Effects of sitagliptin on counter-regulatory and incretin hormones during acute hypoglycaemia in patients with type 1 diabetes: a randomized double-blind placebo-controlled crossover study

Dipeptidyl Peptidase 4 (DPP4) as A Novel Adipokine: Role in Metabolism and Fat Homeostasis

Dipeptidyl peptidase 4 (DPP4) is a molecule implicated in the regulation of metabolic homeostasis and inflammatory processes, and it exerts its main action through its enzymatic activity. DPP4 represents the enzyme most involved in the catabolism of incretin hormones; thus, its activity impacts appetite, energy balance, and the fine regulation of glucose homeostasis. Indeed, DPP4 inhibitors represent a class of antidiabetic agents widely used for the treatment of Type 2 diabetes mellitus (T2DM). DPP4 also acts as an adipokine and is mainly secreted by the adipose tissue, mostly from mature adipocytes of the visceral compartment, where it exerts autocrine and paracrine activities. DPP4 can disrupt insulin signaling within the adipocyte and in other target cells and tissues, where it also favors the development of a proinflammatory environment. This is likely at the basis of the presence of elevated circulating DPP4 levels in several metabolic diseases. In this review, we summarize the most recent evidence of the role of the DPP4 as an adipokine-regulating glucose/insulin metabolism and fat homeostasis, with a particular focus on clinical outcomes associated with its increased secretion in the presence of adipose tissue accumulation and dysfunction.

Glucose-Lowering Therapy beyond Insulin in Type 1 Diabetes: A Narrative Review on Existing Evidence from Randomized Controlled Trials and Clinical Perspective

Background: In Type 1 diabetes (T1D), according to the most recent guidelines, the everyday glucose-lowering treatment is still restricted to the use of subcutaneous insulin, while multiple therapeutic options exist for Type 2 diabetes (T2D). Methods: For this narrative review we unsystematically screened PubMed and Embase to identify clinical trials which investigated glucose-lowering agents as an adjunct to insulin treatment in people with T1D. Published studies up to March 2022 were included. We discuss the safety and efficacy in modifying cardiovascular risk factors for each drug, the current status of research, and provide a clinical perspective. Results: For several adjunct agents, in T1D, the scientific evidence demonstrates improvements in HbA1c, reductions in the risk of hypoglycemia, and achievements of lower insulin requirements, as well as positive effects on cardiovascular risk factors, such as blood lipids, blood pressure, and weight. As the prevalence of obesity, the major driver for double diabetes, is rising, weight and cardiovascular risk factor management is becoming increasingly important in people with T1D. Conclusions: Adjunct glucose-lowering agents, intended to be used in T2D, bear the potential to beneficially impact on cardiovascular risk factors when investigated in the T1D population and are suggested to be more extensively considered as potentially disease-modifying drugs in the future and should be investigated for hard cardiovascular endpoints.

Optimising the Benefits of SGLT2 Inhibitors for Type 1 Diabetes

Sodium-glucose cotransporter 2 (SGLT2) inhibitor clinical studies in type 1 diabetes mellitus (T1DM) have demonstrated reduced HbA1c and lower glucose variability with increased time in optimal glucose range as well as additional benefits of reductions in weight and insulin dose without increasing the incidence of hypoglycaemia. However, the appropriate use of SGLT2 inhibitor therapies within clinical practise to treat people with T1DM remains unclear. In this article we have used consensus expert opinion alongside the available evidence, product indication and most recent clinical guidance to provide support for the diabetes healthcare community regarding the appropriate use of SGLT2 inhibitors, focussing on specific considerations for appropriate prescribing of dapagliflozin within the T1DM management pathway. Its purpose is to provide awareness of the issues surrounding treatment with dapagliflozin in T1DM as well as offer practical guidance that also includes a checklist tool for appropriate dapagliflozin prescribing. The checklist aims to support clinicians in identifying those people with T1DM most likely to benefit from dapagliflozin treatment as well as situations where caution may be required.Funding: AstraZeneca UK Ltd.

