Glucose transporter gene expression: regulation of transcription and mRNA stability

From BBB to PPP: Bioenergetic requirements and challenges for oligodendrocytes in health and disease

Mature myelinating oligodendrocytes, the cells that produce the myelin sheath that insulates axons in the central nervous system, have distinct energetic and metabolic requirements compared to neurons. Neurons require substantial energy to execute action potentials, while the energy needs of oligodendrocytes are directed toward building the lipid-rich components of myelin and supporting neuronal metabolism by transferring glycolytic products to axons as additional fuel. The utilization of energy metabolites in the brain parenchyma is tightly regulated to meet the needs of different cell types. Disruption of the supply of metabolites can lead to stress and oligodendrocyte injury, contributing to various neurological disorders, including some demyelinating diseases. Understanding the physiological properties, structures, and mechanisms involved in oligodendrocyte energy metabolism, as well as the relationship between oligodendrocytes and neighboring cells, is crucial to investigate the underlying pathophysiology caused by metabolic impairment in these disorders. In this review, we describe the particular physiological properties of oligodendrocyte energy metabolism and the response of oligodendrocytes to metabolic stress. We delineate the relationship between oligodendrocytes and other cells in the context of the neurovascular unit, and the regulation of metabolite supply according to energetic needs. We focus on the specific bioenergetic requirements of oligodendrocytes and address the disruption of metabolic energy in demyelinating diseases. We encourage further studies to increase understanding of the significance of metabolic stress on oligodendrocyte injury, to support the development of novel therapeutic approaches for the treatment of demyelinating diseases.

Transcriptome Analysis of Different Aquaculture Substrates on the Immune Response of Babylonia areolata

To assess the impact of different substrates in a recirculating water system on the immune response and antioxidant capacity of Babylonia areolata, we conducted a comparative analysis of the transcriptomes and antioxidant performance of the digestive glands in three substrate environments (sand-S group, ceramic granules-C group, and PVC breeding nest-P group). Transcriptome results revealed that the S group and P group exhibited the highest number of differentially expressed genes (DEGs), with a total of 2218 DEGs, including 928 upregulated and 1290 downregulated DEGs. The C group and P group had 1055 DEGs in common, with 316 upregulated and 739 downregulated DEGs. The C group and S group had the fewest DEGs, with 521 in total, including 303 upregulated and 218 downregulated DEGs. GO enrichment analysis showed that in the S vs P group, terms such as catalytic activity, membrane part, and cellular process were enriched with 287, 262, and 180 DEGs, respectively. In the C vs P group, binding, cellular process, and cell part were enriched with 146, 135, and 127 DEGs, respectively. In the C vs S group, catalytic activity, membrane part, and metabolic process were enriched with 90, 83, and 59 DEGs, respectively. Kegg enrichment analysis revealed significant changes in immune-related pathways in the S vs P group, including lysosome, phagosome, and leukocyte transendothelial migration, with 30, 13, and 10 enriched DEGs, respectively. In the C vs P group, phagosome, drug metabolism-other enzymes, and N-Glycan biosynthesis showed significant changes in immune-related pathways, with 9, 6, and 4 enriched DEGs, respectively. In the C vs S group, lysosome, PPAR signaling pathway, and fatty acid degradation exhibited significant changes in immune-related pathways, with 8, 4, and 3 enriched DEGs, respectively. Regarding antioxidant capacity, the S group showed significantly higher total T-AOC than the other experimental groups, while CAT, SOD, POD, and AKP were lower than in the C and P groups. The ACP level in the Sand group was not significantly different from the P group but significantly lower than the C group. In conclusion, substrate environments significantly influence the immune-related genes and key antioxidant enzyme activities in B. areolata.

The Curious Case of the Missing Limb on FDG PET Imaging

ABSTRACT

A 58-year-old woman with poorly controlled diabetes, peripheral vascular disease, and end-stage renal disease requiring hemodialysis was referred for 18 F-FDG PET/CT to evaluate for source of sepsis. She had history of prior left forefoot and right second toe amputation, as well as left lower-limb dry gangrene for which she declined surgical management. We present a case of a nonamputated lower limb demonstrating regions of absolute photopenia, consistent with dry gangrene.

Review: A species comparison of the kinetic homogeneous and heterogeneous organization of sodium-dependent glucose transport systems along the intestine

The targeted use of carbohydrates by feed and food industries to create balanced and cost-effective diets has generated a tremendous amount of research in carbohydrate digestion and absorption in different species. Specifically, this research has led us to a larger observation that identified different organizations of intestinal sodium-dependent glucose absorption across species, which has not been previously collated and reviewed. Thus, this review will compare the kinetic segregation of sodium-dependent glucose transport across the intestine of different species, which we have termed either homogeneous or heterogeneous systems. For instance, the pig follows a heterogeneous system of sodium-dependent glucose transport with a high-affinity, super-low-capacity (Ha/sLc) in the jejunum, and a high-affinity, super-high-capacity (Ha/sHc) in the ileum. This is achieved by multiple sodium-dependent glucose transporters contributing to each segment. In contrast, tilapia have a homogenous system characterized by high-affinity, high-capacity (Ha/Hc) throughout the intestine. Additionally, we are the first to report glucose transporter patterns across species presented from vertebrates to invertebrates. Finally, other kinetic transport systems are briefly covered to illustrate possible contributions/modulations to sodium-dependent glucose transporter organization. Overall, we present a new perspective on the organization of glucose absorption along the intestinal tract.

Fatty acid transport proteins (FATPs) in cancer

Lipids play pivotal roles in cancer biology. Lipids have a wide range of biological roles, especially in cell membrane synthesis, serve as energetic molecules in regulating energy-demanding processes; and they play a significant role as signalling molecules and modulators of numerous cellular functions. Lipids may participate in the development of cancer through the fatty acid signalling pathway. Lipids consumed in the diet act as a key source of extracellular pools of fatty acids transported into the cellular system. Increased availability of lipids to cancer cells is due to increased uptake of fatty acids from adipose tissues. Lipids serve as a source of energy for rapidly dividing cancerous cells. Surviving requires the swift synthesis of biomass and membrane matrix to perform exclusive functions such as cell proliferation, growth, invasion, and angiogenesis. FATPs (fatty acid transport proteins) are a group of proteins involved in fatty acid uptake, mainly localized within cells and the cellular membrane, and have a key role in long-chain fatty acid transport. FATPs are composed of six isoforms that are tissue-specific and encoded by a specific gene. Previous studies have reported that FATPs can alter fatty acid metabolism, cell growth, and cell proliferation and are involved in the development of various cancers. They have shown increased expression in most cancers, such as melanoma, breast cancer, prostate cancer, renal cell carcinoma, hepatocellular carcinoma, bladder cancer, and lung cancer. This review introduces a variety of FATP isoforms and summarises their functions and their possible roles in the development of cancer.

Molecular identification of glucose transporter 4: The responsiveness to starvation, glucose, insulin and glucagon on glucose transporter 4 in common carp (Cyprinus carpio L.)

