Type 2 diabetes is a disease in which the person initially develops insulin resistance resulting in high glucose levels in the blood. This is also called impaired glucose tolerance. Initially individuals experience high blood glucose levels after eating and eventually this may lead to constant hyperglycaemia.
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The metabolic derangement is called insulin resistance because patients require higher levels of insulin to move glucose in the blood to the inside of cells such as muscles, the heart, the liver and the brain where it is needed for functioning of the cells.
Insulin resistance is the main metabolic event leading to Type 2 diabetes and the reduction of it should therefore also be the major aim of affected individuals and the treating physician or advising dietician.
It is the most common form of diabetes and its incidence is rising in all population groups around the world.
It is strongly associated with obesity, a sedentary lifestyle, and abnormal lipid levels.
Those with a family history of the disease are more at risk than the general population.
Symptoms are more those of a high glucose level than those of starving cells and include excessive thirst and urination, whereas weight loss is a late feature suggesting serious deficiency of insulin.
It is treated, and can often be prevented, with a combination of lifestyle changes, diet and drugs – increased levels of exercise and a decrease in the intake of calories and especially lipids being the most important steps to improved health and longevity.
There are many potential complications of Type 2 diabetes if it is not correctly controlled (such as heart disease), since most organ systems in the body are affected by the disease.
Alternative names
Non-insulin dependent diabetes (NIDDM) or adult onset diabetes – now rarely used.
What is Type 2 diabetes?
Type 2 diabetes is the most common variety of diabetes. It is a disorder of carbohydrate metabolism in which the body effectively becomes resistant to the hormone insulin. Initially, the person with this disorder has impaired tolerance to glucose. This develops into high blood glucose levels after eating and eventually high blood glucose levels even when fasting.
However, some people with Type 2 diabetes remain relatively sensitive to insulin, while others have little or no insulin sensitivity. This difference affects treatment of the disease. In general, those Type 2 diabetics who are not obese retain some sensitivity to insulin.
What causes Type 2 diabetes?
The causes of Type 2 diabetes are complex. Insulin resistance is the main metabolic abnormality leading to the development of Type 2 diabetes. The most recent research suggests that Type 2 diabetes can be seen as a consequence of a series of physiological disruptions, each of which makes the person vulnerable to subsequent disruption of normal glucose metabolism.
Insulin resistance is common and is usually caused by obesity. There are effectively three stages in the development of Type 2 diabetes:
Insulin resistance, for which the body compensates by increasing the secretion of insulin to allow the liver and muscles to continue to function normally.
Eventually the pancreas is unable to produce enough insulin to compensate for the insulin resistance. This leads to a sequence of impaired glucose tolerance, high blood glucose after eating (postprandial hyperglycaemia) and finally, high blood glucose levels even when fasting (fasting hyperglycaemia) and worsening postprandially. These high glucose levels are toxic not only to the large and small blood vessels but also to the cells producing insulin, the so-called beta-cells of the pancreas.
This damage to the beta-cells leads to a decline in their function and eventually less insulin is produced as the disease progresses.
The raised fasting and postprandial glucose levels result in complications which affect the small and large blood vessels of the body, and this contributes to renal failure, eye complications and more importantly, accelerated atherosclerosis leading to strokes and heart disease. The artherosclerotic complications are responsible for 80% of the deaths in diabetics.
Who gets Type 2 diabetes and who is at risk?
The percentage of the population with diabetes is highly variable among geographical regions and populations, so estimates are often inaccurate. A recent figure is 110 million people around the world with diabetes, most of whom (75 – 80%) have Type 2 diabetes. There are particular populations with a very high incidence of Type 2 diabetes. For example, 40% of Pima Indians in North America have Type 2 diabetes. The South African Indian population also have amongst the highest incidence in the world.
The risk factors for Type 2 diabetes are:
Obesity
Lack of exercise
An abnormal lipid profile
A family history of the disease
Who would be the typical person at risk for Type 2 diabetes?
The typical person would be:
an overweight adult
older than 40 years
an individual who does not exercise regularly
the pattern of obesity is usually a predominance of central fat deposition, which means that the belly or waistline are disproportionally enlarged compared to the limbs
a person with a family history of obesity. (Many type 2 diabetics have a family history of obesity and possibly even “late onset diabetes”)
What are the symptoms and signs of Type 2 diabetes?
The main features and symptoms of Type 2 diabetes are:
Overweight
Excessive thirst
Excessive urination
Loss of weight
However, these are late signs that occur when the person is already seriously hyperglycaemic.
Early in the course of the disease there are more subtle signs such as fatigue, greater susceptibility to illness and poor wound healing.
A very common early sign in men is erectile dysfunction, as is candida infection of the tip of the penis (candida balanitis). In women, persistent vaginal candida may be an early sign of Type 2 diabetes, particularly in older women.
How is Type 2 diabetes diagnosed?
Diabetes is diagnosed quite simply by measuring the levels of glucose in the blood. The normal levels are between 3,3 mmol/l and 5,9 mmol/l.
The World Health Organisation defines diabetes as being when one or more of the following are present:
Fasting blood glucose (blood glucose measured before breakfast) is over 6.7 mmol/l on two separate occasions
Random blood glucose (blood glucose measured at any time) is over 10 mmol/l
2 hour blood glucose during glucose tolerance test is over 10 mmol/l
Corresponding values for plasma glucose are 7.8 mml/l and 11.1 mmol/l
In some laboratories the glucose level is measured in plasma and not in blood and the concentration of glucose measured in plasma is 10% greater than that in whole blood
What is a glucose tolerance test?
