Thioglycosides as inhibitors of hSGLT1 and hSGLT2: potential therapeutic agents for the control of hyperglycemia in diabetes

Synthesis of aryl thioglycosides by metal-free arylation of glycosyl thiols with diaryliodonium salts under basic conditions

Herein, we demonstrate the application of unsymmetrical iodonium salts towards S-arylation of glycosyl thiols under metal-free conditions, affording a various stereoretentive thioarylglycosides in moderate to good yields. The application of an inorganic base Cs2CO3 enables the C-S bond formation under mild and experimentally simple conditions at room temperature. The proper choice of auxiliary of the unsymmetrical iodonium salt enables the access to diverse functionalized aryl moieties including biphenyl groups and its incorporation into thioarylglycosides.

Plant glycosides and glycosidases: classification, sources, and therapeutic insights in current medicine

Plant glycosides have a broad spectrum of pharmaceutical activities primarily due to the glycosidic residues present in their structure. Especially, the therapeutic glycosides can be classified into many compounds based on the sugar moiety, chains/ saccharide units, glycosidic linkages, and aglycones. Among many classes, the widely used pharmacological classification is based on the aglycones linked to the glycoside molecule. Based on these non-sugar moiety (aglycones), plant glycosides are further classified into twelve different types of glycosides along with the recent discovery of novel (cannabinoid) glycosides. They are called alcoholic, anthraquinone, coumarin, chromone, cyanogenic, flavonoid, phenolic, cardiac, saponin, thio, steviol, iridoid, and cannabinoid glycosides. Each of the plant glycosides has been discussed in this paper with, origin, structure, and abundant presence in a specific family of plants. Besides, the therapeutic roles of these plant glycosides are further described in detail to validate their efficacies in the human health care system. On the other hand, glycosides are inactive until enzymatic hydrolysis releases their active aglycone, enabling targeted drug delivery. This process enhances aglycone solubility and stability, improving bioavailability and therapeutic efficacy. They target specific receptors or enzymes, minimizing off-target effects and enhancing pharmacological outcomes. Derived from plants, glycosides offer diverse chemical structures for drug development. They are integral to traditional medicine and modern pharmaceuticals, utilized in therapies ranging from cardiology to antimicrobial treatments.

Visible-Light-Mediated Synthesis of Anomeric S-Aryl Glycosides via Electron Donor-Acceptor Complex Using Thianthrenium Salts

S-Aryl glycosides are not only popular glycosyl donors in carbohydrate chemistry but also serve as valuable tools in various biological studies, which has brought significant attention to their preparation. However, there remains a pressing need for greener synthesis methods in this area. In response, a mild, sustainable, and metal- and photocatalyst-free electron donor-acceptor (EDA)-mediated approach for synthesizing S-Aryl glycosides using 1-thiosugar and aryl thianthrenium salt was developed. Our strategy utilizes 1-thiosugar as the donor, overcoming the traditional reliance on electron-rich thiols, such as aryl or carbonyl thiols, typically required for forming EDA complexes.

Pd-Catalyzed Synthesis of 1-(Hetero)aryl Thioglycosides: Strategy for the Trapping of an Acyl Group of Glycosylthioesters by Coupling of Bis-Electrophilic-Nucleophilic Partners

Herein, we describe a stereoretentive palladium-catalyzed cross-coupling between the in situ-generated glycosyl thiolate anion and diverse (hetero)aryl iodides at room temperature for creating the library of (hetero)aryl thioglycosides. The key to success is the judicious pairing of bis-electrophilic-nucleophilic partners with a variety of thioesters in an atom-economical way in which both the glycosyl thiolate anion and the acylium cation are incorporated into the final analogue. The advantage of this method is the acyl transfer on various nucleophilic partners, including a hydroxyl, a primary or secondary amine, an amino acid, and the biologically active hSGLT1 inhibitor.

