Atorvastatin prevents carbohydrate response element binding protein activation in the fructose-fed rat by activating protein kinase A

Diverting hepatic lipid fluxes with lifestyles revision and pharmacological interventions as a strategy to tackle steatotic liver disease (SLD) and hepatocellular carcinoma (HCC)

Steatotic liver disease (SLD) and Hepatocellular Carcinoma (HCC) are characterised by a substantial rewiring of lipid fluxes caused by systemic metabolic unbalances and/or disrupted intracellular metabolic pathways. SLD is a direct consequence of the interaction between genetic predisposition and a chronic positive energy balance affecting whole-body energy homeostasis and the function of metabolically-competent organs. In this review, we discuss how the impairment of the cross-talk between peripheral organs and the liver stalls glucose and lipid metabolism, leading to unbalances in hepatic lipid fluxes that promote hepatic fat accumulation. We also describe how prolonged metabolic stress builds up toxic lipid species in the liver, and how lipotoxicity and metabolic disturbances drive disease progression by promoting a chronic activation of wound healing, leading to fibrosis and HCC. Last, we provide a critical overview of current state of the art (pre-clinical and clinical evidence) regarding mechanisms of action and therapeutic efficacy of candidate SLD treatment options, and their potential to interfere with SLD/HCC pathophysiology by diverting lipids away from the liver therefore improving metabolic health.

Nanodrug regulates ROS homeostasis via enhancing fatty acid oxidation and inhibiting autophagy to overcome tumor drug resistance

The treatment of drug-resistant tumors poses a significant challenge in the field of tumor therapy. Disrupting the homeostasis of reactive oxygen species (ROS) within tumor cells may represent a pivotal strategy for overcoming the prevalent issue of drug resistance. However, the restricted sustainability of ROS generation and the increased autophagy capacity exhibited by tumor cells hinder the application of ROS-based therapies. In this study, we developed liposome nanoparticles (Ato/CQ@L) for co-encapsulation of atorvastatin (Ato), an activator of AMP-activated protein kinase (AMPK), and chloroquine (CQ), an autophagy inhibitor. Upon internalization by tumor cells, Ato upregulated carnitine palmitoyltransferase 1(CPT1) concentration and promoted fatty acid oxidation (FAO) within the tumor cells. The process of FAO coupled with an abundance of fatty acid substrates, facilitates a sustained generation of ROS production. Concurrently, a positive feedback loop is established between escalated concentration of ROS and AMPK protein levels, resulting in a persistent elevation in ROS levels. In addition, CQ disrupted lysosomes, leading to an increased lysosomal pH and reducing autophagy in tumor cells. In both in vivo and in vitro experiments, the Ato/CQ@L treatment group exhibited a considerable enhancement in tumor cell apoptosis, validating the efficacy of this combined therapy. In summary, the combined therapy involving Ato and CQ addresses the inherent limitations of conventional ROS therapy, which include insufficient ROS production and increased autophagy. This approach holds significant potential as a treatment strategy for drug-resistant triple-negative breast cancer.

Serum metabolomic signatures of fatty acid oxidation defects differentiate host-response subphenotypes of acute respiratory distress syndrome

BACKGROUND

Fatty acid oxidation (FAO) defects have been implicated in experimental models of acute lung injury and associated with poor outcomes in critical illness. In this study, we examined acylcarnitine profiles and 3-methylhistidine as markers of FAO defects and skeletal muscle catabolism, respectively, in patients with acute respiratory failure. We determined whether these metabolites were associated with host-response ARDS subphenotypes, inflammatory biomarkers, and clinical outcomes in acute respiratory failure.

METHODS

In a nested case-control cohort study, we performed targeted analysis of serum metabolites of patients intubated for airway protection (airway controls), Class 1 (hypoinflammatory), and Class 2 (hyperinflammatory) ARDS patients (N = 50 per group) during early initiation of mechanical ventilation. Relative amounts were quantified by liquid chromatography high resolution mass spectrometry using isotope-labeled standards and analyzed with plasma biomarkers and clinical data.

RESULTS

Of the acylcarnitines analyzed, octanoylcarnitine levels were twofold increased in Class 2 ARDS relative to Class 1 ARDS or airway controls (P = 0.0004 and < 0.0001, respectively) and was positively associated with Class 2 by quantile g-computation analysis (P = 0.004). In addition, acetylcarnitine and 3-methylhistidine were increased in Class 2 relative to Class 1 and positively correlated with inflammatory biomarkers. In all patients within the study with acute respiratory failure, increased 3-methylhistidine was observed in non-survivors at 30 days (P = 0.0018), while octanoylcarnitine was increased in patients requiring vasopressor support but not in non-survivors (P = 0.0001 and P = 0.28, respectively).

CONCLUSIONS

This study demonstrates that increased levels of acetylcarnitine, octanoylcarnitine, and 3-methylhistidine distinguish Class 2 from Class 1 ARDS patients and airway controls. Octanoylcarnitine and 3-methylhistidine were associated with poor outcomes in patients with acute respiratory failure across the cohort independent of etiology or host-response subphenotype. These findings suggest a role for serum metabolites as biomarkers in ARDS and poor outcomes in critically ill patients early in the clinical course.

Improving Management of Portal Hypertension: The Potential Benefit of Non-Etiological Therapies in Cirrhosis

Portal hypertension is the consequence of cirrhosis and results from increased sinusoidal vascular resistance and hepatic blood inflow. Etiological therapies represent the first intervention to prevent a significant increase in portal pressure due to chronic liver damage. However, other superimposed pathophysiological drivers may worsen liver disease, including inflammation, bacterial translocation, endothelial dysfunction, and hyperactivation of hemostasis. These mechanisms can be targeted by a specific class of drugs already used in clinical practice. Albumin, rifaximin, statins, aspirin, and anticoagulants have been tested in cirrhosis and were a topic of discussion in the last Baveno consensus as non-etiological therapies. Based on the pathogenesis of portal hypertension in cirrhosis, our review summarizes the main mechanisms targeted by these drugs as well as the clinical evidence that considers them a valid complementary option to manage patients with cirrhosis and portal hypertension.

Sugar-Sweetened Beverage, Diet Soda, and Nonalcoholic Fatty Liver Disease Over 6 Years: The Framingham Heart Study

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is associated with sugar-sweetened beverage (SSB) consumption in cross-sectional studies. In a prospective cohort, we examined the association of beverage consumption (SSB and diet soda) with incident NAFLD and changes in hepatic fat in the Framingham Heart Study (FHS).

METHODS

We conducted a prospective observational study of participants from the FHS Third Generation and Offspring cohorts who participated in computed tomography sub-studies. Participants were classified according to their average SSB or diet soda consumption, which was derived from baseline and follow-up food frequency questionnaires: non-consumers (0-<1/month), occasional consumers (1/month-<1/week), and frequent consumers (≥1/week-≥1/day). Hepatic fat was quantified by the liver fat attenuation measurements on computed tomography scan. The primary dependent variable was incident NAFLD; secondarily, we investigated change in liver fat.

RESULTS

The cohorts included 691 Offspring (mean age, 62.8 ± 8.2 years; 57.7% women) and 945 Third Generation participants (mean age, 48.4 ± 6.3 years; 46.6% women). In the Offspring cohort, there was a dose-response relationship with SSB consumption and incident NAFLD. Frequent SSB consumers had 2.53 times increased odds of incident NAFLD compared with non-consumers (95% confidence interval, 1.36-4.7) after multivariable analysis. For Offspring cohort participants, occasional and frequent consumers of SSB had a more adverse increase in liver fat compared with non-consumers.

CONCLUSIONS

Higher average SSB intake is associated with increase in liver fat over 6 years of follow-up and increased odds of incident NAFLD especially among the older cohort, whereas no consistent association was observed for the younger Third Generation cohort.

Vitamin D3 intake as modulator for the early biomarkers of myocardial tissue injury in diabetic hyperlipidaemic rats

CONTEXT

Myocardial cell death occurs within hours following the onset of myocardial ischaemia and its chief cause is atherosclerosis. There is a link between vitamin D3 deficiency and many cardiovascular risk factors.

OBJECTIVE

This study compared the effect of vitamin D3 on early biomarkers of myocardial injury, to that of atorvastatin.