Incretin-based medications (GLP-1 receptor agonists, DPP-4 inhibitors) as a means to avoid hypoglycaemic episodes

Hypoglycaemia is common in both type 1 and type 2 diabetes and has both acute and long-term consequences. Therefore, a key to proper glucose-lowering therapy in diabetes is to avoid or prevent hypoglycaemia. Incretin therapy (DPP-4 inhibitors and GLP-1 receptor agonists) offers an advantage in this respect, because it reduces glucose with a low risk of hypoglycaemia, both in monotherapy and in combination with other therapies. The reason for this low risk of hypoglycaemia is the glucose dependency of action of incretin therapy and the sustainment of glucose counter-regulatory hormone responses to hypoglycaemia, in particular the glucagon response. Incretin therapy is also associated with a low risk of hypoglycaemia in patient groups which are especially vulnerable and susceptible for hypoglycaemia, e.g., subjects with renal impairment, elderly subjects and subjects with on-going insulin therapy. This review summarizes how incretin therapy may meet the challenges of hypoglycaemia and suggests that incretin therapy is a therapy of choice to avoid hypoglycaemia, both in the general diabetes population and in subjects with increased risk or vulnerability for hypoglycaemia.

DPP-4 Inhibition Leads to Decreased Pancreatic Inflammatory Profile and Increased Frequency of Regulatory T Cells in Experimental Type 1 Diabetes

Sitagliptin is a dipeptidyl peptidase-4 inhibitor (iDPP-4), which has been used for type 2 diabetes treatment. Recently, iDPP-4 has been described as a promising treatment of type 1 diabetes (T1D) but is still necessary to evaluate immune effects of sitagliptin. C57BL/6 mice were induced by multiple low doses of streptozotocin. Diabetes incidence, insulin, glucagon, glucagon-like peptide-1 (GLP-1) serum levels, and inflammatory cytokine levels were quantified in pancreas homogenate after 30 and 90 days of treatment. In addition, frequencies of inflammatory and regulatory T cell subsets were determined in the spleen and in the pancreatic lymph nodes. iDPP-4 decreased blood glucose level while increased GLP-1 and insulin levels. After long-term treatment, treated diabetic mice presented decreased frequency of CD4⁺CD26⁺ T cells and increased percentage of CD4⁺CD25^hiFoxp3⁺ T cells in the spleen. Besides, pancreatic lymph nodes from diabetic mice treated with iDPP-4 presented lower percentage of CD11b⁺ cells and decreased levels of inflammatory cytokines in the pancreas. Treatment of type 1 diabetic mice with iDPP-4 improved metabolic control, decreased inflammatory profile in the pancreatic microenvironment, and increased systemic regulatory T cell frequency. Therefore, we suggest the long-term use of sitagliptin as a feasible and effective therapy for T1D.

Understanding of type 1 diabetes mellitus: what we know and where we go

The incidence of type 1 diabetes mellitus (T1DM) in children and adolescents is increasing worldwide. Combined effects of genetic and environmental factors cause T1DM, which make it difficult to predict whether an individual will inherit the disease. Due to the level of self-care necessary in T1DM maintenance, it is crucial for pediatric settings to support achieving optimal glucose control, especially when adolescents are beginning to take more responsibility for their own health. Innovative insulin delivery systems, such as continuous subcutaneous insulin infusion (CSII), and noninvasive glucose monitoring systems, such as continuous glucose monitoring (CGM), allow patients with T1DM to achieve a normal and flexible lifestyle. However, there are still challenges in achieving optimal glucose control despite advanced technology in T1DM administration. In this article, disease prediction and current management of T1DM are reviewed with special emphasis on biomarkers of pancreatic β-cell stress, CSII, glucose monitoring, and several other adjunctive therapies.

Non-insulin pharmacological therapies for treating type 1 diabetes

INTRODUCTION

Despite intensified insulin treatment, many persons with type 1 diabetes (T1D) do not achieve glycemic and metabolic targets. Consequently, non-insulin chemical therapies that improve glycemic control and metabolic parameters without increasing the risk of adverse events (including hypoglycemia) are of interest as adjunct therapies to insulin.

