Creatine and the Liver: Metabolism and Possible Interactions.

The process of creatine synthesis occurs in two steps, catalyzed by L-arginine:glycine amidinotransferase (AGAT) and guanidinoacetate N-methyltransferase (GAMT), which take place mainly in kidney and liver, respectively. This molecule plays an important energy/pH buffer function in tissues, and to guarantee the maintenance of its total body pool, the lost creatine must be replaced from diet or de novo synthesis. Creatine administration is known to decrease the consumption of Sadenosyl methionine and also reduce the homocysteine production in liver, diminishing fat accumulation and resulting in beneficial effects in fatty liver and non-alcoholic liver disease. Different studies have shown that creatine supplementation could supply brain energy, presenting neuroprotective effects against the encephalopathy induced by hyperammonemia in acute liver failure. Creatine is also taken by many athletes for its ergogenic properties. However, little is known about the adverse effects of creatine supplementation, which are barely described in the literature, with reports of mainly hypothetical effects arising from a small number of scientific publications. Antioxidant effects have been found in several studies, although one of the theories regarding the potential for toxicity from creatine supplementation is that it can increase oxidative stress and potentially form carcinogenic compounds.

Understanding nutritional interventions and physical exercise in non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in adults and its prevalence is rising around the world. This pathology is characterized by accumulation of liver fat, which exceeds 5% of liver weight in absence of alcohol consumption, viral infection or other hepatic etiology. Since NAFLD has been associated with obesity, insulin resistance, diabetes or alteration of lipid profiles, it is considered as the liver manifestation of metabolic syndrome. Pathogenic mechanisms of NAFLD have not been clearly elucidated, but different events such as lipid accumulation, insulin resistance, oxidative and endoplasmic reticulum stress, mitochondrial dysfunction and inflammation are involved. Modifications in lifestyle constitute the first line for the management of NAFLD. Nutritional interventions include low fat and carbohydrate diet with higher polyunsaturated fatty acids ingestion. Moreover, supplementation with antioxidant and cytoprotective agents could be useful to decrease oxidative stress, inflammation and fibrosis. Physical activity enables to reduce the expression of lipogenic genes, fat accumulation, or insulin resistance and improves cardiorespiratory fitness. Benefits have been found following both aerobic exercise and resistance training, and remain even after exercise cessation. However, more studies are required to analyze the molecular and cellular mechanisms involved in nutritional and physical intervention, and to define the volume of activity required and its association with weight loss. In this paper, we offer an updated overview of the mechanisms implicated in the progression of NAFLD, and analyze the beneficial effects of nutritional interventions and physical exercise in the prevention and treatment of this condition.

On-line surface plasmon resonance biosensing of vascular endothelial growth factor signaling in intact-human hepatoma cell lines.

Surface plasmon resonance (SPR) monitoring of biorecognition events at intracellular levels is a valuable tool for studying the angiogenic response of carcinoma living cells during tumor growth and proliferation. We report here a comparative study of two different strategies to detect human hepatoma cell interactions between transmembrane vascular endothelial growth factor receptor (VEGFR2) and vascular endothelial growth factor (VEGF). To monitor VEGFR2 activation after VEGF stimulation, intact hepatocellular carcinoma HepG2 or Huh7 cells (2 × 10(5) cells per mL) were directly immobilized on the sensor chip. Distinguishable SPR sensorgrams were obtained for each cell line depending on the time required for VEGFR2 activation. SPR signals for VEGF-VEGFR2 binding were inhibited by the VEGFR inhibitor, CBO-P11. The SPR response after VEGF stimulation/inhibition was in good agreement with the results observed by immunoblotting analysis. In a second approach we used intact cell lines as analytes. SPR analysis was done by injecting HepG2 and HuH7 cell suspensions (2-4 × 10(4) cells per mL) onto a sensor surface previously immobilized with VEGF via a thiol self-assembled monolayer (SAM). Specificity and reproducibility were evaluated reusing the same chip surface over more than 60 complete regeneration cycles. Comparison between both methods yielded differences in terms of reliability, making the latter strategy more effective for the analysis of real samples. The investigation of VEGF signaling in intact human hepatoma living cells by SPR monitoring comprises a novel and promising design for the study of tumor angiogenesis via downregulation of VEGF and VEGFR2 pathways. Further investigation on VEGFR activation and vascular function could contribute to establish a robust and meaningful tool for early cancer diagnostics.