Glucose transporter 4 (GLUT4) is comprehensively investigated in mammals, while the comparative research of GLUT4 in common carp is deficient. To investigate the function of GLUT4, carp glut4 was first isolated. The open reading frame of carp glut4 was 1518 bp in length, encoding 505 amino acids. A high-sequence homology was identified in carp and teleost, and the phylogenetic tree displayed that the carp GLUT4 was clustered with the teleost. A high level of glut4 mRNA was analysed in fat, red muscle and white muscle. After fasting treatment, glut4 mRNA expression was increased significantly in muscle. In the oral glucose tolerance test experiment, glut4 mRNA was also significantly elevated in muscle, gut and fat. Furthermore, intraperitoneal injection of insulin resulted in the upregulation of glut4 gene expression significantly in white muscle, gut and fat. On the contrary, the glut4 mRNA level in the white muscle, gut and fat was markedly downregulated after glucagon injection. These results suggest that GLUT4 might play important roles in food intake and could be regulated by nutrient condition, insulin and glucagon in common carp. Our study is the first to report on GLUT4 in common carp. These data provide a basis for further study on fish GLUT4.

Metabolic Transporters in the Peripheral Nerve-What, Where, and Why?

Cellular metabolism is critical not only for cell survival, but also for cell fate, function, and intercellular communication. There are several different metabolic transporters expressed in the peripheral nervous system, and they each play important roles in maintaining cellular energy. The major source of energy in the peripheral nervous system is glucose, and glucose transporters 1 and 3 are expressed and allow blood glucose to be imported and utilized by peripheral nerves. There is also increasing evidence that other sources of energy, particularly monocarboxylates such as lactate that are transported primarily by monocarboxylate transporters 1 and 2 in peripheral nerves, can be efficiently utilized by peripheral nerves. Finally, emerging evidence supports an important role for connexins and possibly pannexins in the supply and regulation of metabolic energy. In this review, we will first define these critical metabolic transporter subtypes and then examine their localization in the peripheral nervous system. We will subsequently discuss the evidence, which comes both from experiments in animal models and observations from human diseases, supporting critical roles played by these metabolic transporters in the peripheral nervous system. Despite progress made in understanding the function of these transporters, many questions and some discrepancies remain, and these will also be addressed throughout this review. Peripheral nerve metabolism is fundamentally important and renewed interest in these pathways should help to answer many of these questions and potentially provide new treatments for neurologic diseases that are partly, or completely, caused by disruption of metabolism.

Comparison of intestinal glucose flux and electrogenic current demonstrates two absorptive pathways in pig and one in Nile tilapia and rainbow trout

The mucosal-to-serosal flux of ¹⁴C 3-O-methyl-d-glucose was compared against the electrogenic transport of d-glucose across ex vivo intestinal segments of Nile tilapia, rainbow trout, and pig in Ussing chambers. The difference in affinities (K_m "fingerprints") between pig flux and electrogenic transport of glucose, and the absence of this difference in tilapia and trout, suggest two absorptive pathways in the pig and one in the fish species examined. More specifically, the total mucosal-to-serosal flux revealed a super high-affinity, high-capacity (sHa/Hc) total glucose transport system in tilapia; a super high-affinity, low-capacity (sHa/Lc) total glucose transport system in trout and a low-affinity, low-capacity (La/Lc) total glucose transport system in pig. Comparatively, electrogenic glucose absorption revealed similar K_m in both fish species, with a super high-affinity, high capacity (sHa/Hc) system in tilapia; a super high-affinity/super low-capacity (sHa/sLc) system in trout; but a different K_m fingerprint in the pig, with a high-affinity, low-capacity (Ha/Lc) system. This was supported by different responses to inhibitors of sodium-dependent glucose transporters (SGLTs) and glucose transporter type 2 (GLUT2) administered on the apical side between species. More specifically, tilapia flux was inhibited by SGLT inhibitors, but not the GLUT2 inhibitor, whereas trout lacked response to inhibitors. In contrast, the pig responded to inhibition by both SGLT and GLUT2 inhibitors with a higher expression of GLUT2. Altogether, it would appear that two pathways are working together in the pig, allowing it to have continued absorption at high glucose concentrations, whereas this is not present in both tilapia and trout.

Intestinal electrogenic sodium-dependent glucose absorption in tilapia and trout reveal species differences in SLC5A-associated kinetic segmental segregation

Electrogenic sodium-dependent glucose transport along the length of the intestine was compared between the omnivorous Nile tilapia ( Oreochromis niloticus) and the carnivorous rainbow trout ( Oncorhynchus mykiss) in Ussing chambers. In tilapia, a high-affinity, high-capacity kinetic system accounted for the transport throughout the proximal intestine, midintestine, and hindgut segments. Similar dapagliflozin and phloridzin dihydrate inhibition across all segments support this homogenous high-affinity, high-capacity system throughout the tilapia intestine. Genomic and gene expression analysis supported findings by identifying 10 of the known 12 SLC5A family members, with homogeneous expression throughout the segments with dominant expression of sodium-glucose cotransporter 1 (SGLT1; SLC5A1) and sodium-myoinositol cotransporter 2 (SMIT2; SLC5A11). In contrast, trout's electrogenic sodium-dependent glucose absorption was 20-35 times lower and segregated into three significantly different kinetic systems found in different anatomical segments: a high-affinity, low-capacity system in the pyloric ceca; a super-high-affinity, low-capacity system in the midgut; and a low-affinity, low-capacity system in the hindgut. Genomic and gene expression analysis found 5 of the known 12 SLC5A family members with dominant expression of SGLT1 ( SLC5A1), sodium-glucose cotransporter 2 (SGLT2; SLC5A2), and SMIT2 ( SLC5A11) in the pyloric ceca, and only SGLT1 ( SLC5A1) in the midgut, accounting for differences in kinetics between the two. The hindgut presented a low-affinity, low-capacity system partially attributed to a decrease in SGLT1 ( SLC5A1). Overall, the omnivorous tilapia had a higher electrogenic glucose absorption than the carnivorous trout, represented with different kinetic systems and a greater expression and number of SLC5A orthologs. Fish differ from mammals, having hindgut electrogenic glucose absorption and segment specific transport kinetics.

Glia-neuron energy metabolism in health and diseases: New insights into the role of nervous system metabolic transporters

The brain is, by weight, only 2% the volume of the body and yet it consumes about 20% of the total glucose, suggesting that the energy requirements of the brain are high and that glucose is the primary energy source for the nervous system. Due to this dependence on glucose, brain physiology critically depends on the tight regulation of glucose transport and its metabolism. Glucose transporters ensure efficient glucose uptake by neural cells and contribute to the physiology and pathology of the nervous system. Despite this, a growing body of evidence demonstrates that for the maintenance of several neuronal functions, lactate, rather than glucose, is the preferred energy metabolite in the nervous system. Monocarboxylate transporters play a crucial role in providing metabolic support to axons by functioning as the principal transporters for lactate in the nervous system. Monocarboxylate transporters are also critical for axonal myelination and regeneration. Most importantly, recent studies have demonstrated the central role of glial cells in brain energy metabolism. A close and regulated metabolic conversation between neurons and both astrocytes and oligodendroglia in the central nervous system, or Schwann cells in the peripheral nervous system, has recently been shown to be an important determinant of the metabolism and function of the nervous system. This article reviews the current understanding of the long existing controversies regarding energy substrate and utilization in the nervous system and discusses the role of metabolic transporters in health and diseases of the nervous system.

