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In its initial stages, nonalcoholic fatty liver disease presents hypertriglyceridemia and accumulation of lipids in the liver (hepatic steatosis). Bempedoic acid is an ATP:citrate lyase inhibitor that promotes a dual inhibition of the synthesis of cholesterol and fatty acids. However, its effect in the prevention / treatment of hepatic steatosis and hypertriglyceridemia has not been investigated. The aim of our work has been to elucidate whether bempedoic acid, through a mechanism other than ATP:citrate lyase inhibition, reverses these metabolic alterations.The study was carried out in female Sprague-Dawley rats fed, for three months, with a high fat diet supplemented with fructose (10% w/v) in drinking water. During the last month, bempedoic acid (30mg/kg/day) was administered to a group of animals. Zoometric and plasmatic parameters were analyzed, gene and protein expression analysis were performed in liver samples and PPAR-PPRE binding activity was determined.Our interventional model developed hepatic steatosis and hypertriglyceridemia. Despite an increase in total caloric intake, there was no increase in body weight of the animals. The administration of bempedoic acid significantly reduced hepatic steatosis and promoted a marked hepatocyte hypertrophy. There was a 66% increase in the liver weight of the animals treated with the drug that was not accompanied by modifications in the markers of inflammation, oxidative stress, or endoplasmic reticulum stress. Bempedoic acid activated the peroxisome proliferator activated nuclear receptor (PPARα) and its target genes.Bempedoic acid could be an effective therapy for the treatment of fatty liver and associated cardiovascular risk. Bempedoic acid has other mechanisms of action besides the inhibition of ATP: citrate lyase, such as the activation of PPARα, which could explain the reduction in hepatic steatosis and the increase in liver weight observed in animals treated with the drug.

Supplementation with 10% liquid fructose to female rats for 2weeks caused hepatic steatosis through increased lipogenesis and reduced peroxisome proliferator activated receptor (PPAR) α activity and fatty acid catabolism, together with increased expression of the spliced form of X-binding protein-1 (Rebollo et al., 2014). In the present study, we show that some of these effects are preserved after sub-chronic (8weeks) fructose supplementation, specifically increased hepatic expression of lipid synthesis-related genes (stearoyl-CoA desaturase, ×6.7-fold; acetyl-CoA carboxylase, ×1.6-fold; glycerol-3-phosphate acyltransferase, ×1.65-fold), and reduced fatty acid β-oxidation (×0.77-fold), resulting in increased liver triglyceride content (×1.69-fold) and hepatic steatosis. However, hepatic expression of PPARα and its target genes was not modified and, further, livers of 8-week fructose-supplemented rats showed no sign of unfolded protein response activation, except for an increase in p-IRE1 levels. Hepatic mTOR phosphorylation was enhanced (×1.74-fold), causing an increase in the phosphorylation of UNC-51-like kinase 1 (ULK-1) (×2.8-fold), leading to a decrease in the ratio of LC3B-II/LC3B-I protein expression (×0.39-fold) and an increase in the amount of the autophagic substrate p62, indicative of decreased autophagy activity. A harmful cycle may be established in the liver of 8-week fructose-supplemented rats where lipid accumulation may cause defective autophagy, and reduced autophagy may result in decreased free fatty acid formation from triglyceride depots, thus reducing the substrates for β-oxidation and further increasing hepatic steatosis. In summary, the length of supplementation is a key factor in the metabolic disturbances induced by fructose: in short-term studies, PPARα inhibition and ER stress induction are critical events, whereas after sub-chronic supplementation, mTOR activation and autophagy inhibition are crucial.

