Low-dose acarbose does not delay digestion of starch but reduces its bioavailability

Linking Diabetes to Alzheimer's Disease: Potential Roles of Glucose Metabolism and Alpha-Glucosidase

Alzheimer's disease (AD) and type 2 diabetes mellitus (DM) are more prevalent with ageing and cause a substantial global socio-economic burden. The biology of these two conditions is well elaborated, but whether AD and type 2 DM arise from coincidental roots in ageing or are linked by pathophysiological mechanisms remains unclear. Research findings involving animal models have identified mechanisms shared by both AD and type 2 DM. Deposition of β-amyloid peptides and formation of intracellular neurofibrillary tangles are pathological hallmarks of AD. Type 2 DM, on the other hand, is a metabolic disorder characterised by hyperglycaemia and insulin resistance. Several studies show that improving type 2 DM can delay or prevent the development of AD, and hence, prevention and control of type 2 DM may reduce the risk of AD later in life. Alpha-glucosidase is an enzyme that is commonly associated with hyperglycaemia in type 2 DM. However, it is uncertain if this enzyme may play a role in the progression of AD. This review explores the experimental evidence that depicts the relationship between dysregulation of glucose metabolism and AD. We also delineate the links between alpha-glucosidase and AD and the potential role of alpha-glucosidase inhibitors in treating AD.

Extension of the Life Span by Acarbose: Is It Mediated by the Gut Microbiota?

Acarbose can extend the life span of mice through a process involving the gut microbiota. Several factors affect the life span, including mitochondrial function, cellular senescence, telomere length, immune function, and expression of longevity-related genes. In this review, the effects of acarbose-regulated gut microbiota on the life span-influencing factors have been discussed. In addition, a novel theoretical basis for improving our understanding of the mechanisms by which acarbose extends the life span of mice has been suggested.

TLC-MS Bioautography-Based Identification of Free-Radical Scavenging, α-Amylase, and α-Glucosidase Inhibitor Compounds of Antidiabetic Tablet BGR-34

BGR-34 is a polyherbal formulation frequently used to combat diabetes around the globe especially in Asian countries. It provides an attractive treatment option to prediabetics, diabetics, and in metabolic disorders by controlling the altered blood glucose level. The lack of phytopharmacological studies on BGR-34 prompted as to reveal the compounds responsible for the antidiabetic and free-radical scavenging activity of BGR-34. An attempt was made to assess in vitro α-amylase and α-glucosidase enzyme inhibition of BGR-34 along with its free-radical scavenging potential via DPPH scavenging activity. Further, HPTLC profiling and quantitative analysis of berberine and palmatine in BGR-34 were carried out. Thereafter, the TLC-bioautographic-MS analysis was performed to identify the compounds responsible for antidiabetic and antioxidant activities in BGR-34. The results had shown a significant and dose-dependent inhibition potential of BGR-34 against in vitro α-amylase and α-glucosidase enzymatic reactions along with significant inhibition in DPPH free-radical scavenging activity. The HPTLC profiling and quantitative validation studies showed the presence of berberine and palmatine 44.926 ± 0.2907 and 10.507 ± 0.154 μg/g, respectively. The TLC-MS bioautography revealed a total of four DPPH-active, two α-amylase-active, and nine α-glucosidase-active compounds in BGR-34. It was observed from the study that BGR-34 possesses verities of bioactive compounds, which are reasonable not only for its antidiabetic effect but also for its antioxidant activity.

