Abstract-Clinical manifestations of diabetic nephropathy are an expression of diabetic microangiopathy. This review revisits the previously proposed Steno hypothesis and advances our hypothesis that development of endothelial cell dysfunction represents a common pathophysiological pathway of diabetic complications. Specifically, the ability of glucose to scavenge nitric oxide is proposed as the initiation phase of endothelial dysfunction. Gradual accumulation of advanced glycated end products and induction of plasminogen activator inhibitor-1, resulting in the decreased expression of endothelial nitric oxide synthase and reduced generation of nitric oxide, are proposed to be pathophysiologically critical for the maintenance phase of endothelial dysfunction. The proposed conceptual shift toward the role of endothelial dysfunction in diabetic complications may provide new strategies for their prevention. Key Words: nitric oxide synthase Ⅲ collagen Ⅲ plasminogen Ⅲ diabetes mellitus T ype 2 diabetes mellitus has reached epidemic proportions, and one of its ominous complications, diabetic nephropathy, represents today the leading cause of end-stage renal failure. 1,2 Clinical manifestations of diabetic nephropathy include microalbuminuria, heralding incipient nephropathy, followed by albuminuria or nephrotic-range proteinuria, elevated blood pressure, development of glomerulosclerosis, tubulointerstitial fibrosis, and relentless decline in glomerular filtration rate. [1][2][3][4] The most characteristic prognostic feature in this group of patients is the high risk of cardiovascular complications, much more so than in diabetics without nephropathy. Several important mediators of diabetic nephropathy have been proposed, such as transforming growth factor-␤, accumulation of the extracellular matrix, reactive oxygen intermediates, and protein kinase C, to name a few, and have been comprehensively reviewed. [1][2][3][4] However, the pathophysiological origin of clinical presentations of diabetic nephropathy can be traced back to microvasculopathy and macrovasculopathy (Figure 1), and the focus of this review will be on the mechanisms for development and maintenance of endothelial cell dysfunction in diabetic nephropathy.In 1988, Torsten Deckert delivered a Claude Bernard Lecture in which the Steno hypothesis, a unifying proposal that albuminuria of diabetic nephropathy is a sign of the global vascular dysfunction, was introduced. 5 Because only less than one third of patients with type I diabetes mellitus tend to develop renal disease, it was speculated that a genetic predisposition, supposedly at the level of N-deacetylase (a key enzyme responsible for the sulfation of heparan sulfate proteoglycans) gene polymorphism, contributes to the loss of the anionic charge barrier of endothelial cells and basement membranes, resulting in a widespread rise in vascular permeability and vasculopathy. The hypothesis to be developed below takes stock of the above broad view that albuminuria is an indicator of a systemic microvascular l...

Purpose: To investigate the distribution, frequency, and clinical significance of mobilized endothelial progenitor cells (EPC) in hepatocellular carcinoma (HCC). Experimental Design: In healthy controls and patients with HCC, the frequency of circulating EPCs was determined by colony-forming assays, fluorescence-activated cell sorting, and real-time PCR. One hundred sixty-five^amino acid form of vascular endothelial growth factor and platelet-derived growth factor-BB in plasma and tissue were quantified by ELISA. The distribution and frequency of EPCs were evaluated by immunofluorescence, immunohistochemistry, and real-time PCR in normal liver (n = 8), and tumor tissue (TT), adjacent nonmalignant liver tissue (AT), and tumor-free tissue 5 cm from the tumor edge (TF) from 64 patients with HCC. Clinicopathologic data for these patients were evaluated. Results: Compared with values for healthy controls, colony-forming unit scores were higher in the peripheral blood of patients with HCC. Plasma 165-amino acid form of vascular endothelial growth factor and platelet-derived growth factor-BB correlated with the expression level of the AC133 gene, which was also higher in the peripheral blood of patients with HCC. Immunohistochemical analysis showed that EPCs were incorporated into the microvessels in cirrhotic and tumor tissue. Compared with normal liver (9.00), increased AC133 + microvessel density (microvessels/0.74 mm 2

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Summary The causative agent of human African trypanosomiasis, Trypanosoma brucei, lacks de novo purine biosynthesis and depends on purine salvage from the host. The purine salvage pathway is redundant and contains two routes to guanosine-5′-monophosphate (GMP) formation: conversion from xanthosine-5′-monophosphate (XMP) by GMP synthase (GMPS) or direct salvage of guanine by hypoxanthine-guanine phosphoribosyltransferase (HGPRT). We show recombinant T. brucei GMPS efficiently catalyzes GMP formation. Genetic knockout of GMPS in bloodstream parasites led to depletion of guanine nucleotide pools and was lethal. Growth of gmps null cells was only rescued by supraphysiological guanine concentrations (100 μM) or by expression of an extrachromosomal copy of GMPS. Hypoxanthine was a competitive inhibitor of guanine rescue, consistent with a common uptake/metabolic conversion mechanism. In mice, gmps null parasites were unable to establish an infection demonstrating that GMPS is essential for virulence and that plasma guanine is insufficient to support parasite purine requirements. These data validate GMPS as a potential therapeutic target for treatment of HAT. The ability to strategically inhibit key metabolic enzymes in the purine pathway unexpectedly bypasses its functional redundancy by exploiting both the nature of pathway flux and the limited nutrient environment of the parasite's extracellular niche.