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Hormonal regulation of carbohydrate metabolism

how every hormone controls every metabolism in our body shows that each hormone is important for us and this can be seen in this presentation

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Hormonal regulation of carbohydrate metabolism

  2. 2. CONTENTS:  Introduction.  Insulin.  Effect of insulin.  Glucagon.  Effect of glucagon.  Catecholamines.  Effect of epinephrine.  Corticosteroids.  Effect of cortisol.  Growth hormone.  Effect of growth hormone.  Thyroid hormones.  Effect of thyroid hormones.
  3. 3. Why glucose concentration should be maintained or regulated ?  The normal glucose concentration: 140 mg/dL ( postprandial ), 70 to 99 mg/dL ( preprandial ).  A slight variations of this normal level leads to hyperglycaemia or hypoglycaemia.  Thus the level of glucose is regulated by various hormones.  And this hormonal regulation of carbohydrate metabolism is mainly occurs by the internal chemical messengers.  Hormones like insulin, glucagon, epinephrine, cortisol, TH and GH regulates this metabolism.
  4. 4. Insulin:  Insulin is a peptide hormone.  Secreted by 𝛽 cells of islets of Langerhans from pancreas.  Blood glucose level : elevated- leads to insulin secretion.  The secreted insulin carries various anabolic functions  Thus maintain high blood glucose in normal range.
  5. 5. Effect of insulin:  Reduces blood glucose mainly by Uptake of glucose by the cells through GLUT 4 glucose transporters.  In other tissues like Adipose tissue - increases fatty acid and triglyceride synthesis. - Decreases lipolysis. Liver and muscle - increases glycogen synthesis. - Decreases glycogenolysis.
  6. 6. Glucagon:  Glucagon is also a peptide hormone secreted by 𝛼 cells of islets of Langerhans from pancreas.  It is a antagonist of insulin which shows the catabolic activities.  It is secreted when there is fall in blood glucose level from normal range.  Thus it stops insulin secretion during- low blood glucose level.  It increases blood glucose mainly by - Breaking down of stored glycogen and triglycerides.
  7. 7. Effect of glucagon:  In liver Increases glycogenolysis. Increases gluconeogenesis. Increases ketone body synthesis. Decreases glycogen synthesis.  In muscle Increases protien degradation Decreases protien synthesis.  In adipose tissue Increases lipolysis Decreases triacylglycerol synthesis.  The overall effect of glucagon is to stimulate glucose synthesis, use of ketone bodies as fuel for brain and other tissues.
  8. 8. Catecholamines:  These are water soluble compounds having role as both hormones and neurotransmitters.  Ex: epinephrine, nor-epinephrine, dopamine.  Produced in brain and other neuronal tissues acts as neurotransmitters. But this catecholamines produced from adrenal glands acts as hormones.  The epinephrine is synthesised and secreted from adrenal medulla acts as hormone.  it is a fight or flee hormone i.e. it is released during emergency situations.  It is a antagonist of insulin which shows the catabolic activities.  Released when blood glucose level is low and increases blood glucose level.
  9. 9. Effect of epinephrine:  The effect of epinephrine  In liver - Increases glycogenolysis. - Increases gluconeogenesis. - Deceases glycogen synthesis.  In adipose tissue - Increases lipolysis.  In skeletal muscle - Increases glycogenolysis.  Finally it stimulates glucagon secretion and inhibits insulin secretion. Thus utilizing the stored fats and glycogen.
  10. 10. Glucocorticoids:  Cortisol is the primary glucocorticoid in humans.  A variety of stimulus releases the cortisol from adrenal cortex.  It is also a antagonist of insulin which brings about the catabolic effects and increases blood glucose level to the normal level.  In chronic stress cortisol acts to make fuel available to withstand the stress.  And this hormone is a slow acting hormone which alters metabolism by kinds and amounts of certain enzymes synthesized in its target cells.
  11. 11. Effect of cortisol:  Cortisol mainly acts on muscle, liver and adipose tissues and releases glucose.  In adipose tissue - Increases lipolysis.  In liver - Increases gluconeogenesis. - Increases glycogen break down.  In muscle - Increases muscle protein break down. - Decreases protien synthesis.  Thus the overall effect of cortisol is to break down of stored glycogen and fat to yield glucose
  12. 12. Growth hormone:  Growth hormone control various physiological process and metabolism.  And secreted by somatotrophic cells of anterior pituitary gland.  It is secreted when the blood glucose level is low from the normal range.  when there is less plasma fatty acid level and in increased plasma amino acid level stimulates the secretion of GH.  Also during sleep, exercise and in stress condition there will be increased secretion of GH.  And its secretion is regulated by 2 hypothalamic hormones and one stomach hormone i.e. growth hormone releasing hormone (GHRH), somatostatin and ghrelin.
  13. 13. Effect of growth hormone:  If the growth hormone secretion is increased it increases plasma glucose concentration also fatty acid and glycerol concentration in the blood.  It decreases or inhibits the glucose uptake by the adipose tissue and skeletal muscle.  In adipose tissue - Increases lipolysis thus releasing free fatty acids and glycerol which is mobilized to liver where it leads to gluconeogenesis.  In liver - Increases gluconeogenesis. - Increases glycogenolysis.
  14. 14. Thyroid hormones:  It is a mixture of low molecular weight iodinated tyrosine derivatives i.e. T3 and T4  Secreted from thyroid gland under the control of thyroid stimulating hormone (TSH) by pituitary gland.  The normal range of thyroid hormone is 5-12 𝜇g/dL  Above this range leads to hyperthyroidism and below this range leads to hypothyroidism.  During these two diseased condition it shows different effect on carbohydrate metabolism  In hyperthyroidism it shows catabolic activity and in hypothyroidism it shows anabolic activity.
  15. 15. Effect of thyroid hormone:  In hyperthyroidism Increases blood glucose by increasing glycogenolysis In liver. Increases breakdown of muscle protiens. Increases lipolysis. Increases gluconeogenesis and also ketone body synthesis.  In hypothyroidism Decreases blood glucose level by increasing glycogenesis. Increases protein synthesis.
  16. 16. Conclusion:  The concentration of glucose in blood is hormonally regulated  Insulin is the key regulatory hormone which reduces the blood glucose level.  By carrying out the anabolic activities.  The other hormones i.e. glucagon, epinephrine, cortisol, GH and TH are said to be anti- insulin hormones.  Glucagon is also a key regulatory hormone where it increases the blood glucose level by carrying out the catabolic activities.  Epinephrine and cortisol shows their effect during emergency conditions and also during stress.  GH shows its effect during stress and during the high plasma amino acid level and low fatty acid level.  TH shows both catabolic and anabolic effect according to its two different diseased conditions.
  17. 17. Reference:  Principles of Biochemistry, 4th ed – Lehninger.  Functional metabolism: regulation and adaptation 3rd ed- Storey Kenneth B  An article: Otolaryngol Clin North Am. 1975 Jun; 8(2): 335-44: Hormonal regulation of glucose metabolism.  An article: Diabetes Metab Rev. 1987 Jan;3(1): 163-83: Mechanism of hormonal regulation of hepatic glucose metabolism.  An article: Horm Res. 1991; 36 Suppl 1:32-5: Effects of growth hormone on glucose metabolism.  Wikipedia.