Mast Cells are Dependent on Glucose Transporter 1 (GLUT1) and GLUT3 for IgE-mediated Activation

Mast cells (MCs) are known to have a pathological impact in a variety of settings, in particular in allergic conditions. There is also limited evidence implicating MCs in diabetes, raising the possibility that MC function may be influenced by alterations in glucose levels. However, it is not known whether MCs are directly affected by elevated glucose concentrations. Moreover, it is not known which glucose transporters that are expressed by MCs, and whether MCs are dependent on glucose transporters for activation. Here we addressed these issues. We show that MCs express high levels of both glucose transporter 1 (GLUT1/Slc2A1) and GLUT3 (Slc2A3). Further, we show that the inhibition of either GLUT1 or GLUT3 dampens both MC degranulation and cytokine induction in response to IgE receptor crosslinking, and that combined GLUT1 and GLUT3 inhibition causes an even more pronounced inhibition of these parameters. In contrast, the inhibition of GLUT1 or GLUT3, or combined GLUT1 and GLUT3 inhibition, had less impact on the ability of the MCs to respond to activation via compound 48/80. Elevated glucose concentrations did not affect MC viability, and had no stimulatory effect on MC responses to either IgE receptor crosslinking or compound 48/80. Altogether, these findings reveal that MCs are strongly dependent on glucose transport via GLUT1 and/or GLUT3 for optimal responses towards IgE-mediated activation, whereas MC functionality is minimally affected by elevated glucose levels. Based on these findings, antagonists of GLUT1 and GLUT3 may be considered for therapeutic intervention in allergic conditions.

Unlocking the mystery of the feeder organelle and versatile energy metabolism in Cryptosporidium parvum

Xu and colleagues recently revealed the critical role of Cryptosporidium's feeder organelle in nutrient uptake, showcasing the parasite's ability to harness glucose and glucose-6-phosphate from host cells. This illuminates the sophisticated energy metabolism and survival strategies of the parasite, highlighting potential therapeutic targets.

The genetic variant SLC2A1 -rs1105297 is associated with the differential analgesic response to a glucose-based treatment in newborns

ABSTRACT

Neonatal pain is a critical issue in clinical practice. The oral administration of glucose-based solutions is currently one of the most common and effective nonpharmacologic strategies for neonatal pain relief in daily minor procedures. However, a varying degree of analgesic efficacy has been reported for this treatment. Environmental, maternal, and genetic factors may explain this variability and potentially allow for a personalized analgesic approach, maximizing therapeutic efficacy and preventing side effects. We investigated the exposome (ie, the set of clinical and anthropometric variables potentially affecting the response to the therapy) and the genetic variability of the noradrenaline transporter gene (solute carrier family 6 member 2 [ SLC6A2 ]) and 2 glucose transporter genes (solute carrier family 2 member 1 [ SLC2A1 ] and 2 [ SLC2A2 ]) in relation to the neonatal analgesic efficacy of a 33% glucose solution. The study population consisted in a homogeneous sample of more than 1400 healthy term newborns. No association for the exposome was observed, whereas a statistically significant association between the G allele of SLC2A1 -rs1105297 and a fourfold decreased probability of responding to the therapy was identified after multiple-testing correction (odds ratio of 3.98, 95% confidence interval 1.95-9.17; P = 4.05 × 10 -4 ). This allele decreases the expression of SLC2A1-AS1 , causing the upregulation of SLC2A1 in the dorsal striatum, which has been suggested to be involved in reward-related processes through the binding of opioids to the striatal mu-opioid receptors. Altogether, these results suggest the involvement of SLC2A1 in the analgesic process and highlight the importance of host genetics for defining personalized analgesic treatments.

Brain energetics and glucose transport in metabolic diseases: role in neurodegeneration

OBJECTIVES

Neurons and glial cells are the main functional and structural elements of the brain, and the former depends on the latter for their nutritional, functional and structural organization, as well as for their energy maintenance.

METHODS

Glucose is the main metabolic source that fulfills energetic demands, either by direct anaplerosis or through its conversion to metabolic intermediates. Development of some neurodegenerative diseases have been related with modifications in the expression and/or function of glial glucose transporters, which might cause physiological and/or pathological disturbances of brain metabolism. In the present contribution, we summarized the experimental findings that describe the exquisite adjustment in expression and function of glial glucose transporters from physiologic to pathologic metabolism, and its relevance to neurodegenerative diseases.

RESULTS

A exhaustive literature review was done in order to gain insight into the role of brain energetics in neurodegenerative disease. This study made evident a critical involvement of glucose transporters and thus brain energetics in the development of neurodegenerative diseases.

DISCUSSION

An exquisite adjustment in the expression and function of glial glucose transporters from physiologic to pathologic metabolism is a biochemical signature of neurodegenerative diseases.

Glucosylated Hybrid TiO2 /Polymer Nanomaterials for Actively Targeted Sonodynamic Therapy of Cancer

Sonodynamic therapy (SDT) is an anti-cancer therapeutic strategy based on the generation of reactive oxygen species (ROS) upon local ultrasound (US) irradiation of sono-responsive molecules or nanomaterials that accumulate in the tumor. In this work, the sonodynamic efficiency of sono-responsive hybrid nanomaterials composed of amorphous titanium dioxide and an amphiphilic poly(ethylene oxide)-b-poly(propylene oxide) block copolymer is synthesized, fully characterized, and investigated both in vitro and in vivo. The modular and versatile synthetic pathway enables the control of the nanoparticle size between 30 and 300 nm (dynamic light scattering) and glucosylation of the surface for active targeting of tumors overexpressing glucose transporters. Studies on 2D and 3D rhabdomyosarcoma cell cultures reveal a statistically significant increase in the sonodynamic efficiency of glucosylated hybrid nanoparticles with respect to unmodified ones. Using a xenograft rhabdomyosarcoma murine model, it is demonstrated that by tuning the nanoparticle size and surface features, the tumor accumulation is increased by ten times compared to main off-target clearance organs such as the liver. Finally, the SDT of rhabdomyosarcoma-bearing mice is investigated with 50-nm glucosylated nanoparticles. Findings evidence a dramatic prolongation of the animal survival and tumor volumes 100 times smaller than those treated only with ultrasound or nanoparticles.

Glucose Transport and Utilization in the Hippocampus: From Neurophysiology to Diabetes-Related Development of Dementia

The association of diabetes with cognitive dysfunction has at least 60 years of history, which started with the observation that children with type 1 diabetes mellitus (T1D), who had recurrent episodes of hypoglycemia and consequently low glucose supply to the brain, showed a deficit of cognitive capacity. Later, the growing incidence of type 2 diabetes mellitus (T2D) and dementia in aged populations revealed their high association, in which a reduced neuronal glucose supply has also been considered as a key mechanism, despite hyperglycemia. Here, we discuss the role of glucose in neuronal functioning/preservation, and how peripheral blood glucose accesses the neuronal intracellular compartment, including the exquisite glucose flux across the blood-brain barrier (BBB) and the complex network of glucose transporters, in dementia-related areas such as the hippocampus. In addition, insulin resistance-induced abnormalities in the hippocampus of obese/T2D patients, such as inflammatory stress, oxidative stress, and mitochondrial stress, increased generation of advanced glycated end products and BBB dysfunction, as well as their association with dementia/Alzheimer's disease, are addressed. Finally, we discuss how these abnormalities are accompained by the reduction in the expression and translocation of the high capacity insulin-sensitive glucose transporter GLUT4 in hippocampal neurons, which leads to neurocytoglycopenia and eventually to cognitive dysfunction. This knowledge should further encourage investigations into the beneficial effects of promising therapeutic approaches which could improve central insulin sensitivity and GLUT4 expression, to fight diabetes-related cognitive dysfunctions.

The intracellular helical bundle of human glucose transporter GLUT4 is important for complex formation with ASPL

Glucose transporters (GLUTs) are responsible for transporting hexose molecules across cellular membranes. In adipocytes, insulin stimulates glucose uptake by redistributing GLUT4 to the plasma membrane. In unstimulated adipose-like mouse cell lines, GLUT4 is known to be retained intracellularly by binding to TUG protein, while upon insulin stimulation, GLUT4 dissociates from TUG. Here, we report that the TUG homolog in human, ASPL, exerts similar properties, i.e., forms a complex with GLUT4. We describe the structural details of complex formation by combining biochemical assays with cross-linking mass spectrometry and computational modeling. Combined, the data suggest that the intracellular domain of GLUT4 binds to the helical lariat of ASPL and contributes to the regulation of GLUT4 trafficking by cooperative binding.

