Hunger, fat and obesity Flashcards
- Physiology of feeding and satiety: Prof M Ashford
What is energy homeostasis?
Physiological process whereby energy intake is matched to energy expenditure over time, it promotes body fuel stability, energy primarily stored as fat
Body mass index BMI =
weight (kg) / height squared (m)
What effect does obesity have on the brain?
It reprogrammes the brain to defend the new higher weight as the base line and defends against weightloss as if it is a threat to survival.
contols weigh via behaviour, ANS (reguates energy expenditure) and neuroendocrine system
What is satiety?
period of time between termination of one meal and the initiation of next
What is adiposity?
the state of being obese
What is the function of leptin and insulin?
Inform brain (hypothalamus) to alter energy balance - eat less and increase energy burn there are malfunctions of these hormones in the obese state
What is the function of cholecystokinin (CCK)?
- secreted by enteroendocrine cells in duodenum and jejunum
- released in proportion to the amount of lipids and proteins in a meal
- signals via the sensory nerves to the hindbrain specifically the nucleus of solitary tract
What is the function of Peptide YY (PYY3-36)?
- secreted from endocrone mucosal L-celld og the GI tract
- levels rapidly increase after a meal
- it inhibits gastric mobility, slows emptying and reduces food intake
What is the function of Glucagon-like peptide 1 (GLP-1)?
- a product of pro-glucagon gene
- released from L cells in response to food ingestion
- inhibits gastric emptying and reduces food intake
What is the function of Oxyntomodulin (OXM)?
- from pro-glucagon gene – released by oxyntic cells and L cells of the small intestine after a meal
- suppresses appetite the mechanism of this is unknown
What is the function of Obestatin?
- produced from the gene which codes ghrelin
- released by the cells lining the stomach/ small intestine
- thought to reduce food intake, may act to antagonise the actions of ghrelin but it’s actions are unknown
What is gherlin?
- an octanoylated peptide, it is produced and secreted by oxyntic cells in the stomach
- Gherlin levels increase before meals and decrease after
- hypoglycaemia and fasting increase levels
What is the effect of peripheral gherlin?
It stimulates food intake
decreases energy expenditure
decreases fat utilization (also thought to increase lipogenesis and decrease lipid oxidation)
increases body weight
What are the 2 central appetite controllers?
Glutamate - increase food intake when injected into hypothalamic centres - the effect is modest and short lasting
Monoamines - suppress food intake
What are the hormones which report fat status to the brain and where are they released?
Leptin - made and released from fat cells
Insulin - made and released from pancreatic beta cells
The levels of these hormones increase as more fat is stored and they inform the hypothalamus to eat less and burn more