Fructose ingestion is associated with the production of hepatic steatosis and hypertriglyceridemia. For fructose to attain these effects in rats, simultaneous induction of fatty acid synthesis and inhibition of fatty acid oxidation is required. We aimed to determine the mechanism involved in the inhibition of fatty acid oxidation by fructose and whether this effect occurs also in human liver cells. Female rats were supplemented or not with liquid fructose (10% w/v) for 7 or 14 days; rat (FaO) and human (HepG2) hepatoma cells, and human hepatocytes were incubated with fructose 25 mM for 24 h. The expression and activity of the enzymes and transcription factors relating to fatty acid β-oxidation were evaluated. Fructose inhibited the activity of fatty acid β-oxidation only in livers of 14-day fructose-supplemented rats, as well as the expression and activity of peroxisome proliferator activated receptor α (PPARα). Similar results were observed in FaO and HepG2 cells and human hepatocytes. PPARα downregulation was not due to an osmotic effect or to an increase in protein-phosphatase 2A activity caused by fructose. Rather, it was related to increased content in liver of inactive and acetylated peroxisome proliferator activated receptor gamma coactivator 1α, due to a reduction in sirtuin 1 expression and activity. In conclusion, fructose inhibits liver fatty acid oxidation by reducing PPARα expression and activity, both in rat and human liver cells, by a mechanism involving sirtuin 1 down-regulation.

Fructose intake from added sugars correlates with the epidemic rise in obesity, metabolic syndrome and cardiovascular diseases. Fructose intake also causes features of metabolic syndrome in laboratory animals. Therefore, we have investigated whether fructose modifies lipidemia in pregnant rats and produces changes in their fetuses. Thus, fructose administration (10% wt/vol.) in the drinking water of rats throughout gestation leads to maternal hypertriglyceridemia. This change was not observed in glucose-fed rats, although both carbohydrates produced similar changes in liver triglycerides and in the expression of transcription factors and enzymes involved in lipogenesis. After fasting overnight, mothers fed with carbohydrates were found to be hyperleptinemic. However, after a bolus of glucose, leptinemia in fructose-fed mothers showed no response, whereas it increased in parallel in glucose-fed and control mothers. Fetuses from fructose-fed mothers showed hypotriglyceridemia and a higher hepatic triglyceride content than fetuses from control or glucose-fed mothers. A higher expression of genes related to lipogenesis and a lower expression of fatty acid catabolism genes were also found in fetuses from fructose-fed mothers. Moreover, although hyperleptinemic, these fetuses exhibited increased tyrosine phosphorylation of the signal transducer and activator of transcription-3 (STAT-3) protein, without a parallel increase in the serine phosphorylation of STAT-3 nor in the suppressor of cytokine signaling-3 protein levels whose expression is regulated by leptin through STAT-3 activation. Thus, fructose intake during gestation provoked a diminished maternal leptin response to fasting and refeeding and an impairment in the transduction of the leptin signal in the fetuses, which could be responsible for their hepatic steatosis.

Background & Aims Peroxisome proliferator-activated receptor α (PPARα) is a transcription factor activated by ligands that regulates genes related to vascular tone, oxidative stress, and fibrogenesis, pathways implicated in the development of cirrhosis and portal hypertension. This study aims at evaluating the effects of PPARα activation with fenofibrate on hepatic and systemic hemodynamics, hepatic endothelial dysfunction, and hepatic fibrosis in CCl 4 -cirrhotic rats. Methods Mean arterial pressure (MAP), portal pressure (PP), and portal blood flow (PBF) were measured in cirrhotic rats treated with oral fenofibrate (25mg/kg/day, n=10) or its vehicle (n=12) for 7days. The liver was then perfused and dose-relaxation curves to acetylcholine (Ach) were performed. We also evaluated Sirius Red staining of liver sections, collagen-I mRNA expression, and smooth muscle actin (α-SMA) protein expression, cyclo-oxygenase-1 (COX-1) protein expression, and cGMP levels in liver homogenates, and TXB 2 production in perfusates. Nitric oxide (NO) bioavailability and eNOS activation were measured in hepatic endothelial cells (HEC) isolated from cirrhotic rat livers. Results CCl 4 cirrhotic rats treated with fenofibrate had a significantly lower PP (−29%) and higher MAP than those treated with vehicle. These effects were associated with a significant reduction in hepatic fibrosis and improved vasodilatory response to acetylcholine. Moreover, a reduction in COX-1 expression and TXB 2 production in rats receiving fenofibrate and a significant increase in NO bioavailability in HEC with fenofibrate were observed. Conclusions PPARα activation markedly reduced PP and liver fibrosis and improved hepatic endothelial dysfunction in cirrhotic rats, suggesting it may represent a new therapeutic strategy for portal hypertension in cirrhosis.

