Regulation of Food Intake Flashcards
What area of the brain is critical in the regulation of food intake, processing afferent and efferent signals based on interconnecting nuclei?
Hypothalamus
The hypothalamus is subdivided into interconnecting nuclei, that include ____ (there are 5)
Arcuate nucleus (ARC) Paraventricular nucleus (PVN) Ventromedial nucleus (VMN) Dorsomedial nucleus (DMN) Lateral hypothalamic area (LHA)
The hypothalamus receives crosstalk inputs from:
- Neural signals from the GI tract that provide _____ info about stomach filling
- Chemical signals from nutrients in the blood (glucose, amino acids, and fatty acids) that signify _______
- Signals from gastrointestinal hormones
- Signals from _____ released by adipose tissue
- Signals from the _____ ____ (sight, smell, and taste) that influence feeding behavior
Sensory
Satiety
Hormones
Cerebral cortex
The ______ nucleus of the hypothalamus is one of the best characterized brain regions as it relates to the control of feeding behavior due in large part to the presence of 2 distinct neuronal populations
Arcuate
The arcuate nucleus of the hypothalamus is one of the best characterized brain regions as it relates to the control of feeding behavior due in large part to the presence of 2 distinct neuronal populations
What are these populations?
- Pro-opiomelanocortin (POMC) anorexigenic neurons
- Neuropeptide Y (NPY)/agouti-related peptide (AgRP) orexigenic neurons
[signals from the periphery result in changes in the activity of these 2 neuronal subpopulations and the release of their respective neuropeptides influence feeding behavior and energy expenditure]
______ is a hormone that stimulates the POMC anorexigenic pathway and inhibits the _______ pathway, resulting in _______ food intake
Leptin; orexigenic; reduced
POMC neurons suppress appetite by releasing ________ stimulating hormone which is an agonist at the corresponding anorectic receptors
Alpha-melanocyte
[agonist at anorectic melanocortin-4 receptors]
______, a hormone secreted from the stomach, activates AGRP-NPY neurons and _______ food intake
Orexigenic effects are mediated through ____ receptors of NPY, which are located in the second order nucleus (not the arcuate anymore)
Ghrelin; stimulates
Y1
Agrp and Npy ______ food intake and _______ energy expenditures, causing weight _______
Stimulate; decrease; gain
A decrease in what hormone stimulates the expression of AgRP and NPY and suppresses POMC and CART, thereby increasing food intake and decreasing energy expenditure?
Leptin
What gene mutation is the most common cause of monogenic obesity in humans?
Does this gene involve anorexigenic or orexigenic pathway?
MC4R - can be used by EITHER anorexigenic or orexigenic!
______ and _____are important in regulating food intake and energy balance.
What are the effects of activation vs. inhibition of these genes?
MCR-3; MCR-4
Activation reduces food intake while increasing energy expenditure
Inhibition of MCR-3 and MCR-4 greatly increases food intake and decreases energy expenditure
[MCR3 is in arcuate nucleus associated with AGRP/NPY or POMC/CART neurons, MCR4 is in hypothalamus associated with second order neuron]
The secretion of Ghrelin signals that you are hungry 3-4x/day in coordination with _________ rhythm
Circadian
Where is the leptin hormone released from?
Adipose tissue
The GI tract is one of several organs that contribute to the peripheral signaling of food intake and satiety
_____-mediated reflexes are recognized as being critical to the neural control of energy homeostasis, particularly the short-term (homeostatic) and longer-term (hedonic) control of appetite and food intake
______, ______, and _____ all act as NTs/modulators within the brainstem to affect afferent and efferent responses via ____ nerve either directly or indirectly
Vagal
CCK, GLP-1, 5-HT; vagus
Afferent signals from the ________ travel via vagus nerve to the GI tract and hepatic portal system
Nucleus tractus solitarius (NTS)
Efferent information travels on vagus n. from the ______, which is involved in regulation of:
GI _____ and _____ functions
_______ hepatic glucose production
______ glycogen synthesis
_______ pancreatic endocrine (insulin) and exocrine secretion
DMN (dorsal motor nucleus)
Motor; secretory
Decreased
Increased
Increased
_____ = potent appetite stimulator produced by the stomach and regulated by feeding status
Ghrelin
When does Ghrelin secretion peak?
Before meals - makes people feel like eating
[levels fall once food is eaten]
Ghrelin stimulates appetite by activating hypothalamic ____-secreting neurons via ____ receptors
It also increases _____ hormone secretion
NPY; Y1
Growth
Where are the receptors for Ghrelin located? (i.e., in what nuclei of the brain?)
Arcuate nucleus
Lateral hypothalamic area
Accumbens nucleus
Ventral tegmental area
Fat cells produce _____ and secrete it into the bloodstream, where it normally suppresses ghrelin release
Leptin
Stimulation of leptin receptors initiates multiple actions that decrease fat storage including:
Decreased production of appetite stimulators in the hypothalamus such as ____ and _____
Activation of _____ neurons, causing release of a-MSH and activation of ______ receptors
Increased production of ________ hormone in the hypothalamus, which decreases food intake
Increased _____ nerve activity which increases metabolic rate and energy expenditure
Decreased _____ secretion by pancreatic beta cells, which decreases energy storage
NPY; AGRP
POMC; melanocortin
Corticotropin-releasing
Sympathetic
Insulin
Insulin is produced by the _____ cells of the _____ pancreas
It regulates glucose uptake, storage of absorbed nutrients, and caloric or energy balance
It can be transported across the _____ and bind receptors present in areas of the hypothalamus that control food intake, positively acting on _____ and negatively acting on _____
Beta; endocrine
BBB; POMC; NPY
What condition is characterized by the absence of adequate insulin and is associated with increased food intake?