Glucose Supplementation Improves Performance and Alters Glucose Transporters' Expression in Pectoralis major of Heat-Stressed Chickens

Glucose level in birds' tissue decreases due to heat stress (HS)-induced reduction in feed intake (FI); impairing metabolism and growth. The effect of glucose supplementation on the performance of broiler chickens was evaluated under thermoneutral (TN) and HS conditions. Glucose was supplemented at 0 and 6% under TN-(25 °C) and HS-(25 °C-35 °C-25 °C) conditions. The treatments were TN + 0%-glucose (TN0); TN + 6%-glucose (TN6), HS + 0%-glucose (HS0) and HS + 6%-glucose (HS6). There were 6 replicates (19 birds each)/treatment. Heat and glucose supplementation were applied from d28-35. At d35, Pectoralis (P.) major was sampled from one bird/replicate to determine glucose transporters' mRNA expression. Heat application lowered (p < 0.05) FI, body weight gain, and increased feed and water conversion ratios. Glucose supplementation increased total energy intake by 4.9 and 3.2% in TN and HS groups, respectively but reduced FI under TN and HS conditions. The P. major- and drumstick-yield reduced (p < 0.05) in HS0 compared to TN0, TN6 and HS6. Under HS, glucose supplementation improved eviscerated carcass weight by 9% and P. major yield by 14%. Glucose supplementation increased SGLT1 expression with/without heat treatment while HS independently increased the expression of GLUT 1, 5 and 10. Glucose supplementation under HS could improve performance of broilers.

Correlations between class I glucose transporter expression patterns and clinical outcomes in non-small cell lung cancer

BACKGROUND

Glucose transporters (GLUTs) are highly expressed in various cancers. However, the implications of these variable expression patterns are unclear. This study aimed to clarify the correlation between class I GLUT expression patterns and clinical outcomes in non-small cell lung cancer (NSCLC), including their potential role in inflammatory signaling.

METHODS

Biopsy tissues from 132 patients with NSCLC (92 adenocarcinomas [ADC] and 40 squamous cell carcinomas [SQCC]) were analyzed. mRNA expression levels of class I GLUTs (solute carrier 2A [SLC2A]1, SLC2A2, SLC2A3, and SLC2A4) and inflammation-related molecules (toll-like receptors TLR4, RelA/p65, and interleukins IL8 and IL6) were measured. Cellular localization of GLUT3 and GLUT4 was investigated using immunofluorescence.

RESULTS

Single, combined, and negative GLUT (SLC2A) expression were observed in 27/92 (29.3%), 27/92 (29.3%), and 38/92 (41.3%, p < 0.001) of ADC and 8/40 (20.0%), 29/40 (72.5%, p < 0.001), and 3/40 (7.5%) of SQCC, respectively. In ADC, the single SLC2A3-expressed group had a significantly poorer prognosis, whereas the single SLC2A4-expressed group had a significantly better prognosis. The combined expression groups showed no significant difference. SLC2A expression was not correlated with SQCC prognosis. SLC2A4 expression correlated with lower IL8 expression. GLUT3 and GLUT4 expressions were localized in the tumor cytoplasm.

CONCLUSIONS

In lung ADC, single SLC2A3 expression correlated with poor prognosis, whereas single SLC2A4 expression correlated with better prognosis and lower IL8 expression. GLUT3 expression, which is increased by IL8 overexpression, may be suppressed by increasing the expression of GLUT4 through decreased IL8 expression.

Role of monocarboxylate transporters and glucose transporters in prostate cancer

OBJECTIVES

Currently, research of new diagnostic approaches to detect clinically significant prostate cancer is relevant because of the importance of early detection of aggressive forms of the disease, often challenging, even when using modern diagnostic tools. The aim of this review is to present the current knowledge regarding monocarboxylate transporters' and glucose transporters' expression as a component of glycolytic phenotype definition in prostate cancer cells.

METHODS

We searched PubMed and Scopus databases. Twenty-six articles from 2003 to 2022 were included. Literature research and selection were carried out based on the recommendations of the PRISMA statement.

RESULTS

The presence of "lactate shuttle" in the tumor tissue is associated with a worse prognosis. Increased expression of MCT2, MCT4, GLUT1, and down-regulation of GLUT3 are associated with prostate adenocarcinoma. MCT4 expression level correlates with the grade of tumor malignancy and disease prognosis. Up-regulation of GLUT1 and MCT4 is typical for hormone-resistant prostate cancer. Inhibition of MCT1 and MCT4 and GLUT1 in prostate cancer cells reduces their metabolic activity and growth rate, a suitable novel approach for targeted therapy.

CONCLUSION

Review of the current studies showed that expression of certain MCTs and GLUTs types are associated with prostate cancer and some of them correlate with high malignancy and poor prognosis. Detection by immunohistochemistry of these transporters could represent a new diagnostic tool to identify aggressive forms of prostate cancer, and a novel therapeutic target for selective drugs.

Tissue-Specific Modulation of Gluco- and Growth-Regulatory Factor Abundance by Nesfatin-1 and Nesfatin-1-like Peptide in Goldfish

Nesfatin-1 and nesfatin-1-like peptide (Nlp) are derived from precursors nucleobindin-2 and -1, two calcium and DNA binding proteins, respectively. Both peptides exhibit hormone-like actions in mammals and fish. These functions include insulinotropic effects of nesfatin-1 and Nlp seen in mice and their growth hormone suppressive actions reported in goldfish. We hypothesized that nesfatin-1 and Nlp are insulin stimulatory (in adipose tissue) and modulate growth hormone and insulin-like growth factors and glucose transporters in goldfish. To test this, goldfish were intraperitoneally injected with either nesfatin-1 or Nlp (50 ng/g BW) or saline alone (control) and sampled at one-hour post-injection (in vivo study). In a separate study, tissue samples were collected and were incubated with either nesfatin-1 or Nlp for one or six hours (in vitro study). Transcript (mRNA) abundance data from the adipose tissue suggest that both nesfatin-1 and Nlp significantly upregulate the abundance of preproinsulin, insulin receptors, and pcsk1 and pcsk2 mRNAs. Meanwhile, the abundance of preproglucagon mRNA in the adipose tissue was significantly downregulated in both in vivo and in vitro studies. These results agree with the insulinotropic and glucagonostatic roles for nesfatin-1 and Nlp reported in rodents. The transcript abundance of growth regulators (igf1, igf2a, and ghra) and glucose transporters (slc2a2 and slc5a1) were upregulated in the muscle, while an opposite effect on these mRNAs was found in the liver of goldfish following nesfatin-1 and Nlp administration. Our results suggest that both nesfatin-1 and Nlp have tissue-specific regulatory roles on growth and glucoregulatory elements in the liver and muscle of goldfish. This agrees with our previous studies that showed a suppressive action of nesfatin-1 on growth hormone in goldfish liver. The results presented here provide strong supportive/confirmatory evidence for tissue-specific insulinotropic and gluco- and growth-regulatory actions of nesfatin-1 and Nlp in goldfish.

SLC2As as diagnostic markers and therapeutic targets in LUAD patients through bioinformatic analysis

Facilitative glucose transporters (GLUTs), which are encoded by solute carrier 2A (SLC2A) genes, are responsible for mediating glucose absorption. In order to meet their higher energy demands, cancer cells are more likely than normal tissue cells to have elevated glucose transporters. Multiple pathogenic processes, such as cancer and immunological disorders, have been linked to GLUTs. Few studies, meanwhile, have been conducted on individuals with lung adenocarcinoma (LUAD) to evaluate all 14 SLC2A genes. We first identified increased protein levels of SLC2A1, SLC2A5, SLC2A6, and SLC2A9 via HPA database and downregulated mRNA levels of SLC2A3, SLC2A6, SLC2A9, and SLC2A14 by ONCOMINE and UALCAN databases in patients with LUAD. Additionally, lower levels of SLC2A3, SLC2A6, SLC2A9, SLC2A12, and SLC2A14 and higher levels of SLC2A1, SLC2A5, SLC2A10, and SLC2A11 had an association with advanced tumor stage. SLC2A1, SLC2A7, and SLC2A11 were identified as prognostic signatures for LUAD. Kaplan-Meier analysis, Univariate Cox regression, multivariate Cox regression and ROC analyses further revealed that these three genes signature was a novel and important prognostic factor. Mechanistically, the aberrant expression of these molecules was caused, in part, by the hypomethylation of SLC2A3, SLC2A10, and SLC2A14 and by the hypermethylation of SLC2A1, SLC2A2, SLC2A5, SLC2A6, SLC2A7, and SLC2A11. Additionally, SLC2A3, SLC2A5, SLC2A6, SLC2A9, and SLC2A14 contributed to LUAD by positively modulating M2 macrophage and T cell exhaustion. Finally, pathways involving SLC2A1/BUB1B/mitotic cell cycle, SLC2A5/CD86/negative regulation of immune system process, SLC2A6/PLEK/lymphocyte activation, SLC2A9/CD4/regulation of cytokine production might participate in the pathogenesis of LUAD. In summary, our results will provide the theoretical basis on SLC2As as diagnostic markers and therapeutic targets in LUAD.