Management of chronic kidney disease: The current novel and forgotten therapies

Chronic kidney disease (CKD) is a progressive and incurable condition that imposes a significant burden on an aging society. Although the exact prevalence of this disease is unknown, it is estimated to affect at least 800 million people worldwide. Patients with diabetes or hypertension are at a higher risk of developing chronic kidney damage. As the kidneys play a crucial role in vital physiological processes, damage to these organs can disrupt the balance of water and electrolytes, regulation of blood pressure, elimination of toxins, and metabolism of vitamin D. Early diagnosis is paramount to prevent potential complications. Treatment options such as dietary modifications and medications can help slow disease progression. In our narrative review, we have summarized the available therapeutic options to slow the progression of chronic kidney disease. Many new drug treatments have recently become available, offering a beacon of hope and optimism in CKD management. Nonetheless, disease prevention remains the most critical step in disease management. Given the significant impact of CKD on public health, there is a pressing need for further research. With the development of new technologies and advancements in medical knowledge, we hope to find more effective diagnostic tools and treatments for CKD patients.

Electrochemical nickel-catalyzed cross-coupling of glycosyl thiols with preactivated phenols and ketones

An efficient electrochemical nickel-catalyzed cross-coupling reaction has been reported here for the synthesis of S-glycosides from preactivated phenols and ketones under mild conditions. Various glycosyl thiols, including unprotected sugar, and a diverse range of aryl/alkenyl triflates, including some complex biorelevant phenols and ketones, were well tolerated in this method.

New syntheses of thiosaccharides utilizing substitution reactions

Novel synthetic methods published since 2005 affording carbohydrates containing sulfur atom(s) are reviewed. The review is divided to subchapters based on the position of sulfur atom(s) in the sugar molecule. Only those methods that take advantage of substitution are discussed.

Design, Synthesis, and Biological Evaluation of Thioglucoside Analogues of Gliflozin as Potent New Gliflozin Drugs

In this study, we have investigated the potential of two classes of thioglucoside analogues of gliflozins as antidiabetic drugs, one with substitutions of S-atoms in meta-positions (similar to C-glucoside SGLT2 inhibitors, TAGs A, B, and C) and the other with substitutions of S-atoms in ortho-positions (similar to O-glucoside SGLT2 inhibitors, TAGs D, E, F, and G). These TAGs were confirmed to show good stability against β-glucosidase and to have no acute toxicity to cultured cells. Most importantly, TAGs D, E, F, and G all showed high inhibitory activity against SGLT2 (IC50: 2.0-5.9 nM) and thus have great potential to be developed as new gliflozin drugs. Compared with the synthesis of C-glucoside gliflozins, the synthesis of TAGs is simple, efficient, and associated with low costs, high yields, and very mild reaction conditions.

A Robust Copper-Catalyzed Cross-Coupling of Glycosyl Thiosulfonate and Boronic Acids Enables the Construction of Thioglycosides

An efficient and stereoretentive copper-catalyzed cross-coupling of glycosyl thiosulfonate and boronic acid for the construction of thioglycosides is described. The good functional group compatibility of this method allows the preparation of many bioactive aryl/alkenyl thioglycosides, including the hSGLT1 inhibitor.

Atom-Economic Synthesis of Unsymmetrical gem-Diarylmethylthio/Seleno Glycosides via Base Mediated C(O)-S/Se Bond Cleavage and Acyl Transfer Approach of Glycosylthio/Selenoacetates

Herein, we invented the Cs₂CO₃-mediated atom economic method that streamlines the scission of the C(O)-S/Se bond involving the in situ generation of an anomeric thiolate/selenolate anion, which reacted with p-QMs to yield novel unsymmetrical gem-diarylmethylthio/seleno glycosides while retaining the anomeric stereochemistry. Notably, the key features of this protocol involve unprecedented long-range acyl transfer (from S/Se to O), thus affording acylation of the final product which is not yet reported by classical methods. This straightforward protocol offers a mild, short reaction time, synthetically simple approach, and compatibility with 8 types of sugar along with phenylthio/benzylseleno esters.

