AMP-activated protein kinase in the regulation of hepatic energy metabolism: from physiology to therapeutic perspectives

Luteolin alleviates alcoholic liver disease induced by chronic and binge ethanol feeding in mice

Ethanol consumption can lead to hepatic steatosis that contributes to late-stage liver diseases such as cirrhosis and hepatocellular carcinoma. In this study, we investigated the potential protective effect of a flavonoid, luteolin, on ethanol-induced fatty liver development and liver injury. Six-wk-old male C57BL/6 mice were divided into 3 groups: a control group; a group exposed to alcohol by using a chronic and binge ethanol feeding protocol (EtOH); and a group that was administered daily 50 mg/kg of luteolin in addition to ethanol exposure (EtOH + Lut). A chronic and binge ethanol feeding protocol was used, including chronic ethanol consumption (1%, 2%, and 4% for 3 d, and 5% for 9 d) and a binge (30% ethanol) on the last day. Compared with the control group, the EtOH group had a significant elevation in serum concentrations of alanine aminotransferase (ALT) (561%), triglyceride (TG) (47%), and LDL cholesterol (95%), together with lipid accumulation in the liver. Compared with the EtOH group, the EtOH + Lut group had significant reductions in serum concentrations of ALT (43%), TG (22%), LDL cholesterol (52%), and lipid accumulation in the liver. Ethanol elevated liver expression of lipogenic genes including sterol regulatory element-binding protein 1c (Srebp1c) (560%), fatty acid synthase (Fasn) (190%), acetyl-CoA carboxylase (Acc) (48%), and stearoyl-CoA desaturase 1 (Scd1) (286%). Luteolin reduced ethanol-induced expression of these genes in the liver: Srebp1c (79%), Fasn (80%), Acc (60%), and Scd1 (89%). In cultured hepatocytes, luteolin prevented alcohol-induced lipid accumulation and increase in the expression of lipogenic genes. The transcriptional activity of the master regulator of lipid synthesis, sterol regulatory element-binding protein (SREBP), was enhanced by ethanol treatment (160%) and reduced by luteolin administration (67%). In addition, ethanol-induced reduction of AMP-activated protein kinase and SREBP-1c phosphorylation was abrogated by luteolin. Collectively, our study indicates that luteolin is effective in ameliorating ethanol-induced hepatic steatosis and injury.

AMPK activation by isorhamnetin protects hepatocytes against oxidative stress and mitochondrial dysfunction

Arachidonic acid (AA) is a ω-6 polyunsaturated fatty acid that is found in the phospholipids of membranes and released from the cellular membrane lipid bilayer by phospholipase A2. During this process, AA could produce excess reactive oxygen species and induce apoptosis and mitochondrial dysfunction by selectively inhibiting complexes I and III. Isorhamnetin, an O-methylated flavonol aglycone, has been shown to have cardio-protective, anti-adipogenic, anti-tumor, and anti-inflammatory effects. In the present study, we investigated the effects of isorhamnetin on hepatotoxicity and the underlying mechanisms involved. Our in vitro experiments showed that isorhamnetin dose-dependently blocked the hepatotoxicity induced by treatment with AA plus iron in HepG2 cells. Furthermore, isorhamnetin inhibited the AA+iron induced generation of reactive oxygen species and reduction of glutathione, and subsequently maintained mitochondria membrane potential in AA+iron treated HepG2 cells. In addition, isorhamnetin activated AMP-activated protein kinase (AMPK) by Thr-172 phosphorylation of AMPKα, and this was mediated with Ca2+/calmodulin-dependent protein kinase kinase-2 (CaMKK2), but not liver kinase B1. Experiments using CaMKK2 siRNA or its selective inhibitor, STO-609, revealed the role of CaMKK2 in the isorhamnetin-induced activation of AMPK in HepG2 cells. These results indicate isorhamnetin protects against the hepatotoxic effect of AA plus iron, and suggest that the AMPK pathway is involved in the mechanism underlying the beneficial effect of isorhamnetin in the liver.

AMP-activated Protein Kinase (AMPK): Does This Master Regulator of Cellular Energy State Distinguish Insulin Sensitive from Insulin Resistant Obesity?

Although a correlation exists between obesity and insulin resistance, roughly 25 % of obese individuals are insulin sensitive. AMP-activated protein kinase (AMPK) is a cellular energy sensor that among its many actions, integrates diverse physiological signals to restore energy balance. In addition, in many situations it also increases insulin sensitivity. In this context, AMPK activity is decreased in very obese individuals undergoing bariatric surgery who are insulin resistant compared to equally obese patients who are insulin sensitive. In this review, we will both explore what distinguishes these individuals, and evaluate the evidence that diminished AMPK is associated with insulin resistance and metabolic syndrome-associated disorders in other circumstances.

Hugan Qingzhi medication ameliorates hepatic steatosis by activating AMPK and PPARα pathways in L02 cells and HepG2 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Hugan Qingzhi tablet (HQT), a lipid- lowering traditional Chinese medicine formula, has been used for the prevention and treatment of nonalcoholic fatty liver (NAFLD).

AIM OF THE STUDY

This study was realized to evaluate the effects of HQT-medicated serum on hepatic steatosis using in vitro experiments with cells and explore the relevant mechanisms with method of serum pharmacology.

MATERIALS AND METHODS

A model of hepatic steatosis in the L02 and HepG2 cells was induced by free fatty acid (FFA). The components in the HQT-medicated serum were assayed by high-performance liquid chromatography. Intracellular lipid droplets were detected by Oil Red O staining, and their ultrastructure was examined by transmission electron microscope. The biochemical parameters, including triglyceride (TG), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT), total antioxidant capacity (T-AOC), malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione (GSH), were measured with commercial kits. Furthermore, the expression of adiponectin, AMP-activated protein kinase (AMPK) phosphorylation, sterol regulatory element-binding protein 1 (SREBP-1), peroxisome proliferator activated receptor-α (PPARα), carnitine palmitoyltransferase 1 (CPT-1), and acetyl-CoA oxidase 1 (ACOX1) was analyzed by Western blot and/or quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

RESULTS

Moderate- and high-dose HQT-medicated serum reduced (P<0.05 or P<0.01) the accumulation of lipid droplets and the cellular TG content in L02 and HepG2 cells. They caused significant reductions (P<0.01) in LDH, AST, ALT and MDA and significant increase (P<0.05 or P<0.01) in T-AOC in the culture medium. They also caused increase (P<0.05 or P<0.01) in GSH level and SOD activity in FFA-induced steatotic L02 and HepG2 cells. Furthermore, moderate- and high-dose HQT-medicated serum enhanced (P<0.01) adiponectin expression in a concentration-dependent manner and increased (P<0.05 or P<0.01) the phosphorylation of AMPK and the expression of PPARα, CPT-1, and ACOX1, and reduced (P<0.05 or P<0.01) the expression of SREBP-1.