AREAS COVERED

In this review, the authors discuss the efficacy and safety of non-insulin therapies, including pramlintide, glucagon-like peptide-1 (GLP-1) receptor agonists, dipeptidyl peptidase-4 inhibitors (DPP-4), sodium-glucose cotransporter (SGLT1 and SGLT2) inhibitors, metformin, sulfonylureas, and thiazolidinediones as add-on therapies to insulin in T1D.

EXPERT OPINION

The current evidence shows that the efficacy of non-insulin therapies as add-on therapies to insulin is minimal or modest with an average HbA1c reduction of 0.2-0.5% (2-6 mmol/mol). Indeed, the current focus is on the development of SGLT inhibitors as adjuncts to insulin in type 1 diabetes. Studies of subgroups with obesity, residual beta-cell function (including newly diagnosed patients) and patients prone to hypoglycemia could be areas of future research.

The effects of add-on exenatide to insulin on glycemic variability and hypoglycemia in patients with type 1 diabetes mellitus

OBJECTIVE

To investigate the effect of add-on exenatide to insulin on glycemic excursion and the counter-regulatory hormone in response to hypoglycemia in patients with type 1 diabetes mellitus (T1DM).

METHODS

30 patients with T1DM were recruited and randomly assigned to exenatide + insulin-treated group (group 1, n = 15) or insulin-only-treated group (group 2, n = 15) for 4 weeks. All patients had continuous glucose monitor system (CGMS) applied at before (week-0) and after (week-4) treatment to evaluate the glycemic variability. All patients had an arginine-stimulated test at before and after treatment. Six patients from each group also had hypoglycemic clamp test to assess counter-regulatory hormone level.

RESULTS

Patients in the exenatide group had significant reductions in body weight, body mass index (BMI), total insulin dose, bolus insulin dose, fructosamine, and glycemic excursion after 4 weeks' treatment. Compared with patients in group 2, the mean amplitude of glycemic excursion (MAGE) and coefficient of variation (CV) of exenatide group decreased significantly. Similarly, a significant decrease of glucagon (GLC) in the arginine-stimulated test was found in group 1. No significant changes of GLC, growth hormone (GH), cortisol (COR), epinephrine (E), and norepinephrine (NE) were found in both groups during hypoglycemia clamp test. However, patients who had residual islet function in group 1 showed an upward trend of basic C-peptide (C-P) and GLC during the hypoglycemia period.

CONCLUSION

Although exenatide could inhibit glucagon secretion during euglycemia or hyperglycemia in patients with T1DM, it has no effect on GLC and counter-regulatory hormones during hypoglycemia clamp in patients with no functional residual islet test.

Dipeptidyl Peptidase-4 Inhibition Potentiates Stimulated Growth Hormone Secretion and Vasodilation in Women

BACKGROUND

Diminished growth hormone (GH) is associated with impaired endothelial function and fibrinolysis. GH-releasing hormone is the primary stimulus for GH secretion and a substrate of dipeptidyl peptidase-4. We tested the hypothesis that dipeptidyl peptidase-4 inhibition with sitagliptin increases stimulated GH secretion, vasodilation, and tissue plasminogen activator (tPA) activity.

METHODS AND RESULTS

Healthy adults participated in a 2-part double-blind, randomized, placebo-controlled, crossover study. First, 39 patients (29 women) received sitagliptin or placebo on each of 2 days separated by a washout. One hour after study drug, blood was sampled and then arginine (30 g IV) was given to stimulate GH. Vasodilation was assessed by plethysmography and blood sampled for 150 minutes. Following a washout, 19 of the original 29 women received sitagliptin alone versus sitagliptin plus antagonist to delineate GH receptor (GHR)- (n=5), nitric oxide- (n=7), or glucagon-like peptide-1 receptor- (n=7) dependent effects. Sitagliptin enhanced stimulated GH secretion (P<0.01 versus placebo, for 30 minutes) and free insulin-like growth factor-1 (P<0.001 versus placebo, after adjustment for baseline) in women. Vasodilation and tPA increased in all patients, but sitagliptin enhanced vasodilation (P=0.01 versus placebo) and increased tPA (P<0.001) in women only. GHR blockade decreased free insulin-like growth factor-1 (P=0.04 versus sitagliptin alone) and increased stimulated GH (P<0.01), but decreased vascular resistance (P=0.01) such that nadir vascular resistance correlated inversely with GH (rs=-0.90, P<0.001). GHR blockade suppressed tPA. Neither nitric oxide nor glucagon-like peptide-1 receptor blockade affected vasodilation or tPA.

