Categories
Fitness Articles

Understanding Insulin In Our Bodies

Overview

Insulin is made in the beta cells of the pancreas. Its role is to maintain a state of glucose homeostasis in the bloodstream. Insulin responds to hyperglycaemia and is responsible for bring blood glucose levels down. It also promotes the uptake of excess glucose from the blood stream to the liver, muscle cells and adipose cells.

Normal average levels of blood glucose range from 80-120 mg/m , during periods when glucose levels drop below 80 mg/ml, the body is in a state of hypoglycemia and insulin will not be released by the pancreas. Instead, glucagon will be released by the alpha cells in the pancreas. However, if blood glucose levels go above 120 mg/ml (after ingestion of carbohydrates) the blood will be in a state of hyper glycemia, and insulin will be produced in the beta cells of the pancreas, and released into the bloodstream. Insulin then facilitates the storage of the excess blood glucose in various cells.

The production of insulin occurs when glucose in the bloodstream enters the beta cells of the pancreas. This signals the beta cells to produce insulin and release it into the bloodstream. Insulin levels in the blood stream can be measured (determined) by measuring the levels of specific peptides. This allows doctors to determine if a patient has Type 2 diabetes.

Insulin Affect on the Liver

Insulin binds to liver receptors and stimulates the liver to process glucose, which enters through it’s GLUT2 receptors. In a process called glycogenesis, insulin stimulates liver enzymes to convert incoming glucose to glycogen for long-term energy storage. When the glycogen storage is full, insulin will stimulate the liver enzymes to convert incoming glucose to pyruvate, which can be used by the liver for creating energy. Nevertheless, this process is called glycolysis.

Moreover, the liver has limited storage ability for glucose. When glycogen storage are full, and pyruvate is not needed for energy, insulin will then stimulate the liver to convert the excess glucose to fatty acids. A process called the De Novo Lipogenesis. Therefore, the newly formed fatty acids are expressed out of the liver as very low density lipoprotein‘s (VLDL). The VLDL molecules will then be transported to fat cells for storage.

Insulin Affect on Muscles

Muscle cells are dependent on insulin for intake of glucose molecules. Insulin acts on the muscle cells receptor GLUT4 transporter (a gatekeeper that allows glucose entry into the muscle cell) which is dependent on insulin. Insulin stimulates GLUT4 to become hyperactive to uptake glucose into the muscle cell from the bloodstream.  Next, Insulin stimulates the conversion of glucose to glycogen in the muscle cell, in a process called glycogenesis. Glycogen is a muscle cells storage of energy. Muscle cells can store about 500 grams of carbohydrates as glycogen. Insulin is also able to stimulate the muscle cell to convert incoming glucose to pyruvate, to be used in the Krebs cycle to create ATP energy; subsequently, Muscle cells have a limited ability to store glucose as glycogen.

Furthermore, Insulin promotes amino acids uptake from the bloodstream into the muscle cells, facilitating the conversion of amino acids into muscle proteins. A process called protein-genesis.

Insulin Affects on Fat Cells

Fat cells have cell membrane receptors that insulin binds to. Insulin stimulates the GLUT4 transporter (which is insulin-dependent) to become hyperactive, causing glucose uptake into the fat cell. Glucose entering the cell is broken down (by the stimulation of insulin) and converted into glycerol. Additionally, Insulin stimulates the conversion of glucose into fatty acids in a process called De Novo Lipogenesis. In this case, the glycerol and fatty acids are combined to form triglycerides for long-term storage in the fat cells. Consequently, Fat cells have an infinite ability to store glucose as fat.