New Data indicates that Post-prandial blood glucuose plays an important role in overall glycemic control. Although a traditional goal of glycemic control in the treatment of diabetes mellitus is to normalize fasting plasma glucose, emerging data indicate that modulation of postprandial plasma glucose levels plays an important role in overall glycemic control. This article reviews the evidence linking postprandial glucose levels with long-term indices of diabetes control, such as glycosylated hemoglobin, lipid abnormalities, and the risk of microvascular and macrovascular complications. Early in the development of type 2 diabetes, the initial burst of insulin release in response to food intake is compromised, allowing postprandial hyperglycemia to develop. Meal-associated hyperglycemia further contributes to increase insulin resistance and decrease insulin production. Evidence of a strong correlation between high postprandial glycemic levels and the development of vascular complications underscores the significance of treating mealtime glycemia. Emerging drugs that reduce postprandial hyperglycemia include the D-phenylalanine derivative nateglinide, amylin derivative pramlintide, and glucagon-like insulinotropic peptide.
The goal in the management of patients with type 2 diabetes is to control fasting plasma glucose and glycosylated hemoglobin (HbA1c) levels. In patients with well-controlled diabetes (HbA1c <7%, or within 1% of normal) or glucose intolerance (fasting plasma glucose level <126 mg/dL, and a 2-hour plasma glucose of 140 to 200 mg/dL after 75 g of oral glucose), postprandial hyperglycemia has a greater effect on HbA1c than fasting glucose levels. Jovanovic recently reported that the postprandial glucose level at 1 hour is the best predictor of HbA1c in patients with well-controlled type 2 diabetes mellitus. In addition, a French study of patients with type 2 diabetes showed that glucose concentrations at 2 and 5 hours after a meal were better predictors of the HbA1c than prebreakfast or prelunch values. Therefore, in patients with elevated HbA1c, the postprandial plasma glucose levels may play a disproportionate role in the genesis of both microvascular and macrovascular complications of diabetes.
The recent change in plasma glucose threshold for the diagnosis of diabetes was based on evidence such as that from the United Kingdom Prospective Diabetes Study, which showed that 50% of patients with type 2 diabetes already had one or more chronic complications by the time it was diagnosed. The standard for diagnosis is still a plasma glucose level >200 mg/dL at 2 hours after a 75-g glucose load. Postprandial levels >200 mg/dL are seen in 97% of patients with a fasting plasma glucose value of 126 mg/dL. In addition, 52% of patients with fasting plasma glucose <126 mg/dL still have postprandial levels >200 mg/dL. Therefore, patients with fasting glucose levels between 110 and 126 mg/dL should undergo a 2-hour, 75-g glucose challenge to assess their postprandial glucose levels, since early detection and treatment can delay or prevent the onset of complications. Patients should be checking their blood sugars 2 hours after their largest meal.
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