Energy Balance Flashcards
the system that controls energy balance involves
- long and short term signals (signals from gut and adipose tissue) that inform the brain of energy status
- brain centers that integrate information
- response: regulation of hunger intensity and energy expenditure
this systems essential role is….
to prevent starvation
how does this system prevent starvation?
ensuring adequate energy intake to compensate for the energy requirements of basal metabolism, physical activity, growth and reproduction
- is biased towards preventing energy deficiency vs preventing excess energy storage
t/f: weight loss makes you predisposed to weight gain
true
signals informing of energy status - insulin
promotes nutrient uptake and storage in peripheral tissues (adipose, skeletal muscle, liver)
- also in the brain: suppresses appetite/increases energy expenditure (but does not regulate brains glucose uptake)
CCK
cholecystokinin
- regulates digestion and reduces appetite
- enteroendocrine cels in duodenum (induced by HCL, amino acids, fatty acids)
- released in response to food
GLP-1
glucagon like peptide
-promotes insulin secretion, reducing glucagon (reducing appetite)
-enteroendocrine cells in ileum/colon in response to nutrients
peptide YY
increases water/electrolyte absorption in colon, reduces appetite
- enteroendocrine cells in ileum/colon in response to fats
CCK, GLP-1, PYY, and ghrelin from the GI tract
peptide hormones with G-protein coupled receptors; exert short-term effects; affect satiation (feeling of fullness)
ghrelin
- hunger hormone
- increases appetite; also stimulates GH release and other effects (reward cognition)
- enteroendocrine cells primarily in stomach (stimulated by fasting, incr, immediately before a meal; suppressed by eating)
leptin
167 aa hormone secreted by white adipose tissue (circulating leptin levels correlate with fat mass)
- suppresses appetite ( among other things - also affects reproductive function, metabolism, inflammation/immune system, etc)
leptin is a ____ of energy stores:
long term indicator, doesnt change with meals, or acutely affect meal size; decreasing leptin levels indicate a negative energy balance/diminishing fat stores, which leads to compensatory responses to replenish these stores
leptin 1950’s
discovery of obese mouse strain with mutant ob gene (increase food intake, obesity, elevated insulin - model of type 2 diabetes)
leptin 1965:
another genetically obese mouse strain bed, with mutation in db gene (same characterisitcs)
leptin 1994
ob gene mapped (expressed in adipose tissue); leptin ‘discovered’
ob/ob mutant mice
food intake/obesity/insulin levels normalize with blood from wild type
db/db mice
must lack a circulating factor (leptin) that controls these phenotypes
db/db mutant mice
high levels of this circulating factor,but cant respond to it; leptin resistant (no receptor)
leptin receptor
- a cytokine receptor
- ligand binding/receptor homodimeriztion leads to JAK2 recruitment and ultimately the activation of STAT3
1994 leptin discovered…
great hope as an anti-obesity treatment
in most cases obese people already have…
high circulating leptin levels, and do not respond to additional exogenous leptin (appear to be leptin resistant)
genetic leptin deficiency is very
rare
hormones indicating energy status:
receptors in hypothalamus and or vagus nerve
two adjacent groups of neurons in _____ of the hypothalamus act as ______
arcuate nucleus, primary site for integrating these inputs (have receptors for gut/adipose tissue)
