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BY ELENA VOROPAY  Insulin is a great anabolic hormone and may be the most misunderstood hormone among strength athletes. Many mistakenly think that Insulin's main role is anything from making them fat to lowering blood sugar levels. This is false. Insulin's main purpose is to help transport newly eaten nutrients into all cells in the body where these can be converted into usable fuel, not fat.
This action is carefully choreographed by many other organs and enzymes. Without Insulin, you can eat lots of food and actually be in a state of starvation since many of our cells cannot access the calories contained in the glucose very well without the action of Insulin. No Insulin – no nutrients, no fuel for the body, mind and soul. This is why diabetics who do not make Insulin and people with Insulin resistance can become very ill.
How Insulin Was Discovered
The hormone Insulin deserves some honourable attention – it was the first hormone to be identified. We've heard so much about it and its name became a house-hold term standing next to Diet Coke and protein bars. While this happened only recently, the history of Insulin is as old as our knowledge of breads and fruit.
Let's step back a few centuries ago. Ancient Indians are said to have noted ants congregating at the urine of diabetics in the 4th century. Maybe they somehow spread the word around the world and the sweet smell of the urine of diabetics was first noted in the 17th century by the Oxford physician, Thomas Willis. Attempts at treatment began when no more was known about diabetes than the polyuria, or frequent urination. The connection between sugar and the wee syndrome received the first attempt to be resolved by John Rollo, Surgeon-General to the Royal Artillery who treated a patient by dietary restriction in 1706.
The great figure in the story of diabetes, physiology and medicine in the first half of the 19th century was Claude Bernard, a trained pharmacist who discovered that the liver had the ability to store glucose and coul d secrete a sugary substance into the blood. At this time Bernard assumed that this is what caused diabetes. In 1879, a German physician Von Mering disproved Bernard’s liver theory and proposed another one. He said that pancreas, a different organ involved in digestion of food and diabetes have a bridge between them. No-one knew how exactly these were related, and with advances in medicine the connection was further narrowed down to the islets of Langerhans, cells of the pancreas.
The story of the triumphant discovery of the hormone Insulin took place in 1921 in Canada by Fredrick Banting, an unsuccessful orthopaedic surgeon at that time. After reading about the association between the pancreas and diabetes, Banting became convinced that he could find the anti-diabetic substance.
The scientists fastened their belts, rolled up the sleeves and the research began. Involved in the investigations were the previously mentioned Dr. Fredrick Banting, his assistant Charles Best, a medical student at the time of the discovery, and Professor J. J. R. Macleod and Dr. James Collip. In 1921-1922 they tied a string around the pancreatic duct of several dogs. A few weeks later it was found that the pancreatic enzymes of these dogs died and all digestive cells were gone! Nada! These active, which eventually became inactive, cells were absorbed by the immune system and excreted which left the dogs with thousands of pancreatic islets. Banting and Best decided to explore more, so they isolated the protein from these islets. What protein was it? Insulin. This is how it was discovered.
After many failures, the group prepared an Insulin extract from the atrophied pancreas of a dog and injected it in one of two diabetic dogs. Four days later the control dog died, but the dog which received the extract lived for three weeks, dying only after there was no more extract. No doubt diabetes is a deadly disease, but this is good news. The bad news is that one has to suffer from symptoms until the body stops coping with them.
The first patient to receive an Insulin injection made by Banting and Best was a 14-year-old boy. This experiment took place in January 11, 1922, but wasn't successful. Later, some new purified injections were developed and given to a patient on January 23, 1922. This time the patient’s blood glucose levels dropped. Whoa, sweetie!
News spread all over the world and within weeks the researches collaborated to produce Insulin in the United States and Latin America. By the end of 1923, Insulin was being produced commercially and used to treat diabetes in most western countries.
On June 3, 1934, Dr Frederick Banting the co-inventor of Insulin was knighted for his medical discovery with a Nobel Prize.
Anabolism With Insulin Injections
The first successful Insulin preparations came from the pancreatic islets and Insulin protein contained within them from cows (and later pigs). The bovine (cow) and porcine (pig) Insulin was purified, bottled, and sold as Insulin injections. About half a century ago, it worked very well for most people, but some developed an allergy or other types of reactions to the foreign protein of animals which is not native to humans. Wouldn't it be great to find a way to make the hormone as close to human nature as possible? It would have a much lower chance of inducing any undesirable reaction because it is not a foreign protein. This was the goal.
