Physiology of Appetite and Weight Flashcards
How many calories do fat, protein and carbohydrates contribute?
- fat = 9 kcal
- protein = 4 kcal
- carbohydrates = 4kcal
How do we calculate BMI?
- weight (kg)/height(m)2
- (80kg/1.7)2 = 80 / (1.7 squared = 2.89) = 80/2.89 = 27.68kg/m2
Based on BMI, what is the diagnosis of underweight?
- <18.5 kg/m2
Based on BMI, what is the diagnosis of normal weight?
- > 18.5 - 24.9 kg/m2
Based on BMI, what is the diagnosis of overweight?
- > 25- 29.9kg/m2
Based on BMI, what is the diagnosis of obese?
- > 30-39.9kg/m2
Based on BMI, what is the diagnosis of morbidly obese?
- > 40kg/m2
In addition to BMI to calculate if a patient is underweight, overweight or obese, what other measures can be used?
- skin fold thickness
- bio-impedance
- waist circumference
In order which of the 3 macronutrients fat, protein and carbohydrates, which can we survive without for the longest periods?
1st - protein
2nd - fat
3rd - carbohydrates (can last less than 1 week)
What is the main known area of the brain involved in appetite?
- hypothalamus
What hormone released by the stomach is able activate hunger?
- ghrelin
Ghrelin is a hormone released by the stomach and is able to activate hunger. Which cells in the stomach release ghrelin?
- enteroendocrine cells of the stomach
What is the main hormone involved in satiety (hunger supression) and what cells predominantly release this hormone?
- leptin
- releases by adipocytes
Which hormone is released by beta cells in the pancreas that has a role in hunger suppression?
- insulin
There are 2 hormones released by the cells in the GIT, excluding ghrelin?
- peptide YY (PYY) = large intestines
- cholecystokinin (CCK) = small intestines
There are 5 main nuclei at the base of the hypothalamus that are predominantly involved in food intake. Label them in the image below (1-5) using the labels below:
- Lateral nuclei
- Ventromedial nuclei
- Paraventricular nuclei
- Dorsomedial nuclei
- Arcuate nuclei
1 - Lateral nuclei – feeding centre 2 - Dorsomedial nuclei 3 - Arcuate nuclei 4 - Ventromedial nuclei 5 - Paraventricular nuclei
There are 5 main nuclei at the base of the hypothalamus that are predominantly involved in food intake, seen below in the image and listed here:
- Lateral nuclei
- Ventromedial nuclei: satiety centre
- Paraventricular nuclei
- Dorsomedial nuclei
- Arcuate nuclei
Which nuclei is recognised as the feeding centre?
- lateral nuclei
There are 5 main nuclei at the base of the hypothalamus that are predominantly involved in food intake, seen below in the image and listed here:
- Lateral nuclei
- Ventromedial nuclei
- Paraventricular nuclei
- Dorsomedial nuclei
- Arcuate nuclei
Which nuclei is recognised as the satiety (fullness) centre?
- Ventromedial nuclei
There are 5 main nuclei at the base of the hypothalamus that are predominantly involved in food intake, seen below in the image and listed here:
- Lateral nuclei
- Ventromedial nuclei
- Paraventricular nuclei
- Dorsomedial nuclei
- Arcuate nuclei
What is recognised as the satiety centre?
- Ventromedial nuclei
There are 5 main nuclei at the base of the hypothalamus that are predominantly involved in food intake, seen below in the image and listed here:
- Lateral nuclei
- Ventromedial nuclei
- Paraventricular nuclei
- Dorsomedial nuclei
- Arcuate nuclei
If there is a lesion in -the paraventricular, dorsomedial and/or arcuate nuclei, what can this cause?
- appetite and feeding
Ghrelin is the hormone released from endocrine cells in the stomach that stimulate hunger. Which nuclei in the base of the hypothalamus does ghrelin activate nerve fibres in?
- arcuate nucleus
- switchboard regulating the ventromedial nuclei (satiety/fullness center), and the lateral hypothalamic area (feeding centre)
Ghrelin is the hormone released from endocrine cells in the stomach that stimulate hunger. through stimulation of the arcuate nucleus in the base of the hypothalamus. Ghrelin is able to bind with a specific type of receptor on a specific type of neuron. What 2 receptors does ghrelin bind with in the arcuate nucleus?
1 - agouti related protein (AGRP) receptors
2 - neuropeptide Y receptors
Ghrelin is the hormone released from endocrine cells in the stomach that stimulate hunger. through stimulation of the arcuate nucleus in the base of the hypothalamus. Ghrelin is able to bind with agouti related protein (AGRP) receptors and neuropeptide Y receptors on specific neurons that are present on the ventromedial aspect of the arcuate nucleus. What are these 2 neurons called?
