A subset of early-onset familial Alzheimer's disease (FAD) 1 is inherited as an autosomal dominant trait, and presenilin (PS) 1 and 2 genes in addition to ß-amyloid precursor protein (APP) gene were identified as the causative genes. PS1 is mapped to chromosome 14 (1,2), while PS2 is mapped to chromosome 1 (3-5). These PS1 and PS2 genes encode multispanned transmembrane proteins showing high degrees of homology (4,5).Both proteins are located predominantly in the endoplasmic reticulum (ER), and partly in the Golgi apparatus and other compartments (6-8), but their physiological functions remain unclear. More than 50 different mutations have thus far been identified in PS1 (9), while only two mutations have been found in PS2 (10). The residue at position 141 (Asn) in PS2, which is conserved in human and mouse PS1 and PS2, is substituted by Ile (N141I) in the Volga German kindred. Another missense mutation (M239V) in PS2 has been found in Italian FAD families (5).Although the pathogenetic mechanism how Alzheimer's disease (AD) is developed by PS mutations remains unknown, mutations of PS1 and PS2 are known to have similar effects on the production of amyloid ß-protein (Aß) 42, the initially deposited Aß species in senile plaques (11)(12)(13)(14): While Aß42 is normally secreted in much lower quantities than Aß40, these aforementioned mutations induce elevation of the Aß42 levels in cultured cells and transgenic mice (15)(16)(17)(18)(19)(20). It has also been reported that in primary neuronal cultures derived from PS1-knockout mouse embryos, Aß secretion was remarkably decreased, concomitant with the accumulation of the C-terminal fragment of APP (21). The mutation in the two particular Asp residues in the PS1-transmembrane domains induced a profound decrease in the Aß production and an increase in the levels of the C-terminal fragment of APP (22). These observations indicate that PS1 may have a direct or indirect role in the γ -cleavage of APP.We previously reported that the mutant PS2 transgenic mice showed increases in the Aß42 levels in the Tris-saline (TS)-soluble fractions in an age-dependent manner during 2 to 8 months of age (20). On the other hand, a series of Aß quantitation studies of autopsied human tissues has clearly shown that Aß42 already accumulates to a significant extent in the TS- In the present study, we sought to obtain further insight into the effects of mutant PS2on the Aß levels in the TS-insoluble, guanidine hydrochloride-solubilized fraction of the mouse brain, and to characterize the intracellular compartmentalization of insoluble Aß. EXPERIMENTAL PROCEDURESTransgenic mice -The heterozygous PS2 transgenic mice used in this study were from the previously established lines W2 (wild-type PS2 transgenic mice), and M1 and M2(N141I mutant PS2 transgenic mice) (20). Each line of transgenic mice was backcrossed to the C57BL/6J strain, and those mice carrying the PS2 transgene were selected using a transgene-specific PCR assay (20). Littermates without PS2 transgenes were used as the nontransge...

A rat dementia model with cognitive deficits was generated by synapse-specific lesions using botulinum neurotoxin (BoNTx) type B in the entorhinal cortex. To detect cognitive deficits, different tasks were needed depending upon the age of the model animals. Impaired learning and memory with lesions were observed in adult rats using the Hebb-Williams maze, AKON-1 maze and a continuous alternation task in T-maze. Cognitive deficits in lesioned aged rats were detected by a continuous alternation and delayed non-matching-to-sample tasks in T-maze. Adenovirus-mediated BDNF gene expression enhanced neuronal plasticity, as revealed by behavioral tests and LTP formation. Chronic administration of carnitine over time pre-and post-lesions seemed to partially ameliorate the cognitive deficits caused by the synaptic lesion. The carnitine-accelerated recovery from synaptic damage was observed by electron microscopy. These results demonstrate that the BoNTx-lesioned rat can be used as a model for dementia and that cognitive deficits can be alleviated in part by BDNF gene transfer or carnitine administration.

