Impairment of Rat Spatial Learning and Memory in a New Model of Cold Water-Induced Chronic Hypothermia: Implication for Alzheimer’s Disease

Unconjugated PLGA nanoparticles attenuate temperature-dependent β-amyloid aggregation and protect neurons against toxicity: implications for Alzheimer's disease pathology

Conversion of β-amyloid (Aβ) peptides from soluble random-coil to aggregated protein enriched with β-sheet-rich intermediates has been suggested to play a role in the degeneration of neurons and development of Alzheimer’s disease (AD) pathology. Aggregation of Aβ peptide can be prompted by a variety of environmental factors including temperature which can influence disease pathogenesis. Recently, we reported that FDA-approved unconjugated poly (d,l-lactide-co-glycolide) (PLGA) nanoparticles can have beneficial effects in cellular and animal models of AD by targeting different facets of the Aβ axis. In this study, using biochemical, structural and spectroscopic analyses, we evaluated the effects of native PLGA on temperature-dependent Aβ aggregation and its ability to protect cultured neurons from degeneration. Our results show that the rate of spontaneous Aβ_1–42 aggregation increases with a rise in temperature from 27 to 40 °C and PLGA with 50:50 resomer potently inhibits Aβ aggregation at all temperatures, but the effect is more profound at 27 °C than at 40 °C. It appears that native PLGA, by interacting with the hydrophobic domain of Aβ_1–42, prevents a conformational shift towards β-sheet structure, thus precluding the formation of Aβ aggregates. Additionally, PLGA triggers disassembly of matured Aβ_1–42 fibers at a faster rate at 40 °C than at 27 °C. PLGA-treated Aβ samples can significantly enhance viability of cortical cultured neurons compared to neurons treated with Aβ alone by attenuating phosphorylation of tau protein. Injection of native PLGA is found to influence the breakdown/clearance of Aβ peptide in the brain. Collectively, these results suggest that PLGA nanoparticles can inhibit Aβ aggregation and trigger disassembly of Aβ aggregates at temperatures outside the physiological range and can protect neurons against Aβ-mediated toxicity thus validating its unique therapeutic potential in the treatment of AD pathology.

Aqueous extracts of Aconite promote thermogenesis in rats with hypothermia via regulating gut microbiota and bile acid metabolism

Background

Intermittent or prolonged exposure to severe cold stress disturbs energy homeostasis and can lead to hypothermia, heart failure, Alzheimer’s disease, and so on. As the typical “hot” traditional Chinese medicine, Aconite has been widely used to treat cold-associated diseases for thousands of years, but its critical mechanisms for the promotion of thermogenesis are not fully resolved. Gut microbiota and its metabolites play a crucial role in maintaining energy homeostasis. Here, we investigated whether the aqueous extracts of Aconite (AA) can enhance thermogenesis through modulation of the composition and metabolism of gut microbiota in hypothermic rats.

Methods

The therapeutic effects of AA on body temperature, energy intake, and the histopathology of white adipose tissue and brown adipose tissue of hypothermic rats were assessed. Microbiota analysis based on 16 S rRNA and targeted metabolomics for bile acids (BAs) were used to evaluate the composition of gut microbiota and BAs pool. The antibiotic cocktail treatment was adopted to further confirm the relationship between the gut microbiota and the thermogenesis-promoting effects of AA.

Results

Our results showed a sharp drop in rectal temperature and body surface temperature in hypothermic rats. Administration of AA can significantly increase core body temperature, surface body temperature, energy intake, browning of white adipose tissue, and thermogenesis of brown adipose tissue. Importantly, these ameliorative effects of AA were accompanied by the shift of the disturbed composition of gut microbiota toward a healthier profile and the increased levels of BAs. In addition, the depletion of gut microbiota and the reduction of BAs caused by antibiotic cocktails reduced the thermogenesis-promoting effect of AA.

