GI Exam 2 - Regulation of Food Intake

Ovreweight + Obesity

Results from greater energy intake than energy expenditure - we override control mechanisms When greater quantities of energy (in the form of food) enter the body than are expended, body weight increases Patients with a BMI between 25 and 29.9 are considered overweight, but not obese - 50-60% of population An individual is considered obese when weight is 20% (25% in women) or more over the maximum desirable for their height - BMI ≥ 30 - 30% of population When an adult is more than 100 pounds overweight, it is considered morbid obese - BMI ≥ 40 - 1% of population Underweight just as serious a problem - BMI ≤ 24

Cachexia

Metabolic disorder of increased energy expenditure leading to weight loss greater than that caused by reduced food intake alone. Anorexia and cachexia often occur together in many types of cancer or in the "wasting syndrome" observed in patients with acquired immunodeficiency syndrome (AIDS) and chronic inflammatory disorders.

aphagia, hyperphagia

Ventromedial Hypothalamus - Satiety Center Stimulation causes complete satiety or nutritional satisfaction - animal refuses to eat (______________) Bilateral lesions causes marked _____________ and extreme obesity Acts by inhibiting the hunger/feeding center

Anorexia

A reduction in food intake caused primarily by diminished appetite, as opposed to the literal definition of "not eating." Important role of central neural mechanisms in the pathophysiology of anorexia in diseases (e.g., cancer) when other common problems (e.g., pain, nausea) may also cause a person to consume less food

Genetic,

Causes of Obesity: - Energy Intake > Energy Output - Decreased physical activity; sedentary lifestyle - Abnormal feeding regulation - Childhood overeating → once fat is deposited, obesity will be maintained by normal food intake - ____________ - altered set point; fat chemistry (20-25% of cases) - Environmental factors - Psychological - Neurogenic Morbid Obesity: hypothalamic/brainstem lesions (tumors, etc) - rare Functional reorganization of brain centers - more likely Abnormality of neurotransmitters or receptor mechanisms in neural pathways

Appetite

Complex; implies the desire for a specific type or quality of food Includes the desire to eat even when hunger has been appeased

adipose mass, leptin

Long Term Control: Activated if short-term regulators fail & body weight deviates out of acceptable range ___________________ - most likely regulated factor; search is for a signal proportional to adipose mass and has central effects on feeding Hypothalamus senses energy storage via actions of peptide hormone, ________, which is released from adipocytes

TG, size

Long Term Regulation: Feedback Signals From Adipose Tissue Body fat (especially ___) stores regulated variable and any deviation --> change in feeding behavior Hypothalamic receptors monitor and regulate circulating levels of fat metabolites (fatty acids, glycerol, 3-hydroxybutyrate) which signal _______ of body fat stores Increase or decrease in size of fat stores causes compensatory hypo- or hyperphagia and change in metabolic rate to restore body fat stores to normal size

glucose, AA, Lipids, temp, adipose

Long term regulation - maintenance of normal quantities of energy stores in body - Blood concentrations of ______________, _______, _______________. - ___________________ regulation - Feedback signals from ___________ tissue

NPY (Neuropeptide Y) AGRP (Agouti-related protein)

Nuerons + nt in Hypothalamus: Stimulate Feeding & Decrease Energy Expenditure - ________________ - ________________

POMC (Pro-opiomelanocortin), CART

Nuerons + nt in Hypothalamus: Inhibit Feeding & Increase Energy Expenditure - _____________ - Alpha-melanocyte stimulating hormone - _____________________

adiposity

Regulation of Body Weight:Body is concerned with regulation of ________________.

Hunger Hormones

- Agouti-related peptide (AGRP) - Neuropeptide Y (NPY) - Ghrelin - Melanin Concentrating Hormone (MCH) - Orexins A & B - Endorphins - Galanin (GAL) - Cortisol - Amino acids (glutamate and γ-aminobutyric acid - Endocannabinoids

Leptin, insulin CCK

Hormones that regulate appetite: ____________,______________, ___________, ghrelin

Satiety Hormones

- Leptin (via ↓ NPY) - Insulin - Cholecystokinin (CCK) - alpha-Melanocyte Stimulating Hormone (product of POMC) - Corticotropin-releasing hormone (CRH) - Peptide YY (PYY) - Glucagon-like peptide (GLP-1) - Serotonin - Norepinephrine - Bombesin (GRP) - Cocaine and amphetamine-regulated transcript (CART)

Anoxreia

Aversion to eating May be due to a psychological or pathological abnormality

controlled

Body weight set point/range changes readily with changes in physical activity, dietary composition (high fat diet), emotional state, stress, pregnancy, etc. - not strictly ________________.

Hunger

Craving for food; objective or physiological awareness of the need to ingest food; associated with Objective sensations, such as malaise, restlessness, hunger contractions in stomach Subjective sensations due to low levels of nutrients in blood

LH

Feeding/Hunger Center -Without it would lack hunger

filling, satiety, GI, Adipose, cerebral

Hypothalamus receives signals from GI tract: - Sensory information about gastric ____________ -Chemical signals from nutrients in blood that signal ___________: glucose, amino acids, fatty acids - Signals from _____ hormones, hormones from ______________ tissue - Signals from ____________ cortex: sight, smell, taste

thyroid, adrenal islet

Influence secretion of several hormones important in regulating energy balance and metabolism, - _____________ gland - _____________ glands - Pancreatic ________ cells

Protein

Intermediate & Long Term Regulation: Aminostatic (_______________) Theory - levels of amino acid precursors (tryptophan, tyrosine, choline) can affect formation of their respective products such as SEROTONIN, CATECHOLAMINES, and ACH. -These neurotransmitters may be critical to the central regulation of feeding and satiety - Very potent satiating nutrient

