螺内酯对单肾切除糖尿病大鼠肾脏保护作用研究

目的：研究螺内酯对单肾切除糖尿病SD大鼠的肾脏保护作用及机制。方法：48只雄性SD大鼠随机分为单肾切除对照组C组、单肾切除糖尿病模型组D组、单肾切除糖尿病螺内酯干预组S组（50mg/kg/day灌胃）。给药6周后观察各组大鼠生化指标改变,肾组织形态学改变,RT-PCR及Western Blot检测肾组织中HGF水平的变化。结果：给药6周后,D组与C组相比,血糖、24h尿蛋白定量、尿素氮、血肌酐和肾重/体重显著增高（P〈0.05）,螺内酯治疗后可降低糖尿病大鼠的24h尿蛋白定量和肾重/体重,但对其它指标无明显影响;形态学显示,D组与C组相比肾小球系膜区细胞外基质增多及系膜细胞增生,肾小球基底膜增厚,足细胞足突融合、消失;螺内酯治疗后上述病理改变均有不同程度的减轻;RT-PCT、Western Blot结果显示D组和S组HGF表达均增加（P〈0.05）,而D组HGF表达明显低于螺内酯治疗组。结论：螺内酯可能通过上调HGF的水平从而起到保护糖尿病大鼠肾脏作用。     

Suppression of FAT/CD36 mRNA by human growth hormone in pancreatic β-cells

Fatty acid-induced damage in pancreatic β-cells is assumed to play an important role in the development of type 2 diabetes. Lactogens (prolactin, placental lactogen and growth hormone) improve β-cell survival via STAT5 activation but the molecular targets are incompletely characterized. The aim of this study was to examine the effect of human growth hormone (hGH) on mRNAs of fatty acid transport and binding proteins expressed in pancreatic β-cells, and to examine this in relation to β-cell survival after exposure to fatty acids. hGH decreased mRNA levels of FAT/CD36, whereas mRNAs of GPR40, FASN, FABP2, FATP1 and FATP4 were unchanged. RNAi against FAT/CD36 decreased fatty acid-induced apoptosis. Over-expression of constitutively active STAT5 was able to mimic hGH’s suppression of FAT/CD36 expression, whereas dominant negative STAT5 was unable to block the effect of hGH indicating that STAT5 did not bind directly to the FAT/CD36 promoter. The hGH-mediated suppression of FAT/CD36 mRNA was associated with a decrease in palmitate uptake and fatty acid-induced basal hyper-secretion of insulin resulting in improved glucose-stimulated insulin secretion. This study suggests that hGH can protect β-cells against fatty acid-induced damages.     

FADD is essential for glucose uptake and survival of thymocytes

Fas-associated protein with death domain (FADD) has been implicated in T lymphocytes, but the nature of FADD-dependent mechanism in early T cell development has not been completely elucidated. In this study, using T-cell specific deletion mice, we observed that FADD deficiency in thymocytes led to increased apoptosis and reduced cell numbers, which may be attributed to the reduction of Glut1 expression and correspondingly decreased glucose uptake. Furthermore, an abnormal transduction of Akt signaling was discovered in FADD^−/− thymocytes, which may be responsible for the declined Glut1 expression. Collectively, our results demonstrate the new function of FADD in glucose metabolism and survival of early T cells.     

PI3K/Akt is involved in brown adipogenesis mediated by growth differentiation factor-5 in association with activation of the Smad pathway

