Quantitative analysis by HPTLC of the major
lipid classes and
dolichol, and of fatty acyl groups of separated
phosphoglycerides by capillary GLC, has been carried out on the gray matter of frontal cerebral cortex of brains from six
Down's syndrome (DS) and six
Alzheimer's disease (AD) adults, and six each of two corresponding sets of age-matched controls; specimens of DS and control cerebellum and corpus callosum were also analyzed. In DS frontal cortex, but not in AD frontal cortex, compared to their respective controls there was a decrease in the fraction of
phosphatidylethanolamine (PE) and an increase in the fractions of
sphingomyelin (SPM) and
phosphatidylserine (PS). Abnormalities were not found in the proportions of major
lipid classes in DS cerebellum or corpus callosum. The concentration of
dolichol was elevated for age in the frontal cortex of DS and of AD. In the
phosphoglycerides of DS frontal cortex, the fatty acyl composition showed small, but statistically significant, differences from those of age-matched controls, and some slight abnormalities were also detected in DS corpus callosum. The alterations in DS frontal cortex included decreases in (n-6) and increases in (n-3) groups in
choline and
ethanolamine phosphoglycerides (CPG and EPG), as had previously been found in EPG and
serine phosphoglyceride (SPG) of the DS fetal brain. In DS frontal cortex, the proportion of 22:4(n-6) groups was decreased in SPG, and in
inositol phosphoglyceride (IPG) 18:1(n-9) was increased. There were also small but significant alterations in DS frontal cortex in the fractions of shorter chain groups in CPG. In marked contrast, most of the fatty acyl abnormalities seen in DS were absent in the AD frontal cortex. It is therefore suggested that some abnormalities in the composition of cerebral membranes present prenatally in DS may persist into adulthood, and are not directly related to AD-type pathology.