Insulin-like Growth Factor 1 (IGF-1) as a marker of cognitive decline in normal ageing: A review

Diminished levels of insulin-like growth factor-1 may be a risk factor for peripheral neuropathy in type 2 diabetes patients

AIMS/INTRODUCTION

To investigate risk factors for diabetic peripheral neuropathy (DPN) and to explore the connection between insulin-like growth factor-1 (IGF-1) and DPN in individuals with type 2 diabetes.

MATERIALS AND METHODS

A total of 790 patients with type 2 diabetes participated in a cross-sectional study, divided into two groups: those with DPN (DPN) and those without DPN (non-DPN). Blood samples were taken to measure IGF-1 levels and other biochemical markers. Participants underwent nerve conduction studies and quantitative sensory testing.

RESULTS

Patients with DPN exhibited significantly lower levels of IGF-1 compared with non-DPN patients (P < 0.001). IGF-1 was positively correlated with the average amplitude of both motor (P < 0.05) and sensory nerves (P < 0.05), but negatively correlated with the vibration perception threshold (P < 0.05). No significant difference was observed between IGF-1 and nerve conduction velocity (P > 0.05), or the temperature detection threshold (P > 0.05). Multivariate regression analysis identified diabetes duration, HbA1c, and the low levels of IGF-1 as independent risk factors (P < 0.001). Receiver operating characteristic analysis determined that at 8 years duration of diabetes, 8.5% (69.4 mmol/mol) HbA1c and 120 ng/mL IGF-1, the optimal cut-off points, indicated DPN (P < 0.001).

CONCLUSIONS

A reduction of IGF-1 in patients with DPN suggests a potential protective role against axon injury in large fiber nerves of type 2 diabetes patients.

IGF-1's protective effect on OSAS rats' learning and memory

PURPOSE

Patients with obstructive sleep apnea syndrome (OSAS) frequently experience cognitive dysfunction, which may be connected to chronic intermittent hypoxia (CIH). Insulin-like growth factor-1 (IGF-1) is thought to be closely associated with cognitive function, but its role in cognitive impairment caused by OSAS is unclear. The purpose of this study was to investigate the potential protective effect of IGF-1 on cognitive impairment in OSAS rats.

METHODS

Healthy male SD rats (n = 40) were randomly assigned into four groups: control group, CIH group, NS + CIH group, and IGF-1 + CIH group. All experimental rats except for those in the control group were exposed to intermittent hypoxic (IH) environments for 8 h per day over 28 days. Prior to daily exposure to IH, rats in the IGF-1 + CIH group received subcutaneous injections of IGF-1. The Morris water maze test was conducted on all experimental rats. Brain tissue testing methods included Enzyme-Linked Immunosorbent Assay, Hematoxylin and eosin staining, Immunohistochemistry, and Western blotting.

RESULTS

The rat model of OSAS was successfully established following exposure to CIH and exhibited significant cognitive impairment. However, daily subcutaneous injections of IGF-1 partially restored the impaired cognitive function in OSAS rats. Compared with the control group, there was a significant decrease in the expression levels of IGF-1, p-IGF-IR, and SYP in the CIH group; however, these expression levels increased significantly in the IGF-I + CIH group.

CONCLUSION

In OSAS rats, IGF-1 enhances learning memory; this effect may be linked to increased p-IGF-1R and SYP protein production in the hippocampus.

PEAK Mood, Mind, and Marks: a pilot study of an intervention to support university students' mental and cognitive health through physical exercise

Introduction

Regular exercise has the potential to enhance university students' mental and cognitive health. The PEAK Mood, Mind and Marks program (i.e., PEAK) is a neuroscience-informed intervention developed using the Behaviour Change Wheel to support students to exercise three or more times per week to benefit their mental and cognitive health. This pilot study assessed the impact of PEAK on exercise, mental and cognitive health, and implementation outcomes.

Methods

PEAK was delivered to 115 undergraduate university students throughout a 12-week university semester. The primary outcome was weekly exercise frequency. Secondary outcomes were: time spent engaged in moderate-vigorous exercise, sedentary behaviour and perceived mental health and cognitive health. All were measured via online self-report questionnaires. Qualitative interviews with 15 students investigated influences on engagement, the acceptability and appropriateness of PEAK, and its mechanisms of behaviour change. Paired t-tests, Wilcoxon Signed-Rank tests and template analysis were used to analyse quantitative and qualitative data, respectively.

Results

On average, 48.4% of students engaged in the recommended frequency of three or more exercise sessions per week. This proportion decreased towards the end of PEAK. Sedentary behaviour significantly decreased from baseline to end-point, and moderate-vigorous exercise significantly increased among students' who were non-exercisers. Mental wellbeing, stress, loneliness, and sense of belonging to the university significantly improved. There were no significant changes in psychological distress. Concentration, memory, and productivity significantly improved. Sixty-eight percent of students remained engaged in one or more components of PEAK at end-point. Qualitative data indicated students found PEAK to be acceptable and appropriate, and that it improved aspects of their capability, opportunity, and motivation to exercise.

Conclusions

Students are receptive to an exercise-based program to support their mental and cognitive health. Students exercise frequency decreased; however, these figures are likely a conservative estimate of students exercise engagement. Students valued the neuroscience-informed approach to motivational and educational content and that the program's goals aligned with their academic goals. Students identified numerous areas PEAK's content and implementation can be optimised, including use of a single digital delivery platform, more opportunities to connect with peers and to expand the content's cultural inclusivity.

Rare genetic coding variants associated with age-related episodic memory decline implicate distinct memory pathologies in the hippocampus

Background

Approximately 40% of people aged 65 or older experience memory loss, particularly in episodic memory. Identifying the genetic basis of episodic memory decline is crucial for uncovering its underlying causes.

Methods

We investigated common and rare genetic variants associated with episodic memory decline in 742 (632 for rare variants) Ashkenazi Jewish individuals (mean age 75) from the LonGenity study. All-atom MD simulations were performed to uncover mechanistic insights underlying rare variants associated with episodic memory decline.

Results

In addition to the common polygenic risk of Alzheimer's Disease (AD), we identified and replicated rare variant association in ITSN1 and CRHR2 . Structural analyses revealed distinct memory pathologies mediated by interfacial rare coding variants such as impaired receptor activation of corticotropin releasing hormone and dysregulated L-serine synthesis.

Discussion

Our study uncovers novel risk loci for episodic memory decline. The identified underlying mechanisms point toward heterogeneous memory pathologies mediated by rare coding variants.

The mediating role of lower body muscle strength and IGF-1 level in the relationship between age and cognition. A MIDUS substudy

OBJECTIVE

Aging is a natural process associated with a decline in cognition. However, the mediating effect of physical function and circulating myokines on this relationship has yet to be fully clarified. This study investigated how muscle strength and circulating insulin-like growth factor-1 (IGF-1) levels mediate the relationship between age and cognitive functions.

SUBJECTS AND METHODS

A total of 1255 participants aged 25-74 years included in the Midlife in the United States II study were retrospectively analyzed. In this cross-sectional analysis, we applied a serial mediation model to explore the mediating effects of muscle strength and circulating IGF-1 levels on the relationship between age and cognitive functions. We included potential confounding factors related to sociodemographics, lifestyle, and health status as covariates in the model.

RESULTS

The results showed that aging had both direct and indirect effects on cognition. As predicted, muscle strength and IGF-1 levels mediated the relationship between age and specific cognitive functions. In addition, mediation analyses indicated that the association between aging and cognitive flexibility, immediate and delayed memory, and inductive reasoning were partially mediated by muscle strength and IGF-1 levels in a serial manner.

CONCLUSIONS

Our study demonstrated the serial multiple mediation roles of muscle strength and IGF-1 levels on the relationship between age and specific cognitive functions. Further longitudinal research should be performed to confirm the serial mediation results.

Role of the Insulin-like Growth Factor System in Neurodegenerative Disease

The insulin-like growth factor (IGF) system has paracrine and endocrine roles in the central nervous system. There is evidence that IGF signalling pathways have roles in the pathophysiology of neurodegenerative disease. This review focusses on Alzheimer's disease and Parkinson's disease, the two most common neurodegenerative disorders that are increasing in prevalence globally in relation to the aging population and the increasing prevalence of obesity and type 2 diabetes. Rodent models used in the study of the molecular pathways involved in neurodegeneration are described. However, currently, no animal model fully replicates these diseases. Mice with triple mutations in APP, PSEN and MAPT show promise as models for the testing of novel Alzheimer's therapies. While a causal relationship is not proven, the fact that age, obesity and T2D are risk factors in both strengthens the case for the involvement of the IGF system in these disorders. The IGF system is an attractive target for new approaches to management; however, there are gaps in our understanding that first need to be addressed. These include a focus beyond IGF-I on other members of the IGF system, including IGF-II, IGF-binding proteins and the type 2 IGF receptor.

