Biomedical subjects

Tao Jiang

Publications and source records attributed to Tao Jiang.

At least 73 records · Page 4Linked to original sources

PubMed2005

Haplotype-based linkage disequilibrium mapping via direct data mining.

MOTIVATION: With the availability of large-scale, high-density single-nucleotide polymorphism markers and information on haplotype structures and frequencies, a great challenge is how to take advantage of haplotype information in the association mapping of complex diseases in case-control studies. RESULTS: We present a novel approach for association mapping based on directly mining haplotypes (i.e. phased genotype pairs) produced from case-control data or case-parent data via a density-based clustering algorithm, which can be applied to whole-genome screens as well as candidate-gene studies in small genomic regions. The method directly explores the sharing of haplotype segments in affected individuals that are rarely present in normal individuals. The measure of sharing between two haplotypes is defined by a new similarity metric that combines the length of the shared segments and the number of common alleles around any marker position of the haplotypes, which is robust against recent mutations/genotype errors and recombination events. The effectiveness of the approach is demonstrated by using both simulated datasets and real datasets. The results show that the algorithm is accurate for different population models and for different disease models, even for genes with small effects, and it outperforms some recently developed methods.

Algorithms↗

PubMed2005

Immunogenicity and protective efficacy in monkeys of purified inactivated Vero-cell SARS vaccine.

BACKGROUND: In 2003, severe acute respiratory syndrome (SARS) resulted in hundreds of infections and deaths globally. We aim to assess immunogenicity and protective efficacy of purified inactivated Vero-cell SARS vaccine in monkeys. METHODS: The cultures of SARS coronavirus (SARS-CoV) BJ-01 strain infected Vero cells were inactivated with beta-propiolactone. Sequential procedures, including ultrafiltration, gel filtration and ion exchange chromatography, were performed to obtain purified inactivated SARS vaccine. The purified SARS vaccine was analyzed with electron microscope, HPLC and Western blotting. We immunized three groups of cynomolgus macaques fascicularis with adjuvant-containing purified vaccine, purified vaccine and unpurified vaccine, respectively, and a fourth group served as a control. Antibody titers were measured by plaque reduction neutralization test. The vaccinated monkeys were challenged with SARS-CoV BJ-01 strain to observe protective efficacy. Additionally, three groups of rhesus monkeys were immunized with different doses of the purified inactivated SARS vaccine (0.5, 1 and 2mug/time/monkey) on days 0 and 7, and the monkeys were challenged with SARS-CoV GZ-01 strain. We assessed the safety of the SARS vaccine and observed whether the antibody dependent enhancement (ADE) occurred under low levels of neutralizing antibody in rhesus. FINDINGS: The purity of SARS vaccine was 97.6% by HPLC identification and reacted with convalescent sera of SARS patients. The purified SARS vaccine induced high levels of neutralizing antibodies and prevented the replication of SARS-CoV in monkeys. Under low levels of neutralizing antibody, no exacerbation of clinical symptoms was observed when the immunized monkeys were challenged with SARS-CoV. In this preliminary animal trial, no side effects were detected when monkeys were immunized with purified SARS vaccine either at normal or large doses. INTERPRETATION: The purified inactivated SARS vaccine could induce high levels of neutralizing antibody, and protect the monkeys from the challenge of SARS-CoV. The SARS vaccine prepared in the study appeared to be safe in monkeys.

Animals↗

PubMed2005

[Surgical outcomes of different approaches for mesial temporal lobe gliomas].

