THE MOUSE LIVER DISPLAYS CIRCADIAN RHYTHMS IN LIPID CONTENT AND EXPRESSION OF SYNTHESIZING ENZYMES

GORNE, LUCAS D.; ACOSTA RODRIGUEZ, VICTORIA A.; GUIDO, MARIO E.

Mendoza

Congreso; 48 Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2012

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular - SAIB -

Biological clocks are present in different tissues distributed all through the body. In the liver, circadian clocks regulate diverse metabolic processes under a daily basis. In this respect, the temporal control of phospholipids synthesis and particularly of phosphatidylcholine (PC) in the mammalian liver is little known. In the present work, we investigated the circadian variation in the composition of membrane phospholipids (PC, PE, PI). Focused on PC, the most abundant phospholipid, we examined the temporal expression of its synthesizing enzymes choline kinase (CK), cytidylyltransferase (CCT) and phospatidylethanolamine methyl transferase (PEMT). For this, C57BL/6J mice synchronized to a 12:12 h light dark (LD) cycle or kept in constant dark (DD) were euthanized at different times and livers collected for further assays. mRNA levels were determined by RT-qPCR using the clock gene Bmal1 as a positive marker of circadian rhythmicity. We found significant changes in the content of different phospholipids (PI, PE, etc) and in the ratio of PC/PE in both LD and DD. Also, a significant circadian oscillation was found in mRNAlevels of CKa in LD and DD and of PEMT in DD, and a slight LD variation in CKa protein and activity. These results strongly suggest that there is a tight clock driven-control on the phospholipid metabolism and expression of synthesizing enzymes in the liver of mice.