The disorder caused by the chronic imbalance of glucose in the blood due to inadequacy or absence of insulin function or conditions that hamper its functioning is known as diabetes or more appropriately as diabetes mellitus.
Introduction
Our body processes many kinds of sugars commonly referred to as carbohydrates. They can occur as simple sugars also called monosaccharides. Glucose, fructose, ribose, galactose, mannose are a few examples of simple sugars. Two simple sugars linked together are called disaccharides, like sucrose (glucose + fructose), maltose (glucose + glucose), lactose (glucose + galactose). Many monosaccharides linked together chemically form more complex forms of sugars called polysaccharides.
Polysaccharides in association with other compounds like proteins and lipids can form complex carbohydrates like, for example to form structural entities to support joints and other entities like cell membranes. Simple, digestible carbohydrates, made of simple sugars are more like storage units. Starch, glycogen are examples of simple polysaccharides They have to be broken down in the body to simple sugars before they can engage in any biological activity in the body. Then there are indigestible carbohydrates like cellulose which are inert biochemically but serve a very important role as roughage or dietary fibre.
The ever increasingly ubiquitous common sugar in our consumption is a disaccharide made of two simple sugars, glucose and fructose. The sucrose molecule must be broken down into the simple sugars before it can be used as source of energy.
Glucose is by far the most important sugar in the blood as it serves as the main source of energy for the cellular activities in the body. For instance, the brain needs continuous supply of glucose from the blood to meet the very high energy demands of the brain cells. A blood sugar level is commonly taken as synonymous with a blood glucose level.
Body homeostasis
The normal body is remarkable in that it maintains its internal biochemical and physiological balance against external challenges by using metabolic processes as control mechanism with in-built checks and balances.
The body temperature is kept within a very narrow range despite the wide variations of external temperature. The blood pressure is also maintained within well-defined limits. The acidity of the blood is very finely maintained at constant pH. A blood sugar level like some other compounds in the blood is very well maintained. The state of equilibrium that the body maintains is called homeostasis Any wide fluctuations in the internal environment over a period, and the alarm bells should start ringing and medical intervention sought at the earliest.
The glucose balance in the blood or the glucose homeostasis is achieved by the hormone insulin secreted by the beta cells of the pancreas and by another hormone glucagon secreted by the alpha cells of the pancreas. The two hormones have completely opposite mode of actions
An increase in blood sugar is accompanied by release of insulin from the pancreas. Insulin helps transport glucose across the cell membranes into the cells for metabolic action and to release energy. The excess glucose is converted into glycogen and is stored in the skeletal muscles, the adipose tissue, the liver and some other tissues like skin and the glandular tissues., The transport of glucose however in the brain cells is not mediated via insulin but by a diffusion process through the blood brain barrier. The neurons have the highest demand for glucose for its energy needs and require constant supply of glucose. Insulin also has a significant role in the metabolism of not just carbohydrates but also fats and proteins.
Glucagon, the hormone secreted by the alpha cells of the pancreas have the opposite action to that of insulin. It promotes the synthesis of glucose in the cells and also metabolises stored glycogen to glucose when glucose levels drop in the blood. The level of glucagon drops in the presence of high levels of glucose in the blood, as for instance after a meal.
As emphasized insulin is the most vital hormone in maintaining glucose balance in the body. Its deficiency results in extremely high levels of glucose in the blood (hyperglycaemia) which in turn causes excessive excretion of glucose in the urine. Despite the very high levels of glucose in the blood, there is decreased glycogen level, and deficiency of glucose in the muscles and liver. Some tissues like the brain and retina can continue to use glucose from the blood as transport to these tissues are not dependent on insulin. Insulin deficiency has many other metabolic consequences. Like, in addition to carbohydrates, biosynthesis of fatty acids and protein are also diminished.
Diabetes mellitus
The disorder caused by the chronic imbalance of glucose in the blood due to inadequacy or absence of insulin function or conditions that hamper its functioning is known as diabetes. It is more appropriately referred to as diabetes mellitus so as not to confuse it with other disorder, diabetes insipidus which is caused by the decreased production of antidiuretic hormone in the brain.