Alpha-Glucosidase Inhibitor Voglibose Suppresses Azoxymethane-Induced Colonic Preneoplastic Lesions in Diabetic and Obese Mice

Type 2 diabetes mellitus and its related insulin resistance are known to increase the risk of cancer. Anti-diabetic agents can improve insulin resistance and may lead to the suppression of carcinogenesis. This study aimed to investigate the preventive effects of the alpha-glucosidase inhibitor voglibose on the development of azoxymethane-induced colorectal pre-neoplastic lesions in obese and diabetic C57BL/KsJ-db/db mice. The direct effects of voglibose on the proliferation of colorectal cancer cells were also evaluated. Mice were injected with azoxymethane to induce colorectal pre-malignancy and were then administered drinking water with or without voglibose. At the end of the study, the administration of voglibose significantly suppressed the development of colorectal neoplastic lesions. In voglibose-treated mice, serum glucose levels, oxidative stress, as well as mRNA expression of the insulin-like growth factor-1 in the colon mucosa, were reduced. The proliferation of human colorectal cancer cells was not altered by voglibose. These results suggested that voglibose suppressed colorectal carcinogenesis in a diabetes- and obesity-related colorectal cancer model, presumably by improving inflammation via the reduction of oxidative stress and suppressing of the insulin-like growth factor/insulin-like growth factor-1 receptor axis in the colonic mucosa.

The Rate of Glucose Appearance Is Related to Postprandial Glucose and Insulin Responses in Adults: A Systematic Review and Meta-analysis of Stable Isotope Studies

BACKGROUND

It is often assumed that lower postprandial glucose (PPG) and insulin (PPI) responses are induced by slower glucose influx from the gut (e.g., by delayed carbohydrate digestion). However, changes in the rate of appearance of glucose in the peripheral circulation [rate of appearance of exogenous glucose (RaE)] may be accompanied by changes in endogenous glucose production (EGP) and the rate of disappearance of total glucose into tissues (RdT). The quantitative relationships between reductions in RaE and PPG/PPI levels are unclear.

OBJECTIVES

The objective was to perform a meta-analysis to quantify the effect of changes in RaE on changes in PPG and PPI levels (primary) and EGP and RdT (secondary).

METHODS

We systematically searched the Scopus, Medline, and Cochrane library databases through 10 January 2019 for randomized, controlled, carbohydrate-rich interventions that aimed to reduce RaE in humans, measured using dual or triple stable isotope methods. The 2-h net incremental AUCs for all variables were extracted or calculated. Relationships between RaE and outcomes were quantified by weighted regression analyses.

RESULTS

There were 12 articles, including 17 comparisons, that satisfied the inclusion criteria. The subjects were mainly men (60%), with age and BMI ranges of 18-40 y and 20.0-27.5 kg/m2, respectively. A 10% reduction in RaE was associated with reductions in PPG levels, PPI levels, and the RdT of 7% (95% CI: 2%, 12%; P = 0.010), 8% (95% CI: 2%, 13%; P = 0.012), and 11% (95% CI: 4%, 17%; P = 0.005), respectively, but was not significantly associated with a change in EGP (13%; 95% CI: -7%, 33%; P = 0.176). All fluxes together explained 70% and 26% of the variances in PPG and PPI levels, respectively.

CONCLUSIONS

In adults, reducing glucose RaE by diet is associated with significant reductions in PPG levels, PPI levels, and the rate of glucose disposal. This trial was registered in the PROSPERO database with identifier CRD42018084824.

Sotagliflozin, the first dual SGLT inhibitor: current outlook and perspectives

Sotagliflozin is a dual sodium-glucose co-transporter-2 and 1 (SGLT2/1) inhibitor for the treatment of both type 1 (T1D) and type 2 diabetes (T2D). Sotagliflozin inhibits renal sodium-glucose co-transporter 2 (determining significant excretion of glucose in the urine, in the same way as other, already available SGLT-2 selective inhibitors) and intestinal SGLT-1, delaying glucose absorption and therefore reducing post prandial glucose. Well-designed clinical trials, have shown that sotagliflozin (as monotherapy or add-on therapy to other anti-hyperglycemic agents) improves glycated hemoglobin in adults with T2D, with beneficial effects on bodyweight and blood pressure. Similar results have been obtained in adults with T1D treated with either continuous subcutaneous insulin infusion or multiple daily insulin injections, even after insulin optimization. A still ongoing phase 3 study is currently evaluating the effect of sotagliflozin on cardiovascular outcomes (ClinicalTrials.gov NCT03315143). In this review we illustrate the advantages and disadvantages of dual SGLT 2/1 inhibition, in order to better characterize and investigate its mechanisms of action and potentialities.