Bola-Amphiphilic Glycodendrimers: New Carbohydrate-Mimicking Scaffolds to Target Carbohydrate-Binding Proteins

Dendrimers are appealing scaffolds for creating carbohydrate mimics with unique multivalent cooperativity. We report here novel bola-amphiphilic glycodendrimers bearing mannose and glucose terminals, and a hydrophobic thioacetal core responsive to reactive oxygen species. The peculiar bola-amphiphilic feature enabled stronger binding to lectin compared to conventional amphiphiles. In addition, these dendrimers are able to target mannose receptors and glucose transporters expressed at the surface of cells, thus allowing effective and specific cellular uptake. This highlights their great promise for targeted delivery.

ApoE isoform-dependent effects of xanthohumol on high fat diet-induced cognitive impairments and hippocampal metabolic pathways

Consumption of a high fat diet (HFD) is linked to metabolic syndrome and cognitive impairments. This is exacerbated in age-related cognitive decline (ACD) and in individuals with a genetic risk for Alzheimer's disease (AD). Apolipoprotein E (apoE) is involved in cholesterol metabolism. In humans, there are three major isoforms, E2, E3, and E4. Compared to E3, E4 increases ACD and AD risk and vulnerability to the deleterious cognitive effects of a HFD. The plant compound Xanthohumol (XN) had beneficial effects on cognition and metabolism in C57BL/6J wild-type (WT) male mice put on a HFD at 9 weeks of age for 13 weeks. As the effects of XN in the context of a HFD in older WT, E3, and E4 female and male mice are not known, in the current study male and female WT, E3, and E4 mice were fed a HFD alone or a HFD containing 0.07% XN for 10 or 19 weeks, starting at 6 months of age, prior to the beginning of behavioral and cognitive testing. XN showed sex- and ApoE isoform-dependent effects on cognitive performance. XN-treated E4 and WT, but not E3, mice had higher glucose transporter protein levels in the hippocampus and cortex than HFD-treated mice. E3 and E4 mice had higher glucose transporter protein levels in the hippocampus and lower glucose transporter protein levels in the cortex than WT mice. In the standard experiment, regardless of XN treatment, E4 mice had nearly double as high ceramide and sphingomyelin levels than E3 mice and male mice had higher level of glycosylated ceramide than female mice. When the differential effects of HFD in E3 and E4 males were assessed, the arginine and proline metabolism pathway was affected. In the extended exposure experiment, in E3 males XN treatment affected the arginine and proline metabolism and the glycine, serine, and threonine metabolism. Myristic acid levels were decreased in XN-treated E3 males but not E3 females. These data support the therapeutic potential for XN to ameliorate HFD-induced cognitive impairments and highlight the importance of considering sex and ApoE isoform in determining who might most benefit from this dietary supplement.

Structural aspects of the glucose and monocarboxylate transporters involved in the Warburg effect

Cancer cells shift their glucose catabolism from aerobic respiration to lactic fermentation even in the presence of oxygen, and this is known as the "Warburg effect". To accommodate the high glucose demands and to avoid lactate accumulation, the expression levels of human glucose transporters (GLUTs) and human monocarboxylate transporters (MCTs) are elevated to maintain metabolic homeostasis. Therefore, inhibition of GLUTs and/or MCTs provides potential therapeutic strategies for cancer treatment. Here, we summarize recent advances in the structural characterization of GLUTs and MCTs, providing a comprehensive understanding of their transport and inhibition mechanisms to facilitate further development of anticancer therapies.

Glioblastoma Invasiveness and Collagen Secretion Are Enhanced by Vitamin C

Aims: Glioblastoma (GB) is one of the most aggressive brain tumors. These tumors modify their metabolism, increasing the expression of glucose transporters, GLUTs, which incorporate glucose and the oxidized form of vitamin C, dehydroascorbic acid (DHA). We hypothesized that GB cells preferentially take up DHA, which is intracellularly reduced and compartmentalized into the endoplasmic reticulum (ER), promoting collagen biosynthesis and an aggressive phenotype. Results: Our results showed that GB cells take up DHA using GLUT1, while GLUT3 and sodium-dependent vitamin C transporter 2 (SVCT2) are preferably intracellular. Using a baculoviral system and reticulum-enriched extracts, we determined that SVCT2 is mainly located in the ER and corresponds to a short isoform. Ascorbic acid (AA) was compartmentalized, stimulating collagen IV secretion and increasing in vitro and in situ cell migration. Finally, orthotopic xenografts induced in immunocompetent guinea pigs showed that vitamin C deficiency retained collagen, reduced blood vessel invasion, and affected glomeruloid vasculature formation, all pathological conditions associated with malignancy. Innovation and Conclusion: We propose a functional role for vitamin C in GB development and progression. Vitamin C is incorporated into the ER of GB cells, where it favors the synthesis of collagen, thus impacting tumor development. Collagen secreted by tumor cells favors the formation of the glomeruloid vasculature and enhances perivascular invasion. Antioxid. Redox Signal. 37, 538-559.

In Vitro Digestibility and Bioaccessibility of Nutrients and Non-Nutrients Composing Extruded Brewers' Spent Grain

This study aimed to evaluate the effect of the extrusion process on the bioaccessibility of brewers’ spent grain (BSG) nutrients (carbohydrates and proteins) and non-nutrients (bioactive compounds). BSG and extruded BSG (EBSG) were digested in vitro simulating human oral-gastro-intestinal digestion and colonic fermentation. The duodenal bioaccessibility of glucose, amino acids and phenolic compounds was analyzed. The fermentability of the dietary fiber was assessed by analysis of short-chain fatty acids. Additionally, assessment of the bioaccessibility of phenolic compounds after colonic fermentation was undertaken. The antioxidant, anti-inflammatory and antidiabetic properties of the bioaccessible compounds were studied. Extrusion caused no change in the digestibility of gluten and glucose bioaccessibility (p > 0.05). Moreover, the bioaccessibility of amino acids and phenolic compounds significantly increased (p < 0.05) due to extrusion. However, higher short-chain fatty acid content was formed in colonic fermentation of BSG (p < 0.05) compared to EBSG. The latter inhibited intracellular ROS formation in IEC-6 cells and showed anti-inflammatory properties in RAW264.7 cells. With respect to antidiabetic properties, glucose absorption was lower, and the inhibition of carbohydrases higher (p < 0.05), in the presence of EBSG compared to BSG. The effects of EBSG and BSG digests on glucose transporters were not significantly different (p > 0.05). In conclusion, extrusion positively affected the nutritional value and health-promoting properties of BSG.

Glucose Stimulates Gut Motility in Fasted and Fed Conditions: Potential Involvement of a Nitric Oxide Pathway

(1) Background: Type 2 diabetes (T2D) is associated with a duodenal hypermotility in postprandial conditions that favors hyperglycemia and insulin resistance via the gut-brain axis. Enterosynes, molecules produced within the gut with effects on the enteric nervous system, have been recently discovered and pointed to as potential key modulators of the glycemia. Indeed, targeting the enteric nervous system that controls gut motility is now considered as an innovative therapeutic way in T2D to limit intestinal glucose absorption and restore the gut-brain axis to improve insulin sensitivity. So far, little is known about the role of glucose on duodenal contraction in fasted and fed states in normal and diabetic conditions. The aim of the present study was thus to investigate these effects in adult mice. (2) Methods: Gene-expression level of glucose transporters (SGLT-1 and GLUT2) were quantified in the duodenum and jejunum of normal and diabetic mice fed with an HFD. The effect of glucose at different concentrations on duodenal and jejunal motility was studied ex vivo using an isotonic sensor in fasted and fed conditions in both normal chow and HFD mice. (3) Results: Both SGLT1 and GLUT2 expressions were increased in the duodenum (47 and 300%, respectively) and jejunum (75% for GLUT2) of T2D mice. We observed that glucose stimulates intestinal motility in fasted (200%) and fed (400%) control mice via GLUT2 by decreasing enteric nitric oxide release (by 600%), a neurotransmitter that inhibits gut contractions. This effect was not observed in diabetic mice, suggesting that glucose sensing and mechanosensing are altered during T2D. (4) Conclusions: Glucose acts as an enterosyne to control intestinal motility and glucose absorption through the enteric nervous system. Our data demonstrate that GLUT2 and a reduction of NO production could both be involved in this stimulatory contracting effect.

