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OBJECTIVE: To determine whether the relationship between average glucose (AG) levels and hemoglobin A1c (HbA1c) differs across racial/ethnic groups. RESEARCH DESIGN AND METHODS: We performed a prospective substudy of GRADE, a comparative effectiveness randomized trial conducted in 36 centers in the U.S. A total of 1,454 of the 5,047 participants in the GRADE cohort, including 534 non-Hispanic White (NHW), 389 non-Hispanic Black (NHB), and 327 Hispanic White patients and 204 patients of other racial/ethnic backgrounds, were included in the substudy. Continuous glucose monitoring (CGM) performed for 10 days was used to calculate AG10. Immediately after CGM, HbA1c and glycated albumin were measured. Fasting plasma glucose (FPG) and glucose area under the curve (AUC) were derived from a 75-g oral glucose tolerance test. RESULTS: The relationship between AG10 and HbA1c was significantly different for NHB compared with NHW patients and those of other racial/ethnic groups. HbA1c levels were 0.2–0.6 percentage points higher in NHB than in NHW patients for AG10 levels from 100 to 250 mg/dL. For an HbA1c of 7%, AG10 was 11 mg/dL higher for NHW than for NHB patients. Similar findings were observed across races for relationships of FPG and AUC with HbA1c and for glucose measurements with glycated albumin levels. Differences in the relationship between AG10 and HbA1c across racial groups remained after adjustments for any demographic or other differences between racial/ethnic subgroups. CONCLUSIONS: The relationship between several measures of glucose with HbA1c and glycated albumin consistently differed across races. These findings should be considered in setting treatment goals and diagnostic levels. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To describe the individual and joint associations of baseline factors with glycemia, and also with differential effectiveness of medications added to metformin. RESEARCH DESIGN AND METHODS: Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE) participants (with type 2 diabetes diagnosed for <10 years, on metformin, and with HbA1c 6.8–8.5%; N = 5,047) were randomly assigned to a basal insulin (glargine), sulfonylurea (glimepiride), glucagon-like peptide 1 agonist (liraglutide), or dipeptidyl peptidase 4 inhibitor (sitagliptin). The glycemic outcome was HbA1c ≥7.0%, subsequently confirmed. Univariate and multivariate regression and classification and regression tree (CART) analyses were used to assess the association of baseline factors with the glycemic outcome at years 1 and 4. RESULTS: In univariate analyses at baseline, younger age (<58 years), Hispanic ethnicity, higher HbA1c, fasting glucose, and triglyceride levels, lower insulin secretion, and relatively greater insulin resistance were associated with the glycemic outcome at years 1 and/or 4. No factors were associated with differential effectiveness of the medications by year 4. In multivariate analyses, treatment group, younger age, and higher baseline HbA1c and fasting glucose were jointly associated with the glycemic outcome by year 4. The superiority of glargine and liraglutide at year 4 persisted after multiple baseline factors were controlled for. CART analyses indicated that failure to maintain HbA1c <7% by year 4 was more likely for younger participants and those with baseline HbA1c ≥7.4%. CONCLUSIONS: Several baseline factors were associated with the glycemic outcome but not with differential effectiveness of the four medications. Failure to maintain HbA1c <7% was largely driven by younger age and higher HbA1c at baseline. Factors that predict earlier glycemic deterioration could help in targeting patients for more aggressive management. [ABSTRACT FROM AUTHOR]

Objective: To evaluate how model-based parameters of β-cell function change with glucose-lowering treatment and associate with glycemic deterioration in adults with type 2 diabetes (T2D)., Research Design and Methods: In the Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE), β-cell function parameters derived from mathematical modeling of oral glucose tolerance tests were assessed at baseline (N = 4,712) and 1, 3, and 5 years following randomization to insulin glargine, glimepiride, liraglutide, or sitagliptin, added to baseline metformin. Parameters included insulin secretion rate (ISR), glucose sensitivity (insulin response to glucose), rate sensitivity (early insulin response), and potentiation. Linear mixed-effects models were used to compare changes across treatments. With Cox proportional hazards and Classification And Regression Tree (CART) analyses we evaluated associations between model parameters and glycemic failure (A1C >7.5%; 58.5 mmol/mol)., Results: β-Cell function parameters increased variably at year 1 across treatments but subsequently declined for all treatments. Statistically significant changes were noted. Liraglutide led to the greatest increases in ISR, glucose sensitivity and potentiation, remaining above baseline at study end. Sitagliptin improved glucose sensitivity, with modest effects on other parameters. Glimepiride temporarily increased ISR and rate sensitivity but minimally increased glucose sensitivity or potentiation. Rate sensitivity increased most with glargine. Higher β-cell function parameters were protective against glycemic deterioration, but treatment did not alter the relationship between these parameters and glycemic outcomes., Conclusions: Common glucose-lowering medications impact different physiologic components of β-cell function in T2D. Regardless of treatment modality, lower β-cell function associated with early glycemic failure, and β-cell function progressively declined after initial improvement., (© 2025 by the American Diabetes Association.)