**3. Carbohydrate metabolism**

After 24 weeks, a significant decrease in all parameters of carbohydrate metabolism was observed in group I. Level of FPG in group I decreased by 2.67 ± 2.37 mmol/L (21%), р <0.001, FPG decrease in group II has not reached statistical significance with the mean decrease of 0.33 ± 1.6 mmol/L (1.45%), р > 0.05. Postprandial glucose (PPG) decreased by 3.26 ± 2.54 mmol/L (26.35%), р <0.001 in group I and by 0.64 ± 1.2 mmol/L (5.31%), p < 0.05 in group II. HbA1c level decreased by 1.63 ± 1.31% (18.52%), р <0.001 in group I, and by 0.72 ± 0.47% (8.17%) in group II (**Figure 3**).

The largest success in achieving glycemic control in patients on combined treatment is associated with complimentary action of the therapy components. Metformin lowers insulin resistance and hepatic glucose production, while Sitagliptin delays inactivation of GLP-1, thus enhancing glucose-dependent insulin secretion and decreasing glucagon secretion [17]. In addition, it was demonstrated that metformin leads to increase in overall GLP-1 and can

**Figure 3.** Dynamics of carbohydrate metabolism in the groups. GF-glucose fasting, PPG-postprandial glycemia; \*P < 0.05; \*\* P > 0.05.

potentially enhance the effects of DPP-4 inhibitor. It is notable that the study achieved a significant PPG decrease in metformin monotherapy group, which is potentially associated with metformin ability to increase GLP-1 level and to slow down carbohydrate absorption in the intestine.
