Therapeutic targets of brain insulin resistance in sporadic Alzheimer s disease

Abstract

Growing evidence supports roles for brain insulin and insulin-like growth factor (IGF) resistance and metabolic dysfunction in the pathogenesis of Alzheimer's disease (AD). Whether the underlying problem stems from a primary disorder of central nervous system (CNS) neurons and glia, or secondary effects of systemic diseases such as obesity, Type 2 diabetes, or metabolic syndrome, the end-results include impaired glucose utilization, mitochondrial dysfunction, increased oxidative stress, neuroinflammation, and the propagation of cascades that result in the accumulation of neurotoxic misfolded, aggregated, and ubiquitinated fibrillar proteins. This article reviews the roles of impaired insulin and IGF signaling to AD-associated neuronal loss, synaptic disconnection, tau hyperphosphorylation, amyloid-beta accumulation, and impaired energy metabolism, and discusses therapeutic strategies and lifestyle approaches that could be used to prevent, delay the onset, or reduce the severity of AD. Finally, it is critical to recognize that AD is heterogeneous and has a clinical course that fully develops over a period of several decades. Therefore, early and multi-modal preventive and treatment approaches should be regarded as essential. KeywordsAmyloid; Anti-oxidants; Brain diabetes; Brain insulin resistance; Incretins; Insulin; Insulin sensitizers; Liver-Brain-Axis; Metal Chelation; Neuroprotection; Nitrosamine; Oxidative Stress; Polyphenols; Statins; Streptozotocin; Tau; Type 3 diabetes INTRODUCTIONThe gold standard for definitively diagnosing AD is to perform a postmortem examination of the brain, with the objective of demonstrating beyond-normal aging associated densities of neurofibrillary tangles, neuritic plaques, and amyloid-beta 40-42 kD fragments of amyloid beta precursor protein (AβPP-Aβ) deposits in corticolimbic structures, bearing in mind that neurodegeneration frequently involves multiple other cortical regions as well. The common thread among these characteristic lesions is that they harbor insoluble aggregates of abnormally phosphorylated and ubiquitinated tau, and neurotoxic AβPP-Aβ in the form of Send correspondence to: Suzanne M. de la Monte, Rhode Island Hospital, 55 Claverick Street, Room 419, Providence, RI. 02903, Tel: 401-444-7364, Fax: 401-444-2939, Suzanne_DeLaMonte_MD@Brown.edu. HHS Public Access Author manuscriptFront Biosci (Elite Ed). Author manuscript; available in PMC 2015 August 26. Published in final edited form as:Front Biosci (Elite Ed). ; 4: 1582-1605. Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript oligomers, fibrillar aggregates, or extracellular plaques. Secreted AβPP-Aβ oligomers have been demonstrated to be neurotoxic and to inhibit hippocampal long-term potentiation, i.e. synaptic plasticity (1).To improve diagnosis and treatment, we must learn to connect the development and progression of neurodegeneration with molecular, biochemical, physiological, neuroimaging, and clinical abnormalities in AD. Several strategies could be taken to advance this proc...

Iron Deposition Leads to Hyperphosphorylation of Tau and Disruption of Insulin Signaling

“…Insulin signaling is the prominent modulator of cellular activities through its regulation of energy metabolism, mitogenesis, development, synaptic plasticity, and other processes (24, 28). Accumulating evidence reveals that dysfunctional insulin signaling is a major risk factor for the onset of AD, particularly the sporadic type (77). Currently, there is no direct evidence of a role for iron in neural insulin signaling.…”

Insulin-Mediated Changes in Tau Hyperphosphorylation and Autophagy in a Drosophila Model of Tauopathy and Neuroblastoma Cells

“…Moreover, insulin and insulin-sensitizing drugs improve cognitive performance in people at early stages of AD (Freiherr et al, 2013; Roberts et al, 2014). The physiological and pathological role of IR signaling in the CNS is still unknown, but a strong correlation between AD and dysfunction of the insulin-signaling pathway with regard to glucose metabolism in the brain has prompted some investigators to refer to AD as type 3 diabetes or an “insulin resistant” condition of the brain (de la Monte, 2012; Barone et al, 2019).…”