Insulin Peptides as Mediators of the Impact of Life Style in Alzheimer's disease

Identification of IGF-1 Effects on White Adipose Tissue and Hippocampus in Alzheimer's Disease Mice via Transcriptomic and Cellular Analysis

Alzheimer's disease (AD) stands as the most prevalent neurodegenerative disorder, characterized by a multitude of pathological manifestations, prominently marked by the aggregation of amyloid beta. Recent investigations have revealed a compelling association between excessive adiposity and glial activation, further correlating with cognitive impairments. Additionally, alterations in levels of insulin-like growth factor 1 (IGF-1) have been reported in individuals with metabolic conditions accompanied by memory dysfunction. Hence, our research endeavors to comprehensively explore the impact of IGF-1 on the hippocampus and adipose tissue in the context of Alzheimer's disease. To address this, we have conducted an in-depth analysis utilizing APP/PS2 transgenic mice, recognized as a well-established mouse model for Alzheimer's disease. Upon administering IGF-1 injections to the APP/PS2 mice, we observed notable alterations in their behavioral patterns, prompting us to undertake a comprehensive transcriptomic analysis of both the hippocampal and adipose tissues. Our data unveiled significant modifications in the functional profiles of these tissues. Specifically, in the hippocampus, we identified changes associated with synaptic activity and neuroinflammation. Concurrently, the adipose tissue displayed shifts in processes related to fat browning and cell death signaling. In addition to these findings, our analysis enabled the identification of a collection of long non-coding RNAs and circular RNAs that exhibited significant changes in expression subsequent to the administration of IGF-1 injections. Furthermore, we endeavored to predict the potential roles of these identified RNA molecules within the context of our study. In summary, our study offers valuable transcriptome data for hippocampal and adipose tissues within an Alzheimer's disease model and posits a significant role for IGF-1 within both the hippocampus and adipose tissue.

The Role of Insulin-like Growth Factor I in Mechanisms of Resilience and Vulnerability to Sporadic Alzheimer's Disease

Despite decades of intense research, disease-modifying therapeutic approaches for Alzheimer's disease (AD) are still very much needed. Apart from the extensively analyzed tau and amyloid pathological cascades, two promising avenues of research that may eventually identify new druggable targets for AD are based on a better understanding of the mechanisms of resilience and vulnerability to this condition. We argue that insulin-like growth factor I (IGF-I) activity in the brain provides a common substrate for the mechanisms of resilience and vulnerability to AD. We postulate that preserved brain IGF-I activity contributes to resilience to AD pathology as this growth factor intervenes in all the major pathological cascades considered to be involved in AD, including metabolic impairment, altered proteostasis, and inflammation, to name the three that are considered to be the most important ones. Conversely, disturbed IGF-I activity is found in many AD risk factors, such as old age, type 2 diabetes, imbalanced diet, sedentary life, sociality, stroke, stress, and low education, whereas the Apolipoprotein (Apo) E4 genotype and traumatic brain injury may also be influenced by brain IGF-I activity. Accordingly, IGF-I activity should be taken into consideration when analyzing these processes, while its preservation will predictably help prevent the progress of AD pathology. Thus, we need to define IGF-I activity in all these conditions and develop a means to preserve it. However, defining brain IGF-I activity cannot be solely based on humoral or tissue levels of this neurotrophic factor, and new functionally based assessments need to be developed.

Effect of COVID-19 Pandemic on Dietary Habits and Sleep Quality Applying the Pittsburgh Sleep Quality Index in Adult Saudi Population: A Cross-Sectional Study

The study aimed to evaluate the possible correlations between sleep quality and dietary habits in a population of Saudi during the COVID-19 pandemic. Exactly 444 adults completed a web-based cross-sectional study using an electronic questionnaire. Results indicate a significant difference between body mass index (BMI) and bad sleep quality. Smoking is linked to bad sleep quality. Both genders affected by coronavirus had a substantially bad quality compared to non-affected. An association between the degree of craving for sugar and bad sleep quality was found. In addition, there was a statistical difference between males and females who crave sugar very often in bad sleep quality. The result of sleep latency in males was 35.83%, who suffered from a severe sleep disorder, while 41.18% were female. The sleep duration was 65.00%, and 53.90% of males and females slept between 6 and 7 h per day. Sleep efficiency, measured according to the Pittsburgh questionnaire protocol, was measured in percentages, where a value of less than 65.00% is considered the lowest sleep efficiency. Females had a lower sleep efficiency of 25.49% compared to males (13.33%). These differences were statistically significant (p = 0.03). In conclusion, quality and sleep duration were impaired during the COVID-19 pandemic, and the observed changes were associated with diet.

