Gastroenterology

Gastroenterology

Volume 135, Issue 1, July 2008, Pages 282-291.e1
Gastroenterology

Basic—Liver, Pancreas, and Biliary Tract
The Kruppel-Like Factor 6 Genotype Is Associated With Fibrosis in Nonalcoholic Fatty Liver Disease

https://doi.org/10.1053/j.gastro.2008.04.004Get rights and content

Background & Aims: Although nonalcoholic fatty liver disease (NAFLD) is increasingly common, only a minority of affected individuals develop fibrotic liver disease. Based on its role in liver growth and repair, we explored whether Kruppel-like factor 6 (KLF6) plays a role in NAFLD progression. Methods: KLF6 expression in 31 fibrosis scored NAFLD liver biopsy specimens was assessed by real-time polymerase chain reaction. Transfected minigene constructs were used to study the effect of a polymorphism, KLF6-IVS1-27G>A, that promotes KLF6 alternative splicing in vitro. We genotyped KLF6-IVS1-27G>A in 3 groups of patients (UK group 1, n = 306; Italian group 2, n = 109; trio group 3, n = 61 children and parents). Results: KLF6 expression was increased in association with increased steatosis, inflammation, and fibrosis in NAFLD livers. KLF6-IVS1-27G>A promoted alternative splicing of KLF6 and abrogated the up-regulation of both α-smooth muscle actin and collagen 1 in LX-2 cells. Group 1 genotyping identified KLF6-IVS1-27G>A in 44 of 306 (14.4%) patients. Notably, KLF6-IVS1-27G>A was associated significantly with milder NAFLD, with only 25% having more advanced fibrosis compared with 45% of wild-type (wt) individuals. This trend was confirmed in group 2. A linear regression analysis including all 415 patients, adjusted for age, sex, body mass index, and blood glucose level, confirmed that presence of the wt KLF6 allele was an independent predictor of fibrotic NAFLD. Furthermore, we have shown preferential transmission of the wt allele to children with fibrotic NAFLD. Conclusions: We report a functional polymorphism in the KLF6 gene associated with advanced NAFLD and believe further study of KLF6 may enhance our understanding of this disease process.

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Patients

We enrolled 415 patients with biopsy-proven NAFLD at different stages of disease from Newcastle and Turin hospitals according to the regulations and ethical requirements of the participating centers. All patients had clinical features and liver biopsies diagnostic of NAFLD. Women and men consuming greater than 14 or 21 units of alcohol per week, respectively, were excluded, as were any individuals with viral or autoimmune liver diseases. Clinical and laboratory data were collected on the date

KLF6 Expression Is Increased in Association With More Advanced Stages of NAFLD

KLF6 is a ubiquitous transcription factor and immediate early gene induced in response to stressful stimuli. We have compared its expression at the mRNA level using 2 different sets of TaqMan real-time primers and probe, one of which quantifies all isoforms of KLF6 (KLF6 Total) and one of which quantifies the full-length, wild-type version only (KLF6 wt). Both are expressed as an RQ value, relative to the same control gene (glyceraldehyde-3-phosphate dehydrogenase) and the same comparator

Discussion

NAFLD is increasingly common in Western societies. Established predictors of those likely to develop progressive disease characterized by advanced fibrosis include age, increased BMI, and an increased blood glucose level.27 Why some individuals with these risk factors progress and others do not is unclear, but twin and ethnic studies suggest that genetic factors play a role.5, 6 To date, SNPs in a number of genes have been associated with NAFLD severity, including microsomal triglyceride

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Supported by grants from GlaskoSmithKline (H.L.R.); Newcastle upon Tyne Hospitals Special Trustees (H.L.R.); European Association for Study of the Liver Sheila Sherlock fellowship (L.M.); European Research Advisory Board (C.P.D.; H.L.R.), and National Institutes of Health grant DK56621 (S.L.F.).

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