Diabetes: how to recognise it and understand the different characteristics

Answer: The term diabetes mellitus refers to a condition in which blood glucose rises above normal values between 70 and 100 mg per 100 millilitres (dl). Glucose is a substance that supplies energy to all cells; suffice it to say that the brain alone 'burns' 120 grams of glucose in a single day, while the body's total requirement varies between 180 and 200 grams per day. During moderate physical activity, such as jogging, approximately 1-2 grams of glucose are consumed per minute. When fasting blood glucose consistently exceeds 126 mg/dl, diabetes occurs. When values exceed 180 mg/dl, glucose appears in the urine (glycosuria). There are many causes of diabetes, but the most frequent forms are type 1 diabetes mellitus and type 2 diabetes mellitus.

Type 1 diabetes recognises a completely different cause from type 2 diabetes. Type 1 is a chronic autoimmune disease in which the immune system mistakenly attacks and destroys the beta cells of the pancreas, which are responsible for producing insulin. When insulin is missing, glucose remains in the blood, causing hyperglycaemia. When insulin is missing, glucose remains in the blood, causing hyperglycaemia. The exact causes are not fully known, but it is believed that type 1 diabetes is due to genetic and environmental factors, such as viral infections or other factors that can trigger the autoimmune response. In Italia, there is Law No 130 of 15 September 2023, 'Disposizioni concernenti la definizione di un programma diagnostico per l'individuazione del diabete di tipo 1 e della celiachia nella popolazione pediatrica' (Provisions concerning the definition of a diagnostic programme for the detection of type 1 diabetes and coeliac disease in the paediatric population), which provides for national screening (1-17 years) to detect the antibodies responsible for the destruction of insulin-producing cells. This makes it possible to identify those at risk before clinical onset and reduce the risk of diabetic ketoacidosis. In high-risk individuals, research has made new therapeutic approaches available, such as immunomodulatory drugs, which can slow down or delay the onset of diabetes by intervening early in the autoimmune process. Type 1 diabetes can appear at any age, but it most frequently affects children, adolescents and young adults. In Italia and Europe, more than 60-70% of cases occur before the age of 20. It can also occur in adulthood, in a form called Lada (latent autoimmune diabetes in adults): Lada has a slower onset and is often initially confused with type 2.

In type 2 diabetes mellitus, high blood glucose levels are mainly determined by two causes: a reduced sensitivity of the cells to insulin (insulin resistance) and a decreased production of insulin by the beta cells of the pancreas. At an early stage, tissue cells (muscle, liver, visceral adipose tissue) become resistant to insulin and do not respond well to the hormone's signal: the beta cells are then forced to overwork, producing more insulin to maintain normal blood glucose. This results in a condition of compensatory hyperinsulinaemia. Over time, progressive beta-cell exhaustion occurs, with loss of their efficiency and number, and secretion of the hormone becomes insufficient. At a more advanced stage, insulin production is further reduced.

Other mechanisms contribute significantly to hyperglycaemia in type 2 diabetes: these include a defect in the incretin system, which reduces insulin secretion and impairs blood glucose regulation; there is also increased renal reabsorption of glucose, which limits the elimination of glucose in the urine and maintains high blood glucose levels. These mechanisms combine with insulin resistance and beta cell deficiency to cause or exacerbate the hyperglycaemia typical of the disease.