Resumen Introduccion La suplementacion de la dieta con un 10% (p/v) de fructosa en el agua de bebida durante 14 dias en ratas produce hipertrigliceridemia y esteatosis hepatica como consecuencia de una reduccion en la expresion y en la actividad transcripcional de PPARα en el higado. En el presente trabajo hemos estudiado en un modelo in vitro, la linea celular FaO, el posible mecanismo por el cual la fructosa reduce la expresion de PPARα. Material y metodos Las celulas FaO se incubaron en ausencia o presencia de fructosa 25 mM. Se obtuvieron extractos totales y nucleares para la determinacion de los niveles relativos de ARNm por RT-PCR, y de proteinas por Western Blot, de aquellas enzimas y factores de transcripcion implicados en las alteraciones producidas por la fructosa. Asimismo, se valoro la actividad PP2A. Resultados La incubacion con fructosa redujo la expresion de PPARα y sus genes diana ACO y CYP4A1, e incremento los niveles de proteina ChREBP y ARNm de su gen diana L-PK. El inhibidor de PP2A acido okadaico anulo el incremento de la actividad PP2A mediado por la fructosa y evito parcialmente la induccion de L-PK, pero no modifico la reduccion de la expresion de PPARα, ni tampoco la de ACO y CYP4A1. Conclusiones El aumento de los niveles de proteina ChREBP y de ARNm de L-PK, asi como la represion de PPARα mediados por la fructosa, se reproducen en la linea celular FaO tratada con fructosa 25 mM. Los experimentos realizados en presencia de acido okadaico sugieren que la activacion de PP2A por metabolitos de la fructosa no juega un papel relevante en la reduccion de la expresion de PPARα producida por la fructosa.

Resumen Introduccion Existe una asociacion entre el sindrome metabolico (SM) y el lupus eritematoso sistemico (LES). Los ratones hembra New-Zealand Black-White de primera generacion (BWF1) constituyen un modelo de LES humano y presentan caracteristicas del SM. Hemos estudiado en este modelo la evolucion temporal del SM y marcadores de LES, y su relacion con la proporcion de celulas T reguladoras (Tregs). Metodos Treinta y dos ratones hembra New-Zealand White (control) y 32 ratones hembra BWF1 (grupo LES) se estudiaron durante 28 semanas, determinando el consumo de dieta y el peso corporal. Los animales se sacrificaron a las 8, 16, 24 y 36 semanas de vida, determinando: el peso de tejido adiposo visceral, la proporcion de celulas CD4 + , CD4 + CD25 + y Tregs en linfocitos esplenicos, concentraciones plasmaticas y hepaticas de trigliceridos, concentraciones plasmaticas de glucosa, insulina, leptina, anticuerpos anti-dsDNA y creatinina. Resultados Los ratones LES presentaron, hasta las 16 semanas de vida, signos de alteraciones metabolicas, como hiperfagia, hiperleptinemia y un peso superior a los ratones control, asociado al incremento en la masa de tejido adiposo visceral, asi como una mayor proporcion de celulas Treg. A partir de las 16–24 semanas de vida, se produjo un cambio drastico, con un incremento en los niveles plasmaticos de anticuerpos anti-dsDNA, que coincidio con la desaparicion de las manifestaciones de SM. Conclusiones La presencia de resistencia a la leptina en las primeras semanas de vida explicaria no solo la mayor ingesta de alimento presentada por los ratones LES, sino tambien la mayor proporcion de celulas Tregs.