CONCLUSION

The results suggested that HQT-medicated serum exerts a preventive effect against hepatic steatosis, and the potential mechanism might be activation of AMPK and PPARα pathways.

Lipogenesis in cancer progression (review)

In normal tissues, energy-providing lipids come principally from circulating lipids. However, in growing tumors, energy supply is mainly provided by lipids coming from de novo synthesis. It is not surprising to see elevated expression of several lipogenic genes in tumors from different origins. The role of lipogenic genes in the establishment of the primary tumor has been clearly established. A large number of studies demonstrate a role of fatty acid synthase in the activation of cell cycle and inhibition of apoptosis in tumor cells. Other lipogenic genes such as the acetyl CoA carboxylase (ACC) and the stearoyl CoA desaturase 1 (SCD1) are highly expressed in primary tumors and also appear to play a role in their development. However, the role of lipogenesis in the metastatic process is less clear. In the present review, we aim to present the most recent evidences for the key role of lipogenic enzymes in the metastatic process and in epithelial to mesenchymal transition.

LECT2 functions as a hepatokine that links obesity to skeletal muscle insulin resistance

Recent articles have reported an association between fatty liver disease and systemic insulin resistance in humans, but the causal relationship remains unclear. The liver may contribute to muscle insulin resistance by releasing secretory proteins called hepatokines. Here we demonstrate that leukocyte cell-derived chemotaxin 2 (LECT2), an energy-sensing hepatokine, is a link between obesity and skeletal muscle insulin resistance. Circulating LECT2 positively correlated with the severity of both obesity and insulin resistance in humans. LECT2 expression was negatively regulated by starvation-sensing kinase adenosine monophosphate-activated protein kinase in H4IIEC hepatocytes. Genetic deletion of LECT2 in mice increased insulin sensitivity in the skeletal muscle. Treatment with recombinant LECT2 protein impaired insulin signaling via phosphorylation of Jun NH2-terminal kinase in C2C12 myocytes. These results demonstrate the involvement of LECT2 in glucose metabolism and suggest that LECT2 may be a therapeutic target for obesity-associated insulin resistance.

Modulation of lipid metabolism by deep-sea water in cultured human liver (HepG2) cells

It has been found that deep-sea water was associated with lower serum lipid in animal model studies. Herein, we investigated whether DSW exerted a hypolipidemic activity and further elucidated how DSW modulated lipid metabolism in HepG2 cells. Preliminary animal studies showed that DSW exhibited potency to decrease serum total cholesterol, triglycerides, and LDL cholesterol, and increase HDL cholesterol, and the hepatic lipid contents were also significantly lower in the DSW group. When DSW was added to HepG2 cells, it decreased the lipid contents of hepatocyte through the activation of AMP-activated protein kinase, thus inhibiting the synthesis of cholesterol and fatty acid. Besides, LDL receptor was upregulated by activation of sterol regulatory element-binding protein-2. In addition, the levels of apolipoprotein AI and cholesterol 7-alpha-hydroxylase were also raised. Our investigation provided mechanisms by which DSW modulated lipid metabolism and indicated that DSW was worthy of further investigation and could be developed as functional drinking water in the prevention and treatment of hypolipidemic and other lifestyle-related diseases.

Metabolic impact of the glycerol channels AQP7 and AQP9 in adipose tissue and liver

Obesity and secondary development of type 2 diabetes (T2D) are major health care problems throughout the developed world. Accumulating evidence suggest that glycerol metabolism contributes to the pathophysiology of obesity and T2D. Glycerol is a small molecule that serves as an important intermediate between carbohydrate and lipid metabolism. It is stored primarily in adipose tissue as the backbone of triglyceride (TG) and during states of metabolic stress, such as fasting and diabetes, it is released for metabolism in other tissues. In the liver, glycerol serves as a gluconeogenic precursor and it is used for the esterification of free fatty acid into TGs. Aquaporin 7 (AQP7) in adipose tissue and AQP9 in the liver are transmembrane proteins that belong to the subset of AQPs called aquaglyceroporins. AQP7 facilitates the efflux of glycerol from adipose tissue and AQP7 deficiency has been linked to TG accumulation in adipose tissue and adult onset obesity. On the other hand, AQP9 expressed in liver facilitates the hepatic uptake of glycerol and thereby the availability of glycerol for de novo synthesis of glucose and TG that both are involved in the pathophysiology of diabetes. The aim of this review was to summarize the current knowledge on the role of the two glycerol channels in controlling glycerol metabolism in adipose tissue and liver.

PCK2 activation mediates an adaptive response to glucose depletion in lung cancer

Cancer cells are reprogrammed to utilize glycolysis at high rates, which provides metabolic precursors for cell growth. Consequently, glucose levels may decrease substantially in underperfused tumor areas. Gluconeogenesis results in the generation of glucose from smaller carbon substrates such as lactate and amino acids. The key gluconeogenic enzyme, phosphoenolpyruvate carboxykinase (PEPCK), has been shown to provide metabolites for cell growth. Still, the role of gluconeogenesis in cancer is unknown. Here we show that the mitochondrial isoform of PEPCK (PCK2) is expressed and active in three lung cancer cell lines and in non-small cell lung cancer samples. PCK2 expression and activity were enhanced under low-glucose conditions. PEPCK activity was elevated threefold in lung cancer samples over normal lungs. To track the conversion of metabolites along the gluconeogenesis pathway, lung cancer cell lines were incubated with (13)C₃-lactate and label enrichment in the phosphoenolpyruvate (PEP) pool was measured. Under low glucose, all three carbons from (13)C₃-lactate appeared in the PEP pool, further supporting a conversion of lactate to pyruvate, via pyruvate carboxylase to oxaloacetate, and via PCK2 to phosphoenolpyruvate. PCK2 small interfering RNA and the pharmacological PEPCK inhibitor 3-mercaptopicolinate significantly enhanced glucose depletion-induced apoptosis in A549 and H23 cells, but not in H1299 cells. The growth of H23 multicellular spheroids was significantly reduced by 3-mercaptopicolinate. The results of this study suggest that lung cancer cells may utilize at least some steps of gluconeogenesis to overcome the detrimental metabolic situation during glucose deprivation and that in human lung cancers this pathway is activated in vivo.

