PATHOGENESIS of Diabetes

 

  • PATHOGENESIS OF TYPE 1 DIABETES MELLITUS

Type 1 Diabetes was previously called Insulin Dependent Diabetes Mellitus (IDDM).  It refers to cell-mediated autoimmune destruction of pancreatic beta islet cells, which leads to absolute insulin deficiency.   The pathogenesis can be summarized as follows:

  • In a genetically pre-disposed individual
  • Environmental factors trigger an autoimmune process
  • Destruction of Islet cell and deficiency

The immune response leads to development of autoantibodies against various islet cell components, including glutamic acid decarboxylase antibodies (GAD – 65), Islet cell antibodies (ICA512/IA-2) and Insulin antibodies (IAA).

Several viruses like Coxsackie B virus, Rubella virus. Mumps virus, Cytomegalo virus etc. have been associated with inducing viruses.

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  • PATHOGENESIS OF TYPE 2 DIABETES MELLITUS

Type 2 Diabetes Mellitus was previously called Non-Insulin Dependent Diabetes Mellitus (NIDDM) or Adult –Onset Diabetes.  Type 2 Diabetes is characterized by varying degrees of Insulin resistance (Insulin resistance is a condition in which the cell of the body become resistant to effects to insulin.  As a result, higher levels of insulin are needed in order for Insulin to have its effects.  Several factors like genetic factor, obesity, pregnancy, infection, stress, during steroid use induces Insulin resistance) and Insulin deficiency.

The dual defect of Insulin deficiency and Insulin resistance in Type 2 Diabetes is caused by interplay between genetic and environmental factors.

GENETIC FACTORS

Epidemiologic and genetic studies suggest a strong genetic basis for development of Type 2 Diabetes.  In most cases, Insulin resistance is due to obesity but the fat next to intestine, visceral fat, seems to be most important.  Genetics and ethnicity play an important role in the proportion of visceral fat, compared to overall fat.

ENVIRONMENTAL FACTORS

Despite its strong genetic basis, the rising incidence of Type 2 Diabetes over the past few decades strongly suggest a lifestyle link.  It has been suggested that decreased physical activity and increased consumption of higher fat foods are contributing to the increase in obesity.  The increase in obesity increases the number of people at risk for developing Type 2 Diabetes.

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