FoxO proteins: regulation and molecular targets in liver cancer.

Human forkhead box class O (FoxO) transcription factors, activated in response to a wide range of external stimuli, like growth factors, insulin, nutrient levels and oxidative stress, are able to control several specific geneexpression programs. Besides their clear implication in metabolic processes, they appear to play a relevant role in tumour suppression by upregulation of genes involved in cell cycle arrest or apoptosis. Recent research efforts provide new insights into the molecular modulation of FoxO in liver cancer and disclose potential opportunities for developing new antitumor drugs. Through an intricate regulatory model, achieved via several post-translational modifications, including phosphorylation, acetylation, and ubiquitination, which control their subcellular localization and DNA binding activity, FoxO factors act as tumour suppressors. Low levels of FoxOs are associated with poor prognosis in cancer patients, and seem to confer chemotherapy resistance. Within FoxO members, FoxO3a appears to present anti-tumour properties in hepatocellular carcinoma, inducing the expression of pro-apoptotic genes, or interfering with signaling cascades commonly altered in this disease such as Wnt/ß-catenin, PI3K/AKT/mTOR or MAPKs pathways. Here, we describe the main mechanisms of FoxO proteins regulation, and their cross-link with altered pathways in liver cancer. Moreover, based on the current knowledge of FoxO modulation, emphasis is placed on the development of novel agents which specifically activate FoxO family members and could be useful in the treatment of hepatocarcinoma.

Inhibition of VEGF expression through blockade of Hif1α and STAT3 signalling mediates the anti-angiogenic effect of melatonin in HepG2 liver cancer cells.

BACKGROUND: Hepatocellular carcinoma (HCC) growth relies on angiogenesis via vascular endothelial growth factor (VEGF) release. Hypoxia within tumour environment leads to intracellular stabilisation of hypoxia inducible factor 1 alpha (Hif1α) and signal transducer and activator of transcription (STAT3). Melatonin induces apoptosis in HCC, and shows anti-angiogenic features in several tumours. In this study, we used human HepG2 liver cancer cells as an in vitro model to investigate the anti-angiogenic effects of melatonin. METHODS: HepG2 cells were treated with melatonin under normoxic or CoCl2-induced hypoxia. Gene expression was analysed by RT-qPCR and western blot. Melatonin-induced anti-angiogenic activity was confirmed by in vivo human umbilical vein endothelial cells (HUVECs) tube formation assay. Secreted VEGF was measured by ELISA. Immunofluorescence was performed to analyse Hif1α cellular localisation. Physical interaction between Hif1α and its co-activators was analysed by immunoprecipitation and chromatin immunoprecipitation (ChIP). RESULTS: Melatonin at a pharmacological concentration (1 mM) decreases cellular and secreted VEGF levels, and prevents HUVECs tube formation under hypoxia, associated with a reduction in Hif1α protein expression, nuclear localisation, and transcriptional activity. While hypoxia increases phospho-STAT3, Hif1α, and CBP/p300 recruitment as a transcriptional complex within the VEGF promoter, melatonin 1 mM decreases their physical interaction. Melatonin and the selective STAT3 inhibitor Stattic show a synergic effect on Hif1α, STAT3, and VEGF expression. CONCLUSION: Melatonin exerts an anti-angiogenic activity in HepG2 cells by interfering with the transcriptional activation of VEGF, via Hif1α and STAT3. Our results provide evidence to consider this indole as a powerful anti-angiogenic agent for HCC treatment.

Melatonin induces transcriptional regulation of Bim by FoxO3a in HepG2 cells.

