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Diabetes

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Diabetes

How much do you know about diabetes mellitus? Did you know there are two different types of diabetes mellitus? These conditions affect how your body converts food into energy. Let's look at the different types of diabetes mellitus and the suitable management for diabetes. We will also explore a practical experiment for measuring glucose in the urine.

What is sugar diabetes, and what are its symptoms?

Diabetes mellitus or sugar diabetes is a disorder in which the homeostatic mechanism for regulating blood glucose concentration has been impaired. This is due to either being unable to produce insulin or reduced sensitivity of the cells to insulin resulting in an abnormally elevated blood glucose level (hyperglycaemia).

Approximately 350 million people worldwide have diabetes, and over 3 million are in the UK. In a diabetic individual, the cells' ability to uptake glucose has been impaired. As a result, the cells are deprived of glucose and energy despite high blood glucose levels. Individuals with diabetes often complain of tiredness and increased thirst and hunger. They also show signs such as elevated blood glucose levels, glucose in their urine (glycosuria), urinating excessively (polyuria), regular episodes of thrush, weight loss, and blurred vision.

Types of diabetes mellitus (sugar diabetes)

There are two types of diabetes mellitus:

Type I diabetes

Type I diabetes is a disease where the pancreas fails to secrete sufficient insulin required for blood glucose homeostasis. This form of diabetes usually occurs in children and young individuals, often due to an autoimmune disorder.

Autoimmune disorder: the body's immune system destroys its own cells and tissues.

In type I diabetes, the body’s immune system mistakenly targets and destroys β cells in the islets of Langerhans (in the liver). Due to the impaired insulin production, cells cannot use the glucose available in the blood, which is the main reason for fatigue and tiredness reported by diabetic patients.

Control of type I diabetes

Type I diabetes is also known as insulin-dependent diabetes since insulin injections, and a healthy lifestyle can control it. Since insulin is a protein hormone, it cannot be in a tablet since our digestive enzymes would digest it. The insulin dosage is crucial and must be adjusted precisely to the individual’s glucose intake. Doses of too high insulin would significantly lower the glucose concentration (hypoglycaemia) and result in loss of consciousness. Therefore, blood glucose levels need to be regularly monitored. This is achieved by machines, called glucometers, enhanced with biosensors capable of detecting glucose concentrations in the blood.

Type II diabetes

Type II diabetes (also known as insulin-independent diabetes) is due to the reduced sensitivity of the glycoprotein insulin receptors. The cells become less responsive to insulin. This lack of insulin response leads to reduced glucose uptake by the cells (especially liver cells), which results in abnormally elevated blood glucose concentration.

Type II diabetes is more common than type I in the general population, and it usually develops progressively in those aged over 40. Obesity and poor diet are the main risk factors that have been associated with early-onset type II diabetes among young individuals and adolescents.

Control of type II diabetes

Type II diabetes is usually managed by controlling the amount of carbohydrate intake and adjusting it with the individual’s level of physical activity. In some cases, doctors may even prescribe insulin injections or supplemental drugs that increase insulin secretion. In addition to controlling the glucose uptake by the cells, blood glucose levels can also be controlled by regulating the glucose absorption from the gut. Some supplemental drugs can slow down the rate at which glucose is absorbed in the intestine.

Calculating the concentration of glucose in urine (required practical)

An alternative version of Benedict’s Solution can be used to determine the amount of reducing sugar (glucose) present in the sample to carry out the quantitative test on an unknown urine sample.

Benedick's (qualitative) solution is a chemical reagent that contains a mix of sodium carbonate, sodium citrate and copper (II) sulfate pentahydrate. It detects the presence of reducing sugars.

Benedick's qualitative solution will change colour to determine the sugar presence. In this experiment, the alternative version of Benedick's solution is quantitative. It will determine the amount of reducing sugars in a substance. The quantitative version of the test will produce a precipitate that can be titrated (determine the concentration of a substance).

The glucose in the sample undergoes a redox reaction (oxidation and reduction) with copper (II) ions in the solution. Benedict’s solution has a blue colour due to copper (II) ions. Therefore, as these ions react with the glucose, the blue colour of the solution fades away. The intensity of the colour change is directly proportional to the concentration of glucose present in the sample. In other words, a solution with low amounts of glucose would have a blue appearance, while a solution with high amounts of glucose would appear colourless. Urine in healthy individuals does not contain any glucose, so it should remain blue.

