Plasma somatostatin and gastrointestinal peptides in Alzheimer's disease and vascular dementia.

Few markers distinguish between different dementia types. As dementia affects many body systems outside the central nervous system, we investigated gastrointestinal regulatory peptides as possible disease markers in Alzheimer's Disease (AD) and vascular dementia (VaD). Subjects with mild-to-moderate dementia were diagnosed as probable AD and VaD according to defined criteria. Gastrointestinal peptides were stimulated using a standardized meal test, administered after an overnight fast to 58 dementia patients (40 AD, 18 VaD) and 47 controls matched for age and sex. Blood samples were taken at designated time intervals, and basal and stimulated plasma concentrations of eleven peptides were determined by radio-immunoassay. Results were analysed using the Kruskal-Wallis one-way analysis of variance; the Mann-Whitney U test was used in post hoc analysis where appropriate. There were significant differences in somatostatin levels but in none of the other peptides. Basal somatostatin was significantly increased in VaD compared to controls (p<0.05), and AD (p<0.005). Maximum stimulated levels were significantly elevated in VaD compared to AD (p<0.01). Median basal and stimulated levels of somatostatin were increased in VaD compared to AD, but the overlap in individual values between the groups makes it unlikely to be useful in distinguishing the two types of dementia.