BACKGROUND: Melatonin induces apoptosis in many different cancer cell lines, including hepatocellular carcinoma cells. However, the responsible pathways have not been clearly elucidated. A member of the forkhead transcription factors' family, FoxO3a, has been implicated in the expression of the proapoptotic protein Bim (a Bcl-2-interacting mediator of cell death). In this study, we used human HepG2 liver cancer cells as an in vitro model to investigate whether melatonin treatment induces Bim through regulation by the transcription factor FoxO3a. METHODS: Cytotoxicity of melatonin was compared in HepG2 hepatoblastoma cells and primary human hepatocytes. Proapoptotic Bim expression was analysed by reverse transcriptase-polymerase chain reaction and western blot. Reporter gene assays and chromatin immunoprecipitation assays were performed to analyse whether FoxO3a transactivates the Bim promoter. Small interfering RNA (siRNA) was used to study the role of FoxO3a in Bim expression. Immunofluorescence was performed to analyse FoxO3a localisation in HepG2 cells. RESULTS: Melatonin treatment induces apoptosis in HepG2 cells, but not in primary human hepatocytes. The proapoptotic effect was mediated by increased expression of the BH3-only protein Bim. During melatonin treatment, we observed increased transcriptional activity of the forkhead-responsive element and could demonstrate that FoxO3a binds to a specific sequence within the Bim promoter. Furthermore, melatonin reduced phosphorylation of FoxO3a at Thr(32) and Ser(253), and induced its increased nuclear localisation. Moreover, silencing experiments with FoxO3a siRNA prevented Bim upregulation. CONCLUSION: This study shows that melatonin can induce apoptosis in HepG2 hepatocarcinoma cells through the upregulation of proapoptotic Bim mediated by nuclear translocation and activation of the transcription factor FoxO3a.

Effect of melatonin supplementation on food and water intake in streptozotocin-diabetic and non-diabetic male Wistar rats.

The effect of orally supplemented melatonin (MT) at 1 mg/kg bw for 4 weeks on feeding behavior of non-diabetic and diabetic male Wistar rats has been studied by computerized meal pattern analysis. Exogenous MT has a satiating effect in non-diabetic rats, but not in diabetic animals. The changes in feeding behavior induced by MT in non-diabetic animals are related to changes in meal frequency, size and duration leading to lower total food intake during the scotophase. MT administration to diabetic rats resulted in lower drinking time and higher faecal output, without further behavioral effects. We conclude that the notorious metabolic changes occurring in the streptozotocin-diabetic rat can overcome most of the underlying effects of MT supplementation. The possible MT usage for therapeutical purposes could benefit from the lack of behavioral alterations in diabetic animals.

Radiomodifying effect of organic grape juice supplementation on hematological parameters and organ weight in whole-body X-irradiation in rats.

The aim of this study is testing black grape juice as a radiomodifier against whole body X-irradiation using an animal model. Sixteen male Wistar rats were divided into four groups where two were irradiated by X-rays from a 200 kV machine specially designed to biological samples. Animals were fed ad libitum and drank voluntarily 2-10 ml a day of grape juice or placebo (isocaloric glucose and fructose solution) for one week before and two weeks after 6 Gy X-irradiation when they were sacrificed. Results have shown a significant liver weight loss in irradiated placebo group only while grape juice one has presented no losses. Hematological analysis showed typical abnormalities for ionizing radiation exposure, including early leucopenia and anemia. The intake of grape juice induced an increase in granulocyte percent count.

Apoptotic signaling pathways as a target for the treatment of liver diseases.

Dysregulation of apoptosis is a major contributor to the initiation and aggravation of liver injury. Agents that modulate apoptosis may be of therapeutic benefit in a number of liver diseases, and research related to cell type-specific activation or inhibition of apoptotic signaling pathways will provide new strategies for treatment.

[Experimental models on hemorragic shock]. / Modelos experimentales sobre shock hemorrágico.

This review addresses the pathophysiology and treatment of hemorrhagic shock, a condition produced by rapid and significant loss of intravascular volume. Hemorrhagic shock may lead sequentially to hemodynamic instability, decreases in oxygen delivery, decreased tissue perfusion and cellular hypoxia. Multiple organ failure, a systemic inflammatory process that leads to dysfunction of different vital organs, is a frequent complication after hemorrhagic shock and accounts for a high incidence of mortality. The pathogenesis of organ injury secondary to hypovolemic insults is still not completely understood, but both experimental studies and clinical observations indicate that macrophages are activated by translocated endotoxin-bacteria and ischemia/reperfusion. Activated Kupffer cells release pathologically active substances such as inflammatory cytokines, reactive oxygen species, and nitric oxide, all of which may participate in the mechanisms of hemorrhagic shock. Moreover, increased free radical production during hemorrhagic shock and resuscitation gives place to an increase in oxidative stress that would contribute to the organ damage. In the last few years, a number of experiments have been performed in an attempt to understand the pathophysiology and treatment of hemorrhagic shock. Different studies have shown positive effects on hemorrhagic shock treatment by antioxidant, amino acid, and lipid administration.

