Increased insulin levels after OGTT load in peripheral blood and cerebrospinal fluid of patients with dementia of Alzheimer type.

An investigation was carried out to determine whether a disturbance of glycometabolism is associated with dementia of Alzheimer type (AD). The first part of the study was carried out on 108 AD patients and 57 normal controls (NCs). Neither the plasma level of insulin nor that of glucose differed significantly between the two groups before the oral glucose tolerance test (OGTT), whereas there was a significantly greater increase of the plasma insulin in the AD group than in the NC group after the OGTT. The second part of the study was carried out on 54 AD patients, 44 patients with vascular dementia (VD), and 26 NCs. Early in the morning after overnight fasting, there was no significant difference in the fasting plasma level of either glucose or insulin, or the cerebrospinal fluid (CSF) level of glucose, among the three groups, However, the CSF level of insulin was significantly higher in the AD group than in the other two groups. These results suggest that an abnormally high level of insulin, not only in the peripheral blood after OGTT load but also in the CSF after fasting, may be associated with the pathology of AD.