Turnover of synaptic membranes: Age‐related changes and modulation by dietary restriction

Abstract

We examined age-related changes in the turnover rates of synaptic membrane components that might underlie the decrease in synaptic functions in senescence. Synaptic membrane constituents were labeled in vivo with deuterium and the disappearance of the deuterated molecules from synaptic membranes was measured by mass spectrometry. The turnover rates of phosphatidylcholine, phosphatidylethanolamine, cholesterol, and synaptophysin were all shown to slow down with aging. Dietary restriction, which is known to retard various aging processes, was found to decrease the turnover rates of membrane lipid species. Consequently, the fatty acid composition in phospholipids remained unchanged in the synaptic plasma membranes of food restricted mice. In contrast, the turnover rate of synaptophysin was accelerated under dietary restriction. This may mean that increased turnover enhances the removal of damaged proteins from membranes.

α‐tocopherol affects neuronal plasticity in adult rat dentate gyrus: The possible role of PKCδ

“…At the same time, these results do not rule out that other conditions may also play a role. In fact, because synaptophysin is a presynaptic vesicle membrane glycoprotein, a variation in synaptophysin immunoreactivity might reflect changes in the number of vesicles in presynaptic boutons, as occurs in different experimental conditions (Lynch et al, 1994;Nakamura et al, 1999), changes in the rate of synaptophysin synthesis (Mullany and Lynch, 1997), or changes in synaptic vesicle cycle, as previously proposed to occur in aging (Ando et al, 2002;Davies et al, 2003). Hence, our results suggest that -tocopherol not only enhances PSA-NCAM expression but also synaptogenesis in adult rat DG.…”

Energy restriction does not prevent insulin resistance but does prevent liver steatosis in aging rats on a Western-style diet

“…Finally, our results showed that ER also favored the accumulation of less unsaturated fatty acids in liver cholesteryl esters and phospholipids, an effect that may prevent both an age-induced decrease in membrane fluidity as [56][57][58] and lipid peroxidation [38,50,57,[59][60][61][62][63][64].…”

An allometric comparison of microsomal membrane lipid composition and sodium pump molecular activity in the brain of mammals and birds

“…Cholesterol metabolism in the brain is quite complex, and recently it was suggested that cholesterol may be an essential factor in the formation and functioning of synapses (Pfrieger, 2003). Support for this hypothesis comes from studies which show that cholesterol turnover is much lower in the synaptic membranes of adults rats, compared with those of young rats, where presumably a large number of synapses are being established (Ando et al, 2002). Developing neurons synthesise their own cholesterol, however it is thought that neurons in adult brains derive their cholesterol from astrocytes (Pfrieger, 2002), which may in part explain the high levels of cholesterol observed in the present study, as astrocytes are the brain's most abundant cell type.…”