IRP1 deficiency alters mitochondrial metabolism and protects against metabolic syndrome pathologies
Wen Gu, Nicole Wilkinson, Carine Fillebeen, Darren M. Blackburn, Korin Sahinyan, Eric Bonneil, Tao Zhao, Zhi Luo, Vahab D. Soleimani, Vincent Richard, Christoph H. Borchers, Albert Koulman, Benjamin Jenkins, Bernhard Michalke, Hans Zischka, Judith Sailer, Vivek Venkataramani, Othon Iliopoulos, Gary Sweeney, Kostas Pantopoulos
Wen Gu, Nicole Wilkinson, Carine Fillebeen, Darren M. Blackburn, Korin Sahinyan, Eric Bonneil, Tao Zhao, Zhi Luo, Vahab D. Soleimani, Vincent Richard, Christoph H. Borchers, Albert Koulman, Benjamin Jenkins, Bernhard Michalke, Hans Zischka, Judith Sailer, Vivek Venkataramani, Othon Iliopoulos, Gary Sweeney, Kostas Pantopoulos
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Research Article Hepatology Metabolism

IRP1 deficiency alters mitochondrial metabolism and protects against metabolic syndrome pathologies

Abstract

Iron regulatory protein 1 (IRP1) is a posttranscriptional regulator of cellular iron metabolism. In mice, loss of IRP1 causes polycythemia through translational de-repression of HIF2α mRNA, which increases renal erythropoietin production. Here, we show that Irp1–/– mice develop fasting hypoglycemia and are protected against high-fat diet–induced hyperglycemia and hepatic steatosis. Discovery-based proteomics of Irp1–/– livers revealed a mitochondrial dysfunction signature. Seahorse flux analysis in primary hepatocytes and differentiated skeletal muscle myotubes confirmed impaired respiratory capacity, with a shift from oxidative phosphorylation to glycolytic ATP production. This metabolic rewiring was associated with enhanced insulin sensitivity and increased glucose uptake in skeletal muscle. Under metabolic stress, IRP1 deficiency altered the redox balance of mitochondrial iron, resulting in inefficient energy production and accumulation of amino acids and metabolites in skeletal muscles, rendering them unavailable for hepatic gluconeogenesis. These findings identify IRP1 as a critical regulator of systemic energy homeostasis.

Authors

Wen Gu, Nicole Wilkinson, Carine Fillebeen, Darren M. Blackburn, Korin Sahinyan, Eric Bonneil, Tao Zhao, Zhi Luo, Vahab D. Soleimani, Vincent Richard, Christoph H. Borchers, Albert Koulman, Benjamin Jenkins, Bernhard Michalke, Hans Zischka, Judith Sailer, Vivek Venkataramani, Othon Iliopoulos, Gary Sweeney, Kostas Pantopoulos

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Figure 5

Evidence that mitochondrial dysfunction in IRP1-deficient cells is caused by impaired mitochondrial redox speciation of iron.

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Evidence that mitochondrial dysfunction in IRP1-deficient cells is cause...
(A–J) Male WT and Irp1–/– mice (5 weeks old; n = 5–8 per experimental group) received control diet or HFD for 10 weeks. Liver and quadriceps skeletal muscle tissue samples were isolated for biochemical studies at endpoint. Cytosolic and mitochondrial fractions were prepared and used for quantification of total iron and iron speciation analysis. (A and B) Western blot analysis of IRP1, TfR1, ferritin, and β-actin in liver (A) and skeletal muscles (B). (C–F) Total cytosolic iron (C), total mitochondrial iron (D), cytosolic Fe2+/Fe3+ ratios (E), and mitochondrial Fe2+/Fe3+ ratios (F) in liver. (G–J) Total cytosolic iron (G), total mitochondrial iron (H), cytosolic Fe2+/Fe3+ ratios (I), and mitochondrial Fe2+/Fe3+ ratios (J) in skeletal muscles. (K–M) For 10 weeks, 5-week-old male WT and Irp1–/– mice (n = 5–7 per experimental group) received control diet or IDD. (K) GTT after 5 hours’ fasting. Right: pairwise comparisons of data from WT and Irp1–/– mice on IDD at various time points. (L) Pyruvate tolerance test after 6 hours’ fasting. Right: AUC. (M) GTT in 5-week-old male Irp1–/– mice after 5 hours’ fasting. Right: pairwise comparisons of data from Irp1–/– mice with or without iron dextran injections at various time points. In A and B, Western blots for TfR1 and ferritin quantified by densitometry relative to β-actin; average values shown on top (due to experimental variability, quantification of “outlier” sample shown separately). TfR1/β-actin and ferritin/β-actin ratios from WT mice set as 1. In C–J, iron measurements normalized to protein content and expressed as mean ± SD. Data in C–M shown as mean ± SEM. Statistical analysis performed with 2-way ANOVA with Tukey’s multiple-comparison test; 2-tailed Student’s t test for comparisons between 2 groups. *P < 0.05, **P < 0.01.