A Physiologic and Pharmacological Basis for Implementation of Incretin Hormones in the Treatment of Type 2 Diabetes Mellitus

Abstract

Philadelphia, PA 19131-1626 (jeffreyfreemando@aol.com). © 2010 Mayo Foundation for Medical Education and ResearchT he pathophysiologic defects that characterize type 2 diabetes mellitus (DM) include insulin resistance in liver and skeletal muscle and pancreatic β-cell dysfunction. Initially, β cells are able to increase insulin secretion sufficiently to offset insulin resistance, thus maintaining normoglycemia. When β cells are no longer able to compensate, plasma glucose levels increase. 1 Recent findings indicate that defects in β-cell function and increased insulin resistance occur early in the natural history of type 2 DM and can be present for 3 to 6 years before diagnosis. 2 Also, DM-related complications or tissue damage is evident in approximately 50% of individuals with type 2 DM at the time of diagnosis. 3 Progressive β-cell dysfunction is pathognomonic of the natural history of type 2 DM. Data from the longitudinal United Kingdom Prospective Diabetes Study (UKPDS) 16 showed that, over time, patients experience increasing A Physiologic and Pharmacological Basis for Implementation of Incretin Hormones in the Treatment of Type 2 Diabetes MellitusJeffrey S. Freeman, DO Progressive deterioration of β-cell function is a hallmark of type 2 diabetes mellitus (DM). Together with increasing insulin resistance in peripheral tissues (in both the liver and the skeletal muscle), the inability of pancreatic insulin secretion to manage fasting and postprandial glucose levels results in hyperglycemia. Currently available oral antidiabetes agents improve glycemic parameters, but no single drug addresses the numerous pathophysiologic defects known to contribute to hyperglycemia in patients with type 2 DM. Dysregulation in the incretin system is another component of the pathophysiologic processes that lead to DM. Agents used to correct defects in the incretin system, such as glucagon-like peptide 1 receptor agonists and dipeptidyl peptidase 4 inhibitors, offer the potential to restore glucose-dependent insulin secretion and improve β-cell function. Glucagon-like peptide 1 receptor agonists also promote weight loss and provide beneficial effects on cardiovascular risk factors. A new approach that promotes the selection of pharmacotherapy for the treatment of patients with DM, with the goal of slowing or reversing the natural history of the disease, may be in order. Clinicians can select agents to address specific pathophysiologic defects to improve glycemia, with the hope of preventing the development of complications. Even patients receiving intensive therapy that improved mean hemoglobin A 1c (HbA 1c ) levels from 6.9% at baseline to 6.1% at 1 year showed deterioration of results over time; after 6 years, the mean HbA 1c level for these patients was 7.1%. 4 In UKPDS 49, the proportion of patients who maintained target glycemic levels decreased markedly during 9 years of follow-up. This decrease is consistent with progressive deterioration in β-cell function, such that only 50% of patients maintained their glycemic goal...

Effects of saxagliptin and sitagliptin on glycaemic control and pancreatic β‐cell mass in a streptozotocin‐induced mouse model of type 2 diabetes

“…Approximately 25.8 million people in USA have some form of diabetes, with type 2 diabetes mellitus (T2DM) accounting for >90% of cases . T2DM is characterized by progressive pancreatic β‐cell dysfunction, which, coupled with insulin resistance, leads to increasing hyperglycaemia . If lifestyle changes fail to achieve adequate glycaemic control, pharmacologic intervention is necessary.…”

Nuggets of Knowledge: Gliptins for Type 2 diabetes – should we be excited?

“…As they are glucose dependent, the risk of hypoglycaemia is low. 1 The gliptins, such as sitagliptin, saxagliptin and vildagliptin are oral dipeptidyl peptidase-4 (DPP-4) inhibitors. They inhibit the breakdown of GLP-1 and GIP by inhibiting DPP-4, therefore increasing insulin release.…”

Choice of early treatment regimen and impact on β-cell preservation in type 2 diabetes

“…The natural history of type 2 diabetes mellitus (T2DM) is characterised by insulin resistance and a progressive loss of β‐cell function , leading to gradual worsening in glucose tolerance . As insulin secretion decreases and is unable to compensate for insulin resistance, individuals progress from an initial state of euglycaemia to a prediabetic state of impaired fasting glucose [fasting plasma glucose (FPG) of 100–125 mg/dl], impaired glucose tolerance (2‐h plasma glucose of 140–199 mg/dl in the 75‐g oral glucose tolerance test), and elevated glycated haemoglobin (HbA 1c ; 5.7–6.4%) .…”