METHODS

Diabetic hyperlipidaemia was induced in Wistar rats, which were divided into 3 groups: diabetic hyperlipidaemic control, diabetic hyperlipidaemic rats treated with atorvastatin and diabetic hyperlipidaemic rats treated with vitamin D3. Blood glucose, glycated haemoglobin and lipid profile were evaluated. Markers of myocardial injury were examined including cardiac troponin, heart fatty acid binding protein (HFABP) and C-terminal pro-endothelin-1 (CT-pro-ET-1).

RESULTS

Vitamin D3 and atorvastatin intake improved lipid profile and glucose homeostasis, and reduced levels of predictive biomarkers of myocardial injury.

CONCLUSION

Vitamin D3 can be used in a suitable dose as a safe and protective candidate against myocardial injury.

The ameliorative effect of Apium graveolens & curcumin against Non-alcoholic fatty liver disease induced by high fructose-high fat diet in rats

Background

Non-alcoholic fatty liver disease (NAFLD) is a condition resulting from fat aggregates in liver cells and is associated with metabolic syndrome, obesity, and oxidative stress. The present work was designed to investigate the role of celery and curcumin against high-fructose–high-fat (HFHF) diet-induced NAFLD in rats. Thirty male rats were classified into five groups: GP1: control group (rats were fed a normal control diet), GP2: HFHF group as a positive control (rats were fed a HFHF diet) for 20 weeks, GP3: HFHF + sily group, GP4: HFHF + celery group, and GP5: HFHF + cur group (rats in 3, 4, and 5 were treated as in the HFHF group for 16 weeks, then combined treatment daily by gavage for 4 weeks with either silymarin (as a reference drug, 50 mg/kg bw) or celery (300 mg/kg bw) or curcumin (200 mg/kg bw), respectively. The progression of NAFLD was evaluated by estimating tissue serum liver enzymes, glycemic profile, lipid profile, oxidative stress markers in liver tissue, and histopathological examination. Moreover, DNA fragmentation and the released lysosomal enzymes (acid phosphatase, β-galactosidase, and N-acetyl-B-glucosaminidase) were estimated.

Results

Our results showed that HFHF administration for 16 weeks caused liver enzymes elevation, hyperglycemia, and hyperlipidemia. Furthermore, increased hepatic MDA levels along with a decline in GSH levels were observed in the HFHF group as compared to the control group. The results were confirmed by a histopathological study, which showed pathological changes in the HFHF group. DNA fragmentation was also observed, and the lysosomal enzyme activities were increased. On the other hand, oral supplementation of celery and cur improved all these changes compared with positive control groups and HFHF + sily (as a reference drug). Moreover, celery, as well as curcumin co-treatment, reduced HFHF-enhanced DNA fragmentation and inhibited elevated lysosomal enzymes. The celery combined treatment showed the most pronounced ameliorative impact, even more than silymarin did.

Conclusion

Our findings suggest that celery and curcumin consumption may exhibit ameliorative impacts against NALFD progression, while celery showed more ameliorative effect in all parameters.

Dietary Macronutrient Composition Differentially Modulates the Remodeling of Mitochondrial Oxidative Metabolism during NAFLD

Diets rich in fats and carbohydrates aggravate non-alcoholic fatty liver disease (NAFLD), of which mitochondrial dysfunction is a central feature. It is not clear whether a high-carbohydrate driven ‘lipogenic’ diet differentially affects mitochondrial oxidative remodeling compared to a high-fat driven ‘oxidative’ environment. We hypothesized that the high-fat driven ‘oxidative’ environment will chronically sustain mitochondrial oxidative function, hastening metabolic dysfunction during NAFLD. Mice (C57BL/6NJ) were reared on a low-fat (LF; 10% fat calories), high-fat (HF; 60% fat calories), or high-fructose/high-fat (HFr/HF; 25% fat and 34.9% fructose calories) diet for 10 weeks. De novo lipogenesis was determined by measuring the incorporation of deuterium from D₂O into newly synthesized liver lipids using nuclear magnetic resonance (NMR) spectroscopy. Hepatic mitochondrial metabolism was profiled under fed and fasted states by the incubation of isolated mitochondria with [¹³C₃]pyruvate, targeted metabolomics of tricarboxylic acid (TCA) cycle intermediates, estimates of oxidative phosphorylation (OXPHOS), and hepatic gene and protein expression. De novo lipogenesis was higher in the HFr/HF mice compared to their HF counterparts. Contrary to our expectations, hepatic oxidative function after fasting was induced in the HFr/HF group. This differential induction of mitochondrial oxidative function by the high fructose-driven ‘lipogenic’ environment could influence the progressive severity of hepatic insulin resistance.

Statins and nonalcoholic fatty liver disease in the era of precision medicine: More friends than foes

Nonalcoholic fatty liver disease (NAFLD) describes a spectrum of alcohol-like hepatic histological changes, which occur in the absence of any competing causes of chronic liver disease, notably including significant alcohol consumption. A close and bi-directional relationship links NAFLD with the metabolic syndrome (MetS), and concurrent MetS will hasten the progression to more severe forms of NAFLD, including cirrhosis and hepatocellular carcinoma (HCC). Patients with NAFLD will typically exhibit atherogenic dyslipidemia and increased cardiovascular risk (CVR). Statins are among the most widely prescribed lipid-lowering drugs. Their use has historically been hampered, in individuals with liver disease, owing to the fear of hepatotoxicity. However, studies suggest that statins are not only effective in reducing cardiovascular events, but may also exert multiple beneficial effects on the liver. CVR in those with NAFLD has extensively been covered by our group and others. This updated clinical narrative review will critically examine the effects of statins on the pathogenesis of NAFLD, including the key elementary pathological lesions of NAFLD, i.e. steatosis, inflammation and fibrosis, and its liver-related complications, i.e. cirrhosis, portal hypertension and HCC.

Raw orange intake is associated with higher prevalence of non-alcoholic fatty liver disease in an adult population

OBJECTIVES

Non-alcoholic fatty liver disease (NAFLD) is one of the most common public health issues worldwide. Oranges are the most popular fruit consumed in the world. Admittedly, flavonoids in oranges act as antioxidants and improve liver steatosis. However, oranges also are rich in fructose, which is a risk factor in the progress of NAFLD. Therefore, we hypothesize that orange intake may be a double-edged sword in the development of NAFLD. To our knowledge, there currently is little evidence of the effect of dietary orange intake on NAFLD. The aim of this study was to investigate how orange intake is related to NAFLD in a general adult population.

METHODS

We randomly recruited 27,214 adults into the Tianjin Chronic Low-Grade Systemic Inflammation and Health Cohort Study. NAFLD was diagnosed by liver ultrasonography. Raw orange intake was assessed by a validated self-administered food frequency questionnaire. Multiple logistic regression analysis was used to evaluate the association between orange intake and the prevalence of NAFLD.

RESULTS

There was a 27.18% prevalence of NAFLD among the participants. Consumption of orange was positively associated with the prevalence of NAFLD after adjustment for all potential confounding factors (P_trend = 0.04). The odds ratios (95% confidence interval) of the categories of orange intake in the NAFLD were 1.00 (reference) for less than once per week, 1.02 (0.95-1.11) for 1 to 6 times per week, and 1.17 (1.03-1.33) for ≥7 times per week, respectively.

CONCLUSIONS

The present study demonstrated that orange intake is positively associated with the prevalence of NAFLD.

Hepatic regulation of VLDL receptor by PPARβ/δ and FGF21 modulates non-alcoholic fatty liver disease

Objective

The very low-density lipoprotein receptor (VLDLR) plays an important role in the development of hepatic steatosis. In this study, we investigated the role of Peroxisome Proliferator-Activated Receptor (PPAR)β/δ and fibroblast growth factor 21 (FGF21) in hepatic VLDLR regulation.

Methods

Studies were conducted in wild-type and Pparβ/δ-null mice, primary mouse hepatocytes, human Huh-7 hepatocytes, and liver biopsies from control subjects and patients with moderate and severe hepatic steatosis.

Results

Increased VLDLR levels were observed in liver of Pparβ/δ-null mice and in Pparβ/δ-knocked down mouse primary hepatocytes through mechanisms involving the heme-regulated eukaryotic translation initiation factor 2α (eIF2α) kinase (HRI), activating transcription factor (ATF) 4 and the oxidative stress-induced nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathways. Moreover, by using a neutralizing antibody against FGF21, Fgf21-null mice and by treating mice with recombinant FGF21, we show that FGF21 may protect against hepatic steatosis by attenuating endoplasmic reticulum (ER) stress-induced VLDLR upregulation. Finally, in liver biopsies from patients with moderate and severe hepatic steatosis, we observed an increase in VLDLR levels that was accompanied by a reduction in PPARβ/δ mRNA abundance and DNA-binding activity compared with control subjects.

