Incorporating postprandial and fasting plasma glucose into clinical management strategies

Abstract

Background: Targeting plasma glucose is a widely accepted practice in the treatment of both type 1 and type 2 diabetes mellitus (DM). Although clinicians have traditionally relied on fasting plasma glucose (FPG) levels for diagnosis and as a target for therapy, the focus has expanded to include the contribution of postprandial glucose (PPG) to glycosylated hemoglobin (A1C) levels. Objective: This article examines the contributions of FPG and PPG to A1C levels in patients with diabetes and discusses the impact of these findings on insulin treatment strategies for patients who fail to achieve recommended A1C goals. Methods: Relevant articles were identified through a PubMed search of the literature (1975–2007) using the following search terms: fasting plasma glucose, postprandial glucose, postprandial hyperglycemia, and glycemic control. Results: Changes in PPG levels are typically the first signs of abnormal glucose metabolism associated with type 2 DM, and they are a useful measure of glycemic control in patients with near-normal FPG and high A1C levels. A substantial proportion of patients considered to have good glycemic control (A1C <7.0%) may continue to experience elevated PPG levels, which have been linked to an increased risk of cardiovascular disease. FPG levels may predict the degree of postprandial hyperglycemia and the extent of PPG excursion. Conversely, correction of PPG levels may reduce FPG levels by suppressing hepatic glucose production. Evidence indicates that therapy targeting both FPG and PPG is associated with optimal reductions in A1C levels. At very high A1C levels (>9%-10%), FPG may play a greater role in overall glucose control than does PPG, but PPG becomes a more important contributor as A1C levels decrease. Increasing evidence supports the long-term benefits of early initiation of intensive insulin therapy. In particular, prandial insulin therapy may address the issue of postprandial hyperglycemia, which may be insufficiently controlled with oral agents and/or basal insulin alone. Conclusions: Both FPG and PPG affect A1C levels and are important contributors to determining overall glycemic control. Alternative insulin therapies (eg, inhaled insulin) that minimize barriers to insulin therapy and the appropriate targeting of FPG and PPG levels may improve long-term outcomes in patients with diabetes.