Synaptic dysfunction, memory deficits and hippocampal atrophy due to ablation of mitochondrial fission in adult forebrain neurons.

Well-balanced mitochondrial fission and fusion processes are essential for nervous system development. Loss of function of the main mitochondrial fission mediator, dynamin-related protein 1 (Drp1), is lethal early during embryonic development or around birth, but the role of mitochondrial fission in adult neurons remains unclear. Here we show that inducible Drp1 ablation in neurons of the adult mouse forebrain results in progressive, neuronal subtype-specific alterations of mitochondrial morphology in the hippocampus that are marginally responsive to antioxidant treatment. Furthermore, DRP1 loss affects synaptic transmission and memory function. Although these changes culminate in hippocampal atrophy, they are not sufficient to cause neuronal cell death within 10 weeks of genetic Drp1 ablation. Collectively, our in vivo observations clarify the role of mitochondrial fission in neurons, demonstrating that Drp1 ablation in adult forebrain neurons compromises critical neuronal functions without causing overt neurodegeneration.

AMP-activated protein kinase plays an important evolutionary conserved role in the regulation of glucose metabolism in fish skeletal muscle cells

AMPK, a master metabolic switch, mediates the observed increase of glucose uptake in locomotory muscle of mammals during exercise. AMPK is activated by changes in the intracellular AMP:ATP ratio when ATP consumption is stimulated by contractile activity but also by AICAR and metformin, compounds that increase glucose transport in mammalian muscle cells. However, the possible role of AMPK in the regulation of glucose metabolism in skeletal muscle has not been investigated in other vertebrates, including fish. In this study, we investigated the effects of AMPK activators on glucose uptake, AMPK activity, cell surface levels of trout GLUT4 and expression of GLUT1 and GLUT4 as well as the expression of enzymes regulating glucose disposal and PGC1α in trout myotubes derived from a primary muscle cell culture. We show that AICAR and metformin significantly stimulated glucose uptake (1.6 and 1.3 fold, respectively) and that Compound C completely abrogated the stimulatory effects of the AMPK activators on glucose uptake. The combination of insulin and AMPK activators did not result in additive nor synergistic effects on glucose uptake. Moreover, exposure of trout myotubes to AICAR and metformin resulted in an increase in AMPK activity (3.8 and 3 fold, respectively). We also provide evidence suggesting that stimulation of glucose uptake by AMPK activators in trout myotubes may take place, at least in part, by increasing the cell surface and mRNA levels of trout GLUT4. Finally, AICAR increased the mRNA levels of genes involved in glucose disposal (hexokinase, 6-phosphofructokinase, pyruvate kinase and citrate synthase) and mitochondrial biogenesis (PGC-1α) and did not affect glycogen content or glycogen synthase mRNA levels in trout myotubes. Therefore, we provide evidence, for the first time in non-mammalian vertebrates, suggesting a potentially important role of AMPK in stimulating glucose uptake and utilization in the skeletal muscle of fish.

