Long-term intake of 9-PAHPA or 9-OAHPA modulates favorably the basal metabolism and exerts an insulin sensitizing effect in obesogenic diet-fed mice.

PURPOSE: Fatty acid esters of hydroxy fatty acids (FAHFAs) are a large family of endogenous bioactive lipids. To date, most of the studied FAHFAs are branched regioisomers of Palmitic Acid Hydroxyl Stearic Acid (PAHSA) that were reported to possess anti-diabetic and anti-inflammatory activity in humans and rodents. Recently, we have demonstrated that 9-PAHPA or 9-OAHPA intake increased basal metabolism and enhanced insulin sensitivity in healthy control diet-fed mice but induced liver damage in some mice. The present work aims to explore whether a long-term intake of 9-PAHPA or 9-OAHPA may have similar effects in obesogenic diet-fed mice. METHODS: C57Bl6 mice were fed with a control or high fat-high sugar (HFHS) diets for 12 weeks. The HFHS diet was supplemented or not with 9-PAHPA or 9-OAHPA. Whole-body metabolism was explored. Glucose and lipid metabolism as well as mitochondrial activity and oxidative stress status were analyzed. RESULTS: As expected, the intake of HFHS diet led to obesity and lower insulin sensitivity with minor effects on liver parameters. The long-term intake of 9-PAHPA or 9-OAHPA modulated favorably the basal metabolism and improved insulin sensitivity as measured by insulin tolerance test. On the contrary to what we have reported previously in healthy mice, no marked effect for these FAHFAs was observed on liver metabolism of obese diabetic mice. CONCLUSION: This study indicates that both 9-PAHPA and 9-OAHPA may have interesting insulin-sensitizing effects in obese mice with lower insulin sensitivity.

p43, a Truncated Form of Thyroid Hormone Receptor α, Regulates Maturation of Pancreatic ß Cells.

P43 is a truncated form of thyroid hormone receptor α localized in mitochondria, which stimulates mitochondrial respiratory chain activity. Previously, we showed that deletion of p43 led to reduction of pancreatic islet density and a loss of glucose-stimulated insulin secretion in adult mice. The present study was designed to determine whether p43 was involved in the processes of ß cell development and maturation. We used neonatal, juvenile, and adult p43-/- mice, and we analyzed the development of ß cells in the pancreas. Here, we show that p43 deletion affected only slightly ß cell proliferation during the postnatal period. However, we found a dramatic fall in p43-/- mice of MafA expression (V-Maf Avian Musculoaponeurotic Fibrosarcoma Oncogene Homolog A), a key transcription factor of beta-cell maturation. Analysis of the expression of antioxidant enzymes in pancreatic islet and 4-hydroxynonenal (4-HNE) (a specific marker of lipid peroxidation) staining revealed that oxidative stress occurred in mice lacking p43. Lastly, administration of antioxidants cocktail to p43-/- pregnant mice restored a normal islet density but failed to ensure an insulin secretion in response to glucose. Our findings demonstrated that p43 drives the maturation of ß cells via its induction of transcription factor MafA during the critical postnatal window.

FAHFAs Regulate the Proliferation of C2C12 Myoblasts and Induce a Shift toward a More Oxidative Phenotype in Mouse Skeletal Muscle.

Branched fatty acid esters of hydroxy fatty acids (FAHFAs) are endogenous lipids reported to have antidiabetic and anti-inflammatory effects. Since skeletal muscle is a major target for insulin, the aim of this study is to explore for the first time the influence of several FAHFAs in C2C12 myoblasts and in skeletal muscle phenotype in mice. Here, we show that eleven FAHFAs belonging to different families inhibit C2C12 myoblast proliferation. In addition, all FAHFAs decreased mitochondrial cytochrome c oxidase activity without affecting reactive oxygen species production and the mitochondrial network. During C2C12 myoblasts differentiation, we found that two of the most active lipids, 9-PAHPA and 9-OAHPA, did not significantly affect the fusion index and the expression of myosin heavy chains. However, we found that three months' intake of 9-PAHPA or 9-OAHPA in mice increased the expression of more oxidative myosin in skeletal muscle without affecting skeletal muscle mass, number, and mean fiber area, mitochondrial activity, and oxidative stress parameters. In conclusion, our study indicated that the eleven FAHFAs tested decreased the proliferation rate of C2C12 myoblasts, probably through the inhibition of mitochondrial activity. In addition, we found that 9-PAHPA or 9-OAHPA supplementation in mice induced a switch toward a more oxidative contractile phenotype of skeletal muscle. These data suggest that the increase in insulin sensitivity previously described for these two FAHFAs is of muscular origin.

