Kazuyo Yamada

Dietary Lipids Impacts on Healthy Ageing

Healthy ageing is gaining attention in the lipid nutrition field. As in vivo biomarkers of healthy ageing, we have evaluated the survival, learning/memory performance, and physical potencies in rodents fed a diet supplemented with high-linoleic acid (LNA, ω6) safflower oil or high-α-linolenic acid (ALA, ω3) perilla oil for long periods. The results suggested that perilla oil with a low ω6/ω3 ratio is beneficial for healthy ageing. In order to address this issue further, we determined the survival of stroke-prone SHR (SHRSP) rats fed a conventional rodent diet supplemented with 10% fat or oil. Survival was longer with ω3-rich oils compared with ω6-rich oils. However, some kinds of vegetable oils and hydrogenated oils shortened the survival of SHRSP rats to an unusual degree (ca. 40% compared with that of ω6-rich oil) that could not be accounted for by the fatty acid and phytosterol composition of the oils. The observed decrease in platelet counts was associated with pathological changes in the kidney and other organs. Dihydro-vitamin K1 is proposed as a likely candidate as a stroke-stimulating factor in hydrogenated oils. Thus, factors other than fatty acids (ω6/ω3 balance) and phytosterols must be taken into account when fats and oils are evaluated in relation to healthy ageing.

Regional differences of the mouse brain in response to an α-linolenic acid-restricted diet: neurotrophin content and protein kinase activity.

AIMS The purpose of this study was to determine a relatively short-term effect of feeding an α-linolenic acid (ALA, n-3)-restricted, linoleic acid (LA, n-6)-adequate diet on neurotrophin contents and protein kinase activities in brain regions of the mouse. MAIN METHODS After feeding mice a safflower oil (SAF) diet (ALA-restricted, LA-adequate) or perilla oil (PER) diet (containing adequate amounts of ALA and LA) for 4 weeks from weaning, the fatty acid compositions of brain regions were analyzed by capillary column gas-liquid chromatography, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) contents were measured using enzyme-linked immunosorbent assay. KEY FINDINGS The striatum and hippocampus, but not the cerebral cortex, from the SAF group, contained a smaller amount of docosahexaenoic acid (DHA, 22:6n-3) than those from the PER group. The NGF contents in these brain regions were not different between the two dietary groups. However, the striatal BDNF content of the SAF group was significantly lower than that of the PER group. Protein kinase A, protein kinase C, and p44/42 mitogen-activated protein kinase (p44/42 MAPK) activities in brain regions showed no significant difference between the two dietary groups. However, the striatal p38 MAPK activity was significantly lower in the SAF group than in the PER group. No such differences were observed in the hippocampus or the cerebral cortex. SIGNIFICANCE A relatively short-term feeding of an α-linolenic acid-restricted, linoleic acid-adequate diet was found to lower the DHA content, BDNF content and p38 MAPK activity in the mouse striatum.

PMA induces GCMa phosphorylation and alters its stability via the PKC- and ERK-dependent pathway.

The glial cells missing a (GCMa) transcription factor plays a pivotal role in the placental development by regulating the expression of several genes in the placenta that are responsible for the proper formation of the syncytiotrophoblast. It is well known that the function of GCMa is regulated at both transcriptional and post-translational levels by the cyclic AMP (cAMP)/protein kinase A (PKA)-dependent pathway, the activation of which increases the GCMa protein level and leads to trophoblast differentiation into the syncytiotrophoblast. However, little is known about the regulatory control of GCMa by PKC-dependent signaling mechanism(s). To investigate whether GCMa is regulated by PKC-dependent pathway, we treated the human choriocarcinoma JEG-3 cells with phorbol 12-myristate 13-acetate (PMA) and studied its effect on the GCMa protein using a monoclonal anti-GCMa antibody we prepared. PMA caused a transient decrease in the endogenous GCMa protein level in JEG-3 cells that was accompanied by an increase in GCMa phosphorylation. The phosphorylation and degradation of GCMa by PMA treatment was effectively reduced by pretreatment with protein kinase C (PKC) inhibitors and a mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor, indicating a PKC- and MEK-dependent mechanism. Furthermore, we identified the serine residues 328, 378 and 383 to be the phosphorylation sites on GCMa that are involved in the PMA-induced degradation of GCMa. Our data demonstrate for the first time that GCMa is phosphorylated by the PKC- and MEK/extracellular signal-regulated kinase (ERK)-dependent mechanism, and that this phosphorylation is involved in its degradation process.