हिन्दी (Hindi) मे पढ़िये
The human body, organs and the pancreas
Our body is composed of cells grouped into tissues comprising of similar cells. These different tissues in turn form organs like heart, lungs and liver which perform different functions of our body. The pancreas is a similar organ situated in our abdomen. One part of the pancreas (exocrine) is responsible for the secretion of digestive juices which enter the intestine and are responsible for the digestion of the food we eat. And another part (endocrine) secretes various hormones of which insulin plays a major role in the metabolism of glucose. In the endocrine pancreas-the islets of Langerhans- consists of 1-1.5% of the total mass of the pancreas and have a 5-10 times supply of blood compared to the exocrine pancreas. Islets of Langerhans consist of A, B, D and PP cells. B cells secrete insulin and c-peptide in equal amounts and a small amount of proinsulin. Proinsulin has abut 7-8 % of the biologic activity of insulin. C-peptide is an biologically inactive molecule.
The human pancreas secretes about 40-50 units of insulin per day in normal adults. The increase of glucose in the blood stimulates insulin release. Certain substances amplify the glucose induced insulin secretion. Glucagon like peptide 1(GLP-1) is one of them. Substances similar to GLP-1 are used in the treatment of diabetes. In type 2 diabetes mellitus there is a defect in insulin secretion from the beta cells of the pancreas. The concentration of insulin in the blood of fasting humans averages 10 micro units/ml. After taking food insulin secretion rises and reaches a peak within 30-45 minutes and it seldom rises above 100 micro units/ml. This is followed by a rapid decline in concentration and return to baseline by 90-120 minutes. Insulin acts by binding to molecules on the cell surface called receptors.
The major role of insulin is to promote the storage of nutrients that we eat inside our body cells. Insulin promotes the entry of glucose into cells and the conversion of glucose to glycogen (a complex molecule serving as energy store). At the same time insulin prevents the breakdown of glycogen in the cells into glucose. Hence insulin acts to reduce the concentration of blood glucose which is stored inside the cells for either immediate or future use. The main cells which serve as energy stores are the liver, muscle cells and fat cells.
Defects in type 2 diabetes mellitus
In type 2 diabetes mellitus there is resistance to the action of insulin on the cells. It means that even though present in normal quantity insulin does not have the same effect on the cells. Thus entry of glucose and its storage as glycogen is diminished. With increasing number of fat cells in the abdomen insulin resistance increases. Thus in type 2 diabetes there is an insulin secretory defect and insulin action defect although no one knows exactly how this happens.