GLUT-1 and CAIX as intrinsic markers of hypoxia in carcinoma of the cervix: relationship to pimonidazole binding

The presence of hypoxia in tumours results in the overexpression of certain genes, which are controlled via the transcription factor HIF-1. Hypoxic cells are known to be radioresistant and chemoresistant, thus, a reliable surrogate marker of hypoxia is desirable to ensure that treatment may be rationally applied. Recently, the HIF-1-regulated proteins Glut-1 and CAIX were validated as intrinsic markers of hypoxia by comparison with pO(2) measured using oxygen electrodes. We compare the expression of Glut-1 and CAIX with the binding of the bioreductive drug hypoxia marker pimonidazole. Pimonidazole was administered to 42 patients with advanced carcinoma of the cervix, 16 hr before biopsy. Sections of single or multiple biopsies were then immunostained for Glut-1 and CAIX, and the area of staining scored by eye, using a "field-by-field" semi-quantitative averaging system. Using 1 biopsy only, Glut-1 (r = 0.54, p = <0.001) correlated with the level of pimonidazole binding, and Glut-1 and CAIX expression also correlated significantly (r = 0.40, p = <0.009). Thus, our study has shown that HIF-1 regulated genes have potential for future use as predictors of the malignant changes mediated by hypoxia, and warrant further investigation as indicators of response to cancer therapy.

Programming of rat muscle and fat metabolism by in utero overexposure to glucocorticoids

In utero overexposure to glucocorticoids may explain the association between low birth weight and subsequent development of the metabolic syndrome. We previously showed that prenatal dexamethasone (dex) exposure in the rat lowers birth weight and programs adult fasting and postprandial hyperglycemia, associated with increased hepatic gluconeogenesis driven by elevated liver glucocorticoid receptor (GR) expression. This study aimed to determine whether prenatal dex (100 microg/kg per day from embryonic d 15 to embryonic d 21) programs adult GR expression in skeletal muscle and/or adipose tissue and whether this contributes to altered peripheral glucose uptake or metabolism. In utero dex-exposed rats remained lighter until 6 months of age, despite some early catch-up growth. Adults had smaller epididymal fat pads, with a relative increase in muscle size. Although glycogen storage was reduced in quadriceps, 2-deoxyglucose uptake into extensor digitorum longus muscle was increased by 32% (P < 0.05), whereas uptake in other muscles and adipose beds was unaffected by prenatal dex. GR mRNA was not different in most muscles but selectively reduced in soleus (by 23%, P < 0.05). However, GR mRNA was markedly increased specifically in retroperitoneal fat (by 50%, P < 0.02). This was accompanied by a shift from peroxisomal proliferator-activated receptor gamma 1 to gamma 2 expression and a reduction in lipoprotein lipase mRNA (by 28%, P < 0.02). Adipose leptin, uncoupling protein-3 and resistin mRNAs, muscle GLUT-4, and circulating lipids were not affected by prenatal dex. These data suggest that hyperglycemia in 6-month-old rats exposed to dexamethasone in utero is not due to attenuated peripheral glucose disposal. However, increased GR and attenuated fatty acid uptake specifically in visceral adipose are consistent with insulin resistance in this crucial metabolic depot and could indirectly contribute to increased hepatic glucose output.

Retinal neovascular markers in retinopathy of prematurity: aetiological implications

AIM

(1) To determine if expression of the blood-tissue barrier associated glucose transporter GLUT1 is preserved by the neovasculature of retinopathy of prematurity (ROP), in contrast with the reported loss of GLUT1 expression in preretinal vessels of proliferative diabetic retinopathy. (2) To compare the vascular immunophenotype of ROP to juvenile haemangioma, another perinatal neovascular disorder that has recently been shown to express placental type vascular antigens, including GLUT1 and Lewis Y antigen.

METHODS

A retrospective case report was carried out. Immunoreactivities for GLUT1 and Lewis Y antigen were assessed in a human eye with stage 3 ROP and compared with those in a control (paediatric) eye. The presence or absence of endothelial GLUT1 and Lewis Y immunoreactivity was determined in preretinal and intraretinal vessels.

