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PubMed2006

Alpha-glucosidase inhibitors for people with impaired glucose tolerance or impaired fasting blood glucose.

BACKGROUND: Alpha-glucosidase inhibitors (AGIs) reduce blood glucose levels and may thus prevent type 2 diabetes and cardiovascular disease in patients with impaired glucose tolerance. These possible effects, and the effects on quality of life, plasma lipids and body weight, have never been investigated in a systematic literature review and meta-analysis. OBJECTIVES: To assess the effects of alpha-glucosidase inhibitors in patients with impaired glucose tolerance (IGT) or impaired fasting blood glucose (IFBG), or both. SEARCH STRATEGY: We searched The Cochrane Library (Clinical Trials database, formerly known as CENTRAL), PUBMED, EMBASE, Web of Science, LILACS, databases of ongoing trials, reference lists of relevant reviews, and we contacted experts and manufacturers. Date of last search was February 2006. SELECTION CRITERIA: Randomised controlled trials of at least one-year duration in patients with IGT or IFBG, or both, comparing AGI monotherapy with any other intervention. DATA COLLECTION AND ANALYSIS: Two reviewers read all abstracts, assessed quality and extracted data independently. Discrepancies were resolved by consensus or by the judgement of a third reviewer. MAIN RESULTS: We included five trials (2360 participants), all investigating acarbose, that included patients with IGT or patients 'at increased risk for diabetes' (n = 1). Study duration was one, three (n = 2), five and six years. One study was at low risk of bias and four studies at high risk of bias. Except for the outcome incidence of type 2 diabetes in acarbose versus no treatment (two studies), meta-analyses were not possible. Data from the study at low risk of bias suggests that acarbose decreases the occurrence of type 2 diabetes (NNT = 10), cardiovascular events (NNT = 50, based on 47 events, study not initially powered for this outcome), post-load blood glucose (-0.6 mmol/L, 95% CI -1.0 to -0.3) and body mass index (0.3 kg/m(2), 95% CI -0.1 to -0.5). No statistically significant effects were observed on mortality, other morbidity, glycated haemoglobin, fasting blood glucose, lipids and blood pressure. The effects on the incidence of type 2 diabetes were confirmed in two studies at high risk of bias (OR 0.2, 95% CI 0.1 to 0.6). Adverse effects were mostly of gastro-intestinal origin (OR 3.5, 95% CI 2.7 to 4.4). AUTHORS' CONCLUSIONS: There is evidence that acarbose reduces the incidence of type 2 diabetes in patients with IGT. However, it is unclear whether this should be seen as prevention, delay or masking of diabetes. Acarbose may prevent the occurrence of cardiovascular events, but this finding needs to be confirmed in more studies.

Acarbose↗
PubMed1979

Secretion of cellulase and beta-glucosidase by Trichoderma viride ITCC-1433 in submerged culture on different substrates.

Trichoderma viride ITCC-1433 produces high yields of cellulase and especially beta-glucosidase when grown in submerged culture on different carbon sources. Cellulase synthesis was strongly repressed in the presence of glucose and only a low constitutive activity of beta-glucosidase and carboxymethylcellulase, but no Avicelase, could be demonstrated when culturing T. viride on glucose. With carboxymethylcellulose (CMC) as a substrate the secretion of enzyme as well as growth depended on the degree of substitution, but in general CMC cannot be regarded either as a powerful inducer or as a carbon source. With insoluble cellulose, maximum enzyme production and activities were obtained using an alkali-treated cellulose powder. On this substrate the excretion of soluble protein into the culture broth increased and the protein concentration corresponded to cellulolytic activities.

Cellulase↗
PubMed2005

Syntheses and biological activities of chalcone and 1,5-benzothiazepine derivatives: promising new free-radical scavengers, and esterase, urease, and alpha-glucosidase inhibitors.

