Hepatic Adenosine Monophosphate-activated Protein Kinase Research Articles

Regulation of carbohydrate metabolism and insulin secretion in diabetic rats following treatment with Hypericum perforatum L. hairy root aqueous methanol extract

Hairy root (HR) cultures of Hypericum perforatum L. have shown promise in controlling hyperglycemia, regulating blood lipid and enzyme profiles, and improving metabolic function in vivo. These benefits are mainly attributed to the phenolic acids, flavonoids, and xanthones present in HR extracts. However, the specific mechanism underlying these effects remains unclear. This study was performed to elucidate the biochemical and molecular mechanisms driving HR the antihyperglycemic and antidiabetic effects of HR extracts. HR extract (200 mg/kg body weight) was administered daily for 14 days to healthy rats and rats with streptozotocin-induced diabetes, with glibenclamide serving as a positive control. The phenolic composition of the HR extracts was confirmed through high-performance liquid chromatography/diode array detection/electrospray ionization mass spectrometry (HPLC/DAD/ESI-MSn ) analysis. The results showed that HR extract treatment increased the plasma insulin level and pancreatic poly (adenosine diphosphate-ribose) polymerase (PARP) activity in diabetic rats, thus normalizing blood glucose levels. Additionally, it reduced the activity of gluconeogenic enzymes, increased the activity of glycolytic enzymes, and normalized the glycogen content in the liver. HR extract-treated rats also exhibited increased hepatic adenosine monophosphate-activated protein kinase (AMPK) mRNA expression and a decreased protein kinase Cε (PKCε) concentration. In conclusion, HR extract demonstrated insulinotropic effects and effectively regulated hepatic carbohydrate metabolism in diabetic rats by modulating AMPK expression and the PKCε concentration. These findings suggest the potential use of HR extract as an herbal medicine for diabetes treatment and a source of antidiabetic drug development.

Schisanhenol ameliorates non-alcoholic fatty liver disease via inhibiting miR-802 activation of AMPK-mediated modulation of hepatic lipid metabolism

Non-alcoholic fatty liver disease (NAFLD), characterized by hepatic steatosis, is a common metabolic liver disease worldwide. Currently, satisfactory drugs for NAFLD treatment remain lacking. Obesity and diabetes are the leading causes of NAFLD, and compounds with anti-obesity and anti-diabetic activities are considered suitable candidates for treating NAFLD. In this study, biochemical and histological assays revealed that a natural lignan schisanhenol (SAL) effectively decreased lipid accumulation and improved hepatic steatosis in free fatty acid (FFA)-treated HepG2 cells and high-fat diet (HFD)-induced NAFLD mice. Further, molecular analyses, microRNA (miRNA)-seq, and bioinformatics analyses revealed that SAL may improve NAFLD by targeting the miR-802/adenosine monophosphate-activated protein kinase (AMPK) pathway. Liver-specific overexpression of miR-802 in NAFLD mice significantly impaired SAL-mediated liver protection and decreased the protein levels of phosphorylated (p)-AMPK and PRKAB1. Dual-luciferase assay analysis further confirmed that miR-802 inhibits hepatic AMPK expression by binding to the 3ʹ untranslated region of mouse Prkab1 or human PRKAA1. Additionally, genetic silencing of PRKAA1 blocked SAL-induced AMPK pathway activation in FFA-treated HepG2 cells. The results demonstrate that SAL is an effective drug candidate for treating NAFLD through regulating miR-802/AMPK-mediated lipid metabolism.

Vine tea total flavonoids activate the AMPK/mTOR pathway to amelioration hepatic steatosis in mice fed a high-fat diet.

