Biotechnology and molecular biology of the alpha-glucosidase inhibitor acarbose

Acarbose ameliorates Western diet-induced metabolic and cognitive impairments in the 3xTg mouse model of Alzheimer's disease

Age is the greatest risk factor for Alzheimer's disease (AD) as well as for other disorders that increase the risk of AD such as diabetes and obesity. There is growing interest in determining if interventions that promote metabolic health can prevent or delay AD. Acarbose is an anti-diabetic drug that not only improves glucose homeostasis, but also extends the lifespan of wild-type mice. Here, we test the hypothesis that acarbose will not only preserve metabolic health, but also slow or prevent AD pathology and cognitive deficits in 3xTg mice, a model of AD, fed either a Control diet or a high-fat, high-sucrose Western diet (WD). We find that acarbose decreases the body weight and adiposity of WD-fed 3xTg mice, increasing energy expenditure while also stimulating food consumption, and improves glycemic control. Both male and female WD-fed 3xTg mice have worsened cognitive deficits than Control-fed mice, and these deficits are ameliorated by acarbose treatment. Molecular and histological analysis of tau and amyloid pathology identified sex-specific effects of acarbose which are uncoupled from the dramatic improvements in cognition in females, suggesting that the benefits of acarbose on AD may be largely driven by improved metabolic health. In conclusion, our results suggest that acarbose may be a promising intervention to prevent, delay, or even treat AD, especially in individuals consuming a WD.

Targeting Transcriptional Regulators Affecting Acarbose Biosynthesis in Actinoplanes sp. SE50/110 Using CRISPRi Silencing

Acarbose, a pseudo-tetrasaccharide produced by Actinoplanes sp. SE50/110, is an α-glucosidase inhibitor and is used as a medication to treat type 2 diabetes. While the biosynthesis of acarbose has been elucidated, little is known about its regulation. Gene silencing using CRISPRi allows for the identification of potential regulators influencing acarbose formation. For this purpose, two types of CRISPRi vectors were established for application in Actinoplanes sp. SE50/110. The pCRISPomyces2i vector allows for reversible silencing, while the integrative pSETT4i vector provides a rapid screening approach for many targets due to its shorter conjugation time into Actinoplanes sp. These vectors were validated by silencing the known acarbose biosynthesis genes acbB and acbV, as well as their regulator, CadC. The reduction in product formation and the diminished relative transcript abundance of the respective genes served as evidence of successful silencing. The vectors were used to create a CRISPRi-based strain library, silencing 50 transcriptional regulators, to investigate their potential influence in acarbose biosynthesis. These transcriptional regulatory genes were selected from previous experiments involving protein-DNA interaction studies or due to their expression profiles. Eleven genes affecting the yield of acarbose were identified. The CRISPRi-mediated knockdown of seven of these genes significantly reduced acarbose biosynthesis, whereas the knockdown of four genes enhanced acarbose production.

Design, synthesis, and evaluation of novel substituted imidazo[1,2-c]quinazoline derivatives as potential α-glucosidase inhibitors with bioactivity and molecular docking insights

α-Glucosidase inhibitors are important in the treatment of type 2 diabetes by regulating blood glucose levels and reducing carbohydrate absorption. The present study focuses on identifying new inhibitors bearing imidazo[1,2-c]quinazoline backbone through multi-step synthesis. The inhibitory potencies of the novel derivatives were tested against Saccharomyces cerevisiae α-glucosidase, revealing IC50 values ranging from 50.0 ± 0.12 µM to 268.25 ± 0.09 µM. Among them, 2-(4-(((2,3-diphenylimidazo[1,2-c]quinazolin-5-yl)thio)methyl)-1H-1,2,3-triazol-1-yl)-N-(2-methoxyphenyl)acetamide (19e) and 2-(4-((benzo[4,5]imidazo[1,2-c]quinazolin-6-ylthio)methyl)-1H-1,2,3-triazol-1-yl)-N-(2-methoxyphenyl)acetamide (27e) emerged as the most potent inhibitors and were further investigated in various assessments. Finally, molecular docking studies were performed to reveal the crucial binding interactions and to confirm the results obtained from structure-activity relationship (SAR) analysis.

Effect of Genistein on Starch Digestion In Vitro and Its Mechanism of Action

The digestive properties of starch are crucial in determining postprandial glycaemic excursions. Genistein, an active phytoestrogen, has the potential to influence starch digestion rates. We investigated the way genistein affected the digestive properties of starch in vitro. We performed enzyme kinetics, fluorescence spectroscopy, molecular docking, and molecular dynamics (MD) simulations for analysing the inhibitory properties of genistein on starch digestive enzymes as well as clarifying relevant mechanism of action. Our findings demonstrated that, following the addition of 10% genistein, the contents of slowly digestible and resistant starches increased by 30.34% and 7.18%, respectively. Genistein inhibited α-amylase and α-glucosidase, with half maximal inhibitory concentrations of 0.69 ± 0.06 and 0.11 ± 0.04 mg/mL, respectively. Genistein exhibits a reversible and non-competitive inhibiting effect on α-amylase, while its inhibition on α-glucosidase is a reversible mixed manner type. Fluorescence spectroscopy indicated that the presence of genistein caused declining fluorescence intensity of the two digestive enzymes. Molecular docking and MD simulations showed that genistein binds spontaneously to α-amylase via hydrogen bonds, hydrophobic interactions, and π-stacking, whereas it binds with α-glucosidase via hydrogen bonds and hydrophobic interactions. These findings suggest the potential for developing genistein as a pharmacologic agent for regulating glycaemic excursions.

Acarbose ameliorates Western diet-induced metabolic and cognitive impairments in the 3xTg mouse model of Alzheimer's disease

Age is the greatest risk factor for Alzheimer's disease (AD) as well as for other disorders that increase the risk of AD such as diabetes and obesity. There is growing interest in determining if interventions that promote metabolic health can prevent or delay AD. Acarbose is an anti-diabetic drug that not only improves glucose homeostasis, but also extends the lifespan of wild-type mice. Here, we test the hypothesis that acarbose will not only preserve metabolic health, but also slow or prevent AD pathology and cognitive deficits in 3xTg mice, a model of AD, fed either a Control diet or a high-fat, high-sucrose Western diet (WD). We find that acarbose decreases the body weight and adiposity of WD-fed 3xTg mice, increasing energy expenditure while also stimulating food consumption, and improves glycemic control. Both male and female WD-fed 3xTg mice have worsened cognitive deficits than Control-fed mice, and these deficits are ameliorated by acarbose treatment. Molecular and histological analysis of tau and amyloid pathology identified sex-specific effects of acarbose which are uncoupled from the dramatic improvements in cognition, suggesting that the benefits of acarbose on AD are largely driven by improved metabolic health. In conclusion, our results suggest that acarbose may be a promising intervention to prevent, delay, or even treat AD, especially in individuals consuming a Western diet.

A comprehensive in-vitro/in-vivo screening toolbox for the elucidation of glucose homeostasis modulating properties of plant extracts (from roots) and its bioactives

Plant extracts are increasingly recognized for their potential in modulating (postprandial) blood glucose levels. In this context, root extracts are of particular interest due to their high concentrations and often unique spectrum of plant bioactives. To identify new plant species with potential glucose-lowering activity, simple and robust methodologies are often required. For this narrative review, literature was sourced from scientific databases (primarily PubMed) in the period from June 2022 to January 2024. The regulatory targets of glucose homeostasis that could be modulated by bioactive plant compounds were used as search terms, either alone or in combination with the keyword "root extract". As a result, we present a comprehensive methodological toolbox for studying the glucose homeostasis modulating properties of plant extracts and its constituents. The described assays encompass in-vitro investigations involving enzyme inhibition (α-amylase, α-glucosidase, dipeptidyl peptidase 4), assessment of sodium-dependent glucose transporter 1 activity, and evaluation of glucose transporter 4 translocation. Furthermore, we describe a patch-clamp technique to assess the impact of extracts on KATP channels. While validating in-vitro findings in living organisms is imperative, we introduce two screenable in-vivo models (the hen's egg test and Drosophila melanogaster). Given that evaluation of the bioactivity of plant extracts in rodents and humans represents the current gold standard, we include approaches addressing this aspect. In summary, this review offers a systematic guide for screening plant extracts regarding their influence on key regulatory elements of glucose homeostasis, culminating in the assessment of their potential efficacy in-vivo. Moreover, application of the presented toolbox might contribute to further close the knowledge gap on the precise mechanisms of action of plant-derived compounds.

