Apolipoprotein E4 heterologous expression, purification under non-denaturing conditions, and effects on neuronal clonal cell lines.

The ε4 allele of the apolipoprotein E gene (APOE4) constitutes the main genetic risk factor for late-onset Alzheimer disease (AD). High amounts of pure apolipoprotein E4 (ApoE4), in a rapid and reproducible fashion, could be of value for studying its pathophysiological roles in AD. The aim of the present work was to optimize a preparative method to obtain highly purified recombinant ApoE4 (rApoE4) with full biological activity. rApoE4 was expressed in the E. Coli BL21(D3) strain and a soluble form of the protein was purified by a combination of affinity and size-exclusion chromatography that precluded a denaturation step. The structural integrity and the biochemical activity of the purified rApoE4 were confirmed by circular dichroism and a lipid-binding assay. Several biological parameters affected by rApoE4, such as mitochondrial morphology, mitochondrial membrane potential and reactive oxygen species production were studied in CNh cells, a neuronal cell line, and neurodifferentiation and dendritogenesis were analyzed in the SH-SY5Y neuroblastoma cell line. The improved rApoE4 purification technique reported here enables the production of highly purified protein that retain the structural properties and functional activity of the native protein, as confirmed by tests in two different neuronal cell lines in culture.

Sleep disruption in medicine students and its relationship with impaired academic performance: A systematic review and meta-analysis.

Sleep disruption severely impairs learning ability, affecting academic performance in students. This systematic review and meta-analysis aimed at assessing the prevalence of sleep disruption in medical students and its relationship with academic performance. PubMed, Web of Sciences, EBSCO and SciELO databases searches allowed to retrieve 41 papers with data about the prevalence of sleep deprivation, 20 of which also contained data on its association with academic performance. Poor sleep quality was reported by 5646 out of 14,170 students in 29 studies (39.8%, 95% confidence interval = 39.0-40.6%), insufficient sleep duration by 3762/12,906 students in 28 studies (29.1%, 23.3-29.9%) and excessive diurnal sleepiness by 1324/3688 students in 13 studies (35.9%, 34.3-37.4). Academic grades correlated significantly with sleep quality scores (r, 95% CI = 0.15, 0.05-0.26, random-effects model; p = 0.002, n = 10,420 subjects, k = 15 studies) and diurnal sleepiness (r = -0.12, -0.19/-0.06 under the fixed effects model, p < 0.001, n = 1539, k = 6), but not with sleep duration (r = 0.03, -0.12/0.17 under the random-effects model, p = 0.132, n = 2469, k = 9). These findings advocate for an urgent intervention aiming at improving sleep quality among medical students as a way of increasing academic achievements and, ultimately, the quality of health care.