Vine tea (Ampelopsis grossedentata), a traditional Chinese tea, is rich in flavonoids with various biological activities. Our study found that Vine tea total flavonoids (TFs) treatment reduced the body mass and blood lipid levels and improved the hepatic tissue morphology in mice fed the high-fat diet (HFD). In vivo, TF treatment activated the hepatic adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway, initiated autophagy, and regulated the expression levels of proteins for lipid metabolism in those HFD-fed mice. In vitro, TF treatment dramatically reduced the lipid droplets and triacylglycerol content in HepG2 and L02 cells treated with oleic acid (OA). These were associated with the activation of the AMPK/mTOR pathway and autophagy initiation in OA-treated hepatocytes. This phenotype was abolished in the presence of 3-methyladenine, an autophagy inhibitor. Our results indicated that the TF activation of AMPK/mTOR leads to the stimulation of autophagy and a decrease in the buildup of intracellular lipids in hepatocytes, showing the potential of TF as a therapeutic agent for nonalcoholic fatty liver disease. PRACTICAL APPLICATION: Vine tea, a tea drink, has been consumed by Chinese folk for over a thousand years. The result of this study will provide evidence that vine tea total flavonoids have potential use as a functional material for the prevention and amelioration of nonalcoholic fatty liver disease.

Effects of Quercetin Nanoemulsion on Cholesterol Efflux and MicroRNA-33/34a Expression in the Liver of Mice Fed with a High-Cholesterol Diet.

Quercetin is a flavonoid widely present in plants; despite its beneficial physiological activity, it exhibits considerably low bioavailability. Nanoemulsion technology is used for improving the bioavailability of lipophilic phenolic compounds. This study aimed to investigate the potential effects of quercetin nanoemulsion (QN) on regulating the microRNA (miR)-33/34a pathway involved in cholesterol efflux in the liver of mice fed with a high-cholesterol (HC) diet. Subsequently, C57BL/6J mice were divided into four groups and fed a normal chow diet, HC diet supplemented with 1% cholesterol and 0.5% cholic acid, or HC diet supplemented with 0.05% QN or 0.1% QN for 6 weeks. Serum and hepatic lipid profiles were assayed using commercial enzymatic kits. Gene expression and miR levels were quantified using real-time quantitative reverse transcription polymerase chain reaction, and adenosine monophosphate-activated protein kinase (AMPK) activity was measured using an AMPK Kinase Assay kit. QN supplementation improved serum and liver lipid profiles. QN upregulated the mRNA levels of adenosine triphosphate (ATP)-binding cassette subfamily A1, ATP-binding cassette subfamily G1, and scavenger receptor class B type 1, which are related to cholesterol efflux. In the QN group, the hepatic AMPK activity increased, whereas miR-33, and miR-34a expression levels decreased. These results suggest that QN may enhance cholesterol efflux, at least partly through modulating AMPK activity and miR-33/34a expression in the liver.

Effect of Oleanolic acid administration on hepatic AMPK, SIRT-1, IL-6 and NF-κB levels in experimental diabetes.

Diabetes mellitus (DM) is an important public health problem all over the world, considering its complications and increasing prevalence. Oleanolic acid (OA) has anti-diabetic property via modulating glucose metabolism and acting as 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) / Sirtuin-1 (SIRT-1) activator and Interleukin 6 (IL-6) / Nuclear factor kappa B (NF-κB) inhibitor. This research questioned if the OA treatment amliorates the hepatic inflammatory profile in the diabetic rats. Twenty-eight male Sprague Dawley rats were first subjected to either no diabetes induction (healthy) or diabetes induction by i.p. injection of 50mg/kg streptozotocin. Then rats in both groups were treated with either tap water or OA (5mg/kg) within 1 ml tap water by oral gavage for 21 days. The diabetic rats had higher hepatic MDA (2.88x) and serum AST (2.01x), ALP (2.22x), and ALT (4.27x) levels and 50% lower hepatic SOD level than the healthy rats. The OA treatment significantly reversed these antioxidant parameters in the diabetic rats. The diabetic rats had lower AMPK (85%) and hepatic SIRT-1 (47%) levels and higher hepatic NF-κB (53%) and IL-6 (34%) levels than the healthy rats. Comparing with the health rats, the OA treatment increased hepatic SIRT-1 level, but tended to increase hepatic AMPK level and decrease hepatic NF-κB and IL-6 levels in the diabetic rats. It was also partially effective to ameliorate degenerative changes and necrosis in the diabetic rats. The OA treatment can be considered to alleviate oxidative stress and reduce severity of inflammation in hepatocytes in the diabetic subjects.

