Béatrice Bonafos

Dietary fatty acids modulate liver mitochondrial cardiolipin content and its fatty acid composition in rats with non alcoholic fatty liver disease

No data are reported on changes in mitochondrial membrane phospholipids in non-alcoholic fatty liver disease. We determined the content of mitochondrial membrane phospholipids from rats with non alcoholic liver steatosis, with a particular attention for cardiolipin (CL) content and its fatty acid composition, and their relation with the activity of the mitochondrial respiratory chain complexes. Different dietary fatty acid patterns leading to steatosis were explored. With high-fat diet, moderate macrosteatosis was observed and the liver mitochondrial phospholipid class distribution and CL fatty acids composition were modified. Indeed, both CL content and its C18:2n-6 content were increased with liver steatosis. Moreover, mitochondrial ATP synthase activity was positively correlated to the total CL content in liver phospholipid and to CL C18:2n-6 content while other complexes activity were negatively correlated to total CL content and/or CL C18:2n-6 content of liver mitochondria. The lard-rich diet increased liver CL synthase gene expression while the fish oil-rich diet increased the (n-3) polyunsaturated fatty acids content in CL. Thus, the diet may be a significant determinant of both the phospholipid class content and the fatty acid composition of liver mitochondrial membrane, and the activities of some of the respiratory chain complex enzymes may be influenced by dietary lipid amount in particular via modification of the CL content and fatty acid composition in phospholipid.

Mitochondrial T3 receptor p43 regulates insulin secretion and glucose homeostasis

Thyroid hormone is a major determinant of energy expenditure and a key regulator of mitochondrial activity. We have previously identified a mitochondrial triiodothyronine receptor (p43) that acts as a mitochondrial transcription factor of the organelle genome, which leads, in vitro and in vivo, to a stimulation of mitochondrial biogenesis. Here we generated mice specifically lacking p43 to address its physiological influence. We found that p43 is required for normal glucose homeostasis. The p43−/− mice had a major defect in insulin secretion both in vivo and in isolated pancreatic islets and a loss of glucose‐stimulated insulin secretion. Moreover, a high‐fat/high‐sucrose diet elicited more severe glucose intolerance than that recorded in normal animals. In addition, we observed in p43~ mice both a decrease in pancreatic islet density and in the activity of complexes of the respiratory chain in isolated pancreatic islets. These dysfunctions were associated with a down‐regulation of the expression of the glucose transporter Glut2 and of Kir6.2, a key component of the KATP channel. Our findings establish that p43 is an important regulator of glucose homeostasis and pancreatic β‐cell function and provide evidence for the first time of a physiological role for a mitochondrial endocrine receptor.—Blanchet, E., Bertrand, C., Annicotte, J. S., Schlernitzauer, A., Pessemesse, L., Levin, J., Fouret, G., Feillet‐Coudray, C., Bonafos, B., Fajas, L., Cabello, G., Wrutniak‐Cabello, C., Casas, F. Mitochondrial T3 receptor p43 regulates insulin secretion and glucose homeostasis. FASEB J. 26, 40–50 (2012). www.fasebj.org

The mitochondrial-targeted antioxidant MitoQ ameliorates metabolic syndrome features in obesogenic diet-fed rats better than Apocynin or Allopurinol.

Abstract The prevalence of metabolic syndrome (MetS) components including obesity, dyslipidemia, insulin resistance (IR), and hepatic steatosis is rapidly increasing in wealthy societies. It is accepted that inflammation/oxidative stress are involved in the initiation/evolution of the MetS features. The present work was designed to evaluate the effects of three major cellular ROS production systems on obesity, glucose tolerance, and hepatic steatosis development and on oxidative stress onset. To do so, 40 young male Sprague–Dawley rats were divided into 5 groups: 1-control group, 2-high fat (HF) group (60% energy from fat), 3-HF+ MitoQ (mitochondrial ROS scavenger), 4-HF+ Apocynin (NADPH oxidase inhibitor), 5-HF+ Allopurinol (xanthine oxidase inhibitor). After 8 weeks of these treatments, surrogate MetS, mitochondrial function, and oxidative stress markers were measured in blood and liver. As expected, rats that were fed the HF diet exhibited increased body weight, glucose intolerance, overt hepatic steatosis, and increased hepatic oxidative stress. The impacts of the studied ROS inhibitors on these aspects of the MetS were markedly different. MitoQ showed the most clinically relevant effects, attenuating body weight gain and glucose intolerance provoked by the HF diet. Both Apocynin and Allopurinol showed limited effects suggesting secondary roles of xanthine oxidase (XO) or NADPH oxidase-dependent ROS production in the onset of oxidative stress-dependent obesity, glucose intolerance, and hepatic steatosis process. Thus, MitoQ revealed the central role of mitochondrial oxidative stress in the development of MetS and suggested that mitochondria-targeted antioxidants may be worth considering as potentially helpful therapies for MetS features.