Physical and functional cooperation between AP-1 and beta-catenin for the regulation of TCF-dependent genes.

Stabilization of cytoplasmic beta-catenin is a hallmark of a variety of cancers. The stabilized beta-catenin is able to translocate to the nucleus, where it acts as a transcriptional activator of T-cell factor (TCF)-regulated genes. beta-Catenin may cross-talk with many signalling cascades to activate target genes. Whether beta-catenin cooperates with AP-1, another transcriptional complex activated during tumorigenesis is not fully clarified. We show that beta-catenin co-immunoprecipitates with c-Jun and c-Fos. GST pull-down experiments indicate a physical association of the armadillo repeat domain of beta-catenin with the DNA-binding domain of c-Jun and of the C-terminal domain of beta-catenin with the N-terminal domain of c-Fos. Promoter studies indicate that overexpression of AP-1 activates the transcription of two beta-catenin target genes, cyclin D1 and c-myc, by a mechanism independent of the AP-1 site, and fully dependent on the TCF-binding site. We further demonstrate that AP-1/beta-catenin synergism is involved during serum-induced cyclin D1 transcriptional activation. We identify a TCF-binding site on the cyclin D1 promoter which binds in vivo a complex induced by serum, containing beta-catenin, TCF4, c-Fos, c-Jun, JunB and JunD. This novel mechanism of interaction between two signalling cascades might contribute to the potentiation of malignancy.

[Glycine: a cell-protecting anti-oxidant nutrient]. / La glicina: un nutriente antioxidante protector celular.

For many researchers it is still difficult to accept that beneficial effects can be obtained in several disease states with the simplest amino acid, glycine. However, evidence is mounting in favour of this idea. It is now clear that dietary glycine protects against shock caused either by blood loss or endotoxin, reduces alcohol levels in the stomach and improves recovery from alcoholic hepatitis, diminishes liver injury caused by hepatotoxic drugs and blocks programmed cell death and reduces the nephrotoxicity caused by the drug cyclosporin A in the kidney, preventing hypoxia and free radical formation. It could be also useful in other inflammatory diseases since it diminishes cytokines production. We review some of the beneficial effects of glycine and their responsible mechanism, which could led to advice its use in the therapy of different diseases.

Dietary glycine inhibits activation of nuclear factor kappa B and prevents liver injury in hemorrhagic shock in the rat.

We investigated the effects of a glycine-containing diet (5%) on liver injury caused by hemorrhagic shock and resuscitation in rats. Anesthetized rats were bled to a mean arterial blood pressure of 35-40 mm Hg for 1 h and then resuscitated with 60% of shed blood and lactated Ringer's solution. Feeding the rats glycine significantly reduced mortality, the elevation of plasma transaminase levels and hepatic necrosis. The increase in plasma TNFalpha and nitric oxide (NO) was also blunted by glycine feeding. Hemorrhagic shock resulted in oxidative stress (significant elevations in TBARS and in the oxidized/reduced glutathione ratio) and was accompanied by a reduced activity of the antioxidant enzymes Mn- and Cu,Zn-superoxide dismutase, glutathione peroxidase and catalase, overexpression of inducible NO synthase (iNOS), and activation of nuclear factor kappa B (NF-kappaB). Glycine ameliorated oxidative stress and the impairment in antioxidant enzyme activities, inhibited NF-kappaB activation, and prevented expression of iNOS. Dietary glycine blocks activation of different mediators involved in the pathophysiology of liver injury after shock.

Effect of epomediol on ethinyloestradiol-induced changes in bile acid and cholesterol metabolism in rats.