A Novel and Cross-Species Active Mammalian INDY (NaCT) Inhibitor Ameliorates Hepatic Steatosis in Mice with Diet-Induced Obesity.

Mammalian INDY (mINDY, NaCT, gene symbol SLC13A5) is a potential target for the treatment of metabolically associated fatty liver disease (MAFLD). This study evaluated the effects of a selective, cross-species active, non-competitive, non-substrate-like inhibitor of NaCT. First, the small molecule inhibitor ETG-5773 was evaluated for citrate and succinate uptake and fatty acid synthesis in cell lines expressing both human NaCT and mouse Nact. Once its suitability was established, the inhibitor was evaluated in a diet-induced obesity (DIO) mouse model. DIO mice treated with 15 mg/kg compound ETG-5773 twice daily for 28 days had reduced body weight, fasting blood glucose, and insulin, and improved glucose tolerance. Liver triglycerides were significantly reduced, and body composition was improved by reducing fat mass, supported by a significant reduction in the expression of genes for lipogenesis such as SREBF1 and SCD1. Most of these effects were also evident after a seven-day treatment with the same dose. Further mechanistic investigation in the seven-day study showed increased plasma β-hydroxybutyrate and activated hepatic adenosine monophosphate-activated protein kinase (AMPK), reflecting findings from Indy (−/−) knockout mice. These results suggest that the inhibitor ETG-5773 blocked citrate uptake mediated by mouse and human NaCT to reduce liver steatosis and body fat and improve glucose regulation, proving the concept of NaCT inhibition as a future liver treatment for MAFLD.

Polyphenol Enriched Chrysanthemum morifolium Extract Increase Energy Expenditure and Decrease Hepatic Lipid Accumulation in Rats Fed a High Fat Diet

ObjectivesThis study aimed to examine the improvement effects of polyphenol enriched Chrysanthemum morifolium extract (CE) on energy expenditure and hepatic lipid accumulation in rats fed a high-fat diet. MethodsThe polyphenols identified in CE were analyzed by ultra-performance liquid chromatography (UPLC) method. Male Sprague-Dawley rats were randomly divided into four groups. Each group fed a normal diet (NOR), 45% high-fat diet (HF), or HF supplemented with 0.2% CE (CEL), or HF supplemented with 0.4% CE (CEH) for 13 weeks. ResultsPolyphenolic compounds of CE were confirmed that three flavonoids, such as luteolin-7-O-glucoside, luteolin-7-O-glucuronide and apigenin-7-O-glucoside, and three phenolic acids, including chlorogenic acid, 1,5-Dicaffeoylquinic acid and 3,5-Dicaffeoylquinic acid. CE significantly increased oxygen consumption (VO2), carbon dioxide production (VCO2) and energy expenditure (EE) compared with HF. CE supplementation was lower the serum concentrations of total cholesterol (TC), triglyceride (TG), non-esterified fatty acids (NEFAs) and low-density lipoprotein cholesterol (LDL-C), and decreased the levels of hepatic total lipids, TC and TG. Hepatic lipogenic gene expression such as cluster of differentiation 36 (CD36), sterol regulatory element binding protein-1c (SREBP-1c), ATP citrate lyase (ACLY), acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), stearoyl-CoA desaturase 1 (SCD1), and diacylglycerol O-acyltransferase 2 (DGAT2) significantly down-regulated by CE supplementation. The mRNA expression involved in fatty acid oxidation such as peroxisome proliferator-activated receptor alpha (PPARα) and carnitine/palmitoyl-transferase 1α (CPT1α) were up-regulated in the CEH group than HF group. Hepatic adenosine monophosphate-activated protein kinase (AMPK) activity was significantly increased in the CE groups than HF group. ConclusionsIt is suggested that the polyphenol enriched CE might increase energy expenditure and reduce hepatic fat accumulation via modulating hepatic lipogenic and fatty acid oxidation gene expression with increasing AMPK activation. Funding SourcesThis research was supported by the BK21 FOUR (Fostering Outstanding Universities for Research) funded by the Ministry of Education (MOE, Korea) and National Research Foundation of Korea (NRF).