Effects of long-term administration of saturated and n-3 fatty acid-rich diets on lipid utilisation and oxidative stress in rat liver and muscle tissues.

The incidence of metabolic syndrome components including obesity, lipid deregulation, insulin resistance (IR) and non-alcoholic fatty liver disease is increasing rapidly in wealthy societies. The present study was designed to determine the effect of different nutritional lipid patterns (quantity and quality) on lipid utilisation and oxidative stress in the liver and muscle of rats in an integrated fashion. A total of forty-eight Wistar male rats were fed for 12 weeks with a mixed, lard or fish-oil diet, containing either 50 or 300 g lipid/kg. Rats developed liver steatosis associated with moderate liver injury when fed the 30% lipid diets, in spite of the absence of overt obesity or IR, except when fed the lard 30% lipid diet. The intake of the 30% lipid diets decreased hepatic lipogenesis and mitochondriogenesis and increased lipid peroxidation and protein oxidation. Surprisingly, muscle lipid content was not modified whatever the administered diet. The intake of the 30% lipid diets increased the muscle protein expression of fatty acid (FA) translocase/cluster of differentiation 36 (FAT/CD36), PPARg co-activator 1a (PGC-1a) and muscle carnitine palmitoyltransferase 1 (m-CPT1), reflecting increased FA transport in the muscle associated with increased oxidative metabolism. The lard 30% lipid diet led to IR without modifying the muscle lipid content. The fish-oil 30% lipid diet failed to prevent the development of hepatic steatosis and made the tissues more prone to oxidation. Overall, the present study suggests that the FA composition of muscle is more important than lipid accumulation itself in the modulation of insulin sensitivity, and indicates that precaution should be taken when advising an unphysiologically high (pharmacological) supplementation with long-chain n-3 PUFA.

The mitochondrial-targeted antioxidant, MitoQ, increases liver mitochondrial cardiolipin content in obesogenic diet-fed rats

Cardiolipin (CL), a unique mitochondrial phospholipid, plays a key role in several processes of mitochondrial bioenergetics as well as in mitochondrial membrane stability and dynamics. The present study was designed to determine the effect of MitoQ, a mitochondrial-targeted antioxidant, on the content of liver mitochondrial membrane phospholipids, in particular CL, and its fatty acid composition in obesogenic diet-fed rats. To do this, twenty-four 6week old male Sprague Dawley rats were randomized into three groups of 8 animals and fed for 8weeks with either a control diet, a high fat diet (HF), or a HF diet with MitoQ (HF+MitoQ). Phospholipid classes and fatty acid composition were assayed by chromatographic methods in liver and liver mitochondria. Mitochondrial bioenergetic function was also evaluated. While MitoQ had no or slight effects on total liver fatty acid composition and phospholipid classes and their fatty acid composition, it had major effects on liver mitochondrial phospholipids and mitochondrial function. Indeed, MitoQ both increased CL synthase gene expression and CL content of liver mitochondria and increased 18:2n-6 (linoleic acid) content of mitochondrial phospholipids by comparison to the HF diet. Moreover, mitochondrial CL content was positively correlated to mitochondrial membrane fluidity, membrane potential and respiration, as well as to ATP synthase activity, while it was negatively correlated to mitochondrial ROS production. These findings suggest that MitoQ may decrease pathogenic alterations to CL content and profiles, thereby preserving mitochondrial function and attenuating the development of some of the features of metabolic syndrome in obesogenic diet-fed rats.

Combined Strategies for Maintaining Skeletal Muscle Mass and Function in Aging: Myostatin Inactivation and AICAR-Associated Oxidative Metabolism Induction

Myostatin (mstn) blockade, resulting in muscle hypertrophy, is a promising therapy to counteract age-related muscle loss. However, oxidative and mitochondrial deficit observed in young mice with myostatin inhibition could be detrimental with aging. The aim of this study was (a) to bring original data on metabolic and mitochondrial consequences of mstn inhibition in old mice, and (b) to examine whether 4-weeks of AICAR treatment, a pharmacological compound known to upregulate oxidative metabolism, may be useful to improve exercise capacity and mitochondrial deficit of 20-months mstn KO versus wild-type (WT) mice. Our results show that despite the enlarged muscle mass, the oxidative and mitochondrial deficit associated with reduced endurance running capacity is maintained in old mstn KO mice but not worsened by aging. Importantly, AICAR treatment induced a significant beneficial effect on running limit time only in old mstn KO mice, with a marked increase in PGC-1α expression and slight beneficial effects on mitochondrial function. We showed that AICAR effects were autophagy-independent. This study underlines the relevance of aged muscle remodelling by complementary approaches that impact both muscle mass and function, and suggest that mstn inhibition and aerobic metabolism activators should be co-developed for delaying age-related deficits in skeletal muscle.

