5.4.4 Diabetes Flashcards
What is diabetes?
There are over 3 million people suffering from diabetes in the UK
Diabetes is a condition in which the homeostatic control of blood glucose has failed or deteriorated
In individuals with diabetes their insulin function is disrupted which allows the glucose concentration in the blood to rise
The kidneys are unable to filter out this excess glucose in the blood and so it often appears in the urine
The increased glucose concentration also causes the kidneys to produce large quantities of urine, making the individual feel thirsty due to dehydration
There are two different types of diabetes: type I and type II
What is type 1 diabetes?
Type 1 diabetes is a condition in which the pancreas fails to produce sufficient insulin to control blood glucose levels
It normally begins in childhood due to an autoimmune response whereby the body’s immune system (T cells) attacks the β cells of the islets of Langerhans in the pancreas
The β cells detect high blood sugar and synthesise insulin
The lack of insulin also affects glycogen stores which results in an individual feeling fatigued
If the blood glucose concentration reaches a dangerously high level after a meal then organ damage can occur
Type 1 diabetes is normally treated with regular blood tests, insulin injections and a diabetes appropriate diet
Health authorities encourage diabetics to eat a similar diet to the general public. They suggest five portions of fruit and veg a day, minimally processed food and consuming more polysaccharides than monosaccharides or disaccharides
The insulin used by diabetics can be fast-acting or slow-acting; each allowing for a different level of control
If a type I diabetic manages their condition well they can live a very full life
What is type 2 diabetes?
Type II diabetes is more common than type I
It usually develops in those aged 40 and over however more and more young people are developing the condition
In type II diabetes the pancreas still produces insulin but the receptors have reduced in number or no longer respond to it
This reduced sensitivity to insulin occurs in the liver and fat storage tissues
The lack of response to insulin means there is a reduced glucose uptake which leads to an uncontrolled high blood glucose concentration
This can cause the β cells to produce larger amounts of insulin which ultimately damages them
For early-stage type II diabetes, a sugar and fat controlled diet and an exercise regime are usually sufficient treatments
Any food that is rapidly digested into sugar will cause a sudden, dangerous spike in blood sugar
There are several known risk factors for type 2 diabetes:
Obesity
Physical inactivity
High blood pressure
High blood cholesterol
Genetics seems to be another influencing factor for developing type 2 diabetes
Having a relative with type 2 diabetes makes an individual more likely to develop it
Specific ethnic groups are more likely to develop the condition
What is the link between diabetes and blood pressure?
Individuals with poorly controlled diabetes often suffer from high blood pressure
The high blood glucose concentration lowers the water potential of the blood which causes more water to move from the tissues into the blood vessels by osmosis
As a result, there is a larger volume of blood within the circulatory system which causes blood pressure to increase
How can insulin be produced from genetically modified bacteria?
DNA that has been altered by introducing nucleotides from another source is called recombinant DNA (rDNA)
If the organism contains nucleotides from a different species it is called a transgenic organism
Any organism that has introduced genetic material is a genetically modified organism (GMO)
Recombinant DNA has been used to produce recombinant proteins (RP), thus recombinant proteins are manipulated forms of the original protein
Recombinant proteins are generated using microorganisms such as bacteria, yeast, or animal cells in culture. They are used for research purposes and for treatments (eg. diabetes, cancer, infectious diseases, haemophilia)
Most recombinant human proteins are produced using eukaryotic cells (eg. yeast, or animal cells in culture) rather than using prokaryotic cells, as these cells will carry out the post-translational modification (due to the presence of Golgi Apparatus and/or enzymes) that is required to produce a suitable human protein
In 1982, insulin was the first recombinant human protein to be approved for use in diabetes treatment
Bacteria plasmids are modified to include the human insulin gene
Restriction endonucleases are used to cut open plasmids and DNA ligase is used to splice the plasmid and human DNA together
These recombinant plasmids are then inserted into Escherichia coli by transformation (bath of calcium ions and then heat or electric shock)
Once the transgenic bacteria are identified (by markers), they are isolated, purified and placed into fermenters that provide optimal conditions
The transgenic bacteria multiply by binary fission and express the human protein - insulin, which is eventually extracted and purified
What are the advantages of using recombinant insulin?
It is identical to human insulin unless modified to have different properties (eg. act faster, which is useful for taking immediately after a meal or to act more slowly)
There is a reliable supply available to meet demand (no need to depend on the availability of meat stock)
Fewer ethical, moral or religious concerns (proteins are not extracted from cows or pigs)
Fewer rejection problems or side effects or allergic reactions
Cheaper to produce in large volumes
It is useful for people who have animal insulin tolerance
How can insulin be produced from stem cells?
Currently, there is no cure for diabetes but there is ongoing research to see if stem cells could be the answer
Stem cells can be treated so that they differentiate into pancreatic β cells
These newly developed β cells can then be transplanted into the pancreas of a diabetic individual, replacing the damaged cells and allowing them to produce insulin
The early-stage research has had some success using mice as model animals however it has not yet advanced to human trials
Why is insulin taken intravenously?
Insulin is a protein, if it was taken orally it would be digested by the enzyme protease found in the gut before entering the bloodstream