Introduccion Dietas ricas en fructosa producen, en ratas, hipertrigliceridemia y esteatosis hepatica, como consecuencia de una reduccion en la actividad transcripcional del receptor activado con proliferadores peroxisomicos alfa (PPARα), junto con un estado de resistencia parcial a la leptina. En el presente trabajo, hemos estudiado como la fructosa afecta en el ambito molecular al control del metabolismo energetico hepatico. Material y metodos Se distribuyeron de forma aleatorizada a 16 ratas Sprague-Dawley macho en 2 grupos: control y fructosa (10% peso/volumen en agua de bebida, durante 14 dias). Adicionalmente, se distribuyo a 12 ratas en 3 grupos: control, fructosa y fructosa + 1 β-D ribofuranosido de 5-aminoimidazol 4-carboxamida (AICAR) (500 mg/kg/dia, los ultimos 3 dias de dieta fructosa). Se valoraron los valores plasmaticos de trigliceridos, glucosa, leptina, insulina y adiponectina. En el ambito hepatico se determinaron: contenido de trigliceridos y ceramidas, actividad de β-oxidacion, actividad AMPK (AMP activada proteina cinasa), proteina fosfatasa 2A (PP2A) y valores de expresion proteica y de acido ribonucleico mensajero de diferentes genes implicados en el metabolismo energetico. Resultados Las ratas del grupo fructosa presentaron hipertrigliceridemia (×1,3), hiperleptinemia (×1,9) e hiperadiponectinemia (×1,7), incremento en los trigliceridos (×1,6) y ceramidas hepaticas y en la formacion de complejos PPARα-FoxO1. La administracion de AICAR, aunque incremento en un 30% la actividad AMPK hepatica, no revirtio ninguna de las alteraciones descritas. En ratas fructosa no sometidas a ayuno antes del sacrificio, se detecto en higado un marcado incremento en la subunidad catalitica de PP2A (×1,6) y en la capacidad de union de ChREBP (×1,4). Conclusiones El deficit de oxidacion de acidos grasos producido por el consumo de fructosa en forma liquida no es reversible por activacion de la AMPK hepatica. La activacion de PP2A tras la ingesta de fructosa es la alteracion molecular determinante en la aparicion de los cambios metabolicos inducidos por este monosacarido.

Introduccion En ratas, dietas ricas en fructosa producen hipertrigliceridemia y esteatosis hepatica, como consecuencia de una reduccion en la actividad transcripcional del receptor activado por proliferadores peroxisomicos alfa, junto con un estado de resistencia parcial a la leptina. En el presente trabajo, hemos estudiado como la fructose afecta a la via de senalizacion de la leptina. Material y metodos Se distribuyeron de forma aleatorizada 16 ratas Sprague-Dawley macho en 2 grupos: control y fructosa (10% peso/volumen en agua de bebida, durante 14 dias). Se valoraron los valores plasmaticos de trigliceridos, glucosa, leptina, insulina y adiponectina. En el higado se determinaron: contenido de trigliceridos, actividad de β-oxidacion, actividad AMPK (del ingles AMP-activated protein kinase) y valores de expresion proteica y de acido ribonucleico mensajero de diferentes genes de la via de senalizacion de la leptina. Resultados Las ratas fructosa presentaron un incremento en los valores de leptina plasmatica (1.9X) y de la expresion proteica de STAT-3-PTyr705 (1.9X) respecto las ratas control. No se observaron diferencias en las formas fosforilada y activas de STAT-3-PSer727 y de AMPK. Estas 2 fosforilaciones estan controladas por la via de las MAPK (del ingles mitogen activated protein kinase), que tampoco presentaba modificaciones entre los 2 grupos de estudio. El deficit de fosforilacion es consecuencia de una alteracion en la senalizacion del receptor a la leptina (ObRL) que no se fosforila en el residuo Tyr985, ni fosforila a JAK-2 (del ingles Janus-activated kinase 2), posiciones que controlan la via de las MAPK. SOCS-3 (del ingles supresor of cytokine signaling 3), que presenta un incremento en su expresion proteica (2.8X) en las ratas fructosa, puede ser la causa de la falta de activacion de ObRL-PTyr985 y de JAK-2. Conclusiones La administracion de fructosa provoca un incremento en la expresion proteica de SOCS-3. Como consecuencia, se observa la falta de fosforilacion de los residuos Tyr985 de ObRL y de JAK-2, que parecen ser la causa de la falta de actividad de la via de las MAPK y, por lo tanto, del deficit de actividad de AMPK y de STAT-3.