Localized glucose import, glycolytic processing, and mitochondria generate a focused ATP burst to power basement-membrane invasion

Invasive cells use transient, energy-consuming protrusions to breach basement membrane (BM) barriers. Using the ATP sensor PercevalHR during anchor cell (AC) invasion in Caenorhabditis elegans, we show that BM invasion is accompanied by an ATP burst from mitochondria at the invasive front. RNAi screening and visualization of a glucose biosensor identified two glucose transporters, FGT-1 and FGT-2, which bathe invasive front mitochondria with glucose and facilitate the ATP burst to form protrusions. FGT-1 localizes at high levels along the invasive membrane, while FGT-2 is adaptive, enriching most strongly during BM breaching and when FGT-1 is absent. Cytosolic glycolytic enzymes that process glucose for mitochondrial ATP production cluster with invasive front mitochondria and promote higher mitochondrial membrane potential and ATP levels. Finally, we show that UNC-6 (netrin), which polarizes invasive protrusions, also orients FGT-1. These studies reveal a robust and integrated energy acquisition, processing, and delivery network that powers BM breaching.

The glycolytic process in endothelial cells and its implications

Endothelial cells play an obligatory role in regulating local vascular tone and maintaining homeostasis in vascular biology. Cell metabolism, converting food to energy in organisms, is the primary self-sustaining mechanism for cell proliferation and reproduction, structure maintenance, and fight-or-flight responses to stimuli. Four major metabolic processes take place in the energy-producing process, including glycolysis, oxidative phosphorylation, glutamine metabolism, and fatty acid oxidation. Among them, glycolysis is the primary energy-producing mechanism in endothelial cells. The present review focused on glycolysis in endothelial cells under both physiological and pathological conditions. Since the switches among metabolic processes precede the functional changes and disease developments, some prophylactic and/or therapeutic strategies concerning the role of glycolysis in cardiovascular disease are discussed.

Human Glucose Transporters in Renal Glucose Homeostasis

The kidney plays an important role in glucose homeostasis by releasing glucose into the blood stream to prevent hypoglycemia. It is also responsible for the filtration and subsequent reabsorption or excretion of glucose. As glucose is hydrophilic and soluble in water, it is unable to pass through the lipid bilayer on its own; therefore, transport takes place using carrier proteins localized to the plasma membrane. Both sodium-independent glucose transporters (GLUT proteins) and sodium-dependent glucose transporters (SGLT proteins) are expressed in kidney tissue, and mutations of the genes coding for these glucose transporters lead to renal disorders and diseases, including renal cancers. In addition, several diseases may disturb the expression and/or function of renal glucose transporters. The aim of this review is to describe the role of the kidney in glucose homeostasis and the contribution of glucose transporters in renal physiology and renal diseases.

Effects of Cyclic Chronic Heat Stress on the Expression of Nutrient Transporters in the Jejunum of Modern Broilers and Their Ancestor Wild Jungle Fowl

Heat stress (HS) has been reported to disrupt nutrient digestion and absorption in broilers. These effects may be more prominent in fast-growing chickens due to their high metabolic activity. However, the underlying molecular mechanisms are not yet fully elucidated. Hence, the current study aimed to evaluate the effect of chronic HS on jejunal nutrient transport in slow- (Athens Canadian Random Bred, ACRB from 1950), moderate- (The 1995 random bred, 95RAN), rapid- (modern broilers, modern random bred, MRB) growing birds and their ancestor wild jungle fowl (JF). One-day male chicks (n = 150/line) were placed by line in environmentally controlled chambers and kept under the same industry-standard environmental conditions until d28. On d29, an 8-h daily cyclic HS (36°C) was applied to half of the chambers, which lasted until d55, while keeping the rest under thermal neutral (TN, 24°C) conditions. Jejunum tissues were collected for morphology assessment and molecular analysis of carbohydrate-, amino acid-, and fatty acid-transporters. MRB exhibited the highest body weight (BW) followed by 95RAN under both conditions. HS decreased feed intake (FI) in MRB and 95RAN, which resulted in lower BW compared to their TN counterparts; however, no effect was observed in ACRB and JF. MRB showed a greater villus height (VH) to crypt depth (CD) ratio under both environmental conditions. Molecular analyses showed that glucose transporter (GLUT) 2, 5, 10, and 11 were upregulated in MRB compared to some of the other populations under TN conditions. HS downregulated GLUT2, 10, 11, and 12 in MRB while it increased the expression of GLUT1, 5, 10, and 11 in JF. GLUT2 protein expression was higher in JF compared to ACRB and MRB under TN conditions. It also showed an increase in ACRB but no effect on 95RAN and MRB under HS conditions. ACRB exhibited greater expression of the EAAT3 gene as compared to the rest of the populations maintained under TN conditions. HS exposure did not alter the gene expression of amino acid transporters in MRB. Gene expression of CD36 and FABP2 was upregulated in HS JF birds. Protein expression of CD36 was downregulated in HS JF while no effect was observed in ACRB, 95RAN, and MRB. Taken together, these data are the first to show the effect of HS on jejunal expression of nutrient transporters in three broiler populations known to represent 70 years of genetic progress in the poultry industry and a Red Jungle Fowl population representative of the primary ancestor of domestic chickens.

Fructose-rich diet and walnut supplementation differently regulate rat hypothalamic and hippocampal glucose transporters expression

BACKGROUND

Nutritional modulations may be considered a strategy to protect mental health. Neuronal homeostasis is highly dependent on the availability of glucose, which represents the primary energy source for the brain. In this study, we evaluated the effects of walnut intake and fructose-rich diet on the expression of glucose transporters (GLUTs) in two rat brain regions: hypothalamus and hippocampus.

RESULTS

Our results show that walnut supplementation of fructose-fed animals restored the hypothalamic content of GLUT1 and GLUT3 protein. Furthermore, walnut intake did not affect increased hypothalamic GLUT2 content upon fructose consumption. These effects were accompanied by distinctive alterations of hippocampal GLUTs levels. Specifically, walnut intake increased GLUT1 content, whereas GLUT2 protein was decreased within the rat hippocampus after both individual and combined treatments.

CONCLUSION

Overall, our study suggests that walnut supplementation exerted modulatory effects on the glucose transporters within specific brain regions in the presence of developed metabolic disorder. © 2021 Society of Chemical Industry.

Acquired Decline in Ultrafiltration in Peritoneal Dialysis: The Role of Glucose

Ultrafiltration is essential in peritoneal dialysis (PD) for maintenance of euvolemia, making ultrafiltration insufficiency-preferably called ultrafiltration failure-an important complication. The mechanisms of ultrafiltration and ultrafiltration failure are more complex than generally assumed, especially after long-term treatment. Initially, ultrafiltration failure is mainly explained by a large number of perfused peritoneal microvessels, leading to a rapid decline of the crystalloid osmotic gradient, thereby decreasing aquaporin-mediated free water transport. The contribution of peritoneal interstitial tissue to ultrafiltration failure is limited during the first few years of PD, but becomes more important in long-term PD due to the development of interstitial fibrosis, which mainly consists of myofibroblasts. A dual hypothesis has been developed to explain why the continuous exposure of peritoneal tissues to the extremely high dialysate glucose concentrations causes progressive ultrafiltration decline. First, glucose absorption causes an increase of the intracellular NADH/NAD⁺ ratio, also called pseudohypoxia. Intracellular hypoxia stimulates myofibroblasts to produce profibrotic and angiogenetic factors, and the glucose transporter GLUT-1. Second, the increased GLUT-1 expression by myofibroblasts increases glucose uptake in these cells, leading to a reduction of the osmotic gradient for ultrafiltration. Reduction of peritoneal glucose exposure to prevent this vicious circle is essential for high-quality, long-term PD.

