Disturbances in Dynamics of Glucose, Insulin, and C-Peptide in Blood after a Normalized Intake of a Mixed Meal in Obesity and Type 2 Diabetes Mellitus

The aim of the study was to investigate the dynamics of venous blood glucose, insulin, and C-peptide in response to an intake of a mixed meal normalized to body mass in obese patients without and with type 2 diabetes mellitus. Venous blood samples were taken from seven healthy subjects, nine obese patients, and ten obese patients with type 2 diabetes mellitus (mean duration of diabetes 7 years) before and 30, 60, 90, 120, and 180 min after a mixed meal (6 kcal/kg of body mass); additionally, nine patients with obesity and type 2 diabetes mellitus and three healthy volunteers completed the hyperinsulinemic-euglycemic clamp test. In patient groups the energy content of food did not differ but was 1.8 times higher than in the control. An increase in glucose level 1 h after a meal was maximal in patients with type 2 diabetes, and an increase in insulin and C-peptide was higher in obese patients, which is related to impairment of insulin-dependent glucose uptake by tissues and of the rate of insulin secretion (dysfunction of beta-cells) in patients. At the same time, an increase in the total area under the curve “C-peptide–time” demonstrates that the maximal secretory response of beta-cells is comparable in obese patients without and with type 2 diabetes mellitus. The absolute blood glucose level 90 min after a meal closely correlated with the M -index—the marker of systemic sensitivity to insulin ( r s = –0.82, p = 0.002). Our results characterize the features in the regulation of carbohydrate metabolism after intake of a mixed meal, normalized to body mass, in people with varying severity of metabolic disorders, and open up prospects for a wider application of this test in practice.