Pear pomace water extract inhibits adipogenesis and induces apoptosis in 3T3-L1 adipocytes

Obesity occurs when a person's calorie intake exceeds the amount of energy burns, which may lead to pathologic growth of adipocytes and the accumulation of fat in the tissues. In this study, the effect and mechanism of pear pomace extracts on 3T3-L1 adipocyte differentiation and apoptosis of mature adipocytes were investigated. The effects of pear pomace extract on cell viability and the anti-adipogenic and proapoptotic effects were investigated via MTT assay, Oil red O staining, western blot analysis and apoptosis assay. 3T3-L1 preadipocytes were stimulated with DMEM containing 10% FBS, 0.5 mM 3-isobutyl-1-methylxanthine (IBMX), 5 µg/ml insulin and 1 µM dexamethasone for differentiation to adipocytes. 3T3-L1 cells were cultured with PBS or water extract of pear pomace. Water extract of pear pomace effectively inhibited lipid accumulations and expressions of PPAR-γ and C/EBPα in 3T3-L1 cells. It also increased expression of p-AMPK and decreased the expression of SREBP-1c and FAS in 3T3-L1 cells. The induction of apoptosis was observed in 3T3-L1 cells treated with pear pomace. These results indicate that pear pomace water extract inhibits adipogenesis and induces apoptosis of adipocytes and thus can be used as a potential therapeutic substance as part of prevention or treatment strategy for obesity.

Antiobesogenic role of endothelial nitric oxide synthase

The prevalence of obesity has increased remarkably in the past four decades. Because obesity can promote the development of type 2 diabetes and cardiovascular disease, understanding the mechanisms that engender weight gain and discovering safe antiobesity therapies are of critical importance. In particular, the gaseous signaling molecule, nitric oxide (NO), appears to be a central factor regulating adiposity and systemic metabolism. Obese and diabetic states are characterized by a deficit in bioavailable NO, with such decreases commonly attributed to downregulation of endothelial NO synthase (eNOS), loss of eNOS activity, or quenching of NO by its reaction with oxygen radicals. Gain-of-function studies, in which vascular-derived NO has been increased pharmacologically or genetically, reveal remarkable actions of NO on body composition and systemic metabolism. This review addresses the metabolic actions of eNOS and the potential therapeutic utility of harnessing its antiobesogenic effects.

Acylated ghrelin limits fat accumulation and improves redox state and inflammation markers in the liver of high-fat-fed rats

OBJECTIVE

Obesity commonly causes hepatic lipid accumulation that may favor oxidative stress and inflammation with negative clinical impact. Acylated ghrelin (A-Ghr) modulates body lipid distribution and metabolism, and it may exert antioxidant effects in vitro as well as systemic anti-inflammatory effects in vivo. The impact of A-Ghr on liver triglyceride content, redox state and inflammation markers in diet-induced obesity was investigated.

DESIGN AND METHODS

A-Ghr (200-μg/injection: HFG) or saline (HF) were administered subcutaneously twice-daily for 4 days to 12-week-old male rats fed a high-fat diet for 1 month (n = 8-10/group).

RESULTS

Compared to lean animals, liver triglyceride accumulation occurred in HF despite enhanced phosphorylation of the lipid oxidation regulator AMPK and preserved mitochondrial enzyme activities. High triglycerides were accompanied by pro-oxidant changes in redox state and proinflammatory changes in NF-kB and TNF-alpha. A-Ghr limited liver triglyceride excess (P < 0.05 HF > HFG > Control) with concomitant activation of glutathione peroxidase and normalized redox state and cytokines. A-Ghr-induced liver changes were associated with higher plasma adiponectin and lower circulating fatty acids (P < 0.05 HFG vs.

HF) CONCLUSIONS

A-Ghr limits liver triglyceride accumulation and normalizes tissue redox state and inflammation markers in diet-induced obese rats. These results suggest a favorable impact of A-Ghr on hepatic complications of diet-induced obesity.

COH-SR4 reduces body weight, improves glycemic control and prevents hepatic steatosis in high fat diet-induced obese mice

Obesity is a chronic metabolic disorder caused by imbalance between energy intake and expenditure, and is one of the principal causative factors in the development of metabolic syndrome, diabetes and cancer. COH-SR4 (“SR4”) is a novel investigational compound that has anti-cancer and anti-adipogenic properties. In this study, the effects of SR4 on metabolic alterations in high fat diet (HFD)-induced obese C57BL/J6 mice were investigated. Oral feeding of SR4 (5 mg/kg body weight.) in HFD mice for 6 weeks significantly reduced body weight, prevented hyperlipidemia and improved glycemic control without affecting food intake. These changes were associated with marked decreases in epididymal fat mass, adipocyte hypertrophy, increased plasma adiponectin and reduced leptin levels. SR4 treatment also decreased liver triglycerides, prevented hepatic steatosis, and normalized liver enzymes. Western blots demonstrated increased AMPK activation in liver and adipose tissues of SR4-treated HFD obese mice, while gene analyses by real time PCR showed COH-SR4 significantly suppressed the mRNA expression of lipogenic genes such as sterol regulatory element binding protein-1c (Srebf1), acetyl-Coenzyme A carboxylase (Acaca), peroxisome proliferator-activated receptor gamma (Pparg), fatty acid synthase (Fasn), stearoyl-Coenzyme A desaturase 1 (Scd1), carnitine palmitoyltransferase 1a (Cpt1a) and 3-hydroxy-3-methyl-glutaryl-CoA reductase (Hmgcr), as well as gluconeogenic genes phosphoenolpyruvate carboxykinase 1 (Pck1) and glucose-6-phosphatase (G6pc) in the liver of obese mice. In vitro, SR4 activates AMPK independent of upstream kinases liver kinase B1 (LKB1) and Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ). Together, these data suggest that SR4, a novel AMPK activator, may be a promising therapeutic compound for treatment of obesity, fatty liver disease, and related metabolic disorders.

Free radical biology for medicine: learning from nonalcoholic fatty liver disease

Reactive oxygen species, when released under controlled conditions and limited amounts, contribute to cellular proliferation, senescence, and survival by acting as signaling intermediates. In past decades there has been an epidemic diffusion of nonalcoholic fatty liver disease (NAFLD) that represents the result of the impairment of lipid metabolism, redox imbalance, and insulin resistance in the liver. To date, most studies and reviews have been focused on the molecular mechanisms by which fatty liver progresses to steatohepatitis, but the processes leading toward the development of hepatic steatosis in NAFLD are not fully understood yet. Several nuclear receptors, such as peroxisome proliferator-activated receptors (PPARs) α/γ/δ, PPARγ coactivators 1α and 1β, sterol-regulatory element-binding proteins, AMP-activated protein kinase, liver-X-receptors, and farnesoid-X-receptor, play key roles in the regulation of lipid homeostasis during the pathogenesis of NAFLD. These nuclear receptors may act as redox sensors and may modulate various metabolic pathways in response to specific molecules that act as ligands. It is conceivable that a redox-dependent modulation of lipid metabolism, nuclear receptor-mediated, could cause the development of hepatic steatosis and insulin resistance. Thus, this network may represent a potential therapeutic target for the treatment and prevention of hepatic steatosis and its progression to steatohepatitis. This review summarizes the redox-dependent factors that contribute to metabolism alterations in fatty liver with a focus on the redox control of nuclear receptors in normal liver as well as in NAFLD.

