Hormonal regulation of carbohydrate metabolismHormonal regulation of carbohydrate metabolismLiver, extrahepatic tissues and hormones play a major Liver, extrahepatic tissues and hormones play a major role In the regulation of blood glucose. role In the regulation of blood glucose.

Hormonal regulation of glucose in fed state:Hormonal regulation of glucose in fed state:

Increased level of circulating glucose releases insulin Increased level of circulating glucose releases insulin and this hormone reduces the blood glucose level in and this hormone reduces the blood glucose level in many ways many ways

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It stimulates the GLUT-4 transporter to increase It stimulates the GLUT-4 transporter to increase the active transport of glucose across the active transport of glucose across membranes of muscle and adipose tissue. membranes of muscle and adipose tissue. Glucose is rapidly taken Glucose is rapidly taken up into liver via GLUT-up into liver via GLUT-2 transporter2 transporter

In the liver insulin increases the of glycolysis by In the liver insulin increases the of glycolysis by inducing the glycolytic inducing the glycolytic enzymes like enzymes like glucokinase , glucokinase , phosphofructokinase and phosphofructokinase and pyruvate kinase.pyruvate kinase.

Glucokinase is important in regulating Glucokinase is important in regulating blood blood glucose after meal. glucose after meal.

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In the liver and muscle insulin stimulates glycogenesis In the liver and muscle insulin stimulates glycogenesis by stimulating glycogen synthase [by reducing the by stimulating glycogen synthase [by reducing the elevated cAMP levels] and thereby leading to elevated cAMP levels] and thereby leading to suppression of glycogenolysissuppression of glycogenolysis

Insulin inhibits gluconeogenesis by suppressing the Insulin inhibits gluconeogenesis by suppressing the action of action of key enzymes of gluconeogenesis [ puyruvate key enzymes of gluconeogenesis [ puyruvate carboxylase, PEPCK, fructose 1,6-bisphosphatase and carboxylase, PEPCK, fructose 1,6-bisphosphatase and glucose 6-phosphatase]glucose 6-phosphatase]

In adipose tissue, glucose is converted to the glycerol In adipose tissue, glucose is converted to the glycerol 3-phosphate, needed for the formation of 3-phosphate, needed for the formation of triacylglycerol and inhibits the lipolysis by inhibiting triacylglycerol and inhibits the lipolysis by inhibiting hormone sensitive lipase.hormone sensitive lipase.

Insulin increases protein synthesis and decreases Insulin increases protein synthesis and decreases protein catabolism, thereby decreasing releasing amino protein catabolism, thereby decreasing releasing amino acids for gluconeogenesisacids for gluconeogenesis

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Hormonal regulation of fat metabolismHormonal regulation of fat metabolism

Insulin inhibit the activity of hormone sensitive lipase Insulin inhibit the activity of hormone sensitive lipase and reduces the release of free fatty acids and and reduces the release of free fatty acids and glycerol from the adipose tissue, this results in fall in glycerol from the adipose tissue, this results in fall in the circulating plasma free fatty acidsthe circulating plasma free fatty acids

Insulin enhances: Insulin enhances: Triacylglycerol synthesisTriacylglycerol synthesisLipogenesis both in liver and adipose tissueLipogenesis both in liver and adipose tissueby stimulating pyruvate dehydrogenase, acetyl CoA by stimulating pyruvate dehydrogenase, acetyl CoA carboxylase and glycerol phosphate acyltransferasecarboxylase and glycerol phosphate acyltransferase

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Regulation of carbohydrate metabolism in fasting stateRegulation of carbohydrate metabolism in fasting stateGlucagon Glucagon

In the liver, it stimulates glycogenolysis by activating In the liver, it stimulates glycogenolysis by activating glycogen phosphorylase and inhibits glycogen glycogen phosphorylase and inhibits glycogen synthase. It exerts its action on metabolic processes synthase. It exerts its action on metabolic processes through the generation of cAMP through the generation of cAMP Stimulates gluconeogenesisStimulates gluconeogenesisEnhances gluconeogenesis from amino acids and Enhances gluconeogenesis from amino acids and lactatelactateAlanine is the predominant amino acid released from Alanine is the predominant amino acid released from muscle to liver by glucose alanine cyclemuscle to liver by glucose alanine cycle