Contemporary Perspectives on the Warburg Effect Inhibition in Cancer Therapy

In the 1920s, Otto Warburg observed the phenomenon of altered glucose metabolism in cancer cells. Although the initial hypothesis suggested that the alteration resulted from mitochondrial damage, multiple studies of the subject revealed a precise, multistage process rather than a random pattern. The phenomenon of aerobic glycolysis emerges not only from mitochondrial abnormalities common in cancer cells, but also results from metabolic reprogramming beneficial for their sustenance. The Warburg effect enables metabolic adaptation of cancer cells to grow and proliferate, simultaneously enabling their survival in hypoxic conditions. Altered glucose metabolism of cancer cells includes, inter alia, qualitative and quantitative changes within glucose transporters, enzymes of the glycolytic pathway, such as hexokinases and pyruvate kinase, hypoxia-inducible factor, monocarboxylate transporters, and lactate dehydrogenase. This review summarizes the current state of knowledge regarding inhibitors of cancer glucose metabolism with a focus on their clinical potential. The altered metabolic phenotype of cancer cells allows for targeting of specific mechanisms, which might improve conventional methods in anti-cancer therapy. However, several problems such as drug bioavailability, specificity, toxicity, the plasticity of cancer cells, and heterogeneity of cells in tumors have to be overcome when designing therapies based on compounds targeted in cancer cell energy metabolism.

The effects of low-intensity exercise on cardiac glycogenesis and glycolysis in male and ovariectomized female rats on a fructose-rich diet

We previously reported that low-intensity exercise prevented cardiac insulin resistance induced by a fructose-rich diet (FRD). To examine whether low-intensity exercise could prevent the disturbances of key molecules of cardiac glucose metabolism induced by FRD in male and ovariectomized (ovx) female rats, animals were exposed to 10% fructose solution (SF) or underwent both fructose diet and exercise (EF). Exercise prevented a decrease in cardiac GSK-3β phosphorylation induced by FRD in males (p < .001 vs. SF). It also prevented a decrease in PFK-2 phosphorylation in ovx females (p < .001 vs. SF) and increased the expression of PFK-2 in males (p < .05 vs. control). Exercise did not prevent a decrease in plasma membrane GLUT1 and GLUT4 levels in ovx females on FRD. The only effect of exercise on glucose transporters that could be indicated as beneficial is an augmented GLUT4 protein expression in males (p < .05 vs. control). Obtained results suggest that low-intensity exercise prevents harmful effects of FRD towards cardiac glycogenesis in males and glycolysis in ovx females. PRACTICAL APPLICATIONS: Low-intensity exercise, equivalent to brisk walking, was able to prevent disturbances in cardiac glycolysis regulation in ovx female and the glycogen synthesis pathway in male rats. In terms of human health, although molecular mechanisms of beneficial effects of exercise on cardiac glucose metabolism vary between genders, low-intensity running may be a useful non-pharmacological approach in the prevention of cardiac metabolic disorders in both men and postmenopausal women.

Single nucleotide polymorphisms in the bovine SLC2A12 and SLC5A1 glucose transporter genes - the effect on gene expression and milk traits of Holstein Friesian cows

In this study, novel single nucleotide polymorphisms (SNPs) were found in the 5'-regulatory regions (promoters) of the bovine glucose transporter (GT) genes SLC2A12 and SLC5A1. These polymorphisms were shown to associate with certain milk production traits in HF cows, including milk yield, milk composition, and somatic cell count. It was shown that the SNP g.-671C > G (NC_037336.1: g.72224078C > G) in the SLC2A12 gene could be an effective marker of cattle production traits and that genotypes CC and CG are associated with the best productivity. The polymorphisms found in the SLC5A1 gene promoter also influenced milk production traits in HF cows, albeit to a lesser extent, and we propose that these polymorphisms could be useful as genetic markers for milk production traits in marker-assisted selection (MAS); however, this must be confirmed on larger populations of cattle. In addition, the presence of polymorphisms within promoter regions appears to affect the expression of GT genes in the cow mammary gland and modify transcription factor (TF) binding capacity.

Brain Glucose Transporters: Role in Pathogenesis and Potential Targets for the Treatment of Alzheimer's Disease

The most common cause of dementia, especially in elderly people, is Alzheimer’s disease (AD), with aging as its main risk factor. AD is a multifactorial neurodegenerative disease. There are several factors increasing the risk of AD development. One of the main features of Alzheimer’s disease is impairment of brain energy. Hypometabolism caused by decreased glucose uptake is observed in specific areas of the AD-affected brain. Therefore, glucose hypometabolism and energy deficit are hallmarks of AD. There are several hypotheses that explain the role of glucose hypometabolism in AD, but data available on this subject are poor. Reduced transport of glucose into neurons may be related to decreased expression of glucose transporters in neurons and glia. On the other hand, glucose transporters may play a role as potential targets for the treatment of AD. Compounds such as antidiabetic drugs, agonists of SGLT1, insulin, siRNA and liposomes are suggested as therapeutics. Nevertheless, the suggested targets of therapy need further investigations.

Exploring the Physiological Role of Transthyretin in Glucose Metabolism in the Liver

Transthyretin (TTR), a 55 kDa evolutionarily conserved protein, presents altered levels in several conditions, including malnutrition, inflammation, diabetes, and Alzheimer’s Disease. It has been shown that TTR is involved in several functions, such as insulin release from pancreatic β-cells, recovery of blood glucose and glucagon levels of the islets of Langerhans, food intake, and body weight. Here, the role of TTR in hepatic glucose metabolism was explored by studying the levels of glucose in mice with different TTR genetic backgrounds, namely with two copies of the TTR gene, TTR+/+; with only one copy, TTR+/−; and without TTR, TTR−/−. Results showed that TTR haploinsufficiency (TTR+/−) leads to higher glucose in both plasma and in primary hepatocyte culture media and lower expression of the influx glucose transporters, GLUT1, GLUT3, and GLUT4. Further, we showed that TTR haploinsufficiency decreases pyruvate kinase M type (PKM) levels in mice livers, by qRT-PCR, but it does not affect the hepatic production of the studied metabolites, as determined by 1H NMR. Finally, we demonstrated that TTR increases mitochondrial density in HepG2 cells and that TTR insufficiency triggers a higher degree of oxidative phosphorylation in the liver. Altogether, these results indicate that TTR contributes to the homeostasis of glucose by regulating the levels of glucose transporters and PKM enzyme and by protecting against mitochondrial oxidative stress.

A Systematic Review of Glucose Transport Alterations in Alzheimer's Disease

Introduction: Alzheimer's disease (AD) is characterized by cerebral glucose hypometabolism. Hypometabolism may be partly due to reduced glucose transport at the blood-brain barrier (BBB) and across astrocytic and neuronal cell membranes. Glucose transporters (GLUTs) are integral membrane proteins responsible for moving glucose from the bloodstream to parenchymal cells where it is metabolized, and evidence indicates vascular and non-vascular GLUTs are altered in AD brains, a process which could starve the brain of glucose and accelerate cognitive decline. Here we review the literature on glucose transport alterations in AD from human and rodent studies. Methods: Literature published between 1st January 1946 and 1st November 2020 within EMBASE and MEDLINE databases was searched for the terms "glucose transporters" AND "Alzheimer's disease". Human and rodent studies were included while reviews, letters, and in-vitro studies were excluded. Results: Forty-three studies fitting the inclusion criteria were identified, covering human (23 studies) and rodent (20 studies). Post-mortem studies showed consistent reductions in GLUT1 and GLUT3 in the hippocampus and cortex of AD brains, areas of the brain closely associated with AD pathology. Tracer studies in rodent models of AD and human AD also exhibit reduced uptake of glucose and glucose-analogs into the brain, supporting these findings. Longitudinal rodent studies clearly indicate that changes in GLUT1 and GLUT3 only occur after amyloid-β pathology is present, and several studies indicate amyloid-β itself may be responsible for GLUT changes. Furthermore, evidence from human and rodent studies suggest GLUT depletion has severe effects on brain function. A small number of studies show GLUT2 and GLUT12 are increased in AD. Anti-diabetic medications improved glucose transport capacity in AD subjects. Conclusions: GLUT1 and GLUT3 are reduced in hippocampal and cortical regions in patients and rodent models of AD, and may be caused by high levels of amyloid-β in these regions. GLUT3 reductions appear to precede the onset of clinical symptoms. GLUT2 and GLUT12 appear to increase and may have a compensatory role. Repurposing anti-diabetic drugs to modify glucose transport shows promising results in human studies of AD.

