Recent advances in incretin-based therapies

Gut microbiome: Linking together obesity, bariatric surgery and associated clinical outcomes under a single focus

Obesity is increasingly prevalent in the post-industrial era, with increased mortality rates. The gut microbiota has a central role in immunological, nutritional and metabolism mediated functions, and due to its multiplexity, it is considered an independent organ. Modern high-throughput sequencing techniques have allowed phylogenetic exploration and quantitative analyses of gut microbiome and improved our current understanding of the gut microbiota in health and disease. Its role in obesity and its changes following bariatric surgery have been highlighted in several studies. According to current literature, obesity is linked to a particular microbiota profile that grants the host an augmented potential for calorie release, while limited diversity of gut microbiome has also been observed. Moreover, bariatric surgery procedures represent effective interventions for sustained weight loss and restore a healthier microbiota, contributing to the observed fat mass reduction and lean mass increase. However, newer evidence has shown that gut microbiota is only partially recovered following bariatric surgery. Moreover, several targets including FGF15/19 (a gut-derived peptide), could be responsible for the favorable metabolic changes of bariatric surgery. More randomized controlled trials and larger prospective studies that include well-defined cohorts are required to better identify associations between gut microbiota, obesity, and bariatric surgery.

Metabolic and Bariatric Surgery in Adolescents

PURPOSE OF REVIEW

The prevalence of obesity is increasing in all age groups. Following its success in adults, and with limited success using conservative therapies, metabolic and bariatric surgery (MBS) is increasingly being utilized in adolescents. This review highlights the current evidence and guidelines supporting its use.

RECENT FINDINGS

Safety and efficacy mirror results seen in adults. The most recent evidence, as outcomes enter the long term, suggests that comorbidity resolution, including diabetes and hypertension, can even outperform that of adults. Mental health problems persist despite good weight loss. Overall, the positive early weight and comorbidity outcomes are well sustained into the long term. There is a growing need to prevent and treat adolescent obesity. Current evidence supports the use of MBS in adolescents. Ongoing and future studies will provide 10-year outcomes and assist in the refinement of multimodal pathways incorporating MBS for the treatment of severe childhood obesity.

Electronic medical records-based comparison of glycemic control efficacy between sulfonylureas and dipeptidyl peptidase-4 inhibitors added on to metformin monotherapy in patients with type 2 diabetes

Sulfonylurea (SU) and dipeptidyl peptidase-4 (DPP-4) inhibitors are most common secondary agents that are added to metformin monotherapy. Real-world studies have become increasingly important in providing evidence of treatment effectiveness in clinical practice and real-world data could help appropriate therapeutic information. Therefore, this study aims to compare the glycemic effectiveness of SU and DPP-4 inhibitors, which are added to metformin monotherapy in real clinical practice using electronic medical record (EMR) data. EMR data of type 2 diabetes patients treated at Seoul National University Hospital from December 2002 to December 2012 were retrieved and analyzed. The patients were divided into three groups: patients who maintained metformin monotherapy (M), and patients who added SU (MS) or DPP-4 inhibitors (MD) to metformin monotherapy. The mean change in HbA1c level, the proportion of patients achieving the HbA1c target < 7.0%, proportion of patients with treatment failure, and probability of treatment failure occurrence and changes in prescription were evaluated to compare glycemic control efficacy between SU and DPP-4 inhibitors. The MS showed significantly greater reduction in the Hb1Ac level than MD. The proportion of patients achieving HbA1c < 7.0% is higher in MD, whereas the proportion of patients with treatment failure was greater in MS. The probability of the treatment failure and probability of changes in the prescription were lower in MD than MS with hazard ratio of 0.499 and 0.579, respectively. In conclusion, this real-world study suggested that DPP-4 inhibitors are expected to show more durable glycemic control efficacy than SU in long-term use.

Protective effects of DPP-4 inhibitor on podocyte injury in glomerular diseases

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) is a serine protease that inhibits the degradation of glucagon-like peptide 1. DPP-4 inhibitors are used worldwide to treat type 2 diabetes mellitus and were recently shown to have pleiotropic effects such as anti-oxidant, anti-inflammatory, and anti-fibrotic actions. DPP-4 inhibitors improve albuminuria and renal injury including glomerular damage independent of its hypoglycemic effect. Although DPP-4 is mainly expressed in the kidney, the physiological function of DPP-4 remains unclear.

METHODS

The localization of renal DPP-4 activity was determined in human renal biopsy specimens with glycyl-1-prolyl-4-methoxy-2-naphthylamide and the effects of a DPP-4 inhibitor were examined in human cultured podocyte.

RESULTS

DPP-4 activity under normal conditions was observed in some Bowman's capsular epithelial cells and proximal tubules, but not in the glomerulus. DPP-4 activity was observed in crescent formation in anti-neutrophil myeloperoxidase cytoplasmic antigen antibody nephritis, nodular lesions in diabetic nephropathy, and some podocytes in focal segmental glomerulosclerosis. Notably, the DPP-4 inhibitor saxagliptin suppressed DPP-4 activity in podocytes and the proximal tubules. To assess the effect of DPP-4 inhibitor on podocytes, human cultured podocytes were injured by Adriamycin, which increased DPP-4 activity; this activity was dose-dependently suppressed by saxagliptin. Treatment with saxagliptin maintained the structure of synaptopodin and RhoA. Saxagliptin also improved the detachment of podocytes.

CONCLUSIONS

DPP-4 activity induces degradation of synaptopodin and reduction of RhoA, resulting in destruction of the podocyte cytoskeleton. Saxagliptin may have pleiotropic effects to prevent podocyte injury.

Role of linagliptin in preventing the pathological progression of hepatic fibrosis in high fat diet and streptozotocin-induced diabetic obese rats

Liver fibrosis is a common complication of diabetes mellitus, with a major global public health concern. Linagliptin, a dipeptidyl peptidase-4 inhibitor (DPP-4), is classically used to treat type 2 diabetes mellitus and improves insulin resistance. Additional potential influences of linagliptin on liver fibrosis are still unclear. The present study was undertaken to investigate the therapeutic credit of linagliptin in hepatic fibrosis induced by a high-fat diet (HFD) and streptozotocin (STZ) in rats. Moreover, the mechanisms underline its anti-fibrotic effect were explored. To induce liver fibrosis with T2DM; male Sprague-Dawley albino rats were fed on a high-fat high-sucrose diet for 28 days then exposed to a single dose of STZ (30 mg/kg, IP). After two days of STZ injection, a diabetes confirmation test was done and all diabetic rats were constantly fed on HFD for thirty days with or without treatment with linagliptin (6 mg/kg). Hepatotoxicity markers, lipid profile screening, insulin signaling, inflammatory cytokines (TNF-α, IL-6, NF-κB p65), fibrosis markers (Collagen, α-SMA, TGF-β1) and histopathological studies including hematoxylin and eosin (H&E) as well Masson's trichrome stains were performed. In our preliminary study, linagliptin at a dose of 6 mg/kg was chosen as the optimum anti-diabetic dose in rats challenged with STZ. Linagliptin significantly improved insulin sensitivity and lipid profile and reduced inflammatory mediators, and collagen depositions in rats with liver fibrosis and T2DM. In conclusion, above and beyond its anti-diabetic effect, this study introduced linagliptin as a promising option for preventing the pathological progression of liver fibrosis associated with T2DM.