New evidence of exercise training benefits in myostatin-deficient mice: Effect on lipidomic abnormalities.

Myostatin (Mstn) inactivation or inhibition is considered as a promising treatment for various muscle-wasting disorders because it promotes muscle growth. However, myostatin-deficient hypertrophic muscles show strong fatigability associated with abnormal mitochondria and lipid metabolism. Here, we investigated whether endurance training could improve lipid metabolism and mitochondrial membrane lipid composition in mice where the Mstn gene was genetically ablated (Mstn-/- mice). In Mstn-/- mice, 4 weeks of daily running exercise sessions (65-70% of the maximal aerobic speed for 1 h) improved significantly aerobic performance, particularly the endurance capacity (up to +280% compared with untrained Mstn-/- mice), to levels comparable to those of trained wild type (WT) littermates. The expression of oxidative and lipid metabolism markers also was increased, as indicated by the upregulation of the Cpt1, Ppar-δ and Fasn genes. Moreover, endurance training also increased, but far less than WT, citrate synthase level and mitochondrial protein content. Interestingly endurance training normalized the cardiolipin fraction in the mitochondrial membrane of Mstn-/- muscle compared with WT. These results suggest that the combination of myostatin inhibition and endurance training could increase the muscle mass while preserving the physical performance with specific effects on cardiolipin and lipid-related pathways.

High dietary intake of palm oils compromises glucose tolerance whereas high dietary intake of olive oil compromises liver lipid metabolism and integrity.

PURPOSE: Palm (PO) and olive oils (OO) are the two most consumed and/or used oils in the world for food elaboration. These oils should not be confused with the solid palm stearin which is widely used in pastry making. Large number of studies was reported dealing with adverse/beneficial cardiovascular effects of PO and OO, whereas few studies were conducted to compare their potential effects on hepatic steatosis and liver lipid metabolism. The aim of this study was to compare the metabolic effects of high intake of POs (both crude and refined) and virgin OO on surrogate parameters of glucose tolerance, hepatic lipid metabolism and liver integrity. METHODS: Thirty-two young male Wistar rats were divided into four equal groups and fed either control diet (11% energy from fat) or three high-fat diets rich in crude or refined POs or in OO (56% energy from fat), during 12 weeks. Systemic blood and liver biochemical parameters linked to glucose and lipid metabolism as well as hepatic steatosis and liver fatty acid composition were explored. The inflammation and oxidative stress status as well as the expression of several genes/proteins were also analyzed. RESULTS: The major effects of POs intake concerned glucose metabolism and liver fatty acid composition, whereas the major effects of OO intake concerned hepatic TG accumulation, inflammation, and cytolysis. CONCLUSIONS: In conclusion, high dietary intake of PO compromises glucose tolerance whereas high dietary intake of OO compromises hepatic lipid composition and liver integrity. However, adverse hepatic effects of OO observed in this study may not be transposed to human since, (a) the rodent model could lead to different effects than those observed in humans and (b) the average normal OO amounts ingested in the population are lower than those corresponding to a high-fat diet. So, further studies are needed to determine a maximum non-invasive dietary intake of OO.

Skeletal muscle expression of p43, a truncated thyroid hormone receptor α, affects lipid composition and metabolism.

Thyroid hormone is a major regulator of metabolism and mitochondrial function. Thyroid hormone also affects reactions in almost all pathways of lipids metabolism and as such is considered as the main hormonal regulator of lipid biogenesis. The aim of this study was to explore the possible involvement of p43, a 43 Kda truncated form of the nuclear thyroid hormone receptor TRα1 which stimulates mitochondrial activity. Therefore, using mouse models overexpressing p43 in skeletal muscle (p43-Tg) or lacking p43 (p43-/-), we have investigated the lipid composition in quadriceps muscle and in mitochondria. Here, we reported in the quadriceps muscle of p43-/- mice, a fall in triglycerides, an inhibition of monounsaturated fatty acids (MUFA) synthesis, an increase in elongase index and an decrease in desaturase index. However, in mitochondria from p43-/- mice, fatty acid profile was barely modified. In the quadriceps muscle of p43-Tg mice, MUFA content was decreased whereas the unsaturation index was increased. In addition, in quadriceps mitochondria of p43-Tg mice, we found an increase of linoleic acid level and unsaturation index. Last, we showed that cardiolipin content, a key phospholipid for mitochondrial function, remained unchanged both in quadriceps muscle and in its mitochondria whatever the mice genotype. In conclusion, this study shows that muscle lipid content and fatty acid profile are strongly affected in skeletal muscle by p43 levels. We also demonstrate that regulation of cardiolipin biosynthesis by the thyroid hormone does not imply p43.

