Issue 104 / March - April 2015
Insulin and Blood Sugar Balance
The human body needs energy. ATP (Adenosine Triphosphate) is to each cell in the body what gasoline is to a car. This energy is stored inside the bonds of the three phosphate molecules attached to an adenosine nucleotide. The light energy that exists in the sun's rays is converted into chemical energy, stored in the form of carbohydrates, proteins, and fats through the photosynthetic reactions taking place in the chloroplasts of plants. Molecules of chemical energy are broken down in the mitochondria organelle of the cells in order to utilize their energy for ATP synthesis. This chemical energy (ATP) derived from nutrients is used by the eyes to see, the ears to hear, the hands to grab, the feet to walk, the heart to pump blood, the stomach to digest foods, the kidneys to filter blood, red blood cells to carry oxygen, white blood cells to fight germs, and the brain to think, memorize, and remember.
ATP is primarily synthesized from glucose - commonly known as blood sugar (glycolysis) - in approximately 100 trillion cells in our body. Glucose means fast energy. A sensitive metabolic balance is established (homeostasis) to maintain a blood glucose concentration in between 70-100 mg/dl for a nonstop energy flow and to prevent any cellular damage. If this balance is thrown out of order, many medical problems will ensue, primarily cardio-vascular diseases. How is the homeostatic balance of blood sugar maintained in healthy people?
Maintenance of blood sugar balance
The blood sugar balance is provided by the assistance and cooperation of the pancreas, liver, fat tissue, muscle tissue, the brain, the digestive system, and the kidneys. The chiefs of the orchestra here are the insulin and glucagon hormones synthesized in the pancreas, which operate in great harmony and yet have opposite functions. Insulin is in charge of dropping blood sugar; however glucagon increases it.
The fine balance of blood sugar is conserved before we sense it for various energy situations such as exercise, sleep, or various energy intake cases such as overeating or skipping a meal. The real hunger is the 8-10 hour long "night fasting" period. During this time, since there is no food intake, the glucose that cells require for energy production is obtained from reserves in the liver. Thus, cells get their energy and blood sugar levels are kept at normal levels. If there is no additional food intake and the fasting time becomes longer, the glycogen reserves of the liver get consumed within 10-18 hours and necessary energy is obtained from fats and proteins. However, real fullness corresponds to a period of 4-6 hours "after meal." During this time, the complex and macro size carbohydrates are converted to glucose in the liver and this glucose is stored as glycogen. Because the glucose storage capacity of the liver, which has numerous tasks, is limited, the excess glucose is stored by conversion into fatty acids. The unspent excess calories from three meals eaten in five hour intervals will be stored in either the liver or as fat tissue during the 12-18 hour long fullness period. The utilization of fats stored in the humps of camels which form by food intake to compensate for their energy and water needs during long desert travel can be given as an example of this.
In fact, when we say "I am hungry," we acknowledge that the time has come to resupply our ATP reserves of nearly 100 trillion cells. The most important stimulator for the secretion of insulin from the pancreas is glucose. With the first bite, the readied insulin reserves of the pancreas are released into the bloodstream. This event, which takes place approximately within the first 6-10 minutes, is called the first-phase insulin response. With the language of reduced glucagon as a result of increased insulin, the message that it is no longer necessary to release glucose into the blood is transmitted to the liver. The blood sugar levels increase with continuing food intake (hyperglycemia) and this information is relayed to the pancreas through hormones secreted by intestinal cells. As directed by this signal, the proper insulin amount necessary for blood sugar levels is secreted into the bloodstream from the pancreas. This is called the late-phase insulin response.
The tasks of insulin
Cells are in need of insulin to uptake glucose into capillary vessels. Insulin binds itself to its specific receptor on the membrane of a cell, conducting its message, especially to muscle tissue. It's saying, "The glucose food that you need is brought here by the blood vessels, and you can retrieve it." After receiving the message inside the cell, GLUT (glucose transporters) molecules, which are in charge of glucose intake and are stored in the cytoplasmic vesicle pool, are carried to the cellular surface. Molecular gates are established once these molecules merge with the cellular membrane for the entrance of glucose through it. Glucose is inserted into the cell via this gate. The retired GLUTs are collected back in the cytoplasmic pools after cellular energy demand is met.
While these events are taking place, commands are given to the liver to prepare for the load of glucose arriving from the intestines and for adipose tissue to store the excess fat. These meticulous processes last for approximately two hours. The blood sugar level recedes back to its normal limits, but the activities of the liver and the adipose tissue continue at a rapid pace. If overeating occurs, the liver cannot take such a load. This can cause a delay in its functions, which will cause the body to feel tired.
The insulin and glucagon hormones have a half life of 3-5 minutes and are rendered ineffective in the liver and kidneys once they conclude their tasks. Thus, the body prevents lower blood sugar levels because of high insulin concentrations (hypoglycemia) or because of higher glucagon levels; it also prevents higher blood sugar levels (hyperglycemia).
The disruption of the blood sugar balance
Diabetes is the chronic observation of blood sugar above normal limits. This happens when the insulin hormone levels secreted from the pancreas are reduced and not able to carry out their function. There might be genetic factors present that contribute to diabetes; however, stress, a lack of exercise, obesity, and the consumption of processed foods containing elevated levels of carbohydrates often lead to the onset of diabetes in adults. The fine balance in between the liver, pancreas, muscles, and fat tissue can be disrupted by the following reasons:
1. If the number of cells in charge of insulin production in the pancreas decreases, sufficient insulin cannot be produced.
2. The message of insulin cannot be retrieved completely because of a disruption occurring at the receptors where insulin binds on cells, or due to lower numbers.
3. There may be a problem with reactions regarding GLUT production in accordance with the internal message retrieved upon bondage of insulin to the receptors.
4. During fullness, if the necessary suppression of glucagon production in pancreatic cells is not adequate, the glucose release from the liver continues.
5. The secretion of late-phase insulin response hormones in charge of pancreatic stimulation from the intestines is reduced.
6. Emptiness of the stomach is delayed, and a longer absorption time of nutrients occurs.
7. The appetite center is over stimulated and the urge to eat increases.
If the reasons above take place, then the blood sugar level is above normal. Normal blood sugar drops below 140 mg/dl two hours after a meal in healthy people, whereas this cannot be maintained in diabetic patients.
An iron pipe with salty sea water running through it for years is similar to a capillary vessel that has blood with high sugar levels inside it in terms of the damage that they undergo. Once hypertension and cholesterol joins diabetes, the heart, eyes, and kidneys will not function properly. These organs are great blessings granted to our body which we often appreciate only once we lose them. Therefore we must follow an intermediate path in eating and drinking, just as in every situation, avoiding excess.