Excess glycaemic excursions after an oral glucose tolerance test compared with a mixed meal challenge and self-measured home glucose profiles: is the OGTT a valid predictor of postprandial hyperglycaemia and vice versa?

INTRODUCTION

Postprandial hyperglycaemia is often assumed in individuals with high glucose excursions during an oral glucose tolerance test (OGTT), but the relationship between glucose levels during the OGTT and after a mixed meal is yet unclear. We addressed whether (i) glucose concentrations after an oral glucose load are similar to those after a test meal or under daily life conditions and (ii) impaired glucose tolerance (IGT) predicts postprandial hyperglycaemia.

PATIENTS AND METHODS

A total of 60 subjects with normal (NGT), IGT or diabetic (DM) glucose tolerance were examined with an OGTT, a mixed meal challenge (3433 kJ) and a self-determined 10-point home glucose profile.

RESULTS

There was a significant correlation between the 120-min OGTT glucose levels and the glycaemic excursions after the test meal and during everyday conditions. However, glucose excursions during the OGTT exceeded those after the test meal and during everyday conditions by approximately 20 and approximately 30% respectively. Likewise, insulin and C-peptide levels rose to higher levels after oral glucose compared with mixed meal ingestion. The mean self-determined diurnal glucose levels were already 10% higher in subjects with IGT compared with NGT subjects (p < 0.0001).

CONCLUSIONS

Glucose levels reached after an oral glucose challenge and during real life are correlated to some extent, but the absolute levels of glycaemia greatly differ between both conditions. Therefore, 'postchallenge' glucose levels measured during an OGTT might be used as a predictor of 'postprandial hyperglycaemia', but caution should be taken when both terms are used synonymously. Furthermore, subjects with IGT during an OGTT already exhibit increased postprandial glucose levels under real-life conditions. This suggests that IGT should already be considered an overt disease condition rather than merely a high-risk situation.

Efficacy and safety of adding the dipeptidyl peptidase-4 inhibitor alogliptin to metformin therapy in patients with type 2 diabetes inadequately controlled with metformin monotherapy: a multicentre, randomised, double-blind, placebo-controlled study

AIMS

To evaluate the efficacy and safety of alogliptin, a new dipeptidyl peptidase-4 inhibitor, for 26 weeks at once-daily doses of 12.5 and 25 mg in combination with metformin in patients whose HbA(1c) levels were inadequately controlled on metformin alone.

METHODS AND PATIENTS

Patients with type 2 diabetes and inadequate glycaemic control (HbA(1c) 7.0-10.0%) were randomised to continue a stable daily metformin dose regimen (> or = 1500 mg) plus the addition of placebo (n = 104) or alogliptin at once-daily doses of 12.5 (n = 213) or 25 mg (n = 210). HbA(1c), insulin, proinsulin, C-peptide and fasting plasma glucose (FPG) concentrations were determined over a period of 26 weeks.

RESULTS

Alogliptin at either dose produced least squares mean (SE) decreases from baseline in HbA(1c) of -0.6 (0.1)% and in FPG of -17.0 (2.5) mg/dl [-1.0 (0.1) mmol/l], decreases that were significantly (p < 0.001) greater than those observed with placebo. The between treatment differences (alogliptin - placebo) in FPG reached statistical significance (p < 0.001) as early as week 1 and persisted for the duration of the study. Overall, adverse events (AEs) observed with alogliptin were not substantially different from those observed with placebo. This includes low event rates for gastrointestinal side effects and hypoglycaemic episodes. There was no dose-related pattern of AE reporting between alogliptin groups and few serious AEs were reported.

CONCLUSION

Alogliptin is an effective and safe treatment for type 2 diabetes when added to metformin for patients not sufficiently controlled on metformin monotherapy.

Glucose homeostasis and the gastrointestinal tract: insights into the treatment of diabetes

The gastrointestinal tract is increasingly viewed as a critical organ in glucose metabolism because of its role in delivering glucose to the circulation and in secreting multiple glucoregulatory hormones that, in concert with insulin and glucagon, regulate glucose homeostasis. Under normal conditions, a complex interplay of these hormones acts to maintain plasma glucose within a narrow range despite large variations in the availability of glucose, particularly during transition from the fasting to fed state. In the fed state, the rate at which nutrients are passed from the stomach to the duodenum, termed gastric emptying rate, is a key determinant of postprandial glucose flux. In patients with diabetes, the regulation of glucose metabolism is disrupted resulting in fasting and postprandial hyperglycaemia. Elucidation of the role of the gastrointestinal tract, gut-derived glucoregulatory peptides and gastric emptying rate offers a new perspective on glucose homeostasis and the respective importance of these factors in the diabetes state. This review will highlight the importance of the gastrointestinal tract in playing a key role in glucose homeostasis, particularly in the postprandial period, and the role of established or new therapies that either leverage or modify gastrointestinal function to improve glycaemic state.