Learning behaviour and cerebral protein kinase C, antioxidant status, lipid composition in senescence-accelerated mouse: Influence of a phosphatidylcholine-vitamin B₁₂ diet

Our objective was to determine whether dietary supplementation with phosphatidylcholine (PC) plus vitamin B₁₂ could afford beneficial effects on biochemical and biophysical events in the brain of senescence-accelerated mouse (SAM) substrain SAMP8. We measured learning behaviour, hippocampal protein kinase C (PKC) activity, cerebral antioxidant status, phospholipid composition and fatty acid composition in 6-month-old SAMP8 and in age-matched controls (SAM substrain SAMR1). In comparison with SAMR1, SAMP8 showed a significant elevation in total grading score of senescence (P < 0.05) and a significant decline in acquisition (P < 0.05). SAMP8 had a lower hippocampal PKC activity and cerebral PKC-β mRNA abundance than SAMR1. SAMP8 had increased cerebral lipid peroxide levels and proportion of sphingomyelin, and a lower proportion of 20: 4n-6 and 22: 6n-3 in cerebral phosphtidylethanolamine than SAMR1. SAMP8 fed the PC combined with vitamin B₁₂ diet had an increased PKC activity and a higher proportion of 22: 6n-3 than SAMP8 fed the control diet. These results indicate the potential benefit of PC combined with vitamin B₁₂ as a dietary supplement.