Prolonged and enhanced secretion of glucagon-like peptide 1 (7-36 amide) after oral sucrose due to alpha-glucosidase inhibition (acarbose) in Type 2 diabetic patients

Effects of electroacupuncture on intestinal microflora and plasma metabolites in an insulin-resistant mouse model of type 2 diabetes mellitus

OBJECTIVE

To investigate the effects of electroacupuncture (EA) at ST36 on intestinal microflora and plasma metabolites in a mouse model of type 2 diabetes mellitus (T2DM), to provide a theoretical basis and guidance for the clinical treatment of T2DM by traditional Chinese medicine (TCM).

METHODS

Sixteen T2DM db/db mice were randomly divided into treatment (T, n = 8) and model (M, n = 8) groups, and a further eight normal db/m+ mice reared under the same conditions served as a non-diabetic control group (C, n = 8). The general conditions of mice were observed weekly. After obtaining blood and stool samples, the mice were euthanized. Fasting blood glucose (FBG) was measured using a glucometer and fasting insulin (FINS) was measured in plasma by enzyme-linked immunosorbent assay (ELISA). Liver and colon tissues were embedded in paraffin and subjected to hematoxylin-eosin (HE) staining to observe pathological changes in these tissues. In addition, 16S ribosomal RNA (rRNA) sequencing was performed to analyze changes in the intestinal flora and metabolomics was employed to assess changes in metabolites in the blood.

RESULTS

EA significantly reduced FBG and FINS levels and alleviated pathological damage to the liver and colon. Furthermore, EA increased intestinal community richness and diversity by decreasing the relative abundance of Clostridium and incresasing the relative abundance of Lactobacillus. EA also reduced D-fructose levels in T2DM mice according to plasma metabolomics.

CONCLUSION

EA has a positive regulatory effect on the intestinal flora and can regulate blood glucose and improve insulin resistance in T2DM model mice.

Management of type 2 diabetes in patients with compensated liver cirrhosis: Short of evidence, plenty of potential

BACKGROUND AND AIMS

Treatment of type 2 diabetes (T2D) in patients with compensated cirrhosis is challenging due to hypoglycemic risk, altered pharmacokinetics, and the lack of robust evidence on the risk/benefit ratio of various drugs. Suboptimal glycemic control accelerates the progression of cirrhosis, while the frequent coexistence of nonalcoholic fatty liver disease (NAFLD) with T2D highlights the need for a multifactorial therapeutic approach.

METHODS

A literature search was performed in Medline, Google Scholar and Scopus databases till July 2023, using relevant keywords to extract studies regarding the management of T2D in patients with compensated cirrhosis.

RESULTS

Metformin, sodium-glucose co-transporter-2 inhibitors (SGLT2i), and glucagon-like peptide-1 receptor agonists (GLP-1 RA) are promising treatment options for patients with T2D and compensated liver cirrhosis, offering good glycemic control with minimal risk of hypoglycemia, while their pleiotropic actions confer benefits on NAFLD and body weight, and decrease cardiorenal risk. Sulfonylureas cause hypoglycemia, thus should be avoided, while in specific studies, dipeptidyl peptidase-4 inhibitors have been correlated with increased risk of decompensation and variceal bleeding. Despite the benefits of thiazolidinediones in nonalcoholic steatohepatitis, concerns about edema and weight gain limit their use in compensated cirrhosis. Insulin does not exert hepatotoxic effects and can be administered safely in combination with other drugs; however, the risk of hypoglycemia should be considered.

CONCLUSIONS

The introduction of new hepatoprotective diabetes drugs into clinical practice, including tirzepatide, SGLT2i, and GLP-1 RA, sets the stage for future trials to investigate the ideal therapeutic regimen for people with T2D and compensated cirrhosis.

Acarbose diminishes postprandial suppression of bone resorption in patients with type 2 diabetes

AIMS

The alpha-glucosidase inhibitor acarbose is an antidiabetic drug delaying assimilation of carbohydrates and, thus, increasing the amount of carbohydrates in the distal parts of the intestines, which in turn increases circulating levels of the gut-derived incretin hormone glucagon-like peptide 1 (GLP-1). As GLP-1 may suppress bone resorption, acarbose has been proposed to potentiate meal-induced suppression of bone resorption. We investigated the effect of acarbose treatment on postprandial bone resorption in patients with type 2 diabetes and used the GLP-1 receptor antagonist exendin(9-39)NH₂ to disclose contributory effect of acarbose-induced GLP-1 secretion.

METHODS

In a randomised, placebo-controlled, double-blind, crossover study, 15 participants with metformin-treated type 2 diabetes (2 women/13 men, age 71 (57-85 years), BMI 29.7 (23.6-34.6 kg/m²), HbA1c 48 (40-74 mmol/mol)/6.5 (5.8-11.6 %) (median and range)) were subjected to two 14-day treatment periods with acarbose and placebo, respectively, separated by a six-week wash-out period. At the end of each period, circulating bone formation and resorption markers were assessed during two randomised 4-h liquid mixed meal tests (MMT) with infusions of exendin(9-39)NH₂ and saline, respectively. Glucagon-like peptide 2 (GLP-2) was also assessed.

RESULTS

Compared to placebo, acarbose impaired the MMT-induced suppression of CTX as assessed by baseline-subtracted area under curve (P = 0.0037) and nadir of CTX (P = 0.0128). During acarbose treatment, exendin(9-39)NH₂ infusion lowered nadir of CTX compared to saline (P = 0.0344). Neither parathyroid hormone or the bone formation marker procollagen 1 intact N-terminal propeptide were affected by acarbose or GLP-1 receptor antagonism. Acarbose treatment induced a greater postprandial GLP-2 response than placebo treatment (P = 0.0479) and exendin(9-39)NH₂ infusion exacerbated this (P = 0.0002).

CONCLUSIONS

In patients with type 2 diabetes, treatment with acarbose reduced postprandial suppression of bone resorption. Acarbose-induced GLP-1 secretion may contribute to this phenomenon as the impairment was partially reversed by GLP-1 receptor antagonism. Also, acarbose-induced reductions in other factors reducing bone resorption, e.g. glucose-dependent insulinotropic polypeptide, may contribute.

Higher mitochondrial DNA copy number is associated with metformin-induced weight loss

BACKGROUND

Considerable variability exists in response to metformin with few effective biomarkers to guide the treatment. Here we evaluated whether whole blood derived mitochondrial DNA copy number (mtDNA-CN) is a biomarker of metformin response as measured by glucose reduction or weight loss.

METHODS

Using data from the trial of Metformin (n = 304) and AcaRbose (n = 300) in Chinese as the initial Hypoglycaemic treatment (MARCH), we examined the association between mtDNA-CN and two metformin response outcomes of HbA1c reduction and weight loss. The acarbose arm was used as a comparator group. Whole blood mtDNA-CN was estimated by deep whole genome sequencing with adjustments for confounders. Multiple linear regression and repeated measurement analyses were used to evaluate the association between mtDNA-CN and drug response outcomes.

RESULTS

Here we show that glucose reduction is not significantly associated with mtDNA-CN and in either treatment arm. In the metformin arm, each increase of 1 SD in mtDNA-CN is significantly (P = 0.006) associated with a 0.43 kg more weight loss. Repeated measurement analysis shows that after 16 weeks of metformin monotherapy, patients in the top tertile of mtDNA-CN consistently lost 1.21 kg more weight than those in the bottom tertile (P < 0.001). In comparison, mtDNA-CN is not significantly associated with acarbose-induced weight loss.

CONCLUSIONS

Patients with higher mtDNA-CN are likely to lose more weight upon metformin treatment, suggesting mtDNA-CN as a potential novel biomarker for more effective weight management in type 2 diabetes.

Metagenomic analysis reveals crosstalk between gut microbiota and glucose-lowering drugs targeting the gastrointestinal tract in Chinese patients with type 2 diabetes: a 6 month, two-arm randomised trial

AIMS/HYPOTHESIS

The use of oral glucose-lowering drugs, particularly those designed to target the gut ecosystem, is often observed in association with altered gut microbial composition or functional capacity in individuals with type 2 diabetes. The gut microbiota, in turn, plays crucial roles in the modulation of drug efficacy. We aimed to assess the impacts of acarbose and vildagliptin on human gut microbiota and the relationships between pre-treatment gut microbiota and therapeutic responses.

METHODS

This was a randomised, open-labelled, two-arm trial in treatment-naive type 2 diabetes patients conducted in Beijing between December 2016 and December 2017. One hundred participants with overweight/obesity and newly diagnosed type 2 diabetes were recruited from the Pinggu Hospital and randomly assigned to the acarbose (n=50) or vildagliptin (n=50) group using sealed envelopes. The treatment period was 6 months. Blood, faecal samples and visceral fat data from computed tomography images were collected before and after treatments to measure therapeutic outcomes and gut microbiota. Metagenomic datasets from a previous type 2 diabetes cohort receiving acarbose or glipizide for 3 months were downloaded and processed. Statistical analyses were applied to identify the treatment-related changes in clinical variables, gut microbiota and associations.

