Atractylenolide III ameliorates Non-Alcoholic Fatty Liver Disease by activating Hepatic Adiponectin Receptor 1-Mediated AMPK Pathway

Background: Nonalcoholic fatty liver disease (NAFLD) is the most frequent cause of chronic liver diseases worldwide. At present, there are no effective pharmacological therapies for NAFLD except lifestyle intervention-mediated weight loss. Atractylenolide III (ATL III), the major bioactive component found in Atractylode smacrocephala Koidz, has been shown to exert anti-oxidant, anti-tumor, anti-allergic response, anti-bacterial effects and cognitive protection. Here we investigate the therapeutic potential and underlying mechanisms of ATL III for the treatment of NAFLD.Methods: Male C57BL/6J mice were fed a high-fat diet (HFD) and treated with ATL III. Lipid accumulation was analyzed by Oil Red O staining in liver tissues and free fatty acids (FFAs)-treated hepatocytes. AMP-activated protein (AMPK) and sirtuin 1(SIRT1) signaling pathways were inhibited by Compound C and EX527 in vitro, respectively. Small-interfering RNA (siRNA) was used to knockdown adiponectin receptor 1 (AdipoR1) expression in HepG2 cells.Results: ATL III treatment ameliorated liver injury and hepatic lipid accumulation in the HFD-induced NAFLD mouse model as demonstrated by that ATL III administration significantly reduced serum levels of alanine aminotransferase, glutamic oxaloacetic transaminase, triglycerides, total cholesterol and low-density lipoprotein. Furthermore, treatment with ATL III alleviated hepatic oxidative stress, inflammation and fibrosis in the HFD feeding model. To study the underlying mechanisms, we performed Computer Aided Design assay and found that open-formed AdipoR1 and adiponectin receptor 2 were the potential receptors targeted by ATL III. Interestingly, HFD feeding or FFAs treatment only reduced hepatic AdipoR1 expression, while such reduction was abolished by ATL III administration. In addition, in vitro treatment with ATL III activated the AdipoR1 downstream AMPK /SIRT1 signaling pathway and reduced lipid deposition in HepG2 cells, which was diminished by silencing AdipoR1. Finally, inhibition of AMPK or SIRT1, the AdipoR1 downstream signaling, abolished the protective effects of ATL III on lipid deposition and oxidative stress in FFAs-treated HepG2 cells.Conclusion: Our findings suggest that ATL III is a therapeutic drug for the treatment of NAFLD and such protective effect is mediated by activating hepatic AdipoR1-mediated AMPK/SIRT1 signaling pathway.     

Niacin increases diet-induced hepatic steatosis in B6129 mice

Nonalcoholic fatty liver disease (NAFLD) is a very common disorder affecting between 20 and 30% of adults in the United States. However, there is no effective pharmacotherapy for treating NAFLD. Niacin, a water-soluble vitamin (B3), at pharmacological doses, decreases hepatic triglyceride (TG) content in NAFLD through inhibition of diacylglycerol acyltransferase 2, a key enzyme that catalyzes the final step in TG synthesis. Alternatively, some studies indicate that niacin induces fatty liver in high-fat diet (HFD)-fed rats. Therefore, in this study we investigated whether niacin is beneficial in treating NAFLD in two strains of mice, C57BL/6J (B6) and B6129SF2/J (B6129) mice, with 20 weeks of HFD feeding. Niacin treatment was started from week 5 until the end of the study. Niacin treatment increased normalized liver weight, hepatic TG content and NAFLD score in HFD-fed B6129 mice but had no impact on B6 mice. Metabolomics analysis revealed that in B6129 mice, 4-hydroxyphenylpyruvic acid (4-HPP), which is associated with fatty acid oxidation, did not change with HFD feeding but significantly decreased with niacin treatment. Lipidomics analysis discovered that the abundance of phosphocholine (PC), which is critical for very low-density lipoprotein (VLDL)–TG production and secretion, was decreased in HFD-fed B6129 with niacin treatment. In conclusion, niacin had no impact on diet-induced NAFLD development in B6 mice but potentiated hepatic steatosis in HFD-fed B6129 mice due to impaired fatty acid oxidation and decreased VLDL-TG production and secretion.     

