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Maak een oefenexamen van de volgende tekst: Metabolism and Energy balance
Energy balance regulates weight.
Glucostatic theory: maintenance of glucose availability is crucial for life because glucose is the most important energy substrate (for the brain).
Lipostatic theory: the amount of fat is regulated = maintenance of the bodys energy stores. All the storage tissue is fat.

Satiety (VMH) Hunger (LHA)

Hunger
- Ghrelin is released when the stomach is empty and will initiate a meal. As soon as the concentration goes down you stop eating = short term regulation.
- Melanin blocks aMSH and thus leaves the MC4 receptor open which will make you eat more. This will also increase dopamine levels giving you a pleasuring feeling when you eat reward system.

Satiety
Stretch receptors in the stomach signal satiety as the stomach expands during meals. The fatty acids, peptides, and aromatic amino acids trigger the release of cholecystokinin (CCK), which signals to the brain to stop eating and activates digestion enzymes in the pancreas and the production of insulin = short-term regulation. So, its important to consume smaller, more frequent meals for sustained appetite control.

Leptin acts as a negative feedback signal between adipose tissue (fat) and the brain. When you eat more, the fat levels go up, the leptin goes up and tells the brain to stop eating and the food intake is decreased = long term regulation.
Low leptin levels lead to the energy and metabolism going down feeling weak.
- Leptin deficient Obob mouse
no leptin release and thus no reduction in food intake obese
- Leptin receptor deficient Dbdb mouse
Normal leptin release but receptors are not present no signal to the brain.

a) Db/db obese and diabetic mice combined with a lean wt mice db/db overproduces a satiety factor but does not respond to it. Lean wt responds to satiety factor and starves.
b) Db/db obese and diabetic combined with ob/ob obese ob/ob mice do not produce the satiety factor and are obese. Ob/ob mice respond to overproduction of the satiety factor in db/db mice and starve.
c) Ob/ob obese combined with lean wt mice ob/ob mice respond the satiety factor produces in lean wt mice. Production of satiety factor in lean wt mice is not sufficient to cause starvation in ob/ob mice.

Leptin goes to ARC, a small area under the hypothalamus that is a leak in the blood brain barrier. It can interact with:
- NPY (neuropeptide Y): leptin inhibits NPY. NPY is an appetite stimulant, so when leptin levels are high, it suppresses the release of NPY, leading to reduces food intake.
- AgRP: leptin inhibits AgRP. AgRP is an appetite stimulant, and when leptin levels rise, it suppresses AgRP activity, contributing to decreased food intake.
- POMC: leptin activates POMC. This activation leads to the release of a-MSH, which then acts on the MC4 receptor. Activation of the MC4 receptor reduces food intake.

Humans dont have a setpoint but more a set range. Each body has its own ideal weight or weight homeostasis. How much you eat is not only determined by hormones but also by external factors like: stress, social factors, physical activity, hedonics.
- Hedonics: reward motivation from food (overeating)
- Melanin: reward system activated.

a-MSH is a peptide hormone derived from POMC and produced in the pituitary gland and the hypothalamus. It plays many roles in the body, including regulating appetite. A-MSH acts on receptors in the brain, particularly the MC4 receptor, to suppress appetite and reduce food intake.
- Disfunction leads to more fat storage.
- Leptin stimulates a-MSH.

MCH is a hunger factor. It is released when palatable foods are consumed, increasing food intake. MCH also activates ventral tegmental area neurons, which are part of the brains reward system.
- Can be addictive same areas as a drug addiction.
- Dont want obese? block MCH an antagonist for the MCH-1 receptor inhibits the intake of palatable food (stop eating and choose for the healthy food)

Energy balance
Intake = utilization.
If you change things in the total daily energy expenditure the scale can change.

When low energy expenditure:
- Lower heart rate
- Lower body temperature
- Lower resting metabolic rate
- Lower glucose utilization
- Higher fat utilization.




Temperature regulation
The heat gain and loss are balanced.
Normal metabolism generates enough heat to maintain body temperature when the environmental temperature stays between 27.8-30 degrees.

There is a set range for temperature. We have cold receptors that detect things that are colder than the body temperature and we have warm receptors that detect things that are above body temperature.
- Negative feedback sensor for body temperature
o Heat loss dilation of blood vessels and sweating.
o Heat gain shivering and nonshivering thermogenesis.


Two types of thermoreceptors: central thermoreceptors (change in core body temperature) and peripheral thermoreceptors (change in environmental temperature)
Decreased body temperature
The body will conserve the heat to keep most of the warmth and temperature inside the body or heat is produces by exercise and activating the skeletal muscles. (activation of the sympathetic nervous system).
Another response is created by brown fat. It produces oxidation of the FFA in the cells and regenerate heat = nonshivering thermogenesis. It breaks down FFA.
- Babies have a lot of brown fat, because they cannot shiver and are very vulnerable to hypothermia for several reasons. After one year the shivering thermogenesis takes over.
White fat = storage tissue and releases leptin.
Human do have brown fat, but less than babies. And heavier the person the lover the brown fat.

Muscles can produce hormones myokines. The myokine Irisin is released by the muscles when it is activated. The irisin that is produces goes into the circulation and it changes white adipose tissue cells into brown adipose tissue cells. There is an increase in brown adipose tissue cells and an increase in the activation of mitochondria. It generates heat.
- When exercising the muscles produce more irisin so more brown adipose tissue cells.

Increased body temperature
When the body is too hot, the body will increase the sweat glands and dilate the blood vessels. (parasympathetic cholinergic neurons). You can also response by behavior responses.

When you eat you generate heat. The body temperature goes up. Liver temperature determines satiation, the end of a meal. Increased liver temperature decreases meal size.
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