The effects of long-term carnitine supplementation on age-related changes in tissue carnitine levels and in lipid metabolism were investigated. The total carnitine levels in heart, skeletal muscle, cerebral cortex, and hippocampus were ‫ف‬ 20% less in aged rats (22 months old) than in young rats (6 months old). On the contrary, plasma carnitine levels were not affected by aging. Supplementation of acetyl-l -carnitine (ALCAR; 100 mg/kg body weight/day for 3 months) significantly increased tissue carnitine levels in aged rats but had little effect on tissue carnitine levels in young rats. Plasma lipoprotein analyses revealed that triacylglycerol levels in VLDL and cholesterol levels in LDL and in HDL were all significantly higher in aged rats than in young rats. ALCAR treatment decreased all lipoprotein fractions and consequently the levels of triacylglycerol and cholesterol. The reduction in plasma cholesterol contents in ALCAR-treated aged rats was attributable mainly to a decrease of cholesteryl esters rather than to a decrease of free cholesterol. Another remarkable effect of ALCAR was that it decreased the cholesterol content and cholesterol-phospholipid ratio in the brain tissues of aged rats. These results indicate that chronic ALCAR supplementation reverses the age-associated changes in lipid metabolism. Aging causes quantitative and compositional changes in body lipids. Analyses of plasma samples from humans and experimental animals indicate that cholesterol and triacylglycerol levels increase with aging (1-3). Aging increases total cholesterol and decreases phospholipids, leading to increased cholesterol-phospholipid molar ratios in hepatic mitochondria (4), brain (5), and cerebral synaptic membranes (6). These age-related changes in lipid composition in various tissues and organs are thought to account not only for the age-related accumulation of body fat, which is a risk factor for diabetes and atherosclerotic diseases, but also for age-related cellular hypofunction. Therefore, reversing age-related changes in lipid metabolism would help to maintain normal cellular function and prevent common diseases.Carnitine plays an essential role in transporting fatty acids into mitochondria, where they are oxidized to produce energy in tissues (7). Carnitine levels in cardiac and skeletal muscles, both of which are major storage sites of carnitine, appear to decrease with age (8-11). In plasma, however, it is unclear whether carnitine levels decease with age. Some studies have shown an increase in plasma carnitine levels with aging (12, 13), whereas others have found significant decreases in human (14) and rat (10). This inconsistency is a problem because plasma carnitine levels are often used as an index of body carnitine status. Concerning the age-related changes in carnitine levels in tissues and organs, cardiac and skeletal muscles have frequently been investigated (8-11), but other organs have not attracted much attention. One study reported a decrement of carnitine contents in the brain and a drast...

Gangliosides were shown to enhance the release of acetylcholine from synaptosomes on stimulation. The influx of calcium ion into synaptosomes on membrane depolarization was increased by gangliosides. This was hypothesized to be an underlying mechanisms for the enhancement of acetylcholine release. Studies using calcium channel blockers revealed that four distinct types of voltage-dependent calcium channels occurred in cerebrocortical synapses, and that the N-type was primarily responsible for the evoked release of acetylcholine. An additional result suggests that gangliosides may act mainly on the N-type calcium channel. Cholinergic-specific gangliosides, Chol-1 alpha, were assumed to participate in the mechanism of high-affinity choline uptake. These two different actions of gangliosides were found to be mimicked by synthetic ganglioside analogs. Calcium influx was increased by alpha-sialylcholesterol, and choline uptake was accelerated by beta-sialylcholesterol. Gangliosides and sialylcholesterol having these apparently beneficial effects were shown to ameliorate decreased functions of synapses from aged brains.

Effects of gangliosides GM1 and GQ1b on cholinergic synaptic functions were investigated using synaptosomes prepared from mouse brain cortices. Treatment of synaptosomes with GM1 and GQ1b increased high K(+)-evoked acetylcholine (ACh) release in a bell-shaped dose-dependent manner. The peaks of the effects were found to be at 1-5 microM for GM1 and 5-10 microM for GQ1b. ACh synthesis and the levels of ACh in synaptosomes were not affected by the ganglioside treatment. Both gangliosides enhanced depolarization-induced influx of calcium ions into synaptosomes. These results indicate that GM1 and GQ1b gangliosides increase evoked ACh release by modulating voltage-dependent calcium channels in the synaptic plasma membranes. The effect of GM1 on calcium ion influx remained after repetitive washings, but was almost completely abolished when the bound GM1 was removed by trypsin. This indicates that the fraction of GM1 which was tightly bound to, but not incorporated in synaptic plasma membranes, is responsible for activating the calcium channels.