The role of AMPKα2 in the HFD-induced nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is associated with hepatic steatosis, inflammation and liver fibrosis and has become one of the leading causes of hepatocellular carcinoma and liver failure. However, the underlying molecular mechanism of hepatic steatosis and the progression to nonalcoholic steatohepatitis (NASH) are not fully understood. Herein, we discovered that AMPKα2 catalytic subunit showed reduced expression in the liver following high fat diet (HFD) feeding to mice. Importantly, knockout of AMPKα2 in mice aggravated NAFLD, hepatic steatosis, inflammation and fibrosis. On the other hand, hepatocyte-targeted overexpression of AMPKα2 prevented or reversed NAFLD indications. In vivo mechanistic studies revealed that increased phosphorylation of IKKα/β and NF-κB in HFD-fed AMPKα2^−/− mice compared to WT mice, and treatment of these mouse cohorts with an inhibitor of NF-κB signaling for 4 weeks, effectively attenuated the progression of steatohepatitis and metabolic disorder features. In summary, AMPKα2 provides a protective role in the process of hepatic steatosis to NASH progression through suppression of liver NF-κB signaling.     

Mesenchymal stromal cells protect hepatocytes from lipotoxicity through alleviation of endoplasmic reticulum stress by restoring SERCA activity

The aim of this study was to investigate how mesenchymal stromal cells (MSCs) modulate metabolic balance and attenuate hepatic lipotoxicity in the context of non-alcoholic fatty liver disease (NAFLD). In vivo, male SD rats were fed with high-fat diet (HFD) to develop NAFLD; then, they were treated twice by intravenous injections of rat bone marrow MSCs. In vitro, HepG2 cells were cocultured with MSCs by transwell and exposed to palmitic acid (PA) for 24 hours. The endoplasmic reticulum (ER) stressor thapsigargin and sarco/ER Ca²⁺-ATPase (SERCA2)–specific siRNA were used to explore the regulation of ER stress by MSCs. We found that MSC administration improved hepatic steatosis, restored systemic hepatic lipid and glucose homeostasis, and inhibited hepatic ER stress in HFD-fed rats. In hepatocytes, MSCs effectively alleviated the cellular lipotoxicity. Particularly, MSCs remarkably ameliorated the ER stress and intracellular calcium homeostasis induced by either PA or thapsigargin in HepG2 cells. Additionally, long-term HFD or PA stimulation would activate pyroptosis in hepatocytes, which may contribute to the cell death and liver dysfunction during the process of NAFLD, and MSC treatment effectively ameliorates these deleterious effects. SERCA2 silencing obviously abolished the ability of MSCs against the PA-induced lipotoxicity. Conclusively, our study demonstrated that MSCs were able to ameliorate liver lipotoxicity and metabolic disturbance in the context of NAFLD, in which the regulation of ER stress and the calcium homeostasis via SERCA has played a key role.     

Short-term high-fat diet intake leads to exacerbation of concanavalin A-induced liver injury through the induction of procoagulation state

Obesity and high-fat diet (HFD) are known to cause proinflammatory and procoagulation states and suggested to become a risk of developing thromboembolic diseases. Non-alcoholic fatty liver disease (NAFLD) is usually associated with obesity and HFD, and a part of NAFLD is known to progress to nonalcoholic steatohepatitis (NASH), the pathogenesis of which has not been fully elucidated. In the current study, we examined the influence of short-term HFD on hepatic expression of the molecules related to inflammation, coagulation, metabolism, and cellular stresses from the perspective that HFD itself can be a risk for the development to NASH. In the analysis in short-term (4 days to 14 days) HFD-fed mice, we found out that HFD increased hepatic expression of IFN-γ, TNF-α, IL-10, monocyte chemotactic protein-1 (MCP-1), tissue factor (TF), plasminogen activator inhibitor-1 (PAI-1) mRNAs, and fibrin/fibrinogen deposition in the liver tissues. And it was suggested that metabolic alterations and endoplasmic reticulum (ER) stresses induced by the HFD intake were associated with this proinflammatory and procoagulation states. When we administered concanavalin A (Con A) to these HFD-fed mice, the extent of liver injury was dramatically exacerbated in HFD-fed mice. Heparin treatment to Con A-administered, HFD-fed mice (for 4 days) profoundly ameliorated the extent of liver injury. These suggest that even short-term of HFD intake induces proinflammatory and procoagulation states in the liver and thereby increases the susceptibility of the liver to circulating inflammatory stimuli. We think that it may explain a part of NASH pathogenesis.     