The role of the microRNAs in the age-associated oancreatic β-cell dysfunction

Le corps humain emploie le glucose comme source principale d'énergie. L'insuline, sécrétée par les cellules ß-pancreatiques situées dans les îlots de Langerhans, est l'hormone principale assurant un maintien constant du taux de glucose sanguin (glycémie). Les prédispositions génétiques, le manque d'activité physique et un régime déséquilibré peuvent entraîner une perte de sensibilité à l'insuline et des taux de glucose dans le sang élevé (hyperglycémie), une condition nommée diabète de type 2. Cette maladie est initiée par une sensibilité diminuée à l'insuline dans les tissus périphériques, entraînant une demande accrue en insuline. Cette pression continue finie par épuiser les cellules ß-pancreatiques, qui sécrètent alors des niveaux d'insuline insuffisant en trainant l'apparition du diabète. Le vieillissement est un facteur de risque important pour les maladies métaboliques dont le diabète de type 2 faits partis. En effet la majeure partie des diabétiques de type 2 ont plus de 45 ans. Il est connu que le vieillissement entraine une perte de sensibilité à l'insuline, une sécrétion altérée d'insuline, une baisse de réplication et une plus grande mort des ß-cellules pancréatiques. Le but de ma thèse était de mieux comprendre les mécanismes contribuante au dysfonctionnement des cellules ß- pancréatiques lors du vieillissement. Les travaux du « Human Genome Project » ont révélés que seulement 2% de notre génome code pour des protéines. Le reste non-codant fut alors désigné sous le nom de « ADN déchets ». Cependant, l'étude approfondie de cet ADN non-codant ces dernières deux décennies a démontré qu'une grande partie code pour des «MicroARNs », des ARNs courts (20-22 nucleotides) découverts en 1997 chez le vers C.elegans. Depuis lors ces molécules ont été intensivement étudiées, révélant un rôle crucial de ces molécules dans la fonction et la survie des cellules en conditions normales et pathologiques. Le but de cette thèse était d'étudier le rôle des microARNs dans le dysfonctionnement des cellules ß lors du vieillissement. Nos données suggèrent qu'ils peuvent jouer un rôle tantôt salutaire, tantôt nocif sur les cellules ß. Par exemple, certains microARNs réduisent la capacité des cellules ß à se multiplier ou réduisent leur survie, alors que d'autres protègent ces cellules contre la mort. Pour conclure, nous avons démontré les microARNs jouent un rôle important dans le dysfonctionnement des cellules ß lors du vieillissement. Ces nouvelles découvertes préparent le terrain pour la conception de futures stratégies visant à améliorer la résistance des cellules ß pancréatiques afin de trouver de nouveaux traitements du diabète de type 2. -- Le diabète de type 2 est une maladie métabolique due à la résistance à l'action de l'insuline des tissus cibles combinée à l'incapacité des cellules ß pancréatiques à sécréter les niveaux adéquats d'insuline. Le vieillissement est associé à un déclin global des fonctions de l'organisme incluant une diminution de la fonction et du renouvellement des cellules ß pancréatiques. Il constitue ainsi un risque majeur de développement des maladies métaboliques dont le diabète de type 2. Le but de cette thèse était d'étudier le rôle des microARNs (une classe d'ARN non- codants) dans le dysfonctionnement lié au vieillissement des cellules ß. L'analyse par microarray des niveaux d'expression des microARN dans les îlots pancréatiques de rats Wistar mâles âgés de 3 et 12 mois nous a permis d'identifier de nombreux changements d'expression de microARNs associés au vieillissement. Afin d'étudier les liens entre ces modifications et le déclin des cellules ß, les changements observés lors du vieillissement ont été reproduits spécifiquement dans une lignée cellulaire, dans des cellules ß primaires de jeune rats ou de donneurs humains sains. La diminution du miR-181a réduit la prolifération des cellules ß, tandis que la diminution du miR-130b ou l'augmentation du miR-383 protège contre l'apoptose induite par les cytokines. L'augmentation du miR-34a induit l'apoptose et inhibe la prolifération des cellules ß en réponse aux hormones Exendin-4 et prolactine et au facteur de croissance PDGF-AA. Cette perte de capacité réplicative est similaire à celle observée dans des cellules ß de rats âgés de 12 mois. Dans la littérature, la perte du récepteur au PDGF-r-a est associée à la diminution de la capacité proliférative des cellules ß observée lors du vieillissement. Nous avons pu démontrer que PDGF-r-a est une cible directe de miR- 34a, suggérant que l'effet néfaste de miR-34a sur la prolifération des cellules ß est, du moins en partie, lié à l'inhibition de l'expression de PDGF-r-a. L'expression de ce miR est aussi plus élevée dans le foie et le cerveau des animaux de 1 an et augmente avec l'âge dans les ilôts de donneurs non-diabétiques. Ces résultats suggèrent que miR-34a pourrait être non seulement impliqué dans l'affaiblissement des fonctions pancréatiques associé à l'âge, mais également jouer un rôle dans les tissus cibles de l'insuline et ainsi contribuer au vieillissement de l'organisme en général. Pour conclure, les travaux obtenus durant cette thèse suggèrent que des microARNs sont impliqués dans le dysfonctionnement des cellules ß pancréatiques durant le vieillissement. -- Type 2 diabetes is a metabolic disease characterized by impaired glucose tolerance, of the insulin sensitive tissues and insufficient insulin secretion from the pancreatic ß-cells to sustain the organism demand. Aging is a risk factor for the majority of the metabolic diseases including type 2 diabetes. With aging is observed a decline in all body function, due to decrease both in cell efficiency and renewal. The aim of this thesis was to investigate the potential role of microRNAs (short non- coding RNAs) in the pancreatic ß-cell dysfunction associated with aging. Microarray analysis of microRNA expression profile in pancreatic islets from 3 and 12 month old Wistar male rats revealed important changes in several microRNAs. To further study the link between those alterations and the decline of ß-cells, the changes observed in old rats were mimicked in immortalized ß-cell lines, primary young rat and human islets. Downregulation of miR-181a inhibited pancreatic ß-cell proliferation in response to proliferative drugs, whereas downregulation of miR-130b and upregulation of miR-383 protected pancreatic ß-cells from cytokine stimulated apoptosis. Interestingly, miR-34a augmented pancreatic ß-cell apoptosis and inhibited ß-cell proliferation in response to the proliferative chemicals Exendin-4, prolactin and PDGF-AA. This loss of replicative capacity is reminiscent of what we observed in pancreatic ß-cells isolated from 12 month old rats. We further observed a correlation between the inhibitory effect of miR-34a on pancreatic ß-cell proliferation and its direct interfering effect of this microRNA on PDGF-r-a, which was previously reported to be involved in the age-associated decline of pancreatic ß-cell proliferation. Interestingly miR-34a was upregulated in the liver and brain of 1 year old animals and positively correlated with age in pancreatic islets of normoglycemic human donors. These results suggest that miR-34a might be not only involved in the age-associated impairment of the pancreatic ß-cell functions, but also play a role in insulin target tissues and contribute to the aging phenotype on the organism level. To conclude, we have demonstrated that microRNAs are indeed involved in the age-associated pancreatic ß-cell dysfunction and they can play both beneficial and harmful roles in the context of pancreatic ß-cell aging.

