Correlation between sarcopenia and changes in oligodendrocyte lineage cells in the brains of Alzheimer's disease model mice

Background: Alzheimer's disease (AD) is a neurodegenerative disorder primarily characterized by cognitive dysfunction. The discovery and identification of non-cognitive symptoms in the preclinical stage hold promise for early diagnosis and intervention. Previous studies have shown that diagnosed AD patients commonly exhibit alterations in sarcopenia-related indicators, which might represent early symptoms of progression from mild cognitive impairment (MCI) to AD. Methods: This study used 3-month-old APP/PS1 transgenic (AD) mice and C57BL/6J wild-type (WT) mice. Hindlimbs were immobilized with plaster casts for 2 weeks. After immobilization, body, brain, and muscle weights were measured. Behavioral tests were conducted. Immunofluorescence staining was used to assess muscle morphology and analyze oligodendrocyte precursor cells (OPCs) lineage-related indicators. Results: Hindlimb immobilization induced sarcopenia in both AD and WT mice, manifested as decreased body, brain, gastrocnemius (Gas), and soleus (Sol) muscle weights. Immobilized mice showed decreased motor ability and impaired exploration behavior. Long-term spatial learning and memory were also affected. Muscle histological analysis revealed that AD mice exhibited baseline muscle fiber type switching. After immobilization, AD mice showed increased proportions of MyHC IIa fast-twitch fibers in the Sol and MyHC IIb fast-twitch fibers in the tibialis anterior (TA). At the central nervous system level, immobilization inhibited the OPCs proliferation and significantly increased activation of microglia and astrocytes of immobilized mice. Conclusion: Hindlimb immobilization-induced sarcopenia correlated with slow-to-fast fiber transformation, reduced OPCs proliferation, and enhanced neuroinflammation. This study highlights the importance of sarcopenia in the progression of AD-related white matter pathology.