Context: As diabetes is in part an inflammatory condition, the initiation of insulin and/or metformin may beneficially reduce levels of inflammatory biomarkers such as high-sensitivity C-reactive protein (hsCRP).
Objective: To determine whether insulin alone or combined with metformin lowers levels of hsCRP, IL-6, and soluble tumor necrosis factor receptor 2 (sTNFr2) in patients with recent-onset type 2 diabetes mellitus.
Design, setting, and participants: Randomized 2 x 2 factorial trial of open-label insulin glargine and placebo-controlled metformin in 500 adults with type 2 diabetes (median time from diagnosis, 2.0 years), suboptimal glycemic control, and elevated hsCRP levels. Patients were recruited from US office-based practices between October 2006 and December 2008.
Intervention: Random allocation to 1 of 4 treatments (placebo metformin only, placebo metformin and insulin glargine, active metformin only, or active metformin and insulin glargine) with dose titration targeting fasting blood glucose less than 110 mg/dL.
Main outcome measures: Change in hsCRP level (primary end point) and change in IL-6 and sTNFr2 levels (secondary end points) from baseline to 14 weeks.
Results: Levels of glucose and glycated hemoglobin (HbA(1c)) were significantly reduced with active treatment vs placebo (all P values <.001). Levels of hsCRP were reduced in all 4 groups. There was no significant difference in hsCRP reduction among those allocated to insulin (-11.8%; 95% CI, -18.7% to -4.4%) or to no insulin (-17.5%; 95% CI, -23.9% to -10.5%) (P for difference = .25), or among those allocated to active metformin (-18.1%; 95% CI, -24.4% to -11.1%) or placebo metformin (-11.2%; 95% CI, -18.1% to -3.7%) (P for difference = .17). In the individual treatment groups, despite a differential impact on glucose control, reductions in hsCRP in the metformin (-16.1%; 95% CI, -25.1% to -6.1%) and metformin plus insulin (-20.1%; 95% CI, -28.8% to -10.4%) groups were no different than reductions with placebo alone (-19.0%; 95% CI, -27.8% to -9.1%; P = .67 and .87 vs placebo, respectively). By contrast, hsCRP reduction was attenuated with insulin alone (-2.9%, 95% CI, -13.2% to 8.6%; P = .03 vs placebo). Similar findings were noted for levels of IL-6 and sTNFr2.
Conclusion: In patients with recent-onset type 2 diabetes, treatment with insulin or metformin compared with placebo did not reduce inflammatory biomarker levels despite improving glucose control.
Trial registration: clinicaltrials.gov Identifier: NCT00366301.