RESULTS

Ninety-two participants were analysed. After 6 months of acarbose (n=44) or vildagliptin (n=48) monotherapy, both groups achieved significant reductions in HbA_1c (from 60 to 46 mmol/mol [from 7.65% to 6.40%] in the acarbose group and from 59 to 44 mmol/mol [from 7.55% to 6.20%] in the vildagliptin group) and visceral fat areas (all adjusted p values for pre-post comparisons <0.05). Both arms showed drug-specific and shared changes in relative abundances of multiple gut microbial species and pathways, especially the common reductions in Bacteroidetes species. Three months and 6 months of acarbose-induced changes in microbial composition were highly similar in type 2 diabetes patients from the two independent studies. Vildagliptin treatment significantly enhanced fasting active glucagon-like peptide-1 (GLP-1) levels. Baseline gut microbiota, rather than baseline GLP-1 levels, were strongly associated with GLP-1 response to vildagliptin, and to a lesser extent with GLP-1 response to acarbose.

CONCLUSIONS/INTERPRETATION

This study reveals common microbial responses in type 2 diabetes patients treated with two glucose-lowering drugs targeting the gut differently and acceptable performance of baseline gut microbiota in classifying individuals with different GLP-1 responses to vildagliptin. Our findings highlight bidirectional interactions between gut microbiota and glucose-lowering drugs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02999841 FUNDING: National Key Research and Development Project: 2016YFC1304901.

Revisiting the concept of incretin and enteroendocrine L-cells as type 2 diabetes mellitus treatment

The significant growth in type 2 diabetes mellitus (T2DM) prevalence strikes a common threat to the healthcare and economic systems globally. Despite the availability of several anti-hyperglycaemic agents in the market, none can offer T2DM remission. These agents include the prominent incretin-based therapy such as glucagon-like peptide-1 receptor (GLP-1R) agonists and dipeptidyl peptidase-4 inhibitors that are designed primarily to promote GLP-1R activation. Recent interest in various therapeutically useful gastrointestinal hormones in T2DM and obesity has surged with the realisation that enteroendocrine L-cells modulate the different incretins secretion and glucose homeostasis, reflecting the original incretin definition. Targeting L-cells offers promising opportunities to mimic the benefits of bariatric surgery on glucose homeostasis, bodyweight management, and T2DM remission. Revising the fundamental incretin theory is an essential step for therapeutic development in this area. Therefore, the present review explores enteroendocrine L-cell hormone expression, the associated nutrient-sensing mechanisms, and other physiological characteristics. Subsequently, enteroendocrine L-cell line models and the latest L-cell targeted therapies are reviewed critically in this paper. Bariatric surgery, pharmacotherapy and new paradigm of L-cell targeted pharmaceutical formulation are discussed here, offering both clinician and scientist communities a new common interest to push the scientific boundary in T2DM therapy.

Targeting the Enteroendocrine System for Treatment of Obesity

Mimetics of the anorexigenic gut hormone glucagon-like peptide 1 (GLP-1) were originally developed as insulinotropic anti-diabetic drugs but also evoke significant weight loss, leading to their recent approval as obesity therapeutics. Co-activation of receptors for GLP-1 and other gut hormones which reduce food intake - peptide YY (PYY_3-36), cholecystokinin (CCK) and glucose-dependent insulinotropic peptide (GIP) - is now being explored clinically to enhance efficacy. An alternative approach involves pharmacologically stimulating endogenous secretion of these hormones from enteroendocrine cells (EECs) to recapitulate the metabolic consequences of bariatric surgery, where highly elevated postprandial levels of GLP-1 and PYY_3-36 are thought to contribute to improved glycaemia and weight loss.

A head-to-head comparison review of biological and toxicological studies of isomaltulose, d-tagatose, and trehalose on glycemic control

Diabetes mellitus is the most common metabolic disorder contributing to significant morbidity and mortality in humans. Different preventive and therapeutic agents, as well as various pharmacological strategies or non-pharmacological tools, improve the glycemic profile of diabetic patients. Isomaltulose, d-tagatose, and trehalose are naturally occurring, low glycemic sugars that are not synthesized by humans but widely used in food industries. Various studies have shown that these carbohydrates can regulate glucose metabolism and provide support in maintaining glucose homeostasis in patients with diabetes, but also can improve insulin response, subsequently leading to better control of hyperglycemia. In this review, we discussed the anti-hyperglycemic effects of isomaltulose, D-tagatose, and trehalose, comparing their properties with other known sweeteners, and highlighting their importance for the development of the pharmaceutical and food industries.

Inhibitors of α-amylase and α-glucosidase: Potential linkage for whole cereal foods on prevention of hyperglycemia

The strategy of reducing carbohydrate digestibility by controlling the activity of two hydrolyzing enzymes (α-amylase and α-glucosidase) to control postprandial hyperglycemia is considered as a viable prophylactic treatment of type 2 diabetes mellitus (T2DM). Thus, the consumption of foods rich in hydrolyzing enzyme inhibitors is recommended for diet therapy of diabetes. Whole cereal products have gained increasing interests for plasma glucose-reducing effects. However, the mechanisms for whole cereal benefits in relation to T2DM are not yet fully understood, but most likely involve bioactive components. Cereal-derived phenolic compounds, peptides, nonstarch polysaccharides, and lipids have been shown to inhibit α-amylase and α-glucosidase activities. These hydrolyzing enzyme inhibitors seem to make whole cereals become nutritional strategies in managing postmeal glucose for T2DM. This review presents an updated overview on the effects provided by cereal-derived ingredients on carbohydrate digestibility. It suggests that there is some evidence for whole cereal intake to be beneficial in amelioration of T2DM through inhibiting α-glucosidase and α-amylase activities.

Effects of a novel combination of orlistat and acarbose on tolerability, appetite, and glucose metabolism in persons with obesity

OBJECTIVE

There is an unmet medical need for a safe and effective weight loss product with minimal systemic side-effects. In this study, the effect of a novel modified-release fixed-dose combination of orlistat and acarbose (MR-OA) was compared with conventional orlistat (CO) regarding tolerability, appetite and glucose metabolism.

METHODS

Sixty-seven men with obesity, aged 24 to 60 years with body mass indexes (BMIs) 33 to 40 kg m-2 or BMIs 30 to 32 kg m-2 and waist circumference above 102 cm were included. They were randomized to either three different doses of the test formulation MR-OA (60 mg orlistat/20 mg acarbose, 90/30 and 120/40) or CO (Xenical, 120 mg orlistat) for a 2-week study of daily treatment. The participants spent days 1 and 14 at the clinical research centre where they received standardized meals, had blood sampling and filled in questionnaires regarding tolerability and appetite after meals. In days 2 to 13, the participants were at home and continued to fill in the questionnaires daily.

RESULTS

In the MR-OA groups, reports of liquid and oily stools as well as faecal incontinence were fewer, whereas reports of gastric distension and flatulence were higher, compared with the CO group. More participants reported decreased hunger in the 90/30 and 120/40 MR-OA, and postprandial plasma glucose concentration was reduced in all MR-OA groups compared with CO.

CONCLUSIONS

This study shows that by using a modified-release dosage form, orlistat and acarbose can be combined without compromising tolerability. Furthermore, MR-OA shows promising effects regarding reduction of appetite and reduces postprandial glucose. Tolerability is coupled to compliance and thereby efficacy of a treatment; therefore, this novel combination MR-OA could be an effective approach for weight loss treatment. A follow-up study in a more diverse population and for a longer duration with weight loss as primary outcome variable is planned.

Spent coffee (Coffea arabica L.) grounds promote satiety and attenuate energy intake: A pilot study

We evaluated the effects of acute intake of biscuits (B) containing either spent coffee grounds (SCG), (added with fructooligosaccharides; SC-FOS) or SCG antioxidant dietary fiber (SCF), on satiety, energy intake as well as gastrointestinal tolerance of healthy overweight volunteers. The addition of SCG and SCF to the biscuits (SC-FOS-B and SCF-B) increased their protein (11.4% and 12.2%), and total dietary fiber (8.4% and 11.8%) contents. The SCF-B significantly increased satiety perception, impacting ad libitum energy intake compared to the traditional biscuits recipe (TB; no added fiber). Moreover, SC-FOS-B and SCF-B decreased (no-observed-adverse effect) the most frequently reported symptoms by the participants, demonstrating that doses up to 5 g of SCF (per biscuit portion; 45 g) are well tolerated. The use of SCF and SCG as functional ingredients represents a sustainable strategy for the coffee industry and also potentiates the reduction of overweight, one of the leading health problems among the population. PRACTICAL APPLICATIONS: The addition of SCF or SCG as food ingredients increases protein and the dietary fiber content of traditional biscuits. SCF can slow gastric emptying, modulate appetite and thus body weight. SCF attenuates carbohydrate digestion blunting post-prandial blood glucose spikes reducing the risk of type 2 diabetes. SCF can be used as a functional ingredient to formulate foods with health benefits.

