Abstracts

Rationale: The ketogenic diet (KD) has been used as the treatment for medically intractable epilepsy for nearly 90 years. Although how KD inhibits seizures is poorly characterized, metabolic alterations induced by ketone bodies could alter the concentration of glutamate and GABA. Recently, inhibiting glycolysis has been shown to have powerful antiepileptic effects by inhibiting brain-derived neurotrophic factor (BDNF) gene expression. This may give one possible mechanism how synaptic energy metabolism exerts as antiepileptic effects on the neuronal activity. On the other hand, growing evidences have been shown that microenviroment, a neuronal-glial communication, has been receiving renewed attention in epileptic patients. In fact, glial cells have a function as an integrator and a modulator of neuronal activity and synaptic transmission. Glial cells can synthesize and secret a large number of neuroactive compounds, including BDNF, suggesting that glial activity may play an important role in the acute and chronic seizures. In the present study, we investigated some biological and biochemical effects of beta-hydroxy butylate (b-HB), predominant blood ketone body, on rat cortical astrocytes cultures. Methods: Astrocyte primary cultures were prepared as a mixed glial culture from decapitated newborn rats. Purified-astrocytes were maintained in DMEM supplemented with 3% FCS. To investigate the effects of b-HB, b-HB treatment was performed under glucose free condition. GABA transaminase (GABA-T) activity of b-HB-treated astrocytes was assessed by NADH production, resulted in metabolized GABA in vitro. The gene expression BDNF in b-HB-treated astrocytes was analyzed by RT-PCR. Results: In primary astrocytes, GABA-T gene expression and enzymatic activity was significantly reduced by b-HB treatment. BDNF gene expression was also decreased with b-HB treatments. Conclusions: Our results show that b-HB treatment reduces GABA-T enzymatic activity as well as GABA-T gene expression in the primary astrocytes cultures. Reduced GABA-T activity may raise intracellular concentration of GABA, and enhance GABAnergic, neuronal inhibitory activity. b-HB also reduced BDNF gene expression, which shows the excitatory effect against seizures. In summary, these metabolic regulations by b-HB in astrocytes may be associated with the reduced neuronal excitability observed in the ketogenic condition.