Regulation
Glucose levels in the blood need to be kept in homeostasis at a certain range a few hormones: insulin, adiponectin, glucagon and adrenaline. These work to enable glucose to be taken into cells when needed and produced when needed too.
- Insulin and adiponectin are hypoglycaemic (cause fall in blood glucose)
- Glucagon, adrenaline, cortisol, and growth hormone are hyperglycaemic (cause rise)
Insulin and glucagon rise and fall to meet the needs of the body, keeping glucose within correct levels and allowing nourishment of the cells. After a meal glucagon drops as there is a spike in glucose and insulin rises to tell cells to fill themselves up.
Factors which alter production
There are a variety of effects that lead to changes in production of insulin but the big one is blood sugar. if glucose if over 5mmol/L-1 or if there is amino acids circulating (ffas too to a degree) insulin production will be stimulated.
Adrenaline and glucagon inhibit insulin production some gut hormones (like incretins or CCK) increase insulin production with glucose production.
Incretins
Incretins are hormones which are released from the gut and have several effects. You may know examples like GLP-1 and Gastric Inhibitor Peptide.
Insulin effects
Insulin promotes GLUT4 expression in muscle and adipose increasing glucose uptake and it promotes glycogen synthesis in the liver and muscle and lipogenesis in the adipose and liver.
It promotes glucose utilisation and inhibits gluconeogenesis, glycogenolysis, and lipolysis.
It stimulates lipoprotein lipase to promote splitting tags into FFAs and inhibits hormone sensetive lipase.
It promotes amino acid uptake and protein synthesis.
Adiponectin
Glucagon
This opposes the effects of insulin, and is triggered by low glucose, it binds to glucagon receptors on liver and adipocyte cells. Often does the opposite of insulin but not always. Its main job is to make sure there is enough glucose in the blood for the brain and RBCs.
glycogon
- promotes glycogenolysis and lipolysis
- promotes gluconeogenesis
- inhibits glycogen synthesis and glycolysis in liver
- inhibits lipogenesis in adipose
Adrenaline
This has similar effects ot glucagon but it also acts on muscle cells.