Lecture 17: Appetite Regulation Flashcards
Body energy use
60-75% basal metabolism
10% thermogen.
15-30% physical activity
Peripheral appetite signals
- GI, pancreas, adipose
Short term satiety: - Via vagus nerve; CCK, incretins
Long term adiposity: - Endocrine; nutrient related
Brain appetite centers
ARC, PVN in hypothalamus
NST in brain stem
Adiposity -> ARC -> PVN -> NST -> food intake
GI -> satiety -> NST
Neural appetite signals
Gastric emptying -> hunger
Gastric distension -> fullness
Short term peripheral appetite signals
Satiety peptide hormones mainly from GI -> immediate hunger/fullness moment to moment
- CCK, Glucagon-Like Peptide-1
Long term peripheral appetite signals
Adiposity hormones that parallel body fat; describes food store status
- Leptin, insulin
Ghrelin
Gastric hunger peptide hormone; rises before meals and drops after
Stims. appetite/intake, decreases energy use
Satiety peptides
CCK, GLP-1
- Oppose ghrelin
- Decrease gastric emptying, increase satiation
- Mostly from GI to vagus
- Includes incretins (GLP-1) -> increase insulin secretion
Pancreatic endocrine appetite peptides
Insulin, glucagon, pancreatic polypeptide, amylin
Insulin in appetite regulation
Reports fat levels, inhib. appetite @ ARC. Adiposity defines baseline insulin levels
Adipose tissue appetite signals
Adipose tissue = aromatase source, FFA signals, cortisol enzyme source
Leptin secretion
Leptin
Secretion by adipocytes inhibs. appetite, increases energy use @ ARC
Synergy w/ insulin to oppose ghrelin
Permissive for many H-P axes:
- Decreased leptin -> turns off reprod. HPG
- Levels vary w/ stress
Leptin deficiency vs resistance
Hormone Replacement Therapy doesn’t work for resistance, which is more common in humans vs deficiency
2 brain appetite control center circuits
2 circuits in balance
1. Orexigenic (eat)
- Stim. appetite + food intake; decrease energy use
2. Anorexigenic (don’t eat)
- Decrease appetite, food intake; increase energy use
Ghrelin -> orexigenic neurons
Leptin/insulin –| orex., -> anorex. neurons
Orexigenic neurotransmitters
Neuropeptide Y:
- Most common brain NT, released w/ prolonged stress
Agouti-related peptide:
- Coexpress. w/ NPY, potent long-lasting appetite stim.
AgRP/NPY neurons in ARC w/ Ghrelin Rs
Anorexigenic NTs
POMC/alpha-MSH:
- POMC secreted by ARC -> cleavage to alpha-MSH -> MCR binding -> appetite, sex. behavior
- AgRP inhibs. MCRs
CART:
- Concentrated in hypothal.
- Increases locomotor activity, energy use
- Stim. FX ~ cocaine, amphetamines
Obesity genetics vs environment
Multiple mx common for obesity e.g. MCR4 deficiency
Environ. stim.: visual cues, sensory perception, marketing, exercise, portion distortion
Metabolic Syndrome
3 or more of:
- Obesity, T2DM/insulin resist./prediabetes, high TGs, low HDLs, hypertension, polycystic ovary syndrome
- Correlated w/ x2 CV disease risk in 5-10 years
