Exercise has systemic health benefits in people, in part, through improving whole-body insulin sensitivity. The brain is an insulin sensitive organ that is often underdiscussed relative to skeletal muscle, liver, and adipose tissue. While brain insulin action may have only subtle impacts on peripheral regulation of systemic glucose homeostasis, it is important for weight regulation as well as mental health. In fact, brain insulin signaling is also involved in processes that support healthy cognition.

Furthermore, brain insulin resistance has been associated with age-related declines in memory and executive function as well as Alzheimer's disease pathology. Herein, the authors provide an overview of brain insulin sensitivity in relation to cognitive function from animal and human studies, with particular emphasis placed on the impact exercise may have on brain insulin sensitivity. Mechanisms discussed include mitochondrial function, brain growth factors, and neurogenesis, which collectively help combat obesity-related metabolic disease and Alzheimer's dementia.

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Beta blockers, also spelled β-blockers, are a class of medications that are used to manage abnormal heart rhythms, and to protect the heart from a second heart attack after a first heart attack. They are also widely used to treat high blood pressure.

Patients aged ≥ 75 years who receive a beta-blocker after heart failure with reduced ejection fraction (HFrEF) hospitalization have significantly lower 90-day mortality and readmission rates.

Several studies have shown it may also be useful to diminish the risk of Alzheimer disease.

This study aimed to determine the association between beta-blocker use and outcomes among patients with reduced ejection fraction and Alzheimer's disease and related dementias.

Using a random 40% sample of Medicare Parts A, B, and D data the authors identified 357,030 patients with ≥1 hospitalization for reduced ejection fraction between 2008 and 2018. 12.7% of those patients had dementia.

Patients with reduced ejection fraction and dementia had higher 90-day and 1-year mortality compared to patients with reduced ejection fraction-only.

Discontinuing beta-blocker was associated with a 2.2-fold higher risk of 90-day mortality among patients with HF-only and a 2.- fold higher risk of 90-day mortality among patients with reduced ejection fraction + dementia.

Not starting a beta-blocker was associated with a 1.8-fold higher risk of 90-day mortality among patients with reduced ejection fraction-only and a 1.7-fold higher risk of 90-day mortality among patients with reduced ejection fraction + dementia. Similar risks were seen at 1 year.

In conclusion beta-blocker therapy was found to be associated with significantly lower short and long-term mortality rates among all patients with reduced ejection fraction.

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The Parkinson Associated Risk Syndrome study was designed to evaluate whether screening with olfactory testing and dopamine transporter imaging could identify participants at risk for developing Parkinson's disease.

Hyposmia, a reduced ability to smell odors, has been associated with increased risk of Parkinson disease, but, taken alone, lacks specificity. The scientists in a new publication evaluated whether repeating olfactory testing improves the diagnostic characteristics of this screening approach.

The participants that they included in their study completed up to 10 years of clinical and imaging evaluations in the PARS cohort. Olfaction was assessed with the University of Pennsylvania Smell Identification Test at baseline and on average 1.4 years later. Multiple logistic regression and Cox proportional hazards regression were used to estimate the hazard of development of clinical Parkinson disease or abnormal DAT imaging.

DAT scan (Dopamine Transporter Scan) commonly refers to a diagnostic method to investigate if there is a loss of dopaminergic neurons in striatum.

Of 186 studied patients who were initially hyposmic, 28% reverted to normosmia on repeat testing. No initially normosmic subjects and only 2% of reverters developed DAT imaging progression or clinical Parkinson disease, compared to 29% of subjects with persistent hyposmia who developed abnormal DAT and 20% who developed clinical Parkinson disease. The relative risk of clinical conversion to Parkinson disease was 8.3 and of abnormal DAT scan was 12.5 for persistent hyposmia, compared to reversion.

Persistent hyposmia on serial olfactory testing significantly increases the risk of developing clinical Parkinson disease and abnormal DAT imaging, compared to hyposmia on a single test. Repeat olfactory testing may be an efficient and cost-effective strategy to improve identification of at-risk patients for early diagnosis and disease modification studies.

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The predominantly pre-synaptic intrinsically disordered protein α-synuclein is prone to misfolding and aggregation in synucleinopathies, such as Parkinson's disease and Dementia with Lewy bodies. For example molecules of the chaperone machinery are often deposited in Lewy bodies.

