Gene expression profiling in streptozotocin treated mouse liver using DNA microarray

Current landscape of preclinical models of diabetic cardiomyopathy

Patients with diabetes have an increased risk of developing heart failure, preceded by (often asymptomatic) cardiac abnormalities, collectively called diabetic cardiomyopathy (DC). Diabetic heart failure lacks effective treatment, remaining an urgent, unmet clinical need. Although structural and functional characteristics of the diabetic human heart are well defined, clinical studies lack the ability to pinpoint the specific mechanisms responsible for DC. Preclinical animal models represent a vital component for understanding disease aetiology, which is essential for the discovery of new targeted treatments for diabetes-induced heart failure. In this review, we describe the current landscape of preclinical DC models (genetic, pharmacologically induced, and diet-induced models), highlighting their strengths and weaknesses and alignment to features of the human disease. Finally, we provide tools, resources, and recommendations to assist future preclinical translation addressing this knowledge gap.

Differential gene expression in liver tissues of streptozotocin-induced diabetic rats in response to resveratrol treatment

This study was conducted to elucidate the genome-wide gene expression profile in streptozotocin induced diabetic rat liver tissues in response to resveratrol treatment and to establish differentially expressed transcription regulation networks with microarray technology. In addition to measure the expression levels of several antioxidant and detoxification genes, real-time quantitative polymerase chain reaction (qRT-PCR) was also used to verify the microarray results. Moreover, gene and protein expressions as well as enzymatic activities of main antioxidant enzymes; superoxide dismutase (SOD-1 and SOD-2) and glutathione S-transferase (GST-Mu) were analyzed. Diabetes altered 273 genes significantly and 90 of which were categorized functionally which suggested that genes in cellular catalytic activities, oxidation-reduction reactions, co-enzyme binding and terpenoid biosynthesis were dominated by up-regulated expression in diabetes. Whereas; genes responsible from cellular carbohydrate metabolism, regulation of transcription, cell signal transduction, calcium independent cell-to-cell adhesion and lipid catabolism were down-regulated. Resveratrol increased the expression of 186 and decreased the expression of 494 genes in control groups. While cellular and extracellular components, positive regulation of biological processes, biological response to stress and biotic stimulants, and immune response genes were up-regulated, genes responsible from proteins present in nucleus and nucleolus were mainly down-regulated. The enzyme assays showed a significant decrease in diabetic SOD-1 and GST-Mu activities. The qRT-PCR and Western-blot results demonstrated that decrease in activity is regulated at gene expression level as both mRNA and protein expressions were also suppressed. Resveratrol treatment normalized the GST activities towards the control values reflecting a post-translational effect. As a conclusion, global gene expression in the liver tissues is affected by streptozotocin induced diabetes in several specific pathways. The present data suggest the presence of several processes which contribute and possibly interact to impair liver functions in type 1 diabetes, several of which are potentially amenable to therapeutic interventions with resveratrol.

You are what you eat, or are you? The challenges of translating high-fat-fed rodents to human obesity and diabetes

Obesity and type 2 diabetes mellitus (T2DM) are rapidly growing worldwide epidemics with major health consequences. Various human-based studies have confirmed that both genetic and environmental factors (particularly high-caloric diets and sedentary lifestyle) greatly contribute to human T2DM. Interactions between obesity, insulin resistance and β-cell dysfunction result in human T2DM, but the mechanisms regulating the interplay among these impairments remain unclear. Rodent models of high-fat diet (HFD)-induced obesity have been used widely to study human obesity and T2DM. With >9000 publications on PubMed over the past decade alone, many aspects of rodent T2DM have been elucidated; however, correlation to human obesity/diabetes remains poor. This review investigates the reasons for this translational discrepancy by critically evaluating rodent HFD models. Dietary modification in rodents appears to have limited translatable benefit for understanding and treating human obesity and diabetes due—at least in part—to divergent dietary compositions, species/strain and gender variability, inconsistent disease penetrance, severity and duration and lack of resemblance to human obesogenic pathophysiology. Therefore future research efforts dedicated to acquiring translationally relevant data—specifically human data, rather than findings based on rodent studies—would accelerate our understanding of disease mechanisms and development of therapeutics for human obesity/T2DM.

Influence of endotoxin-mediated retinal inflammation on phenotype of diabetic retinopathy in Ins2 Akita mice

AIMS

To evaluate the impact of systemic exposure to bacterial lipopolysaccharide (LPS) on a rodent model of background diabetic retinopathy.

