Aging brain最新文献

Tauopathies are neurodegenerative disorders in which the pathological intracellular aggregation of the protein tau causes cognitive deficits. Additionally, clinical studies report muscle weakness in populations with tauopathy. However, whether neuronal pathological tau species confer muscle weakness, and whether skeletal muscle maintains contractile capacity in primary tauopathy remains unknown. Here, we identified skeletal muscle abnormalities in a mouse model of primary tauopathy, expressing human mutant P301L-tau using adeno-associated virus serotype 8 (AAV8). AAV8-P301L mice showed grip strength deficits, hyperactivity, and abnormal histological features of skeletal muscle. Additionally, spatially resolved gene expression of muscle cross sections were altered in AAV8-P301L myofibers. Transcriptional changes showed alterations of genes encoding sarcomeric proteins, proposing a weakness phenotype. Strikingly, specific force of the soleus muscle was blunted in AAV8-P301L tau male mice. Our findings suggest tauopathy has peripheral consequences in skeletal muscle that contribute to weakness in tauopathy.

Estrogens, such as the biologically active 17-β estradiol (E2), regulate not only reproductive behaviors in adults, but also influence neurodevelopment and neuroprotection in both females and males. E2, contingent upon the timing and concentration of the therapy, is neuroprotective in female and male rodent models of stroke. In Vivo studies suggest that E2 may partially mediate this neuroprotection, particularly in the cortex, via ERα. In Vitro studies, utilizing a chemically induced ischemic injury in cortical explants from both sexes, suggest that ERα or ERβ signaling is needed to mediate the E2 protection. Since we know that the timing and concentration of E2 therapy may be sex-specific, we examined if E2 (1 nM) mediates neuroprotection when female and male cortical explants are separately isolated from postnatal day (PND) 3–4 rat. Changes in basal levels ERα, ERβ, and AR mRNA expression are compared across early post-natal development in the intact cortex and the corresponding days in vitro (DIV) for cortical explants. Following ischemic injury at 7 DIV, cell death and ERα, ERβ and AR mRNA expression was compared in female and male cortical explants. We provide evidence that E2-mediated protection is maintained in isolated cortical explants from females, but not male rats. In female cortical explants, the E2-mediated protection at 24 h occurs secondarily to a blunted transient increase in ERα mRNA at 12 h. These results suggest that cortical E2-mediated protection is influenced by sex and supports data to differentially treat females and males following ischemic injury.

Older adults demonstrate difficulties in sequential decision-making, which is partly attributed to under-recruitment of prefrontal networks. It is, therefore, important to understand the mechanisms that may improve this ability. This study investigated the effectiveness of an 18-sessions, home-based cognitive intervention and the neural mechanisms that underpin individual differences in intervention effects. Participants were required to learn sequential choices in a 3-stage Markov decision-making task that would yield the most rewards. Participants were assigned to better or worse responders group based on their performance at the last intervention session (T18). Better responders improved significantly starting from the fifth intervention session while worse responders did not improve across all training sessions. At post-intervention, only better responders showed condition-dependent modulation of the dorsolateral prefrontal cortex (DLPFC) as measured by fNIRS, with higher DLPFC activity in the delayed condition. Despite large individual differences, our data showed that value-based sequential-decision-making and its corresponding neural mechanisms can be remediated via home-based cognitive intervention in some older adults; moreover, individual differences in recruiting prefrontal activities after the intervention are associated with variations in intervention outcomes. Intervention-related gains were also maintained at three months after post-intervention. However, future studies should investigate the potential of combining other intervention methods such as non-invasive brain stimulation with cognitive intervention for older adults who do not respond to the intervention, thus emphasizing the importance of developing individualized intervention programs for older adults.

Alzheimer’s disease (AD) not only affects cognition and neuropathology, but several other facets capable of negatively impacting quality of life and potentially driving impairments, including altered gut microbiome (GMB) composition and metabolism. Aged (20 + mo) female TgF344-AD and wildtype rats were cognitively characterized on several tasks incorporating several cognitive domains, including task acquisition, object recognition memory, anxiety-like behaviors, and spatial navigation. Additionally, metabolic phenotyping, GMB sequencing throughout the intestinal tract (duodenum, jejunum, ileum, colon, and feces), neuropathological burden assessment and marker gene functional abundance predictions (PICRUSt2) were conducted. TgF344-AD rats demonstrated significant cognitive impairment in multiple domains, as well as regionally specific GMB dysbiosis. Relationships between peripheral factors were investigated using Canonical Correspondence Analysis (CCA), revealing correlations between GMB changes and both cognitive and metabolic factors. Moreover, communities of gut microbes contributing to essential metabolic pathways were significantly altered in TgF344-AD rats. These data indicate dysbiosis may affect cognitive outcomes in AD through alterations in metabolism-related enzymatic pathways that are necessary for proper brain function. Moreover, these changes were mostly observed in intestinal segments required for carbohydrate digestion, not fecal samples. These data support the targeting of intestinal and microbiome health for the treatment of AD.

Aging is a complex and diverse biological process characterized by progressive molecular, cellular, and tissue damage, resulting in a loss of physiological integrity and heightened vulnerability to pathology. This biological diversity corresponds with highly variable cognitive trajectories, which are further confounded by genetic and environmental factors that influence the resilience of the aging brain. Given this complexity, there is a need for neurophysiological indicators that not only discern physiologic and pathologic aging but also closely align with cognitive trajectories. Transcranial Magnetic Stimulation (TMS) may have utility in this regard as a non-invasive brain stimulation tool that can characterize features of cortical excitability. Particularly, as a proxy for central cholinergic function, short-afferent inhibition (SAI) dysfunction is robustly associated with cognitive deficits in the latter stages of Alzheimer’s Disease and Related Dementia (ADRD). In this study, we evaluated SAI in healthy young adults and older adults who, though absent clinical diagnoses, were algorithmically classified as cognitively normal (CN) or cognitively impaired (CI) according to the Jak/Bondi actuarial criteria. We report that SAI is preserved in the Old-CN cohort relative to the young adults, and SAI is significantly diminished in the Old-CI cohort relative to both young and CN older adults. Additionally, diminished SAI was significantly associated with impaired sustained attention and working memory. As a proxy measure for central cholinergic deficits, we discuss the potential value of SAI for discerning physiological and pathological aging.