There is a rapid global rise in obesity, and the link between obesity and diabetes remains somewhat obscure. We identified an adipocytokine, designated as visceral adipose tissue-derived serpin (vaspin), which is a member of serine protease inhibitor family. Vaspin cDNA was isolated by from visceral white adipose tissues (WATs) of Otsuka Long-Evans Tokushima fatty (OLETF) rat, an animal model of abdominal obesity with type 2 diabetes. Rat, mouse, and human vaspins are made up of 392, 394, and 395 amino acids, respectively; exhibit Ϸ40% homology with ␣1-antitrypsin; and are related to serine protease inhibitor family. Vaspin was barely detectable in rats at 6 wk and was highly expressed in adipocytes of visceral WATs at 30 wk, the age when obesity, body weight, and insulin levels peak in OLETF rats. The tissue expression of vaspin and its serum levels decrease with worsening of diabetes and body weight loss at 50 wk. The expression and serum levels were normalized with the treatment of insulin or insulinsensitizing agent, pioglitazone, in OLETF rats. Administration of vaspin to obese CRL:CD-1 (ICR) (ICR) mice fed with high-fat highsucrose chow improved glucose tolerance and insulin sensitivity reflected by normalized serum glucose levels. It also led to the reversal of altered expression of genes relevant to insulin resistance, e.g., leptin, resistin, TNF␣, glucose transporter-4, and adiponectin. In DNA chip analyses, vaspin treatment resulted in the reversal of expression in Ϸ50% of the high-fat high-sucroseinduced genes in WATs. These findings indicate that vaspin exerts an insulin-sensitizing effect targeted toward WATs in states of obesity.metabolic syndrome ͉ diabetes ͉ insulin resistance ͉ mesenteric ͉ white adipose tissue

Diabetic nephropathy is a well-known complication of diabetes and is a leading cause of chronic renal failure in the Western world. It is characterized by the accumulation of extracellular matrix in the glomerular and tubulointerstitial compartments and by the thickening and hyalinization of intrarenal vasculature. The various cellular events and signaling pathways activated during diabetic nephropathy may be similar in different cell types. Such cellular events include excessive channeling of glucose intermediaries into various metabolic pathways with generation of advanced glycation products, activation of protein kinase C, increased expression of transforming growth factor β and GTP-binding proteins, and generation of reactive oxygen species. In addition to these metabolic and biochemical derangements, changes in the intraglomerular hemodynamics, modulated in part by local activation of the renin-angiotensin system, compound the hyperglycemia-induced injury. Events involving various intersecting pathways occur in most cell types of the kidney.

Diabetic nephropathy is characterized by excessive amassing of extracellular matrix (ECM) with thickening of glomerular and tubular basement membranes and increased amount of mesangial matrix, which ultimately progress to glomerulosclerosis and tubulo-interstitial fibrosis. In view of this outcome, it would mean that all the kidney cellular elements, i.e., glomerular endothelia, mesangial cells, podocytes, and tubular epithelia, are targets of hyperglycemic injury. Conceivably, high glucose activates various pathways via similar mechanisms in different cell types of the kidney except for minor exceptions that are related to the selective expression of a given molecule in a particular renal compartment. To begin with, there is an obligatory excessive channeling of glucose intermediaries into various metabolic pathways with generation of advanced glycation products (AGEs), activation of protein kinase C (PKC), increased expression of transforming growth factor-beta (TGF-beta), GTP-binding proteins, and generation of reactive oxygen species (ROS). The ROS seem to be the common denominator in various pathways and are central to the pathogenesis of hyperglycemic injury. In addition, there are marked alterations in intraglomerular hemodynamics, i.e., hyperfiltration, and this along with metabolic derangements adversely compounds the hyperglycemia-induced injury. Here, the information compiled under various subtitles of this article is derived from an enormous amount of data summarized in several excellent literature reviews, and thus their further reading is suggested to gain in-depth knowledge of each of the subject matter.