Monascin and ankaflavin act as natural AMPK activators with PPARα agonist activity to down-regulate nonalcoholic steatohepatitis in high-fat diet-fed C57BL/6 mice

Yellow pigments monascin (MS) and ankaflavin (AK) are secondary metabolites derived from Monascus-fermented products. The hypolipidemic and anti-inflammatory effects of MS and AK indicate that they have potential on preventing or curing nonalcoholic fatty liver disease (NAFLD). Oleic acid (OA) and high-fat diet were used to induce steatosis in FL83B hepatocytes and NAFLD in mice, respectively. We found that both MS and AK prevented fatty acid accumulation in hepatocytes by inhibiting fatty acid uptake, lipogenesis, and promoting fatty acid beta-oxidation mediated by activating peroxisome proliferator-activated receptor (PPAR)-α and AMP-activated kinase (AMPK). Furthermore, MS and AK significantly attenuated high-fat diet-induced elevation of total cholesterol (TC), triaceylglycerol (TG), free fatty acid (FFA), and low density lipoprotein-cholesterol (LDL-C) in plasma. MS and AK promoted AMPK phosphorylation, suppressed the steatosis-related mRNA expression and inflammatory cytokines secretion, as well as upregulated farnesoid X receptor (FXR), peroxisome proliferator-activated receptor gamma co-activator (PGC)-1α, and PPARα expression to induce fatty acid oxidation in the liver of mice. We provided evidence that MS and AK act as PPARα agonists to upregulate AMPK activity and attenuate NAFLD. MS and AK may be supplied in food supplements or developed as functional foods to reduce the risk of diabetes and obesity.

Environmental pollution: a tangible risk for NAFLD pathogenesis

The liver is crucial for human life, and the health of this organ often mirrors the health of the individual. The liver can be the target of several diseases, the most prevalent of which, as a consequence of development and changes in human lifestyles, is the nonalcoholic fatty liver disease (NAFLD). NAFLD is a multifactorial disease that embraces many histo-pathologic conditions and is highly linked to metabolic derangements. Technological progress and industrialization have also had the consequence of releasing pollutants in the environment, for instance pesticides or solvents, as well as by-products of discharge, such as the particulate matter. In the last decade, a growing body of evidence has emerged, shedding light on the potential impact of environmental pollutants on liver health and, in particular, on NAFLD occurrence. These contaminants have a great steatogenic potential and need to be considered as tangible NAFLD risk factors. There is an urgent need for a deeper comprehension of their molecular mechanisms of action, as well as for new lines of intervention to reduce their worldwide diffusion. This review wishes to sensitize the community to the effects of several environmental pollutants on liver health.

Keap1-knockdown decreases fasting-induced fatty liver via altered lipid metabolism and decreased fatty acid mobilization from adipose tissue

AIMS

The purpose of this study was to determine whether Nrf2 activation, via Keap1-knockdown (Keap1-KD), regulates lipid metabolism and mobilization induced by food deprivation (e.g. fasting).

METHODS AND RESULTS

Male C57BL/6 (WT) and Keap1-KD mice were either fed ad libitum or food deprived for 24 hours. After fasting, WT mice exhibited a marked increase in hepatic lipid accumulation, but Keap1-KD mice had an attenuated increase of lipid accumulation, along with reduced expression of lipogenic genes (acetyl-coA carboxylase, stearoyl-CoA desaturase-1, and fatty acid synthase) and reduced expression of genes related to fatty acid transport, such as fatty acid translocase/CD36 (CD36) and Fatty acid transport protein (FATP) 2, which may attribute to the reduced induction of Peroxisome proliferator-activated receptor (Ppar) α signaling in the liver. Additionally, enhanced Nrf2 activity by Keap1-KD increased AMP-activated protein kinase (AMPK) phosphorylation in liver. In white adipose tissue, enhanced Nrf2 activity did not change the lipolysis rate by fasting, but reduced expression of fatty acid transporters--CD36 and FATP1, via a PPARα-dependent mechanism, which impaired fatty acid transport from white adipose tissue to periphery circulation system, and resulted in increased white adipose tissue fatty acid content. Moreover, enhanced Nrf2 activity increased glucose tolerance and Akt phosphorylation levels upon insulin administration, suggesting Nrf2 signaling pathway plays a key role in regulating insulin signaling and enhanced insulin sensitivity in skeletal muscle.

CONCLUSION

Enhanced Nrf2 activity via Keap1-KD decreased fasting-induced steatosis, pointing to an important function of Nrf2 on lipid metabolism under the condition of nutrient deprivation.

Chemoproteomic analysis of intertissue and interspecies isoform diversity of AMP-activated protein kinase (AMPK)

AMP-activated protein kinase (AMPK) is a heterotrimeric enzyme that senses and governs changes in the cellular energy balance represented by concentrations of AMP, ADP, and ATP. Each of its three chains (α, β, and γ) exists as either two or three subtypes, theoretically allowing up to 12 different forms of the complete enzyme. Tissue specificity in the distribution of AMPK subtypes is believed to underpin a range of biological functions for AMPK, a central regulator of metabolic function and response. It is of particular interest for drug discovery purposes to compare AMPK isoforms that are most prevalent in human liver and muscle with isoforms present in key preclinical species. To complement immunocapture/immunodetection methods, which for AMPK are challenged by sequence similarities and difficulties of obtaining accurate relative quantitation, AMPK was captured from lysates of a range of cells and tissues using the ActivX ATP probe. This chemical probe covalently attaches desthiobiotin to one or more conserved lysyl residues in the ATP-binding sites of protein kinases, including AMPK, while also labeling a wide range of ATP-utilizing proteins. Affinity-based recovery of labeled proteins followed by gel-based fractionation of the captured sample was followed by proteomic characterization of AMPK polypeptides. In agreement with transcript-based analysis and previous indications from immunodetection, the results indicated that the predominant AMPK heterotrimer in human liver is α1β2γ1 but that dog and rat livers mainly contain the α1β1γ1 and α2β1γ1 forms, respectively. Differences were not detected between the AMPK profiles of normal and diabetic human liver tissues.

Pharmacologic agents for type 2 diabetes therapy and regulation of adipogenesis

The close link between type 2 diabetes and excess body weight highlights the need to consider the effects on weight of different treatments used for correction of hyperglycaemia. Indeed, specific currently available diabetes therapies can cause weight gain, including insulin and its analogues, sulphonylureas, and thiazolidinediones, while others, such as metformin and the GLP-1 receptor agonists, can promote weight loss. Excess body weight in patients with diabetes is largely due to expansion of adipose tissue, and these drugs could interfere with the mechanisms underlying the expansion and differentiation of adipocyte precursors. Almost all anti-diabetes drugs could also potentially affect adipocyte metabolism directly, by modulating lipogenesis, lipolysis, and fat oxidation. This review will examine the available evidence for specific effects of various anti-diabetes drugs on adipose tissue development and function with the ultimate goal of increasing our understanding of how pharmacological agents can modulate energy balance and body fat.

