Down-regulating insulin-like growth factor-1 receptor reduces amyloid-β deposition in mice cortex induced by chronic sleep restriction

Insulin-Like Growth Factor Signaling in Alzheimer's Disease: Pathophysiology and Therapeutic Strategies

Alzheimer's disease (AD) is the leading cause of dementia among the elderly population, posing a significant public health challenge due to limited therapeutic options that merely delay cognitive decline. AD is associated with impaired energy metabolism and reduced neurotrophic signaling. The insulin-like growth factor (IGF) signaling pathway, crucial for central nervous system (CNS) development, metabolism, repair, cognition, and emotion regulation, includes IGF-1, IGF-2, IGF-1R, IGF-2R, insulin receptor (IR), and six insulin-like growth factor binding proteins (IGFBPs). Research has identified abnormalities in IGF signaling in individuals with AD and AD models. Dysregulated expression of IGFs, receptors, IGFBPs, and disruptions in downstream phosphoinositide 3-kinase-protein kinase B (PI3K/AKT) and mitogen-activated protein kinase (MAPK) pathways collectively increase AD susceptibility. Studies suggest modulating the IGF pathway may ameliorate AD pathology and cognitive decline. This review explores the CNS pathophysiology of IGF signaling in AD progression and assesses the potential of targeting the IGF system as a novel therapeutic strategy. Further research is essential to elucidate how aberrant IGF signaling contributes to AD development, understand underlying molecular mechanisms, and evaluate the safety and efficacy of IGF-based treatments.

WuYou decoction effectively reduces neuronal damage, synaptic dysfunction, and Aβ production in rats exposed to chronic sleep deprivation by modulating the Aβ-related enzymes and SIRT1/Nrf2/NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Chronic sleep deprivation (CSD) can result in neuronal damage, synaptic dysfunction, Aβ production, neuroinflammation, and ultimately cognitive deterioration. WuYou Decoction (WYD), a contemporary prescription, has shown promise in enhancing sleep quality and cognitive performance in individuals with insomnia. However, the specific molecular mechanisms responsible for the neuroprotective effects of WYD on CSD remain incompletely understood.

AIM OF THE STUDY

This study aimed to investigate the neuroprotective effects of WYD on the CSD model and its molecular mechanism.

MATERIALS AND METHODS

UHPLC-MS/MS analysis was utilized to analyze the active ingredients of WYD extract. The study employed the multi-platform water environment method to establish the CSD model in rats. Subsequent to treatment with varying doses of WYD in CSD rats, cognitive function and pathological alterations in hippocampus and cortex, including neuronal damage, synaptic dysfunction, Aβ production, and neuroinflammation, were evaluated through a combination of Morris Water Maze test, HE staining, Nissl staining, Golgi-Cox staining, Transmission electron microscope, ELISA, Immunohistochemistry staining, Immunofluorescence staining and Western blot.

RESULTS

UHPLC-MS/MS analysis revealed a total of 99 active ingredients were identified from the WYD extract. The administration of WYD exhibited a mitigation of cognitive decline in the model of CSD, as evidenced by increased neuron count in the hippocampus and cortex, and improved density and length of dendritic spines in these brain regions. Furthermore, WYD was found to suppress the Aβ production, and inhibit the expression of BACE1, PS1, GFAP, IBA1, IL-1β, IL-6, TNF-α, phosphorylated IκBα (Ser32) and phosphorylated NF-κB p65 (Ser536) in the hippocampus and cortex, while also increasing the levels of PSD95, SYN1, ADAM10, IDE, SIRT1 and Nrf2.

CONCLUSIONS

WYD exhibits neuroprotective properties in CSD, potentially through modulation of the Aβ-related enzymes and SIRT1/Nrf2/NF-κB pathway.

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.