Skeletal muscle overexpression of short isoform Sirt3 altered mitochondrial cardiolipin content and fatty acid composition.

Cardiolipin (CL) is a phospholipid at the heart of mitochondrial metabolism, which plays a key role in mitochondrial function and bioenergetics. Among mitochondrial activity regulators, SIRT3 plays a crucial role in controlling the acetylation status of many enzymes participating in the energy metabolism in particular concerning lipid metabolism and fatty acid oxidation. Data suggest that possible connection may exist between SIRT3 and CL status that has not been evaluated in skeletal muscle. In the present study, we have characterized skeletal muscle lipids as well as mitochondrial lipids composition in mice overexpressing long (SIRT3-M1) and short (SIRT3-M3) isoforms of SIRT3. Particular attention has been paid for CL. We reported no alteration in muscle lipids content and fatty acids composition between the two mice SIRT3 strains and the control mice. However, mitochondrial CL content was significantly decreased in SIRT3-M3 mice and associated to an upregulation of tafazzin gene expression. In addition, mitochondrial phospholipids and fatty acids composition was altered with an increase in the PC/PE ratio and arachidonic acid content and a reduction in the MUFA/SFA ratio. These modifications in mitochondrial membrane composition are associated with a reduction in the enzymatic activities of mitochondrial respiratory chain complexes I and IV. In spite of these mitochondrial enzymatic alterations, skeletal muscle mitochondrial respiration remained similar in SIRT3-M3 and control mice. Surprisingly, none of those metabolic alterations were detected in mitochondria from SIRT3-M1 mice. In conclusion, our data indicate a specific action of the shorter SIRT3 isoform on lipid mitochondrial membrane biosynthesis and functioning.

Branched Fatty Acyl Esters of Hydroxyl Fatty Acids (FAHFAs), Appealing Beneficial Endogenous Fat against Obesity and Type-2 Diabetes.

After a brief overview of the biological significance of FAHFAs, the present Minireview highlights the different strategies developed for their chemical syntheses. The term "FAHFAs" has been introduced in 2014 for fatty acyl esters of hydroxyl fatty acids, found in adipocytes, with antidiabetic properties. However, many other natural products contain this type of branched lipids in their structure. This review was then extended to the synthesis of these subunits, even though the length of the lipid chains and the location of the ester linkages are different, since the developed strategies may be applied to the synthesis of "FAHFA".

20-Week follow-up of hepatic steatosis installation and liver mitochondrial structure and activity and their interrelation in rats fed a high-fat-high-fructose diet.

The incidence of obesity and its metabolic complications are rapidly increasing and become a major public health issue. This trend is associated with an increase in the prevalence of non-alcoholic fatty liver disease (NAFLD), insulin resistance and diabetes. The sequence of events leading to NAFLD progression and mitochondrial dysfunction and their interrelation remains to be elucidated. This study aimed to explore the installation and progression of NAFLD and its association with the liver mitochondrial structure and activity changes in rats fed an obesogenic diet up to 20 weeks. Male Wistar rats were fed either a standard or high-fat-high-fructose (HFHFR) diet and killed on 4, 8, 12, 16 and 20 weeks of diet intake. Rats fed the HFHFR diet developed mildly overweight, associated with increased adipose tissue weight, hepatic steatosis, hyperglycaemia and hyperinsulinaemia after 8 weeks of HFHFR diet. Hepatic steatosis and many biochemical modifications plateaued at 8-12 weeks of HFHFR diet with slight amelioration afterwards. Interestingly, several biochemical and physiological parameters of mitochondrial function, as well as its phospholipid composition, in particular cardiolipin content, were tightly related to hepatic steatosis installation. These results showed once again the interrelation between hepatic steatosis development and mitochondrial activity alterations without being able to say whether the mitochondrial alterations preceded or followed the installation/progression of hepatic steatosis. Because both hepatic steatosis and mitochondrial alterations occurred as early as 4 weeks of diet, future studies should consider these four 1st weeks to reveal the exact interconnection between these major consequences of obesogenic diet intake.

