Long-chain fatty acids (FA) coordinately induce the expression of a panel of genes involved in cellular FA metabolism in cardiac muscle cells, thereby promoting their own metabolism. These effects are likely to be mediated by peroxisome proliferator-activated receptors (PPARs). Whereas the significance of PPARα in FA-mediated expression has been demonstrated, the role of the PPARβ/δ and PPARγ isoforms in cardiac lipid metabolism is unknown. To explore the involvement of each of the PPAR isoforms, neonatal rat cardiomyocytes were exposed to FA or to ligands specific for either PPARα (Wy-14,643), PPARβ/δ (L-165041, GW501516), or PPARγ (ciglitazone and rosiglitazone). Their effect on FA oxidation rate, expression of metabolic genes, and muscle-type carnitine palmitoyltransferase-1 (MCPT-1) promoter activity was determined. Consistent with the PPAR isoform expression pattern, the FA oxidation rate increased in cardiomyocytes exposed to PPARα and PPARβ/δ ligands, but not to PPARγ ligands. Likewise, the FA-mediated expression of FA-handling proteins was mimicked by PPARα and PPARβ/δ, but not by PPARγ ligands. As expected, in embryonic rat heart-derived H9c2 cells, which only express PPARβ/δ, the FA-induced expression of genes was mimicked by the PPARβ/δ ligand only, indicating that FA also act as ligands for the PPARβ/δ isoform. In cardiomyocytes, MCPT-1 promoter activity was unresponsive to PPARγ ligands. However, addition of PPARα and PPARβ/δ ligands dose-dependently induced promoter activity. Collectively, the present findings demonstrate that, next to PPARα, PPARβ/δ, but not PPARγ, plays a prominent role in the regulation of cardiac lipid metabolism, thereby warranting further research into the role of PPARβ/δ in cardiac disease.

Understanding taste is key for optimizing the palatability of seaweeds and other non‐animal‐based foods rich in protein. The lingual papillae in the mouth hold taste buds with taste receptors for the five gustatory taste qualities. Each taste bud contains three distinct cell types, of which Type II cells carry various G protein‐coupled receptors that can detect sweet, bitter, or umami tastants, while type III cells detect sour, and likely salty stimuli. Upon ligand binding, receptor‐linked intracellular heterotrimeric G proteins initiate a cascade of downstream events which activate the afferent nerve fibers for taste perception in the brain. The taste of amino acids depends on the hydrophobicity, size, charge, isoelectric point, chirality of the alpha carbon, and the functional groups on their side chains. The principal umami ingredient monosodium l ‐glutamate, broadly known as MSG, loses umami taste upon acetylation, esterification, or methylation, but is able to form flat configurations that bind well to the umami taste receptor. Ribonucleotides such as guanosine monophosphate and inosine monophosphate strongly enhance umami taste when l ‐glutamate is present. Ribonucleotides bind to the outer section of the venus flytrap domain of the receptor dimer and stabilize the closed conformation. Concentrations of glutamate, aspartate, arginate, and other compounds in food products may enhance saltiness and overall flavor. Umami ingredients may help to reduce the consumption of salts and fats in the general population and increase food consumption in the elderly.