Acute and Chronic Altitude-Induced Cognitive Dysfunction in Children and Adolescents.

OBJECTIVE: To assess whether exposure to high altitude induces cognitive dysfunction in young healthy European children and adolescents during acute, short-term exposure to an altitude of 3450 m and in an age-matched European population permanently living at this altitude. STUDY DESIGN: We tested executive function (inhibition, shifting, and working memory), memory (verbal, short-term visuospatial, and verbal episodic memory), and speed processing ability in: (1) 48 healthy nonacclimatized European children and adolescents, 24 hours after arrival at high altitude and 3 months after return to low altitude; (2) 21 matched European subjects permanently living at high altitude; and (3) a matched control group tested twice at low altitude. RESULTS: Short-term hypoxia significantly impaired all but 2 (visuospatial memory and processing speed) of the neuropsychological abilities that were tested. These impairments were even more severe in the children permanently living at high altitude. Three months after return to low altitude, the neuropsychological performances significantly improved and were comparable with those observed in the control group tested only at low altitude. CONCLUSIONS: Acute short-term exposure to an altitude at which major tourist destinations are located induces marked executive and memory deficits in healthy children. These deficits are equally marked or more severe in children permanently living at high altitude and are expected to impair their learning abilities.

Muscle Characteristics and Substrate Energetics in Lifelong Endurance Athletes.

PURPOSE: The goal of this study was to explore the effect of lifelong aerobic exercise (i.e., chronic training) on skeletal muscle substrate stores (intramyocellular triglyceride [IMTG] and glycogen), skeletal muscle phenotypes, and oxidative capacity (ox), in older endurance-trained master athletes (OA) compared with noncompetitive recreational younger (YA) athletes matched by frequency and mode of training. METHODS: Thirteen OA (64.8 ± 4.9 yr) exercising 5 times per week or more were compared with 14 YA (27.8 ± 4.9 yr) males and females. IMTG, glycogen, fiber types, succinate dehydrogenase, and capillarization were measured by immunohistochemistry in vastus lateralis biopsies. Fat-ox and carbohydrate (CHO)-ox were measured by indirect calorimetry before and after an insulin clamp and during a cycle ergometer graded maximal test. RESULTS: V˙O2peak was lower in OA than YA. The OA had greater IMTG in all fiber types and lower glycogen stores than YA. This was reflected in greater proportion of type I and less type II fibers in OA. Type I fibers were similar in size, whereas type II fibers were smaller in OA compared with YA. Both groups had similar succinate dehydrogenase content. Numbers of capillaries per fiber were reduced in OA but with a higher number of capillaries per area. Metabolic flexibility and insulin sensitivity were similar in both groups. Exercise metabolic efficiency was higher in OA. At moderate exercise intensities, carbohydrate-ox was lower in OA but with similar Fat-ox. CONCLUSIONS: Lifelong exercise is associated with higher IMTG content in all muscle fibers and higher metabolic efficiency during exercise that are not explained by differences in muscle fibers types and other muscle characteristics when comparing older with younger athletes matched by exercise mode and frequency.

