Do Sulphonylureas Preserve Cortical Function During Hypoglycaemia?

• Glucose threshold for development of symptoms and cognitive impairment due to hypoglycaemia [ Time Frame: 1 year ]
  

• Improvement in counter regulatory hormone response to hypoglycaemia [ Time Frame: 1 year ]
  

Low blood glucose (hypoglycaemia) is the most common and important side effect of insulin treatment for diabetes. Most episodes are “mild” and lead to symptoms that alert the individual to raise their blood sugar level by consuming sugar or starch (carbohydrate). The body also responds to low blood sugars by producing hormones such as adrenaline and cortisol, which help to restore blood sugar levels to normal. As the brain relies on sugar for fuel, it does not function properly if blood sugar levels drop too low, resulting in confusion and in extreme cases reduced conscious levels.

Repeated hypoglycaemia can blunt the protective symptoms and hormonal responses to hypoglycaemia limiting patients’ ability to recognise and correct hypoglycaemia, putting them at high risk of even more hypoglycaemia (Heller and Cryer, 1991).

Sulphonylureas are tablets used to treat type 2 diabetes that work by stimulating the pancreas to make more insulin. They do this by closing pores called KATP channels which are found on the surface of many cells and control the rate of firing of cells. In the pancreas, closing them causes cells to fire and release insulin. However, in other tissues such as in the brain, these channels have a protective function and they open up during times of lack of fuel, such as lack of oxygen or sugar, preventing the cells from firing and putting them into a resting mode which reduces their energy requirement(Dunn-Meynell, Rawson and Levin 1998). However, if the brain cells responsible for generating symptoms are put into this resting mode, they may not produce symptoms, which may contribute to hypoglycaemia unawareness.