We have previously demonstrated promotion by growth differentiation factor-5 (GDF5) of brown adipogenesis for systemic energy expenditure through a mechanism relevant to activating the bone morphological protein (BMP) receptor/mothers against decapentaplegic homolog (Smad)/peroxisome proliferator-activated receptor gamma co-activator 1α (PGC-1α) pathway. Here, we show the involvement of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in brown adipogenesis mediated by GDF5. Overexpression of GDF5 in cells expressing adipocyte protein-2 markedly accelerated the phosphorylation of Smad1/5/8 and Akt in white and brown adipose tissues. In brown adipose tissue from heterozygous GDF5^Rgsc451 mutant mice expressing a dominant-negative (DN) GDF5 under obesogenic conditions, the basal phosphorylation of Smad1/5/8 and Akt was significantly attenuated. Exposure to GDF5 not only promoted the phosphorylation of both Smad1/5/8 and Akt in cultured brown pre-adipocytes, but also up-regulated Pgc1a and uncoupling protein-1 expression in a manner sensitive to the PI3K/Akt inhibitor Ly294002 as well as retroviral infection with DN-Akt. GDF5 drastically promoted BMP-responsive luciferase reporter activity in a Ly294002-sensitive fashion. Both Ly294002 and DN-Akt markedly inhibited phosphorylation of Smad5 in the nuclei of brown pre-adipocytes. These results suggest that PI3K/Akt signals play a role in the GDF5-mediated brown adipogenesis through a mechanism related to activation of the Smad pathway.     

Associations study of vitamin D receptor gene polymorphisms with diabetic microvascular complications: a meta-analysis

Background

Emerging evidence from preclinical and clinical studies has shown that vitamin D plays an important role in the pathogenesis of diabetic microvascular complications (DMI). Several potentially functional polymorphisms (ApaI, BsmI, FokI and TaqI) of vitamin D receptor (VDR) gene have been implicated in DMI risk, but individually published studies showed inconclusive results. The aim of this study was to quantitatively summarize the association between VDR polymorphisms and DMI risk.

Methods

We searched all the publications about the associations mentioned as above from PubMed and ISI database updated in December 2013. Meta-analysis of the overall odds ratios (ORs) with 95% confidence intervals (CIs) was calculated with the fixed or random effect model.

Results

Eight studies involving 2734 subjects were included. Allelic and genotypic comparisons between cases and controls were evaluated. Overall analysis suggests that no significant association was observed among the ApaI, BsmI, FokI and TaqI variants and DMI risk in diabetic patients (all P values > 0.05). In the stratified analysis, significant association was observed with diabetic nephropathy (DN) for VDR gene FokI polymorphism under a dominant model (OR 1.35, 95% CI 1.05–1.74, P = 0.02) in Caucasians.

Conclusions

This meta-analysis indicated that the FokI polymorphism in VDR gene might affect individual susceptibility to DN in Caucasians. Further investigations are needed to confirm our results.     

Association of RAGE gene polymorphisms with type 2 diabetes mellitus,diabetic retinopathy and diabetic nephropathy

A meta-analysis was performed to assess the associations of the receptor for advanced glycation end products (RAGE) gene polymorphisms [Gly82Ser (rs2070600), 1704 G/T (rs184003), 429 T/C (rs1800625)] with type 2 diabetes mellitus (T2DM), diabetic retinopathy (DR) and diabetic nephropathy (DN). A comprehensive research was conducted to identify all case-control or cohort studies. The fixed or random effect pooled measure was selected based on the homogeneity test among studies that was evaluated with I². Meta-regression was used to explore the potential sources of between-study heterogeneity. Publication bias was estimated using Peters test. Twenty-nine articles were included. Overall, after excluding articles deviating from Hardy–Weinberg equilibrium in controls and sensitive analysis, no significant association was found between RAGE gene polymorphisms (Gly82Ser, 1704 G/T, 429 T/C) and any of T2DM, DR and DN risk, respectively. Subgroup analysis stratified by ethnicity (Asian and Caucasian) also found no significant association between the above-mentioned three polymorphisms and T2DM risk, respectively. This meta-analysis suggested that there might be no association of RAGE gene polymorphisms (Gly82Ser, 1704 G/T, 429 T/C) with T2DM, DR and DN risk.     

