Up-regulated Desaturase and Elongase Gene Expression Promoted Accumulation of Polyunsaturated Fatty Acid (PUFA) but Not Long-Chain PUFA in Lates calcarifer, a Tropical Euryhaline Fish, Fed a Stearidonic Acid- and γ-Linoleic Acid-Enriched Diet

The limited activity of Δ6 fatty acid desaturase (FAD6) on α-linolenic (ALA, 18:3n-3) and linoleic (LA, 18:2n-6) acids in marine fish alters the long-chain (≥C₂₀) polyunsaturated fatty acid (LC-PUFA) concentration in fish muscle and liver when vegetable oils replace fish oil (FO) in aquafeeds. Echium oil (EO), rich in stearidonic acid (SDA, 18:4n-3) and γ-linoleic acid (GLA, 18:3n-6), may enhance the biosynthesis of n-3 and n-6 LC-PUFA by bypassing the rate-limiting FAD6 step. Nutritional and environmental modulation of the mechanisms in LC-PUFA biosynthesis was examined in barramundi, Lates calcarifer, a tropical euryhaline fish. Juveniles were maintained in either freshwater or seawater and fed different dietary LC-PUFA precursors present in EO or rapeseed oil (RO) and compared with FO. After 8 weeks, growth of fish fed EO was slower compared to the FO and RO treatments. Irrespective of salinity, expression of the FAD6 and elongase was up-regulated in fish fed EO and RO diets, but did not lead to significant accumulation of LC-PUFA in the neutral lipid of fish tissues as occurred in the FO treatment. However, significant concentrations of eicosapentaenoic acid (EPA, 20:5n-3) and arachidonic acid (ARA, 20:4n-6), but not docosahexaenoic acid (DHA, 22:6n-3), appeared in liver and, to a lesser extent, in muscle of fish fed EO with marked increases in the phospholipid fraction. Fish in the EO treatment had higher EPA and ARA in their liver phospholipids than fish fed FO. Endogenous conversion of dietary precursors into neutral lipid LC-PUFA appears to be limited by factors other than the initial rate-limiting step. In contrast, phospholipid LC-PUFA had higher biosynthesis, or selective retention, in barramundi fed EO rather than RO.

Exercise increases skeletal muscle GLUT4 gene expression in patients with type 2 diabetes

The aim of the study was to determine the effect of a single bout of exercise on GLUT4 gene expression in muscle of patients with type 2 diabetes (T2D) and control subjects, matched for age and body mass index. Nine patients with T2D and nine control subjects performed 60 min of cycling exercise at ∼55% peak power (W_max). Skeletal muscle biopsies were obtained at baseline, immediately post and 3-h post exercise. GLUT4 mRNA expression increased (p < 0.05) to a similar extent immediately post exercise in control (∼60%) and T2D (∼66%) subjects, and remained elevated (p < 0.05) 3-h post exercise with no differences between groups. Similarly, p-AMP-activated protein kinase, p38 mitogen-activated kinase and proliferator-activated receptor gamma co-activator-alpha mRNA expression were increased (p < 0.05) post exercise, and were not different between the groups. In conclusion, a single bout of exercise increased skeletal muscle GLUT4 mRNA expression in patients with T2D to a similar extent as in control subjects.

Association of differential gene expression with imatinib mesylate and omacetaxine mepesuccinate toxicity in lymphoblastoid cell lines

Background

Imatinib mesylate is currently the drug of choice to treat chronic myeloid leukemia. However, patient resistance and cytotoxicity make secondary lines of treatment, such as omacetaxine mepesuccinate, a necessity. Given that drug cytotoxicity represents a major problem during treatment, it is essential to understand the biological pathways affected to better predict poor drug response and prioritize a treatment regime.
Methods

We conducted cell viability and gene expression assays to determine heritability and gene expression changes associated with imatinib and omacetaxine treatment of 55 non-cancerous lymphoblastoid cell lines, derived from 17 pedigrees. In total, 48,803 transcripts derived from Illumina Human WG-6 BeadChips were analyzed for each sample using SOLAR, whilst correcting for kinship structure.
Results

Cytotoxicity within cell lines was highly heritable following imatinib treatment (h2 = 0.60-0.73), but not omacetaxine treatment. Cell lines treated with an IC20 dose of imatinib or omacetaxine showed differential gene expression for 956 (1.96%) and 3,892 transcripts (7.97%), respectively; 395 of these (0.8%) were significantly influenced by both imatinib and omacetaxine treatment. k-means clustering and DAVID functional annotation showed expression changes in genes related to kinase binding and vacuole-related functions following imatinib treatment, whilst expression changes in genes related to cell division and apoptosis were evident following treatment with omacetaxine. The enrichment scores for these ontologies were very high (mostly >10).
Conclusions

Induction of gene expression changes related to different pathways following imatinib and omacetaxine treatment suggests that the cytotoxicity of such drugs may be differentially tolerated by individuals based on their genetic background.

