Adiponectin inhibits steatotic CD95/Fas up-regulation by hepatocytes: therapeutic implications for hepatitis C

Adipokines in liver diseases

Adipokines are polypeptides secreted in the adipose tissue in a regulated manner. While some of these molecules are expressed only by adipocytes, resident and infiltrating macrophages and components of the vascular stroma markedly contribute to expression of other adipokines. As a result, adipose tissue inflammation is associated with a modification in the pattern of adipokine secretion. Leptin, adiponectin, and resistin are the best-studied molecules in this class, but cytokines such as tumor necrosis factor or interleukin-6 are also secreted at high levels by the adipose tissue. Several other molecules have been recently identified and are actively investigated. Adipokines interfere with hepatic injury associated with fatty infiltration, differentially modulating steatosis, inflammation, and fibrosis. Several studies have investigated plasma levels of adiponectin in patients with nonalcoholic fatty liver disease, to establish correlations with the underlying state of insulin resistance and with the type and severity of hepatic damage. Hepatitis C is another disease where adipokines may represent a link between viral infection, steatosis, and metabolic disturbances. Identification of the mediators secreted by expanded adipose tissue and their pathogenic role is pivotal in consideration of the alarming increase in the prevalence of obesity and of the detrimental role that this condition exerts on the course of liver diseases.

Coinfection with HIV-1 and HCV--a one-two punch

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease, cirrhosis, and death; it is estimated that 180 million persons are infected with HCV worldwide. The consequences of HCV are worse in those who are coinfected with human immunodeficiency virus 1 (HIV-1), which is unfortunately a common scenario because of shared risk factors of the viruses. More studies into effects of HCV/HIV-1 coinfection are needed, but efforts have been hampered by limitations in our understanding of the combined pathogenesis of the 2 viruses. Gaining insight into the mechanisms that underlie the immunopathogenesis of these persistent viral infections could lead to new therapeutic strategies for patients with HCV/HIV-1 coinfection.

Resveratrol amplifies profibrogenic effects of free fatty acids on human hepatic stellate cells

AIM

To ascertain whether resveratrol affects the expression of free fatty acids (FFA)-induced profibrogenic genes, death receptors, and/or apoptosis-related molecules in human hepatic stellate cells, using the LX-2 cell line.

METHODS

Cells were cultured in the presence of FFAs (2:1 oleate : palmitate) and subsequently treated with resveratrol. Gene expression rates were determined by quantitative real-time PCR. The 50% lethal dose (LD(50)) of resveratrol in the presence of FFAs was assessed with the MTT viability test.

RESULTS

Compared to vehicle controls, incubation of LX-2 cells with 0.5 mM FFAs induced profibrogenic genes (alpha-SMA x 2.9; TGF-beta1 x 1.6; TIMP-1 x 1.4), death receptors (CD95/Fas x 3.8; TNFR-1 x 1.4), and anti-apoptotic molecules (Bcl-2 x 2.3; Mcl-1 x 1.3). Subsequent addition of 15 microM resveratrol (LD(50) = 23.2 microM) significantly (P < 0.05) upregulated further these genes (alpha-SMA x 6.5; TGF-beta1 x 1.9; TIMP-1 x 2.2; CD95/Fas x 13.1, TNFR-1 x 2.1; Bcl-2 x 3.6; Mcl-1 x 1.9). Importantly, this effect was only observed in the presence of FFAs.

CONCLUSION

Resveratrol amplifies the profibrogenic activation of human hepatic LX-2 stellate cells. This finding raises the possibility that in obese patients with elevated FFAs reserveratrol could provoke hepatic fibrogenesis. In-vivo studies are necessary to further validate this conclusion.