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

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

Capsaicin suppresses liver fat accumulation in high-fat diet-induced NAFLD mice

ABSTRACT

Dietary capsaicin exhibits anti-steatosis activity in obese mice. High-fat diet (HFD)-induced mice is a highly studied approach to develop non-alcoholic fatty liver disease (NAFLD). In this study, we determined whether the topical application of capsaicin can improve lesions of NAFLD. The HFD-induced mice were treated with daily topical application of capsaicin for 8 weeks. Topical application of capsaicin reduced liver fat in HFD-fed mice. Capsaicin stimulated carnitine palmitoyl transferase (CPT)-1 and CD36 expression, which are associated with β-oxidation and fatty acids influx of liver while it decreased the expression of key enzymes involved in the synthesis of fatty acids, such as acetyl Co-A carboxylase (ACC) and fatty acid synthase (FAS). Immunohistochemical analysis revealed the elevated level of adiponectin in liver tissue of the capsaicin-treated mice. These results suggest that the topical application of capsaicin suppresses liver fat accumulation through the upregulation of β-oxidation and de novo lipogenesis in HFD-induced NAFLD mice.     

UHRF1 depletion causes a G2/M arrest, activation of DNA damage response and apoptosis

The ECS (endocannabinoid system) plays an important role in the onset of obesity and metabolic disorders, implicating central and peripheral mechanisms predominantly via CB1 (cannabinoid type 1) receptors. CB1 receptor antagonist/inverse agonist treatment improves cardiometabolic risk factors and insulin resistance. However, the relative contribution of peripheral organs to the net beneficial metabolic effects remains unclear. In the present study, we have identified the presence of the endocannabinoid signalling machinery in skeletal muscle and also investigated the impact of an HFD (high-fat diet) on lipid-metabolism-related genes and endocannabinoid-related proteins. Finally, we tested whether administration of the CB1 inverse agonist AM251 restored the alterations induced by the HFD. Rats were fed on either an STD (standard/low-fat diet) or an HFD for 10 weeks and then treated with AM251 (3 mg/kg of body weight per day) for 14 days. The accumulated caloric intake was progressively higher in rats fed on the HFD than the STD, resulting in a divergence in body weight gain. AM251 treatment reduced accumulated food/caloric intake and body weight gain, being more marked in rats fed on the HFD. CB2 (cannabinoid type 2) receptor and PPARα (peroxisome-proliferator-activated receptor α) gene expression was decreased in HFD-fed rats, whereas MAGL (monoglyceride lipase) gene expression was up-regulated. These data suggest an altered endocannabinoid signalling as a result of the HFD. AM251 treatment reduced CB2 receptor, PPARγ and AdipoR1 (adiponectin receptor 1) gene expression in STD-fed rats, but only partially normalized the CB2 receptor in HFD-fed rats. Protein levels corroborated gene expression results, but also showed a decrease in DAGL (diacylglycerol) β and DAGLα after AM251 treatment in STD- and HFD-fed rats respectively. In conclusion, the results of the present study indicate a diet-sensitive ECS in skeletal muscle, suggesting that blockade of CB1 receptors could work towards restoration of the metabolic adaption imposed by diet.     

Moringa peregrina leaf extracts produce anti-obesity,hypoglycemic, anti-hyperlipidemic,and hepatoprotective effects on high-fat diet fed rats