Glucagon-like peptide 1 (GLP-1)

BACKGROUND

The glucagon-like peptide-1 (GLP-1) is a multifaceted hormone with broad pharmacological potential. Among the numerous metabolic effects of GLP-1 are the glucose-dependent stimulation of insulin secretion, decrease of gastric emptying, inhibition of food intake, increase of natriuresis and diuresis, and modulation of rodent β-cell proliferation. GLP-1 also has cardio- and neuroprotective effects, decreases inflammation and apoptosis, and has implications for learning and memory, reward behavior, and palatability. Biochemically modified for enhanced potency and sustained action, GLP-1 receptor agonists are successfully in clinical use for the treatment of type-2 diabetes, and several GLP-1-based pharmacotherapies are in clinical evaluation for the treatment of obesity.

SCOPE OF REVIEW

In this review, we provide a detailed overview on the multifaceted nature of GLP-1 and its pharmacology and discuss its therapeutic implications on various diseases.

MAJOR CONCLUSIONS

Since its discovery, GLP-1 has emerged as a pleiotropic hormone with a myriad of metabolic functions that go well beyond its classical identification as an incretin hormone. The numerous beneficial effects of GLP-1 render this hormone an interesting candidate for the development of pharmacotherapies to treat obesity, diabetes, and neurodegenerative disorders.

Incretin Hormones: The Link between Glycemic Index and Cardiometabolic Diseases

This review aimed to describe the potential mechanisms by which incretin hormones could mediate the relationship between glycemic index and cardiometabolic diseases. A body of evidence from many studies suggests that low glycemic index (GI) diets reduces the risk for type 2 diabetes and coronary heart disease. In fact, despite the extensive literature on this topic, the mechanisms underlying unfavorable effects of high GI foods on health remain not well defined. The postprandial and hormonal milieu could play a key role in the relationship between GI and cardiovascular risk. Incretin hormones, glucagon-like peptide1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), are important regulators of postprandial homeostasis by amplifying insulin secretory responses. Response of GIP and GLP-1 to GI have been studied more in depth, also by several studies on isomaltulose, which have been taken as an ideal model to investigate the kinetics of incretin secretion in response to foods’ GI. In addition, extrapancreatic effects of these incretin hormones were also recently observed. Emerging from this have been exciting effects on several targets, such as body weight regulation, lipid metabolism, white adipose tissue, cardiovascular system, kidney, and liver, which may importantly affect the health status.

Augmented GLP-1 Secretion as Seen After Gastric Bypass May Be Obtained by Delaying Carbohydrate Digestion

CONTEXT

Exaggerated postprandial glucagon-like peptide-1 (GLP-1) secretion seems important for weight loss and diabetes remission after Roux-en-Y gastric bypass (RYGB) and may result from carbohydrate absorption in the distal small intestine.

OBJECTIVE

To investigate distal [GLP-1; peptide YY (PYY)] and proximal [glucose-dependent insulinotropic polypeptide (GIP)] gut hormone secretion in response to carbohydrates hydrolyzed at different rates. We hypothesized that slow digestion restricts proximal absorption, facilitating distal delivery of carbohydrates and thereby enhanced GLP-1 secretion in unoperated individuals, whereas this may not apply after RYGB.

DESIGN

Single-blinded, randomized, crossover study.

SETTING

Hvidovre Hospital, Hvidovre, Denmark.

PARTICIPANTS

Ten RYGB-operated patients and 10 unoperated matched subjects.

INTERVENTIONS

Four separate days with ingestion of different carbohydrate loads, either rapidly/proximally digested (glucose plus fructose; sucrose) or slowly/distally digested (isomaltulose; sucrose plus acarbose).

MAIN OUTCOME MEASURES

GLP-1 secretion (area under the curve above baseline). Secondary outcomes included PYY and GIP.

RESULTS

Isomaltulose enhanced secretion of GLP-1 nearly threefold (P = 0.02) and PYY ninefold (P = 0.08) compared with sucrose in unoperated subjects but had a modest effect after RYGB. Acarbose failed to increase sucrose induced GLP-1 secretion in unoperated subjects and diminished the responses by 50% after RYGB (P = 0.03). In both groups, GIP secretion was reduced by isomaltulose and even more so by sucrose plus acarbose when compared with sucrose intake.

CONCLUSIONS

GLP-1 secretion depends on the rate of carbohydrate digestion, but in a different manner after RYGB. Enhanced GLP-1 secretion is central after RYGB, but it may also be obtained in unoperated individuals by delaying hydrolysis of carbohydrates, pushing their digestion and absorption distally in the small intestine.

Changes in the gut microbiome and fermentation products concurrent with enhanced longevity in acarbose-treated mice

BACKGROUND

Treatment with the α-glucosidase inhibitor acarbose increases median lifespan by approximately 20% in male mice and 5% in females. This longevity extension differs from dietary restriction based on a number of features, including the relatively small effects on weight and the sex-specificity of the lifespan effect. By inhibiting host digestion, acarbose increases the flux of starch to the lower digestive system, resulting in changes to the gut microbiota and their fermentation products. Given the documented health benefits of short-chain fatty acids (SCFAs), the dominant products of starch fermentation by gut bacteria, this secondary effect of acarbose could contribute to increased longevity in mice. To explore this hypothesis, we compared the fecal microbiome of mice treated with acarbose to control mice at three independent study sites.

RESULTS

Microbial communities and the concentrations of SCFAs in the feces of mice treated with acarbose were notably different from those of control mice. At all three study sites, the bloom of a single bacterial taxon was the most obvious response to acarbose treatment. The blooming populations were classified to the largely uncultured Bacteroidales family Muribaculaceae and were the same taxonomic unit at two of the three sites. Propionate concentrations in feces were consistently elevated in treated mice, while the concentrations of acetate and butyrate reflected a dependence on study site. Across all samples, Muribaculaceae abundance was strongly correlated with propionate and community composition was an important predictor of SCFA concentrations. Cox proportional hazards regression showed that the fecal concentrations of acetate, butyrate, and propionate were, together, predictive of mouse longevity even while controlling for sex, site, and acarbose.

CONCLUSION

We observed a correlation between fecal SCFAs and lifespan in mice, suggesting a role of the gut microbiota in the longevity-enhancing properties of acarbose. Treatment modulated the taxonomic composition and fermentation products of the gut microbiome, while the site-dependence of the responses illustrate the challenges facing reproducibility and interpretation in microbiome studies. These results motivate future studies exploring manipulation of the gut microbial community and its fermentation products for increased longevity, testing causal roles of SCFAs in the observed effects of acarbose.

Comparative Effects of Proximal and Distal Small Intestinal Glucose Exposure on Glycemia, Incretin Hormone Secretion, and the Incretin Effect in Health and Type 2 Diabetes

OBJECTIVE

Cells releasing glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are distributed predominately in the proximal and distal gut, respectively. Hence, the region of gut exposed to nutrients may influence GIP and GLP-1 secretion and impact on the incretin effect and gastrointestinal-mediated glucose disposal (GIGD). We evaluated glycemic and incretin responses to glucose administered into the proximal or distal small intestine and quantified the corresponding incretin effect and GIGD in health and type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

Ten healthy subjects and 10 patients with T2DM were each studied on four occasions. On two days, a transnasal catheter was positioned with infusion ports opening 13 cm and 190 cm beyond the pylorus, and 30 g glucose with 3 g 3-O-methylglucose (a marker of glucose absorption) was infused into either site and 0.9% saline into the alternate site over 60 min. Matching intravenous isoglycemic clamp studies were performed on the other two days. Blood glucose, serum 3-O-methylglucose, and plasma hormones were evaluated over 180 min.

RESULTS

In both groups, blood glucose and serum 3-O-methylglucose concentrations were higher after proximal than distal glucose infusion (all P < 0.001). Plasma GLP-1 increased minimally after proximal, but substantially after distal, glucose infusion, whereas GIP increased promptly after both infusions, with concentrations initially greater, but less sustained, with proximal versus distal infusion (all P < 0.001). Both the incretin effect and GIGD were less with proximal than distal glucose infusion (both P ≤ 0.009).

CONCLUSIONS

The distal, as opposed to proximal, small intestine is superior in modulating postprandial glucose metabolism in both health and T2DM.

Efficacy and safety of combination therapy with an α-glucosidase inhibitor and a dipeptidyl peptidase-4 inhibitor in patients with type 2 diabetes mellitus: A systematic review with meta-analysis

AIMS/INTRODUCTION

The combination of dipeptidyl peptidase-4 (DPP4) inhibitors and α-glucosidase inhibitors (AGIs) might provide an additive or synergistic glucose-lowering effect, as they have a complementary mode of action. In the present study, we examined the efficacy and safety of the addition of a DPP4 inhibitor to patients with type 2 diabetes inadequately controlled with an AGI.

MATERIALS AND METHODS

We carried out an electronic search of MEDLINE, EMBASE, the Cochrane Library and Clinicaltrials.gov through October 2016. Randomized controlled trials written in English that compared DPP4 inhibitors plus AGI (DPP4i/AGI) and placebo plus AGI (PCB/AGI) in patients with type 2 diabetes were selected. Data on the study characteristics, efficacy and safety outcomes were extracted, and the risk of potential biases was assessed. The efficacy and safety of DPP4i/AGI and PCB/AGI were compared.