Conclusions

Overall, these findings provide new mechanisms by which PPARβ/δ and FGF21 regulate VLDLR levels and influence hepatic steatosis development.

•

PPARβ/δ deficiency leads to increased levels of hepatic VLDLR levels.

•

FGF21 protects against hepatic steatosis by attenuating ER stress-induced VLDLR upregulation.

•

Human hepatic steatosis is accompanied by increased levels of VLDLR and reduced expression of PPARβ/δ.

•

PPARβ/δ and FGF21 may influence NAFLD development by regulating VLDLR levels.

Added fructose as a principal driver of non-alcoholic fatty liver disease: a public health crisis

Fatty liver disease affects up to one out of every two adults in the western world. Data from animal and human studies implicate added sugars (eg, sucrose and high-fructose corn syrup) in the development of fatty liver disease and its consequences. Added fructose in particular, as a component of added sugars, may pose the greatest risk for fatty liver disease. Considering that there is no requirement for added sugars in the diet, dietary guidelines should recommend reducing the intake of added sugars to just 5% of total calories in order to decrease the prevalence of fatty liver disease and its related consequences.

Atorvastatin reduces lipid accumulation in the liver by activating protein kinase A-mediated phosphorylation of perilipin 5

Statins have been proven to be effective in treating non-alcoholic fatty liver disease (NAFLD). Recently, it was reported that statins decreased the hepatic expression of perilipin 5 (Plin5), a lipid droplet (LD)-associated protein, which plays critical roles in regulating lipid accumulation and lipolysis in liver. However, the function and regulation mechanism of Plin5 have not yet been well-established in NAFLD treatment with statins. In this study, we observed that atorvastatin moderately reduced the expression of Plin5 in livers without changing the protein level of Plin5 in the hepatic LD fraction of mice fed with high-fat diet (HFD). Intriguingly, atorvastatin stimulated the PKA-mediated phosphorylation of Plin5 and reduced the triglyceride (TG) accumulation in hepatocytes with overexpression of wide type (Plin5-WT) compared to serine-155 mutant Plin5 (Plin5-S155A). Moreover, PKA-stimulated FA release of purified LDs carrying Plin5-WT but not Plin5-S155A. Glucagon, a PKA activator, stimulated the phosphorylation of Plin5-WT and inhibited its interaction with CGI-58. The results indicated that atorvastatin promoted lipolysis and reduced TG accumulation in the liver by increasing PKA-mediated phosphorylation of Plin5. This new mechanism of lipid-lowering effects of atorvastatin might provide a new strategy for NAFLD treatment.

Fructose-rich diet differently affects angiotensin II receptor content in the nucleus and a plasma membrane fraction of visceral adipose tissue

The adipose tissue renin-angiotensin system (RAS) is proposed to be a pathophysiological link between adipose tissue dysregulation and metabolic disorders induced by a fructose-rich diet (FRD). RAS can act intracellularly. We hypothesized that adipocyte nuclear membranes possess angiotensin receptor types 1 and 2 (AT1R and AT2R), which couple to nuclear signaling pathways and regulate oxidative gene expression under FRD conditions. We analyzed the effect of consumption of 10% fructose solution for 9 weeks on biochemical parameters, adipocyte morphology, and expression of AT1R, AT2R, AT1R-associated protein (ATRAP), NADPH oxidase 4 (NOX4), matrix metalloproteinase-9 (MMP-9), and manganese superoxide dismutase (MnSOD) in adipose tissue of Wistar rats. We detected AT1R and AT2R in the nuclear fraction. FRD reduced the level of angiotensin receptors in the nucleus, while increased AT1R and decreased AT2R levels were observed in the plasma membrane. FRD increased the ATRAP mRNA level and decreased MnSOD mRNA and protein levels. No significant differences were observed for MMP-9 and NOX4 mRNA levels. These findings coincided with hyperleptinemia, elevated blood pressure and triglycerides, and unchanged visceral adipose tissue mass and morphology in FRD rats. Besides providing evidence for nuclear localization of angiotensin receptors in visceral adipose tissue, this study demonstrates the different effects of FRD on AT1R expression in different cellular compartments. Elevated blood pressure and decreased antioxidant capacity in visceral fat of fructose-fed rats were accompanied by an increased AT1R level in the plasma membrane, while upregulation of ATRAP and a decrease of nuclear membrane AT1R suggest an increased capacity for attenuation of excessive AT1R signaling and visceral adiposity.

Rosuvastatin limits the activation of hepatic stellate cells in diet-induced obese mice

AIM

The aim of this study was to investigate the effects of rosuvastatin in a model of diet-induced obesity and non-alcoholic fatty liver disease, with attention to the activation of hepatic stellate cells (HSCs).

METHOD

Male C57BL/6 mice received a control diet (C; 10% energy as lipids) or a high-fat diet (HF; 50% energy as lipids) for 12 weeks, followed by 7 weeks of treatment. Group CR received control diet + rosuvastatin; group HFR received high-fat diet + rosuvastatin.

RESULTS

The HF group showed higher insulin, total cholesterol, triacylglycerol, and leptin levels than the C group, all of which were significantly diminished by rosuvastatin in the HFR group. The HF group had greater steatosis and activated HSCs than the C group, whereas rosuvastatin diminished the steatosis (less 21%, P < 0.001) and significantly inhibited the activation of the HSCs in the HFR group compared to the HF group. The sterol regulatory element-binding protein-1 and the peroxisome proliferator-activated receptor (PPAR)-γ protein expressions were increased in HF animals and reduced after treatment in the HFR group. By contrast, low PPAR-α and carnitine palmitoyltransferase-1 expressions were found in the HF group, and were restored by rosuvastatin treatment in the HFR group.

CONCLUSION

Rosuvastatin mitigated hepatic steatosis by modulating PPAR balance, favoring PPAR-α over PPAR-γ downstream effects. The effects were accompanied by a diminishing of insulin resistance, the anti-inflammatory adipokine profile, and HSC activation, avoiding non-alcoholic fatty liver disease progression and non-alcoholic steatohepatitis onset in this model.

Response of genes involved in lipid metabolism in rat epididymal white adipose tissue to different fasting conditions after long-term fructose consumption

There has been much concern regarding the dietary fructose contributes to the development of metabolic syndrome. High-fructose diet changes the expression of genes involved in lipid metabolism. Levels of a number of hepatic lipogenic enzymes are increased by a high-carbohydrate diet in fasted-refed model rats/mice. Both the white adipose tissue (WAT) and the liver play a key role in the maintenance of nutrient homeostasis. Here, the aim of this study was to analyze the expression of key genes related to lipid metabolism in epididymal WAT (eWAT) in response to different fasting condition after long-term chronic fructose consumption. Rats were fed standard chow supplemented with 10% w/v fructose solution for 5 weeks, and killed after chow-fasting and fructose withdrawal (fasting) or chow-fasting and continued fructose (fructose alone) for 14 h. Blood parameters and the expression of genes involved in fatty acid synthesis (ChREBP, SREBP-1c, FAS, SCD1), triglyceride biosynthesis (DGAT-1, DGAT-2) and lipid mobilization (ATGL, HSL) in eWAT were analyzed. In addition, mRNA levels of PPAR-γ, CD36 and LPL were also detected. As expected, fructose alone increased the mRNA expression of FAS, SCD1, and correspondingly decreased ATGL and HSL mRNA levels. However, ChREBP, DGAT-2, ATGL and HSL mRNA levels restored near to normal while FAS and SCD1 tend to basic level under fasting condition. The mRNA expression of SREBP-1c, PPAR-γ and LPL did not changed at any situations but CD36 mRNA decreased remarkably in fructose alone group. In conclusion, these findings demonstrate that genes involved in lipid metabolism in rat eWAT are varied in response to different fasting conditions after long-term fructose consumption.

Effect of different doses of statins on the development of type 2 diabetes mellitus in patients with myocardial infarction

BACKGROUND

Cardiovascular diseases and type 2 diabetes mellitus (T2DM) may have common developmental mechanisms associated with lipid metabolism disorders. Dyslipidemia and progression of atherosclerosis in people with T2DM are accompanied by an increase in cardiovascular mortality. This study examined the dose-dependent action of atorvastatin on carbohydrate metabolism and adipokine status in patients within 12 months after myocardial infarction (MI).