CONCLUSIONS

Sitagliptin enhances stimulated GH, vasodilation, and fibrinolysis in women. During sitagliptin, increases in free insulin-like growth factor-1 and tPA occur via the GHR, whereas vasodilation correlates with GH but occurs through a GHR-independent mechanism.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01701973.

DPP-4 Inhibitors as Treatments for Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis

OBJECTIVE

Several clinical studies have reported the application of dipeptidyl peptidase-4 (DPP-4) inhibitors as treatments for type 1 diabetes mellitus (T1DM). This study aims to review the outcomes of these existing studies and to discuss the therapeutic effects of DPP-4 inhibitors on T1DM.

METHODS

We thoroughly searched the Medline, Embase, PubMed, and Cochrane Library databases and ClinicalTrials.gov for studies concerning the use of DPP-4 inhibitors in patients with T1DM.

RESULTS

In preclinical trials, DPP-4 inhibitors improved the pathogenesis of T1DM. However, only a portion of the studies showed potential efficacy regarding clinical glycemic control and other clinical parameters. From this meta-analysis, pooled data from 5 randomized controlled trials revealed that the additional use of DPP-4 inhibitors resulted in a greater decrease in glycated hemoglobin A1c (HbA1c) levels (0.07%, 95% CI (-0.37%-0.23%)) than insulin monotherapy, although the decrease was not significant. A small decrease in postprandial glucose or insulin consumption was confirmed.

CONCLUSION

Although DPP-4 inhibitors may be beneficial for T1DM, existing studies do not strongly support these positive effects in clinical practice. Further optimized clinical trials are needed.

Pharmacological Treatment in Diabetes Mellitus Type 1 - Insulin and What Else?

The basis of treatment in autoimmune diabetes is insulin therapy; however, many clinical cases have proven that this method does not solve all problems. Trials of causal treatment including blocking the autoimmune processes and insulin-producing cells transplants were carried out. Those methods require more research to be concerned as efficient and safe ways of treatment in type 1 diabetes. The use of non-insulin adjunct treatment is a new trend. It has been successfully used in laboratories as well as clinical trials. Metformin is the most widely used drug, together with sodium-glucose co-transporters 2 (SGLT2) inhibitors, amylin analogues, glucagon-like peptide 1 (GLP-1) receptor agonists, and dipeptidyl peptidase-4 (DPP-4) inhibitors. The results of administration of these medicaments give good outcomes in patients with diabetes mellitus type 1. Most likely, in the near future, they will progressively be used in both adult and adolescent patients with type 1 diabetes. Further multicenter, randomized studies are required to evaluate the efficacy of treatment and long term safety of these drugs.

Adjunctive therapy for glucose control in patients with type 1 diabetes

Type 1 diabetes mellitus (T1DM) is characterized by relative or absolute insulin deficiency. Despite treatment with insulin therapy, glycemic goals are not always met, and insulin therapy is sometimes limited by adverse effects, including hypoglycemia and weight gain. Several adjunctive therapies have been evaluated in combination with insulin in patients with T1DM to improve glycemic control while minimizing adverse effects. Pramlintide, an amylin analog, can improve glycemic control, primarily through lowering postprandial blood glucose levels. Patients may experience weight loss and an increased risk of hypoglycemia and require additional mealtime injections. Metformin provides an inexpensive, oral treatment option and may reduce blood glucose, especially in overweight or obese patients with minimal risk of hypoglycemia. Metformin may be more effective in patients with impaired insulin sensitivity. Glucagon-like peptide-1 receptor agonists reduce primarily postprandial blood glucose and insulin dose and promote weight loss. They are expensive, cause transient nausea, may increase risk of hypoglycemia and require additional injections. Sodium-glucose transport-2 inhibitors improve glycemic control, promote weight loss and have low risk of hypoglycemia with appropriate insulin adjustment; however, these agents may increase the risk of diabetic ketoacidosis in patients with T1DM. Patient-specific characteristics should be considered when selecting adjunctive therapy for patients with T1DM. Close monitoring, insulin dose adjustments and patient education are all important to ensure safe and effective use of these agents.

The efficacy and safety of DPP4 inhibitors in patients with type 1 diabetes: A systematic review and meta-analysis

AIMS

Dipeptidyl peptidase-4 (DPP4) inhibitors are a novel class of antidiabetic medication in the treatment of type 2 diabetes mellitus. Several studies have indicated that DPP4 inhibitors could be used for type 1diabetes (T1DM). Here, we performed a meta-analysis to assess the efficacy and safety of DPP4 inhibitor therapy in patients with T1DM.

METHODS

We conducted searches on Medline, Cochrane Library, Web of Science, and EMBASE for relevant studies published before November 21, 2015. Mean difference (MD) with 95% confidence interval (CI) was calculated for the mean glycated hemoglobin (HbA1c) changes and insulin dosage from baseline to endpoint. Risk ratio (RR) with 95% CI was calculated for severe hypoglycemia. Data was extracted by two independent reviewers, and the meta-analysis was performed using Review Manager version 5.3.

RESULTS

Six randomized controlled trials with a total of 228 individuals were finally included into the meta-analysis. DPP4 inhibitors reduced daily insulin dosage significantly (MD -2.41U/day, 95% CI [-3.87, -0.94], P=0.001) but did not reduce HbA1c level (MD 0.0% (0mmol/mol), 95% CI [-0.16, 0.15], P=0.97). Furthermore, DPP4 inhibitors did not change the incidence of severe hypoglycemia (RR 0.81, 95% CI [0.34, 1.93], P=0.64).

CONCLUSION

In patients with T1DM, DPP4 inhibitors combined with insulin do not increase or decrease the risk of hypoglycemia and do not decrease HbA1c levels.

Non-insulin drugs to treat hyperglycaemia in type 1 diabetes mellitus

Insulin treatment of individuals with type 1 diabetes has shortcomings and many patients do not achieve glycaemic and metabolic targets. Consequently, the focus is on novel non-insulin therapeutic approaches that reduce hyperglycaemia and improve metabolic variables without increasing the risk of hypoglycaemia or other adverse events. Several therapies given in conjunction with insulin have been investigated in clinical trials, including pramlintide, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, sodium-glucose co-transporter inhibitors, metformin, sulfonylureas, and thiazolidinediones. These drugs have pleiotropic effects on glucose metabolism and different actions complementary to those of insulin-this Review reports the effects of these drugs on glycaemic control, glucose variability, hypoglycaemia, insulin requirements, and bodyweight. Existing studies are of short duration with few participants; evidence for the efficacy of concomitant treatments is scarce and largely clinically insignificant. A subgroup of patients with type 1 diabetes for whom non-insulin antidiabetic drugs could significantly benefit glycaemic control cannot yet be defined, but we suggest that obese patients prone to hypoglycaemia and patients with residual β-cell function are populations of interest for future trials.

Glucagon-like peptide-1 and cholecystokinin production and signaling in the pancreatic islet as an adaptive response to obesity

Precise control of blood glucose is dependent on adequate β‐cell mass and function. Thus, reductions in β‐cell mass and function lead to insufficient insulin production to meet demand, and result in diabetes. Recent evidence suggests that paracrine signaling in the islet might be important in obesity, and disruption of this signaling could play a role in the pathogenesis of diabetes. For example, we recently discovered a novel islet incretin axis where glucagon‐like peptide‐1 regulates β‐cell production of another classic gut hormone, cholecystokinin. This axis is stimulated by obesity, and plays a role in enhancing β‐cell survival. In the present review, we place our observations in the wider context of the literature on incretin regulation in the islet, and discuss the potential for therapeutic targeting of these pathways.