Insulin-like growth factor-1 and cognition in normoglycemia, prediabetes, and type 2 diabetes mellitus

BACKGROUND

The relationship between insulin-like growth factor-1 (IGF-1) and cognition has been studied in healthy individuals, but not extensively with regards to insulin resistance and type 2 diabetes mellitus (T2DM). In this retrospective observational study, we investigated relationships of IGF-1 with memory and executive function across people with normoglycemia, prediabetes, and T2DM.

METHODS

Data from the Midlife in the United States (MIDUS) study were used. Episodic memory and executive function were assessed using the Brief Test of Adult Cognition by Telephone approximately 21.42 ± 12.10 months prior to measuring IGF-1 levels from a fasting blood sample. Normoglycemia was identified as individuals without a physician diagnosis of diabetes and glycated hemoglobin (HbA1c) ≤5.6%. Prediabetes was identified as those without a physician diagnosis of diabetes and HbA1c between 5.7%-6.4%. T2DM was identified as anyone with a physician diagnosis of diabetes, or HbA1c ≥6.5%, or anyone using an oral hypoglycemic medication. The associations were assessed using linear regressions controlling for age, sex, education, body mass index, C-reactive protein, HbA1c or homeostatic model of insulin resistance, MIDUS wave, exercise, smoking status, sleep quality, alcohol intake, oral hypoglycemic use, and insulin use.

RESULTS

The study included 1400 participants, which consisted of 583 normoglycemic (48.4% female, mean age 51.0 ± 12.2 years), 512 prediabetes (58.4% female, mean age 57.3 ± 11.8 years), and 305 T2DM participants (53.8% female, mean age 57.6 ± 11.5 years). Peripheral IGF-1 concentrations were lower (F2,1397 = 28.29, p < 0.001) in people with prediabetes or T2DM, vs. normoglycemia. Participants with prediabetes or T2DM had lower episodic memory (F2,1397 = 9.21, p < 0.001) and executive function (F2,1397 = 20.29, p < 0.001) composite z-scores than people with normoglycemia. Higher IGF-1 concentrations were associated with better executive performance in individuals with prediabetes (β = 0.115 [0.028, 0.202], p = 0.010), but not in individuals with normoglycemia or T2DM. An interaction between IGF-1 and sex in predicting executive function was observed in the prediabetes group (β = -0.344, p = 0.042), where the relationship was weaker in females (β = 0.106 [-0.012, 0.224], p = 0.077) than males (β = 0.251 [0.123, 0.380], p < 0.001). No associations were seen between IGF-1 and memory.

CONCLUSION

The results suggest that peripheral IGF-1 concentrations may be related to executive function, and that the relationship may be sex-specific and dependent on diabetes status.

Association between serum insulin-like growth factor 1 levels and the improvements of cognitive impairments in a subgroup of schizophrenia: Preliminary findings

BACKGROUND

Numerous studies have implicated abnormal insulin-like growth factor 1 (IGF-1) in the pathophysiology of schizophrenia, but findings have been inconsistent.

METHODS

We conducted a meta-analysis to compare IGF-1 levels in schizophrenia patients with healthy controls and explored factors contributing to variability between estimates. In an independent sample (58 chronic schizophrenia patients and 30 healthy controls), we investigated differences in IGF-1 levels among schizophrenia subgroups with distinct cognitive profiles, identified using k-means clustering based on five cognitive domains from The Repeatable Battery for the Assessment of Neuropsychological Status. Associations between serum IGF-1 levels and clinical and neurocognitive improvements were also examined.

RESULTS

The meta-analysis revealed significantly lower serum IGF-1 levels in schizophrenia patients compared to healthy controls, albeit with high heterogeneity. Medication status, BMI, and severity of negative symptoms were identified as potential contributors to this heterogeneity. In our independent study, antipsychotic treatment led to a significant increase in IGF-1 levels, and lower pre-treatment serum IGF-1 levels correlated with greater improvement in cognitive deficits, particularly in a subgroup with more severe cognitive symptoms.

CONCLUSIONS

Our findings support the "IGF-1 deficiency hypothesis" in the pathogenesis of schizophrenia. Further research is crucial to elucidate the role of IGF-1 in the cognitive impairments associated with schizophrenia.

Nanoemulsion of Ethanolic Extract of Centella asiatica (NanoSECA)Ameliorates Learning and Memory Performance by EnhancingCholinergic Activities, Increasing Antioxidative Levels, and AttenuatingOxidative Stress Markers in Adult Rats

BACKGROUND

Centella asiatica (C. asiatica) has long been traditionally used as a memory enhancer. Nanoemulsion of ethanolic extract C. asiatica (NanoSECA) has been developed to improve brain functions. However, the effect of NanoSECA on enhancing memory and cognitive functions remains unexplored.

OBJECTIVES

This research aimed to investigate the potential of NanoSECA on cognitive tasks and memory enhancement pathways in a normal adult rat model.

METHODS

Thirty male Sprague Dawley rats (7-8 weeks old) were randomly subjected to five groups (n=six per group). Treatment groups were supplemented with NanoSECA and ethanolic extract of C. asiatica (SECA) for 28 days by oral gavages. Different brain sections were isolated, homogenized, and tested for acetylcholinesterase, antioxidants (glutathione and malondialdehyde), and anti-inflammatory agents (nitric oxide, tumour necrosis factor-α, and prostaglandin E2).

RESULTS

NanoSECA supplementation markedly enhanced the acetylcholine, glutathione levels and reduced a distinct diminution in plasma activities of acetylcholinesterase, malondialdehyde, nitric oxide, prostaglandin E, and tumor necrosis factor-α levels.

CONCLUSION

NanoSECA can be used as a memory enhancer through enhanced cholinergic activity, increased antioxidant level, and reduced oxidative stress.

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.

Metabolic diseases and healthy aging: identifying environmental and behavioral risk factors and promoting public health

Aging is a progressive and irreversible pathophysiological process that manifests as the decline in tissue and cellular functions, along with a significant increase in the risk of various aging-related diseases, including metabolic diseases. While advances in modern medicine have significantly promoted human health and extended human lifespan, metabolic diseases such as obesity and type 2 diabetes among the older adults pose a major challenge to global public health as societies age. Therefore, understanding the complex interaction between risk factors and metabolic diseases is crucial for promoting well-being and healthy aging. This review article explores the environmental and behavioral risk factors associated with metabolic diseases and their impact on healthy aging. The environment, including an obesogenic environment and exposure to environmental toxins, is strongly correlated with the rising prevalence of obesity and its comorbidities. Behavioral factors, such as diet, physical activity, smoking, alcohol consumption, and sleep patterns, significantly influence the risk of metabolic diseases throughout aging. Public health interventions targeting modifiable risk factors can effectively promote healthier lifestyles and prevent metabolic diseases. Collaboration between government agencies, healthcare providers and community organizations is essential for implementing these interventions and creating supportive environments that foster healthy aging.

Brain IGF-I regulates LTP, spatial memory, and sexual dimorphic behavior

Insulin-like growth factor-I (IGF-I) exerts multiple actions, yet the role of IGF-I from different sources is poorly understood. Here, we explored the functional and behavioral consequences of the conditional deletion of Igf-I in the nervous system (Igf-I Δ/Δ), and demonstrated that long-term potentiation was impaired in hippocampal slices. Moreover, Igf-I Δ/Δ mice showed spatial memory deficits in the Morris water maze, and the significant sex-dependent differences displayed by Igf-I Ctrl/Ctrl mice disappeared in Igf-I Δ/Δ mice in the open field and rota-rod tests. Brain Igf-I deletion disorganized the granule cell layer of the dentate gyrus (DG), and it modified the relative expressions of GAD and VGLUT1, which are preferentially localized to inhibitory and excitatory presynaptic terminals. Furthermore, Igf-I deletion altered protein modules involved in receptor trafficking, synaptic proteins, and proteins that functionally interact with estrogen and androgen metabolism. Our findings indicate that brain IGF-I is crucial for long-term potentiation, and that it is involved in the regulation of spatial memory and sexual dimorphic behaviors, possibly by maintaining the granule cell layer structure and the stability of synaptic-related protein modules.