A new publication describes a vicious cycle in which parts of a chaperone facilitate the accumulation of toxic α-synuclein, which induces proteostatic stress that itself leads to an increase in insoluble fragments of the chaperone.

Molecular chaperones (proteins that assist the conformational folding or unfolding of large proteins) play important roles in protein misfolding diseases. Heat shock proteins are chaperones that protect cells when stressed by elevated temperatures. Heat shock protein 90 (Hsp90) is one of the most common of those chaperone proteins.

In this new publication, authors from Canada, Brazil and Israel show that STI1, the Hsp90 co-chaperone (proteins that assist chaperones ) co-immunoprecipitated α-synuclein, and co-deposited with Hsp90 and Hsp70 in phosphorylated α-synuclein in ubiquitin-positive inclusions in two mouse models of α-synuclein misfolding.

In Parkinson disease human brains, STI1 was increased, and in neurologically healthy brains, STI1 and α-synuclein location correlated. Nuclear Magnetic Resonance analyses revealed direct interaction of α-synuclein with STI1 and indicated that the STI1 domain ( a region of a protein's polypeptide chain that is self-stabilizing and that folds independently from the rest) TPR2A, but not TPR1 or TPR2B domains, interacted with the C-terminal domain of α-synuclein.

Mice over-expressing STI1 and Hsp90ß presented elevated α-synuclein S129 phosphorylation accompanied by inclusions when injected with α-synuclein pre-formed fibrils.

In contrast, reduced STI1 function decreased protein inclusion formation, S129 α-synuclein phosphorylation, while mitigating motor and cognitive deficits as well as mesoscopic brain atrophy in α-synuclein-over-expressing mice.

In conclusion the authors' findings reveal a vicious cycle in which STI1 facilitates the generation and accumulation of toxic α-synuclein conformers, while α-synuclein-induced proteostatic stress increased insoluble STI1 and Hsp90.

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Resting motor threshold is the minimum intensity that evoked a visible contralateral involuntary finger twitch.

Resting motor threshold asymmetry is the absolute difference between the left and right RMT measurements.

Conflicting results have emerged from studies examining the potential of resting motor threshold as a neurophysiological marker for Alzheimer's disease diagnosis and progression.

In this study, the authors estimated the strength of the association between Resting motor threshold measurements and severity of cognitive impairment in a relatively large sample of clinical trial participants with mild to moderate Alzheimer's disease.

Resting motor threshold for each participant was determined by applying single-pulse transcranial magnetic stimulation repeated at varying intensities over left and right sides of the primary motor cortex.

Cognitive impairment was measured with the Montreal Cognitive Assessment and the Alzheimer Disease Assessment Scale - Cognitive scores.

Although the left and right resting motor threshold was lower in CDR 2 than in CDR 1 participants, neither RMT nor RMT asymmetry correlated significantly with cognitive test scores.

In conclusion, authors' study in a large sample size does not support the idea that resting motor threshold is a sensitive marker of cognitive decline/severity in Alzheimer's disease.

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Greater physical activity and cardiorespiratory fitness are associated with reduced age-related cognitive decline and lower risk for dementia. However, significant gaps remain in the understanding of how physical activity and fitness protect the brain from adverse effects of brain aging.

Cardiorespiratory fitness is a physiological attribute defined as the ability for circulatory and respiratory systems to deliver oxygen.

Cardiorespiratory fitness has a positive relationship with functional connectivity of several cortical networks associated with age-related decline. Furthermore it can occur independent of habitual physical activity.

A 2017 article found evidence for a shared mechanism underlying a favourable cardiovascular fitness profile and ALS susceptibility. The scientists did expose three hypothesis but this one had their favors: A genetic predisposition, for example metabolism, could lead to an increased risk of ALS and a beneficial cardiovascular risk profile. But they were unable to find evidence supporting it.

The scientists in this new publication on contrary found no association between common vascular risk factors and cognitive impairment in patients with Amyotrophic Lateral Sclerosis.

In their cohorte 870 patients, 266 had cognitive impairment. yet no cognitive burden from vascular risk factors was found in patients with Amyotrophic Lateral Sclerosis. On the contrary (and as found in many other studies), the authors first observed that type 2 diabetes mellitus and hyperlipidemia showed protective effects against cognitive decline in Amyotrophic Lateral Sclerosis.

