Comparative evaluation of incretin-based antidiabetic medications and alternative therapies to be added to metformin in the case of monotherapy failure

Feline comorbidities: Pathophysiology and management of the obese diabetic cat

PRACTICAL RELEVANCE

Up to 40% of the domestic feline population is overweight or obese. Obesity in cats leads to insulin resistance via multiple mechanisms, with each excess kilogram of body weight resulting in a 30% decline in insulin sensitivity. Obese, insulin-resistant cats with concurrent beta-cell dysfunction are at risk of progression to overt diabetes mellitus.

APPROACH TO MANAGEMENT

In cats that develop diabetes, appropriate treatment includes dietary modification to achieve ideal body condition (for reduction of insulin resistance), and optimization of diet composition and insulin therapy (for glycemic control and the chance of diabetic remission). Initially, as many obese cats that become diabetic will have lost a significant amount of weight and muscle mass by the time of presentation, some degree of diabetic control should be attempted with insulin before initiating any caloric restriction. Once body weight has stabilized, if further weight loss is needed, a diet with ≤ 12-15% carbohydrate metabolizable energy (ME) and >40% protein ME should be fed at 80% of resting energy requirement for ideal weight, with the goal of 0.5-1% weight loss per week. Other approaches may be necessary in some cats that need either substantial caloric restriction or do not find low carbohydrate diets palatable. Long-acting insulins are preferred as initial choices and oral antidiabetic drugs can be used in combination with diet if owners are unable or unwilling to give insulin injections. Glucagon-like peptide-1 (GLP-1) agonists have recently been investigated for use as adjunctive treatment in diabetic cats and sodium-glucose cotransporter-2 (SGLT2) inhibitors are currently being evaluated in clinical trials.

EVIDENCE BASE

The information in this review is drawn from: epidemiological studies on obesity prevalence; prospective longitudinal studies of development of insulin resistance with obesity; randomized controlled studies; and expert opinion regarding the effect of diet on diabetes management in cats.

Glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1: Incretin actions beyond the pancreas

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the two primary incretin hormones secreted from the intestine on ingestion of various nutrients to stimulate insulin secretion from pancreatic β-cells glucose-dependently. GIP and GLP-1 undergo degradation by dipeptidyl peptidase-4 (DPP-4), and rapidly lose their biological activities. The actions of GIP and GLP-1 are mediated by their specific receptors, the GIP receptor (GIPR) and the GLP-1 receptor (GLP-1R), which are expressed in pancreatic β-cells, as well as in various tissues and organs. A series of investigations using mice lacking GIPR and/or GLP-1R, as well as mice lacking DPP-4, showed involvement of GIP and GLP-1 in divergent biological activities, some of which could have implications for preventing diabetes-related microvascular complications (e.g., retinopathy, nephropathy and neuropathy) and macrovascular complications (e.g., coronary artery disease, peripheral artery disease and cerebrovascular disease), as well as diabetes-related comorbidity (e.g., obesity, non-alcoholic fatty liver disease, bone fracture and cognitive dysfunction). Furthermore, recent studies using incretin-based drugs, such as GLP-1 receptor agonists, which stably activate GLP-1R signaling, and DPP-4 inhibitors, which enhance both GLP-1R and GIPR signaling, showed that GLP-1 and GIP exert effects possibly linked to prevention or treatment of diabetes-related complications and comorbidities independently of hyperglycemia. We review recent findings on the extrapancreatic effects of GIP and GLP-1 on the heart, brain, kidney, eye and nerves, as well as in the liver, fat and several organs from the perspective of diabetes-related complications and comorbidities.

Safety, pharmacokinetics, and pharmacodynamics of single and multiple luseogliflozin dosing in healthy Japanese males: a randomized, single-blind, placebo-controlled trial

Introduction

Luseogliflozin, a sodium glucose cotransporter 2 inhibitor, inhibits reabsorption of glucose in the proximal renal tubule. It was developed for the treatment of type 2 diabetes mellitus.

Methods

For this first human study of luseogliflozin, randomized, single-blind, placebo-controlled, single ascending dose (1–25 mg) and multiple ascending dose (5 or 10 mg/day, 7 days) trials were conducted in healthy male Japanese subjects to investigate safety, pharmacokinetics, and pharmacodynamics.

