Glucose-6-phosphatase inhibitors for the treatment of Type 2 diabetes

The role of glucose-6-phosphatase activity in glucose homeostasis and its potential for diabetes therapy

Glucose-6-phosphatase catalytic subunit (G6PC)1 and G6PC2 are crucial for glucose metabolism, regulating processes like glycolysis, gluconeogenesis, and glycogenolysis. Despite their structural and functional similarities, G6PC1 and G6PC2 exhibit distinct tissue-specific expression patterns, G6P hydrolysis kinetics, and physiological functions. This review provides a comprehensive overview of their enzymology and distinct roles in glucose homeostasis. We examine how inactivating mutations in G6PC1 lead to glycogen storage disease, and how elevated G6PC1 and G6PC2 expression can affect the incidence of diabetic complications, risk for type 2 diabetes mellitus (T2DM) and various cancers. We also discuss the potential of inhibiting G6PC1 and G6PC2 to protect against complications from elevated blood glucose levels, and highlight drug development efforts targeting G6PC1 and G6PC2, and the therapeutic potential of inhibitors for disease prevention.

Postharvest integration of prickly pear betalain-enriched gummies with different sugar substitutes for decoding diabetes type-II and skin resilience - in vitro and in silico study

Postharvest processing plays a crucial role in harnessing the benefits of prickly pear fruit by utilizing betalain as natural colorants to replace artificial colors in model food systems. Prickly pear betalain-enriched gummies were developed using various sugar substitutes, including table sugar, xylitol, stevia, and fructo-oligosaccharides (FOS). These gummies were analyzed for in vitro enzymatic inhibition, anti-inflammatory effects and molecular docking studies for decoding diabetes type-II and skin resilience. FTIR and HPLC confirmed the presence of betalain and isorhamnetin across all gummies. FOS and stevia incorporated gummies exhibited the highest polyphenolics and antioxidant activity. Betalain extract combined with stevia and FOS showed significant in vitro enzyme inhibition compared to other studied gummies. Specifically, FOS gummies showed the highest inhibition rates for α-amylase (23.58 %), α-glucosidase (24.12 %), tyrosinase (54.68 %), and collagenase (2.38 %). Additionally, all samples were non-toxic to RAW cell lines and exhibited anti-inflammatory effects. Molecular docking studies corroborated the in vitro results, and pharmacokinetics profiling confirmed the gummies' suitability for oral consumption and skin safety. The developed prickly pear betalain-enriched gummies, particularly those formulated with fructo-oligosaccharides and stevia, demonstrate significant potential as functional supplements for managing diabetes type-II and skin-related conditions.

Structural insights into glucose-6-phosphate recognition and hydrolysis by human G6PC1

The glucose-6-phosphatase (G6Pase) is an integral membrane protein that catalyzes the hydrolysis of glucose-6-phosphate (G6P) in the endoplasmic reticulum lumen and plays a vital role in glucose homeostasis. Dysregulation or genetic mutations of G6Pase are associated with diabetes and glycogen storage disease 1a (GSD-1a). Studies have characterized the biophysical and biochemical properties of G6Pase; however, the structure and substrate recognition mechanism of G6Pase remain unclear. Here, we present two cryo-EM structures of the 40-kDa human G6Pase: a wild-type apo form and a mutant G6Pase-H176A with G6P bound, elucidating the structural basis for substrate recognition and hydrolysis. G6Pase comprises nine transmembrane helices and possesses a large catalytic pocket facing the lumen. Unexpectedly, G6P binding induces substantial conformational rearrangements in the catalytic pocket, which facilitate the binding of the sugar moiety. In conjunction with functional analyses, this study provides critical insights into the structure, substrate recognition, catalytic mechanism, and pathology of G6Pase.