Sensitivity analyses of gender did not substantially reverse the risk estimates. : T2DM and hyperlipidemia decrease the risk of cognitive impairment in patients with Amyotrophic Lateral Sclerosis.

So the fitness hypothesis in Amyotrophic Lateral Sclerosis seems less probable or more complex than initially stated.

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Aging is by far the most prominent risk factor for Alzheimer's disease, and both aging and Alzheimer's disease are associated with apparent metabolic alterations. Perturbed cerebral glucose metabolism, an invariant pathophysiological feature of Alzheimer's disease, may be a critical contributor to the pathogenesis of this disease. For this reason, Alzheimer's disease has sometime times being called "Type 3 diabetes mellitus".

Circadian rhythms, type 2 diabetes mellitus and Alzheimer's disease are closely related and interacted with each other.
The authors of a new article on MedRxiv have previously showed circadian disruption aggravated progression of Alzheimer's disease in T2DM mice. Time-restricted feeding is shown to be a potential synchronizer. This study aims to determine whether time-restricted feeding has a protect effect against the circadian disruption-aggravated progression of Alzheimer's disease in type 2 diabetes mellitus.

Six-week-old male diabetic mice and wildtype mice were kept under normal 12:12 light/dark cycles or altered 6:18 light/dark cycles with or without time-restricted feeding period. After eight weeks, three behavioral tests (open field test, novel object recognition test, barnes maze test were performed and the circadian gene expression, body weight, lipid levels and Alzheimer's disease-associated tau phosphorylation were evaluated.
The scientists found altered light/dark cycles contributed to disruptive circadian rhythms in the hippocampus of db/db mice, while time-restricted feeding prevented this effect. time-restricted feeding also ameliorated circadian disruption-aggravated increased body weight and lipid accumulation in db/db mice.

Importantly, the db/db mice under circadian disruption showed impaired cognition accompanied by increased tau phosphorylation, whereas time-restricted feeding reversed these changes. The altered light/dark cycles only affected circadian rhythms but not other indicators like plasma/liver lipids, cognition and tau phosphorylation in the wt/wt mice.

Collectively, time-restricted feeding has a protective effect against altered light/dark cycles-aggravated Alzheimer's disease progression in diabetic mice.

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Corticogenesis is the process in which the cerebral cortex of the brain is formed during the development of the nervous system. The cortex is the outer layer of the brain and is composed of up to six layers. Neurons formed in the ventricular zone migrate to their final locations in one of the six layers of the cortex. The process occurs between gestational weeks seven to 18 in humans.

Alpha-synuclein and tau are abundant multifunctional neuronal proteins, and their intracellular deposits have been linked to many neurodegenerative diseases. The Alzheimer's disease is defined by extracellular amyloid-β (Aβ) plaques and intraneuronal neurofibrillary tangles composed of hyperphosphorylated tau protein.

However, accumulating evidence suggests that the presynaptic protein α-synuclein, which is usually associated with synucleinopathies like Parkinson's disease, is also involved in the pathophysiology of AD.

Despite the disease relevance, Alpha-synuclein and tau physiological roles remain elusive, as mice with knockout of either of these genes do not exhibit overt phenotypes.

Shengming Wang and colleagues from China and Japan, hypothesized functional cooperation of αSyn and tau during corticogenesis. To reveal this cooperation, they generated a mice model where αSyn and tau genes were deleted and characterized the functional crosstalk between these proteins during brain development.

Intriguingly, deletion of αSyn and tau reduced Notch signaling and accelerated interkinetic nuclear migration of G2 phase at early embryonic stage.

This significantly altered the balance between the proliferative and neurogenic divisions of progenitor cells, resulting in an overproduction of early-born neurons and enhanced neurogenesis, by which the brain size was enlarged during the embryonic stage in both sexes.

On the other hand, loss of αSyn and tau also perturbed gliogenesis at later embryonic stage, as well as the subsequent glial expansion and maturation at postnatal brain. The expansion and maturation of macroglial cells were suppressed in the αSyntau postnatal brain, which in turn reduced the male αSyntau brain size and cortical thickness to less than the control values.

The authors' findings provide new mechanistic insights and extend therapeutic opportunities for neurodegenerative diseases caused by aberrant αSyn and tau.

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