RESULTS

Immunoreactivity was positive for GLUT1 and negative for Lewis Y in the intraretinal and preretinal neovasculature of the ROP affected eye and in the normal retinal vessels of the control eye.

CONCLUSIONS

Retention of immunoreactivity for GLUT1 distinguishes ROP from proliferative diabetic retinopathy. Furthermore, absence of Lewis Y antigen co-expression distinguishes ROP from juvenile haemangioma, a perinatal form of GLUT1 positive neovascularisation that has recently been linked to placental vasculature.

Enhanced basal activation of mitogen-activated protein kinases in adipocytes from type 2 diabetes: potential role of p38 in the downregulation of GLUT4 expression

Serine and threonine kinases may contribute to insulin resistance and the development of type 2 diabetes. To test the potential for members of the mitogen-activated protein (MAP) kinase family to contribute to type 2 diabetes, we examined basal and insulin-stimulated Erk 1/2, JNK, and p38 phosphorylation in adipocytes isolated from healthy and type 2 diabetic individuals. Maximal insulin stimulation increased the phosphorylation of Erk 1/2 and JNK in healthy control subjects but not type 2 diabetic patients. Insulin stimulation did not increase p38 phosphorylation in either healthy control subjects or type 2 diabetic patients. In type 2 diabetic adipocytes, the basal phosphorylation status of these MAP kinases was significantly elevated and was associated with decreased IRS-1 and GLUT4 in these fat cells. To determine whether MAP kinases were involved in the downregulation of IRS-1 and GLUT4 protein levels, selective inhibitors were used to inhibit these MAP kinases in 3T3-L1 adipocytes treated chronically with insulin. Inhibition of Erk 1/2, JNK, or p38 had no effect on insulin-stimulated reduction of IRS-1 protein levels. However, inhibition of the p38 pathway prevented the insulin-stimulated decrease in GLUT4 protein levels. In summary, type 2 diabetes is associated with an increased basal activation of the MAP kinase family. Furthermore, upregulation of the p38 pathway might contribute to the loss of GLUT4 expression observed in adipose tissue from type 2 diabetic patients.

Antiserum against human glucose transporter 5 is highly specific for microglia among cells of the mononuclear phagocyte system

Human monocytes and a variety of tissue macrophages, including microglia, were studied immunohistochemically to determine the expression of a novel microglial marker, human glucose transporter 5 (hGLUT5), in these cells. The hGLUT5 was not expressed in most peripheral macrophages in the normal state, but weakly expressed in some foamy macrophages in atherosclerotic lesions. There was no hGLUT5 reactivity in blood monocytes. In the lesions of brain infarcts, foamy macrophages (predominantly monocyte-derived cells) in the ischemic core were mostly negative for hGLUT5, while activated and phagocytic microglia in the transitional zone were consistently positive. The present study indicated that unlike other microglial markers, hGLUT5 is rarely present in peripheral macrophages, and that hGLUT5 immunohistochemistry is useful in distinguishing microglia-derived macrophages from monocyte-derived macrophages in acute necrotic lesions.

The locally acting glucocorticosteroid budesonide enhances intestinal sugar uptake following intestinal resection in rats

BACKGROUND AND AIMS

Locally and systemically acting corticosteroids alter the morphology and transport function of the intestine. This study was undertaken to assess the effect of budesonide, prednisone, and dexamethasone on sugar uptake.

METHODS

Adult male Sprague Dawley rats underwent transection or resection of 50% of the middle portion of the small intestine, and in vitro uptake of sugars was measured.

