Endocrine part of Pancreas (Islets of Langerhans) The pancreas is a mixed exocrine-endocrine gland Exocrine function Synthesis and release of digestive enzymes Endocrine function Synthesis and release of hormones affecting carbohydrate metabolism Endocrine part (Islets of Langerhans): • endocrine function of pancreas is performed by the islets of Langerhans. Human pancreas • The islets represent about 2% of the weight of pancreas • contains about 1 to 2 million islets. Islets of Langerhans consist of 4 types of cells: 1. A cells or α cells which secrete glucagon 2. B cells or β cells which secrete insulin 3. D cells or δ cells which secrete somatostatin 4. F cells which secrete pancreatic polypeptide Functions of Insulin (polypeptide hormone OF 51 amino acid) 1. On carbohydrates metabolism: it is the only hypoglycemic hormone in the body: transport and uptake of glucose by the peripheral cells specially muscle, liver & adipose tissue (insulin dependent-tissues) B. glycogenesis (glycogen synthesis ) in muscle and liver. C. Inhibits glycogenolysis (glycogen breakdown) & Inhibits gluconeogenesis and A. 2. On protein metabolism : it is anabolic hormone • enhance amino acid transport & conserves & stores proteins in the body. 3. On fat metabolism : it is a lipogenic hormone • It stimulates lipogenesis in the adipose tissues. 4- On electrolyte metabolism: Insulin increases cellular uptake of K+ plasma K+ level. NB: Insulin independent tissues: they utilize glucose independently on insulin • Brain, RBCs, Intestine, Cornea, Kidney, Liver, Islet (β) cells, placenta, & Spermatocytes Control of insulin secretion (Factors stimulate insulin secretion) 1. level of plasma glucose (hyperglycemia is the most powerful factor in stimulating insulin secretion). 2. level of plasma amino acids e.g arginine 3. level of plasma free fatty acids. 4. level of plasma K+. 5. GIT hormones -e.g Gastric inhibitory polypeptide (GIP) & glucagon-like polypeptide 1 (GLP-1), Gastrin, secretin, CCK & glucagon Diabetes mellitus (DM) Definition •DM is a clinical syndrome due to deficiency of insulin Causes and types of DM •Type1 DM =Insulin Dependent Diabetes Mellitus (IDDM)= Juvenile DM(10%) •Is due to autoimmune destruction of β cells of pancreas •Type2 DM =Non-Insulin Dependent Diabetes Mellitus (NIDDM)= Maturity onset diabetes (90%) • Is due to increase insulin resistance Manifestations 1. Disturbed carbohydrates metabolismHyperglycemia and glucosuria Ployuria , Polydepsia & Polyphagia. 2. Disturbed Proteins metabolism protein catabolism, MuscleWasting, Weight loss 3. Disturbed fat metabolism lypolysis & Hyperlipidemia 4. Hyperkalaemia. Characteristic Type 1 ( 10% ) Type 2 Onset (Age) Usually < 30 Usually > 40 Type of onset Abrupt Gradual Nutritional status Usually thin Usually obese Clinical symptoms Polydipsia, polyphagia, polyurea, Wt loss Often asymptomatic Ketosis Frequent Usually absent Endogenous insulin Absent Present, but relatively ineffective Related lipid abnormalities Hypercholesterolemia frequent, all lipid fractions elevated in ketosis Insulin therapy Required Cholesterol & triglycerides often elevated; carbohydrateinduced hypertriglyceridemia common Required in only 20 - 30% of patients Hypoglycemic drugs Should not be used Clinically indicated Diet Mandatory with insulin Mandatory with or without drug (polypeptide hormone =29 amino acids) 1. On CHO metabolism: hyperglycemic • • It blood glucose level by glycogenolysis & gluconeogenesis. By the Liver which is the primary target of glucagon. N.B.: Glucagon has little or no influence on glucose utilization by peripheral tissues. 2. On fat metabolism: has lipolytic and ketogenic actions. 3. On protein metabolism has no effect on muscles NB: • glucagon Has a positive inotropic effect on the heart moderate increase of cardiac output • glucagon act as a local CNS hormone for the regulation of appetite. 1. blood glucose level (hypoglycemia is the most powerful factor in stimulating glucagon secretion). 2. Protein rich meal and, most powerfully, by th amino acids such as arginine and alanine.