It has been suggested that some cancer cells rely upon fatty acid oxidation (FAO) for energy. Here we show that when FAO was reduced approximately 90% by pharmacological inhibition of carnitine palmitoyltransferase I (CPT1) with low concentrations of etomoxir, the proliferation rate of various cancer cells was unaffected. Efforts to pharmacologically inhibit FAO more than 90% revealed that high concentrations of etomoxir (200 μM) have an off-target effect of inhibiting complex I of the electron transport chain. Surprisingly, however, when FAO was reduced further by genetic knockdown of CPT1, the proliferation rate of these same cells decreased nearly 2-fold and could not be restored by acetate or octanoic acid supplementation. Moreover, CPT1 knockdowns had altered mitochondrial morphology and impaired mitochondrial coupling, whereas cells in which CPT1 had been approximately 90% inhibited by etomoxir did not. Lipidomic profiling of mitochondria isolated from CPT1 knockdowns showed depleted concentrations of complex structural and signaling lipids. Additionally, expression of a catalytically dead CPT1 in CPT1 knockdowns did not restore mitochondrial coupling. Taken together, these results suggest that transport of at least some long-chain fatty acids into the mitochondria by CPT1 may be required for anabolic processes that support healthy mitochondrial function and cancer cell proliferation independent of FAO.

Previously, we identified a novel calcium-independent phospholipase, designated calcium-independent phospholipase A 2 ␥ (iPLA 2 ␥), which possesses dual mitochondrial and peroxisomal subcellular localization signals. To identify the roles of iPLA 2 ␥ in cellular bioenergetics, we generated mice null for the iPLA 2 ␥ gene by eliminating the active site of the enzyme through homologous recombination. Mice null for iPLA 2 ␥ display multiple bioenergetic dysfunctional phenotypes, including 1) growth retardation, 2) cold intolerance, 3) reduced exercise endurance, 4) greatly increased mortality from cardiac stress after transverse aortic constriction, 5) abnormal mitochondrial function with a 65% decrease in ascorbate-induced Complex IVmediated oxygen consumption, and 6) a reduction in myocardial cardiolipin content accompanied by an altered cardiolipin molecular species composition. We conclude that iPLA 2 ␥ is essential for maintaining efficient bioenergetic mitochondrial function through tailoring mitochondrial membrane lipid metabolism and composition.Mitochondria transduce chemical energy from multiple dietary substrates into ATP and heat and are important participants in cellular lipid metabolism and signaling (1, 2). Through the precisely regulated partitioning of energy derived from substrates between ATP synthesis and heat production, a finely tuned dynamic balance is maintained to promote organism survival. In addition, excess energy derived from substrates, not immediately needed to fulfill chemical or thermodynamic demands, is directed into the production of lipid synthetic intermediates for energy storage (e.g. mitochondrial synthesis of lysophosphatidic acid, a precursor of triglycerides). Moreover, mitochondria generate diverse chemical signals that reflect the bioenergetic status of the cell (e.g. NO and cytochrome c) and thus integrate multiple energetic, metabolic, and signaling cascades (1-5).Mitochondrial phospholipases are important participants in the regulation of mitochondrial function and signaling (6 -11). Mitochondrial phospholipases catalyze the production of nonesterified fatty acids that regulate UCP function, release lipid second messengers, such as 2-arachidonoyl lysophosphatidylcholine (LPC), 2 and modulate membrane molecular dynamics (12). Maladaptive activation of phospholipases has deleterious metabolic effects in many systems, and previous studies have implicated calcium-independent phospholipases A 2 (iPLA 2 s) as the enzymic mediators of membrane dysfunction in diabetic cardiomyopathy (13-16). Metabolic flexibility is dependent on the efficient coordinated transitions of substrate flux that occur during alterations in energy sources (e.g. glucose versus fatty acid) or energy demand (e.g. exercise). Obesity and type II diabetes are thought to result from disruption of these transitions (17). Diabetic cardiomyopathy is characterized by altered lipid metabolism (i.e. greatly increased utilization of fatty acids) that results in changes in the chemical composition of cardiac membran...

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In our study, lateral pelvic recurrence was a major cause of locoregional recurrence, and ypN+ and lateral lymph node size were risk factors for lateral pelvic recurrence.

The scavenger receptor FAT/CD36 contributes to the inflammation associated with diabetes, atherosclerosis, thrombosis, and Alzheimer disease. Underlying mechanisms include CD36 promotion of oxidative stress and its signaling to stress kinases. Here we document an additional mechanism for the role of CD36 in inflammation. CD36 regulates membrane calcium influx in response to endoplasmic reticulum (ER) stress, release of arachidonic acid (AA) from cellular membranes by cytoplasmic phospholipase A 2 ␣ (cPLA 2 ␣) and contributes to the generation of proinflammatory eicosanoids. CHO cells stably expressing human CD36 released severalfold more AA and prostaglandin E 2 (PGE 2 ), a major product of AA metabolism by cyclooxygenases, in response to thapsigargin-induced ER stress as compared with control cells. Calcium influx after ER calcium release resulted in phosphorylation of cPLA 2 and its translocation to membranes in a CD36-dependent manner. Peritoneal macrophages from CD36 ؊/؊ mice exhibited diminished calcium transients and reduced AA release after thapsigargin or UTP treatment with decreased ERK1/2 and cPLA 2 phosphorylation. However, PGE 2 production was unexpectedly enhanced in CD36 ؊/؊ macrophages, which probably resulted from a large induction of cyclooxygenase 2 mRNA and protein. The data demonstrate participation of CD36 in membrane calcium influx in response to ER stress or purinergic receptor stimulation resulting in AA liberation for PGE 2 formation. Collectively, these results identify a mechanism contributing to the pleiotropic proinflammatory effects of CD36 and suggest that its targeted inhibition may reduce the acute inflammatory response.