The pathogenesis of diabetic nephropathy remains poorly defined, and animal models that represent the human disease have been lacking. It was demonstrated recently that the severe endothelial dysfunction that accompanies a diabetic state may cause an uncoupling of the vascular endothelial growth factor (VEGF)-endothelial nitric oxide (eNO) axis, resulting in increased levels of VEGF and excessive endothelial cell proliferation. It was hypothesized further that VEGF-NO uncoupling could be a major contributory mechanism that leads to diabetic vasculopathy. For testing of this hypothesis, diabetes was induced in eNO synthase knockout mice (eNOS KO) and C57BL6 controls. Diabetic eNOS KO mice developed hypertension, albuminuria, and renal insufficiency with arteriolar hyalinosis, mesangial matrix expansion, mesangiolysis with microaneurysms, and Kimmelstiel-Wilson nodules. Glomerular and peritubular capillaries were increased with endothelial proliferation and VEGF expression. Diabetic eNOS KO mice showed increased mortality at 5 mo. All of the functional and histologic changes were improved with insulin therapy. Inhibition of eNO predisposes mice to classic diabetic nephropathy. The mechanism likely is due to VEGF-NO uncoupling with excessive endothelial cell proliferation coupled with altered autoregulation consequent to the development of preglomerular arteriolar disease. Endothelial dysfunction in human diabetes is common, secondary to effects of glucose, advanced glycation end products, C-reactive protein, uric acid, and oxidants. It was postulated that endothelial dysfunction should predict nephropathy and that correction of the dysfunction may prevent these important complications.

Fructose intake from added sugars has been implicated as a cause of nonalcoholic fatty liver disease. Here we tested the hypothesis that fructose may interact with high fat diet to induce fatty liver, and to determine if this was dependent on a key enzyme in fructose metabolism, fructokinase. Wild type or fructokinase knockout mice were fed a low fat (11%), high fat (36%) or high fat (36%) and high sucrose (30%) diet for 15 weeks. Both wild type and fructokinase knockout mice developed obesity with mild hepatic steatosis and no evidence for hepatic inflammation on a high fat diet compared to a low fat diet. In contrast, wild type mice fed a high fat and high sucrose diet developed more severe hepatic steatosis with low grade inflammation and fibrosis, as noted by increased CD68, TNF-alpha, MCP-1, alpha-smooth muscle actin, and collagen I and TIMP1 expression. These changes were prevented in the fructokinase knockout mice. Conclusion An additive effect of high fat and high sucrose diet on the development of hepatic steatosis exists. Further, the combination of sucrose with high fat diet may induce steatohepatitis. The protection in fructokinase knockout mice suggests a key role for fructose (from sucrose) in this development of steatohepatitis. These studies emphasize the important role of fructose in the development of fatty liver and nonalcoholic steatohepatitis (NASH).

Midkine (MK) is a multifunctional heparin-binding protein and promotes migration of neutrophils, macrophages, and neurons. In the normal mouse kidney, MK is expressed in the proximal tubules. After renal ischemic reperfusion injury, its expression in proximal tubules was increased. Immediate increase of MK expression was found when renal proximal tubular epithelial cells in culture were exposed to 5 mM H2O2. Histologically defined tubulointerstitial damage was less severe in MK-deficient (Mdk−/−) than in wild-type (Mdk+/+) mice at 2 and 7 days after ischemic reperfusion injury. Within 2 days after ischemic injury, inflammatory leukocytes, of which neutrophils were the major population, were recruited to the tubulointerstitium. The numbers of infiltrating neutrophils and also macrophages were lower in Mdk−/− than in Mdk+/+ mice. Induction of macrophage inflammatory protein-2 and macrophage chemotactic protein-1, chemokines for neutrophils and macrophages, respectively, were also suppressed in Mdk−/− mice. Furthermore, renal tubular epithelial cells in culture expressed macrophage inflammatory protein-2 in response to exogenous MK administration. These results suggested that MK enhances migration of inflammatory cells upon ischemic injury of the kidney directly and also through induction of chemokines, and contributes to the augmentation of ischemic tissue damage.

