Adiponectin, bile acids, and burnt-out nonalcoholic steatohepatitis: new light on an old paradox

Adverse Effect of Nonalcoholic Fatty Liver Disease on the Therapeutic Response in Patients with Chronic Hepatitis B

BACKGROUND AND AIMS

The impact of nonalcoholic fatty liver disease (NAFLD) on the treatment outcome of chronic hepatitis B (CHB) is undefined and deserves an in-depth investigation.

METHODS

Histologically-proven CHB receiving first-line antiviral regimens as initial therapy was enrolled and grouped by the concurrence of NAFLD, and followed up at six monthly intervals. Therapeutic response related data were recorded and compared at multiple time points. Kaplan-Meier and Cox regression analyses were utilized to estimate the impact of NAFLD on complete virological response (CVR).

RESULTS

We enrolled 267 patients (CHB: 164; CHB with NAFLD: 103) with comparable follow-up durations. They were also comparable in baseline HBV DNA levels and HBeAg positivity. Patients with concomitant NAFLD showed less significant decline in HBV DNA, qHBsAg, pgRNA, and liver enzyme levels over time; moreover, their cumulative incidences of CVR were significantly lower and that of low-level viremia (LLV) were significantly higher at 6, 12, 18, 24 months. First CVR of CHB was delayed with the presence NAFLD (11.0 vs. 7.0 months, p<0.001) and further prolonged with higher grade of liver steatosis (Grade 2-3 vs. 1: 13.0 vs. 9.0 months). On multivariate analysis, HBeAg positivity (HR: 0.650, p=0.036), grade of steatosis (G2 [HR: 0.447, p=0.004]; G3 [HR: 0.085, p=0.002]) and HBV DNA (log10 IU/mL) (HR: 0.687, p<0.001) were significantly associated with delayed CVR, whereas grade of necroinflammation (HR: 1. 758, p<0.001) accelerated the CVR.

CONCLUSIONS

In CHB patients receiving initial antiviral therapy, NAFLD was associated with higher levels of HBV DNA, pgRNA, and liver enzymes, and higher incidence of LLV and delayed CVR.

Controlled attenuation parameter value and the risk of hepatocellular carcinoma in chronic hepatitis B patients under antiviral therapy

BACKGROUND

Controlled attenuation parameter (CAP) can evaluate hepatic steatosis in patients with chronic hepatitis B (CHB). However, prognostic implications of CAP value remain unclear. We evaluated the association between CAP and the risk of hepatocellular carcinoma (HCC) in patients with CHB under antiviral therapy and maintained virologic response.

METHODS

A total of 1823 CHB patients who were taking nucleos(t)ide analogue and showing suppressed hepatitis B virus replication were analyzed. The primary outcome was incident HCC during follow-up. Patients were grouped into those with and without advanced chronic liver disease (ACLD) (liver stiffness measurement cutoff: 10 kPa), and those with and without hepatic steatosis (CAP cutoff: 222 dB/m).

RESULTS

During 6.4 years of follow-up, 127 patients (7.0%) newly developed HCC. Among patients with ACLD (n = 382), the cumulative HCC incidence rate was lower for those with CAP ≥ 222 (11.0% at 5 years) than those with CAP < 222 (24.0% at 5 years, p = 0.002), and was an independent factor associated with HCC. When CAP value was further stratified, the cumulative HCC incidence rate decreased in dose-dependent manner according to an increase in CAP value (24.0%, 13.9%, 12.8% and 6.0% at 5 years for those with CAP < 222, 222-246, 247-273 and ≥ 274, respectively). Among patients without ACLD (n = 1441), there was no significance difference in HCC risk according to CAP value (HCC incidence rate: 3.3% and 4.0% at 5 years for those with CAP < 222 and CAP ≥ 222, p = 0.20).

CONCLUSIONS

Among CHB patients under antiviral therapy showing suppressed HBV replication, low CAP value predicted higher risk for HCC among ACLD patients, indicating that CAP value has a prognostic implication in this population.

