The Glycemia Risk Index (GRI) as a Biomarker for Subclinical Endothelial Dysfunction in Type 1 Diabetes: A Cross-Sectional Study

Circulating levels of endothelial progenitor cells (EPCs) involved in endothelial homeostasis are often reduced in people with type 1 diabetes (T1D). The Glycemia Risk Index (GRI) quantifies the quality of glucose control by assessing both hypo- and hyperglycemia risk. We aim to investigate the association between the GRI and circulating EPC levels in people with T1D. This cross-sectional study included 132 adults with T1D, on intensive insulin therapy. We calculated GRI from 14 days continuous glucose monitoring-derived metrics and quantified EPCs count by flow cytometry, stratifying results by GRI zones, ranging from A (lowest risk) to E (highest risk). Higher GRI scores were significantly associated with poorer metabolic parameters. Circulating levels of CD34⁺, CD133⁺, KDR⁺, and CD34⁺KDR⁺ cells were lower in participants with a worse GRI compared to adults with a better GRI. Linear regression analyses showed a negative association between GRI and CD34⁺ (β = -1.079, <i>p</i> = 0.006), CD34⁺CD133⁺ (β = -0.581, <i>p</i> = 0.008), and CD34⁺KDR⁺ (β = -0.147, <i>p</i> = 0.010). No significant association was found between HbA_1c and any EPC phenotype. Adults with T1D and a high GRI level had a lower EPCs count. GRI was significantly associated with certain EPC phenotypes, suggesting its potential role as a biomarker for cardiovascular risk assessment.