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Exploration of global gene expression in human liver steatosis by high-density oligonucleotide microarray.

Inserm 602, Service de Biochimie et Biologie Moléculaire, Hôpital Universitaire Paul Brousse, Université Paris XI, Villejuif Cedex, France.
Laboratory Investigation (Impact Factor: 3.83). 03/2006; 86(2):154-65. DOI: 10.1038/labinvest.3700374
Source: PubMed

ABSTRACT Understanding the molecular mechanisms underlying fatty liver disease (FLD) in humans is of major importance. We used high-density oligonucleotide microarrays (22.3 K) to assess the mechanisms responsible for the development of human liver steatosis. We compared global gene expression in normal (n=9) and steatotic (n=9) livers without histological signs of inflammation or fibrosis. A total of 34 additional human samples including normal (n=11), steatosis (n=11), HCV-related steatosis (n=4) or steatohepatitis associated with alcohol consumption (n=4) or obesity (n=4) were used for immunohistochemistry or quantitative real-time PCR studies. With unsupervised classification (no gene selection), all steatotic liver samples clustered together. Using step-down maxT multiple testing procedure for controlling the Family-Wise Error-Rate at level 5%, 110 cDNAs (100 over- and 10 underexpressed) were found to be differentially expressed in steatotic and normal livers. Of them were genes involved in mitochondrial phosphorylative and oxidative metabolism. The mean ratio of mitochondrial DNA to nuclear DNA content was higher in liver steatosis compared to normal liver biopsies (1.12+/-0.14 vs 0.67+/-0.10; P=0.01). An increased expression of genes involved in inflammation (IL-1R family, TGFB) was also observed and confirmed by quantitative RT-PCR or immunochemistry. In steatohepatitis, an increase of the protein expression of mitochondrial antigens, IL-1R1, IGF2 and TGFB1 was also observed, interleukin 1 receptor being always strongly expressed in steatohepatitis linked to alcohol or obesity. In conclusion, mitochondrial alterations play a major role in the development of steatosis per se. Activation of inflammatory pathways is present at a very early stage of steatosis, even if no morphological sign of inflammation is observed.

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A fatty liver is associated with both hepatic insulin resistance and impaired insulin clearance. Rosi-glitazone may be particularly effective in type 2 diabetic patients who are poorly controlled despite using high insulin doses. Metabolisella oireyhtymällä tarkoitetaan sydän- ja verisuonisairauksien vaaratekijöiden kasaumaa, johon kuuluu keskivartalolihavuuden lisäksi kohonnut verenpaine, paastosokeri ja poikkeavat rasva-arvot (kohonneet triglyseridit ja matala hyvä (HDL)-kolesteroli). Vaikka metabolinen oireyhtymä ja tyypin 2 diabetes ovat yleisempiä lihavilla kuin normaalipainoisilla, on epäselvää, miksi joillekin lihaville näitä häiriöitä ei kehity. Insuliini estää normaalisti maksan sokerin ja rasvojen tuotantoa, mutta rasvaisessa maksassa nämä vaikutukset ovat heikentyneet. Tässä väitöskirjassa selvitettiin, kuinka rasvainen maksa on henkilöillä, joilla on metabolinen oireyhtymä tai tyypin 2 diabetes, ja mikä veren merkkiaine tai kehon koostumuksen poikkeavuus parhaiten heijastaa maksan rasvapitoisuutta. Lisäksi tutkittiin, miten hoito insuliiniherkiste-lääkeaineella (glitatsonilla) vaikuttaa poikkeuksellisen paljon insuliinia (keskimäärin yli 200 yks/vrk) vaativien tyypin 2 diabeetikoiden maksan rasvapitoisuuteen, insuliinitarpeeseen ja hoitotasapainoon. Kaikissa osatöissä maksan rasvapitoisuus mitattiin magneettitutkimuksella. Insuliinin vaikutusta maksassa ja lihaksissa mitattiin suorilla menetelmillä. Tämän lisäksi mitattiin seerumin rasva-arvoja ja paastoinsuliini- ja maksaentsyymipitoisuuksia. Metabolinen oireyhtymä liittyi maksan- muttei lihaksensisäisen rasvan kertymiseen. Maksan rasvaprosentti oli neljä kertaa suurempi henkilöillä, joilla oli metabolinen oireyhtymä kuin henkilöillä, joilla oireyhtymää ei ollut. Seerumin paastoinsuliinin ja C-peptidin pitoisuudet heijastivat parhaiten maksan rasvapitoisuutta. Insuliinin vaikutus oli alentunut henkilöillä, joilla maksan rasvapitoisuus oli koholla. Tyypin 2 diabeetikoilla todettiin olevan merkittävästi enemmän rasvaa maksassa kuin yhtä lihavilla henkilöillä, joilla ei ollut diabetesta. Seerumin maksa-arvot aliarvioivat maksan rasvan määrää tyypin 2 diabeetikoilla. Insuliiniherkiste vähensi maksan rasvapitoisuuden ja insuliinitarpeen puoleen verrattuna tilanteeseen ennen hoitoa. Insuliiniherkistehoidon aikana sokeritasapaino ja maksan insuliiniherkkyys paranivat. Maksa on rasvoittunut henkilöillä, joilla on metabolinen oireyhtymä, ja etenkin potilailla, joilla on tyypin 2 diabetes. Insuliiniherkistehoito vaikuttaa tehokkaalta sellaisilla tyypin 2 diabeetikoille, joilla on korkea insuliinitarve rasvamaksasta johtuen.