METHODS

A total of 156 male MI patients who had received atorvastatin 20 mg/day (78 patients) or 40 mg/day (78 patients) starting from day 1 of onset were enrolled. Glucose, insulin, C-peptide, resistin, adiponectin, and ghrelin levels were measured at baseline, day 12, and months 3 and 12. Patients were monitored for new incidences of T2DM for 12 months after MI.

RESULTS

For acute phase MI, patients had moderate insulin resistance, hyperglycemia, and hyper-insulinemia, high leptin and resistin levels, and low ghrelin and adiponectin levels. Atorvastatin 20 mg/day was more effective at correcting the imbalances. Patients taking atorvastatin 40 mg/day (group 2) following MI showed increases in levels of glucose, insulin, and C-peptide and insulin resistance progression after 12 months of therapy, as evidenced by increased quantitative insulin sensitivity check index scores and detection of new T2DM cases.

CONCLUSION

Atorvastatin improved adipokine profiles and ghrelin levels, with low doses showing more significant effects. Atorvastatin dose prescribed for MI patients should take into account the degree of insulin resistance and adipokine status.

Effect of dietary n-3 fatty acids supplementation on fatty acid metabolism in atorvastatin-administered SHR.Cg-Leprcp/NDmcr rats, a metabolic syndrome model

The effects of cholesterol-lowering statins, which substantially benefit future cardiovascular events, on fatty acid metabolism have remained largely obscured. In this study, we investigated the effects of atorvastatin on fatty acid metabolism together with the effects of TAK-085 containing highly purified eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) ethyl ester on atorvastatin-induced n-3 polyunsaturated fatty acid lowering in SHR.Cg-Lepr^cp/NDmcr (SHRcp) rats, as a metabolic syndrome model. Supplementation with 10mg/kg body weight/day of atorvastatin for 17 weeks significantly decreased plasma total cholesterol and very low density lipoprotein cholesterol. Atorvastatin alone caused a subtle change in fatty acid composition particularly of EPA and DHA in the plasma, liver or erythrocyte membranes. However, the TAK-085 consistently increased both the levels of EPA and DHA in the plasma, liver and erythrocyte membranes. After confirming the reduction of plasma total cholesterol, 300mg/kg body weight/day of TAK-085 was continuously administered for another 6 weeks. Supplementation with TAK-085 did not decrease plasma total cholesterol but significantly increased the EPA and DHA levels in both the plasma and liver compared with rats administered atorvastatin only. Supplementation with atorvastatin alone significantly decreased sterol regulatory element-binding protein-1c, Δ5- and Δ6-desaturases, elongase-5, and stearoyl-coenzyme A (CoA) desaturase-2 levels and increased 3-hydroxy-3-methylglutaryl-CoA reductase mRNA expression in the liver compared with control rats. TAK-085 supplementation significantly increased stearoyl-CoA desaturase-2 mRNA expression. These results suggest that long-term supplementation with atorvastatin decreases the EPA and DHA levels by inhibiting the desaturation and elongation of n-3 fatty acid metabolism, while TAK-085 supplementation effectively replenishes this effect in SHRcp rat liver.

The transcription factor carbohydrate-response element-binding protein (ChREBP): A possible link between metabolic disease and cancer

Carbohydrate-response element-binding protein (ChREBP) has been identified as a transcription factor that binds to carbohydrate response element in the promoter of pyruvate kinase, liver and red blood cells. ChREBP is activated by metabolites derived from glucose and suppressed by adenosine monophosphate (AMP), ketone bodies and cyclic cAMP. ChREBP regulates gene transcription related to glucose and lipid metabolism. Findings from knockout mice and human subjects suggest that ChREBP helps to induce hepatic steatosis, dyslipidemia, and glucose intolerance. Moreover, in tumor cells, ChREBP promotes aerobic glycolysis through p53 inhibition, resulting in tumor cell proliferation. Anti-diabetic and anti-lipidemic drugs such as atorvastatin, metformin, bile acid sequestrants, docosahexaenoic acid and eicosapentaenoic acid may affect ChREBP transactivity. Secretory proteins such as fibroblast growth factor 21 and ANGPTL8 (Betatrophin) may be promising candidates for biologic markers reflecting ChREBP transactivity. Thus, ChREBP is associated with metabolic diseases and cancers, and may be a link between them.

Transient Decrease in Circulatory Testosterone and Homocysteine Precedes the Development of Metabolic Syndrome Features in Fructose-Fed Sprague Dawley Rats

Background. Increased fructose consumption is linked to the development of metabolic syndrome (MS). Here we investigated the time course of development of MS features in high-fructose-fed Sprague Dawley rats along with circulatory testosterone and homocysteine levels. Methods. Rats were divided into control and experimental groups and fed with diets containing 54.5% starch and fructose, respectively, for 4, 12, and 24 weeks. Plasma testosterone and homocysteine levels were measured along with insulin, glucose, and lipids. Body composition, insulin resistance, and hepatic lipids were measured. Results. Increase in hepatic triglyceride content was first observed in metabolic disturbance followed by hypertriglyceridemia and systemic insulin resistance in fructose-fed rats. Hepatic lipids were increased in time-dependent manner by fructose-feeding starting from 4 weeks, but circulatory triglyceride levels were increased after 12 weeks. Fasting insulin and Homeostatis Model Assessment of Insulin Resistance (HOMA-IR) were increased after 12 weeks of fructose-feeding. Decreased visceral adiposity, circulatory testosterone, and homocysteine levels were observed after 4 weeks of fructose-feeding, which were normalized at 12 and 24 weeks. Conclusions. We conclude that transient decrease in circulatory testosterone and homocysteine levels and increased hepatic triglyceride content are the earliest metabolic disturbances that preceded hypertriglyceridemia and insulin resistance in fructose-fed SD rats.

Statins Increase Mitochondrial and Peroxisomal Fatty Acid Oxidation in the Liver and Prevent Non-Alcoholic Steatohepatitis in Mice

BACKGROUND

Non-alcoholic fatty liver disease is the most common form of chronic liver disease in industrialized countries. Recent studies have highlighted the association between peroxisomal dysfunction and hepatic steatosis. Peroxisomes are intracellular organelles that contribute to several crucial metabolic processes, such as facilitation of mitochondrial fatty acid oxidation (FAO) and removal of reactive oxygen species through catalase or plasmalogen synthesis. Statins are known to prevent hepatic steatosis and non-alcoholic steatohepatitis (NASH), but underlying mechanisms of this prevention are largely unknown.

METHODS

Seven-week-old C57BL/6J mice were given normal chow or a methionine- and choline-deficient diet (MCDD) with or without various statins, fluvastatin, pravastatin, simvastatin, atorvastatin, and rosuvastatin (15 mg/kg/day), for 6 weeks. Histological lesions were analyzed by grading and staging systems of NASH. We also measured mitochondrial and peroxisomal FAO in the liver.

RESULTS

Statin treatment prevented the development of MCDD-induced NASH. Both steatosis and inflammation or fibrosis grades were significantly improved by statins compared with MCDD-fed mice. Gene expression levels of peroxisomal proliferator-activated receptor α (PPARα) were decreased by MCDD and recovered by statin treatment. MCDD-induced suppression of mitochondrial and peroxisomal FAO was restored by statins. Each statin's effect on increasing FAO and improving NASH was independent on its effect of decreasing cholesterol levels.

CONCLUSION

Statins prevented NASH and increased mitochondrial and peroxisomal FAO via induction of PPARα. The ability to increase hepatic FAO is likely the major determinant of NASH prevention by statins. Improvement of peroxisomal function by statins may contribute to the prevention of NASH.

Long-term fructose consumption prolongs hepatic stearoyl-CoA desaturase 1 activity independent of upstream regulation in rats

Dietary fructose is considered a risk factor for metabolic disorders, such as fatty liver disease. However, the mechanism underlying the effects of fructose is not well characterized. We investigated the hepatic expression of key regulatory genes related to lipid metabolism following fructose feeding under well-defined conditions. Rats were fed standard chow supplemented with 10% w/v fructose solution for 5 weeks, and killed after chow-fasting and fructose withdrawal (fasting) or chow-fasting and continued fructose (fructose alone) for 14 h. Hepatic deposition of triglycerides was found in rats from both groups. As expected, fructose alone increased mRNA levels of lipogenesis-related genes and correspondingly decreased mRNA levels of lipid oxidative genes in the liver. Interesting, hepatic levels of stearoyl-CoA desaturase (SCD)1 mRNA remained elevated under fructose withdrawn conditions, although expression levels of other genes, including two key transcription factors (carbohydrate response element binding protein (ChREBP) and sterol regulatory element-binding protein (SREBP)-1c) fell to normal levels, indicating that long-term fructose intake increased SCD1 activity, independent of upstream regulatory genes, such as ChREBP and SREBP-1c. In conclusion, SCD1 overexpression in fatty liver disease is not affected by fasting after long-term fructose consumption in rats. Regulation of SCD1 plays an important role in fructose-induced hepatic steatosis.