The promoter activity of human Mfn2 depends on Sp1 in vascular smooth muscle cells

AIMS: Mitofusin-2 (Mfn2) expression is dysregulated in vascular proliferative disorders and its overexpression attenuates the proliferation of vascular smooth muscle cells (VSMCs) and neointimal lesion development after balloon angioplasty. We sought to gain insight into the mechanisms that control Mfn2 expression in VSMCs. METHODS AND RESULTS: We cloned and characterized 2 kb of the 5'-flanking region of the human Mfn2 gene. Its TATA-less promoter contains a CpG island. In keeping with this, 5'-rapid amplification of cDNA ends revealed six transcriptional start sites (TSSs), of which TSS2 and TSS5 were the most frequently used. The strong CpG island was found to be non-methylated under conditions characterized by large differences in Mfn2 gene expression. The proximal Mfn2 promoter contains six putative Sp1 motifs. Sp1 binds to the Mfn2 promoter and its overexpression activates the Mfn2 promoter in VSMCs. Chemical inhibition of Sp1 reduced Mfn2 expression, and Sp1 silencing reduced transcriptional activity of the Mfn2 promoter. In keeping with this view, Sp1 and Mfn2 mRNA levels were down-regulated in the aorta early after an atherogenic diet in apolipoprotein E-knockout mice or in VSMCs cultured in the presence of low serum. CONCLUSION: Sp1 is a key factor in maintaining basal Mfn2 transcription in VSMCs. Given the anti-proliferative actions of Mfn2, Sp1-induced Mfn2 transcription may represent a mechanism for prevention of VSMC proliferation and neointimal lesion and development.

The promoter activity of human Mfn2 depends on Sp1 in vascular smooth muscle cells

AIMS: Mitofusin-2 (Mfn2) expression is dysregulated in vascular proliferative disorders and its overexpression attenuates the proliferation of vascular smooth muscle cells (VSMCs) and neointimal lesion development after balloon angioplasty. We sought to gain insight into the mechanisms that control Mfn2 expression in VSMCs. METHODS AND RESULTS: We cloned and characterized 2 kb of the 5'-flanking region of the human Mfn2 gene. Its TATA-less promoter contains a CpG island. In keeping with this, 5'-rapid amplification of cDNA ends revealed six transcriptional start sites (TSSs), of which TSS2 and TSS5 were the most frequently used. The strong CpG island was found to be non-methylated under conditions characterized by large differences in Mfn2 gene expression. The proximal Mfn2 promoter contains six putative Sp1 motifs. Sp1 binds to the Mfn2 promoter and its overexpression activates the Mfn2 promoter in VSMCs. Chemical inhibition of Sp1 reduced Mfn2 expression, and Sp1 silencing reduced transcriptional activity of the Mfn2 promoter. In keeping with this view, Sp1 and Mfn2 mRNA levels were down-regulated in the aorta early after an atherogenic diet in apolipoprotein E-knockout mice or in VSMCs cultured in the presence of low serum. CONCLUSION: Sp1 is a key factor in maintaining basal Mfn2 transcription in VSMCs. Given the anti-proliferative actions of Mfn2, Sp1-induced Mfn2 transcription may represent a mechanism for prevention of VSMC proliferation and neointimal lesion and development.

Walking-induced muscle fatigue impairs postural control in adolescents with unilateral spastic cerebral palsy.

BACKGROUND: Fatigue is likely to be an important limiting factor in adolescents with spastic cerebral palsy (CP). AIMS: To determine the effects of walking-induced fatigue on postural control adjustments in adolescents with unilateral CP and their typically developing (TD) peers. METHODS: Ten adolescents with CP (14.2±1.7yr) and 10 age-, weight- and height-matched TD adolescents (14.1±1.9yr) walked for 15min on a treadmill at their preferred walking speed. Before and after this task, voluntary strength capacity of knee extensors (MVC) and postural control were evaluated in 3 conditions: eyes open (EO), eyes closed (EC) and with dual cognitive task (EODT). RESULTS: After walking, MVC decreased significantly in CP (-11%, P<0.05) but not in TD. The CoP area was only significantly increased in CP (90%, 34% and 60% for EO, EC and EODT conditions, respectively). The CoP length was significantly increased in the EO condition in CP and TD (20% and 21%) and was significantly increased in the EODT condition by 18% in CP only. CONCLUSIONS: Unlike TD adolescents, treadmill walking for 15min at their preferred speed lead to significant knee extensor strength losses and impairments in postural control in adolescents with unilateral spastic CP.

