Neuronal human BACE1 knock-in induces systemic diabetes in mice

Kaja Plucinska, Ruta Dekeryte, David Koss, Kirsty Shearer, Nimesh Mody, Phillip D. Whitfield, Mary K. Doherty, Marco Mingarelli, Andy Welch, Gernot Riedel, Mirela Delibegovic, Bettina Platt

Research output: Contribution to journalArticle

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Abstract

Aims

β-Secretase 1 (BACE1) is a key enzyme in Alzheimer’s disease pathogenesis that catalyses the amyloidogenic cleavage of amyloid precursor protein (APP). Recently, global Bace1 deletion was shown to protect against diet-induced obesity and diabetes, suggesting that BACE1 is a potential regulator of glucose homeostasis. Here, we investigated whether increased neuronal BACE1 is sufficient to alter systemic glucose metabolism, using a neuron-specific human BACE1 knockin mouse model (PLB4).

Methods

Glucose homeostasis and adiposity were determined by glucose tolerance tests and EchoMRI, lipid species were measured by quantitative lipidomics, and biochemical and molecular alterations were assessed by western blotting, quantitative PCR and ELISAs. Glucose uptake in the brain and upper body was measured via 18FDG-PET imaging.

Results

Physiological and molecular analyses demonstrated that centrally expressed human BACE1 induced systemic glucose intolerance in mice from 4 months of age onward, alongside a fatty liver phenotype and impaired hepatic glycogen storage. This diabetic phenotype was associated with hypothalamic pathology, i.e. deregulation of the melanocortin system, and advanced endoplasmic reticulum (ER) stress indicated by elevated central C/EBP homologous protein (CHOP) signalling and hyperphosphorylation of its regulator eukaryotic translation initiation factor 2α (eIF2α). In vivo 18FDG-PET imaging further confirmed brain glucose hypometabolism in these mice; this corresponded with altered neuronal insulin-related signalling, enhanced protein tyrosine phosphatase 1B (PTP1B) and retinol-binding protein 4 (RBP4) levels, along with upregulation of the ribosomal protein and lipid translation machinery. Increased forebrain and plasma lipid accumulation (i.e. ceramides, triacylglycerols, phospholipids) was identified via lipidomics analysis.

Conclusions/interpretation

Our data reveal that neuronal BACE1 is a key regulator of metabolic homeostasis and provide a potential mechanism for the high prevalence of metabolic disturbance in Alzheimer’s disease.
Original languageEnglish
Pages (from-to)1513-1523
Number of pages11
JournalDiabetologia
Volume59
Issue number7
Early online date2 May 2016
DOIs
Publication statusPublished - Jul 2016

Keywords

  • neuronal BACE1
  • glucose homeostasis
  • ceramide
  • ER stress
  • 18FDG-PET
  • insulin signalling

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