Expression Of Glucose Metabolism-related Genes Research Articles

Exposure to an acute hypoxic stimulus during early life affects the expression of glucose metabolism-related genes at first-feeding in trout

Rainbow trout (Oncorhynchus mykiss) is considered a “glucose-intolerant” species. With the aim of programming trout to improve their metabolic use of dietary carbohydrates, we hypothesised that a hypoxic stimulus applied during embryogenesis could later affect glucose metabolism at the first-feeding stage. An acute hypoxic stimulus (2.5 or 5.0 mg·L−1 O2) was applied for 24 h to non-hatched embryos or early hatched alevins followed by a challenge test with a high carbohydrate diet at first-feeding. The effectiveness of the early hypoxic stimulus was confirmed by the induction of oxygen-sensitive markers such as egln3. At first-feeding, trout previously subjected to the 2.5 mg·L−1 O2 hypoxia displayed a strong induction of glycolytic and glucose transport genes, whereas these glucose metabolism-related genes were affected much less in trout subjected to the less severe (5.0 mg·L−1 O2) hypoxia. Our results demonstrate that an acute hypoxic stimulus during early development can affect glucose metabolism in trout at first-feeding.

Collagen esterification enhances the function and survival of pancreatic β cells in 2D and 3D culture systems

Collagen, one of the most important components of the extracellular matrix (ECM), may play a role in the survival of pancreatic islet cells. In addition, chemical modifications that change the collagen charge profile to a net positive charge by esterification have been shown to increase the adhesion and proliferation of various cell types. The purpose of this study was to characterize and compare the effects of native collagen (NC) and esterified collagen (EC) on β cell function and survival. After isolation by the collagenase digestion technique, rat islets were cultured with NC and EC in 2 dimensional (2D) and 3 dimensional (3D) environments for a long-term duration in vitro. The cells were assessed for islet adhesion, morphology, viability, glucose-induced insulin secretion, and mRNA expression of glucose metabolism-related genes, and visualized by scanning electron microscopy (SEM). Islet cells attached tightly in the NC group, but islet cell viability was similar in both the NC and EC groups. Glucose-stimulated insulin secretion was higher in the EC group than in the NC group in both 2D and 3D culture. Furthermore, the mRNA expression levels of glucokinase in the EC group were higher than those in the NC group and were associated with glucose metabolism and insulin secretion. Finally, SEM observation confirmed that islets had more intact component cells on EC sponges than on NC sponges. These results indicate that modification of collagen may offer opportunities to improve function and viability of islet cells.

Histological and Transcriptional Expression differences between Diabetic Foot and Pressure Ulcers

Decubitus and diabetic foot ulcers remain as important clinical challenges with significant socioeconomic impact. Both are individual forms of chronic wounds with diverse proximal ethiopathogenic triggers. This study aimed to characterize and compare the main histological features as the transcriptional expression profile of a set of wound-healing relevant genes of the ulcers’ granulation tissue. Following patients’ consent, biopsies were collected from sacrolumbar pressure ulcers (N=5, stage IV) and diabetic foot ulcers (N=9, both of neuropathic and ischemic origin) with clean, non-infected granulation tissue. Biopsies fragments were processed for histological analysis and for RNA extraction and subsequent transcriptional expression characterization via RT-PCR. The group of targeted genes included cell proliferation control, extracellular matrix, glucose metabolism, anabolismsurvival, as anti-hypoxia and anti-oxidant defense. Gene expression was determined, normalized with an internal housekeeping gene, and statistically compared. Each class of chronic ulcer granulation tissue: decubitus, and diabetics’ ischemic and neuropathic proved to develop a particular histological pattern thus establishing individual differences. Moreover, diabetes appeared to significantly reduce the expression of numerous genes irrespective to their biological significance. Most importantly, we found that diabetic granulation tissue cells exhibit a sort of “genetic or epigenetic imprinting” for the expression of glucose-metabolism related genes which are deeply involved in type-2 diabetes pathophysiology. Our data indicate that in addition to a protracted inflammation and abnormal angiogenesis, diabetic granulation tissue cells are affected by gene expression failures that may lead to a negative pro-anabolic and energetic balance.