Response Facilitation Induced by Insulin-Like Growth Factor-I in the Primary Somatosensory Cortex of Mice Was Reduced in Aging

Aging is accompanied by a decline in cognition that can be due to a lower IGF-I level. We studied response facilitation induced in primary somatosensory (S1) cortical neurons by repetitive stimulation of whiskers in young and old mice. Layer 2/3 and 5/6 neurons were extracellularly recorded in young (≤ 6 months of age) and old (≥ 20 month of age) anesthetized mice. IGF-I injection in S1 cortex (10 nM; 0.2 μL) increased whisker responses in young and old animals. A stimulation train at 8 Hz induced a long-lasting response facilitation in only layer 2/3 neurons of young animals. However, all cortical neurons from young and old animals showed long-lasting response facilitation when IGF-I was applied in the S1 cortex. The reduction in response facilitation in old animals can be due to a reduction in the IGF-I receptors as was indicated by the immunohistochemistry study. Furthermore, a reduction in the performance of a whisker discrimination task was observed in old animals. In conclusion, our findings indicate that there is a reduction in the synaptic plasticity of S1 neurons during aging that can be recovered by IGF-I. Therefore, it opens the possibility of use IGF-I as a therapeutic tool to ameliorate the effects of heathy aging.

Impact of Sociodemographic Features and Lifestyle on Cognitive Performance of Peruvian Adults

BACKGROUND

Cognitive impairment and dementia may result from a combination of modifiable and nonmodifiable risk and protective factors, such as the environment, educational attainment, time devoted to cognitively stimulating activities, and physical activity.

OBJECTIVE

This study aimed to investigate the mediating role of sociodemographic characteristics and lifestyle factors in the years of education and cognitive performance in Peruvian adults.

METHODS

This cross-sectional study included 1,478 subjects assessed by Addenbrooke's Cognitive Examination Revised (ACE-R). Using mediation models, we evaluated the mediation role of parents' educational level, reading time (RT), and physical activity time (PAT) in the years of education (IYE) and cognitive performance.

RESULTS

People who reported having lived in an urban area during their childhood are estimated to have, on average, 2.085 years more formal education than those who lived in rural areas. In addition, 49% of cognitive performance scores are explained by the mediation effect of reading and physical activity time in the IYE. This implies that higher levels of education, mediated by RT and PAT per week, are 1.596 units associated with higher scores on the ACE-R.

CONCLUSION

Despite the fact that nonmodifiable factors (i.e., childhood residence area, parents' educational level) seem to exert an effect on older adults' cognition, their influence is mediated by other factors that are indeed modifiable (i.e., reading time, physical activity engagement). In this sense, lifestyle changes could help prevent or decrease the risk of cognitive impairment and reduce the disease's impact on vulnerable environments in Latin American and Caribbean countries.

Insulin-like growth factor I mitigates post-traumatic stress by inhibiting AMP-kinase in orexin neurons

Maladaptive coping behaviors are probably involved in post-traumatic stress disorders (PTSD), but underlying mechanisms are incompletely understood. We now report that mice lacking functional insulin-like growth factor I (IGF-I) receptors in orexin neurons of the lateral hypothalamus (Firoc mice) are unresponsive to the anxiolytic actions of IGF-I and develop PTSD-like behavior that is ameliorated by inhibition of orexin neurons. Conversely, systemic IGF-I treatment ameliorated PTSD-like behavior in a wild-type mouse model of PTSD (PTSD mice). Further, systemic IGF-I modified the GABA/Glutamate synaptic structure in orexin neurons of naïve wild-type mice by increasing the dephosphorylation of GABA(B) receptor subunit through inhibition of AMP-kinase (AMPK). Significantly, pharmacological inhibition of AMPK mimicked IGF-I, normalizing fear behavior in PTSD mice. Thus, we suggest that IGF-I enables coping behaviors by balancing E/I input onto orexin neurons in a context-dependent manner. These observations provide a novel therapeutic approach to PTSD through modulation of AMPK.

Reduced Insulin-Like Growth Factor-I Effects in the Basal Forebrain of Aging Mouse

It is known that aging is frequently accompanied by a decline in cognition. Furthermore, aging is associated with lower serum IGF-I levels that may contribute to this deterioration. We studied the effect of IGF-I in neurons of the horizontal diagonal band of Broca (HDB) of young (≤6 months old) and old (≥20-month-old) mice to determine if changes in the response of these neurons to IGF-I occur along with aging. Local injection of IGF-I in the HDB nucleus increased their neuronal activity and induced fast oscillatory activity in the electrocorticogram (ECoG). Furthermore, IGF-I facilitated tactile responses in the primary somatosensory cortex elicited by air-puffs delivered in the whiskers. These excitatory effects decreased in old mice. Immunohistochemistry showed that cholinergic HDB neurons express IGF-I receptors and that IGF-I injection increased the expression of c-fos in young, but not in old animals. IGF-I increased the activity of optogenetically-identified cholinergic neurons in young animals, suggesting that most of the IGF-I-induced excitatory effects were mediated by activation of these neurons. Effects of aging were partially ameliorated by chronic IGF-I treatment in old mice. The present findings suggest that reduced IGF-I activity in old animals participates in age-associated changes in cortical activity.