Sigma Factor Engineering in Actinoplanes sp. SE50/110: Expression of the Alternative Sigma Factor Gene ACSP50_0507 (σHAs) Enhances Acarbose Yield and Alters Cell Morphology

Sigma factors are transcriptional regulators that are part of complex regulatory networks for major cellular processes, as well as for growth phase-dependent regulation and stress response. Actinoplanes sp. SE50/110 is the natural producer of acarbose, an α-glucosidase inhibitor that is used in diabetes type 2 treatment. Acarbose biosynthesis is dependent on growth, making sigma factor engineering a promising tool for metabolic engineering. ACSP50_0507 is a homolog of the developmental and osmotic-stress-regulating Streptomyces coelicolor σHSc. Therefore, the protein encoded by ACSP50_0507 was named σHAs. Here, an Actinoplanes sp. SE50/110 expression strain for the alternative sigma factor gene ACSP50_0507 (sigHAs) achieved a two-fold increased acarbose yield with acarbose production extending into the stationary growth phase. Transcriptome sequencing revealed upregulation of acarbose biosynthesis genes during growth and at the late stationary growth phase. Genes that are transcriptionally activated by σHAs frequently code for secreted or membrane-associated proteins. This is also mirrored by the severely affected cell morphology, with hyperbranching, deformed and compartmentalized hyphae. The dehydrated cell morphology and upregulation of further genes point to a putative involvement in osmotic stress response, similar to its S. coelicolor homolog. The DNA-binding motif of σHAs was determined based on transcriptome sequencing data and shows high motif similarity to that of its homolog. The motif was confirmed by in vitro binding of recombinantly expressed σHAs to the upstream sequence of a strongly upregulated gene. Autoregulation of σHAs was observed, and binding to its own gene promoter region was also confirmed.

Role of MalQ Enzyme in a Reconstructed Maltose/Maltodextrin Pathway in Actinoplanes sp. SE50/110

The pseudotetrasaccharide acarbose, produced by Actinoplanes sp. SE50/110, is a relevant secondary metabolite used in diabetes type II medication. Although maltose plays a crucial role in acarbose biosynthesis, the understanding of the maltose/maltodextrin metabolism and its involvement in acarbose production is at an early stage. Here, we reconstructed the predicted maltose-maltodextrin pathway that involves four enzymes AmlE, MalZ, MalP, and MalQ. An investigation of enzyme activities was conducted through in vitro assays, leading to an expansion of previously postulated substrate spectra. The maltose-induced α-glucosidase AmlE is noteworthy for its high hydrolysis rate of linear α-1,4-glucans, and its capability to hydrolyze various glycosidic bonds. The predicted maltodextrin glucosidase MalZ showed slow hydrolysis activity on linear α-glucans, but it was resistant to acarbose and capable of releasing glucose from acarbose. AmlE compensates for the low activity of MalZ to ensure glucose supply. We determined the enzyme activity of MalP and its dual function as maltodextrin and glycogen phosphorylase. The 4-α-glucanotransferase MalQ plays a central role in the maltose/maltodextrin metabolism, alongside MalP. This study confirmed the simultaneous degradation and synthesis of long-chain α-glucans. The product distribution showed that with an increasing number of glycosidic bonds, less glucose is formed. We found that MalQ, like its sequence homolog AcbQ from the acarbose biosynthetic gene cluster, is involved in the formation of elongated acarviosyl metabolites. However, MalQ does not participate in the elongation of acarbose 7-phosphate, which is likely the more readily available acceptor molecule in vivo. Accordingly, MalQ is not involved in the formation of acarviosyl impurities in Actinoplanes sp. SE50/110.

Acarbose glycosylation by AcbE for the production of acarstatins with enhanced α-amylase inhibitory activity

Acarbose is a potent glycosidase inhibitor widely used in the clinical treatment of type 2 diabetes mellitus (T2DM). Various acarbose analogs have been identified while exploring compounds with improved pharmacological properties. In this study, we found that AcbE from Actinoplanes sp. SE50/110 catalyzes the production of acarbose analogs that exhibit significantly improved inhibitory activity towards α-amylase than acarbose. Recombinant AcbE mainly catalyzed the formation of two new compounds, namely acarstatins A and B, using acarbose as substrate. Using high-resolution mass spectrometry, nuclear magnetic resonance, and glycosidase hydrolysis, we elucidated their chemical structures as O-α-d-maltosyl-(1 → 4)-acarbose and O-α-d-maltotriosyl-(1 → 4)-acarbose, respectively. Acarstatins A and B exhibited 1584- and 1478-fold greater inhibitory activity towards human salivary α-amylase than acarbose. Furthermore, both acarstatins A and B exhibited complete resistance to microbiome-derived acarbose kinase 1-mediated phosphorylation and partial resistance to acarbose-preferred glucosidase-mediated hydrolysis. Therefore, acarstatins A and B have great potential as candidate therapeutic agents for T2DM.

Anti-Obesity and Anti-Diabetic Effects of Ostericum koreanum (Ganghwal) Extract

"Ganghwal" is a widely used herbal medicine in Republic of Korea, but it has not been reported as a treatment strategy for obesity and diabetes within adipocytes. In this study, we determined that Ostericum koreanum extract (OKE) exerts an anti-obesity effect by inhibiting adipogenesis and an anti-diabetic effect by increasing the expression of genes related to glucose uptake in adipocytes and inhibiting α-glucosidase activity. 3T3-L1 preadipocytes were differentiated for 8 days in methylisobutylxanthine, dexamethasone, and insulin medium, and the effect of OKE was confirmed by the addition of 50 and 100 µg/mL of OKE during the differentiation process. This resulted in a reduction in lipid accumulation and the expression of PPARγ (Peroxisome proliferator-activated receptor γ) and C/EBPα (CCAAT enhancer binding protein α). Significant activation of AMPK (AMP-activated protein kinase), increased expression of GLUT4 (Glucose Transporter Type 4), and inhibition of α-glucosidase activity were also observed. These findings provide the basis for the anti-obesity and anti-diabetic effects of OKE. In addition, OKE has a significant antioxidant effect. This study presents OKE as a potential natural product-derived material for the treatment of patients with metabolic diseases such as obesity- and obesity-induced diabetes.

Gut microbiota and therapy for obesity and type 2 diabetes

There has been a major increase in Type 2 diabetes and obesity in many countries, and this will lead to a global public health crisis, which not only impacts on the quality of life of individuals well but also places a substantial burden on healthcare systems and economies. Obesity is linked to not only to type 2 diabetes but also cardiovascular diseases, musculoskeletal disorders, and certain cancers, also resulting in increased medical costs and diminished quality of life. A number of studies have linked changes in gut in obesity development. Dysbiosis, a deleterious change in gut microbiota composition, leads to altered intestinal permeability, associated with obesity and Type 2 diabetes. Many factors affect the homeostasis of gut microbiota, including diet, genetics, circadian rhythms, medication, probiotics, and antibiotics. In addition, bariatric surgery induces changes in gut microbiota that contributes to the metabolic benefits observed post-surgery. Current obesity management strategies encompass dietary interventions, exercise, pharmacotherapy, and bariatric surgery, with emerging treatments including microbiota-altering approaches showing promising efficacy. While pharmacotherapy has demonstrated significant advancements in recent years, bariatric surgery remains one of the most effective treatments for sustainable weight loss. However, access to this is generally limited to those living with severe obesity. This underscores the need for non-surgical interventions, particularly for adolescents and mildly obese patients. In this comprehensive review, we assess longitudinal alterations in gut microbiota composition and functionality resulting from the two currently most effective anti-obesity treatments: pharmacotherapy and bariatric surgery. Additionally, we highlight the functions of gut microbiota, focusing on specific bacteria, their metabolites, and strategies for modulating gut microbiota to prevent and treat obesity. This review aims to provide insights into the evolving landscape of obesity management and the potential of microbiota-based approaches in addressing this pressing global health challenge.

