Inhibiting the Absorption of Dietary Carbohydrates and Fats with Natural Products
Christophe Wiart in Medicinal Plants in Asia for Metabolic Syndrome, 2017
Methanol extract of Sinocrassula indica (Decne.) A. Berger (containing flavonoids including quercetin, luteolin, kaempferol) given orally to rats at a single dose of 500 mg/kg decreased postprandial glycaemia from 166.3 to 121.9 mg/dL at 30 minutes during oral sucrose challenge (tolbutamide: 25 mg/kg: 138.1 mg/dL).76 The same regimen applied to rats challenged with oral glucose decreased glycaemia but had no activity against intraperitoneal glucose loading, indicating an activity elicited at intestinal level.76 It must be noted that glucose released from maltose, maltotriose, dextrin, and sucrose is actively absorbed in brush border enterocytes by integral sodium-dependent glucose transporter-1 (SGLT-1) located in the apical cytoplasmic membrane.77 From the cytoplasm of enterocytes, glucose is released in the general circulation via, at least, glucose transporter 2 located in the basolateral cytoplasmic membrane of enterocytes. The sodium gradient necessary for SGLT1 activity is maintained by a basolateral Na+/K+ ATPase.78 In spontaneous type 2 diabetic obese KK-Ay mice, the extract given orally at a dose of 500 mg/kg/day decreased nonfasting glycaemia by 28% and triglycerides by 14% ,whereas cholesterolaemia and serum-free fatty acids were not affected.79 Quercetin inhibited yeast α-glucosidase with IC50 value of 58.9 μM (acarbose: 130.7 μM).80
Significance of Hormones in Regulation of Metabolism During Exercise
Atko Viru in Adaptation in Sports Training, 2017
Insulin as well as muscular contractions stimulate the uptake of glucose by muscle cells. Both of them induce a twofold increase in the number of glucose transporters in plasma membranes of the rat hindlimb muscles.187 Insulin and contractile effects on glucose uptake are additives suggesting that these stimuli mobilize different pools of glucose transporters.148 Results were obtained showing that in the absence of insulin the glucose uptake by rat hindquarters, isolated immediately after a 45-min run, was on the same level as in nonexercised controls; addition of insulin increased the glucose uptake.17 When prior swimming increased the glucose uptake by the perfused rat hindquarter, the addition of insulin into the perfusate did not further increase the glucose uptake.188 There are also data indicating that muscular contractions caused a seven-fold increase in glucose uptake by the perfused muscle from a diabetic rat despite the lack of insulin in the perfusate.189
Maturation, Barrier Function, Aging, and Breakdown of the Blood–Brain Barrier
Shamim I. Ahmad in Aging: Exploring a Complex Phenomenon, 2017
Glucose transporters: Also, facilitative glucose transport in the brain is affected in different pathophysiological conditions including AD (Guo et al. 2005). Protein expression of the glucose transporter GLUT1 is reduced in brain capillaries in AD, without changes in GLUT1 mRNA structure (Mooradian et al. 1997) or levels of GLUT1 mRNA transcripts (Wu et al. 2005). Furthermore, a reduction in CNS energy metabolites has been seen in several PET scanning studies of AD's patients using fluoro-deoxy-glucose (FDG) (Mosconi et al. 2006, Samuraki et al. 2007, Mosconi et al. 2008), likely because the surface area at the BBB available for glucose transport is substantially reduced in AD (Bailey et al. 2004, Wu et al. 2005). Furthermore, GLUT1 deficiency in mice overexpressing amyloid β-peptide precursor protein leads to early cerebral microvascular degeneration, blood flow reductions, dysregulation, and BBB breakdown. Also, it leads to accelerated amyloid β-peptide pathology, reduced amyloid β clearance, diminished neuronal activity, behavioral deficits, progressive neuronal loss, and neurodegeneration that develop after initial cerebrovascular degenerative changes. Moreover, GLUT1 deficiency in endothelium, but not in astrocytes, initiates the vascular phenotype as shown by BBB breakdown. This indicates that reduced BBB GLUT1 expression worsens AD cerebrovascular degeneration, neuropathology, and cognitive function (Winkler et al. 2015).