The procedure

  1. First, a calibration curve needs to be generated to carry out a quantitative test. Generating a calibration curve is a generic approach for estimating the concentration of a drug or substance in an unknown sample by comparing it to a collection of standard samples with known concentrations.
  2. Serial dilutions of a stock solution are made to set up a series of standard solutions with known glucose concentrations.
  3. The same volume of Benedict’s solution (better to be in excess) is added to our standard solutions.
  4. Samples are then placed in a water bath set at 90°C for approximately 5 minutes to allow colour change to occur.
  5. It is crucial to treat all the standard solutions in the same way. During the reaction, a white precipitate is formed, interfering with the light absorbance and transmission.
  6. To combat this, samples are then filtered to obtain the filtrate.
  7. The same procedures are then repeated on the urine samples with unknown glucose concentrations.
  8. Using the calibration curve generated from the standard solutions, we can then estimate the glucose concentration in the urine samples.

To minimise the issues and discrepancies from the human interpretation of the colour, a colourimeter can be used to measure either the light absorbance or transmission through the samples. The measured values from the standard solutions can then be used to plot the calibration curve.

Materials

  • 10mmol.dm-3 glucose stock solution (generated from dissolving 1.8 g glucose in 1 dm3 distilled water)
  • Distilled water
  • Urine samples from ‘Tom’, ‘Dick’ and ‘Harry.’
  • Benedict’s solution
  • Graduated pipettes or syringes (2 cm3 and 1 cm3)
  • Test tubes
  • Test-tube rack
  • Water bath set at 90°C
  • Colourimeter
  • Cuvettes
  • Gloves
  • Pen
  • Label
  • Graph paper
  • Pencil

Safety instructions

Eye protection should be worn when using Benedict’s solution.

Generating the calibration curve

These are the steps you need to follow to generate the calibration curve.

Preparing the dilutions

In serial dilution, the stock solutions create a series of dilutions. This can be done to create a desired range of concentrations (e.g., 0, 2, 4, 6, 8, 10 mmol.dm-3).

  1. First, the test tubes must be labelled and placed on the testing tube rack.
  2. Amounts of the stock solution are added to the tubes to achieve the desired concentration.
  3. To calculate how much stock solution is needed for each concentration, use the following equation:

Table 1. Dilution of the samples.

Gucose concentration (mmol.dm-3)
The volume of distilled water (mL)
The volume of glucose stock solution (mmol.dm-3)
0
5
0
2
4
1
4
3
2
6
2
3
8
1
4
10
0
5

Colorimeter

The test tube preparation:

  1. A fixed volume of Benedict’s solution (roughly 2 ml) is added to the test tubes.
  2. The solutions are then placed in the water bath for approximately 5 minutes.
  3. Afterwards, the content of the test tubes needs to be filtered to remove the white precipitates, and 1 ml of the filtrate from each test tube is added to a separate cuvette that has been labelled appropriately.

Since we need to measure the changes in the intensity of the blue colour in the solution, we need to set the colourimeter wavelength to red which is the complementary colour to blue (i.e., a blue solution absorbs red while reflecting blue).

Using the colourimeter:

  1. Firstly, the colourimeter needs to be calibrated to zero absorbance. This is achieved by placing the cuvette containing only distilled water (0 mmol.dm-3) in the colourimeter and pressing the reset button. Alternatively, you can read the absorbance and keep in mind that the y axis of your curve needs to start with that value.
  2. Each labelled test cuvette is subsequently placed in the colourimeter, and its absorbance is recorded. Now we can plot a graph of glucose concentration against absorbance of red light by the solution. This is our calibration curve.

Table 2. Standard solution absorbance.

Glucose concentration (mmol dm–3)
Absorbance (arbitrary units)
0
0.00
2
0.76
4
1.00
6
1.15
8
1.22
10
1.39


By using the calibration curve, we can determine the concentration of glucose in the urine samples. For instance, if we assume that the absorbance of Tom, Dick and Harry were 0.00, 0.89, and 1.19, respectively, then we could determine the glucose concentration of Tom, Dick and Harry to be 0.00, 4.70, and 7.00 mmol.dm-3, respectively.

