2 - Regulation of Food Intake Flashcards
Objective: Explain the role of the arcuate nucleus and paraventricular nucleus of the hypothalamus in regulation of appetite
Control Center
Control Regions:
Lateral Nuclei
Ventromedial Nucleus
Paraventricular Nucleus (PVN)
Dorsomedial Nucleus (DVN)
- Hypothalamus = Control Center
- Lateral Nuclei
- Feeding center; stimulation = hyperphagia
- Destruction causes loss of desire to eat
- Ventromedial Nucleus
- Satiety Center
- Stimulation = satiety; lack of eating
- Destruction causes continuous eating
- Paraventricular Nucleus (PVN)
- Lesions = Excessive Eating
- Dorsomedial Nucleus (DVN)
- Lesions = Depress Eating
Objective: Explain the role of the arcuate nucleus and paraventricular nucleus of the hypothalamus in regulation of appetite
Arcuate Nucleus (ARC):
Overview
Role
Neurons: POMC, Orexigenic
Hormones?
Results?
- Overview:
- Multiple hormones released from GI / Adipose converge here to regulate intake/expenditure
- Location lacks full BBB; can integrate neurological/blood signals
- Role: Two Types of Neurons
-
POMC Neurons - a-MSH, CART
- (+) Decrease Food Intake, Increase Energy Expenditure
- a-MSH act on MCR-3/4 receptors in PVN
- (+) MCR-3/4 = Reduce Food Intake, Increase Energy
- (-) MCR-3/4 = Increase Food Intake, Decrease Energy
- CART mutation may cause obesity
-
Orexigenic Neurons - NPY, AgRP
- (+) Increase Food Intake, Decrease Energy Expenditure
-
POMC Neurons - a-MSH, CART
Objective: Summary of ARC Released Substances:
AgRP
a-MSH
CART
NPY
Hypocretin/Orexin
- AgRP
- Stimulates food intake by binding to MCR receptors
- a-MSH
- Inhibits food intake by binding to MCR receptors
- CART
- Inhibits food intake by binding to MCR receptors
- NPY
- Stimulates food intake by binding to Y receptors
- Hypocretin / Orexin
- Stimulates Food Intake
- Increases expression during food deprivation
- Neurons active during fasting
Objectives: Explain the mechanism of action of the different GI hormones involved in regulation of food intake
Leptin
Where is it derived?
Increases?
Anorexigenic Signaling
- Leptin
- Adipocyte-derived protein; as adipocyte tissue increases, leptin levels increase
- Anorexigenic signaling
- Leptin occupies leptin receptors in hypothalamus
- (+) a-MSH, CART
- (-) NPY, AgRP
- (+) Sympathetics
- (-) Insulin secretion (energy storage)
-
Net:
- Decrease food consumption, Increase energy expenditure
Objectives: Explain the mechanism of action of the different GI hormones involved in regulation of food intake
CCK
Type?
Receptor in nervous system?
Net result?
- CCK = Anorexigenic
- Receptor on vagus nerve
- Net:
- Decrease food intake in humans
Objectives: Explain the mechanism of action of the different GI hormones involved in regulation of food intake
Ghrelin
Type?
Stimulates?
Level changes?
- Ghrelin = Orexigenic (only known hormone of this type!)
- Stimulates:
- (+) NPR / AgRP
- Changes:
- Increase: Low calorie diets, cancer anorexia, anorexia nervosa, stress, sleep deprivation
- Decrease: Weight gain, exercise
Objectives: Explain the mechanism of action of the different GI hormones involved in regulation of food intake
Glucagon-like Peptide-1 (GLP-1)
Type?
Production site?
Stimulates?
Clinical increase?
- GLP-1 = Anorexigenic
- Production Site:
- L-Cells in Ileium, Colon from Proglucagon
- Released biphasic (fast, slow)
- Stimulation:
- (+) a-MSH, CART
- (-) AgRP, NPY
- Levels increase following gastric bypass surgery
- Receptor agonists used as weight loss treatment
Objectives: Explain the mechanism of action of the different GI hormones involved in regulation of food intake
Oxyntomodulin (OXM)
PYY
Glucose
- Oxyntomodulin (OXM)
- Anorexigenic
- Reduces food intake
- Proglucagon derived
- PYY
- Anorexigenic
- Reduces food intake
- Reduces gastric empting, delays intestinal transit
- Glucose
- Increases = increased firing in satiety centers in ventromedial and paraventricular nuclei
- Decrease = firing in hunger center of lateral hypothalamus
Objectives: Explain the role of the endocannabinoid system in stimulating food intake
Cannabinoid Receptors and Endocannabinids (ECs)
Binding site?
Effects on food intake?
- THC binds receptor in hypothalamus
- Arachidonic Acid Derivatives
- Increase food intake (sweets and fats)
- Stimulates:
- Orexigenic (stimulates food intake)
- Leptin reduces levels of ECs in animals
What are MCR defects associated with?
What is most common cause of monogenic human obesity?
What does activation of the MCR system do?
Extreme obesity
MCR-4 Mutation
Reduce Appetite
What is the role of AgRP?
What releases the effects of it?
What are mutations associated with?
Natural antagonist of MCR-3/4
Increases feeding by inhibiting a-MSH
Release inhibited by insulin
Excessive formation due to muattion associated with obesity, excessive feeding
What is role of NPY and where is it released?
What does it bind to and what’s its role?
NPY released from Orexigenic Neurons (ARC)
Binds to Y receptors; stimulates appetite
How can ripping cigs cause appetite suppression?
Nicotinic AChRs located on POMC neurons
Nicotine enhances firing of POMC neurons
POMC releases a-MSH; acts on MCR-4
MCR-4 reduces food intake and increases energy spending
- - -
Nicotine -> (+)POMC -> (+) a-MSH -> (+)MCR-4 =
Decrease Food Intake
How do the following affect control of food intake?
Aging
Anorexia Nervos
- Aging
- Decrease Orexigenic levels
- Anorexigenic levels stay the same
- Anorexia Nervosa
- Increased NPY, Decreased Leptin
- Levels can change as weight returns to normal
