Efectos Metabólicos de la Insulina y el Glucagón Flashcards
four main tissues play a dominant role in fuel metabolism ?
liver, adipose, muscle, and brain
communication between tissues mediated by ?
nervous system, availability of circulating substrates, and variation in level of plasma hormones
integration of ENERGY METABOLISM integrated primarily by ?
two peptide hormones: insulin and glucagon (in response to changing substrate levels in the blood), with catecholamines epinepherine and norepinepherine (in response to neural signals) playing a supporting role
kind of metabolic effects of insulin ?
ANABOLIC !! e.g. synthesis of glycogen triacylglycerols (TAG’s) protein
insulin secretion is increased by ?
increase in glucose, amino acids, and gastrointestinal peptide hormones
explain the proportionality between glucokinase 4 phosphorylation activity and the concentration of glucose in the blood?
proportionality results from: 1) lack of direct inhibition of glucokinase by G-6-P, its product. 2) high Km (low affinity) of the enzyme that creates a sigmoidal relationship between velocity of the reaction and substrate concentration and endows hexokinase 4 its ‘glucose-sensing’ ability.
how exactly does glucose-dependent release of insulin happen in the blood?
it is mediated through a rise in calcium concentration in beta cells. glucose taken into beta cells is phosphorylated and metabolized –> ATP produced –> ATP-sensitive potassium (K+) channels close, causing depolarization of the plasma membrane, opening of voltage gated Ca+ channels and influx of Ca+ into the cell. Ca+ causes vesicles containing insulin to be exocytosed from the beta cell .
sulfonylureas are oral agents prescribed for diabetes type 2 patients. how do they function ?
they function by increasing insulin secretion by closing ATP-dependent K+ channels –> membrane depolarized –> voltage gated Ca+ channels open –> Ca+ influx causes insulin-cargoed vesicles to be exocytosed from the beta cell.
role of catecholamines in energy metabolism?
they call for rapid mobilization of energy-yielding fuels like glucose from the liver (via glycogenolysis or gluconeogenesis) and fatty acids from adipose tissue (via lipolysis).
primary metabolism regulator in case of emergency ?
the sympathetic nervous system takes over regulating blood glucose concentration during emergencies e.g. fight or flight rather than peptide hormones insulin and glucagon.
mention the effect of the following on the release of insulin: #amino acids and fatty acids #epinepherine #glucose
amino acids and fatty acids –> promote insulin release epinepherine –> halts insulin release glucose –> promotes insulin release
effects of insulin most prominent on three tissues. identify the 3 tissues along with the insulin effect on them #carbohydrate metabolism.
liver, muscle, adipose. REMEMBER: insulin always calling for SAVING on energy # liver and muscle, insulin increases glycogen synthesis. # muscle and adipose, insulin increases glucose uptake by increasing the number of GLUT 4 transporters. #liver, insulin decreases production of glucose via inhibition of glycogenolysis and gluconeogenesis.
coordinated effect of insulin on adipose tissue?
reduction in release of fatty acids by inhibiting the activity of hormone-sensitive lipase, which degrades lipids in adipose tissues (TAG’s into fatty acids). #increases transport and metabolism of glucose into adipocytes, providing glycerol-3-phosphate substrate for TAG synthesis. #increases the expression of the gene for lipoprotein lipase in adipose tissue, providing fatty acids for esterification to the glycerol. # promotes the conversion of glucose to TAG in the liver. the TAGs are secreted in VLDLs.
effect of insulin on protein synthesis?
stimulates the entry of amino acids into cells and protein synthesis *via activating translation initiation factors.
receptor regulation of insulin ?
elevated levels of insulin promote the degradation of receptors, thereby decreasing the number of surface receptors. *downregulation*
compare and contrast the time course of insulin action regarding different targets.
most immediate response is an increase of glucose transport into adipocytes, skeletal, and cardiac muscle cells that occurs within seconds of insulin binding to membrane receptors. #insulin-induced increase in the amount of many enzymes such as glucokinase, pyruvate kinase, ACC , fatty acid synthase, requires hours to days. thses changes reflect an increase in gene expression through increased transcription.
briefly mention the chief effects of insulin on #Carb metabolism #lipid metabolism #protein synthesis
CARBS: glycogen synthesis in liver and muscle; high glucose uptake by muscle and adipose via GLUT 4; inhibits production of glucose via glycogenolysis and gluconeogenesis #LIPIDS: halt hormone-sensitive lipase; activate lipoprotein lipase to provide free fatty acids for esterification; TAG synthesis in liver to be carried in VLDLs into adipocytes; higher uptake of glucose in adipocytes –> provide glycerol-3-phosphate for TAG backbone #PROTEINS: stimulate entry of amino acids into cells and protein synthesis.
insulin Vs. Glucagon
insulin: body high on energy –> metabolize glucose in headquarters (liver) –> STORE that shit outside ANABOLISM # glucagon: body low on energy –> avoid metabolizing glucose in headquarters–> rather use available energy to provide glucose elsewhere e.g. glycogenolysis and gluconeogenesis
what stimulates glucagon secretion?
low blood glucose levels is primary stimulus. elevated glucagon prevents hypoglycemia
amino acids and glucagon secretion?
amino acids derived from a meal containing protein stimulate glucagon release. glucagon protects against hypoglycemia that would otherwise occur after increased insulin secretion following a protein-rich meal.
catecholamines and glucagon?
during periods of physiologic stress, where catecholamines are produced, glucagon levels are elevated regardless of the concentration of blood glucose, in anticipation of increased glucose use.
effects of the following on glucagon secretion? #amino acids #epinepherine #glucose and insulin
amino acids > stimulate glucagon secretion #epinepherine> stimulate glucagon secretion glucose and insulin> inhibit glucagon secretion
glucagon and CARB metabolism ?
immediate rise in blood glucose after glucagon secretion due to breakdown of liver glycogen stores and hepatic gluconeogenesis
glucagon on LIPID metabolism ?
inhibition of ACC; fatty acid synthesis is halted #glucagon (along with catecholamines primarily)activate hormone sensitive lipase to liberate free fatty acids to be transported into the liver to be oxidized into acetyl coA for the synthesis of ketone bodies.