Metabolic syndrome, characterized by truncal obesity, hypertriglyceridemia, elevated BP, and insulin resistance, is recognized increasingly as a major risk factor for kidney disease and also is a common feature of patients who are on dialysis. One feature that is common to patients with metabolic syndrome is an elevated uric acid. Although often considered to be secondary to hyperinsulinemia, recent evidence supports a primary role for uric acid in mediating this syndrome. Specifically, fructose, which rapidly can cause metabolic syndrome in rats, also raises uric acid, and lowering uric acid in fructose-fed rats prevents features of the metabolic syndrome. Uric acid also can accelerate renal disease in experimental animals and epidemiologically is associated with progressive renal disease in humans. It is proposed that fructose-and purine-rich foods that have in common the raising of uric acid may have a role in the epidemic of metabolic syndrome and renal disease that is occurring throughout the world.J Am Soc Nephrol 17: S165-S168, . doi: 10.1681 T he metabolic syndrome is defined as a syndrome of truncal obesity, insulin resistance, elevated BP, hypertriglyceridemia, and hyperuricemia (Table 1) (1-4). The prevalence of metabolic syndrome has been increasing at an alarming rate throughout the world. In the United States, the current prevalence is estimated to be 27% (29% in women and 25.2% in men) (5); in Europe, it is 15.7% in men and 14.2% in women (6); and in China it is 13.7% (9.8% in men and 17.8% in women) (7).The presence of metabolic syndrome is strongly associated with the development of diabetes (8), hypertension (9), cardiovascular disease (10), and all-cause mortality (11). However, recent studies have emphasized that metabolic syndrome also is both associated with and a risk for the development of chronic kidney disease (CKD). For example, in a recent study, the metabolic syndrome was found to be strongly correlated with CKD (defined as GFR Ͻ60 ml/min) and microalbuminuria, and the risk increased progressively with the number of criteria constituting the syndrome (12). In another study of Native Americans without diabetes, a positive relationship was identified between microalbuminuria and features of the metabolic syndrome (13).The mechanism(s) by which metabolic syndrome might accelerate renal disease remains unclear. One possibility relates to the presence of obesity itself. Obesity has been found to be an independent risk factor for CKD (12,14), and treating obesity might stabilize renal function (15) or reverse early hemodynamic abnormalities and glomerular dysfunction (16). Obesity has been associated with a type of focal segmental glomerulosclerosis (FSGS) called "obesity-related glomerulopathy" (17).Hall et al. (18) proposed that lipid deposition in the inner medulla increases intrarenal pressure, leading to decreased tubular flow, which results in increased sodium reabsorption in Henle loop, volume expansion, and the development of systemic hypertension. Obesity also increases the risk...

Capillary electrophoresis coupled with time-of-flight mass spectrometry was used to explore new serum biomarkers with high sensitivity and specificity for diabetic nephropathy (DN) diagnosis, through comprehensive analysis of serum metabolites with 78 diabetic patients. Multivariate analyses were used for identification of marker candidates and development of discriminative models. Of the 289 profiled metabolites, orthogonal partial least-squares discriminant analysis identified 19 metabolites that could distinguish between DN with macroalbuminuria and diabetic patients without albuminuria. These identified metabolites included creatinine, aspartic acid, γ-butyrobetaine, citrulline, symmetric dimethylarginine (SDMA), kynurenine, azelaic acid, and galactaric acid. Significant correlations between all these metabolites and urinary albumin-to-creatinine ratios (p < 0.009, Spearman's rank test) were observed. When five metabolites (including γ-butyrobetaine, SDMA, azelaic acid and two unknowns) were selected from 19 metabolites and applied for multiple logistic regression model, AUC value for diagnosing DN was 0.927 using the whole dataset, and 0.880 in a cross-validation test. In addition, when four known metabolites (aspartic acid, SDMA, azelaic acid and galactaric acid) were applied, the resulting AUC was still high at 0.844 with the whole dataset and 0.792 with cross-validation. Combination of serum metabolomics with multivariate analyses enabled accurate discrimination of DN patients. The results suggest that capillary electrophoresis-mass spectrometry based metabolome analysis could be used for DN diagnosis.

The renin-angiotensin system plays a pivotal role in regulating blood pressure and is involved in the pathogenesis of kidney disorders and other diseases. Here, we report that the growth factor midkine is what we believe to be a novel regulator of the renin-angiotensin system. The hypertension induced in mice by 5/6 nephrectomy was accompanied by renal damage and elevated plasma angiotensin II levels and was ameliorated by an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin receptor blocker. Notably, ACE activity in the lung, midkine expression in the lung, and midkine levels in the plasma were all increased after 5/6 nephrectomy. Exposure to midkine protein enhanced ACE expression in primary cultured human lung microvascular endothelial cells. Furthermore, hypertension was not induced and renal damage was less severe in midkine-deficient mice. Supplemental administration of midkine protein to midkine-deficient mice restored ACE expression in the lung and hypertension after 5/6 nephrectomy. Oxidative stress might be involved in midkine expression, since expression of NADH/NADPH oxidase-1, -2, and -4 was induced in the lung after 5/6 nephrectomy. Indeed, the antioxidative reagent tempol reduced midkine expression and plasma angiotensin II levels and consequently ameliorated hypertension. These results suggest that midkine regulates the renin-angiotensin system and mediates the kidney-lung interaction after 5/6 nephrectomy.