METHODS

Toll-like receptor 4 (TLR4)-mediated systemic inflammation was induced in Ins2(Akita) heterozygotes and age-matched C57BL6/J-Ins2(+) littermates by single or repeated intraperitoneal injections of the TLR4 ligand LPS (9 µg/g body weight). 24 hours after a single injection in 7-week-old mice retinal Il1b, Tnfa and Vegf transcripts were measured with real-time PCR. Vascular endothelial growth factor (VEGF) protein levels were evaluated with bead-based immunoassay. Leukostasis and endothelial injury were assessed in retinal wholemounts following perfusion with rhodamine or FITC conjugated concanavalin A to label leukocytes and propidium iodide to label dead or injured cells. In mice which had received three fortnightly injections between 10 and 16 weeks of age, retinal thicknesses and vascular structure were evaluated at 17-18 weeks of age using optical coherence tomography (OCT) and fluorescein angiography. Retinal architecture was assesed using resin-based histology.

RESULTS

Compared with normoglycaemic controls, systemic LPS exposure in Ins2(Akita) mice was associated with a 3.5-fold increase in endothelial cell injury and attenuated leukostasis in the retinal vasculature. Hyperglycaemia or acute LPS inflammation did not increase retinal VEGF content. Thinning (10-13 µm) of posterior retina was detected with OCT 2 weeks after repeated exposure to LPS in Ins2(Akita) mice but not in normoglycaemic controls. Capillary networks and retinal morphology were unaffected by recurrent LPS inflammation in Ins2(Akita) and control mice.

CONCLUSIONS

In hyperglycaemic mice, exposure to systemic LPS was associated with two hallmark pathologies of early background diabetic retinopathy, namely, the injury of capillary endothelium and in vivo thinning of the retina.

Rodent models of diabetic cardiomyopathy

Diabetic cardiomyopathy increases the risk of heart failure in individuals with diabetes, independently of co-existing coronary artery disease and hypertension. The underlying mechanisms for this cardiac complication are incompletely understood. Research on rodent models of type 1 and type 2 diabetes, and the use of genetic engineering techniques in mice, have greatly advanced our understanding of the molecular mechanisms responsible for human diabetic cardiomyopathy. The adaptation of experimental techniques for the investigation of cardiac physiology in mice now allows comprehensive characterization of these models. The focus of the present review will be to discuss selected rodent models that have proven to be useful in studying the underlying mechanisms of human diabetic cardiomyopathy, and to provide an overview of the characteristics of these models for the growing number of investigators who seek to understand the pathology of diabetes-related heart disease.

Dietary quercetin alleviates diabetic symptoms and reduces streptozotocin-induced disturbance of hepatic gene expression in mice

Quercetin is a food component that may ameliorate the diabetic symptoms. We examined hepatic gene expression of BALB/c mice with streptozotocin (STZ)-induced diabetes to elucidate the mechanism of the protective effect of dietary quercetin on diabetes-associated liver injury. We fed normal and STZ-induced diabetic mice with diets containing quercetin for 2 wk and compared the patterns of hepatic gene expression in these groups of mice using a DNA microarray. Diets containing 0.1 or 0.5% quercetin lowered the STZ-induced increase in blood glucose levels and improved plasma insulin levels. A cluster analysis of the hepatic gene expressions showed that 0.5% quercetin diet suppressed STZ-induced alteration of gene expression. Gene set enrichment analysis (GSEA) and quantitative RT-PCR analysis showed that the quercetin diets had greatest suppressive effect on the STZ-induced elevation of expression of cyclin-dependent kinase inhibitor p21(WAF1/Cip1) (Cdkn1a). Quercetin also suppressed STZ-induced expression of Cdkn1a in the pancreas. Dietary quercetin might improve liver and pancreas functions by enabling the recovery of cell proliferation through the inhibition of Cdkn1a expression. Unexpectedly, in healthy control mice the 0.5 and 1% quercetin diets reduced the expression of ubiquitin C (Ubc), which has heat-shock element (HSE) in the promoter region, in the liver.

