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The role of 3,5-diiodo-L-thyronine (T), initially considered only a 3,3′,5-triiodo-L-thyronine (T) catabolite, in the bioenergetic metabolism is of growing interest. In this study we investigated the acute effects (within 1 h) of T administration to hypothyroid rats on liver mitochondria fatty acid uptake and β-oxidation rate, mitochondrial efficiency (by measuring proton leak) and mitochondrial oxidative damage (by determining HO release). Fatty acid uptake into mitochondria was measured assaying carnitine palmitoyl transferase (CPT) I and II activities, and fatty acid β-oxidation using palmitoyl-CoA as a respiratory substrate. Mitochondrial fatty acid pattern was defined by gas-liquid chromatography. In hypothyroid + T vs hypothyroid rats we observed a raise in the serum level of nonesterified fatty acids (NEFA), in the mitochondrial CPT system activity and in the fatty acid β-oxidation rate. A parallel increase in the respiratory chain activity, mainly from succinate, occurs. When fatty acids are chelated by bovine serum albumin, a T-induced increase in both state 3 and state 4 respiration is observed, while, when fatty acids are present, mitochondrial uncoupling occurs together with increased proton leak, responsible for mitochondrial thermogenesis. T administration decreases mitochondrial oxidative stress as determined by lower HO production. We conclude that in rat liver mitochondria T acutely enhances the rate of fatty acid β-oxidation, and the activity of the downstream respiratory chain. The T-induced increase in proton leak may contribute to mitochondrial thermogenesis and to the reduction of oxidative stress. Our results strengthen the previously reported ability of T to reduce adiposity, dyslipidemia and to prevent liver steatosis. [ABSTRACT FROM AUTHOR]

Purpose: Regular consumption of extra virgin olive oil (EVOO) is associated with a low incidence of atherosclerotic diseases. The phenolic component contributes to the hypolipidemic action of EVOO, although the biochemical mechanisms leading this beneficial outcome are not fully understood. Since liver plays a pivotal role in the whole body lipid homeostasis, we investigated the short-term effects of EVOO extract, with a high phenol content (HPE), on lipid synthesis in primary rat hepatocytes. Refined olive oil extract, with a low phenol content, was used throughout this study as a control. Methods: Olive oil phenols isolated with methanolic extractions were subsequently analyzed by high performance liquid chromatography, electrospray ionization tandem mass spectrometry, and gas chromatography mass spectrometry. Rat hepatocytes were obtained from collagenase perfusion of liver. A colorimetric assay was performed to exclude cytotoxicity of the extracts. Radioenzymatic methods were used in order to investigate hepatic lipid metabolism. Results: HPE, dose- (0.1-50 μg/mL) and time-dependently (0.5-4 h) inhibited both lipogenesis and cholesterogenesis ( n = 6, P < 0.05), as well as triglycerides synthesis ( n = 5, P < 0.05). We showed that these effects are attributable to a short-term modulation by HPE of the key enzymes implicated in the abovementioned pathways ( n = 5, P < 0.05). Conclusions: The decrease in hepatic lipid synthesis may represent a potential mechanism underlying the hypolipidemic effect of EVOO phenols. [ABSTRACT FROM AUTHOR]

Purpose: Hepatic fatty acid synthesis is influenced by several nutritional and hormonal factors. In this study, we have investigated the effects of distinct experimental diets enriched in carbohydrate or in fat on hepatic lipogenesis. Methods: Male Wistar rats were divided into four groups and fed distinct experimental diets enriched in carbohydrates (70 % w/w) or in fat (20 and 35 % w/w). Activity and expression of the mitochondrial citrate carrier and of the cytosolic enzymes acetyl-CoA carboxylase and fatty acid synthetase were analyzed through the study with assessments at 0, 1, 2, 4, and 6 weeks. Liver lipids and plasma levels of lipids, glucose, and insulin were assayed in parallel. Results: Whereas the high-carbohydrate diet moderately stimulated hepatic lipogenesis, a strong inhibition of this anabolic pathway was found in animals fed high-fat diets. This inhibition was time-dependent and concentration-dependent. Moreover, whereas the high-carbohydrate diet induced an increase in plasma triglycerides, the high-fat diets determined an accumulation of triglycerides in liver. An increase in the plasmatic levels of glucose and insulin was observed in all cases. Conclusions: The excess of sucrose in the diet is converted into fat that is distributed by bloodstream in the organism in the form of circulating triglycerides. On the other hand, a high amount of dietary fat caused a strong inhibition of lipogenesis and a concomitant increase in the level of hepatic lipids, thereby highlighting, in these conditions, the role of liver as a reservoir of exogenous fat. [ABSTRACT FROM AUTHOR]

Short-term effects of 3,5-L-diiodothyronine (T) administration to hypothyroid rats on FF-ATP synthase activity were investigated in liver mitochondria. One hour after T injection, state 4 and state 3 respiration rates were noticeably stimulated in mitochondria subsequently isolated. FF-ATP synthase activity, which was reduced in mitochondria from hypothyroid rats as compared to mitochondria from euthyroid rats, was significantly increased by T administration in both the ATP-synthesis and hydrolysis direction. No change in β-subunit mRNA accumulation and protein amount of the α-β subunit of FF-ATP synthase was found, ruling out a T genomic effect. In T-treated rats, changes in the composition of mitochondrial phospholipids were observed, cardiolipin (CL) showing the greatest alteration. In mitochondria isolated from hypothyroid rats the decrease in the amount of CL was accompanied by an increase in the level of peroxidised CL. T administration to hypothyroid rats enhanced the level of CL and decreased the amount of peroxidised CL in subsequently isolated mitochondria, tending to restore the CL value to the euthyroid level. Minor T-induced changes in mitochondrial fatty acid composition were detected. Overall, the enhanced FF-ATP synthase activity observed following injection of T to hypothyroid rats may be ascribed, at least in part, to an increased level of mitochondrial CL associated with decreased peroxidation of CL. [ABSTRACT FROM AUTHOR]

A tRNA (GAC) gene is located in opposite orientation 552 nucleotides (nt) down-stream of the cytochrome oxidase subunit III ( coxIII) gene in sunflower mitochondria. The comparison with the homologous chloroplast DNA revealed that the tRNA gene is part of a 417 nucleotides DNA insertion of chloroplast origin in the mitochondrial genome. No tRNA is encoded in monocot mitochondrial DNA (mtDNA), whereas two tRNA species are coded for by potato mtDNA. The mitochondrial genomes of different plant species thus seem to encode unique sets of tRNAs and must thus be competent in importing the missing differing sets of tRNAs. [ABSTRACT FROM AUTHOR]