Interestingly, the HFpEF-MetS diet increased oxygen extraction from the coronary arteries but reduced cardiac efficiency in male Ffar4KO hearts (Fig. 3E, F), indicating that loss of Ffar4 affects cardiac oxygen delivery and the ability of the heart to convert oxygen into mechanical function and are likely the result of microvascular rarefaction. This evidence concerns the gene FFAR4 and metabolic syndrome.