OBJECTIVE— Glomerular mesangial expansion and podocyte loss are important early features of diabetic nephropathy, whereas tubulointerstitial injury and fibrosis are critical for progression of diabetic nephropathy to kidney failure. Therefore, we analyzed the expression of genes in glomeruli and tubulointerstitium in kidney biopsies from diabetic nephropathy patients to identify pathways that may be activated in humans but not in murine models of diabetic nephropathy that fail to progress to glomerulosclerosis, tubulointerstitial fibrosis, and kidney failure. RESEARCH DESIGN AND METHODS— Kidney biopsies were obtained from 74 patients (control subjects, early and progressive type 2 diabetic nephropathy). Glomerular and tubulointerstitial mRNAs were microarrayed, followed by bioinformatics analyses. Gene expression changes were confirmed by real-time RT-PCR and immunohistological staining. Samples from db/db C57BLKS and streptozotocin-induced DBA/2J mice, commonly studied murine models of diabetic nephropathy, were analyzed. RESULTS— In human glomeruli and tubulointerstitial samples, the Janus kinase (Jak)-signal transducer and activator of transcription (Stat) pathway was highly and significantly regulated. Jak-1, -2, and -3 as well as Stat-1 and -3 were expressed at higher levels in patients with diabetic nephropathy than in control subjects. The estimated glomerular filtration rate significantly correlated with tubulointerstitial Jak-1, -2, and -3 and Stat-1 expression ( R 2 = 0.30–0.44). Immunohistochemistry found strong Jak-2 staining in glomerular and tubulointerstitial compartments in diabetic nephropathy compared with control subjects. In contrast, there was little or no increase in expression of Jak/Stat genes in the db/db C57BLKS or diabetic DBA/2J mice. CONCLUSIONS— These data suggest a direct relationship between tubulointerstitial Jak/Stat expression and progression of kidney failure in patients with type 2 diabetic nephropathy and distinguish progressive human diabetic nephropathy from nonprogressive murine diabetic nephropathy.

Pennathur S, Brosius FC III. Rosiglitazone reduces renal and plasma markers of oxidative injury and reverses urinary metabolite abnormalities in the amelioration of diabetic nephropathy. Am J Physiol Renal Physiol 295: F1071-F1081, 2008. First published July 30, 2008 doi:10.1152/ajprenal.90208.2008.-Recent studies suggest that thiazolidinediones ameliorate diabetic nephropathy (DN) independently of their effect on hyperglycemia. In the current study, we confirm and extend these findings by showing that rosiglitazone treatment prevented the development of DN and reversed multiple markers of oxidative injury in DBA/2J mice made diabetic by lowdose streptozotocin. These diabetic mice developed a 14.2-fold increase in albuminuria and a 53% expansion of renal glomerular extracellular matrix after 12 wk of diabetes. These changes were largely abrogated by administration of rosiglitazone beginning 2 wk after the completion of streptozotocin injections. Rosiglitazone had no effect on glycemic control. Rosiglitazone had similar effects on insulin-treated diabetic mice after 24 wk of diabetes. Podocyte loss and glomerular fibronectin accumulation, other markers of early DN, were prevented by rosiglitazone in both 12-and 24-wk diabetic models. Surprisingly, glomerular GLUT1 levels did not increase and nephrin levels did not decrease in the diabetic animals; neither changed with rosiglitazone. Plasma and kidney markers of protein oxidation and lipid peroxidation were significantly elevated in the 24-wk diabetic animals despite insulin treatment and were reduced to near-normal levels by rosiglitazone. Finally, urinary metabolites were markedly altered by diabetes. Of 1,988 metabolite features identified by electrospray ionization time of flight mass spectrometry, levels of 56 were altered more than twofold in the urine of diabetic mice. Of these, 21 were returned to normal by rosiglitazone. Thus rosiglitazone has direct effects on the renal glomerulus to reduce reactive oxygen species accumulation to prevent type 1 diabetic mice from development of DN. diabetes; thiazolidinedione; kidney; complications; metabolomics; mass spectrometry EARLY CLINICAL DIABETIC NEPHROPATHY (DN) is characterized by progressive increases in albuminuria which are associated with the development of characteristic histopathological features including thickening of the glomerular basement membrane and mesangial expansion due to accumulation of extracellular matrix proteins (25). One of the areas of general agreement about the pathogenesis of DN is that hyperglycemia and altered hemodynamic properties of diabetic glomeruli lead to multiple changes. These include enhanced expression of the facilitative glucose transporter, GLUT1, leading to enhanced glucose uptake (5, 17), enhanced expression and activation of PKC isoforms, and activation of transforming growth factor (TGF)-␤, which in turn induce increased synthesis and decreased degradation of extracellular matrix proteins such as fibronectin and collagen IV by mesangial cells in the glomerulus (52)...