Proceedings of the 2017 ASPEN Research Workshop-Gastric Bypass: Role of the Gut

The goal of the National Institutes of Health-funded American Society for Parenteral and Enteral Nutrition 2017 research workshop (RW) "Gastric Bypass: Role of the Gut" was to focus on the exciting research evaluating gut-derived signals in modulating outcomes after bariatric surgery. Although gastric bypass surgery has undoubted positive effects, the mechanistic basis of improved outcomes cannot be solely explained by caloric restriction. Emerging data suggest that bile acid metabolic pathways, luminal contents, energy balance, gut mucosal integrity, as well as the gut microbiota are significantly modulated after bariatric surgery and may be responsible for the variable outcomes, each of which was rigorously evaluated. The RW served as a timely and novel academic meeting that brought together clinicians and researchers across the scientific spectrum, fostering a unique venue for interdisciplinary collaboration among investigators. It promoted engaging discussion and evolution of new research hypotheses and ideas, driving the development of novel ameliorative, therapeutic, and nonsurgical interventions targeting obesity and its comorbidities. Importantly, a critical evaluation of the current knowledge regarding gut-modulated signaling after bariatric surgery, potential pitfalls, and lacunae were thoroughly addressed.

Food Intake and Eating Behavior After Bariatric Surgery

Obesity is an escalating global chronic disease. Bariatric surgery is a very efficacious treatment for obesity and its comorbidities. Alterations to gastrointestinal anatomy during bariatric surgery result in neurological and physiological changes affecting hypothalamic signaling, gut hormones, bile acids, and gut microbiota, which coalesce to exert a profound influence on eating behavior. A thorough understanding of the mechanisms underlying eating behavior is essential in the management of patients after bariatric surgery. Studies investigating candidate mechanisms have expanded dramatically in the last decade. Herein we review the proposed mechanisms governing changes in eating behavior, food intake, and body weight after bariatric surgery. Additive or synergistic effects of both conditioned and unconditioned factors likely account for the complete picture of changes in eating behavior. Considered application of strategies designed to support the underlying principles governing changes in eating behavior holds promise as a means of optimizing responses to surgery and long-term outcomes.

Gut adaptation after metabolic surgery and its influences on the brain, liver and cancer

Metabolic surgery is the best treatment for long-term weight loss maintenance and comorbidity control. Metabolic operations were originally intended to change anatomy to alter behaviour, but we now understand that the anatomical changes can modulate physiology to change behaviour. They are no longer considered only mechanically restrictive and/or malabsorptive procedures; rather, they are considered metabolic procedures involving complex physiological changes, whereby gut adaptation influences signalling pathways in several other organs, including the liver and the brain, regulating hunger, satiation, satiety, body weight, glucose metabolism and immune functions. The integrative physiology of gut adaptation after these operations consists of a complex mechanistic web of communication between gut hormones, bile acids, gut microbiota, the brain and both enteric and central nervous systems. The understanding of nutrient sensing via enteroendocrine cells, the enteric nervous system, hypothalamic peptides and adipose tissue and of the role of inflammation has advanced our knowledge of this integrative physiology. In this Review, we focus on the adaptation of gut physiology to the anatomical alterations from Roux-en-Y gastric bypass and vertical sleeve gastrectomy and the influence of these procedures on food intake, weight loss, nonalcoholic fatty liver disease (NAFLD) and cancer. We also aim to demonstrate the underlying mechanisms that could explain how metabolic surgery could be used as a therapeutic option in NAFLD and certain obesity-related cancers.

Glucagon-like peptide-1 analogues exenatide and liraglutide exert inhibitory effect on the early phase of liver regeneration after partial hepatectomy in rats

Glucagon-like peptide-1 (GLP-1) is an incretin known for proliferative and antiapoptotic effects on various tissues. Exenatide and Liraglutide are GLP-1 analogues used in clinical practice as antidiabetic drugs. Since GLP-1 and its analogues exert significant effect on liver metabolism and since changes in intermediary metabolism play an important role in the process of liver regeneration, we decided to determine the effect of Exenatide and Liraglutide on the early phase of liver regeneration and selected metabolic parameters in a model of 2/3 partial hepatectomy (PHx) in rats. Animals were submitted either to PHx or laparotomy and received 3 doses of either GLP-1 analogues (Exenatide - 42 microg/kg b.w., Liraglutide - 0.75 mg/kg b.w.) or saline intraperitoneally. We analyzed body and liver weight, liver bromodeoxyuridine incorporation, liver content of DNA, triacylglycerols and cholesterol and biochemical serum parameters. Bromodeoxyuridine labeling was significantly lower in hepatectomized rats receiving either type of GLP-1 analogues when compared to hepatectomized controls. This effect was more pronounced in the Liraglutide group compared to Exenatide (p<0.001). In addition, liver DNA content was lower in hepatectomized rats receiving Liraglutide than in hepatectomized control rats (p<0.001). In conclusion, GLP-1 analogues Exenatide and Liraglutide significantly inhibited an early phase of liver regeneration after PHx in rats. This inhibitory effect was more pronounced in rats receiving Liraglutide.

The Dietary Furocoumarin Imperatorin Increases Plasma GLP-1 Levels in Type 1-Like Diabetic Rats

Imperatorin, a dietary furocoumarin, is found not only in medicinal plants, but also in popular culinary herbs, such as parsley and fennel. Recently, imperatorin has been shown to activate GPR119 in cells. Another GPR, GPR131, also called TGR5 or G-protein-coupled bile acid receptor 1 (GPBAR1), is known to regulate glucose metabolism. Additionally, TGR5 activation increases glucagon-like peptide (GLP-1) secretion to lower blood sugar levels in animals. Therefore, the present study aims to determine whether the effects of imperatorin on GLP-1 secretion are mediated by TGR5. First, we transfected cultured Chinese hamster ovary cells (CHO-K1 cells) with the TGR5 gene. Glucose uptake was confirmed in the transfected cells using a fluorescent indicator. Moreover, NCI-H716 cells, which secrete GLP-1, were used to investigate the changes in calcium concentrations and GLP-1 levels. In addition, streptozotocin (STZ)-induced type 1-like diabetic rats were used to identify the effects of imperatorin in vivo. Imperatorin dose-dependently increased glucose uptake in CHO-K1 cells expressing TGR5. In STZ diabetic rats, similar to the results in NCI-H716 cells, imperatorin induced a marked increase of GLP-1 secretion that was reduced, but not totally abolished, by a dose of triamterene that inhibited TGR5. Moreover, increases in GLP-1 secretion induced by imperatorin and GPR119 activation were shown in NCI-H716 cells. We demonstrated that imperatorin induced GLP-1 secretion via activating TGR5 and GPR119. Therefore, imperatorin shall be considered as a TGR5 and GPR119 agonist.

