The pathology of diabetes is characterised by changes surrounding the metabolism of glucose, fat and proteins. Type 2 diabetes results from the body’s resistance to, and later the secretion of, insulin; this results in the primary feature that defines diabetes – hyperglycaemia.
Hyperglycaemia defines the presence of high levels of blood sugar that would ordinarily be controlled by naturally produced insulin.
A higher frequency of infections is observed in diabetic patients, and this is due to the hyperglycaemic environment thought to induce a dysfunctional immune system [1].
The deleterious effect of elevated blood sugars on the immune system leads to immunosuppression, and this underlies infection experienced in diabetes type 2.
The science behind these changes continues to be explored, and there are multiple possibilities, including changes in the ability of immune cells to function effectively, altered secretion of molecules that are supposed to protect our wellbeing, in addition to the secretion of molecules that do harm and cause tissue damage in the fight against bacteria, viruses and fungal infections.
Moreover, being ill is able to increase blood sugar levels, further feeding the condition in an already compromised individual.
The result of compromised immunity reduces the body’s capability to fight infections since innate and adaptive immunity are essential to preserving physical health.
The immune system sees a complex relationship between multiple immune cells, bioactive molecules and tissue.
Crucially in combination, these factors act to prevent infection by foreign bodies such as viruses and bacteria, when compromised in conditions such as diabetes, this will increase an individual’s predisposition to non-communicable and communicable disease.
The presence of high levels of sugar in tissues, facilitates the lifecycle and growth of bacteria on tissues, providing a suitable environment for overgrowth and infection, this in combination with an already compromised immune system facilitates infection
Studies have shown that patients with diabetes type 2 are at increased risk of infections in the lower respiratory tract, urinary tract, the skin and mucous membranes [1].
Most frequently, respiratory infections associated with diabetes are caused by Streptococcus pneumoniae and the influenza virus. Streptococcus pneumoniae is the bacteria that underlies the pathology in pneumonia; patients with diabetes are at an increased risk of developing pneumonia. This is of particular importance during the present climate, and the emergence of the COVID-19 virus, patients that have contracted COVID-19 are at risk of developing pneumonia. [2].
Urinary tract infections are commonly seen in diabetic patients, and this is due to altered sensitivity, anatomical and functional changes over a period of time and changes in small blood vessels, damaged through uncontrolled excessive blood sugars. Blood glucose control significantly reduces vascular complications in type 2 diabetes [3].
Foot infection is a common cause of hospitalisation in diabetics, and the infected ulcers may be due to single bacteria; however, over time and with drug resistance these can be occupied by multiple bacteria and if not managed can lead to amputation or death. In addition, this involves neuropathy, diabetic neuropathy results from high blood sugar, due to its ability to promote nerve damage in all tissues. Neuropathy is commonly observed in the extremities, in particular, the legs and feet and is a combination of poor blood supply, due to damaged vessels and nerve damage.
Essentially, management of blood sugar levels will ensure an element of protection from the pathological effects of type 2 diabetes. Diet management, exercise and monitoring play an important role in ensuring that the glucose levels are under control.
There are other methods to minimise the risk of infection, including regular anti-pneumococcal and influenza vaccines. Professional medical practitioners recommend vaccination and will be able to advise on the frequency and necessity.
In view of the increased risk of respiratory infections, socialising with any persons that are known to be suffering from colds or flu should be avoided to reduce the risk of infection.
In summary, hyperglycaemia underlies the mechanisms associated with diabetes and increased risk of infections, these changes include, but are not limited to, a reduction in the response of the immune system – innate and adaptive immunity, these changes leave the patient more exposed to infections.
This article is written by Dr Tracey Evans. She is an experienced Medical Research Scientist with PhD in Neuroscience, MSc in Molecular Neuroscience and BSc (Hons) in Biomedical Sciences working in the United Kingdom