High hydrostatic pressure extract of mulberry leaves ameliorates hypercholesterolemia via modulating hepatic microRNA-33 expression and AMPK activity in high cholesterol diet fed rats.

BackgroundMulberry leaf (Morus alba L.) contains multiple bioactive ingredients and has been used in the treatment of obesity, diabetes, inflammation, and atherosclerosis. High hydrostatic pressure (HHP) processing has been developed for the extraction of bioactive compounds from plants. However, the hypocholesterolemic effect of the HHP extract from mulberry leaves and its underlying mechanism have never been investigated.ObjectiveThe specific aim of the present study was to investigate the hypocholesterolemic property of a novel extract obtained from mulberry leaves under HHP in rats.DesignSprague–Dawley rats were divided into four groups and fed either a normal diet (NOR), a high cholesterol diet containing 1% cholesterol and 0.5% cholic acid (HC), an HC diet containing 0.5% mulberry leaf extract (ML), or a 1% mulberry leaf extract (MH) for 4 weeks.ResultsHigh hydrostatic pressure extract of mulberry leaves significantly reduced the HC-increased serum levels of triglyceride (TG), cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C), and hepatic contents of TG and TC. The HHP extraction from mulberry leaves also increased the HC-decreased fecal TC and bile acid levels without changing body weight, food intake, liver weight, and serum activities of alanine transaminase (ALT) and aspartate transaminase (AST) (P < 0.05). The mulberry leaf extract significantly enhanced the expression of hepatic genes such as cholesterol 7 alpha-hydroxylase (CYP7A1), liver X receptor alpha (LXRα), and ATP-binding cassette transporters, ABCG5/ABCG8, involved in hepatic bile acid synthesis and cholesterol efflux (P < 0.05). In addition, the HHP extraction of mulberry leaves significantly suppressed hepatic microRNA(miR)-33 expression and increased adenosine monophosphate-activated protein kinase (AMPK) activity.ConclusionThese results suggest that the HHP extract of mulberry leaves lowers serum cholesterol levels by partially increasing hepatic bile acid synthesis and fecal cholesterol excretion through the modulation of miR-33 expression and AMPK activation in the liver.

Effect of feeding type 2 diabetes mellitus rats with synbiotic yogurt sweetened with monk fruit extract on serum lipid levels and hepatic AMPK (5' adenosine monophosphate-activated protein kinase) signaling pathway.

Monk fruit extract (MFE) is a natural sweetener that has been used as an ingredient of food and pharmaceutical products. The effects of feeding synbiotic yogurt fortified with MFE to rats with type 2 diabetes induced by high-fat diet and streptozotocin on serum lipid levels and hepatic AMPK signaling pathway were evaluated. Results showed that oral administration of the synbiotic yogurt fortified with MFE could improve serum lipid levels, respiratory exchange rate, and heat level in type 2 diabetic rats. Transcriptome analysis showed that synbiotic yogurt fortified with MFE may affect the expression of genes involved in binding, catalytic activity, and transporter activity. The Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that these differentially expressed genes were related to AMPK signaling pathway, linoleic acid metabolism, and α-linolenic acid metabolism. Western blotting confirmed that synbiotic yogurt fortified with MFE could activate AMPK signaling and improve the protein level of the hepatic gluconeogenic enzyme G6Pase in diabetic rats. The results indicated that MFE could be a novel sweetener for functional yogurt and related products.

Antroquinonol Attenuated Abdominal and Hepatic Fat Accumulation in Rats Fed an Obesogenic Diet.