Novel triple mutant of an extremophilic glycosyl hydrolase enables the rapid synthesis of thioglycosides

In order to expand the toolbox of enzymes available for thioglycoside synthesis, we describe here the first example of an extremophilic glycosyl hydrolase from Halothermothrix orenii (HorGH1) engineered towards thioglycosynthase activity with a novel combination of mutations. Using the triple mutant, HorGH1 M299R/E166A/E354G, a range of thioglycosides from glycosyl fluoride donors and aromatic thiols could be synthesised with exquisite stereoselectivity and good to excellent conversions (61-93%).

Visible-Light-Mediated Stadler-Ziegler Arylation of Thiosugars with Anilines

Here, we report a one-pot Stadler-Ziegler reaction toward the synthesis of 1-thioglycosides in good yield from commercially available anilines and (un)protected 1-glycosyl thiols. This simple and mild approach employs the photoredox catalyst [Ru(bpy)₃](PF₆)₂ under visible light.

Boron-Promoted Umpolung Reaction of Sulfonyl Chlorides for the Stereospecific Synthesis of Thioglycosides via Reductive Deoxygenation Coupling Reactions

S-Glycosides have broad biological activities and serve as stable mimics of natural O-glycoside counterparts and thus are of great therapeutic potential. Herein we disclose an efficient method for the stereospecific synthesis of 1-thioglycosides via a boron-promoted reductive deoxygenation coupling reaction from readily accessible sulfonyl chlorides and glycosyl bromides. Our protocol features mild conditions and excellent functional group tolerance and stereoselectivity. The translational potential of this metal-free approach is demonstrated by the late-stage glycodiversification of natural products and drug molecules.

Transition-metal-free synthesis of aryl 1-thioglycosides with arynes at room temperature

A mild, convenient and transition-metal-free protocol for the synthesis of aryl 1-thioglycosides is presented via arynes generated in situ combined with glycosyl thiols in the presence of TBAF(tBuOH)₄. The methodology provides a general and efficient way to prepare a series of functionalized thioglycosides in good to excellent yields with a perfect control of the anomeric configuration at room temperature. In addition, the reaction conditions tolerate a variety of the pentoses and hexoses, and the reaction also performs smoothly on protected monosaccharides and disaccharides.

Surfactant-mediated thioglycosylation of 1-hydroxy sugars in water

Thioglycosides are an important class of sugars, since they can be used as non-ionic biosurfactants, biomimetic glycosides, and building blocks for carbohydrate synthesis. Previously, Brønsted- or Lewis-acid-catalyzed dehydrative glycosylations between a 1-hydroxy sugar and a thiol have been reported to yield open-chain dithioacetal sugars as the major products instead of the desired thioglycosides. These dithioacetal sugars are by-products derived from the endocyclic bond cleavage of the thioglycosides. Herein, we report dehydrative glycosylation in water mediated by a Brønsted acid-surfactant combined catalyst (BASC). Glycosylations between 1-hydroxy furanosyl/pyranosyl sugars and primary, secondary, and tertiary aliphatic/aromatic thiols in the presence of dodecyl benzenesulfonic acid (DBSA) provided the thioglycoside products in moderate to good yields. Microwave irradiation led to improvements in the yields and a shortening of the reaction time. Remarkably, open-chain dithioacetal sugars were not detected in the DBSA-mediated glycosylations in water. This method is a simple, convenient, and rapid approach to produce a library of thioglycosides without the requirement of anhydrous conditions. Moreover, this work also provides an excellent example of complementary reactivity profiles of glycosylation in organic solvents and water.

SGLT1 Inhibition Attenuates Apoptosis in Diabetic Cardiomyopathy via the JNK and p38 Pathway

