Concept: Non-alcoholic fatty liver disease
The impairment of liver function by low environmentally relevant doses of glyphosate-based herbicides (GBH) is still a debatable and unresolved matter. Previously we have shown that rats administered for 2 years with 0.1 ppb (50 ng/L glyphosate equivalent dilution; 4 ng/kg body weight/day daily intake) of a Roundup GBH formulation showed signs of enhanced liver injury as indicated by anatomorphological, blood/urine biochemical changes and transcriptome profiling. Here we present a multiomic study combining metabolome and proteome liver analyses to obtain further insight into the Roundup-induced pathology. Proteins significantly disturbed (214 out of 1906 detected, q < 0.05) were involved in organonitrogen metabolism and fatty acid β-oxidation. Proteome disturbances reflected peroxisomal proliferation, steatosis and necrosis. The metabolome analysis (55 metabolites altered out of 673 detected, p < 0.05) confirmed lipotoxic conditions and oxidative stress by showing an activation of glutathione and ascorbate free radical scavenger systems. Additionally, we found metabolite alterations associated with hallmarks of hepatotoxicity such as γ-glutamyl dipeptides, acylcarnitines, and proline derivatives. Overall, metabolome and proteome disturbances showed a substantial overlap with biomarkers of non-alcoholic fatty liver disease and its progression to steatohepatosis and thus confirm liver functional dysfunction resulting from chronic ultra-low dose GBH exposure.
Prediabetes and type 2 diabetes mellitus (T2DM) are believed to be common and associated with a worse metabolic profile in patients with nonalcoholic fatty liver disease (NAFLD). However, no previous study has systematically screened this population.
Data on cardiac function in patients with nonalcoholic fatty liver disease (NAFLD) are limited and conflicting. We assessed whether NAFLD is associated with abnormalities in cardiac function in patients with type 2 diabetes.
Non-alcoholic fatty liver disease is marked by hepatic fat accumulation not due to alcohol abuse. Several studies have demonstrated that NAFLD is associated with insulin resistance leading to a resistance in the antilipolytic effect of insulin in the adipose tissue with an increase of free fatty acids (FFAs). The increase of FFAs induces mitochondrial dysfunction and development of lipotoxicity. Moreover, in subjects with NAFLD, ectopic fat also accumulates as cardiac and pancreatic fat. In this review we analyzed the mechanisms that relate NAFLD with metabolic syndrome and dyslipidemia and its association with the development and progression of cardiovascular disease.
Growth hormone (GH) is an important regulator of metabolism and body composition. GH deficiency is associated with increased visceral body fat and other features of the metabolic syndrome. Here we performed a cross-sectional study to explore the association of GH levels with nonalcoholic fatty liver disease (NAFLD), which is considered to be the hepatic manifestation of the metabolic syndrome. A total of 1,667 subjects were diagnosed as NAFLD according the diagnostic criteria, and 5,479 subjects were defined as the controls. The subjects with NAFLD had significantly lower levels of serum GH than the controls. Those with low GH levels had a higher prevalence of NAFLD and the metabolic syndrome. A stepwise logistic regression analysis showed that GH levels were significantly associated with the risk factor for NAFLD (OR = 0.651, 95%CI = 0.574-0.738, P<0.001). Our results showed a significant association between lower serum GH levels and NAFLD.
Recent data suggest that the etiology of several metabolic diseases is closely associated with transcriptome alteration by aberrant histone methylation. We performed DNA microarray and ChIP-on-chip analyses to examine transcriptome profiling and trimethylation alterations to identify the genomic signature of nonalcoholic fatty liver disease (NAFLD), the most common form of chronic liver disease. Transcriptome analysis showed that steatotic livers in high-fat diet-fed apolipoprotein E2 mice significantly altered the expression of approximately 70% of total genes compared with normal diet-fed control livers, suggesting that hepatic lipid accumulation induces dramatic alterations in gene expression in vivo. Also, pathway analysis suggested that genes encoding chromatin-remodeling enzymes, such as jumonji C-domain-containing histone demethylases that regulate histone H3K9 and H3K4 trimethylation (H3K9me3, H3K4me3), were significantly altered in steatotic livers. Thus, we further investigated the global H3K9me3 and H3K4me3 status in lipid-accumulated mouse primary hepatocytes by ChIP-on-chip analysis. Results showed that hepatic lipid accumulation induced aberrant H3K9me3 and H3K4me3 status in peroxisome proliferator-activated receptor alpha and hepatic lipid catabolism network genes, reducing their mRNA expression compared with non-treated control hepatocytes. This study provides the first evidence that epigenetic regulation by H3K9me3 and H3K4me3 in hepatocytes may be involved in hepatic steatosis and the pathogenesis of NAFLD. Thus, control of H3K9me3 and H3K4me3 represents a potential novel NAFLD prevention and treatment strategy.