Glomerular basement membranes (GBM's) were subjected to digestion in situ with glycosaminoglycan-degrading enzymes to assess the effect of removing glycosaminoglycans (GAG) on the permeability of the GBM to native ferritin (NF) . Kidneys were digested by perfusion with enzyme solutions followed by perfusion with NF . In controls treated with buffer alone, NF was seen in high concentration in the capillary lumina, but the tracer did not penetrate to any extent beyond the lamina rara interna (LRI) of the GBM, and little or no NF reached the urinary spaces . Findings in kidneys perfused with Streptomyces hyaluronidase (removes hyaluronic acid) and chondroitinase-ABC (removes hyaluronic acid, chondroitin 4-and 6-sulfates, and dermatan sulfate, but not heparan sulfate) were the same as in controls . In kidneys digested with heparinase (which removes most GAG including heparan sulfate), NF penetrated the GBM in large amounts and reached the urinary spaces .Increased numbers of tracer molecules were found in the lamina densa (LD) and lamina rara externa (LRE) of the GBM . In control kidneys perfused with cationized ferritin (CF), CF bound to heparansulfate rich sites demonstrated previously in the laminae rarae; however, no CF binding was seen in heparinase-digested GBM's, confirming that the sites had been removed by the enzyme treatment.The results demonstrated that removal of heparan sulfate (but not other GAG) leads to a dramatic increase in the permeability of the GBM to NF .There is now widespread agreement that the glomerular basement membrane (GBM) is the main filtration barrier serving to retain plasma proteins in the circulation, and that it has both size-selective and charge-selective properties (1,3,15,16) . Little is known, however, about the role of GBM components in establishing these properties . We have recently presented cytochemical evidence (based on removal with specific enzymes) demonstrating the presence of anionic sites consisting of glycosaminoglycans (GAG) rich in heparan sulfate in the laminae rarae (interna and externa) of the GBM (7) . We have subsequently isolated GAG from purified GBM and have confirmed by quantitative biochemical analysis the presence of GAG (heparan sulfate and hyaluronic acid) in the GBM (8) . Upon fording the GAG, we speculated that these highly charged polymers might play a role in establishing the permeability properties of the GBM to plasma proteins. We here present data that indicate the removal of GAG (heparan sulfate) from the GBM leads to increased permeability of the GBM to native ferritin (NF), thereby providing direct experimental support for this suggestion. MATERIALS AND METHODS MaterialsMale Charles River CD" rats weighing 100-150 g were used . Chondroitinase-ABC (P. vulgaris) and Streptomyces hyaluronidase were purchased from Miles Laboratories, Inc. (Elkhart, Ind.). Heparinase was prepared from F. heparinum (11) . Horse-spleen ferritin (two times crystallized, cadmium free) was obtained from Calbiochem-Behring Corp., American Hoechst Corp . (...

Diabetic nephropathy is a leading cause of end-stage renal failure worldwide. Its morphologic characteristics include glomerular hypertrophy, basement membrane thickening, mesangial expansion, tubular atrophy, interstitial fibrosis and arteriolar thickening. All of these are part and parcel of microvascular complications of diabetes. A large body of evidence indicates that oxidative stress is the common denominator link for the major pathways involved in the development and progression of diabetic micro- as well as macrovascular complications of diabetes. There are a number of macromolecules that have been implicated for increased generation of reactive oxygen species (ROS), such as, NAD(P)H oxidase, advanced glycation end products (AGE), defects in polyol pathway, uncoupled nitric oxide synthase (NOS) and mitochondrial respiratory chain via oxidative phosphorylation. Excess amounts of ROS modulate activation of protein kinase C, mitogen-activated protein kinases, and various cytokines and transcription factors which eventually cause increased expression of extracellular matrix (ECM) genes with progression to fibrosis and end stage renal disease. Activation of renin-angiotensin system (RAS) further worsens the renal injury induced by ROS in diabetic nephropathy. Buffering the generation of ROS may sound a promising therapeutic to ameliorate renal damage from diabetic nephropathy, however, various studies have demonstrated minimal reno-protection by these agents. Interruption in the RAS has yielded much better results in terms of reno-protection and progression of diabetic nephropathy. In this review various aspects of oxidative stress coupled with the damage induced by RAS are discussed with the anticipation to yield an impetus for designing new generation of specific antioxidants that are potentially more effective to reduce reno-vascular complications of diabetes.

Diabetic kidney disease (DKD) is associated with oxidative stress and mitochondrial injury. Myo-inositol oxygenase (MIOX), a tubular-specific enzyme, modulates redox imbalance and apoptosis in tubular cells in diabetes, but these mechanisms remain unclear. We investigated the role of MIOX in perturbation of mitochondrial quality control, including mitochondrial dynamics and autophagy/mitophagy, under highglucose (HG) ambience or a diabetic state. HK-2 or LLC-PK1 cells subjected to HG exhibited an upregulation of MIOX accompanied by mitochondrial fragmentation and depolarization, inhibition of autophagy/ mitophagy, and altered expression of mitochondrial dynamic and mitophagic proteins. Furthermore, dysfunctional mitochondria accumulated in the cytoplasm, which coincided with increased reactive oxygen species generation, Bax activation, cytochrome C release, and apoptosis. Overexpression of MIOX in LLC-PK1 cells enhanced the effects of HG, whereas MIOX siRNA or D-glucarate, an inhibitor of MIOX, partially reversed these perturbations. Moreover, decreasing the expression of MIOX under HG ambience increased PTEN-induced putative kinase 1 expression and the dependent mitofusin-2-Parkin interaction. In tubules of diabetic mice, increased MIOX expression and mitochondrial fragmentation and defective autophagy were observed. Dietary supplementation of D-glucarate in diabetic mice decreased MIOX expression, attenuated tubular damage, and improved renal functions. Notably, D-glucarate administration also partially attenuated mitochondrial fragmentation, oxidative stress, and apoptosis and restored autophagy/mitophagy in the tubular cells of these mice. These results suggest a novel mechanism linking MIOX to impaired mitochondrial quality control during tubular injury in the pathogenesis of DKD and suggest D-glucarate as a potential therapeutic agent for the amelioration of DKD.

