The goal of this observational study is to explore inter- and intra-individual determinants of postprandial glucose response in patients with type 1 diabetes using continous glucose monitoring (CGM).

Blood samples and anthropometrics will be collected during hospital visit. Participants will be asked to:

• record a seven-day food diary
• complete EPIC food frequency questionnaire
• complete questionnaires on sleep hygiene
• collect a stool sample

Postprandial glucose response (PGR) is a main determinant of blood glucose control in people with type 1 diabetes (T1D) and it's still difficult to manage also in patients treated with advanced technologies. Dietary composition of meals represents one of main determinant of PGR. However, growing evidence indicates that PGR to the ingestion of the same meal may significantly differ between individuals. This effect could be explained by non-nutritional determinants, including gut microbiota composition. On this background, the aim of the study is to investigate the relative contribution of intra- and inter-individual variability in determining PGR in individuals with type 1 diabetes.

Patients with T1D regularly attending the diabetes outpatient clinic of Federico II University Teaching Hospital, will be recruited. Participants' eating habits will be collected through a 7-day food record and the European Prospective Investigation into Cancer and Nutrition (EPIC) questionnaire. Fasting blood samples will be collected for the evaluation of serum short-chain fatty acids, zonulin, metabolomic, and epigenetics. Moreover, participants will be asked to collect at home a faecal sample to determine gut microbiota composition (16s RNA sequencing). Patients will be asked to complete web-based questionnaires on sleep hygiene (Pittsburgh Sleep Quality Index, Epworth).

Postprandial glucose response will be assessed by data derived from continuous glucose monitoring (CGM) used for clinical care.

The association between the PGR, calculated as incremental AUC using the trapezoidal method, and gut microbiota composition will be assessed. Moreover, the association between PGR, dietary composition, metabolomics and epigenetics will be investigated.

Inclusion Criteria:

• Type 1 Diabetes

Exclusion Criteria:

• Pregnancy and/or breastfeeding
• Other chronic or acute diseases
• Use of antibiotics in the past 3 months

The study population will consist of individuals with type 1 diabetes using continuous glucose monitoring (CGM) and regularly attending the Diabetes Outpatient Clinic of Federico II University Teaching Hospital (Naples, Italy).