Regulation of Food Intake Flashcards
What are the five areas in the hypothalamus that can control feeding and satiety?
- Lateral nucleus
- Ventromedial nucleus
- Paraventricular nucleus
- Dorsomedial nucleus
- Arcuate nucleus:
- has NPY/AgRP and POMC paths
What pathway in the arcuate nucleus decreases food intake?
- a-melanocortin (a-MSH) pathway that secretes POMC and decreases food intake
- Insulin, Leptin, and CCK stimulates this anorexigenic path that causes release of POMC to the neurons of the PVN
- In the PVN, POMC will bind to MCR-4 receptors which results in sympathetic activity and energy expenditure
What pathway in the arcuate nucleus increases food intake?
- NPY pathway stimulated by hunger signals such as Ghrelin
- NPY will bind to Y1R releasing AgRP, an antagonist of the MCR-4 receptor found in the PVN
- This results in suppression of the anorexigenic pathway and stimulation of food intake
- Insulin leptin and CCK inhibit this pathway
- Called orexigenic pathway
What two genes have mutations related to obesity?
- POMC and MCR-4 genes
- receptor that inhibits food intake
- POMC also is part of anorexigenic path
What is Prader-Willi-Syndrome?
- partial deletion of chromosome 15 or loss of paternally expressed genes
- Results in neonatal hypotonia, slow feeding, small hands and feet, mental retardation, hypogonadism, hyperphagia, severe obesity and elevated ghrelin
- obese patients usually have decreased ghrelin
What happens if vagal activity is blocked in regards to the stomach and meal sizes?
The amount of food in the stomach doesn’t influence meal size like it normally would
How does the vagal NTS circuit work?
- The vagus nerve sends signals to the Nucleus Tractus Solitarius and gets integrated with information from the hypothalamus to decide the appropriate feeding behaviour and metabolic responses
If there is an absence of higher centers input to regualte food intake, what will occur?
The hindbrain takes over regulation of food intake
What does the Lateral hypothalamic area do/have?
- It is the hunger center and it has neurons that project throughout the brain to release orexigenic peptide melanin concentrating hormone (MCH) or orexins A and B
- Hunger response is generated
What is the ventromedial hypothalamic nucleus?
Satiety center
What does the PVN do?
Recieves info from Arcuate nucleus and sends axons to cerebral cortex and brainstem
What does Ghrelin result in?
- Increases appetite
- Increases gastric motility
- Increases gastric acid secretion
- Increases adipogenesis
- Decreases ilsulin secretion
How does Ghrelin work and where does it come from?
- Secreted in stomach by endocrine cells
- It binds to GH secretagogue receptors and stimulates neurons that release NPY
- Initiates feeding response
What is insulins role in hunger?
- It will bind to receptors in the POMC and NPY pathways
- inhibits NPY
- Stimulates POMC
- Results in decreased appetite and increased metabolism
How does increased eating relate to insulin and T1 DM patients?
there is an increase in food intake associated with decreased insulin secretion as insulin will normallly decrease appetite and increase metabolism
What is CCK’s role in feeding?
- Released from I cells in duodenum
- Elicits Satiety
- acts on vagus nerve which sends signals to the NTS and goes to the hypothalamus circuit to decrease ghrelin and decrease gastric emptying and increase gastric distention
What releases PYY & what does it do?
- Released by L cells w/n iileum and colon following a meal
- Binds to Y2R receptors in the hypothalamus and inhibits NPY neurons and releases the inhibition of POMC neurons
- Net response is to promote anorexogenic pathway
Where is leptin released from and what does it do, and what increases its secretion?
- Secreted from adipose and binds receptors in POMC and NPY pathways
- Inhibits NPY
- Stimulates POMC
- Appetite suppression hormone!
- increases metabolism and decreases ghrelin release
- As fat stores increase or intake of meal occurs more leptin is released
Obesity is associated with ___ levels of ___. and failure to respond to exogenous versions of this.
High Leptin
What signals are involved in long term regulation of energy balance?
Adiposity signals
What modulates food intake on a meal by meal basis?
Gut peptides
Where is GLP-1 released from & what deoes it do? Describe the levels when eating and fasting.
- Reduces food intake suppresses glucagon secretion and delays gastric emptying
- Co secreted with PYY from L cells int he intestine
- Levels rise after meal and fall during fasting
What does Oxyntomodulin do and where is it released from?
- Anorectic effect
- Released from L cells of intestine in response to ingested food and in proportion to caloric intake
What does PP do and where is it from?
- Secreted from pancreatic islets of langerhans
- Decreases food intake by binding Y4R in hypothalamus
- Can also act on vagus nerve to produce anorectic effect
