Ablation of amyloid precursor protein increases insulin-degrading enzyme levels and activity in brain and peripheral tissues

Joshua A. Kulas, Whitney F. Franklin, Nicholas A. Smith, Gunjan D. Manocha, Kendra L. Puig, Kumi Nagamoto-Combs, Rachel D. Hendrix, Giulio Taglialatela, Steven W. Barger, Colin K. Combs

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

The amyloid precursor protein (APP) is a type I transmembrane glycoprotein widely studied for its role as the source of β-amyloid peptide, accumulation of which is causal in at least some cases of Alzheimer's disease (AD). APP is expressed ubiquitously and is involved in diverse biological processes. Growing bodies of evidence indicate connections between AD and somatic metabolic disorders related to type 2 diabetes, and App-/- mice show alterations in glycemic regulation. We find that App-/- mice have higher levels of insulin-degrading enzyme (IDE) mRNA, protein, and activity compared with wild-type controls. This regulation of IDE by APP was widespread across numerous tissues, including liver, skeletal muscle, and brain as well as cell types within neural tissue, including neurons, astrocytes, and microglia. RNA interference-mediated knockdown of APP in the SIM-A9 microglia cell line elevated IDE levels. Fasting levels of blood insulin were lower in App-/- than App+/+ mice, but the former showed a larger increase in response to glucose. These low basal levels may enhance peripheral insulin sensitivity, as App-/- mice failed to develop impairment of glucose tolerance on a high-fat, high-sucrose ("Western") diet. Insulin levels and insulin signaling were also lower in the App-/- brain; synaptosomes prepared from App-/- hippocampus showed diminished insulin receptor phosphorylation compared with App+/+ mice when stimulated ex vivo. These findings represent a new molecular link connecting APP to metabolic homeostasis and demonstrate a novel role for APP as an upstream regulator of IDE in vivo.

Original languageEnglish (US)
Pages (from-to)E106-E120
JournalAmerican journal of physiology. Endocrinology and metabolism
Volume316
Issue number1
DOIs
StatePublished - Jan 1 2019

    Fingerprint

Keywords

  • Alzheimer’s disease
  • amyloid precursor protein
  • insulin
  • insulin-degrading enzyme
  • microglia

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

Cite this

Kulas, J. A., Franklin, W. F., Smith, N. A., Manocha, G. D., Puig, K. L., Nagamoto-Combs, K., Hendrix, R. D., Taglialatela, G., Barger, S. W., & Combs, C. K. (2019). Ablation of amyloid precursor protein increases insulin-degrading enzyme levels and activity in brain and peripheral tissues. American journal of physiology. Endocrinology and metabolism, 316(1), E106-E120. https://doi.org/10.1152/ajpendo.00279.2018