An imbalance of energy intake and expenditure leads to fat accumulation and metabolic disorders. The aim of the study was to investigate the effects of antroquinonol on diet-induced obesity. Thirty-two rats were divided into a control group (C), an obesogenic group (OB), and two experimental groups consuming 25 (OB-AQ25) and 50 mg/kg (OB-AQ50) antroquinonol (n = 8). After a 12-week experimental period, we collected blood, liver, abdominal fat, and gastrocnemius muscle tissue for analysis. The obesogenic diet induced greater weight gain and fat accumulation, and increased hepatic lipids, and tumor necrosis factor-α and interleukin-1β concentrations in rats. Antroquinonol consumption reduced epididymal and hepatic lipids and inflammatory cytokines. We found that antroquinonol upregulated hepatic adenosine monophosphate-activated protein kinase and downregulated sterol regulatory element-binding protein-1 protein expressions and downregulated fatty acid synthase mRNA expression. In addition, gastrocnemius fibronectin type III domain containing 5 protein expression was also higher in the B group. In conclusion, our results suggested that consuming antroquinonol may ameliorate diet-induced abdominal and hepatic fat accumulation. PRACTICAL APPLICATION: Antroquinonol is a bioactive compound derived from Antrodia camphorate which is traditionally used in Chinese medicinal cuisine, and is used for developing functional foods in Taiwan. This is the first study investigating the possible effects of antroquinonol on obesity and we found that antroquinonol can ameliorate diet-induced obesity, and therefore may be used in further studies and functional food development.

Compound K attenuates glucose intolerance and hepatic steatosis through AMPK-dependent pathways in type 2 diabetic OLETF rats

Background/AimsNon-alcoholic fatty liver disease is associated with insulin resistance. Compound K (CK) is the final metabolite of panaxadiol ginsenosides that have been shown to exert antidiabetic effects. However, the molecular mechanism of the antidiabetic effects in the liver have not been elucidated; further, whether CK has beneficial effects in hepatosteatosis remains unclear. Therefore, we evaluated the effect of CK on hepatosteatosis as well as its mechanism in high-fat diet (HFD)-fed type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats.MethodsTwenty-four-week-old male OLETF rats were assigned to four groups: control (saline), CK 10 mg/kg, CK 25 mg/kg, or metformin 300 mg/kg (positive control); all treatments were administered orally for 12 weeks.ResultsFasting glucose levels of the CK25 group were significantly lower than those of the control group during the 12 weeks. The results of the oral glucose tolerance test showed that both the glucose concentration after glucose loading and the fasting insulin levels of the CK25 group were significantly lower than those of the control. Hepatosteatosis was significantly improved by CK25. CK25 and metformin significantly increased the phosphorylation of hepatic adenosine monophosphate-activated protein kinase (AMPK). CK25 significantly inhibited the expression of sterol regulatory element-binding protein-1c and fatty acid synthase, while upregulating that of peroxisome proliferator-activated receptor-α and carnitine palmitoyltransferase-1.ConclusionsCK improved glucose intolerance and hepatosteatosis in HFD-fed OLETF rats through AMPK activation, which has dual mode of action that involves decreasing the synthesis of fatty acids and increasing fatty acid oxidation.

Melinjo (Gnetum gnemon) extract intake during lactation stimulates hepatic AMP-activated protein kinase in offspring of excessive fructose-fed pregnant rats

Excessive maternal fructose intake during pregnancy and in early postnatal life has metabolic consequences for the offspring. We investigated the effects of melinjo (Gnetum gnemon) extract (MeE) intake during lactation on the expression and phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) in the liver of offspring from excessive fructose-fed pregnant dams. Pregnant Wistar rats received a normal diet and 100g/L fructose solution during gestation ad libitum. At delivery, dams were divided into two groups: a control diet (FC) or a 0.1% MeE-containing diet (FM) fed during lactation. The dams that were not treated with fructose were fed a control diet (CC). At postnatal week 3, some pups were sacrificed, while the remaining continued to receive a normal diet and were sacrificed at week 17. Blood chemistry and phosphorylation levels of AMPK and acetyl-coenzyme A carboxylase (ACC) were evaluated. Plasma glucose levels in FC female offspring increased compared to that receiving CC at weeks 3 and 17; however, the levels in FM female offspring decreased at week 17. The insulin levels in FM female offspring decreased significantly compared to that in FC female offspring at week 3. Hepatic AMPK phosphorylation was upregulated in FM offspring at week 3 and in female, but not male, offspring at week 17. ACC phosphorylation in FM female offspring was upregulated at week 17. Our results suggest that maternal MeE intake during lactation may modulate the hepatic AMPK pathways in female offspring.