This present research investigated the anti-obesity and hepatoprotective effects of ethanolic Moringa peregrina leaf (MPLE) and bark extracts (MPBE), in the rats fed with a high-fat diet (HFD). Healthy male rats (n = 48) were randomly distributed to six groups (n = 8): control AIN-93 diet; HFD; HFD + MPBE bark extracts ((300 mg/kg); HFD + MPBE (600 mg/kg); HFD + MPLE (300 mg/kg); HFD + MPLE (600 mg/kg). HFD-fed rats in the Moringa peregrina (MP) treatment groups received orally administered MP leaf or bark extract daily for eight weeks. The results revealed that both doses of MP leaf extract significantly reduced HFD-induced increases in their food intake and the gained body weight, fat pad weights (visceral, subcutaneous, and epididymal), glucose and insulin plasma levels, and leptin and resistin serum levels in HFD-fed rats. Concomitantly, MP leaf extract improved glucose levels after oral or intraperitoneal glucose tolerance tests, reduced serum cholesterol, triglycerides, and the low-density lipoprotein LDL concentration, reduced hepatic triglycerides and cholesterol levels, and increased serum high-density lipoproteins HDL levels and triglycerides and cholesterol levels in fecal. Moreover, the administration of MPLE to HFD-fed rats improved liver architecture, reduced fat accumulation, reduced hepatic malondialdehyde, tumor necrosis factor-α, and interleukin-6 levels. Hepatic glutathione peroxidase, superoxide dismutase, and catalase activities were significantly increased. All observed effects were more pronounced in HFD-fed rats treated with a 600 mg/kg MP dose. However, neither dose of MPBE altered the measured markers in the HFD-fed rats. In conclusion, MPLE showed potential anti-obesity and hepatoprotective activity in HFD-induced obese rats, mediated by reduced lipid absorption, anti-hyperlipidemic effects, and hepatic antioxidant effects.     

Modulation of gut microbiota contributes to curcumin-mediated attenuation of hepatic steatosis in rats

BackgroundStructural disruption of gut microbiota contributes to the development of non-alcoholic fatty liver disease (NAFLD) and modulating the gut microbiota represents a novel strategy for NAFLD prevention. Although previous studies have demonstrated that curcumin alleviates hepatic steatosis, its effect on the gut microbiota modulation has not been investigated.MethodsNext generation sequencing and multivariate analysis were utilized to evaluate the structural changes of gut microbiota in a NAFLD rat model induced by high fat-diet (HFD) feeding.ResultsWe found that curcumin attenuated hepatic ectopic fat deposition, improved intestinal barrier integrity, and alleviated metabolic endotoxemia in HFD-fed rats. More importantly, curcumin dramatically shifted the overall structure of the HFD-disrupted gut microbiota toward that of lean rats fed a normal diet and altered the gut microbial composition. The abundances of 110 operational taxonomic units (OTUs) were altered by curcumin. Seventy-six altered OTUs were significantly correlated with one or more hepatic steatosis associated parameters and designated ‘functionally relevant phylotypes’. Thirty-six of the 47 functionally relevant OTUs that were positively correlated with hepatic steatosis associated parameters were reduced by curcumin.ConclusionThese results indicate that curcumin alleviates hepatic steatosis in part through stain-specific impacts on hepatic steatosis associated phylotypes of gut microbiota in rats.General significanceCompounds with antimicrobial activities should be further investigated as novel adjunctive therapies for NAFLD.     

Chitosan reduces inflammation and protects against oxidative stress in a hyperlipidemic rat model: relevance to nonalcoholic fatty liver disease

Background

An altered lipid profile may lead to the development of inflammation and NAFLD (Non-alcoholic fatty liver disease). Although statins have a positive effect on blood lipid levels their long-term use is known to cause adverse effects, in this backdrop there is an interest in natural compounds which may affect lipid metabolism and prevent NAFLD. We have examined the effect of Chitosan on rats subjected to a high-fat diet.

Methods and results

Male Wistar middle aged rats (12–16 months) were treated with high-fat diet orally for two months for creating a NAFLD model. Rats were also supplemented with Chitosan (2% chitosan daily) for 2 months. We assessed the activity of antioxidant enzymes, the histopathological profile of the liver. Inflammatory cytokines and adiponectin levels were also measured in serum. HFD induced significant changes in liver tissue and inflammatory markers (Il-6, TNF- alpha, NF-KB). Chitosan treatment protected rats from HFD induced alterations.

Conclusions

The findings suggest that Chitosan can effectively improve liver lipid metabolism by normalizing cholesterol, triglyceride, lowering NF-KB expression, and protecting the liver from oxidative stress by improving hepatic function. Chitosan also regulates genes related to lipidemic stress i,e leptin and adiponectin.