RESULTS

Of 756 potentially relevant published articles and 40 registered trials, five studies including 845 patients randomized to DPP4i/AGI and 832 patients randomized to PCB/AGI were included for meta-analysis. Compared with PCB/AGI, DPP4i/AGI showed a greater reduction in glycated hemoglobin (weighted mean difference -1.2%, 95% confidence interval -1.6 to -0.8), fasting plasma glucose and 2-h postprandial plasma glucose levels, with no increase in bodyweight. The risks of hypoglycemia and gastrointestinal adverse events were similar between DPP4i/AGI and PCB/AGI.

CONCLUSIONS

The addition of a DPP4 inhibitor to patients with type 2 diabetes inadequately controlled with an AGI achieved better glycemic control without further increasing the risk of weight gain and hypoglycemia.

Targeted intestinal delivery of incretin secretagogues-towards new diabetes and obesity therapies

A new strategy under development for the treatment of type 2 diabetes and obesity is to mimic some of the effects of bariatric surgery by delivering food-related stimuli to the distal gastrointestinal tract where they should enhance the release of gut hormones such as glucagon-like peptide-1 (GLP-1) and peptideYY (PYY). Methods include inhibition of food digestion and absorption in the upper GI tract, or oral delivery of stimuli in capsules or pelleted form to protect them against gastric degradation. A variety of agents have been tested in humans using capsules, microcapsules or pellets, delivering nutrients, bile acids, fatty acids and bitter compounds. This review examines the outcomes of these different approaches and supporting evidence from intestinal perfusion studies.

Associations between changes in glucagon-like peptide-1 and bodyweight reduction in patients receiving acarbose or metformin treatment

BACKGROUND

The present post hoc analysis investigated whether changes in endogenous glucagon-like peptide-1 (∆GLP-1) levels are associated with weight loss in newly diagnosed diabetes patients.

METHODS

In all, 784 subjects from the Metformin and AcaRbose in Chinese as initial Hypoglycemic treatment (MARCH) study were stratified according to ∆GLP-1. Changes in clinical and physiological parameters were evaluated across ∆GLP-1 subgroups (low, medium, and high) to assess correlations between ∆GLP-1 and weight loss in acarbose- versus metformin-treated groups.

RESULTS

After 24 weeks treatment, greater ∆GLP-1 was associated with significantly greater weight loss (-2 vs -1 kg in the medium/high vs low ∆GLP-1 groups, respectively) and reduction in body mass index (BMI; -0.88, -0.83, and -0.69 kg/m² in the high, medium, and low ∆GLP-1 groups, respectively). In the acarbose-treated group, there was a significant association between ∆GLP-1 and BMI reductions, and greater ∆GLP-1 across the high, medium, and low ∆GLP-1 groups was correlated with greater weight loss (-2.8, -2.1, and -1.9 kg, respectively) and reductions in fasting plasma glucose (-1.57, -1.28, and -1.02 mmol/L, respectively) at Week 24. No significant differences were found across ∆GLP-1 subgroups in metformin-treated patients (P > 0.05). Multivariate linear regression analysis revealed that gender, baseline BMI, and ∆GLP-1 at Week 24 were associated with weight loss. Baseline BMI and ∆GLP-1 in the acarbose-treated group and baseline BMI in the metformin-treated group predicted weight loss at Week 24.

CONCLUSION

Changes in GLP-1 levels are associated with weight loss in newly diagnosed Chinese diabetes patients receiving acarbose.

The α-glucosidase inhibitor voglibose stimulates delayed gastric emptying in healthy subjects: a crossover study with a 13C breath test

The gastrointestinal effects of α-glucosidase inhibitors have not been sufficiently investigated. The aim of this study was to determine whether a single dose of pre-prandial voglibose might affect the rate of gastric emptying, determined using the ¹³C breath test. Ten healthy male volunteers participated in this randomized, two-way crossover study. The subjects fasted overnight and received 0.2 mg voglibose or a placebo 2 h before a test meal. They were then served a liquid test meal consisting of 200 kcal per 200 ml that contained 100 mg ¹³C-acetate. Breath samples were collected under both conditions until 150 min after the meal. A comparison of the control and voglibose conditions revealed that for gastric emptying rates (with values expressed as median: range), T_1/2 [(87.9: 78.0–104.9 min) vs (88.4: 74.3–106.3 min), p = 1], T_lag [(47.1: 39.6–60.1 min) vs (45.4: 31.2–63.3 min), p = 0.432], β [(1.89: 1.68–2.18) vs (1.90: 1.35–2.15), p = 0.846] and κ [(0.81: 0.71–0.98) vs (0.81: 0.50–0.94), p = 0.922] did not significantly differ between conditions. A significant difference between the control and voglibose conditions was found for the GEC [(4.28: 4.09–4.44) vs (4.06: 3.69–4.50), p = 0.0138]. In conclusion, this study demonstrated that the ingestion of oral voglibose led to delayed gastric emptying of a liquid meal.

Ghrelin, CCK, GLP-1, and PYY(3-36): Secretory Controls and Physiological Roles in Eating and Glycemia in Health, Obesity, and After RYGB

The efficacy of Roux-en-Y gastric-bypass (RYGB) and other bariatric surgeries in the management of obesity and type 2 diabetes mellitus and novel developments in gastrointestinal (GI) endocrinology have renewed interest in the roles of GI hormones in the control of eating, meal-related glycemia, and obesity. Here we review the nutrient-sensing mechanisms that control the secretion of four of these hormones, ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and peptide tyrosine tyrosine [PYY(3-36)], and their contributions to the controls of GI motor function, food intake, and meal-related increases in glycemia in healthy-weight and obese persons, as well as in RYGB patients. Their physiological roles as classical endocrine and as locally acting signals are discussed. Gastric emptying, the detection of specific digestive products by small intestinal enteroendocrine cells, and synergistic interactions among different GI loci all contribute to the secretion of ghrelin, CCK, GLP-1, and PYY(3-36). While CCK has been fully established as an endogenous endocrine control of eating in healthy-weight persons, the roles of all four hormones in eating in obese persons and following RYGB are uncertain. Similarly, only GLP-1 clearly contributes to the endocrine control of meal-related glycemia. It is likely that local signaling is involved in these hormones' actions, but methods to determine the physiological status of local signaling effects are lacking. Further research and fresh approaches are required to better understand ghrelin, CCK, GLP-1, and PYY(3-36) physiology; their roles in obesity and bariatric surgery; and their therapeutic potentials.

Single-dose acarbose decreased glucose-dependent insulinotropic peptide and glucagon levels in Chinese patients with newly diagnosed type 2 diabetes mellitus after a mixed meal

BACKGROUND

Acarbose slows down the intestinal absorption of carbohydrates, but its effects on the secretion of incretins are still poorly known. This study aimed to examine the effects of single-dose acarbose on the secretion of incretins in patients with newly diagnosed type 2 diabetes mellitus (T2DM).

METHODS

In this pilot study, twenty-three patients diagnosed with T2DM were randomly assigned to the oral glucose tolerance test (OGTT) group (n = 11) and the mixed meal test (MMT) group (n = 12). Fourteen subjects with normal OGTT were included as controls. Plasma glucose, insulin, glucagon, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic peptide (GIP) were measured at 0 (fasting), 15, 30, 60, 90, and 120 min after nutrient load. A week later, controls underwent MMT, the OGTT group underwent OGTT receiving 100 mg acarbose, and the MMT group underwent MMT receiving 100 mg acarbose. The same blood markers were measured again.

RESULTS

No significant difference was observed in the OGTT group before and after administering acarbose. In the MMT group, postprandial levels of glucose (P < 0.01), insulin (P < 0.01), glucagon at 15 min (P < 0.05), glucagon area under the curve (AUC) (P < 0.05), GIP levels at 30 min (P < 0.05), and GIP AUC (P < 0.05) were decreased after receiving acarbose with a mixed meal, but GLP-1 levels and GLP-1 AUC did not change.

CONCLUSIONS

Single-dose acarbose could reduce the secretion of GIP and glucagon after a mixed meal in patients with newly diagnosed T2DM. The influence of acarbose on incretin levels could be related to the types of carbohydrate being consumed.

TRIAL REGISTRATION

This study was registered with the Chinese Clinical Trial Registry (Registration Number: ChiCTR-TRC-14004260 , Date of Registration: 2014-01-19).

Acarbose reduces body weight irrespective of glycemic control in patients with diabetes: results of a worldwide, non-interventional, observational study data pool

OBJECTIVE

The objective of this study is to examine the effect of acarbose, an alpha-glucosidase inhibitor, on body weight in a real-life setting by pooling data from post-marketing surveillance.

METHODS

Data from 10 studies were pooled (n=67,682) and the effect of acarbose on body weight was analysed taking into account baseline body weight, glycemic parameters and other baseline characteristics.