Stress exposure alters brain mRNA expression of the genes involved in insulin signalling, an effect modified by a high fat/high fructose diet and cinnamon supplement

In occidental societies, high fat and high sugar diets often coincide with episodes of stress. The association is likely to modify brain energy control. Brain insulin signalling is rarely studied in stressed individuals consuming high fat diets. Furthermore the effects of cinnamon supplement are not known in these conditions. Therefore, we exposed rats, over a 12-week period, to a control (C) or a high fat/high fructose (HF/HFr) diet that induces peripheral insulin resistance. A cinnamon supplement (C+CN and HF/HFr +CN) was added or not. After diet exposure, one group of rats was exposed to a 30-min restraint followed by a 10-min open-field test, their combination featuring a moderate stressor, the other rats staying unstressed in their home cages. The insulin signalling in hippocampus and frontal cortex was studied through the mRNA expression of the following genes: insulin receptor (Ir), insulin receptor substrate (Irs1), glucose transporters (Glut1 and Glut3), glycogen synthase (Gys1) and their modulators, Akt1 and Pten. In C rats, stress enhanced the expression of Ir, Irs1, Glut1, Gys1 and Akt1 mRNA. In C+CN rats, stress induced an increase in Pten but a decrease in Gys1 mRNA expression. In HF/HFr rats, stress was associated with an increase in Pten mRNA expression. In HF/HFr+CN rats, stress increased Pten mRNA expression but also decreased Gys1 mRNA expression. This suggests that a single moderate stress favours energy refilling mechanisms, an effect blunted by a previous HF/HFr diet and cinnamon supplement.

Exercise training, Glut-4 protein abundance and glutamine in skeletal muscle of mature and very old horses

Two groups of unfit Standardbred mares (adult: 9-14 years, 540 kg, n=7) and old (20-25 years, 530 kg, n=5) were used to test two hypotheses, first, that aging and training would alter plasma and muscle glutamine [Gln] and glutamate [Glu] and second, that aging and training would alter Glut-4 expression in skeletal muscle. All animals were housed on pasture with free access to grass and all received hay and supplementation with a commercially prepared supplement (15% crude protein and 3.00 Mcal/kg dry matter) in individual stalls. Mares were fed to meet or exceed NRC (2007) nutrient recommendations for moderate to heavy exercise. The mares were exercise trained in a free-stall motorised circular exercise machine for 30 min/d, 5 d/week, for 8 weeks. Work intensity during training was set at a relative intensity of ~60% of the maximum heart rate, previously determined during an incremental exercise test (GXT). Blood samples and muscle biopsies (gluteus) obtained before and after 8 weeks of training were used for measurement of [Gln], [Glu] and Glut-4 abundance. Samples were collected before the initiation of training and at 24 h after cessation of last bout of exercise in the training period. All samples were immediately frozen in liquid nitrogen and stored at -80 °C until enzymatic analysis for [Gln], [Glu] and Western Blot analysis for Glut-4 protein abundance. Data were analysed by one-way or two-way ANOVA for repeated measures and the Pearson correlation method. Post-hoc differences were identified with the Tukey test. Significance was set at P<0.05. There were no differences (P>0.05) in muscle [Glu] due to aging. Training decreased (P<0.05) muscle [Glu] from 7,561±701 nmol/g of tissue (mean ± standard error) in pre-training samples to 4,491±701 nmol/g of tissue post-training. Plasma [Gln] decreased (P<0.05) with training (368±14 nmol/ml vs 317±14 nmol/ml). There was a trend (P=0.063) towards an effect of aging. There were significant interactions between age and training for plasma [Gln]. Old mares had lower (P<0.05) post-exercise plasma [Gln] (224±21 nmol/ml) when compared with pre-exercise plasma [Gln] (372±21 nmol/ml). Post-training, plasma [Gln] was lower (P<0.05) in the old mares compared to adult mares [Gln] (224±21 nmol/ml vs 410±18 nmol/ml). There was an effect (P<0.05) of age on muscle [Gln] (old = 6,126 ±870 nmol/g of tissue; adult = 3,176±735 nmol/g of tissue); however, there were no changes (P>0.05) due to training. Glut-4 abundance analysis did not differ (P>0.05) between the young adult and old horses; however, there was a trend (P=0.063) towards an effect of training when samples from both groups were pooled. It was concluded that training and aging produce changes in plasma and muscle [Gln], which may affect immune function in athletic horses, but not in Glut-4.

Potential role of marine algae extract on 3T3-L1 cell proliferation and differentiation: an in vitro approach

Background

From ancient times, marine algae have emerged as alternative medicine and foods, contains the rich source of natural products like proteins, vitamins, and secondary metabolites, especially Chlorella vulgaris (C. vulgaris) contains numerous anti-inflammatory, antioxidants and wound healing substances. Type 2 diabetes mellitus is closely associated with adipogenesis and their factors. Hence, we aimed to investigate the chemical constituents and adipogenic modulatory properties of C. vulgaris in 3T3-L1 pre-adipocytes.

Results

We analysed chemical constituents in ethanolic extract of C. vulgaris (EECV) by LC–MS. Results revealed that the EECV contains few triterpenoids and saponin compounds. Further, the effect of EECV on lipid accumulation along with genes and proteins expressions which are associated with adipogenesis and lipogenesis were evaluated using oil red O staining, qPCR and western blot techniques. The data indicated that that EECV treatment increased differentiation and lipid accumulation in 3T3-L1 cells, which indicates positive regulation of adipogenic and lipogenic activity. These increases were associated with up-regulation of PPAR-γ2, C/EBP-α, adiponectin, FAS, and leptin mRNA and protein expressions. Also, EECV treatments increased the concentration of glycerol releases as compared with control cells. Troglitazone is a PPAR-γ agonist that stimulates the PPAR-γ2, adiponectin, and GLUT-4 expressions. Similarly, EECV treatments significantly upregulated PPAR-γ2, adiponectin, GLUT-4 expressions and glucose utilization. Further, EECV treatment decreased AMPK-α expression as compared with control and metformin treated cells.

Conclusion

The present research findings confirmed that the EECV effectively modulates the lipid accumulation and differentiation in 3T3-L1 cells through AMPK-α mediated signalling pathway.

Glucose Transporters at the Blood-Brain Barrier: Function, Regulation and Gateways for Drug Delivery

Glucose transporters (GLUTs) at the blood-brain barrier maintain the continuous high glucose and energy demands of the brain. They also act as therapeutic targets and provide routes of entry for drug delivery to the brain and central nervous system for treatment of neurological and neurovascular conditions and brain tumours. This article first describes the distribution, function and regulation of glucose transporters at the blood-brain barrier, the major ones being the sodium-independent facilitative transporters GLUT1 and GLUT3. Other GLUTs and sodium-dependent transporters (SGLTs) have also been identified at lower levels and under various physiological conditions. It then considers the effects on glucose transporter expression and distribution of hypoglycemia and hyperglycemia associated with diabetes and oxygen/glucose deprivation associated with cerebral ischemia. A reduction in glucose transporters at the blood-brain barrier that occurs before the onset of the main pathophysiological changes and symptoms of Alzheimer's disease is a potential causative effect in the vascular hypothesis of the disease. Mutations in glucose transporters, notably those identified in GLUT1 deficiency syndrome, and some recreational drug compounds also alter the expression and/or activity of glucose transporters at the blood-brain barrier. Approaches for drug delivery across the blood-brain barrier include the pro-drug strategy whereby drug molecules are conjugated to glucose transporter substrates or encapsulated in nano-enabled delivery systems (e.g. liposomes, micelles, nanoparticles) that are functionalised to target glucose transporters. Finally, the continuous development of blood-brain barrier in vitro models is important for studying glucose transporter function, effects of disease conditions and interactions with drugs and xenobiotics.

Gene expression related to lipid and glucose metabolism in white adipose tissue

PROBLEM

A number of endogenous and external factors influence the development of obesity. However, the factors responsible for these differences in obesity pathogenesis between males and females are largely unknown.

METHODS

We investigated the expression of 35 genes related to lipid and glucose metabolism and to receptors for insulin signaling in white adipose tissue (WAT) of 8-week-old 129/Sv mice and mice fed standard diet (STD) or high fat diet (HFD) for 35 weeks in males and females.

RESULTS

At 8 weeks, the expression levels of two genes for fatty acid synthesis, Acaca and Fasn, were higher in females than in males. Female mice fed a STD for 35 weeks also had higher expression levels of an additional four genes related to glucose transporters (Slc2a1 and Slc2a4) and adipokines (Adipoq and Nampt). The expression levels of these six genes were also higher in females than in males fed a HFD for 35 weeks. At 43 weeks old, the female-to-male expression ratio of these six genes was similar for the STD and HFD groups. Furthermore, glucose tolerance testing showed that the half-life for the elimination of elevated blood glucose was shorter in females than males, although blood glucose parameters were generally similar between females and males.

CONCLUSIONS

These findings suggest that sex and aging may cause diet-independent differences in gene expression levels in female and male mice, and that higher expression of these genes in females could contribute to higher metabolic activity and resistance to obesity compared with males.

Mediastinal germ cell tumour causing superior vena cava tumour thrombosis

We report a rare case of a 35-year-old man who presented with a 1-week history of retrosternal chest pain of moderate intensity. A positron emission tomography CT (PET-CT) showed a large fluorodeoxy-glucose (FDG)-avid heterogeneously enhancing necrotic mass in the anterosuperior mediastinum with a focal FDG-avid thrombosis of the superior vena cava (SVC) suggestive of tumour thrombus and vascular invasion. α-Fetoprotein levels were raised (5690 IU/L). Image guided biopsy of the mediastinal mass was suggestive of non-seminomatous germ cell tumour (NSGCT). The patient received four cycles of BEP (bleomycin, etoposide and cisplatin) along with therapeutic anticoagulation with low-molecular-weight heparin. Follow-up whole body PET-CT revealed complete resolution of mediastinal mass and SVC tumour thrombosis. The documentation of FDG-PET-avid tumour thrombus resolving with chemotherapy supports the concept of circulating tumour cells being important not only in common solid tumours such as breast and colon cancer but also in relatively less common tumours such as NSGCT. The detection of circulating tumour cells could help deploy aggressive regimens upfront.

Trigonelline attenuates the adipocyte differentiation and lipid accumulation in 3T3-L1 cells

Trigonelline is a natural alkaloid mainly found in Trigonella Foenum Graecum (fenugreek) Fabaceae and other edible plants with a variety of medicinal applications. Therefore, we investigated the molecular mechanism of trigonelline (TG) on the inhibition of adipocyte differentiation and lipid accumulation in 3T3-L1 cells. Trigonelline suppressed lipid droplet accumulation in a concentration (75 and 100 μM) dependent manner. Treatment of adipocyte with of TG down regulates the peroxisome proliferator-activated receptor (PPARγ) and CCAAT element binding protein (C/EBP-α) mRNA expression, which leads to further down regulation of other gene such as adiponectin, adipogenin, leptin, resistin and adipocyte fatty acid binding protein (aP2) as compared with respective control cells on 5th and 10th day of differentiation. Further, addition of triognelline along with troglitazone to the adipocyte attenuated the troglitazone effects on PPARγ mediated differentiation and lipid accumulation in 3T3-L1 cells. Trigonelline might compete against troglitazone for its binding to the PPARγ. In addition, adipocyte treated with trigonelline and isoproterenol separately. Isoproterenol, a lipolytic agent which inhibits the fatty acid synthase and GLUT-4 transporter expression via cAMP mediated pathway, we found that similar magnitude response of fatty acid synthase and GLUT-4 transporter expression in trigonelline treated adipocyte. These results suggest that the trigonelline inhibits the adipogenesis by its influences on the expression PPARγ, which leads to subsequent down regulation of PPAR-γ mediated pathway during adipogenesis. Our findings provide key approach to the mechanism underlying the anti-adipogenic activity of trigonelline.

Positron emission tomography: clinical applications in oncology. Part 1

Positron emission tomography is a functional diagnostic imaging technique, which can accurately measure in vivo distribution of a radiopharmaceutical with high resolution. The ability of positron emission tomography to study various biologic processes opens up new possibilities for both research and day-to-day clinical use. Positron emission tomography has progressed rapidly from being a research technique in laboratories to a routine clinical imaging modality becoming part of armamentarium for the medical profession. The most widely used radiotracer in positron emission tomography is 18F-fluoro-2-deoxy-D-glucose (FDG), which is an analog of glucose. FDG uptake in cells is directly proportional to glucose metabolism of cells. Since glucose metabolism is increased many fold in malignant tumors, positron emission tomography has a high sensitivity and high negative predictive value. Positron emission tomography with FDG is now the standard of care in initial staging, monitoring the response to therapy and management of lung cancer, colorectal cancer, lymphoma, melanoma, esophageal cancer, head and neck cancer and breast cancer. The aim of this article is to review the clinical applications of positron emission tomography in oncology.

Low positive yield from routine inclusion of the brain in whole-body 18F-FDG PET/CT imaging for noncerebral malignancies: results from a large population study

OBJECTIVE

This retrospective study was conducted to assess the incremental value, if any, of including the brain in whole-body fluorine-18 fluorodeoxyglucose (F-FDG) positron emission tomography/computed tomography (PET/CT) studies in patients with extracalvarial primary malignancies.

METHODS

The scan data of 5110 F-FDG PET/CT studies conducted from March 2009 to December 2011 were reviewed.

RESULTS

Abnormal brain lesions were detected in 76/5110 patients who had undergone F-FDG PET/CT studies. Among them, 16 patients had lesions with F-FDG uptake less than that of the surrounding background and 54 had lesions with increased F-FDG uptake. Six patients had neither increased nor decreased tracer uptake in their brain lesions (identified on the CT component of the study). In the first group of patients, infarct was seen in four patients, treated brain metastases were seen in eight (five surgical and three through external beam radiotherapy), and untreated metastases were seen in four patients. In the 54 patients with increased uptake, metastatic lesions were identified in 51 and central nervous system involvement by systemic lymphoma in three. The third group showed metastases in four patients and central nervous system involvement by systemic lymphoma in one; one patient was lost to follow-up without a final diagnosis. Out of 63 patients with untreated cerebral metastases detected on the F-FDG PET/CT study, cerebral metastases were unknown before F-FDG PET/CT in 40 patients. Of these 40 patients, the brain was the only site of metastatic involvement in eight patients.

