Obesity Flashcards
An increase in what turns on the ventromedial hypothalamus?
Blood glucose - from eating
What two hormones does the paraventricular nucleus in the hypothalamus secrete?
Corticotropin-releasing hormone
Thyrotropin-releasing hormone
What two areas of the hypothalamus are involved in the regulation of food intake?
Arcuate nucleus
Paraventricular nucleus
Why is the arcuate nucleus a privileged site?
It can sample the peripheral circulation through semi-permeable capillaries in the underlying median eminence
What is the PVN adjacent to?
The superior part of the third ventricle in the anterior hypothalamus
What turns on the lateral hypothalamus?
A decrease in blood glucose - when someone is hungry
What does a lesion of the VMH lead to?
Hyperphagia - excessive eating or increase appetite
What is leptin and what is it produced by?
Adipostat - produced by adipose tissue
What are leptin levels proportional to?
Body fat
Which part of the brain does leptin act on?
Arcuate nucleus of hypothalamus
What is the effect of leptin on the brain?
Inhibits circuits that stimulate eating and activate circuits that increase energy expenditure
For which receptor is ghrelin an endogenous ligand for?
Growth hormone secratogogue receptor (GHS-R)
What is the effect of insulin in the CNS?
Reduction in food intake
Where is ghrelin produced?
The fundus of the stomach
What are the two effects of ghrelin?
Stimulate growth hormone
Increase food intake
What secretes peptide YY and when is it secreted?
From endocrine L cells of the small and large bowel
Release into circulation after meals
What does peptide YY do?
Inhibits food intake
What is co-secreted with peptide YY?
Glucagon-like-peptide-1 (GLP-1)
What does GLP-1 do?
Inhibits feeding
Enhances insulin secretion
Suppresses glucagon secretion
What releases neuropeptide Y?
Neurons that extend from arcuate nucleus to the paraventricular nucleus
What stimulates secretion of neuropeptide Y?
Low leptin and insulin levels
What does neuropeptide Y do?
Stimulates food intake
When is there a rapid increase of neuropeptide Y in the PVN?
Before mealtimes and they remain elevated as long as food is withheld
How does neuropeptide stimulate feeding?
Through activation of Y1 and Y5 receptors
How does AgRP increase food intake?
Through antagonism of the melanocortin MC3 and MC4 receptors and thus block action of anorexigenic agonist alpha-MSH
Are the effects of AgRP short- or long-lived?
Long-lived
Where is AgRP exclusively found?
In neurons of arcuate nucleus
What do virtually all AgRP neurone co-secrete?
Neuropeptide Y
What are neuropeptide Y/AgRP neurons inhibited by?
Leptin
Insulin
What are neuropeptide Y/AgRP neurons activated by?
Ghrelin
What does alpha-MSH stand for, and what is it also known as?
Alpha-melanocyte-stimulating hormone, also known as alpha-melanocortin
What stimulates the release of melanocortin?
Leptin
What does melanocortin do?
Inhibit food intake
What are melanocortins derived from?
Precursor molecule proopiomelanocortin (POMC)
What does POMC give rise to in the anterior pituitary?
ACTH
What does ACTH do?
Stimulates adrenal steroidogenesis
What is co-expressed with POMC in the arcuate nucleus?
cocaine-and-amphetamine-regulated-transcipt (CART)
What are classed as anorexigenic peptides?
CART
alpha-MSH
In regards to serotonin, what drugs cause reduction in feeding?
Drugs that inhibit reuptake of serotonin or agonists of 5-HT receptors
In terms of regulating appetite, what are the 3 important subregions of the hypothalamus?
Lateral
Ventromedial
Arcuate nucleus
What region of the brain is thought to “know” your weight set point?
Lateral hypothalamus
What does a lesion of the lateral hypothalamus cause?
A decline in body weight