RESULTS

The mean relative reduction in body weight was 1.45 ± 3.24% at the 3-month visit (n=43,510; mean baseline 73.4 kg) and 1.40 ± 3.28% at the last visit (n=54,760; mean baseline 73.6 kg) (both p<0.0001). These reductions were dependent on baseline body weight (overweight: -1.33 ± 2.98% [n=13,498; mean baseline 71.6 kg]; obese: -1.98 ± 3.40% [n=20,216; mean baseline 81.3 kg]). When analysed by baseline glycemic parameter quartiles, the reduction was independent of fasting plasma glucose (FPG), postprandial plasma glucose (PPG), glycated hemoglobin (HbA1c) and postprandial glucose excursion (PPGE). A bivariate analysis of covariance identified female sex, South East Asian and East Asian ethnicity, younger age, higher body mass index, short duration of diabetes, and no previous treatment as factors likely to impact positively on body weight reduction with acarbose.

CONCLUSIONS

This post-hoc analysis showed that acarbose treatment reduces body weight independent of glycemic control status but dependent on baseline body weight.

Difference in postprandial GLP-1 response despite similar glucose kinetics after consumption of wheat breads with different particle size in healthy men

Purpose

Underlying mechanisms of the beneficial health effects of low glycemic index starchy foods are not fully elucidated yet. We varied the wheat particle size to obtain fiber-rich breads with a high and low glycemic response and investigated the differences in postprandial glucose kinetics and metabolic response after their consumption.

Methods

Ten healthy male volunteers participated in a randomized, crossover study, consuming ¹³C-enriched breads with different structures; a control bread (CB) made from wheat flour combined with wheat bran, and a kernel bread (KB) where 85 % of flour was substituted with broken wheat kernels. The structure of the breads was characterized extensively. The use of stable isotopes enabled calculation of glucose kinetics: rate of appearance of exogenous glucose, endogenous glucose production, and glucose clearance rate. Additionally, postprandial plasma concentrations of glucose, insulin, glucagon, incretins, cholecystokinin, and bile acids were analyzed.

Results

Despite the attempt to obtain a bread with a low glycemic response by replacing flour by broken kernels, the glycemic response and glucose kinetics were quite similar after consumption of CB and KB. Interestingly, the glucagon-like peptide-1 (GLP-1) response was much lower after KB compared to CB (iAUC, P < 0.005). A clear postprandial increase in plasma conjugated bile acids was observed after both meals.

Conclusions

Substitution of 85 % wheat flour by broken kernels in bread did not result in a difference in glucose response and kinetics, but in a pronounced difference in GLP-1 response. Thus, changing the processing conditions of wheat for baking bread can influence the metabolic response beyond glycemia and may therefore influence health.

Electronic supplementary material

The online version of this article (doi:10.1007/s00394-016-1156-6) contains supplementary material, which is available to authorized users.

Incretins

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the known incretin hormones in humans, released predominantly from the enteroendocrine K and L cells within the gut. Their secretion is regulated by a complex of integrated mechanisms involving direct contact for the activation of different chemo-sensors on the brush boarder of K and L cells and several indirect neuro-immuno-hormonal loops. The biological actions of GIP and GLP-1 are fundamental determinants of islet function and blood glucose homeostasis in health and type 2 diabetes. Moreover, there is increasing recognition that GIP and GLP-1 also exert pleiotropic extra-glycaemic actions, which may represent therapeutic targets for human diseases. In this review, we summarise current knowledge of the biology of incretin hormones in health and metabolic disorders and highlight the therapeutic potential of incretin hormones in metabolic regulation.

Practical prospects for boosting hepatic production of the "pro-longevity" hormone FGF21

Fibroblast growth factor-21 (FGF21), produced mainly in hepatocytes and adipocytes, promotes leanness, insulin sensitivity, and vascular health while down-regulating hepatic IGF-I production. Transgenic mice overexpressing FGF21 enjoy a marked increase in median and maximal longevity comparable to that evoked by calorie restriction - but without a reduction in food intake. Transcriptional factors which promote hepatic FGF21 expression include PPARα, ATF4, STAT5, and FXR; hence, fibrate drugs, elevated lipolysis, moderate-protein vegan diets, growth hormone, and bile acids may have potential to increase FGF21 synthesis. Sirt1 activity is required for optimal responsiveness of FGF21 to PPARα, and Sirt1 activators can boost FGF21 transcription. Conversely, histone deacetylase 3 (HDAC3) inhibits PPARα's transcriptional impact on FGF21, and type 1 deacetylase inhibitors such as butyrate therefore increase FGF21 expression. Glucagon-like peptide-1 (GLP-1) increases hepatic expression of both PPARα and Sirt1; acarbose, which increases intestinal GLP-1 secretion, also increases FGF21 and lifespan in mice. Glucagon stimulates hepatic production of FGF21 by increasing the expression of the Nur77 transcription factor; increased glucagon secretion can be evoked by supplemental glycine administered during post-absorptive metabolism. The aryl hydrocarbon receptor (AhR) has also been reported recently to promote FGF21 transcription. Bilirubin is known to be an agonist for this receptor, and this may rationalize a recent report that heme oxygenase-1 induction in the liver boosts FGF21 expression. There is reason to suspect that phycocyanorubin, a bilirubin homolog that is a metabolite of the major phycobilin in spirulina, may share bilirubin's agonist activity for AhR, and perhaps likewise promote FGF21 induction. In the future, regimens featuring a plant-based diet, nutraceuticals, and safe drugs may make it feasible to achieve physiologically significant increases in FGF21 that promote metabolic health, leanness, and longevity.

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.

Effects of Miglitol, Acarbose, and Sitagliptin on Plasma Insulin and Gut Peptides in Type 2 Diabetes Mellitus: A Crossover Study

INTRODUCTION

Both dipeptidyl peptidase-4 inhibitors and α-glucosidase inhibitors (α-GI) have been reported to change the incretin and insulin secretion. To examine the effects of acarbose, miglitol, and sitagliptin on glucose metabolism and secretion of gut peptides, we conducted a crossover study in patients with type 2 diabetes mellitus (T2DM).

METHODS

Eleven Japanese patients with T2DM underwent four meal tolerance tests with single administration of acarbose, miglitol, sitagliptin, or nothing. Fasting and postprandial plasma levels of glucose, insulin, glucagon, active glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), ghrelin, and des-acyl ghrelin were measured.

RESULTS

Early-phase insulin secretion was reduced following acarbose and miglitol, and the areas under the curve (AUC) of insulin at 180 min following acarbose and miglitol were significantly lower than sitagliptin. AUC of plasma glucose at 180 min after acarbose, miglitol, and sitagliptin tended to be lower than in controls, and plasma glucose levels at 30-60 min following miglitol were significantly lower than in controls. Plasma glucagon, ghrelin, and des-acyl ghrelin levels did not differ among the four conditions. Postprandial plasma active GLP-1 levels and AUC of GLP-1 increased significantly in both the sitagliptin and miglitol groups compared to control. Postprandial plasma total GIP levels increased following sitagliptin but decreased after acarbose and miglitol. Changes in incretin levels tended to be greater with miglitol than acarbose.

CONCLUSION

These results showed that sitagliptin and α-GIs, miglitol more so than acarbose, improved hyperglycemia in patients with T2DM after single administration, and had different effects on insulin and incretin secretion.

TRIAL REGISTRATION

UMIN-CTR number, UMIN000009981.

Distinct action of the α-glucosidase inhibitor miglitol on SGLT3, enteroendocrine cells, and GLP1 secretion

Oral ingestion of carbohydrate triggers glucagon-like peptide 1 (GLP1) secretion, but the molecular mechanism remains elusive. By measuring GLP1 concentrations in murine portal vein, we found that the ATP-sensitive K(+) (KATP) channel is not essential for glucose-induced GLP1 secretion from enteroendocrine L cells, while the sodium-glucose co-transporter 1 (SGLT1) is required, at least in the early phase (5 min) of secretion. By contrast, co-administration of the α-glucosidase inhibitor (α-GI) miglitol plus maltose evoked late-phase secretion in a glucose transporter 2-dependent manner. We found that GLP1 secretion induced by miglitol plus maltose was significantly higher than that by another α-GI, acarbose, plus maltose, despite the fact that acarbose inhibits maltase more potently than miglitol. As miglitol activates SGLT3, we compared the effects of miglitol on GLP1 secretion with those of acarbose, which failed to depolarize the Xenopus laevis oocytes expressing human SGLT3. Oral administration of miglitol activated duodenal enterochromaffin (EC) cells as assessed by immunostaining of phosphorylated calcium-calmodulin kinase 2 (phospho-CaMK2). In contrast, acarbose activated much fewer enteroendocrine cells, having only modest phospho-CaMK2 immunoreactivity. Single administration of miglitol triggered no GLP1 secretion, and GLP1 secretion by miglitol plus maltose was significantly attenuated by atropine pretreatment, suggesting regulation via vagal nerve. Thus, while α-GIs generally delay carbohydrate absorption and potentiate GLP1 secretion, miglitol also activates duodenal EC cells, possibly via SGLT3, and potentiates GLP1 secretion through the parasympathetic nervous system.