Hexose Transporters in Cancer: From Multifunctionality to Diagnosis and Therapy

Cancer cells increase their metabolic activity by enhancing glucose uptake through overexpression of hexose transporters (Gluts). Gluts also have the capacity to transport other molecules besides glucose, including fructose, mannose, and dehydroascorbic acid (DHA), the oxidized form of vitamin C. The majority of research studies in this field have focused on the role of glucose transport and metabolism in cancer, leaving a substantial gap in our knowledge of the contribution of other hexoses and DHA in cancer biology. Here, we summarize the most recent advances in understanding the role that the multifunctional transport capacity of Gluts plays in biological and clinical aspects of cancer, and how these characteristics can be exploited in the search for novel diagnostic and therapeutic strategies.

Honeybees Exerted Inhibitory Effects on Glucose Uptake and Transport by Interacting with Glucose Transporters in Human Intestinal Cells

Bee pollen possesses potential hypoglycemic effects but its inhibitory mechanisms on glucose absorption and transportation in intestinal cells still need to be clarified. Here, we determined the inhibitory effects of bee pollen extract originating from Camellia sinensis L. (BP-Cs) as well as its representative phenolic compounds on glucose uptake and transport through a human intestinal Caco-2 cell monolayer model. It showed that three representative phenolic compounds, including gallic acid (GA), 3-O-[6'-O-(trans-p-coumaroyl)-β-d-glucopyranosyl]kaempferol (K1), and 3-O-[2',6'-di-O-(trans-p-coumaroyl)-β-d-glucopyranosyl]kaempferol (K2), with contents of 27.7 ± 0.86, 9.88 ± 0.54, and 7.83 ± 0.46 μg/mg in BP-Cs extract, respectively, exerted mutual antagonistic actions interacting with glucose transporters to inhibit glucose uptake and transport based on their combination index (CI) and molecular docking analysis. K1, K2, and GA might compete with d-glucose to form hydrogen bonds with the same active residues including GLU-412, GLY-416, GLN-314, and TRP-420 in GLUT2. These findings provide us a deep understanding of the mechanisms underlying the anti-hyperglycemia by bee pollen, which provide a new sight on dietary intervention strategies against diabetes.

Modulation of Insulin Sensitivity by Insulin-Degrading Enzyme

Insulin-degrading enzyme (IDE) is a highly conserved and ubiquitously expressed metalloprotease that degrades insulin and several other intermediate-size peptides. For many decades, IDE had been assumed to be involved primarily in hepatic insulin clearance, a key process that regulates availability of circulating insulin levels for peripheral tissues. Emerging evidence, however, suggests that IDE has several other important physiological functions relevant to glucose and insulin homeostasis, including the regulation of insulin secretion from pancreatic β-cells. Investigation of mice with tissue-specific genetic deletion of Ide in the liver and pancreatic β-cells (L-IDE-KO and B-IDE-KO mice, respectively) has revealed additional roles for IDE in the regulation of hepatic insulin action and sensitivity. In this review, we discuss current knowledge about IDE’s function as a regulator of insulin secretion and hepatic insulin sensitivity, both evaluating the classical view of IDE as an insulin protease and also exploring evidence for several non-proteolytic functions. Insulin proteostasis and insulin sensitivity have both been highlighted as targets controlling blood sugar levels in type 2 diabetes, so a clearer understanding the physiological functions of IDE in pancreas and liver could led to the development of novel therapeutics for the treatment of this disease.

Effect of Hydrolyzable Tannins on Glucose-Transporter Expression and Their Bioavailability in Pig Small-Intestinal 3D Cell Model

Intestinal transepithelial transport of glucose is mediated by glucose transporters, and affects postprandial blood-glucose levels. This study investigates the effect of wood extracts rich in hydrolyzable tannins (HTs) that originated from sweet chestnut (Castanea sativa Mill.) and oak (Quercus petraea) on the expression of glucose transporter genes and the uptake of glucose and HT constituents in a 3D porcine-small-intestine epithelial-cell model. The viability of epithelial cells CLAB and PSI exposed to different HTs was determined using alamarBlue^®. qPCR was used to analyze the gene expression of SGLT1, GLUT2, GLUT4, and POLR2A. Glucose uptake was confirmed by assay, and LC–MS/ MS was used for the analysis of HT bioavailability. HTs at 37 µg/mL were found to adversely affect cell viability and downregulate POLR2A expression. HT from wood extract Tanex at concentrations of 4 µg/mL upregulated the expression of GLUT2, as well as glucose uptake at 1 µg/mL. The time-dependent passage of gallic acid through enterocytes was influenced by all wood extracts compared to gallic acid itself as a control. These results suggest that HTs could modulate glucose uptake and gallic acid passage in the 3D cell model.

Potent Synergistic Interactions between Lopinavir and Azole Antifungal Drugs against Emerging Multidrug-Resistant Candida auris

The limited therapeutic options and the recent emergence of multidrug-resistant Candida species present a significant challenge to human medicine and underscore the need for novel therapeutic approaches. Drug repurposing appears as a promising tool to augment the activity of current azole antifungals, especially against multidrug-resistant Candida auris In this study, we evaluated the fluconazole chemosensitization activities of 1,547 FDA-approved drugs and clinical molecules against azole-resistant C. auris This led to the discovery that lopinavir, an HIV protease inhibitor, is a potent agent capable of sensitizing C. auris to the effect of azole antifungals. At a therapeutically achievable concentration, lopinavir exhibited potent synergistic interactions with azole drugs, particularly with itraconazole against C. auris (fractional inhibitory concentration index [ΣFICI] ranged from 0.04 to 0.09). Additionally, the lopinavir/itraconazole combination enhanced the survival rate of C. auris-infected Caenorhabditis elegans by 90% and reduced the fungal burden in infected nematodes by 88.5% (P < 0.05) relative to that of the untreated control. Furthermore, lopinavir enhanced the antifungal activity of itraconazole against other medically important Candida species, including C. albicans, C. tropicalis, C. krusei, and C. parapsilosis Comparative transcriptomic profiling and mechanistic studies revealed that lopinavir was able to significantly interfere with the glucose permeation and ATP synthesis. This compromised the efflux ability of C. auris and consequently enhanced the susceptibility to azole drugs, as demonstrated by Nile red efflux assays. Altogether, these findings present lopinavir as a novel, potent, and broad-spectrum azole-chemosensitizing agent that warrants further investigation against recalcitrant Candida infections.

Exploring the Biochemical Foundations of a Successful GLUT1-Targeting Strategy to BNCT: Chemical Synthesis and In Vitro Evaluation of the Entire Positional Isomer Library of ortho-Carboranylmethyl-Bearing Glucoconjugates

Boron neutron capture therapy (BNCT) is a noninvasive binary therapeutic modality applicable to the treatment of cancers. While BNCT offers a tumor-targeting selectivity that is difficult to match by other means, the last obstacles preventing the full harness of this potential come in the form of the suboptimal boron delivery strategies presently used in the clinics. To address these challenges, we have developed delivery agents that target the glucose transporter GLUT1. Here, we present the chemical synthesis of a number of ortho-carboranylmethyl-substituted glucoconjugates and the biological assessment of all positional isomers. Altogether, the study provides protocols for the synthesis and structural characterization of such glucoconjugates and insights into their essential properties, for example, cytotoxicity, GLUT1-affinity, metabolism, and boron delivery capacity. In addition to solidifying the biochemical foundations of a successful GLUT1-targeting approach to BNCT, we identify the most promising modification sites in d-glucose, which are critical in order to further develop this strategy toward clinical use.

In Vitro Bioaccessibility of Extractable Compounds from Tannat Grape Skin Possessing Health Promoting Properties with Potential to Reduce the Risk of Diabetes

Diabetes pathogenesis encompasses oxidative stress, inflammation, insulin malfunctioning and partial or total insulin secretion impairment, which leads to a constant hyperglycemia. Polyphenols are known to possess bioactive properties, being Tannat grape skin a natural and sustainable source of these compounds. The present study aimed to find out the bioaccessibility of health-promoting molecules composing a multifunctional extract from Tannat grape skin obtained under hydro-alcoholic-acid conditions. The identification of phenolic compounds in the samples was performed by ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Subsequently, the samples were in vitro digested mimicking the human oral gastrointestinal conditions and the bioactivity of the digest (antioxidant, anti-inflammatory and modulation of glucose metabolism) was assessed. Effect on glucose metabolism was estimated by measuring carbohydrases activity and the functionality of glucose transporters of small intestine cells in presence and absence of the digested extract. Flavonoids, phenolic acids and phenolic alcohols were the major phenol compounds detected in the extract. The bioaccessible compounds protected the intestinal cells and macrophages against the induced formation of reactive oxygen species (ROS) and nitric oxide (NO). In addition, glucose transporters were inhibited by the digested extract. In conclusion, the bioaccessible compounds of the extract, including phenols, modulated key biochemical events involved in the pathogenesis of diabetes such as oxidative stress, inflammation and glucose absorption. The extract was effective under prevention with co-administration conditions supporting its potential for either reducing the risk or treating this disease.

