Antioxidant dietary approach in treatment of fatty liver: New insights and updates

Bioactive food and exercise in chronic kidney disease: Targeting the mitochondria

Chronic kidney disease (CKD), which affects 10%-15% of the population, associates with a range of complications-such as cardiovascular disease, frailty, infections, muscle and bone disorders and premature ageing-that could be related to alterations of mitochondrial number, distribution, structure and function. As mitochondrial biogenesis, bioenergetics and the dynamic mitochondrial networks directly or indirectly regulate numerous intra- and extracellular functions, the mitochondria have emerged as an important target for interventions aiming at preventing or improving the treatment of complications in CKD. In this review, we discuss the possible role of bioactive food compounds and exercise in the modulation of the disturbed mitochondrial function in a uraemic milieu.

GCN2 deficiency protects against high fat diet induced hepatic steatosis and insulin resistance in mice

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic lipid deposition and oxidative stress. It has been demonstrated that general control nonderepressible 2 (GCN2) is required to maintain hepatic fatty acid homeostasis under conditions of amino acid deprivation. However, the impact of GCN2 on the development of NAFLD has not been investigated. In this study, we used Gcn2^-/- mice to investigate the effect of GCN2 on high fat diet (HFD)-induced hepatic steatosis. After HFD feeding for 12 weeks, Gcn2^-/- mice were less obese than wild-type (WT) mice, and Gcn2^-/- significantly attenuated HFD-induced liver dysfunction, hepatic steatosis and insulin resistance. In the livers of the HFD-fed mice, GCN2 deficiency resulted in higher levels of lipolysis genes, lower expression of genes related to FA synthesis, transport and lipogenesis, and less induction of oxidative stress. Furthermore, we found that knockdown of GCN2 attenuated, whereas overexpression of GCN2 exacerbated, palmitic acid-induced steatosis, oxidative & ER stress, and changes of peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FAS) and metallothionein (MT) expression in HepG2 cells. Collectively, our data provide evidences that GCN2 deficiency protects against HFD-induced hepatic steatosis by inhibiting lipogenesis and reducing oxidative stress. Our findings suggest that strategies to inhibit GCN2 activity in the liver may provide a novel approach to attenuate NAFLD development.

Inhibitory Effect of Astaxanthin on Oxidative Stress-Induced Mitochondrial Dysfunction-A Mini-Review

Oxidative stress is a major contributor to the pathogenesis of various human diseases as well as to the aging process. Mitochondria, as the center of cellular metabolism and major regulators of redox balance, play a critical role in disease development and progression. Mitochondrial dysfunction involving structural and metabolic impairment is prominent in oxidative stress-related diseases. Increased oxidative stress can damage mitochondria, and subsequent mitochondrial dysfunction generates excesses of mitochondrial reactive oxygen species that cause cellular damage. Mitochondrial dysfunction also activates the mitochondrial apoptotic pathway, resulting in cellular death. Astaxanthin, a red-colored xanthophyll carotenoid, exerts an anti-oxidative and anti-inflammatory effect on various cell lines. In this manner astaxanthin maintains mitochondrial integrity under various pathological conditions. In this review, the inhibitory effects of astaxanthin on oxidative stress-induced mitochondrial dysfunction and related disease development are discussed.

Efficacy of curcumin/turmeric on liver enzymes in patients with non-alcoholic fatty liver disease: A systematic review of randomized controlled trials

Background

Several studies reported that curcumin supplementation could improve non-alcoholic fatty liver disease (NAFLD). The aim of this study was to evaluate the efficacy of curcumin/turmeric supplementation on liver enzymes in patients with NAFLD.

Methods

PubMed, Scopus, Web of Science and Google Scholar were systematically searched until December 2017. We included randomized controlled trials (RCTs) which examined effect of curcumin/turmeric supplementation on NAFLD in adult participants. Main outcome was alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Potential risks of bias (ROB) were assessed by using Cochrane ROB tool.

Results

All included studies showed low ROB in most of item of Cochrane ROB tool. Meta-analysis of 4 randomized controlled trials including 228 subjects showed a trend toward significant reduction of ALT blood concentrations in subgroup with ≥1000 mg/day curcumin supplementation (–11.36 IU/L, 95% CI: –22.75 to 0.02; I²:51%). Meta-analysis showed a significant reduction of AST in studies with 8-weeks administration (–9.22 IU/L, 95% CI: –12.77 to –5.67; I²: 49%).

Conclusion

This review suggests that curcumin/turmeric might have a favorable effect on NAFLD in higher dosage. Further high-quality studies with large-scale and higher dosage are warranted.

Sensitive and early detection of mitochondrial dysfunction in the liver of NASH model mice by PET imaging with 18F-BCPP-BF

BACKGROUND

Nonalcoholic fatty liver disease is a common disorder that progresses from simple fatty liver (steatosis) to nonalcoholic steatohepatitis (NASH). It is thought that mitochondrial dysfunction plays a critical role in the progression of NASH. In this study, we developed a non-invasive method for early diagnosis and staging of NASH that directly measures mitochondrial complex-I (MC-I) activity in the liver of NASH model mice by positron emission tomography (PET) imaging using the novel tracer 2-tert-butyl-4-chloro-5-[6-(4-[¹⁸F]fluorobutoxy)-pyridin-3-ylmethoxy]-2H-pyridazin-3-one (¹⁸F-BCPP-BF). Liver uptake of ¹⁸F-BCPP-BF in NASH and age-matched control mice was measured as a standard uptake value over a period of 1 to 12 weeks. Histopathological evaluation of the liver tissue was performed by haematoxylin and eosin staining, and fibrosis was assessed by Masson's trichrome staining.