Metformin decreases high-fat diet-induced renal injury by regulating the expression of adipokines and the renal AMP-activated protein kinase/acetyl-CoA carboxylase pathway in mice

Metabolic syndrome is characterized by insulin resistance, dyslipidemia and hypertension. These metabolic changes contribute to the development of obesity-induced kidney injury. AMP-activated protein kinase (AMPK) is a ubiquitous enzyme that is involved in the cellular metabolic response to metabolic stress. Metformin, an AMPK activator, has been reported to exert a protective effect against non-alcoholic steatohepatitis. However, little is known about its role in the pathogenesis of obesity-induced renal injury. The aim of this study was to investigate the effects of metformin on high-fat diet (HFD)-induced kidney injury. Obesity was induced by HFD (60% of total calories from fat, 20% protein and 20% carbohydrates) in 6-week-old C57BL/6 mice. Mice were fed HFD plus 0.5% metformin. The effects of metformin on HFD-induced renal injury were evaluated by determining metabolic parameters, serum adipokine levels and renal AMPK/acetyl-CoA carboxylase (ACC) activities, as well as a histological examination. HFD induced metabolic derangement, systemic insulin resistance and glomerular mesangial matrix expansion. The administration of metformin reduced HFD-induced metabolic derangement and renal injury. The administration of metformin reduced the HFD-induced increase in adipokine expression and macrophage infiltration. Moreover, renal AMPK activity, which was decreased by HFD, was recovered following the administration of metformin; in addition, fatty acid oxidation was increased by the inhibition of ACC. These results indicate that metformin exerts beneficial effects on obesity-induced renal injury by regulating systemic inflammation, insulin resistance and the renal AMPK/ACC pathway. The clinical application of metformin to obese or early diabetic patients may be helpful in preventing obesity- or diabetes-related kidney disease.

Berberine metabolites exhibit triglyceride-lowering effects via activation of AMP-activated protein kinase in Hep G2 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizoma coptidis (Huanglian in Chinese) is commonly used in Chinese folk medicine to treat diarrhea, diabetes, hypertension, hyperlipidemia and tumors. This herb has increasingly gained attention because of its use as a hypolipidemic herb. Berberine (BBR) is the most important constituent of R. coptidis that contribute to the pharmacological efficacy of the herb.

AIM OF THE STUDY

Pharmacokinetic studies have indicated that BBR has poor oral bioavailability. Interestingly, several reports show that absorbed BBR is extensively metabolized in rats and humans. We speculate that the BBR metabolites might be responsible for the pharmacological effects. The aim of this study is to examine BBR metabolites for their triglyceride (TG)-lowering activities and the molecular mechanism to clarify BBR genuine effective forms in vivo.

MATERIALS AND METHODS

Four BBR metabolites were examined their TG-lowering effects with a commercial triglyceride assay kit. Real-time PCR and Western blotting were used to confirm genes and proteins of interest, respectively.

RESULTS

Among those BBR metabolites, M2 exhibited the more potential effects on TG-lowering and AMP-activated protein kinase (AMPK) activation in Hep G2 cells as compared with BBR. Moreover, BBR and M2 inhibited gene expressions of acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), glycerol-3-phosphate acyltransferase (GPAT) and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), but motivated gene expression of medium chain acyl-CoA dehydrogenase (mCAD) significantly.

CONCLUSIONS

The results suggested that the TG-lowering effects of BBR and M2 might be partially mediated by the up-regulation of lipolysis gene expressions and down-regulation of lipogenesis gene expressions through activation of the AMPK signaling pathway. BBR and its metabolites might be in vivo active forms of oral doses of BBR, and M2 might be a promising drug candidate against hyperlipidemia.

Multiple regulatory layers of SREBP1/2 by SIRT6

The NAD(+)-dependent protein deacetylase SIRT6 regulates genome stability, cancer, and lifespan. Mice overexpressing SIRT6 (MOSES) have lower low-density lipoprotein cholesterol levels and are protected against the physiological damage of obesity. Here, we examined the role of SIRT6 in cholesterol regulation via the lipogenic transcription factors SREBP1 and SREBP2, and AMP-activated protein kinase (AMPK). We show that SIRT6 represses SREBP1 and SREBP2 by at least three mechanisms. First, SIRT6 represses the transcription levels of SREBP1/SREBP2 and that of their target genes. Second, SIRT6 inhibits the cleavage of SREBP1/SREBP2 into their active forms. Third, SIRT6 activates AMPK by increasing the AMP/ATP ratio, which promotes phosphorylation and inhibition of SREBP1 by AMPK. Reciprocally, the expression of miR33a and miR33b from the introns of SREBP2 and SREBP1, respectively, represses SIRT6 levels. Together, these findings explain the mechanism underlying the improved cholesterol homeostasis in MOSES mice, revealing a relationship between fat metabolism and longevity.

Tetrahydrobiopterin has a glucose-lowering effect by suppressing hepatic gluconeogenesis in an endothelial nitric oxide synthase-dependent manner in diabetic mice

Endothelial nitric oxide synthase (eNOS) dysfunction induces insulin resistance and glucose intolerance. Tetrahydrobiopterin (BH4) is an essential cofactor of eNOS that regulates eNOS activity. In the diabetic state, BH4 is oxidized to 7,8-dihydrobiopterin, which leads to eNOS dysfunction owing to eNOS uncoupling. The current study investigates the effects of BH4 on glucose metabolism and insulin sensitivity in diabetic mice. Single administration of BH4 lowered fasting blood glucose levels in wild-type mice with streptozotocin (STZ)-induced diabetes and alleviated eNOS dysfunction by increasing eNOS dimerization in the liver of these mice. Liver has a critical role in glucose-lowering effects of BH4 through suppression of hepatic gluconeogenesis. BH4 activated AMP kinase (AMPK), and the suppressing effect of BH4 on gluconeogenesis was AMPK-dependent. In addition, the glucose-lowering effect and activation of AMPK by BH4 did not appear in mice with STZ-induced diabetes lacking eNOS. Consecutive administration of BH4 in ob/ob mice ameliorated glucose intolerance and insulin resistance. Taken together, BH4 suppresses hepatic gluconeogenesis in an eNOS-dependent manner, and BH4 has a glucose-lowering effect as well as an insulin-sensitizing effect in diabetic mice. BH4 has potential in the treatment of type 2 diabetes.

Nutrition and healthy ageing: calorie restriction or polyphenol-rich "MediterrAsian" diet?