1 - AGRP neurons
2 - neuropeptide Y neurons
Ghrelin is the hormone released from endocrine cells in the stomach that stimulate hunger. Ghrelin is able to bind with agouti related protein (AGRP) and neuropeptide Y receptors located on AGRP and neuropeptide Y neurons. These neurons can then synthesise and release 2 peptides called AGRP and neuropeptide Y, which are a specific class of peptide that stimulates hunger. What is this class of peptide called?
- orexigenic peptides
- stimulates hunger
Leptin, cholecystokinin and insulin are all released in response to food, and are involved in suppressing hunger. Which nuclei in the base of the hypothalamus do all 3 hormones bind with?
- arcuate nucleus
Leptin, cholecystokinin and insulin are all released in response to food, and are involved in suppressing hunger. All 3 hormones then bind with a specific receptor in the arcuate nucleus. What is this receptor called and what neuron are these located on?
- pro-opiomelanocortin receptors
- pro-opiomelanocortin neurons
Leptin, cholecystokinin and insulin are all released in response to food, and are involved in suppressing hunger. All 3 hormones then bind with a specific receptor in the arcuate nucleus. These receptors are called pro-opiomelanocortin (POMC) receptors and are located on POMC neurons. Once leptin, insulin and CCK have bound with POMC neurons they are able to secrete to specific peptide hormones that can then stimulate satiety (fullness). What are these 2 peptide called?
- α-melanocyte stimulating hormone (α-MSH) (MCR-3 and MCR-4 receptors)
- cocaine and amphetamine-regulating transcript (CART)
Leptin, cholecystokinin and insulin are all released in response to food, and are involved in suppressing hunger. All 3 hormones then bind with a specific receptor in the arcuate nucleus. These receptors are called pro-opiomelanocortin (POMC) receptors and are located on POMC neurons. Once leptin, insulin and CCK have bound with POMC neurons they are able to secrete to specific peptide hormones that can then stimulate satiety (fullness). These 2 peptides are called α-melanocyte stimulating hormone (α-MSH) and cocaine and amphetamine-regulating transcript (CART). Both α-MSH and CART are a specific class of peptide that are known to induce satiety (fullness). What is this class of peptide called?
- anorexigenic peptides
- stimulates satiety
The following hormones have the following functions through binding with the arcuate nucleus in the base of the hypothalamus:
- ghrelin = stimulates hunger through release of orexigenic peptides (agouti related protein (AGRP) and neuropeptide Y
- leptin, insulin and cholecystokinin = stimulates satiety (fullness) through the release of anorexigenic peptides (α-melanocyte stimulating hormone (α-MSH) and cocaine and amphetamine-regulating transcript (CART)).
As part of complex positive and negative feedback loops these hormones are also able to do what?
- ghrelin = inhibit the release of anorexigenic peptides and therefore satiety (fullness)
- leptin, insulin and cholecystokinin = inhibits the release orexigenicof peptides (hunger)
Which neuron and receptor involved in appetite have been linked with obesity due to mutations in the their genes?
- pro-opiomelanocortin (POMC neurons)
- α-melanocyte stimulating hormone (α-MSH) specifically MCR-4 receptors
Lower sensitivity or a lack of leptin, the satiety (fullness) hormone has been linked with which metabolic disorder?
- obesity
Is leptin able to cross the blood brain barrier?
- yes
Leptin is released into the blood from adipose tissue in response to satiety (fullness). If leptin receptors are stimulated, what does this do to adipose levels in the body?
- decreases adipose stores
- if we are fuller we consumer less food, so less fat can be produced
What is the diagnosis of being overweight based on BMI?
- 25 - 30kg/m2
What are 2 of the most common genetic obesity associated syndromes?
1 - prader-willi
2 - bardet-biedl
Which drug has been used to treat obesity that acts on inhibiting fat digestion?
- orlistat
- binds to pancreatic lipase and inhibits fat digestion and absorption
Orlistat has been used to treat obesity through binding with pancreatic lipase, inhibiting fat digestion and absorption. What affect can this have on vitamins?
- reduce absorption of fat soluble vitamins
- namely ADEK
Although there is no clear pharmacological treatment, there is one option that is invasive is surgery, but has been shown to significantly reduce weight in patients. What is this surgery called?
- gastric bypass (digestion and absorption are skipped)
- gastric band (can be tightened or loosened using saline)
What are the 3 main advantages to surgical interventions for obesity, such as gastric bypass and bands?
1 - weight loss 25-30%
2 - resolution or improvement of co-morbidities
3 - life-long treatment cost savings
What are the main disadvantages to surgical interventions for obesity, such as gastric bypass and bands?
- perioperative mortality / morbidity
- complications
- requires long-term follow-up
- weight re-gain
- expensive
