Insulin action in phosphatidic acid (PA) formation in synaptic terminals from adult and aged rats.

ZULIAN, SANDRA E.; ILINCHETA DE BOSCHERO, MÓNICA G.; GIUSTO, NORMA M.

Villa Carlos Paz-Córdoba-Argentina

Congreso; XLIV Reunión Anual-Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2008

Insulin action in phosphatidic acid (PA) formation in synaptic terminals from adult and aged rats. Sandra E. Zulian, Mónica G. Ilincheta de Boschero and Norma M. Giusto. Instituto de Investigaciones Bioquímicas de Bahía Blanca (UNS-CONICET), Bahía Blanca, Argentina PA formation is stimulated by insulin in cerebral cortex (CC) synaptosomes from adult rats. DAGK acts in response to increased DAG generated by PIP2-PLC and PLD-PAP2 pathways, this action being reinforced by an additional DAGK activation mechanism exerted by the hormone. We carried out studies on CC and hippocampal (Hp) synaptosomes to evaluate basal and insulin-activated PA synthesis from exogenous di-16:0 (DPG), di-18:1 (DOG) and 18:0-20:4 (SAG) in adult (3 m of age) and aged (24-26 m of age) rats. DAGK assay shows detergent (OG) and substrate (SAG) preference as well as insensitivity to R59022 and R59949 (DAGK inhibitors), both of which indirectly indicate DAGKe activity under our assay conditions. The majority of CC synaptosomes processed for immunofluorescence reveal the presence of DAGKe rather than DAGKz. Also, whereas DAGs content is increased, DAGK activity is inhibited in CC synaptosomes from aged with respect to adult rats. PA formation from SAG in CC and Hp synaptosomes is preferentially diminished. However, DAGK is stimulated by insulin in synaptic terminals from Hp and CC from aged rats and hormone preferentially stimulates PA formation from SAG in Hp synaptosomes. Our results suggest that 20:4-PA formation is potentially involved in inositol lipid homeostasis at the synapse. This molecular mechanism could be one of the beneficial effects of insulin on the brain.