Glycyrrhizic acid increases glucagon like peptide-1 secretion via TGR5 activation in type 1-like diabetic rats

Glycyrrhizic acid (GA) is belonged to triterpenoid saponin that is contained in the root of licorice and is known to affect metabolic regulation. Recently, glucagon like peptide-1 (GLP-1) has widely been applied in diabetes therapeutics. However, the role of GLP-1 in GA-induced anti-diabetic effects is still unknown. Therefore, we are interested in understanding the association of GLP-1 with GA-induced effects. In type 1-like diabetic rats induced by streptozotocin (STZ-treated rats), GA increased the level of plasma GLP-1, which was blocked by triamterene at a dose sufficient to inhibit Takeda G-protein-coupled receptor 5 (TGR5). The direct effect of GA on TGR5 has been identified using the cultured Chinese hamster ovary cells (CHO-K1 cells) transfected TGR5 gene. Moreover, in intestinal NCI-H716 cells that secreted GLP-1, GA promoted GLP-1 secretion with a marked elevation of calcium levels. However, both effects of GA were reduced by ablation of TGR5 with siRNA in NCI-H716 cells. Therefore, we demonstrated that GA can enhance GLP-1 secretion through TGR5 activation.

Renoprotective Effects of the Dipeptidyl Peptidase-4 Inhibitor Sitagliptin: A Review in Type 2 Diabetes

Diabetic nephropathy (DN) is now the single commonest cause of end-stage renal disease (ESRD) worldwide and one of the main causes of death in diabetic patients. It is also acknowledged as an independent risk factor for cardiovascular disease (CVD). Since sitagliptin was approved, many studies have been carried out revealing its ability to not only improve metabolic control but also ameliorate dysfunction in various diabetes-targeted organs, especially the kidney, due to putative underlying cytoprotective properties, namely, its antiapoptotic, antioxidant, anti-inflammatory, and antifibrotic properties. Despite overall recommendations, many patients spend a long time well outside the recommended glycaemic range and, therefore, have an increased risk for developing micro- and macrovascular complications. Currently, it is becoming clearer that type 2 diabetes mellitus (T2DM) management must envision not only the improvement in glycaemic control but also, and particularly, the prevention of pancreatic deterioration and the evolution of complications, such as DN. This review aims to provide an overview of the current knowledge in the field of renoprotective actions of sitagliptin, namely, improvement in diabetic dysmetabolism, hemodynamic factors, renal function, diabetic kidney lesions, and cytoprotective properties.

Protective Effects of Vildagliptin against Pioglitazone-Induced Bone Loss in Type 2 Diabetic Rats

Long-term use of thiazolidinediones (TZDs) is associated with bone loss and an increased risk of fracture in patients with type 2 diabetes (T2DM). Incretin-based drugs (glucagon-like peptide-1 (GLP-1) agonists and dipeptidylpeptidase-4 (DPP-4) inhibitors) have several benefits in many systems in addition to glycemic control. In a previous study, we reported that exendin-4 might increase bone mineral density (BMD) by decreasing the expression of SOST/sclerostin in osteocytes in a T2DM animal model. In this study, we investigated the effects of a DPP-4 inhibitor on TZD-induced bone loss in a T2DM animal model. We randomly divided 12-week-old male Zucker Diabetic Fatty (ZDF) rats into four groups; control, vildagliptin, pioglitazone, and vildagliptin and pioglitazone combination. Animals in each group received the respective treatments for 5 weeks. We performed an intraperitoneal glucose tolerance test (IPGTT) before and after treatment. BMD and the trabecular micro-architecture were measured by DEXA and micro CT, respectively, at the end of the treatment. The circulating levels of active GLP-1, bone turnover markers, and sclerostin were assayed. Vildagliptin treatment significantly increased BMD and trabecular bone volume. The combination therapy restored BMD, trabecular bone volume, and trabecular bone thickness that were decreased by pioglitazone. The levels of the bone formation marker, osteocalcin, decreased and that of the bone resorption marker, tartrate-resistant acid phosphatase (TRAP) 5b increased in the pioglitazone group. These biomarkers were ameliorated and the pioglitazone-induced increase in sclerostin level was lowered to control values by the addition of vildagliptin. In conclusion, our results indicate that orally administered vildagliptin demonstrated a protective effect on pioglitazone-induced bone loss in a type 2 diabetic rat model.

Injectable and Thermosensitive Hydrogel Containing Liraglutide as a Long-Acting Antidiabetic System

Diabetes, a global epidemic, has become a serious threat to public health. The present study is aimed at constructing an injectable thermosensitive PEG-polyester hydrogel formulation of liraglutide (Lira), a "smart" antidiabetic polypeptide, in the long-acting treatment of type 2 diabetes mellitus. A total of three thermosensitive poly(ε-caprolactone-co-glycolic acid)-poly(ethylene glycol)-poly(ε-caprolactone-co-glycolic acid) (PCGA-PEG-PCGA) triblock copolymers with similar molecular weights but different ε-caprolactone-to-glycolide (CL-to-GA) ratios were synthesized. The polymer aqueous solutions exhibited free-flowing sols at room temperature and formed in situ hydrogels at body temperature. While the different bulk morphologies, stabilities of aqueous solutions, and the varying in vivo persistence time of hydrogels in ICR mice were found among the three copolymers, all of the Lira-loaded gel formulations exhibited a sustained drug release manner in vitro regardless of CL-to-GA ratios. The specimen with a powder form in the bulk state, a stable aqueous solution before heating, and an appropriate degradation rate in vivo was selected as the optimal carrier to evaluate the in vivo efficacy. A single injection of the optimal gel formulation showed a remarkable hypoglycemic efficacy up to 1 week in diabetic db/db mice. Furthermore, three successive administrations of this gel formulation within one month significantly lowered glycosylated hemoglobin and protected islets of db/db mice. As a result, a promising once-weekly delivery system of Lira was developed, which not only afforded long-term glycemic control but also significantly improved patient compliance.

Angelica dahurica Extracts Improve Glucose Tolerance through the Activation of GPR119

G protein-coupled receptor (GPR) 119 is expressed in pancreatic β-cells and intestinal L cells, and is involved in glucose-stimulated insulin secretion and glucagon-like peptide-1 (GLP-1) release, respectively. Therefore, the development of GPR119 agonists is a potential treatment for type 2 diabetes. We screened 1500 natural plant extracts for GPR119 agonistic actions and investigated the most promising extract, that from Angelica dahurica (AD), for hypoglycemic actions in vitro and in vivo. Human GPR119 activation was measured in GeneBLAzer T-Rex GPR119-CRE-bla CHO-K1 cells; intracellular cAMP levels and insulin secretion were measured in INS-1 cells; and GLP-1 release was measured in GLUTag cells. Glucose tolerance tests and serum plasma insulin levels were measured in normal C57BL6 mice and diabetic db/db mice. AD extract-treated cells showed significant increases in GPR119 activation, intracellular cAMP levels, GLP-1 levels and glucose-stimulated insulin secretion as compared with controls. In normal mice, a single treatment with AD extract improved glucose tolerance and increased insulin secretion. Treatment with multiple doses of AD extract or n-hexane fraction improved glucose tolerance in diabetic db/db mice. Imperatorin, phellopterin and isoimperatorin were identified in the active fraction of AD extract. Among these, phellopterin activated GPR119 and increased active GLP-1 and insulin secretion in vitro and enhanced glucose tolerance in normal and db/db mice. We suggest that phellopterin might have a therapeutic potential for the treatment of type 2 diabetes.

IDegLira: Redefining insulin optimisation using a single injection in patients with type 2 diabetes

In type 2 diabetes (T2D), treatment is optimised to minimise hyperglycaemia and the risk of microvascular complications. While there are a number of effective treatments, intensive treatment is associated with negative side effects such as increased hypoglycaemia and weight gain. With complementary modes of action, glucagon-like peptide-1 receptor agonists (GLP-1RAs) and a basal insulin in combination offer an alternative to basal-bolus therapy in T2D. This review describes the rationale behind this treatment combination and presents clinical data available for IDegLira, the first basal insulin (insulin degludec) and GLP-1RA (liraglutide) co-formulation available in one pen for a single injection daily.