Acarbose, lente carbohydrate, and prebiotics promote metabolic health and longevity by stimulating intestinal production of GLP-1

The α-glucosidase inhibitor acarbose, which slows carbohydrate digestion and blunts postprandial rises in plasma glucose, has long been used to treat patients with type 2 diabetes or glucose intolerance. Like metformin, acarbose tends to aid weight control, postpone onset of diabetes and decrease risk for cardiovascular events. Acarbose treatment can favourably affect blood pressure, serum lipids, platelet aggregation, progression of carotid intima-media thickness and postprandial endothelial dysfunction. In mice, lifetime acarbose feeding can increase median and maximal lifespan-an effect associated with increased plasma levels of fibroblast growth factor 21 (FGF21) and decreased levels of insulin-like growth factor-I (IGF-I). There is growing reason to suspect that an upregulation of fasting and postprandial production of glucagon-like peptide-1 (GLP-1)-stemming from increased delivery of carbohydrate to L cells in the distal intestinal tract-is largely responsible for the versatile health protection conferred by acarbose. Indeed, GLP-1 exerts protective effects on vascular endothelium, the liver, the heart, pancreatic β cells, and the brain which can rationalise many of the benefits reported with acarbose. And GLP-1 may act on the liver to modulate its production of FGF21 and IGF-I, thereby promoting longevity. The benefits of acarbose are likely mimicked by diets featuring slowly-digested 'lente' carbohydrate, and by certain nutraceuticals which can slow carbohydrate absorption. Prebiotics that promote colonic generation of short-chain fatty acids represent an alternative strategy for boosting intestinal GLP-1 production. The health benefits of all these measures presumably would be potentiated by concurrent use of dipeptidyl peptidase 4 inhibitors, which slow the proteolysis of GLP-1 in the blood.

Early therapy for type 2 diabetes in China

Diabetes is a huge burden in China, where about 100 million people have been diagnosed with the disease. Treatments are needed that are optimal for treating Chinese patients with diabetes. Chinese patients with type 2 diabetes are characterised by having relatively low bodyweight and significant β-cell deterioration. β-cell failure results in deficiency of insulin secretion, particularly at the early phase of insulin secretion in Chinese patients. As a result, postprandial hyperglycaemia is more pronounced in Chinese patients with early type 2 diabetes than most other ethnic groups. These characteristics point to the key strategies when considering early therapy for Chinese patients with type 2 diabetes, including control of postprandial hyperglycaemia and β-cell preservation. Besides metformin, insulin secretagogues and α-glucosidase inhibitors that target postprandial hyperglycaemia are recommended for drug-naive patients. Short-term intensive insulin therapy is suggested for patients with severe hyperglycaemia at diagnosis to help restore β-cell function. Use of incretin-based drugs is also recommended when treatment fails with metformin, insulin secretagogues, and α-glucosidase inhibitors. Although data on antidiabetic drugs in Chinese patients are growing, there are still gaps in the evidence base. Research is needed to strengthen the evidence-based treatment guidelines for Chinese patients with type 2 diabetes.

Effects of miglitol, sitagliptin, and initial combination therapy with both on plasma incretin responses to a mixed meal and visceral fat in over-weight Japanese patients with type 2 diabetes. "the MASTER randomized, controlled trial"

AIM

To assess changes in circulating incretin levels and body fat compositions with initial combination therapy with α-glucosidase inhibitor and dipeptidyl peptidase-4 inhibitor in patients with type 2 diabetes (T2D).

METHODS

In this multicenter open-label 24-week trial, Japanese over-weight (BMI ≥ 25 kg/m(2)) patients with T2D not taking medication or taking metformin and/or sulfonylurea were randomly assigned to receive either 50mg of miglitol three times a day (M, n=14), 50mg of sitagliptin once a day (S, n=14), or a combination of both (M+S, n=13). Changes in plasma incretin levels during a meal tolerance test (MTT) and body fat composition with impedance method were evaluated.

RESULTS

During MTT, postprandial plasma glucose levels decreased more after M+S than after M or S, and postprandial serum insulin levels decreased significantly after M and M+S whereas they increased after S. After M, active gastric inhibitory polypeptide (aGIP) decreased significantly at 30 min despite a significant increase at 120 min. After S, aGIP levels increased significantly throughout the MTT. After M+S, aGIP increased significantly at 0 and 120 min despite of significant decrease at 30 min. M+S further enhanced postprandial active glucagon-like peptide-1 levels during MTT than S did. Total body fat mass decreased significantly after M and M+S. Visceral fat mass decreased significantly only after M+S. Serum adiponectin increased significantly only after M+S.

CONCLUSIONS

In over-weight patients with T2D, M+S may have a beneficial effect on adiposity with relation to these different effects on two incretins.

Acarbose monotherapy and weight loss in Eastern and Western populations with hyperglycaemia: an ethnicity-specific meta-analysis

OBJECTIVE

To demonstrate if weight loss achieved with acarbose in individuals with hyperglycaemia differs between Eastern and Western populations.

METHODS

Databases and reference lists of clinical trials on acarbose were searched. Eligible studies were randomised controlled trials of acarbose monotherapy in populations with hyperglycaemia of more than 12-week duration that provided data on body weight (BW) or body mass index (BMI).

RESULTS

A total of 34 trials (6082 participants) were included. The effect of acarbose on BW was superior to that of placebo [weighted mean difference (WMD) = -0.52, 95% confidence interval (CI) -0.78 to -0.25], nateglinide (WMD = -1.33, 95% CI -1.51 to -0.75) and metformin (WMD = -0.67, 95% CI -1.14 to -0.20). Compared with placebo, there was a significantly greater weight loss of 0.92 kg (p < 0.05, I(2)  = 88.8%) with acarbose in Eastern populations (WMD = -1.20, 95% CI -1.51 to -0.75) than that in Western populations (WMD = -0.28, 95% CI -0.59 to 0.03). Across all studies, the acarbose group achieved a significantly larger absolute weight loss of (change from baseline) 1.35 kg (p < 0.05, I(2)  = 94.3%) in Eastern populations (WMD = -2.26, 95% CI -2.70 to -1.81) than in Western populations (WMD = -0.91, 95% CI -1.36 to -0.47). Nevertheless, the possible risk of bias in Eastern studies may influence the results.

CONCLUSION

The effect of acarbose on weight loss seems to be more pronounced in Eastern than in Western populations with hyperglycaemia, and is superior to that of placebo, nateglinide and metformin across both ethnicities.

Comparison of the effects of slowly and rapidly absorbed carbohydrates on postprandial glucose metabolism in type 2 diabetes mellitus patients: a randomized trial

BACKGROUND

Isomaltulose attenuates postprandial glucose and insulin concentrations compared with sucrose in patients with type 2 diabetes mellitus (T2DM). However, the mechanism by which isomaltulose limits postprandial hyperglycemia has not been clarified.

OBJECTIVE

The objective was therefore to assess the effects of bolus administration of isomaltulose on glucose metabolism compared with sucrose in T2DM.

DESIGN

In a randomized, double-blind, crossover design, 11 participants with T2DM initially underwent a 3-h euglycemic-hyperinsulinemic (0.8 mU · kg(-1) · min(-1)) clamp that was subsequently combined with 1 g/kg body wt of an oral (13)C-enriched isomaltulose or sucrose load. Hormonal responses and glucose kinetics were analyzed during a 4-h postprandial period.

RESULTS

Compared with sucrose, absorption of isomaltulose was prolonged by ∼50 min (P = 0.004). Mean plasma concentrations of insulin, C-peptide, glucagon, and glucose-dependent insulinotropic peptide were ∼10-23% lower (P < 0.05). In contrast, glucagon-like peptide 1 (GLP-1) was ∼64% higher (P < 0.001) after isomaltulose ingestion, which results in an increased insulin-to-glucagon ratio (P < 0.001) compared with sucrose. The cumulative amount of systemic glucose appearance was ∼35% lower after isomaltulose than after sucrose (P = 0.003) because of the reduction in orally derived and endogenously produced glucose and a higher first-pass splanchnic glucose uptake (SGU). Insulin action was enhanced after isomaltulose compared with sucrose (P = 0.013).

CONCLUSIONS

Ingestion of slowly absorbed isomaltulose attenuates postprandial hyperglycemia by reducing oral glucose appearance, inhibiting endogenous glucose production (EGP), and increasing SGU compared with ingestion of rapidly absorbed sucrose in patients with T2DM. In addition, GLP-1 secretion contributes to a beneficial shift in the insulin-to-glucagon ratio, suppression of EGP, and enhancement of SGU after isomaltulose consumption. This trial was registered at clinicaltrials.gov as NCT01070238.

Therapies for inter-relating diabetes and obesity - GLP-1 and obesity

INTRODUCTION

The dramatic rise in the prevalence of obesity and type 2 diabetes mellitus (T2DM) is associated with increased mortality, morbidity as well as public health care expenses worldwide. The need for effective and long-lasting pharmaceutical treatment is obvious. The record of anti-obesity drugs has been poor so far and the only efficient treatment today is bariatric surgery. Research has indicated that appetite inhibiting hormones from the gut may have a therapeutic potential in obesity. The gut incretin hormone, glucagon-like peptide-1 (GLP-1), appears to be involved in both peripheral and central pathways mediating satiety. Clinical trials have shown that two GLP-1 receptor agonists exenatide and liraglutide have a weight-lowering potential in non-diabetic obese individuals. Furthermore, they may also hold a potential in preventing diabetes as compared to other weight loss agents.