Beta vulgaris L. beetroot protects against iron-induced liver injury by restoring antioxidant pathways and regulating cellular functions

Beta vulgaris L. is a root vegetable that is consumed mainly as a food additive. This study aimed to describe the protective effect of B. vulgaris on Fe2+-mediated oxidative liver damage through in vitro, ex vivo, and in silico studies to establish a strong rationale for its protective effect. To induce oxidative damage, we incubated the livers of healthy male rats with 0.1 mM FeSO4 to induce oxidative injury and coincubated them with an aqueous extract of B. vulgaris root (BVFE) (15-240 µg/mL). Induction of liver damage significantly (p < .05) decreased the levels of GSH, SOD, CAT, and ENTPDase activities, with a corresponding increase in MDA and NO levels and Na+/K+ ATPase, G6 Pase, and F-1,6-BPase enzyme activities. BVFE treatment (p < .05) reduced these levels and activities to almost normal levels, with the most prominent effects observed at 240 µg/mL BVFE. An HPLC investigation revealed sixteen compounds in BVFE, with quercetin being the most abundant. Chlorogenic acid and iso-orientation showed the highest binding affinities for G6 Pase and Na+/K + ATPase, respectively. These findings suggest that B. vulgaris can protect against Fe2+-mediated liver damage by suppressing oxidative stress and cholinergic and purinergic activities while regulating gluconeogenesis. Overall, the hepatoprotective activity of this extract might be driven by the synergistic effect of the identified compounds and their probable interactions with target proteins.

Oleic Acid and Succinic Acid: A Potent Nutritional Supplement in Improving Hepatic Glycaemic Control in Type 2 Diabetic Sprague-Dawley Rats

Nutritional supplements are gaining traction for their effects in mitigating the impacts of various health conditions. In particular, many supplements are being proposed to reduce the impacts of type 2 diabetes (T2D), a metabolic condition that has reached global epidemic proportions. Recently, a supplement of oleic acid (OA) and succinic acid (SA; 1 : 1, w/w) was reported to improve glycaemic control in type 2 diabetic (T2D) Sprague-Dawley (S-D) rats through ameliorating insulin release and sensitivity. Here, we investigate the effects of the supplement (OA and SA) on hepatic and pancreatic function in T2D S-D rats. Eighteen (18) S-D rats were rendered diabetic and were divided into three equal groups: diabetic control, diabetic treatment, and diabetic glibenclamide. Another 12 S-D rats were obtained and served as the normal groups. The animals were treated daily with the vehicle, OA and SA (800 mg/kg body weight (bw); 1 : 1), or glibenclamide (10 mg/kg bw) which served as the positive control. The findings indicated that treatment with the supplement resulted in a 35.69 ± 4.22% reduction (p=0.006) in blood glucose levels (BGL). Analysis of hepatic enzymes depicted that the nutritional supplement reduced the activity of the gluconeogenesis enzyme, glucose-6-phosphatase (G6P) while improved the activity of catabolic enzymes such as glucose-6-phosphate dehydrogenase (G6PD) and pyruvate kinase (PK). Furthermore, the supplement attenuated oxidative stress through restoration of catalase (CAT) and superoxide dismutase (SOD), while reducing malondialdehyde (MDA) levels. Finally, the supplement showed no liver or kidney toxicity and improved the size and number of pancreatic islets of Langerhans, indicating its potential application in treating T2D. The study highlighted that a supplement of the two organic acids may be beneficial in reducing the rate of pathogenesis of type 2 diabetes. Therefore, it may offer therapeutic value as a dietary or nutritional supplement in the approach against diabetes and its complications.

Gluconeogenesis Flux in Metabolic Disease

Gluconeogenesis is a critical biosynthetic process that helps maintain whole-body glucose homeostasis and becomes altered in certain medical diseases. We review gluconeogenic flux in various medical diseases, including common metabolic disorders, hormonal imbalances, specific inborn genetic errors, and cancer. We discuss how the altered gluconeogenic activity contributes to disease pathogenesis using data from experiments using isotopic tracer and spectroscopy methodologies. These in vitro, animal, and human studies provide insights into the changes in circulating levels of available gluconeogenesis substrates and the efficiency of converting those substrates to glucose by gluconeogenic organs. We highlight ongoing knowledge gaps, discuss emerging research areas, and suggest future investigations. A better understanding of altered gluconeogenesis flux may ultimately identify novel and targeted treatment strategies for such diseases.