Results

There were no serious adverse events, adverse events leading to discontinuation, or episodes of hypoglycemia. After administration of a single oral dose of luseogliflozin, its maximum plasma level (C_max) and area under the concentration–time curve increased in a dose-dependent manner, and no food effects were observed on pharmacokinetics. The mean time taken to reach C_max (T_max) ranged from 0.667 to 2.25 h. The mean plasma half-life of luseogliflozin (T_1/2) after multiple dosing for 7 days ranged from 9.14 to 10.7 h, and no detectable accumulation of luseogliflozin was observed. Urinary glucose excretion increased in a dose-dependent manner, ranging from 18.9 to 70.9 g (single-dose study).

Conclusion

Luseogliflozin was well tolerated and showed favorable pharmacokinetic and pharmacodynamic profiles in healthy male Japanese subjects.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-014-0102-3) contains supplementary material, which is available to authorized users.

Aerosolized GLP-1 for treatment of diabetes mellitus and irritable bowel syndrome

Diabetes is a global burden and the prevalence of the disease, in particular diabetes mellitus type 2 is rapidly increasing worldwide. After introduction of insulin into clinical therapy about 90 years ago a major number of pharmaceuticals has been developed for treatment of diabetes mellitus type 2. One of these, the incretin glucagon-like peptide 1 (GLP-1), like insulin, needs subcutaneous administration causing inconvenience to patients. However, administration of GLP-1 plays also a role for treatment of irritable bowel syndrome (IBS). To improve patient convenience inhaled insulin (Exubera(®)) was developed and approved but failed market acceptance some years ago. Recently, another inhalative insulin (Afrezza(®)) received market approval and GLP-1 may serve as another candidate drug for inhalative administration. This review analyzes the current literature investigating alternative administration of GLP-1 and GLP-1 analogs focusing on inhalation. Several formulations for inhalative administration of GLP-1 and analogs were investigated in animal studies, whereas there are only few clinical data. However, feasibility of GLP-1 inhalation has been shown and should be further investigated as such type of drug administration may serve for improvement of therapy in patients with diabetes mellitus or irritable bowel syndrome.

Treating diabetes today: a matter of selectivity of sulphonylureas

It is well known that sulphonylureas (SUs), commonly used in the treatment of type 2 diabetes mellitus, stimulate insulin secretion by closing ATP-sensitive K(+) (K(ATP) ) channels in pancreatic β-cells by binding to the SU receptor SUR1. SUs are now known also to activate cAMP sensor Epac2 (cAMP-GEFII) to Rap1 signalling, which promotes insulin granule exocytosis. For SUs to exert their full effects in insulin secretion, they are required to activate Epac2 as well as to inhibit the β-cell K(ATP) channels. As Epac2 is also necessary for potentiation of glucose-induced insulin secretion by cAMP-increasing agents, such as incretin, Epac2 is a target of both cAMP and SUs. The distinct effects of various SUs appear to be because of their different actions on Epac2/Rap1 signalling as well as K(ATP) channels. Differently from other SUs, gliclazide is unique in that it is specific for β-cell K(ATP) channel and does not activate Epac2.

Species-specific actions of incretin: from the evolutionary perspective

Two modes of incretin-based therapy, incretin mimetics (ie, glucagon-like peptide-1 (GLP-1) agonists) and incretin enhancers (ie, inhibitors of dipeptidyl peptidase IV (DPP-IV)), have recently been introduced into the clinical use. From the viewpoint of evolutionary endocrinology of GLP-1 and their receptors, the incretin action of GLP-1 seems to be relatively recent. Exendin-3 and exendin-4 are paralogs of GLP-1 from the lizards, and the synthetic exendin-4, exenatide, is a paralog of GLP-1. It has recently been indicated that GLP-1 and its receptor are expressed in the taste buds of the tongue, suggesting their possible function in the taste sensing signal pathway. In order to elucidate unknown functions of GLP-1 and its agonists and enhancers, ie, other than incretin actions in humans, it is possibly useful to consider GLP-1 from the viewpoint of integrated systems biology and evolutionary endocrinology.