Introduccion Dietas ricas en fructosa producen, en roedores, hipertrigliceridemia y esteatosis hepatica. En el presente estudio, quisimos valorar como afectaba la administracion de este hidrato de carbono a la actividad hepatica de transactivacion y transrepresion del receptor activado por proliferadores peroxisomicos α (PPARα). Material y metodos Se aleatorizo a 24 ratas Sprague-Dawley en 3 grupos de tratamiento: control, fructosa y glucosa (10% peso/volumen [p/v] hidrato de carbono en agua de bebida, durante 14 dias). En plasma se valoraron los valores de trigliceridos, acidos grasos libres, glucosa, insulina y leptina. En tejido hepatico se determino: contenido de trigliceridos, actividad de betaoxidacion de los acidos grasos, valores de expresion (ARN mensajero, proteina y actividad de union proteina-ADN) de los genes objeto de nuestro estudio. Resultados La administracion de fructosa produjo un incremento de 1,9 y 1,8 veces en los valores de trigliceridos plasmaticos y hepaticos, respectivamente. Las concentraciones de leptina se incrementaron 2,4 veces en estos animales, sin que apareciera hiperglucemia ni resistencia a la insulina. La actividad de transactivacion de PPARα se redujo, asi como la actividad de betaoxidacion hepatica de los acidos grasos (48%). La actividad de transrepresion de PPARα tambien se redujo en estos animales, y se produjo un incremento del 30% en la actividad del factor NF-κB en las ratas fructosa frente a animales control. Estos resultados no se observaron tras la administracion de glucosa; no obstante, los 2 hidratos de carbono modificaron de forma similar la expresion hepatica de factores de transcripcion y enzimas clave implicados en la sintesis de acidos grasos. Conclusiones La hipertrigliceridemia y la esteatosis hepatica inducida por la ingesta de fructosa son el resultado de una reduccion en el catabolismo hepatico de los acidos grasos asociado a un deficit de actividad PPARα.

Introduccion La funcion de la apolipoproteina A-II (apo A-II) en el metabolismo lipoproteico y su relacion con la arteriosclerosis es poco conocida. Los estudios realizados en humanos y ratones modificados geneticamente han demostrado un efecto directo de la apo A-II en el metabolismo de los trigliceridos y los acidos grasos libres (AGL) y la sensibilidad a la insulina. El objetivo principal de este estudio es la identificacion de proteinas diferencialmente expresadas en el higado de ratones transgenicos de apo A-II humana (h) y su potencial relacion con el metabolismo de los trigliceridos y la glucosa. Material y metodos Se realizaron estudios metabolicos de las lipoproteinas ricas en trigliceridos, la betaoxidacion hepatica y la prueba de tolerancia a la glucosa en ratones transgenicos de apo A-IIh y en controles en situacion de ayunas y tras una carga oral de aceite de oliva. Los cambios en el perfil de expresion proteica se analizaron mediante el analisis comparativo de geles bidimensionales y la identificacion de proteinas mediante espectrometria de masas MALDI-TOF. Resultados Los ratones transgenicos de apo A-IIh presentaban un incremento del colesterol y los trigliceridos de las lipoproteinas que contienen apo B, hipertrigliceridemia aumentada tras la carga oral de acido oleico, asi como un aclaramiento acelerado de la glucosa tras la prueba de sobrecarga de glucosa. Estos cambios estaban asociados a una reduccion en el catabolismo de las lipoproteinas ricas en trigliceridos y la tasa de betaoxidacion hepatica, pero sin cambios significativos en la actividad de la lipoproteina lipasa. De las mas de 1.000 manchas resueltas en el rango pH 3 a 10, se identificaron 55 alteraciones significativas en los ratones transgenicos en comparacion con los ratones controles, 16 de las cuales estaban relacionadas directamente con el metabolismo de los AGL y los carbohidratos. Conclusiones La sobreexpresion apo A-IIh en ratones transgenicos induce hipertrigliceridemia posprandial debido, al menos en parte, a un defecto en el catabolismo de las lipoproteinas ricas en trigliceridos. La aproximacion proteomica nos ha permitido detectar y caracterizar diferencias en el proteoma hepatico de los ratones transgenicos de apo A-IIh y establecer proteinas potencialmente involucradas en el metabolismo de los AGL. Se requieren mas estudios bioquimicos y moleculares para investigar el significado funcional de los cambios encontrados.