OBJECTIVE: To analyze the surgical outcomes of different approaches for mesial temporal lobe gliomas. METHODS: Microsurgery was performed via trans-sylvian, trans-temporal, or subtemporal approaches on 62 patients with mesial temporal lobe gliomas, 33 with localized tumors within the mesial temporal structures (type A), 19 in anterior portion (type A1), and 14 extending to posterior portion (type A2); 19 patients with multicompartmental tumors involving the mesial temporal lobe, insular lobe, and posterior frontorbital gurus (type B); 14 patients with tumors involving the temporal pole and lateral areas of the temporal horn (type C); and 6 patients with tumors infiltrating the brain stem, basal nuclei and thalamus (type D). RESULTS: Trans-sylvian approach was performed in 25 cases of which total tumor removal was achieved in 14 cases, subtotal removal in 6 cases, and gross removal in 5 cases. Primary visual deficits worsened after surgery in 5 cases. Trans-temporal approach was used in 23 cases of which total tumor resection was achieved in 15 cases, subtotal resection in 5 cases, and gross resection in 3 cases. Primary visual deficits worsened after surgery in 5 cases. Four patients in which preoperative vision were good presented with visual deficits postoperatively. Subtemporal approach was used in 14 cases of which total tumor removal was achieved in 10 cases, and subtotal removal in 4 cases. All 14 patients did not develop worsened vision after surgery. CONCLUSION: Trans-sylvian and subtemporal approaches can reduce possible harm to parenchyma and optic radiation, whereas approaches to the temporal horn through the superior and middle temporal gyri will induce damage to parenchyma and optic radiation.

Adolescent↗

PubMed2005

Phase separation of the reaction system induced by CO2 and conversion enhancement for the esterification of acetic acid with ethanol in ionic liquid.

The effect of CO2 on the phase behavior of the reaction system and equilibrium conversion for esterification of acetic acid and ethanol in ionic liquid (1-butyl-3-methylimidazolium hydrogen sulfate, [bmim][HSO4]) was studied at 60.0 degrees C up to 15 MPa. It was demonstrated that there was only one phase in the reaction system in the absence of CO2. The reaction system underwent two-phase-->three-phase-->two-phase transitions with increasing pressure. The pressure of CO2 or the phase behavior of the system affected the equilibrium conversion of the reaction markedly. As the pressure was less than 3.5 MPa, there were two phases in the system, and the equilibrium conversion increased as pressure was increased. In the pressure range of 3.5-9.5 MPa, there existed three phases, and the equilibrium conversion increased more rapidly with increasing pressure. As the pressure was higher than 9.5 MPa, the reaction system entered another two-phase region and the equilibrium conversion was nearly independent of pressure. The total equilibrium conversion was 64% without CO2 and could be as high as 80% as pressure was higher than 9.0 MPa. The apparent equilibrium constants (K(x)) in different phases were also determined, showing that the K(x) in the middle phase or top phase was much greater than that in the bottom phase.

Journal Article↗

PubMed2005

Synthesis of single-crystal gold nanosheets of large size in ionic liquids.

Large-size single-crystal gold nanosheets have been successfully prepared by microwave heating of HAuCl(4) in ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, without any additional template agent. Transmission electron microscopy (TEM), electron diffraction (ED), scanning electron microscopy (SEM), and X-ray powder diffraction (XRD) were used to characterize the resultant gold nanosheets. It was demonstrated that the ionic liquid could act as template agent for the formation of gold nanosheets. The present synthesis route is very simple and fast. It can be expected that the method can be extended to the fabrication of other metal nanosheets in ionic liquids.

Journal Article↗

PubMed2005

Diet-induced obesity in C57BL/6J mice causes increased renal lipid accumulation and glomerulosclerosis via a sterol regulatory element-binding protein-1c-dependent pathway.