Background: Recent studies have revealed that a novel selective sodium-glucose cotransporter 1 (SGLT1) inhibiton has shown beneficial effects in cardiovascular diseases. However, the question of whether SGLT1 inhibition influences diabetic cardiomyopathy (DCM) remains unanswered. In this study, we investigated the influence and underlying mechanism of SGLTI inhibition on DCM. Methods: SGLT1 levels were measured in diabetic patients with similar conditions who visited our hospital from January to December 2019. Wistar male rats (n = 50) were divided into five groups: control, diabetes induced by streptozotocin infusion, and diabetes treated with 0.5, 1.0, or 1.5 mg/kg mizagliflozin via stomach gavage for 12 weeks. H9C2 cardiomyocytes were treated with mizagliflozin and then exposed to a high glucose concentration (30 mmol/L). TUNEL assays were performed, and bcl2, bax, p-p38, p-Erk, p-JNK and caspase-3 levels were measured. We used siRNA and an SGLT1 overexpression plasmid to detect the effects of SGLT1. Results: SGLT1 levels were significantly elevated in DCM patients, and receiver operating characteristic (ROC) curve analysis identified SGLT1 as influencing DCM. The area under the curve (AUC) was 0.705 (p < 0.05), with 65.8% sensitivity, and 62.2% specificity. SGLT1 inhibition appeared to attenuate apoptosis in DCM via the JNK and p38 pathway. Conclusion: SGLT1 can be used as a marker for the diagnosis of DCM, and SGLT1 inhibition can attenuate apoptosis, thereby suppressing DCM development via the JNK and p38 pathway.

Thioglycoligase derived from fungal GH3 β-xylosidase is a multi-glycoligase with broad acceptor tolerance

The synthesis of customized glycoconjugates constitutes a major goal for biocatalysis. To this end, engineered glycosidases have received great attention and, among them, thioglycoligases have proved useful to connect carbohydrates to non-sugar acceptors. However, hitherto the scope of these biocatalysts was considered limited to strong nucleophilic acceptors. Based on the particularities of the GH3 glycosidase family active site, we hypothesized that converting a suitable member into a thioglycoligase could boost the acceptor range. Herein we show the engineering of an acidophilic fungal β-xylosidase into a thioglycoligase with broad acceptor promiscuity. The mutant enzyme displays the ability to form O-, N-, S- and Se- glycosides together with sugar esters and phosphoesters with conversion yields from moderate to high. Analyses also indicate that the pKa of the target compound was the main factor to determine its suitability as glycosylation acceptor. These results expand on the glycoconjugate portfolio attainable through biocatalysis.

8-Hydroxyquinoline Glycoconjugates Containing Sulfur at the Sugar Anomeric Position-Synthesis and Preliminary Evaluation of Their Cytotoxicity

One of the main factors limiting the effectiveness of many drugs is the difficulty of their delivery to their target site in the cell and achieving the desired therapeutic dose. Moreover, the accumulation of the drug in healthy tissue can lead to serious side effects. The way to improve the selectivity of a drug to the cancer cells seems to be its conjugation with a sugar molecule, which should facilitate its selective transport through GLUT transporters (glucose transporters), whose overexpression is seen in some types of cancer. This was the idea behind the synthesis of 8-hydroxyquinoline (8-HQ) derivative glycoconjugates, for which 1-thiosugar derivatives were used as sugar moiety donors. It was expected that the introduction of a sulfur atom instead of an oxygen atom into the anomeric position of the sugar would increase the stability of the obtained glycoconjugates against untimely hydrolytic cleavage. The anticancer activity of new compounds was determined based on the results of the MTT cytotoxicity tests. Because of the assumption that the activity of this type of compounds was based on metal ion chelation, the effect of the addition of copper ions on cell proliferation was tested for some of them. It turned out that cancer cells treated with glycoconjugates in the presence of Cu2+ had a much slower growth rate compared to cells treated with free glycoconjugates in the absence of copper. The highest cytotoxic activity of the compounds was observed against the MCF-7 cell line.

Therapeutic approaches to diabetic cardiomyopathy: Targeting the antioxidant pathway

