Plasma β-amyloid peptides in canine aging and cognitive dysfunction as a model of Alzheimer's disease

Aging dogs naturally demonstrate cognitive impairment and neuropathology that model early Alzheimer's disease (AD). In particular, there is evidence that canine cognitive dysfunction syndrome (CDS) in aged dogs is accompanied by cortical deposition of Aβ peptides and neurodegeneration. Plasma Aβ levels have been examined in humans as putative biomarkers for AD, but to date, no similar studies have been conducted for canine dementia. The aim of the present study was to assess plasma Aβ1-42 and Aβ1-40 levels in a blind study using pet dogs that were either successfully aging or exhibiting CDS. The severity of cognitive impairment was assessed using an owner-based questionnaire. On average, young dogs presented significantly higher plasma levels of Aβ1-42 and Aβ1-40 than aged, cognitively unimpaired dogs. Notably, among aged dogs, the levels of Aβ1-42 and the Aβ42/40 ratio were significantly higher in those showing mild cognitive impairment than in either cognitively unimpaired or severely affected dogs. These results suggest that increased plasma Aβ1-42 levels and Aβ42/40 ratio could be a biomarker for canine cognitive dysfunction, which is considered an excellent natural model of early AD.

Research highlights► Plasma Aβ was analyzed for the first time in relation to age in a pet dog population. ► Aged dogs with cognitive dysfunction have higher Aβ42 plasma levels than controls. ► Aβ42 levels were higher in mildly cognitive impaired than in severely affected dogs. ► Plasma Aβ42 could be an early biomarker for cognitive dysfunction in aged dogs. ► Canine cognitive dysfunction syndrome appears as an excellent natural model for early AD.