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.

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.

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.

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:

$Quantityofthestocksolution\left({cm}^{-3}\right)=\frac{Desiredconcentration}{Stockconcentration}\times totalvolume\left({cm}^{-3}\right)$

Table 1. Dilution of the samples.

Fig. 1 - Serial dilution of the stock glucose solution to create desired concentrations

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.

Fig. 2 - Filtrates are added to cuvettes, and the absorbance of light through them is measured with a colourimeter

Table 2. Standard solution absorbance.

Fig. 3 - The calibration curve