The global epidemic of cardiovascular disease continues unabated and remains the leading cause of death both in the US and worldwide. We hereby summarize the available therapies for diabetes and cardiovascular disease in diabetics. Clearly, the current approaches to diabetic heart disease often target the manifestations and certain mediators but not the specific pathways leading to myocardial injury, remodeling and dysfunction. Better understanding of the molecular events determining the evolution of diabetic cardiomyopathy will provide insight into the development of specific and targeted therapies. Recent studies largely increased our understanding of the role of enhanced inflammatory response, ROS production, as well as the contribution of Cyp-P450-epoxygenase-derived epoxyeicosatrienoic acid (EET), Peroxisome Proliferator-Activated Receptor Gamma Coactivator-1α (PGC-1α), Heme Oxygenase (HO)-1 and 20-HETE in pathophysiology and therapy of cardiovascular disease. PGC-1α increases production of the HO-1 which has a major role in protecting the heart against oxidative stress, microcirculation and mitochondrial dysfunction. This review describes the potential drugs and their downstream targets, PGC-1α and HO-1, as major loci for developing therapeutic approaches beside diet and lifestyle modification for the treatment and prevention of heart disease associated with obesity and diabetes.

Electrochemical nickel-catalyzed Migita cross-coupling of 1-thiosugars with aryl, alkenyl and alkynyl bromides

An efficient electrochemical route towards the synthesis of thioglycosides is reported. This approach involves a S–C cross-coupling from protected and unprotected thiosugars with aryl bromides under base free conditions.

SGLT1 inhibition boon or bane for diabetes-associated cardiomyopathy

Chronic hyperglycaemia is a peculiar feature of diabetes mellitus (DM). Sequential metabolic abnormalities accompanying glucotoxicity are some of its implications. Glucotoxicity most likely corresponds to the vascular intricacy and metabolic alterations, such as increased oxidation of free fatty acids and reduced glucose oxidation. More than half of those with diabetes also develop cardiac abnormalities due to unknown causes, posing a major threat to the currently available marketed preparations which are being used for treating these cardiac complications. Even though impairment in cardiac functioning is the principal cause of death in individuals with type 2 diabetes (T2D), reducing plasma glucose levels has little effect on cardiovascular disease (CVD) risk. In vitro and in vivo studies have demonstrated that inhibitors of sodium glucose transporter (SGLT) represent a putative therapeutic intervention for these pathological conditions. Several clinical trials have reported the efficacy of SGLT inhibitors as a novel and potent antidiabetic agent which along with its antihyperglycaemic activity possesses the potential of effectively treating its associated cardiac abnormalities. Thus, hereby, the present review highlights the role of SGLT inhibitors as a successful drug candidate for correcting the shifts in deregulation of cardiac energy substrate metabolism together with its role in treating diabetes-related cardiac perturbations.

Glycosylation in health and disease

The glycome describes the complete repertoire of glycoconjugates composed of carbohydrate chains, or glycans, that are covalently linked to lipid or protein molecules. Glycoconjugates are formed through a process called glycosylation and can differ in their glycan sequences, the connections between them and their length. Glycoconjugate synthesis is a dynamic process that depends on the local milieu of enzymes, sugar precursors and organelle structures as well as the cell types involved and cellular signals. Studies of rare genetic disorders that affect glycosylation first highlighted the biological importance of the glycome, and technological advances have improved our understanding of its heterogeneity and complexity. Researchers can now routinely assess how the secreted and cell-surface glycomes reflect overall cellular status in health and disease. In fact, changes in glycosylation can modulate inflammatory responses, enable viral immune escape, promote cancer cell metastasis or regulate apoptosis; the composition of the glycome also affects kidney function in health and disease. New insights into the structure and function of the glycome can now be applied to therapy development and could improve our ability to fine-tune immunological responses and inflammation, optimize the performance of therapeutic antibodies and boost immune responses to cancer. These examples illustrate the potential of the emerging field of 'glycomedicine'.

What does sodium-glucose co-transporter 1 inhibition add: Prospects for dual inhibition

