Eliciting the mitochondrial unfolded protein response via NAD(+) repletion reverses fatty liver disease

With no approved pharmacological treatment, non-alcoholic fatty liver disease (NAFLD) is now the most common cause of chronic liver disease in western countries and its worldwide prevalence continues to increase along with the growing obesity epidemic. Here we show that a high-fat high-sucrose (HFHS) diet, eliciting chronic hepatosteatosis resembling human fatty liver, lowers hepatic NAD(+) levels driving reductions in hepatic mitochondrial content, function and ATP levels, in conjunction with robust increases in hepatic weight, lipid content and peroxidation in C57BL/6J mice. In an effort to assess the effect of NAD(+) repletion on the development of steatosis in mice, nicotinamide riboside (NR), a precursor for NAD(+) biosynthesis, was given to mice concomitant, as preventive strategy (NR-Prev), and as a therapeutic intervention (NR-Ther), to a HFHS diet. We demonstrate that NR prevents and reverts NAFLD by inducing a SIRT1- and SIRT3-dependent mitochondrial unfolded protein response (UPR(mt) ), triggering an adaptive mitohormetic pathway to increase hepatic β-oxidation and mitochondrial complex content and activity. The cell-autonomous beneficial component of NR treatment was revealed in liver-specific Sirt1 KO mice (Sirt1(hep-/-) ), while Apolipoprotein E-deficient (Apoe(-/-) ) mice challenged with a high-fat high-cholesterol diet (HFC), affirmed the use of NR in other independent models of NAFLD. CONCLUSION Our data warrant the future evaluation of NAD(+) boosting strategies to manage the development or progression of NAFLD. This article is protected by copyright. All rights reserved.

Physical activity and liver diseases

Regular physical activity beneficially impacts the risk of onset and progression of several chronic diseases. However, research regarding the effects of exercising on chronic liver diseases is relatively recent. Most authors focused on non-alcoholic fatty liver disease (NAFLD), in which increasing clinical and experimental data indicate that skeletal muscle cross-talking to the adipose tissue and the liver regulates intrahepatic fat storage. In this setting physical activity is considered required in combination with calories restriction to allow an effective decrease of intrahepatic lipid component, and despite that evidence is not conclusive, some studies suggest that vigorous activity might be more beneficial than moderate activity to improve NAFLD/NASH. Evidence regarding the effects of exercise on the risk of hepatocellular carcinoma is scarce; some epidemiological studies indicate a lower risk in patients regularly and vigorously exercising. In compensated cirrhosis exercise acutely increases portal pressure, but in longer term it has been proved safe and probably beneficial. Decreased aerobic capacity (VO2) correlates with mortality in patients with decompensated cirrhosis, who are almost invariably sarcopenic. In these patients VO2 is improved by physical activity, which might also reduce the risk of hepatic encephalopathy through an increase in skeletal muscle mass. In solid organ transplantation recipients exercise is able to improve lean mass, muscle strength and as a consequence, aerobic capacity. Few data exist in liver transplant recipients, in whom exercise should be object of future studies given its high potential of providing long-term beneficial effects. Despite evidence is far from complete, physical activity should be seen as an important part of the management of patients with liver disease in order to improve their clinical outcome. This article is protected by copyright. All rights reserved.

The story of HCC in NAFLD: from epidemiology, across pathogenesis, to prevention and treatment.

BACKGROUND & AIMS Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide. An increasing number of reports describe HCC in the setting of obesity and diabetes, two major risk factors for non-alcoholic fatty liver disease (NAFLD). The increasing incidence of these conditions and the emerging evidence of HCC in non-cirrhotic NAFLD prioritize a better understanding of NAFLD-related HCC epidemiology and pathogenesis in order to target screening policies and develop preventive-therapeutic strategies. In this review, we focus on the epidemiological impact of this condition, suggesting a possible link between HCC in cryptogenic cirrhosis and NAFLD. Furthermore, we analyse the suggested pathogenic mechanisms and the possible preventive-therapeutic strategies.

Hepatocellular carcinoma and lifestyles.

The majority of hepatocellular carcinoma occurs over pre-existing chronic liver diseases that share cirrhosis as an endpoint. In the last decade, a strong association between lifestyle and hepatocellular carcinoma has become evident. Abundance of energy-rich food and sedentary lifestyles have caused metabolic conditions such as obesity and diabetes mellitus to become global epidemics. Obesity and diabetes mellitus are both tightly linked to non-alcoholic fatty liver disease and also increase hepatocellular carcinoma risk independent of cirrhosis. Emerging data suggest that physical activity not only counteracts obesity, diabetes mellitus and non-alcoholic fatty liver disease, but also reduces cancer risk. Physical activity exerts significant anticancer effects in the absence of metabolic disorders. Here, we present a systematic review on lifestyles and hepatocellular carcinoma.

Prevention of Rebleeding From Esophageal Varices in Patients With Cirrhosis Receiving Small-Diameter Stents Versus Hemodynamically Controlled Medical Therapy

BACKGROUND & AIMS Patients with cirrhosis and variceal hemorrhage have a high risk of rebleeding. We performed a prospective randomized trial to compare the prevention of rebleeding in patients given a small-diameter covered stent vs those given hepatic venous pressure gradient (HVPG)-based medical therapy prophylaxis. METHODS We performed an open-label study of patients with cirrhosis (92% Child class A or B, 70% alcoholic) treated at 10 medical centers in Germany. Patients were assigned randomly more than 5 days after variceal hemorrhage to groups given a small covered transjugular intrahepatic portosystemic stent-shunt (TIPS) (8 mm; n = 90), or medical reduction of portal pressure (propranolol and isosorbide-5-mononitrate; n = 95). HVPG was determined at the time patients were assigned to groups (baseline) and 2 weeks later. In the medical group, patients with an adequate reduction in HVPG (responders) remained on the drugs whereas nonresponders underwent only variceal band ligation. The study was closed 10 months after the last patient was assigned to a group. The primary end point was variceal rebleeding. Survival, safety (adverse events), and quality of life (based on the Short Form-36 health survey) were secondary outcome measures. RESULTS A significantly smaller proportion of patients in the TIPS group had rebleeding within 2 years (7%) than in the medical group (26%) (P = .002). A slightly higher proportion of patients in the TIPS group experienced adverse events, including encephalopathy (18% vs 8% for medical treatment; P = .05). Rebleeding occurred in 6 of 23 patients (26%) receiving medical treatment before hemodynamic control was possible. Per-protocol analysis showed that rebleeding occurred in a smaller proportion of the 32 responders (18%) than in nonresponders who received variceal band ligation (31%) (P = .06). Fifteen patients from the medical group (16%) underwent TIPS placement during follow-up evaluation, mainly for refractory ascites. Survival time and quality of life did not differ between both randomized groups. CONCLUSIONS Placement of a small-diameter, covered TIPS was straightforward and prevented variceal rebleeding in patients with Child A or B cirrhosis more effectively than drugs, which often required step-by-step therapy. However, TIPS did not increase survival time or quality of life and produced slightly more adverse events. Clinical Trial no: ISRCTN 16334693.