Circulating progenitor cells during exercise, muscle electro-stimulation and intermittent hypobaric hypoxia in patients with traumatic brain injury. A pilot study

BACKGROUND: Circulating progenitor cells (CPC) treatments may have great potential for the recovery of neurons and brain function. OBJECTIVE: To increase and maintain CPC with a program of exercise, muscle electro-stimulation (ME) and/or intermittent-hypobaric-hypoxia (IHH), and also to study the possible improvement in physical or psychological functioning of participants with Traumatic Brain Injury (TBI). METHODS: Twenty-one participants. Four groups: exercise and ME group (EEG), cycling group (CyG), IHH and ME group (HEG) and control group (CG). Psychological and physical stress tests were carried out. CPC were measured in blood several times during the protocol. RESULTS: Psychological tests did not change. In the physical stress tests the VO2 uptake increased in the EEG and the CyG, and the maximal tolerated workload increased in the HEG. CPC levels increased in the last three weeks in EEG, but not in CyG, CG and HEG. CONCLUSIONS: CPC levels increased in the last three weeks of the EEG program, but not in the other groups and we did not detect performed psychological test changes in any group. The detected aerobic capacity or workload improvement must be beneficial for the patients who have suffered TBI, but exercise type and the mechanisms involved are not clear.

Terutroban, A TP-receptor antagonist, reduces portal pressure in cirrhotic rats.

Increased production of vasoconstrictive prostanoids, such as thromboxane A2 (TXA2 ), contributes to endothelial dysfunction and increased hepatic vascular tone in cirrhosis. TXA2 induces vasoconstriction by way of activation of the thromboxane-A2 /prostaglandin-endoperoxide (TP) receptor. This study investigated whether terutroban, a specific TP receptor blocker, decreases hepatic vascular tone and portal pressure in rats with cirrhosis due to carbon tetrachloride (CCl4 ) or bile duct ligation (BDL). Hepatic and systemic hemodynamics, endothelial dysfunction, liver fibrosis, hepatic Rho-kinase activity (a marker of hepatic stellate cell contraction), and the endothelial nitric oxide synthase (eNOS) signaling pathway were measured in CCl4 and BDL cirrhotic rats treated with terutroban (30 mg/kg/day) or its vehicle for 2 weeks. Terutroban reduced portal pressure in both models without producing significant changes in portal blood flow, suggesting a reduction in hepatic vascular resistance. Terutroban did not significantly change arterial pressure in CCl4 -cirrhotic rats but decreased it significantly in BDL-cirrhotic rats. In livers from CCl4 and BDL-cirrhotic terutroban-treated rats, endothelial dysfunction was improved and Rho-kinase activity was significantly reduced. In CCl4 -cirrhotic rats, terutroban reduced liver fibrosis and decreased alpha smooth muscle actin (α-SMA), collagen-I, and transforming growth factor beta messenger RNA (mRNA) expression without significant changes in the eNOS pathway. In contrast, no change in liver fibrosis was observed in BDL-cirrhotic rats but an increase in the eNOS pathway. CONCLUSION: Our data indicate that TP-receptor blockade with terutroban decreases portal pressure in cirrhosis. This effect is due to decreased hepatic resistance, which in CCl4 -cirrhotic rats was linked to decreased hepatic fibrosis, but not in BDL rats, in which the main mediator appeared to be an enhanced eNOS-dependent vasodilatation, which was not liver-selective, as it was associated with decreased arterial pressure. The potential use of terutroban for portal hypertension requires further investigation.

