The effects of dietary restriction on age-related changes in rat serum prostaglandins

This study investigated whether or not dietary restriction (DR), consisting of 60% of the daily caloric allowance of ad libitum fed (AL) rats, has a modulating effect on prostaglandins (PGs), thromboxane (TXA), and lipids in the serum of rats. Results showed that DR rats had consistently, 30-40% lower overall lipid peroxide levels than AL rats. On the other hand, the age-related increases in arachidonic acid contents observed in AL rats were significantly suppressed by DR during aging; while unsaturated/saturated fatty acid ratios remained consistently higher (15-50%) in DR rats than in AL rats. Serum PGE2 and PGF2 levels in DR rats were maintained at consistently higher levels (30-65% and 40-90%, respectively) than in AL rat serum. PGI2 levels (as measured by 6-keto PGF2) in serum of DR rats were also consistently higher (40-50%) than those of AL rats, while TXA2 levels sustained lower levels (15-20%) than those of AL rats, showing a significantly higher (27-38%) PGI2/TXA2 ratios in DR than in AL rats. Thus, our study clearly indicated that DR effectively modulates prostaglandin levels by preventing age-related decreases in PGI2 levels and increases in TXA2 levels. These findings, with the other known beneficial actions of DR, strongly suggest vascular activity to be well-regulated in DR animals.