Addressing the Biochemical Foundations of a Glucose-Based "Trojan Horse"-Strategy to Boron Neutron Capture Therapy: From Chemical Synthesis to In Vitro Assessment

Boron neutron capture therapy (BNCT) for cancer is on the rise worldwide due to recent developments of in-hospital neutron accelerators which are expected to revolutionize patient treatments. There is an urgent need for improved boron delivery agents, and herein we have focused on studying the biochemical foundations upon which a successful GLUT1-targeting strategy to BNCT could be based. By combining synthesis and molecular modeling with affinity and cytotoxicity studies, we unravel the mechanisms behind the considerable potential of appropriately designed glucoconjugates as boron delivery agents for BNCT. In addition to addressing the biochemical premises of the approach in detail, we report on a hit glucoconjugate which displays good cytocompatibility, aqueous solubility, high transporter affinity, and, crucially, an exceptional boron delivery capacity in the in vitro assessment thereby pointing toward the significant potential embedded in this approach.

Salacia chinensis exerts its antidiabetic effect by modulating glucose-regulated proteins and transcription factors in high-fat diet fed-streptozotocin-induced type 2 diabetic rats

This study aimed to investigate the properties of Salacia chinensis (Celastraceae, SC) and its molecular mechanism in the type 2 diabetic rats. Forty-two Wistar rats were divided into six groups (n = 7): control, SC (100 mg/kg, per os), high-fat diet (HFD), HFD + SC (100 mg/kg), HFD + streptozotocin (STZ, 40 mg/kg, i.p.), and HFD + STZ+SC. SC decreased serum glucose, insulin, triglycerides, free fatty acid, and malondialdehyde levels, but increased serum total antioxidant capacity (0.33 ± 0.02 versus. 0.79 ± 0.03), compared with the untreated group (p < .001). Additionally, SC elevated the expression of glucose-regulated proteins GLUT2, PPAR-ɣ, p-IRS, and Nrf2, but downregulated NF-κB in the liver and kidney (p < .001). In conclusion, SC could improve insulin resistance by modulation of glucose-regulated proteins and transcription factors in diabetic rats. PRACTICAL APPLICATIONS: Present data has contributed to the current ethnomedicinal benefits of SC, through which the SC intake regulated the carbohydrate metabolism and increased the antioxidant capacity. The balance of transcription factors can mediate these efficacies partially and various key proteins involved in energy metabolism, along with oxidative stress and insulin sensitivity.

Insulin Treatment Reduces Susceptibility to Atrial Fibrillation in Type 1 Diabetic Mice

Diabetes has been identified as an independent risk factor for atrial fibrillation (AF), the most common chronic cardiac arrhythmia. Whether or not glucose and insulin disturbances observed during diabetes enhance arrhythmogenicity of the atria, potentially leading to AF, is not well-known. We hypothesized that insulin deficiency and impaired glucose transport provide a metabolic substrate for the development and maintenance of AF during diabetes. Transesophageal atrial pacing was used to induce AF in healthy, streptozotocin-induced insulin-deficient type 1 diabetic, and insulin-treated diabetic mice. Translocation of insulin-sensitive glucose transporters (GLUTs) to the atrial cell surface was measured using a biotinylated photolabeling assay in the perfused heart. Fibrosis and glycogen accumulation in the atrium were measured using histological analysis. Diabetic mice displayed mild hyperglycemia, increased duration and frequency of AF episodes vs. age-matched controls (e.g., AF duration: 19.7 ± 6.8 s vs. 1.8 ± 1.1 s, respectively, p = 0.032), whereas insulin-treated diabetic animals did not. The translocation of insulin-sensitive GLUT-4 and -8 to the atrial cell surface was significantly downregulated in the diabetic mice (by 67 and 79%, respectively; p ≤ 0.001), and rescued by insulin treatment. We did not observe fibrosis or glycogen accumulation in the atria of diabetic mice. Therefore, these data suggest that insulin and glucose disturbances were sufficient to induce AF susceptibility during mild diabetes.

Sex-dependent alterations of dopamine receptor and glucose transporter density in rat hypothalamus under long-term clozapine and haloperidol medication

OBJECTIVE

Sex-dependent disturbances of peripheral glucose metabolism are known complications of antipsychotic drug treatment. The influence of long-term clozapine and haloperidol medication on hypothalamus, maintaining aspects of internal body homeostasis, has not yet been completely clarified.

METHODS

After puberty, male and female Sprague Dawley rats were fed orally with ground pellets containing haloperidol (1 mg/kgBW/day) or clozapine (20 mg/kgBW/day) for 12 weeks. The hypothalamic protein expression of dopamine receptors D2R and D4R, melanocortin receptor MC4R, and glucose transporters Glut1 and Glut3 was examined. Glucose, glycogen, lactate, and pyruvate levels were determined, also malondialdehyde equivalents as markers of oxidative stress.

RESULTS

D2R expression was increased in the male haloperidol and clozapine group but decreased in females medicated with clozapine. D4R expression was upregulated under clozapine medication. While females showed increased Glut1, Glut3 was elevated in both male and female clozapine-medicated animals. We found no changes of hypothalamic malondialdehyde, glycogen, and MC4R. Hypothalamic lactate was elevated in the female clozapine group.

CONCLUSION

Clozapine sex-dependently affects the expression of D2R, Glut1, and Glut3. The upregulation of the glucose transporters indicates glucose deprivation in the endothelial cells and consequently in astrocytes and neurons. Increased hypothalamic lactate in females under clozapine points to enhanced glycolysis with a higher glucose demand to produce the required energy. Haloperidol did not change the expression of the glucose transporters and upregulated D2R only in males.

Phosphate Transporter Profiles in Murine and Human Thymi Identify Thymocytes at Distinct Stages of Differentiation

Thymocyte differentiation is dependent on the availability and transport of metabolites in the thymus niche. As expression of metabolite transporters is a rate-limiting step in nutrient utilization, cell surface transporter levels generally reflect the cell's metabolic state. The GLUT1 glucose transporter is upregulated on actively dividing thymocytes, identifying thymocytes with an increased metabolism. However, it is not clear whether transporters of essential elements such as phosphate are modulated during thymocyte differentiation. While PiT1 and PiT2 are both phosphate transporters in the SLC20 family, we show here that they exhibit distinct expression profiles on both murine and human thymocytes. PiT2 expression distinguishes thymocytes with high metabolic activity, identifying immature murine double negative (CD4⁻CD8⁻) DN3b and DN4 thymocyte blasts as well as immature single positive (ISP) CD8 thymocytes. Notably, the absence of PiT2 expression on RAG2-deficient thymocytes, blocked at the DN3a stage, strongly suggests that high PiT2 expression is restricted to thymocytes having undergone a productive TCRβ rearrangement at the DN3a/DN3b transition. Similarly, in the human thymus, PiT2 was upregulated on early post-β selection CD4⁺ISP and TCRαβ⁻CD4^hiDP thymocytes co-expressing the CD71 transferrin receptor, a marker of metabolic activity. In marked contrast, expression of the PiT1 phosphate importer was detected on mature CD3⁺ murine and human thymocytes. Notably, PiT1 expression on CD3⁺DN thymocytes was identified as a biomarker of an aging thymus, increasing from 8.4 ± 1.5% to 42.4 ± 9.4% by 1 year of age (p < 0.0001). We identified these cells as TCRγδ and, most significantly, NKT, representing 77 ± 9% of PiT1⁺DN thymocytes by 1 year of age (p < 0.001). Thus, metabolic activity and thymic aging are associated with distinct expression profiles of the PiT1 and PiT2 phosphate transporters.