Postprandial regulation of hepatic glucokinase and lipogenesis requires the activation of TORC1 signaling in rainbow trout (Oncorhynchus mykiss)

To assess the potential involvement of TORC1 (target of rapamycin complex 1) signalling in the regulation of post-prandial hepatic lipid and glucose metabolism-related gene expression in trout, we employed intraperitoneal administration of rapamycin to achieve an acute inhibition of the TOR pathway. Our results reveal that rapamycin inhibits the phosphorylation of TORC1 and its downstream effectors (S6K1, S6 and 4E-BP1), without affecting Akt and the Akt substrates Forkhead-box Class O1 (FoxO1) and glycogen synthase kinase 3α/β (GSK 3α/β). These results indicate that acute administration of rapamycin in trout leads to the inhibition of TORC1 activation. No effect is observed on the expression of genes involved in gluconeogenesis, glycolysis and fatty acid oxidation, but hepatic TORC1 inhibition results in decreased sterol regulatory element binding protein 1c (SREBP1c) gene expression and suppressed fatty acid synthase (FAS) and glucokinase (GK) at gene expression and activity levels, indicating that FAS and GK activity is controlled at a transcriptional level in a TORC1-dependent manner. This study demonstrates for the first time in fish that post-prandial regulation of hepatic lipogenesis and glucokinase in rainbow trout requires the activation of TORC1 signalling.

Effect of nutrient intake on intramuscular glucose metabolism during the early growth stage in cross-bred steers (Japanese Black male × Holstein female)

The objective was to investigate the impact of nutrient intake during the early growth period on the expression of glucose metabolism-related genes in skeletal muscle of cross-bred cattle. From 1.5 to 5 months of age, group H (n=7) animals were intensively fed a high-protein and low-fat milk replacer [crude protein (CP) 28%; ether extracts (EE) 18%; max: 2.0 kg, 12 l/day], and group R (n=7) animals were fed a restricted amount of normal milk replacer (CP 25%; EE 23%; max 0.5 kg, 4 l/day). From 6 to 10 months of age, group H cattle were fed a high-nutrition total mixed ration mainly prepared from grain feed, and group R cattle were fed only roughage. Blood samples were taken from each animal at three biopsy times (1.5, 5 and 10 months of age), and the blood plasma concentration of glucose and insulin was analysed. In glucose concentration, there were no significant differences; however, the concentrations of insulin were higher in group H than in group R at 5 and 10 months of age. Muscle samples were taken by biopsy from longissimus thoracis muscle (LT) at 1.5, 5 and 10 months of age. We analysed mRNA expression levels using the quantitative real-time polymerase chain reaction (PCR) assay for glucose transporters (GLUT1 and GLUT4), insulin receptor, phosphatidylinositol 3-kinase (PI-3K), protein kinase B (PKB, also known as Akt), hexokinase 1 (HK1) and tumour necrosis factor alpha (TNFα). Although no differences were detected at 1.5 and 5 months of age, at 10 months of age, GLUT1, HK1 and TNFα mRNA expression levels were significantly higher in group H than in group R. These results suggested Glut1 that affects insulin-independently mediated glucose uptake was more responsive to improved nutrition during early growth stage than GLUT4 that insulin-dependently mediated glucose uptake in LT of cattle.

Effects of dietary Se deficiency on the metabolic phenotype and glucose metabolism‐related gene expression of the diet‐restricted GPX1 overexpressing mice