1. Epomediol is a terpenoid compound that has been reported to stimulate bile acid synthesis and to reverse 17alpha- ethinyloestradiol-induced cholestasis. The aim of the present study was to investigate the contribution of changes in bile acid and cholesterol metabolism to the protective effects of epomediol in ethinyloestradiol-treated rats. Animals received epomediol for 5 days at 100 mg/kg daily, i.p., ethinyloestradiol for 5 days at 5 mg/kg, s.c., or a combination of both drugs. 2. When compared with control animals, epomediol treatment resulted in a significant increase in bile flow (+42%) and in the secretion of bile acids (+74%) and cholesterol (+42%). Ethinyloestradiol administration caused a significant decrease in bile flow (-43%), bile acid secretion (-37%) and cholesterol secretion (-45%). Bile flow, bile acid secretion and cholesterol secretion were significantly increased in animals receiving ethinyloestradiol plus epomediol compared with ethinyloestradiol-treated rats (+13, +29 and +31%, respectively). 3. Both cholesterol 7alpha-hydroxylase and hydroxy-3- methylglutaryl coenzyme A reductase activities were significantly increased in epomediol-treated rats (+30 and +96%, respectively). Cholesterol 7alpha-hydroxylase activity was significantly reduced by ethinyloestradiol (-22%) and did not differ from control values in animals receiving epomediol plus ethinyloestradiol. Levels of cholesterol 7alpha-hydroxylase mRNA were elevated (+41%) by epomediol, but were not significantly modified by ethinyloestradiol or ethinyloestradiol plus epomediol. 4. It is concluded that epomediol enhances bile acid secretion by increasing the expression of cholesterol 7alpha-hydroxylase. Changes in bile acid metabolism contribute to the effects of epomediol in rats with ethinyloestradiol-induced cholestasis.

Enhancement of bile acid pool size, synthesis and secretion by epomediol in the rat.

Epomediol is a terpenoid compound that has been reported to reverse 17alpha-ethinylestradiol-induced cholestasis and to have a choleretic effect related to the biliary secretion of epomediol glucuronide. The aim of this study was to investigate the contribution of changes in bile acid metabolism to epomediol-induced effects on bile formation. Twenty-four-hour bile collections were performed in animals that had received intraperitoneal epomediol for five days at 100 mg/kg daily. Epomediol-treated rats had a 24% larger bile acid pool and 28% greater bile acid synthesis than controls when measured by the "washout" technique. There was no change in the fractional turnover rate and the cycling frequency of the pool. Both basal bile flow and bile acid secretion were significantly increased (+42% and +74%, respectively). Linear regression analysis between bile flow and bile acid secretion revealed that both bile acid-dependent fraction and bile acid-independent fraction were significantly increased (+40 and +27, respectively), with no change in the choleretic capacity of bile acids. Cholesterol secretion was increased by 42%, but there were no significant differences in phospholipid secretion. Cholesterol 7alpha-hydroxylase and HMG-CoA reductase activities were significantly higher in epomediol-treated rats (+39% and +97%, respectively). The activities of NADPH-cytochrome c reductase and aniline hydroxylase were also significantly elevated (+26% and +64%, respectively). It is concluded that epomediol treatment expands the bile acid pool through an enhanced bile acid synthesis. Choleresis induced by the drug is partly related to the increase in bile acid secretion.

Physical exercise and improvement of liver oxidative metabolism in the elderly.

Drug metabolizing capacity is generally reduced in the elderly, and physical exercise has been reported to increase drug oxidative metabolism. The purpose of this investigation was to study the effects of engagement in a program of regular physical exercise on the clearance and metabolite excretion of antipyrine, a marker of oxidative metabolism, in elderly subjects. The saliva clearance of antipyrine and the production clearances of antipyrine metabolites were studied in 37 elderly women (mean age 66 years). Subjects attended 60-min sessions three times a week for 12 weeks. Each session consisted of both aerobic (training of cardiorespiratory capacity) and nonaerobic (training of muscular strength/endurance and flexibility/coordination) exercises performed at 50-75% of maximum oxygen uptake. Antipyrine was administered orally and pharmacokinetic parameters were obtained from saliva and urine samples. After 3 months of participation in the exercise program, salivary antipyrine clearance was significantly increased by 17% mean (SEM) 0.42 (0.02) vs 0.36 (0.02) ml/min/kg; P < 0.05) and the half-life of antipyrine was significantly reduced by 18% (17.9 (1.1) vs 22.3 (1.3) h; P < 0.05). No significant change with exercise was observed in the renal clearance of antipyrine or in the norantipyrine formation clearance, but significant increases were found for hydroxymethylantipyrine [42 (5) vs 32 (4) microl/kg/min; P < 0.05; +31%] and 4-hydroxyantipyrine [243 (18) vs 194 (17) microl/kg/min; P < 0.05; +25%] formation clearances. These findings indicate that regular exercise leads to increased disposition of antipyrine in the elderly and that the main metabolic pathways of the compound are changed differentially.