Effect of vascular endothelial growth factor upregulation on retinal gene expression in the Kimba mouse

Background:  The Kimba mouse carries a human vascular endothelial growth factor transgene causing retinal neovascularisation similar to that seen in diabetic retinopathy. Here, we examine the relationship between differential gene expression induced by vascular endothelial growth factor overexpression and the architectural changes that occur in the retinae of these mice.

Methods:  Retinal gene expression changes in juvenile and adult Kimba mice were assayed by microarray and compared with age-matched wild-type littermates. Transcription of selected genes was validated by quantitative real-time polymerase chain reaction. Protein translation was determined using immunohistochemistry and enzyme-linked immunosorbent assay.

Results:  Semaphorin 3C was upregulated, and nuclear receptor subfamily 2, group 3, member 3 (Nr2e3) was downregulated in juvenile Kimba mice. Betacellulin and endothelin 2 were upregulated in adults. Semaphorin 3C colocalized with glial fibrillary acidic protein in Müller cells of Kimba retinae at greater signal intensities than in wild type. Endothelin 2 colocalised to Müller cell end feet and extended into the outer limiting membrane. Endothelin receptor type B staining was most pronounced in the inner nuclear layer, the region containing Müller cell somata.

Conclusions:  An early spike in vascular endothelial growth factor induced significant long-term retinal neovascularisation associated with changes to the retinal ganglion, photoreceptor and Müller cells. Overexpression of vascular endothelial growth factor led to dysregulation of photoreceptor metabolism through differential expression of Nr2e3, endothelin 2, betacellulin and semaphorin 3C. Alterations in the expression of these genes may therefore play key roles in the pathological mechanisms that result from retinal neovascularisation.

Impact of obesity and leptin treatment on adipocyte gene expression in Psammomys obesus

We examined the effects of leptin treatment on the expression of key genes in adipocyte metabolism in Psammomys obesus (P. obesus), a polygenic rodent model of obesity. Lean and obese P. obesus were given three daily intraperitoneal injections of either saline or leptin (total of 45 mg/kg per day) for 7 days. In lean animals, leptin treatment led to reductions in food intake, body weight and fat mass. Pair-fed animals matched for the reduction in food intake of the lean leptin-treated animals demonstrated similar reductions in body weight and fat mass. In obese P. obesus, leptin treatment failed to have any effect on body weight or body fat mass, indicating leptin resistance. Lipoprotein lipase, hormone-sensitive lipase and peroxisome proliferator activated receptor gamma 2 mRNA levels were significantly reduced in lean leptin-treated animals, whereas pair-fed animals were similar to lean controls. Uncoupling protein 2 and glycerol phosphate acyltransferase were also reduced in the lean leptin-treated animals, but not significantly so. Obese animals did not show any gene expression changes after leptin treatment. In conclusion, high circulating concentrations of leptin in lean P. obesus resulted in decreased gene expression of a number of key lipid enzymes, independent of changes in food intake, body weight and fat mass. These effects of leptin were not found in obese P. obesus.

Hub-based reliable gene expression algorithm to classify ER+ and ER- breast cancer subtypes

Identifying gene signatures that are associatedwith the estrogen receptor based breast cancer samples is achallenging problem that has significant implications in breastcancer diagnosis and treatment. Various existing approaches foridentifying gene signatures have been developed but are not ableto achieve the satisfactory results because of their severallimitations. Subnetwork-based approaches have shown to be arobust classification method that uses interaction datasets suchas protein-protein interaction datasets. It has been reported thatthese interaction datasets contain many irrelevant interactionsthat have no biological meaning associated with them, and thusit is essential to filter out those interactions which can improvethe classification results. In this paper, we therefore, proposed ahub-based reliable gene expression algorithm (HRGE) thateffectively extracts the significant biologically-relevantinteractions and uses hub-gene topology to generate thesubnetwork based gene signatures for ER+ and ER- breastcancer subtypes. The proposed approach shows the superiorclassification accuracy amongst the other existing classifiers, inthe validation dataset.

Paracrine control of milk protein gene expression in tammar wallaby

Stephen utilised the unique lactation strategy of the tammar wallaby to identify factors within the mammary gland that determine the composition of milk and how the milk composition changes throughout lactation in order to provide immunity both to the nursing mammary gland and the suckling.