Young human PRP promotes the rejuvenation of aged bone marrow mesen -chymal stem cells and the therapeutic effect on ischemic heart disease

Bone marrow mesenchymal stem cell (BMSC) transplantation is an effective treatment for ischemic heart disease, but its effectiveness is limited in aging populations due to decreased viability and injury resistance of autologous BMSCs. The purpose of this study was to compare the differences between platelet-rich plasma (PRP) derived from young and aged donors, and to investigate whether it is possible to enhance the viability of elderly human BMSCs (hBMSCs) using PRP, and to apply the rejuvenated hBMSCs for the treatment of ischemia. The key growth factors in PRP, including IGF-1, EGF, and PDGF-BB, were found to have significant differences between young and old individuals. Our results showed that PRP could enhance the proliferation, cloning, and rejuvenation of aged hBMSCs, with a superior effect observed when using PRP derived from younger donors. In the SD rat infarct model, the application of hBMSCs optimized with PRP resulted in a smaller infarct area compared to the control group (NC-Old). Specifically, the infarct area in the group treated with hBMSCs cultured with PRP from young donors (YPRP-Old) was smaller than that in the group treated with PRP from older donors (OPRP-Old). The survival rate of hBMSCs after transplantation, the number of neovascularization in the infarct area of SD rats and the recovery of cardiac function were all higher in the YPRP-Old group than the OPRP-Old group, and both groups were better than the group treated with aged hBMSCs alone. In conclusion, PRP may provide a new stem cell transplantation therapy option for ischemic diseases.

The Effects of a Mixture of Cadmium, Lead, and Mercury on Metabolic Syndrome and Its Components, as well as Cognitive Impairment: Genes, MicroRNAs, Transcription Factors, and Sponge Relationships : The Effects of a Mixture of Cadmium, Lead, and Mercury on Metabolic Syndrome and Its Components, as well as Cognitive Impairment: Genes, MicroRNAs, Transcription Factors, and Sponge Relationships

Converging evidence indicates heavy metal-induced genes, transcription factors (TFs), and microRNAs (miRNAs) are critical pathological components of metabolic syndrome (MetS) and cognitive impairment. Thus, our goals are to identify the interaction of mixed heavy metals (cadmium + lead + mercury) with genes, TFs, and miRNAs involved in MetS and its components, as well as cognitive impairment development. The most commonly retrieved genes for each disease were different, but essential biological pathways such as oxidative stress, altered lipoprotein metabolism, fluid shear stress and atherosclerosis, apoptosis, the IL-6 signaling pathway, and Alzheimer's disease were highlighted. The genes CASP3, BAX, BCL2, IL6, TNF, APOE, HMOX1, and IGF were found to be mutually affected by the heavy metal mixture studied, suggesting the importance of apoptosis, inflammation, lipid, heme, and glucose metabolism in MetS and cognitive impairment, as well as the potentiality of targeting these genes in prospective therapeutic intervention for these diseases. EGR2, ATF3, and NFE2L2 were noted as the most key TFs implicated in the etiology of MetS and its components, as well as cognitive impairment. We also found six miRNAs induced by studied heavy metals were the mutual miRNAs linked to MetS, its components, and cognitive impairment. In particular, we used miRNAsong to construct and verify a miRNA sponge sequence for these miRNAs. These sponges are promising molecules for the treatment of MetS and its components, as well as cognitive impairment.

Body fat and components of sarcopenia relate to inflammation, brain volume and neurometabolism in older adults

Obesity and sarcopenia are associated with cognitive impairments at older age. Current research suggests that blood biomarkers may mediate this body-brain crosstalk, altering neurometabolism and brain structure eventually resulting in cognitive performance changes. Seventy-four older adults (60-85 years old) underwent bio-impedance body composition analysis, handgrip strength measurements, 8-Foot Up-and-Go (8UG) test, Montreal Cognitive Assessment (MoCA), blood analysis of interleukin-6 (IL-6), kynurenine, and insulin-like growth factor-1 (IGF-1), as well as brain magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (¹H-MRS), estimating neurodegeneration and neuroinflammation. Normal fat% or overweight was associated with larger total gray matter volume compared to underweight or obesity in older adults and obesity was associated with higher N-acetylaspartate/Creatine levels in the sensorimotor and dorsolateral prefrontal cortex. Muscle strength, not muscle mass/physical performance, corresponded to lower kynurenine and higher N-acetylaspartate/Creatine levels in the dorsal posterior cingulate and dorsolateral prefrontal cortex. The inflammatory and neurotrophic blood biomarkers did not significantly mediate these body-brain associations. This study used a multimodal approach to comprehensively assess the proposed mechanism of body-brain crosstalk.

Effects of Resistance Exercise on Neuroprotective Factors in Middle and Late Life: A Systematic Review and Meta-Analysis

Neuroprotective factors are involved in brain functioning. Although physical exercise has been shown to have a positive influence on these factors, the effect of resistance exercise on them is not well known. This systematic review and meta-analysis aimed to 1) estimate the efficacy of resistance exercise on major neuroprotective factors, such as insulin-like growth factor-1 (IGF-1), brain-derived neurotrophic factor (BDNF), and vascular endothelial growth factor (VEGF), in middle and late life and 2) determine whether the effect is dose dependent. A systematic search was conducted in CINAHL, Cochrane CENTRAL, MEDLINE, Scopus, PEDro, SPORTDiscus, and Web of Science up to November 2022. Random effects models were used to estimate standardized mean differences (SMDs) and their respective 95% confidence intervals (CI) for the effect of resistance exercise on peripheral IGF-1, BDNF or VEGF levels in older adults. Thirty randomized clinical trials with 1247 subjects (53.25% women, 45-92 years) were included in the systematic review, and 27 were selected for the meta-analysis. A significant effect of resistance exercise on IGF-1 levels was observed (SMD: 0.48; 95% CI: 0.27, 0.69), being more effective when performing 3 sessions/week (SMD: 0.55; 95% CI: 0.31, 0.79) but not on BDNF (SMD: 0.33; 95% CI: -0.29, 0.94). The effect on VEGF could not be determined due to the scarcity of studies. Our data support the resistance training recommendation in middle and late life, at a frequency of at least 3 sessions/week, to mitigate the neurological and cognitive consequences associated with aging, mainly through IGF-1.

Identification of the molecular mechanism of insulin-like growth factor-1 (IGF-1): a promising therapeutic target for neurodegenerative diseases associated with metabolic syndrome

Neurodegenerative disorders are accompanied by neuronal degeneration and glial dysfunction, resulting in cognitive, psychomotor, and behavioral impairment. Multiple factors including genetic, environmental, metabolic, and oxidant overload contribute to disease progression. Recent evidences suggest that metabolic syndrome is linked to various neurodegenerative diseases. Metabolic syndrome (MetS) is known to be accompanied by symptoms such as hyperglycemia, abdominal obesity, hypertriglyceridemia, and hypertension. Despite advances in knowledge about the pathogenesis of neurodegenerative disorders, effective treatments to combat neurodegenerative disorders caused by MetS have not been developed to date. Insulin growth factor-1 (IGF-1) deficiency has been associated with MetS-related pathologies both in-vivo and in-vitro. IGF-1 is essential for embryonic and adult neurogenesis, neuronal plasticity, neurotropism, angiogenesis, metabolic function, and protein clearance in the brain. Here, we review the evidence for the potential therapeutic effects of IGF-1 in the neurodegeneration related to metabolic syndrome. We elucidate how IGF-1 may be involved in molecular signaling defects that occurs in MetS-related neurodegenerative disorders and highlight the importance of IGF-1 as a potential therapeutic target in MetS-related neurological diseases.

The physiological mechanism and effect of resistance exercise on cognitive function in the elderly people

Background

As brain function declines and cognitive ability declines, the benefits of resistance exercise to the brain of older people are gradually gaining attention.

Objective

The purpose of this review is to explore the mechanism and relationship between physiological factors such as vascular and neuronal degeneration and cognitive decline, and to categorize the differences in the effects of an acute and chronic resistance exercise intervention on cognitive function in healthy elderly people and the possible regulators of cognitive effects.

