7.9 Appetite Regulation by Gut Hormones Flashcards
What is satiety
The satisfied feeling of being full after eating. Early satiety is feeling full sooner than normal or after eating less than usual
Where in the brain is appetite regulation controlled
The main brain regions responsible for the regulation of appetite and food intake are the hypothalamus and brain stem.
Describe the short term control of food intake
Short term episodic signalling that is mainly mediated by the GI
Describe the long term control of food intake
Long term tonic signalling primarily from adipose tissue, using signalling molecules such as insulin, leptin, adiponectin and resistin
What are orexigenic hormones
Hormones that increase hunger and reduce satiety
What are anorexigenic hormones
Hormones that reduce hunger and promote satiety
What are the main gastrointestinal hormones involved in appetite regulation
peptide YY, cholecystokinin (CCK), ghrelin and glucagon like peptide 1 (GLP-1)
Describe cholecystokinin (CCK)
CCK is produced in the I cells in the duodenum and jejunum and secreted in response to luminal nutrient intake (mostly fats). CCK promotes feelings of satiety by delaying gastric emptying, increasing pancreatic enzyme secretion and reducing food intake.
Describe peptide YY
Peptide YY is a satiety hormone whose anorexigenic effects are attributed to delayed gastric emptying, this is dose related and dependent on the amount of fat in the meal. PPY is part of the pancreatic polypeptide family. It acts on the hypothalamus and the gut.
Describe GLP-1
GLP-1 is produced and secreted by the L cells of the distal small intestine and NTS of the brainstem in response to an ingested meal. This hormone influences glucose homeostasis by increasing insulin secretion and suppressing glucagon secretion in a glucose dependent manner. GLP-1 also slows the rate of gastric emptying, this slows nutrient absorption and contributes to the reduction of post prandial glycaemia. This all enhance satiety
Describe ghrelin
Ghrelin is an orexigenic hormone influencing appetite and energy homeostasis. It is produced chronically in the unfed state, primarily in the stomach. Ghrelin circulating in the blood is present as mostly unacylated ghrelin and some acylated ghrelin. It’s concentration peaks in response to fasting and anticipation of the coming meal and there is a drop in ghrelin after eating. It works in opposition to satiety hormones to increase the rate of gastric emptying and increase hunger
Describe the satiety cascade
Satiety hormones have effects on appetite at a range of time frames and locations.
They targets sensory mechanisms like smell, taste, temperature and texture of the food, inhibiting eating in the short term.
They also target cognitive mechanisms affecting beliefs towards food, inhibiting eating in the short term.
They also have affects post ingestion, altering gastric distension, gastric emptying and release of hormones.
They also has post absorptive effects, with mechanisms arising from the metabolism of glucose, fats and amino acids after absorption into the blood stream.
What is gastric emptying
Gastric emptying refers to the rate at which food empties from the stomach, it also plays an important role in the control of gastric distension, supply of nutrients to the small intestine and hence satiety. Increasing the calorie content of the meal lengthens gastric emptying times. Satiety and food intake are closely related to gastrointestinal transit
Describe how the gut microbiota helps to modulate energy balance
Metabolites and microbial products from the microbiota act as signalling molecules that modulate appetite, gut motility, energy uptake and storage and energy expenditure. The gut communicates with the brain via blood borne substances or spinal and vagal nerves, the signalling from the gut can alter peptide YY and GLP-1 levels.
Give an example of the gut microbiota modulating energy balance.
Short chain fatty acids produced by fermentation from bacteria interact with the GPR41 receptor to stimulate the secretion of PPY from enteroendocrine cells and stimulate the secretion of leptin from adipocytes
