The following points highlight the top three functions of various types of pancreatic hormones. The Functions are: 1. Functions of Insulin 2. Functions of Glucagon 3. Functions of Somatostatin.
Pancreatic Hormones Functions # 1. Functions of Insulin:
Insulin is secreted from β-cells of islets.
It shows following functions.
1. On carbohydrate metabolism:
(a) It stimulates glycogenesis in muscle cells and liver by increasing activities of glycogen synthetase, hexokinase II and a microsomal glucokinase.
(b) It enhances combustion of sugar by inducing glycolysis with the help of pyruvate kinase, glucokinase and phosphofructokinase.
(c) It regulates hepatic gluconeogenesis by inducing pyruvate carboxylase, G-6-phosphatase etc.
2. On protein metabolism:
(a) It stimulates the synthesis of tissue protein by taking amino acids from blood.
(b) It depresses protein catabolism and reduces the process of gluconeogenesis from protein.
3. On fat metabolism:
(a) It helps in the accumulation of depot fat i.e. lipogenesis. It produces pyruvic acid from glucose oxidation, the part of the pyruvic acid after decarboxylation is converted to acetic acid which will give rise to neutral fats.
(b) It increases the activity of lipoprotein lipase in adipose tissues. The enzymes catalyzes hydrolysis of chylomicrons and lipoproteins to yield fatty acids which enter the adipose tissue cells.
(c) It increases ketone bodies from fatty acids in liver. The presence of ketone bodies can cause severe acidosis and coma in patients.
(d) It reduces the free fatty acids level in blood by depressing the activity adipose tissue lipase.
Pancreatic Hormones Function 2. # Functions of Glucagon:
It is secreted from a-cells of pancreatic islets.
It performs following functions:
1. On carbohydrate metabolism:
(a) It increases liver glycogenesis’ and increased blood glucose concentration. It has no effect on glycogen phosphorylase of muscles.
(b) It depresses glycogenesis in the liver by reducing glycogen synthetase activity.
(c) It increases the gluconeogenesis in the liver from proteins by inducing pyruvate carboxylase and FDPase.
2. On protein metabolism:
(a) It reduces protein synthesis by depressing the incorporation of amino acids into peptide chains.
(b) It stimulates protein catabolism and thus increases nitrogenous waste metabolites.
3. On fat metabolism:
(a) It increases free fatty acids and glycerol in blood by lipolysis.
(b) It increases adenyl cyclase activity in adipose tissue that results in increased lipolysis.
(c) It has ketogenic effects. It increases fatty acid oxidation and ketosis to supply more fatty acids to the liver.
4. On GI tract:
(a) It increases the volume of secretion by the small intestine.
(b) It may stimulated gastric and pancreatic enzymes.
5. On mineral metabolism:
(a) It promotes cellular release of potassium, calcium and inorganic phosphate.
(b) It tends to decrease hypercalcaemia and hypophosphatemia by increasing calcitonin.
6. On heart:
It has an ionotropic effect on the heart and increases the force of myocardial contraction, cardiac output and arterial blood pressure.
Pancreatic Hormones 3. # Functions of Somatostatin:
1. It may control the peristaltic activity of GI tract.
2. It may regulate insulin and glucagon secretion by paracrine action.
3. It helps in transport of nutrients from GI tract to the circulation.
4. It decreases HCI secretion of stomach in empty state.