Type 1 diabetes
______ is released mainly in response to fat and proteins entering the duodenum; it enters the blood and acts as a hormone to influence several GI functions such as gallbladder contraction, gastric emptying, gut motility, and gastric acid secretion
CCK
______ is a small peptide from the small intestine from cells in the ileum and colon. It has low baseline levels that increase quickly when eating. Increased levels decrease appetite
PYY
[pancreatic peptide tyrosine tyrosine]
Where are PYY receptors located?
In arcuate nucleus [acted on by vagus n. input to brainstem]
________ is produced from the proglucagon gene and released from small intestine in response to a meal; it acts to reduce gastric motility and secretion
Oxyntomodulin
[studies suggest its systemic administration can reduce food intake and body weight]
______ is released from the L cells of the small intestine in response to food ingestion. It is a potent inducer of glucose dependent insulin release
Glucagon-like peptide 1
How can glucagon-like peptide 1 influence food intake?
By acting on nucleus of solitary tract in brainstem and paraventricular nucleus of hypothalamus (anorexigenic)
What 3 hormones from the pancreas inhibit hunger?
Amylin
Insulin
Pancreatic polypeptide (PP)
What 4 hormones from the lower SI inhibit hunger?
Peptide YY
GLP-1
Oxyntomodulin
Uroguanilin
What hormone from the colon stimulates hunger?
Insulin-like peptide 5 (ILP-5)
What are the 4 most common weight loss surgery procedures in the US?
Adjustable gastric band (Lap band)
Roux-en-Y Gastric Bypass (RNY)
Duodenal switch (DS)
Vertical sleeve gastrectomy (gastric sleeve)
Which of the following is characterized by creating a small stomach pouch and bypassing 3-5 feet of intestine, resultin gin 50-75% weight loss and resolution of T2D in 80% of patients?
A. Lap band
B. Gastric bypass
C. Sleeve gastrectomy
D. Duodenal switch
B. Gastric bypass
Which of the following is characterized by removal of a portion of the stomach as well as a bypass of a large amount of small intestine, resulting in decreased absorption of nutrients and weight loss slightly over 75%, and resolution of T2D in over 90%?
A. Lap band
B. Gastric bypass
C. Sleeve gastrectomy
D. Duodenal switch
D. Duodenal switch
Which of the following is characterized by a device wrapped around the upper stomach, restricting its food capacity, and is adjustable using saline solution injection into access port. Patients typically lose 40-50% of their excess weight and T2D resolves in 50-60%
A. Lap band
B. Gastric bypass
C. Sleeve gastrectomy
D. Duodenal switch
A. Lap band
Which of the following is characterized by removal of the left side of the stomach, leaving a stomach roughly the size and shape of a banana, with weight loss aroung 50-75% and T2D resolution in 60% of patients?
A. Lap band
B. Gastric bypass
C. Sleeve gastrectomy
D. Duodenal switch
C. Sleeve gastrectomy
Why is RNY considered the gold standard in weight loss surgical procedures?
It produces favorable changes in gut hormones that reduce appetite and enhance satiety with a 50% maintenance rate of that weight loss
After RNY surgery, the activity of the _______ reward pathway and other reward centers is reduced in response to food pictures, especially visual representations of high caloric density food. This is associated with a decreased desire to eat.
Studies indicate that ____ and _____ are suppressed in obese patients and increase after RNY surgery, likely due to the anatomical changes that occur
Mesolimbic
PYY; GLP-1
What taste changes occur after bariatric surgery?
Taste sensation is often decreased in obese patients compared to lean controls; after RNY, the acuity for sweet and sour tastes is increased to levels that resemble lean subjects
How do the following change after diet-induced weight loss?
Energy expenditure
Fat oxidation
Thyroid hormones
Energy expenditure decreases
Fat oxidation decreases
Thyroid hormones decrease
How do the following change after diet-induced weight loss?
Cortisol
GIP
Leptin
Cortisol increases
GIP increases
Leptin decreases
How do the following change after diet-induced weight loss?
PYY
Amylin
Insulin
PYY decreases
Amylin decreases
Insulin decreases
How do the following change after diet-induced weight loss?
Ghrelin
Appetite
Pancreatic polypeptide
Ghrelin increases
Appetite increases
Pancreatic polypeptide increases
Complications of anorexia nervosa
Weakening of stomach muscles
Damage to nerves that signal the stomach to digest and pass food
Longer emptying time = bacterial problems
Hardening of food in stomach = bezoars
Increase in frequency of ulcers
Shrunken stomach cannot accommodate normal amts of food
What happens to leptin, ghrelin, and PYY levels in anorexia nervosa patients?
Leptin levels decrease
Ghrelin levels increase
PYY levels increase - these are the only ones that do not normalize with weight recovery
Complications of bulimia nervosa
Swollen/painful parotid glands
Reflux d/t floppy LES, can lead to Barret’s esophagus and esophageal cancer
Mallory weiss tears (in esophagus)
Arrhythmias, palpitations, death
Difficulty swallowing d/t loss of muscle tone in esophagus