RESULTS

Significant mitochondrial dysfunction was detected as early as 1 week after commencing the diet, and MC-I activity in the liver measured by PET was reduced by > 50% relative to that in age-matched control mice after 6 weeks. Liver uptake of ¹⁸F-BCPP-BF was low throughout the 12-week experimental period. Histopathological examination revealed that steatosis, inflammation, and ballooning progressed from 1 to 6 weeks, with fibrosis observed from 6 to 12 weeks.

CONCLUSIONS

PET scans and histopathological analysis revealed that mitochondrial dysfunction in the liver contributed to the progression of NASH. PET imaging with ¹⁸F-BCPP-BF is a useful tool for detecting NASH at early stages and for monitoring therapeutic response.

Grape Leucoanthocyanidin Protects Liver Tissue in Albino Rabbits with Nonalcoholic Hepatic Steatosis

Nonalcoholic fatty liver disease (NAFLD) is a common ailment. It is usually found in association with diabetes or obesity. There are no approved drugs to treat this condition. The study of flavonoid consumption has increased over the decades due to their antioxidative properties, although the literature is scarce when it comes to their effects in liver tissue. The purpose of this study was to evaluate the role of leucoanthocyanidin in nonalcoholic hepatic steatosis. Thirty male albino rabbits were divided in 3 groups. Group 1 had a regular commercial diet. The second group had a regular diet and 10 mL of egg yolk and 1.5 g of pure cholesterol. The rabbits of the third group were on the same regimen as the second, but were also treated with grape leucoanthocyanidin (50 mg/kg/day) for 100 days. On the last day of the experiment, the animals were euthanized, and the livers excised and fixated in a 10% formalin solution. Afterwards, fragments of each liver were removed and histologically processed and analyzed. The stereological evaluation showed that leucoanthocyanidin reduced NAFLD in comparison with the nontreated group. This was also observed in the histological analysis of the liver tissue, as the treated group had less foci of fatty tissue. Leucoanthocyanidin may therefore be a promising substance to treat NAFLD, although further studies are needed.

Role of mitochondria and mitochondria-targeted agents in non-alcoholic fatty liver disease

Mitochondria play a pivotal role in the fatty acid oxidation and have been found to be affected early during the macrovesicular fat accumulation in the hepatocytes. The fatty infiltration is the primary cause of oxidative stress and inflammation in the non-alcoholic fatty liver disease (NAFLD), which can lead to the peroxidation of phospholipids, such as cardiolipin. Oxidative stress-induced damage to mitochondrial DNA can result in the impairment of oxidative phosphorylation and further increases the generation of reactive oxygen species. The mitochondrial damage may eventually lead to apoptotic death of hepatocytes. The apoptosis along with the generated cytokines from the stellate and Kupffer cells further augment the fibrotic changes to advance the disease. Hence, alleviation of the mitochondrial impairment, particularly in the early stages of NAFLD, may prevent the progression of the disease. Among the various experimentally studied mitochondrial-targeted agents, triphenylphosphonium cation ligated ubiquinone Q10 and vitamin E, Szeto-Scheller peptides, and superoxide dismutase mimetic-salen manganese complexes (EUK-8 and EUK-134) have been found to be most promising. In addition to these mitochondrial-targeted agents, a novel area of therapy called mitotherapy have also emerged. However, clinical studies conducted so far are still fragmentary to validate their efficacy. This review article discusses the mitochondria-targeted molecules and their potential role in the treatment of NAFLD.

Resveratrol modifies biliary secretion of cholephilic compounds in sham-operated and cholestatic rats

AIM

To investigate the effect of resveratrol on biliary secretion of cholephilic compounds in healthy and bile duct-obstructed rats.

METHODS

Resveratrol (RSV) or saline were administered to rats by daily oral gavage for 28 d after sham operation or reversible bile duct obstruction (BDO). Bile was collected 24 h after the last gavage during an intravenous bolus dose of the Mdr1/Mrp2 substrate azithromycin. Bile acids, glutathione and azithromycin were measured in bile to quantify their level of biliary secretion. Liver expression of enzymes and transporters relevant for bile production and biliary secretion of major bile constituents and drugs were analyzed at the mRNA and protein levels using qRT-PCR and Western blot analysis, respectively. The TR-FRET PXR Competitive Binding Assay kit was used to determine the agonism of RSV at the pregnane X receptor.

RESULTS

RSV increased bile flow in sham-operated rats due to increased biliary secretion of bile acids (BA) and glutathione. This effect was accompanied by the induction of the hepatic rate-limiting transporters for bile acids and glutathione, Bsep and Mrp2, respectively. RSV also induced Cyp7a1, an enzyme that is crucial for bile acid synthesis; Mrp4, a transporter important for BA secretion from hepatocytes to blood; and Mdr1, the major apical transporter for xenobiotics. The findings were supported by increased biliary secretion of azithromycin. The TR-FRET PXR competitive binding assay confirmed RSV as a weak agonist of the human nuclear receptor PXR, which is a transcriptional regulator of Mdr1/Mrp2. RSV demonstrated significant hepatoprotective properties against BDO-induced cirrhosis. RSV also reduced bile flow in BDO rats without any corresponding change in the levels of the transporters and enzymes involved in RSV-mediated hepatoprotection.

CONCLUSION

Resveratrol administration for 28 d has a distinct effect on bile flow and biliary secretion of cholephilic compounds in healthy and bile duct-obstructed rats.