A detailed review on the phytochemical profiles and anti-diabetic mechanisms of Momordica charantia

Diabetes mellitus is the most well-known endocrine dilemma suffered by hundreds of million people globally, with an annual mortality of more than one million people. This high mortality rate highlights the need for in-depth study of anti-diabetic agents. This review explores the phytochemical contents and anti-diabetic mechanisms of M. charantia (cucurbitaceae). Studies show that M. charantia contains several phytochemicals that have hypoglycemic effects, thus, the plant may be effective in the treatment/management of diabetes mellitus. Also, the biochemical and physiological basis of M. charantia anti-diabetic actions is explained. M. charantia exhibits its anti-diabetic effects via the suppression of MAPKs and NF-κβin pancreatic cells, promoting glucose and fatty acids catabolism, stimulating fatty acids absorption, inducing insulin production, ameliorating insulin resistance, activating AMPK pathway, and inhibiting glucose metabolism enzymes (fructose-1,6-bisphosphate and glucose-6-phosphatase). Reviewed literature was obtained from credible sources such as PubMed, Scopus, and Web of Science.

Effect of Microalgae Arthrospira on Biomarkers of Glycemic Control and Glucose Metabolism: A Systematic Review and Meta-analysis

Diabetes mellitus and insulin resistance are associated with an increased risk of cardiovascular disease (CVD) incidence and a higher rate of CVD-related death. In this study, the effects of Arthrospira (Spirulina) a blue-green algae supplementation on biomarkers of glycemic control and glucose metabolism has been evaluated. PubMed, Scopus, and ISI Web of Science were searched systematically of English human subjects and PubMed for pre-clinical animal studies (rats and mice) from January 2008 until November 2020. The pooled weighted mean difference (MD) and its 95% confidence interval (CI) were calculated and pooled using a random-effect model. Seven clinical and 27 preclinical studies were included. Pooled results of the clinical studies showed that Arthrospira supplementation significantly reduced the fasting blood sugar (FBS): (0.63- 2.90-) 1.77-, total cholesterol (TC): (0.46- ، 4.61-) 2.54-, triglycerides (TG): (0.89- ، 6.54-) 3.71- and increased the high-density lipoprotein cholesterol (HDL-C): (3.86 ، 0.67) 2.27; however, Arthrospira was not significantly effective in terms of reducing the glycated hemoglobin A1c (HbA1C): (1.04 ، 2.23-) 0.59- and low-density lipoprotein cholesterol (LDL-C). Pooled results of preclinical studies showed that Arthrospira supplementation reduced FBS [-10.31 (-12.49, -8.13)] and HbA1C [-5.12 (-8.06, -2.19)] significantly in diabetic animals. Sub-group analysis of clinical studies showed that intervention duration less than 2 months [-2.52 (-4.37, -0.67)] and the dose less than 2 gram [-3.22 (-5.67, -0.76)] showed significant improvement in terms of reducing the FBS in humans. It can be concluded that Arthrospira can be considered as an effective FBS, TG, TC, and HDL-C adjusting nutraceutical agent for diabetes mellitus. Due to the differences in the results of clinical and animal studies in terms of HbA1c, more studies are needed for a definitive conclusion.