Involvement of adenosine monophosphate–activated protein kinase in the influence of timed high-fat evening diet on the hepatic clock and lipogenic gene expression in mice

A high-fat diet may result in changes in hepatic clock gene expression, but potential mechanisms are not yet elucidated. Adenosine monophosphate–activated protein kinase (AMPK) is a serine/threonine protein kinase that is recognized as a key regulator of energy metabolism and certain clock genes. Therefore, we hypothesized that AMPK may be involved in the alteration of hepatic clock gene expression under a high-fat environment. This study aimed to examine the effects of timed high-fat evening diet on the activity of hepatic AMPK, clock genes, and lipogenic genes. Mice with hyperlipidemic fatty livers were induced by orally administering high-fat milk via gavage every evening (19:00-20:00) for 6 weeks. Results showed that timed high-fat diet in the evening not only decreased the hepatic AMPK protein expression and activity but also disturbed its circadian rhythm. Accordingly, the hepatic clock genes, including clock, brain-muscle-Arnt-like 1, cryptochrome 2, and period 2, exhibited prominent changes in their expression rhythms and/or amplitudes. The diurnal rhythms of the messenger RNA expression of peroxisome proliferator–activated receptorα, acetyl-CoA carboxylase 1α, and carnitine palmitoyltransferase 1 were also disrupted; the amplitude of peroxisome proliferator–activated receptorγcoactivator 1α was significantly decreased at 3 time points, and fatty liver was observed. These findings demonstrate that timed high-fat diet at night can change hepatic AMPK protein levels, activity, and circadian rhythm, which may subsequently alter the circadian expression of several hepatic clock genes and finally result in the disorder of hepatic lipogenic gene expression and the formation of fatty liver.

The molecular basis of the antidiabetic action of quercetin in cultured skeletal muscle cells and hepatocytes

Background:Quercetin is universally distributed in the plant kingdom and is the most abundant flavonoid in the human diet. In a previous study, we have reported that quercetin stimulated glucose uptake in cultured C2C12 skeletal muscle through an insulin-independent mechanism involving adenosine monophosphate-activated protein kinase (AMPK). AMPK is a key regulator of the whole body-energy homeostasis. In skeletal muscle, activation of AMPK increases glucose uptake through the stimulation of the glucose transporter GLUT4 translocation to the plasma membrane. In liver, AMPK decreases glucose production mainly through the downregulation of the key gluconeogenesis enzymes such as phosphoenolpyruvate carboxylase (PEPCK) and Glucose -6-phosphate (G6Pase).Objective:To study the effect of quercetin on glucose homeostasis in muscle and liver.Materials and Methods:L6 skeletal muscle cells, murine H4IIE and human HepG2 hepatocytes were treated with quercetin (50 μM) for 18 h.Results:An 18 h treatment with quercetin (50 μM) stimulated AMPK and increased GLUT4 translocation and protein content in cultured rat L6 skeletal muscle cells. On the other hand, we report that quercetin induced hepatic AMPK activation and inhibited G6pase in H4IIE hepatocytes. Finally, we have observed that quercetin exhibited a mild tendency to increase the activity of glycogen synthase (GS), the rate-limiting enzyme of glycogen synthesis, in HepG2 hepatocytes.Conclusions:Overall, these data demonstrate that quercetin positively influences glucose metabolism in the liver and skeletal muscle, and therefore appear to be a promising therapeutic candidate for the treatment of in type 2 diabetes.