Evaluation of Acarbose Bioequivalence in Healthy Chinese Populations Using Novel Pharmacodynamic End Points

Acarbose is a widely used α-glucosidase inhibitor for the management of postprandial hyperglycemia in patients with type 2 diabetes mellitus. Recent pilot studies on acarbose bioequivalence (BE) have successfully identified additional pharmacodynamic (PD) parameters as valid end points. Nevertheless, there was a scarcity of published pivotal studies using novel PD parameters. The purpose of the study is to investigate the acarbose BE using the new PD parameters. The study was conducted with an open, randomized, 2-period crossover design. A total of 64 healthy Chinese volunteers received either the reference (R) or test (T) acarbose at a dose of 2×50 mg orally, followed by a 1-week washout period. After sucrose treatment (baseline) and sucrose/acarbose co-administration, serum glucose, and insulin concentrations were assessed. The rectifying approach yielded geometric mean ratios of 102.9% for maximum serum glucose concentration with deduction of glucose concentration at 0 hour and 105.3% for the area under the serum glucose concentration-time curve profile 0-2 hours after coadministration of sucrose and acarbose with deduction of baseline (AUC0-2 h,r ). The 90% confidence intervals of maximum serum glucose concentration with deduction of glucose concentration at 0 hour and the area under the serum glucose concentration-time curve profile 0-2 hours after coadministration of sucrose and acarbose with deduction of baseline all fell within the acceptance limits. The incidence of adverse events after the T or R drug was comparable, and healthy subjects were well tolerated. The findings of our investigation clearly show that the PD parameters of the rectifying method exhibit enhanced suitability and sensitivity when assessing acarbose BE in healthy participants. The T and R drugs were bioequivalent using the novel PD parameters, and both drugs demonstrated good safety and tolerability.

Exploring the interactive mechanism of acarbose with the amylase SusG in the starch utilization system of the human gut symbiont Bacteroides thetaiotaomicron through molecular modeling

The α-amylase, SusG, is a principal component of the Bacteroides thetaiotaomicron (Bt) starch utilization system (Sus) used to metabolize complex starch molecules in the human gastrointestinal (GI) tract. We previously reported the non-microbicidal growth inhibition of Bt by the acarbose-mediated arrest of the Sus as a potential therapeutic strategy. Herein, we report a computational approach using density functional theory (DFT), molecular docking, and molecular dynamics (MD) simulation to explore the interactive mechanism between acarbose and SusG at the atomic level in an effort to understand how acarbose shuts down the Bt Sus. The docking analysis reveals that acarbose binds orthosterically to SusG with a binding affinity of -8.3 kcal/mol. The MD simulation provides evidence of conformational variability of acarbose at the active site of SusG and also suggests that acarbose interacts with the main catalytic residues via a general acid-base double-displacement catalytic mechanism. These results suggest that small molecule competitive inhibition against the SusG protein could impact the entire Bt Sus and eliminate or reduce the system's ability to metabolize starch. This computational strategy could serve as a potential avenue for structure-based drug design to discover other small molecules capable of inhibiting the Sus of Bt with high potency, thus providing a holistic approach for selective modulation of the GI microbiota.

Biological significance of carbohydrate active enzymes and searching their inhibitors for therapeutic applications

Glycans are the most abundant and diverse group of biomolecules with a crucial role in all the biological processes. Their structural and functional diversity is not genetically encoded, but depends on Carbohydrate Active Enzymes (CAZymes) which carry out all catalytic activities in terms of synthesis, modification, and degradation. CAZymes comprise large families of enzymes with specific functions and are widely used for various commercial applications ranging from biofuel production to textile and food industries with impact on biorefineries. To understand the structure and functional mechanism of these CAZymes for their modification for industrial use, together with knowledge of therapeutic aspects of their dysfunction associated with various diseases, CAZyme inhibitors can be used as a valuable tool. In search for new inhibitors, the screening of various secondary metabolites using high-throughput techniques and rational design techniques have been explored. The inhibitors can thus help tune CAZymes and are emerging as a potential research interest.

The 4-α-Glucanotransferase AcbQ Is Involved in Acarbose Modification in Actinoplanes sp. SE50/110

The pseudo-tetrasaccharide acarbose, produced by Actinoplanes sp. SE50/110, is a α-glucosidase inhibitor used for treatment of type 2 diabetes patients. In industrial production of acarbose, by-products play a relevant role that complicates the purification of the product and reduce yields. Here, we report that the acarbose 4-α-glucanotransferase AcbQ modifies acarbose and the phosphorylated version acarbose 7-phosphate. Elongated acarviosyl metabolites (α-acarviosyl-(1,4)-maltooligosaccharides) with one to four additional glucose molecules were identified performing in vitro assays with acarbose or acarbose 7-phosphate and short α-1,4-glucans (maltose, maltotriose and maltotetraose). High functional similarities to the 4-α-glucanotransferase MalQ, which is essential in the maltodextrin pathway, are revealed. However, maltotriose is a preferred donor and acarbose and acarbose 7-phosphate, respectively, serve as specific acceptors for AcbQ. This study displays the specific intracellular assembly of longer acarviosyl metabolites catalyzed by AcbQ, indicating that AcbQ is directly involved in the formation of acarbose by-products of Actinoplanes sp. SE50/110.

In Vitro α-Amylase, α-Glucosidase, Pancreatic Lipase, Xanthine Oxidase Inhibiting Activity of Agaricus bisporus Extracts

In this study, the α-amylase inhibitory activity, α-glucosidase inhibitory activity, pancreatic lipase inhibitory activity, and Xanthine Oxidase inhibitory activity of the fruiting body extracts of 5 varieties of Agaricus bisporus (AB) were confirmed. First, the α-amylase inhibitory activity of AB12, AB13, AB18, AB34, and AB40 methanol extracts was lower than that of acarbose, a positive control, in all concentration ranges. The α-glucosidase inhibitory activity of the AB40, AB13, and AB12 methanol extracts at the extract concentration of 1.0 mg/mL was 80.5%, 81.3%, and 78.5%, respectively, similar to that of acarbose, a positive control. The pancreatic lipase inhibitory activity of the methanol extract of Agaricus bisporus fruiting body was significantly lower than that of the positive control orlistat in the concentration range of 50 ∼ 1.000 (mg/mL). The Xanthine Oxidase inhibitory activity was 0.5 ∼ 8.0 mg/mL of each extract, which was significantly lower than that of the positive control allopurinol in the same concentration range. However, the Xanthine Oxidase inhibitory activity of AB13 and AB40 at 8.0 mg/mL was about 70%, which was higher than that of other mushrooms. In conclusion, five kinds of Agaricus bisporus fruiting bodies seem to have inhibitory effects on enzymes such as α-amylase, α-glucosidase, pancreatic lipase, and Xanthine Oxidase that degrade starch and protein. In particular, it has an inhibitory effect and a reduction effect on xanthine oxidase that causes gout, so it is expected that it can be developed and used as a food or health supplement with health functional properties through future research.

Microbiota: A potential orchestrator of antidiabetic therapy

The gut microbiota, as a 'new organ' of humans, has been identified to affect many biological processes, including immunity, inflammatory response, gut-brain neural circuits, and energy metabolism. Profound dysbiosis of the gut microbiome could change the metabolic pattern, aggravate systemic inflammation and insulin resistance, and exacerbate metabolic disturbance and the progression of type 2 diabetes (T2D). The aim of this review is to focus on the potential roles and functional mechanisms of gut microbiota in the antidiabetic therapy. In general, antidiabetic drugs (α-glucosidase inhibitor, biguanides, incretin-based agents, and traditional Chinese medicine) induce the alteration of microbial diversity and composition, and the levels of bacterial component and derived metabolites, such as lipopolysaccharide (LPS), short chain fatty acids (SCFAs), bile acids and indoles. The altered microbial metabolites are involved in the regulation of gut barrier, inflammation response, insulin resistance and glucose homeostasis. Furthermore, we summarize the new strategies for antidiabetic treatment based on microbial regulation, such as pro/prebiotics administration and fecal microbiota transplantation, and discuss the need for more basic and clinical researches to evaluate the feasibility and efficacy of the new therapies for diabetes.

