Insulin (Hormone) - Role of Insulin in the Body and Effect on Blood Glucose
Since diabetes is a disease that affects your body's ability to use glucose, let's start by looking at what glucose is and how your body controls it. Glucose is a. Insulin's main task is to help turn carbohydrates from food into the energy that keeps the body running. After they are eaten, carbs are broken down into the sugar. The pancreas secretes insulin and glucagon, both of which play a vital role in regulating blood sugar levels. The two hormones work in balance.
How insulin works The body converts energy from carbohydrates into glucose. The body's cells need glucose for energy, but most cells cannot directly use glucose.
Insulin acts like a key to allow glucose to access the cells.
It attaches to insulin receptors on cells throughout the body, telling those cells to open up and allow glucose to enter. Low levels of insulin are constantly circulating throughout the body. When insulin rises, this signals to the liver that blood glucose is also high.
- How Insulin and Glucagon Work
- How insulin and glucagon work to regulate blood sugar levels
- Coordination and control - The human endocrine system
The liver absorbs glucose, then changes it to a storage molecule called glycogen. When blood sugar levels drop, glucagon signals the liver to convert the glycogen back to glucose.
This makes blood sugar levels go up. Insulin also supports healing after an injury by delivering amino acids to the muscles. Amino acids help build the protein found in muscle tissue, so when insulin levels are low, muscles may not heal properly.
How glucagon works The liver must store glucose to power the cells during times of low blood sugar. Skipping meals and poor nutrition can lower blood sugar. By storing glucose, the liver makes sure blood glucose levels stay steady between meals or during sleep. When blood glucose falls, cells in the pancreas secrete glucagon. Glucagon instructs the liver to convert glycogen to glucose. A Hormone's Work Insulin's main task is to help turn carbohydrates from food into the energy that keeps the body running.
After they are eaten, carbs are broken down into the sugar glucose, which then enters the bloodstream for distribution. Beta cells in the pancreas detect the rise in blood glucose and produce insulin in response. The hormone travels around the body in the blood, signaling to cells all over that soup's on and it's time to let glucose in.
Insulin is the "key" that opens the cells to glucose.
A Quick Guide to Insulin, the Key to Glucose: Diabetes Forecast®
As insulin does its work and cells gobble up glucose, blood glucose levels begin to fall. The beta cells detect this drop in blood glucose and taper off the flow of insulin. This ensures that the glucose in the blood will plateau at a healthy level and not go too low. The absence of insulin in the blood is also a signal that the body hasn't eaten for a while and should tap fat stores instead of glucose for its energy needs.
Though its job is being a hormone, insulin is also a protein, manufactured by the body using information written in the genes. The beta cells are the only cells in the body with the natural capacity to make insulin. This specialization means that the beta cells are the body's last and only hope for regulating blood glucose levels on its own.
Insulin in Diabetes Diabetes develops when the beta cells fail to produce enough insulin to keep blood glucose levels in a healthy range.
Upon eating a meal, there is a release of insulin, signaling glucose availability in the blood.
Insulin indirectly activates PP-1 and phosphodiesterase. The PP-1 directly dephosphorylates glycogen phosphorylase a, reforming the inactive glycogen phosphorylase b.
This activity removes the second messenger generated by glucagon and epinephrine and inhibits PKA. In this manner, PKA can no longer cause the phosphorylation cascade that ends with formation of active glycogen phosphorylase a.The Role of Insulin in the Human Body
These modifications initiated by insulin end glycogenolysis in order to preserve what glycogen stores are left in the cell and trigger glycogenesis rebuilding of glycogen.
Phosphorylase a and phosphorylase b each exist in two forms a T tense inactive state and R relaxed state. Phosphorylase b is normally in the T state, inactive due to the physiological presence of ATP and Glucose 6 phosphate, and Phosphorylase a is normally in the R state active.