ChREBP regulates fructose-induced glucose production independently of insulin signaling

Obese, insulin-resistant states are characterized by a paradoxical pathogenic condition in which the liver appears to be selectively insulin resistant. Specifically, insulin fails to suppress glucose production, yet successfully stimulates de novo lipogenesis. The mechanisms underlying this dysregulation remain controversial. Here, we hypothesized that carbohydrate-responsive element-binding protein (ChREBP), a transcriptional activator of glycolytic and lipogenic genes, plays a central role in this paradox. Administration of fructose increased hepatic hexose-phosphate levels, activated ChREBP, and caused glucose intolerance, hyperinsulinemia, hypertriglyceridemia, and hepatic steatosis in mice. Activation of ChREBP was required for the increased expression of glycolytic and lipogenic genes as well as glucose-6-phosphatase (G6pc) that was associated with the effects of fructose administration. We found that fructose-induced G6PC activity is a major determinant of hepatic glucose production and reduces hepatic glucose-6-phosphate levels to complete a homeostatic loop. Moreover, fructose activated ChREBP and induced G6pc in the absence of Foxo1a, indicating that carbohydrate-induced activation of ChREBP and G6PC dominates over the suppressive effects of insulin to enhance glucose production. This ChREBP/G6PC signaling axis is conserved in humans. Together, these findings support a carbohydrate-mediated, ChREBP-driven mechanism that contributes to hepatic insulin resistance.

Early Effects of Treatment Low-Dose Atorvastatin on Markers of Insulin Resistance and Inflammation in Patients with Myocardial Infarction

Dyslipidemia is one of the primary causes of cardiovascular disease. Therefore, attention has been focused on the development of drugs that normalize lipid levels and exert an effect on markers of atherothrombosis, insulin resistance (IR), and inflammation. Atorvastatin is a drug with not only lipid-lowering potential, but it has multiple non-lipid effects. This study aimed to evaluate atorvastatin effects on lipid, adipokine, IR, and inflammatory statuses in patients with myocardial infarction (MI) in an in-hospital setting. This study included 66 patients with confirmed ST-segment elevation MI, who were treated with atorvastatin 20 mg/day starting on day 1 of MI, without any dose changes. The comparison group consisted of 60 patients receiving standard anti-anginal and anti-thrombotic therapy. During the hospital stay, both groups showed a reduction in total cholesterol level and free fatty acids and increased concentrations of apolipoprotein A, especially those patients receiving atorvastatin. On day 1 of MI, patients in both groups had elevated levels of leptin by 2.9- to 3.3-fold, but the leptin levels decreased by 40.3% and were significantly lower than in patients not taking statins. The treatment with atorvastatin was associated with a decrease in C-reactive protein and interleukin-6 by 23.1 and 49.2%, respectively, compared with baseline values. In the group of patients on standard therapy, there was a decrease of interleukin-6 by 31.7%. Atorvastatin administered early on during hospitalization to patients with MI contributed to the improvement of lipid, adipokine and pro-inflammatory statuses and decreased IR.

Atorvastatin enhances kainate-induced gamma oscillations in rat hippocampal slices

Atorvastatin has been shown to affect cognitive functions in rodents and humans. However, the underlying mechanism is not fully understood. Because hippocampal gamma oscillations (γ, 20-80 Hz) are associated with cognitive functions, we studied the effect of atorvastatin on persistent kainate-induced γ oscillation in the CA3 area of rat hippocampal slices. The involvement of NMDA receptors and multiple kinases was tested before and after administration of atorvastatin. Whole-cell current-clamp and voltage-clamp recordings were made from CA3 pyramidal neurons and interneurons before and after atorvastatin application. Atorvastatin increased γ power by ~ 50% in a concentration-dependent manner, without affecting dominant frequency. Whereas atorvastatin did not affect intrinsic properties of both pyramidal neurons and interneurons, it increased the firing frequency of interneurons but not that of pyramidal neurons. Furthermore, whereas atorvastatin did not affect synaptic current amplitude, it increased the frequency of spontaneous inhibitory post-synaptic currents, but did not affect the frequency of spontaneous excitatory post-synaptic currents. The atorvastatin-induced enhancement of γ oscillations was prevented by pretreatment with the PKA inhibitor H89, the ERK inhibitor U0126, or the PI3K inhibitor wortmanin, but not by the NMDA receptor antagonist D-AP5. Taken together, these results demonstrate that atorvastatin enhanced the kainate-induced γ oscillation by increasing interneuron excitability, with an involvement of multiple intracellular kinase pathways. Our study suggests that the classical cholesterol-lowering agent atorvastatin may improve cognitive functions compromised in disease, via the enhancement of hippocampal γ oscillations.

Emodin ameliorates hepatic steatosis through endoplasmic reticulum-stress sterol regulatory element-binding protein 1c pathway in liquid fructose-feeding rats

AIM

To investigate the effects of emodin on the treatment of non-alcoholic fatty liver in rats induced by liquid fructose-feeding in rats and the possible underlying mechanisms.

METHODS

Sprague-Dawley rats were divided into the control, fructose-feeding group, and three fructose-feeding groups treated with 40, 80 and 160 mg/kg emodin, respectively. After 4 weeks of feeding, liquid consumption, food intake, bodyweight, liver index, serum triglyceride (TG), glucose and aminotransferases (aspartate aminotransferase [AST] and alanine aminotransferase [ALT]), liver TG contents and histology features were examined. The hepatic expression of lipogenic and fatty acid oxidation key enzymes, and an upstream transcriptional factor, sterol regulatory element-binding protein 1c (SREBP1c) were determined. Glucose regulated protein 78 (GRP78), a liver endoplasmic reticulum stress (ERS) marker and the unfolded protein response (UPR) related proteins were also measured.

RESULTS

Emodin reduced bodyweight, liver index, serum TG levels of fructose-feeding rats with no significant difference in serum glucose, AST and ALT levels. Emodin improved hepatic steatosis by inhibiting SREBP1c activation and its target genes, and enhancing carnitine palmitoyltransferase 1 expression in fructose-feeding rats. Emodin resolved hepatic ERS and the UPR induced by liquid fructose in rats.

CONCLUSION

Emodin is capable of improving the lipid accumulation through the ERS-SREBP1c pathway in fructose-induced non-alcoholic fatty liver disease.

Docosahexaenoic Acid Ameliorates Fructose-Induced Hepatic Steatosis Involving ER Stress Response in Primary Mouse Hepatocytes

The increase in fructose consumption is considered to be a risk factor for developing nonalcoholic fatty liver disease (NAFLD). We investigated the effects of docosahexaenoic acid (DHA) on hepatic lipid metabolism in fructose-treated primary mouse hepatocytes, and the changes of Endoplasmic reticulum (ER) stress pathways in response to DHA treatment. The hepatocytes were treated with fructose, DHA, fructose plus DHA, tunicamycin (TM) or fructose plus 4-phenylbutyric acid (PBA) for 24 h. Intracellular triglyceride (TG) accumulation was assessed by Oil Red O staining. The mRNA expression levels and protein levels related to lipid metabolism and ER stress response were determined by real-time PCR and Western blot. Fructose treatment led to obvious TG accumulation in primary hepatocytes through increasing expression of fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC), two key enzymes in hepatic de novo lipogenesis. DHA ameliorates fructose-induced TG accumulation by upregulating the expression of carnitine palmitoyltransferase 1A (CPT-1α) and acyl-CoA oxidase 1 (ACOX1). DHA treatment or pretreatment with the ER stress inhibitor PBA significantly decreased TG accumulation and reduced the expression of glucose-regulated protein 78 (GRP78), total inositol-requiring kinase 1 (IRE1α) and p-IRE1α. The present results suggest that DHA protects against high fructose-induced hepatocellular lipid accumulation. The current findings also suggest that alleviating the ER stress response seems to play a role in the prevention of fructose-induced hepatic steatosis by DHA.