     

Green Tea Extract Rich in Epigallocatechin-3-Gallate Prevents Fatty Liver by AMPK Activation via LKB1 in Mice Fed a High-Fat Diet

Supplementation with epigallocatechin-3-gallate has been determined to aid in the prevention of obesity. Decaffeinated green tea extract appears to restore a normal hepatic metabolic profile and attenuate high-fat diet (HFD)-induced effects, thereby preventing non-alcoholic fatty liver disease in mice. Mice were maintained on either a control diet (CD) or HFD for 16 weeks and supplemented with either water or green tea extract (50 mg/kg/day). The body mass increase, serum adiponectin level, and lipid profile were measured over the course of the treatment. Furthermore, the AMPK pathway protein expression in the liver was measured. From the fourth week, the weight gain in the CD + green tea extract (CE) group was lower than that in the CD + water (CW) group. From the eighth week, the weight gain in the HFD + water (HFW) group was found to be higher than that in the CW group. Moreover, the weight gain in the HFD + green tea extract (HFE) group was found to be lower than that in the HFW group. Carcass lipid content was found to be higher in the HFW group than that in the CW and HFE groups. Serum analysis showed reduced non-esterified fatty acid level in the CE and HFE groups as compared with their corresponding placebo groups. Increased adiponectin level was observed in the same groups. Increased VLDL-TG secretion was observed in the HFW group as compared with the CW and HFE groups. Increased protein expression of AdipoR2, SIRT1, pLKB1, and pAMPK was observed in the HFE group, which explained the reduced expression of ACC, FAS, SREBP-1, and ChREBP in this group. These results indicate that the effects of decaffeinated green tea extract may be related to the activation of AMPK via LKB1 in the liver of HFD-fed mice.     

Angiotensin II Reduces Cardiac AdipoR1 Expression through AT1 Receptor/ROS/ERK1/2/c-Myc Pathway

Adiponectin, an abundant adipose tissue-derived protein, exerts protective effect against cardiovascular disease. Adiponectin receptors (AdipoR1 and AdipoR2) mediate the beneficial effects of adiponectin on the cardiovascular system. However, the alteration of AdipoRs in cardiac remodeling is not fully elucidated. Here, we investigated the effect of angiotensin II (AngII) on cardiac AdipoRs expression and explored the possible molecular mechanism. AngII infusion into rats induced cardiac hypertrophy, reduced AdipoR1 but not AdipoR2 expression, and attenuated the phosphorylations of adenosine monophosphate-activated protein kinase and acetyl coenzyme A carboxylase, and those effects were all reversed by losartan, an AngII type 1 (AT1) receptor blocker. AngII reduced expression of AdipoR1 mRNA and protein in cultured neonatal rat cardiomyocytes, which was abolished by losartan, but not by PD123319, an AT2 receptor antagonist. The antioxidants including reactive oxygen species (ROS) scavenger NAC, NADPH oxidase inhibitor apocynin, Nox2 inhibitor peptide gp91 ds-tat, and mitochondrial electron transport chain complex I inhibitor rotenone attenuated AngII-induced production of ROS and phosphorylation of extracellular signal-regulated kinase (ERK) 1/2. AngII-reduced AdipoR1 expression was reversed by pretreatment with NAC, apocynin, gp91 ds-tat, rotenone, and an ERK1/2 inhibitor PD98059. Chromatin immunoprecipitation assay demonstrated that AngII provoked the recruitment of c-Myc onto the promoter region of AdipoR1, which was attenuated by PD98059. Moreover, AngII-induced DNA binding activity of c-Myc was inhibited by losartan, NAC, apocynin, gp91 ds-tat, rotenone, and PD98059. c-Myc small interfering RNA abolished the inhibitory effect of AngII on AdipoR1 expression. Our results suggest that AngII inhibits cardiac AdipoR1 expression in vivo and in vitro and AT1 receptor/ROS/ERK1/2/c-Myc pathway is required for the downregulation of AdipoR1 induced by AngII.     

Visfatin-induced lipid raft redox signaling platforms and dysfunction in glomerular endothelial cells

