The levels of plasma plasmalogen in retired female rats decrease by ovariectomy and intake of cholesterol-diet.

Plasmalogens are functional glycerophospholipids that play important biological roles in the human body and are associated with various diseases. In our previous study, plasma choline plasmalogen level was reported to be strongly associated with factors of atherosclerosis and decreases with age. In this study, we created an animal model of low plasma plasmalogen and clarified the effect of aging on plasma plasmalogen metabolism and other plasma lipids in ovariectomized rats. Consequently, in the ovariectomized model using retired rats (Retire + OVX rats), we found a reduction in the ratio of plasmalogen in total phospholipids and an increase in cholesterol in plasma. Furthermore, this was more pronounced with the intake of a high-cholesterol diet in the Retire + OVX rats and is similar to the changes in plasmalogen and cholesterol levels in human atherosclerosis. In summary, this suggests that the ovariectomy model using retired rats is a useful model for low plasma plasmalogen levels.

Structural changes in cell wall pectic polymers contribute to freezing tolerance induced by cold acclimation in plants.

Subzero temperatures are often lethal to plants. Many temperate herbaceous plants have a cold acclimation mechanism that allows them to sense a drop in temperature and prepare for freezing stress through accumulation of soluble sugars and cryoprotective proteins. As ice formation primarily occurs in the apoplast (the cell wall space), cell wall functional properties are important for plant freezing tolerance. Although previous studies have shown that the amounts of constituent sugars of the cell wall, in particular those of pectic polysaccharides, are altered by cold acclimation, the significance of this change during cold acclimation has not been clarified. We found that ß-1,4-galactan, which forms neutral side chains of the acidic pectic rhamnogalacturonan-I, accumulates in the cell walls of Arabidopsis and various freezing-tolerant vegetables during cold acclimation. The gals1 gals2 gals3 triple mutant, which has reduced ß-1,4-galactan in the cell wall, exhibited impaired freezing tolerance compared with wild-type Arabidopsis during initial stages of cold acclimation. Expression of genes involved in the galactan biosynthesis pathway, such as galactan synthases and UDP-glucose 4-epimerases, was induced during cold acclimation in Arabidopsis, explaining the galactan accumulation. Cold acclimation resulted in a decrease in extensibility and an increase in rigidity of the cell wall in the wild type, whereas these changes were not observed in the gals1 gals2 gals3 triple mutant. These results indicate that the accumulation of pectic ß-1,4-galactan contributes to acquired freezing tolerance by cold acclimation, likely via changes in cell wall mechanical properties.