PREP1 deficiency downregulates hepatic lipogenesis and attenuates steatohepatitis in mice.
OBJECTIVE
The aim of this study was to investigate the function of Prep1 (also known as Pknox1) in hepatic lipogenesis.


METHODS
The hepatic lipogenesis pathway was evaluated by real-time RT-PCR and Western blot. Biochemical variables were assessed using a clinical chemistry analyser.


RESULTS
Serum triacylglycerols and liver expression of fatty acid synthase (FAS) were significantly decreased in Prep1 hypomorphic heterozygous (Prep1 (i/+) ) mice compared with their non-hypomorphic littermates. Upstream FAS expression, phosphorylation of protein kinase C (PKC)ζ, liver kinase B1 (LKB1), AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) increased in Prep1 (i/+) mice, while protein and mRNA levels of the lipid phosphatase inhibitor of PKCζ, SH2-containing inositol 5'-phosphatase 2 (SHIP2), was more than 60% reduced. Consistent with these findings, HepG2 cells transfected with Prep1 cDNA exhibited increased triacylglycerol accumulation and FAS expression, with strongly reduced PKCζ, LKB1, AMPK and ACC phosphorylation. Further experiments revealed the presence of both Prep1 and its major partner Pbx1 at the Ship2 (also known as Inppl1) promoter. PBX-regulating protein 1 (PREP1) and pre-B cell leukaemia transcription factor 1 (PBX1) enhanced Ship2 transcription. The PREP1HR mutant, which is unable to bind PBX1, exhibited no effect on Ship2 function, indicating transcriptional activation of Ship2 by the PREP1/PBX1 complex. Treatment with a methionine- and choline-deficient diet (MCDD) induced steatosis in both Prep1 (i/+) and non-hypomorphic control mice. However, alanine aminotransferase increase, intracellular triacylglycerol content and histological evidence of liver steatosis, inflammation and necrosis were significantly less evident in Prep1 (i/+) mice, indicating that Prep1 silencing protects mice from MCDD-induced steatohepatitis.


CONCLUSIONS
Our results indicate that Prep1 silencing reduces lipotoxicity by increasing PKCζ/LKB1/AMPK/ACC signalling, while levels of PREP1 expression may determine the risk of steatohepatitis and its progression.
Department of Translational Medical Sciences, 'Federico II' University of Naples and Institute of Experimental Endocrinology and Oncology, National Council of Research, Via Pansini 5, 80131, Naples, Italy.
Francesco
F
Oriente
Serena
S
Cabaro
Antonietta
A
Liotti
Michele
M
Longo
Luca
L
Parrillo
Teresa Bruna
TB
Pagano
Gregory Alexander
GA
Raciti
Dmitry
D
Penkov
Orlando
O
Paciello
Claudia
C
Miele
Pietro
P
Formisano
Francesco
F
Blasi
Francesco
F
Beguinot
D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D050156:Adipogenesis; D000818:Animals; D015153:Blotting, Western; D015536:Down-Regulation; D064429:Fatty Acid Synthases / Q000378:metabolism*; D005234:Fatty Liver / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation; D020868:Gene Silencing; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007333:Insulin Resistance; D050155:Lipogenesis; D008099:Liver / Q000473:pathology*; D008297:Male; D051379:Mice; D011493:Protein Kinase C / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism*; D000099221:Protein Kinase C zeta
D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase; D064429:Fatty Acid Synthases; D018398:Homeodomain Proteins; D011493:Protein Kinase C; D014280:Triglycerides; D000099221:Protein Kinase C zeta; C491412:Pknox1 protein, mouse