RESULTS

The 50% enterectomy did not alter jejunal or ileal uptake of glucose or fructose. Prednisone had no effect on the uptake of glucose or fructose in resected animals. In contrast, in resected rats budesonide increased by over 120% the value of the jejunal maximal transport rate for the uptake of glucose, and increased by over 150% ileal uptake of fructose. Protein abundance and mRNA expression of the sodium dependent glucose transporter in brush border membrane (SGLT1), sodium independent fructose transporter in the brush border membrane (GLUT5), sodium independent glucose and fructose transporter in the basolateral and brush border membranes (GLUT2), and Na(+)/K(+) ATPase alpha1 and beta1 did not explain the enhancing effect of budesonide on glucose or fructose uptake. Budesonide, prednisone, and dexamethasone reduced jejunal expression of the early response gene c-jun. In resected animals, expression of the mRNA of ornithine decarboxylase (ODC) in the jejunum was reduced, and corticosteroids reduced jejunal expression of the mRNA of proglucagon.

CONCLUSIONS

These data suggest that the influence of corticosteroids on sugar uptake in resected animals may be achieved by post translational processes involving signalling with c-jun, ODC, and proglucagon, or other as yet unknown signals. It remains to be determined whether budesonide may be useful to stimulate the absorption of sugars following intestinal resection in humans.

Impaired cardiac function and IGF-I response in myocytes from calmodulin-diabetic mice: role of Akt and RhoA

This study characterized the cardiac contractile function and IGF-I response in a transgenic diabetic mouse model. Mechanical properties were evaluated in cardiac myocytes from OVE26 diabetic and FVB wild-type mice, including peak shortening (PS), time to PS (TPS), time to 90% relengthening (TR(90)) and maximal velocity of shortening/relengthening (+/-dL/dt). Intracellular Ca(2+) was evaluated as Ca(2+)-induced Ca(2+) release [difference in fura 2 fluorescent intensity (Delta FFI)] and fluorescence decay rate (tau). Sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)2a, phospholamban (PLB), Na(+)-Ca(2+) exchanger (NCX), GLUT4, and the serine-threonine kinase Akt were assessed by Western blot. RhoA and IGF-I/IGF-I receptor mRNA levels were determined by RT-PCR and Northern blot. OVE26 myocytes displayed decreased PS, +/-dL/dt, and Delta FFI associated with prolonged TPS, TR(90), and tau. SERCA2a, NCX, and Akt activation were reduced, whereas PLB and RhoA were enhanced in OVE26 hearts. GLUT4 was unchanged. IGF-I enhanced PS and Delta FFI in FVB but not OVE26 myocytes. IGF-I mRNA was increased, but IGF-I receptor mRNA was reduced in OVE26 hearts and livers. These results validate diabetic cardiomyopathy in OVE26 mice due to reduced SERCA2, NCX, IGF-I response, and Akt activation associated with enhanced RhoA level, suggesting a therapeutic potential for Akt and RhoA.

Luminal polyamines upregulate transmural glucose transport in the rat small intestine

BACKGROUND

Polyamines, which are contained in many foods, play an important role in the growth and differentiation of the enterocyte, but their role in glucose transport is unclear. Using isolated rat small intestine and a nonrecirculating perfusion system, we studied the effect of luminal polyamines on glucose uptake and on the concentration of sodium-glucose transporter 1 (SGLT1) and glucose transporter 5 (GLUT5) proteins.

METHODS

In the control group, 300mg glucose solution was administered through the jejunum, and the glucose concentration in the portal vein was measured for 15 min. In treatment groups, various concentrations of polyamine (putrescine [Put] or spermine [Spm]) were administered simultaneously with the glucose. At the end of the perfusion period, the amount of SGLT1, GLUT5, and aminopeptidase N (APN) in the brush border membrane was subjected to Western blot analysis.

RESULTS

Glucose concentration in the portal vein increased after the simultaneous administration of glucose and polyamines, and the area under the curve (AUC) after the 15-min perfusion was enhandced to 188%, 196%, 132%, and 192% by 0.5mM Spm, 4mM Spm, 1 mM Put, and 8 mM Put, respectively. The brush border membrane concentration of SGLT1 protein 15 min after polyamine administration was also enhanced in all treatment groups, and it correlated with the AUC. The concentration of GLUT5, on the other hand, was reduced by 4mM Spm, and the concentration of APN was not affected by polyamine administration.

CONCLUSIONS

Luminal polyamines increase glucose absorption in the small intestine via the rapid enhancement of SGLT1 protein in the brush border membrane.

Expression and localisation of GLUT1 and GLUT12 glucose transporters in the pregnant and lactating rat mammary gland

Glucose plays a major role in mammary gland function during lactation as it is used both as a fuel and as a precursor of milk components. In rats, previous studies have shown that the facilitative glucose transporter GLUT1 is expressed in mammary epithelial cells. We have used confocal immunofluorescence to localise GLUT1 and GLUT12, a recently identified member of the sugar transporter family, in pregnant and lactating rat mammary gland. GLUT12 staining was observed in the cytoplasm of mammary epithelial cells at day 20 of pregnancy, and at 1 and 6 days postpartum. Furthermore, GLUT12 staining was present at the apical plasma membrane of epithelial cells during lactation. In contrast, GLUT1 protein localised to the cytoplasm and basolateral surface of mammary epithelial cells. Forced weaning resulted in decreased cytoplasmic GLUT1 staining intensity, but no change in GLUT12 staining. The results suggest a possible role for GLUT12 in the metabolism of mammary epithelial cells during pregnancy and lactation.

Localisation of breast cancer resistance protein in microvessel endothelium of human brain

Movement of substrates between blood and brain is known to be influenced by P-glycoprotein (P-gp) at the luminal surface of the endothelium lining brain microvessels and by multidrug resistance associated protein 1 (MRP1) at the basolateral surface of the choroid plexus epithelium. Here, using RT-PCR and Western blotting, we investigate other ABC transporters in both normal and tumour human brain tissue and demonstrate the presence of breast cancer resistance protein (BCRP). Immunofluorescence confocal microscopy demonstrates that BCRP is located at the blood-brain barrier, mainly at the luminal surface of microvessel endothelium. This localization closely resembles that of P-gp. BCRP has several substrates in common with P-gp and may pose an additional barrier to drug access to the brain.

Polarized glucose transporters and mRNA expression properties in newly developed rat syncytiotrophoblast cell lines, TR-TBTs

In this study, we have established new syncytiotrophoblast cell lines (TR-TBTs) from the recently developed transgenic rat harboring temperature-sensitive simian virus 40 large T-antigen gene (Tg-rat). Four conditionally immortalized syncytiotrophoblast cell lines (TR-TBT 18d-1 approximately 4) were obtained from pregnant Tg-rats at gestational day 18. These cell lines had a syncytium-like morphology, could be prepared as monolayers, expressed cytokeratins and rat syncytiotrophoblast markers, and exhibited apical or basal GLUT1 localizations and apical GLUT3 localizations. TR-TBTs express large T-antigen and grow well at 33 degrees C with a doubling time of about 30 h. TR-TBTs have processes for the uptake of dehydroepiandrosteron-3-sulfate (DHEAS) and these are predominantly located on the basal side, and this is the first report of an in vitro model of blood placental barrier (BPB) able to incorporate DHEAS. Therefore, TR-TBTs are an appropriate in vitro model for investigating carrier-mediated transport functions at the BPB. Moreover, TR-TBTs express betaine/GABA transporter (GAT-2/BGT-1), concentrative nucleoside transporter 2 (CNT2), equilibrative nucleoside transporter 1 (ENT1), and ENT2 and the expression of these transporters has been reported in blood-brain barrier (BBB). Thus, the expression patterns of nucleoside and neurotransmitter transporters examined are quite similar in both the BPB and BBB.

Effects of chronic undernutrition on glucose uptake and glucose transporter proteins in rat heart

