An Overwiew of Diabetes - What you need to know
Diabetes is a metabolic disorder characterized by hyperglycemia due to an absolute or relative lack of insulin or a cellular resistance to insulin. It is a multifactorial disorder caused by diminished insulin action since it affects basically the whole body. In older classification there were two main types of diabetes i.e. type 1 and type 2 but the newer classification is as follows;
Type 1: immune mediated or idiopathic
Type 2: insulin resistance /insulin deficiency
Type 3: genetic syndromes, drug induced, hormonal, malnutrition related
Type 4: gestational diabetes
Type 1 diabetes is a disease of insulin deficiency. The immune-mediated form of the disease is common in the West compared to the East. Type 1 diabetes is prominent as a disease of childhood, reaching a peak incidence around the time of puberty, but it can present at any age.
Type 2 diabetes is relatively common in all populations enjoying an affluent lifestyle. The four major determinants are increasing age, obesity, ethnicity and family history. It is becoming a global health problem. It is estimated that 15.7 million people around the world are affected and among those 10.3 are diagnosed while 5.4 are undiagnosed. Overall prevalence within the UK is 2–3%, and the lifetime risk is around 15%. It is 2–4 times as prevalent in people of South Asian, African and Caribbean ancestry who live in the UK, and the life-time risk in these groups exceeds 30%.
Diabetes can present in many ways; there can be an acute presentation with polyuria (excessive passage of urine), thirst and weight lost lasting for 2 to 6 weeks or a chronic presentation with non specific fatigue, malaise, visual blurring, and genital candidacies. Nonetheless certain individuals directly present with complications related to diabetes since it is a multisystem disorder like staphylococcal skin infections, retinopathy noted during a visit to the optician, a polyneuropathy causing tingling and numbness in the feet, erectile dysfunction, arterial disease, resulting in myocardial infarction or peripheral gangrene.
Sometimes patients can be completely asymptomatic and can be found to have elevated blood glucose or glycosuria which is found as an incidental finding. Sometimes patients do present with emergencies related with diabetes such as diabetic ketoacidosis and non-ketotic hyperosmolar coma.
For diagnosing diabetes there is a criteria defined by WHO as stated below;
· Fasting plasma glucose > 7.0 mmol/L (126 mg/dL)
· Random plasma glucose > 11.1 mmol/L (200 mg/dL)
· One abnormal laboratory value is diagnostic in symptomatic individuals; two values are needed in asymptomatic people.
The glucose tolerance test is only required for borderline cases and for the diagnosis of gestational diabetes.
The glucose tolerance test – WHO criteria
Normal <7.0 mmol/L
Impaired glucose tolerance <7.0 mmol/L
Diabetes Mellitus >7.0 mmol/L
2 hours after glucose
Normal <7.8 mmol/L
Impaired glucose tolerance 7.8–11.0 mmol/L
Diabetes Mellitus ≥11.1 mmol/L
Impaired glucose tolerance (IGT) is not a clinical entity but a risk factor for future diabetes and cardiovascular disease. Obesity and lack of regular physical exercise make progression to frank diabetes more likely. Individuals with IGT have the same risk of cardiovascular disease as in frank diabetes but do not develop the specific microvascular complications.
Most important thing to know in a patient with diabetes mellitus is that there are a lot of complications related to the long term control of the disease. The complications are of two types namely macrovascular complications and microvascular complications.
The pathogenesis of each group of complications is different and difficult to explain but there are several described mechanisms.
1. Non-enzymatic glycosylation of a wide variety of proteins, e.g. haemoglobin, collagen, LDL and tubulin in peripheral nerves. This leads to an accumulation of advanced glycosylated end-products causing injury and inflammation via stimulation of pro-inflammatory factors, e.g. complement, cytokines.
2. Polyol pathway. The metabolism of glucose by increased intracellular aldose reductase leads to accumulation of sorbitol and fructose. This causes changes in vascular permeability, cell proliferation and capillary structure via stimulation of protein kinase C and TGF-β.
3. Abnormal microvascular blood flow impairs supply of nutrients and oxygen. Microvascular occlusion is due to vasoconstrictors, e.g. endothelins and thrombogenesis, and leads to endothelial damage.
4. Other factors include the formation of reactive oxygen species and growth factors stimulation (TGF-β) and vascular endothelial growth factor (VEGF). These growth factors are released by ischaemic tissues and cause endothelial cells to proliferate.
5. Haemodynamic changes, e.g. in kidney.
Atherosclerosis mainly attributes in causing macrovascular complications. It affects coronary vessels causing increase in incidence of ischemic heart disease, cerebral vessels causing cerebrovascular accidents (CVA) and peripheral blood vessels causing peripheral vascular disease (PVD).
Microvascular complications affect small vessels in the whole body but effects are apparent in three particular sites giving serious effects i.e. retina causing retinopathy, renal glomerulus causing nephropathy, nerve sheaths causing neuropathy. Here the strict glycaemic control can delay both these complications yet it cannot be prevented entirely.
Treatment of diabetes is based on;
1. Lifestyle modifications including diet and exercise
2. Treating with oral hypoglycaemic agents
3. Insulin therapy
Management is aimed at controlling hyperglycaemia and preventing hypoglycaemia; delaying or treating complications; improving wellbeing of the patient. Patient should be informed regarding all the complications related to the disease and also regarding adverse effects related to treatment. They should also be aware of the symptoms and signs of hypoglycaemia and emergencies. It is very important to have the patient compliance and give psychological support to the patient since management lasts throughout the lifetime of the patient.