Methods

Using PubMed, Elsevier, Web of Science, X-MOL, CNKI, and Taiwan academic literature database, the research papers published in relevant journals at home and abroad until April 2022 were searched with Chinese and English keywords such as Resistance exercise, the elderly, hippocampus, memory performance, neurons, cognitive function. Pedro scale was used to check the quality of various documents, and the relevant research documents were obtained with the resistance exercise elements as the main axis for comprehensive analysis.

Results and conclusion

(1) Resistance exercise can have a beneficial effect on the brain function of the elderly through blood flow changes, stimulate nerve conduction substances and endocrine metabolism, promote cerebrovascular regeneration and gray matter volume of the brain, and prevent or delay the cognitive function degradation such as memory and attention of the elderly; (2) Acute resistance can temporarily stimulate hormone secretion in vivo and significantly improve the effect of short-term memory test, but it has little effect on the cognitive performance of the elderly; (3) Moderate-high intensity resistance exercise (50-80%1RM, 1-3 times/week, 2-3 groups/time) lasting for at least 6 months is more prominent for the improvement of cognitive function of the elderly, while the parameters such as resistance exercise intensity, exercise amount, duration, evaluation test time and differences of subjects may have different degrees of influence on cognitive benefits.

Exosome-transported lncRNA H19 regulates insulin-like growth factor-1 via the H19/let-7a/insulin-like growth factor-1 receptor axis in ischemic stroke

LncRNA (long non-coding RNA) H19 is a transcript of the H19 gene that is expressed during embryogenesis. We previously discovered a role for circular lncRNA H19 in the onset and prognosis of cerebral ischemic stroke. In this study, we used serum from patients with ischemic stroke, and mouse and cell culture models to elucidate the roles of plasma and neuronal exosomes in the regulatory effect of lncRNA H19 on insulin-like growth factor-1 and its mechanism in ischemic stroke, using western blotting, quantitative real-time polymerase chain reaction, and enzyme-linked immunosorbent assays. Plasma exosomal lncRNA H19 was negatively associated with blood levels of insulin-like growth factor-1 in samples from patients with cerebral ischemic stroke. In a mouse model, levels of exosomal lncRNA H19 were positively correlated with plasma and cerebral lncRNA H19. In a cell co-culture model, we confirmed that lncRNA H19 was transported from neurons to astrocytes by exosomes to induce downregulation of insulin-like growth factor-1 through the H19/let-7a/insulin-like growth factor-1 receptor axis. This study provides the first evidence for the transportation of lncRNA H19 by exosomes and the relationship between lncRNA H19 and insulin-like growth factor-1.

Estrogen deficiency exacerbates learning and memory deficits associated with glucose metabolism disorder in APP/PS1 double transgenic female mice

Alterations in glucose metabolism occur in the brain in the early stage of Alzheimer's disease (AD), and menopausal women have more severe metabolic dysfunction and are more prone to dementia than men. Although estrogen deficiency-induced changes in glucose metabolism have been previously studied in animal models, their molecular mechanisms in AD remain elusive. To investigate this issue, double transgenic (APP/PS1) female mice were subjected to bilateral ovariectomy at 3 months of age and were sacrificed 1 week, 1 month and 3 months after surgery to simulate early, middle and late postmenopause, respectively. Our analysis demonstrated that estrogen deficiency exacerbates learning and memory deficits in this mouse model of postmenopause. Estrogen deficiency impairs the function of mitochondria in glucose metabolism. It is possible that the occurrence of AD is associated with the aberrant mitochondrial ERβ-mediated IGF-1/IGF-1R/GSK-3β signaling pathway. In this study, we established a potential mechanism for the increased risk of AD in postmenopausal women and proposed a therapeutic target for AD due to postmenopause.

Serum clinical laboratory tests and risk of incident dementia: a prospective cohort study of 407,190 individuals

Prevention of dementia is a public health priority, and the identification of potential biomarkers may provide benefits for early detection and prevention. This study investigates the association of common serum laboratory tests with the risk of incident dementia. Among 407,190 participants from the UK Biobank (median follow-up of 9.19 years), we investigated the linear and nonlinear effects of 30 laboratory measures on the risk of all-cause dementia using Cox models and restricted cubic spline models. We found that dementia incidence was associated with low vitamin D concentration (hazard ratio 0.994, 95% confidence interval 0.993-0.996), indicators of endocrine disorders: IGF-1 level (P for non-linearity = 1.1E-05), testosterone level (P for non-linearity = 0.006); high sex-hormone-binding globulin level (HR 1.004, 95% CI: 1.003-1.006); reduced liver function: lower alanine aminotransferase (HR 0.990, 95% CI: 0.986-0.995); renal dysfunction: cystatin C level (P for non-linearity = 0.028); oxidative stress: lower urate level (HR 0.998, 95% CI: 0.998-0.999); lipids dysregulation: lower LDL (HR 0.918, 95% CI: 0.872-0.965) and triglycerides (HR 0.924, 95% CI: 0.882-0.967) concentrations; insulin resistance: high glucose (HR 1.093, 95% CI: 1.045-1.143) and HbA1c (HR 1.017, 95% CI: 1.009-1.025) levels; immune dysbiosis: C-reactive protein (P for non-linearity = 5.5E-09). In conclusion, markers of vitamin D deficiency, GH-IGF-1 axis disorders, bioactive sex hormone deficiency, reduced liver function, renal abnormalities, oxidation, insulin resistance, immune dysbiosis, and lipids dysregulation were associated with incident dementia. Our results support a contributory role of systemic disorders and diverse biological processes to onset of dementia.

Square-Stepping Exercise Program Effects on Fall-Related Fitness and BDNF Levels in Older Adults in Korea: A Randomized Controlled Trial

The risk of dementia increases with age. To mitigate this risk, we examined the effect of a square-stepping exercise (SSE) program on fall-related fitness and brain-derived neurotrophic factor (BDNF) levels. Twenty older adults in Korea were randomly assigned to either the experimental or control group (each group n = 10). Participants performed SSE for 70 min per session, twice a week, for 12 weeks with a certified instructor. The average age of the participants was 74.80 ± 6.763 years in the exercise group and 72.50 ± 6.519 years in the control group. The experiment group showed significant improvement (p < 0.01) in the lower muscle strength post-intervention. The paired t-test revealed a significant improvement (p < 0.01) in the experimental group and a significant difference in the interaction effect (p < 0.01) in the BDNF levels. There was a significant improvement (p < 0.05) in the BDNF levels in the experimental group and a significant decrease (p < 0.05) in the control group. The SSE program had a positive effect on fall-related fitness and BDNF levels.

Research Progress on Neuroprotection of Insulin-like Growth Factor-1 towards Glutamate-Induced Neurotoxicity

Insulin-like growth factor-1 (IGF-1) and its binding proteins and receptors are widely expressed in the central nervous system (CNS), proposing IGF-1-induced neurotrophic actions in normal growth, development, and maintenance. However, while there is convincing evidence that the IGF-1 system has specific endocrine roles in the CNS, the concept is emerging that IGF-I might be also important in disorders such as ischemic stroke, brain trauma, Alzheimer’s disease, epilepsy, etc., by inducing neuroprotective effects towards glutamate-mediated excitotoxic signaling pathways. Research in rodent models has demonstrated rescue of pathophysiological and behavioral abnormalities when IGF-1 was administered by different routes, and several clinical studies have shown safety and promise of efficacy in neurological disorders of the CNS. Focusing on the relationship between IGF-1-induced neuroprotection and glutamate-induced excitatory neurotoxicity, this review addresses the research progress in the field, intending to provide a rationale for using IGF-I clinically to confer neuroprotective therapy towards neurological diseases with glutamate excitotoxicity as a common pathological pathway.

Reduced circulating growth hormone and insulin-like growth factor-1 and delayed growth of premature rats are aggravated by longer daily duration of chronic intermittent hypoxia exposure

OBJECTIVE

This study mainly aimed to investigate the effect of daily duration of chronic intermittent hypoxia (CIH) exposure on circulating growth hormone (GH)/insulin-like growth factor-1 (IGF-1) concentrations and body weight changes of premature rats.