The development of non-alcoholic fatty liver disease (NAFLD) is a multiple step process. Here, we show that activation of cdk4 triggers the development of NAFLD. We found that cdk4 protein levels are elevated in mouse models of NAFLD and in patients with fatty livers. This increase leads to C/EBPα phosphorylation on Ser193 and formation of C/EBPα-p300 complexes, resulting in hepatic steatosis, fibrosis, and hepatocellular carcinoma (HCC). The disruption of this pathway in cdk4-resistant C/EBPα-S193A mice dramatically reduces development of high-fat diet (HFD)-mediated NAFLD. In addition, inhibition of cdk4 by flavopiridol or PD-0332991 significantly reduces development of hepatic steatosis, the first step of NAFLD. Thus, this study reveals that activation of cdk4 triggers NAFLD and that inhibitors of cdk4 may be used for the prevention/treatment of NAFLD.
We performed integrative network analyses to identify targets that can be used for effectively treating liver diseases with minimal side effects. We first generated co-expression networks (CNs) for 46 human tissues and liver cancer to explore the functional relationships between genes and examined the overlap between functional and physical interactions. Since increased de novo lipogenesis is a characteristic of nonalcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma (HCC), we investigated the liver-specific genes co-expressed with fatty acid synthase (FASN). CN analyses predicted that inhibition of these liver-specific genes decreases FASN expression. Experiments in human cancer cell lines, mouse liver samples, and primary human hepatocytes validated our predictions by demonstrating functional relationships between these liver genes, and showing that their inhibition decreases cell growth and liver fat content. In conclusion, we identified liver-specific genes linked to NAFLD pathogenesis, such as pyruvate kinase liver and red blood cell (PKLR), or to HCC pathogenesis, such as PKLR, patatin-like phospholipase domain containing 3 (PNPLA3), and proprotein convertase subtilisin/kexin type 9 (PCSK9), all of which are potential targets for drug development.
Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease whose prevalence has reached global epidemic proportions. Although the disease is relatively benign in the early stages, when severe clinical forms, including nonalcoholic steatohepatitis (NASH), cirrhosis and even hepatocellular carcinoma, occur, they result in worsening the long-term prognosis. A growing body of evidence indicates that NAFLD develops from a complex process in which many factors, including genetic susceptibility and environmental insults, are involved. In this review, we focused on the genetic component of NAFLD, with special emphasis on the role of genetics in the disease pathogenesis and natural history. Insights into the topic of the genetic susceptibility in lean individuals with NAFLD and the potential use of genetic tests in identifying individuals at risk are also discussed.
Background and Aims: There has been increasing evidence that vitamin D deficiency may increase the risk of metabolic syndrome. Since metabolic syndrome is a major risk factor for non-alcoholic fatty liver disease (NAFLD), we aimed to investigate the association between vitamin D and the severity and mortality of NAFLD. Methods: Data was obtained from the United States Third National Health and Nutrition Examination Survey conducted in 1988-1994, with follow-up mortality data through 2011. NAFLD was defined by ultrasonographic detection of hepatic steatosis in the absence of other liver diseases and categorized as normal, mild, moderate or severe. The severity of hepatic fibrosis was determined by NAFLD fibrosis score (NFS). ANOVA (F-test) was used to evaluate the association between vitamin D level and degree of NAFLD, and Cox proportional hazards regression analysis was used for survival analyses. Results: Vitamin D levels for normal, mild, moderate and severe steatosis were 25.1 ± 0.29 ng/mL, 24.7 ± 0.42 ng/mL, 23.7 ± 0.37 ng/mL and 23.6 ± 0.60 ng/mL, respectively (trend p < 0.001). Likewise, vitamin D levels for low, intermediate and high NFS categories were 24.7 ± 0.38 ng/mL, 23.4 ± 0.42 ng/mL and 21.5 ± 0.57 ng/mL, respectively (trend p < 0.001). After median-follow up over 19 years, vitamin D deficiency was significantly associated with diabetes- and Alzheimer's disease-related mortality (hazard ratio (HR): 3.64, 95%CI: 1.51-8.82 and HR: 4.80, 95%CI: 1.53-15.1, respectively), with a borderline significance in overall mortality (HR: 1.16, 95%CI: 0.99-1.36, p = 0.06). Conclusions: Vitamin D level was inversely related to the degree of liver steatosis and fibrosis. Moreover, vitamin D deficiency was associated with diabetes- and Alzheimer's disease-related mortality in NAFLD patients.