AREAS COVERED

The purpose of this review is to cover the background for the GLP-1-based therapies and their potential in obesity and pre-diabetes. Up-to-date literature on incretin-based therapies will be summarized with a special mention of their weight-lowering properties. The literature updated to August 2014 from PubMed was identified using the combinations: GLP-1, GLP-1 receptor agonists, incretins, obesity and pre-diabetes.

EXPERT OPINION

The incretin impairment, which seems to exist in both obesity and diabetes, may link these two pathologies and underlines the potential of GLP-1-based therapies in the prevention and treatment of these diseases.

Incretin enhancement without hyperinsulinemia: α-glucosidase inhibitors

The α-glucosidase inhibitors are a time-tested, but under-utilized, class of oral hypoglycemic effects. Recent understanding of the importance of the incretin pathway, coupled with evidence about the incretin enhancing effects of these molecules, is covered in this editorial. The authors call for greater recognition of the beneficial effects of this class of drugs in the management of Type 2 diabetes.

Cardiovascular risk stratification and management in pre-diabetes

Prediabetes, covering individuals with impaired fasting glycemia, impaired glucose tolerance, or high-risk HbA1c levels, is associated with a ∼20 % increased risk of developing cardiovascular disease (CVD) compared with normoglycemic individuals. It is well-known that lifestyle or pharmacologic interventions can prevent diabetes in prediabetic people; however, the evidence is less clear regarding prevention of CVD. Most diabetes prevention trials have failed to show beneficial effects on CVD morbidity and mortality despite significant improvements of CVD risk factors in individuals with prediabetes. Another challenge is how to estimate CVD risk in prediabetic people. In general, prediction models for CVD do not take glucose levels or prediabetes status into account, thereby underestimating CVD risk in these high-risk individuals. More evidence within risk stratification and management of CVD risk in prediabetes is needed in order to recommend useful and effective strategies for early prevention of CVD.

Effects of miglitol taken just before or after breakfast on plasma glucose, serum insulin, glucagon and incretin levels after lunch in men with normal glucose tolerance, impaired fasting glucose or impaired glucose tolerance

Aims/Introduction:  One of the reasons for the poor adherence to α-glucosidase inhibitor (αGI) treatment is the need to take medication three times a day. We hypothesized that the administration of miglitol might be effective for the next meal if the miglitol-induced inhibition of α-glucosidase activity persists until the next meal. In the present study, we evaluated whether the administration of miglitol just before or after breakfast was effective for postprandial glucose excursion after lunch without taking miglitol at lunch.

MATERIALS AND METHODS

  We measured the plasma glucose, serum insulin and glucagon, plasma active glucagon-like peptide-1 (GLP-1), and total glucose-dependent insulinotropic polypeptide levels in non-diabetic men. Miglitol was given to each patient according to four different intake schedules (control: no drug; intake 1: drug given just before breakfast [50 mg]; intake 2: drug given 30 min after the start of breakfast [50 mg]; intake 3: drug given at the same time as intake 2, but without eating breakfast [50 mg]).

RESULTS

  Both intake 1 and intake 2 had a smaller area under the curve (AUC) for plasma glucose excursion after lunch, compared with the control. Intake 2 had a larger AUC for active GLP-1 after lunch, compared with intake 1.

CONCLUSIONS

  Intake 1 and intake 2 can improve postprandial hyperglycemia after lunch. The results of the present study raise the possibility that the administration of miglitol twice a day might be effective and might help to improve treatment adherence among diabetic patients. This trial was registered with UMIN Clinical Trial Registry (no. UMIN000002896). (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00129.x, 2011).

Effects of consumption of main and side dishes with white rice on postprandial glucose, insulin, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 responses in healthy Japanese men

The co-ingestion of protein, fat and fibre with carbohydrate reportedly affects postprandial glucose, insulin and incretin (glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1)) responses. However, the effects of combination dishes with carbohydrate-rich foods at typically eaten amounts remain unclear. The objective of the present study was to evaluate the effects of consuming recommended amounts of side dishes with boiled white rice in the same meal on postprandial plasma glucose, insulin and incretin hormone responses. A total of nine healthy male volunteers consumed four different meals in a random order on separate days. The test meals were as follows: S, white rice; SM, addition of protein-rich main dishes to the S meal; SMF, addition of a fat-rich food item to the SM meal; SMFV, addition of vegetables to the SMF meal. Plasma glucose, GIP and GLP-1 and serum insulin concentrations were determined during a 3 h period after consumption of these meals. Postprandial glucose responses were lower after SMFV meal consumption than after consumption of the other meals. The incremental AUC for GIP (0–180 min) were largest after consumption of the SMF and SMFV meals, followed by that after SM meal consumption, and was smallest after S meal consumption (P< 0·05). Furthermore, we found GIP concentrations to be dose dependently increased by the fat content of meals of ordinary size, despite the amount of additional fat being small. In conclusion, the combination of recommended amounts of main and vegetable side dishes with boiled white rice is beneficial for lowering postprandial glucose concentrations, with an increased incretin response, when compared with white rice alone.

Efficacy of adding once- and thrice-daily voglibose in Japanese type 2 diabetic patients treated with alogliptin

We investigated the efficacy of once- and thrice-daily voglibose, an alpha-glucosidase inhibitor, as an add-on therapy to alogliptin, a dipeptidyl peptidase-4 inhibitor, on glycemic control in Japanese type 2 diabetic patients. In this 12-week, parallel-group, randomized, open-label, three-arm trial, 151 participants treated with alogliptin were randomly allocated to the following three arms; one was the group to initiate once-daily voglibose, another was to initiate thrice daily voglibose, and the other was the control group. The primary endpoint was the change of hemoglobin A1c levels at the end of the study, which was revealed to be significantly different among groups (p < 0.001). The once- and thrice-daily voglibose groups had a significantly greater reduction than the control group; the difference was -0.27% and -0.33% in the once- and thrice-daily voglibose group, respectively (both p < 0.001). No significant difference was observed between the two voglibose groups (p = 0.615). On the other hand, the increase of 1,5-anhydroglucitol levels were 3.3 and 5.5 μg/ml greater in the once- and thrice-daily voglibose groups than the control group (both p < 0.001). The thrice-daily voglibose group had a greater increase of 1,5- anhydroglucitol levels compared to the once-daily voglibose group (p = 0.005). In conclusion, once- and thrice-daily voglibose as an add-on to alogliptin significantly improved glycemic control in Japanese type 2 diabetic patients.

Acarbose compared with metformin as initial therapy in patients with newly diagnosed type 2 diabetes: an open-label, non-inferiority randomised trial

BACKGROUND

Metformin is the only first-line oral hypoglycaemic drug for type 2 diabetes recommended by international guidelines with proven efficacy, safety, and cost-effectiveness. However, little information exists about its use in Asian populations. We aimed to ascertain the effectiveness of the α-glucosidase inhibitor acarbose, extensively adopted in China, compared with metformin as the alternative initial therapy for newly diagnosed type 2 diabetes.

METHODS

In this 48-week, randomised, open-label, non-inferiority trial, patients who were newly diagnosed with type 2 diabetes, with a mean HbA1c of 7·5%, were enrolled from 11 sites in China. After a 4-week lifestyle modification run-in, patients were assigned to 24 weeks of monotherapy with metformin or acarbose as the initial treatment, followed by a 24-week therapy phase during which add-on therapy was used if prespecified glucose targets were not achieved. Primary endpoints were to establish whether acarbose was non-inferior to metformin in HbA1c reduction at week 24 and week 48 timepoints. The non-inferiority margin was 0·3%, with an expected null difference in the change from baseline to week 48 in HbA1c. Analysis was done on a modified intention-to-treat population. This study was registered with Chinese Clinical Trial Registry, number ChiCTR-TRC-08000231.

FINDINGS

Of the 788 patients randomly assigned to treatment groups, 784 patients started the intended study drug. HbA1c reduction at week 24 was -1·17% in the acarbose group and -1·19% in the metformin group. At week 48, the HbA1c reduction was -1·11% (acarbose) and -1·12% (metformin) with difference 0·01% (95% CI -0·12 to 0·14, p=0·8999). Six (2%) patients in the acarbose group and seven (2%) patients in the metformin group had serious adverse events, and two (1%) and four (1%) had hypoglycaemic episodes.

INTERPRETATION

This study provides evidence that acarbose is similar to metformin in efficacy, and is therefore a viable choice for initial therapy in Chinese patients newly diagnosed with type 2 diabetes.

FUNDING

Bayer Healthcare (China) and Double Crane Phama.