Epithelial glucose transport is accomplished by Na+ -glucose co-transporters, SGLT1 and SGLT2. In the intestine, uptake of dietary glucose is for its majority mediated by SGLT1, and humans with mutations in the SGLT1 gene show glucose/galactose malabsorption. In the kidney, both transporters, SGLT1 and SGLT2, are expressed and recent studies identified that SGLT2 mediates up to 97% of glucose reabsorption. Humans with mutations in the SGLT2 gene show familial renal glucosuria. In the last three decades, significant progress was made in understanding the physiology of these transporters and their potential as therapeutic targets. Based on the structure of phlorizin, a natural compound acting as a SGLT1/2 inhibitor, initially several SGLT2, and later SGLT1 and dual SGLT1/2 inhibitors have been developed. Interestingly, SGLT2 knockout or treatment with SGLT2 selective inhibitors only causes a fractional glucose excretion in the magnitude of ∼60%, an effect mediated by up-regulation of renal SGLT1. Based on these findings the hypothesis was brought forward that dual SGLT1/2 inhibition might further improve glycaemic control via targeting two distinct organs that express SGLT1: the intestine and the kidney. Of note, SGLT1/2 double knockout mice completely lack renal glucose reabsorption. This review will address the rationale for the development of SGLT1 and dual SGLT1/2 inhibitors and potential benefits compared to sole SGLT2 inhibition.

Convergent Synthesis of N,S-bis Glycosylquinolin-2-ones via a Pd-G3-XantPhos Precatalyst Catalysis

Buchwald-Hartwig-Migita cross-coupling of 1-thiosugars with α- or β-3-iodo-N-glycosylquinolin-2-ones has been accomplished under mild and operationally simple reaction conditions through the use of a Pd-G3 XantPhos palladacycle precatalyst. This new methodology has been successfully applied to a variety of α- or β-mono-, di-, and poly-thiosugar derivatives to efficiently synthesize a series of α- or β-N,S-bis-glycosyl quinolin-2-ones, which are difficult to synthesize by classical methods.

Spotlight on ertugliflozin and its potential in the treatment of type 2 diabetes: evidence to date

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are the latest therapeutic strategy in the treatment of type 2 diabetes mellitus (T2DM). Using an insulin-independent mechanism (glycosuria), they reduce glucose toxicity and improve insulin sensitivity and β-cell function. The promising results obtained in clinical trials show that SGLT2 significantly improves glycemic control and provides greater cardiovascular protection, combined with a reduction in body weight and blood pressure (BP). This review focuses on ertugliflozin, a new, highly selective, and reversible SGLT2 inhibitor. Clinical trials published to date show that ertugliflozin, both as a monotherapy and as an add-on to oral antidiabetic agents, is safe and effective in reducing glycosylated hemoglobin (HbA1c), body weight, and BP in T2DM patients.

Sodium glucose cotransporter SGLT1 as a therapeutic target in diabetes mellitus

INTRODUCTION

Glycemic control is important in diabetes mellitus to minimize the progression of the disease and the risk of potentially devastating complications. Inhibition of the sodium-glucose cotransporter SGLT2 induces glucosuria and has been established as a new anti-hyperglycemic strategy. SGLT1 plays a distinct and complementing role to SGLT2 in glucose homeostasis and, therefore, SGLT1 inhibition may also have therapeutic potential.

AREAS COVERED

This review focuses on the physiology of SGLT1 in the small intestine and kidney and its pathophysiological role in diabetes. The therapeutic potential of SGLT1 inhibition, alone as well as in combination with SGLT2 inhibition, for anti-hyperglycemic therapy are discussed. Additionally, this review considers the effects on other SGLT1-expressing organs like the heart.

EXPERT OPINION

SGLT1 inhibition improves glucose homeostasis by reducing dietary glucose absorption in the intestine and by increasing the release of gastrointestinal incretins like glucagon-like peptide-1. SGLT1 inhibition has a small glucosuric effect in the normal kidney and this effect is increased in diabetes and during inhibition of SGLT2, which deliver more glucose to SGLT1 in late proximal tubule. In short-term studies, inhibition of SGLT1 and combined SGLT1/SGLT2 inhibition appeared to be safe. More data is needed on long-term safety and cardiovascular consequences of SGLT1 inhibition.

Diversity-oriented synthesis of fused thioglycosyl benzo[e][1,4]oxathiepin-5-ones and benzo[f][1,4]thiazepin-5(2H)-ones by a sequence of palladium-catalyzed glycosyl thiol arylation and deprotection–lactonization reactions

An efficient synthesis of thioglycosylated benzo[e][1,4]-oxathiepin-5-one and benzothiazepinone derivatives has been reported.