A series of 2,4-diaryl-2,3,4,5-tetrahydro- (36-40) and 2,4-diaryl-2,3-dihydro-1,5-benzothiazepines (25-35) have been synthesized from the corresponding chalcones 1-24. Both the benzothiazepines and chalcones were evaluated as DPPH free-radical scavengers and as inhibitors of cholinesterases, urease, and alpha-glucosidase. Compounds 2, 5, 6, 7, 10, 13, 18, 21, 36a, 37a, 37b, and 39a showed significant cholinesterase inhibiting activities. Among the 15 dihydro-1,5-benzothiazepines, 26, 32, and 35 exhibited significant radical-scavenging activities; and six tetrahydro-1,5-benzothiazepines (35, 36a, 36b, 37a, 37b, and 39a) were found to be inhibitors of AChE and BChE. Compounds 22, 25, 26, 33, 35, 36a, 37b, and 39a inhibited urease, and 25 and 27-31 were found to be potent inhibitors of alpha-glucosidase.

Butyrylcholinesterase↗
PubMed1987

Miglitol may have a blood glucose lowering effect unrelated to inhibition of alpha-glucosidase.

Miglitol is an alpha-glucosidase inhibitor which lowers blood glucose and insulin concentrations in healthy volunteers after a starch meal. It also lowers blood glucose concentrations after a starch meal in patients with non-insulin-dependent diabetes mellitus, but under these circumstances insulin is unaffected. We have studied the effect of miglitol after a glucose load in six healthy male volunteers. Although one would expect an alpha-glucosidase inhibitor to have no effect on blood glucose concentrations after a glucose load, miglitol produced a significant decrease in blood glucose concentrations after the absorption peak. This could be due to enhancement of insulin effects or to depression of anti-insulin factors.

1-Deoxynojirimycin↗
PubMed1996

Novel alpha-glucosidase inhibitors identified using multiple cyclic peptide combinatorial libraries.

Twenty-six cyclic synthetic peptide combinatorial libraries (disulfides and lactams) of varying size and composition, representing 6.8 x 10(3) to 4.7 x 10(7) individual peptides, were synthesized along with their respective linear analogs. One of the hexapeptide lactam libraries (cyclo[xXxXxN]) was found to have significant alpha-glucosidase inhibitory activity. This library was carried through an iterative process of synthesis and screening, during which all of the five mixture positions (x and X) were successively defined. As the result of this process, potent and selective alpha-glucosidase inhibitors were identified.

Amino Acid Sequence↗
PubMed1986

Effects of two new alpha-glucosidase inhibitors on glycemic control in patients with insulin-dependent diabetes mellitus.

BAYo1248 and BAYm1099 are two new alpha-glucosidase inhibitors. Postprandial glucose tolerance was significantly improved and postprandial insulin requirements were significantly reduced as compared to placebo after breakfast and lunch when 20 mg BAYo1248 were administered prior to breakfast and after breakfast, lunch and dinner when 50 mg BAYm1099 were given prior to all three main meals. Postprandial breath H2 concentrations were mildly increased when these alpha-glucosidase inhibitors were given and no patient complained of any adverse effects (such as flatulence, abdominal pain or diarrhea). BAYo1248 and BAYm1099 might be useful adjuncts to insulin in the treatment of patients with insulin-dependent diabetes mellitus.

1-Deoxynojirimycin↗
PubMed1987

The effect of short-term alpha-glucosidase inhibition on carbohydrate and lipid metabolism in type II (noninsulin-dependent) diabetics.

With use of the alpha-glucosidase inhibitor bay g 5421 (acarbose), it is possible to improve glycemic profiles in diabetics without a concomitant increase in insulin levels or weight reduction. We have taken advantage of this feature to test whether an improvement in glycemic control alone can ameliorate some of the known abnormalities of type II diabetes (ie, impaired insulin secretion, elevated rate of basal hepatic glucose output, peripheral insulin resistance). We have studied eight type II diabetics (mean +/- SE fasting serum glucose 193 +/- 25 mg/dL) before and after 2 weeks of acarbose therapy (100 mg with each meal). Assessment of endogenous insulin secretion, peripheral and hepatic insulin sensitivity, and adipose tissue lipoprotein lipase (ATLPL) activity were performed. Results showed significant lowering of postprandial glucose excursions above basal but no change in basal serum glucose levels, marked reduction in fasting and day-long triglyceride levels and in spite of a reduction in ATLPL activity, an increase in hepatic sensitivity to insulin's ability to suppress hepatic glucose output, and no effect on peripheral insulin sensitivity. In conclusion, inhibition of carbohydrate digestion with alpha-glucosidase inhibitors ameliorates many of the metabolic abnormalities in type II (noninsulin-dependent diabetics), suggesting that agents of this type can be of therapeutic value.