Types of Diabetes mellitus
There are three types of diabetes: Insulin dependent (Type l), insulin independent (Type ll) and gestational diabetes. The gestational diabetes occurs during pregnancy but clears post-partum. Provided diabetes is well managed, the baby does not come to any harm. The mother is more prone to developing diabetes later in life.
Type l Diabetes
Insulin-dependent diabetes, Type l diabetes usually takes hold in childhood. Beta-cells of the pancreas are destroyed or are dysfunctional and produce little or no unable insulin. The cause of the destruction of the beta-cells is the auto-immune attack on the beta-cells by the body’s own immune mechanism which does not recognise the cells as belonging to the body but as foreign invasive bodies, A viral infection or some genetic factor may dispose the immune system to such auto-immune attack. For this reason, patients with Type l diabetes must always rely on exogenous supply of insulin which is injected in the body to control hyperglycaemia and ketoacidosis.
Ketoacidosis is the built up of ketoacids in the blood. Ketoacids are partial breakdown products of fatty acids from the fats. In the absence of insulin and therefore the unavailability of glucose, the body utilizes fats for its energy need. The result is the build of ketones in the blood that causes brain to swell and predisposes the body to go into shock. The signs of ketoacidosis include acetone smell in the breath high levels of ketones and glucose in the urine, hyperventilation, dehydration, fatigue, state of confusion, thirst and frequent urination, vomiting, abdominal pain, coma.
The condition is extremely life threatening and must be treated as a medical emergency. It is vital the patients are aware of the nature of the condition and fully comply with the regime insulin medication as prescribed by their doctors.
Type ll Diabetes
Insulin-independent diabetes, Type ll diabetes is adult-onset diabetes usually takes hold after the age of about 35 years. This is a chronic condition and is characterised by hyperglycaemia. The condition is further aggravated by excessive production of the hormone glucagon which promotes the synthesis of glucose in the cells and releases glucose from the stored glycogen when the glucose levels drop in the blood.
Ketoacidosis is common in Type l diabetes, it is rare in Type ll diabetes, but other features like the need for frequent urination, thirst and tiredness are similar in both the conditions. Whereas Type l diabetes is always treated with insulin, insulin treatment in diabetes type ll is usually not required. The reason being there may be some beta-cells producing insulin, although insulin treatment may be required high glucose levels in some patients.
The other key issues in type ll diabetes are the dysfunctional B-cells and insulin resistance. Insulin resistance occurs when target tissues are unable to respond to insulin. Consequence of the insulin resistance is the uncontrolled glucose production by the liver and diminished of glucose by the muscle and adipose tissues. Insulin resistance may arise due to structural defect of insulin or insulin-receptors, which may adversely affect the glucose uptake by the cells. Obesity may be a factor in insulin resistance as evidenced when the condition improves with weight reduction.
It is possible that type ll diabetes may worsen with aging as the pancreas deteriorates and there are less beta-cells to produce insulin. It is important that blood glucose is maintained within limits to offset harmful complications of hyperglycaemia, especially in the blood capillaries in the kidneys, nerves and eyes. There is also the risk of heart disease and stroke. Hyperglycaemia also predisposes patients to hyperosmolar syndrome- meaning continued very high concentrations of circulating glucose in the blood. This condition causes excessive thirst, frequent urination, dry mouth, dry skin, rapid pulse rate, shortness of breath, confusion and may even lead to coma.
Treatment of diabetes involves medicines, recommended dietary and exercise regimes and certain lifestyle disciplines. Apart from insulin, which is not usually required in type ll diabetes, there are several medications available to control glucose levels in the blood. Various medication strategies are available to control blood glucose levels in type ll diabetes: medicines to stop sugar production in the liver (Metformin) or to remove sugar from the blood (Glitazones) or to increase the release of insulin from the pancreas (Su[fonylureas and Glinides) or to slow carbohydrate absorption or to reduce sugar production in the liver and slow food absorption or premeal medication that prevent the reabsorption of glucose. Medications are prescribed by doctors after a thorough assessment of prevailing conditions of the patients.