Enhancement of acarbose production by genetic engineering and fed-batch fermentation strategy in Actinoplanes sp. SIPI12-34

Background

Acarbose, as an alpha-glucosidase inhibitor, is widely used clinically to treat type II diabetes. In its industrial production, Actinoplanes sp. SE50/110 is used as the production strain. Lack of research on its regulatory mechanisms and unexplored gene targets are major obstacles to rational strain design. Here, transcriptome sequencing was applied to uncover more gene targets and rational genetic engineering was performed to increase acarbose production.

Results

In this study, with the help of transcriptome information, a TetR family regulator (TetR1) was identified and confirmed to have a positive effect on the synthesis of acarbose by promoting the expression of acbB and acbD. Some genes with low expression levels in the acarbose biosynthesis gene cluster were overexpressed and this resulted in a significant increase in acarbose yield. In addition, the regulation of metabolic pathways was performed to retain more glucose-1-phosphate for acarbose synthesis by weakening the glycogen synthesis pathway and strengthening the glycogen degradation pathway. Eventually, with a combination of multiple strategies and fed-batch fermentation, the yield of acarbose in the engineered strain increased 58% compared to the parent strain, reaching 8.04 g/L, which is the highest fermentation titer reported.

Conclusions

In our research, acarbose production had been effectively and steadily improved through genetic engineering based on transcriptome analysis and fed-batch culture strategy.

Graphical Abstract

Biochemical Characterization of GacI, a Bifunctional Glycosyltransferase-Phosphatase Enzyme Involved in Acarbose Biosynthesis in Streptomyces glaucescens GLA.O

Acarbose, a pseudotetrasaccharide produced by several strains of Actinoplanes and Streptomyces, is an α-glucosidase inhibitor clinically used to control type II diabetes. Bioinformatic analysis of the biosynthetic gene clusters of acarbose in Actinoplanes sp. SE50/110 (the acb cluster) and Streptomyces glaucescens GLA.O (the gac cluster) revealed their distinct genetic organizations and presumably biosynthetic pathways. However, to date, only the acarbose pathway in the SE50/110 strain has been extensively studied. Here, we report that GacI, one of the proteins that appear to be different between the two pathways, is a bifunctional glycosyltransferase family 5 (GT5)-phosphatase (PP) enzyme that functions at two different steps in acarbose biosynthesis in S. glaucescens GLA.O. In the acb pathway, the GT and the PP reactions are performed by two different enzymes. Truncated GacI proteins having only the GT or the PP domain showed comparable catalytic activity with the full-length GacI, indicating that domain separation does not significantly affect their respective catalytic activity. GacI, which is widely distributed in many Streptomyces, represents the first example of naturally occurring GT5-PP bifunctional enzymes biochemically characterized.

Alternative methods to assess the impurity profile of a monographed API using acarbose as an example

Even though the impurity analysis of the Ph. Eur. is considered well-studied, its methodology should be reviewed periodically to ensure that it is working properly, and all impurities are captured by the section "Related substances" of the monograph. Within this study, the biotechnological produced antidiabetic drug acarbose was chosen to demonstrate some of the advantages as well as the shortcomings arising from the current related substances test of acarbose. Due to its weak chromophore, acarbose is studied by UV detection at 210 nm after being separated on aminopropyl-silyl stationary phases. Thus, the use of alternative detection techniques, such as charge aerosol detection (CAD) and a volatile mobile phase can be beneficial here. Since a simple method transfer to a mobile phase usable with the CAD was not possible, more stable stationary phases were tested. For the rapid determination of the sum of impurities, a method was developed using a pentafluorophenyl column and a mobile phase of 0.1% TFA in water. Maltose and maltotriose were further identified as additional impurities of the API. Furthermore, a method was developed and validated by means of an Amide-HILIC phase, that adequately separated acarbose and all of its impurities. However, the sensitivity of this method needs to be further improved. Additionally, a method was also developed and validated, taking into account the temperature stability of graphite columns. Thus, the separation was carried out at temperatures of about 90 °C to solve the problem of anomerization of acarbose and some of its impurities. In comparison with the other developed methods, the elution order was changed and has to be confirmed, but all components were separated and detected at a sufficient LOQ of 0.10%.

Synthesis of Novel 2,3-Dihydro-1,5-Benzothiazepines as α-Glucosidase Inhibitors: In Vitro, In Vivo, Kinetic, SAR, Molecular Docking, and QSAR Studies

In the present study, a series of 2,3-dihydro-1,5-benzothiazepine derivatives 1B-14B has been synthesized sand characterized by various spectroscopic techniques. The enzyme inhibitory activities of the target analogues were assessed using in vitro and in vivo mechanism-based assays. The tested compounds 1B-14B exhibited in vitro inhibitory potential against α-glucosidase with IC50 = 2.62 ± 0.16 to 10.11 ± 0.32 μM as compared to the standard drug acarbose (IC50 = 37.38 ± 1.37 μM). Kinetic studies of the most active derivatives 2B and 3B illustrated competitive inhibitions. Based on the α-glucosidase inhibitory effect, the compounds 2B, 3B, 6B, 7B, 12B, 13B, and 14B were chosen in vivo for further evaluation of antidiabetic activity in streptozotocin-induced diabetic Wistar rats. All these evaluated compounds demonstrated significant antidiabetic activity and were found to be nontoxic in nature. Moreover, the molecular docking study was performed to elucidate the binding interactions of most active analogues with the various sites of the α-glucosidase enzyme (PDB ID 3AJ7). Additionally, quantitative structure-activity relationship (QSAR) studies were performed based on the α-glucosidase inhibitory assay. The value of correlation coefficient (r) 0.9553 shows that there was a good correlation between the 1B-14B structures and selected properties. There is a correlation between the experimental and theoretical results. Thus, these novel compounds could serve as potential candidates to become leads for the development of new drugs provoking an anti-hyperglycemic effect.

Harnessing Rare Actinomycete Interactions and Intrinsic Antimicrobial Resistance Enables Discovery of an Unusual Metabolic Inhibitor

Bacterial natural products have historically been a deep source of new medicines, but their slowed discovery in recent decades has put a premium on developing strategies that enhance the likelihood of capturing novel compounds. Here, we used a straightforward approach that capitalizes on the interactive ecology of “rare” actinomycetes. Specifically, we screened for interactions that triggered the production of antimicrobials that inhibited the growth of a bacterial strain with exceptionally diverse natural antimicrobial resistance. This strategy led to the discovery of a family of antimicrobials we term the dynaplanins. Heterologous expression enabled identification of the dynaplanin biosynthetic gene cluster, which was missed by typical algorithms for natural product gene cluster detection. Genome sequencing of partially resistant mutants revealed a 2-oxo acid dehydrogenase E2 subunit as the likely molecular target of the dynaplanins, and this finding was supported by computational modeling of the dynaplanin scaffold within the active site of this enzyme. Thus, this simple strategy, which leverages microbial interactions and natural antibiotic resistance, can enable discovery of molecules with unique antimicrobial activity. In addition, these results indicate that primary metabolism may be a direct target for inhibition via chemical interference in competitive microbial interactions.

Complete biosynthetic pathway to the antidiabetic drug acarbose

Acarbose is a bacterial-derived α-glucosidase inhibitor clinically used to treat patients with type 2 diabetes. As type 2 diabetes is on the rise worldwide, the market demand for acarbose has also increased. Despite its significant therapeutic importance, how it is made in nature is not completely understood. Here, we report the complete biosynthetic pathway to acarbose and its structural components, GDP-valienol and O-4-amino-(4,6-dideoxy-α-D-glucopyranosyl)-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose. GDP-valienol is derived from valienol 7-phosphate, catalyzed by three cyclitol modifying enzymes, whereas O-4-amino-(4,6-dideoxy-α-D-glucopyranosyl)-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose is produced from dTDP-4-amino-4,6-dideoxy-D-glucose and maltose by the glycosyltransferase AcbI. The final assembly process is catalyzed by a pseudoglycosyltransferase enzyme, AcbS, which is a homologue of AcbI but catalyzes the formation of a non-glycosidic C-N bond. This study clarifies all previously unknown steps in acarbose biosynthesis and establishes a complete pathway to this high value pharmaceutical.