EpinephrineEpinephrine Favors glycogenolysis in liver and muscle through Favors glycogenolysis in liver and muscle through cAMP dependent activation of adenylyl cyclase cAMP dependent activation of adenylyl cyclase which converts ATP to cAMP [stimulates phosphorylase]which converts ATP to cAMP [stimulates phosphorylase]

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GlucocorticoidsGlucocorticoidsIncreases: Increases: Gluconeogenesis, Gluconeogenesis, Protein catabolism to provide amino acids for gluconeogenesisProtein catabolism to provide amino acids for gluconeogenesisAcitivity of aminotransferase [to convert pyruavte to alanine]Acitivity of aminotransferase [to convert pyruavte to alanine]Hepatic uptake of amino acidsHepatic uptake of amino acidsActivity of key enzymes of gluconeogenesisActivity of key enzymes of gluconeogenesisGlucocorticoids inhibit the utilization of glucose in extrahepaticGlucocorticoids inhibit the utilization of glucose in extrahepatictissuestissuesAnterior pituitary hormonesAnterior pituitary hormonesGrowth hormone and ACTH antagonize the action of insulin byGrowth hormone and ACTH antagonize the action of insulin byelevating the blood glucose levelelevating the blood glucose levelGH decreases glucose uptake in the muscle and GH decreases glucose uptake in the muscle and ACTH decreases glucose utilization by the tissueACTH decreases glucose utilization by the tissueThyroxineThyroxineAccelerates liver glycogenolysis and increase the rate of Accelerates liver glycogenolysis and increase the rate of absorption of hexoses from the intestineabsorption of hexoses from the intestine

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Hormonal regulation of fat metabolismHormonal regulation of fat metabolism

Normally InsulinNormally InsulinInhibit the activity of hormone sensitive lipase and reduces the Inhibit the activity of hormone sensitive lipase and reduces the release of free fatty acids and glycerol from the adipose tissuerelease of free fatty acids and glycerol from the adipose tissueEnhances Enhances Triacylglycerol synthesis, lipogenesis both in liver and adipose Triacylglycerol synthesis, lipogenesis both in liver and adipose tissue by stimulating pyruvate dehydrogenase, acetyl CoA tissue by stimulating pyruvate dehydrogenase, acetyl CoA carboxylase and glycerol phosphate acyltransferasecarboxylase and glycerol phosphate acyltransferase

Starvation associated with Starvation associated with decreased activity of insulin and increased activity of glucagon, therefore the hyperglycemic , therefore the hyperglycemic hormones antagonizes the action of insulinhormones antagonizes the action of insulin

Norepinephrine, glucagon, ACTH,GH and vasopressin Norepinephrine, glucagon, ACTH,GH and vasopressin accelerate the release of free fatty acids from adipose tissue and accelerate the release of free fatty acids from adipose tissue and raise the plasma free fatty acid concentration by increasing the raise the plasma free fatty acid concentration by increasing the lipolysis of the TGlipolysis of the TG

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cAMP, by stimulating cAMP dependent protein kinase , cAMP, by stimulating cAMP dependent protein kinase , activates hormone sensitive lipaseactivates hormone sensitive lipaseGlucagon, epinephrine & norepinephrine inactivate the enzyme by cAMP dependent phosphorylation and inhibit the fatty acid synthesis

Hormonal regulation of cholesterol metabolismThe HMG CoA reductase is the regulatory enzyme of cholesterol synthesis Insulin and thyroid hormones Increase HMG CoA reductase activity through dephosphorylation of the enzyme [active]

Glucagon and glucocorticoids Glucagon and glucocorticoids decreasedecrease HMG-CoA HMG-CoA reductase activityreductase activity through cAMP dependent phosphorylation [inactive].

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