Plasma insulin and glucose levels in elderly female subjects with Alzheimer's disease

Background:  The function of insulin in the central nervous system has been intensively investigated recently. Epidemiological studies have shown that hyperinsulinemia or diabetes mellitus is a risk factor for Alzheimer's disease. Several studies have reported plasma levels of insulin and glucose in subjects with Alzheimer's disease, however, the results were conflicting. A recent study suggested that fasting plasma insulin levels in subjects with Alzheimer's disease depend on apolipoprotein E genotype, specifically, subjects with Alzheimer's disease who were not apolipoprotein-E4-homozygotes had higher plasma insulin levels. The purpose of this study was to clarify plasma levels of insulin and glucose in subjects with Alzheimer's disease.
Methods:  We performed a 75 g oral glucose tolerance test (OGTT) in elderly female subjects with Alzheimer's disease (AD) and age-matched female non-demented subjects (mean age of the subjects involved was 82.9 ± 8.1 years). All subjects were non-apolipoprotein E4-homozygotes, and scores for mini-mental state examination of all AD subjects were less than 16.
Results:  When fasting plasma levels of insulin and glucose in all recruited subjects were compared, those of glucose and insulin were significantly lower in AD subjects, possibly due to their lower body mass index (BMI). When only subjects with normal glucose metabolism in OGTT were included, BMI was comparable. Although plasma levels of fasting glucose and insulin were still lower in AD subjects, the difference lacked statistical significance.
Conclusion:  We failed to show that subjects with AD who were not apolipoprotein-E4-homozygotes had higher fasting plasma insulin levels compared with non-demented subjects.