Adipokines have been reported to contribute to glomerular injury during obesity or diabetes mellitus. However, the mechanisms mediating the actions of various adipokines on the kidney remained elusive. The present study was performed to determine whether acid sphingomyelinase (ASM)-ceramide associated lipid raft (LR) clustering is involved in local oxidative stress in glomerular endothelial cells (GECs) induced by adipokines such as visfatin and adiponectin. Using confocal microscopy, visfatin but not adiponectin was found to increase LRs clustering in the membrane of GECs in a dose and time dependent manner. Upon visfatin stimulation ASMase activity was increased, and an aggregation of ASMase product, ceramide and NADPH oxidase subunits, gp91^phox and p47^phox was observed in the LR clusters, forming a LR redox signaling platform. The formation of this signaling platform was blocked by prior treatment with LR disruptor filipin, ASMase inhibitor amitriptyline, ASMase siRNA, gp91^phox siRNA and adiponectin. Corresponding to LR clustering and aggregation of NADPH subunits, superoxide (O₂^?) production was significantly increased (2.7 folds) upon visfatin stimulation, as measured by electron spin resonance (ESR) spectrometry. Functionally, visfatin significantly increased the permeability of GEC layer in culture and disrupted microtubular networks, which were blocked by inhibition of LR redox signaling platform formation. In conclusion, the injurious effect of visfatin, but not adiponectin on the glomerular endothelium is associated with the formation of LR redox signaling platforms via LR clustering, which produces local oxidative stress resulting in the disruption of microtubular networks in GECs and increases the glomerular permeability.     

Glucose and lipid metabolism alterations in liver and adipose tissue pre-dispose p47phox knockout mice to systemic insulin resistance

Oxidative stress due to enhanced production or reduced scavenging of reactive oxygen species (ROS) has been associated with diet (dyslipidemia) induced obesity and insulin resistance (IR). The present study was undertaken to assess the role of p47^phox in IR using wild type (WT) and p47^phox?/? mice, fed with different diets (HFD, LFD or Chow). Augmented body weight, glucose intolerance and reduced insulin sensitivity were observed in p47^phox?/? mice fed with 45% HFD and 10% LFD. Further, body fat and circulating lipids were increased significantly with 5 weeks LFD feeding in p47^phox?/? mice, while parameters of energy homeostasis were reduced as compared with WT mice. LFD fed knockout (KO) mice showed an enhanced hepatic glycogenolysis, and reduced insulin signalling in liver and adipose tissue, while skeletal muscle tissue remained unaffected. A significant increase in hepatic lipids, adiposity, as well as expression of genes regulating lipid synthesis, breakdown and efflux were observed in LFD fed p47^phox?/? mice after 5 weeks. On the other hand, mice lacking p47^phox demonstrated altered glucose tolerance and tissue insulin sensitivity after 5 weeks chow feeding, while changes in body weight, respiratory exchange ratio (RER) and heat production are non-significant. Our data demonstrate that lack of p47^phox is sufficient to induce IR through altered glucose and lipid utilization by the liver and adipose tissue.     

Targeting the gut microbiota with resveratrol: a demonstration of novel evidence for the management of hepatic steatosis

Resveratrol is a natural polyphenol that has been reported to reduce the risk of obesity and nonalcoholic fatty liver disease (NAFLD). Recent evidence has demonstrated that the gut microbiota plays an important role in the protection against NAFLD and other metabolic diseases. The present study aimed to investigate the relationship between the gut microbiota and the beneficial effects of resveratrol on the amelioration of NAFLD in mice. We observed marked decreases in body weight and liver steatosis and improved insulin resistance in high-fat diet (HFD)-fed mice treated with resveratrol. Furthermore, we found that resveratrol treatment alleviated NAFLD in HFD-fed mice by improving the intestinal microenvironment, including gut barrier function and gut microbiota composition. On the one hand, resveratrol improved gut intestinal barrier integrity through the repair of intestinal mucosal morphology and increased the expression of physical barrier- and physiochemical barrier-related factors in HFD-fed mice. On the other hand, in HFD-fed mice, resveratrol supplementation modulated the gut bacterial composition. The resveratrol-induced gut microbiota was characterized by a decreased abundance of harmful bacteria, including Desulfovibrio, Lachnospiraceae_NK4A316_group and Alistipes, as well as an increased abundance of short-chain fatty acid (SCFA)-producing bacteria, such as Allobaculum, Bacteroides and Blautia. Moreover, transplantation of the HFDR-microbiota into HFD-fed mice sufficiently decreased body weight, liver steatosis and low-grade inflammation and improved hepatic lipid metabolism. Collectively, resveratrol would provide a potentially dietary intervention strategy against NAFLD through modulating the intestinal microenvironment.     