We previously reported that diet‐restriction rescued all the type 2 diabetes‐like phenotypes except for hyperinsulinemia in mice overexpressing the Se‐dependent glutathione peroxidase 1 (OE). This study was to determine effects of dietary Se deficiency on the metabolic phenotypes and related gene expression in pancreatic islets of the diet‐restricted OE mice over their wild‐type (WT) mice. Forty‐seven individually reared male OE and WT mice were fed Se‐adequate (0.4 mg Se/kg) or Se‐deficient (< 0.02 mg Se/kg) diet at 2 g/d starting at 4 wk of age for 2 wk, 2.5 g/d for the second 2 wk, and 3 g/d for another 8 wk. Dietary Se deficiency equalized the lower body weight of the Se‐adequate OE mice to that of the WT mice, but showed no significant effect on fasting plasma glucose concentration, body insulin or glucose tolerance or the glucose‐stimulated insulin secretion in either genotype. While the genotype effect (P < 0.05) was seen on islet mRNA levels of pdx1, beta2, p53, and glut2, dietary Se deficiency up‐regulated (P < 0.05) those of gk1, ins1, pdx1, preglucagon, and ucp2. There was a strong genotype and dietary Se interaction on islet mRNA levels of beta2, p53 and glut2. In conclusion, dietary Se deficiency affected the body weights and the islet mRNA expression of glucose metabolism‐related genes in the diet‐restricted OE and WT mice, but did not remove their genotype difference in hyperinsulinemia (NIH DK 53018).

Regulation of glycolysis and expression of glucose metabolism-related genes by reactive oxygen species in contracting skeletal muscle cells

Contractile activity induces a marked increase in glycolytic activity and gene expression of enzymes and transporters involved in glucose metabolism in skeletal muscle. Muscle contraction also increases the production of reactive oxygen species (ROS). In this study, the effects of treatment with N-acetylcysteine (NAC), a potent antioxidant compound, on contraction-stimulated glycolysis were investigated in electrically stimulated primary rat skeletal muscle cells. The following parameters were measured: 2-[ 3H]deoxyglucose (2-DG) uptake; activities of hexokinase, phosphofructokinase (PFK), and glucose-6-phosphate dehydrogenase (G6PDH); lactate production; and expression of the glucose transporter 4 (GLUT4), hexokinase II (HKII), and PFK genes after one bout of electrical stimulation in primary rat myotubes. NAC treatment decreased ROS signal by 49% in resting muscle cells and abolished the muscle contraction-induced increase in ROS levels. In resting cells, NAC decreased mRNA and protein contents of GLUT4, mRNA content and activity of PFK, and lactate production. NAC treatment suppressed the contraction-mediated increase in 2-DG uptake; lactate production; hexokinase, PFK, and G6PDH activities; and gene expression of GLUT4, HKII, and PFK. Similar to muscle contraction, exogenous H 2O 2 (500 nM) administration increased 2-DG uptake; lactate production; hexokinase, PFK, and G6PDH activities; and gene expression of GLUT4, HKII, and PFK. These findings support the proposition that ROS endogenously produced play an important role in the changes in glycolytic activity and gene expression of GLUT4, HKII, and PFK induced by contraction in skeletal muscle cells.

Mildronate decreases carnitine availability and up-regulates glucose uptake and related gene expression in the mouse heart

Aims l-carnitine has been shown to play a central role in both fat and carbohydrate metabolisms. This study investigated whether acute and long-term treatments with an l-carnitine biosynthesis inhibitor, mildronate (3-(2,2,2-trimethylhydrazinium) propionate), modulate glucose uptake. Main methods The effects of acute and long-term administration of mildronate at a dose of 200 mg/kg (i.p. daily for 20 days) were tested in mouse blood plasma and heart. Key findings Acute administration of mildronate in vivo, or in vitro administration with perfusion buffer in isolated heart experiments, did not induce any effects on glucose blood concentration and uptake in the heart. Mildronate long-term treatment significantly decreased carnitine concentration in plasma and heart tissues, as well as increased the rate of insulin-stimulated glucose uptake by 35% and the expression of glucose transporter 4, hexokinase II, and insulin receptor proteins in mouse hearts. In addition, expression of both carnitine palmitoyltransferases IA and IB were significantly increased. Mildronate long-term treatment statistically significantly decreased fed state blood glucose from 6 ± 0.2 to 5 ± 0.1 mM, but did not affect plasma insulin and C-peptide levels. Significance Our experiments demonstrate for the first time that long-term mildronate treatment decreases carnitine content in the mouse heart and leads to increased glucose uptake and glucose metabolism-related gene expression.