CONCLUSION

Inclusion of the brain routinely in whole-body F-FDG PET/CT studies detected previously unknown metastases in only 0.7% (40/5110) of studies, with negligible impact (0.15%) on staging.

Plin2 inhibits cellular glucose uptake through interactions with SNAP23, a SNARE complex protein

Although a link between excess lipid storage and aberrant glucose metabolism has been recognized for many years, little is known what role lipid storage droplets and associated proteins such as Plin2 play in managing cellular glucose levels. To address this issue, the influence of Plin2 on glucose uptake was examined using 2-NBD-Glucose and [(3)H]-2-deoxyglucose to show that insulin-mediated glucose uptake was decreased 1.7- and 1.8-fold, respectively in L cell fibroblasts overexpressing Plin2. Conversely, suppression of Plin2 levels by RNAi-mediated knockdown increased 2-NBD-Glucose uptake several fold in transfected L cells and differentiated 3T3-L1 cells. The effect of Plin2 expression on proteins involved in glucose uptake and transport was also examined. Expression of the SNARE protein SNAP23 was increased 1.6-fold while levels of syntaxin-5 were decreased 1.7-fold in Plin2 overexpression cells with no significant changes observed in lipid droplet associated proteins Plin1 or FSP27 or with the insulin receptor, GLUT1, or VAMP4. FRET experiments revealed a close proximity of Plin2 to SNAP23 on lipid droplets to within an intramolecular distance of 51 Å. The extent of targeting of SNAP23 to lipid droplets was determined by co-localization and co-immunoprecipitation experiments to show increased partitioning of SNAP23 to lipid droplets when Plin2 was overexpressed. Taken together, these results suggest that Plin2 inhibits glucose uptake by interacting with, and regulating cellular targeting of SNAP23 to lipid droplets. In summary, the current study for the first time provides direct evidence for the role of Plin2 in mediating cellular glucose uptake.

Human subcutaneous adipose tissue Glut 4 mRNA expression in obesity and type 2 diabetes

Cellular resistance to insulin caused by reduced glucose transport and metabolism is a primary defect leading to the development of metabolic disease. While the etiology of insulin resistance is multifactorial, reduced insulin action is associated with impaired activity of the glucose transporter GLUT4 in insulin-sensitive tissues. Yet, the role of adipose tissue GLUT4 deregulation in the pathogenesis of insulin resistance, obesity, and diabetes is still unclear. In this study, we assessed the relative GLUT4 level in human subcutaneous adipose tissue from obese, diabetic, and diabetic obese versus control subjects, using a real-time PCR method. GLUT4 mRNA levels were considerably decreased among type 2 diabetic patients compared with those of the controls (P < 0.01), whereas no such difference was found between obese and normal-weight controls. Multiple linear regressions analysis in both diabetic non-obese and diabetic obese groups showed a negative correlation between GLUT4 mRNA expression and both markers of obesity or insulin resistance (P < 0.01). However, in obese group, GLUT4 was inversely associated only with HOMA-IR (P < 0.01). Our findings showed that adipose GLUT4 gene expression changes were more related to insulin resistance and type 2 diabetes rather than to obesity.

The role of glucose transporters in brain disease: diabetes and Alzheimer’s Disease

The occurrence of altered brain glucose metabolism has long been suggested in both diabetes and Alzheimer’s diseases. However, the preceding mechanism to altered glucose metabolism has not been well understood. Glucose enters the brain via glucose transporters primarily present at the blood-brain barrier. Any changes in glucose transporter function and expression dramatically affects brain glucose homeostasis and function. In the brains of both diabetic and Alzheimer’s disease patients, changes in glucose transporter function and expression have been observed, but a possible link between the altered glucose transporter function and disease progress is missing. Future recognition of the role of new glucose transporter isoforms in the brain may provide a better understanding of brain glucose metabolism in normal and disease states. Elucidation of clinical pathological mechanisms related to glucose transport and metabolism may provide common links to the etiology of these two diseases. Considering these facts, in this review we provide a current understanding of the vital roles of a variety of glucose transporters in the normal, diabetic and Alzheimer’s disease brain.

Pyrophosphatase overexpression is associated with cell migration, invasion, and poor prognosis in gastric cancer

Inorganic pyrophosphatase (PPase) catalyzes the hydrolysis of pyrophosphate to form orthophosphate. Pyrophosphate can substitute for ATP under certain circumstances. We previously conducted a proteomic analysis to investigate tumor-specific protein expression in gastric cancer, and PPase was identified as a potential gastric tumor-specific marker; it was therefore selected for further study. Clinicopathological analysis, using proteomic analysis and immunohistochemistry, was used to validate PPase as a prognostic marker in gastric cancers. Proteomic analysis showed that PPase was overexpressed in patients with lymph node (LN) metastases and high tumor node metastasis (TNM) stages (p < 0.05). Based on immunohistochemistry, patients whose tumors overexpressed PPase had higher T stages, LN metastasis, a higher TNM stage, a higher cancer recurrence rate, and shorter survival times than patients whose tumors exhibited PPase underexpression (p < 0.05). Gain-of-function and loss-of-function approaches were employed to examine the malignant phenotypes of PPase-overexpressing or PPase-depleted cells. A decrease in PPase expression caused a significant decrease in gastric cancer cell migration and invasion in vitro, whereas forced overexpression of PPase enhanced migration but not invasion. Our findings indicate that PPase is involved in gastric tumor progression and that PPase may be a useful marker for poor prognosis of human gastric cancers.

Hepatic FXR: key regulator of whole-body energy metabolism

The farnesoid X receptor (FXR) is a nuclear receptor whose activation leads to alterations in pathways involved in energy metabolism. For example, it serves as a bile acid receptor in tissues such as the liver, and as an energy metabolism regulator in liver, muscle and adipose tissue. However, the effects of FXR activation are not exclusive to the tissue where it is present, because receptor crosstalk affects tissues throughout the body. It has been demonstrated that FXR regulates the metabolism of not just bile acids, but also of fats and hydrocarbon metabolites. FXR is currently under study as a therapeutic target for the treatment of diseases of excess, such as diabetes. Here we review the effects of FXR activation in the response of an organism to excess energy.

Cardiovascular and metabolic safety profiles of the fluoroquinolones

INTRODUCTION

Certain fluoroquinolones share similar indications of use. A comparison among Cardiovascular and metabolic (i.e., dysglycemia) safety profiles of the fluoroquinolones might be particularly useful for the prescribers' decision-making process as well as to hypothesize future researcher purposes.

AREAS COVERED

A literature search was conducted using keywords apt to identify information on safety profile of the fluoroquinolones. Publications concerned with descriptive and etiological surveys were manually reviewed.