Glucagon secretion is increased in patients with Type 2 diabetic nephropathy

AIMS

Currently little is known about the relationship between renal function, albuminuria and glucagon; we analyzed the secretion of glucagon (GLA) and C-peptide in Type 2 diabetic patients with different degrees of nephropathy.

METHODS

357 patients with Type 2 diabetes including 119 cases without nephropathy and 238 cases with nephropathy were divided into four groups according to the stages of diabetic nephropathy. Patients with diabetic nephropathy were further classified according to the level of estimated glomerular filtration rate (eGFR). OGTT and insulin, C-peptide, glucagon releasing tests were performed in all patients. Characteristics of glucagon and C-peptide secretion in different groups were compared. Glucagon/glucose ratio (GLA/GLU) and glucagon/insulin ratio (GLA/INS) were used to represent the inhibition of glucose or insulin on glucagon secretion, respectively.

RESULTS

With the progress of diabetic nephropathy, glucagon level increased significantly; the glucagon peak after glucose load delayed from 60 min to 120 min, whereas C-peptide level decreased significantly. Related factors analysis suggested that glucagon was independently correlated with eGFR. Further analysis showed that glucagon level was higher in group with eGFR<60 ml/min compared with that in group with eGFR≥60 ml/min. In addition, both GLA/INS and GLA/GLU were higher in group with eGFR<60 ml/min compared with those in group with eGFR≥60 ml/min.

CONCLUSIONS

Patients with Type 2 diabetic nephropathy have worsened islet alpha and beta cell function. Therefore medications based on the regulation of glucagon secretion may improve glycemic control and also be beneficial for delaying the progress of diabetic nephropathy.

Baseline ALT levels as a marker of glycemic response to treatment with GLP-1 receptor agonists

BACKGROUND AND OBJECTIVES

This study aimed to assess if ALT levels, as a marker of non-alcoholic fatty liver disease, may predict HbA1c response to treatment with GLP-1 receptor agonists (GLP-1 RAs).

PATIENTS AND METHODS

A retrospective, longitudinal, analytical study was conducted including patients with type 2 diabetes mellitus continuously treated with GLP-1 agonists (85% with liraglutide) for one year. Patients were divided into two groups according to baseline ALT levels, with 24 U/L (the median of the distribution) as the cut-off point. The dependent variable was HbA1c change (one-year follow-up minus baseline). The predictive value of ALT levels above 24 U/L and ALT change was analyzed using multivariate linear regression adjusted to age, gender, diabetes duration, type and dose of GLP-1 RA, baseline HbA1c, baseline body mass index (BMI), and change in BMI.

RESULTS

A total of 117 patients (48% females) aged 58.6 (SD 9.6) years were enrolled into the study. Treatment was associated with a change in ALT of -4.3 U/L (p=0.041) and a change in HbA1c of -1.1% (p<0.0001). Decreases in HbA1c (-1.41% vs -0.76%; p=0.045) and ALT (-9.25 vs 0.46 U/L; p=0.002) were significantly higher in patients with ALT levels above the median. In the multivariate analysis, both ALT>24 U/L (b=-0.74; 95%CI: -1.31 to -0.18; p=0.011) and ALT change (b=0.028; 95%CI: 0.010 to 0.046; p=0.003), were significant response predictors.

CONCLUSIONS

Elevated baseline transaminase values and decreased transaminase levels during follow-up are associated to a favorable glycemic response to GLP-1 RAs.

Incretin-based therapies for obesity treatment

Currently, obesity and its associated complications are considered major public health problems worldwide. Because the causes are multifactorial and complex, different treatment methods are used, which include diet and exercise, as well as the use of drugs, although they can have adverse side effects. A new target for the treatment of obesity may be the incretin system, which consists of hormones that seem to contribute to weight loss. In this sense, some studies have shown a relationship between weight loss and drugs related to incretin system, including glucagon-like peptide-1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors. The objective of this review is to summarize the association between the incretin system and obesity treatment.

Treatment escalation options for patients with type 2 diabetes after failure of exenatide twice daily or glimepiride added to metformin: results from the prospective European Exenatide (EUREXA) study

AIMS

To evaluate third-line thiazolidinedione (TZD) or glimepiride therapy in patients inadequately controlled on metformin + exenatide twice daily, and third-line exenatide twice daily in patients inadequately controlled on metformin + glimepiride.

METHODS

In this randomized, open-label, multicentre trial, 144 patients with type 2 diabetes inadequately controlled [glycated haemoglobin (HbA1c) >9% (75 mmol/mol) after 3 months' treatment or >7% (53 mmol/mol) at two consecutive visits 3 months apart, after 6 months' treatment] on metformin + exenatide twice daily were re-randomized to add-on TZD or glimepiride, and 166 patients inadequately controlled on metformin + glimepiride received add-on exenatide twice daily. Changes in HbA1c, body mass index (BMI), lipids, hypoglycaemia and vital signs were evaluated.

RESULTS

The median duration of triple therapy was ∼2 years. In patients inadequately controlled on metformin + exenatide twice daily, add-on TZD decreased HbA1c levels significantly better than add-on glimepiride: 130-week difference 0.48% [95% confidence interval (CI) 0.19-0.77] or 5.2 mmol/mol (95% CI 2.1-8.4; p = 0.001), but with significantly increased BMI and systolic blood pressure. The ratio of documented symptomatic (blood glucose ≤70 mg/dl [3.9 mmol/l]) hypoglycaemia rates for add-on glimepiride to add-on TZD was 8.48 (p < 0.0001). Add-on exenatide twice daily after metformin + glimepiride significantly reduced HbA1c levels: mean [standard deviation (s.d.)] change from baseline -0.35 (0.89)% [-3.8 (9.7) mmol/mol] and BMI: mean (s.d.) change from baseline -0.82 (1.9) kg/m(2) at 130 weeks, with a slightly increased rate of documented symptomatic hypoglycaemia from metformin + glimepiride (ratio 1.49).

CONCLUSIONS

TZD, but not glimepiride, was an effective and well tolerated third-line therapy in patients without glycaemic control after long-term therapy with metformin + exenatide twice daily. Exenatide twice daily was an effective and well tolerated third-line therapy in patients inadequately controlled on metformin + glimepiride.

DPP-4 inhibition with linagliptin ameliorates cognitive impairment and brain atrophy induced by transient cerebral ischemia in type 2 diabetic mice

Background

It is unclear whether dipeptidylpeptidase-4 (DPP-4) inhibition can counteract the impairment of cognitive function and brain injury caused by transient cerebral ischemia in type 2 diabetes. The present study was undertaken to test our hypothesis that linagliptin, a DPP-4 inhibitor, administration following transient cerebral ischemia can ameliorate cognitive impairment and brain injury in diabetic mice.

Methods

db/db mice, a model of obese type 2 diabetes, were subjected to transient cerebral ischemia by 17 min of bilateral common carotid artery occlusion (BCCAO), and were administered (1) vehicle or (2) linagliptin for 8 weeks or 1 week. For the long-term experiment on 8 weeks of linagliptin treatment, cognitive function, and volume and neuronal cell number of hippocampus and cortex were estimated in each group of mice. For the short-term experiment on 1 week of linagliptin treatment, cerebral IgG extravasation, Iba-1 positive cell number (reactive microglia), oxidative stress, and claudin-5 and gp91phox protein levels were measured in each group of mice.