The market demand for acarbose, a drug used for treatment of patients affected by type-2 diabetes, has increased. In this article, the authors report the acarbose complete biosynthetic pathway, clarifying previously unknown steps and identifying a pseudoglycosyltransferase enzyme, AcbS, a homologue of AcbI that catalyzes the formation of a non-glycosidic C-N bond.

Inflammatory Mechanisms of Diabetes and Its Vascular Complications

The main cause of death in patients with type 2 DM is cardiovascular complications resulting from the progression of atherosclerosis. The pathophysiology of the association between diabetes and its vascular complications is complex and multifactorial and closely related to the toxic effects of hyperglycemia that causes increased generation of reactive oxygen species and promotes the secretion of pro-inflammatory cytokines. Subsequent oxidative stress and inflammation are major factors of the progression of type 2 DM and its vascular complications. Data on the pathogenesis of the development of type 2 DM and associated cardiovascular diseases, in particular atherosclerosis, open up broad prospects for the further development of new diagnostic and therapeutic approaches.

Enzymic catalyzing affinity to substrate affects inhibitor-enzyme binding interactions: Inhibition behaviors of EGCG against starch digestion by individual and co-existing α-amylase and amyloglucosidase

The inhibition of (-)-epigallocatechin-gallate (EGCG) against starch digestion by α-amylase (AA), amyloglucosidase (AMG) and co-existing enzymes (AA/AMG) were comparatively studied. EGCG inhibited AA only at slowly-digestible-starch (SDS) phase. This resulted from high catalytic efficiency of AA for rapidly-digestible-starch (RDS), counteracting the inhibition at this phase. EGCG inhibited AMG and AA/AMG during whole process. At RDS phase, the catalytic velocity of AMG was always higher than AA/AMG because of an antagonistic effect of two enzymes. However, at SDS phase with EGCG, the catalytic velocity of AA/AMG was higher than AMG. This is because binding of EGCG with both enzymes caused more unbound AMG that generated more glucose in co-existing AA/AMG than AMG. Although EGCG-AA binding affinity was higher than EGCG-AMG, competitive inhibition of EGCG against AA was weaker than AMG, indicating relatively higher binding/catalyzing affinity of AA to starch significantly weakened EGCG-AA binding due to competitive relationship between starch and EGCG.

Chemical Variation of Chenpi (Citrus Peels) and Corresponding Correlated Bioactive Compounds by LC-MS Metabolomics and Multibioassay Analysis

The peel of Citrus reticulata “Chachi” (CP) possesses various health-promoting benefits and is not only one of the most famous Chinese herbal medicine, but also an ingredient in fermented foods. In the present study, the effects of storage years (1-, 3-, 4-, 5-, 6-, and 11-years) on the chemical profiling and potential bioactive compounds of CP were compared by metabolomics and in vitro bioactivity analysis. With the increase of storage time, the content of hesperidin significantly decreased, but nobiletin, 3,5,6,7,8,3′,4′-heptamethoxyflavone, and tangeretin were increased. Meanwhile, the antioxidant activity of CP was enhanced. Phenolic acids, flavonol glycosides, fatty acids, and alkyl glycosides were marker compounds that were responsible for distinguishing the storage time of CP. Correlation analysis suggested that some polyphenols including quercetin-glucoside, quinic acid, trihydroxydimethoxyflavone, and rutin were potential antioxidant compounds in CP. The dichloromethane and n-butanol fractions showed the better antioxidant capacity and inhibitory effects on glucose-hydrolysis enzymes. They mainly contained ferulic acid, nobiletin, 3,5,6,7,8,3′,4′-heptamethoxyflavone, kaempferol, and hesperidin.

HPLC-DAD phenolics analysis, α-glucosidase, α-amylase inhibitory, molecular docking and nutritional profiles of Persicaria hydropiper L

BACKGROUND

Natural phenolic compounds and Phenolics-rich medicinal plants are also of great interest in the management of diabetes. The current study was aimed to analyze phenolics in P. hydropiepr L extracts via HPLC-DAD analysis and assess their anti-diabetic potentials using in-vitro and in-silico approaches.

METHODS

Plant crude methanolic extract (Ph.Cme) was evaluated for the presence of phenolic compounds using HPLC-DAD analysis. Subsequently, samples including crude (Ph.Cr), hexane (Ph.Hex), chloroform (Ph.Chf), ethyl acetate (Ph.EtAc), butanol (Ph.Bt), aqueous (Ph.Aq) and saponins (Ph.Sp) were tested for α-glucsidase and α-amylase inhibitory potentials and identified compounds were docked against these target enzymes using Molecular Operating Environment (MOE) software. Fractions were also analyzed for the nutritional contents and acute toxicity was performed in animals.

RESULTS

In HPLC-DAD analysis of Ph.Cme, 24 compounds were indentfied and quantified. Among these, Kaemferol-3-(p-coumaroyl-diglucoside)-7-glucoside (275.4 mg g- 1), p-Coumaroylhexose-4-hexoside (96.5 mg g- 1), Quercetin-3-glucoronide (76.0 mg g- 1), 4-Caffeoylquinic acid (58.1 mg g- 1), Quercetin (57.9 mg g- 1), 5,7,3'-Trihydroxy-3,6,4',5'-tetramethoxyflavone (55.5 mg g- 1), 5-Feruloylquinic acid (45.8 mg g- 1), Cyanidin-3-glucoside (26.8 mg g- 1), Delphinidin-3-glucoside (24 mg g- 1), Quercetin-3-hexoside (20.7 mg g- 1) were highly abundant compounds. In α-glucosidase inhibition assay, Ph.Sp were most effective with IC50 value of 100 μg mL-1. Likewise in α-amylase inhibition assay, Ph.Chf, Ph.Sp and Ph.Cme were most potent fractions displayed IC50 values of 90, 100 and 200 μg mL-1 respectively. Docking with the α-glucosidase enzyme revealed top ranked conformations for majority of the compounds with Kaemferol-3-(p-coumaroyl-diglucoside)-7-glucoside as the most active compound with docking score of - 19.80899, forming 14 hydrogen bonds, two pi-H and two pi-pi linkages with the Tyr 71, Phe 158, Phe 177, Gln 181, Arg 212, Asp 214, Glu 276, Phe 300, Val 303, Tyr 344, Asp 349, Gln 350, Arg 439, and Asp 408 residues of the enzyme. Likewise, docking with α-amylase revealed that most of the compounds are well accommodated in the active site residues (Trp 59, Tyr 62, Thr 163, Leu 165, Arg 195, Asp 197, Glu 240, Asp 300, His 305, Asp 356) of the enzyme and Cyanidin-3-rutinoside displayed most active compound with docking score of - 15.03757.

CONCLUSIONS

Phytochemical studies revealed the presence of highly valuable phenolic compounds, which might be responsible for the anti-diabetic potentials of the plant samples.

A Systematic Review of Orthosiphon stamineus Benth. in the Treatment of Diabetes and Its Complications

(1) Background: Orthosiphon stamineus Benth. is a traditional medicine used in the treatment of diabetes and chronic renal failure in southern China, Malaysia, and Thailand. Diabetes is a chronic metabolic disease and the number of diabetic patients in the world is increasing. This review aimed to systematically review the effects of O. stamineus in the treatment of diabetes and its complications and the pharmacodynamic material basis. (2) Methods: This systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), using the databases ScienceDirect, PubMed, and Web of Science. (3) Results: Thirty-one articles related to O. stamineus and diabetes were included. The mechanisms of O. stamineus in the treatment of diabetes and its complications mainly included inhibiting α-amylase and α-glucosidase activities, antioxidant and anti-inflammatory activities, regulating lipid metabolism, promoting insulin secretion, ameliorating insulin resistance, increasing glucose uptake, promoting glycolysis, inhibiting gluconeogenesis, promoting glucagon-likepeptide-1 (GLP-1) secretion and antiglycation activity. Phenolic acids, flavonoids and triterpenoids might be the main components for hypoglycemia effects in O. stamineus. (4) Conclusion: O. stamineus could be an antidiabetic agent to treat diabetes and its complications. However, it needs further study on a pharmacodynamic substance basis and the mechanisms of effective constituents.