Myostatin deficiency is associated with lipidomic abnormalities in skeletal muscles.

Myostatin (Mstn) deficiency leads to skeletal muscle overgrowth and Mstn inhibition is considered as a promising treatment for muscle-wasting disorders. Mstn gene deletion in mice also causes metabolic changes with decreased mitochondria content, disturbance in mitochondrial respiratory function and increased muscle fatigability. However the impact of MSTN deficiency on these metabolic changes is not fully elucidated. Here, we hypothesized that lack of MSTN will alter skeletal muscle membrane lipid composition in relation with pronounced alterations in muscle function and metabolism. Indeed, phospholipids and in particular cardiolipin mostly present in the inner mitochondrial membrane, play a crucial role in mitochondria function and oxidative phosphorylation process. We observed that Mstn KO muscle had reduced fat membrane transporter levels (FAT/CD36, FABP3, FATP1 and FATP4) associated with decreased lipid oxidative pathway (citrate synthase and ß-HAD activities) and impaired lipogenesis (decreased triglyceride and free fatty acid content), indicating a role of mstn in muscle lipid metabolism. We further analyzed phospholipid classes and fatty acid composition by chromatographic methods in muscle and mitochondrial membranes. Mstn KO mice showed increased levels of saturated and polyunsaturated fatty acids at the expense of monounsaturated fatty acids. We also demonstrated, in this phenotype, a reduction in cardiolipin proportion in mitochondrial membrane versus the proportion of others phospholipids, in relation with a decrease in the expression of phosphatidylglycerolphosphate synthase and cardiolipin synthase, enzymes involved in cardiolipin synthesis. These data illustrate the importance of lipids as a link by which MSTN deficiency can impact mitochondrial bioenergetics in skeletal muscle.

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.

A mitochondrial-targeted ubiquinone modulates muscle lipid profile and improves mitochondrial respiration in obesogenic diet-fed rats.

The prevalence of the metabolic syndrome components including abdominal obesity, dyslipidaemia and insulin resistance is increasing in both developed and developing countries. It is generally accepted that the development of these features is preceded by, or accompanied with, impaired mitochondrial function. The present study was designed to analyse the effects of a mitochondrial-targeted lipophilic ubiquinone (MitoQ) on muscle lipid profile modulation and mitochondrial function in obesogenic diet-fed rats. For this purpose, twenty-four young male Sprague-Dawley rats were divided into three groups and fed one of the following diets: (1) control, (2) high fat (HF) and (3) HF+MitoQ. After 8 weeks, mitochondrial function markers and lipid metabolism/profile modifications in skeletal muscle were measured. The HF diet was effective at inducing the major features of the metabolic syndrome--namely, obesity, hepatic enlargement and glucose intolerance. MitoQ intake prevented the increase in rat body weight, attenuated the increase in adipose tissue and liver weights and partially reversed glucose intolerance. At the muscle level, the HF diet induced moderate TAG accumulation associated with important modifications in the muscle phospholipid classes and in the fatty acid composition of total muscle lipid. These lipid modifications were accompanied with decrease in mitochondrial respiration. MitoQ intake corrected the lipid alterations and restored mitochondrial respiration. These results indicate that MitoQ protected obesogenic diet-fed rats from some features of the metabolic syndrome through its effects on muscle lipid metabolism and mitochondrial activity. These findings suggest that MitoQ is a promising candidate for future human trials in the metabolic syndrome prevention.

Impact of high dietary lipid intake and related metabolic disorders on the abundance and acyl composition of the unique mitochondrial phospholipid, cardiolipin.

Excessive dietary lipid intake, coupled with lack of exercise, are the major causes of the development and progression of metabolic syndrome features e. g. obesity, hepatic steatosis, insulin resistance, type 2 diabetes and cardiovascular diseases. These metabolic diseases are associated with both structural and functional alterations of mitochondria. Cardiolipin (CL) is a unique phospholipid that is almost exclusively localized in the mitochondrial inner membrane. Cardiolipin is at the heart of mitochondrial metabolism playing a key role in several processes of mitochondrial bioenergetics as well as in mitochondrial membrane stability and dynamics, and in many of the mitochondrial-dependent steps of apoptosis. Indeed, alterations to CL content and acyl chain profile have been associated with mitochondrial dysfunction in multiple tissues in Barth syndrome and in many other physio-pathological conditions. After a brief overview of the biological roles of CL, we highlight the consequences of lipid overload-related nutritional manipulations as well as related metabolic disorders on both CL content and its fatty acid composition in the major metabolic tissues, the heart, muscle and liver. The goal of this review is to fill a void in the CL literature concerning the effects of CL abundance and form that arise following high lipid supplementation and the related metabolic disorders.