Supercritical carbon dioxide extracts of small cardamom and yellow mustard seeds have fasting hypoglycaemic effects: diabetic rat, predictive iHOMA2 models and molecular docking study

In the present investigation, the supercritical carbon dioxide (SC-CO2) extracts of small cardamom (SC) and yellow mustard (YM) seeds have been investigated for their efficacies in combating type 2 diabetes in streptozotocin-induced Wistar albino rats. Fasting blood glucose (FBG) levels in the rats were monitored on days 8, 15 and 21. On day 15, FBG level reduced appreciably by 31·49 % in rats treated with SC seed extract and by 32·28 % in rats treated with YM seed extract, comparable to metformin (30·70 %) and BGR-34 (a commercial polyherbal drug) (31·81 %) administered rats. Either extract exhibited desirable effects on hepatic glucose-6-phosphatase, glucose-6-phosphate dehydrogenase (G6PD) and catalase activities in controlling diabetes. A molecular docking exercise was conducted to identify specific compounds in the extracts which possessed augmenting effect on G6PD. The results revealed that all the bioactive compounds in the extracts have binding affinities with the enzyme and contributed to the antidiabetic efficacies of the extracts as G6PD augmenters. The effects of the extracts on insulin sensitivity and glucose uptake were investigated using non-invasive modelling by iHOMA2 software. This in vitro approach indicated that extract administration resulted in increased both insulin sensitivity of the liver and glucose uptake in the gut. The findings of the present study attest these SC-CO2 extracts of the spices as safe alternatives of metformin and BGR-34 in combating type 2 diabetes and could be safely subjected to clinical studies. These extracts could also be employed in designing proactive food supplements in mitigating the metabolic disorder.

Natural products as modulators of retinoic acid receptor-related orphan receptors (RORs)

Covering: 1994 to 2020 Retinoic acid receptor-related orphan receptors (RORs) belong to a subfamily of the nuclear receptor superfamily and possess prominent roles in circadian rhythm, metabolism, inflammation, and cancer. They have been subject of research for over two decades and represent attractive but challenging drug targets. Natural products were among the first identified ligands of RORs and continue to be of interest to this day. This review focuses on ligands and indirect modulators of RORs from natural sources and explores their roles in a therapeutic context.

Down-regulation of hepatic G-6-Pase expression in hyperglycemic rats: Intervention with biogenic gold nanoconjugate

Chronic diabetes extensively complicates the glucose metabolism to onset and progress the complication. Concurrently, several contemporary medicines, especially organo-metallic formulations, are emerging to treat hyperglycemia. The current study aims to emphasize the gold nanoparticles (GNPs) potential for glucose metabolism regulation in Streptozotocin (STZ) induced diabetes. Quantitative real-time polymerase chain reaction (RT-PCR) was carried out to detect the mRNA expression of Glucose transporters 2 (GLUT2), Glucokinase (GK) and Glucose 6 Phosphatase (G-6-Pase). The study shows remarkable results such as the prognostic effect of GNPs in reinforcing the repression of enzyme complex G-6-Pase about 13.3-fold when compared to diabetes control. Also, molecular docking studies showed significant inhibition of G-6-Pase by the terpenoid ligands with alpha and beta amyrin from leaf extract of Couroupita guianensis. Thus the study explored the novel mechanism of G-6-Pase downregulated by GNPs intervention that majorly contributes to the regulation of circulatory glucose homeostasis during diabetes.

The polypharmacy reduction potential of cinnamic acids and some related compounds in pre- and post-onset management of type 2 diabetes mellitus

Objectives. This review assesses the polypharmacy reduction potential of cinnamic acids (CAs) and some related compounds in managing three or more of the cluster of seven, pre- and post-type 2 diabetes mellitus (T2DM)-related features (central obesity, hyperglycemia, hypertension, dyslipidemia, pro-thrombosis, oxidation, and inflammation).

Methods. Google scholar and Pubmed were searched for cinnam*, chlorogenic acid, ferulic acid, and caffeic acid in conjunction with each of pre- and post-onset T2DM, central obesity, hyperglycemia, hypertension, dyslipidemia, pro-thrombosis, oxidation, and inflammation. The study was divided into an introduction followed by findings on the impacts of each of the CAs including trans-CA acid, the E isomer of a CA-based thiazolidinedione and a metabolite of that isomer, as well as p-methoxy CA, various cinnamic amides and some other CA-related compounds (chlorogenic acid, cinnamaldehyde, ferulic and caffeic acid).

