Abstract

Background: Hemoglobin A<inf>1c</inf> (HbA<inf>1c</inf>) interpretation can be affected by genetic and hematologic factors that alter erythrocyte turnover. This study investigated red blood cell (RBC) profiles and metabolomic alterations linked to glycemic variability in type 2 diabetes (T2D) and evaluated the effects of common RBC genetic disorders on HbA<inf>1c</inf> interpretation. Methods: Participants were recruited in Nakhon Si Thammarat, Thailand. In Phase 1, 244 normoglycemic participants and 447 individuals with T2D were enrolled. In Phase 2, 45 participants from each group were analyzed for hematologic and biochemical parameters. In Phase 3, liquid chromatography-mass spectrometry (LC-MS)-based RBC metabolomics were performed in 10 individuals without diabetes and 14 individuals with diabetes. Results: Fasting blood glucose, fructosamine, and ferritin showed no significant differences, whereas HbA<inf>1c</inf> was significantly lower in those with RBC disorders for both individuals without diabetes (P = .001) and individuals with diabetes (P < .001) groups. Red blood cells with hypochromic microcytosis in β-thalassemia heterozygote (BTH) were used as a model to explore metabolomic changes associated with normal and high HbA<inf>1c</inf> levels. Multivariate analyses revealed distinct clustering patterns in high-HbA<inf>1c</inf> cases. Interestingly, 5-oxo-L-proline exhibited the highest fold change (FC = 6.90, P = .0004), followed by 5-aminolevulinate and D-gluconic acid, along with increased oxidized/reduced glutathione and decreased NADH and sphingomyelin. Conclusions: Distinct RBC metabolic signatures were observed in BTHs with elevated HbA<inf>1c</inf>, highlighting alterations in redox and heme metabolism. These findings provide a basis for future investigations into RBC-derived metabolites as complementary tools for glycemic assessment in individuals with thalassemia and hemoglobinopathies.