8. Regulation of Food Intake Flashcards
Where are the neuronal centers that control feeding and satiety located
Hypothalamus
The Orexigenic and Anorexigenic pathways occur where
Arcuate Nucleus
What is the Anorexigenic pathway
‘Satiety Pathway’
-POMC/CART release a-melanocortin (a-MSH) that binds to MCR-4 in second order neuron
Stimulated by Insulin, Leptin and CCK
What is the Orexigenic pathway
‘Hunger Pathway’
- Neuropeptide Y (NPY) stimulates food intake
- Agouti-related peptide (AGRP) is an antagonist of MCR-4
Stimulated by Ghrelin
Inhibited by Insulin, Leptin and CCK
What are some genetic causes of obesity
- Leptin or leptin receptor gene deficiency
- MCR-4 receptor gene mutation
- POMC deficiency
- Prader-Willi syndrome
What about Prader-Willi syndrome causes obesity
Paradoxically elevated ghrelin (always feel famished)
Why is the vagus nerve a possibility for obesity therapies
- Several peptides that stimulate satiety and decrease feeding activate receptors on vagal afferents
- If vagal activity is blocked, the amount of material in hte stomach no longer influences meal size
What area of the brainstem is crucial in the interpreting and relaying of peripheral signals and what ganglion does the vagus nerve synapse on
NTS- nucleus solitarius tract
Nodose ganglion
What is the general function of the anorexigenic and orexigenic pahtways
Anorexigenic- promotes satiety
Orexigenic- promotes appetite
What secretes Ghrelin and what are its actions
Secreted by endocrine cells in the stomach
Actions- Initiates feeding response Increase: appetite, gastric motility, gastric acid secretion, adipogenesis Decrease: insulin secretion? Stimulates neurons that release NPY
What does Insulin do to the anorexic and orexic pathways
Inhibits NPY pathway
Stimulates POMC pathway
What secretes CCK and what are its actions
Secreted by I cells in the duodenum
Elicits satiety by decreasing ghrelin and gastric emptying
What secretes PYY and what are its actions
Secreted by L cells of the ileum and colon following a meal
Inhibits NPY neurons and stops the inhibition of POMC neurons
What secretes Leptin and what are its actions
Secreted by adipose tissues
Inhibits NPY pathway and stimulates POMC pathway
APPETITE SUPPRESSING hormone
How do leptin levels affect obesity
- Obese children may high congenital leptin deficiency and will respond administration of leptin
- Most obese people have high leptin levels and leptin resistance
What are involved in the long-term regulation of energy balance, while gut peptides modulate food intake on a meal-by meal basis
Adiposity signals
What are the effects of glucagon-like peptide-1 (GLP-1) on food intake and what is secreted with it
GLP-1 is co-secreted with PYY from L cells in the intestine
-Reduces food intake, suppresses glucagon secretion and delays gastric emptying
What is the general effect of Oxyntomodulin
Anorectic effect
Released from L cells of intestines in response to ingested food and IN PROPORTION TO CALORIC INTAKE
What is the general effect of Amylin
Anorectic effect (inhibit NPY release)
Most generally what does Glucagon do to food intake
Reduces food intake
What is the general effect of Pancreatic Peptide (PP)
- Decrease food intake through Y4R in brainstem and hypothalamus
- Produces an anorectic effect via vagus nerve
What are some gut-brain axis complications associated with anorexia nervosa (AN)
- BASAL and PULSATILE secretion of leptin is REDUCED in assocation with reductions in fat mass
- Ghrelin resistance
- Polymorphisms
- Elevated levels of PYY
