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FASEB J. 2016 Oct;30(10):3378-3387. Epub 2016 Jun 23.

Hypophosphatemia promotes lower rates of muscle ATP synthesis.

Author information

1
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA.
2
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, USA.
3
Department of Radiology and Biomedical Engineering, Yale University School of Medicine, New Haven, Connecticut, USA.
4
Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, USA.
5
Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, USA; and.
6
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA; Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark.
7
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA; Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, USA; Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, USA; Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark gerald.shulman@yale.edu.

Abstract

Hypophosphatemia can lead to muscle weakness and respiratory and heart failure, but the mechanism is unknown. To address this question, we noninvasively assessed rates of muscle ATP synthesis in hypophosphatemic mice by using in vivo saturation transfer [31P]-magnetic resonance spectroscopy. By using this approach, we found that basal and insulin-stimulated rates of muscle ATP synthetic flux (VATP) and plasma inorganic phosphate (Pi) were reduced by 50% in mice with diet-induced hypophosphatemia as well as in sodium-dependent Pi transporter solute carrier family 34, member 1 (NaPi2a)-knockout (NaPi2a-/-) mice compared with their wild-type littermate controls. Rates of VATP normalized in both hypophosphatemic groups after restoring plasma Pi concentrations. Furthermore, VATP was directly related to cellular and mitochondrial Pi uptake in L6 and RC13 rodent myocytes and isolated muscle mitochondria. Similar findings were observed in a patient with chronic hypophosphatemia as a result of a mutation in SLC34A3 who had a 50% reduction in both serum Pi content and muscle VATP After oral Pi repletion and normalization of serum Pi levels, muscle VATP completely normalized in the patient. Taken together, these data support the hypothesis that decreased muscle ATP synthesis, in part, may be caused by low blood Pi concentrations, which may explain some aspects of muscle weakness observed in patients with hypophosphatemia.-Pesta, D. H., Tsirigotis, D. N., Befroy, D. E., Caballero, D., Jurczak, M. J., Rahimi, Y., Cline, G. W., Dufour, S., Birkenfeld, A. L., Rothman, D. L., Carpenter, T. O., Insogna, K., Petersen, K. F., Bergwitz, C., Shulman, G. I. Hypophosphatemia promotes lower rates of muscle ATP synthesis.

KEYWORDS:

[31P]MRS; inorganic phosphate; saturation transfer

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