Ghrelin, Glucagon like peptide-1, Leptin Flashcards
Permissiveness
- A hormone that has no effects on a specific function but will enhance the effects of another hormone with moderate effects on that function
Ex. TH has a permissive action on epinephrine effects on fatty acid release
Additive actions
Responses to multiple hormonal inputs may be additive (glucagon and epinephrine) when the combined effect is equal in magnitude to the sum of effects of both hormones
1+1=2
Synergistic
The net effect is much more than the combined individual effects of each of the hormone involved
Ex. Glucagon + epinephrine + cortisol (1+1+1= 5, not 3)
Reinforcement
The same hormone acts on multiple tissues to exert actions that produce a common effect
Ex. Cortisol acts on muscle, adipose tissue and liver to increase glucose production. By acting on muscle and adipose, it is further increases liver glucose production (hepatic actions on glucose production are reinforced!)
Push-pull mechanism
The same hormone acts on two cells/tissues with opposing roles to elicit a magnified, rapid, response that is required. Additionally, it also acts directly to accelerate that effect
Ex. Epinephrine inhibits the insulin secretion from beta cells, while increasing glucagon production from alpha cells. This causes glucose production from liver. Also, epinephrine acts directly on the liver to increase glucose output.
Divergent functions
Same neurotransmitter elicits different functions depending on its target receptor and/or signaling molecules
Ex. Norepinephrine binding to different receptors can result in different effects on the ion channels of cells
Convergent functions
Multiple neurotransmitters and hormones act via different receptors and same or different receptors-mediated mechanisms to affect a common function
Ex. GABA and acetylcholine act on different receptors but eventually have the same effect by increasing intracellular potassium levels
Metabolic hormones with both divergent and convergent manner
Convergent: Insulin, IGF-1 and GH are counter regulatory hormones in terms of glucose and lipid metabolism, but there act convergently on protein metabolism
Divergent: GH acts via different signaling pathways to cause divergent effects on metabolism, cell proliferation, differentiation, or development
Where is ghrelin produced?
stomach
Metabolic actions of Ghrelin
- Stimulates food intake in the brain
- White Adipose tissue: Increases lipogenesis, decreases lipolysis and lipid oxidation
- Brown adipose tissue: decreases thermogenesis
- Pancreas: insulin secretion, decreases insulin sensitivity
- Liver: increases gluconeogenesis, glycogenolysis, hepatic lipid storage
- Stomach: increases gastric acid secretion and gastric emptying
GLP-1 metabolic actions
Stomach
- Decreases gastric emptying and acid secretion
Pancreas
- Increases insulin secretion/biosynthesis, somatostatin, beta-cell proliferation,
- Decreases glucagon secretion and beta-cell apoptosis
Gut
- Increases growth
- Decreases motility, lipoprotein secretion
Liver
- Decreases steatosis, VLDL and glucose production
WAT
- Increases perfusion, lipolysis, glucose uptake
BAT
- Increase thermogenesis
Skeletal muscle
- Increases perfusion and glucose uptake
Trulicity
A once a week GLP-1 analogue for type 2 diabetes treatment in humans
- Alters chain to increase half-life of GLP-1
Leptin (adipose tissue)
- Directly proportional to white adipose tissue mass
- Decreases appetite, increases energy expenditure and FA oxidation, causes changes in circulating hormones
- Obesity still occurs due to leptin resistance (despite high circulating leptin)