Results. Trans-CA has a potential to manage three, while each of chlorogenic acid, cinnamalde-hyde, caffeic acid and ferulic acid has a potential to manage all seven members of the cluster. Other CA-related compounds identified may manage only one or two of the cluster of seven.

Conclusions. Much of the work has been done in animal models of pre- and post-onset T2DM and non-pre- or post-onset T2DM humans and animals, along with some cell culture and in vitro work. Very little work has been done with human pre- and post-onset T2DM. While there is potential for managing 3 or more members of the cluster with many of these compounds, a definitive answer awaits large pre- and post-T2DM onset clinical trials with humans.

Multi-target antidiabetic mechanisms of mexicanolides from Swietenia humilis

BACKGROUND

Swietenia humilis seeds are consumed in Mexico to treat type 2 diabetes; the antihyperglycemic effect of this species was previously demonstrated and related to the presence of tetranortriterpenoids of the mexicanolide class.

PURPOSE AND STUDY DESIGN

The present investigation was conducted to determine the mechanism of action of selected mexicanolides, including 2-hydroxy-destigloyl-6-deoxyswietenine acetate (1), methyl-2-hydroxy-3-β-tigloyloxy-1-oxomeliac-8(30)-enate (2) and humilinolide H (3), using in vivo experiments with hyperglycemic mice, and cell-based models.

METHODS

Nicotinamide-streptozotocin hyperglycemic mice (50-130 mg/kg, i.p.) were used to build antihyperglycemic drug-response curves using an oral glucose tolerance test model. In vitro studies were carried out on INSE1, H4IIE and C2C12 cells to assess insulin secretion, glucose-6-phosphatase inhibition, glucose uptake and mitochondrial bioenergetics, respectively.

RESULTS

The combination of the decoction of S. humilis or 2-hydroxy-destigloyl-6-deoxyswietenine acetate (mexicanolide 1) with glibenclamide resulted in a reduction of the antihyperglycemic effect while a significant increase was observed when they were dosed with metformin. These effects were related to K_ATP SUR blockade, insulin secretion in INSE1 cells, and modulation of 5-HT₂ receptors. Furthermore, mexicanolides 1-3 inhibited glucose-phosphatase in H4IIE cells, and enhanced glucose uptake and spare respiratory capacity in C2C12 myotubes.

CONCLUSION

S. humilis mexicanolides interact with pharmacological targets at pancreas (K_ATP channels), liver (glucose-6-phosphatase), and skeletal muscle (mitochondria and possibly glucose transporters) to modulate glucose homeostasis, and could be a promising resource to treat type 2 diabetes.

Ameliorative potential of Lavandula stoechas in metabolic syndrome via multitarget interactions

ETHNOPHARMACOLOGICAL IMPORTANCE

Decoction and infusion prepared from aerial parts of Lavandula stoechas L. (L. stoechas) have been traditionally used as remedy against several components of metabolic syndrome (MetS) and associated disorders including type II diabetes and cardiovascular diseases by Anatolian people.

AIM OF THE STUDY

The aim is to elucidate the potential ameliorative effects of L. stoechas aqueous extracts on insulin resistance and inflammation models through multitarget in vitro approaches and also to elucidate mechanism of action by analyzing transcriptional and metabolic responses.

MATERIALS AND METHODS

An aqueous extract was prepared and fractionated to give rise to ethyl acetate (EE) and butanol (BE) extracts. The anti-insulin resistance effects of BE and EE were evaluated on palmitate induced insulin resistance model of H4IIE, C2C12 and 3T3L1 cells by using several metabolic parameters. Specifically, whole genome transcriptome analysis was performed by using microarray over 55.000 genes in control, insulin resistant and EE (25 µg/mL) treated insulin resistant H4IIE cells. Anti-inflammatory effects of both extracts were analyzed in LPS-stimulated RAW264.7 macrophages.

