks
- Fast food, prepacked meals
- In animal experiments fructose causes insulin resistance and diabetes.
- Also in humans fructose causes increase in triglycerides.
- Fructose causes liver steatosis in mice.
- Tumour cells can metabolize fructose better than other sugars.
How does the country you grow up in effect your chances of becoming obese?
- You would think brands would be relatively consistent across countries in terms of the amount of sugar they add.
- But this isn’t true: the brands take advantage of culture norms and what people are used to i.e. if you have grown up in a country that eats very sweet food you will not like the taste of unsweet food/ brands and vice and versa
What fact demonstrates how obesity has a genetic component?
- Environment must have an effect cause levels of obesity increased over a very short time (too fast for genetics to be the only factor)
- But the genetic plays an important role as well. 9 out of the 10 most obese nations= in the pacific, shows genetic makeup plays a role. Could be that the only people that had enough energy to survive the journey through the ocean were very good at absorbing energy. Offspring therefore also gain this advantage. Except in the current climate it’s not an advantage cause our diet is energy rich enough and this results in obesity.
How was leptin discovered?
- Some mice were obese
- Found that these mice lacked leptin