Obesity and metabolic syndrome are associated with glomerulosclerosis and proteinuria, but the mechanisms are not known. The purpose of this study was to determine if there is altered renal lipid metabolism and increased expression of sterol regulatory element-binding proteins (SREBPs) in a model of diet-induced obesity. C57BL/6J mice that were fed a high fat, 60 kcal % saturated (lard) fat diet (HFD) developed obesity, hyperglycemia, and hyperinsulinemia compared with those that were fed a low fat, 10 kcal % fat diet (LFD). In contrast, A/J mice were resistant when fed the same diet. C57BL/6J mice with HFD exhibited significantly higher levels of renal SREBP-1 and SREBP-2 expression than those mice with LFD, whereas in A/J mice there were no changes with the same treatment. The increases in SREBP-1 and SREBP-2 expression in C57BL/6J mice resulted in renal accumulation of triglyceride and cholesterol. There were also significant increases in the renal expression of plasminogen activator inhibitor-1 (PAI-1), vascular endothelial growth factor (VEGF), type IV collagen, and fibronectin, resulting in glomerulosclerosis and proteinuria. To determine a role for SREBPs per se in modulating renal lipid metabolism and glomerulosclerosis we performed studies in SREBP-1c(-/-) mice. In contrast to control mice, in the SREBP-1c(-/-) mice with HFD the accumulation of triglyceride was prevented, as well as the increases in PAI-1, VEGF, type IV collagen, and fibronectin expression. Our results therefore suggest that diet-induced obesity causes increased renal lipid accumulation and glomerulosclerosis in C57BL/6J mice via an SREBP-1c-dependent pathway.

Animal Feed↗

PubMed2005

[Effects of aldose reductase on the transforming growth factor-beta1-induced expression of fibronectin and collagen IV: experiment with cultured rat mesangial cells].

OBJECTIVE: To study the effects of aldose reductase (AR) on the transforming growth factor (TGF)-beta1-induced expression of fibronectin (FN) and collagen IV. METHODS: Restriction endonucleases digestion and ligation were used to reconstruct the eukaryotic expression plasmid pCDNA3-AR. Rat mesangial cells (MsCs) were isolated, cultured, and transfected with pCDNA3-AR, or blank vector. The AR expression in the MsCs was examined by immunofluorescence analysis. RT-PCR was performed to detect the mRNA expression of AR in the MsCs and Western blotting was used to detect the protein expression of AR. AR inhibitors (ARIs), Sorbinil and Zopolrestat were added and co-incubated, then TGF)-beta1 was added and Western blotting was used to analyze the protein expression of FN, collagen IV (Col IV), and mitogen-activated protein kinases (MAPKs) in the MsCs. RESULTS: Immunofluorescence analysis showed stronger expression of AR in the MsCs transfected with AR then in the normal MsCs and the MsCs transfected with blank vector. In comparison with the normal MsCs and those transfected with blank vector, the MsCs transfected with AR showed stronger protein expression of FN and Col IV (all P < 0.05). After incubation of ARIs the protein expression of FN and Col IV decreased by 1.8 and 2.0 times respectively in the MsCs transfected with AR (all P < 0.05). After stimulation of TGF-beta1, the protein expression of FN and Col IV increased in both the normal MsCs and those transfected with AR (P < 0.05 for the latter). After preincubation with ARIs the protein expression of FN and Col IV in the MsCs transfected decreased significantly (both P < 0.05). After stimulation of TGF-beta1, the normal MsCs showed increased expression of phospho-ERK, phospho-JNK, and phospho-p38; the MsCs preincubated with ARIs showed reduced expression of phospho-JNK and phospho-p38; and the MsCs transfected with AR showed increased expression of phosphor-JNK (P < 0.05). CONCLUSIONS: AR can regulates the expression of FN and Col IV with the stimulation of TGF-beta1 as AR gene is one of the responsive genes of TGF-beta1, which may have relations with the activation of JNK-MAPK and p38-MAPK signaling pathways induced by TGF-beta1. AR may play a role in the pathogenesis of glomerulosclerosis.

Aldehyde Reductase↗

PubMed2005

Crystal structure of pyridoxal kinase in complex with roscovitine and derivatives.