RESULTS

Both EE and BE at low doses (25-50 µg/mL) significantly decreased hepatic gluconeogenesis in H4IIE cell line by suppressing the expression of PEPCK and G6Pase. In C2C12 myotubes, both extracts increased the insulin stimulated glucose uptake more effectively than metformin. Both extracts decreased the isoproterenol induced lipolysis in 3T3L1 cell line. Moreover, they also effectively increased the expression of lipoprotein lipase protein level in insulin resistant myotubes at low doses. EE increased the protein level of PPARγ and stimulated the activation AKT in insulin resistant H4IIE and C2C12 cell lines. The results obtained from biochemical assays, mRNA/protein studies and whole genome transcriptome analyses were found to be complementary and provided support for the hypothesis that EE might be biologically active against insulin resistance and act through the inhibition of liver gluconeogenesis and AKT activation. Besides, LPS induced inflammation in RAW264.7 macrophages was mainly inhibited by EE through suppression of iNOS/NO signaling, IL1β and COX-2 genes. HPLC-TOF/MS analysis of EE of L. stoechas mainly resulted in caffeic acid, apigenin, luteolin, rosmarinic acid and its methyl ester, 4-hydroxybenzoic acid, vanillic acid, ferrulic acid and salicylic acid.

CONCLUSION

Data suggest that EE of L. stoechas contains phytochemicals that can be effective in the treatment/prevention of insulin resistance and inflammation. These results validate the traditional use of L. stoechas in Anatolia against several metabolic disorders including metabolic syndrome.

α-Bromophosphonate analogs of glucose-6-phosphate are inhibitors of glucose-6-phosphatase

Glucose-6-phosphatase (G6Pase) is an essential metabolic enzyme that has upregulated activity in Type II diabetes. Synthetic analogs of the G6Pase substrate, glucose-6-phosphate (G6P), may provide new tools to probe enzyme activity, or lead to specific inhibitors of glycosylphosphatase enzymes. Here we have developed synthetic routes to a panel of non-hydrolyzable G6P analogs containing α-bromo, α,α-dibromo, and α-bromo-α,β-unsaturated phosphonates compatible with a carbohydrate nucleus. We confirm that these functionalities have potency as inhibitors of G6Pase in vitro, providing a series of new phosphate isosteres that can be exploited for inhibitor design.

Structure-activity relationships of semisynthetic mumbaistatin analogs

Mumbaistatin (1), a new anthraquinone natural product, is one of the most potent known inhibitors of hepatic glucose-6-phosphate translocase, an important target for the treatment of type II diabetes. Its availability, however, has been limited due to its extremely low yield from the natural source. Starting from DMAC (5, 3,8-dihydroxyanthraquinone-2-carboxylic acid), a structurally related polyketide product of engineered biosynthesis, we developed a facile semisynthetic method that afforded a variety of mumbaistatin analogs within five steps. This work was facilitated by the initial development of a DMAC overproduction system. In addition to reinforcing the biological significance of the anthraquinone moiety of mumbaistatin, several semisynthetic analogs were found to have low micromolar potency against the translocase in vitro. Two of them were also active in glucose release assays from primary hepatocytes. The synergistic combination of biosynthesis and synthesis is a promising avenue for the discovery of new bioactive substances.

The biochemistry and molecular biology of the glucose-6-phosphatase system

Progress has continued to be made over the past 4 years in our understanding of the glucose-6-phosphatase (G6Pase) system. The gene for a second component of the system, the putative glucose-6-P transporter (G6PT), was cloned, and mutations in this gene were found in patients diagnosed with glycogen storage disease type 1b. The functional characterization of this putative G6PT has been initiated, and the relationship between substrate transport via the G6PT and catalysis by the system's catalytic subunit continues to be explored. A lively debate over the feasibility of various aspects of the two proposed models of the G6Pase system persists, and the functional/structural relationships of the individual components of the system remain a hot topic of interest in G6Pase research. New evidence supportive of physiologic roles for the biosynthetic functions of the G6Pase system in vivo also has emerged over the past 4 years.