An isoenzyme of glycogen phosphorylase exists in the liver sensitive to glucose concentration, as the liver acts as a glucose exporter. In essence, liver phosphorylase is responsive to glucose, which causes a very responsive transition from the R to T form, inactivating it; furthermore, liver phosphorylase is insensitive to AMP.
The term literally means "under-sweet blood" Gr. It can produce a variety of symptoms and effects but the principal problems arise from an inadequate supply of glucose to the brain, resulting in impairment of function neuroglycopenia. Effects can range from mild dysphoria to more serious issues such as seizures, unconsciousness, and rarely permanent brain damage or death.
The most common forms of hypoglycemia occur as a complication of treatment of diabetes mellitus with insulin or oral medications. Hypoglycemia is less common in non-diabetic persons, but can occur at any age, from many causes. Among the causes are excessive insulin produced in the body hyperinsulinemiainborn errors of metabolism, medications and poisons, alcohol, hormone deficiencies, prolonged starvation, alterations of metabolism associated with infection, and organ failure.
Hypoglycemia is treated by restoring the blood glucose level to normal by the ingestion or administration of dextrose or carbohydrate foods. In some circumstances it is treated by injection or infusion of glucagon.
Principles of Biochemistry/Glucose, Glycogen and Diabetes - Wikibooks, open books for an open world
Recurrent hypoglycemia may be prevented by reversing or removing the underlying cause, by increasing the frequency of meals, with medications like diazoxide, octreotide, or glucocorticoids, or by surgical removal of much of the pancreas.
The level of blood glucose low enough to define hypoglycemia may be different for different people, in different circumstances, and for different purposes, and occasionally has been a matter of controversy. Most healthy adults maintain fasting glucose levels above 4. It can sometimes be difficult to determine whether a person's symptoms are due to hypoglycemia. Criteria referred to as Whipple's triad are used to determine a diagnosis of hypoglycemia: Symptoms known to be caused by hypoglycemia Low glucose at the time the symptoms occur Reversal or improvement of symptoms or problems when the glucose is restored to normal The glycogen phosphorylase monomer is a large protein, composed of amino acids with a mass of While the enzyme can exist as an inactive monomer or tetramer, it is biologically active as a dimer of two identical subunits.
Note the relative positioning of the central tower helices, as well as the increased interactions between subunits in the R state. PDB3CEH, PDB3E3O The glycogen phosphorylase dimer has many regions of biological significance, including catalytic sites, glycogen binding sites, allosteric sites, and a reversibly phosphorylated serine residue. Perhaps the most important regulatory site is Ser14, the site of reversible phosphorylation very close to the subunit interface.
Binding of AMP at this site, corresponding in a change from the T state of the enzyme to the R state, results in small changes in tertiary structure at the subunit interface leading to large changes in quaternary structure.
This site is most likely the site at which the enzyme binds to glycogen granules before initiating cleavage of terminal glucose molecules. The brain type is predominant in adult brain and embryonic tissues, whereas the liver and muscle types are predominant in adult liver and skeletal muscle, respectively. Glycogen is catabolized by removal of a glucose monomer through cleavage with inorganic phosphate to produce glucosephosphate. This derivative of glucose is then converted to glucosephosphate, an intermediate in glycolysis.
The hormones glucagon and epinephrine stimulate glycogenolysis. Glycogenolysis takes place in the muscle and liver tissues, where glycogen is stored, as a hormonal response to epinephrine e. Liver hepatic cells can consume the glucosephosphate in glycolysis or remove the phosphate group using the enzyme glucosephosphatase and release the free glucose into the bloodstream for uptake by other cells. Muscle cells in humans do not possess glucosephosphatase and, hence, will not release glucose, but instead use the glucosephosphate in glycolysis.
First step The overall reaction for the 1st step is: Glycogen phosphorylase EC 2. This is the only case in which a glycogen metabolite is not glucosephosphate. These glucan transferase and debranching enzyme activities are from two separate catalytic sites on the same protein. Third step Diabetes[ edit ] The term diabetes was coined by Aretaeus of Cappadocia.