A 36-kDa ␤-galactoside mammalian lectin protein, designated as galectin-9, was isolated from mouse embryonic kidney by using a degenerate primer polymerase chain reaction and cloning strategy. Its deduced amino acid sequence had the characteristic conserved sequence motif of galectins. Endogenous galectin-9, extracted from liver and thymus, as well as recombinant galectin-9 exhibited specific binding activity for the lactosyl group. It had two distinct N-and C-terminal carbohydrate-binding domains connected by a link peptide, with no homology to any other protein. Galectin-9 had an alternate splicing isoform, exclusively expressed in the small intestine with a 31-amino acid insertion between the N-terminal domain and link peptide. Sequence homology analysis revealed that the C-terminal carbohydrate-binding domain of mouse galectin-9 had extensive similarity to that of monomeric rat galectin-5. The presence of galectin-5 in the mouse could not be demonstrated by polymerase chain reaction or by Northern or Southern blot genomic DNA analyses. Sequence comparison of rat galectin-5 and rat galectin-9 cDNA did not reveal identical nucleotide sequences in the overlapping C-terminal carbohydrate-binding domain, indicating that galectin-9 is not an alternative splicing isoform of galectin-5. However, galectin-9 had a sequence identical with that of its intestinal isoform in the overlapping regions in both species. Southern blot genomic DNA analyses, using the galectin-9 specific probe derived from the N-terminal carbohydrate-binding domain, indicated the presence of a novel gene encoding galectin-9 in both mice and rats. In contrast to galectin-5, which is mainly expressed in erythrocytes, galectin-9 was found to be widely distributed, i.e. in liver, small intestine, thymus > kidney, spleen, lung, cardiac and skeletal muscle > reticulocyte, brain. Collectively, these data indicate that galectin-9 is a new member of the galectin gene family and has a unique intestinal isoform.There is growing evidence that specific carbohydrate moieties and their putative binding proteins, i.e. lectins, play diverse roles in mammalian physiology and development and in various pathological states (1). The mammalian lectins are classified into four categories, C-type lectins (including selectins), P-type lectins, pentraxins, and galectins; the latter are referred to as S-type or S-Lac lectins (2, 3). Galectins are endowed with two essential biochemical properties: 1) characteristic amino acid homologous sequences; and 2) affinity for ␤-galactoside sugars, i.e. carbohydrate-binding domain. In addition, all the known galectins lack a signal peptide, have a cytoplasmic localization, and are secreted as soluble proteins by a nonclassical secretory pathway (4). Seven mammalian galectins, i.e. galectins-1 (5), -2 (6), -3 (7), -4 (8), -5 (9), -7 (10, 11), and -8 (12), have been cloned and characterized. Structural analyses of various galectins indicate the presence of homodimers of carbohydrate-binding domains in galectin-1 and galectin-2, a monom...

Cationized ferritin (CF) of narrow pI range (7.3-7.5) and the basic dye ruthenium red (RR) have been used as cationic probes to partially characterize anionic sites previously demonstrated in the glomerular basement membrane (GBM). When CF was given i.v. to normal rats and the left kidney was fixed by perfusion 15 min thereafter, clusters of CF molecules were found throughout the lamina rara interna (LRI), lamina rara externa (LRE), and mesangial matrix distributed at regular (-60 nm) intervals. When kidneys were perfused with aldehyde fixative containing RR, small (20 nm) RR-stained particles were seen in the same locations distributed with the same 60 nm repeating pattern, forming a quasiregular, lattice-like arrangement. Fine (-3 nm) filaments connected the sites and extended between them and the membranes of adjoining endothelial and epithelial cells 9 When CF was given i.v. followed by perfusion with RR in situ, both probes localized to the same sites 9 CF remained firmly bound after prolonged perfusion with 0.1-0 9 M KCI or NaCI. It was displaced by perfusion with buffers of high ionic strength (0 9149 M KCI) or pH (<3.0 or >10.0). CF also bound (clustered at -60 nm intervals) to isolated GBM's, and binding was lost when such isolated GBM's were treated with buffers of high ionic strength or pH. These experiments demonstrate the existence of a quasi-regular, lattice-like network of anionic sites in the LRI and LRE and the mesangial matrix 9 The sites are demonstrable in vivo (by CF binding), in fixed kidneys (by RR staining), and in isolated GBM's (by CF binding). The results obtained with CF show that the binding of CF (and probably also RR) to the laminae rarae is electrostatic in nature since it is displaced by treatment with buffers of high ionic strength or pH. With RR the sites resemble in morphology and staining properties the proteoglycan particles found in connective tissue matrices and in association with basement membranes in several other locations 9 KEY WORDS cationized ferritin red proteoglycans 9 ionic interaction isolated GBM's 9 ruthenium Recent studies have shown that the glomerular capillary wall contains fixed negatively charged sites which may be important in maintaining nor- J. CELL BIOLOGY 9The Rockefeller University Press 9