Acarbose↗
PubMed1988

Intestinal and metabolic responses to an alpha-glucosidase inhibitor in normal volunteers.

Postprandial hyperglycemia in diabetic patients can be modified by delaying the digestion and/or absorption of dietary carbohydrates. We have studied an orally active alpha-glucosidase inhibitor, Bay 1099, in normal volunteers to determine whether these inhibitors can decrease postprandial rises in serum glucose without causing gastrointestinal symptoms or significant fecal caloric wastage. Six subjects were given 25, 50, or 100 mg of Bay 1099 or placebo before meals for 1 week, each with a 1-week washout period. Fasting and postprandial concentrations of glucose, insulin, glucagon, enteroglucagon, and gastrointestinal inhibitory peptide (GIP) were measured after the first and last dose of Bay 1099, and the fecal excretions of protein, fat, fiber, and total calories were measured on the last three days of each diet. The passage of unabsorbed carbohydrate into the colon was determined by breath hydrogen analysis three times during each study week. Increasing doses of Bay 1099 were found to decrease the postprandial rise in serum glucose concentration, delay the time to peak insulin concentration, and decrease the output of GIP after the meal. No adaptation was apparent after 1 week of therapy. A dose of inhibitor (50 mg tid), which greatly improves postprandial glucose and hormone output in diabetes, was associated with minimal symptoms and no excess fecal caloric losses. Thus, glucosidase inhibitors such as Bay 1099 may be useful in the management of patients with carbohydrate intolerance.

1-Deoxynojirimycin↗
PubMed1991

Inhibition of HIV and SIV infectivity by blockade of alpha-glucosidase activity.

Processing of HIV and SIV envelope oligosaccharides is critical for proper intracellular trafficking and function. An inhibitor of alpha-glucosidases I and II, N-butyl deoxynojirimycin (N-BuDNJ), retards HIV-1 and SIVmac spread in lymphocytes and monocytes by diminishing virus infectivity, and also causes a reduction in syncytia formation between infected cells and uninfected lymphocytes. N-BuDNJ retards envelope processing from the precursor form to the mature surface (SU) and transmembrane proteins in HIV-1- and SIVmac-infected cells, as well as in cells infected with vaccinia-HIV-1 envelope recombinant virus. However, no significant reduction is seen in the amount of SU in released virus particles, though the virus particle-associated SU from N-BuDNJ-treated cells has an altered electrophoretic mobility. In contrast, N-BuDNJ had no effect on GAG protein synthesis and processing. These findings demonstrate a critical requirement for oligosaccharide processing by alpha-glucosidases I and II for HIV-1 and SIVmac envelope processing and fusogenicity.

1-Deoxynojirimycin↗
PubMed1990

Inhibitory effect of a new alpha-glucosidase inhibitor on fatty liver in Zucker fatty rats.

The livers of Zucker fatty (fa/fa) and lean (Fa/-) rats treated with standard rat chow diet containing 0, 10 or 50 ppm alpha-glucosidase inhibitor (AO-128) for 10 weeks were studied morphologically and biochemically. Light microscopic examination of livers from untreated Zucker fatty rats showed severe steatosis. The triglyceride content in the livers from Zucker fatty rats was significantly higher than that from lean rats (73 +/- 9 micrograms/mg protein for Zucker fatty rats vs. 30 +/- 10 for lean rats, p less than 0.01). Administration of the inhibitor caused a marked decrease in the number and size of lipid droplets in the hepatocytes from Zucker fatty rats and a decrease in the triglyceride content in the liver (73 +/- 9 micrograms/mg protein for untreated, 54 +/- 16 for 10-ppm-treated and 48 +/- 23 for 50-ppm-treated rats, p less than 0.05). This is the first report showing an inhibitory effect of an alpha-glucosidase inhibitor on steatosis in Zucker fatty rats.

