P6: Functional relationship between locomotion and structural muscle fibers in Alzheimer’s Disease, an experimental report from 3xTg-AD mice

Abstract

Introduction: Motor impairment remains underexplored in Alzheimer’s disease. We previously described the functional impairment of gait and exploratory activity of male 3xTg-AD mice at different stages of Alzheimer’s disease progression. We describe movement limitations and muscle weakness as indicators of severity.

Methods: In the present report, a cross-sectional study was carried out that analyzed the muscular structure of the quadriceps and triceps surae muscles of transgenic (3xTg-AD) and non-transgenic males in the early (6 months), intermediate (12 months), and advanced (16 months) stages of Alzheimer’s disease. Longitudinal sections of the quadriceps and triceps surae stained with hematoxylin and eosin (H&E) were evaluated. Using conventional histological techniques, they were then rinsed with PBS, pH 7.4. For the F-actine immunohistochemistry, the sections were blocked by incubating them in IgG-free 2% bovine serum albumin (BSA, Sigma) for 60 min. Then specimens were incubated for 10 minutes with 0.2% Triton X-100 in PBS at room temperature. The slides were incubated overnight at 4 °C with F-actin (Santa Cruz Biotechnology Inc., CA, USA). Slides were counterstained with VectaShield using 4, 60-diamino-2-phenylindole dihydrochloride (DAPI) (Vector Labs., CA, USA) for nuclei staining and visualized in the blue channel.

Results: Lower fluorescence labeling was detected in 3xTg-AD mice at all ages, with a greater decline at older ages. Signs of sarcopenia are also present in an advanced stage of AD, with differences in fiber distribution, the number of cell nuclei, and the presence of adipose tissue.

Conclusions: The previously reported gait alterations in Alzheimer’s disease could be the result of structural deficiencies due to sarcopenia and poor muscle contraction, which leads to the limitations of movement in locomotion reported in 3xTg-AD mice.