Diabetes - Key takeaways

  • Diabetes mellitus or sugar diabetes is caused by the inability to regulate blood glucose concentration.
  • The signs and symptoms of diabetes mellitus are: elevated blood glucose levels, presence of glucose in their urine (glycosuria), urinating excessively (polyuria), regular episodes of thrush, weight loss and blurred vision
  • There are two types of diabetes mellitus:
  • Generating a calibration curve is a generic approach for estimating the concentration of a drug or substance in an unknown sample by comparing it to a collection of standard samples with known concentrations.
  • Benedict's solution (blue) turns colourless in the presence of reducing sugars such as glucose.

Frequently Asked Questions about Diabetes

Type I diabetes is thought to be an autoimmune disorder wherein the body’s immune system destroys the insulin-producing beta cells in the pancreas.

The most common cause of type 2 diabetes is obesity, inactive lifestyle, and unhealthy diet

Diabetes is a disorder of abnormally high blood glucose levels due to either low levels of insulin production in the body or low response of the cells to insulin. Since the cells are unable to take up glucose from the blood, individuals with diabetes quickly feel tired.

Type II diabetes is when the cells in the body, especially in the liver, have become insensitive to insulin resulting in hyperglycaemia.

Type I diabetes is often due to an autoimmune disorder wherein the body’s immune system destroys the insulin-producing beta cells in the pancreas.

The presence of glucose in urine (glycosuria) could be due to either diabetes or kidney damage.

First a set volume of Benedict’s solution is added to the sample. Then the light absorbance by the solution is measured using a colourimeter. The reading obtained is then used to determine the concentration on a calibration curve.

Elevated concentration of glucose in urine could be a sign of diabetes or renal failure which need medical attention.

The presence of glucose in urine (glycosuria) could be due to either diabetes or kidney damage.

Final Diabetes Quiz

Question

What is type I diabetes characterised by?

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Answer

Type I diabetes is an acute onset, usually before 30 years of age. It also includes the destruction of the pancreatic beta cells.

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Question

What is type II diabetes characterised by?

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Answer

Type II is more commonly seen in adults over 30-40 years of age. Insensitivity of insulin receptors on the tissue cells to insulin followed by impaired insulin secretion.

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Question

How is the type I diabetes controlled?


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Answer

Insulin injections, having a healthy lifestyle, and diet control type I diabetes. 

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Question

How is type II diabetes controlled?


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Answer

Low carbs and high fibre diet. Increased physical activity. Treatment may be supplemented by insulin injections, drugs that increase insulin secretion in the body, and/or drugs that reduce glucose absorption in the gut.

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Question

Why is it important to filter the content of the test tubes after reaction with Benedict’s solution? 


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Answer

The reaction produces a white precipitate that may interfere with light absorbance and hence result in inaccurate data.

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Question

What are the early signs of diabetes?


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Answer

Individuals with diabetes often complain of tiredness, and increased thirst and hunger. They also show signs such as hyperglycaemia, presence of glucose in their urine (glycosuria), urinating excessively (polyuria), regular episodes of thrush, weight loss and blurred vision.

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Question

What colour is Benedict’s solution?


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Answer

Blue

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Question

What colour does Benedict’s solution turn into in presence of glucose?       


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Answer

Colourless

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Question

What amount of glucose is normally present in the urine?


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Answer

 zero

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Question

What is a calibration curve?


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Answer

Generating a calibration curve is a generic approach for estimating the concentration of a drug or substance in an unknown sample by comparing it to a collection of standard samples with known concentrations.

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Question

Why do diabetic individuals have a very pale urine?


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Answer

The presence of glucose lowers the water potential in the filtrate and reduces how much water can be reabsorbed from the filtrate in the kidneys producing dilute and pale urine.

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Question

What equation is used in serial dilution?


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Answer

Volume from the stock solution = (Desired concentrion/ Stock concentration)*total volume

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Question

Where is insulin secreted from?


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Answer

Insulin is secreted from the Beta cells of the islets of Langerhans.

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Question

What is the main cause of type I diabetes?


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Answer

The main cause of type I diabetes is autoimmune destruction of the beta cells of the islets of Langerhans.

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Question

What is the main cause of type II diabetes?


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Answer

The main cause of type II diabetes is poor diet, lack of physical activity, and genetic predisposition.

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