The high energy demands of myocardium are met through the metabolism of lipids and glucose. Importantly, enhanced glucose utilization rates are crucial adaptations of the cardiac cell to some pathological conditions, such as hypertrophy and ischemia, but the effects of undernutrition on heart glucose metabolism are unknown. Our previous studies have shown that undernutrition increases insulin-induced glucose uptake by skeletal muscle. Consequently, we considered the possibility of a similar adaptation in the heart. With this aim, undernourished rats both in the basal state and after euglycemic hyperinsulinemic clamps were used to determine the following parameters in myocardium: glucose uptake, glucose transporter (GLUT) content, and some key components of the insulin signaling cascade. Heart membranes were prepared by subcellular fractionation in sucrose gradients. Although GLUT-4, GLUT-1, and GLUT-3 proteins and GLUT-4/1 mRNAs were reduced by undernutrition, basal and insulin-stimulated 2-deoxyglucose uptake were significantly enhanced. Phosphoinositol 3-kinase activity remained greater than control values in both conditions. The abundance of p85alpha and p85beta regulatory subunits of phosphoinositol 3-kinase was increased as was phospho-Akt during hyperinsulinemia. These changes seem to improve the insulin stimulus of GLUT-1 translocation, as its content was increased at the surface membrane. Such adaptations associated with undernutrition must be crucial to improvement of cardiac glucose uptake.

Prognostic significance of p53, Ki-67, VEGF and Glut-1 in resected stage I adenocarcinoma of the lung

OBJECTIVES

The purpose of this study was to evaluate the prognostic significance of various biological factors in patients with resected stage I adenocarcinoma.

METHODS

We immunohistochemically examined 47 specimens of surgically resected adenocarcinomas to evaluate the expression of the biological markers p53, Ki-67, vascular endothelial growth factor (VEGF) and glucose transporter-1 (Glut-1). Angiogenesis grade and tumor vessel invasion was also investigated. Actuarial survival was analyzed by the Kaplan-Meier method. Clinical variables and biological markers were analyzed using the Cox's proportional hazards model for multivariate analysis to identify independent prognostic factors.

RESULTS

The overall survival rate for the whole series was 85.1% at 3 years and 71.9% at 5 years, with a median survival time of 73 months. Differentiation, Ki-67, Glut-1, VEGF, tumor vessel invasion and microvessel density (MVD) were significant prognostic factors by univariate analysis, with Glut-1 expression the most important prognostic factor for survival (P<0.0001). After multivariate analysis, only Glut-1 expression remained as a prognostic factor for survival.

CONCLUSION

Glut-1 expression can be a predictor for prognosis in patients with resected stage I adenocarcinoma of the lung.

IGF-I attenuates diabetes-induced cardiac contractile dysfunction in ventricular myocytes

Diabetic cardiomyopathy is characterized by impaired ventricular contraction and altered function of insulin-like growth factor I (IGF-I), a key factor for cardiac growth and function. Endogenous IGF-I has been shown to alleviate diabetic cardiomyopathy. This study was designed to evaluate exogenous IGF-I treatment on the development of diabetic cardiomyopathy. Adult rats were divided into four groups: control, control + IGF-I, diabetic, and diabetic + IGF-I. Streptozotocin (STZ; 55 mg/kg) was used to induce experimental diabetes immediately followed by a 7-wk IGF-I (3 mg. kg(-1). day(-1) ip) treatment. Mechanical properties were assessed in ventricular myocytes including peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR(90)) and maximal velocities of shortening/relengthening (+/-dL/dt). Intracellular Ca(2+) transients were evaluated as Ca(2+)-induced Ca(2+) release and Ca(2+) clearing constant. Levels of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA), phospholamban (PLB), and glucose transporter (GLUT4) were assessed by Western blot. STZ caused significant weight loss and elevated blood glucose, demonstrating the diabetic status. The diabetic state is associated with reduced serum IGF-I levels, which were restored by IGF-I treatment. Diabetic myocytes showed reduced PS and +/-dL/dt as well as prolonged TPS, TR(90), and intracellular Ca(2+) clearing compared with control. IGF-I treatment prevented the diabetes-induced abnormalities in PS, +/-dL/dt, TR(90), and Ca(2+) clearing but not TPS. The levels of SERCA and GLUT4, but not PLB, were significantly reduced in diabetic hearts compared with controls. IGF-I treatment restored the diabetes-induced decline in SERCA, whereas it had no effect on GLUT4 and PLB levels. These results suggest that exogenous IGF-I treatment may ameliorate contractile disturbances in cardiomyocytes from diabetic animals and could provide therapeutic potential in the treatment of diabetic cardiomyopathy.

