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Type 1 Diabetes Mellitus: Theories of Causes of diabetes, a growing epidemic

Diabetes, Infant and Children | August 3, 2014 | Author: The Super Pharmacist

diabetes

Type 1 Diabetes Mellitus: Theories of Causes of diabetes, a growing epidemic

Type 1 diabetes mellitus, commonly called type 1 diabetes, is a lifelong disease characterised by a high level of sugar (glucose) in the blood.

In type 1 diabetes, the body loses its ability to produce insulin. Insulin is required to store glucose from the bloodstream into the tissues of the body. Cells use glucose as a source of energy to function. Without enough insulin, glucose builds up in the bloodstream instead of going into the cells. The body is unable to use this glucose for cellular energy.

This leads to the symptoms of type 1 diabetes which include increased thirst and hunger, frequent urination, unexplained weight loss, or, in severe cases, "diabetic coma" (diabetic ketoacidosis). Type 1 diabetes can occur at any age. It is most often diagnosed in children, adolescents, or young adults. Other names formerly used for type 1 diabetes include juvenile diabetes and insulin-dependent diabetes mellitus (IDDM).

causes of diabetes type 1Type 1 diabetes can often be confused with type 2 diabetes. However, there are some key differences. In type 1 diabetes, the body produces no insulin because the insulin-producing "beta cells" in the pancreas gland have been destroyed.

Although the immune system normally only attacks disease-causing organisms like bacteria or viruses, in the case of type 1 diabetes, it malfunctions and attacks its own pancreatic beta cells. This results in a complete deficiency of the insulin hormone.

Type 1 diabetes is considered an auto-immune disorder.

Type 2 diabetes, on the other hand, is a metabolic disease where the body still produces insulin but is not able to use it properly. This is called insulin resistance. As type 2 diabetes gets worse, the pancreas may make less and less insulin.

Unlike the lifelong nature and constant insulin delivery required by type 1 diabetes, type 2 can often be managed with diet and lifestyle changes. If not managed with diet and exercise successfully, treatment may require oral medications, and when all else fails insulin injections are sometimes required.

What Causes Type 1 Diabetes?

Type 1 diabetes is considered an autoimmune disease where, in certain genetically susceptible individuals, the body's immune system attacks its own tissues, specifically the insulin-producing beta cells of the pancreas. The exact cause of the immune system malfunction is unknown but certain risk factors for the disorder have been proposed including hereditary predisposition, environmental factors and dietary practices.

Hereditary predisposition

Looking at family histories demonstrates an important part in determining who is likely to develop type 1 diabetes. Although the genetic aspect of type 1 diabetes mellitus is complex, with multiple genes involved, there is a high sibling relative risk. Whereas dizygotic twins have a 5-6% concordance rate for type 1 DM, monozygotic twins will share the diagnosis more than 50% of the time by the age of 40 years. For the child of a parent with type 1 diabetes, the risk varies according to whether the mother or the father has diabetes. Children whose mother has type 1 diabetes have a 2-3% risk of developing the disease, whereas those whose father has the disease have a 5-6% risk. When both parents are diabetic, the risk rises to almost 30%.

Environmental factors

Environmental factors, such as foods, viruses, and toxins, may play a role in the development of type 1 diabetes, but the exact nature of their role has not been determined. Some theories suggest that environmental factors trigger the autoimmune destruction of beta cells in people with a genetic susceptibility to diabetes. Other theories suggest that environmental factors play an ongoing role in diabetes, even after diagnosis. 

A virus cannot cause diabetes on its own, but people are sometimes diagnosed with type 1 diabetes during or after a viral infection, suggesting a link between the two. Also, the onset of type 1 diabetes occurs more frequently during the winter when viral infections are more common. Viruses possibly associated with type 1 diabetes mellitus include enterovirus, coxsackievirus B, cytomegalovirus, adenovirus, rubella, and mumps. Scientists have described several ways these viruses may damage or destroy beta cells or possibly trigger an autoimmune response in susceptible people. Early upper respiratory infection may also be a risk factor for type 1 diabetes. In an analysis of data on 148 children considered genetically at risk for diabetes, upper respiratory infections in the first year of life were associated with an increased risk for type 1 diabetes.

