Lec 51 Neurobiology of Feeding Flashcards
What is equation of BMI?
BMI = weight in KG/(height in m)^2
What are diagnostic criteria for anorexia nervosa?
- body weight 15% or more below normal
- fear of being fat despite being underweight
- grossly distorted body image
- in women often accompanies by amenorrhea
What BM I for overweight? oese?
BMI > 25 overweight
BMI > 30 obese
What are health risks associated wtih obesity?
- CV disease
- diabetes
some forms of cancer
What hormones are increased in anorexic? decreased?
increase: cortisol, growth hormone
decreased: thyroid hormone
What is definition bulimia?
alternating periods of bing + purge
What happens to feeding in lesion of lateral hypothalamus?
extreme hypophagia, starvation
—> LH contains pro-appetite orexigenic factors
What happens to finding in lesion of medial hypothalamus?
hyperphagia and obesity
particularly ventromedial hypothalamus
–> MH contains anti-appetite anorexigenic factors
What is a major brain reward system?
mesolimbic dopamine system = DA neurons from ventral tegmental of midbrain to ventral striatum (nucleus accumbens) and limbic cortex
How is mesolimbic dopamine system associated with feeding?
mediates desire for food a a primary rewarding substance (appetite)
– particularly fat, salt, sugar
How does hypothalamus control feeding behavior?
intragrates need for food via signals from periphery (hunger)
What is role of cerebral cortex in feeding control?
exerts control over feeding behavior based on cognitive experiences
may integrate with psych and social factors
How is efficiency of mitochondria tied to body weight?
more efficient = use less energy = gain weight
less efficient = use more energy = lose weight
What hormone is the major controller of appetite in the body? Where is it made? where does it act primarily?
leptin
synthesized in fat cells –> amount of leptin proportional to volume of fat
act: primarily on hypothalamus
What is action of leptin when you lose weight?
losing weight decreases leptin
- -> get increased orexigenic and decreased anorexigenic factors
- -> increased food intake, parasympathetic tone, decreased energy use
What is function of leptin?
acts in hypothalamus
- decreases feding
- increases energy utilized by: increasing activity, increasing thermogenesis (mitochrodrial effect)
- decreases energy storage (less fat)
What is mech of Ob and Db mice?
Ob = knockout of gene that produces leptin Db = knockout of gene that encodes for leptin receptor
How does leptin enter brain?
transported to hypothalamic region by specific transport protein
What is the leptin receptor?
receptor for leptin
activates JAK-STAT pathway
Where does leptin act specifically and what specific peptides does it inhibit/stimulate?
acts in arcuate nucleus of hypothalamus to
- inhibit NPY and AgRP = two orexigenics
- stimulates aMSH and CART = 2 anorexigenics
Where do leptin’s targets act?
- act on other peptides in hypothalamus that mediate reduction in feeding + increased energy use
–> NPY and AgRP stimulate MCH and inhibit CRF/TRF
–> a-MSH and CART stimulate CRF and inhibit MCH [but luckily aMSH and CART are downregulated by leptin]
- inhibit MCH in lateral hypothalamus
- stimulate CRF and TRF in paraventricular nucleus in medial hypothalamus
MCH = melanin-concentrating hormone = orex. CRF = corticotropin releasing = anorex. TRF = thyrotropin releasing = anorex.
What type of nerve cells make releasing factors in paraventricular nucleus of hypothalamus?
parvocellular neurons
What else besides MCH exists in lateral hypothalamus that is associated with weight?
orexin
What is neuropeptide Y (NPY)? where is it synthesized?
- most powerful orexigenic factor known
- synthesized in arcuate nucleus