Results

Linagliptin administration almost completely suppressed the circulating DPP-4 activity in db/db mice, but did not significantly reduce blood glucose or ameliorate glucose intolerance in db/db mice. Linagliptin administration following transient cerebral ischemia significantly counteracted cognitive impairment in diabetic mice, as estimated by water maze test and passive avoidance test. Linagliptin administration ameliorated the decrease in cerebral volume and neuronal cell number in hippocampus and cortex of diabetic mice. Linagliptin administration significantly reduced the increase in cerebral IgG extravasation and the increase in reactive microglia caused by transient cerebral ischemia in diabetic mice. Furthermore, linagliptin significantly suppressed the increase in cerebral oxidative stress in transient cerebral ischemia-subjected diabetic mice. Furthermore, linagliptin significantly increased cerebral claudin-5 and significantly decreased gp91phox in diabetic mice subjected to transient cerebral ischemia.

Conclusions

DPP-4 inhibition with linagliptin counteracted cognitive impairment and brain atrophy induced by transient cerebral ischemia in diabetic mice, independently of blood glucose lowering effect. This cerebroprotective effect of linagliptin was associated with the suppression of blood-brain barrier disruption and the attenuation of cerebral oxidative stress. Thus, our present work highlights DPP-4 inhibition as a promising therapeutic strategy for cognitive impairment and cerebral vascular complications in type 2 diabetes.

Minimizing Hypoglycemia and Weight Gain with Intensive Glucose Control: Potential Benefits of a New Combination Therapy (IDegLira)

Due to the progressive nature of type 2 diabetes (T2D), the majority of patients require increasing levels of therapy to achieve and maintain good glycemic control. At present, once patients become uncontrolled on oral antidiabetic therapies, the two primary treatment options are glucagon-like peptide-1 receptor agonists (GLP-1RAs) or basal insulin, although earlier use of GLP-1RAs has also been advocated. While both of these drug classes have proven efficacy in treating T2D, there can be limitations to their use in some patients, and resistance to further treatment intensification among both patients and physicians. More recently, treatment incorporating both a GLP-1RA and a basal insulin has been used successfully in the clinic and the first such combination product, IDegLira (insulin degludec + liraglutide), has recently been approved for use in Europe. IDegLira combines insulin degludec and the GLP-1RA liraglutide in a single injection. In both insulin-naïve and basal insulin-treated individuals with T2D, IDegLira has demonstrated greater reductions in glycated hemoglobin (HbA_1c) than either of the individual components, with a low rate of hypoglycemia and weight loss. IDegLira may provide a new option for patients requiring treatment intensification but for whom increased weight or a higher risk of hypoglycemia are barriers. This article discusses the rationale behind combining these two drug classes and reviews the available clinical evidence for the efficacy and safety of IDegLira.

An essential signal peptide peptidase identified in an RNAi screen of serine peptidases of Trypanosoma brucei

The serine peptidases of Trypanosoma brucei have been viewed as potential drug targets. In particular, the S9 prolyl oligopeptidase subfamily is thought to be a good avenue for drug discovery. This is based on the finding that some S9 peptidases are secreted and active in the mammalian bloodstream, and that they are a class of enzyme against which drugs have successfully been developed. We collated a list of all serine peptidases in T. brucei, identifying 20 serine peptidase genes, of which nine are S9 peptidases. We screened all 20 serine peptidases by RNAi to determine which, if any, are essential for bloodstream form T. brucei survival. All S9 serine peptidases were dispensable for parasite survival in vitro, even when pairs of similar genes, coding for oligopeptidase B or prolyl oligopeptidase, were targeted simultaneously. We also found no effect on parasite survival in an animal host when the S9 peptidases oligopeptidase B, prolyl oligopeptidase or dipeptidyl peptidase 8 were targeted. The only serine peptidase to emerge from the RNAi screen as essential was a putative type-I signal peptide peptidase (SPP1). This gene was essential for parasite survival both in vitro and in vivo. The growth defect conferred by RNAi depletion of SPP1 was rescued by expression of a functional peptidase from an RNAi resistant SPP1 gene. However, expression of catalytically inactive SPP1 was unable to rescue cells from the SPP1 depleted phenotype, demonstrating that SPP1 serine peptidase activity is necessary for T. brucei survival.

Alogliptin: a new dipeptidyl peptidase-4 inhibitor with potential anti-atherogenic properties

OBJECTIVES

The aim of this study is to evaluate the effects of alogliptin on metabolic profiles in relation to those of glycemic control.

PATIENTS AND METHODS

Treatment naïve subjects with type 2 diabetes received 12.5-25 mg/d alogliptin monotherapy (n = 59). A novel parameter called A1c index was used to assess the glycemic efficacy. The subjects were divided into three groups according to this index; super-responders, average responders and poor-responders. At 3 months, levels of the metabolic parameters were compared with those at baseline between super-responders (n = 20) and poor-responders (n = 21).

RESULTS

At baseline, total cholesterol, non-high density lipoprotein cholesterol and atherogenic index were significantly higher in super-responders than poor-responders. At 3 months, significant increases of beta-cell function (HOMA-B) and decreases of insulin resistance (HOMA-R) or these atherogenic lipids were observed in super-responders, while significant increases of HOMA-R were observed in poor-responders. Significant correlations were observed between A1c index and the changes of these atherogenic lipids. In super-responders, significant correlations were observed between the changes (Δ) of glycemic parameters (A1c index or fasting blood sugar) and ΔHOMA-R and/or ΔHOMA-B, while in poor-responders, significant correlations were observed between ΔHOMA-R and ΔHOMA-B. Lean subjects gained weight and the changes of body mass index had significant negative correlations with A1c index.

CONCLUSIONS

These results indicate that (1) glucose lowering efficacy of alogliptin is closely linked to atherogenic lipids. (2) alogliptin can down-regulate atherogenic lipids. (3) glycemic efficacy of alogliptin appears to be determined by the balance of its capacity in modulating insulin resistance and beta-cell function.

Potential side effects to GLP-1 agonists: understanding their safety and tolerability

INTRODUCTION

Glucagon-like peptide 1 receptor (GLP-1Rx) agonists might elicit unwelcome side effects and concerns have recently been raised about their safety.

AREAS COVERED

Available evidence about safety, tolerability and potential adverse events relative to GLP-1Rx agonists presently used. We searched the MEDLINE database using the terms: 'GLP-1 receptor agonists', 'Incretin therapy side effects', 'exenatide', ' liraglutide', 'exenatide long-acting release', 'lixisenatide'. Articles were selected on the basis of the study design and importance, in the light of authors' clinical experience and personal judgment. The main safety concern about GLP-1Rx agonists use is the possible association with increased risk of pancreatitis and/or tumors. This concern stems mainly from limited observations in animal models not confirmed in similar studies. Furthermore, clinical studies reporting association between GLP-1Rx agonist use and pancreatitis/cancer are marred by several biases and both clinical trials and post-marketing analyses failed to demonstrate a significant association.