Diabetes is first recorded in English, in the form diabete, in a medical text written around InThomas Willis added the word mellitus, from the Latin meaning "honey", a reference to the sweet taste of the urine.
This sweet taste had been noticed in urine by the ancient Greeks, Chinese, Egyptians, Indians, and Persians. InMatthew Dobson confirmed that the sweet taste was because of an excess of a kind of sugar in the urine and blood of people with diabetes.
Diabetes mellitus appears to have been a death sentence in the ancient era. Hippocrates makes no mention of it, which may indicate that he felt the disease was incurable. Aretaeus did attempt to treat it but could not give a good prognosis; he commented that "life with diabetes is short, disgusting and painful.
He further identified it with obesity and sedentary lifestyle, advising exercises to help "cure" it. The ancient Indians tested for diabetes by observing whether ants were attracted to a person's urine, and called the ailment "sweet urine disease" Madhumeha.
The Chinese, Japanese and Korean words for diabetes are based on the same ideographs which mean "sugar urine disease". In medieval Persia, Avicenna — provided a detailed account on diabetes mellitus in The Canon of Medicine, "describing the abnormal appetite and the collapse of sexual functions," and he documented the sweet taste of diabetic urine. Like Aretaeus before him, Avicenna recognized a primary and secondary diabetes. He also described diabetic gangrene, and treated diabetes using a mixture of lupine, trigonella fenugreekand zedoary seed, which produces a considerable reduction in the excretion of sugar, a treatment which is still prescribed in modern times.
Avicenna also "described diabetes insipidus very precisely for the first time", though it was later Johann Peter Frank — who first differentiated between diabetes mellitus and diabetes insipidus. This high blood sugar produces the classical symptoms of polyuria frequent urinationpolydipsia increased thirst and polyphagia increased hunger.
There are three main types of diabetes: Also referred to as insulin-dependent diabetes mellitus, IDDM for short, and juvenile diabetes. Formerly referred to as non-insulin-dependent diabetes mellitus, NIDDM for short, and adult-onset diabetes.
It may precede development of type 2 DM. Pathophysiology[ edit ] Mechanism of insulin release in normal pancreatic beta cells. Insulin production is more or less constant within the beta cells, irrespective of blood glucose levels. It is stored within vacuoles pending release, via exocytosis, which is primarily triggered by food, chiefly food containing absorbable glucose.
The chief trigger is a rise in blood glucose levels after eating The fluctuation of blood sugar red and the sugar-lowering hormone insulin blue in humans during the course of a day with three meals.
One of the effects of a sugar-rich vs a starch-rich meal is highlighted. Insulin is the principal hormone that regulates uptake of glucose from the blood into most cells primarily muscle and fat cells, but not central nervous system cells. Therefore deficiency of insulin or the insensitivity of its receptors plays a central role in all forms of diabetes mellitus. Humans are capable of digesting some carbohydrates, in particular those most common in food; starch, and some disaccharides such as sucrose, are converted within a few hours to simpler forms most notably the monosaccharide glucose, the principal carbohydrate energy source used by the body.
The rest are passed on for processing by gut flora largely in the colon. Insulin is used by about two-thirds of the body's cells to absorb glucose from the blood for use as fuel, for conversion to other needed molecules, or for storage. Lowered glucose levels result both in the reduced release of insulin from the beta cells and in the reverse conversion of glycogen to glucose when glucose levels fall. This is mainly controlled by the hormone glucagon which acts in the opposite manner to insulin.
Glucose thus forcibly produced from internal liver cell stores as glycogen re-enters the bloodstream; muscle cells lack the necessary export mechanism. Normally liver cells do this when the level of insulin is low which normally correlates with low levels of blood glucose. Insulin or its lack is the principal signal in converting many of the bidirectional processes of metabolism from a catabolic to an anabolic direction, and vice versa.