Background and Objectives: Diabetic retinopathy (DR) is a major microvascular complication of diabetes mellitus (DM) and a leading cause of blindness among working-age adults. Advanced glycation end products (AGEs) contribute to DR pathogenesis through oxidative stress and inflammation. This study aimed to evaluate the association between AGE levels and DR severity in Lithuanian patients with type 1 (T1D) and type 2 (T2D) diabetes. Materials and Methods: An observational cross-sectional study enrolled 152 patients with T1D and T2D from a tertiary university hospital. AGE values were measured with a non-invasive AGE Reader device. DR severity was assessed through ophthalmological examination. Results: The overall DR prevalence was 54.6%. AGE values increased with the severity of DR, though not significantly between the DR groups (p = 0.386). The mean AGE value was higher in T2D compared with the T1D group (2.429 vs. 2.217, p = 0.011). In T1D, AGE values were higher in the advanced DR group compared with the non-DR patients (2.445 vs. 1.905, p = 0.007), whereas no significant difference was found in the T2D subgroups. In T1D, AGEs correlated positively with both DM duration and higher HbA1c (p < 0.05). Patients with AGE values > 2.35 in T1D and 2.15 in T2D had an increased likelihood of having advanced DR. Patients in the non-DR group had significantly lower AGE values compared to those in the advanced DR group (OR = 0.118, 95% CI 0.025–0.566, p = 0.008). Conclusions: AGEs measured using skin autofluorescence may indicate DR severity in T1D but not in T2D and might not be a suitable standalone risk predictor. DM duration remains a significant determinant of advanced DR, highlighting the importance of early monitoring and timely intervention.

Background and Objectives: Neuropeptide Y (NPY) family peptides and dipeptidyl peptidase-4 (DPP-4) are involved in gastrointestinal regulation and may contribute to obesity and type 2 diabetes mellitus (T2DM) pathophysiology. This study investigates their expression in jejunal muscular tissue and associations with gastrointestinal symptoms in patients with obesity, with (OB+/DM+) and without T2DM (OB+/DM−). Materials and Methods: This cross-sectional study includes forty-four patients undergoing laparoscopic Roux-en-Y gastric bypass divided based on T2DM status. Gastrointestinal symptoms were assessed using the Gastrointestinal Symptom Rating Scale (GSRS) questionnaire, and jejunal tissue samples were analyzed for DPP-4, NPY, peptide YY (PYY), and pancreatic polypeptide (PP) mRNA and protein levels. Results: DPP-4, NPY, PYY, and PP gene expression in jejunal muscular tissue was similar between groups. In the OB+/DM+ group, PP protein was higher, while DPP-4 and PYY were lower compared to the OB+/DM− group. Significant positive correlations between DPP-4 and NPY, PYY, and PP were found in the OB+/DM− group, while only DPP-4 and PYY correlated in the OB+/DM+ group. Gastrointestinal symptoms in the OB+/DM− group showed positive correlations with PP (abdominal pain), DPP-4 (indigestion), and NPY (constipation). Conclusions: The study demonstrates significant differences in DPP-4, PYY, and PP protein expression between patients with obesity, with or without T2DM. Peptide correlations with gastrointestinal symptoms in non-diabetic patients suggest distinct regulatory mechanisms, warranting further research.