Longitudinal Effects of Glucose-Lowering Medications on β-Cell Responses and Insulin Sensitivity in Type 2 Diabetes: The GRADE Randomized Clinical Trial

Diabetes Care. 2024 Apr 1;47(4):580-588. doi: 10.2337/dc23-1070.

Abstract

Objective: To compare the long-term effects of glucose-lowering medications (insulin glargine U-100, glimepiride, liraglutide, and sitagliptin) when added to metformin on insulin sensitivity and β-cell function.

Research design and methods: In the Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE) cohort with type 2 diabetes (n = 4,801), HOMA2 was used to estimate insulin sensitivity (HOMA2-%S) and fasting β-cell function (HOMA2-%B) at baseline and 1, 3, and 5 years on treatment. Oral glucose tolerance test β-cell responses (C-peptide index [CPI] and total C-peptide response [incremental C-peptide/incremental glucose over 120 min]) were evaluated at the same time points. These responses adjusted for HOMA2-%S in regression analysis provided estimates of β-cell function.

Results: HOMA2-%S increased from baseline to year 1 with glargine and remained stable thereafter, while it did not change from baseline in the other treatment groups. HOMA2-%B and C-peptide responses were increased to variable degrees at year 1 in all groups but then declined progressively over time. At year 5, CPI was similar between liraglutide and sitagliptin, and higher for both than for glargine and glimepiride [0.80, 0.87, 0.74, and 0.64 (nmol/L)/(mg/dL) * 100, respectively; P < 0.001], while the total C-peptide response was greatest with liraglutide, followed in descending order by sitagliptin, glargine, and glimepiride [1.54, 1.25, 1.02, and 0.87 (nmol/L)/(mg/dL) * 100, respectively, P < 0.001]. After adjustment for HOMA2-%S to obtain an estimate of β-cell function, the nature of the change in β-cell responses reflected those in β-cell function.

Conclusions: The differential long-term effects on insulin sensitivity and β-cell function of four different glucose-lowering medications when added to metformin highlight the importance of the loss of β-cell function in the progression of type 2 diabetes.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Blood Glucose
  • C-Peptide
  • Diabetes Mellitus, Type 2* / drug therapy
  • Glucose / therapeutic use
  • Humans
  • Hypoglycemic Agents / therapeutic use
  • Insulin Glargine / therapeutic use
  • Insulin Resistance* / physiology
  • Liraglutide / pharmacology
  • Liraglutide / therapeutic use
  • Metformin* / therapeutic use
  • Sitagliptin Phosphate / therapeutic use
  • Sulfonylurea Compounds*

Substances

  • glimepiride
  • Insulin Glargine
  • Hypoglycemic Agents
  • Glucose
  • Liraglutide
  • C-Peptide
  • Blood Glucose
  • Metformin
  • Sitagliptin Phosphate
  • Sulfonylurea Compounds