The aging population: implications for the burden of neurologic disease

Novel adult cortical neuron processing and screening method illustrates sex- and age-dependent effects of pharmaceutical compounds

Neurodegenerative diseases and neurotraumatic injuries are typically age-associated disorders that can reduce neuron survival, neurite outgrowth, and synaptic plasticity leading to loss of cognitive capacity, executive function, and motor control. In pursuit of reducing the loss of said neurological functions, novel compounds are sought that promote neuron viability, neuritogenesis, and/or synaptic plasticity. Current high content in vitro screenings typically use cells that are iPSC-derived, embryonic, or originate from post-natal tissues; however, most patients suffering from neurodegenerative diseases and neurotrauma are of middle-age and older. The chasm in maturity between the neurons used in drug screens and those in a target population is a barrier for translational success of in vitro results. It has been historically challenging to culture adult neurons let alone conduct screenings; therefore, age-appropriate drug screenings have previously not been plausible. We have modified Miltenyi's protocol to increase neuronal yield, neuron purity, and neural viability at a reduced cost to expand our capacity to screen compounds directly in primary adult neurons. To our knowledge, we developed the first morphology-based screening system using adult cortical neurons and the first to incorporate age and sex as biological variables in a screen using adult cortical neurons. By using primary adult cortical neurons from mice that were 4 to 48 weeks old for screening pharmaceutical agents, we have demonstrated age- and sex-dependent effects on neuritogenesis and neuron survival in vitro. Utilizing age- and sex-appropriate in vitro models to find novel compounds increasing neuron survival and neurite outgrowth, made possible by our modified adult neuron processing method, will greatly increase the relevance of in vitro screening for finding neuroprotective compounds.

Advanced glycation end products in brain during aging

Aging is a main risk factor for many diseases including neurodegenerative disorders. Numerous theories and mechanisms including accumulation of advanced glycation end products (AGEs) have been put forward in explaining brain aging. However, a focused study on the status of AGEs in the brain during progressive aging in connection with interrelated cellular processes like ubiquitin-proteasome system (UPS), unfolded protein response, autophagy-lysosome system and apoptosis is lacking. Hence, in this study, we investigated the levels of AGEs in the brain of 5-, 10-, 15- and 20-months old WNIN rats. Endoplasmic reticulum (ER) stress response, UPS components, autophagy flux, neurotrophic and presynaptic markers along with cell death markers were analyzed by immunoblotting. The neuronal architecture was analyzed by H&E and Nissl staining. The results demonstrated progressive accumulation of AGEs in the brain during aging. Adaptive ER stress response was observed by 10-months while maladaptive ER stress response was seen at 15- and 20-months of age along with impaired UPS and autophagy, and perturbations in neuronal growth factors. All these disturbances intensify with age to further exaggerate cell death mechanisms. There was a shrinkage of the cell size with aging and Congo-red staining revealed β-amyloid accumulation in higher ages. Together these results suggest that progressive accumulation of AGEs with aging in the brain may lead to neuronal damage by affecting ER homeostasis, UPS, autophagic flux, and neuronal growth factors.

Applied neuroanatomy elective to reinforce and promote engagement with neurosensory pathways using interactive and artistic activities

One in six Americans is currently affected by neurologic disease. As the United States population ages, the number of neurologic complaints is expected to increase. Thus, there is a pressing need for more neurologists as well as more neurology training in other specialties. Often interest in neurology begins during medical school, so improving education in medical neural courses is a critical step toward producing more neurologists and better neurology training in other specialists. To this end, a novel applied neuroanatomy elective was designed at the University of Texas Health Science Center at San Antonio (UTHSCSA) to complement the traditional first-year medical neuroscience course and promote engagement and deep learning of the material with a focus on neurosensory pathways. The elective covered four neurosensory modalities (proprioception/balance, vision, auditory, and taste/olfaction) over four sessions, each with a short classroom component and a much longer activity component. At each session, students reviewed the neurosensory pathways through structured presentations and then applied them to preplanned interactive activities, many of which allowed students to utilize their artistic talents. Students were required to complete subjective pre-course and post-course surveys and reflections. The survey results and positive student comments suggest that the elective was a valuable tool when used in parallel with the traditional medical neuroscience course in promoting engagement and reinforcement of the neurosensory material.

Association between neurological disorders, functioning, and mortality in the elderly

OBJECTIVES

In aging populations, the prevalence of neurological disorders increases, which imposes high population burden in terms of mortality, disability, and impaired quality of life. The aim of this study was to assess the prevalence of common neurological disorders and signs and their association with functioning and mortality in an elderly general population.

MATERIALS AND METHODS

We used data from the Memory and Morbidity in Augsburg Elderly (MEMO) project, a population-based study of 385 individuals aged ≥65. The prevalence of neurological disorders and signs was assessed by physical examination and medical interview. The basic and instrumental activities of daily living were assessed (ADL, IADL). We assessed the association of neurological disorders and signs with everyday functioning and prospectively analyzed their relationship with mortality.

RESULTS

We observed considerably impaired functioning for cases with stroke, TIA, PD, and mild motor parkinsonian signs (MMPS). All-cause mortality was significantly increased in participants with stroke and MMPS, even after adjusting for co-variables (HR = 2.71 and 1.80, respectively).

CONCLUSIONS

We found that not only specific neurological disorders, but also earlier symptoms are related to impaired functioning and predict mortality in the elderly. These findings have potential clinical relevance for screening and early detection of individuals at risk.

The biphasic pattern of age-specific malignant brain tumor mortality rates

Many aging-associated neurologic disorders, including primary malignant brain tumors (MBT), share a common biphasic age-specific mortality rate pattern: initially increasing exponentially with age, and then declining. A modeling study using MBT mortality was conducted to determine if the observed biphasic pattern of MBT age-specific mortality rates emerges if one assumes that there exists a population subset that is inherently susceptible to MBT, and that the risk of mortality from MBT in that susceptible population subset continues to increase exponentially with age. A hypothetical population was subjected to 1988 general mortality risks. A population subset susceptible to MBT was subjected to both exponentially increasing 1988 general and MBT mortality risks. Expected MBT age-specific mortality rates in the total population (both general and MBT susceptible subsets) were determined. Expected MBT age-specific mortality rates in the total population initially increase exponentially with age, and then decline. Moreover, when the size of the MBT-susceptible population subset was set at 1/125 of the size of the general population size, the modeled pattern of age-specific MBT mortality rates closely mimicked the observed pattern of age-specific MBT mortality rates. The observed biphasic pattern of age-specific MBT mortality rates can be explained by the existence of an MBT-susceptible population subset in whom the risk of MBT mortality increases exponentially with age and population subset depletion occurs.