We sought to investigate if, similar to what has been described in other rodent tissues, ageing changes the activity of several transcription factors, namely signal transducer and activator of transcription, nuclear factor-kappa B (NFkappaB), activated protein-1 (AP-1) and peroxisome proliferator-activated receptor (PPAR), in cortex of Sprague-Dawley rats. We also investigated if the administration of two hypolipidemic drugs, gemfibrozil (GFB) and atorvastatin (ATV), could prevent those changes. To this purpose, we determined the expression and binding activity of these transcription factors in cortex samples from 3-month and 18-month old male and female rats, and in 18-month old rats of both sexes treated for 21 days with a daily dose of 3mg GFB/kg or 10mg ATV/kg. Ageing increased rat cortex NFkappaB binding activity by 35-40%, and decreased by 22-26% the amount of PPARalpha in rats of both sexes, while cortex AP-1 binding activity and c-Jun content were reduced only in old females (-26 and -50%, respectively). Cortex cyclooxigenase-2 (COX-2) and receptor for activated C-kinase 1 (RACK1) expression was also reduced by old age. Hypolipidemic drugs prevented the age-related decrease of cortex AP-1 in old females and increased AP-1 binding activity and c-Jun protein in cortex from both old male and female rats. GFB increased also by 80% the cortex PPARalpha content in old males. Our data indicate that 18-month old rats show signs of cortex biochemical deterioration related to the ageing process, and that hypolipidemic drug administration partially prevents the appearance of some of the age-related changes in cortex biochemistry.

Introduccion El tratamiento con fibratos provoca cambios tanto en el contenido de lipidos biliares como en la composicion de los acidos biliares, lo que conduce a un incremento de la incidencia de colelitiasis en humanos. Los mecanismos moleculares implicados en estos cambios, observados en pacientes tratados con fibratos durante un largo periodo, todavia no han sido descritos. El objetivo de este estudio ha sido investigar el efecto del tratamiento con fibratos en los factores clave implicados en la sintesis de acidos biliares y en la secrecion biliar de lipidos en pacientes con colelitiasis. Pacientes y metodo Pacientes con colelitiasis y valores de colesterol unido a lipoproteinas de baja densidad (cLDL) elevados (> 130 mg/dl) fueron aleatorizados y asignados al tratamiento con bezafibrato (400 mg/dia), fenofibrato (200 mg/dia), gemfibrozilo (900 mg/dia) o placebo, durante 8 semanas antes de proceder a la intervencion quirurgica (colecistectomia electiva). La obtencion de muestras hepaticas tuvo lugar en el momento de la operacion y mediante RT-PCR se determinaron los valores de ARNm de colesterol 7-α-hidroxilasa (CYP7A1), hepatocyte nuclear factor-4 (HNF-4), transportadores ATP-binding cassette: MDR3, ABCG5, ABCG8 y el homologo humano del receptor scavanger BI (CLA-1). Resultados Fenofibrato, bezafibrato y gemfibrozilo redujeron de forma significativa los valores de cLDL y trigliceridos plasmaticos. Los 3 fibratos ensayados redujeron los valores de ARNm de CYP7A1, pero solo el bezafibrato incremento significativamente los valores de ABCG5. Ninguno de los farmacos por separado produjo cambios importantes en los valores de ARNm de los restantes genes probados, pero los fibratos como grupo incrementaron el ARNm de MDR-3 y ABCG5. Conclusiones Estos resultados muestran por primera vez que la administracion de fibratos a humanos, a dosis similares a las farmacologicas, reduce la expresion de la colesterol 7-α-hidroxilasa e incrementan la expresion de MDR-3 y ABCG5.

