Enhanced free cholesterol, SREBP-2 and StAR expression in human NASH.
OBJECTIVE
Non-alcoholic fatty liver disease (NAFLD) pathogenesis remains unknown. Due to the emerging role of free cholesterol (FC) in NAFLD, our aim was to examine the correlation between FC accumulation in patients with NAFLD and the expression of enzymes that regulate cholesterol homeostasis.


METHODS
Filipin staining, indicative of FC accumulation, and real-time PCR analyses were performed in 31 NAFLD patients and in seven controls.


RESULTS
All NASH patients (n=14) and 4 out of 17 patients with steatosis exhibited filipin staining compared to controls (0 out of 7 subjects with normal liver histology and BMI). Sterol regulatory element-binding protein-2 (SREBP-2) mRNA levels were 7- and 3-fold higher in NASH and steatosis patients, respectively, compared to controls. Since hydroxymethylglutaryl-CoA (HMG-CoA) reductase is the key enzyme in cholesterol synthesis and transcriptionally controlled by SREBP-2 we measured its mRNA levels, being 3- to 4-fold higher in NAFLD compared to controls, without any difference between NASH and steatosis patients. Fatty acid synthase (FAS) and SREBP-1c expression were not significantly induced in NAFLD, while ATP-binding cassette sub-family G member 1 (ABCG1), a transporter involved in cholesterol egress, and acyl-CoA-cholesterol acyltransferase mRNA levels were modestly increased (1.5- to 2.5-fold, p<0.05), regardless of fibrosis. Interestingly, mRNA levels of steroidogenic acute regulatory protein (StAR), a mitochondrial-cholesterol transporting polypeptide, increased 7- and 15-fold in steatosis and NASH patients, respectively, compared to controls.


CONCLUSIONS
FC increases in NASH and correlates with SREBP-2 induction. Moreover, StAR overexpression in NASH suggests that mitochondrial FC may be a player in disease progression and a novel target for intervention.
Caballero
Francisco
F
Centro de Investigaciones Biomédicas Esther Koplowitz, IMDiM, Hospital Clínic i Provincial and CIBEREHD, IDIBAPS, Department of Cell Death and Proliferation, Instituto Investigaciones Biomédicas de Barcelona, Spain.
Fernández
Anna
A
De Lacy
Antonio M
AM
Fernández-Checa
Jose C
JC
Caballería
Juan
J
García-Ruiz
Carmen
C
D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000328:Adult; D000818:Animals; D002784:Cholesterol / Q000378:metabolism*; D017931:DNA Primers; D048909:Diabetes Complications / Q000235:genetics / Q000378:metabolism; D005234:Fatty Liver / Q000150:complications / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005372:Filipin / Q000378:metabolism; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D009767:Obesity, Morbid / Q000150:complications / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051780:Sterol Regulatory Element Binding Protein 1 / Q000235:genetics; D051782:Sterol Regulatory Element Binding Protein 2 / Q000235:genetics*; D000098682:Steroidogenic Acute Regulatory Protein
C419353:ABCG1 protein, human; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters; D017931:DNA Primers; D010750:Phosphoproteins; D012333:RNA, Messenger; C497387:SREBF1 protein, human; C497390:SREBF2 protein, human; D051780:Sterol Regulatory Element Binding Protein 1; D051782:Sterol Regulatory Element Binding Protein 2; D000098682:Steroidogenic Acute Regulatory Protein; D005372:Filipin; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases