Brain bioenergetics in rats with acute hyperphenylalaninemia

Area of Science:

• Biochemistry
• Neuroscience
• Metabolic Disorders

Background:

• Phenylketonuria (PKU) is an inherited metabolic disorder characterized by deficient phenylalanine hydroxylase (PAH) activity.
• Elevated phenylalanine (Phe) levels in PKU patients lead to severe neurological complications, including intellectual deficits and hypomyelination.
• Understanding the impact of hyperphenylalaninemia (HPA) on brain bioenergetics is crucial for developing effective therapeutic strategies.

Purpose of the Study:

• To investigate the acute effects of induced hyperphenylalaninemia (HPA) on brain energy metabolism in a rat model.
• To assess alterations in mitochondrial function, key metabolic enzyme activities, and energy substrate levels in different brain regions.

Main Methods:

• Wistar rats were induced into a hyperphenylalaninemia (HPA) state via subcutaneous administration of phenylalanine (Phe) and a PAH inhibitor (p-Cl-Phe).
• Control rats received a saline injection.
• Brain bioenergetics were assessed in cerebral cortex, striatum, and hippocampus by measuring mitochondrial mass, enzyme activities, metabolite levels, and gene expression.

Main Results:

• HPA rats exhibited reduced mitochondrial mass, glycogen levels, and activities of key respiratory chain complexes (I-IV, ATP synthase) in the cerebral cortex.
• Alterations in metabolic enzyme activities (LDH, α-KGDH, IDH, PDH) and energy status markers (Pi, phospho-AMPK) were observed across cerebral cortex, striatum, and hippocampus.
• Specific changes included decreased pyruvate dehydrogenase and Complex IV activities in the hippocampus and striatum, respectively.

Conclusions:

• Acute hyperphenylalaninemia significantly impairs brain bioenergetics in multiple regions, including the cerebral cortex, striatum, and hippocampus.
• These findings highlight the detrimental effects of elevated Phe on neuronal energy production and mitochondrial function.
• The study provides insights into the biochemical mechanisms underlying neurological deficits in PKU.