Significant metabolic deficits were observed in the superchiasmatic nucleus (SCN) of Tg2576 Alzheimer's disease mice.
Reductions in glucose, glutamate, , and glutamine indicate impaired GABAergic glucose oxidation and neurotransmitter cycling.
Low levels of the redox co-factor NADPH and glutathione suggest a state of redox disbalance.
There is decreased expression of the core clock protein Bmal1, particularly in activated astrocytes.
A reduction in GABA transporter 1 (GAT1) expression in astrocytes points to decreased GABA recycling.
Simplified
BACKGROUND: Circadian rhythm disturbance is commonly observed in Alzheimer's disease (AD). In mammals, these rhythms are orchestrated by the superchiasmatic nucleus (SCN). Our previous study in the Tg2576 AD mouse model suggests that inflammatory responses, most likely manifested by low production, may be one of the underlying perpetrators for the changes in circadian rhythmicity and sleep disturbance in AD. However, the mechanistic connections between SCN dysfunction, GABA modulation, and inflammation in AD is not fully understood.
OBJECTIVE: To reveal influences of amyloid pathology in Tg2576 mouse brain on metabolism in SCN and to identify key metabolic sensors that couple SCN dysfunction with GABA modulation and inflammation.
METHODS: High resolution magic angle spinning (HR-MAS) NMR in conjunction with multivariate analysis was applied for metabolic profiling in SCN of control and Tg2576 female mice. Immunohistochemical analysis was used to detect neurons, astrocytes, expression of GABA transporter 1 (GAT1) and Bmal1.
RESULTS: Metabolic profiling revealed significant metabolic deficits in SCN of . Reductions in glucose, glutamate, GABA, and glutamine provide hints toward an impaired GABAergic glucose oxidation and neurotransmitter cycling in SCN of AD mice. In addition, decreased redox co-factor NADPH and glutathione support a redox disbalance. Immunohistochemical examinations showed low expression of the core clock protein, Bmal1, especially in activated astrocytes. Moreover, decreased expression of GAT1 in astrocytes indicates low GABA recycling in this cell type.
CONCLUSION: Our results suggest that redox disbalance and compromised GABA signaling are important denominators and connectors between neuroinflammation and clock dysfunction in AD.
Key numbers
significantly reduced in SCN of
Decrease in levels
Comparison of levels in SCN of Tg2576 vs. wild-type mice.
Glucose and glutamate levels significantly decreased in SCN of
Reduction in glucose and glutamate
Metabolic profiling of SCN in Tg2576 vs. wild-type mice.
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