Enhanced AMPK phosphorylation contributes to the beneficial effects of Lactobacillus rhamnosus GG supernatant on chronic-alcohol-induced fatty liver disease

BackgroundWe have previously demonstrated that Lactobacillus rhamnosus GG culture supernatant (LGGs) prevents acute-alcohol-exposure-induced hepatic steatosis and injury. The protective effects of LGGs were attributed to the improved intestinal barrier function leading to decreased endotoxemia. The purpose of this study was to determine whether LGGs was effective in protecting against chronic-alcohol-induced hepatic steatosis and injury and to evaluate the underlying mechanisms of LGGs on hepatic lipid metabolism. MethodsC57BL/6N mice were fed liquid diet containing 5% alcohol or pair-fed isocaloric maltose dextrin for 4 weeks. LGGs at a dose equivalent to 109 CFU/day/mouse was given in the liquid diet. Hepatic steatosis, liver enzymes and hepatic apoptosis were analyzed. ResultsLGGs prevented alcohol-mediated increase in hepatic expression of lipogenic genes, sterol regulatory element binding protein-1 and stearoyl-CoA desaturase-1 and increased the expression of peroxisome proliferator activated receptor-α, peroxisome proliferator-activated receptor gamma coactivator protein-1α and carnitine palmitoyltransferase-1, leading to increased fatty acid β-oxidation. Importantly, chronic alcohol exposure decreased adenosine-monophosphate-activated protein kinase (AMPK) phosphorylation and increased acetyl-CoA carboxylase activity, which were attenuated by LGGs administration. LGGs also decreased Bax expression and increased Bcl-2 expression, which attenuated alcohol-induced hepatic apoptosis. These LGGs-regulated molecular changes resulted in the attenuation of chronic-alcohol-exposure-mediated increase in hepatic fat accumulation and liver injury. ConclusionsProbiotic LGG culture supernatant is effective in the prevention of chronic-alcohol-exposure-induced hepatic steatosis and injury. LGGs likely exerts its beneficial effects, at least in part, through modulation of hepatic AMPK activation and Bax/Bcl-2-mediated apoptosis.

Short-term calorie restriction improves glucose homeostasis in old rats: involvement of AMPK.

The occurrence of metabolic disorders, such as diabetes, obesity, atherosclerosis, and hypertension, increases with age. Inappropriate food intake, when combined with genetic and hormonal factors, can trigger the occurrence of these diseases in aged organisms. This study investigated whether short-term calorie restriction (CR; 40% of the intake of control animals (CTL) for 21 days) benefits 1-year-old (CR1yr) and 2-year-old (CR2yr) Wistar rats, with regard to insulin secretion and action. Plasma insulin and the insulin secreted by isolated islets were measured with radioimmunoassay, and the insulin sensitivity of peripheral tissues was assessed with the intraperitoneal glucose tolerance test (IPGTT), intraperitoneal insulin tolerance test, and hepatic and muscle adenosine monophosphate-activated protein kinase (AMPK) phosphorylation measurements. Body weight, epididymal fat pad, epididymal fat pad/body weight index, plasma glucose, and insulin were lower in the CR1yr than in the control (CTL1yr) rats. Serum cholesterol, triglycerides, and protein, as well as hepatic and muscle glycogen content, were similar between the CR and CTL groups. The IPGTT was higher in CR2yr and CTL2yr rats than in CR1yr and CTL1yr rats, and insulin sensitivity was higher in CR1yr and CR2yr rats than in their respective CTLs. This was associated with an increase in hepatic and muscle AMPK phosphorylation. No differences in glucose-induced insulin secretion in the isolated islets were observed between CRs and their respective CTL rats. In conclusion, short-term calorie restriction provoked more severe alterations in CR1yr than CR2yr rats. The normoglycemia observed in both CR groups seems to be due to an increase in insulin sensitivity, with the involvement of liver and muscle AMPK.

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

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. 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. 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). 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.

