A 100-kDa urinary protein is associated with insulin resistance in offspring of type 2 diabetic patients

A cost-effective method for purification and characterization of human urinary albumin

We describe a simplified approach for the purification and characterization of urinary albumin, a key biomarker currently used for understanding the onset and prognosis of microalbuminuria. Urinary albumin was purified from human urine collected from diabetic kidney disease patients by using 2-stage tangential flow filtration process and set of column chromatography steps. The relative molecular mass of urinary albumin is 66,871 Da (SYNAPT G2 High Definition Mass Spectrometry System). Isolated urinary albumin was analyzed by SDS-PAGE, Western blotting, immunoelectrophoresis, Ouchterlony double-immunodiffusion, single radial immunodiffusion, size-exclusion HPLC and peptide mass fingerprint analysis. The size-exclusion HPLC elution profile of the purified urinary albumin was similar to that of a reference form of native albumin. Peptide mass fingerprint analysis of the purified urinary albumin yielded peptides that partially matched with known sequence of ALBU_HUMAN (P02768). This is the first report of purification and validation of immunochemically reactive form of urinary albumin from a large volume of urine of diabetic kidney disease patients. In this purification approach, the cost of the purified albumin is significantly lower.

Glomerular epithelial cells in the urine: what has to be done to make them worthwhile?

The significance of the native urine sediment in the differential of glomerular diseases needs no further comment. However, the question arises whether it could be useful to develop a more specific diagnostic approach to identify the origin of renal epithelial cells that can be detected in the urine sediments as well. Especially the detection of podocytes in the urine could be a valuable noninvasive method to get information about the disease activity or disease type and could be used as a follow-up after a biopsy in an outpatient setting. So far, there are only a few studies that analyzed the clinical relevance of renal epithelial cells in the urine systematically or prospectively. The reason for this could be the nature of the material since it will remain unclear whether detachment and changes in the urine milieu have a direct effect on the expression of marker proteins on the detected cells. Dedifferentiation or transdifferentiation of cells that goes along with changed marker expression is certainly also part of the underlying disease process. This review summarizes the available information on marker proteins that have been successfully used in the diagnostic of "podocytes" in the urine. Furthermore, it gives an overview of marker expression on podocytes in situ in development and disease and examines the role of glomerular epithelial shedding in the urine at the interface of basic science and clinical medicine.

Insulin resistance in diabetic nephropathy--cause or consequence?

Insulin resistance (IR) is associated with multiple risk factors for cardiovascular disease. Many studies have shown that IR is present in chronic renal failure (CRF), and recent evidence suggests that IR can also occur in the early stages of renal disease. Patients with diabetic nephropathy (DN) have an increase in cardiovascular mortality, and since IR may be a contributing factor, this emphasizes the importance of a detailed understanding of the mechanisms linking IR and renal dysfunction at different stages of DN. IR can be detected early on in DN, e.g. at the stage of microalbuminuria (MA) and this could indicate a common genetic trait for IR and DN. As DN progresses further, IR is aggravated and it may, in addition to other factors, possibly accelerate the decline in renal function toward end-stage renal disease (ESRD). Several potentially modifiable mechanisms including circulating hormones, neuroendocrine pathways and chronic inflammation, are said to contribute to the worsening of IR. In ESRD, uremic toxins are of major importance. In this review article, we address the association between different stages of DN and IR and attempt to summarize major findings on potential mechanisms linking DN and IR. We conclude that IR is a consequence, and potentially also a cause of DN. In addition, there are probably genetic and environmental background factors that predispose to both IR and DN.