Topiramate treatment causes skeletal muscle insulin sensitization and increased Acrp30 secretion in high-fat-fed male Wistar rats

We show that Topiramate (TPM) treatment normalizes whole body insulin sensitivity in high-fat diet (HFD)-fed male Wistar rats. Thus drug treatment markedly lowered glucose and insulin levels during glucose tolerance tests and caused increased insulin sensitization in adipose and muscle tissues as assessed by euglycemic clamp studies. The insulin-stimulated glucose disposal rate increased twofold (indicating enhanced muscle insulin sensitivity), and suppression of circulating FFAs increased by 200 to 300%, consistent with increased adipose tissue insulin sensitivity. There were no effects of TPM on hepatic insulin sensitivity in these TPM-treated HFD-fed rats. In addition, TPM administration resulted in a three- to fourfold increase in circulating levels of total and high-molecular-weight (HMW) adiponectin (Acrp30). Western blot analysis revealed normal AMPK (Thr(172)) phosphorylation in liver with a twofold increased phospho-AMPK in skeletal muscle in TPM-treated rats. In conclusion, 1) TPM treatment prevents overall insulin resistance in HFD male Wistar rats; 2) drug treatment improved insulin sensitivity in skeletal muscle and adipose tissue associated with enhanced AMPK phosphorylation; and 3) the tissue "specific" effects are associated with increased serum levels of adiponectin, particularly the HMW component.     

Ketogenic essential amino acids replacement diet ameliorated hepatosteatosis with altering autophagy-associated molecules

Ketogenic amino acid (KAA) replacement diet has been shown to cure hepatic steatosis, a serious liver disease associated with diverse metabolic defects. In this study, we investigated the effects of KAA replacement diet on nutrition sensing signaling pathway and analyzed whether induction of hepatic autophagy was involved. Mice are fed with high fat diet (HFD) or KAA replacement in high-fat diet (30% fat in food; HFD)-fed (HFD^KAAR) and sacrificed at 8, 12, 16 weeks after initiation of experimental food. Hepatic autophagy was analyzed in protein expression of several autophagy-associated molecules and in light chain-3 green fluorescent protein (LC-3 GFP) transgenic mice. HFD^KAAR showed increased AMP-activated protein kinase (AMPK) phosphorylation and enhanced liver kinase B1 (LKB1) expression compared to control HFD-fed mice. The KAA-HFD-induced activation of AMPK was associated with an increased protein expression of sirtuin 1 (Sirt1), decreased forkhead box protein O3a (Foxo3a) level, and suppression of mammalian target of rapamycin (mTOR) phosphorylation compared with the HFD-fed mice. The intervention study revealed that a KAA-replacement diet also ameliorated all the established metabolic and autophagy defects in the HFD-fed mice, suggesting that a KAA-replacement diet can be used therapeutically in established diseases. These results indicate that KAA replacement in food could be a novel strategy to combat hepatic steatosis and metabolic abnormalities likely involvement of an induction of autophagy.     

Effects of high fructose intake on the development of hypertension in the spontaneously hypertensive rats: the role of AT1R/gp91PHOX signaling in the rostral ventrolateral medulla

Both genetic and dietary factors determine the development of hypertension. Whether dietary factor impacts the development of hereditary hypertension is unknown. Here, we evaluated the effect of daily high-fructose diet (HFD) on the development of hypertension in adolescent spontaneously hypertensive rats (SHR). Six-week-old SHR were randomly divided into two groups to receive HFD or normal diet (ND) for 3 weeks. The temporal profile of systolic blood pressure, alongside the sympathetic vasomotor activity, in the SHR-HFD showed significantly greater increases at 9–12 weeks of age compared with the age-matched SHR-ND group. Immunofluorescence was used to identify the distribution of reactive oxygen species (ROS), oxidants and antioxidants in rostral ventrolateral medulla (RVLM) where sympathetic premotor neurons reside. In RVLM of SHR-HFD, the levels of ROS accumulation and lipid peroxidation were elevated. The changes in protein expression were measured by Western blot. NADPH oxidase subunit gp91^phox and angiotensin II type I receptor were up-regulated in RVLM neuron. On the other hand, the expression of extracellular superoxide dismutase was suppressed. Both molecular and hemodynamic changes in the SHR-HFD were rescued by oral pioglitazone treatment from weeks 7 to 9. Furthermore, central infusion with tempol, a ROS scavenger, effectively ameliorated ROS accumulation in RVLM and diminished the heightened pressor response and enhanced sympathetic activity in the SHR-HFD. Together, these results suggest that HFD intake at adolescent SHR may impact the development of hypertension via increasing oxidative stress in RVLM which could be effectively attenuated by pioglitazone treatment.