Diet plays an important role in mammalian health and the prevention of chronic diseases such as cardiovascular disease (CVD). Incidence of CVD is low in many parts of Asia (e.g., Japan) and the Mediterranean area (e.g., Italy, Spain, Greece, and Turkey). The Asian and the Mediterranean diets are rich in fruit and vegetables, thereby providing high amounts of plant bioactives including polyphenols, glucosinolates, and antioxidant vitamins. Furthermore, oily fish which is rich in omega-3 fatty acids is an important part of the Asian (e.g., Japanese) and also of the Mediterranean diets. There are specific plant bioactives which predominantly occur in the Mediterranean (e.g., resveratrol from red wine, hydroxytyrosol, and oleuropein from olive oil) and in the Asian diets (e.g., isoflavones from soybean and epigallocatechin gallate from green tea). Interestingly, when compared to calorie restriction which has been repeatedly shown to increase healthspan, these polyphenols activate similar molecular targets such as Sirt1. We suggest that a so-called "MediterrAsian" diet combining sirtuin-activating foods (= sirtfoods) of the Asian as well as Mediterranean diet may be a promising dietary strategy in preventing chronic diseases, thereby ensuring health and healthy ageing. Future (human) studies are needed which take the concept suggested here of the MediterrAsian diet into account.

The effects of chronic candesartan treatment on cardiac and hepatic adenosine monophosphate-activated protein kinase in rats submitted to surgical stress

INTRODUCTION

adenosine monophosphate-activated protein kinase (AMPK) plays a prominent role as a metabolic stress sensor, and it has recently been suggested that the renin-angiotensin system, in addition to its role in stress regulation, may play a significant role in regulating the AMPK system. This study aimed to evaluate the effects of candesartan, an angiotensin II receptor blocker, on cardiac and hepatic AMPK activity basally as well as after surgical stress under general anesthesia.

MATERIALS AND METHODS

Male Wistar rats were treated with 5 mg/kg/day candesartan in their drinking water for two weeks. Levels of cardiac and hepatic AMPK activity were determined, using a kinase activity assay, basally and after surgical stress under general anesthesia.

RESULTS

Chronic administration of candesartan increased hepatic AMPK activity approximately 4 times (p<0.05) while no significant change was demonstrated in cardiac AMPK. Cardiac and hepatic AMPK activities were not significantly increased by surgical stress alone performed under anesthesia. However, chronic treatment with candesartan decreased AMPK activity in both liver and heart after surgical stress under anesthesia (p<0.01 for both comparisons).

CONCLUSIONS

While chronic candesartan treatment may stimulate AMPK activity in certain organs such as the liver, when combined with surgical stress under anesthesia it inhibits pathways regulating AMPK activity.

Salsalate and adiponectin ameliorate hepatic steatosis by inhibition of the hepatokine fetuin-A

Fetuin-A was recently identified as a novel hepatokine which is associated with obesity, insulin resistance and non-alcoholic fatty liver disease. Salsalate, a prodrug of salicylate with an anti-inflammatory effect and lower side effect profile, significantly lowers glucose and triglyceride levels, and increased adiponectin concentrations in randomized clinical trials. In this study, we examined the effects and regulatory mechanisms of salsalate and full length-adiponectin (fAd) on fetuin-A expression, steatosis and lipid metabolism in palmitate-treated HepG2 cells. Incubation of hepatocytes with palmitate significantly increased fetuin-A and SREBP-1c expression which lead to steatosis and knock-down of fetuin-A by siRNA restored these changes. Salsalate significantly down-regulated palmitate-induced fetuin-A mRNA expression and secretion in a dose- and time-dependent manner. Inhibition of palmitate-induced fetuin-A by salsalate was mediated by AMPK-mediated reduction of NFκB activity, which was blocked by AMPK siRNA or an inhibitor of AMPK. Salsalate attenuated the excessive steatosis by palmitate through SREBP-1c regulation in hepatocytes. Furthermore, fAd also showed suppression of palmitate-induced fetuin-A through the AMPK pathway and improvement of steatosis accompanied by restoration of SREBP-1c, PAPR-α and CD36. In preliminary in vivo experiments, salsalate treatment inhibited high fat diet (HFD)-induced steatosis as well as fetuin-A mRNA and protein expression in SD rats. In conclusion, salsalate and fAd improved palmitate-induced steatosis and impairment of lipid metabolism in hepatocytes via fetuin-A inhibition through the AMPK-NFκB pathway.

Alcoholic liver disease: pathogenesis, management, and novel targets for therapy

Alcohol use is a leading cause of preventable morbidity and mortality worldwide, with much of its negative impact as the result of alcoholic liver disease (ALD). ALD is a broad term that encompasses a spectrum of phenotypes ranging from simple steatosis to steatohepatitis, progressive fibrosis, cirrhosis, and hepatocellular carcinoma. The mechanisms underlying the development of these different disease stages are incompletely understood. Standard treatment of ALD, which includes abstinence, nutritional support, and corticosteroids, has not changed in the last 40 years despite continued poor outcomes. Novel therapies are therefore urgently needed. The development of such therapies has been hindered by inadequate resources for research and unsuitable animal models. However, recent developments in translational research have allowed for identification of new potential targets for therapy. These targets include: (i) CXC chemokines, (ii) IL-22/STAT3, (iii) TNF receptor superfamily, (iv) osteopontin, (v) gut microbiota and lipopolysaccharide (LPS), (vi) endocannabinoids, and (vii) inflammasomes. We review the natural history, risk factors, pathogenesis, and current treatments for ALD. We further discuss the findings of recent translational studies and potential therapeutic targets.

Proteomic analysis of the inhibitory effect of epigallocatechin gallate on lipid accumulation in human HepG2 cells

Background

(−)-Epigallocatechin-3-gallate (EGCG), the most abundant catechin found in green tea, effectively reduces body weight and tissue and blood lipid accumulation. To explore the mechanism by which EGCG inhibits cellular lipid accumulation in free fatty acid (FFA) induced HepG2 cell culture, we investigated the proteome change of FFA-induced HepG2 cells exposed to EGCG using two-dimensional gel electrophoresis and mass spectrometry.

Results

In this study, 36 protein spots showed a significant change in intensity by more than 1.5-fold from the control group to the FFA group and from the FFA group to the FFA + EGCG group. Among them, 24 spots were excised from gels and identified by LC-MS/MS. In total, 18 proteins were successfully identified. All identified proteins were involved in lipid metabolism, glycometabolism, antioxidant defense, respiration, cytoskeleton organization, signal transduction, DNA repair, mRNA processing, iron storage, or were chaperone proteins. This indicated that these physiological processes may play roles in the mechanism of inhibition of lipid accumulation by EGCG in FFA-induced HepG2 cells. Western blotting analysis was used to verify the expression levels of differentially expressed proteins, which agree with the proteomic results.

Conclusions

From the proteomic analysis, we hypothesized that EGCG reduced cellular lipid accumulation in FFA-induced HepG2 cells through the activation of AMP-activated protein kinase (AMPK) resulting from the generation of reactive oxygen species (ROS). The induction of ROS may be a result of EGCG regulation of the antioxidant defense system. Activation of AMPK shifted some FFA toward oxidation, away from lipid and triglyceride storage, and suppressed hepatic gluconeogenesis. The findings of this study improve our understanding of the molecular mechanisms of inhibition of lipid accumulation by EGCG in HepG2 cells.