The human microbiome encodes resistance to the antidiabetic drug acarbose

The human microbiome encodes a large repertoire of biochemical enzymes and pathways, most of which remain uncharacterized. Here, using a metagenomics-based search strategy, we discovered that bacterial members of the human gut and oral microbiome encode enzymes that selectively phosphorylate a clinically used antidiabetic drug, acarbose1,2, resulting in its inactivation. Acarbose is an inhibitor of both human and bacterial α-glucosidases3, limiting the ability of the target organism to metabolize complex carbohydrates. Using biochemical assays, X-ray crystallography and metagenomic analyses, we show that microbiome-derived acarbose kinases are specific for acarbose, provide their harbouring organism with a protective advantage against the activity of acarbose, and are widespread in the microbiomes of western and non-western human populations. These results provide an example of widespread microbiome resistance to a non-antibiotic drug, and suggest that acarbose resistance has disseminated in the human microbiome as a defensive strategy against a potential endogenous producer of a closely related molecule.

Ultrasound-assisted enzymatic extraction of Corni Fructus alpha-glucosidase inhibitors improves insulin resistance in HepG2 cells

Corni Fructus (CF) is a traditional medicine and beneficial food with multifaceted protective effects against diabetes and its complications. Since alpha-glucosidase inhibitors (GIs) are promising first-choice oral antihyperglycemic drugs for diabetes, we examined whether GIs from CF (GICF) are useful for diabetes treatment. Therefore, GICF was extracted by ultrasound-assisted enzymatic extraction (UAEE) that is optimized by a three-level, four-factor Box-Behnken design and determined by ultra-performance liquid chromatography. Compared to 36.31 mg g^-1 without enzyme treatment, the GICF yield increased to 70.44 mg g^-1via UAEE under optimum conditions (0.5% compound enzyme extracted in 23 min at 46 °C and pH 4.8). The activity (91.99%) of GICF was as predicted (93.28%). When GICF was used in an insulin-resistant HepG2 cell model, it significantly ameliorated the glucose metabolism in a dose-dependent manner. Our findings indicate that UAEE may be an innovative method for functional food extraction and a potential strategy for high-quality food ingredient (such as GI) production with high efficiency and productivity.

Evaluating the Inhibitory Effects of Dichloromethane and Methanol Extracts of Salvia macilenta and Salvia officinalis on the Diabetes Marker Enzyme, Alpha-Glucosidase: An Approach for the Treatment of Diabetes

Background: Diabetes mellitus is believed to be the most serious metabolic disease. One of the treatments for diabetes is to delay glucose uptake by inhibiting carbohydrate-hydrolyzing enzymes. Alpha-glucosidase inhibitors delay glucose uptake. Objectives: The present study was conducted aiming to evaluate the efficacy of Salvia extracts in inhibiting diabetes marker enzymes and their effects on the treatment of diabetes. Methods: This experimental study was performed in vitro. The studied plants included Salvia macilenta and Salvia officinalis. The inhibitory effects of their dichloromethane and methanol extracts were also investigated. After calculating the percentage of inhibition and IC50, Km and Vmax using GraphPad Prism 7 were also calculated. The statistical analysis was performed employing GraphPad Instat 3 software. Results: The results herein showed that the greatest inhibitory effect on alpha-glucosidase belonged to the methanol extract of S. macilenta with IC50 = 8.73 ± 0.26 mg/mL compared to that of acarbose with IC50 = 8.82 ± 0.14 mg/mL as a standard. The IC50 of dichloromethane extract of S. officinalis was 8.95 ± 0.23 mg/mL. Conclusions: The extracts had significant inhibitory effects on alpha-glucosidase. However, methanol extract of S. macilenta and dichloromethane extract of S. officinalis demonstrated the greatest inhibitory effects on alpha-glucosidase compared to acarbose as a standard.

Discovery of α-Glucosidase Inhibitors from Marine Microorganisms: Optimization of Culture Conditions and Medium Composition

Various studies showed that the suppression of α-glucosidase activity can impede the glucose absorption in our body, and therefore, it can be used to treat type 2 diabetes. Hence, the compounds with anti-α-glucosidase have gained considerable attention because of their potential application in diabetes treatment. In previous literature studies, these anti-α-glucosidase compounds were extracted from plants and fungus. Less studies are being conducted to identify the anti-α-glucosidase compounds in the microbial community. In this study, 23 marine bacterial strains were screened for their potential to suppress the α-glucosidase activity. The highest inhibitory activity was exhibited by isolated L06 which was identified as Oceanimonas smirnovii EBL6. The cultivation conditions, such as temperature and pH, were optimized to increase the production of α-glucosidase inhibitors by Oceanimonas smirnovii EBL6 strain. The result findings showed that the highest yield of α-glucosidase inhibitors can be obtained at the culture time of 120 h, fermentation temperature of 30 °C, and pH 4.6. Under these conditions, the inhibitory activity of α-glucosidase can reach 81%. The IC₅₀ of n-butanol extract was 13.89 μg/ml, while standard acarbose was 31.16 μg/ml. Overall, these findings suggest that Oceanimonas smirnovii produces α-glucosidase inhibitors and could been applied in the biochemical and medicinal fields in the future.

Microbial Oligosaccharides with Biomedical Applications

Microbial oligosaccharides have been regarded as one of the most appealing natural products attributable to their potent and selective bioactivities, such as antimicrobial activity, inhibition of α-glucosidases and lipase, interference of cellular recognition and signal transduction, and disruption of cell wall biosynthesis. Accordingly, a handful of bioactive oligosaccharides have been developed for the treatment of bacterial infections and type II diabetes mellitus. Given that naturally occurring oligosaccharides have increasingly gained recognition in recent years, a comprehensive review is needed. The current review highlights the chemical structures, biological activities and divergent biosynthetic origins of three subgroups of oligomers including the acarviosine-containing oligosaccharides, saccharomicins, and orthosomycins.

Enzymatic Hydrolysis-Responsive Supramolecular Hydrogels Composed of Maltose-Coupled Amphiphilic Ureas

Maltose is a ubiquitous disaccharide produced by the hydrolysis of starch. Amphiphilic ureas bearing hydrophilic maltose moiety were synthesized via the following three steps: I) construction of urea derivatives by the condensation of 4-nitrophenyl isocyanate and alkylamines, II) reduction of the nitro group by hydrogenation, and III) an aminoglycosylation reaction of the amino group and the unprotected maltose. These amphiphilic ureas functioned as low molecular weight hydrogelators, and the mixtures of the amphipathic ureas and water formed supramolecular hydrogels. The gelation ability largely depended on the chain length of the alkyl group of the amphiphilic urea; amphipathic urea having a decyl group had the highest gelation ability (minimum gelation concentration=0.4 mM). The physical properties of the supramolecular hydrogels were evaluated by measuring their thermal stability and dynamic viscoelasticity. These supramolecular hydrogels underwent gel-to-sol phase transition upon the addition of α-glucosidase as a result of the α-glucosidase-catalyzed hydrolysis of the maltose moiety of the amphipathic urea.