NIR triggered glycosylated gold nanoshell as a photothermal agent on melanoma cancer cells
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Samira Nouri, Elham Mohammadi, Bita Mehravi, Fatemehsadat Majidi, Khadijeh Ashtari, Ali Neshasteh-Riz, Samira Einali
Conjugation of groups which target the surface of nanoparticles can be applied for enhancing the permeability and retention of nanoparticles to cancer cells. Different groups have been developed to target nanoparticles and incorporate them into cells. Glucose is one of these groups for targeting cancer cells which have an excessive demand for glucose. This requirement is met through enhancing cellular uptake of glucose by particular transporters [18–20]. The glucose transporter-1 (Glut-1) is a membrane protein which facilitates the intra-cellular uptake of glucose. The overexpression of Glut-1 is associated with high glucose transfer to cancer cells [19,20]. Accumulation of glucose in the tumour cells is very high because of their high rate of proliferation and angiogenesis [18]. This property can also be employed for cancer treatment. For enhancing the potential localized photothermal therapy, glucosamine can be conjugated to GNs surfaces. This modification improves internalization and accumulation of GNs in the cells. Subsequently, the effects of photothermal therapy can increase considerably while reducing its side effects [2,9,14,21,22].
Blood-brain barrier receptors and transporters: an insight on their function and how to exploit them through nanotechnology
Published in Expert Opinion on Drug Delivery, 2019
Rui Pedro Moura, Cláudia Martins, Soraia Pinto, Flávia Sousa, Bruno Sarmento
Glucose transporters (GLUTs) are a group of glycoproteins composed of 12 transmembrane α-helixes, assembled in tags of 3 sharing similar structure. GLUTs possess other two and three extracellular and intracellular helixes, respectively. Similarly to the previously mentioned receptors, after undergoing protein synthesis, these transporters are carried to the endoplasmic reticulum for post-translational modifications, consisting of adequate protein folding, glycosylation, and phosphorylation [74]. The main role of GLUTs is the transport of glucose or other hexose and/or pentose sugars from the blood to the interior of the cell. Thus, GLUTs are expressed in several tissues throughout the body. Since there are many members of the GLUT family, each one of them may have higher or lower expression levels, depending on the biologic site where it is located. In what concerns the brain, it has been described that GLUT1, is mainly expressed in endothelial cells with a considerably high glycosylation percentage, presenting a molecular weight of 55 kDa. Also, GLUT1 is thoroughly expressed in astrocytes and other cellular components of the neurovascular unit, although with a considerably lower rate of glycosylation, holding a molecular weight of 45 kDa. GLUT3 is the main transporter expressed by neurons. The microglia present a wide expression of GLUT5; however, it holds a lower affinity for glucose and a higher affinity towards fructose [75].
Higher Glucose Enhances Breast Cancer Cell Aggressiveness
Published in Nutrition and Cancer, 2020
Julianna M. Santos, Fazle Hussain
Our finding that an increase in expression of key glycolytic enzymes requires an increase in glucose uptake, prompted us to study the effect of higher glucose on glucose uptake. MCF-7 (Fig. 3a–f) and MB231 (Fig. 3h–m) fluorescent micrographs, accompanied by their inverted images, after incubation with a glucose analog conjugated to a fluorescent molecule (2-NBDG, fluorescently-tagged glucose derivative). Cells were kept in culture media for 72 h with different D-(+)-glucose concentrations: 5 (physiological) and higher 15 and 30 mM. The fluorescence intensity was quantified for MCF-7 (Fig. 3g) and MB231 (Fig. 3n). The former did not show a significant increase in glucose uptake, whereas the latter increased significantly the glucose uptake with 30 mM glucose. These results corroborate our previous finding that MB231 is more glucose dependent than MCF-7. In addition, higher glucose can induce overexpression of glucose transporters reflecting an increased glucose uptake. Thus, the glucose dependence is not just related to increase of expression of glycolytic enzymes but also the increase in glucose uptake.
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