In the 1980's technology had advanced and scientists came to the point where we could make human Insulin. The technology which made this approach possible was the development of recombinant DNA techniques. In simple terms, the human gene which codes for the Insulin protein was copied and then put inside of bacteria. Researchers played with genes for a while and finally made the bacteria which wanted to constantly make Insulin. Today, big vats of bacteria make tons of human Insulin which pharmaceutical companies use.
Some bodybuilder's looking for big muscle gains actually inject Insulin, especially when they are at their phase of 'bulking up' and taking various other 'supplemental nutrients'. Don't try this at home, you may end up being fat, Insulin-resistant, diabetic, and so on. If you get yourself to the point of Insulin injections, you may be wasting your time reading this and don't need to know anything about nutrition and natural foods. Why? Foods are drugs. Drugs are dangerous, expensive and definitely not recommended. There are much better ways to replenish your cellular energy. I say – eat carbohydrates, drink water, rest, periodise your training and be a merry bodybuilder!
Where Does Natural Insulin Come From?
Food. Well, not really. But the starting material is the sugar, the simplest energy form which fuels every activity in the body. No carbs – no Insulin, no energy, inefficient metabolism and eventually you may find yourself lying on the ground unconscious. Your brain stops. It takes a while, but it will happen.Maybe it would be convenient to get an IV with Insulin in its pure form to get its nutrient delivery job done, but this is not very practical nor appetising. This is why we eat carbohydrates.
The bloodstream’s capacity for glucose is about 80 calories, worth of 20 carbohydrate grams. Usually, this number is kept constant and controlled by many neuro-chemicals, hormones and enzymes. The main two hormones responsible for monitoring blood sugar levels are Insulin and Glucagon.
Insulin and Glucagon both have the same job to do – ensure your blood sugar levels are stable. The levels of these two hormones are counter-balanced. It's like these two work their own shifts, on their own terms, with each having different methods and tools. Although there is always a low level of Insulin secreted by the pancreas, the amount secreted into the blood increases as the blood glucose rises. Similarly, as blood glucose falls, the amount of Insulin secreted by the pancreatic islets goes down.
In your body, these hormones are secreted by groups of cells within the pancreas, an organ that sits behind the stomach and has many functions in addition to Insulin production, such as producing digestive enzymes and other hormones. Most of pancreas is made up of the acinar cells which make up the enzymes you need to break down proteins and fats into the smaller structures before these can flow down various channels into the pancreatic duct and then out into the duodenum of the intestines. The secretions are alkaline to balance the acidic juices and partially digested food coming into the duodenum from the stomach.
A small proportion, just 1-2 % of the pancreas is made up of other types of cells called islets of Langerhans. These cells sit in tiny groups scattered throughout the tissue of the pancreas, like small islands – an easy way to remember the name. These host alpha cells which produce Glucagon and beta cells which secrete Insulin directly into the bloodstream. Despite the miniature number of these cells, Insulin is produced in far greater amounts under normal conditions than any other hormones produced by different types of cells within pancreatic islets.
Our bodies desire blood glucose to be maintained between 70 mg/dl and 110 mg/dl (mg/dl means milligrams of glucose in 100 millilitres of blood). If you go below 70 – you have "hypoglycaemia" or low blood sugar. If you have eaten, the blood sugar will go above 110, but should be below 180. This is the optimal range. Above 180 is termed "hyperglycaemia". At this point, the “take me to the sky and make me fly high” energy spike, normally seen if you eat too much sugar too fast or gulp on a 2-litre bottle of soda in 5 minutes, will stimulate your pancreas to make lots of Insulin.
When glucose levels fall below normal range, so do Insulin levels. Your liver senses the alarm or falling energy and it stops making glycogen – there is nothing to make it from. So, without Insulin, many of our cells in the body would not be able to take up and use glucose and would have to resort to alternative fuels like fatty acids or ketones for energy.
Insulin is a hormone, and like many hormones, Insulin is a protein made up of 51 different amino acids. It is one of the smallest proteins in the body structured with two poly-peptide chains linked by two disulphide bonds, connecting the amino acid Cysteine to Cysteine. There is also a third disulphide bond that connects these same amino acids within Chain A. Chain A consists of 21 amino acids and chain B contains 30 amino acids. The one special thing about Insulin is its change in structure to become useful in the human body. In case you are wondering, Insulin's empirical formula is: C254 H377 N65 O75 S6 and it has a molecular weight of 5734.