A review of the anti-inflammatory properties of antidiabetic agents providing protective effects against vascular complications in diabetes

The global prevalence of Type 2 diabetes mellitus and its associated complications are growing rapidly. Although the role of hyperglycemia is well recognized in the pathophysiology of diabetic complications, its exact underlying mechanisms are not fully understood. In this regard, accumulating evidence suggests that the role of inflammation appears pivotal, with studies showing that most diabetic complications are associated with an inflammatory response. Several classes of antidiabetic agents have been introduced for controlling glycemia, with evidence that these pharmacological agents may have modulatory effects on inflammation beyond their glucose-lowering activity. Here we review the latest evidence on the anti-inflammatory effects of commonly used antidiabetic medications and discuss the relevance of these effects on preventing diabetic complications.

Inhibitory Reactivity of Capsaicin with α-Amylase and α-Glucosidase Related to Antidiabetes using Molecular Docking and Quantum Calculation Methods

This work aims to investigate the inhibitory activity of capsaicin, which is one of capsaicinoid compounds, on these enzymes using a molecular docking and quantum calculation. Acarbose, a commercial diabetes drug, was also investigated for comparison. The docking results revealed that acarbose yields better inhibition efficiency with binding free energy (ΔGbinding) of about -8.2 to -11.9 kcal/mol, and inhibition constant (Ki) of about 0.0002 to 0.4 µM, whereas capsaicin provided the ΔGbinding of -5.8 to -6.1 kcal/mol and Ki of 23.7 to 45.9 µM. The total binding energy (ΔEbinding) between each inhibitor and amino acids in active site of enzyme obtained from quantum calculation with MP2/6-31G(d,p) level is in agreement with the ΔGbinding, i.e. the ΔEbinding of acarbose was larger negative than that of capsaicin. The amino acids interacting with inhibitor as hydrogen bond mainly contribute to the total binding energy. Nevertheless, it could be concluded that capsaicinoids have high potential to be developed as an alternative drug for diabetes disease.

The effect of small doses of fructose and allulose on postprandial glucose metabolism in type 2 diabetes: A double-blind, randomized, controlled, acute feeding, equivalence trial

AIM

To assess and compare the effect of small doses of fructose and allulose on postprandial blood glucose regulation in type 2 diabetes.

METHODS

A double-blind, multiple-crossover, randomized, controlled, acute feeding, equivalence trial in 24 participants with type 2 diabetes was conducted. Each participant was randomly assigned six treatments separated by >1-week washouts. Treatments consisted of fructose or allulose at 0 g (control), 5 g or 10 g added to a 75-g glucose solution. A standard 75-g oral glucose tolerance test protocol was followed with blood samples at -30, 0, 30, 60, 90 and 120 minutes. The primary outcome measure was plasma glucose incremental area under the curve (iAUC).

RESULTS

Allulose significantly reduced plasma glucose iAUC by 8% at 10 g compared with 0 g (717.4 ± 38.3 vs. 777.5 ± 39.9 mmol × min/L, P = 0.015) with a linear dose response gradient between the reduction in plasma glucose iAUC and dose (P = 0.016). Allulose also significantly reduced several related secondary and exploratory outcome measures at 5 g (plasma glucose absolute mean and total AUC) and 10 g (plasma glucose absolute mean, absolute and incremental maximum concentration [Cmax ], and total AUC) (P < .0125). There was no effect of fructose at any dose. Although allulose showed statistically significant reductions in plasma glucose iAUC compared with fructose at 5 g, 10 g and pooled doses, these reductions were within the pre-specified equivalence margins of ±20%.

CONCLUSION

Allulose, but not fructose, led to modest reductions in the postprandial blood glucose response to oral glucose in individuals with type 2 diabetes. There is a need for long-term randomized trials to confirm the sustainability of these improvements.

