Boxer, Adam L.

ABSTRACT Insulin resistance causes diminished glucose uptake in similar regions of the brain in Alzheimer's disease (AD) and type 2 diabetes mellitus (DM2). Brain tissue studies suggested that insulin resistance is caused by low insulin receptor signaling attributable to its abnormal association with more phospho (P)‐serine‐type 1 insulin receptor substrate (IRS‐1) and less P‐tyrosine‐IRS‐1. Plasma exosomes enriched for neural sources by immunoabsorption were obtained once from 26 patients with AD, 20 patients with DM2, 16 patients with frontotemporal dementia (FTD), and matched case control subjects. At 2 time points, they were obtained from 22 others when cognitively normal and 1 to 10 yr later when diagnosed with AD. Mean exosomal levels of extracted P‐serine 312‐IRS‐1 and P‐pan‐tyrosine‐IRS‐1 by ELISA and the ratio of P‐serine 312‐IRS‐1 to P‐pan‐tyrosine‐IRS‐1 (insulin resistance factor, R) for AD and DM2 and P‐serine 312‐IRS‐1 and R for FTD were significantly different from those for case control subjects. The levels of R for AD were significandy higher than those for DM2 or FTD. Stepwise discriminant modeling showed correct classification of 100% of patients with AD, 97.5% of patients with DM2, and 84% of patients with FTD. In longitudinal studies of 22 patients with AD, exosomal levels of P‐serine 312‐IRS‐1, P‐pan‐tyrosine‐IRS‐1, and R were significantly different 1 to 10 yr before and at the time of diagnosis compared with control subjects. Insulin resistance reflected in R values from this blood test is higher for patients with AD, DM2, and FTD than case control subjects; higher for patients with AD than patients with DM2 or FTD; and accurately predicts development of AD up to 10 yr prior to clinical onset.—Kapogiannis, D., Boxer, A., Schwartz, J. B., Abner, E. L., Biragyn, A., Masharani, U., Frassetto, L., Petersen, R. C., Miller, B. L., Goetzl, E. J. Dysfunctionally phosphorylated type 1 insulin receptor substrate in neural‐derived blood exosomes of preclinical Alzheimer's disease. FASEB J . 29, 589‐596 (2015). www.fasebj.org

Abstract Background Proteins pathogenic in Alzheimer's disease (AD) were extracted from neurally derived blood exosomes and quantified to develop biomarkers for the staging of sporadic AD. Methods Blood exosomes obtained at one time‐point from patients with AD (n = 57) or frontotemporal dementia (FTD) (n = 16), and at two time‐points from others (n = 24) when cognitively normal and 1 to 10 years later when diagnosed with AD were enriched for neural sources by immunoabsorption. AD‐pathogenic exosomal proteins were extracted and quantified by enzyme‐linked immunosorbent assays. Results Mean exosomal levels of total tau, P‐T181‐tau, P‐S396‐tau, and amyloid β 1–42 (Aβ1–42) for AD and levels of P‐T181‐tau and Aβ1–42 for FTD were significantly higher than for case‐controls. Step‐wise discriminant modeling incorporated P‐T181‐tau, P‐S396‐tau, and Aβ1–42 in AD, but only P‐T181‐tau in FTD. Classification of 96.4% of AD patients and 87.5% of FTD patients was correct. In 24 AD patients, exosomal levels of P‐S396‐tau, P‐T181‐tau, and Aβ1–42 were significantly higher than for controls both 1 to 10 years before and when diagnosed with AD. Conclusions Levels of P‐S396‐tau, P‐T181‐tau, and Aβ1–42 in extracts of neurally derived blood exosomes predict the development of AD up to 10 years before clinical onset.

Abstract Recent evidence indicates that sensory and motor changes may precede the cognitive symptoms of Alzheimer's disease (AD) by several years and may signify increased risk of developing AD. Traditionally, sensory and motor dysfunctions in aging and AD have been studied separately. To ascertain the evidence supporting the relationship between age‐related changes in sensory and motor systems and the development of AD and to facilitate communication between several disciplines, the National Institute on Aging held an exploratory workshop titled “Sensory and Motor Dysfunctions in Aging and AD.” The scientific sessions of the workshop focused on age‐related and neuropathologic changes in the olfactory, visual, auditory, and motor systems, followed by extensive discussion and hypothesis generation related to the possible links among sensory, cognitive, and motor domains in aging and AD. Based on the data presented and discussed at this workshop, it is clear that sensory and motor regions of the central nervous system are affected by AD pathology and that interventions targeting amelioration of sensory‐motor deficits in AD may enhance patient function as AD progresses.

Frontotemporal degeneration (FTD) encompasses a spectrum of related neurodegenerative disorders with behavioral, language, and motor phenotypes for which there are currently no effective therapies. This is the second of two articles that summarize the presentations and discussions that occurred at two symposia in 2011 sponsored by the Frontotemporal Degeneration Treatment Study Group, a collaborative group of academic and industry researchers that is devoted to developing treatments for FTD. This article discusses the current status of FTD clinical research that is relevant to the conduct of clinical trials, and why FTD research may be an attractive pathway for developing therapies for neurodegenerative disorders. The clinical and molecular features of FTD, including rapid disease progression and relatively pure molecular pathology, suggest that there are advantages to developing drugs for FTD as compared with other dementias. FTD qualifies as orphan indication, providing additional advantages for drug development. Two recent sets of consensus diagnostic criteria will facilitate the identification of patients with FTD, and a variety of neuropsychological, functional, and behavioral scales have been shown to be sensitive to disease progression. Moreover, quantitative neuroimaging measurements demonstrate progressive brain atrophy in FTD at rates that may surpass Alzheimer's disease. Finally, the similarities between FTD and other neurodegenerative diseases with drug development efforts already underway suggest that FTD researchers will be able to draw on this experience to create a road map for FTD drug development. We conclude that FTD research has reached sufficient maturity to pursue clinical development of specific FTD therapies.

Frontotemporal degeneration (FTD) is a common cause of dementia for which there are currently no approved therapies. Over the past decade, there has been an explosion of knowledge about the biology and clinical features of FTD that has identified a number of promising therapeutic targets as well as animal models in which to develop drugs. The close association of some forms of FTD with neuropathological accumulation of tau protein or increased neuroinflammation due to progranulin protein deficiency suggests that a drug's success in treating FTD may predict efficacy in more common diseases such as Alzheimer's disease. A variety of regulatory incentives, clinical features of FTD such as rapid disease progression, and relatively pure molecular pathology suggest that there are advantages to developing drugs for FTD as compared with other more common neurodegenerative diseases such as Alzheimer's disease. In March 2011, the Frontotemporal Degeneration Treatment Study Group sponsored a conference entitled “FTD, the Next Therapeutic Frontier,” which focused on preclinical aspects of FTD drug development. The goal of the meeting was to promote collaborations between academic researchers and biotechnology and pharmaceutical researchers to accelerate the development of new treatments for FTD. Here we report the key findings from the conference, including the rationale for FTD drug development; epidemiological, genetic, and neuropathological features of FTD; FTD animal models and how best to use them; and examples of successful drug development collaborations in other neurodegenerative diseases.