A potentially functional polymorphism in the regulatory region of let-7a-2 is associated with an increased risk for diabetic nephropathy

Diabetic nephropathy (DN) is a major diabetic complication. However, the initiating molecular events triggering DN are unknown. MicroRNAs (miRNAs) have recently been identified as regulators that modulate the target gene expression and are involved in DN. However, the evidence of the mechanism is still insufficient in human samples. In this study, microRNA microarray assay was used to study gene differential expression profiles in DN and diabetes mellitus (DM) patients. One of the specific differentially expressed microRNAs, let-7a, was down-expressed in DN. Additionally, the expression of let-7a was also decreased in DN by real-time RT PCR in the patients' samples. Moreover, single nucleotide polymorphism (SNP) analysis was used to evaluate the relationship between three SNPs in the regulatory region of let-7a-2 gene and the risk of DN in the Chinese Han population by means of PCR-restriction fragment length polymorphism (RFLP-PCR). Also, the genotype and allele frequencies of let-7a-2 polymorphism were tested in 274 individuals, including 108 DN, 104 DM patients and 62 health control individuals (CON). It was found that a variant rs1143770 and the distributions of CT/TT genotypes were significantly different in three groups, and the CT + TT genotypes frequencies were significantly higher in DN and DM groups than that in CON group. In conclusion, let-7a-2 might participate in the regulation of the occurrence of DN, and a potential variant rs1143770 was significantly associated with the increased risk for DN.     

Specificity for Homooligomer versus Heterooligomer Formation in Integrin Transmembrane Helices

Transmembrane (TM) helices engage in homomeric and heteromeric interactions that play essential roles in the folding and assembly of TM proteins. However, features that explain their propensity to interact homomerically or heteromerically and determine the strength of these interactions are poorly understood. Integrins provide an ideal model system for addressing these questions because the TM helices of full-length integrins interact heteromerically when integrins are inactive, but isolated TM helices are also able to form homodimers or homooligomers in micelles and bacterial membranes. We sought to determine the features defining specificity for homointeractions versus heterointeractions by conducting a comprehensive comparison of the homomeric and heteromeric interactions of integrin αIIbβ3 TM helices in biological membranes. Using the TOXCAT assay, we found that residues V700, M701, A703, I704, L705, G708, L709, L712, and L713, which are located on the same face of the β3 helix, mediate homodimer formation. We then characterized the β3 heterodimer by measuring the ability of β3 helix mutations to cause ligand binding to αIIbβ3. We found that mutating V696, L697, V700, M701, A703. I704, L705, G708, L712, and L713, but not the small residue-X₃-small residue motif S699-X₃-A703, caused constitutive αIIbβ3 activation, as well as persistent focal adhesion kinase phosphorylation dependent on αIIbβ3 activation. Because αIIb and β3 use the same face of their respective TM helices for homomeric and heteromeric interactions, the interacting surface on each has an intrinsic “stickiness” predisposing towards helix-helix interactions in membranes. The residues responsible for heterodimer formation comprise a network of interdigitated side chains with considerable geometric complementarity; mutations along this interface invariably destabilize heterodimer formation. By contrast, residues responsible for homomeric interactions are dispersed over a wider surface. While most mutations of these residues are destabilizing, some stabilized homooligomer formation. We conclude that the αIIbβ3 TM heterodimer shows the hallmark of finely tuned heterodimeric interaction, while homomeric interaction is less specific.     

p38 MAPK pathway is involved in high glucose-induced thioredoxin interacting protein induction in mouse mesangial cells

Excessive reactive oxygen species (ROS) play a key role in the pathogenesis of diabetic nephropathy. The thioredoxin (TRX) system, a major thiol antioxidant system, regulates the reduction of intracellular ROS. Here we show that high glucose (HG) inhibits TRX ROS-scavenging function through p38 mitogen-activated protein kinase (MAPK)-mediated induction of thioredoxin interacting protein (TXNIP) in mouse mesangial cells (MMCs). Knockdown of TXNIP in MMCs reversed HG-induced reduction of TRX activity and inhibited HG-induced activation of p38 MAPK and increased synthesis of TGF-β1 and fibronectin. These data suggest that HG-induced overexpression of TXNIP in MMCs, which may be via the p38 MAPK pathway.