DNA content, chromatin supraorganization, nuclear glycoproteins and RNA amounts in hepatocytes of mice expressing insulin-dependent diabetes

Chromatin supraorganization and extensibility and nuclear glycoprotein content have been reported to change in hepatocytes from mice during development and aging, as well as under starvation and refeeding conditions. In non-obese diabetic (NOD) mice, the expression of insulin-dependent diabetes may be accompanied by metabolic changes in the liver. These changes are likely to be similar to those involved in the aging processes of non-diabetic animals. Therefore, we hypothesized that the chromatin organization, as well as the physical properties and compositions of hepatocyte nuclei would also be affected in NOD mice in the same way as those in aged non-diabetic mice. Nuclear image parameters were evaluated by image analysis of Feulgen-stained preparations. Chromatin extensibility in response to gravity was observed with polarized light after lysis and toluidine blue staining. The Con-A response of nuclear glycoproteins was evaluated with scanning microspectrophotometry. These characteristics were assessed using hepatocyte imprints from female NOD mice after a 28-day period of diabetes expression. Observations and measurements were made in comparison to healthy BALB/c mice. Total RNA amounts were determined for livers of NOD and BALB/c mice. Enhanced polyploidy levels, a decrease in chromatin higher-order packing states, an increased frequency of extended chromatin fiber formation, and deeper Con-A-responsive chromatin areas were observed in the hepatocytes of the NOD mice expressing insulin-dependent diabetes. Reduced amounts of total RNA were also found in the livers of these mice. Our findings for NOD mice expressing insulin-dependent diabetes are consistent with previously reported data for old-aged mice of the inbred strain A/Uni and may reflect changes in transcriptional activities associated with the stressful physiological demands on the liver during the expression of diabetes.

Differential expression of chicken hepatic genes responsive to PFOA and PFOS

The effects of PFOS and PFOA on the gene expression patterns of chickens that were exposed to either PFOS or PFOA at low doses were investigated with the use of microarray techniques. Twelve Genechip Chicken Genome Arrays were used to study hepatic gene expression in 6-week-old chickens (Gallus gallus) that were exposed to either PFOA (0.1, 0.5, or 5mg/mL), PFOS (0.02 or 0.1mg/mL), or a saline vehicle control (0.9% NaCl in Milli-Q water) via subcutaneous implantation of a 2mL osmotic pump for 4 weeks or for 4 weeks with a further 4 weeks of depuration. Over 240 and 480 genes were significantly affected by PFOS after 4 weeks of exposure and after 4 weeks of exposure with a further 4 weeks of depuration, respectively and over 290 and 320 genes were significantly affected by PFOA, correspondingly. For PFOS, the genes that were affected after 4 weeks of exposure were mainly related to the transport of electrons and oxygen, and the metabolism of lipids and fatty acids; while the genes that were affected after 4 weeks of exposure with a further 4 weeks of depuration were mainly related to the transport of electrons and ions, and protein amino acid phosphorylation and proteolysis. For PFOA, the genes that were affected after 4 weeks of exposure were related to the transport of ions, lipids, and electrons and cytochromes; while the genes that were affected after 4 weeks of exposure with a further 4 weeks of depuration were related to protein amino acid phosphorylation and proteolysis, the transport of ions, and the metabolism of fatty acids and lipids. The results also showed that the gene expression patterns between chickens that were treated with PFOS and those that were treated with PFOA were different, which points to the importance of the separate evaluation of the toxicities of PFOS and PFOA. Specifically, the gene expressions of CYP8B and NOV were studied.

The DHR96 nuclear receptor regulates xenobiotic responses in Drosophila

Exposure to xenobiotics such as plant toxins, pollutants, or prescription drugs triggers a defense response, inducing genes that encode key detoxification enzymes. Although xenobiotic responses have been studied in vertebrates, little effort has been made to exploit a simple genetic system for characterizing the molecular basis of this coordinated transcriptional response. We show here that approximately 1000 transcripts are significantly affected by phenobarbital treatment in Drosophila. We also demonstrate that the Drosophila ortholog of the human SXR and CAR xenobiotic receptors, DHR96, plays a role in this response. A DHR96 null mutant displays increased sensitivity to the sedative effects of phenobarbital and the pesticide DDT as well as defects in the expression of many phenobarbital-regulated genes. Metabolic and stress-response genes are also controlled by DHR96, implicating its role in coordinating multiple response pathways. This work establishes a new model system for defining the genetic control of xenobiotic stress responses.