Conclusions

Our results demonstrated that AA promoted thermogenesis in rats with hypothermia via regulating gut microbiota and BAs metabolism. Our findings can also provide a novel solution for the treatment of thermogenesis-associated diseases such as rheumatoid arthritis, obesity, and type 2 diabetes.

Examining the association between apparent temperature and admissions for schizophrenia in Hefei, China, 2005-2014: A time-series analysis

BACKGROUND

Many studies have investigated the association between schizophrenia and daily mean temperature, but the conclusions were not consistent. Apparent temperature (AT), a comprehensive indicator of temperature and humidity, reflected human thermal sensation more objectively than temperature. We aimed to investigate the relationship between high/low AT and schizophrenia hospitalizations in Hefei, China, and further to identify vulnerable subpopulations.

METHODS

Poisson generalized linear regression model combined with distributed lag non-linear model (DLNM) was applied to quantify the relationship between AT and schizophrenia hospitalizations, compared with the AT of minimum admissions (3.3 °C). Stratified analysis was conducted by sex, marital status and age. Separate models for AT and temperature were compared as well.

RESULTS

The high AT (90th, 28.3 °C) exerted the greatest effect at lag0, with RR = 1.062 (95%CI, 1.019-1.106). The effect of the low AT (10th, -4.7 °C) was first observed at lag3 (RR = 1.007, 95%CI: 1.000-1.015), and increased to the maximum at lag7 (RR = 1.018, 95%CI: 1.009-1.027). The male patients, the married patients and patients aged 41-60 years appeared to be more vulnerable to both high and low ATs. The values of Akaike Information Criterion and mean squared error (MSE) in model with AT were smaller than that with temperature.

CONCLUSIONS

Both high and low ATs were associated with increase in schizophrenia hospitalizations. More protective measures should be taken to avoid adverse AT exposure in susceptible groups.

Thermoregulatory profile of neurodegeneration-induced dementia of the Alzheimer's type using intracerebroventricular streptozotocin in rats

AIM

Here, we have extensively investigated the relationship between thermoregulation and neurodegeneration-induced dementia of the Alzheimer's type using intracerebroventricular injections of streptozotocin (icv-STZ).

METHODS

Male Wistar rats were treated with bilateral injections of icv-STZ, and their thermoregulatory profiles (core body temperature, tail-skin temperature, cold and heat defence responses and thermal place preference) were evaluated. Spatial memory, locomotor activity, social interaction, brain ventricular volume, and Aβ_1-42 and tau protein levels in the brain were analysed to characterize the effects of STZ on the brain and behaviour.

RESULTS

In addition to deficits in spatial memory, reduced social interaction and an increased brain ventricular volume, icv-STZ rats presented a pattern of hyperthermia, as demonstrated by an increased core body temperature. Hyperthermia was due to the activation of both autonomic heat conservation and behavioural cold avoidance, as STZ-treated rats presented tail-cutaneous vasoconstriction and an altered thermal preference. They also showed a distinct cold defence response when exposed to cold.

CONCLUSION

Our data bring evidence that icv-STZ in rats causes hyperthermia, with activation of both autonomic and behavioural thermoregulatory defence responses when challenged at colder temperatures, leading us to hypothesize that they are more efficient in preventing hypothermia. These data are relevant for a better understanding of neurodegenerative disease mechanisms.

Hypothermia as a risk factor for Alzheimer disease

Alzheimer disease (AD), which is associated with chronic and progressive neurodegeneration, is the most prevalent cause of dementia linked to aging. Among the risk factors for AD, age stands as the greatest one, with the vast majority of people with AD being 65 years of age or older. Nevertheless, the pathophysiologic mechanisms underlying the link between aging and the development of AD, although not completely understood, might reveal important aspects for the understanding of this pathology. Thus, there is significant evidence that the impaired thermal homeostasis associated with normal aging leads to a variety of metabolic changes that could be associated with AD development. In this chapter, we assess the clinical and biochemical evidence implicating hypothermia as a risk factor for the development of AD and the impact of hypothermia on the two pathologic hallmarks of AD: accumulation of senile plaques of amyloid-beta and neurofibrillary tangles of aberrant hyperphosphorylated tau protein.