Efficacy of fibre additions to flatbread flour mixes for reducing post-meal glucose and insulin responses in healthy Indian subjects

The incidence of type 2 diabetes mellitus (T2DM) is increasing worldwide, including in developing countries, particularly in South Asia. Intakes of foods generating a high postprandial glucose (PPG) response have been positively associated with T2DM. As part of efforts to identify effective and feasible strategies to reduce the glycaemic impact of carbohydrate-rich staples, we previously found that addition of guar gum (GG) and chickpea flour (CPF) to wheat flour could significantly reduce the PPG response to flatbread products. On the basis of the results of an exploratory study with Caucasian subjects, we have now tested the effect of additions of specific combinations of CPF with low doses of GG to a flatbread flour mix for their impacts on PPG and postprandial insulin (PPI) responses in a South-Asian population. In a randomised, placebo-controlled full-cross-over design, fifty-six healthy Indian adults consumed flatbreads made with a commercial flatbread mix (100 % wheat flour) with no further additions (control) or incorporating 15 % CPF in combination with 2, 3 or 4 % GG. The flatbreads with CPF and 3 or 4 % GG significantly reduced PPG (both ≥15 % reduction in positive incremental AUC, P<0·01) and PPI (both ≥28 % reduction in total AUC, P<0·0001) compared with flatbreads made from control flour. These results confirm the efficacy and feasibility of the addition of CPF with GG to flatbread flour mixes to achieve significant reductions in both PPG and PPI in Indian subjects.

Modelling the effect of insulin on the disposal of meal-attributable glucose in type 1 diabetes

The management of postprandial glucose excursions in type 1 diabetes has a major impact on overall glycaemic control. In this work, we propose and evaluate various mechanistic models to characterize the disposal of meal-attributable glucose. Sixteen young volunteers with type 1 diabetes were subject to a variable-target clamp which replicated glucose profiles observed after a high-glycaemic-load ([Formula: see text]) or a low-glycaemic-load ([Formula: see text]) evening meal. [6,6-[Formula: see text]] and [U-[Formula: see text];1,2,3,4,5,6,6-[Formula: see text]] glucose tracers were infused to, respectively, mimic: (a) the expected post-meal suppression of endogenous glucose production and (b) the appearance of glucose due to a standard meal. Six compartmental models (all a priori identifiable) were proposed to investigate the remote effect of circulating plasma insulin on the disposal of those glucose tracers from the non-accessible compartments, representing e.g. interstitium. An iterative population-based parameter fitting was employed. Models were evaluated attending to physiological plausibility, posterior identifiability of their parameter estimates, accuracy-via weighted fitting residuals-and information criteria (i.e. parsimony). The most plausible model, best representing our experimental data, comprised: (1) a remote effect x of insulin active above a threshold [Formula: see text] = 1.74 (0.81-2.50) [Formula: see text] min[Formula: see text] [median (inter-quartile range)], with parameter [Formula: see text] having a satisfactory support: coefficient of variation CV = 42.33 (31.34-65.34) %, and (2) steady-state conditions at the onset of the experiment ([Formula: see text]) for the compartment representing the remote effect, but not for the masses of the tracer that mimicked endogenous glucose production. Consequently, our mechanistic model suggests non-homogeneous changes in the disposal rates for meal-attributable glucose in relation to plasma insulin. The model can be applied to the in silico simulation of meals for the optimization of postprandial insulin infusion regimes in type 1 diabetes.

Pancreatic regulation of glucose homeostasis

In order to ensure normal body function, the human body is dependent on a tight control of its blood glucose levels. This is accomplished by a highly sophisticated network of various hormones and neuropeptides released mainly from the brain, pancreas, liver, intestine as well as adipose and muscle tissue. Within this network, the pancreas represents a key player by secreting the blood sugar-lowering hormone insulin and its opponent glucagon. However, disturbances in the interplay of the hormones and peptides involved may lead to metabolic disorders such as type 2 diabetes mellitus (T2DM) whose prevalence, comorbidities and medical costs take on a dramatic scale. Therefore, it is of utmost importance to uncover and understand the mechanisms underlying the various interactions to improve existing anti-diabetic therapies and drugs on the one hand and to develop new therapeutic approaches on the other. This review summarizes the interplay of the pancreas with various other organs and tissues that maintain glucose homeostasis. Furthermore, anti-diabetic drugs and their impact on signaling pathways underlying the network will be discussed.