Clinical significance of glucose transporter 1 (GLUT1) expression in human breast carcinoma

Glucose uptake and glycolytic metabolism are enhanced in cancer cells compared to normal cells and tissues. Increased expression of glucose transporter 1 (GLUT1) has been reported in human malignant cells. The aim of this study is to determine the expression of the facilitative glucose transporter protein GLUT1 in human breast carcinomas and a possible correlation between GLUT1 expression and clinical outcome including disease-free or overall survival. One hundred consecutive formalin-fixed, paraffin-embedded sections of invasive breast carcinomas were evaluated by means of immunohistochemical staining of GLUT1. Forty-seven (47%) of 100 breast carcinomas showed positive staining for GLUT1. Expression of GLUT1 correlated significantly with nuclear grade (P < 0.001), estrogen receptor status (P = 0.002), and progesterone receptor status (P = 0.001). The mean disease-free survival periods of GLUT1-positive and -negative patients were 47 +/- 2.4 months and 54.3 +/- 1.3 months, respectively (P = 0.017). The mean overall survival periods of GLUT1-positive and -negative patients were 48.7 +/- 2.2 and 56.1+/- 1.3 months, respectively (P = 0.043). In the multivariate analysis, disease-free survival correlated significantly with GLUT1, tumor size, and lymph node involvement (P = 0.043, P = 0.014, and P = 0.045, respectively). In analysis of overall survival, however, lymph node involvement, tumor size, and nuclear grade were statistically significant (P = 0.024, P = 0.023, and P = 0.003, respectively). Our data suggest that absence of GLUT1 expression significantly increases disease-free survival. These findings demonstrate that GLUT1 expression in breast carcinoma can be a marker of aggressive biological behavior and identifies a worse prognosis in breast carcinoma patients.

Exercise training increases the activity of pyruvate dehydrogenase complex in skeletal muscle of diabetic rats

The effects of diabetes and exercise training on the activity of pyruvate dehydrogenase (PDH) complex in skeletal muscle were examined in rats. Male Sprague-Dawley rats were divided into four groups as follows: non-diabetic sedentary, non-diabetic trained, diabetic sedentary, and diabetic trained groups. Diabetic rats were prepared by a bolus injection of intravenous streptozotocin (50 mg/kg body weight). Exercise training was performed by having rats run on a treadmill at a speed of 25 m/min for 45 min/day, 6 days/wk for 4 wks. Exercise training decreased serum concentrations of glucose and non-esterified fatty acid in diabetic rats. GLUT4 content in skeletal muscle in sedentary rats was significantly decreased by diabetes; however, exercise training significantly increased the GLUT4 content in diabetic rats. The total and actual activities and the proportion of actual activity of the PDH complex were decreased in diabetic sedentary rats. Exercise training did not affect the total activity of the PDH complex in non-diabetic rats, whereas it increased the total activity in diabetic rats to the same level as that in non-diabetic rats. In diabetic rats, exercise training tended to increase the proportion of actual activity of the PDH complex from 2.7 +/- 0.4% to 4.7 +/- 0.8%, although the proportion of actual activity in non-diabetic rats was decreased by exercise training. The present study suggests that exercise training may improve glucose metabolism in the skeletal muscle of streptozotocin-induced diabetic rats probably through the mechanisms of increasing both GLUT4 content and the activity of the PDH complex.

Defective insulin secretion in pancreatic beta cells lacking type 1 IGF receptor

Defective insulin secretion is a feature of type 2 diabetes that results from inadequate compensatory increase of beta cell mass and impaired glucose-dependent insulin release. beta cell proliferation and secretion are thought to be regulated by signaling through receptor tyrosine kinases. In this regard, we sought to examine the potential proliferative and/or antiapoptotic role of IGFs in beta cells by tissue-specific conditional mutagenesis ablating type 1 IGF receptor (IGF1R) signaling. Unexpectedly, lack of functional IGF1R did not affect beta cell mass, but resulted in age-dependent impairment of glucose tolerance, associated with a decrease of glucose- and arginine-dependent insulin release. These observations reveal a requirement of IGF1R-mediated signaling for insulin secretion.