First Insulin Response
 Think of your gastro-intestinal tract as your body's gateway to feeding muscle. As soon as you put food in your mouth your digestion starts in full-blown mechanism and you put Insulin to action. This is known as the early Insulin release from the granules which were made and pre-stored before you even made your meal selection. Generally, regardless of the foods you eat, as long as they have carbohydrates, your blood glucose goes up. Dietary fats and proteins provide calories and energy, but they have little or no effect on blood sugar. One reason is that these nutrients are digested and metabolised differently than sugars. These complex essential fatty acids and amino acids have other more important tasks to do in your body, such as building new cells and tissues, making neural connections and supporting immunity. In terms of actual energy, your body treats carbohydrates as the ultimate fuel you need for your muscles to contract, for your heart to beat, for your brain to think, for your lungs to breathe.
First, membrane depolarisation of the beta cells within pancreas causes extra-cellular Calcium to rush into the cell. This in turn pushes Insulin stored in secretory granules out of the cell. Most cells through out the human body, such as liver, muscle, fat cells, have special receptors for Insulin. When the hormone binds to these receptors, it and these cells activate other receptors designed to absorb the glucose from the blood stream.
Second Insulin Response
Just after you eat a meal, your body is ready to receive the glucose, fatty acids and amino acids absorbed from the food. Every tasty treat is broken down into smaller molecules, converted to sugars and absorbed through the lining of your digestive tract, all sugars are transported to the liver where galactose and fructose are converted to glucose and released into the bloodstream. Now is the time for your blood sugar levels to rise.
So, sugars naturally elevate your body’s levels of Insulin, a hormone with powerful anabolic effect. When the newly ingested sugar raises the blood sugar level in excess of its capacity of 20 grams, the pancreas releases Insulin into the bloodstream to transport the excess glucose to body tissues. This excess glucose is said to be “Insulin-carried.”The degree to which Insulin is raised may be a result of two things – the amount of carbohydrates you eat, their impact on blood sugar levels, whether you were fasting or feasting a few hours before eating, how hungry are your tissues for nutrients and whether you are under stress. All these things are naturally managed within your system to maintain the equilibrium.
Insulin must be present for the uptake of glucose in all body tissues except the brain. This is the second phase response of Insulin synthesis, the phase where Insulin transports the nutrients to the receptors in the tissues.
The active version of the Insulin hormone is not created immediately upon food entering the body and there are several steps for this protein to take in order to become something your body can use. Once food enters the body, it immediately is detected and the Insulin mRNA is translated as a single chain precursor called preproInsulin in the pancreas. Made up of an A, B, and C chains, and a signal peptide, preproInsulin is a lot longer than Insulin – it has 110 amino acids. Soon after, the preproInsulin turns into shorter version, known as proInsulin. It has only 86 amino acids long, but still contains the A, B, and C chains. In order to make active Insulin for the body to use properly, proInsulin is then exposed to several specific endopeptidases which cut the C chain. All is left is the A and B chains, which is considered the Insulin hormone with 51 amino acids. From the very beginning, the preproInsulin is more than twice the length of Insulin which now you can get to do the job of nutrient delivery.
Normally the cell membranes are impermeable to glucose, but they have Insulin receptors which bind the hormone to the cell. These are called GLUT receptors. Theey are found on the plasma membrane of every cell and the membrane of at least one type of organelle.
As the levels of Insulin in the blood begin to rise, this causes glucose transport proteins (GLUT) to increase their activity and drive more glucose into the liver, muscle cells, fat tissue to absorb the incoming molecules of pure energy. When Insulin attaches to GLUT receptors on the cell, it causes a conformational change. What sort of change? The welcoming signal. GLUT is the front door which can be opened by the only key – Insulin. If the key matches properly, the cell's door opens and allows the nutrients, or the molecules, to come in. This opening in the receptors is a door not just for sugars, but for amino acids, fatty acids, minerals, vitamins and other stuff like Creatine as well. When a cell has Insulin attached to it, is able to activate other receptors designed to absorb the nourishment from the blood stream and move it to the inside of the cell where energy is produced. Normally, when the receptors are healthy, they sense the hormonal nourishing alarm from Insulin and readily suck the food calories to their best ability.
