. Tau deletion promotes brain insulin resistance. J Exp Med. 2017 Aug 7;214(8):2257-2269. Epub 2017 Jun 26 PubMed.

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  1. This is an interesting report by Elodie Marciniak, Luc Buee, David Blum, and colleagues providing evidence that tau is necessary for proper brain insulin signaling. Results are significant, as they highlight an as-yet-unexplored physiological role of tau, as well as lead us to speculate whether brain insulin resistance could contribute to tauopathies.

    Several reports have now demonstrated that insulin-induced responses are blunted in Alzheimer's disease brains (Ma et al., 2009Moloney et al., 2010; Bomfim et al., 2012; Talbot et al., 2012). The current report opens new fields of investigation by implicating tau as a key regulator of brain insulin signaling through PTEN phosphatase regulation. It would be important to determine next whether mouse models of tauopathies present brain insulin resistance, and whether it depends on tau phosphorylation, cleavage, or aggregation.

    Downregulation of brain insulin receptors was shown to trigger memory impairment (Nisticò et al., 2010; Grillo et al., 2015) and tau phosphorylation (Schubert et al., 2004). Although tau regulation of insulin signaling does not appear to directly involve insulin receptors, defective brain insulin signaling could be part of a feed-forward loop driving neuronal malfunction in tauopathies, as now suggested

    Finally, the findings that tau regulates non-hippocampal metabolic actions of insulin in the brain is in line with recent evidence underscoring disturbances of peripheral metabolism in AD (Clarke et al., 2015; Crane et al., 2015). Further investigation of tau and insulin intersections would thus indicate whether stimulating brain insulin signaling through repurposed anti-diabetic agents holds potential to attenuate cognitive and metabolic symptoms of tauopathies, as currently under investigation in the AD field.

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    . Alzheimer-associated Aβ oligomers impact the central nervous system to induce peripheral metabolic deregulation. EMBO Mol Med. 2015 Jan 23;7(2):190-210. PubMed.

    . Glucose levels and risk of dementia. N Engl J Med. 2013 Nov 7;369(19):1863-4. PubMed.

    . Hippocampal Insulin Resistance Impairs Spatial Learning and Synaptic Plasticity. Diabetes. 2015 Nov;64(11):3927-36. Epub 2015 Jul 27 PubMed.

    . Beta-amyloid oligomers induce phosphorylation of tau and inactivation of insulin receptor substrate via c-Jun N-terminal kinase signaling: suppression by omega-3 fatty acids and curcumin. J Neurosci. 2009 Jul 15;29(28):9078-89. PubMed.

    . Defects in IGF-1 receptor, insulin receptor and IRS-1/2 in Alzheimer's disease indicate possible resistance to IGF-1 and insulin signalling. Neurobiol Aging. 2010 Feb;31(2):224-43. PubMed.

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    . Role for neuronal insulin resistance in neurodegenerative diseases. Proc Natl Acad Sci U S A. 2004 Mar 2;101(9):3100-5. PubMed.

    . Demonstrated brain insulin resistance in Alzheimer's disease patients is associated with IGF-1 resistance, IRS-1 dysregulation, and cognitive decline. J Clin Invest. 2012 Apr;122(4):1316-38. PubMed.

    View all comments by Mychael Lourenco

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