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Diabetes

In recent years there has been an explosion in the number of people living with diabetes. Today, we are seeing children younger than ever, develop diabetes as a result of obesity and poor diet.

According to the World Health Organisation (WHO)

  • In 2014, 1 in 10 people globally were suffering from diabetes; in the UK 1 in 16.
  • in 2012, 1.5 million deaths were directly attributed to diabetes.
  • More than 80% of diabetes deaths occur in low and middle income countries.
  • The WHO predicts that by the year 2030, diabetes will be the 7th leading cause of death.
  • By 2035, a staggering 592 million people are projected to develop the disease.

Diet, physical activity, normal body weight, and abstinence from tobacco can prevent or delay the onset of type 2 diabetes [1].

What causes Diabetes?

Diabetes mellitus, or simply diabetes, is a metabolic problem wherein the body cannot process glucose to be used as energy. Diabetes results either from an inability of the body to produce insulin (type 1 DM), or the inability of the body to appropriately respond to insulin (type 2 DM). Insulin is a hormone produced by the Beta cells of the Pancreas, it acts on body tissues to help them take up glucose from blood. The inability of cells to take up glucose, leads to excess glucose in the blood; hyperglycaemia. Hyperglycaemia is the hallmark of diabetes and the mechanism by which the disease wreaks havoc on body organs.

Glucose is a monosaccharide; the simplest form of carbohydrate which the body uses as energy. However, since glucose is a relatively big molecule, on its own it cannot cross the cell membrane and enter cells (where it can be used to produce energy for cell function). It therefore needs a carrier which helps it cross the cell membrane and enter the cell; this carrier takes the form of the hormone insulin. The hormone insulin is made by the pancreas in response to high blood glucose levels. If the blood glucose level is high, insulin is secreted in order to facilitate absorption of glucose into body cells. And if blood glucose is low, insulin secretion is halted [2].

Types of Diabetes 

There are three major types of diabetes; gestational diabetes, type 1 diabetes, and type 2 diabetes. Each of them is discussed below.

Gestational Diabetes Mellitus

During early pregnancy the surge in pregnancy hormones (namely progesterone) lead to increased appetite, delayed gastric emptying, increased fat deposition, and lowered blood glucose levels. As the pregnancy progresses, the blood glucose level of a pregnant woman after eating (postprandial glucose levels) increases steadily; while insulin sensitivity decreases steadily too. Gestational diabetes occurs when insulin sensitivity is not compensated through the increased secretion of maternal insulin [3].

Type 1 Diabetes Mellitus

Type 1 diabetes mellitus (DM) used to be referred to as insulin dependent diabetes mellitus or juvenile diabetes. Type 1 DM is more commonly seen in young adults and children. It is considered an autoimmune disorder where there is gradual destruction of the beta cells of the pancreas; these cells are responsible for insulin production. This leads to an absolute insulin deficiency, causing blood glucose levels to soar, since there is no insulin available to carry glucose molecules across the cell membrane and into the cell for metabolism. For survival, Type 1 DM patients are insulin dependent and needs to take insulin each day.

Although insulin treatment is almost 100 years old, many people globally still suffer from a lack of access to this essential medication. In sub-saharan Africa, the life expectancy of a child with type 1 diabetes is less than 1 year. In Mali, insulin is only available in 1 in 5 treatment centres; and in Mozambique, diabetes treatment can cost up to 75% of a persons yearly income. For more information on the global campaign to grant insulin access to 100% of people living with insulin dependent diabetes, see the 100 campaign.  [http://www.100campaign.org]

Type 2 Diabetes Mellitus

Type 2 DM is the most common type diagnosed in patients, and amounts to as many as 90 to 95% of cases. In type 2 DM the disease process begins with insulin resistance precipitated by hormones, medications, diet, and most commonly obesity. Insulin resistance makes body tissues increasingly unresponsive to the presence of insulin. Until over time, the body’s production of insulin does not adequately maintain blood sugar levels (particularly after a meal), and the result is uncontrolled hyperglycaemia; or diabetes.

Although initially, the pancreas produces adequate to high amounts of insulin in order to overcome insulin resistance, over time the insulin producing beta cells of the pancreas become over-wrought, leading to progressive beta cell failure, and a reduced capacity for insulin production.This beta cell burnout means that exogenous insulin is required to keep blood sugar levels controlled; hence the use of insulin in people with type 2 DM [4].

Risk Factors for Diabetes Mellitus

Risk factors vary for each of the three types of diabetes discussed, although there is reasonable overlap. Below is a list of predisposing factors for each [4].

Risk Factors: DM Type 1

  • Environmental Factors – studies have shown that children exposed early to cereal proteins and cow’s milk have a higher risk of acquiring Type 1 DM as opposed to breastfed babies. Studies also show a strong correlation between people diagnosed with type 1 DM after a viral infection, however a virus alone cannot cause Type 1 DM so researchers suspect an autoimmune response in susceptible people.
  • Autoimmune Destruction of Beta Cells – Recent studies indicate that people who are susceptible to type 1 DM respond to insulin like it is an antigen; (a foreign substance that the body tries to eliminate, triggering an inflammatory immune response). In diabetes the body produces antibodies against insulin and proteins made by beta cells of the pancreas, until eventually the beta cells too, are destroyed.
  • Genetic Susceptibility – Family history of type 1 DM is a risk factor.

Risk Factors: DM Type 2

  • Physical inactivity and Obesity – central obesity, or excess abdominal fat, as well as physical inactivity are both risk factors. These two risk factors are also a stepping stone toward insulin resistance.
  • Insulin Resistance – this is a condition where liver, fat, and muscle cells do not respond to insulin properly causing the pancreas to overwork itself to compensate for the improper response of cells to insulin. So long as beta cells of the pancreas retain their capacity to produce insulin, in proportion to the reduced sensitivity (or insulin resistance) of body tissues; blood glucose levels remain normal.
  • Abnormal Liver Production of Glucose – in non diabetics, when blood glucose levels are high, insulin is secreted and this process sends signals to the liver to stop producing glucose, and instead store glucose to help normalise blood glucose levels. Conversely, when blood glucose levels are low, the pancreas secretes the hormone glucagon which stimulates the liver to produce glucose, while the pancreas stops secreting insulin. However, for reasons not yet understood, type 2 diabetics have higher glucagon levels which exacerbate their hyperglycemic condition.
  • Genetic Susceptibility and race – genes also play a significant role in a person’s susceptibility to type 2 DM, as does race. If a parent or sibling has type 2 DM, an individual is likely to have type 2 DM too. Compared to non-Hispanic whites, Pacific Islander Americans, native Hawaiians, Asian Americans, Hispanics, Native Americans, Alaska natives, and African Americans are more susceptible.

References

1.  Global status report on noncommunicable diseases 2010. Geneva, World Health Organization, 2011.

2.Centers for Disease Control and Prevention: Diabetes

3.University of Maryland Medical Center: Diabetes – Type 1

4.National Institute of Diabetes and Digestive and Kidney Diseases: cause of Diabetes

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