Neuronal overexpression of insulin receptor substrate 2 leads to increased fat mass, insulin resistance, and glucose intolerance during aging
- 554 Downloads
The insulin receptor substrates (IRS) are adapter proteins mediating insulin's and IGF1's intracellular effects. Recent data suggest that IRS2 in the central nervous system (CNS) is involved in regulating fuel metabolism as well as memory formation. The present study aims to specifically define the role of chronically increased IRS2-mediated signal transduction in the CNS. We generated transgenic mice overexpressing IRS2 specifically in neurons (nIRS2 tg) and analyzed these in respect to energy metabolism, learning, and memory. Western blot (WB) analysis of nIRS2 tg brain lysates revealed increased IRS2 downstream signaling. Histopathological investigation of nIRS2 tg mice proved unaltered brain development and structure. Interestingly, nIRS2 tg mice showed decreased voluntary locomotoric activity during dark phase accompanied with decreased energy expenditure (EE) leading to increased fat mass. Accordingly, nIRS2 tg mice develop insulin resistance and glucose intolerance during aging. Exploratory behavior, motor function as well as food and water intake were unchanged in nIRS2 tg mice. Surprisingly, increased IRS2-mediated signals did not change spatial working memory in the T-maze task. Since FoxO1 is a key mediator of IRS2-transmitted signals, we additionally generated mice expressing a dominant negative mutant of FoxO1 (FoxO1DN) specifically in neurons. This mutant mimics the effect of increased IRS2 signaling on FoxO-mediated transcription. Interestingly, the phenotype observed in nIRS2 tg mice was not present in FoxO1DN mice. Therefore, increased neuronal IRS2 signaling causes decreased locomotoric activity in the presence of unaltered exploratory behavior and motor coordination that might lead to increased fat mass, insulin resistance, and glucose intolerance during aging independent of FoxO1-mediated transcription.
KeywordsIRS2 Brain Mice Insulin resistance Diabetes Locomotoric activity
This work was supported by AFI #08813. JZ was supported by a student's grant of the Medical Faculty, University of Cologne. We thank Andre Kleinridders for his kind introduction and troubleshooting in transgenic mouse generation. Also, we thank Thomas Wunderlich for kindly providing the pCAGGS targeting vector. Thanks also to Jens Alber for excellent technical assistance, Prof. Wilhelm Stoffel for providing the T-maze, and Prof. Martina Deckert and Mariana Carstov for advice and help on immunohistochemistry.
- Choudhury AI, Heffron H, Smith MA, Al-Qassab H, Xu AW, Selman C, Simmgen M, Clements M, Claret M, Maccoll G, Bedford DC, Hisadome K, Diakonov I, Moosajee V, Bell JD, Speakman JR, Batterham RL, Barsh GS, Ashford ML, Withers DJ (2005) The role of insulin receptor substrate 2 in hypothalamic and beta cell function. J Clin Invest 115(4):940–950PubMedGoogle Scholar
- Craft S, Baker LD, Montine TJ, Minoshima S, Watson GS, Claxton A, Arbuckle M, Callaghan M, Tsai E, Plymate SR, Green PS, Leverenz J, Cross D, Gerton B (2012) Intranasal insulin therapy for Alzheimer disease and amnestic mild cognitive impairment: a pilot clinical trial. Arch Neurol 69(1):29–38PubMedCrossRefGoogle Scholar
- Freude S, Hettich MM, Schumann C, Stohr O, Koch L, Kohler C, Udelhoven M, Leeser U, Muller M, Kubota N, Kadowaki T, Krone W, Schroder H, Bruning JC, Schubert M (2009b) Neuronal IGF-1 resistance reduces Abeta accumulation and protects against premature death in a model of Alzheimer's disease. FASEB J 23(10):3315–3324PubMedCrossRefGoogle Scholar
- Killick R, Scales G, Leroy K, Causevic M, Hooper C, Irvine EE, Choudhury AI, Drinkwater L, Kerr F, Al-Qassab H, Stephenson J, Yilmaz Z, Giese KP, Brion JP, Withers DJ, Lovestone S (2009) Deletion of Irs2 reduces amyloid deposition and rescues behavioural deficits in APP transgenic mice. Biochem Biophys Res Commun 386(1):257–262PubMedCrossRefGoogle Scholar
- Stohr O, Hahn J, Moll L, Leeser U, Freude S, Bernard C, Schilbach K, Markl A, Udelhoven M, Krone W, Schubert M (2011a) Insulin receptor substrate-1 and −2 mediate resistance to glucose-induced caspase-3 activation in human neuroblastoma cells. Biochim Biophys Acta 1812(5):573–580PubMedCrossRefGoogle Scholar
- Stohr O, Schilbach K, Moll L, Hettich MM, Freude S, Wunderlich FT, Ernst M, Zemva J, Bruning JC, Krone W, Udelhoven M, Schubert M (2011b) Insulin receptor signaling mediates APP processing and beta-amyloid accumulation without altering survival in a transgenic mouse model of Alzheimer's disease. Age (Dordr)Google Scholar
- Tschop MH, Speakman JR, Arch JR, Auwerx J, Bruning JC, Chan L, Eckel RH, Farese RV Jr, Galgani JE, Hambly C, Herman MA, Horvath TL, Kahn BB, Kozma SC, Maratos-Flier E, Muller TD, Munzberg H, Pfluger PT, Plum L, Reitman ML, Rahmouni K, Shulman GI, Thomas G, Kahn CR, Ravussin E (2012) A guide to analysis of mouse energy metabolism. Nat Methods 9(1):57–63CrossRefGoogle Scholar
- Udelhoven M, Leeser U, Freude S, Hettich MM, Laudes M, Schnitker J, Krone W, Schubert M (2010b) Identification of a region in the human IRS2 promoter essential for stress induced transcription depending on SP1, NFI binding and ERK activation in HepG2 cells. J Mol Endocrinol 44(2):99–113PubMedCrossRefGoogle Scholar
- Yamada M, Ohnishi H, Sano S, Nakatani A, Ikeuchi T, Hatanaka H (1997) Insulin receptor substrate (IRS)-1 and IRS-2 are tyrosine-phosphorylated and associated with phosphatidylinositol 3-kinase in response to brain-derived neurotrophic factor in cultured cerebral cortical neurons. J Biol Chem 272(48):30334–30339PubMedCrossRefGoogle Scholar
- Zemva J, Schilbach K, Stöhr O, Moll L, Franko A, Krone W, Wiesner RJ and Schubert M (2012) Central FoxO3a and FoxO6 expression is downregulated in obesity induced diabetes but not in aging. Exp Clin Endocrinol Diabetes 120(6):340–350Google Scholar