High-phosphate diet reduces mouse bone quality in vivo and alters metabolic gene expression of osteoclasts and osteoblasts in vitro

Introduction: Inorganic phosphate (Pi) is used extensively as a preservative and flavor enhancer in processed foods consumed as part of a western diet. We reported that healthy, male mice fed a high-Pi (HP) diet for 12 weeks have decreased maximal exercise capacity but normal cardiac function. Expression of fatty acid and glucose metabolism genes are decreased and increased, respectively, and mitochondrial function is significantly impaired in skeletal muscle after HP diet. We also recently published that healthy, male mice fed HPD for 18 weeks display decreased tissue mineral density and increased fragility of femurs without altering bone volume. The number of osteoclasts and osteoblasts, cells responsible for bone turnover, are increased in femurs from HP diet-fed mice. However, whether HP diet impacts metabolic gene expression in osteoclasts and osteoblasts is not known. Hypothesis: HP diet dysregulates bone metabolic gene expression similar to skeletal muscle metabolic gene expression. Methods: Primary osteoclast progenitors and osteoblasts were isolated from mouse bone marrow and long bones, respectively. Osteoclasts were differentiated from progenitors using Receptor activator of nuclear factor-κB ligand (RANKL) and Macrophage Colony-Stimulating Factor (MCSF). Osteoblasts that migrated out of long bone fragments after Liberase digestion were collected and cultured. Cell-specific markers were measured by qPCR: tartrate-resistant acid phosphatase (TRAP) and cathepsin K (CTSK) were used to identify osteoclasts and collagenase I (COL1A1) and osteocalcin (OCN) were used to identify osteoblasts. TRAP and alkaline phosphatase staining were also used to identify osteoclasts and osteoblasts, respectively. Osteoclasts and osteoblasts were cultured in normal (1mM) or HP (3mM) media for five and seven days, respectively, and metabolic gene expression was quantified by qPCR. Results: qPCR and staining of cell-specific markers indicate that we can obtain pure cell populations. HP treatment of osteoclasts results in decreased expression of metabolic genes lactate dehydrogenase subunit A (LDHA), hexokinase I (HK1), short-chain enoyl-CoA hydratase 1 (ECHS1), and short-chain acyl-CoA dehydrogenase (ACADS). HP treatment of osteoblasts results in decreased expression of LDHA and hexokinase II (HK2). We also found that the number and morphology of osteoclasts and osteoblasts do not change after HP treatment. Conclusions: HP dysregulates metabolic gene expression in osteoclasts and osteoblasts, but to a different extent than what we detect in skeletal muscle. Glucose and fatty acid metabolism-related gene expression is decreased in osteoclasts, whereas only glucose-related genes are decreased in osteoblasts. Our results suggest that there are cell-specific metabolic responses to Pi dysregulation, which may be required to maintain normal physiological function for each tissue. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.