Slowly digestible starch--a review

The link between carbohydrate intake and health is becoming increasingly important for consumers, particularly in the areas of glycemic index (GI) and extended energy-releasing starches. From a physiological point of view, slowly digestible starch (SDS) delivers a slow and sustained release of blood glucose along with the benefits resulting from low glycemic and insulinemic response. SDS has been implicated in several health problems, including diabetes, obesity, and cardiovascular diseases (metabolic syndromes). It may also have commercial potential as a novel functional ingredient in a variety of fields, such as nutrition, medicine, and agriculture. The present review assesses this form of digestion by analyzing methods to prepare and evaluate SDS, and factors affecting its transformation, its health benefits, and its applications.

Acarbose: safe and effective for lowering postprandial hyperglycaemia and improving cardiovascular outcomes

α-Glucosidase inhibitors (AGIs) are a class of oral glucose-lowering drugs used exclusively for treatment or prevention of type 2 diabetes mellitus. AGIs act by altering the intestinal absorption of carbohydrates through inhibition of their conversion into simple sugars (monosaccharides) and thus decrease the bioavailability of carbohydrates in the body, significantly lowering blood glucose levels. The three AGIs used in clinical practice are acarbose, voglibose and miglitol. This review will focus on the cardiovascular properties of acarbose. The current available data suggest that AGIs (particularly acarbose) may be safe and effective for the treatment of prediabetes and diabetes.

Novel hypothesis to explain why SGLT2 inhibitors inhibit only 30-50% of filtered glucose load in humans

Inhibitors of sodium-glucose cotransporter 2 (SGLT2) are a novel class of antidiabetes drugs, and members of this class are under various stages of clinical development for the management of type 2 diabetes mellitus (T2DM). It is widely accepted that SGLT2 is responsible for >80% of the reabsorption of the renal filtered glucose load. However, maximal doses of SGLT2 inhibitors fail to inhibit >50% of the filtered glucose load. Because the clinical efficacy of this group of drugs is entirely dependent on the amount of glucosuria produced, it is important to understand why SGLT2 inhibitors inhibit <50% of the filtered glucose load. In this Perspective, we provide a novel hypothesis that explains this apparent puzzle and discuss some of the clinical implications inherent in this hypothesis.

Absorption patterns of meals containing complex carbohydrates in type 1 diabetes

AIMS/HYPOTHESIS

Successful postprandial glycaemia management requires understanding of absorption patterns after meals containing variable complex carbohydrates. We studied eight young participants with type 1 diabetes to investigate a large low-glycaemic-load (LG) meal and another eight participants to investigate a high-glycaemic-load (HG) meal matched for carbohydrates (121 g).

METHODS

On Visit 1, participants consumed an evening meal. On follow-up Visit 2, a variable-target glucose clamp was performed to reproduce glucose and insulin levels from Visit 1. Adopting stable-label tracer dilution methodology, we measured endogenous glucose production on Visit 2 and subtracted it from total glucose appearance measured on Visit 1 to obtain meal-attributable glucose appearance.

RESULTS

After the LG meal, 25%, 50% and 75% of cumulative glucose appearance was at 88 ± 21, 175 ± 39 and 270 ± 54 min (mean ± SD), whereas glucose from the HG meal appeared significantly faster at 56 ± 12, 100 ± 25 and 153 ± 39 min (p < 0.001 to 0.003), and resulted in a 50% higher peak appearance (p < 0.001). Higher apparent bioavailability by 15% (p = 0.037) was observed after the LG meal. We documented a 20 min deceleration of dietary mixed carbohydrates compared with dietary glucose for the HG meal and a twofold deceleration for the LG meal.