Combining citrulline with atorvastatin preserves glucose homeostasis in a murine model of diet-induced obesity

BACKGROUND AND PURPOSE

NO is a crucial regulator of energy and lipid metabolism, whose homeostasis is compromised during obesity. Combination of citrulline and atorvastatin potentiated NO production in vitro. Here we have assessed the effects of this combination in mice with diet-induced obesity (DIO).

EXPERIMENTAL APPROACH

C57BL/6J male mice were given a standard diet (control) or a high fat-high sucrose diet (DIO) for 8 weeks. DIO mice were then treated with DIO alone, DIO with citrulline, DIO with atorvastatin or DIO with citrulline and atorvastatin (DIOcit-stat) for 3 weeks. Thereafter, body composition, glucose tolerance, insulin sensitivity and liver fat metabolism were measured.

KEY RESULTS

DIOcit-stat mice showed lower body weight, fat mass and epididymal fat depots compared with other DIO groups. Unlike other DIO groups, glucose tolerance and insulin sensitivity of DIOcit-stat, along with blood glucose and insulin concentrations in response to feeding, were restored to control values. Refeeding-induced changes in liver lipogenic activity were also reduced in DIOcit-stat mice compared with those of DIO animals. This was associated with decreased gene expression of the transcription factor SREBP-1, liver X receptor α, ChREBP and of target lipogenic enzymes in the liver of DIOcit-stat mice compared with those of other DIO groups.

CONCLUSIONS AND IMPLICATIONS

The citrulline-atorvastatin combination prevented fat mass accumulation and maintained glucose homeostasis in DIO mice. Furthermore, it potentiated inhibition of hepatic de novo lipogenesis activity. This combination has potential for preservation of glucose homeostasis in patients receiving statin therapy.

Dose-dependent effects of atorvastatin on myocardial infarction

Background

Dyslipidemia is a key factor determining the development of both myocardial infarction (MI) and its subsequent complications. Dyslipidemia is associated with endothelial dysfunction, activation of inflammation, thrombogenesis, and formation of insulin resistance. Statin therapy is thought to be effective for primary and secondary prevention of complications associated with atherosclerosis.

Methods

This study examined 210 patients with Segment elevated MI (ST elevated MI) who were treated with atorvastatin from the first 24 hours after MI. Group 1 (n=110) were given atorvastatin 20 mg/day. Group 2 (n=100) were given atorvastatin 40 mg/day. At days 1 and 12 after MI onset, insulin resistance levels determined by the homeostasis model assessment of insulin resistance index, lipid profiles, and serum glucose, insulin, adipokine, and ghrelin levels were measured.

Results

Free fatty acid levels showed a sharp increase during the acute phase of MI. Treatment with atorvastatin 20 mg/day, and especially with 40 mg/day, resulted in a decrease in free fatty acid levels. The positive effect of low-dose atorvastatin (20 mg/day) is normalization of the adipokine status. Administration of atorvastatin 20 mg/day was accompanied with a statistically significant reduction in glucose levels (by 14%) and C-peptide levels (by 38%), and a decrease in the homeostasis model assessment of insulin resistance index on day 12.

Conclusion

Determination of atorvastatin dose and its use during the in-hospital period and subsequent periods should take into account changes in biochemical markers of insulin resistance and adipokine status in patients with MI.

High consumption of fructose rather than glucose promotes a diet-induced obese phenotype in Drosophila melanogaster

During the last 20 years, there has been a considerable scientific debate about the possible mechanisms of induction of metabolic disorders by reducing monosaccharides such as glucose or fructose. In this study, we report the metabolic rearrangement in response to consumption of these monosaccharides at concentrations ranging from 0.25% to 20% in a Drosophila model. Flies raised on high-glucose diet displayed delay in pupation and increased developmental mortality compared with fructose consumers. Both monosaccharides at high concentrations promoted an obese-like phenotype indicated by increased fly body mass, levels of uric acid, and circulating and stored carbohydrates and lipids; and decreased percentage of water in the body. However, flies raised on fructose showed lower levels of circulating glucose and higher concentrations of stored carbohydrates, lipids, and uric acid. The preferential induction of obesity caused by fructose in Drosophila was associated with increased food consumption and reduced mRNA levels of DILP2 and DILP5 in the brain of adult flies. Our data show that glucose and fructose differently affect carbohydrate and lipid metabolism in Drosophila in part by modulation of insulin/insulin-like growth factor signaling. Some reported similarities with effects observed in mammals make Drosophila as a useful model to study carbohydrate influence on metabolism and development of metabolic disorders.

An integrated metabonomic approach to studying metabolic profiles in rat models with insulin resistance induced by high fructose

Insulin resistance (IR) is a common risk factor for the development of metabolic diseases, and has gradually become a hot issue for research. It was reported that excessive feeding with high fructose induced insulin resistance in both humans and rats. The aim of this study was to investigate the progression of IR and identify potential biomarkers in urine, plasma and fecal extracts of high fructose-fed rats using a (1)H NMR-based metabonomics approach. The biochemical analysis was also performed. The levels of pyruvate and lactate in the plasma of the IR model rats were reduced significantly, and the levels of citrate and α-ketoglutaric acid (α-KG) in their urine, and the levels of succinate in their feces also decreased, suggesting perturbation of energy metabolism. Decreased levels of taurine in urine and fecal extracts during the whole experiment, together with increased levels of creatine/creatinine in urine, revealed liver and kidney injuries. Decreased levels of choline-containing metabolites in urine and increased levels of betaine in urine and plasma demonstrated altered transmethylation. Changes in hippurate, acetate, propionate and n-butyrate levels suggested disturbance of the intestinal flora in the IR rats. This study indicated that (1)H NMR-based metabonomics can provide biochemical information on the progression of IR and offers a non-invasive means for the discovery of potential biomarkers.

Morin reduces hepatic inflammation-associated lipid accumulation in high fructose-fed rats via inhibiting sphingosine kinase 1/sphingosine 1-phosphate signaling pathway

SphK1/S1P signaling pathway is involved in the development of hepatic inflammation and injury. But its role in high fructose-induced NAFLD has not yet been reported. The aim of this study was to elucidate the crucial role of SphK1/S1P signaling pathway in high fructose-induced hepatic inflammation and lipid accumulation in rats. Moreover, the hepatoprotective effects of morin, a flavonoid with anti-inflammatory and anti-hyperlipedimic activities, on these hepatic changes in rats were investigated. High fructose-fed rats were orally treated with morin (30 and 60mg/kg) and pioglitazone (4mg/kg) for 8 weeks, respectively. Fructose feeding induced hyperlipidemia, and activated SphK1/S1P signaling pathway characterized by the elevation of SphK1 activity, S1P production as well as SphK1, S1PR1 and S1PR3 protein levels, which in turn caused NF-κB signaling activation to produce IL-1β, IL-6 and TNF-α and inflammation in the liver of rats. Subsequently, hepatic insulin and leptin signaling impairment and lipid metabolic disorder were observed in this animal model, resulting in liver lipid accumulation. Morin restored high fructose-induced the activation of hepatic SphK1/S1P signaling pathway in rats. Subsequently, the reduced NF-κB signaling activation by morin decreased inflammatory cytokine production, recovered insulin and leptin signaling impairment to reduce lipid accumulation and injury in the rat liver. These effects of morin were confirmed in Buffalo rat liver (BRL3A) cell model stimulated with 5mM fructose. Thus, the inhibition of hepatic SphK1/S1P signaling pathway may be a novel mechanism by which morin exerts hepatoprotection in high fructose-fed rats, possibly involving liver inflammation inhibition and lipid accumulation recovery.

Modest fructose beverage intake causes liver injury and fat accumulation in marginal copper deficient rats

OBJECTIVE

Dietary fructose and copper interaction may play an important role in the pathogenesis of nonalcoholic fatty liver disease. In this study, whether or not modest fructose consumption (3% fructose, w/v) (which is more closely related to the American lifestyle with regard to sugar beverage consumption) affects copper status, and causes liver injury and fat accumulation in marginal copper deficient rats was investigated.

DESIGN AND METHODS

Male weanling Sprague-Dawley rats were fed either an adequate copper (6 ppm) or a marginally copper deficient (1.6 ppm) diet for 4 weeks. Deionized water or deionized water containing 3% fructose (w/v) was given ad lib.

