Influence of TNF gene polymorphisms in Japanese patients with NASH and simple steatosis

Causes and metabolic consequences of Fatty liver

Type 2 diabetes and cardiovascular disease represent a serious threat to the health of the population worldwide. Although overall adiposity and particularly visceral adiposity are established risk factors for these diseases, in the recent years fatty liver emerged as an additional and independent factor. However, the pathophysiology of fat accumulation in the liver and the cross-talk of fatty liver with other tissues involved in metabolism in humans are not fully understood. Here we discuss the mechanisms involved in the pathogenesis of hepatic fat accumulation, particularly the roles of body fat distribution, nutrition, exercise, genetics, and gene-environment interaction. Furthermore, the effects of fatty liver on glucose and lipid metabolism, specifically via induction of subclinical inflammation and secretion of humoral factors, are highlighted. Finally, new aspects regarding the dissociation of fatty liver and insulin resistance are addressed.

New proposal for the staging of nonalcoholic steatohepatitis: evaluation of liver fibrosis on Gd-EOB-DTPA-enhanced MRI

PURPOSE

We investigated whether the gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI was useful for nonalcoholic steatohepatitis (NASH) staging based on the severity of liver fibrosis.

MATERIALS AND METHODS

Twenty-one male Sprague-Dawley rats aged 7 weeks, weighing about 150g in NASH group were fed a choline-deficient diet for 4, 7 or 10 weeks, and seven rats in the control group were fed a standard diet (n=7). After the feeding period, the rats were subjected to contrast-enhanced MRI (2D-FLASH; TR/TE=101/2.9ms, flip angle 90 degrees ). Gd-DTPA (0.1mmol Gd/kg) and Gd-EOB-DTPA (0.025mmol Gd/kg) were injected at 24-h intervals, and the speed of contrast injection was 1mL/s. Signal intensities of the liver were measured and the relative enhancement (RE), the time of maximum RE (T(max)) and elimination half-life of RE (T(1/2)) in the liver were compared. The fibrosis rate (%) was calculated with the following formula: fibrosis/whole areax100.

RESULTS

The fibrosis rates of each group were as follows: 0.52, 0.79, 2.84, and 0.50% (4, 7, 10 weeks and control groups). The fibrosis rate of the 10 weeks group was significantly higher than the control and 4 or 7 weeks groups. Although there was no difference between the T(max) and T(1/2) of each group after Gd-DTPA injection, the T(max) and T(1/2) of the 10 weeks group were significantly prolonged in comparison with the control and 4 or 7 weeks groups after Gd-EOB-DTPA injection (p<0.01). There was a significant correlation between the fibrosis rate and T(max) or T(1/2) after Gd-EOB-DTPA injection (r=0.90 or 0.97).

CONCLUSION

It was possible to assess the progress of liver fibrosis in NASH by evaluating the signal intensity-time course on Gd-EOB-DTPA-enhanced MRI.

Non-alcoholic fatty liver disease: an overview of prevalence, diagnosis, pathogenesis and treatment considerations

The global increase in the prevalence of obesity has heralded a rise in associated liver injury namely NAFLD (non-alcoholic fatty liver disease). It is estimated that 20–30% of adult populations in developed countries have NAFLD and, although high quality data is currently lacking, the condition is clearly increasing in children also. NAFLD should be suspected in those with commonly available simple clinical signs and biochemistry consistent with insulin resistance. A small number of individuals with NAFLD, often considered a relatively benign condition, will progress to more severe stages of liver disease including NASH (non-alcoholic steatohepatitis) with or without fibrosis, cirrhosis and occasionally hepatocellular carcinoma. NAFLD is also commonly associated with an increased risk of developing Type 2 diabetes and treatable features of insulin resistance such as dyslipidaemia and dysglycaemia. Histological examination of liver tissue remains the only proven method to distinguish between simple steatosis and NASH, a condition far more likely to progress to cirrhosis. Identification of an imaging technique or non-invasive marker to achieve this distinction is therefore much sought after and would allow larger clinical trials and better clinical assessment. Case series and pilot studies of lifestyle advice, insulin sensitizers and other medications have shown improvements in liver histology and serum liver enzymes but robust randomized controlled studies are needed. Furthermore, the cost/benefit ratio of any new therapies, and any potential harms, must be evaluated carefully before being clinically advocated.

The Kruppel-like factor 6 genotype is associated with fibrosis in nonalcoholic fatty liver disease

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 alpha-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.

Association between PPARGC1A polymorphisms and the occurrence of nonalcoholic fatty liver disease (NAFLD)

BACKGROUND

Genetic factors as well as environmental factors are important in the development of NAFLD and in this study we investigated associations between polymorphisms of peroxisome proliferators-activated receptor gamma coactivator 1alpha polymorphism (PPARGC1A) and NAFLD.

AIMS

We recruited 115 patients with biopsy-proven NAFLD, 65 with NASH and 50 with simple steatosis, and 441 healthy control subjects and investigated 15 SNPs of PPARGC1A.

RESULTS

SNP rs2290602 had the lowest p value in the dominant mode (p = 0.00095), and the odds ratio for NAFLD (95% CI) was 2.73 (1.48 - 5.06). rs2290602 was significantly associated with NAFLD even when the most conservative Bonferroni's correction was applied (p = 0.0143). The frequency of the T allele of rs2290602 was significantly higher in the NASH patients than in the control subjects (p = 0.00093, allele frequency mode), and its frequency in the NASH patients tended to be higher than in the simple steatosis patients (p = 0.09). The results of the real-time RT-PCR study showed that intrahepatic mRNA expression of PPARGC1A was lower in the TT group than in the GG or GT group at SNP rs2290602 (p = 0.0454).