Infant feeding practices

Some studies have suggested that dietary factors may raise or lower the risk of developing type 1 diabetes. For example, breastfed infants and infants receiving vitamin D supplements may have a reduced risk of developing type 1 diabetes, while early exposure to cow’s milk and cereal proteins may increase risk. Nitrites and nitrosamines in the diet have also been proposed as possible risk factors.

Why Is Type 1 Diabetes Becoming More Common?

causes of diabetes type 1While there is no clear explanation for the rising incidence of type 1 diabetes, certain contributing factors have been proposed and possible mechanisms developed in the hope of better understanding the condition.

Genetic variations likely explain some of the differing incidence and prevalence rates among people worldwide. Yet even among ethnically similar populations, type 1 diabetes incidence can vary. For example, Finns have a six times higher incidence in type 1 diabetes than Russians living across the border.

The genes that confer a high risk of type 1 diabetes, however, are the same in these populations, implying that environmental factors contribute to the differing incidence rates. As another example, type 1 diabetes incidence is much higher in Sweden and other Nordic countries than in Lithuania and other Baltic states. Yet the genetic risk of type 1 is similar in all of these countries. While genetic factors are thought to explain some of the geographic variability in type 1 diabetes occurrence, they cannot account for its rapidly increasing frequency.

'Latitude' hypothesis

Many of the countries with high incidence are located closer to the polar areas of the globe, both to the north and the south. Even within countries, latitude can make a difference. One Australian study, for example, found that type 1 diabetes was three times more common (prevalent) in more southerly regions of that country than in northerly regions. Like all rules, however, there are exceptions. For example, Sardinia, Italy's high incidence of type 1 diabetes does not fit the rule. Variations within countries also do not always correspond to latitude. Vitamin D, which is produced by the skin when exposed to sunlight, is a possible explanation for this pattern. In a study of 51 regions around the world, areas with lower levels of ultraviolet B radiation (the main source of vitamin D in humans) had a higher incidence of type 1 diabetes. Vitamin D deficiency appears to be a risk factor for type 1 diabetes mellitus, and vitamin D cannot be produced adequately by the skin during the winter in areas closer to the polar regions.

Socioeconomic factors

Most countries with a high incidence of type 1 diabetes mellitus are westernised, developed countries. Some studies have found a higher incidence of type 1 diabetes mellitus in wealthier populations or in people with higher socioeconomic status, such as Chile and the U.S. Higher socioeconomic status may play a role in relation to differences in nutrition or lifestyle. These factors could include high growth rates in early life, improved hygiene and fewer infections or more milk consumption.

Environmental contaminants

Another possibility is that persistent organic pollutants play a role in the development of type 1 diabetes mellitus. Persistent organic pollutants evaporate and migrate to the polar regions of the earth; some can even interfere with vitamin D synthesis. The incidence of type 1 diabetes mellitus is now rising even in countries with historically low incidence, suggesting a "catch-up" phenomenon. Levels of most persistent organic pollutants have declined recently in developed countries. In developing and some former Soviet countries, however, some persistent organic pollutants (like DDT) are still in use, and contamination due to open dumping is also a concern. Levels of some organochlorine pesticides (such as DDT) are now higher in people living in developing countries than in developed nations. Perhaps contamination resulting from industrialisation contributed to the rising incidence in many now-developed, high-incidence countries, and other countries, where contamination began later, are now "catching up."

Accelerator hypothesis

The “accelerator hypothesis” proposed by Wilkin, is a compelling theory. This investigator suggested that increasing body weight in younger children acts as an accelerator mechanism for an increased risk of developing type 1 diabetes mellitus. In fact, an inverse relationship was found between age at diagnosis and body mass index (BMI) at diagnosis and at 12 months after diagnosis, as well as weight at diagnosis and weight change since birth. Essentially, the age at diagnosis becomes younger as children become heavier; suggesting that being overweight accelerates insulin resistance, leading to the development of type 1 diabetes in genetically-predisposed individuals. Several articles have been published supporting Wilkin's accelerator hypothesis. Among these is a study by Libman et al., (2003) in the United States which showed an overall significant increase in the prevalence of being overweight in children with type 1 diabetes mellitus from 12.6% (1979–1989) to 36.8% (1990–1998).36 Read more about type 1 diabetes including our articles:

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