Pyridoxal kinase (PDXK) catalyzes the phosphorylation of pyridoxal, pyridoxamine, and pyridoxine in the presence of ATP and Zn2+. This constitutes an essential step in the synthesis of pyridoxal 5'-phosphate (PLP), the active form of vitamin B6, a cofactor for over 140 enzymes. (R)-Roscovitine (CYC202, Seliciclib) is a relatively selective inhibitor of cyclin-dependent kinases (CDKs), currently evaluated for the treatment of cancers, neurodegenerative disorders, renal diseases, and several viral infections. Affinity chromatography investigations have shown that (R)-roscovitine also interacts with PDXK. To understand this interaction, we determined the crystal structure of PDXK in complex with (R)-roscovitine, N6-methyl-(R)-roscovitine, and O6-(R)-roscovitine, the two latter derivatives being designed to bind to PDXK but not to CDKs. Structural analysis revealed that these three roscovitines bind similarly in the pyridoxal-binding site of PDXK rather than in the anticipated ATP-binding site. The pyridoxal pocket has thus an unexpected ability to accommodate molecules different from and larger than pyridoxal. This work provides detailed structural information on the interactions between PDXK and roscovitine and analogs. It could also aid in the design of roscovitine derivatives displaying strict selectivity for either PDXK or CDKs.

Animals↗

PubMed2005

Roscovitine targets, protein kinases and pyridoxal kinase.

(R)-Roscovitine (CYC202) is often referred to as a "selective inhibitor of cyclin-dependent kinases." Besides its use as a biological tool in cell cycle, neuronal functions, and apoptosis studies, it is currently evaluated as a potential drug to treat cancers, neurodegenerative diseases, viral infections, and glomerulonephritis. We have investigated the selectivity of (R)-roscovitine using three different methods: 1) testing on a wide panel of purified kinases that, along with previously published data, now reaches 151 kinases; 2) identifying roscovitine-binding proteins from various tissue and cell types following their affinity chromatography purification on immobilized roscovitine; 3) investigating the effects of roscovitine on cells deprived of one of its targets, CDK2. Altogether, the results show that (R)-roscovitine is rather selective for CDKs, in fact most kinases are not affected. However, it binds an unexpected, non-protein kinase target, pyridoxal kinase, the enzyme responsible for phosphorylation and activation of vitamin B6. These results could help in interpreting the cellular actions of (R)-roscovitine but also in guiding the synthesis of more selective roscovitine analogs.

Adenosine Triphosphate↗

PubMed2005

Replication of biological organizations through a supercritical fluid route.

A novel and simple method to replicate biological organizations (cotton and pollen grains) with high precision was proposed, in which the precursor dissolved in supercritical CO2 reacted with the surface active groups and adsorbed surface water on biological templates, followed by in situ SCF extraction of the byproducts and unreacted precursor, resulting in inorganic replicas faithfully copying both the macro- and microstructures of the biotemplates.

Carbon Dioxide↗

PubMed2005

Calorie restriction modulates renal expression of sterol regulatory element binding proteins, lipid accumulation, and age-related renal disease.

Sterol regulatory element binding proteins (SREBP) are major regulators of fatty acid and cholesterol synthesis. This study found that age-related renal matrix deposition and proteinuria were associated with increased renal expression of SREBP-1 and SREBP-2 and increased renal accumulation of triglyceride and cholesterol. Because calorie restriction (CR) modulates age-related renal disease, it then was determined whether the effects of CR are mediated partially by modulation of renal lipid metabolism. Compared with ad libitum (AL)-fed 24-month-old (24 m) F344BN rats, CR resulted in significant decreases in extracellular matrix accumulation (periodic acid-Schiff staining and immunofluorescence of type IV collagen and fibronectin) and proteinuria. A significant decrease was also observed in the renal expression of growth factors (connective tissue growth factor and vascular endothelial growth factor) and matrix metalloproteinase inhibitor (plasminogen activator inhibitor-1). These structural and functional changes were associated with significant decreases in renal nuclear SREBP-1 (5.2 in 24 m AL versus 3.3 densitometry units in 24 m CR; P < 0.01) and SREBP-2 (7.1 in 24 m AL versus 4.1 densitometry units in 24 m CR; P < 0.01) protein abundance and renal triglyceride and cholesterol contents. It is interesting that serum leptin level was significantly increased as a function of aging, and CR resulted in significant reduction in serum leptin level. Because it was shown previously that increased renal expression of SREBP-1a per se caused renal lipid accumulation, glomerulosclerosis, and proteinuria, the results suggest that CR modulates age-related renal disease in part by modulation of renal SREBP expression and renal lipid accumulation.