CONCLUSION

This is the first study to demonstrate a significant association between genetic variations in PPARGC1A and NAFLD. This finding suggested that PPARGC1A polymorphism and lower expression of PPARGC1A mRNA in the liver are an important genetic contribution to etiology of NAFLD.

Genetic polymorphisms of adiponectin and tumor necrosis factor-alpha and nonalcoholic fatty liver disease in Chinese people

BACKGROUND AND AIM

Hypoadiponectinemia and high tumor necrosis factor-alpha (TNF-alpha) levels are associated with the development of nonalcoholic fatty liver disease (NAFLD). This study aimed to investigate the genetic polymorphisms of adiponectin and TNF-alpha in Chinese NAFLD patients and their association with disease severity.

METHODS

Seventy-nine patients with histology-proven NAFLD (61 with simple steatosis and 18 with stage 2-4 fibrosis) and 40 controls were tested for the nucleotide polymorphisms at adiponectin -11 391, -11 377, +45, and +276 and TNF-alpha promoters -863, -308, and -238.

RESULTS

There was no significant deviation in the adiponectin and TNF-alpha gene polymorphisms between NAFLD patients and controls, or between patients with simple steatosis and those with stage 2-4 fibrosis. NAFLD patients with -11377G and +45G at the adiponectin gene were more likely to have hypertriglyceridemia. On multivariate analysis, older age, higher body mass index, and higher fasting glucose were independent factors associated with stage 2-4 fibrosis in NAFLD patients.

CONCLUSIONS

Adiponectin and TNF-alpha gene polymorphisms were not shown to be associated with NAFLD or significant fibrosis in Chinese people. The adiponectin -11377G and +45G alleles were associated with hypertriglyceridemia in NAFLD patients. Since the current study is not adequately powered to detect smaller differences in allele frequencies, larger-sized studies in different ethnic groups are required.

Cytokines in the pathogenesis of fatty liver and disease progression to steatohepatitis: implications for treatment

Nonalcoholic fatty liver disease (NAFLD) has emerged as a growing public health problem worldwide. NAFLD represents a wide spectrum of conditions ranging from fatty liver, that in general follows a benign nonprogressive clinical course, to nonalcoholic steatohepatitis (NASH), a serious form of NAFLD, that may progress to cirrhosis and end-stage liver disease. The mechanisms responsible for NAFLD development and disease progression remain incompletely understood, but are of great clinical interest as current therapies are limited. Future therapies will be predicted based upon the understanding of its pathogenesis. This review focuses on the growing evidence from both experimental and human studies suggesting a central role of cytokines in the pathogenesis of NAFLD. We review the role of cytokines as key regulators of insulin sensitivity and hepatic lipid overloading, liver injury and inflammation, and fibrosis and cirrhosis, with an emphasis on potential therapeutic implications.

Genes and nonalcoholic fatty liver disease

Whereas most individuals with nonalcoholic fatty liver disease (NAFLD) will have steatosis, only a minority will ever develop progressive disease. Family studies and interethnic variations in susceptibility suggest that genetic factors may be important in determining disease risk. Although no genetic associations with advanced NAFLD have been replicated in large studies, preliminary data suggest that polymorphisms in the genes encoding microsomal triglyceride transfer protein, superoxide dismutase 2, the CD14 endotoxin receptor, tumor necrosis factor-alpha, transforming growth factor-beta, and angiotensinogen may be associated with steatohepatitis and/or fibrosis. With the advent of high-throughput gene analyses and the reduced cost of whole genome-wide scans, it seems likely that genes contributing to inherited susceptibility to this common disease will be identified in the near future.

Familial aggregation in patients with non-alcoholic steatohepatitis

We encountered three families that showed NASH accumulation. In family #1, a 21-year-old son and 10-year-old daughter were diagnosed with nonalcoholic steatohepatitis (NASH). They shared two adiponectin-gene single nucleotide polymorphisms (SNP). In family #2, a 51-year-old mother and 27-year-old son were diagnosed with NASH and shared the SNPs of other genes. In family #3, a 66-year-old mother and 34-year-old son were diagnosed with NASH and shared the SNPs of other genes. SNP sites differed among the three families, suggesting that the genes associated with the occurrence of NASH might be different in each patient.

Fatty Liver

Although the epidemic of obesity has been accompanied by an increase in the prevalence of the metabolic syndrome, not all obese develop the syndrome and even lean individuals can be insulin resistant. Both lean and obese insulin resistant individuals have an excess of fat in the liver which is not attributable to alcohol or other known causes of liver disease, a condition defined as nonalcoholic fatty liver disease (NAFLD) by gastroenterologists. The fatty liver is insulin resistant. Liver fat is highly significantly and linearly correlated with all components of the metabolic syndrome independent of obesity. Overproduction of glucose, VLDL, CRP, and coagulation factors by the fatty liver could contribute to the excess risk of cardiovascular disease associated with the metabolic syndrome and NAFLD. Both of the latter conditions also increase the risk of type 2 diabetes and advanced liver disease. The reason why some deposit fat in the liver whereas others do not is poorly understood. Individuals with a fatty liver are more likely to have excess intraabdominal fat and inflammatory changes in adipose tissue. Intervention studies have shown that liver fat can be decreased by weight loss, PPARγ agonists, and insulin therapy.