Changes of the expressions of multiple metabolism genes in rat pancreatic islets after ventromedial hypothalamic lesioning

Transcriptome, histological, and physiological responses of Amur sleeper (Perccottus glenii) during cold stress, freezing, and recovery

Freeze tolerance is a survival strategy employed by some ectotherms living in extremely cold environments. Some fish in extremely cold areas can recover from their frozen state, but they also have to endure cold stress. Amur sleeper (Perccottus glenii) can recover from a completely frozen state. To explore the response of freeze-resistant fish to low temperatures, we analyzed histological alterations, and antioxidant and carbohydrate-lipid metabolizing enzymes of P. glenii under low temperatures. So far, sensory genes regulating P. glenii during cold stress, freezing, and recovery have not been identified. Ultrastructure results indicated that glycogen content and mitochondrial ridge decreased during cold stress and freezing, whereas the number of endoplasmic reticulum increased during recovery. Plasma glucose and glycerol levels of the three treatment groups significantly increased. Lactate dehydrogenase and pyruvate kinase levels significantly increased during cold stress and freezing, and hexokinase levels significantly increased during cold stress. In total, 30,560 unigenes were found (average length 1724 bp, N50 2843 bp). In addition, 7370 differentially expressed genes (DEGs; including 2938 upregulated genes and 4432 downregulated genes) were identified. KEGG analysis revealed that the DEGs were enriched in carbohydrate and lipid metabolism, lipid synthesis, immune system, and anti-apoptosis. Genes involved in glycolysis and phospholipid metabolism were significantly upregulated during cold stress; genes related to circadian rhythm, oxidative phosphorylation, and lipid synthesis were significantly upregulated during freezing; and genes involved in the immune system and anti-apoptosis were significantly upregulated during recovery. Our results attempt to offer new insights into the physiological mechanisms of complex adaptation in P. glenii and provide useful information for future studies on the mechanism underlying freezing/recovery in animals.

Hepatoprotective Effect of Grape Seed and Skin Extract Against Lithium Exposure Examined by the Window of Proteomics

Context

The liver is the organ by which the majority of substances are metabolized, including psychotropic drugs. Lithium (Li) used as drug for many neurological disorders such as bipolar disorders.

Objective

This study aims to assess lithium toxicity and to evaluate the hepatic-protective properties of a grape skin seed and extract (GSSE).

Materials and methods

Twenty-four male Wistar rats were exposed for 30 days to either various lithium concentrations, GSSE alone, or lithium supplemented with GSSE. The proteomic analysis revealed alterations of liver protein profiles after lithium treatments that were successfully identified by mass spectrometry.

Results

Lithium treatment induced an oxidative damage by the alteration of antioxidant enzymes activities such as superoxide dismutase, CAT, and Gpx. The regulated proteins are mainly involved in the respiratory electron transport chain, detoxification processes, ribosomal stress pathway, glycolysis, and cytoskeleton. Proteins were differentially expressed in a dose-dependent manner. Interestingly, GSSE reversed the situation and restored the level of liver proteins whose abundance was modified after lithium treatment, arguing for its protective activity.

Conclusion

Our data demonstrated the ability of proteomic analysis to underline the toxicity mechanisms of lithium in animal models. Based on these results, GSSE may be envisaged as a nutritional supplement to weaken the liver toxicity of lithium.

Thioredoxin-1 Overexpression in the Ventromedial Nucleus of the Hypothalamus Preserves the Counterregulatory Response to Hypoglycemia During Type 1 Diabetes in Male Rats

We previously showed that the glutathione precursor, N-acetylcysteine (NAC), prevented hypoglycemia-associated autonomic failure (HAAF) and impaired activation of ventromedial hypothalamus (VMH) glucose-inhibited (GI) neurons by low glucose after recurrent hypoglycemia (RH) in nondiabetic rats. However, NAC does not normalize glucose sensing by VMH GI neurons when RH occurs during diabetes. We hypothesized that recruiting the thioredoxin (Trx) antioxidant defense system would prevent HAAF and normalize glucose sensing after RH in diabetes. To test this hypothesis, we overexpressed Trx-1 (cytosolic form of Trx) in the VMH of rats with streptozotocin (STZ)-induced type 1 diabetes. The counterregulatory response (CRR) to hypoglycemia in vivo and the activation of VMH GI neurons in low glucose using membrane potential sensitive dye in vitro was measured before and after RH. VMH Trx-1 overexpression normalized both the CRR and glucose sensing by VMH GI neurons in STZ rats. VMH Trx-1 overexpression also lowered the insulin requirement to prevent severe hyperglycemia in STZ rats. However, like NAC, VMH Trx-1 overexpression did not prevent HAAF or normalize activation of VMH GI neurons by low glucose in STZ rats after RH. We conclude that preventing HAAF in type 1 diabetes may require the recruitment of both antioxidant systems.

Gene Expression Analysis in Rat Pancreas Observed with Whole-Transcript Exon Array after Ventromedial Hypothalamic Lesions

BACKGROUND

It was reported previously that using Affymetrix Rat Genome 230 2.0, one of a class of standard 3' based arrays, ventromedial hypothalamic (VMH) lesions affected the expressions of cell proliferation-related genes, neuron-related genes, and metabolism-related genes. The released Affymetrix Rat Gene 1.0 ST array has 2 major differences compared with standard 3' based arrays, including Rat Genome 230 2.0: it interrogates the entire mRNA transcript and uses DNA targets.

PURPOSE

This study is aimed at assessing the impact of these differences on the array performance.

METHODS

The study used Rat Gene 1.0 ST array, one of a class of whole-transcript rat exon arrays to examine the cellular mechanisms of gene regulation in the rat pancreas after VMH lesions.

RESULTS

Although the results showed that VMH lesions regulated genes involved in enzymes, metabolism, transport, binding differentiation, migration, morphology, apoptosis, neuron and immunity, the probes identified by these 2 arrays were remarkably different.

CONCLUSION

This study also confirmed that VMH lesions may affect the expression of many functional genes in rat pancreas.

Ventromedial hypothalamic lesions downregulate multiple immune signaling pathways in rat pancreatic islets

It was recently reported that ventromedial hypothalamic lesions change the expression of cell proliferation-related genes and metabolism-related genes in rat pancreatic islets. This study has examined how gene families involved in immune responses are regulated in rat pancreatic islets after VMH lesions formation. Total pancreatic islets RNA was extracted, and differences in the gene expression profiles between rats at day 3 after VMH lesioning and sham-VMH-lesioned rats were investigated using DNA microarray and real-time polymerase chain reaction. VMH lesions downregulated multiple immune signaling pathways in rat pancreatic islets. Real-time polymerase chain reaction also confirmed that gene expressions of RT1 class II, locus Bb (RT1-Bb) was up-regulated and Spi-B transcription factor (Spib) was downregulated at day 3 after the VMH lesions. Ventromedial hypothalamic lesions may change the expression of multiple immune response genes in rat pancreatic islets.