METHODS

40 healthy male SD rats aged six weeks were enrolled in this study. These rats were randomly divided into four groups (n = 10 per group), including normal control (NC) group (normal oxygen exposure every day), CIH-1 group (daily CIH exposure for 2 h), CIH-2 group (daily CIH exposure for 4 h), and CIH-3 group (daily CIH exposure for 8 h). The serum GH/IGF-1 concentrations and body weights in all rats were determined after 30 days of normal oxygen or CIH exposure.

RESULTS

No significant difference was found with respect to the baseline body weight among the four groups of rats. After establishments of animal models with a duration of 30 days, significant differences were found respect to body weight, body weight changes, and serum GH/IGF-1 concentrations among the four groups of rats with a same trend (all P < 0.05): the highest values were all in NC group rats, followed CIH-1 group, CIH-2 group, and CIH-3 group rats. Among all the rats, the body weight changes correlated significantly with both serum GH and IGF-1 concentrations (both P < 0.05).

CONCLUSION

CIH decreases circulating GH/IGF-1 concentrations and causes growth delay in premature rats. Such effects could be aggravated by increased daily duration of CIH exposures.

Strategies to Modulate the Redifferentiation of Chondrocytes

Because of the low self-healing capacity of articular cartilage, cartilage injuries and degenerations triggered by various diseases are almost irreversible. Previous studies have suggested that human chondrocytes cultured in vitro tend to dedifferentiate during the cell-amplification phase and lose the physiological properties and functions of the cartilage itself, which is currently a critical limitation in the cultivation of cartilage for tissue engineering. Recently, numerous studies have focused on the modulation of chondrocyte redifferentiation. Researchers discovered the effect of various conditions (extracellular environment, cell sources, growth factors and redifferentiation inducers, and gene silencing and overexpression) on the redifferentiation of chondrocytes during the in vitro expansion of cells, and obtained cartilage tissue cultured in vitro that exhibited physiological characteristics and functions that were similar to those of human cartilage tissue. Encouragingly, several studies reported positive results regarding the modulation of the redifferentiation of chondrocytes in specific conditions. Here, the various factors and conditions that modulate the redifferentiation of chondrocytes, as well as their limitations and potential applications and challenges are reviewed. We expect to inspire research in the field of cartilage repair toward the future treatment of arthropathy.

Relationships between endogenous circadian period, physiological and cognitive parameters and sex in aged gray mouse lemurs (Microcebus murinus)

The biological clock generates circadian rhythms, with an endogenous period tau close to 24 h. The circadian resonance theory proposes that lifespan is reduced when endogenous period goes far from 24 h. It has been suggested that daily resetting of the circadian clock to the 24 h external photoperiod might induce marginal costs that would accumulate over time and forward accelerate aging and affect fitness. In this study, we aimed to evaluate the link between the endogenous period and biomarkers of aging in order to investigate the mechanisms of the circadian resonance theory. We studied 39 middle-aged and aged Microcebus murinus, a nocturnal non-human primate whose endogenous period is about 23.1 h, measuring the endogenous period of locomotor activity, as well as several physiological and behavioral parameters (rhythm fragmentation and amplitude, energetic expenditure, oxidative stress, insulin-like growth factor-1 (IGF-1) concentrations and cognitive performances) in both males and females. We found that aged males with tau far from 24 h displayed increased oxidative stress. We also demonstrated a positive correlation between tau and IGF-1 concentrations, as well as learning performances, in males and females. Together these results suggest that a great deviation of tau from 24 h leads to increased biomarkers of age-related impairments.

Effect of silencing C-erbB-2 on esophageal carcinoma cell biological behaviors by inhibiting IGF-1 pathway activation

OBJECTIVE

C-erbB-2 has been confirmed to be an oncogene that participates in cell growth, differentiation and division of tumors. We are wondered if its silenced expression can exert an anti-tumor effect. Therefore, this study is conducted to investigate the mechanism of C-erbB-2 silencing and IGF-1 pathway on esophageal carcinoma (EC) cell biological behaviors.

METHODS

The objects of study were 84 EC patients from Heping Hospital Affiliated to Changzhi Medical College, with the collection of EC tissue and adjacent normal tissue (> 5 cm away from cancer tissue). C-erbB-2 protein expression in EC tissues was detected by immunohistochemistry. Human EC cell line Eca-109 was purchased from Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. Based on different transfection protocols, EC cells with logarithmic growth phase of 3-5 passages were divided into blank control group, oe-C-erbB-2 NC group, siRNA C-erbB-2 NC group, oe-C-erbB-2 group, siRNA C-erbB-2 group, OSI-906 group, Rg5 group, Rg5 + siRNA C-erbB-2 NC group and Rg5 + siRNA C-erbB-2 group. Cell proliferation was detected by MTT assay; cell cycle distribution and apoptosis by flow cytometry; C-erbB-2, IGF-1, IGF-1R and Akt mRNA and protein expressions by qRT-PCR and western blot; and cell invasion and migration by Transwell assay and scratch test. Tumor growth was observed in male BALB/c nude mice (Shanghai Experimental Animal Center) based on Eca109 cell implantation, raising, and measurement.

RESULTS

C-erbB-2, IGF-1, IGF-1R and Akt expression were higher in EC tissues than those in adjacent tissues (all P < 0.05). Compared with blank control group, both si-C-erbB-2 and OSI-906 groups had decreased IGF-1, IGF-1R and Akt mRNA and protein expressions, decreased cell proliferation, migration and invasion, prolonged G0/G1 phase, shortened S phase, increased cell apoptosis, and inhibited tumor growth (all P < 0.05); while opposite trends were detected in C-erbB-2 vector and Rg5 groups (all P < 0.05), without statistical differences in siRNA C-erbB-2 + Rg5 group (all P > 0.05).

CONCLUSION

Silencing C-erbB-2 expression may inhibit EC cell proliferation, promote cell apoptosis and block cell cycle progression by inhibiting IGF-1 pathway activation. The beneficial effect of silencing C-erbB-2 expression can be reversed by promoting the activation of IGF-1 pathway. Findings in our study may provide potential reference for understanding the molecular mechanism of EC and supply possible axis for preventing the development of EC from the perspective of molecular biology.

Age-related alterations in the cerebrovasculature affect neurovascular coupling and BOLD fMRI responses: Insights from animal models of aging

The present and future research efforts in cognitive neuroscience and psychophysiology rely on the measurement, understanding, and interpretation of blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to effectively investigate brain function. Aging and age-associated pathophysiological processes change the structural and functional integrity of the cerebrovasculature which can significantly alter how the BOLD signal is recorded and interpreted. In order to gain an improved understanding of the benefits, drawbacks, and methodological implications for BOLD fMRI in the context of cognitive neuroscience, it is crucial to understand the cellular and molecular mechanism of age-related vascular pathologies. This review discusses the multifaceted effects of aging and the contributions of age-related pathologies on structural and functional integrity of the cerebral microcirculation as they has been investigated in animal models of aging, including age-related alterations in neurovascular coupling responses, cellular and molecular mechanisms involved in microvascular damage, vascular rarefaction, blood-brain barrier disruption, senescence, humoral deficiencies as they relate to, and potentially introduce confounding factors in the interpretation of BOLD fMRI.

Physical Exercise-Induced Myokines in Neurodegenerative Diseases

Neurodegenerative diseases (NDs), such as Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS), are disorders characterized by progressive degeneration of the nervous system. Currently, there is no disease-modifying treatments for most NDs. Meanwhile, numerous studies conducted on human and animal models over the past decades have showed that exercises had beneficial effects on NDs. Inter-tissue communication by myokine, a peptide produced and secreted by skeletal muscles during exercise, is thought to be an important underlying mechanism for the advantages. Here, we reviewed studies about the effects of myokines regulated by exercise on NDs and their mechanisms. Myokines could exert beneficial effects on NDs through a variety of regulatory mechanisms, including cell survival, neurogenesis, neuroinflammation, proteostasis, oxidative stress, and protein modification. Studies on exercise-induced myokines are expected to provide a novel strategy for treating NDs, for which there are no adequate treatments nowadays. To date, only a few myokines have been investigated for their effects on NDs and studies on mechanisms involved in them are in their infancy. Therefore, future studies are needed to discover more myokines and test their effects on NDs.

Investigating the Relationship Between IGF-I, IGF-II, and IGFBP-3 Concentrations and Later-Life Cognition and Brain Volume

BACKGROUND

The insulin/insulin-like signaling (IIS) pathways, including insulin-like growth factors (IGFs), vary with age. However, their association with late-life cognition and neuroimaging parameters is not well characterized.

