Olfactory Signatures in the Food Finding Test in Mice With Normal and Alzheimer's Disease-Pathological Aging With Special Concerns on the Effects of Social Isolation.

Daniela Marín-Pardo,Lydia Giménez-Llort

doi:10.3389/fnins.2021.733984

Abstract

The temporal course and the severity of the involution of sensory systems through aging can be critical since they ensure the ability to perceive and recognize the world. In older people, sensory impairments significantly increase their risk of biological, psychological, and social impoverishment. Besides this, olfactory loss is considered an early biomarker in Alzheimer’s disease (AD) neurodegenerative process. Here we studied olfactory ethograms in middle-aged male and female gold-standard C57BL/6 mice and 3xTg-AD mice, a genetic model of AD that presents cognitive dysfunction and a conspicuous neuropsychiatric-like phenotype. A paradigm involving 1-day food deprivation was used to investigate the ethological patterns shown in the olfactory inspection of a new cage and the sniffing, finding, and eating of hidden food pellets. The sniffing–find–eat temporal patterns were independent of the loss of weight and unveiled (fast) olfactory signatures in Alzheimer’s disease, differing from those (slow progressive) in normal aging. Male 3xTg-AD mice exhibited an early signature than female mice, opposite to animals with normal aging. The sequence of actions was correlated in male and female 3xTg-AD mice in contrast to control mice. Social isolation, naturally occurring in male 3xTg-AD due to the death of cage mates, emphasized their olfactory patterns and disrupted the behavioral correlates. The paradigm provided distinct contextual, sex, and genotype olfactory ethogram signatures useful to investigate olfactory function in normal and AD-pathological aging. Isolation had an impact on enhancing the changes in the olfactory signature here described, for the first time, in the 3xTg-AD model of Alzheimer’s disease.

Highlights

Throughout life, sensory systems must ensure our ability to perceive and recognize the world
In the present brief report, we have studied the olfactory signatures in male and female mice with normal and neurodegenerative aging associated with advanced stages of Alzheimer’s disease (AD)
At the beginning of the experiments, before the animals were submitted to food deprivation for 14 h, the weight of 3xTg-AD mice was lower than that of controls [Wpre, genotype∗∗∗, F(1, 86) = 34.369, p < 0.001]

Summary

Introduction

Throughout life, sensory systems must ensure our ability to perceive and recognize the world. Olfactory Signatures in Aging and AD deficiencies significantly increase their risk of biological, psychological, and social impoverishment (Dziechciaz and Filip, 2014). Sensory deficits have been proposed as predictors of cognitive decline in older adults and as early indicators of the prodromal stages of Alzheimer’s disease. Olfactory dysfunction has attracted much attention among researchers in the field of brain damage and is a well-known marker for many neurological diseases (Wilson et al, 2009). By causing such vulnerability and/or disability, sensory deficiencies significantly increase the risk of the impoverishment of older people on a biological, psychological, and social level (Volkers and Scherder, 2011). Emergent literature unveiled anosmia as being more predictive of 5-year mortality risk than cardiovascular disease (Van Regemorter et al, 2020)

Methods

Results

Conclusion