Occlusal disharmony transiently decrease cognition via cognitive suppressor molecules and partially restores...

Area of Science:

• Neuroscience
• Oral Health
• Immunology

Background:

• Occlusal disharmony is linked to systemic physiological changes, including hormonal and neural alterations.
• The impact of occlusal disharmony on cognitive function, particularly learning and memory, remains poorly understood.
• Alzheimer's disease-associated molecules are implicated in cognitive regulation.

Purpose of the Study:

• To investigate the hypothesis that hyperocclusion (excessive biting force) impairs cognition through the expression of Alzheimer's disease-associated molecules in the brain.
• To elucidate the relationship between occlusal disharmony, central nervous system cytokine and cognitive-regulated molecule expression, and learning/memory deficits.

Main Methods:

• A hyperocclusion mouse model was utilized to assess the effects on cytokine expression, hippocampal cognitive suppressor molecules, and behavioral cognition.
• Mice of two age groups (2-month-old and 12-month-old) were subjected to hyperocclusal loading.
• Measurements included serum and hippocampal interleukin-1β, amyloid-β, phosphorylated tau, and cognitive suppressor clearing proteins, alongside behavioral tests.

Main Results:

• Hyperocclusion significantly increased interleukin-1β in young (2-month-old) mice's serum and hippocampus within one week, with no effect in older (12-month-old) mice.
• Young mice exhibited transiently reduced social and long-term cognitive abilities post-hyperocclusion, which recovered through the expression of cognitive suppressor clearing proteins.
• Amyloid-β and phosphorylated tau levels were elevated in the hippocampus of young mice after hyperocclusion, but remained unchanged in older mice.

Conclusions:

• Occlusal disharmony-induced interleukin-1β may drive the accumulation of cognitive suppressors like amyloid-β and phosphorylated tau.
• The brain activates clearance proteins to counteract these molecules, providing transient protection against cognitive impairment in young individuals.
• Older individuals do not exhibit the same protective response, suggesting age-dependent vulnerability to occlusal disharmony-related cognitive changes.