Consumption of Soy Protein Isolate Reduces Hepatic SREBP-1c and Lipogenic Gene Expression in Wild-Type Mice, but Not in FXR-Deficient Mice

We examined to determine whether hepatic gene expression is affected in mice in which blood lipid levels remain unchanged fed soy protein isolate (SPI) for a short time. We also examined SPI-mediated effects in farnesoid X receptor (FXR)-deficient mice. Compared with casein, SPI affected the expression of various hepatic genes related to lipid metabolism in the wild-type mice. No effects of SPI were observed in the FXR-deficient mice, suggesting the importance of FXR. Hepatic peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) gene expression was reduced by SPI, and this might be associated with a decrease in FXR expression. Decreased FXR led to decreased expression of its target, the bile-salt export pump necessary for bile acid secretion and dietary lipid absorption. The earliest response to SPI was a decrease in hepatic sterol regulatory element-binding protein (SREBP)-1c mRNA, on day 3. SPI activated hepatic adenosine monophosphate-activated protein kinase (AMPK), which can lead to a reduction in SREBP-1c mRNA. These data indicate the importance of SREBP-1c and PGC-1α/FXR in SPI-mediated alterations in hepatic gene expression.

A High‐Fat Diet Has a Tissue‐Specific Effect on Adiponectin and Related Enzyme Expression

This study was designed to test whether adiponectin plays a role in diet-induced obesity and insulin resistance and acts as a mediator to induce or inhibit specific metabolic pathways involved in lipid metabolism Forty C57BL/6J male mice were fed either a high-fat (HF) or control diet for 4 months, and adiponectin, its receptors, and enzyme expression in liver and muscle tissue were measured. Mice fed the HF diet exhibited significantly greater weight gain, abnormal oral glucose tolerance test curves, and elevated homeostasis model assessment of insulin resistance (5.3 +/- 0.89 vs. 2.8 +/- 0.39). A significant reduction of adiponectin RNA expression (51%) and protein levels (15%) was observed in the adipose tissue of HF animals; however, serum adiponectin levels did not differ between groups (7.12 +/- 0.34 mug/mL vs. 6.44 +/- 0.38 microg/mL). Expression of hepatic mRNA of AdipoR1 and AdipoR2 was reduced by 15% and 25%, respectively, in animals fed the HF diet. In contrast, receptor mRNA expression of AdipoR1 and AdipoR2 increased by 25% and 30%, respectively, in muscle tissue. No effect was found on hepatic adenosine monophosphate-activated protein kinase expression; however, a significant reduction of phosphoadenosine monophosphate kinase levels in muscles was observed. Hepatic acetyl-coenzyme A carboxylase was similar between groups, but in muscles, the inactive form phosphoacetyl-coenzyme A carboxylase was significantly reduced (p < 0.05). The HF diet led to decreased insulin sensitivity accompanied by impaired activity of adiponectin-related enzymes in skeletal muscles but not in the liver. These results suggest that the HF diet has a tissue-specific effect on adiponectin and associated enzyme expression.

Aging Elevates Basal Adenosine Monophosphate-Activated Protein Kinase (AMPK) Activity and Eliminates Hypoxic Activation of AMPK in Mouse Liver

Despite the central role of adenosine monophosphate-activated protein kinase (AMPK) in the cellular stress response, it is unknown whether age-related changes in AMPK activity play a role in the diminished stress tolerance that is characteristic of aging. To address this question, we determined in the mouse liver how normal aging affects 1) basal AMPK activity, and 2) the degree to which AMPK activity is increased by in vivo hypoxia. We found that the basal activity of AMPK alpha1, but not alpha2, was higher in livers from 24-month-old mice compared to those from 5-month-old mice. Furthermore, while hypoxia elevated AMPK alpha1 and alpha2 activities in livers from 5-month-old mice, hypoxia failed to increase the activity of either isoform of AMPK in 24-month-old mice. These findings suggest that age-associated changes in hepatic AMPK activity may play a role in the physiological changes that occur in the liver with normal aging.