Physiology of feeding Flashcards
Name some consequences of Obesity?
Metabolic syndrome Central obesity Dyslipidemia Insulin resistance Type 2 Diabetes Cardiovascular disease
What does BMI =?
Weight/square of height
What is an overweight BMI?
25 - 29.9
What is an obese BMI?
30 - 39.9
What is a morbidly obese BMI?
40 or over
What does severe obesity by the age of 20/30 do?
shortens life by
13 years for men
8 years for women
What does long term obesity increase the risk of?
Stroke Dementia Respiratory Diseases (sleep apnoea) Heart Disease Gallbladder disease Osteoarthritis Diabetes Cancer Hyperuricemia Gout NAFLD (fatty liver)
What is brain reprogramming and what is it caused by?
Your brain views the extra weight (fat) as normal & dieting as threat to body survival
i.e. defends new weight
Caused by: long term obesity
How does the CNS influence body weight and energy levels?
Integration of:
- Behaviour - feeding and physical activity
- ANS activity - regulates energy expenditure
- Neuroendocrine system - secretion of hormones
What is the neural site responsible for the CNS influences?
Hypothalamus
What is the site of integration?
Brain
What is Satiation?
sensation of fullness generated during a meal
signals increase during meals
What is Satiety?
period of time between termination of one meal and the initiation of next
What is Adiposity?
state of being obese
What tells the brain how much you are eating?
Peptides - act on vagal afferents
Name some Satiation signals?
Cholecystokinin (CCK) – secreted from enteroendocrine cells in duodenum and jejunum. Released in proportion to lipids and proteins in meal. Inhibits gastric motility, slows emptying and reduces food intake (Hypo).
Glucagon-like peptide 1 (GLP-1) – product of pro-glucagon gene. Also released from L cells in response to food ingestion. Inhibits gastric emptying and reduces food intake (Hypo, NTS)
Oxyntomodulin (OXM) – Also from pro-glucagon gene and released from oxyntic cells of small intestine after meal. Acts to suppress appetite.
Obestatin – peptide produced from gene that encodes ghrelin and released from cells lining stomach/small intestine. Suggested to reduce food intake – may act to antagonise the actions of ghrelin.
What is Ghrelin?
Octanoylated peptide, produced and secreted by oxyntic cells in stomach. Ghrelin levels increase before meals and decrease after meals.
Levels are raised by fasting and hypoglycaemia
Peripheral ghrelin stimulates food intake (Hypo) and decreases fat utilization
Signals are sensed in the hypothalamus
What drugs increase food appetite/intake?
Glutamate
Gaba
opioids
- increase food intake when injected into hypothalamic centres
What drugs decrease food intake/appetite?
Monoamines act to suppress food intake - many drugs developed to act on these systems
Which 2 hormones report fat status to the brain? (adiposity signals)
Leptin - made & released from fat cells
Insulin - made & released from pancreatic cells
What is the mechanism of Leptin and Insulin?
Levels in blood increase as more fat is stored
Inform brain (hypothalamus) to alter energy
balance - eat less and increase energy burn
This malfunctions in obese state
What can neuron specific deletion of the leptin receptor (Ob-Rb) result in?
Obesity
Where are insulin and leptin receptors found?
hypothalamus
What family is leptin a family of?
Cytokine
What pathway is affected by drug abusers as well as adictive things like chocolate?
Dopamine pathway
What drug is used to treat obesity/cause weight loss?
Orlistat - Inhibits pancreatic lipase decreasing triglyceride absorption
What are the side effects of Orlistat?
cramping and severe diarrhoea
What other treatments work?
Bariatric Surgery:
Gastric by-pass surgery
What are thermogenic adipocytes?
increase energy expenditure uncoupling of oxidative metabolism from ATP production
- function of uncoupling protein 1 (UCP1) which accelerates fuel oxidation and produces heat and therefore weight loss