Gene Cascade Shift and Pathway Enrichment in Rat Kidney Induced by Acarbose Through Comparative Analysis

Acarbose is an effective anti-diabetic drug to treat type 2 diabetes mellitus (T2DM), a chronic degenerative metabolic disease caused by insulin resistance. The beneficial effects of acarbose on blood sugar control in T2DM patients have been confirmed by many studies. However, the effect of acarbose on patient kidney has yet to be fully elucidated. In this study, we report in detail the gene expression cascade shift, pathway and module enrichment, and interrelation network in acarbose-treated Rattus norvegicus kidneys based on the in-depth analysis of the GSE59913 microarray dataset. The significantly differentially expressed genes (DEGs) in the kidneys of acarbose-treated rats were initially screened out by comparative analysis. The enriched pathways for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were further identified. The protein-protein interaction (PPI) analysis for DEGs was achieved through the STRING database mining. Pathway interrelation and hub genes for enriched pathways were further examined to uncover key biological effects of acarbose. Results revealed 44 significantly up-regulated genes and 86 significantly down-regulated genes (130 significant differential genes in total) in acarbose-treated rat kidneys. Lipid metabolism pathways were considerably improved by acarbose, and the physical conditions in chronic kidney disease (CKD) patients were improved possibly through the increase of the level of high-density lipoprotein (HDL) by lecithin-cholesterol acyl-transferase (LCAT). These findings suggested that acarbose may serve as an ideal drug for CKD patients, since it not only protects the kidney, but also may relieve the complications caused by CKD.

Identification of Docetaxel as a Potential Drug to Promote HDL Biogenesis

Objective: Our recent studies showed that desmocollin 1 (DSC1) binds to apoA-I in order to inhibit apoA-I-mediated high density lipoprotein (HDL) biogenesis in atherosclerotic plaques. To promote HDL biogenesis in the plaque, here we search for small molecules that block apoA-I-DSC1 interactions. Approach and Results: We combined mutational and computational mapping methods to show that amino acid residues 442-539 in the mature DSC1 protein form an apoA-I binding site (AIBS). Using a crystal structure of the AIBS, we carried out virtual screening of 10 million small molecules to estimate their binding affinities to the AIBS, followed by the selection of 51 high-affinity binding molecules as potential inhibitors of apoA-I-DSC1 interactions. Among the 51, the chemotherapy drug docetaxel showed the highest potency in promoting apoA-I-mediated HDL biogenesis in primary human skin fibroblasts with the half-maximal effective concentration of 0.72 nM. In silico docking studies suggest that the taxane ring in docetaxel binds to the AIBS and that the carbon-13 sidechain of the taxane tightens/stabilizes the binding. The HDL biogenic effect of docetaxel was also observed in two predominant cell types in atherosclerosis, macrophages and smooth muscle cells. Importantly, docetaxel promoted HDL biogenesis at concentrations much lower than those required for inducing cytotoxicity. Conclusion: Determination of the AIBS in DSC1 and AIBS structure-based virtual screening allowed us to identify docetaxel as a strong HDL biogenic agent. With the remarkable potency in promoting HDL biogenesis, a chemotherapy drug docetaxel may be repurposed to enhance atheroprotective HDL functions.

Comparative proteome analysis of Actinoplanes utahensis grown on various saccharides based on 2D-DIGE and MALDI-TOF/TOF-MS

Comparative proteomes of Actinoplanes utahensis ZJB-03852 grown on various saccharides (glucose, maltotriose, maltose, glucose + maltose) were analyzed using 2D-DIGE and MALDI-TOF/TOF-MS. Acarbose was detected in all groups except in the glucose only culture. The abundance of acarbose synthesis proteins AcbV, AcbK, AcbL and AcbN was highest in the medium containing mixed glucose and maltose. The accumulation of Zwf and Xpk1 in acarbose-producing media indicated that the cyclitol moiety of acarbose was derived from pentose phosphate pathway. The elevation of GlnA supported that glutamine was a good nitrogen source of the nitrogen-atom in acarbose synthesis. SIGNIFICANCE: Non-insulin-dependent diabetes mellitus, also known as Type II diabetes, constitutes >90% of the diabetes mellitus worldwide. Acarbose is clinically utilized to treat Type II diabetes, but the fermentation process of acarbose-producing Actinoplanes is usually accompanied with structural analogues of acarbose. In this study, we compared the proteomics of Actinoplanes utahensis ZJB-03852 grown on various saccharides by 2D-DIGE and MALDI-TOF/TOF-MS. Our findings highlighted the importance of key proteins in the formation of acarbose and its analogues when A. utahensis was cultivated in various saccharides. These results revealed fundamental data to elucidate the complexity of formation of acarbose analogues.

Selection, purification, and evaluation of acarbose-an α-glucosidase inhibitor from Actinoplanes sp

Actinoplanes sp. A1094 strain had been selected for its high production of acarbose from 20 different strains of Actinoplanes sp. can be found in wild. The content for glucosidase inhibitor of acarbose concentration was recorded at 1.12 g/L. The conducted analysis of 16S rRNA sequence of Actinoplanes sp. A1094 showed 99% similar identity to the corresponding sequence of Actinoplanes hulinensis. Acarbose was purified from Actinoplanes hulinensis 1094 with a yield of 8.48%, purity of 98% and further identified by LC/MS and NMR methods (C₂₅H₄₃NO₁₈; m/z: 645.6 g/mol). The purified acarbose was used to evaluate the hypoglycemia in streptozotocin (STZ)-induced diabetic mice model. The purified acarbose reduced postprandial blood glucose level in comparison with Glucobay® as medication for control type 2 diabetes in a combination therapy. Notably, the outcomes of native acarbose on fasting blood glucose levels in mice resemble akin to the commercial product and the acarbose accumulating fermentation and metabolic engineering from the cell gene in which would reduce in production cost. Therefore, acarbose from Actinoplanes hulinensis 1094 could be potentially used to make products for the treatment of type II diabetes.

An Innovative Short-Clustered Maltodextrin as Starch Substitute for Ameliorating Postprandial Glucose Homeostasis

Dietary starch is usually associated with elevated postprandial glycemic response. This is a potential risk factor of type 2 diabetes. Here, a 1,4-α-glucan branching enzyme (GBE) was employed to reassemble α-1,4 and α-1,6 glycosidic bonds in starch molecules. Structural characterization showed that GBE-catalyzed molecular reassembly created an innovative short-clustered maltodextrin (SCMD), which showed a dense internal framework along with shortened external chains. Such short-clustered molecules obstructed digestive enzymes attack and displayed dramatically reduced digestibility. Therefore, SCMD was served as a dietary starch substitute to improve postprandial glucose homeostasis. A 22.3% decrease in glycemic peak was therefore detected in ICR mice following SCMD intake (10.7 mmol/L), compared with that in the control (13.8 mmol/L). Moreover, an attenuated insulin response (40.5% lower than that in control) to SCMD intake was regarded suitable for diabetes management. These novel discoveries demonstrate that enzymatically rebuilding starch molecules may be a meaningful strategy for diabetes management.

Chemical synthesis, inhibitory activity and molecular mechanism of 1-deoxynojirimycin–chrysin as a potent α-glucosidase inhibitor

Hyperglycemia can be efficaciously regulated by inhibiting α-glucosidase activity and this is regarded as an effective strategy to treat type 2 diabetes.

The expression of the acarbose biosynthesis gene cluster in Actinoplanes sp. SE50/110 is dependent on the growth phase

BACKGROUND

Actinoplanes sp. SE50/110 is the natural producer of the diabetes mellitus drug acarbose, which is highly produced during the growth phase and ceases during the stationary phase. In previous works, the growth-dependency of acarbose formation was assumed to be caused by a decreasing transcription of the acarbose biosynthesis genes during transition and stationary growth phase.

RESULTS

In this study, transcriptomic data using RNA-seq and state-of-the-art proteomic data from seven time points of controlled bioreactor cultivations were used to analyze expression dynamics during growth of Actinoplanes sp. SE50/110. A hierarchical cluster analysis revealed co-regulated genes, which display similar transcription dynamics over the cultivation time. Aside from an expected metabolic switch from primary to secondary metabolism during transition phase, we observed a continuously decreasing transcript abundance of all acarbose biosynthetic genes from the early growth phase until stationary phase, with the strongest decrease for the monocistronically transcribed genes acbA, acbB, acbD and acbE. Our data confirm a similar trend for acb gene transcription and acarbose formation rate. Surprisingly, the proteome dynamics does not follow the respective transcription for all acb genes. This suggests different protein stabilities or post-transcriptional regulation of the Acb proteins, which in turn could indicate bottlenecks in the acarbose biosynthesis. Furthermore, several genes are co-expressed with the acb gene cluster over the course of the cultivation, including eleven transcriptional regulators (e.g. ACSP50_0424), two sigma factors (ACSP50_0644, ACSP50_6006) and further genes, which have not previously been in focus of acarbose research in Actinoplanes sp. SE50/110.

