An observational, single-center, prospective study was conducted to examine the impact of CM on the development of T2DM and the personalization of initial SST in patients with newly diagnosed T2DM who had not previously received SST. These patients were hospitalized at the V.P. Demikhov City Clinical Hospital between October 2021 and February 2022 due to hyperglycemia detected incidentally at their place of residence. The sample consisted of men and women aged 18 to 80 years.

After hospitalization, the diagnosis of newly diagnosed T2DM was confirmed twice using any available laboratory diagnostic methods: fasting venous blood glucose greater than 7.0 mmol/L or greater than 11.1 mmol/L when randomly determined; glucose greater than 11.1 mmol/L 2 hours after oral administration of 75 g of glucose; and HbA1c greater than 6.5%.

After double confirmation of the T2DM diagnosis, 100 patients with newly diagnosed T2DM who had not previously received SST and met the inclusion criteria were included in the study.

At the first visit, after assessing patient compliance with the inclusion and exclusion criteria, anamnesis was collected, anthropometric analysis was performed, and intravenous blood was drawn for hormonal (insulin, C-peptide, glucagon, GLP-1) and biochemical blood tests (glucose, HbA1c, TC, LDL, HDL, TG, creatinine, urea, ALT, AST, total bilirubin). Glucagon and GLP-1 levels in the blood were measured on an empty stomach (0 min. point) and 30 minutes after a standard breakfast (30 min. point). Also, at the first visit, in order to assess the composition of the CM, 100 patients underwent stool sampling for 16S rRNA sequencing.

At the 2nd visit, as laboratory test results became available, patients were randomized to monotherapy or combination therapy groups depending on the HbA1c level in accordance with the 2019 Algorithms for Specialized Care for Patients with Diabetes Mellitus [164]. Metformin was prescribed as monotherapy at a daily dose of 2000 mg (n = 20), and innovative CAPs were added to metformin as combination therapy: DPP-4 inhibitors (n = 20) / GLP-1 arginine (n = 20) / NGLT-2 inhibitors (n = 20) or DPP-4 inhibitors + insulin glargine 300 U/ml (n = 20)/ The effectiveness of the treatment was assessed at the third visit based on HbA1c levels after three months of treatment. If target glycemic levels were not achieved after three months of treatment, the HbA1c levels were adjusted at the third visit based on national recommendations.

Inclusion Criteria:

• Newly diagnosed T2DM
• No ketoacidosis
• Age ≥ 18 years, ≤ 80 years
• BMI > 25 kg/m2
• No history of taking hypoglycemic drugs (HGD)
• No use of drugs that affect BM composition

Exclusion Criteria:

• Presence of type 1 diabetes
• Presence of chronic gastrointestinal diseases: ulcerative colitis, Crohn's disease, celiac disease, irritable bowel syndrome, multiple intestinal polyposis, chronic pancreatitis with frequent exacerbations (more than 6-7 times per year)
• Presence of acute gastrointestinal diseases: acute pancreatitis, acute cholecystitis, enteritis, colitis, exacerbation of gastric ulcer or duodenal ulcer
• Previous gastrointestinal surgery within the last 3 months Gastrointestinal surgery within the last 3 months.
• Severe infectious diseases (HIV, hepatitis B, hepatitis C, tuberculosis, Covid-19)
• Glomerular filtration rate (GFR) < 30 ml/min/1.73 m2
• Mental illness
• Alcoholism, drug addiction
• Pregnancy or lactation
• Cancer
• History of blood transfusion, organ transplant, or bone marrow transplant

Patients were hospitalized at the V.P. Demikhov City Clinical Hospital between October 2019 and February 2021 due to hyperglycemia detected incidentally at their place of residence. The sample consisted of men and women aged 18 to 80 years.