Expression during rat fetal development of GLUT12--a member of the class III hexose transporter family

Glucose is an essential molecule for most mammalian cells, and is particularly important during fetal development, when cells are rapidly dividing and differentiating. In rats, GLUT1 is present at high levels in most fetal tissues, with levels decreasing after birth. We used immunohistochemistry to localise GLUT12 protein, a recently identified member of the sugar transporter family, and GLUT1 during rat fetal development. GLUT12 staining was observed in heart muscle from gestational days 15 to 21. GLUT12 staining in skeletal muscle increased from gestational days 17 to 21, and GLUT12 was also detected in brown adipose tissue. The expression of GLUT12 in insulin-responsive tissues supports a potential role for GLUT12 in the provision of glucose to these tissues before the appearance of GLUT4. GLUT12 protein was also expressed in fetal chondrocytes from gestational day 15 onward, in kidney distal tubules and collecting ducts from day 19, and in lung bronchioles from day 19. The specific pattern of expression observed in the rat fetus suggests that GLUT12 may be important in hexose delivery to developing tissues.

Characterization of an in vitro rhesus macaque blood-brain barrier

The blood-brain barrier (BBB) has been modeled in vitro in a number of species, including rat, cow and human. Coculture of multiple cell types is required for the correct expression of tight junction proteins by microvascular brain endothelial cells (MBEC). Markers of inflammation, especially MHC-II, and cell adhesion molecules, such as VCAM-1, are not expressed on the luminal surface of the barrier under resting conditions. The rhesus macaque model has been used to study early events of HIV-neuropathogenesis in vivo, but a suitable in vitro model has not been available for detailed mechanistic studies. Here we describe an in vitro rhesus macaque blood-brain barrier that utilizes autologous MBEC and astrocytes. We believe that this model is highly relevant for examining immunological events at the blood-brain barrier and demonstrate its potential usefulness for examining early events in AIDS neuropathogenesis.

Energy restriction reduces long-chain saturated fatty acids associated with plasma lipids in aging male rats

Energy restriction is associated with decreased plasma insulin and glucose concentrations, whereas long-chain saturated fatty acids (LCSFA) are strongly associated with insulin resistance. Our hypothesis is that energy restriction reduces LCSFA associated with plasma lipids in adult aging rats. Plasma LCSFA associated with triglycerides (TG), nonesterified fatty acids and phospholipids, as well as glucose, insulin, free fatty acids, TG and adipocyte glucose transport and insulin-sensitive glucose transporter (GLUT4) content were determined in aging, energy restricted [ER; 60% of ad libitum (AL) intake] and AL rats. In ER rats, plasma glucose concentrations were lower than in AL rats at each age. In contrast, body weight and plasma TG concentrations increased with age in both groups, but especially in the AL rats. In AL rats, combined LCSFA associated with plasma lipids was greater than in ER rats (P < 0.0001). Adipocyte insulin-stimulated glucose transport decreased in both groups with age but was most severe in AL rats, whereas GLUT4 was reduced only in AL rats. In ER rats it is possible that decreased plasma LCSFA contribute to reduced blood glucose concentrations as well as increased adipocyte GLUT4 compared with AL rats.

Changes in skeletal muscle GLUT4 content and muscle membrane glucose transport following 6 weeks of exercise training