Linagliptin provides effective, well-tolerated add-on therapy to pre-existing oral antidiabetic therapy over 1 year in Japanese patients with type 2 diabetes

AIMS

To evaluate the long-term safety and efficacy of linagliptin as add-on therapy to one approved oral antidiabetic drug (OAD) in Japanese patients with type 2 diabetes mellitus and insufficient glycaemic control.

METHODS

This 52-week, multicentre, open-label, parallel-group study evaluated once-daily linagliptin 5 mg as add-on therapy to one OAD [biguanide, glinide, glitazone, sulphonylurea (SU) or α-glucosidase inhibitors (A-GI)] in 618 patients. After a 2-week run-in, patients on SU or A-GI were randomized to either linagliptin (once daily, 5 mg) or metformin (twice or thrice daily, up to 2250 mg/day) as add-on therapy. Patients receiving the other OADs received linagliptin add-on therapy (non-randomized).

RESULTS

Adverse events were mostly mild or moderate, and rates were similar across all groups. Hypoglycaemic events were rare, except in the SU group. Overall, 26 (5.8%) hypoglycaemic events were reported in patients receiving linagliptin (non-randomized). Hypoglycaemic events were similar for linagliptin and metformin added to A-GI (1/61 vs. 2/61, respectively) or SU (17/124 vs. 10/63, respectively). Significant reductions in glycated haemoglobin (HbA1c) levels (between -0.7 and -0.9%) occurred throughout the study period for the background therapy groups that received linagliptin (baseline HbA1c 7.9-8.1%). The decline in HbA1c levels was indistinguishable between linagliptin and metformin groups when administered as add-on therapy to A-GI or SU.

CONCLUSIONS

Once-daily linagliptin showed safety and tolerability over 1 year and provided effective add-on therapy leading to significant HbA1c reductions, similar to metformin, over 52 weeks in Japanese patients.

Effects of 24-week treatment with acarbose on glucagon-like peptide 1 in newly diagnosed type 2 diabetic patients: a preliminary report

Background

Treatment with the alpha-glucosidase inhibitor (AGI) acarbose is associated with a significant reduction the risk of cardiovascular events. However, the underlying mechanisms of this effect are unclear. AGIs were recently suggested to participate in stimulating glucagon-like peptide 1 (GLP-1) secretion. We therefore examined the effects of a 24-week treatment of acarbose on endogenous GLP-1, nitric oxide (NO) levels, nitric oxide synthase (NOS) activity, and carotid intima-media thickness (CIMT) in newly diagnosed patients with type 2 diabetes (T2D).

Methods

Blood was drawn from 24 subjects (14 male, 10 female, age: 50.7 ± 7.36 years, BMI: 26.64 ± 3.38 kg/m², GHbA1c: 7.00 ± 0.74%) with drug-naïve T2D at 0 and 120 min following a standard mixed meal for the measurements of active GLP-1, NO and NOS. The CIMT was measured prior to and following 24 weeks of acarbose monotherapy (mean dose: 268 mg daily).

Results

Following 24 weeks of acarbose treatment, both fasting and postprandial plasma GLP-1 levels were increased. In patients with increased postprandial GLP-1 levels, serum NO levels and NOS activities were also significantly increased and were positively related to GLP-1 levels. Although the CIMT was not significantly altered following treatment with acarbose, a decreased CIMT was negatively correlated with increased GLP-1 levels.

Conclusions

Twenty-four weeks of acarbose monotherapy in newly diagnosed patients with T2D is associated with significantly increased levels of both fasting and postprandial GLP-1 as well as significantly increased NO levels and NOS activity for those patients in whom postprandial GLP-1 levels were increased. Therefore, the benefits of acarbose on cardiovascular risk may be related to its stimulation of GLP-1 secretion.

Miglitol administered before breakfast increased plasma active glucagon-like peptide-1 (GLP-1) levels after lunch in patients with type 2 diabetes treated with sitagliptin

We recently reported that the administration of miglitol alone just before breakfast improved postprandial hyperglycemia and increased active glucagon-like peptide-1 (GLP-1) levels after lunch in men without diabetes. Miglitol and dipeptidyl peptidase-4 inhibitors, such as sitagliptin, enhance plasma active GLP-1 concentrations via different mechanisms; therefore, combined therapy with these agents was more effective than monotherapy. In this study, we compared the effectiveness of the administration of miglitol alone just before breakfast on the plasma glucose, serum insulin and glucagon, and plasma incretin levels in sitagliptin-treated patients with type 2 diabetes. We measured the plasma glucose, serum insulin and glucagon, plasma active GLP-1, and total glucose-dependent insulinotropic polypeptide levels before breakfast, at 120 min after breakfast, before lunch, and 60 and 120 min after lunch in patients with diabetes who are receiving sitagliptin. This trial was performed for the following 2 days on each subject (Day 1: no miglitol, Day 2: miglitol alone [50 mg] administered just before breakfast). The area under the curve (AUC) of the plasma glucose levels after lunch in the miglitol-treated group tended to be lower than that in the miglitol-untreated group, but the difference was not statistically significant. Miglitol alone administered at breakfast increased the AUC of the active plasma GLP-1 levels after lunch in sitagliptin-treated patients with diabetes. Our results suggest that the once-daily administration of miglitol as a "GLP-1 enhancer" in combination with sitagliptin was effective for the treatment for patients with diabetes.

Potential new approaches to modifying intestinal GLP-1 secretion in patients with type 2 diabetes mellitus: focus on bile acid sequestrants

Type 2 diabetes mellitus is associated with a progressive decline in insulin-producing pancreatic β-cells, an increase in hepatic glucose production, and a decrease in insulin sensitivity. The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) stimulate glucose-induced insulin secretion; however, in patients with type 2 diabetes, the incretin system is impaired by loss of the insulinotropic effects of GIP as well as a possible reduction in secretion of GLP-1. Agents that modify GLP-1 secretion may have a role in the management of type 2 diabetes. The currently available incretin-based therapies, GLP-1 receptor agonists (incretin mimetics) and dipeptidyl peptidase-4 (DPP-4) inhibitors (CD26 antigen inhibitors) [incretin enhancers], are safe and effective in the treatment of type 2 diabetes. However, they may be unable to halt the progression of type 2 diabetes, perhaps because they do not increase secretion of endogenous GLP-1. Therapies that directly target intestinal L cells to stimulate secretion of endogenous GLP-1 could possibly prove more effective than treatment with GLP-1 receptor agonists and DPP-4 inhibitors. Potential new approaches to modifying intestinal GLP-1 secretion in patients with type 2 diabetes include G-protein-coupled receptor (GPCR) agonists, α-glucosidase inhibitors, peroxisome proliferator-activated receptor (PPAR) agonists, metformin, bile acid mimetics and bile acid sequestrants. Both the GPCR agonist AR231453 and the novel bile acid mimetic INT-777 have been shown to stimulate GLP-1 release, leading to increased insulin secretion and improved glucose tolerance in mice. Similarly, a study in insulin-resistant rats demonstrated that the bile acid sequestrant colesevelam increased GLP-1 secretion and improved glucose levels and insulin resistance. In addition, the bile acid sequestrant colestimide (colestilan) has been shown to increase GLP-1 secretion and decrease glucose levels in patients with type 2 diabetes; these results suggest that the glucose-lowering effects of bile acid sequestrants may be partly due to their ability to increase endogenous GLP-1 levels. Evidence suggests that GPCR agonists, α-glucosidase inhibitors, PPAR agonists, metformin, bile acid mimetics and bile acid sequestrants may represent a new approach to management of type 2 diabetes via modification of endogenous GLP-1 secretion.

Postprandial glucose, insulin and glucagon-like peptide 1 responses to sucrose ingested with berries in healthy subjects

Berries are often consumed with sucrose. They are also rich sources of polyphenols which may modulate glycaemia after carbohydrate ingestion. The present study investigated the postprandial glucose, insulin and glucagon-like peptide 1 (GLP-1) responses to sucrose ingested with berries, in comparison with a similar sucrose load without berries. A total of twelve healthy subjects were recruited to a randomised, single-blind, placebo-controlled crossover study. They participated in two meal tests on separate days. The berry meal was a purée (150 g) made of bilberries, blackcurrants, cranberries and strawberries with 35 g sucrose. The control meal included the same amount of sucrose and available carbohydrates in water. Fingertip capillary and venous blood samples were taken at baseline and at 15, 30, 45, 60, 90 and 120 min after starting to eat the meal. Glucose, insulin and GLP-1 concentrations were determined from the venous samples, and glucose also from the capillary samples. Compared to the control meal, ingestion of the berry meal resulted in lower capillary and venous plasma glucose and serum insulin concentrations at 15 min (P = 0·021,P < 0·007 andP = 0·028, respectively), in higher concentrations at 90 min (P = 0·028,P = 0·021 andP = 0·042, respectively), and in a modest effect on the GLP-1 response (P = 0·05). It also reduced the maximum increases of capillary and venous glucose and insulin concentrations (P = 0·009,P = 0·011 andP = 0·005, respectively), and improved the glycaemic profile (P < 0·001 andP = 0·003 for capillary and venous samples, respectively). These results suggest that the glycaemic control after ingestion of sucrose can be improved by simultaneous consumption of berries.