Impact of Dietary Phosphate Excess on Exercise Capacity and Visceral Adiposity

Project Summary/Abstract Inorganic phosphate (Pi) is used in excess as a preservative and flavor enhancement in processed foods. Accordingly, 25% US adult consume Pi at 3-4 fold higher than the recommended daily allowance on a regular basis. While the impact of dietary Pi excess in the setting of chronic kidney disease has been well- studied, its impact on human health in the general population remains incompletely understood. Our recent study in mice demonstrated that dietary Pi loading that mimic the level of US adult consumption leads to reduced spontaneous locomotor activity, exercise capacity, and reduced resting metabolic rate when in normal mice by impairing skeletal muscle mitochondrial function and fat oxidation. These metabolic changes were related to downregulation of numerous genes involved in fatty acid release, transport, and oxidation. Furthermore, our pilot study from the third examination of the Dallas Heart Study (DHS-3) provided support for the animal data as a robust association between higher dietary Pi intake and lower in vivo mitochondrial function using 7-Tesla 31P magnetic resonance spectroscopy and oxygen uptake during exercise was observed. More importantly, an association between higher dietary Pi intake and markers of insulin resistance, including higher liver and muscle fat content was uncovered. Therefore, we propose an ancillary study to the already funded 3rd examination of the DHS to test the impact of dietary Pi excess on physical activity and cardiorespiratory fitness. We will also conduct a randomized crossover study to determine if this phosphotoxicity on the muscle mitochondrial function and exercise capacity is restored by lowering dietary Pi content, which is independent of total energy intake and other nutritional components. The proposed translational studies in otherwise healthy humans have the potential to shift current clinical practice paradigms by identifying phosphate as a key modifiable cardiometabolic risk factor in the general population.