METHODS

Using data from the British 1946 birth cohort, we investigated associations of IGF-I, IGF-II and IGF binding protein 3 (IGFBP-3; measured at 53 and 60-64 years of age) with cognitive performance [word-learning test (WLT) and visual letter search (VLS) at 60-64 years and 69 years of age] and cognitive state [Addenbrooke's Cognitive Exam III (ACE-III) at 69-71 years of age], and in a proportion, quantified neuroimaging measures [whole brain volume (WBV), white matter hyperintensity volume (WMHV), hippocampal volume (HV)]. Regression models included adjustments for demographic, lifestyle, and health factors.

RESULTS

Higher IGF-I and IGF-II at 53 years of age was associated with higher ACE-III scores [ß 0.07 95% confidence interval (CI) (0.02, 0.12); scoreACE-III 89.48 (88.86, 90.1), respectively). IGF-II at 53 years of age was additionally associated with higher WLT scores [scoreWLT 20 (19.35, 20.65)]. IGFBP-3 at 60 to 64 years of age was associated with favorable VLS score at 60 to 64 and 69 years of age [ß 0.07 (0.01, 0.12); ß 0.07 (0.02, 0.12), respectively], higher memory and cognitive state at 69 years of age [ß 0.07 (0.01, 0.12); ß 0.07 (0.01, 0.13), respectively], and reduced WMHV [ß -0.1 (-0.21, -0.00)]. IGF-I/IGFBP-3 at 60 to 64 years of was associated with lower VLS scores at 69 years of age [ß -0.08 (-0.15, -0.02)].

CONCLUSIONS

Increased measure in IIS parameters (IGF-I, IGF-II, and IGFBP-3) relate to better cognitive state in later life. There were apparent associations with specific cognitive domains (IGF-II relating to memory; IGFBP-3 relating to memory, processing speed, and WMHV; and IGF-I/IGFBP-3 molar ratio related to slower processing speed). IGFs and IGFBP-3 are associated with favorable cognitive function outcomes.

Insulin-like growth factor-1 short-period therapy stimulates bone marrow cells in obese swiss mice

Bone marrow cells (BMCs) from obese Swiss mice fed with Western diet show mitochondrial dysfunction. Obesity interferes with BMCs disrupting energetic metabolism, stimulating apoptosis, and reducing cell proliferation since adipose tissue releases inflammatory adipokines into the medullar microenvironment. These changes lead to reduction of BMC differentiation capacity and hematopoiesis impairment, a process responsible for blood cell continuous production through hematopoietic stem cells (HSCs). This work aimed to analyze the effects of IGF-1 therapy on BMC viability in Western diet-induced obesity, in vivo. We observed that after only 1 week of treatment, obese Swiss mice presented reduced body weight and visceral fat and increased mitochondrial oxidative capacity and coupling, indicating mitochondrial function improvement. In addition, IGF-1 was able to reduce apoptosis of total BMCs, stem cell subpopulations (hematopoietic and mesenchymal), and leukocytes, restoring all progenitor hematopoietic lineages. The treatment also contributed to increase proliferative capacity of hematopoietic stem cells and leukocytes, keeping the hematopoietic and immune systems balanced. Therefore, we conclude that IGF-1 short period therapy improved BMC survival, proliferation, and differentiation capacity in obese Swiss mice.

Effects of caloric restriction on monoaminergic neurotransmission, peripheral hormones, and olfactory memory in aged rats

Aging is associated with a reduced ability to identify and discriminate scents, and olfactory dysfunction has been linked to preclinical stages of neurodegenerative diseases in humans. Moreover, emerging evidence suggests that smell-driven behaviors are regulated by hormones like insulin or leptin, and by metabolic parameters like glucose, which in turn may influence monoaminergic neurotransmission in brain areas related to cognition. Several studies have suggested that dietary interventions like caloric restriction (CR) can mitigate the age-induced decline in memory by modifying metabolic parameters and brain monoaminergic levels. The present study explored the effects of CR on age-dependent olfactory memory deficits, as well as their relationship with peripheral leptin, insulin and glucose levels, and brain monoamines. To this end, aged rats (24-months-old) fed on a CR diet or with ad libitum access to food, and adult rats (3-4 months), were trained in an odor discrimination task (ODT). The peripheral plasma levels of insulin, leptin, and glucose, and of monoamines and metabolites/precursors in brain areas related to olfactory learning and memory processes, such as the striatum and frontal cortex (FC), were determined. The data obtained indicated that CR attenuated the age-dependent decline in olfactory sensitivity in old animals fed ad libitum, which was correlated with the performance in ODT retention trial, as well as with leptin plasma levels. CR enhanced dopamine levels in the striatum, while it attenuated the age-related decline in serotonin levels in the striatum and FC. Such findings support a positive effect of CR on age-dependent olfactory sensitivity decline and dysfunctions in brain monoamine levels.

Brain insulin, insulin-like growth factor 1 and glucagon-like peptide 1 signalling in Alzheimer's disease

Although the brain was once considered an insulin-independent organ, insulin signalling is now recognised as being central to neuronal health and to the function of synapses and brain circuits. Defective brain insulin signalling, as well as related signalling by insulin-like growth factor 1 (IGF-1), is associated with neurological disorders, including Alzheimer's disease, suggesting that cognitive impairment could be related to a state of brain insulin resistance. Here, I briefly review key epidemiological/clinical evidence of the association between diabetes, cognitive decline and AD, as well as findings of reduced components of insulin signalling in AD brains, which led to the initial suggestion that AD could be a type of brain diabetes. Particular attention is given to recent studies illuminating mechanisms leading to neuronal insulin resistance as a key driver of cognitive impairment in AD. Evidence of impaired IGF-1 signalling in AD is also examined. Finally, we discuss potentials and possible limitations of recent and on-going therapeutic approaches based on our increased understanding of the roles of brain signalling by insulin, IGF-1 and glucagon-like peptide 1 in AD.

Genome-Wide Association Analysis of Growth Curve Parameters in Chinese Simmental Beef Cattle

The objective of the present study was to perform a genome-wide association study (GWAS) for growth curve parameters using nonlinear models that fit original weight-age records. In this study, data from 808 Chinese Simmental beef cattle that were weighed at 0, 6, 12, and 18 months of age were used to fit the growth curve. The Gompertz model showed the highest coefficient of determination (R² = 0.954). The parameters' mature body weight (A), time-scale parameter (b), and maturity rate (K) were treated as phenotypes for single-trait GWAS and multi-trait GWAS. In total, 9, 49, and 7 significant SNPs associated with A, b, and K were identified by single-trait GWAS; 22 significant single nucleotide polymorphisms (SNPs) were identified by multi-trait GWAS. Among them, we observed several candidate genes, including PLIN3, KCNS3, TMCO1, PRKAG3, ANGPTL2, IGF-1, SHISA9, and STK3, which were previously reported to associate with growth and development. Further research for these candidate genes may be useful for exploring the full genetic architecture underlying growth and development traits in livestock.

Cognitive Gains of Aerobic Exercise in Patients With Ischemic Cerebrovascular Disorder: A Systematic Review and Meta-Analysis

Background: Cognitive impairment has become an important problem in ischemic cerebrovascular disorder survivors as disease related deaths have been significantly reduced. Aerobic exercise, the most prevalent mode of physical activity, positively contributes to cognition in both healthy population and people with cognitive impairment. However, studies on its associations with cognitive gains in patients with ischemic cerebrovascular disease showed mixed findings. Objective: To explore the cognitive effects of aerobic exercise on ischemic cerebrovascular disorder survivors and investigate the possible moderators on exercise benefits. Method: Randomized controlled trials investigating the effects of sole aerobic exercise on cognitive function in population with ischemic intracranial vascular disorder compared to any control group who did not receive the intervention were enrolled in this systematic review and meta-analysis. Four online database (Pubmed, Cochrane Library, Embase, and Web of Science) were searched. Results: The initial search returned 1,522 citations and ultimately 11 studies were included in the systematic review. Analysis of seven studies showed the beneficial but not statistically significant impact of aerobic exercise on global cognitive function (0.13; 95% Cl -0.09 to 0.35; p = 0.25). Participants already with cognitive impairment benefited more from this intervention (0.31; 95% Cl 0.07-0.55; p = 0.01) and moderate intensity might be the optimal choice (0.34; 95% Cl -0.01 to 0.69; p = 0.06). The program duration and initiation time after stroke occurrence did not predict better cognitive outcome. Aerobic exercise was not associated with improvement of processing speed and executive function, the two subdomains of cognitive function. Conclusions: Aerobic exercise may contribute to cognitive gains in survivors of ischemic cerebrovascular disorder, especially for population already with cognitive decline. Our findings suggest that the adoption of moderate intensity aerobic exercise might improve cognition in such population.