Two of these transporters have been found in skeletal muscle: GLUT 1, which is found on the plasma membrane of all cells and functions optimally during fasting. Foetal tissues, erythrocytes of the blood and endothelial cells of barrier tissues, such as blood-brain barrier,are the major cites for GLUT 1. Muscles also have it, just at very low levels. GLUT 4 is the major isoform in heart and skeletal muscles, as well as in the fat tissue. One interesting receptor, GLUT 5, is responsible for uptake of fructose by the muscles when this sugar is available. Why is it interesting? Because fructose is an exceptional sugar which is metabolised very differently from other carbohydrates. It has been a subject of many controvercial arguments and is currently blamed for the obesity epidemic. We know so much more about glucose, another simple sugar, but the question of how fructose is metabolised within the muscles is not fully settled yet.
There are also other glucose transporters, GLUT 2 and GLUT 7 (found in the kidneys, liver, cells of the digestive tract), GLUT 3 (expressed mostly in neurons and in the placenta), but these don't do much for the muscles.
In simple terms, the main sugar transporters work this way - when you get hungry and don't have sufficient glucose in your blood, GLUT 1 goes up to keep you alive and activate the stored glucose to be used for energy. As soon as you eat – it goes down. GLUT 4, on the other hand, is the protein which transports glucose from the blood to the muscles, so it is stimulated by high sugar concentrations in the blood and mediated by Insulin.
Both Insulin and exercise stimulate the translocation of GLUT 4 transporters from an intracellular pool to the surface of the muscle cells, or the plasma membrane, but they do so independently.
What does all this biochemistry mean to you? That your brain, blood, immune cells, internal organs, and certainly muscle cells and fat tissues are extremely sensitive to Insulin and readily take in the sugars whenever it is available. They depend on constant carbohydrate supply, even though carbohydrates were thought to be non-essential nutrients. This also means that both, exercise and diet may increase or decrease your sensitivity to Insulin, depending on how you manage the supply of goods. If you force-feed your body with sugars, they can also be transformed into fat and stored in adipose cells, which love extra food so much, I think they can grow just from the mere mention of the word.
So, What Is The Function of Insulin?
First of all, Insulin helps to transport sugars and other nutrients from the blood to the liver. In this way, your body maintains a steady blood-glucose concentration and gives energy to the never-resting heart and brain, immune cells and maintenance of lean tissues. Only as a result of this nutrient delivery your blood sugar levels go down. As you can see, lowering glucose concentration is not the primary purpose of Insulin, but comes as some kind of good 'side effect', if I can call it this way.
Because of its many functions, Insulin has earned its honourable title – a potent anabolic regulator of the muscle. This hormone helps to increase muscle strength and mass, boost immune response and supply raw materials for energetic use, increase protein synthesis and uptake by the tissues, ensure amino acid and good fats get to the places of need. A very unknown feature of Insulin is its effect on the heart function and blood flow. Studies have shown that Insulin infusion increases blood flow by more than 100%! This also helps with detoxification and removal of metabolic wastes, such as carbon dioxide, lactic acid, various pathogenic toxins and LDL or “bad” cholesterol. And who do you think is responsible for the strength and endurance of your muscles? Insulin, indeed. It helps to decrease protein degradation and suppress the effects of catabolic stress hormones such as Cortisol, the potent muscle tissue scavengers.
What Else Can Insulin Do For Your Muscles?
Nourish them with other essentials, such as proteins, fats, vitamins, minerals, and supplements like Creatine, BCAAs, Glutamine, L-carnitine, HMB, etc. All nutrients you eat and drink are processed in the liver, the main site for amino acid turnover – the metabolic/catabolic cycle. This largest gland stores the energy needed for your muscles to move and feeds your cells and tissues with essentials for growth and recuperation. But there is no way your liver would ever have energy to do its job unless it wasn't for Insulin and the ever controversial carbohydrates. Nothing can beat the power of Insulin!
Insulin is not a “fattening” hormone!
So, carbohydrates are not fattening and Insulin is not a villain You need this hormone, but you need to control it. And when you eat to promote Insulin surges, you've got to be sure that you have the ideal profile of macro-nutrients in your blood to ensure that this Insulin surge leads to muscle gain and not fat gain. This is where meal combinations come into play.
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