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 K(ATP) channel. Our findings establish that p43 is an important regulator of glucose homeostasis and pancreatic ß-cell function and provide evidence for the first time of a physiological role for a mitochondrial endocrine receptor.

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.

Furan fatty acid extracted from Hevea brasiliensis latex increases muscle mass in mice.

Skeletal muscle is essential for locomotion and plays a crucial role in energy homeostasis. It is regulated by nutrition, genetic factors, physical activity and hormones. Furan fatty acids (FuFAs) are minor fatty acids present in small quantities in food from plants and animals origin. Recently, we showed that a preventive nutritional supplementation with furan fatty acid in a DIO mouse model reduces metabolic disorders. The present study was designed to determine the influence of FuFA-F2 extracted from Hevea brasiliensis latex on skeletal muscle phenotype. In C2C12 myotubes we found that FuFA-F2 whatever the concentration used increased protein content. We revealed that in C2C12 myotubes FuFA-F2 (10 µM) increases protein synthesis as shown by the stimulation of mTOR phosphorylation. Next, to confirm in vivo our results C57Bl6 mice were supplemented by oral gavage with vehicle or FuFA-F2 (20 mg/kg) for 3 and a half weeks. We found that mice supplemented with FuFA-F2 had a greater lean mass than the control mice. In line with this observation, we revealed that FuFA-F2 increased muscle mass and promoted more oxidative muscle metabolism in mice as attested by cytochrome c oxidase activity. In conclusion, we demonstrated that FuFA-F2 stimulates muscle anabolism in mice in vitro and in vivo, mimicking in part physical activity. This study highlights that in vivo FuFA-F2 may have health benefits by increasing muscle mass and oxidative metabolism.

Rhythm and ROS: Hepatic Chronotherapeutic Features of Grape Seed Proanthocyanidin Extract Treatment in Cafeteria Diet-Fed Rats.

Polyphenols play a key role in the modulation of circadian rhythms, while the cafeteria diet (CAF) is able to perturb the hepatic biological rhythm and induce important ROS production. Consequently, we aimed to elucidate whether grape seed proanthocyanidin extract (GSPE) administration recovers the CAF-induced hepatic antioxidant (AOX) misalignment and characterize the chronotherapeutic properties of GSPE. For this purpose, Fischer 344 rats were fed a standard diet (STD) or a CAF and concomitantly treated with GSPE at two time-points (ZT0 vs. ZT12). Animals were euthanized every 6 h and the diurnal rhythms of hepatic ROS-related biomarkers, hepatic metabolites, and AOX gene expression were examined. Interestingly, GSPE treatment was able to recover the diurnal rhythm lost due to the CAF. Moreover, GSPE treatment also increased the acrophase of Sod1, as well as bringing the peak closer to that of the STD group. GSPE also corrected some hepatic metabolites altered by the CAF. Importantly, the differences observed at ZT0 vs. ZT12 due to the time of GSPE administration highlight a chronotherapeutic profile on the proanthocyanin effect. Finally, GSPE could also reduce diet-induced hepatic oxidative stress not only by its ROS-scavenging properties but also by retraining the circadian rhythm of AOX enzymes.

Preventive nutritional supplementation with furan fatty acid in a DIO mouse model increases muscle mass and reduces metabolic disorders.