Diferential gene expression and adiposity reduction induced by ascorbic acid supplementation in a cafeteria model of obesity

Obesity is considered as an inflammatory disease, in which free radical-induced oxidative stress and excessive intake of macronutrients exacerbate their symptoms. In this context, we assessed in rats the possible preventive effect of the supplementation with an antioxidant molecule, ascorbic acid, in order to reduce the adiposity induced by the intake of a high-fat diet. For this purpose, during 56 days, three groups of male Wistar rats were fed on: a) standard pelleted diet, b) Cafeteria diet, c) ascorbate-supplemented (750 mg/kg of body weight) Cafeteria diet. At the end of the experimental period, microarray analysis was used to identify genes transcriptionally induced or repressed by both experimental dietary models (Cafeteria diet supplemented or not with ascorbic acid) in subcutaneous adipose tissue. Dietary ascorbic acid was able to protect against high fat diet effects, reducing the increase of body weight, total body fat and enlargement of different adipose depots induced by the Cafeteria diet without affecting food intake. An association analysis accurately and differentially allowed the detection of gene expression changes related with adiposity and insulin resistance. The genes that more strongly correlated with body fat and HOMA insulin resistance index were involved in adipocyte differentiation, lipid and glucocorticoid metabolism, cell cycle regulation, as well as in several insulin-induced processes. Some other transcripts are regulated by the vitamin C-mediated reduction of adiposity, such as genes that participate in glucocorticoid metabolism, adipogenesis, pentose phosphate pathway, or tricarboxylic acid cycle. This strategy was able to link variations in adipose tissue gene expression with markers of diet-induced obesity in rats, such as insulin resistance and body fat content.

Gene Expression Profiles in Rat Liver Treated With Perfluorooctanoic Acid (PFOA)

Perfluorooctanoic acid (PFOA; Pentadecafluorooctanoic acid) is widely used in various industrial applications. It is persistent in the environment and does not appear to undergo further degradation or transformation. PFOA is found in tissues including blood of wildlife and humans; however, the environmental fate and biological effects of PFOA remain unclear. Microarray techniques of gene expression have become a powerful approach for exploring the biological effects of chemicals. Here, the Affymetrix, Inc. rat genome 230 2.0 GeneChip was used to identify alterations in gene regulation in Sprague-Dawley rats treated with five different concentrations of PFOA. Male rats were exposed by daily gavage to 1, 3, 5, 10, or 15 mg PFOA/kg, body weight (bw)/day for 21 days and at the end of the exposure, liver was isolated and total liver RNA were used for the gene chip analysis. Over 500 genes, whose expression was significantly (p < 0.0025) altered by PFOA at two-fold changes compared to control, were examined. The effects were dose-dependent with exposure to 10 mg PFOA/kg, bw/day, causing alteration in expression of the greatest number of genes (over 800). Approximately 106 genes and 38 genes were consistently up- or down-regulated, respectively, in all treatment groups. The largest categories of induced genes were those involved in transport and metabolism of lipids, particularly fatty acids. Other induced genes were involved in cell communication, adhesion, growth, apoptosis, hormone regulatory pathways, proteolysis and peptidolysis and signal transduction. The genes expression of which was suppressed were related to transport of lipids, inflammation and immunity, and especially cell adhesion. Several other genes involved in apoptosis; regulation of hormones; metabolism; and G-protein coupled receptor protein signaling pathways were significantly suppressed.

Morphological and gene expression analysis in mouse primary cultured hepatocytes exposed to streptozotocin

Streptozotocin (SZ) is known to exert toxic effects not only on pancreatic islet beta cells but also on other organs including the liver. For analyzing direct effects of SZ on hepatocytes, we performed morphological analysis and DNA microarray analysis on mouse primary cultured hepatocytes. Hepatocytes were taken from non-treated Crj:CD-1(ICR) mice. The primary cultured hepatocytes were treated with SZ at concentrations of 0, 1, 3, 10, 30 and 100 mM. After the treatment for about 6 or 24h, cell survival assay using tetrazolium salt (WST-1), light microscopic/electron microscopic analysis and gene expression analysis were performed. For the gene expression analysis, target (labeled cRNA) prepared from total RNA of the hepatocytes was hybridized to the GeneChip Murine Genome U74A V.2 (Affymetrix). The signal intensity calculation and scaling were performed using Microarray Suite Software Ver 5.0. IC50 of the cell survival assay was around 62 mM at 6 h exposure and 7 mM at 24 h exposure. Marked chromatin margination was observed in nuclei of the hepatocytes treated with SZ at concentrations of 3 or 10mM. Gene expression analysis revealed similar expression changes to those of in vivo, i.e. up-regulation in cell proliferation/ apoptosis related genes, and down-regulation of lipid metabolism related genes. These results potently supported the hypothesis that many of the hepatic alteration including histopathological and gene expression changes are induced by direct effect of SZ rather than by the secondary effect of the hyperglycemia or hypoinsulinemia.