Moderate chronic administration of Vineatrol‐enriched red wines improves metabolic, oxidative, and inflammatory markers in hamsters fed a high‐fat diet

SCOPE High-fat (HF) diets contribute to the development of cardiovascular diseases and the metabolic syndrome. This study was undertaken to investigate the beneficial effects of Vineatrol®-enriched red wines on blood lipids, oxidative stress and inflammation, and the role of some metabolic pathway regulatory proteins. METHODS AND RESULTS Golden Syrian hamsters received an HF diet for 13 wk, in the presence or absence of red wines supplemented with Vineatrol® (RWV) or not. The HF diet increased plasma cholesterol, triglycerides, glucose, and insulin, which were attenuated by RWV treatment. RWV protected against the HF-induced increase in liver nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and spared antioxidant enzyme activities. RWV did not reduce either liver steatosis or increased plasma leptin due to the HF diet, but greatly improved adiponectinemia. In the liver, RWV affected the inflammatory response by decreasing polymorphonuclear cell number and lowering TNF-α and IL-6 levels. Moreover, the increase in NF-κB activity in the HF group liver was prevented by RWV. Finally, RWV partially corrected low SIRT1 levels due to the HF diet but had no influence on SIRT3 or p-AMPK protein levels. CONCLUSION Our studies suggest that RWV is capable of reversing the atherogenic process induced by an HF diet in hamster tissues.

Hyposensitivity to the amnesic effects of scopolamine or amyloid β25–35 peptide in heterozygous acetylcholinesterase knockout (AChE+/−) mice

We examined the sensitivity of AChE(+/-) mice to the amnesic effects of scopolamine and amyloid beta peptide. AChE(+/-) and AChE(+/+) littermates, tested at 5-9 weeks of age, failed to show any difference in locomotion, exploration and anxiety in the open-field test, or in-place learning in the water-maze. However, when treated with the muscarinic receptor antagonist scopolamine (0.5, 5mg/kg s.c.) 20 min before each water-maze training session, learning impairments were observed at both doses in AChE(+/+) mice, but only at the highest dose in AChE(+/-) mice. The central injection of Abeta(25-35) peptide (9 nmol) induced learning deficits only in AChE(+/+) but not in AChE(+/-) mice. Therefore, the hyper-activity of cholinergic systems in AChE(+/-) mice did not result in increased memory abilities, but prevented the deleterious effects of muscarinic blockade or amyloid toxicity.

Genetic ablation of acetylcholinesterase alters muscle function in mice.

Although acetylcholinesterase (AChE) knockout mice survive, they have abnormal neuromuscular function. We analysed further the effects of the mutation on hind limb muscle contractile properties. Tibialis anterior muscle from AChE KO mice is unable to maintain tension during a short period of repetitive nerve stimulation (tetanic fade) and has an increased twitch tension in response to a single nerve electric stimulation. In response to direct muscle stimulation, we found that maximal velocity of shortening of soleus muscle is increased and maximum tetanic force is decreased in AchE KO mice versus control animals. As the contractile properties of the soleus muscle were altered by AChE ablation, our results suggest cellular and molecular changes in AChE ablated muscle containing both fast and slow muscle fibres.

Effect of fluoxetine on neuromuscular function in acetylcholinesterase (AChE) knockout mice.

Congenital myasthenic syndromes (CMS) are a heterogeneous group of diseases caused by genetic defects affecting neuromuscular transmission. The causal mutations have been described in number of cases. The slow channel myasthenic syndrome (slow-channel-CMS) results in a marked prolongation of channel opening in stimulated receptors (nAChR) and the end plate acetylcholinesterase (AChE) deficiency congenital myasthenic syndrome (ColQ-CMS) results in an increased action of acetylcholine (ACh) at the synapse. Anticholinesterase medication is detrimental in these cases. The successful treatment of slow-channel-CMS patients with the antidepressant serotonin re-uptake inhibitor fluoxetine has been reported. At high concentration it has a non-depolarizing effect on nicotinic receptors. This led us to the idea that fluoxetine could protect AChR from a relative excess of ACh. We investigated the possible use of fluoxetine as treatment in the AChE KO mouse. Treatment at 6 mg/kg from 3 weeks to 2 months increased slightly the daily weight gain but not the final weight at 2 months in AChE-/- mice. Isometric force production of Tibialis anterior in response to electric nerve stimulation was measured in situ in AChE-/- and wild type mice treated or not by fluoxetine. The results show that the maximum twitch force in response to a single nerve stimulation, the maximal tetanic force (P0) in response to repetitive nerve stimulation and the tetanic fade are not changed in AChE-/- mice treated with fluoxetine versus control AChE-/- mice.