Lipostatic

Intermediate & Long Term Regulation: ________________ Theory - Increasing plasma fatty acid levels while eating stimulates the satiety center - Hypothesis is supported by discovery of LH neurons that are sensitive to the application of free fatty acids - Least potent satiating nutrient despite CCK release

Glucostatic

Intermediate & Long Term Regulation: _____________________ Theory - glucose utilization is an important regulator of hunger - High blood glucose and/or high level of glucose metabolism stimulates the satiety center - There are insulin-dependent, glucose-sensitive neurons (glucostats) in the hypothalamus - Inter-meal --> low glucose use of neurons --> hunger --> eating until satiety signals terminate feeding when glucose use becomes high

overeat, undereat

Intermediate & Long Term Regulation: Interrelation between body temperature and food intake - When an animal is exposed to cold, it tends to ________________: Increase metabolic rate, provide fat for insulation - When animal is exposed to heat, it tends to ____________. Caused by interaction within the hypothalamus between the temperature-regulating system and the food intake-regulating system

Hyperphagia, anorexia, tonically

Lateral hypothalamus (Hunger/Feedign Center) Stimulation causes voracious eating (__________________) Bilateral lesions cause disinterest in food and weight loss (__________________) leading to inanition. Weight loss, muscle weakness, decreased metabolism Directly excites the emotional and motor drive for to search for food and controls amount of food eaten Excites brain stem centers controlling chewing, salivation, swallowing ________________ active; inhibited by stimulation of the satiety center

appetite, melaocortin intake, metabolic, insulin

Leptin Actions: Reduces food intake and lowers body weight via: - Reduction of NPY & AGRP→ ________________ suppression - Activation of POMC neurons → release of α-MSH and activation of ______________ receptors - Increase in CRH → ↓ food __________ - Increased SNS activity → ↑ _____________ rate - Decreased __________ secretion → ↓ energy storage

receptors

Most obese individuals have leptin levels proportionate to body mass, so feedback flaw may involve _____________ or other mechanisms that prevent normal adjustment in eating behavior Ratio of leptin levels in cerebral spinal fluid relative to serum levels lower in the obese

Inanition

Opposite of obesity characterized by extreme weight loss Can be caused by inadequate availability of food or by pathophysiological conditions that greatly decrease the desire for food, including psychogenic disturbances, hypothalamic abnormalities, and factors released from peripheral tissues.

PVN, DVN, Arcuate

Paraventricular, Dorsomedial & Arcuate Nuclei of Hypothalamus Major role in regulating food intake - Lesions of _______ - excessive eating - Lesions of _______ - depress eating - ________________ nuclei - sites in hypothalamus where multiple hormones released from GI tract & adipose tissue and nervous signals converge to regulate food intake & energy expenditure

Satiety

Postprandial levels that affect the interval to the next meal, regulating meal frequency Amount of food causing satiety depends, in part, on whether energy stores are full - nutritional satisfaction Influenced by learned habits

Satiation

Processes that promote meal termination, limiting meal size; opposite of hunger; feeling of fulfillment in the quest for food Results from ingestion of a meal in a normal individual

VMH

Satiety Center - Without it would be very much hungry

CCK, Glucagon, GRP, Leptin

Short Term control of satiety: Hormonal, Chemical Feedback: - ________ (fat) - _______________, Somatostatin - Bombesin (________) - ____________(?) - Effect lasts 2 hr

Gastrointestinal Filling

Short Term control of satiety: _______________________: Distension of stomach and small intestine (volume; mechanoreceptors) Effect lasts 1-2 hr

filling, CCK, PYY, GLP, Ghrelin

Short term regulation - prevents overeating at each meal - GI ____________/stretch - GI hormones: ______, _______, _______ - _______________ - Oral receptors

Leptin

Source - white adipose tissue Production by adipocytes at levels closely related to total body fat mass but link to gene expression elusive Circulates in blood, crosses blood brain barrier, binds to receptors at multiple sites in hypothalamus, especially POMC neurons of arcuate nuclei & PVN Down-regulated by decreased fat mass

Ghrelin

Source: - Primarily STOMACH fundus (parietal cells), small intestine - Minor amounts from kidney & pituitary, others Stimulus: - Decreased energy stores - Levels increase pre-prandial (fasting state), but not a "catalyst" to hunger - is a meal initiation signal - Gastric bypass surgery reduces levels - Level fall rapid by food intake - Injection stimulates food intake in animals - ? Orexigenic hormone

Anorexia, Bulemia

________________ - Abnormal psychic state in which a person loses all desire for food and even becomes nauseated by food _____________ - normal or over-intake of food. Abuse of laxatives, emetics. Bingeing and purging

Set point

________________ /range theory - any change in adiposity (not weight) is compared with an internally set standard for adiposity Feedback response relative to deviation from this set point Feedback elicits proportional metabolic or behavioral response, which opposes deviation from the set point Deviation of weight within an acceptable range above or below usual weight Maintenance of weight within this acceptable range can be controlled by dietary habits, short-term (meal-to-meal) regulation, or both Deviation of weight outside this acceptable range would initiate more potent, long-term regulatory systems instead of (or in addition to) the short-term regulators. Set point/range model - body tries to stabilize body weight or adiposity

Brain Stem

__________________: Mechanics of feeding; salivation, licking lips, chewing, swallowing

Prefrontal cortex, Limbic

____________________, or cortical areas of the ____________ system: Areas responsible for determining quality of food that is ingested - remembers previous unpleasant experience (e.g., food poisoning)

Hypothalamus

____________________: controls quantity of food intake and excites the lower centers to activity

Amygdala

_____________________: Some areas →↑ feeding, others ↓ feeding Bilateral destruction causes a "PSYCHIC BLINDNESS" in choice & quality