We determined whether high fatty acid oxidation rates during aerobic reperfusion of ischemic hearts could be explained by a decrease in malonyl-CoA levels, which would relieve inhibition of carnitine palmitoyl-transferase 1, the rate-limiting enzyme involved in mitochondrial uptake of fatty acids. Isolated working rat hearts perfused with 1.2 mM palmitate were subjected to 30 min of global ischemia, followed by 60 min of aerobic reperfusion. Fatty acid oxidation rates during reperfusion were 136% higher than rates seen in aerobically perfused control hearts, despite the fact that cardiac work recovered to only 16% of pre-ischemic values. Neither the activity of carnitine palmitoyltransferase 1, or the IC50 value of malonyl-CoA for carnitine palmitoyl-transferase 1 were altered in mitochondria isolated from aerobic, ischemic, or reperfused ischemic hearts. Levels of malonyl-CoA were extremely low at the end of reperfusion compared to levels seen in aerobic controls, as was the activity of acetyl-CoA carboxylase, the enzyme which produces malonyl-CoA. The activity of 5'-AMP-activated protein kinase, which has been shown to phosphorylate and inactivate acetyl-CoA carboxylase in other tissues, was significantly increased at the end of ischemia, and remained elevated throughout reperfusion. These results suggest that accumulation of 5'-AMP during ischemia results in an activation of AMP-activated protein kinase, which phosphorylates and inactivates ACC during reperfusion. The subsequent decrease in malonyl-CoA levels wil result in accelerated fatty acid oxidation rates during reperfusion of ischemic hearts.

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Perfluorooctanoic acid (PFOA) is an octanoic acid derivative to which all aliphatic hydrocarbons are substituted by fluorine. PFOA and its salts are commercially used in various industrial processes. The chemical is persistent in the environment and does not undergo biotransformation. It was reported that PFOA is found not only in the serum of occupationally exposed workers but also general populations. Recent studies have suggested that the biological half-life of PFOA in humans is 4.37 years based on study of occupationally exposed workers. It is increasingly suspect that PFOA accumulates and affects human health, although the toxicokinetics of PFOA in humans remain unclear. In experimental animals, PFOA seems low in toxicity. PFOA is well-absorbed following oral and inhalation exposure, and to a lesser extent following dermal exposure. Once absorbed in the body, it distributes predominantly to the liver and plasma, and to a lesser extent the kidney and lungs. PFOA is excreted in both urine and feces. Biological half-life of PFOA is quite different between species and sexes and the difference is due mainly to the difference in renal clearance. In rats, renal clearance of PFOA is regulated by sex hormones, especially testosterone. PFOA is excreted into urine by active tubular secretion, and certain organic anion transporters are though to be responsible for the secretion. Fecal excretion is also important in the elimination of PFOA. There is evidence that PFOA undergoes enterohepatic circulation resulting in reduced amounts of fecal excretion. Elucidation of the mechanisms of transport in biological systems leads to elimination and detoxification of this chemical in the human body.

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Acetyl-CoA carboxylase (ACC) is regarded in liver and adipose tissue to be the rate-limiting enzyme for fatty acid biosynthesis; however, in heart tissue it functions as a regulator of fatty acid oxidation. Because the control of fatty acid oxidation is important to the functioning myocardium, the regulation of ACC is a key issue. Two cardiac isoforms of ACC exist, with molecular masses of 265 kDa and 280 kDa (ACC265 and ACC280). In this study, these proteins were purified from rat heart and used in subsequent phosphorylation and immunoprecipitation experiments. Our results demonstrate that 5 H AMP-activated protein kinase (AMPK) is able to phosphorylate both ACC265 and ACC280, resulting in an almost complete loss of ACC activity. Although cAMP-dependent protein kinase phosphorylated only ACC280, a dramatic loss of ACC activity was still observed, suggesting that ACC280 contributes most, if not all, of the total heart ACC activity. ACC280 and ACC265 copurified under all experimental conditions, and purification of heart ACC also resulted in the specific copurification of the a 2 isoform of the catalytic subunit of AMPK. Although both catalytic subunits of AMPK were expressed in crude heart homogenates, our results suggest that a 2 , and not a 1 , is the dominant isoform of AMPK catalytic subunit regulating ACC in the heart. Immunoprecipitation studies demonstrated that specific antibodies for both ACC265 and ACC280 were able to coimmunoprecipitate the alternate isoform along with the a 2 isoform of AMPK. Taken together, the immunoprecipitation and the purification studies suggest that the two isoforms of ACC in the heart exist in a heterodimeric structure, and that this structure is tightly associated with the a 2 subunit of AMPK.

Perfluoroalkyl chemicals have been used since the 1950s in a wide variety of industrial and consumer products. Among them, perfluofooctanoic acid (PFOA) was used primarily in an ammonium salt form as an emulsifier in the production of fluoropolymers, such as poly(tetrafluoroethylene) and poly(vinylidine fluoride).1) These polymers have been used in various consumers and industrial products, such as water-repellants for leather paper and textiles. The toxicity of PFOA has been characterized in numerous studies with various species.2) Early studies have shown that organic fluorine accumulated in the serum of occupationally exposed people.3) Resent studies have revealed that PFOA and pefluorooctanesulfonic acid have been found in water, [4][5][6] sediment, 7) wildlife 8-10) and human. [11][12][13][14][15] These findings suggest that general population is exposed to such perfluorochemicals which have globally spread at very low levels.PFOA is thought to remain in humans for long time by the study that has estimated PFOA half-life for 9 retirees from chemical plant to be 4.37 years on the average. 16) On the other hand, several studies that have been carried out on the fate of PFOA in experimental animals including rats have shown that biological half-life of PFOA in male rats was calculated to be 105 h after an intraperitoneal administration at the dose of 50 mg/kg, 17) 9 d after an intraperitoneal administration at a dose of 4 mg/kg, 18) and 6.8 d after an intravenous administration at a dose of 20 mg/kg, 19) respectively. In the studies using experimental animals, PFOA has been shown to be mainly distributed to the liver and serum/plasma, and easily excreted into urine. [18][19][20] The reason for such species difference in half-life of PFOA between humans and experimental animals may be due to the differences in the proteins responsible for distribution, binding and transport of PFOA. Alternative explanation is that the concentrations of PFOA used for the calculation of half-life of PFOA were quite different between humans and the experimental animals. In fact, serum concentrations of PFOA were shown be 11.7 mg/ml 24 h after an intraperitoneal administration at a dose of 4 mg/kg 18) and 61.5 mg/ml 24 h after an intravenous injection at a dose of 20 mg, 19) respectively, while serum samples of human that have been used for the calculation of half-life contained PFOA at the concentrations of 0.06-1.84 mg/ml.16) To date, however, toxicokinetic study has not been performed at the serum concentrations of PFOA corresponding to the levels in serum of humans.In the view of toxicological aspects, it is important to know the toxicokinetic data of PFOA at very low serum concentrations. In the present study, we demonstrated that tissue distribution of PFOA at very low dose is markedly different from those at high doses in experimental animals. MATERIALS AND METHODSMaterials PFOA was purchased from Sigma Aldrich Japan (Tokyo, Japan Faculty of Pharmaceutical Sciences, Josai University; 1-1 Keyakidai, Sakado, Saitama 350-0295,...