EXPERT OPINION

Cardiac alterations and blood glucose impairments might be associated with any fluoroquinolone. However, the benefit/risk profile of these agents could be stratified for the single compounds. Several predisposing factors, such as diabetes, heart illnesses and their related pharmacotherapies, might exacerbate the risk of potentially serious adverse events. In this context, the opportunity of the more appropriate choice among different fluoroquinolones could be applicable.

Effects of Sulfonylureas on Peroxisome Proliferator-Activated Receptor γ Activity and on Glucose Uptake by Thiazolidinediones

BACKGROUND

Sulfonylurea primarily stimulates insulin secretion by binding to its receptor on the pancreatic β-cells. Recent studies have suggested that sulfonylureas induce insulin sensitivity through peroxisome proliferator-activated receptor γ (PPARγ), one of the nuclear receptors. In this study, we investigated the effects of sulfonylurea on PPARγ transcriptional activity and on the glucose uptake via PPARγ.

METHODS

Transcription reporter assays using Cos7 cells were performed to determine if specific sulfonylureas stimulate PPARγ transactivation. Glimepiride, gliquidone, and glipizide (1 to 500 µM) were used as treatment, and rosiglitazone at 1 and 10 µM was used as a control. The effects of sulfonylurea and rosiglitazone treatments on the transcriptional activity of endogenous PPARγ were observed. In addition, 3T3-L1 adipocytes were treated with rosiglitazone (10 µM), glimepiride (100 µM) or both to verify the effect of glimepiride on rosiglitazone-induced glucose uptake.

RESULTS

Sulfonylureas, including glimepiride, gliquidone and glipizide, increased PPARγ transcriptional activity, gliquidone being the most potent PPARγ agonist. However, no additive effects were observed in the presence of rosiglitazone. When rosiglitazone was co-treated with glimepiride, PPARγ transcriptional activity and glucose uptake were reduced compared to those after treatment with rosiglitazone alone. This competitive effect of glimepiride was observed only at high concentrations that are not achieved with clinical doses.

CONCLUSION

Sulfonylureas like glimepiride, gliquidone and glipizide increased the transcriptional activity of PPARγ. Also, glimepiride was able to reduce the effect of rosiglitazone on PPARγ agonistic activity and glucose uptake. However, the competitive effect does not seem to occur at clinically feasible concentrations.

Dietary carbohydrate-to-protein ratio affects TOR signaling and metabolism-related gene expression in the liver and muscle of rainbow trout after a single meal

Most teleost fish are known to require high levels of dietary proteins. Such high-protein intake could have significant effects, particularly on insulin-regulated gene expression. We therefore analyzed the effects of an increase in the ratio of dietary carbohydrates/proteins on the refeeding activation of the Akt-target of rapamycin (TOR) signaling pathways in rainbow trout and the effects on the expression of several genes related to hepatic and muscle metabolism and known to be regulated by insulin, amino acids, and/or glucose. Fish were fed once one of three experimental diets containing high (H), medium (M), or low (L) protein (P) or carbohydrate (C) levels after 48 h of feed deprivation. Activation of the Akt/TOR signaling pathway by refeeding was severely impaired by decreasing the proteins-to-carbohydrates ratio. Similarly, postprandial regulation of several genes related to glucose (Glut4, glucose-6-phosphatase isoform 1), lipid (fatty acid synthase, ATP-citrate lyase, sterol responsive element binding protein, carnitine palmitoyltransferase 1, and 3-hydroxyacyl-CoA dehydrogenase), and amino acid metabolism (serine dehydratase and branched-chain α-keto acid dehydrogenase E2 subunit) only occurred when fish were fed the high-protein diet. On the other hand, diet composition had a low impact on the expression of genes related to muscle protein degradation. Interestingly, glucokinase was the only gene of those monitored whose expression was significantly upregulated by increased carbohydrate intake. In conclusion, this study demonstrated that macro-nutrient composition of the diet strongly affected the insulin/amino acids signaling pathway and expression pattern of genes related to metabolism.

Kinetic analysis and modeling of daptomycin batch fermentation by Streptomyces roseosporus

In this study, Streptomyces roseosporus was subjected to helium-neon (He-Ne) laser (632.8 nm) irradiation to improve the production ability of extracellular antibiotic daptomycin. Under the optimum irradiation dosage of 18 mW for 22 min, a stable positive mutant strain S. roseosporus LC-54 was obtained. The maximum A21978C (daptomycin is a semisynthetic antimicrobial substance derived from the A21978C complex) yield of this mutant strain was 296 mg/l, which was 146% higher than that of the wild strain. The mutant strain grew more quickly and utilized carbohydrate sources more efficiently than the wild strain. The batch culture kinetics was investigated in a 7 l bioreactor. The logistic equation for growth, the Luedeking-Piret equation for daptomycin production, and Luedeking-Piret-like equations for carbon substrate consumption were established. This model appeared to provide a reasonable description for each parameter during the growth phase and fitted fairly well with the experiment data.

Can 18F-FDG-PET response during radiotherapy be used as a predictive factor for the outcome of head and neck cancer patients?

OBJECTIVES

We investigated if (18F) fluoro-2-deoxy-D-glucose positron emission tomography (F-FDG-PET) during radiotherapy or concurrent chemoradiotherapy adds information about the treatment outcome compared with an FDG-PET study before treatment.

METHODS

Forty-three patients with head and neck cancer were treated with helical tomotherapy. F-FDG-PET was performed at baseline and during the treatment after 47 Gy. Tracer accumulation at the tumor site was assessed visually and semiquantitatively using the maximal standardized uptake values (SUV(max)). With median SUV(max) of both the studies as cutoff, patients were categorized into low and high SUV(max) groups. For visual analysis, two independent observers classified patients as complete metabolic responders (CMR) or noncomplete metabolic responders (NCMR).

RESULTS

At baseline the median SUV(max) was 8.11 (2.41-15.13). The overall survival (OS) and disease-free survival (DFS) were 81 and 67% versus 50 and 40% for the low and high SUV(max), respectively. OS was significantly different (P=0.027). During therapy, median SUV(max) was 4.03 (1.94-7.58). OS and DFS were 82 and 63%, versus 47 and 42% for the low and high SUV(max) group, respectively. OS was significantly different (P=0.026). No significant differences between CMR versus NCMR in OS (72 vs. 60%), and DFS (56 vs. 49%) were found.

CONCLUSION

Categorizing patients on the basis of a semiquantitative approach resulted in significant differences in OS for both the scans before and during therapy. Future work on a larger number of patients is warranted to determine SUV(max) cutoff values which could be used for the early identification of patients with poor treatment outcome or perhaps other therapeutic approaches.