Aging↗

PubMed2005

MB06322 (CS-917): A potent and selective inhibitor of fructose 1,6-bisphosphatase for controlling gluconeogenesis in type 2 diabetes.

In type 2 diabetes, the liver produces excessive amounts of glucose through the gluconeogenesis (GNG) pathway and consequently is partly responsible for the elevated glucose levels characteristic of the disease. In an effort to find safe and efficacious GNG inhibitors, we targeted the AMP binding site of fructose 1,6-bisphosphatase (FBPase). The hydrophilic nature of AMP binding sites and their widespread use for allosteric regulation of enzymes in metabolic pathways has historically made discovery of AMP mimetics suitable for drug development difficult. By using a structure-based drug design strategy, we discovered a series of compounds that mimic AMP but bear little structural resemblance. The lead compound, MB05032, exhibited high potency and specificity for human FBPase. Oral delivery of MB05032 was achieved by using the bisamidate prodrug MB06322 (CS-917), which is converted to MB05032 in two steps through the action of an esterase and a phosphoramidase. MB06322 inhibited glucose production from a variety of GNG substrates in rat hepatocytes and from bicarbonate in male Zucker diabetic fatty rats. Analysis of liver GNG pathway intermediates confirmed FBPase as the site of action. Oral administration of MB06322 to Zucker diabetic fatty rats led to a dose-dependent decrease in plasma glucose levels independent of insulin levels and nutritional status. Glucose lowering occurred without signs of hypoglycemia or significant elevations in plasma lactate or triglyceride levels. The findings suggest that potent and specific FBPase inhibitors represent a drug class with potential to treat type 2 diabetes through inhibition of GNG.

Adenosine Monophosphate↗

PubMed2005

Affinity monoliths for ultrafast immunoextraction.

Affinity monoliths based on a copolymer of glycidyl methacrylate and ethylene dimethacrylate were developed for ultrafast immunoextractions. Rabbit immunoglobulin G (IgG) and anti-FITC antibodies were used as model ligands for this work. The antibody content of the monoliths was optimized by varying both the polymerization and immobilization conditions for preparing such supports. The temperature and porogen composition used during polymerization showed significant effects on monolith morphology and on the amount of antibodies that could be coupled to these materials. The effects of various immobilization procedures and coupling conditions were also evaluated, including the coupling temperature, pH, protein concentration, and use of high buffer concentrations. The maximum ligand density obtained for rabbit IgG was approximately 60 mg/g. When a 4.5 mm i.d. x 0.95 mm monolith disk containing anti-FITC antibodies was used, 95% extraction of fluorescein was achieved in 100 ms. These properties make such monoliths attractive for work in the rapid isolation of analytes from biological samples. Similar columns can be developed for other targets by varying the types of antibodies or binding agents placed within the monoliths.

Animals↗

PubMed2005

More reliable protein NMR peak assignment via improved 2-interval scheduling.