Animals↗
PubMed2006

Antidiabetic activity of lipophilic (-)-epigallocatechin-3-gallate derivative under its role of alpha-glucosidase inhibition.

(-)-Epigallocatechin-3-gallate (EGCG), a component of catechins, has been shown to reduce blood glucose levels. In the present study, we investigated the antidiabetic activity and its mechanism of lipophilic EGCG derivative (L-EGCGd) in streptozotocin (STZ)-induced diabetic rats. L-EGCGd was chemically modified from traditional hydrophilic EGCG. After 30 days treatment, plasma levels of glucose were significantly reduced by 40.5+/-7.0% and 17.0+/-2.8% in groups administered 50 or 25 mg kg(-1)d(-1) L-EGCGd, respectively, as compared with that in the diabetic control group. Lipid metabolites, such as total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDLC) were effectively attenuated by L-EGCGd administration, but plasma HDLC levels did not change significantly. The oral glucose tolerance test (OGTT) greatly revealed the improved ability of glucose tolerance with treatment of L-EGCGd. L-EGCGd only retarded the postprandial rise in blood glucose with sucrose loading but not glucose loading. And activity of alpha-glucosidase was inhibited by 50% at the concentration of 246.6 microg ml(-1) L-EGCGd. As a result, we first demonstrated that the purified form of compound L-EGCGd possessed the hypoglycemic effect under its role of alpha-glucosidase inhibition, and therefore should be possibly accepted as an alternative oral medication protecting patients against postprandial hyperglycemic toxicity on the treatment of diabetes and its complications.

Animals↗
PubMed2004

Synergetic inhibition of genistein and D-glucose on alpha-glucosidase.

Synergetic inhibitory effect of genistein (I2) and D-glucose (I1) on alpha-glucosidase has been studied with kinetics method. It was concluded that the inhibitory effect was much greater when I2 and I1 were both added to the reactant solution simultaneously than that they were added, respectively, which suggesting the inhibitors bind to the different sites of alpha-glucosidase at the same time, and demonstrating synergetic inhibition.

Drug Synergism↗
PubMed2005

Biaryls and heterobiaryls as alpha-glucosidase and protein tyrosine phosphatase inhibitors.

Various 6-aryl-4-substituted-2H-pyran-2-one-3-carbonitriles (1a-d) have been synthesized as precursor for the synthesis of 3,4-dihydro-1H-isothiochroman (2a) and benzocycloalkanes (2b-e). Highly functionalized 9-thiaphenanthrene (3b) and phenanthrene (3a) have also been obtained from the reaction of 1c with thiochroman-4-one and 1-tetralone separately. Similarly 4 has been obtained by the ring transformation of 1d by 4-trifluoromethylacetophenone. Most of the synthesized compounds were evaluated for alpha-glucosidase and protein tyrosine phosphatase inhibitory activities. Some of the compounds, 2a, 3a and b and 4 displayed better alpha-glucosidase inhibitory activity compared to standard drug acarbose.

Enzyme Inhibitors↗
PubMed2006

Alpha-glucosidase inhibitory effect of mulberry (Morus alba) leaves on Caco-2.

The effects of brewing time on dry weight content and alpha-glucosidase inhibitory active component released from mulberry (Morus alba) tea were studied. Different tea products showed significant differences in inhibitory activity against both sucrase and maltase. The most effective enzyme inhibition was observed when 3 to 5 min brewing time was applied in tea preparation. In a Caco-2 cell culture experiment the tea reduced the liberated glucose contents in both apical and basal sides of the cell monolayers. It can be concluded that hot water extract of mulberry leaves does have inhibitory effect against alpha-glucosidases, sucrase and maltase enzymes, and has a potential to be consumed as antidiabetic herb tea.

