9 research outputs found
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
Resistència a la insulina i disfunció endotelial sinusoïdal a la malaltia hepà tica per dipòsit de greix
La malaltia hepĂ tica per dipòsit de greix (MHDG) constitueix la manifestaciĂł hepĂ tica de la sĂndrome metabòlica. La seva incidència augmenta en les societats occidentals paral•lelament a la de l'obesitat. El dipòsit de greix intrahepĂ tic pot conduir al desenvolupament de dany hepatocitari, inflamaciĂł, fibrosi i cirrosi, però no es coneixen els mecanismes que promouen la progressiĂł de la malaltia. No existeix un tractament farmacològic eficaç per a aquesta malaltia.
La resistència a la insulina, el fet fisiopatològic subjacent a la sĂndrome metabòlica, condueix al desenvolupament de disfunciĂł endotelial perifèrica. No obstant això, l'endoteli sinusoidal hepĂ tic Ă©s fenotĂpicament diferent al perifèric, i es desconeix si la resistència a la insulina genera disfunciĂł endotelial en la circulaciĂł hepĂ tica. L'adequada funciĂł de l'endoteli sinusoĂŻdal Ă©s necessĂ ria per al manteniment d'un ambient antiinflamatori, antifibrogènic i antitrombòtic en el fetge.
En aquest estudi hipotetitzem que a la MHDG, associada a resistència a la insulina, existeix disfunció endotelial sinusoïdal que contribueix a la progressió del dany hepà tic.
Els objectius d'estudi van ser determinar en un model animal de EHDG si aquesta s'associa amb disfunció endotelial del sinusoïdal, els possibles mecanismes implicats, incloent la seva relació amb la resistència a la insulina, i si aquesta contribueix al desenvolupament de lesió hepà tica. Per respondre a aquestes preguntes es van caracteritzar les respostes vasculars de la circulació hepà tica mitjançant perfusió aïllada de fetge, i es van estudiar els mecanismes que determinen la biodisponibilitat de NO mitjançant tècniques moleculars en fetge complet. Es van estudiar, a més els efectes de la correcció de la insulino resistència sobre aquestes alteracions.
En el primer estudi, després d'administrar a rates durant 3 dies una dieta rica en greix, aquestes van presentar esteatosi en absència d'inflamació. Això es va acompanyar d'un increment del contingut intrahepà tic de triglicèrids i à cids grassos lliures. Les rates amb fetges esteatòsics van presentar resistència vascular a la insulina i, més concretament, resistència a la insulina a nivell del endoteli sinusoidal hepà tic. Això es va acompanyar d'una menor capacitat de la insulina per fosforilar eNOS. Aquestes alteracions es van deure, si més no en part, per la regulació a l'alça de iNOS. El pre-tractament amb un fà rmac sensibilitzador de la insulina va atenuar la l'acumulació intrahepà tic de triglicèrids i à cids grassos lliures, va prevenir el desenvolupament de resistència a la insulina a nivell i va restaurar la capacitat de la insulina per fosforilar eNOS en rates alimentades durant 3 dies amb una dieta rica en greix.
En el segon estudi, vam demostrar que l'administraciĂł durant un mes d'una dieta rica en greix provoca esteatosi en absència d'inflamaciĂł i fibrosi. Això es va acompanyar d'alteracions inclosa en la sĂndrome metabòlica, com l'obesitat, hipertrigliceridèmia, hiperglucèmia, hiperinsulinèmia i hipertensiĂł arterial. Aquestes rates van presentar un augment de la pressiĂł portal de perfusiĂł, a causa de canvis funcionals, aixĂ com disfunciĂł endotelial sinusoĂŻdal. A nivell molecular això es va traduir en un una menor fosforilaciĂł de Akt i eNOS en els fetges de rates alimentades amb una dieta rica en greix. Aquests canvis funcionals es van produir en absència de canvis fenotĂpics en les cèl•lules endotelials sinusoĂŻdals. Concloem d'aquest segon estudi que els resultats obtinguts en aquest estudi reforçarien la idea de considerar la disfunciĂł endotelial hepĂ tica com un esdeveniment precoç que podria constituir una diana terapèutica per tractar aquesta malaltia.Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome. NAFLD incidence is increasing in western societies, paralleling the increase of obesity. The deposit of fat in the hepatocytes leads in some patients to the development of hepatocyte injury, inflammation, fibrosis and cirrhosis, but the mechanisms that govern the progression of liver injury are not well understood. There is not an effective pharmacological treatment for NAFLD.