Protein NMR peak assignment refers to the process of assigning a group of "spin systems" obtained experimentally to a protein sequence of amino acids. The automation of this process is still an unsolved and challenging problem in NMR protein structure determination. Recently, protein NMR peak assignment has been formulated as an interval scheduling problem (ISP), where a protein sequence P of amino acids is viewed as a discrete time interval I (the amino acids on P one-to-one correspond to the time units of I), each subset S of spin systems that are known to originate from consecutive amino acids from P is viewed as a "job" j(s), the preference of assigning S to a subsequence P of consecutive amino acids on P is viewed as the profit of executing job j(s) in the subinterval of I corresponding to P, and the goal is to maximize the total profit of executing the jobs (on a single machine) during I. The interval scheduling problem is max SNP-hard in general; but in the real practice of protein NMR peak assignment, each job j(s) usually requires at most 10 consecutive time units, and typically the jobs that require one or two consecutive time units are the most difficult to assign/schedule. In order to solve these most difficult assignments, we present an efficient 13/7-approximation algorithm for the special case of the interval scheduling problem where each job takes one or two consecutive time units. Combining this algorithm with a greedy filtering strategy for handling long jobs (i.e., jobs that need more than two consecutive time units), we obtain a new efficient heuristic for protein NMR peak assignment. Our experimental study shows that the new heuristic produces the best peak assignment in most of the cases, compared with the NMR peak assignment algorithms in the recent literature. The above algorithm is also the first approximation algorithm for a nontrivial case of the well-known interval scheduling problem that breaks the ratio 2 barrier.

Algorithms↗

PubMed2005

Robust and accurate cancer classification with gene expression profiling.

Robust and accurate cancer classification is critical in cancer treatment. Gene expression profiling is expected to enable us to diagnose tumors precisely and systematically. However, the classification task in this context is very challenging because of the curse of dimensionality and the small sample size problem. In this paper, we propose a novel method to solve these two problems. Our method is able to map gene expression data into a very low dimensional space and thus meets the recommended samples to features per class ratio. As a result, it can be used to classify new samples robustly with low and trustable (estimated) error rates. The method is based on linear discriminant analysis (LDA). However, the conventional LDA requires that the within-class scatter matrix S(w) be nonsingular. Unfortunately, Sw is always singular in the case of cancer classification due to the small sample size problem. To overcome this problem, we develop a generalized linear discriminant analysis (GLDA) that is a general, direct, and complete solution to optimize Fisher's criterion. GLDA is mathematically well-founded and coincides with the conventional LDA when S(w) is nonsingular. Different from the conventional LDA, GLDA does not assume the nonsingularity of S(w), and thus naturally solves the small sample size problem. To accommodate the high dimensionality of scatter matrices, a fast algorithm of GLDA is also developed. Our extensive experiments on seven public cancer datasets show that the method performs well. Especially on some difficult instances that have very small samples to genes per class ratios, our method achieves much higher accuracies than widely used classification methods such as support vector machines, random forests, etc.

Algorithms↗

PubMed2005

Role of altered renal lipid metabolism and the sterol regulatory element binding proteins in the pathogenesis of age-related renal disease.

BACKGROUND: There are well-known changes in age-related renal function and structure, including glomerulosclerosis and decline in glomerular filtration rate (GFR). The purpose of this study was to identify a potential role for lipids in mediating age-related renal disease. METHODS: Mice of five different age groups (3, 6, 12, 19, and 23 months old) were studied. RESULTS: We have found that in C57BL/6 mice there was a progressive increase in age-related glomerulosclerosis [increase in periodic acid-Schiff (PAS) staining and accumulation of extracellular matrix proteins including type IV collagen and fibronectin], increased glomerular basement thickness and podocyte width and effacement, and increased proteinuria. These changes were associated with age-related increase in lipid accumulation as determined by increased Oil Red O staining in kidney sections. Biochemical analysis indicated that these lipid deposits corresponded to significant increases in renal triglyceride and cholesterol content. We have also found significant age-related increases in the nuclear transcription factors, sterol regulatory element-binding proteins (SREBP-1 and SREBP-2), protein abundance and increased expression or activity of their target enzymes that play an important role in lipid synthesis. CONCLUSION: Our results indicated that there was an age-related increase in renal expression of SREBP-1 and SREBP-2 with resultant increases in lipid synthesis and triglyceride and cholesterol accumulation in the kidney. Because we have previously shown that increased expression of SREBPs in the kidney per se results in glomerulosclerosis and proteinuria, our data suggested that increased SREBPs' expression resulting in increased renal lipid accumulation may play an important role in age-related nephropathy.

