TYPES OF DIABETIC

Types:

There are three types of Diabetes:

• Type 1 Diabetes
• Type 2 Diabetes
• Gestational Diabetes

Type 1 diabetes

Type 1 diabetes is an autoimmune disease. In genetically susceptible individuals, an inflammation of pancreatic beta cells is triggered, most likely by a viral infection. Because beta cells are the only ones able to produce and secrete insulin, complete insulin deficiency ensues. As a result, all Type 1 diabetic patients require insulin replacement therapy. The only exception is during the 'honeymoon period' that some patients experience shortly after diagnosis and initial treatment, owing to some residual insulin secretion early in the progress of the disease.

Type 2 diabetes

Type 2 diabetes is a prime example of a disease caused by a combination of genetic and environmental factors. The genetic influence is greater than for Type 1 diabetes: the identical twin of a Type 2 diabetic patient is almost certain to develop the disease. On the other hand, lifestyle factors such as diet and exercise are also important determinants; in times of scarce food supply, for instance, the incidence of Type 2 diabetes is very low.

A good example of the interplay of genetics and lifestyle are the Pima Indians. Those living in Mexico have a diabetes prevalence of about 8%, whereas those who have emigrated to the USA, where the lifestyle is more sedentary and access to energy-dense (fatty) food is easier, have a diabetes prevalence of about 50%.

he most important risk factor for Type 2 diabetes is obesity. Epidemiological studies have shown that, compared to lean individuals, very obese men and women (body mass index >35) have a 60- and 90-fold increased probability of developing Type 2 diabetes, respectively (see figure). In terms of genetics, Type 2 diabetes is a multifactorial disease for which no single gene is responsible.

In contrast to patients with overt Type 2 diabetes, patients with pre-diabetes (characterised by insulin resistance) do not exhibit hyperglycaemia when fasting. However, after a challenge like an oral glucose tolerance test (oGTT), during which 75 grams of glucose are ingested, patients exhibit pathologically high glucose levels (see Table 1). These patients, therefore, are characterised as having impaired glucose tolerance.

For a limited period, pancreatic beta cells are able to produce enough insulin to overcome the insulin resistance, so many pre-diabetic patients actually have elevated plasma insulin levels. However, in most patients, the rate of beta-cell death exceeds that of beta-cell formation in the pancreas, resulting in fewer insulin-producing beta cells. When the insulin-producing capacity of the pancreas is overtaken by the increased demand caused by insulin resistance, the patient develops overt Type 2 diabetes.

Three main factors contribute to hyperglycaemia:

1. Insulin resistance in the muscle tissue, causing the muscles to take up less glucose from the blood.
2. Impaired insulin secretion by the pancreas.
3. Increased glucose production by the liver as a consequence of hepatic insulin resistance.

In the last few years, it has been demonstrated that adipose (fat) tissue and the central nervous system also play important roles in the pathogenesis of Type 2 diabetes.