Human gut microbiota Agathobaculum butyriciproducens improves cognitive impairment in LPS-induced and APP/PS1 mouse models of Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease, and is characterized by the accumulation and presence of amyloid plaques (Aβ), tangles, dementia, and cognitive impairment. Currently, there is no known cure for AD; however, recently, the association between alteration of the gut microbiota and AD pathology has been explored to find novel therapeutic approaches. Microbiota-targeted intervention has been suggested as an attractive therapeutic approach for AD. Agathobaculum butyriciproducens (SR79) is a strict anaerobic and butyric acid-producing bacteria. We hypothesized that administration of SR79 might have a beneficial effect on cognitive deficits and AD pathologies. To determine the therapeutic effects of SR79 on AD pathologies, APP/PS1 transgenic and lipopolysaccharide -induced cognitive impairment mouse models were used. In the lipopolysaccharide -induced cognitive deficit model, the administration of SR79 improved cognitive function and decreased microglia activation. In addition, the administration of SR79 to APP/PS1 mice significantly improved novel object recognition and percent alteration results in novel object recognition and Y-maze alteration tests. Furthermore, Aβ plaque deposition and microglial activation were markedly reduced in the parietal cortex and hippocampus after SR79 treatment in APP/PS1 mice. SR79 treatment significantly decreased gene expression levels of IL-1β and C1QB and increased the gene expression levels of IGF-1 and thereby the downstream signaling pathway in the cortex of APP/PS1 mice. In conclusion, SR79 administration improved cognitive function and AD pathologies through the regulation of neuroinflammation and IGF-1 signaling in an animal model.

Insulin-like growth factor-I activates NFκB and NLRP3 inflammatory signalling via ROS in cancer cells

Previous studies have demonstrated that insulin-like growth factor-I (IGF-1) and reactive oxygen species (ROS) are involved in the development and progression of various cancers. However, their regulatory mechanism remains unknown. In this study, we treated cancer cells (HeLa, HepG2 and SW1116 cells) and normal cells (NCM-460) with IGF-1 at different concentrations and for different times and found that cancer cells produced large amounts of cytoplasmic ROS in cancer cells but not in normal cells. Further mechanistic analysis demonstrated that IGF-1 activated NFκB and NLRP3 inflammatory signalling in HeLa cells; systematic analysis indicated that IGF-1 activates NFκB and NLRP3, and the activation was cytosolic ROS- and NADPH oxidase 2 (NOX2)-dependent. Additionally, through coimmunoprecipitation experiments, we found that the IRS-1/COX2/mPGES-1/MAPKs/RAC2/NOX2 pathway nexus was involved in IGF-1-induced NFκB and NLRP3 production. Finally, we validated the regulatory mechanisms through IRS-1, mPGES-1 or NOX2 inhibition using their respective selective inhibitors or shRNA knockdown. Taken together, this is the first report on the mechanism by which IGF-1 activates NFκB and NLRP3 inflammatory signalling via ROS. These findings pave the way for an in-depth study of the role of IGF-1 and ROS in inflammation associated with the development and progression of cancer.

The effect of soy intervention on insulin-like growth factor 1 levels: A meta-analysis of clinical trials

A low insulin-like growth factor 1 (IGF-1) level is known to be associated with many disorders. Several studies have shown that soy consumption may influence IGF-1, but the findings remain inconclusive. In this work, we conducted a systematic review and meta-analysis to provide a more accurate estimation of the effect of soy consumption on plasma IGF-1. A comprehensive systematic search was performed in Scopus, Embase, Web of Science, and PubMed/MEDLINE databases from inception until October 2019. Eight studies fulfilled the eligibility criteria. The pooled weighted mean difference (WMD) of the eligible studies was calculated with random-effects approach. Overall, a significant increment in plasma IGF-1 was observed following soy intervention (WMD: 13.5 ng/ml, 95% CI: 5.2, 21.8, I2 = 97%). Subgroup analyses demonstrated a significantly greater increase in IGF-1, when soy was administered at a dosage of ≤40 g/day (WMD: 11.7 ng/ml, 95% CI: 10.9 to 12.6, I2 = 98%), and when the intervention duration was <12 weeks (WMD: 26.6 ng/ml, 95% CI: 9.1 to 44.1, I2 = 0.0%). In addition, soy intervention resulted in a greater increase in IGF-1 among non-healthy subjects (WMD: 36 ng/ml, 95% CI: 32.7 to 39.4, I2 = 84%) than healthy subjects (WMD: 9.8 ng/ml, 95% CI: 8.9 to 10.7, I2 = 90%). In conclusion, this study provided the first meta-analytical evidence that soy intake may increase IGF-1 levels, but the magnitude of the increase is dependent on the intervention dosage, duration, and health status of the participants.

Growth hormone (GH) and synaptogenesis

Growth hormone (GH) is known to exert several roles during development and function of the nervous system. Initially, GH was exclusively considered a pituitary hormone that regulates body growth and metabolism, but now its alternative extrapituitary production and pleiotropic functions are widely accepted. Through excess and deficit models, the critical role of GH in nervous system development and adult brain function has been extensively demonstrated. Moreover, neurotrophic actions of GH in neural tissues include pro-survival effects, neuroprotection, axonal growth, synaptogenesis, neurogenesis and neuroregeneration. The positive effects of GH upon memory, behavior, mood, sensorimotor function and quality of life, clearly implicate a beneficial action in synaptic physiology. Experimental and clinical evidence about GH actions in synaptic function modulation, protection and restoration are revised in this chapter.

Measuring successful aging: an exploratory factor analysis of the InCHIANTI Study into different health domains

Advocating continued health into old age, so called successful aging, is a growing public health goal. However, the development of tools to measure aging is limited by the lack of appropriate outcome measures, and operational definitions of successful aging. Using exploratory factor analysis, we attempted to identify distinguishable health domains with representative variables of physical function, cognitive status, social interactions, psychological status, blood biomarkers, disease history, and socioeconomic status from the InCHIANTI study. We then used logistic and mixed effect regression models to determine whether the resulting domains predicted outcomes of successful aging over a nine-year follow-up. A four-domain health model was identified: neuro-sensory function, muscle function, cardio-metabolic function and adiposity. After adjustment for age and gender, all domains contributed to the prediction of walking speed (R²=0.73). Only the muscle function domain predicted dependency (R²=0.50). None of the domains were a strong, significant predictor of self-rated health (R²=0.18) and emotional vitality (R²=0.23). Cross-sectional findings were essentially replicated in the longitudinal analysis extended to nine-year follow-up. Our results suggest a multi-domain health model can predict objective but not subjective measures of successful aging.

Microarray Profile of Long Noncoding RNA and Messenger RNA Expression in a Model of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by a deficiency in cognitive skills. Although long noncoding RNAs (lncRNAs) have been proposed as associated with AD, the aberrant lncRNAs expression and the co-expression of lncRNAs-mRNAs network in AD remains unclear. Therefore, in this study, lncRNA microarray was performed on the brain of APP/PS1 mice at different age, widely used as an AD mouse model, and on age-matched wide-type controls. Our results identified a total of 3306 lncRNAs and 2458 mRNAs as aberrantly expressed among AD mice at different age and their age-matched control. Gene Ontology and pathway analysis of the AD-related lncRNAs and mRNAs indicated that neuroinflammation-related and synaptic transmission signaling pathways represented the main enriched pathways. An lncRNA-mRNA-miRNA network between the differentially expressed transcripts was constructed. Moreover, an mRNA-miRNA network between both significantly dysregulated and highly conserved genes was also constructed, and among this network, the IGF1, P2RX7, TSPO, SERPINE1, EGFR, HMOX1, and NFE212 genes were predicted to play a role in the development of AD. In conclusion, this study illustrated the prognostic value of lncRNAs and mRNAs associated to AD pathology by microarray analysis and might provide potential novel biomarkers in the diagnosis and treatment of AD.