As a self-help, diabetic patients should pay particular attention to lifestyle disciplines. It is important that regular sleep patterns are established. Sleep deprivation leads to increased production of cortisol which may inhibit insulin function and raise glucose levels in the blood. Exercise, in addition to enhancing insulin sensitivity, may help reduce abdominal obesity.
Particular attention should be paid to diet. It should should be balanced and free of processed food, should be rich in fruits and vegetable with adequate amount of fibres. Sugar in our diet is spiralling out of control. Our consumption of sugar is far too excessive and unless steps are taken to drastically cut back, we face a very unhealthy future. There is a mistaken belief that fructose is a good for diabetics and hence the high consumption fructose corn syrup. Fructose is only metabolised in the liver cells and follows a different metabolic pathway than glucose. It promotes synthesis of triglycerides and cholesterol which then translates into obesity, cardiovascular diseases, diabetes, fatty liver. Thus, like alcohol it may be responsible for fatty liver. Fruits have fructose, but this fructose does not have the detrimental effects of high fructose corn syrup, fruits are rich in fibres, vitamins and minerals and are very essential to a healthy diet.
There are over-the-counter supplements for the sugar control. These are supplements like cinnamon, chromium or multi nutrient supplements designed to provide nutritional support for healthy blood sugar levels. but they are supplements and never a substitute for a prescribed course of medicine
It may be a good practise for people to be screened for prediabetes and diabetes, particularly people in their late thirties and abdominal obesity. In prediabetes the blood glucose is high but not high enough be diabetic, but early signs of diabetes may be present.
There are three main methods available for testing the glucose concentration in the blood. Any of these could be used to diagnose prediabetes or diabetes in patients. a) fasting plasma glucose, b) Oral glucose challenge where glucose level in the blood is measured two hours after the oral administration of 75gm of anhydrous glucose. c) measurement of glycated haemoglobin HbA1c.
A random of blood glucose test showing glucose concentration of greater than 11.1 millimolar or higher suggests diagnosis of diabetes. The test should always be done again to get definitive confirmation.
Blood samples following an overnight fast should show glucose concentration of less than 5.6 millimolar for normal subjects. A concentration level between 5.6 and 6.9 millimolar suggests prediabetic condition. A concentration level of 7 millimolar on two separate occasions confirms diagnosis of diabetes.
In the oral glucose challenge test, the fasting sugar level is measure followed by the glucose drink. Glucose concentrations are monitored periodically for the next two hours. A blood glucose level less than 7.8 millimolar is normal (no diabetes), Levels between 7.8 and 11.0 millimolar suggests prediabetic and a reading over 11.1 millimolar confirms diabetes.
The advantage of the Hb1Ac is that it measures average glucose blood glucose level for the past 2-3 months, so does not involve fasting or administration of glucose for the glucose challenge. The results are expressed as percentage of haemoglobin glycated. For normal range it is less than 5.7%, for prediabetes the range is 5.5% to 6.4% and for diabetes it is 6.5% and higher.
However, the results of the HbA1c are very cautiously interpreted. Young people and people with some other medical conditions are excluded. Caution is exercised where there are abnormal blood cells turn over, abnormality of haemoglobin types, severe anaemia, recent blood transfusion or surgery affecting the blood cells turn over.
Diabetes mellitus is a chronic illness, requiring careful life-long medication and management to maintain blood glucose levels within normal range; failure to do so can result in serious complications of health. If regular mealtimes and medications are not followed there is, in addition to hyperglycaemia, also danger of hypoglycaemia (blood glucose level less than 3.5 millimolar), which may result from an overdose of insulin producing medicines or skipping meals or excessive drinking of alcohol. Low blood glucose levels may cause dizziness, tiredness, irregular heartbeats, confusion, fainting. The hypoglycaemia can be self-treated by taking a food or drink containing carbohydrate or glucose for faster relief.
With proper care patients can and do live a very healthy and fulfilled life. Research and development in the field are making great progress, with some of the focus on long-acting, smart delivery medications, implants of healthy beta cells or stem cell treatment to introduce new insulin-producing beta-cells into diabetic patients. Future looks very bright for the treatment, remission and even cure of diabetes.