Notch signaling suppresses glucose metabolism in mesenchymal progenitors to restrict osteoblast differentiation
Seung-Yon Lee, Fanxin Long
Seung-Yon Lee, Fanxin Long
Published October 4, 2018
Citation Information: J Clin Invest. 2018;128(12):5573-5586. https://doi.org/10.1172/JCI96221.
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Research Article Bone biology

Notch signaling suppresses glucose metabolism in mesenchymal progenitors to restrict osteoblast differentiation

Abstract

Notch signaling critically controls cell fate decisions in mammals, both during embryogenesis and in adults. In the skeleton, Notch suppresses osteoblast differentiation and sustains bone marrow mesenchymal progenitors during postnatal life. Stabilizing mutations of Notch2 cause Hajdu-Cheney syndrome, which is characterized by early-onset osteoporosis in humans, but the mechanism whereby Notch inhibits bone accretion is not fully understood. Here, we report that activation of Notch signaling by either Jagged1 or the Notch2 intracellular domain suppresses glucose metabolism and osteoblast differentiation in primary cultures of bone marrow mesenchymal progenitors. Importantly, deletion of Notch2 in the limb mesenchyme increases both glycolysis and bone formation in the long bones of postnatal mice, whereas pharmacological reduction of glycolysis abrogates excessive bone formation. Mechanistically, Notch reduces the expression of glycolytic and mitochondrial complex I genes, resulting in a decrease in mitochondrial respiration, superoxide production, and AMPK activity. Forced activation of AMPK restores glycolysis in the face of Notch signaling. Thus, suppression of glucose metabolism contributes to the mechanism, whereby Notch restricts osteoblastogenesis from bone marrow mesenchymal progenitors.

Authors

Seung-Yon Lee, Fanxin Long

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Figure 1

Notch signaling suppresses glycolysis in bone marrow mesenchymal progenitors.

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Notch signaling suppresses glycolysis in bone marrow mesenchymal progeni...
(A) Relative mRNA levels of the indicated genes assayed by RT-qPCR in R26-NICD2 BMSCs infected with Ad-GFP or Ad-Cre and treated with mineralization media for 48 hours. n = 3. (B) AP or von Kossa staining in R26-NICD2 BMSCs infected with Ad-GFP or Ad-Cre after 4 days or 2 weeks, respectively, in mineralization media. (C) Glucose consumption and lactate production by R26-NICD2 BMSCs infected with Ad-GFP or Ad-CRE in regular growth media for 48 hours. n = 3. (D) Diagram of glycolysis and its key enzymes. (E) Western blots in R26-NICD2 BMSCs infected with Ad-GFP or Ad-CRE for 24 or 48 hours. Protein levels were normalized to β-actin and designated 1 in samples infected with Ad-GFP. Quantification (mean ± SD) was determined from 3 independent samples. (F) Glucose consumption and lactate production from WT BMSCs with or without Jagged1 stimulation for 48 hours. n = 3. (G) Western blots in WT BMSCs with or without Jagged1 stimulation for the indicated durations. Protein levels were normalized to β-actin or tubulin, and quantification (mean ± SD) was determined from 3 independent samples. *P < 0.05, by 2-tailed Student’s t test (A, C, and E–G). Hk2: hexokinase 2; Pfkfb3/4: 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 or 4; F-2,6-P: fructose 2,6-bisphosphate; Pfk1: phosphofructokinase 1; Eno: enolase; Ldha: lactate dehydrogenase a; Pkm: pyruvate kinase, muscle.