RESULTS

Modest fructose consumption further impaired copper status in the marginal copper deficient rats and increased hepatic iron accumulation. Liver injury and fat accumulation were significantly induced in the marginal copper deficient rats exposed to fructose.

CONCLUSIONS

Our data suggest that modest fructose consumption can impair copper status and lead to hepatic iron overload, which in turn, may lead to liver injury and fatty liver in marginal copper deficient rats. This study provides important information on dietary fructose and copper interaction, suggesting that dietary fructose-induced low copper availability might be an important mechanism underlying fructose-induced fatty liver.

[PPARβ/δ Activation prevents hypertriglyceridemia caused by a high fat diet. Involvement of AMPK and PGC-1α-Lipin1-PPARα pathway]

INTRODUCTION

Excessive consume of hypercaloric and high in saturated fat food causes an atherogenic dyslipidemia. In this study we analyzed the effects of PPARβ/δ activator GW501516 on the hypertriglyceridemia induced by a high-fat diet.

METHODS

Male mice were randomized in three groups: control (standard chow), high fat diet (HFD, 35% fat by weight, 58% Kcal from fat) and high fat diet plus GW501516 (3mg/Kg/day). Treatment duration was three weeks.

RESULTS

HFD-induced hypertriglyceridemia was accompanied by a reduction in hepatic levels of phospho-AMPK and in PGC-1α and Lipin1 mRNA levels. All these effects were reversed by GW501516 treatment. The lack of changes in phospho-AMPK levels after GW501516 treatment in HFD-fed animals could be the result of an increase in the AMP/ATP ratio. GW501516 treatment also increased Lipin1 protein levels in the nucleus, led to the amplification of the PGC-1α-PPARα pathway and increased PPARα DNA-binding activity, as well as the expression of PPARα-target genes involved in fatty acid oxidation. GW501516 also increased β-hydroxibutirate plasmatic levels, a hepatic β-oxidation end product. Finally, GW501516 increased the hepatic levels of the PPARα endogenous ligand 16:0/18:1-PC and the expression of the VLDL receptor.

CONCLUSION

These data indicate that the hypotriglyceridemic effect of GW501516 in mice subjected to HFD-fed mice is accompanied by an increase in phospho-AMPK levels and the amplification of the PGC-1α-Lipin1-PPARα pathway.

Fructose consumption enhances glucocorticoid action in rat visceral adipose tissue

The rise in consumption of refined sugars high in fructose appears to be an important factor for the development of obesity and metabolic syndrome. Fructose has been shown to be involved in genesis and progression of the syndrome through deregulation of metabolic pathways in adipose tissue. There is evidence that enhanced glucocorticoid regeneration within adipose tissue, mediated by the enzyme 11beta-hydroxysteroid dehydrogenase Type 1 (11βHSD1), may contribute to adiposity and metabolic disease. 11βHSD1 reductase activity is dependent on NADPH, a cofactor generated by hexose-6-phosphate dehydrogenase (H6PDH). We hypothesized that harmful effects of long-term high fructose consumption could be mediated by alterations in prereceptor glucocorticoid metabolism and glucocorticoid signaling in the adipose tissue of male Wistar rats. We analyzed the effects of 9-week drinking of 10% fructose solution on dyslipidemia, adipose tissue histology and both plasma and tissue corticosterone level. Prereceptor metabolism of glucocorticoids was characterized by determining 11βHSD1 and H6PDH mRNA and protein levels. Glucocorticoid signaling was examined at the level of glucocorticoid receptor (GR) expression and compartmental redistribution, as well as at the level of expression of its target genes (GR, phosphoenolpyruvate carboxyl kinase and hormone-sensitive lipase). Fructose diet led to increased 11βHSD1 and H6PDH expression and elevated corticosterone level within the adipose tissue, which was paralleled with enhanced GR nuclear accumulation. Although the animals did not develop obesity, nonesterified fatty acid and plasma triglyceride levels were elevated, indicating that fructose, through enhanced prereceptor metabolism of glucocorticoids, could set the environment for possible later onset of obesity.

Way back for fructose and liver metabolism: Bench side to molecular insights

The World Health Organization recommends that the daily intake of added sugars should make up no more than 10% of total energy. The consumption of sugar-sweetened beverages is the main source of added sugars. Fructose, together with glucose, as a component of high fructose corn syrups or as a component of the sucrose molecule, is one of the main sweeteners present in this kind of beverages. Data from prospective and intervention studies clearly point to high fructose consumption, mainly in the form of sweetened beverages, as a risk factor for several metabolic diseases in humans. The incidence of hypertension, nonalcoholic fatty liver disease (NAFLD), dyslipidemia (mainly hypertriglyceridemia), insulin resistance, type 2 diabetes mellitus, obesity, and the cluster of many of these pathologies in the form of metabolic syndrome is higher in human population segments that show high intake of fructose. Adolescent and young adults from low-income families are especially at risk. We recently reviewed evidence from experimental animals and human data that confirms the deleterious effect of fructose on lipid and glucose metabolism. In this present review we update the information generated in the past 2 years about high consumption of fructose-enriched beverages and the occurrence of metabolic disturbances, especially NAFLD, type 2 diabetes mellitus, and metabolic syndrome. We have explored recent data from observational and experimental human studies, as well as experimental data from animal and cell models. Finally, using information generated in our laboratory and others, we provide a view of the molecular mechanisms that may be specifically involved in the development of liver lipid and glucose metabolic alterations after fructose consumption in liquid form.

Treatment with ginger ameliorates fructose-induced Fatty liver and hypertriglyceridemia in rats: modulation of the hepatic carbohydrate response element-binding protein-mediated pathway

Ginger has been demonstrated to improve lipid derangements. However, its underlying triglyceride-lowering mechanisms remain unclear. Fructose overconsumption is associated with increase in hepatic de novo lipogenesis, thereby resulting in lipid derangements. Here we found that coadministration of the alcoholic extract of ginger (50 mg/kg/day, oral gavage, once daily) over 5 weeks reversed liquid fructose-induced increase in plasma triglyceride and glucose concentrations and hepatic triglyceride content in rats. Plasma nonesterified fatty acid concentration was also decreased. Attenuation of the increased vacuolization and Oil Red O staining area was evident on histological examination of liver in ginger-treated rats. However, ginger treatment did not affect chow intake and body weight. Further, ginger treatment suppressed fructose-stimulated overexpression of carbohydrate response element-binding protein (ChREBP) at the mRNA and protein levels in the liver. Consequently, hepatic expression of the ChREBP-targeted lipogenic genes responsible for fatty acid biosynthesis was also downregulated. In contrast, expression of neither peroxisome proliferator-activated receptor- (PPAR-) alpha and its downstream genes, nor PPAR-gamma and sterol regulatory element-binding protein 1c was altered. Thus the present findings suggest that in rats, amelioration of fructose-induced fatty liver and hypertriglyceridemia by ginger treatment involves modulation of the hepatic ChREBP-mediated pathway.

The antihypertensive actions of statins: modulation by salt intake

Hydroxy methyl glutaryl CoA inhibitors (statins) are the agents most frequently used to reduce elevated serum cholesterol. In addition to their cholesterol lowering effects, statins also have nonlipid lowering pleiotropic properties. These include reducing oxidative stress, renin-angiotensin and endothelin synthesis and activity, and improving nitric oxide (NO) synthesis and availability. Thus, one would predict that statins might be able to exert an antihypertensive effect. Experimental models bear out the blood pressure lowering effects but the data from clinical trials have been inconsistent perhaps due to inappropriate experimental designs, sample size, blood pressure measurement techniques etc. Moreover, although experimental models strongly suggest a role for salt intake in the potential antihypertensive responses to statins, available clinical trials fail to report salt intake in the studied populations. The statins' antihypertensive effects remain an unsettled hypothesis and calls for a large clinical trial at a wide range of doses and a controlled salt intake. Statins meanwhile remain as a excellent option to control high cholesterol and in tissue injury prevention.