Distinct Prognostic Values of the mRNA Expression of Glucose Transporters in Non-Small Cell Lung Cancer

Glucose is the major source of energy for cells. Facilitative glucose transporters (GLUTs) mediate the transport of glucose into cells. The GLUT family has 14 members that are expressed in different tissues of the body and play essential roles in sustaining the energy demand. However, the prognostic value of the majority of GLUTs in lung cancer remains elusive and should be further evaluated in clinical studies. Thus, we investigated the prognostic data of GLUTs in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) patients through the "Kaplan-Meier (KM) plotter" database. In the current study, we found that 12 members of the GLUTs family were significantly associated with prognosis of LUAD patients, but GLUT8 was not. High expression levels of GLUT10, GLUT12, and GLUT13 were significantly associated with better overall survival (OS) in LUAD, while the other 9 members were associated with worse OS. However, GLUT family members were not correlated with OS in LUSC, although high mRNA expression level of GLUT1 tend to show an inferior OS (P=0.057). The prognostic value of GLUTs according to smoking status was also assessed. In conclusion, our study provides new insights into the prognostic values of GLUT members in LUAD, but the molecular mechanisms by which GLUTs contribute to disease aggression and the different functional roles of GLUT members need further study.

Combined deletion of Glut1 and Glut3 impairs lung adenocarcinoma growth

Glucose utilization increases in tumors, a metabolic process that is observed clinically by 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET). However, is increased glucose uptake important for tumor cells, and which transporters are implicated in vivo? In a genetically-engineered mouse model of lung adenocarcinoma, we show that the deletion of only one highly expressed glucose transporter, Glut1 or Glut3, in cancer cells does not impair tumor growth, whereas their combined loss diminishes tumor development. 18F-FDG-PET analyses of tumors demonstrate that Glut1 and Glut3 loss decreases glucose uptake, which is mainly dependent on Glut1. Using 13C-glucose tracing with correlated nanoscale secondary ion mass spectrometry (NanoSIMS) and electron microscopy, we also report the presence of lamellar body-like organelles in tumor cells accumulating glucose-derived biomass, depending partially on Glut1. Our results demonstrate the requirement for two glucose transporters in lung adenocarcinoma, the dual blockade of which could reach therapeutic responses not achieved by individual targeting.

Defying Multidrug Resistance! Modulation of Related Transporters by Flavonoids and Flavonolignans

Multidrug resistance (MDR) is a major challenge for the 21th century in both cancer chemotherapy and antibiotic treatment of bacterial infections. Efflux pumps and transport proteins play an important role in MDR. Compounds displaying inhibitory activity toward these proteins are prospective for adjuvant treatment of such conditions. Natural low-cost and nontoxic flavonoids, thanks to their vast structural diversity, offer a great pool of lead structures with broad possibility of chemical derivatizations. Various flavonoids were found to reverse both antineoplastic and bacterial multidrug resistance by inhibiting Adenosine triphosphate Binding Cassette (ABC)-transporters (human P-glycoprotein, multidrug resistance-associated protein MRP-1, breast cancer resistance protein, and bacterial ABC transporters), as well as other bacterial drug efflux pumps: major facilitator superfamily (MFS), multidrug and toxic compound extrusion (MATE), small multidrug resistance (SMR) and resistance-nodulation-cell-division (RND) transporters, and glucose transporters. Flavonoids and particularly flavonolignans are therefore highly prospective compounds for defying multidrug resistance.

Differential Expression of Glucose Transporters and Hexokinases in Prostate Cancer with a Neuroendocrine Gene Signature: A Mechanistic Perspective for 18F-FDG Imaging of PSMA-Suppressed Tumors

Although the incidence of de novo neuroendocrine prostate cancer (PC) is rare, recent data suggest that low expression of prostate-specific membrane antigen (PSMA) is associated with a spectrum of neuroendocrine hallmarks and androgen receptor (AR) suppression in PC. Previous clinical reports indicate that PCs with a phenotype similar to neuroendocrine tumors can be more amenable to imaging by ¹⁸F-FDG than by PSMA-targeting radioligands. In this study, we evaluated the association between neuroendocrine gene signature and ¹⁸F-FDG uptake-associated genes including glucose transporters (GLUTs) and hexokinases, with the goal of providing a genomic signature to explain the reported ¹⁸F-FDG avidity of PSMA-suppressed tumors. Methods: Data-mining approaches, cell lines, and patient-derived xenograft models were used to study the levels of 14 members of the SLC2A family (encoding GLUT proteins), 4 members of the hexokinase family (genes HK1-HK3 and GCK), and PSMA (FOLH1 gene) after AR inhibition and in correlation with neuroendocrine hallmarks. Also, we characterize a neuroendocrine-like PC (NELPC) subset among a cohort of primary and metastatic PC samples with no neuroendocrine histopathology. We measured glucose uptake in a neuroendocrine-induced in vitro model and a zebrafish model by nonradioactive imaging of glucose uptake using a fluorescent glucose bioprobe, GB2-Cy3. Results: This work demonstrated that a neuroendocrine gene signature associates with differential expression of genes encoding GLUT and hexokinase proteins. In NELPC, elevated expression of GCK (encoding glucokinase protein) and decreased expression of SLC2A12 correlated with earlier biochemical recurrence. In tumors treated with AR inhibitors, high expression of GCK and low expression of SLC2A12 correlated with neuroendocrine histopathology and PSMA gene suppression. GLUT12 suppression and upregulation of glucokinase were observed in neuroendocrine-induced PC cell lines and patient-derived xenograft models. A higher glucose uptake was confirmed in low-PSMA tumors using a GB2-Cy3 probe in a zebrafish model. Conclusion: A neuroendocrine gene signature in neuroendocrine PC and NELPC associates with a distinct transcriptional profile of GLUTs and hexokinases. PSMA suppression correlates with GLUT12 suppression and glucokinase upregulation. Alteration of ¹⁸F-FDG uptake-associated genes correlated positively with higher glucose uptake in AR- and PSMA-suppressed tumors. Zebrafish xenograft tumor models are an accurate and efficient preclinical method for monitoring nonradioactive glucose uptake.

Aged garlic extract and S-allylcysteine increase the GLUT3 and GCLC expression levels in cerebral ischemia

BACKGROUND

During cerebral ischemia, energy restoration through the regulation of glucose transporters and antioxidant defense mechanisms is essential to maintain cell viability. Antioxidant therapy has been considered effective to attenuate brain damage; moreover, the regulation of transcription factors that positively regulate the expression of glucose transporters is associated with this therapy. Recently, it has been reported that the use of antioxidants such as S-allylcysteine (SAC), a component of aged garlic extract (AGE), improves survival in experimental models of cerebral ischemia.

OBJECTIVES

The aim of this study was to determine the effect of AGE and SAC on the level of mRNA expression of the main neuronal glucose transporter (GLUT3) and the glutamate cysteine ligase catalytic subunit (GCLC) in rats with transient focal cerebral ischemia.

MATERIAL AND METHODS

Cerebral ischemia was induced in male Wistar rats by middle cerebral artery occlusion (MCAO) for 2 h. The animals were sacrificed after different reperfusion times (0-48 h). Animals injected with AGE (360 mg/kg, intraperitoneally (i.p.)) and SAC (300 mg/kg, i.p.) at the beginning of reperfusion were sacrificed after 2 h. The mRNA expression level was analyzed in the fronto-parietal cortex using quantitative polymerase chain reaction (qPCR).

RESULTS

Two major increases in GLUT3 expression at 1 h and 24 h of reperfusion were found. Both treatments increased GLUT3 and GCLC mRNA levels in control and under ischemic/reperfusion injury animals.

CONCLUSIONS

This data suggests that SAC and AGE might induce neuroprotection, while controlling reactive oxygen species (ROS) levels, as indicated by the increase in GCLC expression, and regulating the energy content of the cell by increasing glucose transport mediated by GLUT3.

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.

Synthesis of Indomorphan Pseudo-Natural Product Inhibitors of Glucose Transporters GLUT-1 and -3

Bioactive compound design based on natural product (NP) structure may be limited because of partial coverage of NP-like chemical space and biological target space. These limitations can be overcome by combining NP-centered strategies with fragment-based compound design through combination of NP-derived fragments to afford structurally unprecedented "pseudo-natural products" (pseudo-NPs). The design, synthesis, and biological evaluation of a collection of indomorphan pseudo-NPs that combine biosynthetically unrelated indole- and morphan-alkaloid fragments are described. Indomorphane derivative Glupin was identified as a potent inhibitor of glucose uptake by selectively targeting and upregulating glucose transporters GLUT-1 and GLUT-3. Glupin suppresses glycolysis, reduces the levels of glucose-derived metabolites, and attenuates the growth of various cancer cell lines. Our findings underscore the importance of dual GLUT-1 and GLUT-3 inhibition to efficiently suppress tumor cell growth and the cellular rescue mechanism, which counteracts glucose scarcity.