Lifespan Changes in the Countermanding Performance of Young and Middle Aged Adult Rats

AGING-ASSOCIATED COGNITIVE DECLINE IS REVERSED BY D-SERINE SUPPLEMENTATION

Brain aging is a natural process that involves structural and functional changes that lead to cognitive decline, even in healthy subjects. This detriment has been associated with N-methyl-D-aspartate receptor (NMDAR) hypofunction due to a reduction in the brain levels of D-serine, the endogenous NMDAR co-agonist. However, it is not clear if D-serine supplementation could be used as an intervention to reduce or reverse age-related brain alterations. In the present work, we aimed to analyze the D-serine effect on aging-associated alterations in cellular and large-scale brain systems that could support cognitive flexibility in rats. We found that D-serine supplementation reverts the age-related decline in cognitive flexibility, frontal dendritic spine density, and partially restored large-scale functional connectivity without inducing nephrotoxicity; instead, D-serine restored the thickness of the renal epithelial cells that were affected by age. Our results suggest that D-serine could be used as a therapeutic target to reverse age-related brain alterations.SIGNIFICANT STATEMENTAge-related behavioral changes in cognitive performance occur as a physiological process of aging. Then, it is important to explore possible therapeutics to decrease, retard or reverse aging effects on the brain. NMDA receptor hypofunction contributes to the aging-associated cognitive decline. In the aged brain, there is a reduction in the brain levels of the NMDAR co-agonist, D-Serine. However, it is unclear if chronic D-serine supplementation could revert the age-detriment in brain functions. Our results show that D-serine supplementation reverts the age-associated decrease in cognitive flexibility, functional brain connectivity, and neuronal morphology. Our findings raise the possibility that restoring the brain levels of D-serine could be used as a therapeutic target to recover brain alterations associated with aging.

Hypertension accelerates age-related intrarenal small artery (IRSA) remodelling and stiffness in rats with possible involvement of AGEs and RAGE

OBJECTIVES

To study changes in morphology, advanced glycation end products (AGEs) and the AGEs receptor, RAGE, that occur with ageing in intrarenal small arteries (IRSAs) of spontaneously hypertensive rats (SHRs) and to investigate the possible roles of hypertension, AGEs and RAGE in the progression of IRSA remodelling and stiffness with ageing in rats.

METHODS

Ageing SHRs and ageing normotensive Wistar Kyoto (WKY) rats were studied. The minimal renal vascular resistance (minRVR) was measured. Renal arcuate arteries (RAAs) and interlobular arteries (RILAs), the expression of α-smooth muscle actin, proliferating cell nuclear antigen, AGEs, RAGE and the plasma concentrations of AGEs were also examined.

RESULTS

The IRSA minRVR, wall thickening, cell proliferation and collagen deposition in RILAs and RAAs gradually increased with age in SHRs and were much higher in 24-week-old SHRs than in age-matched WKY rats (p<0.05); these indexes in WKY rats were only elevated in the 72-week group (p<0.05). The expression of RAGE in the RAA and RILA tunica media in SHRs was upregulated by 24 weeks and 12 weeks (p<0.05), respectively, while AGEs levels in the plasma and in the IRSA tunica media were increased by 48 weeks (p<0.05) and increased gradually with age. The levels of both RAGE and AGEs in WKY rats were increased only at 72 weeks (p<0.05).

CONCLUSION

Hypertension accelerates the development of age-related IRSA remodelling and stiffness in rats, which may be related to upregulation of RAGE in the IRSA tunica media and increased expression of AGEs at the late stage.