TNF-α inhibits PPARβ/δ activity and SIRT1 expression through NF-κB in human adipocytes

The mechanisms linking low-grade chronic inflammation with obesity-induced insulin resistance have only been partially elucidated. PPARβ/δ and SIRT1 might play a role in this association. In visceral adipose tissue (VAT) from obese insulin-resistant patients we observed enhanced p65 nuclear translocation and elevated expression of the pro-inflammatory cytokines TNF-α and IL-6 compared to control subjects. Inflammation was accompanied by a reduction in the levels of SIRT1 protein and an increase in PPARβ/δ mRNA levels. Stimulation of human mature SGBS adipocytes with TNF-α caused similar changes in PPARβ/δ and SIRT1 to those reported in obese patients. Unexpectedly, PPAR DNA-binding activity and the expression of PPARβ/δ-target genes was reduced following TNF-α stimulation, suggesting that the activity of this transcription factor was inhibited by cytokine treatment. Interestingly, the PPARβ/δ ligand GW501516 prevented the expression of inflammatory markers and the reduction in the expression of PPARβ/δ-target genes in adipocytes stimulated with TNF-α. Consistent with a role for NF-κB in the changes caused by TNF-α, treatment with the NF-κB inhibitor parthenolide restored PPAR DNA-binding activity, the expression of PPARβ/δ-target genes and the expression of SIRT1 and PPARβ/δ. These findings suggest that the reduction in PPARβ/δ activity and SIRT1 expression caused by TNF-α stimulation through NF-κB helps perpetuate the inflammatory process in human adipocytes.

Nonalcoholic fatty liver disease: a nutritional approach

Nonalcoholic fatty liver disease (NAFLD) is among the most common causes of chronic liver disease in many countries, and its prevalence is increasing. NAFLD is often considered to be a hepatic component of metabolic syndrome, and studies have established that insulin resistance plays a major role in the pathogenesis of NAFLD. Treatments for NAFLD primarily target insulin resistance. Interestingly, the most common environmental cause of insulin resistance is diet. This article examines the correlations between NAFLD and diet and provides some diet recommendations based on the most current data available.

Differing endoplasmic reticulum stress response to excess lipogenesis versus lipid oversupply in relation to hepatic steatosis and insulin resistance

Mitochondrial dysfunction and endoplasmic reticulum (ER) stress have been implicated in hepatic steatosis and insulin resistance. The present study investigated their roles in the development of hepatic steatosis and insulin resistance during de novo lipogenesis (DNL) compared to extrahepatic lipid oversupply. Male C57BL/6J mice were fed either a high fructose (HFru) or high fat (HFat) diet to induce DNL or lipid oversupply in/to the liver. Both HFru and HFat feeding increased hepatic triglyceride within 3 days (by 3.5 and 2.4 fold) and the steatosis remained persistent from 1 week onwards (p<0.01 vs Con). Glucose intolerance (iAUC increased by ∼60%) and blunted insulin-stimulated hepatic Akt and GSK3β phosphorylation (∼40–60%) were found in both feeding conditions (p<0.01 vs Con, assessed after 1 week). No impairment of mitochondrial function was found (oxidation capacity, expression of PGC1α, CPT1, respiratory complexes, enzymatic activity of citrate synthase & β-HAD). As expected, DNL was increased (∼60%) in HFru-fed mice and decreased (32%) in HFat-fed mice (all p<0.05). Interestingly, associated with the upregulated lipogenic enzymes (ACC, FAS and SCD1), two (PERK/eIF2α and IRE1/XBP1) of three ER stress pathways were significantly activated in HFru-fed mice. However, no significant ER stress was observed in HFat-fed mice during the development of hepatic steatosis. Our findings indicate that HFru and HFat diets can result in hepatic steatosis and insulin resistance without obvious mitochondrial defects via different lipid metabolic pathways. The fact that ER stress is apparent only with HFru feeding suggests that ER stress is involved in DNL per se rather than resulting from hepatic steatosis or insulin resistance.

The PPARβ/δ activator GW501516 prevents the down-regulation of AMPK caused by a high-fat diet in liver and amplifies the PGC-1α-Lipin 1-PPARα pathway leading to increased fatty acid oxidation

Metabolic syndrome-associated dyslipidemia is mainly initiated by hepatic overproduction of the plasma lipoproteins carrying triglycerides. Here we examined the effects of the peroxisome proliferator-activated receptors (PPAR)-β/δ activator GW501516 on high-fat diet (HFD)-induced hypertriglyceridemia and hepatic fatty acid oxidation. Exposure to the HFD caused hypertriglyceridemia that was accompanied by reduced hepatic mRNA levels of PPAR-γ coactivator 1 (PGC-1)-α and lipin 1, and these effects were prevented by GW501516 treatment. GW501516 treatment also increased nuclear lipin 1 protein levels, leading to amplification in the PGC-1α-PPARα signaling system, as demonstrated by the increase in PPARα levels and PPARα-DNA binding activity and the increased expression of PPARα-target genes involved in fatty acid oxidation. These effects of GW501516 were accompanied by an increase in plasma β-hydroxybutyrate levels, demonstrating enhanced hepatic fatty acid oxidation. Moreover, GW501516 increased the levels of the hepatic endogenous ligand for PPARα, 16:0/18:1-phosphatidilcholine and markedly enhanced the expression of the hepatic Vldl receptor. Interestingly, GW501516 prevented the reduction in AMP-activated protein kinase (AMPK) phosphorylation and the increase in phosphorylated levels of ERK1/2 caused by HFD. In addition, our data indicate that the activation of AMPK after GW501516 treatment in mice fed HFD might be the result of an increase in the AMP to ATP ratio in hepatocytes. These findings indicate that the hypotriglyceridemic effect of GW501516 in HFD-fed mice is accompanied by an increase in phospho-AMPK levels and the amplification of the PGC-1α-lipin 1-PPARα pathway.

Reduction of liver fructokinase expression and improved hepatic inflammation and metabolism in liquid fructose-fed rats after atorvastatin treatment

Consumption of beverages that contain fructose favors the increasing prevalence of metabolic syndrome alterations in humans, including non-alcoholic fatty liver disease (NAFLD). Although the only effective treatment for NAFLD is caloric restriction and weight loss, existing data show that atorvastatin, a hydroxymethyl-glutaryl-CoA reductase inhibitor, can be used safely in patients with NAFLD and improves hepatic histology. To gain further insight into the molecular mechanisms of atorvastatin's therapeutic effect on NAFLD, we used an experimental model that mimics human consumption of fructose-sweetened beverages. Control, fructose (10% w/v solution) and fructose+atorvastatin (30 mg/kg/day) Sprague-Dawley rats were sacrificed after 14 days. Plasma and liver tissue samples were obtained to determine plasma analytes, liver histology, and the expression of liver proteins that are related to fatty acid synthesis and catabolism, and inflammatory processes. Fructose supplementation induced hypertriglyceridemia and hyperleptinemia, hepatic steatosis and necroinflammation, increased the expression of genes related to fatty acid synthesis and decreased fatty acid β-oxidation activity. Atorvastatin treatment completely abolished histological signs of necroinflammation, reducing the hepatic expression of metallothionein-1 and nuclear factor kappa B binding. Furthermore, atorvastatin reduced plasma (x 0.74) and liver triglyceride (x 0.62) concentrations, decreased the liver expression of carbohydrate response element binding protein transcription factor (x 0.45) and its target genes, and increased the hepatic activity of the fatty acid β-oxidation system (x 1.15). These effects may be related to the fact that atorvastatin decreased the expression of fructokinase (x 0.6) in livers of fructose-supplemented rats, reducing the metabolic burden on the liver that is imposed by continuous fructose ingestion.

Fructose: a highly lipogenic nutrient implicated in insulin resistance, hepatic steatosis, and the metabolic syndrome

As dietary exposure to fructose has increased over the past 40 years, there is growing concern that high fructose consumption in humans may be in part responsible for the rising incidence of obesity worldwide. Obesity is associated with a host of metabolic challenges, collectively termed the metabolic syndrome. Fructose is a highly lipogenic sugar that has profound metabolic effects in the liver and has been associated with many of the components of the metabolic syndrome (insulin resistance, elevated waist circumference, dyslipidemia, and hypertension). Recent evidence has also uncovered effects of fructose in other tissues, including adipose tissue, the brain, and the gastrointestinal system, that may provide new insight into the metabolic consequences of high-fructose diets. Fructose feeding has now been shown to alter gene expression patterns (such as peroxisome proliferator-activated receptor-γ coactivator-1α/β in the liver), alter satiety factors in the brain, increase inflammation, reactive oxygen species, and portal endotoxin concentrations via Toll-like receptors, and induce leptin resistance. This review highlights recent findings in fructose feeding studies in both human and animal models with a focus on the molecular and biochemical mechanisms that underlie the development of insulin resistance, hepatic steatosis, and the metabolic syndrome.