The increase in obesity has become a major global health problem and is associated with numerous metabolic dysfunctions. Furan fatty acids (FuFAs) are minor lipids present in our diet. Recently we showed that FuFA-F2 extracted from Hevea brasiliensis latex stimulates muscle anabolism in mice in vitro and in vivo, mimicking in part physical activity. While skeletal muscle is essential for energy metabolism and is the predominant site of insulin-mediated glucose uptake in the post prandial state, our results suggested that FuFA-F2 could have favorable effects against obesity. The aim of this work was therefore to study whether a preventive nutritional supplementation with FuFA-F2 (40 mg or 110 mg/day/kg of body weight) in a diet-induced obesity (DIO) mouse model may have beneficial effects against obesity and liver and skeletal muscle metabolic dysfunction. We showed that 12 weeks of FuFA-F2 supplementation in DIO mice decreased fat mass, increased lean mass and restored normal energy expenditure. In addition, we found that FuFA-F2 improved insulin sensitivity. We revealed that FuFA-F2 increased muscle mass but had no effect on mitochondrial function and oxidative stress in skeletal muscle. Furthermore, we observed that FuFA-F2 supplementation reduced liver steatosis without impact on mitochondrial function and oxidative stress in liver. Our findings demonstrated for the first time that a preventive nutritional supplementation with a furan fatty acid in DIO mice reduced metabolic disorders and was able to mimic partly the positive effects of physical activity. This study highlights that nutritional FuFA-F2 supplementation could be an effective approach to treat obesity and metabolic syndrome.

9-PAHPA long term intake in DIO and db/db mice ameliorates insulin sensitivity but has few effects on obesity and associated metabolic disorders.

Branched fatty acid esters of hydroxy fatty acids are endogenous lipids reported to have antidiabetic and anti-inflammatory effects. Recently, we showed that 9-palmitic acid esters of hydroxypalmitic acid (9-PAHPA) and 9-oleic acid esters of hydroxypalmitic acid increased insulin sensitivity in mice when incorporated to a chow diet or to a high fat and high sucrose diet. However, preventive supplementation with 9-PAHPA and 9-oleic acid esters of hydroxypalmitic acid in high fat and high sucrose diet mice did not impair significant weight gain or the development of hyperglycemia. The aim of this work was therefore to study whether in two animal models of obesity, namely the classical diet-induced obesity (DIO) and the db/db mice, 9-PAHPA may have beneficial effects against obesity and liver and skeletal muscle metabolic dysfunction. In DIO mice, we observed that 9-PAHPA increased body weight and fat mass. In line with this observation, we found that 9-PAHPA supplementation decreased energy expenditure. In liver and in skeletal muscle, mitochondrial activities and oxidative stress parameters were not modified by 9-PAHPA supplementation. In db/db mice, 9-PAHPA had no effect on the dramatic weight gain and hyperglycemia. In addition, 9-PAHPA supplementation did not correct either the hepatomegaly and hepatic steatosis or the severe muscle atrophy recorded compared with db/+ animals. Likewise, supplementation with 9-PAHPA did not impact the different metabolic parameters analyzed, either in the liver or in the skeletal muscles. However, it decreased insulin resistance in DIO and db/db mice. In conclusion, our study indicated that a long-term intake of 9-PAHPA in DIO and db/db mice improved insulin sensitivity but had only few effects on obesity and associated metabolic disorders.

Lack of myostatin alters intermyofibrillar mitochondria activity, unbalances redox status, and impairs tolerance to chronic repetitive contractions in muscle.

Loss of myostatin (mstn) function leads to a decrease in mitochondrial content, a reduced expression of cytochrome c oxidase, and a lower citrate synthase activity in skeletal muscle. These data suggest functional or ultrastructural mitochondrial abnormalities that can impact on muscle endurance characteristics in such phenotype. To address this issue, we investigated subsarcolemmal and intermyofibrillar (IMF) mitochondrial activities, skeletal muscle redox homeostasis, and muscle fiber endurance quality in mstn-deficient mice [mstn knockout (KO)]. We report that lack of mstn induced a decrease in the coupling of IMF mitochondria respiration, with significantly higher basal oxygen consumption. No lysis of mitochondrial cristae or excessive swelling were observed in mstn KO mice compared with wild-type (WT) mice. Concerning redox status, mstn KO gastrocnemius exhibited a significant decrease in lipid peroxidation levels (-56%; P < 0.01 vs. WT) together with a significant upregulation of the antioxidant glutathione system. In contrast, superoxide dismutase and catalase activities were altered in mstn KO, gastrocnemius and soleus with a reduction of up to 80% compared with WT animals. The force production observed after contractile endurance test was significantly lower in extensor digitorum longus and soleus muscles of mstn KO mice compared with the controls (17 ± 3 and 36 ± 5% vs. 28 ± 4 and 56 ± 5%, respectively, P < 0.05). Together, these findings indicate that, besides an increased skeletal muscle mass, genetic mstn inhibition has differential effects on redox homeostasis and mitochondrial function that would have functional consequences on muscle response to endurance exercise.