Porcine Insulin-Like Growth Factor (IGF) Binding Protein Blocks IGF-I Action on Porcine Adipose Tissue 1

Abstract

A growth hormone-dependent insulin-like growth factor (IGF) binding protein (IGFBP) purified from porcine serum specifically blocked the acute insulin-like effects of IGF-I on lipogenesis and glucose oxidation in porcine adipose tissue. This inhibition was dose dependent with half-maximal effective concentrations of IGFBP of 530 ng/ml for lipogenesis and 590 ng/ml for glucose oxidation in the presence of 10^-8 M IGF-I. The IGFBP also caused decreased rates of lipogenesis following a 1-hr preincubation of tissue with IGF-I (10^-8 M). The IGFBP had no effect on insulin action on porcine adipose tissue.

These findings demonstrate the inhibitory effects of a highly purified porcine serum IGFBP on the biologic effects of IGF-I in vitro, and provide evidence that the growth hormone-dependent IGFBP blocks the acute insulin-like actions of IGF-I in vivo.