Mechanistic insights into the pathogenesis of neurodegenerative diseases: towards the development of effective therapy

Neurodegeneration is a prevalent and one of the emerging reasons for morbidity, mortality, and cognitive impairment in aging. Dementia is one of such conditions of neurodegeneration, partially manageable, irreversible, and worsens over time. This review is focused on biological and psychosocial risk factors associated with Alzheimer's and Parkinson's diseases, highlighting the value of cognitive decline. We further emphasized on current therapeutic strategies from pharmacological and non-pharmacological perspectives focusing on their effects on cognitive impairment, protein aggregation, tau pathology, and improving the quality of life. Deeper mechanistic insights into the multifactorial neurodegeneration could offer the design and development of promising diagnostic and therapeutic strategies.

Association between diet and sleep quality: A systematic review

Dietary habits are considered a leading behavioral risk factor for human health. There is growing scientific evidence suggesting that diet and sleep may be related. The aim of this study was to review the evidence of association between diet and sleep quality. A systematic search in electronic databases PubMed, Embase, Scopus, and the Cochrane Central Register of Controlled Trials was conducted from their inception to November 2019. Studies investigating parameters of diet quality (including dietary patterns or individual healthy/unhealthy foods) and sleep quality (assessed through self-reported or objective methods) were included. The NIH Quality Assessment Tools were used to evaluate the study quality. Twenty-nine studies were reviewed: in summary, consumption of healthy foods was associated with better sleep quality, while higher intake of processed and free-sugar rich foods was associated with worse sleep features. Despite a certain consistency between studies have been observed, the overall poor-to-fair quality of study design (mostly represented by cross-sectional investigations) does not allow to conclude a causal relation. However, diet-related variables are associated with sleep quality, but further studies are needed to corroborate this finding.

Circulating Insulin-Like Growth Factor I is Involved in the Effect of High Fat Diet on Peripheral Amyloid β Clearance

Obesity is a risk factor for Alzheimer’s disease (AD), but underlying mechanisms are not clear. We analyzed peripheral clearance of amyloid β (Aβ) in overweight mice because its systemic elimination may impact brain Aβ load, a major landmark of AD pathology. We also analyzed whether circulating insulin-like growth factor I (IGF-I) intervenes in the effects of overweight as this growth factor modulates brain Aβ clearance and is increased in the serum of overweight mice. Overweight mice showed increased Aβ accumulation by the liver, the major site of elimination of systemic Aβ, but unaltered brain Aβ levels. We also found that Aβ accumulation by hepatocytes is stimulated by IGF-I, and that mice with low serum IGF-I levels show reduced liver Aβ accumulation—ameliorated by IGF-I administration, and unchanged brain Aβ levels. In the brain, IGF-I favored the association of its receptor (IGF-IR) with the Aβ precursor protein (APP), and at the same time, stimulated non-amyloidogenic processing of APP in astrocytes, as indicated by an increased sAPPα/sAPPβ ratio after IGF-I treatment. Since serum IGF-I enters into the brain in an activity-dependent manner, we analyzed in overweight mice the effect of brain activation by environmental enrichment (EE) on brain IGF-IR phosphorylation and its association to APP, as a readout of IGF-I activity. After EE, significantly reduced brain IGF-IR phosphorylation and APP/IGF-IR association were found in overweight mice as compared to lean controls. Collectively, these results indicate that a high-fat diet influences peripheral clearance of Aβ without affecting brain Aβ load. Increased serum IGF-I likely contributes to enhanced peripheral Aβ clearance in overweight mice, without affecting brain Aβ load probably because its brain entrance is reduced.

Endosomal-lysosomal dysfunction in metabolic diseases and Alzheimer's disease

The endosomal-lysosomal pathways and related autophagic processes are responsible for proteostasis, involving complexes between lysosomes and autophagosomes. Lysosomes are a key component of homeostasis, involved in cell signaling, metabolism, and quality control, and they experience functional compromise in metabolic diseases, aging, and neurodegenerative diseases. Many genetic mutations and risk factor genes associated with proteinopathies, as well as with metabolic diseases like diabetes, negatively influence endocytic trafficking and autophagic clearance. In contrast, health-improving exercise induces autophagy-lysosomal degradation, perhaps promoting efficient digestion of injured organelles so that undamaged organelles ensure cellular healthiness. Reductions in lysosomal hydrolases are implicated in Alzheimer's, Parkinson's, and lysosomal storage diseases, as well as obesity-related pathology, and members of the cathepsin enzyme family are involved in clearing both Aβ42 and α-synuclein. Upregulation of cathepsin hydrolases improves synaptic and memory functions in models of dementia and in exercising humans, thus identifying lysosomal-related systems as vital for healthy cognitive aging.

Exercise and Hippocampal Memory Systems

No medications prevent or reverse age-related cognitive decline. Physical activity (PA) enhances memory in rodents, but findings are mixed in human studies. As a result, exercise guidelines specific for brain health are absent. Here, we re-examine results from human studies, and suggest the use of more sensitive tasks to evaluate PA effects on age-related changes in the hippocampus, such as relational memory and mnemonic discrimination. We discuss recent advances from rodent and human studies into the underlying mechanisms at both the central and peripheral levels, including neurotrophins and myokines that could contribute to improved memory. Finally, we suggest guidelines for future research to help expedite well-founded PA recommendations for the public.