CONCLUSION

In conclusion, we have demonstrated, that a genome wide transcriptome and proteome analysis in a high temporal resolution is well suited to study the acarbose biosynthesis and the transcriptional and post-transcriptional regulation thereof.

A maltose-regulated large genomic region is activated by the transcriptional regulator MalT in Actinoplanes sp. SE50/110

Actinoplanes sp. SE50/110 is the industrially relevant producer of acarbose, which is used in the treatment of diabetes mellitus. Recent studies elucidated the expression dynamics in Actinoplanes sp. SE50/110 during growth. From these data, we obtained a large genomic region (ACSP50_3900 to ACSP50_3950) containing 51 genes, of which 39 are transcribed in the same manner. These co-regulated genes were found to be stronger transcribed on maltose compared with glucose as a carbon source. The transcriptional regulator MalT was identified as an activator of this maltose-regulated large genomic region (MRLGR). Since most of the genes are poorly annotated, the function of this region is farther unclear. However, comprehensive BLAST analyses indicate similarities to enzymes involved in amino acid metabolism. We determined a conserved binding motif of MalT overlapping the -35 promoter region of 17 transcription start sites inside the MRLGR. The corresponding sequence motif 5'-TCATCC-5nt-GGATGA-3' displays high similarities to reported MalT binding sites in Escherichia coli and Klebsiella pneumoniae, in which MalT is the activator of mal genes. A malT deletion and an overexpression mutant were constructed. Differential transcriptome analyses revealed an activating effect of MalT on 40 of the 51 genes. Surprisingly, no gene of the maltose metabolism is affected. In contrast to many other bacteria, MalT is not the activator of mal genes in Actinoplanes sp. SE50/110. Finally, the MRLGR was found partly in other closely related bacteria of the family Micromonosporaceae. Even the conserved MalT binding site was found upstream of several genes inside of the corresponding regions. KEY POINTS : • MalT is the maltose-dependent activator of a large genomic region in ACSP50_WT. • The consensus binding motif is similar to MalT binding sites in other bacteria. • MalT is not the regulator of genes involved in maltose metabolism in ACSP50_WT.

Transcriptome analysis of Actinoplanes utahensis reveals molecular signature of saccharide impact on acarbose biosynthesis

Different carbon sources lead to differential acarbose production in Actinoplanes. To uncover the underlying differentiation in the context of genes and pathways, we performed transcriptome sequencing of Actinoplanes utahensis ZJB-03852 grown on different saccharides, such as glucose, maltose, or the saccharide complex consisting of glucose plus maltose. The differentially expressed genes were classified into GO (gene ontology) terms and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways for functional annotations. Key enriched modules were uncovered. Our data revealed that both maltose and its complex with glucose gave improved acarbose titer. Sugar transportation, cytochrome oxidase, protein synthesis and amino acid metabolism modules were enriched under the saccharide complex condition, while ferritin metabolism gene expressions were enriched in the glucose medium. Our results provided the foundation for uncovering the mechanism of carbon source on acarbose production in A. utahensis.

An overview on the role of bioactive α-glucosidase inhibitors in ameliorating diabetic complications

Recently the use of bioactive α-glucosidase inhibitors for the treatment of diabetes have been proven to be the most efficient remedy for controlling postprandial hyperglycemia and its detrimental physiological complications, especially in type 2 diabetes. The carbohydrate hydrolysing enzyme, α-glucosidase, is generally competitively inhibited by the α-glucosidase inhibitors and results in the delayed glucose absorption in small intestine, ultimately controlling the postprandial hyperglycemia. Here we have reviewed the most recent updates in the bioactive α-glucosidase inhibitors category. This review provides an overview of the α-glucosidase inhibitory potentials and efficiency of controlling postprandial hyperglycemia of various bioactive compounds such as flavonoids, phenolic compound, polysaccharide, betulinic acid, tannins, anthocyanins, steroids, polyol, polyphenols, galangin, procyanidins, hydroxyl-α-sanshool, hydroxyl-β-sanshool, erythritol, ganomycin, caffeoylquinic acid, resin glycosides, saponins, avicularin, oleanolic acids, urasolic acid, ethanolic extracts etc., from various dietary and non-dietary naturally occurring sources.

A rapid analytical method for the quantitative determination of the sugar in acarbose fermentation by infrared spectroscopy and chemometrics

In this article, a rapid analytical method for the quantitative determination of the glucose and maltose in the industrial acarbose fermentation was established by the combination application of infrared spectroscopy and chemometrics. The spectra of the 398 acarbose samples were collected by a portable infrared fast analyzer and the concentration of the glucose and maltose in the acarbose fermentation solution were determinate by high performance liquid chromatography (HPLC) as the referent database. Four spectral pretreatment methods, first derivative (FD), second derivative (SD), Savitzky-Golay (SG) convolution smoothing and mean center (MC) were employed to eliminate the optical interference from background and other noise information. The best result was obtained with FD+SG(21, 3)+MC method. The effects of different principal component numbers (PCs) on the parameters were also optimized. Two models of PLS and MLR, were used to predict the concentration of the glucose and maltose. The FD+SG(21, 3)+MC method was chosen as best method, with 12 PCs for glucose and 11 for maltose as optimized parameters. The PLS model was significantly better than the MLR model. Furthermore, both the predicted values and the reference values of glucose and maltose models showed superior linear relationship within the calibration range. The absolute errors of the predicted values and their corresponding reference values of glucose and maltose in the PLS model were within ±0.14 and ±0.35 confidence intervals, respectively. The prediction correct rate was 98.3%, which indicated that the prediction results of model were excellent.

In vitro antioxidant, anticholinesterases, anti-α-amylase, and anti-α-glucosidase effects of Algerian Salvia aegyptiaca and Salvia verbenaca

In this study, Salvia aegyptiaca and Salvia verbenaca aerial part decoction and methanol extracts (SAE DE, SAE ME, SVR DE, and SVR ME) were screened for their in vitro antioxidant, anti-Alzheimer, and antidiabetic enzymes inhibition activities. The antioxidant properties of Salvia extracts were determined using DPPH radical scavenging, ABTS radical scavenging, Alkaline DMSO superoxide radical scavenging, β-carotene bleaching, reducing power, and metal chelating activity assays. All extracts showed high antioxidant capacity and the antioxidant properties with the best performance were detected in the SAE ME and SVR ME. The extracts of S. aegyptiaca and S. verbenaca showed a low inhibitory activity of acetylcholinesterase (AChE), whereas, the methanol extract of S. aegyptiaca had the highest inhibitory activity on butyrylcholinesterase (BChE) (71.60 ± 4.33% for 100 µg/ml) compared to the other extracts. In vitro inhibitory effect on diabetic enzymes showed that the ME inhibited α-amylase enzyme with an IC₅₀ 86 and 101 µg/ml for SAE and SVR, respectively. Similarly, both extracts inhibited α-glucosidase with (IC₅₀ 97 and 150 µg/ml, respectively). The decoction extracts exhibited lower activity on both enzymes. PRACTICAL APPLICATIONS: It is becoming evident that oxidative stress is involved in several acute and chronic diseases. Counteracting free radical generation has become one of the widest fields of research worldwide. This study deals with the in vitro antioxidant activity of two plants from the Salvia genus as well as the assessment of their in vitro inhibitory properties of four key enzymes implicated in diabetes and Alzheimer's disease. Concerning the practical applications of our work, it can be explored in its antioxidant part as a food supplement to prevent the excess of free radicals in the body and also in other industrial practices. Another potential use is in the prevention and amelioration of both diabetes and Alzheimer's disease symptoms for the extracts that had enzyme inhibitory activity, but this deserves further toxicological and in vivo studies.