EXPERT OPINION

As stated by both FDA and EMA, the safety concerns emerged so far about GLP-1RX agonists should not affect present prescribing habits. Thus, although a strict data monitoring must be encouraged, they should not prevent access to the benefits of an innovative treatment, such as GLP-1Rx agonists use, to a large diabetic population still confronted with unmet needs.

The clinical development program of lixisenatide: a once-daily glucagon-like Peptide-1 receptor agonist

Lixisenatide (AVE0010) is a once-daily glucagon-like peptide-1 (GLP-1) receptor agonist used in the treatment of type 2 diabetes. Phase II dose-finding and pharmacodynamic studies identified the 20 µg once-daily dose as having the optimum combination of efficacy, convenience and tolerability. Lixisenatide was prospectively investigated in a series of 11 multinational, randomised, controlled phase III trials (GLP-1 agonist AVE0010 in paTients with type 2 diabetes mellitus for Glycemic cOntrol and sAfety evaLuation [GetGoal] programme) that included a direct head-to-head study with exenatide. The GetGoal programme established the efficacy and safety profile of lixisenatide 20 µg once daily across the spectrum of patients with type 2 diabetes, including patients not treated with anti-diabetic agents, those failing on oral agents and as an adjunct to basal insulin therapy. The main efficacy endpoints were met in all studies, with the baseline to endpoint reductions in HbA1c consistently ranging from 0.7% to 1.0%. In a head-to-head comparison with exenatide 10 μg twice daily, lixisenatide 20 μg once daily was non-inferior for HbA1c reduction, achieved with threefold fewer patients with symptomatic hypoglycemia events and better gastrointestinal tolerability. Three randomised trials of lixisenatide treatment added to basal insulin showed significantly improved glycemic control over placebo, with pronounced postprandial glucose reductions and good tolerability. Discontinuations for adverse events were consistently low, ranging from 2.5% to 10.4%. As the provision of individualized care moves center stage in diabetes management, lixisenatide with once-daily dosing, a single maintenance dose and fixed-dose pens offers an important treatment option for type 2 diabetes.

DPP-4 inhibitor linagliptin ameliorates cardiovascular injury in salt-sensitive hypertensive rats independently of blood glucose and blood pressure

Background

It remains to be elucidated whether dipeptidylpeptidase-4 (DPP-4) inhibitor can ameliorate cardiovascular injury in salt-sensitive hypertension. The present study was undertaken to test our hypothesis that linagliptin, a DPP-4 inhibitor, administration initiated after onset of hypertension and cardiac hypertrophy can ameliorate cardiovascular injury in Dahl salt-sensitive hypertensive rats (DS rats).

Methods

High-salt loaded DS rats with established hypertension and cardiac hypertrophy were divided into two groups, and were orally given (1) vehicle or (2) linagliptin (3 mg/kg/day) once a day for 4 weeks, and cardiovascular protective effects of linagliptin in DS rats were evaluated.

Results

Linagliptin did not significantly affect blood pressure and blood glucose levels in DS rats. Linagliptin significantly lessened cardiac hypertrophy in DS rats, as estimated by cardiac weight and echocardiographic parameters. Linagliptin significantly ameliorated cardiac fibrosis, cardiac macrophage infiltration, and coronary arterial remodeling in DS rats. Furthermore, linagliptin significantly mitigated the impairment of vascular function in DS rats, as shown by the improvement of acetylcholine-induced or sodium nitroprusside-induced vascular relaxation by linagliptin. These cardiovascular protective effects of linagliptin were associated with the attenuation of oxidative stress, NADPH oxidase subunits, p67^phox and p22 ^phox, and angiotensin-converting enzyme (ACE).

Conclusions

Our results provided the experimental evidence that linagliptin treatment initiated after the appearance of hypertension and cardiac hypertrophy protected against cardiovascular injury induced by salt-sensitive hypertension, independently of blood pressure and blood glucose. These beneficial effects of linagliptin seem to be attributed to the reduction of oxidative stress and ACE.

Analyzing a dipeptide library to identify human dipeptidyl peptidase IV inhibitor

Human dipeptidyl peptidase IV (hDPPIV) inhibitors provide an effective strategy for the treatment of type 2 diabetes. Because certain peptides are known to act as hDPPIV inhibitors, a dataset of possible peptides with their inhibition intensities will facilitate the development of functional food for type 2 diabetes. In this study, we examined a total of 337 dipeptides with respect to their hDPPIV inhibitory effects. Amino acid residues at N-termini dominated their inhibition intensities. Particularly highly inhibitory dipeptides discovered included the following novel dipeptides: Thr-His, Asn-His, Val-Leu, Met-Leu, and Met-Met. Using our dataset, prime candidates contributing to the hDPPIV inhibitory effect of soy protein hydrolyzates were successfully identified. Possible dietary proteins potentially able to produce particularly highly hDPPIV inhibitory peptides are also discussed on the basis of the dataset.

Blood pressure and cardiovascular effects of new and emerging antidiabetic agents

Despite remarkable declines in US cardiovascular disease morbidity and mortality over the last several decades, the prevalence of risk factors such as type 2 diabetes and hypertension remains high, associated with increasing obesity rates. Although optimal glycemic control remains a primary focus to decrease the disease burden, the FDA has issued guidance recommendations for documenting cardiovascular disease-related safety with research trials on new antidiabetic agents with more demanding requirements compared to past approval of existing therapies. This review will discuss the public health impact of type 2 diabetes, specifically with comorbid hypertension; mechanisms of action of the newest antidiabetic drug classes; and preliminary findings and potential clinical significance of the favorable blood pressure and body weight effects of the sodium-glucose cotransporter 2 inhibitors and glucagon-like peptide 1 receptor agonists; and additionally discuss two recent large cardiovascular outcome trials with dipeptidyl peptidase-4 inhibitors.

Teneligliptin as an initial therapy for newly diagnosed, drug naive subjects with type 2 diabetes

BACKGROUND

Teneligliptin is a novel, highly selective dipeptidyl peptidase-4 (DPP-4) inhibitor. The aim of this study is to explore the glycemic and non-glycemic efficacies of teneligliptin as an initial therapy.

METHODS

Newly diagnosed, drug naive Japanese subjects with type 2 diabetes (T2DM) were assigned to 20 mg/day teneligliptin monotherapy (n = 31). At 3 months, levels of glycemic and other parameters were compared with those at baseline.

RESULTS

Significant reductions of HbA1c (from 10.34 ± 2.06 to 8.38 ± 2.23%) and fasting blood glucose (FGB, from 211.3 ± 68.4 to 167.3 ± 70.2 mg/dL) levels were observed without any clinically significant adverse events. However, significant increases of uric acids (UA) levels were observed and two subjects reported mild hypoglycemic events. Homeostasis model assessment-B (HOMA-B) levels significantly increased, while high HOMA-R levels significantly decreased. Significant correlations were observed between the changes (Δ) of HbA1c and those of HOMA-B, and between ΔFBG and ΔHOMA-R. No changes in lipid and body weight were noted.

CONCLUSIONS

Teneligliptin might be effectively and safely used as an initial therapy for newly diagnosed T2DM. Glycemic efficacy of teneligliptin is obtained through activating beta-cell function as well as decreasing insulin resistance.

Alogliptin: a new dipeptidyl peptidase-4 inhibitor for type 2 diabetes mellitus

OBJECTIVE

To review the pharmacology, pharmacokinetics, safety, and efficacy of alogliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor in the management of type 2 diabetes mellitus (T2DM).

