PI3-kinase mutation linked to insulin and growth factor resistance in vivo
Jonathon N. Winnay, … , C. Ronald Kahn, Pål R. Njølstad
Jonathon N. Winnay, … , C. Ronald Kahn, Pål R. Njølstad
Published March 14, 2016
Citation Information: J Clin Invest. 2016;126(4):1401-1412. https://doi.org/10.1172/JCI84005.
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Research Article Metabolism

PI3-kinase mutation linked to insulin and growth factor resistance in vivo

Abstract

The phosphatidylinositol 3-kinase (PI3K) signaling pathway is central to the action of insulin and many growth factors. Heterozygous mutations in the gene encoding the p85α regulatory subunit of PI3K (PIK3R1) have been identified in patients with SHORT syndrome — a disorder characterized by short stature, partial lipodystrophy, and insulin resistance. Here, we evaluated whether SHORT syndrome–associated PIK3R1 mutations account for the pathophysiology that underlies the abnormalities by generating knockin mice that are heterozygous for the Pik3r1Arg649Trp mutation, which is homologous to the mutation found in the majority of affected individuals. Similar to the patients, mutant mice exhibited a reduction in body weight and length, partial lipodystrophy, and systemic insulin resistance. These derangements were associated with a reduced capacity of insulin and other growth factors to activate PI3K in liver, muscle, and fat; marked insulin resistance in liver and fat of mutation-harboring animals; and insulin resistance in vitro in cells derived from these mice. In addition, mutant mice displayed defective insulin secretion and GLP-1 action on islets in vivo and in vitro. These data demonstrate the ability of this heterozygous mutation to alter PI3K activity in vivo and the central role of PI3K in insulin/growth factor action, adipocyte function, and glucose metabolism.

Authors

Jonathon N. Winnay, Marie H. Solheim, Ercument Dirice, Masaji Sakaguchi, Hye-Lim Noh, Hee Joon Kang, Hirokazu Takahashi, Kishan K. Chudasama, Jason K. Kim, Anders Molven, C. Ronald Kahn, Pål R. Njølstad

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Figure 5

p85WT/R649W mice display impaired insulin signaling in vivo.

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p85WT/R649W mice display impaired insulin signaling in vivo. (A) Analysi...
(A) Analysis of insulin signaling in adipose tissue, liver, and skeletal muscle of p85WT/WT and p85WT/R649W mice administered insulin (5 U) or vehicle. Immunoblot analysis was performed with the indicated antibodies. (B) Quantification of p-AKT (S473) performed using ImageJ. Results are presented as mean ± SEM (n = 5–6 animals). (C) AKT activity was assessed in skeletal muscle and liver (n = 4–5 animals). (D) Immunofluorescence performed on liver sections using anti-PIP3 antibody (original magnification, ×40). (E) Immunoblot analysis of insulin signaling in primary hepatocytes isolated from p85WT/WT and p85WT/R649W mice in the absence or presence of insulin (10 nM) for the indicated times (n = 3). *P < 0.05; **P < 0.01; ***P < 0.001; #P < 0.0005, unpaired Student’s t test.