Gymnemic acids inhibit sodium-dependent glucose transporter 1

To evaluate the activity of botanicals used in Chinese Traditional Medicine as hypoglycemic agents for diabetes type II prevention and/or treatment, extracts prepared from 26 medicinal herbs were screened for their inhibitory activity on sodium-dependent glucose transporter 1 (SGLT1) by using two-electrode voltage-clamp recording of glucose uptake in Xenopus laevis oocytes microinjected with cRNA for SGLT1. Showing by far the strongest SGLT1 inhibitory effect, the phytochemicals extracted from Gymnema sylvestre (Retz.) Schult were located by means of activity-guided fractionation and identified as 3-O-β-D-glucuronopyranosyl-21-O-2-tigloyl-22-O-2-tigloyl gymnemagenin (1) and 3-O-β-D-glucuronopyranosyl-21-O-2-methylbutyryl-22-O-2-tigloyl gymnemagenin (2) by means of LC-MS/MS, UPLC-TOF/MS, and 1D/2D-NMR experiments. Both saponins exhibited low IC50 values of 5.97 (1) and 0.17 μM (2), the latter of which was in the same range as found for the high-affinity inhibitor phlorizin (0.21 μM). As SGLT1 is found in high levels in brush-border membranes of intestinal epithelial cells, these findings demonstrate for the first time the potential of these saponins for inhibiting electrogenic glucose uptake in the gastrointestinal tract.

Forces and dynamics of glucose and inhibitor binding to sodium glucose co-transporter SGLT1 studied by single molecule force spectroscopy

Single molecule force spectroscopy was employed to investigate the dynamics of the sodium glucose co-transporter (SGLT1) upon substrate and inhibitor binding on the single molecule level. CHO cells stably expressing rbSGLT1 were probed by using atomic force microscopy tips carrying either thioglucose, 2'-aminoethyl β-d-glucopyranoside, or aminophlorizin. Poly(ethylene glycol) (PEG) chains of different length and varying end groups were used as tether. Experiments were performed at 10, 25 and 37 °C to address different conformational states of SGLT1. Unbinding forces between ligands and SGLT1 were recorded at different loading rates by changing the retraction velocity, yielding binding probability, width of energy barrier of the binding pocket, and the kinetic off rate constant of the binding reaction. With increasing temperature, width of energy barrier and average life time increased for the interaction of SGLT1 with thioglucose (coupled via acrylamide to a long PEG) but decreased for aminophlorizin binding. The former indicates that in the membrane-bound SGLT1 the pathway to sugar translocation involves several steps with different temperature sensitivity. The latter suggests that also the aglucon binding sites for transport inhibitors have specific, temperature-sensitive conformations.

SGLT inhibitors as new therapeutic tools in the treatment of diabetes

Recently, the idea has been developed to lower blood glucose blood glucose levels in diabetes by inhibiting sugar reabsorption sugar reabsorption in the kidney kidney . The main target is thereby the early proximal tubule proximal tubule where secondary active transport secondary active transport of the sugar is mediated by the sodium-D: -glucose D-glucose cotransporter SGLT2 SGLT2 . A model substance for the inhibitors inhibitors is the O-glucoside O-glucoside phlorizin phlorizin which inhibits transport transport competitively. Its binding to the transporter involves at least two different domains: an aglucone binding aglucone binding site at the transporter surface, involving extramembranous loops extramembraneous loops , and the sugar binding sugar binding /translocation site buried in a hydrophilic pocket of the transporter. The properties of these binding sites differ between SGLT2 and SGLT1 SGLT1 , which mediates sugar absorption sugar absorption in the intestine intestine . Various O-, C-, N- and S-glucosides have been synthesized with high affinity affinity and high specificity specificity for SGLT2 SGLT2 . Some of these glucosides are in clinical trials clinical trials and have been proven to successfully increase urinary glucose excretion urinary glucose excretion and to decrease blood sugar blood sugar levels without the danger of hypoglycaemia hypoglycaemia during fasting fasting in type 2 diabetes type 2 diabetes .