Addition of insulin glargine or NPH insulin to metformin monotherapy in poorly controlled type 2 diabetic patients decreases IGF-I bioactivity similarly

Aims/hypothesis The aim of this study was to compare IGFI bioactivity 36 weeks after the addition of insulin glargine (A21Gly,B31Arg,B32Arg human insulin) or NPH insulin to metformin therapy in type 2 diabetic patients who had poor glucose control under metformin monotherapy. Methods In the Lantus plus Metformin (LANMET) study, 110 poorly controlled insulin-naive type 2 diabetic patients were randomised to receive metformin with either insulin glargine (G+MET) or NPH insulin (NPH+MET). In the present study, IGF-I bioactivity was measured, retrospectively, in 104 out of the 110 initially included LANMET participants before and after 36 weeks of insulin therapy. IGF-I bioactivity was measured using an IGF-I kinase receptor activation assay. Results After 36 weeks of insulin therapy, insulin doses were comparable between the G+MET (68±5.7 U/day) and NPH+MET (71±6.2 U/day) groups (p=0.68). Before insulin therapy, circulating IGF-I bioactivity was similar between the G+MET (134±9 pmol/l) and NPH+MET (135 ±10 pmol/l) groups (p=0.83). After 36 weeks, IGF-I bioactivity had decreased significantly (p=0.001) and did not differ between the G+MET (116±9 pmol/l) and NPH+MET (117± 10 pmol/l) groups (p=0.91). At baseline and after insulin therapy, total IGF-I concentrations were comparable in both groups (baseline: G+MET 13.3±1.0 vs NPH+MET 13.3± 1.0 nmol/l, p=0.97; and 36 weeks: 13.4±1.0 vs 13.1± 0.9 nmol/l, p=0.71). Total IGF-I concentration did not change during insulin therapy (13.3±0.7 vs 13.3±0.7 nmol/l, baseline vs 36 weeks, p=0.86). Conclusions/interpretation Addition of insulin glargine or NPH insulin to metformin monotherapy in poorly controlled type 2 diabetic patients decreases serum IGF-I bioactivity in a similar manner