Abstract. It has been postulated that protein filtered through glomeruli activates tubular epithelial cells, which secrete vasoactive and inflammatory substances including chemokines, leading to tubulointerstitial renal injury. The present study was designed to investigate the role of monocyte chemoattractant protein-1 (MCP-1) in this process and to evaluate the effectiveness of a kidney-targeted gene transfer technique using hydrodynamic pressure. Naked plasmid encoding 7ND (an MCP-1 antagonist) or a control plasmid was introduced into the left kidney of rats. Three days after gene transfer (day 0), intraperitoneal administration of bovine serum albumin (10 mg/g body wt per day) was started and continued for 14 or 21 d. RT-PCR showed that 7ND mRNA was expressed only in the gene-transfected kidney. Immunostaining showed that 7ND protein was localized in the interstitial cells. Macrophage infiltration was significantly reduced in the left kidney of rats treated with 7ND on days 14 and 21. In the right kidney, such effects were not observed. 7ND also attenuated tubular damage and decreased the number of apoptotic cells. Computer-assisted analysis revealed that the areas positively stained for ␣-smooth muscle actin (␣SMA), fibronectin-EDA, type I collagen, and collagen fibrils were significantly reduced in the 7ND-treated kidney on day 21. Furthermore, 7ND gene therapy significantly reduced MCP-1 and TGF-␤1 mRNA expression. These results demonstrate that MCP-1 plays an important role in the development of tubulointerstitial inflammation, tubular damage, and fibrosis induced by proteinuria. The fact that 7ND gene therapy had little effect on the contralateral kidney indicates that 7ND acted locally. This strategy may have a potential usefulness as a gene therapy against tubulointerstitial renal injury.Besides being a hallmark of glomerular disease, proteinuria has been shown to be an independent factor that induces and maintains renal damage. Cellular infiltration and fibrosis in the interstitium are common characteristics for virtually all progressive renal diseases with proteinuria. It has been postulated that protein filtered through glomeruli activates tubular epithelial cells, induces cellular infiltration into the interstitium, and subsequently causes interstitial fibrosis (1). Secretion of vasoactive mediators (e.g., endothelins), and chemokines, (e.g., monocyte chemoattractant protein-1 [MCP-1] and osteopontin) are induced in the tubules by protein-overload proteinuria (2,3). These substances are considered to promote inflammation and fibrosis of the interstitium, resulting in renal scarring (4,5). From among these mediators, we focused on MCP-1, a C-C chemokine with potent monocyte chemotactic and activating properties. It has been shown that MCP-1 is upregulated in various experimental and human renal diseases (6,7). MCP-1 expression is enhanced in tubular cells by bovine serum albumin (BSA) via a NF-B-dependent pathway (8). MCP-1 can also induce fibrosis through recruitment and activation of macrophages t...

E-selectin and its ligands are essential for extravasation of leukocytes in inflammation. Here, we report that basigin (Bsg)/CD147 is a ligand for E-selectin that promotes renal inflammation in ischemia/ reperfusion. The selectins and their ligands are essential for leukocyte tethering/rolling on endothelial cells and the initiation of inflammatory response. The selectins are C-type lectins and consist of three members, i.e., P-, L-, and E-selectin. 1,2 P-selectin is expressed upon inflammatory stimulation in platelets and endothelial cells. L-selectin is constitutively expressed on the tip of leukocyte microvilli and implicated in lymphocyte homing to lymph nodes. 3 E-selectin is specifically induced in the endothelium upon inflammatory stimulation. Thus, E-and P-selectin closely collaborate with one another and play a major role in leukocyte recruitment to inflammatory sites. 4 -6 Among the several glycoproteins reported to bind to E-selectin, three have been identified as representative physiologic E-selectin ligands on neutrophils. There are P-selectin glycoprotein ligand-1 (PSGL-1), E-selectin ligand-1, and CD44, and all three play distinct roles during tethering and slow rolling of neutrophils on the endothelium. 7 A minimal recognition motif for all selectins is sialylated and fucosylated glycan determinants, such as sialyl Lewis X, that decorate the terminal extensions of carbohydrates of these molecules. 8,9 However, because of the poor immunogenicity of highly gly-