Induction of AMPK activity corrects early pathophysiological alterations in the subtotal nephrectomy model of chronic kidney disease

The rat kidney ablation and infarction (A/I) model of subtotal or 5/6th nephrectomy is the most commonly studied model of nondiabetic chronic kidney disease (CKD). The A/I kidney at 1 wk exhibits reductions in kidney function, as determined by glomerular filtration rate, and diminished metabolic efficiency as determined by oxygen consumption per sodium transport (QO2/TNa). As renoprotective AMPK activity is affected by metabolic changes and cellular stress, we evaluated AMPK activity in this model system. We show that these early pathophysiological changes are accompanied by a paradoxical decrease in AMPK activity. Over time, these kidney parameters progressively worsen with extensive kidney structural, functional, metabolic, and fibrotic changes observed at 4 wk after A/I. We show that induction of AMPK activity with either metformin or 5-aminoimidazole-4-carboxamide ribonucleotide increases AMPK activity in this model and also corrects kidney metabolic inefficiency, improves kidney function, and ameliorates kidney fibrosis and structural alterations. We conclude that AMPK activity is reduced in the subtotal nephrectomy model of nondiabetic CKD, that altered regulation of AMPK is coincident with the progression of disease parameters, and that restoration of AMPK activity can suppress the progressive loss of function characteristic of this model. We propose that induction of AMPK activity may prove an effective therapeutic target for the treatment of nondiabetic CKD.

Potential of incretin-based therapies for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is becoming an epidemic, paralleling the increased prevalence of obesity and diabetes, which are risk factors. In this review, we present the current pre-clinical evidence showing that GLP-1 analogues and DPP4 inhibitors can improve hepatic steatosis. Although some of the effects could be due to overall improvement in metabolic parameters, there are data to support improvements independent of weight loss, as well as direct effects on the hepatocyte in vitro. Multiple hepatocyte signal transduction pathways appear to be activated by GLP-1 and its analogues, with both AMP-activated protein kinase and Akt proposed to be key players in improving hepatic steatosis. However, it is controversial as to whether the pancreatic-type GLP-1 receptor is present or responsible for conferring the GLP-1 signal in the hepatocyte. In total, the data support the need for more rigorous prospective clinical trials to further investigate the potential of incretin therapies for treatment of NAFLD.

Metabolic regulation by the mitochondrial phosphatase PTPMT1 is required for hematopoietic stem cell differentiation

The regulation and coordination of mitochondrial metabolism with hematopoietic stem cell (HSC) self-renewal and differentiation is not fully understood. Here we report that depletion of PTPMT1, a PTEN-like mitochondrial phosphatase, in inducible or hematopoietic-cell-specific knockout mice resulted in hematopoietic failure due to changes in the cell cycle and a block in the differentiation of HSCs. Surprisingly, the HSC pool was increased by ∼40-fold in PTPMT1 knockout mice. Reintroduction of wild-type PTPMT1, but not catalytically deficient PTPMT1 or truncated PTPMT1 lacking mitochondrial localization, restored differentiation capabilities of PTPMT1 knockout HSCs. Further analyses demonstrated that PTPMT1 deficiency altered mitochondrial metabolism and that phosphatidylinositol phosphate substrates of PTPMT1 directly enhanced fatty-acid-induced activation of mitochondrial uncoupling protein 2. Intriguingly, depletion of PTPMT1 from myeloid, T lymphoid, or B lymphoid progenitors did not cause any defects in lineage-specific knockout mice. This study establishes a crucial role of PTPMT1 in the metabolic regulation of HSC function.

AMP-activated protein kinase: a target for old drugs against diabetes and cancer

The AMP-activated protein kinase (AMPK) is considered a key checkpoint to ensure energy balance in both cells and organisms. AMPK is an αβγ heterotrimer controlled by allosteric regulation by AMP, ADP and ATP, auto-inhibitory features and phosphorylation, with the threonine-172 phosphorylation on the catalytic α-subunit by LKB1, CaMKKβ or Tak1 being essential for its fully activation. AMPK acts as a protective response to energy stress in numerous systems, but it is also a key player in diabetes and related metabolic diseases and cancer. Pharmacological activation of AMPK by metformin or other compounds holds a considerable potential to reverse the metabolic abnormalities associated with type 2 diabetes. In cancer, correction of the dysregulated metabolic pathway LKB1/AMPK/mTORC1 can lower the Warburg effect, suggesting AMPK as a potential target for cancer prevention and/or treatment. In this commentary, we review recent findings that support the role and function of AMPK in normal and pathological conditions. We also discuss how the activation of AMPK by naturally occurring compounds could help to prevent the development of numerous chronic diseases contributing in such a way to the well-being of ageing population.

Disruption of the cereblon gene enhances hepatic AMPK activity and prevents high-fat diet-induced obesity and insulin resistance in mice

A nonsense mutation in cereblon (CRBN) causes a mild type of mental retardation in humans. An earlier study showed that CRBN negatively regulates the functional activity of AMP-activated protein kinase (AMPK) in vitro by binding directly to the α1-subunit of the AMPK complex. However, the in vivo role of CRBN was not studied. For elucidation of the physiological functions of Crbn, a mouse strain was generated in which the Crbn gene was deleted throughout the whole body. In Crbn-deficient mice fed a normal diet, AMPK in the liver showed hyperphosphorylation, which indicated the constitutive activation of AMPK. Since Crbn-deficient mice showed significantly less weight gain when fed a high-fat diet and their insulin sensitivity was considerably improved, the functions of Crbn in the liver were primarily investigated. These results provide the first in vivo evidence that Crbn is a negative modulator of AMPK, which suggests that Crbn may be a potential target for metabolic disorders of the liver.

Site-specific antioxidative therapy for prevention of atherosclerosis and cardiovascular disease

Oxidative stress has been implicated in pathophysiology of aging and age-associated disease. Antioxidative medicine has become a practice for prevention of atherosclerosis. However, limited success in preventing cardiovascular disease (CVD) in individuals with atherosclerosis using general antioxidants has prompted us to develop a novel antioxidative strategy to prevent atherosclerosis. Reducing visceral adipose tissue by calorie restriction (CR) and regular endurance exercise represents a causative therapy for ameliorating oxidative stress. Some of the recently emerging drugs used for the treatment of CVD may be assigned as site-specific antioxidants. CR and exercise mimetic agents are the choice for individuals who are difficult to continue CR and exercise. Better understanding of molecular and cellular biology of redox signaling will pave the way for more effective antioxidative medicine for prevention of CVD and prolongation of healthy life span.

