Sapolsky Chapter 5

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Sapolsky Chapter 5

• Ulcers, the Runs, and Hot Fudge Sundaes

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Stress food consumption

• Usual effect of stress on digestion Shut down
  all of the above.
• BUT 2/3s of people under stress eat MORE than
  usual (hyperphagic)
• 1/3 eat less (hypophagic).
• Rats respond similarly.

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Stress food consumption

• Timing is everything!
• CRH (from hypothalamus ? ant. pit.) tends to
  suppress food intake.
• Also transmitter in brain ? SNS
• CRH is released within seconds of a stressor,
  continues during stressor, and is cleared within
  minutes after stress ends.
• Effects on body are rapid.

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Stress food consumption

• ACTH ? glucocorticoids (GCs) ? increase appetite.
• GCs released within minutes of stressor,
  continue during stressor work for hours may
  take hours to be cleared.
• GCs work, in part, by decreasing brains
  sensitivity to leptin (a hormone from fat cells
  that decreases appetite).
• Endorphins (from ant pit) also increase appetite.

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The mouse on the right lacks leptin receptors.
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Stress food consumption

• Therefore, GCs would not mediate the stress
  response, but the RECOVERY from stress.
• Timing
• Constant stress (CRH may win ? decrease appetite)
  
• Repeated intermittent stressors (GCs around for a
  long time after each stressor ? increase appetite)

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Stress food consumption

• Individual differences
• How much GCs secreted with each stressor?
• How long does liver take to break GCs down?
• Elissa Epel GC hypersecreters eat more after
  stress.
• Also crave sweets.
• High-CG responders dont have higher GCs, or eat
  more, when NOT stressed.
• Normally restrained eaters more likely to overeat
  in response to stress.

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GC hypersecreters eat more after
stressespecially sweets.
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Apples pears

• GCs increase storage of fat, especially in
  abdomen (visceral fat) ? apple shape.
• Waist-to-hip ratio is greater than 1.
• Abdominal fat cells more sensitive to GCs than
  those around hips (gluteal fat ? pear shape).
• GCs increase abdominal fat storage only in
  presence of high insulin sign of recovery phase.

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Apples pears

• Apple shape is bad news!!
• Fat released from abdominal fat cells ? liver ?
  converted to glucose ? hyperglycemia insulin
  resistance
• Fat from gluteal fat cells ? evenly distributed
• GC response in apples is longer than in
  pears.

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Mary Dalman starchy comfort food decreases
stress response. Operant conditioning!
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Energy mobilization during a stressor

• In mammals 10 23 of energy is spent on
  digestion.
• Mouth Breaks down food mechanically.
• Stomach Breaks down food mechanically.
• The muscle walls contract violently on one side
  of your stomach, and hunks of food are flung
  against the far wall, breaking them down in a
  cauldron of acids and enzymes.
• Intestines Snake dance of peristalsis

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Stomach contracts 3/minute
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Energy mobilization during a stressor

• Increase SNS and decrease PNS activity
• Shut down digestion
• Saves energy
• Diverts blood to muscles, heart, brain

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Bowels in an uproar

• Much of what we eat cannot be digested.
• Dead weight!
• Get rid of it!
• SNS decreases activity in stomach and small
  intestine, but INCREASES muscle movement in large
  intestine.
• Diarrhea not enough time to absorb H2O.

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Stress and functional GI disorders

• No obvious organic cause
• Irritable bowel syndrome
• Ulcers

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Irritable bowel syndrome

• Abdominal pain, diarrhea, bloating, constipation
• Constipation???
• Disorganized contractions?
• Small intestine shuts down?
• May be due to excess sensitivity to stress
• Greater GC response to standard stressor
• Less sensitive to cutaneous pain, more so to
  visceral pain
• No excess contractions during sleep

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Irritable bowel syndrome

• Hypersensitive gut can stimulate SNS ? vicious
  circle!
• Traumatic stress early in life ? vulnerable to
  IBS in adulthood

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Irritable bowel syndrome

• BUT not all studies find a link between stress
  and IBS. WHY?
• Severity of symptoms and intensity of stressors
  wax and wane.
• Many studies are retrospective, not prospective
• Stressors that increase risk may have been years
  before
• IBS may be a hodge-podge of diseases with
  multiple causes.

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These foods make IBS worse.
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Ulcers

• Ulcer hole in the wall of an organ
• In stomach or organs immediately bordering it
  peptic ulcer
• Observed by Selye
• In stomach itself gastric ulcer
• In esophagus esophageal ulcer
• In duodenum duodenal ulcer
• Most common

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Ulcers

• Occasionally ulcers form rapidly, when stress is
  overwhelming.
• Massive hemorrhage or infection, burns, trauma
• More gradual ulcers due to stress???

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Ulcers

• Revolution Helicobacter pylori (Hp)
• Robert Warren Barry Marshall bacterium causes
  ulcers
• Nearly laughed out of the room!!
• How could bacterium live in acidic stomach?
• Hp caused ulcers in mice.
• Swallowed Hp bilge himself ? gastritis!
• Others tried to prove him wrong, but proved him
  RIGHT!!

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Helicobacter pylori
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Ulcers

• Hp contributes to 85-100 of ulcers stomach
  cancer in Western countries.
• May be most common bacterium.
• Found in 100 of people in developing world.
• Acid-resistant structure, wrapped in bicarbonate
  coat
• Lives in stomach wall ? gastritis
• Ulcers now treated with antibiotic.

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Ulcers

• BUT up to 15 of duodenal ulcers are in people
  w/o Hp.
• Also, only 10 of those with Hp get ulcers.
• Other factors alcohol, aspirin, smoking, genes
• Stress!
• 2X 3X increase in ulcers
• Even controlling for life-style factors

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Ulcers

• Combination of Hp, lifestyle, and stress
• Ulcers if you have a lot of any one factor.
• Also true for rats, as long as there is at least
  some Hp.

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Why doesnt your stomach digest itself?

• Thick coating of mucus
• Mixed with bicarbonate to neutralize acid
• Bicarbonate 2-10 of the maximum rate of acid
  secretion.
• Walls are thick and multi-layered .

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Cross section of stomach lining
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How does stress ? ulcers?
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Acid rebound

• During prolonged stress digestion shuts down.
• Decreased acid release
• Decreased mucus
• Decreased thickness of stomach lining
• Celebrate end of stress ?
• PNS rebounds ? lots of acid in less-protected
  stomach Hp ? ulcer.
• Ulcers form AFTER stress, not during it.

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Decreased blood flow

• Cant flush away the acid
• Cant produce scavengers for free radicals
• Products of oxidative metabolism
• Stress is over, blood flow returns ? increased
  oxidative metabolism ? increased oxygen radicals
  ? increased damage.
• Damage occurs AFTER stress
• Like acid rebound

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Immune suppression

• Stress inhibits the immune system
• ? Hp thrives ? ulcers

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Insufficient prostaglandins

• Prostaglandins increase blood flow.
• GCs inhibits synthesis of prostaglandins.
• Stomach cant heal micro-ulcers.
• Aspirin inhibits prostaglandin formation.
• May be why high doses of aspirin ? ulcers.

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Stomach contractions

• Stress ? slow waves of stomach contractions
  (1/min).
• May cause structural damage, if theres no food
  in stomach.
• Stress doesnt cause peptic ulcers to form.
• But it intensifies the probability or virulence
  of biological villains that do cause ulcers.
• It also impairs defense mechanisms.