Analyzing the genes related to Alzheimer's disease via a network and pathway-based approach

Background

Our understanding of the molecular mechanisms underlying Alzheimer’s disease (AD) remains incomplete. Previous studies have revealed that genetic factors provide a significant contribution to the pathogenesis and development of AD. In the past years, numerous genes implicated in this disease have been identified via genetic association studies on candidate genes or at the genome-wide level. However, in many cases, the roles of these genes and their interactions in AD are still unclear. A comprehensive and systematic analysis focusing on the biological function and interactions of these genes in the context of AD will therefore provide valuable insights to understand the molecular features of the disease.

Method

In this study, we collected genes potentially associated with AD by screening publications on genetic association studies deposited in PubMed. The major biological themes linked with these genes were then revealed by function and biochemical pathway enrichment analysis, and the relation between the pathways was explored by pathway crosstalk analysis. Furthermore, the network features of these AD-related genes were analyzed in the context of human interactome and an AD-specific network was inferred using the Steiner minimal tree algorithm.

Results

We compiled 430 human genes reported to be associated with AD from 823 publications. Biological theme analysis indicated that the biological processes and biochemical pathways related to neurodevelopment, metabolism, cell growth and/or survival, and immunology were enriched in these genes. Pathway crosstalk analysis then revealed that the significantly enriched pathways could be grouped into three interlinked modules—neuronal and metabolic module, cell growth/survival and neuroendocrine pathway module, and immune response-related module—indicating an AD-specific immune-endocrine-neuronal regulatory network. Furthermore, an AD-specific protein network was inferred and novel genes potentially associated with AD were identified.

Conclusion

By means of network and pathway-based methodology, we explored the pathogenetic mechanism underlying AD at a systems biology level. Results from our work could provide valuable clues for understanding the molecular mechanism underlying AD. In addition, the framework proposed in this study could be used to investigate the pathological molecular network and genes relevant to other complex diseases or phenotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-017-0252-z) contains supplementary material, which is available to authorized users.

A culture-brain link: Negative age stereotypes predict Alzheimer's disease biomarkers

Although negative age stereotypes have been found to predict adverse outcomes among older individuals, it was unknown whether the influence of stereotypes extends to brain changes associated with Alzheimer's disease. To consider this possibility, we drew on dementia-free participants, in the Baltimore Longitudinal Study of Aging, whose age stereotypes were assessed decades before yearly magnetic resonance images and brain autopsies were performed. Those holding more-negative age stereotypes earlier in life had significantly steeper hippocampal-volume loss and significantly greater accumulation of neurofibrillary tangles and amyloid plaques, adjusting for relevant covariates. These findings suggest a new pathway to identifying mechanisms and potential interventions related to the pathology of Alzheimer's disease.

Physiopathology of Dementia in Iranian Traditional Medicine

Recently, an article published in this journal by Dr Seifaddini and colleagues. In that article, the authors tried to connect dementia, including Alzheimer's disease, with a condition mentioned in Iranian traditional medical condition, Raoonat and Homgh In this condition, intellectual functions of the brain are disturbed and therefore, learning and decision-making abilities are damaged. This condition is not age limited and affects thinking ability but not memory. On the other hand, there is a condition described in Iranian traditional medicine, which completely matches with Alzheimer's disease. This condition is explained under the title of Nesyan (forgetfulness). Nesyan has 5 subdivisions, one of which is caused by the inclination of the brain normal temperament to more coldness and dryness. By performing animal studies, we have recently shown that this kind of Nesyan is related with Alzheimer's disease. Studies on the traditional recommendations on treatment of this kind of Nesyan can be useful in treatment of Alzheimer's disease.