Endoplasmic reticulum (ER) stress & diabetes.

The endoplasmic reticulum (ER) is a central organelle entrusted with lipid synthesis, protein folding and protein maturation. It is endowed with a quality control system that facilitates the recognition and targeting of aberrant proteins for degradation. When the capacity of this quality control system is exceeded, a stress response (ER stress) is switched on. Prolonged stress leads to apoptosis and may thus be an important factor in the pathogenesis of many diseases. A complex homeostatic signaling pathway, known as the unfolded protein response (UPR), has evolved to maintain a balance between the load of newly synthesized proteins and the capacity of the ER to aid in their maturation. Dysfunction of the UPR plays an important role in certain diseases, especially those involving tissues dedicated to extracellular protein synthesis. Diabetes is an example of such a disease, since pancreatic beta-cells depend on efficient UPR signaling to meet the demands for constantly varying levels of insulin synthesis. Recent studies have indicated that the importance of the UPR in diabetes is not restricted to the beta-cell but also to tissues of peripheral insulin resistance such as liver and adipose tissue. Better understanding of the basic mechanisms of ER stress and development of insulin resistance/type 2 diabetes is pivotal for the identification of newer molecular targets for therapeutic interventions.

Proteomic analysis of urinary protein markers for accurate prediction of diabetic kidney disorder.

AIM OF THE STUDY: Microalbuminuria is currently the only diagnostic tool available for early diagnosis of diabetic nephropathy. The test is based on immunological detection of small quantities of albumin in the urinary samples of diabetes patients. There are several limitations of the use of microalbuminuria as an index of renal function. It is therefore desirable to identify additional protein markers that would augment prediction of diabetic nephropathy. The aim of this study is to identify urinary protein markers for specific and more accurate prediction of nephropathy in diabetes patients. DESIGN: 100 registered Type II diabetic patients were studied. Abundant proteins of microalbuminuria positive urinary samples of these patients were analyzed by proteomics approaches of 2-Dimentional Gel Electrophoresis (2DGE) and mass spectrometry. RESULTS: 2-DGE analysis of the urine sample revealed four main proteins along with albumin in these samples. These were zinc alpha-2 glycoprotein, alpha-1 acid glycoprotein, alpha-1 microglobulin and IgG as identified by Matrix Assisted Laser Desorption Ionization-Tune of Flight (MALDI-ToF) and by western blot. Twenty control samples and three cases with microalbuminuria negative to positive transition does suggest the early and co-appearance of the markers with albumin. We have also analyzed full length spectrum of these samples by MALDI-ToF. CONCLUSION: Our study shows the presence of additional proteins in urine samples of microalbuminuria positive diabetes patients. These proteins can be used as markers for specific and accurate clinical analysis of Diabetic nephropathy. We propose a mass spectrometry based high throughput diagnostic approach to detect these markers in the urine sample.