Relative and absolute contributions of postprandial and fasting plasma glucose to daytime hyperglycaemia and HbA(1c) in subjects with Type 2 diabetes

Diabet Med. 2009 Oct;26(10):974-80. doi: 10.1111/j.1464-5491.2009.02809.x.

Abstract

Aims: To determine the relative and absolute contributions of postprandial glucose (PPG) and fasting or preprandial plasma glucose (FPG) to daytime hyperglycaemia and HbA(1c) respectively, in persons with type 2 diabetes (T2DM).

Methods: Subjects (n = 52; 37 men) had 12hr plasma glucose (PG) profiles determined in response to three serial identical test meals. PPG exposure was calculated for each meal. Excess hyperglycaemia was calculated above a PG concentration of 5.5 mmol/l. Fasting hyperglycaemia was the difference between excess hyperglycaemia and PPG exposure. Subjects were divided into three groups according to HbA(1c)-(Gp1:<7.3%;Gp2:7.3%-8.0%;Gp3:>8.0%) and the relative contribution of PPG exposure and fasting hyperglycaemia to excess hyperglycaemia calculated for each meal. The absolute contribution of PPG and fasting hyperglycaemia to excess HbA(1c) (mean HbA(1c)-5.1%) was also calculated.

Results: The relative contributions of PPG exposure to excess hyperglycaemia for the three groups were: 58.3%, 54.3% and 35.4% (P = 0.483-Group 1 vs. Group 2; P = 0.002-Group 2 vs. Group 3) for meal 1; 69.8%, 54.7% and 23.7% (P = 0.163-Group 1 vs. Group 2; P = 0.005-Group 2 vs. Group 3) for meal 2; 85.8%, 70.2% and 48.6% (P = 0.153-Group 1 vs. Group 2; P = 0.046-Group 2 vs. Group 3) for meal 3. Absolute contributions of PPG to excess HbA(1c) in the three groups were 1.4%, 1.6% and 1.3% (P = NS).

Conclusion: The relative contribution of postprandial glucose to excess hyperglycaemia decreases as glycaemic control deteriorates, being dominant with HbA(1c)</= 7.3%, irrespective of the timing of the meal during the day. However, the absolute contribution of postprandial glucose to excess HbA(1c) does not differ significantly ( approximately 1.5%) with varying glycaemic control.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Blood Glucose / metabolism*
  • Diabetes Mellitus, Type 2 / blood
  • Fasting / physiology
  • Female
  • Glycated Hemoglobin A / metabolism*
  • Humans
  • Hyperglycemia / metabolism*
  • Male
  • Middle Aged
  • Postprandial Period / physiology

Substances

  • Blood Glucose
  • Glycated Hemoglobin A