CONCLUSIONS/INTERPRETATION

Absorption patterns may be influenced by glycaemic load and/or meal composition, affecting optimum prandial insulin dosing in type 1 diabetes.

Applications of stable isotopes in clinical pharmacology

This review aims to present an overview of the application of stable isotope technology in clinical pharmacology. Three main categories of stable isotope technology can be distinguished in clinical pharmacology. Firstly, it is applied in the assessment of drug pharmacology to determine the pharmacokinetic profile or mode of action of a drug substance. Secondly, stable isotopes may be used for the assessment of drug products or drug delivery systems by determination of parameters such as the bioavailability or the release profile. Thirdly, patients may be assessed in relation to patient-specific drug treatment; this concept is often called personalized medicine. In this article, the application of stable isotope technology in the aforementioned three areas is reviewed, with emphasis on developments over the past 25 years. The applications are illustrated with examples from clinical studies in humans.

Factors related to colonic fermentation of nondigestible carbohydrates of a previous evening meal increase tissue glucose uptake and moderate glucose-associated inflammation

BACKGROUND

Evening meals that are rich in nondigestible carbohydrates have been shown to lower postprandial glucose concentrations after ingestion of high-glycemic-index breakfasts. This phenomenon is linked to colonic fermentation of nondigestible carbohydrates, but the underlying mechanism is not fully elucidated.

OBJECTIVE

We examined the way in which glucose kinetics and related factors change after breakfast as a result of colonic fermentation.

DESIGN

In a crossover design, 10 healthy men ingested as an evening meal white wheat bread (WB) or cooked barley kernels (BA) that were rich in nondigestible carbohydrates. In the morning after intake of 50 g (13)C-enriched glucose, the dual-isotope technique was applied to determine glucose kinetics. Plasma insulin, free fatty acid, interleukin-6, tumor necrosis factor-alpha, and short-chain fatty acid concentrations and breath-hydrogen excretion were measured.

RESULTS

The plasma glucose response after the glucose drink was 29% lower after the BA evening meal (P = 0.019). The insulin response was the same, whereas mean (+/-SEM) tissue glucose uptake was 30% higher (20.2 +/- 1.9 compared with 15.5 +/- 1.8 mL/2 h; P = 0.016) after the BA evening meal, which indicated higher peripheral insulin sensitivity (P = 0.001). The 4-h mean postprandial interleukin-6 (19.7 +/- 5.1 compared with 5.1 +/- 0.7 pg/mL; P = 0.024) and tumor necrosis factor-alpha (7.8 +/- 2.1 compared with 5.3 +/- 1.6 pg/mL; P = 0.008) concentrations after the glucose drink were higher after the WB evening meal. Butyrate concentrations (P = 0.041) and hydrogen excretion (P = 0.005) were higher in the morning after the BA evening meal.

CONCLUSION

In healthy subjects, factors related to colonic fermentation of nondigestible carbohydrates increase peripheral insulin sensitivity and moderate glucose-associated inflammation.

Alpha-glucosidase inhibitors in the early treatment of type 2 diabetes

Alpha-glucosidase inhibitors (AGIs) are drugs that inhibit the absorption of carbohydrates from the gut and may be used in the treatment of patients with type 2 diabetes or impaired glucose tolerance. There is currently no evidence that AGIs are beneficial to prevent or delay mortality or micro- or macrovascular complications in type 2 diabetes. Its beneficial effects on glycated hemoglobin are comparable to metformin or thiazolidinediones, and probably slightly inferior to sulphonylurea. In view of the total body of evidence metformin seems to be superior to AGIs. More long-term studies are needed to study the effects of AGIs compared to other drugs. For patient with impaired glucose tolerance AGIs may prevent, delay or mask the occurrence of type 2 diabetes. A possible beneficial effect on cardiovascular events should be confirmed in new studies.