Unsaturated free fatty acids (FFA) are able to prevent deleterious effects of saturated FFA in skeletal muscle cells although the mechanisms involved are still not completely understood. FFA act as endogenous ligands of peroxisome proliferator-activated receptors (PPAR), transcription factors regulating the expression of genes involved in lipid metabolism. The aim of this study was to determine whether activation of PPARδ, the most common PPAR subtype in skeletal muscle, plays a role in mediating the protective effect of unsaturated FFA on saturated FFA-induced damage in skeletal muscle cells and to examine an impact on mitochondrial respiration. Mouse C2C12 myotubes were treated for 24 h with different concentrations of saturated FFA (palmitic acid), unsaturated FFA (oleic, linoleic and α-linolenic acid), and their combinations. PPARδ agonist GW501516 and antagonist GSK0660 were also used. Both mono- and polyunsaturated FFA, but not GW501516, prevented palmitic acid-induced cell death. Mono- and polyunsaturated FFA proved to be effective activators of PPARδ compared to saturated palmitic acid; however, in combination with palmitic acid their effect on PPARδ activation was blocked and stayed at the levels observed for palmitic acid alone. Unsaturated FFA at moderate physiological concentrations as well as GW501516, but not palmitic acid, mildly uncoupled mitochondrial respiration. Our results indicate that although unsaturated FFA are effective activators of PPARδ, their protective effect on palmitic acid-induced toxicity is not mediated by PPARδ activation and subsequent induction of lipid regulatory genes in skeletal muscle cells. Other mechanisms, such as mitochondrial uncoupling, may underlie their effect.

• Keywords
• Mitochondrial respiration, Mitochondrial uncoupling, PPARδ, PPARδ agonist, Saturated fatty acid, Skeletal muscle cells, Unsaturated fatty acids,
• MeSH
• Cell Death drug effects   MeSH
• Cell Line MeSH
• Dietary Fats, Unsaturated pharmacology   MeSH
• Muscle, Skeletal drug effects   metabolism   MeSH
• Palmitic Acid toxicity   MeSH
• Mice MeSH
• Receptors, Cytoplasmic and Nuclear metabolism   MeSH
• Gene Expression Regulation, Enzymologic drug effects   MeSH
• Sulfones pharmacology   MeSH
• Muscle Cells drug effects   metabolism   MeSH
• Thiazoles pharmacology   MeSH
• Thiophenes pharmacology   MeSH
• Cell Survival MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Dietary Fats, Unsaturated MeSH
• GSK0660 MeSH Browser
• GW 501516 MeSH Browser
• Palmitic Acid MeSH
• Ppard protein, mouse MeSH Browser
• Receptors, Cytoplasmic and Nuclear MeSH
• Sulfones MeSH
• Thiazoles MeSH
• Thiophenes MeSH

BACKGROUND: The lipophilic positively charged moiety of triphenylphosphonium (TPP+) has been used to target a range of biologically active compounds including antioxidants, spin-traps and other probes into mitochondria. The moiety itself, while often considered biologically inert, appears to influence mitochondrial metabolism. METHODOLOGY/PRINCIPAL FINDINGS: We used the Seahorse XF flux analyzer to measure the effect of a range of alkylTPP+ on cellular respiration and further analyzed their effect on mitochondrial membrane potential and the activity of respiratory complexes. We found that the ability of alkylTPP+ to inhibit the respiratory chain and decrease the mitochondrial membrane potential increases with the length of the alkyl chain suggesting that hydrophobicity is an important determinant of toxicity. CONCLUSIONS/SIGNIFICANCE: More hydrophobic TPP+ derivatives can be expected to have a negative impact on mitochondrial membrane potential and respiratory chain activity in addition to the effect of the biologically active moiety attached to them. Using shorter linker chains or adding hydrophilic functional groups may provide a means to decrease this negative effect.

• MeSH
• Cell Line MeSH
• Electron Transport Chain Complex Proteins metabolism   MeSH
• Heterocyclic Compounds pharmacology   MeSH
• Rats MeSH
• Membrane Potential, Mitochondrial drug effects   MeSH
• Organophosphorus Compounds pharmacology   MeSH
• Rats, Wistar MeSH
• Oxygen Consumption drug effects   MeSH
• Mitochondria, Muscle metabolism   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Electron Transport Chain Complex Proteins MeSH
• Heterocyclic Compounds MeSH
• Organophosphorus Compounds MeSH
• tris(o-phenylenedioxy)cyclotriphosphazene MeSH Browser