The Role of Promyelocytic Leukemia Protein in Steatosis-Associated Hepatic Tumors Related to Chronic Hepatitis B virus Infection

The persistence of hepatitis B surface antigen (HBsAg) is a risk factor for the development of steatosis-associated tumors in chronic hepatitis B virus (HBV) infection, yet little is known about the metabolic link with this factor. We correlated HBV-related pathogenesis in genetically engineered mice and human carriers with metabolic proteomics and lipogenic gene expression profiles. The immunohistochemistry showed that the promyelocytic leukemia protein (PML, a tumor suppressor involved in genome maintenance and fatty acid oxidation), being inversely influenced by the dynamic HBsAg levels from acute phase to seroclearance, appeared as a lipo-metabolic switch linking HBsAg-induced steatosis (lipogenesis) to HBsAg-lost fat-burning hepatocarcinogenesis (lipolysis). Knockdown of PML in HBsAg-transgenic mice predisposed to obesity and drove early steatosis-specific liver tumorigenesis. Proteome analysis revealed that the signaling pathways corresponding to energy metabolism and its regulators were frequently altered by suppression or depletion of PML in the HBsAg-transgenic mice, mainly including oxidative phosphorylation and fatty acid metabolism. Expression profiling further identified upregulation of stearoyl-CoA desaturase 1 (Scd1) and epigenetic methylation of NDUFA13 in the mitochondrial respiratory chain and the cell cycle inhibitor CDKN1c in concordance to the increased severity of lipodystrophy and neoplasia in the livers of HBsAg-transgenic mice with PML insufficiency. The defect in lipolysis in PML-deficient HBsAg-transgenic mice made the HBsAg-induced adipose-like liver tumors vulnerable to synthetic lethality from toxic saturated fat accumulation with a Scd1 inhibitor. Our findings provide mechanistic insights into the evolution of steatosis-associated hepatic tumors driven by reciprocal interactions of HBsAg and PML, and a potential utility of lipid metabolic reprogramming as a treatment target.

Myeloid Cell-Specific Lipin-1 Deficiency Stimulates Endocrine Adiponectin-FGF15 Axis and Ameliorates Ethanol-Induced Liver Injury in Mice

Lipin-1 is a phosphatidate phosphohydrolase (PAP) required for the generation of diacylglycerol during glycerolipid synthesis, and exhibits dual functions in the regulation of lipid metabolism. Lipin-1 has been implicated in the pathogenesis of alcoholic liver disease (ALD). In the present study, we assessed lipin-1 function in myeloid cells in ALD using a myeloid cell-specific lipin-1 knockout (mLipin-1KO) mouse model. Utilizing the Gao-binge ethanol feeding protocol, matched mLipin-1KO mice and littermate loxP control (WT) mice were pair-fed with either an ethanol-containing diet or an ethanol-free diet (control). Surprisingly, deletion of lipin-1 in myeloid cells dramatically attenuated liver inflammatory responses and ameliorated liver injury that would normally occur following the ethanol feeding protocol, but slightly exacerbated the ethanol-induced steatosis in mice. Mechanistically, myeloid cell-specific lipin-1 deficiency concomitantly increased the fat-derived adiponectin and ileum-derived fibroblast growth factor (FGF) 15. In concordance with concerted elevation of circulating adiponectin and FGF15, myeloid cell-specific lipin-1 deficiency diminished hepatic nuclear factor kappa B (NF-κB) activity, limited liver inflammatory responses, normalized serum levels of bile acids, and protected mice from liver damage after ethanol challenge. Our novel data demonstrate that myeloid cell-specific deletion of lipin-1 ameliorated inflammation and alcoholic hepatitis in mice via activation of endocrine adiponectin-FGF15 signaling.

Challenges and Management of Liver Cirrhosis: Practical Issues in the Therapy of Patients with Cirrhosis due to NAFLD and NASH

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome and comprises a liver disease spectrum ranging from steatosis to nonalcoholic steatohepatitis (NASH) with risk of progression to liver cirrhosis and hepatocellular carcinoma (HCC). Associated metabolic conditions and comorbidities such as obesity, diabetes and cardiovascular diseases are common and require concerted management. Adiponutrin (PNPLA3) variants may help to identify NAFLD patients at higher risk for liver disease progression towards advanced fibrosis and HCC. The therapeutic options in NAFLD/NASH include lifestyle modification, pharmacological treatment, bariatric surgery for patients with morbid obesity and treatment of complications of liver cirrhosis and HCC, including liver transplantation. Insulin sensitizers and antioxidative treatment strategies with vitamin E are among the best-established pharmacological approaches, but both drugs have long-term safety issues and there is limited evidence in cirrhotic patients. Treatment of concomitant/underlying metabolic conditions with statins or metformin may also have beneficial effects on portal hypertension, complications of liver cirrhosis and HCC prevention. The bile acid receptor FXR may be a promising novel therapeutic target for the treatment of NAFLD/NASH, fibrosis and portal hypertension, but the prognostic implications of associated changes in low- and high-density lipoprotein cholesterol require further studies. Morbidly obese NASH patients can benefit from bariatric surgery which may reduce liver fibrosis but carries a risk of decompensation in patients with advanced liver cirrhosis. When carefully selected, patients with NASH cirrhosis undergoing liver transplantation have a good outcome. This review summarizes recent progress in the management of patients with liver cirrhosis due to NASH.