After an overnight fast, 75 mg of glucose is taken in 250-300 ml of water
Blood samples are taken in the fasting state and two hours after the glucose has been taken
It is used to diagnose glucose intolerance
When is glucose tolerance impaired?
It is present when the fasting blood glucose is below 6.7 mmol/l and the 2 hour blood glucose value is between 6.7 and 10 mmol/l
Corresponding values for plasma glucose are 7.8 mml/l and 11.1 mmol/l.
Can Type 2 diabetes be prevented?
Type 2 diabetes is a disease of lifestyle in most cases, and can thus often be prevented. There is good evidence to show that controlling weight, getting plenty of exercise and eating a diet low in fats and high in complex carbohydrates – fruit and vegetables – lowers the risk of Type 2 diabetes in most people.
Many medical authorities recommend that anyone who has a family history of Type 2 diabetes should have their blood glucose checked regularly, particularly once they are older than 40. Some doctors recommend that anyone over the age of 40, regardless of family history, should have regular blood glucose checks.
If impaired glucose tolerance is detected, then early prevention such as weight loss, exercise and a change of diet may well prevent or at least delay the onset of Type 2 diabetes.
How is Type 2 diabetes treated?
The mainstay of treatment in Type 2 diabetes is lifestyle change – weight loss, a structured exercise programme and a diet low in fat and with plenty of fruit and vegetables. Any diabetic should consult a dietician early in the disease to work out the correct diet for their lifestyle. It is of utmost importance that individuals attempt to stop smoking, and if it is not possible to stop, reduce the habit to an absolute minimum.
However, recent research has shown that in most people, even the correct diet along with exercise will eventually not be sufficient to control their blood glucose and that drugs have to be used.
The broad range of metabolic defects present often requires treatment with combinations of more than one drug. Furthermore, with time, as the ability of the pancreas to produce sufficient insulin wanes, increasing doses of medications and insulin injections may be required to control the blood
sugar. The blood sugar levels should be reviewed by the patients doctor on a regular basis.
The medications used for treating Type 2 diabetes have the following
aims:
Medications that lower the blood sugar levels
Oral Hypoglycaemic Agents (OHA's).
There is an increasing array of tablets that are now effective in lowering glucose levels in Type2 diabetics. They differ in their modes of action, side effect profile,
cost and dosing schedule. The choice of which is most suitable needs to
be made on an individual basis after a full medical assessment.
Meglitinides: (E.g. Starlix, Novonorm). These are newer and more
expensive treatments that are used in combination with metformin.
Thiazolidinediones: (E.g. Actos, Avandia). This new class of
drug helps overcome insulin resistance and they may have some other beneficial
effects on the underlying metabolic defects.
Insulin
Insulin injections may be necessary in controlling the sugar levels and are usually started when the OHA's become ineffective. Insulin treatment should not be delayed once the sugar levels are not adequately controlled on
tablets. Insulin is usually combined with metformin as this increases the patient's sensitivity to the insulin and often reduces the dose of insulin that is needed.
Medications that help prevent or treat the complications of diabetes
It is imperative that the associated metabolic problems in Type 2
diabetes are adequately treated as this has been shown to help prevent the
serious cardiovascular and other complications for which the diabetic patient is
at risk.
The most important conditions that require treatment are hypertension
and the lipid abnormalities, both of which are commonly associated with Type 2
diabetes.
Some of the commonly used medications which offer specific benifits in
diabetes include:
ACE Inhibitors: (E.g. ramipril/Tritace or Ramace, perindopril/Coversyl, lisinopril/Zestril, captopril/Capoten). These are antihypertensive medications which may offer additional
protection against kidney and cardiovascular complications.
ARB's (E.g. losartan/Cozaar, irbesartan/Approvel). These
are used to treat hypertension and have also recently been shown to be of
benefit in slowing the progression of the kidney complications in Type 2
diabetics.
"Statins": (E.g. atorvastatin/Lipitor, pravastatin/Prava,
simvastatin/Zocor). While a low fat and low cholestrol diet is
important in diabetics, it is often insufficient. The "statins"
are a powerful group of cholesterol lowering agents that are useful in
treating the abnormal lipid profile and helping to achieve the strict targets
for cholestrol that need to be attained in order to lessen the risk of
cardiovascular disease.
Asprin has been shown to be of benefit in preventing cardiovascular
events such as heart attacks and strokes and should be used in Type 2
diabetics who are at risk or who have a history of previous cardiovascular
events.
Viagra®. Erectile dysfunction is a common problem in male
diabetics and newer forms of treatment are becoming available. Viagra may
be an effective, although expensive, option.
What is the outcome of Type 2 diabetes?
Type 2 diabetics have a very high incidence of heart disease, and this is their main cause of death. However, this can be prevented, or at least controlled, by taking great care to control blood glucose, blood pressure and lipid levels.
There are also long-term complications of Type 2 diabetes - potentially to every organ system in the body if blood glucose, blood pressure and lipid levels are not adequately controlled.
When to see your doctor
Consult your doctor if you develop symptoms of:
Excessive thirst
Excessive urination
Weight loss
- particularly if you have a family history of diabetes, you must see your doctor as soon as possible.
If you are already diabetic and you develop these symptoms, then this is an indication that your blood glucose is out of control and you should see your doctor immediately.
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