Objective-We hypothesized that GLUT4 is a predominant facilitative glucose transporter in vascular smooth muscle cells (VSMCs), and GLUT4 is necessary for agonist-induced VSMC contraction. Methods and Results-Glucose deprivation and indinavir, a GLUT4 antagonist, were used to assess the role of GLUT4and non-GLUT4 transporters in vascular reactivity. In isolated endothelium-denuded mouse aorta, Ϸ50% of basal glucose uptake was GLUT4-dependent. Norepinephrine-mediated contractions were dependent on both GLUT4 and non-GLUT4 transporters, serotonin (5-HT)-mediated contractions were mainly GLUT4-dependent, and prostaglandin (PG) F 2␣ -mediated contractions were dependent on non-GLUT4 transporters, whereas indinavir had no effect in GLUT4 knockout vessels. We also observed a 46% decrease in GLUT4 expression in aortas from angiotensin II hypertensive mice. Indinavir caused a less profound attenuation of maximal 5-HT-mediated contraction in these vessels, corresponding to the lower GLUT4 levels in the hypertensive aortas. Finally, and somewhat surprisingly, chronic GLUT4 knockout was associated with increased vascular reactivity compared with that in wild-type animals, suggesting that chronic absence or reduction of GLUT4 expression in VSMCs leads to opposite effects observed with acute inhibition of GLUT4. Conclusions-Thus, we conclude that GLUT4 is constitutively expressed in large arteries and likely participates in basal glucose uptake. In addition, GLUT4, as well as other non-GLUT4 facilitative glucose transporters, are necessary for agonist-induced contraction, but each transporter participates in VSMC contraction selectively, depending on the agonist, and changes in GLUT4 expression may account for some of the functional changes associated with vascular diseases like hypertension. Key Words: glucose Ⅲ GLUT4 Ⅲ indinavir Ⅲ vascular smooth muscle M ammalian cells use glucose for the generation of ATP through oxidative and nonoxidative metabolism, but because the lipid bilayer of cellular membranes is impermeable to carbohydrates, the cell must rely on a system of hexose transporters to facilitate uptake of these sugars. To date, at least 13 facilitative glucose transporters have been cloned. 1 The GLUT transporters are homologous glycosylated polypeptides with distinct substrate specificity, affinity, and tissue distribution. 2 GLUT4 is considered the major insulin-responsive transporter expressed in fat and striated muscle tissues. 2 In these tissues, the majority of GLUT4 molecules (Ϸ90%) are sequestered in intracellular vesicles in the absence of insulin or other stimuli such as muscle contraction. 3,4 In the presence of these stimuli, the GLUT4-containing vesicles translocate to the plasma membrane where they participate in glucose uptake.Vascular smooth muscle has been shown to express GLUT1 5 as well as GLUT4. 6 -10 However, the expression of other facilitative glucose transporters in vascular smooth muscle is unknown. Previous studies from our laboratory have demonstrated that in vascular diseases caused by ...