Comparison of three analytical methods for the determination of quinolones in pig muscle samples

This work presents a comparison between three analytical methods developed for the simultaneous determination of eight quinolones regulated by the European Union (marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin, difloxacin, sarafloxacin, oxolinic acid and flumequine) in pig muscle, using liquid chromatography with fluorescence detection (LC-FD), liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The procedures involve an extraction of the quinolones from the tissues, a step for clean-up and preconcentration of the analytes by solid-phase extraction and a subsequent liquid chromatographic analysis. The limits of detection of the methods ranged from 0.1 to 2.1 ng g−1 using LC-FD, from 0.3 to 1.8 using LC-MS and from 0.2 to 0.3 using LC-MS/MS, while inter- and intra-day variability was under 15 % in all cases. Most of those data are notably lower than the maximum residue limits established by the European Union for quinolones in pig tissues. The methods have been applied for the determination of quinolones in six different commercial pig muscle samples purchased in different supermarkets located in the city of Granada (south-east Spain).

Role of Myotonic Dystrophy Protein Kinase [DMPK] in Glucose Homeostasis and Muscle Insulin Action

Myotonic dystrophy 1 (DM1) is caused by a CTG expansion in the 3′-unstranslated region of the DMPK gene, which encodes a serine/threonine protein kinase. One of the common clinical features of DM1 patients is insulin resistance, which has been associated with a pathogenic effect of the repeat expansions. Here we show that DMPK itself is a positive modulator of insulin action. DMPK-deficient (dmpk−/−) mice exhibit impaired insulin signaling in muscle tissues but not in adipocytes and liver, tissues in which DMPK is not expressed. Dmpk−/− mice display metabolic derangements such as abnormal glucose tolerance, reduced glucose uptake and impaired insulin-dependent GLUT4 trafficking in muscle. Using DMPK mutants, we show that DMPK is required for a correct intracellular trafficking of insulin and IGF-1 receptors, providing a mechanism to explain the molecular and metabolic phenotype of dmpk−/− mice. Taken together, these findings indicate that reduced DMPK expression may directly influence the onset of insulin-resistance in DM1 patients and point to dmpk as a new candidate gene for susceptibility to type 2-diabetes.

Role of Myotonic Dystrophy Protein Kinase [DMPK] in Glucose Homeostasis and Muscle Insulin Action

Myotonic dystrophy 1 (DM1) is caused by a CTG expansion in the 3′-unstranslated region of the DMPK gene, which encodes a serine/threonine protein kinase. One of the common clinical features of DM1 patients is insulin resistance, which has been associated with a pathogenic effect of the repeat expansions. Here we show that DMPK itself is a positive modulator of insulin action. DMPK-deficient (dmpk−/−) mice exhibit impaired insulin signaling in muscle tissues but not in adipocytes and liver, tissues in which DMPK is not expressed. Dmpk−/− mice display metabolic derangements such as abnormal glucose tolerance, reduced glucose uptake and impaired insulin-dependent GLUT4 trafficking in muscle. Using DMPK mutants, we show that DMPK is required for a correct intracellular trafficking of insulin and IGF-1 receptors, providing a mechanism to explain the molecular and metabolic phenotype of dmpk−/− mice. Taken together, these findings indicate that reduced DMPK expression may directly influence the onset of insulin-resistance in DM1 patients and point to dmpk as a new candidate gene for susceptibility to type 2-diabetes.

Sinusoidal Endothelial Dysfunction Precedes Inflammation and Fibrosis in a Model of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome. Most morbidity associated with the metabolic syndrome is related to vascular complications, in which endothelial dysfunction is a major pathogenic factor. However, whether NAFLD is associated with endothelial dysfunction within the hepatic vasculature is unknown. The aims of this study were to explore, in a model of diet-induced overweight that expresses most features of the metabolic syndrome, whether early NAFLD is associated with liver endothelial dysfunction. Wistar Kyoto rats were fed a cafeteria diet (CafD; 65% of fat, mostly saturated) or a control diet (CD) for 1 month. CafD rats developed features of the metabolic syndrome (overweight, arterial hypertension, hypertryglyceridemia, hyperglucemia and insulin resistance) and liver steatosis without inflammation or fibrosis. CafD rats had a significantly higher in vivo hepatic vascular resistance than CD. In liver perfusion livers from CafD rats had an increased portal perfusion pressure and decreased endothelium-dependent vasodilation. This was associated with a decreased Akt-dependent eNOS phosphorylation and NOS activity. In summary, we demonstrate in a rat model of the metabolic syndrome that shows features of NAFLD, that liver endothelial dysfunction occurs before the development of fibrosis or inflammation.