Insulin-Like Growth Factor (IGF) Binding Protein-2, Independently of IGF-1, Induces GLUT-4 Translocation and Glucose Uptake in 3T3-L1 Adipocytes

Figure 2

IGFBP-2 stimulates glucose uptake in insulin receptor and IGF-1 receptor-independent mechanism. (a) Effect of the insulin receptor (INSR) blocker S961 (black bars) on basal and insulin, IGF-1, IGF-1 LR3, and IGFBP-2-induced glucose uptake (white bars). (b) Effect of the IGF-1 receptor blocker PPP (black bars) on basal and insulin, IGF-1, IGF-1 LR3, and IGFBP-2 induced glucose uptake (white bars). Differentiated 3T3-L1 adipocytes were incubated with 100 nM S961 for 2 h or 60 nM PPP for 4 h before treatment with insulin, IGF-1, IGF-1 LR3, or IGFBP-2 for 30 min. (c and d) Relative mRNA expression, normalized to 36B4, and Western blot analysis of INSR following siRNA transfection, respectively. (e, f, and g) Effect of 30 min treatment with insulin, IGF-1, and IGFBP-2 on glucose uptake in control siRNA and INSR siRNA transfected 3T3-L1 adipocytes. Each experiment was performed with three technical replicates and total number of experiments was three. The glucose uptake values are percentage of the controls. The results are presented as mean ± SEM. , , and .

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