It is well known that gemfibrozil increases the biliary output of cholesterol and phospholipids, but we have little knowledge about the impact these changes have on liver cholesterol and phospholipid biosynthetic pathways. In the present study, no changes were detected in liver lipids and CTP:phosphocholine cytidylyltransferase after gemfibrozil administration to rats. On the contrary, 3-hydroxy-3-methylglutaryl-CoA reductase mRNA (9.9-fold) and Rd activity (16.7-fold) and phosphatidate phosphohydrolase activity (1.7-fold) increased, while plasma apo B-cholesterol (40%) and triglyceride (43%) levels decreased. As a part of a compensatory homeostatic response, we report for the first time that gemfibrozil administration to rats increased the hepatic sterol regulatory element binding protein-2 (SREBP-2) mRNA (2.9-fold) and mature protein (2.2-fold) levels. An early increase in the transcriptional activity of SREBP-2 elicited by gemfibrozil administration might be responsible for the observed changes in HMG-CoA reductase, phosphatidate phosphohydrolase, and SREBP-2 expression.

We studied whether two typical effects of fibrates, induction of stearoyl-CoA desaturase (EC 1.14.99.5) and peroxisome proliferation, are related. The effect of bezafibrate on the activity and mRNA of stearoyl-CoA desaturase and acyl-CoA oxidase in the liver and epididymal white adipose tissue of male Sprague-Dawley rats was determined. The same parameters were measured in HepG2 cells, a cell line resistant to peroxisome proliferation, following incubation with ciprofibrate. Bezafibrate increased the hepatic mRNA levels (14.5-fold on day 7) and activity (9.3-fold on day 15) of acyl-CoA oxidase. Stearoyl-CoA desaturase mRNA levels were transiently increased (2.7-fold on day 7), while its activity remained increased at the end of the treatment (2.4-fold). In white adipose tissue, bezafibrate increased the mRNA (5-fold) and activity (1.9-fold) of acyl-CoA oxidase, while stearoyl-CoA desaturase was not modified. Ciprofibrate addition to HepG2 cells cultured in 7% fetal bovine serum (FBS) only increased the stearoyl-CoA desaturase mRNA (1.9-fold). When cells were cultured in 0.5% FBS, ciprofibrate increased acyl-CoA oxidase mRNA (2.2-fold), while the increase in stearoyl-CoA desaturase mRNA was identical (1.9-fold). Further, its activity was also increased (1.5-fold). Incubation of HepG2 cells in the presence of cycloheximide did not alter the capacity of ciprofibrate to induce stearoyl-CoA desaturase mRNA, whereas the presence of actinomycin abolished the induction. In addition, preincubation of HepG2 cells with ciprofibrate increased the rate of stearoyl-CoA desaturase mRNA degradation. The results presented in this study suggest that fibrates induce stearoyl-CoA desaturase activity and mRNA levels independently of peroxisome proliferation.

Fibrates are hypolipidemic drugs that are also able to improve glucose tolerance in animals and diabetic patients through an unknown mechanism. Since uncoupling proteins (UCP) seem to play an important role in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM), we examined whether treatment of rats with bezafibrate for 3, 7, or 15 days modified UCP mRNA levels. Using RT-PCR, we observed a weak ectopic expression of UCP-1 and a 2-fold increase in UCP-3 mRNA levels in white adipose tissue after 7 and 15 days of treatment. Moreover, bezafibrate administration caused a 1. 7-fold induction in UCP-3 mRNA levels in skeletal muscle on day 7. Since UCP-3 mRNA levels are reduced in skeletal muscle of diabetic patients, this effect may be involved in the improvement of insulin sensitivity caused by bezafibrate in NIDDM.