Revisiting the mechanisms of metformin action in the liver

Although considerable efforts have been made since the 1950s to better understand the action of metformin, the first line therapeutic for type 2 diabetes, its mechanisms of action has not been fully elucidated. The main antidiabetic effect of this drug is to decrease hepatic glucose production. A plausible molecular mechanism of action now emerges from recent breakthroughs that place metformin at the control of energy homeostasis. Metformin was shown to induce a mild and transient inhibition of the mitochondrial respiratory chain complex 1. The resulting decrease in hepatic energy state activates the AMP-activated protein kinase (AMPK), a cellular metabolic sensor, and provided a generally accepted mechanism for metformin action on hepatic gluconeogenic program. However, the role of AMPK activation in metformin action has recently been challenged by loss-of-function experiments. Recent evidence showed that metformin-induced inhibition of hepatic glucose output is mediated by reducing cellular energy charge rather than direct inhibition of gluconeogenic gene expression. Furthermore, recent data support a novel mechanism of action for metformin involving antagonism of glucagon signaling pathways by inducing the accumulation of AMP, which inhibits adenylate cyclase and reduced levels of cAMP.

The endocannabinoid system in energy homeostasis and the etiopathology of metabolic disorders

Endocannabinoids and cannabinoid CB1 receptors are known to play a generalized role in energy homeostasis. However, clinical trials with the first generation of CB1 blockers, now discontinued due to psychiatric side effects, were originally designed to reduce food intake and body weight rather than the metabolic risk factors associated with obesity. In this review, we discuss how, in addition to promoting energy intake, endocannabinoids control lipid and glucose metabolism in several peripheral organs, particularly the liver and adipose tissue. Direct actions in skeletal muscle and pancreas are also emerging. This knowledge may help in the design of future therapies for the metabolic syndrome.

Rosemary (Rosmarinus officinalis L.) extract regulates glucose and lipid metabolism by activating AMPK and PPAR pathways in HepG2 cells

An epidemic of metabolic disorders such as obesity and diabetes is rising dramatically. Using natural products as potential preventive and therapeutic interventions for these disorders has drawn worldwide attention. Rosemary has been shown to lower blood glucose and cholesterol levels and mitigate weight gain in several in vivo studies. However, the mechanisms are essentially unknown. We investigated the effects of rosemary extract on metabolism and demonstrated that rosemary extract significantly increased glucose consumption in HepG2 cells. The phosphorylation of AMP-activated protein kinase (AMPK) and its substrate, acetyl-CoA carboxylase (ACC), was increased by rosemary extract. Rosemary extract also transcriptionally regulated the genes involved in metabolism, including SIRT1, PPARγ coactivator 1α (PGC1α), glucose-6-phosphatase (G6Pase), ACC, and low-density lipoprotein receptor (LDLR). Furthermore, the PPARγ-specific antagonist GW9662 diminished rosemary's effects on glucose consumption. Overall, our study suggested that rosemary potentially increases liver glycolysis and fatty acid oxidation by activating AMPK and PPAR pathways.

Deregulation of signalling pathways in prognostic subtypes of hepatocellular carcinoma: novel insights from interspecies comparison

Hepatocellular carcinoma is a frequent and fatal disease. Recent researches on rodent models and human hepatocarcinogenesis contributed to unravel the molecular mechanisms of hepatocellular carcinoma dedifferentiation and progression, and allowed the discovery of several alterations underlying the deregulation of cell cycle and signalling pathways. This review provides an interpretive analysis of the results of these studies. Mounting evidence emphasises the role of up-regulation of RAS/ERK, P13K/AKT, IKK/NF-kB, WNT, TGF-ß, NOTCH, Hedgehog, and Hippo signalling pathways as well as of aberrant proteasomal activity in hepatocarcinogenesis. Signalling deregulation often occurs in preneoplastic stages of rodent and human hepatocarcinogenesis and progressively increases in carcinomas, being most pronounced in more aggressive tumours. Numerous changes in signalling cascades are involved in the deregulation of carbohydrate, lipid, and methionine metabolism, which play a role in the maintenance of the transformed phenotype. Recent studies on the role of microRNAs in signalling deregulation, and on the interplay between signalling pathways led to crucial achievements in the knowledge of the network of signalling cascades, essential for the development of adjuvant therapies of liver cancer. Furthermore, the analysis of the mechanisms involved in signalling deregulation allowed the identification of numerous putative prognostic markers and novel therapeutic targets of specific hepatocellular carcinoma subtypes associated with different biologic and clinical features. This is of prime importance for the selection of patient subgroups that are most likely to obtain clinical benefit and, hence, for successful development of targeted therapies for liver cancer.

The Extract of Herbal Medicines Activates AMP-Activated Protein Kinase in Diet-Induced Obese Rats

Our study investigated whether the extract of six herbal medicines (OB-1) has an inhibitory effect on obesity. High-fat diet-(HFD-) induced rats and controls were treated with 40 mg/100 g body weight of OB-1 or saline once a day for 5 weeks. After significant changes in body weight were induced, OB-1 and saline were administered to each subgroup of HFD and control groups for additional 5 weeks. No statistically significant decrease of body weight in OB-1-treated rats was found compared to controls. However, OB-1-treated rats were found to be more active in an open-field test and have a reduction in the size of adipocytes compared to controls. We observed no changes in the mRNA expressions of leptin and adiponectin from adipocytes between OB-1- and saline-treated rats with HFD-induced obesity group. However, OB-1 treatments were shown to be inversely correlated with accumulation of lipid droplets in liver tissue, suggesting that OB-1 could inhibit a lipid accumulation by blocking the pathway related to lipid metabolism. Moreover, the phosphorylation of AMP-activated protein kinase (AMPK) was significantly increased in OB-1-treated rats with HFD compared to controls. These results suggest that OB-1 has no direct antiobesity effect and, however, could be a regulator of cellular metabolism.

Curcumin prevents liver fat accumulation and serum fetuin-A increase in rats fed a high-fat diet

Fetuin-A is synthesized in the liver and is secreted into the bloodstream. Clinical studies suggest involvement of fetuin-A in metabolic disorders such as visceral obesity, insulin resistance, diabetes, and fatty liver. Curcumin is extracted from the rhizome Curcuma longa and has been shown to possess potent antioxidant, anticarcinogenic, anti-inflammatory, and hypoglycemic properties. In this study, we investigated the effect of curcumin treatment on serum fetuin-A levels as well as hepatic lipids and prooxidant-antioxidant status in rats fed a high-fat diet (HFD). Male Sprague-Dawley rats were divided into six groups. Group 1 was fed control diet (10 % of total calories from fat). Groups 2 and 3 were given curcumin (100 and 400 mg/kg bw/day, respectively ) by gavage for 8 weeks and were fed control diet. Group 4 was fed with HFD (60 % of total calories from fat). Groups 5 and 6 received HFD together with the two doses of curcumin, respectively. Curcumin treatment appeared to be effective in reducing liver triglycerides and serum fetuin-A levels. These findings suggest that the reduction of fetuin-A may contribute to the beneficial effects of curcumin in the pathogenesis of obesity.