DATA SOURCES

Searches were conducted in MEDLINE (1946-August 2013) and Embase (1974-August 2013) for English language articles using key words alogliptin, SYR-332, Nesina, Oseni, and Kazano. References of articles were reviewed to identify any additional sources.

STUDY SELECTION AND DATA EXTRACTION

Articles with adequate sample sizes, evaluating clinically relevant end points were included.

DATA SYNTHESIS

Alogliptin is a highly selective and potent competitive inhibitor of DPP-4. The DPP-4 enzyme rapidly inactivates the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide. GLP-1, which releases postprandial insulin in response to meals, is thought to be deficient in patients with T2DM. Studies evaluating the role of alogliptin in T2DM have shown significant reductions in blood glucose and hemoglobin A1C (A1C) levels. Alogliptin doses of 12.5 to 25 mg once daily reduced A1C by 0.56% to 0.59% as monotherapy. Patients given alogliptin in addition to other antidiabetic agentsexperienced additional A1C lowering of 0.4% to 0.8%. Side effects of alogliptin include nasopharyngitis, upper-respiratory tract infections, and headache. Alogliptin demonstrates a neutral effect on weight. A large trial evaluating the cardiovascular safety of alogliptin is currently being conducted.

CONCLUSIONS

Alogliptin is the fourth DDP-4 inhibitor approved in the US for the treatment of T2DM. It is available alone (Nesina) and in fixed-dose combinations with metformin (Kazano) and pioglitazone (Oseni). It has no demonstrable advantages over other agents in its class.

Unimolecular dual incretins maximize metabolic benefits in rodents, monkeys, and humans

We report the discovery and translational therapeutic efficacy of a peptide with potent, balanced co-agonism at both of the receptors for the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). This unimolecular dual incretin is derived from an intermixed sequence of GLP-1 and GIP, and demonstrated enhanced antihyperglycemic and insulinotropic efficacy relative to selective GLP-1 agonists. Notably, this superior efficacy translated across rodent models of obesity and diabetes, including db/db mice and ZDF rats, to primates (cynomolgus monkeys and humans). Furthermore, this co-agonist exhibited synergism in reducing fat mass in obese rodents, whereas a selective GIP agonist demonstrated negligible weight-lowering efficacy. The unimolecular dual incretins corrected two causal mechanisms of diabesity, adiposity-induced insulin resistance and pancreatic insulin deficiency, more effectively than did selective mono-agonists. The duration of action of the unimolecular dual incretins was refined through site-specific lipidation or PEGylation to support less frequent administration. These peptides provide comparable pharmacology to the native peptides and enhanced efficacy relative to similarly modified selective GLP-1 agonists. The pharmacokinetic enhancement lessened peak drug exposure and, in combination with less dependence on GLP-1-mediated pharmacology, avoided the adverse gastrointestinal effects that typify selective GLP-1-based agonists. This discovery and validation of a balanced and high-potency dual incretin agonist enables a more physiological approach to management of diseases associated with impaired glucose tolerance.

The association between postprandial urinary C-peptide creatinine ratio and the treatment response to liraglutide: a multi-centre observational study

AIMS

The response to glucagon-like peptide 1 receptor agonist treatment may be influenced by endogenous β-cell function. We investigated whether urinary C-peptide creatinine ratio assessed before or during liraglutide treatment was associated with treatment response.

METHODS

A single, outpatient urine sample for urinary C-peptide creatinine ratio was collected 2 h after the largest meal of the day among two separate groups: (1) subjects initiating liraglutide (0.6 → 1.2 mg daily) or (2) subjects already treated with liraglutide for 20-32 weeks. The associations between pretreatment and on-treatment urinary C-peptide creatinine ratio and HbA1c change at 32 weeks were assessed using univariate and multivariate analyses (the ratio was logarithm transformed for multivariate analyses). Changes in HbA1c according to pretreatment urinary C-peptide creatinine ratio quartiles are shown.

RESULTS

One hundred and sixteen subjects (70 pretreatment, 46 on treatment) with Type 2 diabetes from 10 diabetes centres were studied. In univariate analyses, neither pretreatment nor on-treatment urinary C-peptide creatinine ratio correlated with HbA1c change (Spearman rank correlation coefficient, r = -0.17, P = 0.17 and r = -0.20, P = 0.19, respectively). In multi-linear regression analyses, entering baseline HbA1c and log urinary C-peptide creatinine ratio, pretreatment and on-treatment log urinary C-peptide creatinine ratio became significantly associated with HbA1c change (P = 0.048 and P = 0.040, respectively). Mean (sd) HbA1c changes from baseline in quartiles 1 to 4 of pretreatment urinary C-peptide creatinine ratio were -3 ± 17 mmol/mol (-0.3 ± 1.6%) (P = 0.52), -12 ± 15 mmol/mol (-1.1 ± 1.4%) (P = 0.003), -11 ± 13 mmol/mol (-1.0 ± 1.2%) (P = 0.002) and -12±17 mmol/mol (-1.1±1.6%) (P=0.016), respectively.

CONCLUSIONS

Postprandial urinary C-peptide creatinine ratios before and during liraglutide treatment were weakly associated with the glycaemic response to treatment. Low pretreatment urinary C-peptide creatinine ratio may be more useful than higher values by predicting poorer glycaemic response.

Trp-Arg-Xaa tripeptides act as uncompetitive-type inhibitors of human dipeptidyl peptidase IV

Human dipeptidyl peptidase IV (hDPPIV, alternative name: CD26) inhibitors provide an effective strategy for the treatment of type 2 diabetes. Recently, our research group discovered a non substrate-mimic inhibitory dipeptide, Trp-Arg, by the systematic analysis of a dipeptide library. In the present study, a tripeptide library Trp-Arg-Xaa (where Xaa represents any amino acid) was analyzed to investigate the interactions of peptidergic inhibitors with hDPPIV. Trp-Arg-Glu showed the highest inhibitory effect toward hDPPIV (Ki=130 μM). All of the tested 19 Trp-Arg-Xaa tripeptides showed unique uncompetitive-type inhibition. The inhibition mechanism of Trp-Arg-Xaa is discussed based on the crystal structure of hDPPIV. The information obtained by this study suggests a novel concept for developing hDPPIV inhibitory peptides and drugs.

Can medical therapy mimic the clinical efficacy or physiological effects of bariatric surgery?

The number of bariatric surgical procedures performed has increased dramatically. This review discusses the clinical and physiological changes, and in particular, the mechanisms behind weight loss and glycaemic improvements, observed following the gastric bypass, sleeve gastrectomy and gastric banding bariatric procedures. The review then examines how close we are to mimicking the clinical or physiological effects of surgery through less invasive and safer modern interventions that are currently available for clinical use. These include dietary interventions, orlistat, lorcaserin, phentermine/topiramate, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, pramlintide, dapagliflozin, the duodenal-jejunal bypass liner, gastric pacemakers and gastric balloons. We conclude that, based on the most recent trials, we cannot fully mimic the clinical or physiological effects of surgery; however, we are getting closer. A 'medical bypass' may not be as far in the future as we previously thought, as the physician's armamentarium against obesity and type 2 diabetes has recently got stronger through the use of specific dietary modifications, novel medical devices and pharmacotherapy. Novel therapeutic targets include not only appetite but also taste/food preferences, energy expenditure, gut microbiota, bile acid signalling, inflammation, preservation of β-cell function and hepatic glucose output, among others. Although there are no magic bullets, an integrated multimodal approach may yield success. Non-surgical interventions that mimic the metabolic benefits of bariatric surgery, with a reduced morbidity and mortality burden, remain tenable alternatives for patients and health-care professionals.