ATP Citrate (pro-S)-Lyase↗

PubMed2005

Differential oxidation of deoxyribose in DNA by gamma and alpha-particle radiation.

Emerging evidence points to the importance of deoxyribose oxidation in the toxicity of oxidative DNA damage, including the formation of protein-DNA crosslinks and base adducts. With the goal of understanding the differences in deoxyribose oxidation chemistry known to occur with different oxidants, we have compared the formation of one product of 3'-oxidation of deoxyribose in DNA, 3'-phosphoglycolaldehyde (PGA) residues, in isolated DNA and cells exposed to ionizing radiations. A recently developed gas chromatography/negative chemical ionization mass spectrometry method was used to quantify PGA residues in purified DNA and in human TK6 lymphoblastoid cells exposed to gamma radiation (60Co) and alpha particles (241Am). The level of PGA residues was then correlated with the total quantity of deoxyribose oxidation determined by plasmid topoisomer analysis. Alpha-particle irradiation (0-100 Gy) of purified DNA in 50 mM potassium phosphate (pH 7.4) produced a linear dose response of 0.13 PGA residues per 10(6) nucleotides per gray. When normalized to an estimate of the total number of deoxyribose oxidation events (2.0 per 10(6) nucleotides per gray), PGA formation occurred in 7% (+/-0.5) of deoxyribose oxidation events produced by alpha-particle radiation. In contrast, the efficiency of PGA formation in gamma-irradiated DNA was found to be 1% (+/-0.02), which indicates a shift in the chemistry of deoxyribose oxidation, possibly as a result of the different track structures of the two types of ionizing radiation. Studies with gamma radiation were extended to TK6 cells, in which it was observed that gamma radiation produced a linear dose response of 0.0019 PGA residues per 10(6) nucleotides per gray. This is consistent with an approximately 1000-fold quenching effect in cells, similar to the results of other published studies of oxidative DNA damage in vivo.

Alpha Particles↗

PubMed2005

Regulation of renal lipid metabolism, lipid accumulation, and glomerulosclerosis in FVBdb/db mice with type 2 diabetes.

Diabetic kidney disease has been associated with the presence of lipid deposits, but the mechanisms for the lipid accumulation have not been fully determined. In the present study, we found that db/db mice on the FVB genetic background with loss-of-function mutation of the leptin receptor (FVB-Lepr(db) mice or FVBdb/db) develop severe diabetic nephropathy, including glomerulosclerosis, tubulointerstitial fibrosis, increased expression of type IV collagen and fibronectin, and proteinuria, which is associated with increased renal mRNA abundance of transforming growth factor-beta, plasminogen activator inhibitor-1, and vascular endothelial growth factor. Electron microscopy demonstrates increases in glomerular basement membrane thickness and foot process (podocyte) length. We found that there is a marked increase in neutral lipid deposits in glomeruli and tubules by oil red O staining and biochemical analysis for cholesterol and triglycerides. We also detected a significant increase in the renal expression of adipocyte differentiation-related protein (adipophilin), a marker of cytoplasmic lipid droplets. We examined the expression of sterol regulatory element-binding protein (SREBP)-1 and -2, transcriptional factors that play an important role in the regulation of fatty acid, triglyceride, and cholesterol synthesis. We found significant increases in SREBP-1 and -2 protein levels in nuclear extracts from the kidneys of FVBdb/db mice, with increases in the mRNA abundance of acetyl-CoA carboxylase, fatty acid synthase, and 3-hydroxy-3-methylglutaryl-CoA reductase, which mediates the increase in renal triglyceride and cholesterol content. Our results indicate that in FVBdb/db mice, renal triglyceride and cholesterol accumulation is mediated by increased activity of SREBP-1 and -2. Based on our previous results with transgenic mice overexpressing SREBP-1 in the kidney, we propose that increased expression of SREBPs plays an important role in causing renal lipid accumulation, glomerulosclerosis, tubulointerstitial fibrosis, and proteinuria in mice with type 2 diabetes.

Animals↗