Beverages↗
PubMed2006

Purification and characterisation of an intracellular enzyme with beta-glucosidase and beta-galactosidase activity from the thermophilic fungus Talaromyces thermophilus CBS 236.58.

An intracellular beta-glycoside hydrolase with beta-glucosidase and beta-galactosidase activity, designated beta-glucosidase BGL1, was isolated to apparent homogeneity from the thermophilic ascomycete Talaromyces thermophilus CBS 236.58. The monomeric enzyme has a molecular mass of 50 kDa (SDS-PAGE) and an isoelectric point of 4.5-4.6. The enzyme is active with both glucosides such as cellobiose and galactosides including lactose; based on the catalytic efficiencies determined glucosides are the preferred substrates. beta-Galactosidase activity of BGL1 is activated by various mono and divalent cations including Na+, K+ and Mg2+, and it is moderately inhibited by its reaction products glucose and galactose. Its pH optimum for the hydrolysis of galactosides is in the range of 5.5-6.0, and its optimum temperature was found to be 50 degrees C (15 min assay). In addition to its hydrolytic activity, BGL1 shows a significant transferase activity which results in the formation of galacto-oligosaccharides. These have recently attracted interest because of possible applications in food industry. The highest yields of oligosaccharides was approximately 20% when using 38 gl(-1) lactose as the starting material.

Cellulases↗
PubMed2006

alpha-Glucosidase inhibitory activity of the methanolic extract from Tournefortia hartwegiana: an anti-hyperglycemic agent.

Tournefortia hartwegiana is a Mexican medicinal plant that is used for the treatment of diabetes, diarrhea and kidney pain. In a previous investigation, the methanolic extract of Tournefortia hartwegiana (METh) showed significant hypoglycemic and anti-diabetic properties on normoglycemic and alloxanized rats. In this context, the purpose of the present study was to establish one of the possible modes of action of METh to induce anti-diabetic activity. METh (310mg/kg) effect on alpha-glucosidase activity was investigated. METh intragastric administration was conducted to determine oral glucose tolerance test (OGTT), using different substrates: glucose, sucrose and maltose. The increase in plasma glucose level was significantly suppressed (P<0.05) by the extract after substrates administration. On the other hand, METh inhibited alpha-glucosidase activity in vitro, in a concentration-dependent manner (IC(50) of 3.16mg/mL). These results suggest that METh might exert its anti-diabetic effect by suppressing carbohydrate absorption from intestine, and thereby reducing the post-prandial increase of blood glucose. On the other hand, the bio-guided fractionation of this extract led to the isolation of: beta-sitosterol (1), stigmasterol (2), lupeol (3), ursolic acid (4), oleanolic acid (5), saccharose (6) and myo-inositol (7), using various chromatographic techniques.

Animals↗
PubMed2005

Effect of two alpha-glucosidase inhibitors, voglibose and acarbose, on postprandial hyperglycemia correlates with subjective abdominal symptoms.

To assess the possible difference in effectiveness of 2 alpha-glucosidase inhibitors, voglibose and acarbose, the relationship between postprandial hyperglycemia and subjective abdominal symptoms was investigated. A total of 21 inpatients with type 2 diabetes were recruited to a single-center, 2-period, crossover trial. The subjects were given acarbose (150 mg/d) or voglibose (0.9 mg/d) under an isocaloric diet, and the postprandial (2 hours) increment in blood glucose level, M value which is a marker for fluctuation of blood glucose levels, and subjective abdominal symptom score were monitored. There was no significant difference between the 2 agents in postprandial increment in blood glucose level, M value, and subjective symptom score. When patients were divided according to subjective symptoms, however, the sum postprandial glucose increments were significantly different according to the agent (P = .03), with favorable efficacy in patients in whom the alpha-glucosidase inhibitor caused abdominal symptoms, demonstrating a significant interaction (P = .04) between treatment and symptomatic grouping. The results demonstrated that 50 mg acarbose and 0.3 mg voglibose had similar overall effects on postprandial hyperglycemia as well as subjective symptoms, but marked interindividual variation existed. Subjective symptoms may be a predictor of the divergent clinical response to each agent.

Acarbose↗