Insulin-resistance, the underlying pathophysiological feature of the metabolic syndrome, is associated with peripheral endothelial dysfunction. However, the sinusoidal endothelium is phenotypically different from the peripheral endothelium, and it is not known whether insulin resistance induces sinusoidal endothelial dysfunction. An adequate sinusoidal endothelial function is required to maintain an anti-inflammatory, antifibrogenic and antithrombotic environment in the liver.
We hypothesize in this project that in NAFLD, which is associated with insulin-resistance, there is sinusoidal endothelial dysfunction, and that this is relevant to the development of liver injury.
In the first study, we have demonstrated that after 3-days high fat feeding, rats developed steatosis without the presence of inflammation. Insulin resistance was present at the liver vasculature, and specifically, at the liver sinusoidal endothelium. This was accompanied by a reduction of the ability of insulin to phosphorylate eNOS. The conclusions of this first study were that vascular insulin resistance precedes inflammation, and can contribute to the progression of the disease.
In the second study we demonstrate that rats fed for one month with a high fat diet presented steatosis without fibrosis or inflammation. This was accompanied by alterations resembling metabolic syndrome, endothelial dysfunction and a decreased liver eNOS and Akt phosphorylation. This was due to functional alterations (and no structural) at the sinusoidal endothelial cells, without phenotypical changes occurring at this level. We concluded that endothelial dysfunction is a primary event that precedes inflammation in a model of NAFLD, and might constitute a useful target for devising new therapies for this disease
Intrahepatic vascular changes in non-alcoholic fatty liver disease: Potential role of insulin-resistance and endothelial dysfunction
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
Hematoxylin/eosin (H/E), oil-red, Mason’s Thricrome images and steatosis area from livers from rats fed a control diet (CD) or a high fat diet (CafD).
<p>(original magnification, x100 or x200 as displayed in the figures).</p
Liver inflammation and hepatic stellate cells phenotype.
<p><b>A</b>) Immunohistochemistry showing CD43 (a pan-leukocyte marker) immunostaining in livers from high fat feeding (CafD) and control rats (CD). The administration for 1 month of a high fat diet did not induce liver inflammation (original magnification: x200). <b>B</b>) Cafeteria diet did not induce activation of HSC as assessed by immunohistochemistry for α-SMA.</p
Baseline characteristics and hemodynamics of rats fed for 1 month a control (CD) or a cafeteria (CafD) diet.
<p>Data is presented as mean ± SD. (FFA: free fatty acids).</p
Endothelial cells phenotype.
<p>Cafeteria diet did not induce changes in <b>A</b>) SE-1 expression nor <b>B</b>) CD31, which are closely correlated with fenestrations and capillarization at the sinusoidal endothelial cells. <b>C</b>) Cafeteria diet did not induce <i>de novo</i> expression of CD34, a marker of loss of LSEC phenotype.</p
Ex-vivo assessment of liver circulation.
<p>Portal Perfusion Pressure (PPP) in CafD (n = 12) and CD rats (n = 12) in the absence (<b>A</b>) or the presence (<b>B</b>) of the NO donor sodium nitroprusside (SNP). Livers from rats fed cafeteria diet showed an increased PPP. No differences were observed in the presence of SNP (CD: control diet; CafD: cafeteria diet).</p