The heart as an endocrine organ

The concept of the heart as an endocrine organ arises from the observation that the atrial cardiomyocytes in the mammalian heart display a phenotype that is partly that of endocrine cells. Investigations carried out between 1971 and 1983 characterised, by virtue of its natriuretic properties, a polypeptide referred to atrial natriuretic factor (ANF). Another polypeptide isolated from brain in 1988, brain natriuretic peptide (BNP), was subsequently characterised as a second hormone produced by the mammalian heart atria. These peptides were associated with the maintenance of extracellular fluid volume and blood pressure. Later work demonstrated a plethora of other properties for ANF and BNP, now designated cardiac natriuretic peptides (cNPs). In addition to the cNPs, other polypeptide hormones are expressed in the heart that likely act upon the myocardium in a paracrine or autocrine fashion. These include the C-type natriuretic peptide, adrenomedullin, proadrenomedullin N-terminal peptide and endothelin-1. Expression and secretion of ANF and BNP are increased in various cardiovascular pathologies and their levels in blood are used in the diagnosis and prognosis of cardiovascular disease. In addition, therapeutic uses for these peptides or related substances have been found. In all, the discovery of the endocrine heart provided a shift from the classical functional paradigm of the heart that regarded this organ solely as a blood pump to one that regards this organ as self-regulating its workload humorally and that also influences the function of several other organs that control cardiovascular function.

Early use of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) in type 2 diabetes

OBJECTIVE

To evaluate the efficacy and safety of the available glucagon-like peptide-1 receptor agonists (GLP-1 RAs) exenatide and liraglutide (marketed as Byetta * and Victoza † , respectively) in first- or second-line pharmacotherapy for type 2 diabetes (T2D), described here as 'early use'.

RESEARCH DESIGN AND METHODS

MEDLINE, EMBASE and Google Scholar databases were queried for clinical trial reports using the terms incretin, GLP-1, exenatide and liraglutide. Relevant articles were those that employed these agents in treatment-naïve patients with T2D and in patients who had failed on metformin monotherapy. Additional targeted searches were conducted on diabetes treatment guidelines and on the range of physiological responses to GLP-1 RAs. Most evidence is level I and II.

RESULTS

Effective therapy for T2D should be implemented early in the course of this progressive disease. The recently revised 2013 Canadian Diabetes Association (CDA) guidelines now identify the GLP-1 RAs among various injected and oral agents recommended for the management of T2D. The rationale for early use of GLP-1 RAs in T2D management is manifold: these agents offer effective management of hyperglycemia in early-stage T2D, minimal risk of hypoglycemia, weight loss, improvement in multiple non-glycemic cardiovascular risk factors, and potential enhancement of patient adherence to antihyperglycemic treatment. Available data from clinical trials support second-line use of GLP-1 RAs among patients who fail on metformin, as well as first-line use of these agents in a subset of T2D patients.

CONCLUSIONS

The ability to achieve glycemic targets using GLP-1 RAs while simultaneously avoiding hypoglycemia and weight gain could provide substantial reassurance to physicians and patients who might otherwise resist the transition to injected therapies. Exenatide and liraglutide represent appropriate second-line choices for pharmacological treatment of T2D, as indicated in the 2013 CDA guidelines.

Dipeptidyl peptidase IV and its inhibitors: therapeutics for type 2 diabetes and what else?

The proline-specific dipeptidyl aminopeptidase IV (DPP IV, DPP-4, CD26), widely expressed in mammalians, releases X-Pro/Ala dipeptides from the N-terminus of peptides. DPP IV is responsible of the degradation of the incretin peptide hormones regulating blood glucose levels. Several families of DPP IV inhibitors have been synthesized and evaluated. Their positive effects on the degradation of the incretins and the control of blood glucose levels have been demonstrated in biological models and in clinical trials. Presently, several DPP IV inhibitors, the "gliptins", are approved for type 2 diabetes or are under clinical evaluation. However, the gliptins may also be of therapeutic interest for other diseases beyond the inhibition of incretin degradation. In this Perspective, the biological functions and potential substrates of DPP IV enzymes are reviewed and the characteristics of the DPP IV inhibitors are discussed in view of type 2 diabetes and further therapeutic interest.

Mechanisms underlying weight loss after bariatric surgery

The clinical efficacy of bariatric surgery has encouraged the scientific investigation of the gut as a major endocrine organ. Manipulation of gastrointestinal anatomy through surgery has been shown to profoundly affect the physiological and metabolic processes that control body weight and glycaemia. The most popular bariatric surgical procedures are gastric bypass, adjustable gastric banding and vertical sleeve gastrectomy. Even though these procedures were designed with the aim of causing restriction of food intake and nutrient malabsorption, evidence suggests that their contributions to weight loss are minimal. Instead, these interventions reduce body weight by decreasing hunger, increasing satiation during a meal, changing food preferences and energy expenditure. In this Review, we have explored these mechanisms as well as their mediators. The hope is that that their in-depth investigation will enable the optimization and individualization of surgical techniques, the development of equally effective but safer nonsurgical weight-loss interventions, and even the understanding of the pathophysiology of obesity itself.

Antidiabetic agents: past, present and future

Treatment of diabetes mellitus requires, at a certain stage of its course, drug intervention. This article reviews the properties of available antidiabetic medications and highlights potential targets for developing newer and safer drugs. Antidiabetic agents are grouped in the article as parts I, II and III according to the history of development. Part I groups early developed drugs, during the 20th century, including insulin, sulfonylureas, the metiglinides, insulin sensitizers, biguanides and α-glucosidase inhibitors. Part II groups newer drugs developed during the early part of the 21st century, the past decade, including GLP-1 analogs, DPP-VI inhibitors, amylin analogs and SGLT2 inhibitors. Part III groups potential targets for future design of newer antidiabetic agents with less adverse effects than the currently available antidiabetic drugs.

Linagliptin: A thorough Characterization beyond Its Clinical Efficacy

Linagliptin, one of the five dipeptidyl peptidase-4 inhibitors available, has recently entered the market both in the US and in most European countries for treatment of type 2 diabetes mellitus. It presents a xanthine-based structure, and is characterized by unique pharmacokinetics, with non-linear profile, long terminal half-life allowing prolonged exposure to the drug. It is eliminated predominately through the intestinal tract and only minimally into urine, so that it can be administered, without any dose adjustment, in conditions of renal impairment. Linagliptin is effective in modifying all parameters of hyperglycemia either in monotherapy, or as add-on therapy, together with metformin or a sulfonylurea. It also exhibits a good tolerability profile with few side effects, absence (when used in monotherapy), or low risk (when in combination with a sulfonylurea) of hypoglycemia. More importantly it has a weight neutral effect. A comprehensive report of the literature on linagliptin is provided, paying attention in particular to preclinical studies, interactions with other drugs, safety and tolerability, and results obtained in animal models that highlight properties of linagliptin suggestive of potential additional uses. Particularly promising appear the data demonstrating a positive effect of linagliptin on metabolic dysfunction and renal and/or cardiovascular damage together with more recently reported effects of linagliptin on tissue repair and neuroprotection.