Safety profile of the fluoroquinolones: focus on levofloxacin

The fluoroquinolone class of antibacterial agents are among the most frequently prescribed drugs, with utility in a broad range of bacterial infections. Although very useful agents, the fluoroquinolones as a class are associated with a number of adverse events, some with considerable clinical significance. In the past 15-20 years, tolerability concerns have led to restrictions on the use of the fluoroquinolones and, in some instances, the withdrawal of agents from the market. This review focuses on the safety and tolerability of levofloxacin, a third-generation fluoroquinolone, relative to other fluoroquinolones. A literature search was performed of the MEDLINE database encompassing the dates 1980-2009, using as keywords the drug names levofloxacin and concurrently marketed fluoroquinolones combined with the words 'safety', 'adverse effect' or 'adverse drug reaction', or the name of the specific adverse effect. Adverse events commonly associated with the fluoroquinolones include gastrointestinal and CNS toxicity (most frequently headache and dizziness), as well as other adverse events including ECG abnormalities (for example QT interval prolongation), disrupted glucose metabolism, phototoxicity, tendon and joint disorders, hypersensitivity and skin disorders, and hepatic toxicity. Package inserts for the fluoroquinolones in Europe and the US contain warnings regarding these risks. US package inserts also carry 'black-box' warnings regarding the risk of tendon rupture and joint disorders with these agents; however, there is a substantial body of evidence to indicate that there are marked differences in the tolerability profiles of the individual agents within the fluoroquinolone class. These differences may be explained, at least in part, by structural differences: all fluoroquinolones share a basic quinolone core, with differences in specific side chains underlying the adverse event relationships. Furthermore, many of the fluoroquinolone-associated adverse effects and toxicities occur more frequently in patients with pre-existing risk factors, or in certain subpopulations. Notably, package inserts for the fluoroquinolones carry warnings regarding use in the elderly, paediatric patients and patients with pre-existing, or factors predisposing to, seizure disorders. Because of this, many adverse reactions with these agents could be prevented by improving patient screening and education. The recent withdrawal of gatifloxacin due to dysglycaemia makes it timely to review the safety and tolerability of the individual agents in this class. Overall, it appears that levofloxacin is relatively well tolerated, with low rates of clinically important adverse events such as CNS toxicity, cardiovascular toxicity and dysglycaemia.

Evolutionary structural and functional conservation of an ortholog of the GLUT2 glucose transporter gene (SLC2A2) in zebrafish

In mammals, GLUT2 plays an essential role in glucose homeostasis. From an evolutionary perspective, relatively little is known about the biology of GLUT2, or other GLUTs, in nonmammalian vertebrates. Here, we have conducted studies to functionally characterize GLUT2 in zebrafish. First, we cloned the zebrafish ortholog of GLUT2 (zfGLUT2) encoding a protein of 504 amino acids with high-sequence identity to other known vertebrate GLUT2 proteins. The zfGLUT2 gene consists of 11 exons and 10 introns, spanning 20 kb and mapping to a region of chromosome 2 that exhibits conserved synteny with human chromosome 3. When expressed in Xenopus oocytes, zfGLUT2 transported 2-deoxyglucose (2-DG) with similar affinity than mammalian GLUT2 (K(m) of 11 mM). Transport of 2-DG was competed mostly by D-fructose and D-mannose and was inhibited by cytochalasin B. During early development, zfGLUT2 expression was detected already at 10 h postfertilization and remained elevated in 5-day larvae, when it was clearly localized to the liver and intestinal bulb. In the adult, zfGLUT2 expression was highest in testis, brain, skin, kidney, and intestine, followed by liver and muscle. In the intestine, zfGLUT2 transcripts were detected in absorptive enterocytes, and its mRNA levels were altered by fasting and refeeding, suggesting that its expression in the intestine may be regulated by the nutritional status. These results indicate that the structure and function of GLUT2 has been remarkably well conserved during vertebrate evolution and open the way for the use of zebrafish as a model species in which to study the biology and pathophysiology of GLUT2.

Expression of rainbow trout glucose transporters GLUT1 and GLUT4 during in vitro muscle cell differentiation and regulation by insulin and IGF-I

Insulin is an important factor for the maintenance of glucose homeostasis, enhancing glucose uptake in its target tissues in a process that has been conserved between fish and mammals. In fish skeletal muscle cells, like in mammals, insulin promotes GLUT4 translocation to the plasma membrane and, consequently, glucose uptake, but its role regulating the expression of glucose transporters in vitro has not been demonstrated to date. Thus, we investigated the expression of GLUT4 and GLUT1 throughout skeletal muscle cell differentiation and their regulation by insulin and IGF-I using a primary culture of trout muscle cells. GLUT4 expression gradually increased during the muscle cell differentiation process, whereas GLUT1 expression remained fairly constant. Insulin and IGF-I similarly increased the mRNA levels of GLUT4 in myoblasts and myotubes. On the other hand, IGF-I appeared to be more potent than insulin in stimulating GLUT1 expression, particularly at the myoblast stage. Therefore, this work provides the first demonstration in nonmammalian vertebrates that insulin and IGF-I may act directly on trout muscle cells to regulate the expression of GLUT4 and GLUT1.

Functional studies of the T295M mutation causing Glut1 deficiency: glucose efflux preferentially affected by T295M

Glucose transporter type 1 (Glut1) deficiency syndrome (Glut1 DS, OMIM: #606777) is characterized by infantile seizures, acquired microcephaly, developmental delay, hypoglycorrhachia (CSF glucose <40 mg/dL), and decreased erythrocyte glucose uptake (56.1 +/- 17% of control). Previously, we reported two patients with a mild Glut1 deficiency phenotype associated with a heterozygous GLUT1 T295M mutation and normal erythrocyte glucose uptake. We assessed the pathogenicity of T295M in the Xenopus laevis oocyte expression system. Under zero-trans influx conditions, the T295M Vmax (590 pmol/min/oocyte) was 79% of the WT value and the Km (14.3 mM) was increased compared with WT (9.6 mM). Under zero-trans efflux conditions, both the Vmax (1216 pmol/min/oocyte) and Km (8.8 mM) in T295M mutant Glut1 were markedly decreased in comparison to the WT values (7443 pmol/min/oocyte and 90.8 mM). Western blot analysis and confocal studies confirmed incorporation of the T295M mutant protein into the plasma membrane. The side chain of M295 is predicted to block the extracellular "gate" for glucose efflux in our Glut-1 molecular model. We conclude that the T295M mutation specifically alters Glut1 conformation and asymmetrically affects glucose flux across the cell by perturbing efflux more than influx. These findings explain the seemingly paradoxical findings of Glut1 DS with hypoglycorrhachia and "normal" erythrocyte glucose uptake.

Disturbance of cellular glucose transport by two prevalently used fluoroquinolone antibiotics ciprofloxacin and levofloxacin involves glucose transporter type 1

Dysglycemia and central nervous system (CNS) complications are the known adverse effects of fluoroquinolone antibiotics. Ciprofloxacin and levofloxacin are among the most prescribed antibiotics. In this study we demonstrate that ciprofloxacin and levofloxacin disturb glucose transport into HepG2 cells and such inhibition is associated with inhibited glucose transporter type 1 (GLUT1) function. When exposed to ciprofloxacin or levofloxacin at maximum plasma concentrations (C(max)) and 5x of C(max) concentrations, GLUT1 mRNA expression, cell surface GLUT1 protein expression and glucose uptake were significantly reduced. These findings imply that disturbed cellular glucose transport and GLUT1 function may underlie the dysglycemic and CNS effects of ciprofloxacin and levofloxacin.

