Abstract. in order to increase our understanding of diabetes-related muscle weakness, we carried out a mass spectrometry-based proteomic analysis of skeletal muscle preparations from the Goto-Kakizaki rat model of type-2 diabetes. Fluorescence difference in-gel electrophoresis was performed to determine potential differences in the global protein expression profile of muscle extracts. Besides changes in contractile proteins and metabolic enzymes, the abundance of the small stress proteins αB-crystallin and Hsp27 was significantly increased. The up-regulation of the lowmolecular-mass heat shock protein Hsp27 was confirmed by an alternative fluorescent staining method of two-dimensional gels and immunoblotting. The observed protein alterations in the cellular stress response, distinct metabolic pathways, regulatory mechanisms and the contractile apparatus might be directly or indirectly associated with peripheral resistance to insulin signalling, making these newly identified muscle proteins potential biomarkers of type-2 diabetes. increased levels of molecular chaperones suggest considerably enhanced cellular stress levels in diabetic muscle fibres.
IntroductionThe application of gel electrophoresis-based proteomics in diabetes research is a fast growing field (1), including the proteomic analysis of diabetic skeletal muscle tissues (2-7). Since diabetes is increasingly prevalent in the general population, research into the complex pathophysiological mechanisms that underlie abnormal signaling in crucial target organs, such as skeletal muscle, is of central importance (8-10). It is now clear that type-2 diabetes mellitus represents a group of heterogeneous disorders with abnormal expression patterns in various genes and protein products (11-13). Peripheral insulin resistance in the liver, adipose tissue and muscles, as well as impaired pancreatic β-cell functioning, are the principal features of type-2 diabetes (11). The worldwide incidence of type-2 diabetes is dramatically increasing (14) and it has been estimated that the incidence of diabetes will rise to a staggering 4.4% by the year 2030, with 366 million affected patients (15). Importantly, type-2 diabetes is associated with a loss of skeletal muscle mass and contractile strength (16-19) warranting detailed investigations into diabetes-related muscle weakness (20). In this respect, large-scale biochemical approaches, such as gel electrophoresis-based proteomics, are ideal analytical tools for an unbiased identification of novel protein factors that are associated with abnormal functioning in diabetic fibres.High-resolution two-dimensional gel electrophoresis has long been established as one of the most powerful biochemical techniques for the comparative analysis of large protein complements (21-23). The more recent combination of advanced gel electrophoretic methods with mass spectrometry has further reinforced the central importance of gel electrophoretic techniques for analytical protein chemistry (24-26). The unprecedented advancements of mass spectrome...