Comparative studies of early liver dysfunction in senescence-accelerated mouse using mitochondrial proteomics approaches.

The liver is a complex and unique organ responsible for a breadth of functions crucial to sustaining life, especially for various metabolic processes in its mitochondria. Senescence-accelerated mouse prone/8 (SAMP8), a widely used aging model, exhibits an oxidative stress-induced aging phenotype and severe mitochondria-related liver pathology that are not seen in senescence-accelerated mouse resistant/1 (SAMR1). Here we used both two-dimensional electrophoresis- and ICAT-based mitochondrial proteomics analysis to view the liver mitochondrial protein alterations between SAMP8 and SAMR1. Compared with SAMR1, decreased expression and activity of mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase were detected in SAMP8 at 6 months old (SAMP8-6m). As the key enzyme of ketogenesis, 3-hydroxy-3-methylglutaryl-CoA synthase is well known to be transcriptionally regulated by peroxisome proliferator-activated receptor alpha, which was also expressed at lower levels in SAMP8-6m livers. In addition, down-regulation of two peroxisome proliferator-activated receptor alpha target gene products (acyl-CoA oxidase and enoyl-CoA hydratase), elevation of triglyceride, and reduction of acetyl-CoA were observed, indicating abnormal fatty acid metabolism in SAMP8-6m livers. In addition eight proteins (NDUAA, NDUBA, NDUB7, NDUS1, NDUS3, NDUV1, ETFA, and UCRI) of mitochondrial complexes were down-regulated in SAMP8-6m, resulting in mitochondria-related liver dysfunction characterized by enhanced oxidative stress-induced molecular damage (lipid peroxide and oxidized protein) and depressed energy production (ATP). Glutamine synthetase and ornithine aminotransferase involved in glutamine synthesis were up-regulated in SAMP8 livers at both 1 and 6 months old that may be related to the accumulation of glutamate and glutamine. Our work provided useful clues to understanding the molecular mechanism underlying liver dysfunction in senescence-accelerated mouse.