Mitochondria are fundamental organelles producing energy and reactive oxygen species (ROS); their impaired functions play a key role in endothelial dysfunction. Hydroxytyrosol (HT), a well-known olive oil antioxidant, exerts health benefits against vascular diseases by improving endothelial function. However, the HT role in mitochondrial oxidative stress in endothelial dysfunction is not clear yet. To investigate the HT effects on mitochondrial ROS production in the inflamed endothelium, we used an in vitro model of endothelial dysfunction represented by cultured endothelial cells, challenged with phorbol myristate acetate (PMA), an inflammatory, prooxidant, and proangiogenic agent. We found that the pretreatment of endothelial cells with HT (1–30 μmol/L) suppressed inflammatory angiogenesis, a crucial aspect of endothelial dysfunction. The HT inhibitory effect is related to reduced mitochondrial superoxide production and lipid peroxidation and to increased superoxide dismutase activity. HT, in a concentration-dependent manner, improved endothelial mitochondrial function by reverting the PMA-induced reduction of mitochondrial membrane potential, ATP synthesis, and ATP5β expression. In PMA-challenged endothelial cells, HT also promoted mitochondrial biogenesis through increased mitochondrial DNA content and expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha, nuclear respiratory factor-1, and mitochondrial transcription factor A. These results highlight that HT blunts endothelial dysfunction and pathological angiogenesis by ameliorating mitochondrial function, thus suggesting HT as a potential mitochondria-targeting antioxidant in the inflamed endothelium.

Nonalcoholic fatty liver disease (NAFLD) represents the most common chronic liver disease in western countries, being considered the hepatic manifestation of metabolic syndrome. Cumulative lines of evidence suggest that olive oil, used as primary source of fat by Mediterranean populations, may play a key role in the observed health benefits on NAFLD. In this review, we summarize the state of the art of the knowledge on the protective role of both major and minor components of olive oil on lipid metabolism during NAFLD. In particular, the biochemical mechanisms responsible for the increase or decrease in hepatic lipid content are critically analyzed, taking into account that several studies have often provided different and/or conflicting results in animal models fed on olive oil-enriched diet. In addition, new findings that highlight the hypolipidemic and the antisteatotic actions of olive oil phenols are presented. As mitochondrial dysfunction plays a key role in the pathogenesis of NAFLD, the targeting of these organelles with olive oil phenols as a powerful therapeutic approach is also discussed. V C 2015 IUBMB Life, 67(1):9-17, 2015

Growing evidence shows that, among triiodothyronine derivatives, 3,5 diiodo-L-thyronine (T2) plays an important role in energy metabolism and fat storage. In the present study, short-term effects of T2 administration to hypothyroid rats on fatty acid oxidation rate and bioenergetic parameters were investigated. Within 1 h following T2 injection, state 3 and state 4 respiration rates, which were reduced in hypothyroid mitochondria, were noticeably increased particularly in succinate- with respect to glutamate/malate-energized mitochondria. Maximal respiratory activity, observed when glutamate/malate/succinate were simultaneously present in the respiratory medium, was significantly stimulated by T2 treatment. A T2-induced increase in respiratory rates was also observed when palmitoyl-CoA or L-palmitoylcarnitine were used as substrates. No significant change in respiratory control index and ADP/O ratio was observed. The activities of the mitochondrial respiratory chain complexes, especially Complex II, were increased in T2-treated rats. In the latter, Complex V activities, assayed in both ATP synthesis and hydrolysis direction, were enhanced. The rate of fatty acid oxidation, followed by conversion of [14C]palmitate to CO2 and ketone bodies, was higher in hepatocytes isolated from T2-treated rats. This increase occurs in parallel with the raise in the activity of carnitine palmitoyltransferase-I, the rate limiting enzyme of fatty acid β-oxidation, assayed in situ in digitonin-permeabilized hepatocytes. Overall, these results indicate that T2 rapidly increases the ability of mitochondria to import and oxidize fatty acids. An emerging idea in the literature is the ability of T2 to reduce adiposity and dyslipidemia and to prevent the development in liver steatosis. The results of the present study, showing a rapid T2-induced increase in the ability of mitochondria to import and oxidize fatty acids, may contribute to understand the biochemical mechanisms of T2-metabolic effects.

Short-term effects of 3,5-L-diiodothyronine (T(2)) administration to hypothyroid rats on F(o)F(1)-ATP synthase activity were investigated in liver mitochondria. One hour after T(2) injection, state 4 and state 3 respiration rates were noticeably stimulated in mitochondria subsequently isolated. F(o)F(1)-ATP synthase activity, which was reduced in mitochondria from hypothyroid rats as compared to mitochondria from euthyroid rats, was significantly increased by T(2) 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 F(o)F(1)-ATP synthase was found, ruling out a T(2) genomic effect. In T(2)-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(2) 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(2)-induced changes in mitochondrial fatty acid composition were detected. Overall, the enhanced F(o)F(1)-ATP synthase activity observed following injection of T(2) to hypothyroid rats may be ascribed, at least in part, to an increased level of mitochondrial CL associated with decreased peroxidation of CL.

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.