Gut hormones in Addiction Flashcards
What are the key factors involved in regulating eating behaviour?
External cues (sight, smell, taste)
Internal cues (hormones, autonomic nervous system, gut and fat tissue)
Psychological cues (eating behaviour, reward sensitivity, food preference).
This system is under homeostatic control.
What are some brain regions activated in response to food cues?
Amygdala- emotional respones.
Nucleus accumbens- reward expectancy, motivation ,drive
Dorsal striatum- habitual behaviours, learned association
Insula- taste cortex, decision making, multimodal integration.
Orbitofrontal cortex- salience. Repeated food tastes less pleasant as its activation decreases.
How do you measure food responses?
fMRi, measure CBF.
Show photos of healthy and unhealthy food. (low energy and high energy).
Rate how appealing the pictures are.
You can see network of activation and identify regions of interest (ROIs).
What were the ROIs identified?
Orbitofrontal cortex Amygdala Nucleus accumbens Putamen Anterior insula Caudate
What is the food reward in obesity?
In response to food cues, people with obesity have heightened response.
Giving the food gives less activity with a higher BMI in the dorsal striatum and caudate.
The ability to suppress desire is impaired.
Different studies show different activation in obese vs thin patients.
What were the problems with the review that said obesity is not a measure of food reward?
BMI is not a measure of adiposity.
Not a measure of hormonal mediators.
There is heterogeneity of obese phenotype.
BMI not a behavioural measure
Source of obese patients
Nutritional state (fasted/fed)
Inter- individual differences in food preference
What are some criteria for food addiction?
Substance taken in larger amount and for longer period than intended.
Persistent desire to quit/
Important social activities reduced.
Tolerance
Withdrawal symptoms (taken substances to relieve withdrawal)
Clinical significant impairment or distress.
How would you assess food addiction?
Yale food addiction scale. 25 questions.
What was found on a study in imaging the brain in people with high scores on the scale?
In anticipation of receiving a chocolate milkshake, there was increased activation in the vmPFC and amygdala.
Are we unnecessarily medicalising food addiction?
Finlayson considered addiction as just hedonic overeating- that is just a summation of various eating disorders- emotional eating, uncontrolled eating, binge eating, hedonic heating. We NEED food to survive, but we don’t need drugs to survive.
What is the difference in food bias when you are fasted?
You are biased towards high energy foods- it gives an increased activation signal.
How does the brain know you have eaten?
Hormones.
Peripheral signals when you eat from intestine- PYY, GLP-1.
Increased weight- leptin increases.
Losing weight- leptin and hormones go down.
Fasting- ghrelin increases.
These signals are proportional to the amount we have eaten. Act on brainstem/hypothalamus/indirectly through vagus nerve?
THESE CIRCUITS ALTER THE RESPONSES TO FOOD CUES.
What is the action of injected ghrelin and GLP-1?
Ghrelin mimics fasting, and increases brain hedonic response to food- increases appeal.
Giving GLP-1 reduced response to food cues.
What was the effect of gastric bypass and banding surgery?
Bypass had a large effect on weight loss. Bypass stomach- undigested food straight to small bowel, so huge increases in PYY and GLP1. Less response to food cues and activation in response to taste compared to banding patients.
Banding had a lower effect- increases vagal signals by stretching stomach.
How did somatostatin work?
Supposed to supress PYY and GLP-1, to reverse the bypass the procedure.
Went down more in the bypass than the banding because they were higher in the bypass. Increased reactivity and appeal of food cues.
Therefore you can reverse the reduced food reward.
