No abstract

We previously described a heterozygous mouse model overexpressing human HA-tagged 24S-hydroxylase (CYP46A1) utilizing a ubiquitous expression vector. In this study, we generated homozygotes of these mice with circulating levels of 24OH 30–60% higher than the heterozygotes. Female homozygous CYP46A1 transgenic mice, aged 15 months, showed an improvement in spatial memory in the Morris water maze test as compared to the wild type mice. The levels of N-Methyl-D-Aspartate receptor 1, phosphorylated-N-Methyl-D-Aspartate receptor 2A, postsynaptic density 95, synapsin-1 and synapthophysin were significantly increased in the hippocampus of the CYP46A1 transgenic mice as compared to the controls. The levels of lanosterol in the brain of the CYP46A1 transgenic mice were significantly increased, consistent with a higher synthesis of cholesterol. Our results are discussed in relation to the hypothesis that the flux in the mevalonate pathway in the brain is of importance in cognitive functions.

Ismail et al. show that 27-hydroxycholesterol, a peripheral cholesterol metabolite capable of passing the blood–brain barrier, reduces brain glucose uptake by upregulating the renin-angiotensin system and inhibiting GLUT4. This alteration affects memory processes and is likely to have implications on neurodegenerative diseases.

BackgroundPolypharmacy is common among older adults. However, little is known about the composition of polypharmacy: which are the most frequently used drugs, and how much do these drugs contribute to the overall prevalence of polypharmacy.MethodsA total of 822,619 Swedes aged ≥75 years was identified from the Total Population Register. Through record-linkage with the Swedish Prescribed Drug Register and the Social Services Register we could analyze concurrent drug use in the entire population (both individuals living in the community and institution) on the 31 December 2013.ResultsThe prevalence of polypharmacy (≥5 drugs) was 45%. The most frequently used drugs were cardiovascular drugs, analgesics, and psychotropics. By excluding the ten most frequently used drug classes or compounds, the prevalence of polypharmacy was reduced by 69% and 51% respectively. The majority of the users of either one of the 10 most frequently used drugs concurrently used at least 4 other drug classes (66%-85%).ConclusionAlmost half of the individuals aged ≥75 years are exposed to polypharmacy in Sweden. A handful of drugs make a large contribution to the overall prevalence of polypharmacy and the majority of drugs prescribed to persons aged ≥75 years are used in combination with other drugs. This highlights the high use of drugs, and the need to consider other concurrent drug treatments when prescribing for older adults.

Hypercholesterolemia is a risk factor for neurodegenerative diseases, but how high blood cholesterol levels are linked to neurodegeneration is still unknown. Here, we show that an excess of the blood–brain barrier permeable cholesterol metabolite 27-hydroxycholesterol (27-OH) impairs neuronal morphology and reduces hippocampal spine density and the levels of the postsynaptic protein PSD95. Dendritic spines are the main postsynaptic elements of excitatory synapses and are crucial structures for memory and cognition. Furthermore, PSD95 has an essential function for synaptic maintenance and plasticity. PSD95 synthesis is controlled by the REST–miR124a–PTBP1 axis. Here, we report that high levels of 27-OH induce REST–miR124a–PTBP1 axis dysregulation in a possible RxRγ-dependent manner, suggesting that 27-OH reduces PSD95 levels through this mechanism. Our results reveal a possible molecular link between hypercholesterolemia and neurodegeneration. We discuss the possibility that reduction of 27-OH levels could be a useful strategy for preventing memory and cognitive decline in neurodegenerative disorders.