Bile acids are nutrient signaling hormones

Bile salts play crucial roles in allowing the gastrointestinal system to digest, transport and metabolize nutrients. They function as nutrient signaling hormones by activating specific nuclear receptors (FXR, PXR, Vitamin D) and G-protein coupled receptors [TGR5, sphingosine-1 phosphate receptor 2 (S1PR2), muscarinic receptors]. Bile acids and insulin appear to collaborate in regulating the metabolism of nutrients in the liver. They both activate the AKT and ERK1/2 signaling pathways. Bile acid induction of the FXR-α target gene, small heterodimer partner (SHP), is highly dependent on the activation PKCζ, a branch of the insulin signaling pathway. SHP is an important regulator of glucose and lipid metabolism in the liver. One might hypothesize that chronic low grade inflammation which is associated with insulin resistance, may inhibit bile acid signaling and disrupt lipid metabolism. The disruption of these signaling pathways may increase the risk of fatty liver and non-alcoholic fatty liver disease (NAFLD). Finally, conjugated bile acids appear to promote cholangiocarcinoma growth via the activation of S1PR2.

Globular adiponectin and its downstream target genes are up-regulated locally in human colorectal tumors: ex vivo and in vitro studies

OBJECTIVE

Low plasma adiponectin levels are linked to obesity, insulin resistance, and the risk of several types of malignancy. Despite the decline in circulating adiponectin concentrations, the increase in the expression of adiponectin receptors AdipoR1 and AdipoR2 is greater in cancerous than in normal colonic tissue. The purpose of this study was to obtain new information regarding local adiponectin signaling in the pathogenesis of colorectal cancer (CRC).

METHODS

We characterized the expressions of adiponectin and several of its downstream targets in paired samples of tumor tissue and adjacent noncancerous mucosa in 60 surgical patients with colorectal adenocarcinomas.

RESULTS

Adiponectin was expressed in both colorectal tumors and the adjacent mucosa. The expressions of adiponectin mRNA and its globular protein variant (gAd), adiponectin receptor type 1 and 5' AMP-activated protein kinase (AMPK) mRNA were significantly higher in colorectal tumors than in the adjacent mucosa. This finding was accompanied by increased mRNA expression of genes encoding proteins involved in fatty-acid trafficking and oxidation. The potential interference between adiponectin stimulation and AMPK activation through AMPK1 was examined in an in vitro model with the aid of silencing-RNA experiments. Furthermore, AMPK mRNA expression on tumors was positively correlated with a more advanced tumor stage in the patients.

CONCLUSION

We propose that the globular adiponectin-AMPK pathway functions in an autocrine manner in colorectal tumors, explaining some of the beneficial changes in cellular oxidative capacity in tumors in favor of tumorigenesis.

Adiponectin is better predictor of subclinical atherosclerosis than liver function tests in patients with nonalcoholic fatty liver disease

Adiponectin has recently been considered as a possible link between liver dysfunction and atherosclerosis in patients with nonalcoholic fatty liver disease (NAFLD). The present study was designed to evaluate the relation between circulating adiponectin and arterial stiffness parameters, such as pulse wave velocity (PWV) and aortic augmentation index (AI), in patients with hepatic steatosis. The study group consisted of 52 subjects with NAFLD. PWV and AI were performed using SphygmoCor (version 7.1, AtCor Medical, Sydney, Australia). Metabolic parameters, homeostasis model assessment-insulin resistance, and adiponectin levels were determined. Adiponectin was significantly, positively associated with AI (r = 0.467; P < .0001) and with PWV (r = 0.348; P = .011). No association between arterial stiffness parameters and liver function tests was observed. In a multiple linear regression analysis, adiponectin remained a significant predictor of PWV even after controlling for age, gender, and MAP. Serum adiponectin levels were significantly associated with indices of subclinical atherosclerosis, such as PWV and AI in patients with NAFLD. This association was independent of age, gender, and blood pressure level and suggests an active role of adiponectin in the pathophysiology of vascular disease in this particular population group.