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Jenica H Kakadia Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
Children's Health Research Institute, London, Ontario, Canada

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Muhammad U Khalid Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada

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Ilka U Heinemann Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada

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Victor K Han Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
Children's Health Research Institute, London, Ontario, Canada
Department of Pediatrics, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada

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Mechanisms underlying limitations in glucose supply that restrict fetal growth are not well established. IGF-1 is an important regulator of fetal growth and IGF-1 bioavailability is markedly inhibited by IGFBP-1 especially when the binding protein is hyperphosphorylated. We hypothesized that the AMPK–mTORC1 pathway increases IGFBP-1 phosphorylation in response to glucose deprivation. Glucose deprivation in HepG2 cells activated AMPK and TSC2, inhibited mTORC1 and increased IGFBP-1 secretion and site-specific phosphorylation. Glucose deprivation also decreased IGF-1 bioavailability and IGF-dependent activation of IGF-1R. AICAR (an AMPK activator) activated TSC2, inhibited mTORC1, and increased IGFBP-1 secretion/phosphorylation. Further, siRNA silencing of either AMPK or TSC2 prevented mTORC1 inhibition and IGFBP-1 secretion and phosphorylation in glucose deprivation. Our data suggest that the increase in IGFBP-1 phosphorylation in response to glucose deprivation is mediated by the activation of AMPK/TSC2 and inhibition of mTORC1, providing a possible mechanistic link between glucose deprivation and restricted fetal growth.

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