This study examined changes in skeletal muscle GLUT4 content and glucose transport in isolated muscle membranes (GT) from horses before and 2 min after standardised submaximal exercise tests (SET) prior to and after completion of 6 weeks of training. Seven horses, age 3-9 years, body mass mean +/- s.e. 530 +/- 19 kg, and sedentary for at least 4 months, completed 6 weeks of training on a treadmill. An initial SET (UT) was performed on a 4 degree incline at a speed equivalent to 55% of pretraining VO2max and was repeated post-training at the same absolute workload (ABS). A third SET (REL) was performed at 55% of post-training VO2max. There was no significant pre- to postexercise change in GLUT4 content before or after training. Following training, total GLUT4 content was increased 2- or 3-fold in pre-exercise biopsies (pre UT: 0.30 +/- 0.05; pre ABS: 1.05 +/- 0.32; pre REL: 1.34 +/- 0.28 arbitrary units) (P<0.05) with similar increases in postexercise GLUT4 content (P<0.05) (post UT: 033 +/- 0.06; post ABS: 1.19 +/- 0.44; post REL: 1.43 +/- 0.31). GT increased 2.5- to 6-fold in postexercise muscle membrane vesicles in UT over a range of glucose concentrations. After training (ABS and REL), there was a 25-50% attenuation (P<0.05) in membrane GT in response to exercise in ABS and REL. These finding indicate that moderate intensity exercise training increased middle gluteal muscle GLUT4 content, but this change was not reflected in an increase in muscle membrane glucose transport activity in postexercise muscle samples.

GLUT4 expression at the plasma membrane is related to fibre volume in human skeletal muscle fibres

In this study we examined the relationship between GLUT4 expression at the plasma membrane and muscle fibre size in fibre-typed human muscle fibres by immunocytochemistry and morphometry in order to gain further insight into the regulation of GLUT4 expression. At the site of the plasma membrane, GLUT4 was more abundantly expressed in slow as compared to fast fibres at the same fibre diameter (p < 0.01) and the GLUT4 expression increased with increasing fibre radius independently of fibre type (p < 0.01). The GLUT4 density at the surface of slow fibres of both diabetic and obese was reduced compared to control subjects at the same diameter (p < 0.001). Fast fibres in obese and type 2 diabetic subjects expressed a fibre-volume-dependent GLUT4 expression (p < 0.001), while this did not reach significance in slow fibres (obese p = 0.18 and diabetic p = 0.06). Our results show that increasing fibre volume is associated with increasing GLUT4 expression in both slow and fast fibres. Based on the possible dependency of GLUT4 expression on volume, we hypothesize that the reduced GLUT4 expression in obesity and type 2 diabetes may partly be compensated for by physical activity.

Glucose transporter 1 gene expression is related to thyroid neoplasms with an unfavorable prognosis: an immunohistochemical study

PURPOSE

An accelerated rate of glucose metabolism mediated by overexpression of key regulatory glycolytic enzymes and glucose transporters is among the most characteristic biochemical marker of malignant transformed cells. In thyroid neoplasms, however, an increased uptake of glucose [measured by 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) and positron emission tomography (PET)] seems to be restricted to more aggressive and high-grade tumors, whereas tumors with favorable prognosis demonstrate no significant tracer uptake. We therefore studied the expression of glucose transporters in thyroid carcinomas with different grades of malignancy.

METHODS

Sections of formalin-fixed and paraffin-embedded tissue obtained from 45 patients with thyroid cancer (5 anaplastic, 20 papillary and 20 follicular tumors) were investigated. Polyclonal rabbit antiglucose transporter antibodies, reactive with glucose transporters 1-5 (GLUT1-5), were used after heat pretreatment of the sections. Staining was performed by the avidin-biotin conjugate immunoperoxidase reaction and evaluated semiquantitatively.

RESULTS

Expression of GLUT1 transporter on the cell membrane was closely related to the grade of malignancy in thyroid neoplasms (Fisher exact test p < 0.05). All anaplastic tumors showed a high level of GLUT1 expression in the cytoplasm and on the cell membrane. Positive membranous staining in differentiated tumors was detected predominantly in neoplasms with unfavorable prognosis, e.g., in widely invasive follicular or metastatic tumors, whereas low or no immunoreactivity could be seen in well-differentiated tumors or in normal thyroid epithelium.

CONCLUSIONS

These data indicate that overexpression of GLUT1 on the cell membrane of thyroid neoplasms is closely related to tumors demonstrating a more aggressive biological behavior. Therefore, determination of GLUT1 expression in thyroid cancer tissue may be a prognostic marker, and FDG-PET may be a helpful technique in identifying patients at a higher risk.