The Continuing Evolution of Insulin-like Growth Factor Signaling

The insulin-like growth factors (IGFs; IGF1/IGF2), known for their regulation of cell and organismal growth and development, are evolutionarily conserved ligands with equivalent peptides present in flies ( D. melanogaster), worms ( C. elegans) among others. Two receptor tyrosine kinases, the IGF1 receptor and the insulin receptor mediate the actions of these ligands with a family of IGF binding proteins serving as selective inhibitors of IGF1/2. This treatise reviews recent findings on IGF signaling in cancer biology and central nervous system function. This includes overexpression of IGF1 receptors in enhancing tumorigenesis, acquired resistance and contributions to metastasis in multiple cancer types. There is accumulating evidence that insulin resistance, a hallmark of type 2 diabetes, occurs in the central nervous system, independent of systemic insulin resistance and characterized by reduced insulin and IGF1 receptor signaling, and may contribute to dementias including Alzheimer’s Disease and cognitive impairment. Controversy over the role(s) of IGF signaling in cancer and whether its inhibition would be of benefit, still persist and extend to IGF1’s role in longevity and central nervous system function.

The association between serum insulin-like growth factor 1 and cognitive impairments in patients with schizophrenia

Accumulating evidence has shown that insulin-like growth factors (IGFs) are implicated in schizophrenia. Altered serum levels of IGF-1 have been found in schizophrenia patients and are associated with psychopathological symptoms. However, whether there is a relationship between IGF-1 and cognitive impairment in schizophrenia remains unknown. Thirty schizophrenia patients and 26 healthy controls were recruited for this study. The Positive and Negative Syndrome Scale was adopted to assess schizophrenic symptoms, and a battery of neuropsychological tests was employed to evaluate cognitive function. Serum IGF-1 content was determined by enzyme-linked immunosorbent assay (ELISA). We found that patients with schizophrenia performed more poorly than healthy controls in most cognitive tasks, excluding visual memory. The serum IGF-1 concentrations in schizophrenia patients were much lower than those in controls. Correlation analyses revealed that the levels of serum IGF-1 were positively correlated with executive function and attention scores in patients. Furthermore, IGF-1 was an independent contributor to deficits in executive function and attention among schizophrenia patients. Collectively, serum IGF-1 levels were significantly correlated with cognitive performance in schizophrenia patients, indicating that decreased IGF-1 levels might contribute to the pathophysiology of schizophrenia-associated cognitive impairments. The regulation of IGF-1 signaling might be a potential treatment strategy for cognitive impairments in schizophrenia.

Does hyperglycemia downregulate glucose transporters in the brain?

Diabetes is a metabolic condition associated with hyperglycemia manifested by the elevation of blood glucose levels occurring when the pancreas decreases or stops the production of insulin, in case of insulin resistance or both. The current literature supports that insulin resistance may be responsible for the memory decline associated with diabetes. Glucose transporters (GLUTs) are a family of proteins involved in glucose transport across biological membranes. GLUT-1 and GLUT-3 are involved in glucose delivery to the brain. Evidence suggests that both transporters are downregulated in chronic peripheral hyperglycemia. Here we show the mechanisms of glucose transport and its influence on cognitive function, including a hypothesis of how peripheral hyperglycemia related genes network interactions may lead to glucose transporters downregulation and its possible consequences.

Biochemical Parameters in Cognitive Functions

Cognitive impairment is a common disease. Many studies attempt to explain the mechanisms of these dysfunctions formation, including correlations between cognitive functions and biochemical parameters. Scientists search for substances that would be indicators of cognitive functions and which could be determined in the cerebrospinal fluid or blood of the subjects. To date, they have isolated a few of such substances; however, research on their specificity, validity and the possibility of their use in diagnostics and prognostic assessment is still ongoing. However, there have been only few reports in the literature systematizing the existing knowledge on this subject, and they are mostly related to Alzheimer's disease, not cognition in general, or referring only to a specific group of substances. This article discusses the most important biochemical exponents of cognitive functions.

The role of exercise in the reversal of IGF-1 deficiencies in microvascular rarefaction and hypertension

Hypertension has been linked with peripheral and central reductions in vascular density, and with devastating effects on brain function. However, the underlying mechanisms in the relationship between blood pressure and cognitive impairment have yet to be fully elucidated. Here, we review compelling evidence from two lines of inquiry: one that links microvascular rarefaction with insulin-like growth factor 1 (IGF-1) deficiencies, and another which posits that vascular dysfunction precedes hypertension. Based on the findings from experimental and clinical studies, we propose that these lines of evidence converge, and suggest that age-related declines in IGF-1 concentrations precede microvascular rarefaction, initiate an increase in vascular resistance, and therefore are causally linked to onset of hypertension. Physical exercise provides a relevant model for supporting our premise, given the well-established effects of exercise in attenuating vascular dysfunction, hypertension, IGF-1 deficiency, and cognitive decline. We highlight here the role of exercise-induced increases in blood flow in improving vascular integrity and enhancing angiogenesis via the actions of IGF-1, resulting in reversal of rarefaction and hypertension, and enhancement of cerebral blood flow and cognition.

Decreased Levels of Serum IGF-1 and Vitamin D Are Associated With Cognitive Impairment in Patients With Type 2 Diabetes

PURPOSE

To determine the association of serum insulin-like growth factor 1 (IGF-1) and vitamin D levels with cognition status in patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 173 patients with T2DM were recruited and divided into mild cognitive impairment (MCI) group (n = 94) and normal cognition (NC) group (n = 79). Levels of IGF-1 and 25(OH)D were measured and compared, and the correlations among IGF-1, 25(OH)D, and cognitive function were analyzed.

RESULTS

Insulin-like growth factor 1 and 25(OH)D levels significantly decreased in MCI group than those in the NC group (both P < .001). Multiple stepwise regression analysis revealed that IGF-1 (β = .146, P < .001) and 25(OH)D (β = .199, P < .001) independently predicted Montreal Cognitive Assessment (MoCA) scores. Partial least square regression showed that contributions of both 25(OH)D (P < .001) and IGF-1 (P < .001) to MoCA scores were significant, while no cross-effect was observed between them (P = .714).

CONCLUSIONS

Low serum IGF-1 and 25(OH)D levels may separately predict poor cognitive performance in patients with diabetes.

Elevations in Serum Dickkopf-1 and Disease Progression in Community-Dwelling Older Adults With Mild Cognitive Impairment and Mild-to-Moderate Alzheimer's Disease

Background: Disruption of Wnt signaling has been implicated in dysfunctional synaptic plasticity, the degree of which correlates with Alzheimer's disease severity. We sought to examine whether serum levels of Dickkopf-1 (Dkk-1), a Wnt antagonist, are associated with global disease progression in older adults with mild cognitive impairment (MCI) and mild-to-moderate AD. Methods: We prospectively followed 88 older adults with MCI and mild-to-moderate AD attending a Memory Clinic. Cognitive performance, functional performance and neuropsychological symptoms were assessed at baseline and after 1 year. We reviewed neuroimaging for white matter changes and medial temporal atrophy, and performed ApoE genotyping at baseline. Serum Dkk-1 was assayed at baseline and 1 year, along with blood biomarkers of inflammation and endocrine dysfunction. We defined global disease progression ("progressors") as an increase in Clinical Dementia Rating Sum-of-Boxes (CDR-SB) score by >2 points at 1 year. Results: Fifteen (17.0%) participants had global disease progression. At baseline, there was no difference in cognitive performance and neuropsychiatric symptoms between groups, although progressors were more impaired in instrumental activities of daily living (p = 0.008). Progressors had significantly greater deterioration in cognitive performance (p = 0.002), with significantly worse functional performance and more severe neuropsychiatric symptoms (p = 0.042) at follow-up. Serum inflammatory and endocrine biomarkers at baseline and 1 year were similar between progressors and non-progressors. Serum Dkk-1 had increased significantly from baseline amongst progressors, while non-progressors exhibited decremental Dkk-1 over time (Dkk-1_change: 354.304 ± 670.467 vs. -173.582 ± 535.676 ng/ml, p = 0.001). Adjusting for age, gender and baseline cognitive performance, incremental Dkk-1 independently predicted global cognitive decline (p = 0.012). Conclusion: Our results suggest progressively dysfunctional Wnt signaling through Dkk-1 antagonism contributes to disease progression amongst older adults with MCI and mild-moderate AD.