Standardized uptake values of uterine leiomyoma with 18F-FDG PET/CT: variation with age, size, degeneration, and contrast enhancement on MRI

OBJECTIVE

To assess the effect of age, size, the degree of degeneration, and contrast enhancement on magnetic resonance imaging (MRI) on 18F-fluoro-2-deoxyglucose (18F-FDG) uptake in uterine leiomyomas using quantitative standardized uptake values (SUVs).

METHODS

A total of 61 leiomyomas of 41 patients, who underwent combined positron emission tomography/computed tomography (PET/CT) using 18F-FDG and contrast-enhanced MRI were included in this study. Sixty-one leiomyomas were divided into two groups: "non-degenerated" leiomyomas showing distinct low signal intensity on T2-weighted images and intermediate signal intensity on T1-weighted images, and "degenerated" leiomyomas showing other types of signal intensity. Sixty-one leiomyomas were also divided into two groups of "strongly enhancing" leiomyomas and "weakly enhancing" leiomyomas in terms of their degree of contrast enhancement on MRI.

RESULTS

The mean values of the maximum and average SUVs for the total of 61 leiomyomas were 2.34 +/- 0.75 (range 1.59-5.15) and 1.74 +/- 0.50 (0.66-3.95), respectively. There was a moderate negative correlation between the maximum and average SUVs and age (r = -0.43 and P = 0.00016, r = -0.31 and P = 0.029, respectively). Although there was a mild positive correlation between maximum SUV and size (r = 0.35 and P = 0.011), there was no significant difference between average SUV and size. Although there was no significant difference in average SUV between "degenerated" and "non-degenerated" leiomyomas, the maximum SUV of "degenerated" leiomyomas was significantly higher than that of "non-degenerated" leiomyomas (P = 0.0012). The degree of contrast enhancement on MRI was not significantly correlated with 18F-FDG uptake.

CONCLUSIONS

Mild or moderate uptake of 18F-FDG is often observed in uterine leiomyoma and declines with age, and should not be confused with malignant accumulation.

Long-term stability of RNA in post-mortem bovine skeletal muscle, liver and subcutaneous adipose tissues

Background

Recovering high quality intact RNA from post-mortem tissue is of major concern for gene expression studies in animals and humans. Since the availability of post-mortem tissue is often associated with substantial delay, it is important that we understand the temporal variation in the stability of total RNA and of individual gene transcripts so as to be able to appropriately interpret the data generated from such studies. Hence, the objective of this experiment was to qualitatively and quantitatively assess the integrity of total and messenger RNA extracted from bovine skeletal muscle, subcutaneous adipose tissue and liver stored at 4°C at a range of time points up to 22 days post-mortem. These conditions were designed to mimic the environment prevailing during the transport of beef from the abattoir to retail outlets.

Results

The 28S and 18S rRNA molecules of total RNA were intact for up to 24 h post-mortem in liver and adipose tissues and up to 8 days post-mortem in skeletal muscle. The mRNA of housekeeping genes (GAPDH and ACTB) and two diet-related genes (RBP5 and SCD) were detectable up to 22 days post-mortem in skeletal muscle. While the mRNA stability of the two housekeeping genes was different in skeletal muscle and liver, they were similar to each other in adipose tissue. After 22 days post-mortem, the relative abundance of RBP5 gene was increased in skeletal muscle and in adipose tissue and decreased in liver. During this period, the relative abundance of SCD gene also increased in skeletal muscle whereas it decreased in both adipose tissue and liver.

Conclusion

Stability of RNA in three tissues (skeletal muscle, subcutaneous adipose tissue and liver) subjected to long-term post-mortem storage at refrigeration temperature indicated that skeletal muscle can be a suitable tissue for recovering biologically useful RNA for gene expression studies even if the tissue is subjected to post-mortem storage for weeks, whereas adipose tissue and liver should be processed within 24 hours post-mortem.

PPARgamma and GLUT-4 expression as developmental regulators/markers for preadipocyte differentiation into an adipocyte

In this document, we have integrated knowledge about two major cellular markers found in cells of the adipocyte lineage (an adipogenic marker and a metabolic marker). This review provides information as to how differentiation of a cell (such as an adipofibroblast, fibroblast or preadipocyte) to become a viable (and new) adipocyte is under different regulation than that experienced by an immature adipocyte that is just beginning to accumulate lipid. The differentiation, prior to lipid-filling, involves PPARgamma. Subsequently, lipid-filling of the adipocyte relies on a late subset of genes and, depending on depot specificity, involves GLUT-4 or any number of other metabolic markers.

Novel findings regarding Glut-4 expression in adipose tissue and muscle in horses – A preliminary report

One of the hallmarks of insulin resistance is a reduction in glucose transporter-4 (Glut-4) expression in adipose tissue but not in skeletal muscle. However, while Glut-4 has been demonstrated in skeletal and cardiac muscles in horses it has not been demonstrated in adipose tissue. The initial objectives of the present study were: (1) to test the hypothesis that Glut-4 expression would vary between selected key skeletal muscles; (2) to test the hypothesis that it would also vary between representative adipose tissue depots, and (3) to see whether expression would be greater in adipose tissue compared to muscle. Glut-4 expression was determined by Western blot using samples obtained from post mortem biopsies obtained from four muscles (gluteus medius, semitendinosus, heart, and diaphragm), and four adipose tissues (subcutaneous, retroperitoneal, mesenteric, and omental) in three horses. There were no differences (P>0.05) in Glut-4 protein expression between the muscles sampled. Likewise there were no differences (P>0.05) in Glut-4 protein expression between fat depots. There was a significant difference (P=0.03) when pooled means for Glut-4 expression in muscle (58.8+/-2.5 densitometry units) were compared with adipose tissue (115.8+/-15.7). This difference in Glut-4 expression in these two tissues with distinctly different metabolic reasons for taking up glucose may warrant further investigation to see if there are more pronounced differences in Glut-4 expression in muscle and adipose tissue in various populations of horses.

Gatifloxacin affects GLUT1 gene expression and disturbs glucose homeostasis in vitro

Gatifloxacin may induce life-threatening dysglycemia. The facilitated glucose transporter type 1 (GLUT1) protein is ubiquitously expressed in many tissues. Disturbed GLUT1 protein function weakens the systemic glycemic control and may cause dysglycemia. In this study we demonstrate that gatifloxacin modulates the transcription and reduces the expression and function of GLUT1 gene in HepG2 cells. When treated with gatifloxacin at concentrations of 3.4 mug/ml (8.4 muM) and 17 mug/ml (42 muM), GLUT1 promoter activity was stimulated by 2.8 and 3.8 folds, GLUT1 mRNA expression was decreased by 41% and 31%, and glucose uptake was decreased by 41% and 52%, respectively. Our findings imply that disturbed GLUT1 gene expression and protein function may underlie the dysglycemic effect of gatifloxacin.

Advances in alimentary tract imaging

Advances in imaging techniques are changing the way radiologists undertake imaging of the gastrointestinal tract and their ability to answer questions posed by surgeons. In this paper we discuss the technological improvements of imaging studies that have occurred in the last few years and how these help to better diagnosing alimentary tract disease.